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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/38583-8.txt b/38583-8.txt new file mode 100644 index 0000000..03cf3f6 --- /dev/null +++ b/38583-8.txt @@ -0,0 +1,9525 @@ +Project Gutenberg's Heroes of Science: Physicists, by William Garnett + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Heroes of Science: Physicists + +Author: William Garnett + +Release Date: January 15, 2012 [EBook #38583] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: PHYSICISTS *** + + + + +Produced by Albert László, P. G. Máté, Matthew Wheaton and +the Online Distributed Proofreading Team at +http://www.pgdp.net (This file was produced from images +generously made available by The Internet Archive) + + + + + + + + + + HEROES OF SCIENCE. + + + + + HEROES OF SCIENCE. + + PHYSICISTS. + + BY + + WILLIAM GARNETT, M.A., D.C.L., + + + FORMERLY FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE; PRINCIPAL OF + THE DURHAM COLLEGE OF SCIENCE, NEWCASTLE-UPON-TYNE; HON. MEMBER + OF THE NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL + ENGINEERS. + + PUBLISHED UNDER THE DIRECTION OF THE COMMITTEE OF GENERAL + LITERATURE AND EDUCATION APPOINTED BY THE SOCIETY FOR PROMOTING + CHRISTIAN KNOWLEDGE. + + LONDON: + SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE, + NORTHUMBERLAND AVENUE, CHARING CROSS, W.C.; + + 43, QUEEN VICTORIA STREET, E.C.; + 26, ST. GEORGE'S PLACE, HYDE PARK CORNER, S.W. + BRIGHTON: 135, NORTH STREET. + + NEW YORK: E. & J. B. YOUNG AND CO. + + + + +PREFACE. + + +The following pages claim no originality, and no merits beyond that of +bringing within reach of every boy and girl material which would +otherwise be available only to those who had extensive libraries at +their command, and much time at their disposal. In the schools and +colleges in which the principles of physical science are well taught, +the history of the discoveries whereby those principles have been +established has been too much neglected. The series to which the +present volume belongs is intended, in some measure, to meet this +deficiency. + +A complete history of physical science would, if it could be written, +form a library of considerable dimensions. The following pages deal +only with the biographies of a few distinguished men, who, by birth, +were British subjects, and incidental allusions only are made to +living philosophers; but, notwithstanding these narrow restrictions, +the foundations of the Royal Society of London, of the American +Philosophical Society, of the great Library of Pennsylvania, and of +the Royal Institution, are events, some account of which comes within +the compass of the volume. The gradual development of our knowledge of +electricity, of the mechanical theory of heat, and of the undulatory +theory of optics, will be found delineated in the biographies +selected, though no continuous history is traced in the case of any +one of these branches of physics. + +The sources from which the matter contained in the following pages has +been derived have been, in addition to the published works of the +subjects of the several sketches, the following:-- + +"The Encyclopædia Britannica." + +"Memoir of the Honourable Robert Boyle," by Thomas Birch, M.A., +prefixed to the folio edition of his works, which was published in +London in 1743. + +"Life of Benjamin Franklin," from his own writings, by John Bigelow. + +Dr. G. Wilson's "Life of Cavendish," which forms the first volume of +the publications of the Cavendish Society; and the "Electrical +Researches of the Hon. Henry Cavendish, F.R.S.," edited by the late +Professor James Clerk Maxwell. + +"The Life of Sir Benjamin Thompson, Count Rumford," by George E. +Ellis, published by the American Academy of Arts and Sciences, in +connection with the complete edition of his works. + +"Memoir of Thomas Young," by the late Dean Peacock. + +Dr. Bence Jones's "Life of Faraday;" and Professor Tyndall's "Faraday +as a Discoverer." + +"Life of James Clerk Maxwell," by Professor Lewis Campbell and William +Garnett. + +It is hoped that the perusal of the following sketches may prove as +instructive to the reader as their preparation has been to the writer. + + WM. GARNETT. + + NEWCASTLE-UPON-TYNE, + _December, 1885_. + + + + +CONTENTS. + + + PAGE +INTRODUCTION 1 +ROBERT BOYLE 5 +BENJAMIN FRANKLIN 38 +HENRY CAVENDISH 125 +COUNT RUMFORD 148 +THOMAS YOUNG 194 +MICHAEL FARADAY 237 +JAMES CLERK MAXWELL 278 +CONCLUSION 309 + + + + +HEROES OF SCIENCE. + + + + +INTRODUCTION. + + +The dawn of true ideas respecting mechanics has been described in the +volume of this series devoted to astronomers. At the time when the +first of the following biographies opens there were a few men who held +sound views respecting the laws of motion and the principles of +hydrostatics. Considerable advance had been made in the subject of +geometrical optics; the rectilinear propagation of light and the laws +of reflection having been known to the Greeks and Arabians, whilst +Willebrod Snellius, Professor of Mathematics at Leyden, had correctly +enunciated the laws of refraction very early in the seventeenth +century. Pliny mentions the action of a sphere of rock-crystal and of +a glass globe filled with water in bringing light to a focus. Roger +Bacon used segments of a glass sphere as lenses; and in the eleventh +century Alhazen made many measurements of the angles of incidence and +refraction, though he did not succeed in discovering the law. Huyghens +developed to a great extent the undulatory theory; while Newton at the +same time made great contributions to the subject of geometrical +optics, decomposed white light by means of a prism, investigated the +colours of thin plates, and some cases of diffraction, and speculated +on the nature, properties, and functions of the ether, which was +equally necessary to the corpuscular as to the undulatory theory of +light, if any of the phenomena of interference were to be explained. +The velocity of light was first measured by Roemer, in 1676. The +camera obscura was invented by Baptista Porta, a wealthy Neapolitan, +in 1560; and Kepler explained the action of the eye as an optical +instrument, in 1604. Antonio de Dominis, Archbishop of Spalatro, +discovered the fringe of colours produced by sunlight once reflected +from the interior of a globe of water, and this led, in Newton's +hands, to the complete explanation of the rainbow. + +The germ of the mechanical theory of heat is to be found in the +writings of Lord Bacon. The first thermometers which were blown in +glass with a bulb and tube hermetically sealed, were made by a +craftsman in Florence, in the time of Torricelli. The graduations on +these thermometers were made by attaching little beads of coloured +glass to their stems, and they were carried about Europe by members of +the Florentine Academy, in order to learn whether ice melted at the +same temperature in all latitudes. + +In electricity the attraction of light bodies by amber when rubbed, +was known at least six hundred years before the Christian era, and the +shocks of the torpedo were described by Pliny and by Aristotle; but +the phenomena were not associated in men's minds until recent times. +Dr. Gilbert, of Colchester, Physician to Queen Elizabeth, may be +regarded as the founder of the modern science. He distinguished two +classes of bodies, viz. electrics, or those which would attract light +bodies when rubbed; and non-electrics, or those which could not be so +excited. The first electric machine was constructed by Otto von +Guericke, the inventor of the Magdeburg hemispheres, who mounted a +ball of sulphur so that it could be made rapidly to rotate while it +was excited by the friction of the hand. He observed the repulsion +which generally follows the attraction of a light body by an +electrified object after the two have come in contact. He also noticed +that certain bodies placed near to electrified bodies possessed +similar powers of attraction to those of the electrified bodies +themselves. Newton replaced the sulphur globe of Otto von Guericke by +a globe of glass. Stephen Gray discovered the conduction of +electricity, in 1729, when he succeeded in transmitting a charge to a +distance of 886 feet along a pack-thread suspended by silk strings so +as to insulate it from the earth. Desaguliers showed that Gilbert's +"electrics" were simply those bodies which could not conduct +electricity, while all conductors were "non-electrics;" and Dufay +showed that all bodies could be electrified by friction if supported +on insulating stands. He also showed that there were two kinds of +electrification, and called one _vitreous_, the other _resinous_. +Gray, Hawksbee, and Dr. Wall all noticed the similarity between +lightning and the electric discharge. The prime conductor was first +added to the electric machine by Boze, of Wittenberg; and Winkler, of +Leipsic, employed a cushion instead of the hand to produce friction +against the glass. The accumulation of electricity in the Leyden jar +was discovered accidentally by Cuneus, a pupil of Muschenbroeck, of +Leyden, about 1745, while attempting to electrify water in a bottle +held in his hand. A nail passed through the cork, by which the +electricity was communicated to the water. On touching the nail after +charging the water, he received the shock of the Leyden jar. This +brings the history of electrical discovery down to the time of +Franklin. + + + + +ROBERT BOYLE. + + +Robert Boyle was descended from a family who, in Saxon times, held +land in the county of Hereford, and whose name in the Doomsday Book is +written Biuvile. His father was Richard Boyle, Earl of Cork, to whom +the fortunes of the family were largely due. Richard Boyle was born in +the city of Canterbury, October 3, 1566. He was educated at Bene't +College (now Corpus Christi College), Cambridge, and afterwards became +a member of the Middle Temple. Finding his means insufficient for the +prosecution of his legal studies, he determined to seek his fortune +abroad. In 1595 he married, at Limerick, one of the daughters of +William Apsley, who brought him land of the value of £500 per annum. +In his autobiography the Earl of Cork writes:-- + + When first I arrived at Dublin, in Ireland, the 23rd of June + 1588, all my wealth then was twenty-seven pounds three shillings + in money, and two tokens which my mother had given me, viz. a + diamond ring, which I have ever since and still do wear, and a + bracelet of gold worth about ten pounds; a taffety doublet cut + with and upon taffety, a pair of black velvet breeches laced, a + new Milan fustian suit laced and cut upon taffety, two cloaks, + competent linen, and necessaries, with my rapier and dagger. And + since, the blessing of God, whose heavenly providence guided me + hither, hath enriched my weak estate, in beginning with such a + fortune, as I need not envy any of my neighbours, and added no + care or burthen of my conscience thereunto. And the 23rd of + June, 1632, I have served my God, Queen Elizabeth, King James, + and King Charles, full forty-four years, and so long after as it + shall please God to enable me. + +Richard Boyle's property in Ireland increased so rapidly that he was +accused to Queen Elizabeth of receiving pay from some foreign power. +When about to visit England in order to clear himself of this charge, +the rebellion in Munster broke out; his lands were wasted, and his +income for the time destroyed. Reaching London, he returned to his old +chambers in the Middle Temple, until he entered the service of the +Earl of Essex, to whom the government of Ireland had been entrusted. +The charges against him were then resumed, and he was made a prisoner, +and kept in confinement until the Earl of Essex had gone over to +Ireland. At length he obtained a hearing before the queen, who fully +acquitted him of the charges, gave him her hand to kiss, and promised +to employ him in her own service; at the same time she dismissed Sir +Henry Wallop, who was Treasurer for Ireland, and prominent among +Boyle's accusers, from his office. + +A few days afterwards, Richard Boyle was appointed by the queen Clerk +to the Council of Munster, and having purchased a ship of Sir Walter +Raleigh, he returned to Ireland with ammunition and provisions. + +"Then, as Clerk of the Council, I attended the Lord President in all +his employments, and waited upon him at the siege of Kingsale, and was +employed by his Lordship to her Majesty, with the news of that happy +victory; in which employment I made a speedy expedition to the court; +for I left my Lord President at Shannon Castle, near Corke, on the +Monday morning, about two of the clock, and the next day, being +Tuesday, I delivered my packet, and supped with Sir Robert Cecil, +being then principal Secretary of State, at his house in the Strand; +who, after supper, held me in discourse till two of the clock in the +morning; and by seven that morning called upon me to attend him to the +court, where he presented me to her Majesty in her bed-chamber, who +remembered me, calling me by my name, and giving me her hand to kiss, +telling me that she was glad that I was the happy man to bring the +first news of that glorious victory ... and so I was dismissed with +grace and favour." + +In reading of this journey from Cork to London, it is almost necessary +to be reminded that it took place two hundred and fifty years before +the introduction of steam-boats and railways. At the close of the +rebellion, Richard Boyle purchased from Sir Walter Raleigh all his +lands in Munster; and on July 25, 1603, he married his second wife, +Catharine, the only daughter of Sir Geoffrey Fenton, principal +Secretary of State, and Privy Councillor in Ireland, "with whom I +never demanded any marriage portion, neither promise of any, it not +being in my consideration; yet her father, after my marriage, gave me +one thousand pounds in gold with her. But that gift of his daughter +unto me I must ever thankfully acknowledge as the crown of all my +blessings; for she was a most religious, virtuous, loving, and +obedient wife unto me all the days of her life." He was knighted by +the Lord Deputy of Ireland, Sir George Carew, on his wedding-day; was +sworn Privy Councillor of State of the Kingdom of Ireland in 1612; +created Lord Boyle, Baron of Youghall, September 29, 1616; Lord +Viscount of Dungarvon and Earl of Cork, October 26, 1620; one of the +Lords Justices of Ireland, with a salary of £1200 per annum, in 1629; +and Lord High Treasurer of Ireland, November 9, 1631. + +Robert Boyle, the seventh son of the Earl of Cork, was born January +25, 1627. His mother died February 16, 1630. The earl lived in +prosperity in Ireland till the breaking out of the rebellion in 1641, +and died at Youghall in September, 1643. It is said that when Cromwell +saw the vast improvements which the earl had made on his estate in +Munster, he declared that "if there had been an Earl of Cork in every +province, it would have been impossible for the Irish to have raised a +rebellion." + +At a very early age Robert was sent by his father to a country nurse, +"who, by early inuring him, by slow degrees, to a coarse but cleanly +diet, and to the usual passion of the air, gave him so vigorous a +complexion that both hardships were made easy to him by custom, and +the delights of conveniences and ease were endeared to him by their +rarity." Making the acquaintance of some children who stuttered in +their speech, he, by imitation, acquired the same habit, "so +contagious and catching are men's faults, and so dangerous is the +familiar commerce of those condemnable customs, that, being imitated +but in jest, come to be learned and acquired in earnest." Before going +to school he studied French and Latin, and showed considerable +aptitude for scholarship. He was then sent to Eton, where his master +took much notice of him, and "would sometimes give him unasked +play-days, and oft bestow upon him such balls and tops and other +implements of idleness as he had taken away from others that had +unduly used them." + +While at school, in the early morning, a part of the wall of the +bedroom, with the bed, chairs, books, and furniture of the room above, +fell on him and his brother. "His brother had his band torn about his +neck, and his coat upon his back, and his chair crushed and broken +under him; but by a lusty youth, then accidentally in the room, was +snatched from out the ruins, by which [Robert] had, in all +probability, been immediately oppressed, had not his bed been +curtained by a watchful Providence, which kept all heavy things from +falling on it; but the dust of the crumbled rubbish raised was so +thick that he might there have been stifled had not he remembered to +wrap his head in the sheet, which served him as a strainer, through +which none but the purer air could find a passage." At Eton he spent +nearly four years, "in the last of which he forgot much of that Latin +he had got, for he was so addicted to more solid parts of knowledge +that he hated the study of bare words naturally, as something that +relished too much of pedantry to consort with his disposition and +designs." On leaving Eton he joined his father at Stalbridge, in +Dorsetshire, and was sent to reside with "Mr. W. Douch, then parson of +that place," who took the supervision of his studies. Here he renewed +his acquaintance with Latin, and devoted some attention to English +verse, spending some of his idle hours in composing verses, "most of +which, the day he came of age, he sacrificed to Vulcan, with a design +to make the rest perish by the same fate." A little later he returned +to his father's house in Stalbridge, and was placed under the tutelage +of a French gentleman, who had been tutor to two of his brothers. + +In October, 1638, Robert Boyle and his brother were sent into France. +After a short stay at Lyons, they reached Geneva, where Robert +remained with his tutor for about a year and three quarters. During +his residence here an incident occurred which he regarded as the most +important event of his life, and which we therefore give in his own +words. + +"To frame a right apprehension of this, you must understand that, +though his inclinations were ever virtuous, and his life free from +scandal and inoffensive, yet had the piety he was master of already so +diverted him from aspiring unto more, that Christ, who long had lain +asleep in his conscience (as He once did in the ship), must now, as +then, be waked by a storm. For at a time which (being the very heat of +summer) promised nothing less, about the dead of night, that adds most +terror to such accidents, [he] was suddenly waked in a fright with +such loud claps of thunder (which are oftentimes very terrible in +those hot climes and seasons), that he thought the earth would owe an +ague to the air, and every clap was both preceded and attended with +flashes of lightning, so frequent and so dazzling that [he] began to +imagine them the sallies of that fire that must consume the world. The +long continuance of that dismal tempest, where the winds were so loud +as almost drowned the noise of the very thunder, and the showers so +hideous as almost quenched the lightning ere it could reach his eyes, +confirmed him in his apprehensions of the day of judgment's being at +hand. Whereupon the consideration of his unpreparedness to welcome +it, and the hideousness of being surprised by it in an unfit +condition, made him resolve and vow that, if his fears were that night +disappointed, all his further additions to his life should be more +religiously and watchfully employed. The morning came, and a serene, +cloudless sky returned, when he ratified his determinations so +solemnly, that from that day he dated his conversion, renewing, now he +was past danger, the vow he had made whilst he believed himself to be +in it; and though his fear was (and he blushed it was so) the occasion +of his resolution of amendment, yet at least he might not owe his more +deliberate consecration of himself to piety to any less noble motive +than that of its own excellence." + +After leaving Geneva, he crossed the Alps and travelled through +Northern Italy. Here he spent much time in learning Italian; "the rest +of his spare hours he spent in reading the modern history in Italian, +and the new paradoxes of the great stargazer Galileo, whose ingenious +books, perhaps because they could not be so otherwise, were confuted +by a decree from Rome; his highness the Pope, it seems, presuming, and +that justly, that the infallibility of his chair extended equally to +determine points in philosophy as in religion, and loth to have the +stability of that earth questioned in which he had established his +kingdom." + +Having visited Rome, he at length returned to France, and was detained +at Marseilles, awaiting a remittance from the earl to enable him to +continue his travels. Through some miscarriage, the money which the +earl sent did not arrive, and Robert and his brother had to depend on +the credit of the tutor to procure the means to enable them to return +home. They reached England in the summer of 1644, "where we found +things in such confusion that, although the manor of Stalbridge were, +by my father's decease, descended unto me, yet it was near four months +before I could get thither." On reaching London, Robert Boyle resided +for some time with his sister, Lady Ranelagh, and was thus prevented +from entering the Royalist Army. Later on he returned for a short time +to France; visited Cambridge in December, 1645, and then took up his +residence at Stalbridge till May, 1650, where he commenced the study +of chemistry and natural philosophy. + +It was in October, 1646, that Boyle first made mention of the +"_invisible college_," which afterwards developed into the Royal +Society. Writing to a Fellow of Magdalen College, Cambridge, in +February, 1647, he says, "The corner-stones of the _invisible_, or, as +they term themselves, the _philosophical college_, do now and then +honour me with their company." It appears that a desire to escape from +the troubles of the times had induced several persons to take refuge +in philosophical pursuits, and, meeting together to discuss the +subjects of their study, they formed the "invisible college." Boyle +says, "I will conclude their praises with the recital of their +chiefest fault, which is very incident to almost all good things, and +that is, that there is not enough of them." Dr. Wallis, one of the +first members of the society, states that Mr. Theodore Hooke, a German +of the Palatinate, then resident in London, "gave the first occasion +and first suggested those meetings and many others. These meetings we +held sometimes at Dr. Goddard's lodging, in Wood Street (or some +convenient place near), on occasion of his keeping an operator in his +house, for grinding glasses for telescopes and microscopes, and +sometimes at a convenient place in Cheapside; sometimes at Gresham +College, or some place near adjoining. Our business was (precluding +theology and State affairs) to discourse and consider of philosophical +inquiries, and such as related thereunto; as physic, anatomy, +geometry, astronomy, navigation, statics, magnetics, chemics, +mechanics, and natural experiments, with the state of these studies as +then cultivated at home and abroad. About the year 1648-49 some of us +being removed to Oxford, first Dr. Wilkins, then I, and soon after Dr. +Goddard, our company divided. Those in London continued to meet there +as before, and we with them when we had occasion to be there. And +those of us at Oxford, with Dr. Ward, since Bishop of Salisbury, Dr. +Ralph Bathurst, now President of Trinity College in Oxford, Dr. Petty, +since Sir William Petty, Dr. Willis, then an eminent physician in +Oxford, and divers others, continued such meetings in Oxford, and +brought those studies into fashion there; meeting first at Dr. +Petty's lodgings, in an apothecary's house, because of the convenience +of inspecting drugs and the like, as there was occasion; and after his +remove to Ireland (though not so constantly) at the lodgings of Dr. +Wilkins, then Warden of Wadham College; and after his removal to +Trinity College in Cambridge, at the lodgings of the Honourable Mr. +Robert Boyle, then resident for divers years in Oxford. These meetings +in London continued, and after the king's return, in 1660, were +increased with the accession of divers worthy and honourable persons, +and were afterwards incorporated by the name of the _Royal Society_, +and so continue to this day." + +Boyle was only about twenty years of age when he wrote his "Free +Discourse against Swearing;" his "Seraphic Love; or, Some Motives and +Incentives to the Love of God;" and his "Essay on Mistaken Modesty." +"Seraphic Love" was the last of a series of treatises on love, but the +only one of the series that he published, as he considered the others +too trifling to be published alone or in conjunction with it. In a +letter to Lady Ranelagh, he refers to his laboratory as "a kind of +Elysium," and there were few things which gave him so much pleasure as +his furnaces and philosophical experiments. In 1652 he visited +Ireland, returning in the following summer. In the autumn he was again +obliged to visit Ireland, and remained there till the summer of 1654, +though residence in that country was far from agreeable to him. He +styled it "a barbarous country, where chemical spirits were so +misunderstood, and chemical instruments so unprocurable, that it was +hard to have any hermetic thoughts in it." On his return he settled in +Oxford, and there his lodgings soon became the centre of the +scientific life of the university. Boyle and his friends may be +regarded as the pioneers of experimental philosophy in this country. +To Boyle the methods of Aristotle appeared little more than +discussions on words; for a long time he refused to study the +philosophy of Descartes, lest he should be turned aside from reasoning +based strictly on the results of experiment. The method pursued by +these philosophers had been fully discussed by Lord Bacon, but at best +his experimental methods, though most complete and systematic, existed +only upon paper, and it was reserved for Boyle and his friends to put +the Baconian philosophy into actual practice. + +It was during his residence at Oxford that he invented the air-pump, +which was afterwards improved for him by Hooke, and with which he +conducted most of those experiments on the "spring" and weight of the +air, which led up to the investigations that have rendered his name +inseparably connected with "the gaseous laws." The experiments of +Galileo and of Torricelli had shown that the pressure of the air was +capable of supporting a column of water about thirty-four feet in +height, or a column of mercury nearly thirty inches high. The younger +Pascal, at the request of Torricelli, had carried a barometer to the +summit of the Puy de Dome, and demonstrated that the height of the +column of mercury supported by the air diminishes as the altitude is +increased. Otto von Guericke had constructed the Magdeburg +hemispheres, and shown that, when exhausted, they could not be +separated by sixteen horses, eight pulling one way and eight the +other. He was aware that the same traction could have been produced by +eight horses if one of the hemispheres had been attached to a fixed +obstacle; but, with the instincts of a popular lecturer, he considered +that the spectacle would thus be rendered less striking, and it was +prepared for the king's entertainment. Boyle wished for an air-pump +with an aperture in the receiver sufficiently large for the +introduction of various objects, and an arrangement for exhausting it +without filling the receiver with water or otherwise interfering with +the objects placed therein. His apparatus consisted of a large glass +globe capable of containing about three gallons or thereabouts, +terminating in an open tube below, and with an aperture of about four +inches diameter at the top. Around this aperture was cemented a turned +brass ring, the inner surface being conical, and into this conical +seat was fitted a brass plate with a thick rim, but drilled with a +small hole in the centre. To this hole, which was also conical, was +fitted a brass stopper, which could be turned round when the receiver +was exhausted. By attaching a string to this stopper, which was so +long as to enter the receiver to the depth of two or three inches, and +turning the stopper in its seat, the string could be wound up, and +thus objects could be moved within the receiver. The tube at the +bottom of the receiver communicated with a stop-cock, and this with +the upper end of the pumpbarrel, which was inverted, so that this +stop-cock, which was at the top of the barrel, took the place of the +foot-valve. The piston was solid, made of wood, and surrounded with +sole leather, which was kept well greased. There being no valve in the +piston, it was necessary to place an exhaust-valve in the upper end of +the cylinder. This consisted of a small brass plug closing a conical +hole so that it could be removed at pleasure. The construction of the +cylinder was, therefore, similar to that of an ordinary force-pump, +except that the valves had to be moved by hand (as in the early forms +of the steam-engine). The piston was raised and depressed by means of +a rack and pinion. The pumps could be used either for exhausting the +receiver or for forcing air into it, according to the order in which +the "valves" were opened. If the stop-cock communicating with the +receiver were open while the piston was being drawn down, and the +brass plug removed so as to open the exhaust-valve when the piston was +being forced up, the receiver would gradually be exhausted. If the +brass plug were removed during the descent of the piston, and the +stop-cock opened during its ascent, air would be forced into the +receiver. In the latter case it was necessary to take special +precautions to prevent the brass plate at the top of the receiver +being raised from its seat. All joints were made air-tight with +"diachylon," and when, through the bursting of a glass bulb within it, +the receiver became cracked, the crack was rendered air-tight by the +same means. Other receivers of smaller capacity were also provided, on +account of the greater readiness with which they could be exhausted. + +With this apparatus Boyle carried out a long series of experiments. He +could reduce the pressure in the large receiver to somewhat less than +that corresponding to an inch of mercury, or about a foot of water. +Squeezing a bladder so as to expel nearly all the air, tying the neck, +and then introducing it into the receiver, he found, on working the +pump, that the bladder swelled so that at length it became completely +distended. In order to account for this great expansibility, Boyle +pictured the constitution of the air in the following way. He supposed +the air to consist of separate particles, each resembling a spiral +spring, which became tightly wound when exposed to great pressure, but +which expanded so as to occupy a larger circle when the pressure was +diminished. Each of these little spirals he supposed to rotate about a +diameter so as to exclude every other body from the sphere in which it +moved. Increasing the length of the diameter tenfold would increase +the volume of one of these spheres, and therefore the volume of the +gas, a thousandfold. Possibly this was only intended as a mental +illustration, exhibiting a mechanism by which very great expansion +might conceivably be produced, and scarcely pretending to be +considered a _theory_ of the constitution of the air. Boyle's first +idea seems to have been derived from a lock of wool in which the +elasticity of each fibre caused the lock to expand after it had been +compressed in the hand. In another passage he speaks of the air as +consisting of a number of bodies capable of striking against a surface +exposed to them. He demonstrated the weight of the air by placing a +delicate balance within the receiver, suspending from one arm a +bladder half filled with water, and balancing it with brass weights. +On exhausting the air, the bladder preponderated, and, by repeating +the experiment with additional weights on the other arm until a +balance was effected in the exhausted receiver, he determined the +amount of the preponderance. In another experiment he compressed air +in a bladder by tying a pack-thread round it, balanced it from one arm +of his balance in the open air; then, pricking the bladder so as to +relieve the pressure, he found that with the escape of the compressed +air the weight diminished. + +One of the most important of his experiments with the air-pump was the +following. He placed within the receiver the cistern of a mercurial +barometer, the tube of which was made to pass through the central hole +in the brass plate, from which the stopper had been removed. The space +around the tube was filled up with cement, and the receiver +exhausted. At each stroke of the pump the mercury in the barometer +tube descended, but through successively diminishing distances, until +at length it stood only an inch above the mercury in the cistern. The +experiment was then repeated with a tube four feet long and filled +with water. This constituted the nineteenth experiment referred to +later on. A great many strokes of the pump had to be made before the +water began to descend. At length it fell till the surface in the tube +stood only about a foot above that in the tank. Placing vessels of +ordinary spring-water and of distilled rain-water in the receiver, he +found that, after the exhaustion had reached a certain stage, bubbles +of gas were copiously evolved from the spring-water, but not from the +distilled water. On another occasion he caused warm water to boil by a +few strokes of the pump; and, continuing the exhaustion, the water was +made to boil at intervals until it became only lukewarm. The +experiment was repeated with several volatile liquids. He also noticed +the cloud formed in the receiver when the air was allowed rapidly to +expand; but the mechanical theory of heat had not then made sufficient +progress to enable him to account for the condensation by the loss of +heat due to the work done by the expanding air. The very minute +accuracy of his observations is conspicuous in the descriptions of +most of his experiments. That the air is the usual medium for the +conveyance of sound was shown by suspending a watch by a linen thread +within the receiver. On exhausting the air, the ticking of the watch +ceased to be heard. A pretty experiment consisted in placing a bottle +of a certain fuming liquid within the receiver; on exhausting the air, +the fumes fell over the neck of the bottle and poured over the stand +on which it was placed like a stream of water. Another experiment, the +thirty-second, is worthy of mention on account of the use to which it +was afterwards applied in the controversy respecting the cause of +suction. The receiver, having been exhausted, was removed from the +cylinder, the stop-cock being turned off, and a small brass valve, to +which a scale-pan was attached, was placed just under the aperture of +the tube below the stop-cock. On turning the latter, the stream of air +raised the valve, closing the aperture, and the atmospheric pressure +supported it until a considerable weight had been placed in the +scale-pan. Because the receiver could not be exhausted so thoroughly +as the pump-cylinder, Boyle attempted to measure the pressure of the +air by determining what weight could be supported by the piston. He +found first that a weight of twenty-eight pounds suspended directly +from the piston was sufficient to overcome friction when air was +admitted above the piston. When the access of air to the top of the +piston was prevented, more than one hundred pounds additional weight +was required to draw down the piston. The diameter of the cylinder was +about three inches. + +Boyle's style of reasoning is well illustrated by the following from +his paper on "The Spring of the Air:"-- + +"In the next place, these experiments may teach us what to judge of +the vulgar axiom received for so many ages as an undoubted truth in +the peripatetick schools, that Nature abhors and flieth a vacuum, and +that to such a degree that no human power (to go no higher) is able to +make one in the universe; wherein heaven and earth would change +places, and all its other bodies rather act contrary to their own +nature than suffer it.... It will not easily, then, be intelligibly +made out how hatred or aversation, which is a passion of the soul, can +either for a vacuum or any other object be supposed to be in water, or +such like inanimate body, which cannot be presumed to know when a +vacuum would ensue, if they did not bestir themselves to prevent it; +nor to be so generous as to act contrary to what is most conducive to +their own particular preservation for the public good of the universe. +As much, then, of intelligible and probable truth as is contained in +this metaphorical expression seems to amount but to this--that by the +wise Author of nature (who is justly said to have made all things in +number, weight, and measure) the universe, and the parts of it, are so +contrived that it is hard to make a vacuum in it, as if they +studiously conspired to prevent it. And how far this itself may be +granted deserves to be further considered. + +"For, in the next place, our experiments seem to teach that the +supposed aversation of Nature to a vacuum is but accidental, or in +consequence, partly of the weight and fluidity, or, at least, +fluxility of the bodies here below; and partly, and perhaps +principally, of the air, whose restless endeavour to expand itself +every way makes it either rush in itself or compel the interposed +bodies into all spaces where it finds no greater resistance than it +can surmount. And that in those motions which are made _ob fugam +vacui_ (as the common phrase is), bodies act without such generosity +and consideration as is wont to be ascribed to them, is apparent +enough in our thirty-second experiment, where the torrent of air, that +seemed to strive to get into the emptied receiver, did plainly prevent +its own design, by so impelling the valve as to make it shut the only +orifice the air was to get [in] at. And if afterwards either Nature or +the internal air had a design the external air should be attracted, +they seemed to prosecute it very unwisely by continuing to suck the +valve so strongly, when they found that by that suction the valve +itself could not be drawn in; whereas, by forbearing to suck, the +valve would, by its own weight, have fallen down and suffered the +excluded air to return freely, and to fill again the exhausted +vessel.... + +"And as for the care of the public good of the universe ascribed to +dead and stupid bodies, we shall only demand why, in our nineteenth +experiment, upon the exsuction of the ambient air, the water deserted +the upper half of the glass tube, and did not ascend to fill it up +till the external air was let in upon it. Whereas, by its easy and +sudden rejoining that upper part of the tube, it appeared both that +there was then much space devoid of air, and that the water might, +with small or no resistance, have ascended into it, if it could have +done so without the impulsion of the readmitted air; which, it seems, +was necessary to mind the water of its formerly neglected duty to the +universe." + +Boyle then goes on to explain the phenomena correctly by the pressure +of the air. Elsewhere he accounts for the diminished pressure on the +top of a mountain by the diminished weight of the superincumbent +column of air. + +The treatise on "The Spring of the Air" met with much opposition, and +Boyle considered it necessary to defend his doctrine against the +objections of Franciscus Linus and Hobbes. In this defence he +described the experiment in connection with which he is most generally +remembered. Linus had admitted that the air might possess a certain +small amount of elasticity, but maintained that the force with which +mercury rose in a barometer tube was due mainly to a totally different +action, as though a string were pulling upon it from above. This was +his funicular hypothesis. Boyle undertook to show that the pressure of +the air might be made to support a much higher column of mercury than +that of the barometer. To this end he took a glass tube several feet +in length, and bent so as to form two vertical legs connected below. +The shorter leg was little more than a foot long, and hermetically +closed at the top. The longer leg was nearly eight feet in length, and +open at the top. The tube was suspended by strings upon the staircase, +the bend at the bottom pressing lightly against the bottom of a box +placed to receive the mercury employed in case of accident. Each leg +of the tube was provided with a paper scale. Mercury was poured in at +the open end, the tube being tilted so as to allow some of the air to +escape from the shorter limb until the mercury stood at the same level +in both legs when the tube was vertical. The length of the closed tube +occupied by the air was then just twelve inches. The height of the +barometer was about 29-1/8 inches. Mercury was gently poured into the +open limb by one operator, while another watched its height in the +closed limb. The results of the experiments are given in the table on +the opposite page. + +In this table the third column gives the result of adding to the +second column the height of the barometer, which expresses in inches +of mercury the pressure of the air on the free surface of the mercury +in the longer limb. The fourth column gives the total pressure, in +inches of mercury, on the hypothesis that the pressure of the air +varies inversely as the volume. The agreement between the third and +fourth columns is very close, considering the roughness of the +experiment and that no trouble appears to have been taken to +_calibrate_ the shorter limb of the tube, and justified Boyle in +concluding that the hypothesis referred to expresses the relation +between the volume and pressure of a given mass of air. + + +-----------+---------------+----------------+--------------+ + |Length of |Height of |Total pressure |Total pressure| + |closed tube|mercury in open|on air in inches|according to | + |occupied |tube above that|of mercury. |Boyle's law. | + |by air. |in closed tube.| | | + +-----------+---------------+----------------+--------------+ + | 12 | 0 | 29-2/16 | 29-2/16 | + | 11-1/2 | 1-7/16 | 30-9/16 | 30-6/16 | + | 11 | 2-13/16 | 31-15/16 | 31-12/16 | + | 10-1/2 | 4-6/16 | 33-8/16 | 33-1/7 | + | 10 | 6-3/16 | 35-5/16 | 35 | + | 9-1/2 | 7-14/16 | 37 | 36-15/19 | + | 9 | 10-1/16 | 39-3/16 | 38-7/8 | + | 8-1/2 | 12-8/16 | 41-10/16 | 41-2/17 | + | 8 | 15-1/16 | 44-3/16 | 43-11/16 | + | 7-1/2 | 17-15/16 | 47-1/16 | 46-3/5 | + | 7 | 21-3/16 | 50-5/16 | 50 | + | 6-1/2 | 25-3/16 | 54-5/16 | 53-10/13 | + | 6 | 29-11/16 | 58-13/16 | 58-2/8 | + | 5-3/4 | 32-3/16 | 61-5/16 | 60-13/23 | + | 5-1/2 | 34-15/16 | 64-1/16 | 63-6/11 | + | 5-1/4 | 37-15/16 | 67-1/16 | 66-4/7 | + | 5 | 41-9/16 | 70-11/16 | 70 | + | 4-3/4 | 45 | 74-2/16 | 73-11/19 | + | 4-1/2 | 48-12/16 | 77-14/16 | 77-2/3 | + | 4-1/4 | 53-11/16 | 82-13/16 | 82-4/17 | + | 4 | 58-2/16 | 87-14/16 | 87-1/8 | + | 3-3/4 | 63-15/16 | 93-1/16 | 93-1/5 | + | 3-1/2 | 71-5/16 | 100-7/16 | 99-6/7 | + | 3-1/4 | 78-11/16 | 107-13/16 | 107-7/13 | + | 3 | 88-7/16 | 117-9/16 | 116-4/8 | + +-----------+---------------+----------------+--------------+ + +To extend the investigation so as to include expansion below +atmospheric pressure, a different apparatus was employed. It consisted +of a glass tube about six feet in length, closed at the lower end and +filled with mercury. Into this bath of mercury was plunged a length of +quill tube, and the upper end was sealed with wax. When the wax and +air in the tube had cooled, a hot pin was passed through the wax, +making a small orifice by which the amount of air in the tube was +adjusted so as to occupy exactly one inch of its length as measured by +a paper scale attached thereto, after again sealing the wax. The quill +tube was then raised, and the height of the surface of the mercury in +the tube above that in the bath noticed, together with the length of +the tube occupied by the air. The difference between the height of the +barometer and the height of the mercury in the tube above that in the +bath gave the pressure on the imprisoned air in inches of mercury. The +result showed that the volume varied very nearly in the inverse ratio +of the pressure. A certain amount of air, however, clung to the sides +of the quill tube when immersed in the mercury, and no care was taken +to remove it by boiling the mercury or otherwise; in consequence of +this, as the mercury descended, this air escaped and joined the rest +of the air in the tube. This made the pressure rather greater than it +should have been towards the end of the experiment, and when the tube +was again pressed down into the bath it was found that, when the +surfaces of the mercury within and without the tube were at the same +level, the air occupied nearly 1-1/8 inch instead of one inch of the +tube. These experiments first established the truth of the great law +known as "Boyle's law," which states that _the volume of a given mass +of a perfect gas varies inversely as the pressure to which it is +exposed_. + +Another experiment, to show that the pressure of the air was the cause +of suction, Boyle succeeded in carrying out at a later date. Two discs +of marble were carefully polished, so that when a little spirit of +turpentine was placed between them the lower disc, with a pound weight +suspended from it, was supported by the upper one. The apparatus was +introduced into the air-pump, and a considerable amount of shaking +proved insufficient to separate the discs. After sixteen strokes of +the pump, on opening the communication between the receiver and +cylinder, when no mechanical vibration occurred, the discs separated. + +Upon the Restoration in 1660, the Earl of Clarendon, who was Lord +Chancellor of England, endeavoured to persuade Boyle to enter holy +orders, urging the interest of the Church as the chief motive for the +proceeding. This made some impression upon Boyle, but he declined for +two reasons--first, because he thought that he would have a greater +influence for good if he had no share in the patrimony of the Church; +and next, because he had never felt "an inward motion to it by the +Holy Ghost." + +In 1649 an association was incorporated by Parliament, to be called +"the President and Society for the Propagation of the Gospel in New +England," whose object should be "to receive and dispose of moneys in +such manner as shall best and principally conduce to the preaching and +propagating the gospel among the natives, and for the maintenance of +schools and nurseries of learning for the education of the children of +the natives; for which purpose a general collection was appointed to +be made in and through all the counties, cities, towns, and parishes +of England and Wales, for a charitable contribution, to be as the +foundation of so pious and great an undertaking." The society was +revived by special charter in 1661, and Boyle was appointed president, +an office he continued to hold until shortly before his death. The +society afterwards enlarged its sphere of operations, and became the +Society for the Propagation of the Gospel in Foreign Parts. + +In the same year (1661) Boyle published "Some Considerations on the +Usefulness of Experimental Natural Philosophy," etc., and in 1663 an +extremely interesting paper on "Experiments and Considerations +touching Colours." In the course of this paper he describes some very +beautiful experiments with a tincture of _Lignum nephriticum_, wherein +the dichroism of the extract is made apparent. Boyle found that by +transmitted light it appeared of a bright golden colour, but when +viewed from the side from which it was illuminated the light emitted +was sky blue, and in some cases bright green. By arranging experiments +so that some parts of the liquid were seen by the transmitted light +and some by the scattered light, very beautiful effects were produced. +Boyle endeavoured to learn something of the nature of colours by +projecting spectra on differently coloured papers, and observing the +appearance of the papers when illuminated by the several spectral +rays. He also passed sunlight, concentrated by a lens, through plates +of differently coloured glass superposed, allowing the light to fall +on a white paper screen, and observing the tint of the light which +passed through each combination. But the most interesting of these +experiments was the actual mixture of light of different colours by +forming two spectra, one by means of a fixed prism, the other by a +prism held in the hand, and superposing the latter on the former so +that different colours were made to coincide. This experiment was +repeated in a modified form, nearly two hundred years later, by +Helmholtz, who found that the mixture of blue and yellow lights +produced pink. Unfortunately, Boyle's spectra were far from pure, for, +the source of light being of considerable dimensions, the different +colours overlapped one another, as in Newton's experiments, and in +consequence some of his conclusions were inaccurate. Thus blue paper +in the yellow part of the spectrum appeared to Boyle green instead of +black, but this was due to the admixture of green light with the +yellow. He concluded that bodies appear black because they damp the +light so as to reflect very little to the eye, but that the surfaces +of white bodies consist of innumerable little facets which reflect the +light in all directions. In the same year he published some +"Observations on a Diamond, which shines in the Dark;" and an +extensive treatise on "Some Considerations touching the Style of the +Holy Scriptures." Next year appeared several papers from his pen, the +most important being "Occasional Reflections upon Several Subjects," +the wide scope of which may be gathered from the title. His "New +Experiments and Observations touching Cold" were printed in 1665. In +this paper he discussed the cause of the force exerted by water in +freezing, methods of measuring degrees of cold, the action of +freezing-mixtures, and many other questions. He contended that cold +was probably only privative, and not a positive existence. + +Lord Bacon had asserted that the "essential self" of heat was probably +motion and nothing more, and had adduced several experiments and +observations in support of this opinion. In his paper on the +mechanical origin of heat and cold, Boyle maintained that heat was +motion, but motion of the very small particles of bodies, very +intense, and taking place in all directions; and that heat could be +produced by any means whatever by which the particles of bodies could +be agitated. On one occasion he caused two pieces of brass, one convex +and the other concave, to be pressed against each other by a spring, +and then rubbed together in a vacuum by a rotary motion communicated +by a shaft which passed air-tight through the hole in the cover of the +receiver, a little emery being inserted between them. In the second +experiment the brasses became so hot that he "could not endure to hold +[his] hand on either of them." This experiment was intended, like the +rubbing of the blocks of ice in vacuo by Davy, to meet the objection +that the heat developed by friction was due to the action of the air. +The following extract from a paper intended to show that the sense of +touch cannot be relied upon for the estimation of temperature, shows +that Boyle possessed a very clear insight into the question:--"The +account upon which we judge a body to be cold seems to be that we feel +its particles less vehemently agitated than those of our fingers or +other parts of the organ of touching; and, consequently, if the temper +of that organ be changed, the object will appear more or less cold to +us, though itself continue of one and the same temperature." To +determine the expansion of water in freezing, he filled the bulb and +part of the stem of a "bulb tube," or, as it was then generally +called, "a philosophical egg," with water, and applying a +freezing-mixture, at first to the bottom of the bulb, he succeeded in +freezing the water without injury to the glass, and found that 82 +volumes of water expanded to 91-1/8 volumes of ice--an expansion of +about 11-1/8 per cent. Probably air-bubbles caused the ice to appear +to have a greater volume than it really possessed, the true expansion +being about nine per cent. of the volume of the water at 4°C. The +expansion of water in freezing he employed in order to compress air to +a greater extent than he had been able otherwise to compress it. +Having nearly filled a tube with water, but left a little air above, +and then having sealed the top of the tube, he froze the water from +the bottom upwards, so that in expanding it compressed the air to +one-tenth of its former volume. + +Magnetism and electricity came in for some share of Boyle's attention. +He carried out a number of experiments on magnetic induction, and +found that lodestones, as well as pieces of iron, when heated and +allowed to cool, became magnetized by the induction of the earth. His +later experiments with exhausted receivers were not made with his +first pump, but with a two-barrelled pump, in which the pistons were +connected by a cord passing over a large fixed pulley, so that, when +the receiver was nearly exhausted, the pressure of the air on the +descending piston during the greater part of the stroke nearly +balanced that on the ascending piston. In this respect the pump +differed only from Hawksbee's in having the pulley and cord instead of +the pinion and two racks. It also resembled Hawksbee's pump in having +self-closing valves in the pistons and at the bottom of the cylinders, +which, in this pump, had their open ends at the top. The pistons were +alternately raised and lowered by the feet of the operator, which were +placed in stirrups, of which one was fixed on each piston. The lower +portions of the barrels were filled with water, through which the air +bubbled, and this, occupying the clearance, enabled a much higher +degree of exhaustion to be produced than could be obtained without its +employment. + +In 1665 Boyle was nominated Provost of Eton, but declined to accept +the appointment. His "Hydrostatical Paradoxes," published about this +time, contain all the ordinary theorems respecting the pressure of +fluids under the action of gravity demonstrated experimentally. + +In 1677 Boyle printed, at his own expense, five hundred copies of the +four Gospels and the Acts of the Apostles in the Malayan tongue. This +was but one of his many contributions towards similar objects. + +On November 30, 1680, the Royal Society chose Boyle for President. He, +however, declined to accept the appointment, because he had +conscientious objections to taking the oath required of the President +by the charter of the Society. + +It appears that very many of Boyle's manuscripts, which were written +in bound books, were taken away, and others mutilated by "corrosive +liquors." In May, 1688, he made this known to his friends, but, though +these losses put him on his guard, he complained afterwards that all +his care and circumspection had not prevented the loss of "six +centuries of matters of fact in one parcel," besides many other +smaller papers. His works, however, which have been published are so +numerous that it would take several pages for the bare enumeration of +their titles, many of them being devoted to medical subjects. The +edition published in London in 1743 comprises nearly three thousand +pages of folio. Boyle always suffered from weak eyes, and in +consequence he declined to revise his proofs. In the advertisement to +the original edition of his works the publisher mentioned this, and at +the same time pleaded his own business engagements as an excuse for +not revising the proofs himself! It was partly on account of the +injury to his manuscripts, and partly through failing health, that in +1689 he set apart two days in the week, during which he declined to +receive visitors, that he might devote himself to his work, and +especially to the reparation of the injured writings. About this time +he succeeded in procuring the repeal of an Act passed in the fifth +year of Henry IV. to the effect "that none from thenceforth should use +to multiply gold or silver, or use the craft of multiplication; and if +any the same do, they should incur the pain of felony." By this repeal +it was made legal to extract gold and silver from ores, or from their +mixtures with other metals, in this country provided that the gold and +silver so procured should be put to no other use than "the increase of +moneys." It is curious that Boyle seems always to have believed in the +possibility of transmuting other metals into gold. + +His sister, Lady Ranelagh, died on December 23, 1691, and Boyle +survived her but a few days, for he died on December 30, and his body +was interred near his sister's grave in the chancel of St. +Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works, +writes, "The men of wit and learning have, in all ages, busied +themselves in explaining nature by words; but it is Mr. Boyle alone +who has wholly laid himself out in showing philosophy in action. The +single point he perpetually keeps in view is to render his reader, not +a talkative or a speculative, but an actual and practical philosopher. +Himself sets the example; he made all the experiments he possibly +could upon natural bodies, and communicated them with all desirable +candour and fidelity." The second part of his treatise on "The +Christian Virtuoso," Boyle concluded with a number of aphorisms, of +which the following well represent his views respecting science:-- + +"I think it becomes Christian philosophers rather to try whether they +can investigate the final causes of things than, without trial, to +take it for granted that they are undiscoverable." + +"The book of Nature is a fine and large piece of tapestry rolled up, +which we are not able to see all at once, but must be content to wait +for the discovery of its beauty and symmetry, little by little, as it +gradually comes to be more unfolded or displayed." + + + + +BENJAMIN FRANKLIN. + + +Among those whose contributions to physics have immortalized their +names in the annals of science, there is none that holds a more +prominent position in the history of the world than Benjamin Franklin. +At one time a journeyman printer, living in obscure lodgings in +London, he became, during the American War of Independence, one of the +most conspicuous figures in Europe, and among Americans his reputation +was probably second to none, General Washington not excepted. + +Professor Laboulaye says of Franklin: "No one ever started from a +lower point than the poor apprentice of Boston. No one ever raised +himself higher by his own unaided forces than the inventor of the +lightning-rod. No one has rendered greater service to his country than +the diplomatist who signed the treaty of 1783, and assured the +independence of the United States. Better than the biographies of +Plutarch, this life, so long and so well filled, is a source of +perpetual instruction to all men. Every one can there find counsel and +example." + +A great part of the history of his life was written by Franklin +himself, at first for the edification of the members of his own +family, and afterwards at the pressing request of some of his friends +in London and Paris. His autobiography does not, however, comprise +much more than the first fifty years of his life. The first part was +written while he was the guest of the Bishop of St. Asaph, at Twyford; +the second portion at Passy, in the house of M. de Chaumont; and the +last part in Philadelphia, when he was retiring from public life at +the age of eighty-two. The former part of this autobiography was +translated into French, and published in Paris, in 1793, though it is +not known how the manuscript came into the publisher's hands. The +French version was translated into English, and published in England +and America, together with such other of Franklin's works as could be +collected, before the latter part was given to the world by Franklin's +grandson, to whom he had bequeathed his papers, and who first +published them in America in 1817. + +For a period of three hundred years at least Franklin's family lived +on a small freehold of about thirty acres, in the village of Ecton, in +Northamptonshire, the eldest son, who inherited the property, being +always brought up to the trade of a smith. Franklin himself "was the +youngest son of the youngest son for five generations back." His +grandfather lived at Ecton till he was too old to follow his business, +when he went to live with his second son, John, who was a dyer at +Banbury. To this business Franklin's father, Josiah, was apprenticed. +The eldest son, Thomas, was brought up a smith, but afterwards became +a solicitor; the other son, Benjamin, was a silk-dyer, and followed +Josiah to America. He was fond of writing poetry and sermons. The +latter he wrote in a shorthand of his own inventing, which he taught +to his nephew and namesake, in order that he might utilize the sermons +if, as was proposed, he became a Presbyterian minister. Franklin's +father, Josiah, took his wife and three children to New England, in +1682, where he practised the trade of a tallow-chandler and +soap-boiler. Franklin was born in Boston on January 6 (O.S.), 1706, +and was the youngest of seventeen children, of whom thirteen grew up +and married. + +Benjamin being the youngest of ten sons, his father intended him for +the service of the Church, and sent him to the grammar school when +eight years of age, where he continued only a year, although he made +very rapid progress in the school; for his father concluded that he +could not afford the expense of a college education, and at the end of +the year removed him to a private commercial school. At the age of ten +young Benjamin was taken home to assist in cutting the wicks of +candles, and otherwise to make himself useful in his father's +business. His enterprising character as a boy is shown by the +following story, which is in his own words:-- + + There was a salt marsh that bounded part of the mill-pond, on + the edge of which, at high-water, we used to stand to fish for + minnows. By much trampling we had made it a mere quagmire. My + proposal was to build a wharf there fit for us to stand upon, + and I showed my comrades a large heap of stones, which were + intended for a new house near the marsh, and which would very + well suit our purpose. Accordingly, in the evening, when the + workmen were gone, I assembled a number of my play-fellows, and + working with them diligently, like so many emmets, sometimes two + or three to a stone, we brought them all away and built our + little wharf. The next morning the workmen were surprised at + missing the stones, which were found in our wharf. Inquiry was + made after the removers; we were discovered and complained of; + several of us were corrected by our fathers; and, though I + pleaded the usefulness of the work, mine convinced me that + nothing was useful which was not honest. + +Until twelve years of age Benjamin continued in his father's business, +but as he manifested a great dislike for it, and his parents feared +that he might one day run away to sea, they set about finding some +trade which would be more congenial to his tastes. With this view his +father took him to see various artificers at their work, that he +might observe the tastes of the boy. This experience was very +valuable to him, as it taught him to do many little jobs for himself +when workmen could not readily be procured. During this time Benjamin +spent most of his pocket-money in purchasing books, some of which he +sold when he had read them, in order to buy others. He read through +most of the books in his father's very limited library. These mainly +consisted of works on theological controversy, which Franklin +afterwards considered to have been not very profitable to him. + +"There was another bookish lad in the town, John Collins by name, with +whom I was intimately acquainted. We sometimes disputed, and very fond +we were of argument, and very desirous of confuting one another, which +disputatious turn, by the way, is apt to become a very bad habit, +making people often very disagreeable in company by the contradiction +that is necessary to bring it into practice; and thence, besides +souring and spoiling the conversation, is productive of disgusts and +perhaps enmities when you may have occasion for friendship. I had +caught it by reading my father's books of dispute about religion. +Persons of good sense, I have since observed, seldom fall into it, +except lawyers, university men, and men of all sorts that have been +bred at Edinburgh." + +At length Franklin's fondness for books caused his father to decide to +make him a printer. His brother James had already entered that +business, and had set up in Boston with a new press and types which +he had brought from England. He signed his indentures when only twelve +years old, thereby apprenticing himself to his brother until he should +attain the age of twenty-one. The acquaintance which he formed with +booksellers through the printing business enabled him to borrow a +better class of books than he had been accustomed to, and he +frequently sat up the greater part of the night to read a book which +he had to return in the morning. + +While working with his brother, the young apprentice wrote two +ballads, which he printed and sold in the streets of Boston. His +father, however, ridiculed the performance; so he "escaped being a +poet." He adopted at this time a somewhat original method to improve +his prose writing. Meeting with an odd volume of the _Spectator_, he +purchased it and read it "over and over," and wished to imitate the +style. "Making short notes of the sentiment in each sentence," he laid +them by, and afterwards tried to write out the papers without looking +at the original. Then on comparison he discovered his faults and +corrected them. Finding his vocabulary deficient, he turned some of +the tales into verse, then retranslated them into prose, believing +that the attempt to make verses would necessitate a search for several +words of the same meaning. "I also sometimes jumbled my collection of +hints into confusion, and after some weeks endeavoured to reduce them +into the best order, before I began to form the full sentence and +complete the paper. This was to teach me method in the arrangement of +my thoughts." + +Meeting with a book on vegetarianism, Franklin determined to give the +system a trial. This led to some inconvenience in his brother's +house-keeping, so Franklin proposed to board himself if his brother +would give him half the sum he paid for his board, and out of this he +was able to save a considerable amount for the purpose of buying +books. Moreover, the time required for meals was so short that the +dinner hour afforded considerable leisure for reading. It was on his +journey from Boston to Philadelphia that he first violated vegetarian +principles; for, a large cod having been caught by the sailors, some +small fishes were found in its stomach, whereupon Franklin argued that +if fishes ate one another, there could be no reason against eating +them, so he dined on cod during the rest of the journey. + +After reading Xenophon's "Memorabilia," Franklin took up strongly with +the Socratic method of discussion, and became so "artful and expert in +drawing people, even of superior knowledge, into concessions, the +consequence of which they did not foresee," that some time afterwards +one of his employers, before answering the most simple question, would +frequently ask what he intended to infer from the answer. This +practice he gradually gave up, retaining only the habit of expressing +his opinions with "modest diffidence." + +In 1720 or 1721 James Franklin began to print a newspaper, the _New +England Courant_. To this paper, which he helped to compose and print, +Benjamin became an anonymous contributor. The members of the staff +spoke highly of his contributions, but when the authorship became +known, James appears to have conceived a jealousy of his younger +brother, which ultimately led to their separation. An article in the +paper having offended the Assembly, James was imprisoned for a month +and forbidden to print the paper. He then freed Benjamin from his +indentures, in order that the paper might be published in his name. At +length, some disagreement arising, Benjamin took advantage of the +cancelling of his indentures to quit his brother's service. As he +could get no employment in Boston, he obtained a passage to New York, +whence he was recommended to go to Philadelphia, which he reached +after a very troublesome journey. His whole stock of cash then +consisted of a Dutch dollar and about a shilling's worth of coppers. +The coppers he gave to the boatmen with whom he came across from +Burlington. His first appearance in Philadelphia, about eight o'clock +on a Sunday morning, was certainly striking. A youth between seventeen +and eighteen years of age, dressed in his working clothes, which were +dirty through his journey, with his pockets stuffed out with stockings +and shirts, his aspect was not calculated to command respect. + +"Then I walked up the street, gazing about till near the market-house +I met a boy with bread. I had made many a meal on bread, and, +inquiring where he got it, I went immediately to the baker's he +directed me to, in Second Street, and ask'd for bisket, intending such +as we had in Boston; but they, it seems, were not made in +Philadelphia. Then I asked for a threepenny loaf, and was told they +had none such. So, not considering or knowing the difference of money, +and the greater cheapness, nor the name of his bread, I bad him give +me three-penny-worth of any sort. He gave me, accordingly, three great +puffy rolls. I was surpriz'd at the quantity, but took it, and having +no room in my pockets, walk'd off with a roll under each arm, and +eating the other. Thus I went up Market Street as far as Fourth +Street, passing by the door of Mr. Read, my future wife's father; when +she, standing at the door, saw me, and thought I made, as I certainly +did, a most awkward, ridiculous appearance. Then I turned and went +down Chestnut Street and part of Walnut Street, eating my roll all the +way, and, coming round, found myself again at Market Street Wharf, +near the boat I came in, to which I went for a draught of the river +water; and, being filled out with one of my rolls, gave the other two +to a woman and her child that came down the river in the boat with us, +and were waiting to go further." + +In Philadelphia Franklin obtained an introduction, through a gentleman +he had met at New York, to a printer, named Keimer, who had just set +up business with an old press which he appeared not to know how to +use, and one pair of cases of English type. Here Franklin obtained +employment when the business on hand would permit, and he put the +press in order and worked it. Keimer obtained lodgings for him at the +house of Mr. Read, and, by industry and economical living, Franklin +found himself in easy circumstances. Sir William Keith was then +Governor of Pennsylvania, and hearing of Franklin, he called upon him +at Keimer's printing-office, invited him to take wine at a +neighbouring tavern, and promised to obtain for him the Government +printing if he would set up for himself. It was then arranged that +Franklin should return to Boston by the first ship, in order to see +what help his father would give towards setting him up in business. In +the mean while he was frequently invited to dine at the governor's +house. Notwithstanding Sir William Keith's recommendation, Josiah +Franklin thought his son too young to take the responsibility of a +business, and would only promise to assist him if, when he was +twenty-one, he had himself saved sufficient to purchase most of the +requisite plant. On his return to Philadelphia, he delivered his +father's letter to Sir William Keith, whereon the governor, stating +that he was determined to have a good printer there, promised to find +the means of equipping the printing-office himself, and suggested the +desirability of Franklin's making a journey to England in order to +purchase the plant. He promised letters of introduction to various +persons in England, as well as a letter of credit to furnish the +money for the purchase of the printing-plant. These letters Franklin +was to call for, but there was always some excuse for their not being +ready. At last they were to be sent on board the ship, and Franklin, +having gone on board, awaited the letters. When the governor's +despatches came, they were all put into a bag together, and the +captain promised to let Franklin have his letters before landing. On +opening the bag off Plymouth, there were no letters of the kind +promised, and Franklin was left without introductions and almost +without money, to make his own way in the world. In London he learned +that Governor Keith was well known as a man in whom no dependence +could be placed, and as to his giving a letter of credit, "he had no +credit to give." + +A friend of Franklin's, named Ralph, accompanied him from America, and +the two took lodgings together in Little Britain at three shillings +and sixpence per week. Franklin immediately obtained employment at +Palmer's printing-office, in Bartholomew Close; but Ralph, who knew no +trade, but aimed at literature, was unable to get any work. He could +not obtain employment, even among the law stationers as a copying +clerk, so for some time the wages which Franklin earned had to support +the two. At Palmer's Franklin was employed in composing Wollaston's +"Religion of Nature." On this he wrote a short critique, which he +printed. it was entitled "A Dissertation on Liberty and Necessity, +Pleasure and Pain." The publication of this he afterwards regretted, +but it obtained for him introductions to some literary persons in +London. Subsequently he left Palmer's and obtained work at Watts's +printing-office, where he remained during the rest of his stay in +London. The beer-drinking capabilities of some of his fellow-workmen +excited his astonishment. He says:-- + + We had an alehouse boy who attended always in the house to + supply the workmen. My companion at the press drank every day a + pint before breakfast, a pint at breakfast with his bread and + cheese, a pint between breakfast and dinner, a pint at dinner, a + pint in the afternoon about six o'clock, and another when he had + done his day's work. I thought it a detestable custom, but it + was necessary, he suppos'd, to drink _strong_ beer, that he + might be _strong_ to labour. I endeavoured to convince him that + the bodily strength afforded by beer could only be in proportion + to the grain or flour of the barley dissolved in the water of + which it was made; that there was more flour in a pennyworth of + bread; and therefore, if he would eat that with a pint of water, + it would give him more strength than a quart of beer. He drank + on, however, and had four or five shillings to pay out of his + wages every Saturday night for that muddling liquor; an expense + I was free from. And thus these poor devils keep themselves + always under. + +Afterwards Franklin succeeded in persuading several of the compositors +to give up "their muddling breakfast of beer and bread and cheese," +for a porringer of hot-water gruel, with pepper, breadcrumbs, and +butter, which they obtained from a neighbouring house at a cost of +three halfpence. + +Among Franklin's fellow-passengers from Philadelphia to England was an +American merchant, a Mr. Denham, who had formerly been in business in +Bristol, but failed and compounded with his creditors. He then went to +America, where he soon acquired a fortune, and returned in Franklin's +ship. He invited all his old creditors to dine with him. At the dinner +each guest found under his plate a cheque for the balance which had +been due to him, with interest to date. This gentleman always remained +a firm friend to Franklin, who, during his stay in London, sought his +advice when any important questions arose. When Mr. Denham returned to +Philadelphia with a quantity of merchandise, he offered Franklin an +appointment as clerk, which was afterwards to develop into a +commission agency. The offer was accepted, and, after a voyage of +nearly three months, Franklin reached Philadelphia on October 11, +1726. Here he found Governor Keith had been superseded by Major +Gordon, and, what was of more importance to him, that Miss Read, to +whom he had become engaged before leaving for England, and to whom he +had written only once during his absence, had married. Shortly after +starting in business, Mr. Denham died, and thus left Franklin to +commence life again for himself. Keimer had by this time obtained a +fairly extensive establishment, and employed a number of hands, but +none of them were of much value; and he made overtures to Franklin to +take the management of his printing-office, apparently with the +intention of getting his men taught their business, so that he might +afterwards be able to dispense with the manager. Franklin set the +printing-house in order, started type-founding, made the ink, and, +when necessary, executed engravings. As the other hands improved under +his superintendence, Keimer began to treat his manager less civilly, +and apparently desired to curtail his stipend. At length, through an +outbreak of temper on the part of Keimer, Franklin left, but was +afterwards induced to return in order to prepare copper-plates and a +press for printing paper money for New Jersey. + +While working for Keimer, Franklin formed a club, which was destined +to exert considerable influence on American politics. The club met on +Friday evenings, and was called the Junto. It was essentially a +debating society, the subject for each evening's discussion being +proposed at the preceding meeting. One of the rules was that the +existence of the club should remain a secret, and that its members +should be limited to twelve. Afterwards other similar clubs were +formed by its members; but the existence of the Junto was kept a +secret from them. The club lasted for about forty years, and became +the nucleus of the American Philosophical Society, of which Franklin +was the first president. This, and the fact that many of the great +questions that arose previously to the Declaration of Independence +were discussed in the Junto in the first instance, give to the club a +special importance. The following are specimens of subjects discussed +by the club:-- + +"Is sound an entity or body?" + +"How may the phenomena of vapours be explained?" + +"Is self-interest the rudder that steers mankind, the universal +monarch to whom all are tributaries?" + +"Which is the best form of government? and what was that form which +first prevailed among mankind?" + +"Can any one particular form of government suit all mankind?" + +"What is the reason that the tides rise higher in the Bay of Fundy +than the Bay of Delaware?" + +"Is the emission of paper money safe?" + +"What is the reason that men of the greatest knowledge are not the +most happy?" + +"How may the possessions of the Lakes be improved to our advantage?" + +"Why are tumultuous, uneasy sensations united with our desires?" + +"Whether it ought to be the aim of philosophy to eradicate the +passions." + +"How may smoky chimneys be best cured?" + +"Why does the flame of a candle tend upwards in a spire?" + +"Which is least criminal--a bad action joined with a good intention, +or a good action with a bad intention?" + +"Is it consistent with the principles of liberty in a free government +to punish a man as a libeller when he speaks the truth?" + +On leaving Keimer's, Franklin went into partnership with one of his +fellow-workmen, Hugh Meredith, whose father found the necessary +capital, and a printing-office was started which soon excelled its two +rivals in Philadelphia. Franklin's industry attracted the attention of +the townsfolk, and inspired the merchants with confidence in the +prospects of the new concern. Keimer started a newspaper, which he had +not the ability to carry on; Franklin purchased it from him for a +trifle, remodelled it, and continued it in a very spirited manner +under the title of the _Pennsylvania Gazette_. His political articles +soon attracted the attention of the principal men of the state; the +number of subscribers increased rapidly, and the paper became a source +of considerable profit. Soon after, the printing for the House of +Representatives came into the hands of the firm. Meredith never took +to the business, and was seldom sober, and at length was bought out by +his partner, on July 14, 1730. The discussion in the Junto on paper +currency induced Franklin to publish a paper entitled "The Nature and +Necessity of a Paper Currency." This was a prominent subject before +the House, but the introduction of paper money was opposed by the +capitalists. They were unable, however, to answer Franklin's +arguments; the point was carried in the House, and Franklin was +employed to print the money. The amount of paper money in Pennsylvania +in 1739 amounted to £80,000; during the war it rose to more than +£350,000. + +"In order to secure my credit and character as a tradesman, I took +care not only to be in _reality_ industrious and frugal, but to avoid +all appearances to the contrary. I drest plainly; I was seen at no +places of idle diversion. I never went out a-fishing or shooting; a +book, indeed, sometimes debauch'd me from my work, but that was +seldom, snug, and gave no scandal; and, to show that I was not above +my business, I sometimes brought home the paper I purchas'd at the +stores thro' the streets on a wheelbarrow. Thus being esteem'd an +industrious, thriving young man, and paying duly for what I bought, +the merchants who imported stationery solicited my custom; others +proposed supplying me with books, and I went on swimmingly. In the +mean time, Keimer's credit and business declining daily, he was at +last forc'd to sell his printing-house to satisfy his creditors." + +On September 1, 1730, Franklin married his former _fiancée_, whose +previous husband had left her and was reported to have died in the +West Indies. The marriage was a very happy one, and continued over +forty years, Mrs. Franklin living until the end of 1774. Industry and +frugality reigned in the household of the young printer. Mrs. Franklin +not only managed the house, but assisted in the business, folding and +stitching pamphlets, and in other ways making herself useful. The +first part of Franklin's autobiography concludes with an account of +the foundation of the first subscription library. By the co-operation +of the members of the Junto, fifty subscribers were obtained, who each +paid in the first instance forty shillings, and afterwards ten +shillings per annum. "We afterwards obtained a charter, the company +being increased to one hundred. This was the mother of all the North +American subscription libraries, now so numerous. It is become a great +thing itself, and continually increasing. These libraries have +improved the general conversation of the Americans, made the common +tradesmen and farmers as intelligent as most gentlemen from other +countries, and perhaps have contributed in some degree to the stand so +generally made throughout the colonies in defence of their +privileges." + +Ten years ago this library contained between seventy and eighty +thousand volumes. + +Franklin's success in business was attributed by him largely to his +early training. "My circumstances, however, grew daily easier. My +original habits of frugality continuing, and my father having, among +his instructions to me when a boy, frequently repeated a proverb of +Solomon, 'Seest thou a man diligent in his business? he shall stand +before kings; he shall not stand before mean men,' I from thence +considered industry as a means of obtaining wealth and distinction, +which encourag'd me, tho' I did not think that I should ever +literally _stand before kings_, which, however, has since happened; +for I have stood before _five_, and even had the honour of sitting +down with one, the King of Denmark, to dinner." + +After his marriage, Franklin conceived the idea of obtaining moral +perfection. He was not altogether satisfied with the result, but +thought his method worthy of imitation. Assuming that he possessed +complete knowledge of what was right or wrong, he saw no reason why he +should not always act in accordance therewith. His principle was to +devote his attention to one virtue only at first for a week, at the +end of which time he expected the practice of that virtue to have +become a habit. He then added another virtue to his list, and devoted +his attention to the same for the next week, and so on, until he had +exhausted his list of virtues. He then commenced again at the +beginning. As his moral code comprised thirteen virtues, it was +possible to go through the complete curriculum four times in a year. +Afterwards he occupied a year in going once through the list, and +subsequently employed several years in one course. A little book was +ruled, with a column for each day and a line for each virtue, and in +this a mark was made for every failure which could be remembered on +examination at the end of the day. It is easy to believe his +statement: "I am surprised to find myself so much fuller of faults +than I had imagined; but I had the satisfaction of seeing them +diminish." + +"This my little book had for its motto these lines from Addison's +'Cato':-- + + "'Here will I hold. If there's a Power above us + (And that there is, all Nature cries aloud + Thro' all her work), He must delight in virtue; + And that which He delights in must be happy.' + +"Another from Cicero:-- + +"'O vitæ Philosophia dux! O virtutum indagatrix expultrixque vitiorum! +Unus dies ex præceptis tuis actus, peccanti immortalitati est +anteponendus.' + +"Another from the Proverbs of Solomon, speaking of wisdom and virtue:-- + +"'Length of days is in her right hand; and in her left hand riches and +honour. Her ways are ways of pleasantness, and all her paths are +peace.' + +"And conceiving God to be the fountain of wisdom, I thought it right +and necessary to solicit His assistance for obtaining it; to this end +I formed the following little prayer, which was prefixed to my tables +of examination, for daily use:-- + +"'O powerful Goodness! bountiful Father! merciful Guide! increase in +me that wisdom which discovers my truest interest. Strengthen my +resolutions to perform what that wisdom dictates. Accept my kind +offices to Thy other children as the only return in my power for Thy +continual favours to me.' + +"I used also sometimes a little prayer which I took from Thomson's +Poems, viz.:-- + + "'Father of light and life, Thou Good Supreme! + Oh teach me what is good; teach me Thyself! + Save me from folly, vanity, and vice, + From every low pursuit; and fill my soul + With knowledge, conscious peace, and virtue pure; + Sacred, substantial, never-failing bliss!'" + +The senses in which Franklin's thirteen virtues were to be understood +were explained by short precepts which followed them in his list. The +list was as follows:-- + +"1. TEMPERANCE. + +"Eat not to dulness; drink not to elevation. + +"2. SILENCE. + +"Speak not but what may benefit others or yourself; avoid trifling +conversation. + +"3. ORDER. + +"Let all your things have their places; let each part of your business +have its time. + +"4. RESOLUTION. + +"Resolve to perform what you ought; perform without fail what you +resolve. + +"5. FRUGALITY. + +"Make no expense but to do good to others or yourself; _i.e._ waste +nothing. + +"6. INDUSTRY. + +"Lose no time; be always employed in something useful; cut off all +unnecessary actions. + +"7. SINCERITY. + +"Use no hurtful deceit; think innocently and justly; and, if you +speak, speak accordingly. + +"8. JUSTICE. + +"Wrong none by doing injuries, or omitting the benefits that are your +duty. + +"9. MODERATION. + +"Avoid extremes; forbear resenting injuries so much as you think they +deserve. + +"10. CLEANLINESS. + +"Tolerate no uncleanness in body, clothes, or habitation. + +"11. TRANQUILLITY. + +"Be not disturbed at trifles, or accidents common or unavoidable. + +"12. CHASTITY. + +"13. HUMILITY. + +"Imitate Jesus and Socrates." + +The last of these was added to the list at the suggestion of a Quaker +friend. Franklin claims to have acquired a good deal of the +_appearance_ of it, but concluded that in reality there was no passion +so hard to subdue as _pride_. "For even if I could conceive that I had +completely overcome it, I should probably be proud of my humility." +The virtue which gave him most trouble, however, was order, and this +he never acquired. + +In 1732 appeared the first copy of "Poor Richard's Almanack." This was +prepared, printed, and published by Franklin for about twenty-five +years in succession, and nearly ten thousand copies were sold +annually. Besides the usual astronomical information, it contained a +collection of entertaining anecdotes, verses, jests, etc., while the +"little spaces that occurred between the remarkable events in the +calendar" were filled with proverbial sayings, inculcating industry +and frugality as helps to virtue. These sayings were collected and +prefixed to the almanack of 1757, whence they were copied into the +American newspapers, and afterwards reprinted as a broad-sheet in +England and in France. + +In 1733 Franklin commenced studying modern languages, and acquired +sufficient knowledge of French, Italian, and Spanish to be able to +read books in those languages. In 1736 he was chosen Clerk to the +General Assembly, an office to which he was annually re-elected until +he became a member of the Assembly about 1750. There was one member +who, on the second occasion of his election, made a long speech +against him. Franklin determined to secure the friendship of this +member. Accordingly he wrote to him to request the loan of a very +scarce and curious book which was in his library. The book was lent +and returned in about a week, with a note of thanks. The member ever +after manifested a readiness to serve Franklin, and they became great +friends--"Another instance of the truth of an old maxim I had learned, +which says, '_He that has once done you a kindness will be more ready +to do you another than he whom you yourself have obliged_.' And it +shows how much more profitable it is prudently to remove, than to +resent, return, and continue inimical proceedings." + +In 1737 Franklin was appointed Deputy-Postmaster-General for +Pennsylvania. He was afterwards made Postmaster-General of the +Colonies. He read a paper in the Junto on the organization of the City +watch, and the propriety of rating the inhabitants on the value of +their premises in order to support the same. The subject was also +discussed in the other clubs which had sprung from the Junto, and thus +the way was prepared for the law which a few years afterwards carried +Franklin's proposals into effect. His next scheme was the formation of +a fire brigade, in which he met with his usual success, and other +clubs followed, until most of the men of property in the city were +members of one club or another. The original brigade, known as the +Union Fire Company, was formed December 7, 1736. It was in active +service in 1791. + +Franklin founded the American Philosophical Society in 1743. The +head-quarters of the society were fixed in Philadelphia, where it was +arranged that there should always be at least seven members, viz. a +physician, a botanist, a mathematician, a chemist, a mechanician, a +geographer, and a general natural philosopher, besides a president, +treasurer, and secretary. The other members might be resident in any +part of America. Correspondence was to be kept up with the Royal +Society of London and the Dublin Society, and abstracts of the +communications were to be sent quarterly to all the members. Franklin +became the first secretary. + +Spain, having been for some years at war with England, was joined at +length by France. This threatened danger to the American colonies, as +France then held Canada, and no organization for their defence +existed. Franklin published a pamphlet entitled "Plain Truth," setting +forth the unarmed condition of the colonies, and recommending the +formation of a volunteer force for defensive purposes. The pamphlet +excited much attention. A public meeting was held and addressed by +Franklin; at this meeting twelve hundred joined the association. At +length the number of members enrolled exceeded ten thousand. These all +provided themselves with arms, formed regiments and companies, elected +their own officers, and attended once a week for military drill. +Franklin was elected colonel of the Philadelphia Regiment, but +declined the appointment, and served as a private soldier. The +provision of war material was a difficulty with the Assembly, which +consisted largely of Quakers, who, though they appeared privately to +be willing that the country should be put in a state of defence, +hesitated to vote in opposition to their peace principles. Hence it +was that, when the Government of New England asked a grant of +gunpowder from Pennsylvania, the Assembly voted £3000 "for the +purchasing of bread, flour, wheat, or _other grain_." Pebble-powder +was not then in use. When it was proposed to devote £60, which was a +balance in the hands of the Union Fire Company, as a contribution +towards the erection of a battery below the town, Franklin suggested +that it should be proposed that a fire-engine be purchased with the +money, and that the committee should "buy a great gun, which is +certainly a _fire-engine_." + +The "Pennsylvania fireplace" was invented in 1742. A patent was +offered to Franklin by the Governor of Pennsylvania, but he declined +it on the principle "_that, as we enjoy great advantages from the +inventions of others, we should be glad of an opportunity to serve +others by any invention of ours; and this we should do freely and +generously_." An ironmonger in London made slight alterations, which +were not improvements, in the design, and took out a patent for the +fireplace, whereby he made a "small fortune." Franklin never contested +the patent, "having no desire of profiting by patents himself," and +"hating disputes." This fireplace was designed to burn wood, but, +unlike the German stoves, it was completely open in front, though +enclosed at the sides and top. An air-chamber was formed in the middle +of the stove, so arranged that, while the burning wood was in contact +with the front of the chamber, the flame passed above and behind it on +its way to the flue. Through this chamber a constant current of air +passed, entering the room heated, but not contaminated, by the +products of combustion. In this way the stove furnished a constant +supply of fresh warm air to the room, while it possessed all the +advantages of an open fireplace. Subsequently Franklin contrived a +special fireplace for the combustion of coal. In the scientific +thought which he devoted to the requirements of the domestic +economist, as in very many other particulars, Franklin strongly +reminds us of Count Rumford. + +The next important enterprise which Franklin undertook, partly through +the medium of the Junto, was to establish an academy which soon +developed into the University of Philadelphia. The members of the club +having taken up the subject, the next step was to enlist the sympathy +of a wider constituency, and this Franklin effected, in his usual way, +by the publication of a pamphlet. He then set on foot a subscription, +the payments to extend over five years, and thereby obtained about +£5000. A house was taken and schools opened in 1749. The classes soon +became too large for the house, and the trustees of the academy then +took over a large building, or "tabernacle," which had been erected +for George Whitefield when he was preaching in Philadelphia. The hall +was divided into stories, and at a very small expense adapted to the +requirements of the classes. Franklin, having taken a partner in his +printing business, took the oversight of the work. Afterwards the +funds were increased by English subscriptions, by a grant from the +Assembly, and by gifts of land from the proprietaries; and thus was +established the University of Philadelphia. + +Having practically retired from business, Franklin intended to devote +himself to philosophical studies, having commenced his electrical +researches some time before in conjunction with the other members of +the Library Company. Public business, however, crowded upon him. He +was elected a member of the Assembly, a councillor and afterwards an +alderman of the city, and by the governor was made a justice of the +peace. As a member of the Assembly, he was largely concerned in +providing the means for the erection of a hospital, and in arranging +for the paving and cleansing of the streets of the city. In 1753 he +was appointed, in conjunction with Mr. Hunter, Postmaster-General of +America. The post-office of the colonies had previously been conducted +at a loss. In a few years, under Franklin's management, it not only +paid the stipends of himself and Mr. Hunter, but yielded a +considerable revenue to the Crown. But it was not only in the conduct +of public business that Franklin's merits were recognized. By this +time he had secured his reputation as an electrician, and both Yale +College and Cambridge University (New England) conferred on him the +honorary degree of Master of Arts. In the same year that he was made +Postmaster-General of America he was awarded the Copley Medal and +elected a Fellow of the Royal Society of London, the usual fees being +remitted in his case. + +Before his election as member, Franklin had for several years held the +appointment of Clerk to the Assembly, and he used to relieve the +dulness of the debates by amusing himself in the construction of magic +circles and squares, and "acquired such a knack at it" that he could +"fill the cells of any magic square of reasonable size with a series +of numbers as fast as" he "could write them." Many years afterwards +Mr. Logan showed Franklin a French folio volume filled with magic +squares, and afterwards a magic "square of 16," which Mr. Logan +thought must have been a work of great labour, though it possessed +only the common properties of making 2056 in every row, horizontal, +vertical, and diagonal. During the evening Franklin made the square +shown on the opposite page. "This I sent to our friend the next +morning, who, after some days, sent it back in a letter, with these +words: 'I return to thee thy astonishing and most stupendous piece of +the magical square, in which----;' but the compliment is too +extravagant, and therefore, for his sake as well as my own, I ought +not to repeat it. Nor is it necessary; for I make no question that you +will readily allow this square of 16 to be the most magically magical +of any magic square ever made by any magician." + +The square has the following properties:--Every straight row of +sixteen numbers, whether vertical, horizontal, or diagonal, makes +2056. + +Every bent row of sixteen numbers, as shown by the diagonal lines in +the figure, makes 2056. + +If a square hole be cut in a piece of paper, so as to show through it +just sixteen of the little squares, and the paper be laid on the magic +square, then, wherever the paper is placed, the sum of the sixteen +numbers visible through the hole will be 2056. + +[Illustration: + + 200 217 232 249 8 25 40 57 72 89 104 121 136 153 168 185 + 58 39 26 7 250 231 218 199 186 167 154 135 122 103 90 71 + 198 219 230 251 6 27 38 59 70 91 102 123 134 155 166 187 + 60 37 28 5 252 229 220 197 188 165 156 133 124 101 92 69 + 201 216 233 248 9 24 41 56 73 88 105 120 137 152 169 184 + 55 42 23 10 247 234 215 202 183 170 151 138 119 106 87 74 + 203 214 235 246 11 22 43 54 75 86 107 118 139 150 171 182 + 53 44 21 12 245 236 213 204 181 172 149 140 117 108 85 76 + 205 212 237 244 13 20 45 52 77 84 109 116 141 148 173 180 + 51 46 19 14 243 238 211 206 179 174 147 142 115 110 83 78 + 207 210 239 242 15 18 47 50 79 82 111 114 143 146 175 178 + 49 48 17 16 241 240 209 208 177 176 145 144 113 112 81 80 + 196 221 228 253 4 29 36 61 68 93 100 125 132 157 164 189 + 62 35 30 3 254 227 222 195 190 163 158 131 126 99 94 67 + 194 223 226 255 2 31 34 63 66 95 98 127 130 159 162 191 + 64 33 32 1 256 225 224 193 192 161 160 129 128 97 96 65 +] + +In 1754 war with France appeared to be again imminent, and a Congress +of Commissioners from the several colonies was arranged for. Of +course, Franklin was one of the representatives of Pennsylvania, and +was also one of the members who independently drew up a plan for the +union of all the colonies under one government, for defensive and +other general purposes, and his was the plan finally approved by +Congress for the union, though it was not accepted by the Assemblies +or by the English Government, being regarded by the former as having +too much of the _prerogative_ in it, by the latter as being too +_democratic_. Franklin wrote respecting this scheme: "The different +and contrary reasons of dislike to my plan makes me suspect that it +was really the true medium; and I am still of opinion that it would +have been happy for both sides of the water if it had been adopted. The +colonies, so united, would have been sufficiently strong to have +defended themselves; there would then have been no need of troops from +England; of course, the subsequent pretence for taxing America, and +the bloody contest it occasioned, would have been avoided." + +With this war against France began the struggle of the Assemblies and +the proprietaries on the question of taxing the estates of the latter. +The governors received strict instructions to approve no bills for the +raising of money for the purposes of defence, unless the estates of +the proprietaries were specially exempted from the tax. The Assembly +of Pennsylvania resolved to contribute £10,000 to assist the +Government of Massachusetts Bay in an attack upon Crown Point, but the +governor refused his assent to the bill for raising the money. At this +juncture Franklin proposed a scheme by which the money could be raised +without the consent of the governor. His plan was successful, and the +difficulty was surmounted for the time, but was destined to recur +again and again during the progress of the war. + +The British Government, not approving of the scheme of union, whereby +the colonies might have defended themselves, sent General Braddock to +Virginia, with two regiments of regular troops. On their arrival they +found it impossible to obtain waggons for the conveyance of their +baggage, and the general commissioned Franklin to provide them in +Pennsylvania. By giving his private bond for their safety, Franklin +succeeded in engaging one hundred and fifty four-horse waggons, and +two hundred and fifty-nine pack-horses. His modest warnings against +Indian ambuscades were disregarded by the general, the little army was +cut to pieces, and the remainder took to flight, sacrificing the whole +of their baggage and stores. Franklin was never fully recouped by the +British Government for the payments he had to make on account of +provisions which the general had instructed him to procure for the use +of the army. + +After this, Franklin appeared for some time in a purely military +capacity, having yielded to the governor's persuasions to undertake +the defence of the north-western frontier, to raise troops, and to +build a line of forts. After building and manning three wooden forts, +he was recalled by the Assembly, whose relations with the governor had +become more and more strained. At length the Assembly determined to +send Franklin to England, to present a petition to the king respecting +the conduct of the proprietaries, viz. Richard and Thomas Penn, the +successors of William Penn. A bill had been framed by the House to +provide £60,000 for the king's use in the defence of the province. +This the governor refused to pass, because the proprietary estates +were not exempted from the taxation. The petition to the king was +drawn up, and Franklin's baggage was on board the ship which was to +convey him to England, when General Lord Loudon endeavoured to make an +arrangement between the parties. The governor pleaded his +instructions, and the bond he had given for carrying them out, and the +Assembly was prevailed upon to reconstruct the bill in accordance with +the governor's wishes. This was done under protest; in the mean time +Franklin's ship had sailed, carrying his baggage. After a great deal +of unnecessary delay on account of the general's inability to decide +upon the despatch of the packet-boats, Franklin at last got away from +New York, and, having narrowly escaped shipwreck off Falmouth, he +reached London on July 27, 1757. + +On arriving in London, Franklin was introduced to Lord Granville, who +told him that the king's instructions were laws in the colonies. +Franklin replied that he had always understood that the Assemblies +made the laws, which then only required the king's consent. "I +recollected that, about twenty years before, a clause in a bill +brought into Parliament by the Ministry had proposed to make the +king's instructions laws in the colonies, but the clause was thrown +out by the Commons, for which we adored them as our friends and the +friends of liberty, till, by their conduct towards us in 1765, it +seem'd that they had refus'd that point of sovereignty to the king +only that they might reserve it for themselves." A meeting was shortly +afterwards arranged between Franklin and the proprietaries at Mr. T. +Penn's house; but their views were so discordant that, after some +discussion, Franklin was requested to give them in writing the heads +of his complaints, and the whole question was submitted to the opinion +of the attorney- and solicitor-general. It was nearly a year before +this opinion was given. The proprietaries then communicated directly +with the Assembly, but in the mean while Governor Denny had consented +to a bill for raising £100,000 for the king's use, in which it was +provided that the proprietary estates should be taxed with the others. +When this bill reached England, the proprietaries determined to oppose +its receiving the royal assent. Franklin engaged counsel on behalf of +the Assembly, and on his undertaking that the assessment should be +fairly made between the estates of the proprietaries and others, the +bill was allowed to pass. + +By this time Franklin's career as a scientific investigator was +practically at an end. Political business almost completely occupied +his attention, and in one sense the diplomatist replaced the +philosopher. His public scientific career was of short duration. It +may be said to have begun in 1746, when Mr. Peter Collinson presented +an "electrical tube" to the Library Company in Philadelphia, which was +some time after followed by a present of a complete set of electrical +apparatus from the proprietaries, but by 1755 Franklin's time was so +much taken up by public business that there was very little +opportunity for experimental work. Throughout his life he frequently +expressed in his letters his strong desire to return to philosophy, +but the opportunity never came, and when, at the age of eighty-two, he +was liberated from public duty, his strength was insufficient to +enable him to complete even his autobiography. + +It was on a visit to Boston in 1746 that Franklin met with Dr. Spence, +a Scotchman, who exhibited some electrical experiments. Soon after his +return to Philadelphia the tube arrived from Mr. Collinson, and +Franklin acquired considerable dexterity in its use. His house was +continually full of visitors, who came to see the experiments, and, to +relieve the pressure upon his time, he had a number of similar tubes +blown at the glass-house, and these he distributed to his friends, so +that there were soon a number of "performers" in Philadelphia. One of +these was Mr. Kinnersley, who, having no other employment, was induced +by Franklin to become an itinerant lecturer. Franklin drew up a scheme +for the lectures, and Kinnersley obtained several well-constructed +instruments from Franklin's rough and home-made models. Kinnersley and +Franklin appear to have worked together a good deal, and when +Kinnersley was travelling on his lecture tour, each communicated to +the other the results of his experiments. Franklin sent his papers to +Mr. Collinson, who presented them to the Royal Society, but they were +not at first judged worthy of a place in the "Transactions." The paper +on the identity of lightning and electricity was sent to Dr. Mitchell, +who read it before the Royal Society, when it "was laughed at by the +connoisseurs." The papers were subsequently published in a pamphlet, +but did not at first receive much attention in England. On the +recommendation of Count de Buffon, they were translated into French. +The Abbé Nollet, who had previously published a theory of his own +respecting electricity, wrote and published a volume of letters +defending his theory, and denying the accuracy of some of Franklin's +experimental results. To these letters Franklin made no reply, but +they were answered by M. le Roy. M. de Lor undertook to repeat in +Paris all Franklin's experiments, and they were performed before the +king and court. Not content with the experiments which Franklin had +actually performed, he tried those which had been only suggested, and +so was the first to obtain electricity from the clouds by means of the +pointed rod. This experiment produced a great sensation everywhere, +and was afterwards repeated by Franklin at Philadelphia. Franklin's +papers were translated into Italian, German, and Latin; his theory met +with all but universal acceptance, and great surprise was expressed +that his papers had excited so little interest in England. Dr. Watson +then drew up a summary of all Franklin's papers, and this was +published in the "Philosophical Transactions;" Mr. Canton verified the +experiment of procuring electricity from the clouds by means of a +pointed rod, and the Royal Society awarded to Franklin the Copley +Medal for 1753, which was conveyed to him by Governor Denny. + +We must now give a short account of Franklin's contributions to +electrical science. + +"The first is the wonderful effect of pointed bodies, both in _drawing +off_ and _throwing off_ the electrical fire." + +It will be observed that this statement is made in the language of the +_one_-fluid theory, of which Franklin may be regarded as the author. +This theory will be again referred to presently. Franklin electrified +a cannon-ball so that it repelled a cork. On bringing near it the +point of a bodkin, the repulsion disappeared. A blunt body had to be +brought near enough for a spark to pass in order to produce the same +effect. "To prove that the electrical fire is _drawn off_ by the +point, if you take the blade of the bodkin out of the wooden handle, +and fix it in a stick of sealing-wax, and then present it at the +distance aforesaid, or if you bring it very near, no such effect +follows; but sliding one finger along the wax till you touch the +blade, and the ball flies to the shot immediately. If you present the +point in the dark, you will see, sometimes at a foot distance or more, +a light gather upon it like that of a fire-fly or glow-worm; the less +sharp the point, the nearer you must bring it to observe the light; +and at whatever distance you see the light, you may draw off the +electrical fire, and destroy the repelling." + +By laying a needle upon the shot, Franklin showed "that points will +_throw off_ as well as _draw off_ the electrical fire." A candle-flame +was found to be equally efficient with a sharp point in drawing off +the electricity from a charged conductor. The effect of the +candle-flame Franklin accounted for by supposing the particles +separated from the candle to be first "attracted and then repelled, +carrying off the electric matter with them." The effect of points is a +direct consequence of the law of electrical repulsion. When a +conductor is electrified, the density of the electricity is greatest +where the curvature is greatest. Thus, if a number of spheres are +electrified from the same source, the density of the electricity on +the different spheres will vary inversely as their diameters. The +force tending to drive the electricity off a conductor is everywhere +proportional to the density, and hence in the case of the spheres will +be greatest for the smallest sphere. On this principle, the density of +electricity on a perfectly sharp point, if such could exist, on a +charged conductor, would be infinite and the force tending to drive it +off would be infinite also. Hence a moderately sharp point is +sufficient to dissipate the electricity from a highly charged +conductor, or to neutralize it if the point is connected to earth and +brought near the conductor so as to be electrified by induction. + +Franklin next found that, if the person rubbing the electric tube +stood upon a cake of resin, and the person taking the charge from the +tube stood also on an insulating stand, a stronger spark would pass +between these two persons than between either of them and the earth; +that, after the spark had passed, neither person was electrified, +though each had appeared electrified before. These experiments +suggested the idea of _positive_ and _negative_ electrification; and +Franklin, regarding the electric fluid as corresponding to positive +electrification, remarked that "you may circulate it as Mr. Watson has +shown; you may also accumulate or subtract it upon or from any body, +as you connect that body with the rubber or with the receiver, the +common stock being cut off." Thus Franklin regarded electricity as a +fluid, of which everything in its normal state possesses a certain +amount; that, by appropriate means, some of the fluid may be removed +from one body and given to another. The former is then electrified +negatively, the latter positively, and all processes by which bodies +are electrified consist in the removal of electricity from one body or +system and giving it to another. He regarded the electric fluid as +repelling itself and attracting matter. Æpinus afterwards added the +supposition that matter, when devoid of electricity, is +self-repulsive, and thus completed the "one-fluid theory," and +accounted for the repulsion observed between negatively electrified +bodies. + +It had been usual to employ water for the interior armatures of Leyden +jars, or phials, as they were then generally called. Franklin +substituted granulated lead for the water, thereby improving the +insulation by keeping the glass dry. With these phials he contrived +many ingenious experiments, and imitated lightning by discharging them +through the gilding of a mirror or the gold lines on the cover of a +book. He found that the inner and outer armatures of his Leyden jars +were oppositely electrified. "Here we have a bottle containing at the +same time a _plenum_ of electrical fire and a _vacuum_ of the same +fire; and yet the equilibrium cannot be restored between them but by a +communication _without_! though the plenum presses violently to +expand, and the hungry vacuum seems to attract as violently in order +to be filled." The charging of Leyden jars by cascade, that is by +insulating all the jars except the last, connecting the outer armature +of the first with the inner armature of the second, and so on +throughout the series, was well understood by Franklin, and he knew +too that by this method the extent to which each jar could be charged +from a given source varied inversely as the number of jars. The +discharge of the Leyden jar by alternate contacts was also carried out +by him; and he found that, if the jar is first placed on an insulating +stand, it may be held by the hook (or knob) without discharging it. +Franklin, in fact, appears to have known almost as much about the +Leyden jar as is known to-day. He found that, when the armatures were +removed from a jar, no discharge would pass between them, but when a +fresh pair of armatures were supplied to the glass, the jar could be +discharged. "We are of opinion that there is really no more electrical +fire in the phial after what is called its _charging_ than before, nor +less after its _discharging_; excepting only the small spark that +might be given to and taken from the non-electric matter, if separated +from the bottle, which spark may not be equal to a five-hundredth part +of what is called the explosion. + +"The phial will not suffer what is called a _charging_ unless as much +fire can go out of it one way as is thrown in by another. + +"When a bottle is charged in the common way, its _inside_ and +_outside_ surfaces stand ready, the one to give fire by the hook, the +other to receive it by the coating; the one is full and ready to throw +out, the other empty and extremely hungry; yet, as the first will not +_give out_ unless the other can at the same time _receive in_, so +neither will the latter receive in unless the first can at the same +time give out. When both can be done at once, it is done with +inconceivable quickness and violence." + +Then follows a very beautiful illustration of the condition of the +glass in the Leyden jar. + +"So a straight spring (though the comparison does not agree in every +particular), when forcibly bent, must, to restore itself, contract +that side which in the bending was extended, and extend that which was +contracted; if either of these two operations be hindered, the other +cannot be done. + +"Glass, in like manner, has, within its substance, always the same +quantity of electrical fire, and that a very great quantity in +proportion to the mass of the glass, as shall be shown hereafter. + +"This quantity proportioned to the glass it strongly and obstinately +retains, and will have neither more nor less, though it will suffer a +change to be made in its parts and situation; _i.e._ we may take away +part of it from one of the sides, provided we throw an equal quantity +into the other." + +"The whole force of the bottle, and power of giving a shock, is in the +GLASS ITSELF; the non-electrics in contact with the two surfaces +serving only to _give_ and _receive_ to and from the several parts of +the glass, that is, to give on one side and take away from the other." + +All these statements were, as far as possible, fully substantiated by +experiment. They are perfectly consistent with the views held by +Cavendish and by Clerk Maxwell, and, though the phraseology is not +that of the modern text-books, the statements themselves can hardly be +improved upon to-day. + +One of Franklin's early contrivances was an electro-motor, which was +driven by the alternate electrical attraction and repulsion of leaden +bullets which discharged Leyden jars by alternate contacts. Franklin +concluded his account of these experiments as follows:-- + + Chagrined a little that we have been hitherto able to produce + nothing in this way of use to mankind, and the hot weather + coming on, when electrical experiments are not so agreeable, it + is proposed to put an end to them for this season, somewhat + humorously, in a party of pleasure, on the banks of Skuylkil. + Spirits, at the same time, are to be fired by a spark sent from + side to side through the river, without any other conductor than + the water--an experiment which we some time since performed, to + the amazement of many. A turkey is to be killed for our dinner + by the _electrical shock_, and roasted by the _electrical jack_ + before a fire kindled by the _electrified bottle_, when the + healths of all the famous electricians in England, Holland, + France, and Germany, are to be drunk in _electrified bumpers_, + under the discharge of guns from the _electrical battery_. + +Franklin's electrical battery consisted of eleven large panes of glass +coated on each side with sheet lead. The electrified bumper was a thin +tumbler nearly filled with wine and electrified as a Leyden jar, so +as to give a shock through the lips. + +Franklin's theory of the manner in which thunder-clouds become +electrified he found to be not consistent with his subsequent +experiments. In the paper which he wrote explaining this theory, +however, he shows some knowledge of the effects of bringing conductors +into contact in diminishing their capacity. He states that two +gun-barrels electrified equally and then united, will give a spark at +a greater distance than one alone. Hence he asks, "To what a great +distance may ten thousand acres of electrified cloud strike and give +its fire, and how loud must be that crack? + +"An electrical spark, drawn from an irregular body at some distance, +is scarcely ever straight, but shows crooked and waving in the air. So +do the flashes of lightning, the clouds being very irregular bodies. + +"As electrified clouds pass over a country, high hills and high trees, +lofty towers, spires, masts of ships, chimneys, etc., as so many +prominences and points, draw the electrical fire, and the whole cloud +discharges there. + +"Dangerous, therefore, is it to take shelter under a tree during a +thunder-gust. It has been fatal to many, both men and beasts. + +"It is safer to be in the open field for another reason. When the +clothes are wet, if a flash in its way to the ground should strike +your head, it may run in the water over the surface of your body; +whereas, if your clothes were dry, it would go through the body, +because the blood and other humours, containing so much water, are +more ready conductors. + +"Hence a wet rat cannot be killed by the exploding electrical bottle +[a quart jar], while a dry rat may." + +In the above quotations we see, so to speak, the germ of the +lightning-rod. This was developed in a letter addressed to Mr. +Collinson, and dated July 29, 1750. The following quotations will give +an idea of its contents:-- + +"The electrical matter consists of particles extremely subtile, since +it can permeate common matter, even the densest metals, with such ease +and freedom as not to receive any perceptible resistance.[1] + +[Footnote 1: Franklin was aware of the resistance of conductors (see +p. 96).] + +"If any one should doubt whether the electrical matter passes through +the substance of bodies or only over and along their surfaces, a shock +from an electrified large glass jar, taken through his own body, will +probably convince him. + +"Common matter is a kind of sponge to the electrical fluid. + +"We know that the electrical fluid is _in_ common matter, because we +can pump it _out_ by the globe or tube. We know that common matter has +near as much as it can contain, because when we add a little more to +any portion of it, the additional quantity does not enter, but forms +an electrical atmosphere." + +To illustrate the action of a lightning-conductor on a thunder-cloud, +Franklin suspended from the ceiling a pair of scales by a twisted +string so that the beam revolved. Upon the floor, in such a position +that the scale-pans passed over it, he placed a blunt steel punch. The +scale-pans were suspended by silk threads, and one of them +electrified. When this passed over the punch it dipped towards it, and +sometimes discharged into it by a spark. When a needle was placed with +its point uppermost by the side of the punch, no attraction was +apparent, for the needle discharged the scale-pan before it came near. + +"Now, if the fire of electricity and that of lightning be the same, as +I have endeavoured to show at large in a former paper ... these scales +may represent electrified clouds.... The horizontal motion of the +scales over the floor may represent the motion of the clouds over the +earth, and the erect iron punch a hill or high building; and then we +see how electrified clouds, passing over hills or high buildings at +too great a height to strike, may be attracted lower till within their +striking distance; and lastly, if a needle fixed on the punch, with +its point upright, or even on the floor below the punch, will draw the +fire from the scale silently at a much greater than the striking +distance, and so prevent its descending towards the punch; or if in +its course it would have come nigh enough to strike, yet, being first +deprived of its fire, it cannot, and the punch is thereby secured from +its stroke;--I say, if these things are so, may not the knowledge of +this power of points be of use to mankind, in preserving houses, +churches, ships, etc., from the stroke of the lightning, by directing +us to fix, on the highest parts of those edifices, upright rods of +iron made sharp as a needle, and gilt to prevent rusting, and from the +foot of those rods a wire down the outside of the building into the +ground, or down round one of the shrouds of a ship, and down her side +till it reaches the water? Would not these pointed rods probably draw +the electrical fire silently out of a cloud before it came nigh enough +to strike, and thereby secure us from that most sudden and terrible +mischief?" + +Franklin goes on to suggest the possibility of obtaining electricity +from the clouds by means of a pointed rod fixed on the top of a high +building and insulated. Such a rod he afterwards erected in his own +house. Another rod connected to the earth he brought within six inches +of it, and, attaching a small bell to each rod, he suspended a little +ball or clapper by a silk thread, so that it could strike either bell +when attracted to it. On the approach of a thunder-cloud, and +occasionally when no clouds were near, the bells would ring, +indicating that the rod had become strongly electrified. On one +occasion Franklin was disturbed by a loud noise, and, coming out of +his bedroom, he found an apparently continuous and very luminous +discharge taking place between the bells, forming a stream of fire +about as large as a pencil. + +A very pretty experiment of Franklin's was that of the _golden fish_. +A small piece of gold-leaf is cut into a quadrilateral having one of +its angles about 150°, the opposite angle about 30°, and the other two +right angles. "If you take it by the tail, and hold it at a foot or +greater horizontal distance from the prime conductor, it will, when +let go, fly to it with a brisk but wavering motion, like that of an +eel through the water; it will then take place under the prime +conductor, at perhaps a quarter or half an inch distance, and keep a +continual shaking of its tail like a fish, so that it seems animated. +Turn its tail towards the prime conductor, and then it flies to your +finger, and seems to nibble it. And if you hold a [pewter] plate under +it at six or eight inches distance, and cease turning the globe, when +the electrical atmosphere of the conductor grows small it will descend +to the plate and swim back again several times with the same fish-like +motion; greatly to the entertainment of spectators. By a little +practice in blunting or sharpening the heads or tails of these +figures, you may make them take place as desired, nearer or further +from the electrified plate." + +By the discharge of the battery, Franklin succeeded in melting and +volatilizing gold-leaf, thin strips of tinfoil, etc. His views on the +nature of light are best given in his own words. + +"I am not satisfied with the doctrine that supposes particles of +matter called light, continually driven off from the sun's surface, +with a swiftness so prodigious! Must not the smallest particle +conceivable have, with such a motion, a force exceeding that of a +twenty-four pounder discharged from a cannon?... Yet these particles, +with this amazing motion, will not drive before them, or remove, the +least and lightest dust they meet with. + +"May not all the phenomena of light be more conveniently solved by +supposing universal space filled with a subtile elastic fluid, which, +when at rest, is not visible, but whose vibrations affect that fine +sense in the eye, as those of air do the grosser organs of the ear? We +do not, in the case of sound, imagine that any sonorous particles are +thrown off from a bell, for instance, and fly in straight lines to the +ear; why must we believe that luminous particles leave the sun and +proceed to the eye? Some diamonds, if rubbed, shine in the dark +without losing any part of their matter. I can make an electrical +spark as big as the flame of a candle, much brighter, and therefore +visible further; yet this is without fuel; and I am persuaded no part +of the electrical fluid flies off in such case to distant places, but +all goes directly and is to be found in the place to which I destine +it. May not different degrees of the vibration of the abovementioned +universal medium occasion the appearances of different colours? I +think the electric fluid is always the same; yet I find that weaker +and stronger sparks differ in apparent colour, some white, blue, +purple, red: the strongest, white; weak ones, red. Thus different +degrees of vibration given to the air produce the seven different +sounds in music, analogous to the seven colours, yet the medium, air, +is the same." + +Mr. Kinnersley having called Franklin's attention to the fact that a +sulphur globe when rubbed produced electrification of an opposite kind +from that produced by a glass globe, Franklin repeated the experiment, +and noticed that the discharge from the end of a wire connected with +the conductor was different in the two cases, being "long, large, and +much diverging when the glass globe is used, and makes a snapping (or +rattling) noise; but when the sulphur one is used it is short, small, +and makes a hissing noise; and just the reverse of both happens when +you hold the same wire in your hand and the globes are worked +alternately.... When the brush is long, large, and much diverging, the +body to which it is joined seems to be throwing the fire out; and when +the contrary appears it seems to be drinking in." + +On October 19, 1752, Franklin wrote to Mr. Peter Collinson as +follows:-- + + As frequent mention is made in public papers from Europe of the + success of the Philadelphia experiment for drawing the electric + fire from clouds by means of pointed rods of iron erected on + high buildings, etc., it may be agreeable to the curious to be + informed that the same experiment has succeeded in + Philadelphia, though made in a different and more easy manner, + which is as follows:-- + + Make a small cross of two light strips of cedar, the arms so + long as to reach to the four corners of a large thin silk + handkerchief when extended. Tie the corners of the handkerchief + to the extremities of the cross, so you have the body of a kite; + which, being properly accommodated with a tail, loop, and + string, will rise in the air like those made of paper; but this + being of silk is fitter to bear the wet and wind of a + thunder-gust without tearing. To the top of the upright stick of + the cross is to be fixed a very sharp-pointed wire, rising a + foot or more above the wood. To the end of the twine, next the + hand, is to be tied a silk ribbon, and, where the silk and twine + join, a key may be fastened. This kite is to be raised when a + thunder-gust appears to be coming on, and the person who holds + the string must stand within a door or window, or under some + cover so that the silk ribbon may not be wet, and care must be + taken that the twine does not touch the frame of the door or + window. As soon as any of the thunder-clouds come over the kite, + the pointed wire will draw the electric fire from them, and the + kite, with all the twine, will be electrified, and the loose + filaments of the twine will stand out every way, and be + attracted by an approaching finger. And when the rain has wetted + the kite and twine so that it can conduct the electric fire + freely, you will find it stream out plentifully from the key on + the approach of your knuckle. At this key the phial may be + charged, and from electric fire there obtained spirits may be + kindled, and all the other electric experiments be performed + which are usually done by the help of a rubbed glass globe or + tube, and thereby the sameness of the electric matter with that + of lightning completely demonstrated. + +Having, in September, 1752, erected the iron rod and bells in his own +house, as previously mentioned, Franklin succeeded, in April, 1753, in +charging a Leyden jar from the rod, and found its charge was negative. +On June 6, however, he obtained a positive charge from a cloud. The +results of his observations led him to the conclusion "_That the +clouds of a thunder-gust are most commonly in a negative state of +electricity, but sometimes in a positive state._" + +In order to illustrate a theory respecting the electrification of +clouds, Franklin placed a silver can on a wine-glass. Inside the can +was placed a considerable length of chain, which could be drawn out by +means of a silk thread. He electrified the can from a Leyden jar until +it would receive no more electricity. Then raising the silk thread, he +gradually drew the chain out of the can, and found that the greater +the length of chain drawn out the greater was the charge which the jar +would give to the system, and as the chain was raised, spark after +spark passed from the jar to the silver can, thus showing that the +capacity of the system was increased by increasing the amount of +chain exposed. + +In 1755 Franklin observed the effects of induction; for, having +attached to his prime conductor a tassel made of damp threads and +electrified the conductor, he found that the threads repelled each +other and stood out. Bringing an excited glass tube near the other end +of the conductor, the threads were found to diverge more, "because the +atmosphere of the prime conductor is pressed by the atmosphere of the +excited tube, and driven towards the end where the threads are, by +which each thread acquires more atmosphere." When the excited tube was +brought near the threads, they closed a little, "because the +atmosphere of the glass tube repels their atmospheres, and drives part +of them back on the prime conductor." A number of other experiments +illustrating electrical induction were also carried out. + +In writing to Dr. Living, of Charlestown, under date March 18, 1755, +Franklin gave the following extracts of the minutes of his experiments +as explaining the train of thought which led him to attempt to obtain +electricity from the clouds:-- + +"_November 7, 1749._ Electrical fluid agrees with lightning in these +particulars: 1. Giving light. 2. Colour of the light. 3. Crooked +direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or +noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies +it passes through. 9. Destroying animals. 10. Melting metals. 11. +Firing inflammable substances. 12. Sulphureous smell. The electric +fluid is attracted by points. We do not know whether this property is +in lightning. But since they agree in all the particulars wherein we +can already compare them, is it not probable they agree likewise in +this? Let the experiment be made." + +Another experiment very important in its bearing on the theory of +electricity was described by Franklin in the same letter to Dr. +Living. It was afterwards repeated in a much more complete form by +Cavendish, who deduced from it the great law that electrical repulsion +varies inversely as the square of the distance between the charges. +The same experiment was repeated in other forms by Faraday, who had no +means of knowing what Cavendish had done. Franklin writes:-- + + I electrified a silver fruit-can on an electric stand, and then + lowered into it a cork ball of about an inch in diameter, + hanging by a silk string, till the cork touched the bottom of + the can. The cork was not attracted to the inside of the can, as + it would have been to the outside, and though it touched the + bottom, yet, when drawn out, it was not found to be electrified + by that touch, as it would have been by touching the outside. + The fact is singular. You require the reason? I do not know it. + Perhaps you may discover it, and then you will be so good as to + communicate it to me. I find a frank acknowledgment of one's + ignorance is not only the easiest way to get rid of a + difficulty, but the likeliest way to obtain information, and + therefore I practise it. I think it is an honest policy. + +A note appended to this letter runs as follows:-- + + Mr. F. has since thought that, possibly, the mutual repulsion of + the inner opposite sides of the electrized can may prevent the + accumulating an electric atmosphere upon them, and occasion it + to stand chiefly on the outside. But recommends it to the + further examination of the curious. + +The explanation in this note is the correct one, and from the fact +that in the case of a completely closed hollow conductor the charge is +not only _chiefly_ but _wholly_ on the outside, the law of inverse +squares above referred to follows as a mathematical consequence. + +On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin +complained that, though he always (except once) assigned to +lightning-rods the alternative duty of either _preventing_ a stroke or +of _conducting_ the lightning with safety to the ground, yet in Europe +attention was paid only to the _prevention_ of the stroke, which was +only a _part_ of the duty assigned to the conductors. This is followed +by the description of the effect of a stroke upon a church-steeple at +Newbury, in New England. The spire was split all to pieces, so that +nothing remained above the bell. The lightning then passed down a wire +to the clock, then down the pendulum, without injury to the building. +"From the end of the pendulum, down quite to the ground, the building +was exceedingly rent and damaged, and some stones in the +foundation-wall torn out and thrown to the distance of twenty or +thirty feet." The pendulum-rod was uninjured, but the fine wire +leading from the bell to the clock was vaporized except for about two +inches at each end. + +Mr. James Alexander, of New York, having proposed to Franklin that the +velocity of the electric discharge might be measured by discharging a +jar through a long circuit of river-water, Franklin, in his reply, +explained that such an experiment, if successful, would not determine +the actual velocity of electricity in the conductor. He compared the +electricity in conductors to an incompressible fluid, so that when a +little additional fluid is injected at one end of a conductor, an +equal amount must be extruded at the other end--his view apparently +being identical with that of Maxwell, who held that all electric +displacements must take place _in closed circuits_. + +"Suppose a tube of any length open at both ends.... If the tube be +filled with water, and I inject an additional inch of water at one +end, I force out an equal quantity at the other in the very same +instant. + +"And the water forced out at one end of the tube is not the very same +water that was forced in at the other end at the same time; it was +only one motion at the same time. + +"The long wire, made use of in the experiment to discover the velocity +of the electric fluid, is itself filled with what we call its natural +quantity of that fluid, before the hook of the Leyden bottle is +applied at one end of it. + +"The outside of the bottle being at the time of such application in +contact with the other end of the wire, the whole quantity of electric +fluid contained in the wire is, probably, put in motion at once. + +"For at the instant the hook, connected with the inside of the bottle, +_gives out_, the coating or outside of the bottle _draws in_, a +portion of that fluid.... + +"So that this experiment only shows the extreme facility with which +the electric fluid moves in metal; it can never determine the +velocity. + +"And, therefore, the proposed experiment (though well imagined and +very ingenious) of sending the spark round through a vast length of +space, by the waters of Susquehannah, or Potowmack, and Ohio, would +not afford the satisfaction desired, though we could be sure that the +motion of the electric fluid would be in that tract, and not +underground in the wet earth by the shortest way." + +In his investigations of the source of electricity in thunder-clouds, +Franklin tried an experiment which has been frequently repeated with +various modifications. Having insulated a large brass plate which had +been previously heated, he sprinkled water upon it, in order, if +possible, to obtain electricity by the evaporation of the water, but +no trace of electrification could be detected. + +During his visit to England, Franklin wrote many letters to Mr. +Kinnersley and others on philosophical questions, but they consisted +mainly of accounts of the work done by other experimenters in England, +his public business occupying too much of his attention to allow him +to conduct investigations for himself. In one of his letters, speaking +of Lord Charles Cavendish, he says:-- + + It were to be wished that this noble philosopher would + communicate more of his experiments to the world, as he makes + many, and with great accuracy. + +When the controversy between the relative merits of points and knobs +for the terminals of lightning-conductors arose, Franklin wrote to Mr. +Kinnersley:-- + + Here are some electricians that recommend knobs instead of + points on the upper end of the rods, from a supposition that the + points invite the stroke. It is true that points draw + electricity at greater distances in the gradual silent way; but + knobs will draw at the greatest distance a stroke. There is an + experiment which will settle this. Take a crooked wire of the + thickness of a quill, and of such a length as that, one end of + it being applied to the lower part of a charged bottle, the + upper may be brought near the ball on the top of the wire that + is in the bottle. Let one end of this wire be furnished with a + knob, and the other may be gradually tapered to a fine point. + When the point is presented to discharge the bottle, it must be + brought much nearer before it will receive the stroke than the + knob requires to be. Points, besides, tend to repel the + fragments of an electrical cloud; knobs draw them nearer. An + experiment, which I believe I have shown you, of cotton fleece + hanging from an electrized body, shows this clearly when a point + or a knob is presented under it. + +The following quotation from Franklin's paper on the method of +securing buildings and persons from the effects of lightning is worthy +of attention, for of late years a good deal of money has been wasted +in providing insulators for lightning-rods. A few years ago the vicar +and churchwardens of a Lincolnshire parish were strongly urged to go +to the expense of insulating the conductor throughout the whole height +of the very lofty tower and spire of their parish church. Happily they +were wise enough to send the lightning-rod man about his business. But +this is not the only case which has come under the writer's notice, +showing that there is still a widespread impression that +lightning-conductors should be carefully insulated. Franklin says:-- + +"The rod may be fastened to the wall, chimney, etc., with staples of +iron. The lightning will not leave the rod (a good conductor) to pass +into the wall (a bad conductor) through these staples. It would +rather, if any were in the wall, pass out of it into the rod, to get +more readily by that conductor into the earth."[2] + +[Footnote 2: See p. 141.] + +The conditions to be secured in a lightning-conductor are, firstly, a +sharp point projecting above the highest part of the building, and +gilded to prevent corrosion; secondly, metallic continuity from the +point to the lower end of the conductor; and, thirdly, a good +earth-contact. The last can frequently be secured by soldering the +conductor to iron water-pipes underground. Where these are not +available, a copper plate, two or three feet square, imbedded in clay +or other damp earth, will serve the purpose. The method of securing a +building which is erected on granite or other foundation affording no +good earth-connection, will be referred to in a subsequent +biographical sketch. + +The controversy of points _versus_ knobs was again revived in London +when Franklin was in Paris, and the War of Independence had begun. +Franklin was consulted on the subject, the question having arisen in +connection with the conductor at the palace. His reply was +characteristic. + +"As to my writing anything on the subject, which you seem to desire, I +think it not necessary, especially as I have nothing to add to what I +have already said upon it in a paper read to the committee who ordered +the conductors at Purfleet, which paper is printed in the last French +edition of my writings. + +"I have never entered into any controversy in defence of my +philosophical opinions. I leave them to take their chance in the +world. If they are _right_, truth and experience will support them; if +_wrong_, they ought to be refuted and rejected. Disputes are apt to +sour one's temper and disturb one's quiet. I have no private interest +in the reception of my inventions by the world, having never made, nor +proposed to make, the least profit by any of them. The king's changing +his _pointed_ conductors for _blunt_ ones is, therefore, a matter of +small importance to me. If I had a wish about it, it would be that he +had rejected them altogether as ineffectual. For it is only since he +thought himself and family safe from the thunder of Heaven, that he +dared to use his own thunder in destroying his innocent subjects." + +The paper referred to was read before "the committee appointed to +consider the erecting conductors to secure the magazines at Purfleet," +on August 27, 1772. It described a variety of experiments clearly +demonstrating the effect of points in discharging a conductor. This +was a committee of the Royal Society, to whom the question had been +referred on account of Dr. Wilson's recommendation of a blunt +conductor. The committee decided in favour of Franklin's view, and +when, in 1777, the question was again raised and again referred to a +committee of the Royal Society, the decision of the former committee +was confirmed, "conceiving that the experiments and reasons made and +alleged to the contrary by Mr. Wilson are inconclusive." + +Though Franklin's scientific reputation rests mainly on his electrical +researches, he did not leave other branches of science untouched. +Besides his work on atmospheric electricity, he devoted a great deal +of thought to meteorology, especially to the vortical motion of +waterspouts. The Gulf-stream received a share of his attention. His +improvements in fireplaces have already been noticed; the cure of +smoky chimneys was the subject of a long paper addressed to Dr. +Ingenhousz, and of some other letters. One of his experiments on the +absorption of radiant energy has been deservedly remembered. + +"My experiment was this: I took a number of little square pieces of +broad-cloth from a tailor's pattern-card, of various colours. There +were black, deep blue, lighter blue, green, purple, red, yellow, +white, and other colours or shades of colours. I laid them all out +upon the snow in a bright, sun-shiny morning. In a few hours (I cannot +now be exact as to the time) the black, being warmed most by the sun, +was sunk so low as to be below the stroke of the sun's rays; the dark +blue almost as low, the lighter blue not quite so much as the dark, +the other colours less as they were lighter; and the quite white +remained on the surface of the snow, not having entered it at all. + +"What signifies philosophy that does not apply to some use? May we not +learn from hence that black clothes are not so fit to wear in a hot, +sunny climate or season, as white ones?" + +Franklin knew much about electricity, but his knowledge of human +nature was deeper still. This appears in all his transactions. His +political economy was, perhaps, not always sound, but his judgment of +men was seldom at fault. + +"Finally, there seem to be but three ways for a nation to acquire +wealth. The first is by _war_, as the Romans did, in plundering their +conquered neighbour: this is _robbery_. The second by _commerce_, +which is generally _cheating_. The third by _agriculture_, the only +_honest way_, wherein man receives a real increase of the seed thrown +into the ground, in a kind of continual miracle wrought by the hand of +God in his favour, as a reward for his innocent life and his virtuous +industry." + +When Franklin reached London in 1757 he took up his abode with Mrs. +Margaret Stevenson, in Craven Street, Strand. For Mrs. Stevenson and +her daughter Mary, then a young lady of eighteen, he acquired a +sincere affection, which continued throughout their lives. Miss +Stevenson spent much of her time with an aunt in the country, and some +of Franklin's letters to her respecting the conduct of her "higher +education" are among the most interesting of his writings. Miss +Stevenson treated him as a father, and consulted him on every question +of importance in her life. When she was a widow and Franklin eighty +years of age, he urged upon her to come to Philadelphia, for the sake +of the better prospects which the new country offered her boys. In +coming to England, Franklin brought with him his son William, who +entered the Middle Temple, but he left behind his only daughter, +Sarah, in charge of her mother. To his wife and daughter he +frequently sent presents from London, and his letters to Mrs. Franklin +give a pretty full account of all his doings while in England. During +his visit he received the honorary degrees of D.C.L. from the +University of Oxford, and LL.D. from that of Edinburgh. At Cambridge +he was sumptuously entertained. In August, 1762, he started again for +America, and reached Philadelphia on November 1, after an absence of +five years. His son William had shortly before been appointed Governor +of New Jersey. From this time William Franklin became very much the +servant of the proprietaries and of the English Government, but no +offer of patronage produced any effect on the father. + +Franklin's stay in America was of short duration, but while there he +was mainly instrumental in quelling an insurrection in Pennsylvania. +He made a tour of inspection through the northern colonies in the +summer of 1763, to regulate the post-offices. The disorder just +referred to in the province caused the governor, as well as the +Assembly, to determine on the formation of a militia. A committee, of +which Franklin was a member, drew up the necessary bill. The governor +claimed the sole power of appointing officers, and required that +trials should be by court-martial, some offences being punishable with +death. The Assembly refused to agree to these considerations. The ill +feeling was increased by the governor insisting on taxing all +proprietary lands at the same rate as uncultivated land belonging to +other persons, whether the proprietary lands were cultivated or not. +The Assembly, before adjourning, expressed an opinion that peace and +happiness would not be secured until the government was lodged +directly in the Crown. When the Assembly again met, petitions to the +king came in from more than three thousand inhabitants. In the mean +while the British Ministry had proposed the Stamp Act, which was +similar in principle to the English Stamp Act, which requires that all +agreements, receipts, bills of exchange, marriage and birth +certificates, and all other legal documents should be provided with an +inland revenue stamp of a particular value, in order that they might +be valid. As soon as the Assembly was convened, it determined to send +Franklin to England, to take charge of a petition for a change of +government. The merchants subscribed £1100 towards his expenses in a +few hours, and in twelve days he was on his journey, being accompanied +to the ship, a distance of sixteen miles, by a cavalcade of three +hundred of his friends, and in thirty days he reached London. Arrived +in London, he at once took up his abode in his old lodgings with Mrs. +Stevenson. He was a master of satire, equalled only by Swift, and +during the quarrels which preceded the War of Independence, as well as +during the war, he made good use of his powers in this respect. +Articles appeared in some of the English papers tending to raise an +alarm respecting the competition of the colonies with English +manufacturers. Franklin's contribution to the discussion was a +caricature of the English press writers. + +"It is objected by superficial readers, who yet pretend to some +knowledge of those countries, that such establishments [manufactories +for woollen goods, etc.] are not only improbable, but impossible, for +that their sheep have but little wool, not in the whole sufficient for +a pair of stockings a year to each inhabitant; that, from the +universal dearness of labour among them, the working of iron and other +materials, except in a few coarse instances, is impracticable to any +advantage. + +"Dear sir, do not let us suffer ourselves to be amused with such +groundless objections. The very tails of the American sheep are so +laden with wool that each has a little car or waggon on four little +wheels to support and keep it from trailing on the ground. Would they +caulk their ships, would they even litter their horses with wool, if +it were not both plenty and cheap? And what signifies the dearness of +labour, when an English shilling passes for five and twenty? Their +engaging three hundred silk throwsters here in one week for New York +was treated as a fable, because, forsooth, they have 'no silk there to +throw!' Those who make this objection perhaps do not know that, at the +same time, the agents for the King of Spain were at Quebec, to +contract for one thousand pieces of cannon to be made there for the +fortification of Mexico, and at New York engaging the usual supply of +woollen floor-carpets for their West India houses. Other agents from +the Emperor of China were at Boston, treating about an exchange of raw +silk for wool, to be carried in Chinese junks through the Straits of +Magellan. + +"And yet all this is as certainly true as the account said to be from +Quebec in all the papers of last week, that the inhabitants of Canada +are making preparations for a cod and whale fishery this summer in the +upper Lakes. Ignorant people may object that the upper Lakes are +fresh, and that cod and whales are salt-water fish; but let them know, +sir, that cod, like other fish when attacked by their enemies, fly +into any water where they can be safest; that whales, when they have a +mind to eat cod, pursue them wherever they fly; and that the grand +leap of the whale in the chase up the Falls of Niagara is esteemed, by +all who have seen it, as one of the finest spectacles in nature." + +One of Franklin's chief objects in coming to England was to prevent +the passing of Mr. Grenville's bill, previously referred to as the +Stamp Act. The colonists urged that they had always been liberal in +their votes, whenever money was required by the Crown, and that +taxation and representation must, in accordance with the British +constitution, go hand-in-hand, so that the English Parliament had no +right to raise taxes in America, so long as the colonists were +unrepresented in Parliament. "Had Mr. Grenville, instead of that act, +applied to the king in Council for such requisitional letters [_i.e._ +requests to the Assemblies for voluntary grants], to be circulated by +the Secretary of State, I am sure he would have obtained more money +from the colonies by their voluntary grants than he himself expected +from the sale of stamps. But he chose compulsion rather than +persuasion, and would not receive from their good will what he thought +he could obtain without it." The Stamp Act was passed, stamps were +printed, distributors were appointed, but the colonists would have +nothing to do with the stamps. The distributors were compelled to +resign their commissions, and the captains of vessels were forbidden +to land the stamped paper. The cost of printing and distributing +amounted to £12,000; the whole return was about £1500, from Canada and +the West Indies. + +The passing of the Stamp Act was soon followed by a change of +Ministry, when the question again came before Parliament. Franklin +submitted to a long examination before a Committee of the whole House. +The feeling prevalent in America respecting the Stamp Act may be +inferred from some of his answers. + +"31. _Q._ Do you think the people of America would submit to pay the +stamp duty if it was moderated? + +"_A._ No, never, unless compelled by force of arms. + +"36. _Q._ What was the temper of America towards Great Britain before +the year 1763?[3] + +[Footnote 3: The date of the Sugar Act.] + +"_A._ The best in the world. They submitted willingly to the +government of the Crown, and paid, in their courts, obedience to the +Acts of Parliament. Numerous as the people are in the several old +provinces, they cost you nothing in forts, citadels, garrisons, or +armies to keep them in subjection. They were governed by this country +at the expense only of a little pen, ink, and paper; they were led by +a thread. They had not only a respect, but an affection, for Great +Britain--for its laws, its customs and manners, and even a fondness +for its fashions, that greatly increased the commerce. Natives of +Britain were always treated with particular regard; to be an +_Old-Englandman_ was, of itself, a character of some respect, and gave +a kind of rank among us. + +"37. _Q._ And what is their temper now? + +"_A._ Oh, very much altered. + +"50. _Q._ Was it an opinion in America before 1763 that the Parliament +had no right to lay taxes and duties there? + +"_A._ I never heard any objection to the right of laying duties to +regulate commerce; but a right to lay internal taxes was never +supposed to be in Parliament, as we are not represented there. + +"59. _Q._ You say the colonies have always submitted to external +taxes, and object to the right of Parliament only in laying internal +taxes; now, can you show that there is any kind of difference between +the two taxes to the colony on which they may be laid? + +"_A._ I think the difference is very great. An _external_ tax is a +duty laid on commodities imported; that duty is added to the first +cost and other charges on the commodity, and, when it is offered to +sale, makes a part of the price. If the people do not like it at that +price, they refuse it; they are not obliged to pay it. But an +_internal_ tax is forced upon the people without their consent, if not +laid by their own representatives. The Stamp Act says we shall have no +commerce, make no exchange of property with each other, neither +purchase, nor grant, nor recover debts; we shall neither marry nor +make our wills, unless we pay such and such sums; and thus it is +intended to extort our money from us, or ruin us by the consequences +of refusing to pay it. + +"61. _Q._ Don't you think cloth from England absolutely necessary to +them? + +"_A._ No, by no means absolutely necessary; with industry and good +management they may very well supply themselves with all they want. + +"62. _Q._ Will it not take a long time to establish that manufacture +among them? and must they not in the mean while suffer greatly? + +"_A._ I think not. They have made a surprising progress already. And I +am of opinion that, before their old clothes are worn out, they will +have new ones of their own making. + +"84. _Q._ If the Act is not repealed, what do you think will be the +consequence? + +"_A._ A total loss of the respect and affection the people of America +bear to this country, and of all the commerce that depends on that +respect and affection. + +"85. _Q._ How can the commerce be affected? + +"_A._ You will find that, if the Act is not repealed, they will take a +very little of your manufactures in a short time. + +"86. _Q._ Is it in their power to do without them? + +"_A._ I think they may very well do without them. + +"87. _Q._ Is it their interest not to take them? + +"_A._ The goods they take from Britain are either necessaries, mere +conveniences, or superfluities. The first, as cloth, etc., with a +little industry they can make at home; the second they can do without +till they are able to provide them among themselves; and the last, +which are much the greatest part, they will strike off immediately. +They are mere articles of fashion, purchased and consumed because the +fashion in a respected country; but will now be detested and rejected. +The people have already struck off, by general agreement, the use of +all goods fashionable in mournings, and many thousand pounds' worth +are sent back as unsaleable. + +"173. _Q._ What used to be the pride of the Americans? + +"_A._ To indulge in the fashions and manufactures of Great Britain. + +"174. _Q._ What is now their pride? + +"_A._ To wear their old clothes over again till they can make new +ones." + +The month following Franklin's examination, the repeal of the Stamp +Act received the royal assent. Thereupon Franklin sent his wife and +daughter new dresses, and a number of other little luxuries (or toilet +necessaries). + +In 1767 Franklin visited Paris. In the same year his daughter married +Mr. Richard Bache. Though Parliament had repealed the Stamp Act, it +nevertheless insisted on its right to tax the colonies. The Duty Act +was scarcely less objectionable than its predecessor. On Franklin's +return from the Continent, he heard of the retaliatory measures of the +Boston people, who had assembled in town-meetings, formally resolved +to encourage home manufactures, to abandon superfluities, and, after a +certain time, to give up the use of some articles of foreign +manufacture. These _associations_ afterwards became very general in +the colonies, so that in one year the importations by the colonists of +New York fell from £482,000 to £74,000, and in Pennsylvania from +£432,000 to £119,000. + +The effect of the Duty Act was to encourage the Dutch and other +nations to smuggle tea and probably other India produce into America. +The exclusion from the American markets of tea sent from England +placed the East India Company in great difficulties; for while they +were unable to meet their bills, they had in stock two million pounds' +worth of tea and other goods. The balance of the revenue collected +under the Duty Act, after paying salaries, etc., amounted to only £85 +for the year, and for this a fleet had to be maintained, to guard the +fifteen hundred miles of American coast; while the fall in East India +Stock deprived the revenue of £400,000 per annum, which the East India +Company would otherwise have paid. At length a licence was granted to +the East India Company to carry tea into America, duty free. This, of +course, excluded all other merchants from the American tea-trade. A +quantity of tea sent by the East India Company to Boston was destroyed +by the people. The British Government then blockaded the port. This +soon led to open hostilities. Franklin worked hard to effect a +reconciliation. He drew up a scheme, setting forth the conditions +under which he conceived a reconciliation might be brought about, and +discussed it fully with Mr. Daniel Barclay and Dr. Fothergill. This +scheme was shown to Lord Howe, and afterwards brought before the +Ministry, but was rejected. Other plans were considered, and Franklin +offered to pay for the tea which had been destroyed at Boston. All his +negotiations were, however, fruitless. At last he addressed a memorial +to the Earl of Dartmouth, Secretary of State, complaining of the +blockade of Boston, which had then continued for nine months, and had +"during every week of its continuance done damage to that town, equal +to what was suffered there by the India Company;" and claiming +reparation for such injury beyond the value of the tea which had been +destroyed. The memorial also complained of the exclusion of the +colonists from the Newfoundland fisheries, for which reparation would +one day be required. This memorial was returned to Franklin by Mr. +Walpole, and Franklin shortly afterwards returned to Philadelphia. + +During this visit to England he had lost his wife, who died on +December 19, 1774; and his friend Miss Stevenson had married and been +left a widow. + +In April, 1768, Franklin was appointed Agent for Georgia, in the +following year for New Jersey, and in 1770 for Massachusetts, so that +he was then the representative in England of four colonies, with an +income of £1200 per annum. + +In 1771 he spent three weeks at Twyford, with the Bishop of St. Asaph, +who remained a fast friend of Franklin's until his death. In 1772 he +was nominated by the King of France as Foreign Associate of the +Academy of Sciences. + +During his negotiations with the British Government Franklin wrote two +satirical pieces, setting forth the treatment which the American +colonists were receiving. The first was entitled "Rules for Reducing a +Great Empire to a Small One," the rules being precisely those which, +in Franklin's opinion, had been followed by the British Government in +its dealings with America. The other was "An Edict by the King of +Prussia," in which the king claimed the right of taxing the British +nation; of forbidding English manufacture, and compelling Englishmen +to purchase Prussian goods; of transporting prisoners to Britain, and +generally of exercising all such controls over the English people as +had been claimed over America by various Acts of the English +Parliament, on the ground that England was originally colonized by +emigrants from Prussia. + +Before Franklin reached America, the War of Independence, though not +formally declared, had fairly begun. He was appointed a member of the +second Continental Congress, and one of a committee of three to confer +with General Washington respecting the support and regulation of the +Continental Army. This latter office necessitated his spending some +time in the camp. On October 3, 1775, he wrote to Priestley:-- + + Tell our dear good friend, Dr. Price, who sometimes has his + doubts and despondencies about our firmness, that America is + determined and unanimous; a very few Tories and placemen + excepted, who will probably soon export themselves. Britain, at + the expense of three millions, has killed a hundred and fifty + Yankees this campaign, which is £20,000 a head; and at Bunker's + Hill she gained a mile of ground, half of which she lost again + by our taking the post on Ploughed Hill. During the same time + sixty thousand children have been born in America. From these + _data_ his mathematical head will easily calculate the time and + expense necessary to kill us all and conquer our whole + territory. + +In 1776 Franklin, then seventy years old, was appointed one of three +Commissioners to visit Canada, in order, if possible, to promote a +union between it and the States. Finding that only one Canadian in +five hundred could read, and that the state of feeling in Canada was +fatal to the success of the Commissioners, they returned, and Franklin +suggested that the next Commission sent to Canada should consist of +schoolmasters. On the 4th of July Franklin took part in the signing of +the Declaration of Independence. When the document was about to be +signed, Mr. Hancock remarked, "We must be unanimous; there must be no +pulling different ways; we must all hang together." Franklin replied, +"Yes, we must indeed all hang together, or most assuredly we shall all +hang separately." + +In the autumn of 1776 Franklin was unanimously chosen a Special +Commissioner to the French Court. He took with him his two grandsons, +William Temple Franklin and Benjamin Franklin Bache, and leaving +Marcus Hook on October 28, crossed the Atlantic in a sloop of sixteen +guns. In Paris he met with an enthusiastic reception. M. de Chaumont +placed at his disposal his house at Passy, then about a mile from +Paris, but now within the city. Here he resided for nine years, being +a constant visitor at the French Court, and certainly one of the most +conspicuous figures in Paris. He was obliged to serve in many +capacities, and was very much burdened with work. Not only were there +his duties as Commissioner at the French Court, but he was also made +Admiralty Judge and Financial Agent, so that all the coupons for the +payment of interest on the money borrowed for the prosecution of the +war, as well as all financial negotiations, either with the French +Government or contractors, had to pass through his hands. Perhaps the +most unpleasant part of his work was his continued applications to the +French Court for monetary advances. The French Government, as is well +known, warmly espoused the cause of the Americans, and to the utmost +of its ability assisted them with money, material, and men. Franklin +was worried a good deal by applications from French officers for +introductions to General Washington, that they might obtain employment +in the American Army. At last he framed a model letter of +recommendation, which may be useful to many in this country in the +present day. It was as follows:-- + + SIR, + + The bearer of this, who is going to America, presses me to give + him a letter of recommendation, though I know nothing of him, + not even his name. This may seem extraordinary, but I assure you + it is not uncommon here. Sometimes, indeed, one unknown person + brings another equally unknown, to recommend him; and sometimes + they recommend one another! As to this gentleman, I must refer + you to himself for his character and merits, with which he is + certainly better acquainted than I can possibly be. I recommend + him, however, to those civilities which every stranger, of whom + one knows no harm, has a right to; and I request you will do him + all the good offices and show him all the favour that, on + further acquaintance, you shall find him to deserve. + + "I have the honour to be," etc. + +Captain Wickes, of the _Refusal_, having taken about a hundred British +seamen prisoners, Franklin and Silas Deane, one of the other +Commissioners, wrote to Lord Stormont, the British ambassador, +respecting an exchange. Receiving no answer, they wrote again, and +ventured to complain of the treatment which the American prisoners +were receiving in the English prisons, and in being compelled to fight +against their own countrymen. To this communication Lord Stormont +replied:-- + + The king's ambassador receives no applications from rebels, + unless they come to implore his Majesty's mercy. + +To this the Commissioners rejoined:-- + + In answer to a letter, which concerns some of the most material + interests of humanity, and of the two nations, Great Britain and + the United States of America, now at war, we received the + enclosed _indecent_ paper, as coming from your Lordship, which + we return for your Lordship's more mature consideration. + +At first the British Government, regarding the Americans as rebels, +did not treat their prisoners as prisoners of war, but threatened to +try them for high treason. Their sufferings in the English prisons +were very great. Mr. David Hartley did much to relieve them, and +Franklin transmitted money for the purpose. When a treaty had been +formed between France and the States, and France had engaged in the +war, and when fortune began to turn in favour of the united armies, +the American prisoners received better treatment from the English +Government, and exchanges took place freely. In April, 1778, Mr. +Hartley visited Franklin at Passy, apparently for the purpose of +preventing, if possible, the offensive and defensive alliance between +America and France. Very many attempts were made to produce a rupture +between the French Government and the American Commissioners, but +Franklin insisted that no treaty of peace could be made between +England and America in which France was not included. In 1779 the +other Commissioners were recalled, and Franklin was made Minister +Plenipotentiary to the Court of France. + +In a letter to Mr. David Hartley, dated February 2, 1780, Franklin +showed something of the feelings of the Americans with respect to the +English at that time:-- + + You may have heard that accounts upon oath have been taken in + America, by order of Congress, of the British barbarities + committed there. It is expected of me to make a school-book of + them, and to have thirty-five prints designed here by good + artists, and engraved, each expressing one or more of the horrid + facts, in order to impress the minds of children and posterity + with a deep sense of your bloody and insatiable malice and + wickedness. Every kindness I hear of done by an Englishman to an + American prisoner makes me resolve not to proceed in the work. + +While at Passy, Franklin addressed to the _Journal of Paris_ a paper +on an economical project for diminishing the cost of light. The +proposal was to utilize the sunlight instead of candles, and thereby +save to the city of Paris the sum of 96,075,000 livres per annum. His +reputation in Paris is shown by the following quotation from a +contemporary writer:-- + + I do not often speak of Mr. Franklin, because the gazettes tell + you enough of him. However, I will say to you that our Parisians + are no more sensible in their attentions to him than they were + towards Voltaire, of whom they have not spoken since the day + following his death. Mr. Franklin is besieged, followed, + admired, adored, wherever he shows himself, with a fury, a + fanaticism, capable no doubt of flattering him and of doing him + honour, but which at the same time proves that we shall never be + reasonable, and that the virtues and better qualities of our + nation will always be balanced by a levity, an inconsequence, + and an enthusiasm too excessive to be durable. + +Franklin always advocated free trade, even in time of war. He was of +opinion that the merchant, the agriculturist, and the fisherman were +benefactors to mankind. He condemned privateering in every form, and +endeavoured to bring about an agreement between all the civilized +powers against the fitting out of privateers. He held that no +merchantmen should be interfered with unless carrying war material. He +greatly lamented the horrors of the war, but preferred anything to a +dishonourable peace. To Priestley he wrote:-- + + Perhaps as you grow older you may ... repent of having murdered + in mephitic air so many honest, harmless mice, and wish that, to + prevent mischief, you had used boys and girls instead of them. + In what light we are viewed by superior beings may be gathered + from a piece of late West India news, which possibly has not yet + reached you. A young angel of distinction, being sent down to + this world on some business for the first time, had an old + courier-spirit assigned him as a guide. They arrived over the + seas of Martinico, in the middle of the long day of obstinate + fight between the fleets of Rodney and De Grasse. When, through + the clouds of smoke, he saw the fire of the guns, the decks + covered with mangled limbs and bodies dead or dying; the ships + sinking, burning, or blown into the air; and the quantity of + pain, misery, and destruction the crews yet alive were thus with + so much eagerness dealing round to one another,--he turned + angrily to his guide, and said, 'You blundering blockhead, you + are ignorant of your business; you undertook to conduct me to + the earth, and you have brought me into hell!' 'No, sir,' says + the guide, 'I have made no mistake; this is really the earth, + and these are men. Devils never treat one another in this cruel + manner; they have more sense and more of what men (vainly) call + humanity.' + +Franklin maintained that it would be far cheaper for a nation to +extend its possessions by purchase from other nations than to pay the +cost of war for the sake of conquest. + +Two British armies, under General Burgoyne and Lord Cornwallis, having +been wholly taken prisoners during the war, at last, after two years' +negotiations, a definitive treaty of peace was signed on September 3, +1782, between Great Britain and the United States, Franklin being one +of the Commissioners for the latter, and Mr. Hartley for the former. +On the same day a treaty of peace between Great Britain and France was +signed at Versailles. The United States Treaty was ratified by the +king on April 9, and therewith terminated the seven years' War of +Independence. Franklin celebrated the surrender of the armies of +Burgoyne and Cornwallis by a medal, on which the infant Hercules +appears strangling two serpents. + +When peace was at length realized, a scheme was proposed for an +hereditary knighthood of the order of Cincinnatus, to be bestowed upon +the American officers who had distinguished themselves in the war. +Franklin condemned the hereditary principle. He pointed out that, in +the ninth generation, the "young noble" would be only "one five +hundred and twelfth part of the present knight," 1022 men and women +being counted among his ancestors, reckoning only from the foundation +of the knighthood. "Posterity will have much reason to boast of the +noble blood of the then existing set of Chevaliers of Cincinnatus." + +On May 2, 1785, Franklin received from Congress permission to return +to America. He was then in his eightieth year. On July 12 he left +Passy for Havre, whence he crossed to Southampton, and there saw for +the last time his old friend, the Bishop of St. Asaph, and his family. +He reached his home in Philadelphia early in September, and the day +after his arrival he received a congratulatory address from the +Assembly of Pennsylvania. In the following month he was elected +President of the State, and was twice re-elected to the same office, +it being contrary to the constitution for any president to be elected +for more than three years in succession. + +The following extract from a letter, written most probably to Tom +Paine, is worthy of the attention of some writers:-- + + I have read your manuscript with some attention. By the argument + it contains against a particular Providence, though you allow a + general Providence, you strike at the foundations of all + religion. For without the belief of a Providence that takes + cognizance of, guards, and guides, and may favour particular + persons, there is no motive to worship a Deity, to fear His + displeasure, or to pray for His protection. I will not enter + into any discussion of your principles, though you seem to + desire it. At present I shall only give you my opinion, that, + though your reasonings are subtle, and may prevail with some + readers, you will not succeed so as to change the general + sentiments of mankind on that subject, and the consequence of + printing this piece will be a great deal of odium drawn upon + yourself, mischief to you, and no benefit to others. He that + spits against the wind spits in his own face. + + But were you to succeed, do you imagine any good would be done + by it? You yourself may find it easy to live a virtuous life + without the assistance afforded by religion; you having a clear + perception of the advantages of virtue and the disadvantages of + vice, and possessing strength of resolution sufficient to enable + you to resist common temptations. But think how great a portion + of mankind consists of weak and ignorant men and women, and of + inexperienced, inconsiderate youth of both sexes, who have need + of the motives of religion to restrain them from vice, to + support their virtue, and retain them in the practice of it till + it becomes _habitual_, which is the great point for its + security. And perhaps you are indebted to her originally, that + is, to your religious education, for the habits of virtue upon + which you now justly value yourself. You might easily display + your excellent talents of reasoning upon a less hazardous + subject, and thereby obtain a rank with our most distinguished + authors. For among us it is not necessary, as among the + Hottentots, that a youth, to be raised into the company of men, + should prove his manhood by beating his mother. + + I would advise you, therefore, not to attempt unchaining the + tiger, but to burn this piece before it is seen by any other + person; whereby you will save yourself a great deal of + mortification by the enemies it may raise against you, and + perhaps a good deal of regret and repentance. If men are so + wicked _with religion_, what would they be _if without_ it? I + intend this letter itself as a _proof_ of my friendship, and + therefore add no _professions_ to it; but subscribe simply + yours. + +During the last few years of his life Franklin suffered from a painful +disease, which confined him to his bed and seriously interfered with +his literary work, preventing him from completing his biography. +During this time he was cared for by his daughter, Mrs. Bache, who +resided in the same house with him. He died on April 17, 1790, the +immediate cause of death being an affection of the lungs. He was +buried beside his wife in the cemetery of Christ Church, Philadelphia, +the marble slab upon the grave bearing no other inscription than the +name and date of death. In his early days (1728) he had written the +following epitaph for himself:-- + + THE BODY + + OF + + BENJAMIN FRANKLIN, + + PRINTER, + + (LIKE THE COVER OF AN OLD BOOK, + ITS CONTENTS TORN OUT + AND STRIPT OF ITS LETTERING AND GILDING,) + LIES HERE, FOOD FOR WORMS. + BUT THE WORK SHALL NOT BE LOST, + FOR IT WILL (AS HE BELIEVED) APPEAR ONCE MORE + IN A NEW AND MORE ELEGANT EDITION, + REVISED AND CORRECTED + BY + + THE AUTHOR. + +When the news of his death reached the National Assembly of France, +Mirabeau rose and said:-- + +"Franklin is dead! + +"The genius, which gave freedom to America, and scattered torrents of +light upon Europe, is returned to the bosom of the Divinity. + +"The sage, whom two worlds claim; the man, disputed by the history of +the sciences and the history of empires, holds, most undoubtedly, an +elevated rank among the human species. + +"Political cabinets have but too long notified the death of those who +were never great but in their funeral orations; the etiquette of +courts has but too long sanctioned hypocritical grief. Nations ought +only to mourn for their benefactors; the representatives of free men +ought never to recommend any other than the heroes of humanity to +their homage. + +"The Congress hath ordered a general mourning for one month throughout +the fourteen confederated States on account of the death of Franklin; +and America hath thus acquitted her tribute of admiration in behalf of +one of the fathers of her constitution. + +"Would it not be worthy of you, fellow-legislators, to unite +yourselves in this religious act, to participate in this homage +rendered in the face of the universe to the rights of man, and to the +philosopher who has so eminently propagated the conquest of them +throughout the world? + +"Antiquity would have elevated altars to that mortal who, for the +advantage of the human race, embracing both heaven and earth in his +vast and extensive mind, knew how to subdue thunder and tyranny. + +"Enlightened and free, Europe at least owes its remembrance and its +regret to one of the greatest men who has ever served the cause of +philosophy and liberty. + +"I propose, therefore, that a decree do now pass, enacting that the +National Assembly shall wear mourning during three days for Benjamin +Franklin." + + + + +HENRY CAVENDISH. + + +It would not be easy to mention two men between whom there was a +greater contrast, both in respect of their characters and lives, than +that which existed between Benjamin Franklin and the Honourable Henry +Cavendish. The former of humble birth, but of great public spirit, +possessed social qualities which were on a par with his scientific +attainments, and toward the close of his life was more renowned as a +statesman than as a philosopher; the latter, a member of one of the +most noble families of England, and possessed of wealth far exceeding +his own capacity for the enjoyment of it, was known to very few, was +intimate with no one, and devoted himself to scientific pursuits +rather for the sake of the satisfaction which his results afforded to +himself than from any hope that they might be useful to mankind, or +from any desire to secure a reputation by making them known, and +passed a long life, the most uneventful that can be imagined. + +Though the records of his family may be traced to the Norman +Conquest, the famous Elizabeth Hardwicke, the foundress of two ducal +families and the builder of Hardwicke Hall and of Chatsworth as it was +before the erection of the present mansion, was the most remarkable +person in the genealogy. Her second son, William, was raised to the +peerage by James I., thus becoming Baron Cavendish, and was +subsequently created first Earl of Devonshire by the same monarch. His +great-grandson, the fourth earl, was created first Duke of Devonshire +by William III., to whom he had rendered valuable services. He was +succeeded by his eldest son in 1707, and the third son of the second +duke was Lord Charles Cavendish, the father of Henry and Frederick, of +whom Henry was the elder, having been born at Nice, October 13, 1731. +His mother died when he was two years old, and very little indeed is +known respecting his early life. In 1742 he entered Dr. Newcome's +school at Hackney, where he remained until he entered Peterhouse, in +1749. He remained at Cambridge until February, 1753, when he left the +university without taking his degree, objecting, most probably, to the +religious tests which were then required of all graduates. In this +respect his brother Frederick followed his example. On leaving +Cambridge Cavendish appears to have resided with his father in +Marlborough Street, and to have occasionally assisted him in his +scientific experiments, but the investigations of the son soon +eclipsed those of the father. It is said that the rooms allotted to +Henry Cavendish "were a set of stables, fitted up for his +accommodation," and here he carried out many of his experiments, +including all those electrical investigations in which he forestalled +so much of the work of the present century. + +During his father's life, or, at any rate, till within a few years of +its close, Henry Cavendish appears to have enjoyed a very narrow +income. He frequently dined at the Royal Society Club, and on these +occasions would come provided with the five shillings to be paid for +the dinner, but no more. Upon his father's death, which took place in +1783, when Henry was more than fifty years of age, his circumstances +were very much changed, but it seems that the greater part of his +wealth was left him by an uncle who had been an Indian officer, and +this legacy may have come into his possession before his father's +death. He appears to have been very liberal when it was suggested to +him that his assistance would be of service, but it never occurred to +him to offer a contribution towards any scientific or public +undertaking, and though at the time of his death he is said to have +had more money in the funds than any other person in the country, +besides a balance of £50,000 on his current account at his bank, and +various other property, he bequeathed none to scientific societies or +similar institutions. Throughout the latter part of his life he seems +to have been quite careless about money, and to have been satisfied if +he could only avoid the trouble of attending to his own financial +affairs. Hence he would allow enormous sums to accumulate at his +banker's, and on one occasion, being present at a christening, and +hearing that it was customary for guests to give something to the +nurse, he drew from his pocket a handful of guineas, and handed them +to her without counting them. After his father's death, Cavendish +resided in his own house on Clapham Common. Here a few rooms at the +top of the house were made habitable; the rest were filled with +apparatus of all descriptions, among which the most numerous examples +were thermometers of every kind. He seldom entertained visitors, but +when, on rare occasions, a guest had to be entertained, the repast +invariably consisted of a leg of mutton. His extreme shyness caused +him to dislike all kinds of company, and he had a special aversion to +being addressed by a stranger. On one occasion, at a reception given +by Sir Joseph Banks, Dr. Ingenhousz introduced to him a distinguished +Austrian philosopher, who professed that his main object in coming to +England was to obtain a sight of so distinguished a man. Cavendish +listened with his gaze fixed on the floor; then, observing a gap in +the crowd, he made a rush to the door, nor did he pause till he had +reached his carriage. His aversion to women was still greater; his +orders for the day he would write out and leave at a stated time on +the hall-table, where his house-keeper, at another stated time, would +find them. Servants were allowed access to the portion of the house +which he occupied only at fixed times when he was away; and having +once met a servant on the stairs, a back staircase was immediately +erected. His regular walk was down Nightingale Lane to Wandsworth +Common, and home by another route. On one occasion, as he was crossing +a stile, he saw that he was watched, and thenceforth he took his walks +in the evening, but never along the same road. There were only two +occasions on which it is recorded that scientific men were admitted to +Cavendish's laboratory. The first was in 1775, when Hunter, Priestley, +Romayne, Lane, and Nairne were invited to see the experiments with the +artificial torpedo. The second was when his experiment on the +formation of nitric acid by electric sparks in air had been +unsuccessfully attempted by Van Marum, Lavoisier, and Monge, and he +"thought it right to take some measures to authenticate the truth of +it." + +Besides his house at Clapham, Cavendish occupied (by his instruments) +a house in Bloomsbury, near the British Museum, while a "mansion" in +Dean Street, Soho, was set apart as a library. To this library a +number of persons were admitted, who could take out the books on +depositing a receipt for them. Cavendish was perfectly methodical in +all his actions, and whenever he borrowed one of his own books he duly +left the receipt in its place. The only relief to his solitary life +was afforded by the meetings of the Royal Society, of which he was +elected a Fellow in 1760; by the occasional receptions at the +residence of Sir Joseph Banks, P.R.S.; and by his not infrequent +dinners with the Royal Society Club at the Crown and Anchor; and he +may sometimes have joined the social gatherings of another club which +met at the Cat and Bagpipes, in Downing Street. It was to his visits +to the Royal Society Club that we are indebted for the only portrait +that exists of him. Alexander, the draughtsman to the China Embassy, +was bent upon procuring a portrait of Cavendish, and induced a friend +to invite him to the club dinner, "where he could easily succeed, by +taking his seat near the end of the table, from whence he could sketch +the peculiar great-coat of a greyish-green colour, and the remarkable +three-cornered hat, invariably worn by Cavendish, and obtain, +unobserved, such an outline of the face as, when inserted between the +hat and coat, would make, he was quite sure, a full-length portrait +that no one could mistake. It was so contrived, and every one who saw +it recognized it at once." Another incident is recorded of the Royal +Society Club which, perhaps, reflects as much credit upon Cavendish as +upon the Society. "One evening we observed a very pretty girl looking +out from an upper window on the opposite side of the street, watching +the philosophers at dinner. She attracted notice, and one by one we +got up and mustered round the window to admire the fair one. +Cavendish, who thought we were looking at the moon, hustled up to us +in his odd way, and when he saw the real object of our study, turned +away with intense disgust, and grunted out, 'Pshaw!'" + +In the spring and autumn of 1785, 1786, 1787, and 1793, Cavendish made +tours through most of the southern, midland, and western counties, and +reached as far north as Whitby. The most memorable of these journeys +was that undertaken in 1785, since during its course he visited James +Watt at the Soho Works, and manifested great interest in Watt's +inventions. This was only two years after the great controversy as to +the discovery of the composition of water, but the meeting of the +philosophers was of the most friendly character. On all these journeys +considerable attention was paid to the geology of the country. + +Allusion has already been made to the two committees of the Royal +Society to which the questions of the lightning-conductors at +Purfleet, and of points _versus_ knobs for the terminals of +conductors, were referred. Cavendish served on each of these +committees, and supported Franklin's view against the recommendation +of Mr. Wilson. On the first committee he probably came into personal +communication with Franklin himself. + +Cavendish's life consisted almost entirely of his philosophical +experiments. In other respects it was nearly without incident. He +appears to have been so constituted that he must subject everything to +accurate measurement. He rarely made experiments which were not +_quantitative_; and he may be regarded as the founder of "quantitative +philosophy." The labour which he expended over some of his +measurements must have been very great, and the accuracy of many of +his results is marvellous considering the appliances he had at +disposal. When he had satisfied himself with the result of an +experiment, he wrote out a full account and preserved it, but very +seldom gave it to the public, and when he did publish accounts of any +of his investigations it was usually a long time after the experiments +had been completed. One of the consequences of his reluctance to +publish anything was the long controversy on the discovery of the +composition of water, which was revived many years afterwards by +Arago's _éloge_ on James Watt; but a much more serious result was the +loss to the world for so many years of discoveries and measurements +which had to be made over again by Faraday, Kohlrausch, and others. +The papers he published appeared in the _Philosophical Transactions of +the Royal Society_, to which he began to communicate them in 1766. On +March 25, 1803, he was elected one of the eight Foreign Associates of +the Institute of France. His _éloge_ was pronounced by Cuvier, in +1812, who said, "His demeanour and the modest tone of his writings +procured him the uncommon distinction of never having his repose +disturbed either by jealousy or by criticism." Dr. Wilson says, "He +was almost passionless. All that needed for its apprehension more than +the pure intellect, or required the exercise of fancy, imagination, +affection, or faith, was distasteful to Cavendish. An intellectual +head thinking, a pair of wonderfully acute eyes observing, and a pair +of very skilful hands experimenting or recording, are all that I +realize in reading his memorials." He appeared to have no eye for +beauty; he cared nothing for natural scenery, and his apparatus, +provided it were efficient, might be clumsy in appearance and of the +cheapest materials; but he was extremely particular about accuracy of +construction in all essential details. He reminds us of one of our +foremost men of science, who, when his attention was directed to the +beautiful lantern tower of a cathedral, behind which the full moon was +shining, remarked, "I see form and colour, but I don't know what you +mean by beauty." + +The accounts of Cavendish's death differ to some extent in their +details, but otherwise are very similar. It appears that he requested +his servant, "as he had something particular to engage his thoughts, +and did not wish to be disturbed by any one," to leave him and not to +return until a certain hour. When the servant came back, at the time +appointed, he found his master dead. This was on February 24, 1810, +after an illness of only two or three days. + +It is mainly on account of his researches in electricity that the +biography of Cavendish finds a place in this volume. These +investigations took place between the years 1760 and 1783, and, as +already stated, were all conducted in the stables attached to his +father's house in Marlborough Street. It was by these experiments that +electricity was first brought within the domain of measurement, and +many of the numerical results obtained far exceeded in accuracy those +of any other observer until the instruments of Sir W. Thomson rendered +many electrical measurements a comparatively easy matter. The near +agreement of Cavendish's results with those of the best modern +electricians has made them a perpetual monument to the genius of their +author. It was at the request of Sir W. Thomson, Mr. Charles +Tomlinson, and others, that Cavendish's electrical researches might be +given to the public, that the Duke of Devonshire, in 1874, entrusted +the manuscripts to the care of the late Professor Clerk Maxwell. They +had previously been in the hands of Sir William Snow Harris, who +reported upon them, but after his death, in 1867, the report could not +be found. The papers, with an introduction and a number of very +valuable notes by the editor, were published by the Cambridge +University Press, just before the death of Clerk Maxwell, in 1879. Sir +W. Thomson quotes the following illustration of the accuracy of +Cavendish's work:--"I find already that the capacity of a disc was +determined experimentally by Cavendish as 1/1·57 of that of a sphere +of the same radius. Now we have capacity of disc = (2/[pi])_a_ = +_a_/1·571!" + +Cavendish adopted Franklin's theory of electricity, treating it as an +incompressible fluid pervading all bodies, and admitting of +displacement only in a closed circuit, unless, indeed, the disturbance +might extend to infinity. This fluid he supposed, with Franklin, to be +self-repulsive, but to attract matter, while matter devoid of +electricity, and therefore in the highest possible condition of +negative electrification, he supposed, with Æpinus, to be, like +electricity, self-repulsive. One of Cavendish's earliest experiments +was the determination of the precise law according to which electrical +action varies with the distance between the charges. Franklin had +shown that there was no sensible amount of electricity on the interior +of a deep hollow vessel, however its exterior surface might be +charged. Cavendish mounted a sphere of 12·1 inches in diameter, so +that it could be completely enclosed (except where its insulating +support passed through) within two hemispheres of 13·3 inches +diameter, which were carried by hinged frames, and could thus be +allowed to close completely over the sphere, or opened and removed +altogether from its neighbourhood. A piece of wire passed through one +of the hemispheres so as to touch the inner sphere, but could be +removed at pleasure by means of a silk string. The hemispheres being +closed with the globe within them, and the wire inserted so as to make +communication between the inner and outer spheres, the whole apparatus +was electrified by a wire from a charged Leyden jar. This wire was +then removed by means of a silken string and "the same motion of the +hand which drew away the wire by which the hemispheres were +electrified, immediately after that was done, drew out the wire which +made the communication between the hemispheres and the inner globe, +and, immediately after that was drawn out, separated the hemispheres +from each other," and applied the electrometer to the inner globe. "It +was also contrived so that the electricity of the hemispheres and of +the wire by which they were electrified was discharged as soon as they +were separated from each other.... The inner globe and hemispheres +were also both coated with tinfoil to make them the more perfect +conductors of electricity." The electrometer consisted of a pair of +pith-balls; but, though the experiment was several times repeated, +they shewed no signs of electrification. From this it was clear that, +as there could have been no communication between the globe and +hemispheres when the connecting wire was withdrawn, there must have +been no electrification on the globe while the hemispheres, though +themselves highly charged, surrounded it. To test the delicacy of the +experiment, a charge was given to the globe less than one-sixtieth of +that previously given to the hemispheres, and this was readily +detected by the electrometer. From the result Cavendish inferred that +there is no reason to think the inner globe to be at all charged +during the experiment. "Hence it follows that the electric attraction +and repulsion must be inversely as the square of the distance, and +that, when a globe is positively electrified, the redundant fluid in +it is lodged entirely on its surface." This conclusion Cavendish +showed to be a mathematical consequence of the absence of +electrification from the inner sphere; for, were the law otherwise, +the inner sphere must be electrified positively or negatively, +according as the inverse power were higher or lower than the second, +and that the accuracy of the experiment showed the law must lie +between the 2-1/50 and the 1-49/50 power of the distance. With his +torsion-balance, Coulomb obtained the same law, but Cavendish's method +is much easier to carry out, and admits of much greater accuracy than +that of Coulomb. Cavendish's experiment was repeated by Dr. +MacAlister, under the superintendence of Clerk Maxwell, in the +Cavendish Laboratory, the absence of electrification being tested by +Thomson's quadrant electrometer, and it was shown that the deviation +from the law of inverse squares could not exceed one in 72,000. + +The distinction between _electrical charge_ or _quantity of +electricity_ and "_degree of electrification_" was first clearly made +by Cavendish. The latter phrase was subsequently replaced by +_intensity_, but _electric intensity_ is now used in another sense. +Cavendish's phrase, _degree of electrification_, corresponds precisely +with our notion of electric _potential_, and is measured by the work +done on a unit of electricity by the electric forces in removing it +from the point in question to the earth or to infinity. Along with +this notion Cavendish introduced the further conception of the amount +of electricity required to raise a conductor to a given degree of +electrification, that is, the capacity of the conductor. In modern +language, the _capacity_ of a conductor is defined as "the number of +units of electricity required to raise it to unit potential;" and this +definition is in precise accordance with the notion of Cavendish, who +may be regarded as the founder of the mathematical theory of +electricity. Finding that the capacities of similar conductors are +proportional to their linear dimensions, he adopted a sphere of one +inch diameter as the unit of capacity, and when he speaks of a +capacity of so many "inches of electricity," he means a capacity so +many times that of his one-inch sphere, or equal to that of a sphere +whose diameter is so many inches. The modern unit of capacity in the +electro-static system is that of a sphere of _one centimetre radius_, +and the capacity of any sphere is numerically equal to its radius +expressed in centimetres. Cavendish determined the capacities of +nearly all the pieces of apparatus he employed. For this purpose he +prepared plates of glass, coated on each side with circles of tinfoil, +and arranged in three sets of three, each plate of a set having the +same capacity, but each set having three times the capacity of the +preceding. There was also a tenth plate, having a capacity equal to +the whole of the largest set. The capacity of the ten plates was thus +sixty-six times that of one of the smallest set. With these as +standards of comparison, he measured the capacities of his other +apparatus, and, when possible, modified his conductors so as to make +them equal to one of his standards. His large Leyden battery he found +to have a capacity of about 321,000 "inches of electricity," so that +it was equivalent to a sphere more than five miles in diameter. One of +his instruments employed in the measurement of capacities was a "trial +plate," consisting of a sheet of metal, with a second sheet which +could be made to slide upon it and to lie entirely on the top of the +larger plate, or to rest with any portion of its area extending over +the edge of the former. This was a conductor whose capacity could be +varied at will within certain limits. Finding the capacity of two +plates of tinfoil on glass much greater than his calculations led him +to expect, Cavendish compared them with two equal plates having air +between, and found their capacity very much to exceed that of the air +condenser. The same was the case, though in a less degree, with +condensers having shellac or bee's-wax for their dielectrics, and thus +Cavendish not only discovered the property to which Faraday afterwards +gave the name of "specific inductive capacity," but determined its +measure in these dielectrics. He also discovered that the apparent +capacity of a Leyden jar increases at first for some time after it has +been charged--a phenomenon connected with the so-called residual +charge of the Leyden jar. Another feature on which he laid some +stress, and which was brought to his notice by the comparison of his +coated panes, was the creeping of electricity over the surface of the +glass beyond the edge of the tinfoil, which had the same effect on the +capacity as an increase in the dimensions of the tinfoil. The +electricity appeared to spread to a distance of 0·07 inch all round +the tinfoil on glass plates whose thickness was 0·21 inch, and 0·09 +inch in the case of plates 0·08 inch thick. + +His paper on the torpedo was read before the Royal Society in 1776. +The experiments were undertaken in order to determine whether the +phenomena observed by Mr. John Walsh in connection with the torpedo +could be so far imitated by electricity as to justify the conclusion +that the shock of the torpedo is an electric discharge. For this +purpose Cavendish constructed a wooden torpedo with electrical organs, +consisting of a pewter plate on each side, covered with leather. The +plates were connected with a charged Leyden battery, by means of wires +carried in glass tubes, and thus the battery was discharged through +the water in which the torpedo was immersed, and which was rendered of +about the same degree of saltness as the sea. Cavendish compared the +shock given through the water with that given by the model fish in +air, and found the difference much greater than in the case of the +real torpedo, but, by increasing the capacity of the battery and +diminishing the potential to which it was charged, this discrepancy +was diminished, and it was found to be very much less in the case of a +second model having a leather, instead of a wooden, body, so that the +body of the fish itself offered less resistance to the discharge. One +of the chief difficulties lay in the fact that no one had succeeded in +obtaining a visible spark from the discharge of the torpedo, which +will not pass through the smallest thickness of air. Cavendish +accounted for this by supposing the quantity of electricity discharged +to be very great, and its potential very small, and showed that the +more the charge was increased and the potential diminished in his +model, the more closely did it imitate the behaviour of the torpedo. + +But the main interest in this paper lies in the indications which it +gives that Cavendish was aware of the laws which regulate the flow of +electricity through multiple conductors, and in the comparisons of +electrical resistance which are introduced. It had been formerly +believed that electricity would always select the shortest or best +path, and that the whole of the discharge would take place along that +route. Franklin seems to have assumed this in the passage quoted[4] +respecting the discharge of the lightning down the uninsulated +conductor instead of through the building. The truth, however, is +that, when a number of paths are open to an electric current, it will +divide itself between them in the inverse ratios of their resistances, +or directly as their conductivities, so that, however great the +resistance of one of the conductors, some portion, though it may be a +very small fraction, of the discharge will take place through it. But +this law does not hold in the case of insulators like the air, through +which electricity passes only by disruptive discharges, and which +completely prevent its passage unless the electro-motive force is +sufficient to break through their substance. In the case of the +lightning-conductor, however, its resistance is generally so small in +comparison with that of the building it is used to protect, that +Franklin's conclusion is practically correct. + +[Footnote 4: Page 96.] + +In his paper on the torpedo Cavendish stated that some experiments had +shown that iron wire conducted 400,000,000 times better than rain or +distilled water, sea-water 100 times, and saturated solution of +sea-salt about 720 times, better than rain-water. Maxwell pointed out +that this comparison of iron wire with sea-water would agree almost +precisely with the measurements of Matthiesen and Kohlrausch at 11°C. +The records of the experiments which led to these results were found +among Cavendish's unpublished papers, and the experiments also showed +that the conductivity of saline solutions was very nearly proportional +to the percentage of salt contained, when this was not very large--a +result also obtained long afterwards by Kohlrausch. In making these +measurements Cavendish was his own galvanometer. The solutions were +contained in glass tubes more than three feet long, and a wire +inserted to different distances into the solution; thus the discharge +could be made to pass through any length of the liquid column less +than that of the tube itself. From the Leyden battery of forty-nine +jars, six jars of nearly equal capacity were selected and charged +together, and the charge of one jar only was employed for each shock. +The discharge passed through the column of liquid contained in the +tube, from a wire inserted at the further end, until it reached the +sliding wire, when nearly the whole current betook itself to the wire +on account of its smaller resistance, and thence passed through the +galvanometer, which was Cavendish himself. Two tubes were generally +compared together, and the jars discharged alternately through the +tubes, and the tube which gave the greatest shock was assumed to +possess the least resistance. The wires were then adjusted till the +shocks were nearly equal, and positions determined which made the +first tube possess a greater and then a less resistance than the +second. From these positions the length of the column of liquid was +estimated which would make the resistances of the two tubes exactly +equal. But the result which has the greatest theoretical interest was +obtained by discharging the Leyden jars through wide and narrow tubes +containing the same solutions. By these experiments Cavendish found +that the resistances of the conductors were independent of the +strengths of the currents flowing in them; that is to say, he +established Ohm's law for electrolytes in a form which carried with it +its full explanation. This was in January, 1781. Ohm's law was first +formally stated in 1827. The physical fact which is expressed by it is +that the ratio of the electro-motive force to the current produced is +the same for the same conductor, otherwise under the same physical +conditions, however great or small that electro-motive force may be. + +Cavendish devoted considerable attention to the subject of heat, +especially thermometry. In many of his investigations on latent and +specific heat he worked on the same lines as Black, and at about the +same time; but it is difficult to determine the exact date of some of +Cavendish's work, as he frequently did not publish it for a long time +after its completion, and most of Black's results were made public +only to his lecture audience. Cavendish, however, improved upon Black +in his mode of stating some of his results. The heat, for instance, +which is absorbed by a body in passing from the solid to the liquid, +or from the liquid to the gaseous, condition, Black called "latent +heat," and supposed it to become latent within the substance, ready to +reveal itself when the body returned to its original condition. This +heat Cavendish spoke of as being _destroyed_ or _generated_, and this +is in accordance with what we now know respecting the nature of heat, +for when a body passes from the solid to the liquid, or from the +liquid or solid to the gaseous, condition, a certain amount of work +has to be done, and a corresponding amount of heat is used up in the +doing of it. When the body returns to its original condition, the heat +is restored, as when a heavy body falls to the ground, or a bent +spring returns to its original form. Cavendish's determination of the +so-called latent heat of steam was very slightly in error. + +About 1760 very extraordinary beliefs were current respecting the +excessive degree of cold and the rapid variations of temperature which +take place in the Arctic regions. Braun, of St. Petersburg, had +observed that mercury, in solidifying in the tube of a thermometer, +descended through more than four hundred degrees, and it was assumed +that the melting point of mercury was about 400° below Fahrenheit's +zero. It then became necessary to suppose that, while the mercury in a +thermometer was freezing, there was a variation of temperature to this +extent, and thus these wild reports became current. Cavendish and +Black independently explained the anomaly, and each suggested the same +method of determining the freezing point of mercury. Cavendish, +however, had a piece of apparatus prepared which he sent to Governor +Hutchins, at Albany Fort, Hudson's Bay. It consisted of an outer +vessel, in which the mercury was allowed to freeze, but not throughout +the whole of its mass, and the bulb of the thermometer was kept +immersed in the liquid metal in the interior. In this way the mercury +in the thermometer was cooled down to the melting point without +commencing to solidify, and the temperature was found to be between +39° and 40° below Fahrenheit's zero. + +As a chemist, Cavendish is renowned for his eudiometric analysis, +whereby he determined the percentage of oxygen in air with an amount +of accuracy that would be creditable to a chemist of to-day, and for +his discovery of the composition of water; but to the world generally +he is perhaps best known by the famous "Cavendish experiment" for +determining the mass, and hence the mean density, of the earth. The +apparatus was originally suggested by the Rev. John Michell, but was +first employed by Cavendish, who thereby determined the mean density +of the earth to be 5·45. At the request of the Astronomical Society, +the investigation was afterwards taken up by Mr. Francis Baily, who, +after much labour, discovered that the principal sources of error were +due to radiation of heat, and consequent variation of temperature of +parts of the apparatus during the experiment. To minimize the +radiation and absorption, he gilded the principal portions of the +apparatus and the interior of the case in which it was contained, and +his results then became consistent. Cavendish had himself suggested +the cause of the discrepancy, but the gilding was proposed by +Principal Forbes. As a mean of many hundreds of experiments, Mr. Baily +deduced for the mean density of the earth 5·6604. Cavendish's +apparatus was a delicate torsion-balance, whereby two leaden balls +were supported upon the extremities of a wooden rod, which was +suspended by a thin wire. These balls were about two inches in +diameter, and the experiment consisted in determining the deflection +of the wooden arm by the attraction of two large solid spheres of lead +brought very near the balls, and so situated that the attraction of +each tended to twist the rod horizontally in the same direction. The +force required to produce the observed deflection was calculated from +the time of swing of the rod and balls when left to themselves. The +force exerted upon either ball by a known spherical mass of metal, +with its centre at a known distance, being thus determined, it was +easy to calculate what mass, having its centre at the centre of the +earth, would be required to attract one of the balls with the force +with which the earth was known to attract it. + +Dr. Wilson sums up Cavendish's view of life in these words:-- + + His theory of the universe seems to have been that it consisted + _solely_ of a multitude of objects which could be weighed, + numbered, and measured; and the vocation to which he considered + himself called was to weigh, number, and measure as many of + these objects as his allotted three score years and ten would + permit. This conviction biased all his doings--alike his great + scientific enterprises and the petty details of his daily life. + [Greek: _Panta metrô, kai arithmô, kai stathmô_], was his motto; + and in the microcosm of his own nature he tried to reflect and + repeat the subjection to inflexible rule and the necessitated + harmony which are the appointed conditions of the macrocosm of + God's universe. + + + + +COUNT RUMFORD. + + +Benjamin Thompson, like Franklin, was a native of Massachusetts, his +ancestors for several generations having been yeomen in that province, +and descendants of the first colonists of the Bay. In the diploma of +arms granted him when he was knighted by George III., he is described +as "son of Benjamin Thompson, late of the province of Massachusetts +Bay, in New England, gent." He was born in the house of his +grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26, +1753. His father died at the age of twenty-six, on November 7, 1754, +leaving the infant Benjamin and his mother to the care of the +grandparents. The widow married Josiah Pierce, junior, in March, 1756, +and with her child, now a boy of three, went to live in a house but a +short distance from her former residence. + +Young Thompson appears to have received a sound elementary education +at the village school. From some remarks made by him in after years +to his friend, M. Pictet, it has been inferred that he did not receive +very kind treatment at the hands of his stepfather. It is clear, +however, that the most affectionate relationships always obtained +between him and his mother, and the latter appears to have had no +cause to complain of the treatment she received from her second +husband, with whom she lived to a very good old age. That Thompson in +early boyhood developed some tendencies which did not meet with ready +sympathy from those around him is, however, equally clear. His +guardians destined him for a farmer, like his ancestors, and his +experiments in mechanics, which took up much of his playtime and in +all probability not a few hours which should have been devoted to less +interesting work, were not regarded as tending towards the end in +view. Hence he was probably looked upon as "indolent, flighty, and +unpromising." Later on he was sent to school in Byfield, and in 1764, +at the age of eleven, "was put under the tuition of Mr. Hill, an able +teacher in Medford, a town adjoining Woburn." At length, his friends +having given up all hope of ever making a farmer of the boy, he was +apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an +importer of British goods and dealer in miscellaneous articles. He +lived with his master, and seems to have done his work in a manner +satisfactory on the whole, but there is evidence that he would, during +business hours, occupy his spare moments with mechanical contrivances, +which he used to hide under the counter, and even ventured +occasionally to practise on his fiddle in the store. He stayed with +Mr. Appleton till the autumn of 1769, and during this time he attended +the ministry of the Rev. Thomas Barnard. This gentleman seems to have +taken great interest in the boy, and to have taught him mathematics, +so that at the age of fifteen he was able "to calculate an eclipse," +and was delighted when the eclipse commenced within six seconds of his +calculated time. Thompson, while an apprentice, showed a great faculty +for drawing and designing, and used to carve devices for his friends +on the handles of their knives or other implements. It was at this +time he constructed an elaborate contrivance to produce perpetual +motion, and on one evening it is said that he walked from Salem to +Woburn, to show it to Loammi Baldwin, who was nine years older than +himself, but his most intimate friend. Like many other devices +designed for the same purpose, it had only one fault--it wouldn't go. + +It was in 1769, while preparing fireworks for the illumination on the +abolition of the Stamp Act, that Thompson was injured by a severe +explosion as he was grinding his materials in a mortar. His note-book +contained many directions for the manufacture of fireworks. + +During Thompson's apprenticeship those questions were agitating the +public mind which finally had their outcome in the War of +Independence. Mr. Appleton was one of those who signed the agreement +refusing to import British goods, and this so affected the trade of +the store that he had no further need for the apprentice. Hence it was +that, in the autumn of 1769, Thompson went to Boston as +apprentice-clerk in a dry goods store, but had to leave after a few +months, through the depression in trade consequent on the +non-importation agreement. + +His note-book, containing the entries made at this time, comprised +several comic sketches very well drawn, and a quantity of business +memoranda which show that he was very systematic in keeping his +accounts. His chief method of earning money, or rather of making up +the "Cr." side of his accounts, was by cutting and cording wood. A +series of entries made in July and August, 1771, show the expense he +incurred in constructing an electrical machine. It is not easy to +determine, from the list of items purchased, the character of the +machine he constructed; but it is interesting to note that the price +in America at that time of nitric acid was _2s. 6d._ per ounce; of +lacquer, _40s._ per pint; of shellac, _5s._ per ounce; brass wire, +_40s._ per pound; and iron wire, _1s. 3d._ per yard. The nature of the +problems which occupied his thoughts during the last year or two of +his business life are apparent in the following letters:-- + + Woburn, August 16, 1769. + + Mr. Loammi Baldwin, + + SIR, + + Please to inform me in what manner fire operates upon clay to + change the colour from the natural colour to red, and from red + to black, etc.; and how it operates upon silver to change it to + blue. + + I am your most humble and obedient servant, + + BENJAMIN THOMPSON + + God save the king. + + + Woburn, August, 1769. + + Mr. Loammi Baldwin, + + SIR, + + Please to give the nature, essence, beginning of existence, and + rise of the wind in general, with the whole theory thereof, so + as to be able to answer all questions relative thereto. + + Yours, + + BENJAMIN THOMPSON. + +This was an extensive request, and the reply was probably not +altogether satisfactory to the inquirer. On the back of the above +letter was written:-- + + Woburn, August 15, 1769. + + SIR, + + There was but few beings (for inhabitants of this world) created + before the airy element was; so it has not been transmitted down + to us how the Great Creator formed the matter thereof. So I + shall leave it till I am asked only the Natural Cause, and why + it blows so many ways in so short a time as it does. + +Thompson appears now to have given up business and commenced the study +of medicine under Dr. Hay, to whom for a year and a half he paid +forty shillings per week for his board. During this time he paid part +of his expenses by keeping school for a few weeks consecutively at +Wilmington and Bradford, and another part was paid by cords of wood. +His business capacity, as well as his dislike of ordinary work, is +shown by some arrangements which he made for getting wood cut and +corded at prices considerably below those at which he was himself paid +for it. His note-book made at this time contains, besides business +entries, several receipts for medicines and descriptions of surgical +operations, in some cases illustrated by sketches. In his work he was +methodical and industrious, and the life of a medical student suited +his genius far better than that of a clerk in a dry goods store. When +teaching at Wilmington he seems to have attracted attention by the +gymnastic performances with which he exercised both himself and his +pupils. While a student with Dr. Hay, he attended some of the +scientific lectures at Harvard College. The pleasure and profit which +he derived from these lectures are sufficiently indicated by the fact +that forty years afterwards he made the college his residuary legatee. + +Thompson won such a reputation as a teacher during the few weeks that +he taught in village schools in the course of his student life, that +he received an invitation from Colonel Timothy Walker to come to +Concord, in New Hampshire, on the Merrimack, and accept a permanent +situation in a higher grade school. It was from this place that he +afterwards took his title, for the early name of Concord was Rumford, +and the name was changed to Concord "to mark the restoration of +harmony after a long period of agitation as to its provincial +jurisdiction and its relation with its neighbours." + +The young schoolmaster of Concord was soon on very intimate terms with +the minister of the town, the Rev. Timothy Walker,[5] a man who was so +much respected that he had thrice been sent to Britain on diplomatic +business. Mr. Walker's daughter had been married to Colonel Rolfe, a +man of wealth and position, and, with the exception of the Governor of +Portsmouth, said to have been the first man in New Hampshire to drive +a curricle and pair of horses. Thompson soon married--or, as he told +Pictet, was married to--the young widow. Whatever may have been +implied by this other way of putting the question, there is no doubt +that Thompson always had the greatest possible respect for his +father-in-law, and ever remembered him with sincere gratitude. The +fortunes of the gallant young schoolmaster now appeared to be made; +when the engagement was settled, the carriage and pair were brought +out again, and the youth was attired in his favourite scarlet as a man +of wealth and position. In this garb he drove to Woburn, and +introduced his future wife to his mother, whose surprise can be better +imagined than described. + +[Footnote 5: Father of the colonel.] + +The exact date of Thompson's marriage is not known. His daughter +Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion +on October 18, 1774. It is needless to say that the engagement to Mrs. +Rolfe terminated the teaching at the school. + +Thompson now had a large estate and ample means to improve it. He gave +much attention to gardening, and sent to England for garden seeds. In +some way he attracted the attention of Governor Wentworth, the +Governor of Portsmouth, who invited him to the Government House, and +was so taken with the former apprentice, medical student, and +schoolmaster, that he gave him at once a commission as major. This +appointment was the cause of the misfortunes which almost +immediately began to overtake him. He incurred the jealousy of his +fellow-officers, over whom he had been appointed, and he failed to +secure the confidence of the civilians of Concord. + +Public feeling in New England was very much excited against the mother +country. Representations were sent to the British Government, but +appeared to be treated with contempt. Very many of these documents +were found, after the war was over, unopened in drawers at the +Colonial Office. British ministers appeared to know little about the +needs of their American dependencies, and relations rapidly became +more and more strained. The patriots appointed committees to watch +over the patriotism of their fellow-townsmen, and thus the freedom of +a free country was inaugurated by an institution bordering in +character very closely upon the Inquisition; and the Committees of +Correspondence and Safety accepted evidence from every spy or +eavesdropper who came before them with reports of suspected persons. +Thompson was accused of "Toryism;" the only definite charge against +him being that he had secured remission of punishment for some +deserters from Boston who had for some time worked upon his estate. He +was summoned before the Committee of Safety, but refused to make any +confession of acts injurious to his country, on the ground that he had +nothing to confess. His whole after-life shows that his sympathies +were very much on the side of monarchy and centralization, but at this +time there appears to have been no evidence that could be brought +against him. The populace, however, stormed his house, and he owed his +safety to the fact that he had received notice of their intentions, +and had made his escape a few hours before. This was in November, +1774. Thompson then took refuge at Woburn, with his mother, but the +popular ill feeling troubled him here, so that his life was one of +great anxiety. + +While at Woburn, his wife and child joined him, and stayed there for +some months. At length he was arrested and confined in the town upon +suspicion of being inimical to the interests of his country. When he +was brought before the Committee of Inquiry, there was no evidence +brought against him. Major Thompson then petitioned to be heard +before the Committee of the Provincial Congress at Washington. This +petition he entrusted to his friend Colonel Baldwin to present. The +petition was referred by the committee to Congress, by whom it was +deferred for the sake of more pressing business. At length he secured +a hearing in his native town, but the result was indecisive, and he +did not obtain the public acquittal that he desired, though the +Committee of Correspondence found that the "said Thompson" had not "in +any one instance shown a disposition unfriendly to American liberty; +but that his general behaviour has evinced the direct contrary; and as +he has now given us the strongest assurances of his good intentions, +we recommend him to the friendship, confidence, and protection of all +good people in this and the neighbouring provinces." This decision, +however, does not appear to have been made public; and Thompson, on +his release, retired to Charlestown, near Boston. When the buildings +of Harvard College were converted into barracks, Major Thompson +assisted in the transfer of the books to Concord. It is said that, +after the battle of Charlestown, Thompson was introduced to General +Washington, and would probably have received a commission under him +but for the opposition of some of the New Hampshire officers. He +afterwards took refuge in Boston, and it does not appear that he ever +again saw his wife or her father. His daughter he did not see again +till 1796, when she was twenty-two years of age. On March 24, 1776, +General Washington obliged the British troops to evacuate Boston; +Thompson was the first official bearer of this intelligence to London. +Of course, his property at Concord was confiscated to the commonwealth +of Massachusetts, and he himself was proscribed in the Alienation Act +of New Hampshire, in 1778. + +When Thompson reached London with the intelligence of the evacuation +of Boston, Lord George Germaine, the Secretary for War, saw that he +could afford much information which would be of value to the +Government. An appointment was soon found for him in the Colonial +Office, and afterwards he was made Secretary of the Province of +Georgia, in which latter capacity, however, he had no duties to +fulfil. Throughout his career in the Colonial Office he remained on +very intimate terms with Lord George Germaine, and generally +breakfasted with him. In July, 1778, he was guest of Lord George at +Stoneland Lodge, and here, in company with Mr. Ball, the Rector of +Withyham, he undertook experiments "to determine the most advantageous +situation for the vent in firearms, and to measure the velocities of +bullets and the recoil under various circumstances." + +The results of these investigations procured for him the friendship of +Sir Joseph Banks, the President of the Royal Society, and Thompson was +not the man to lose opportunities for want of making use of them. In +1779 he was elected a Fellow of the Royal Society, "as a gentleman +well versed in natural knowledge and many branches of polite +learning." In the same year he went for a cruise in the _Victory_ with +Sir Charles Hardy, in order to pursue his experiments on gunpowder +with heavy guns. Here he studied the principles of naval artillery, +and devised a new code of marine signals. In 1780 he was made +Under-Secretary of State for the Northern Department, and in that +capacity had the oversight of the transport and commissariat +arrangements for the British forces. + +On the defeat of Cornwallis, Lord George Germaine and his department +had to bear the brunt of Parliamentary dissatisfaction. Lord George +resigned his position in the Government, and was created Viscount +Sackville. He had, however, previously conferred on Thompson a +commission as lieutenant-colonel in the British army, and Thompson, +probably foreseeing the outcome of events and its effect on the +Ministry, was already in America when Lord George resigned. He had +intended landing at New York, but contrary winds drove him to +Charlestown. It is needless to trace the sad events which preceded the +end of the war. It was to be expected that many bitter statements +would be made by his countrymen respecting Thompson's own actions as +colonel commanding a British garrison, for at length he succeeded in +reaching Long Island, and taking the command of the King's American +Dragoons, who were there awaiting him. The spirit of war always acts +injuriously on those exposed to its influence, and Lieutenant-Colonel +Thompson in Long Island was doubtless a very different man from that +which we find him to have been before and after; nor were the months +so spent very fruitful in scientific work. + +In 1783, before the final disbanding of the British forces, Thompson +returned to England, and was promoted to the rank of colonel, with +half-pay for the rest of his life. Still anxious for military service, +he obtained permission to travel on the Continent, in hopes of serving +in the Austrian army against the Turks. He took with him three English +horses, which rendered themselves very objectionable to his +fellow-travellers while crossing the Channel in a small boat. Thompson +went to Strasbourg, where he attracted the attention of the Prince +Maximilian, then Field-Marshal of France, but afterwards Elector of +Bavaria. On leaving Strasbourg, the prince gave him an introduction to +his uncle, the Elector of Bavaria. He stayed some days at Munich, but +on reaching Vienna learned that the war against the Turks would not be +carried on, so he returned to Munich, and thence to England. + +M. Pictet gives the following as Rumford's account of the manner in +which he was cured of his passion for war:-- + +"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I +was cured in season of this martial folly. I met, at the house of the +Prince de Kaunitz, a lady, aged seventy years, of infinite spirit and +full of information. She was the wife of General Bourghausen. The +emperor, Joseph II., came often to pass the evening with her. This +excellent person conceived a regard for me; she gave me the wisest +advice, made my ideas take a new direction, and opened my eyes to +other kinds of glory than that of victory in battle.'" + +If the course in life which Colonel Thompson afterwards took was due +to the advice of this lady, she deserves a European reputation. The +Elector of Bavaria, Charles Theodore, gave Thompson a pressing +invitation to enter his service in a sort of semi-military and +semi-civil capacity, to assist in reorganizing his dominions and +removing the abuses which had crept in. Before accepting this +appointment, it was necessary to obtain the permission of George III. +The king not only approved of the arrangement, but on February 23, +1784, conferred on the colonel the honour of knighthood. Sir Benjamin +then returned to Bavaria, and was appointed by the elector colonel of +a regiment of cavalry and general aide-de-camp. A palatial residence +in Munich was furnished for him, and here he lived more as a prince +than a soldier. It was eleven years before he returned, even on a +visit, to England, and these years were spent by him in works of +philanthropy and statesmanship, to which it is difficult to find a +parallel. At one time he is found reorganizing the military system of +the country, arranging a complete system of military police, erecting +arsenals at Mannheim and Munich; at another time he is carrying out +scientific investigations in one of these arsenals; and then he is +cooking cheap dinners for the poor of the country. + +One great evil of a standing army is the idleness which it develops in +its members, unfitting them for the business of life when their +military service is ended. Thompson commenced by attacking this evil. +In 1788 he was made major-general of cavalry and Privy Councillor of +State, and was put at the head of the War Department, with +instructions to carry out any schemes which he had developed for the +reform of the army and the removal of mendicity. Four years after his +arrival in Munich he began to put some of his plans into operation. +The pay of the soldiers was only threepence per day, and their +quarters extremely uncomfortable, while their drill and discipline +were unnecessarily irksome. Thompson set to work to make "soldiers +citizens and citizens soldiers." The soldier's pay, uniform, and +quarters were improved; the discipline rendered less irksome; and +schools in which the three R's were taught were connected with all the +regiments,--and here not only the soldiers, but their children as well +as other children, were taught gratuitously. Not only were the +soldiers employed in public works, and thus accustomed to habits of +industry, while they were enlivened in their work by the strains of +their own military bands, but they were supplied with raw material of +various kinds, and allowed, when not on duty, to manufacture various +articles and sell them for their own benefit--an arrangement which in +this country to-day would probably raise a storm of opposition from +the various trades. The garrisons were made permanent, so that +soldiers might all be near their homes and remain there, and in time +of peace only a small portion of the force was required to be in +garrison at any time, so that the great part of his life was spent by +each soldier at home. Each soldier had a small garden appropriated to +his use, and its produce was his sole property. Garden seeds, and +especially seed potatoes, were provided for the men, for at that time +the potato was almost unknown in Bavaria. Under these circumstances a +reform was quickly effected; idle men began to take interest in their +gardens, and all looked on Sir Benjamin as a benefactor. + +Having thus secured the co-operation of the army, Thompson determined +to attack the mendicants. The number of beggars may be estimated from +the fact that in Munich, with a population of sixty thousand, no less +than two thousand six hundred beggars were seized in a week. In the +towns, they possessed a complete organization, and positions of +advantage were assigned in regular order, or inherited according to +definite customs. In the country, farm labourers begged of travellers, +and children were brought up to beggary from their infancy. Of course, +the evils did not cease with simple begging. Children were stolen and +ill treated, for the purpose of assisting in enlisting sympathy, and +the people had come to regard these evils as inevitable. Thompson +organized a regular system of military patrol through every village of +the country, four regiments of cavalry being set apart for this work. +Then on January 1, 1790, when the beggars were out in full force to +keep their annual holiday, Thompson, with the other field officers and +the magistrates of the city, gave the signal, and all the beggars in +Munich were seized upon by the three regiments of infantry then in +garrison. The beggars were taken to the town hall, and their names and +addresses entered on lists prepared for the purpose. They were ordered +to present themselves next day at the "military workhouse," and a +committee was appointed to inquire into the condition of each, the +city being divided into sixteen districts for that purpose. Relieved +of an evil which they had regarded as inevitable, the townspeople +readily subscribed for the purpose of affording systematic relief, +while tradesmen sent articles of food and other requisites to "the +relief committee." In the military workhouse the former mendicants +made all the uniforms for the troops, besides a great deal of clothes +for sale in Bavaria and other countries. Thompson himself fitted up +and superintended the kitchen, where food was daily cooked for between +a thousand and fifteen hundred persons; and, under Sir Benjamin's +management, a dinner for a thousand was cooked at a cost for fuel of +fourpence halfpenny--a result which has scarcely been surpassed in +modern times, even at Gateshead. + +That Thompson's work was appreciated by those in whose interest it was +undertaken is shown by the fact that when, on one occasion, he was +dangerously ill, the poor of Munich went in public procession to the +cathedral to pray for him, though he was a foreigner and a Protestant. +Perhaps it may appear that his philanthropic work has little to do +with physical science; but with Thompson everything was a scientific +experiment, conducted in a truly scientific manner. For example, the +lighting of the military workhouse afforded matter for a long series +of experiments, described in his papers on photometry, coloured +shadows, etc. The investigations on the best methods of employing fuel +for culinary purposes led to some of his most elaborate essays; and +his essay on food was welcomed alike in London and Bavaria at a time +of great scarcity, and when famine seemed impending. + +The Emperor Joseph was succeeded by Leopold II., but during the +interregnum the Elector of Bavaria was Vicar of the Empire, and he +employed the power thus temporarily placed in his hands in raising Sir +Benjamin to the dignity of Count of the Holy Roman Empire, with the +order of the White Eagle, and the title which the new count selected +was the old name of the village in New England where he had spent the +two or three years of his wedded life. + +In 1795 Count Rumford returned to England, in order to publish his +essays, and to make known in this country something of the work in +which he had been engaged. Soon after his arrival he was robbed of +most of his manuscripts, the trunk containing them being stolen from +his carriage in St. Paul's Churchyard. On the invitation of Lord +Pelham, he visited Dublin, and carried out some of his improvements in +the hospitals and other institutions of that city. On his return to +London he fitted up the kitchen of the Foundling Hospital. + +Lady Thompson lived to hear of her husband's high position in Bavaria, +but died on January 29, 1792. When Rumford came to London in 1795, he +wrote to his daughter, who was then twenty-one years of age, to meet +him there, and on January 29, 1796, she started in the _Charlestown_, +from Boston. She remained with her father for more than three years, +and her autobiography gives much information respecting the count's +doings during this time. + +While in London, Count Rumford attained a high reputation as a curer +of smoky chimneys. One firm of builders found full employment in +carrying out work in accordance with his instructions; and in his +hotel at Pall Mall he conducted experiments on fireplaces. He +concluded that the sides of a fireplace ought to make an angle of 135° +with the back, so as to throw the heat straight to the front; and that +the width of the back should be one-third of that of the front +opening, and be carried up perpendicularly till it joins the breast. +The "Rumford roaster" gained a reputation not less than that earned +by his open fireplace. + +It was during this stay in London that Rumford presented to the Royal +Society of London, and to the American Academy of Sciences £1000 Three +per Cent. Stock, for the purpose of endowing a medal to be called the +Rumford Medal, and to be given each alternate year for the best work +done during the preceding two years in the subjects of heat and light. +He directed that two medals, one in gold and the other in silver, +should be struck from the same die, the value of the two together to +amount to £60. Whenever no award was made, the interest was to be +added to the principal, and the excess of the income for two years +over £60 was to be presented in cash to the recipient of the medal. At +present the amount thus presented is sufficient to pay the composition +fee for life membership of the Royal Society. The first award of the +medal was made in 1802, to Rumford himself. The other recipients have +been John Leslie, William Murdock, Étienne-Louis Malus, William +Charles Wells, Humphry Davy, David Brewster, Augustin Jean Fresnel, +Macedonio Melloni, James David Forbes, Jean Baptiste Biot, Henry Fox +Talbot, Michael Faraday, M. Regnault, F. J. D. Arago, George Gabriel +Stokes, Neil Arnott, M. Pasteur, M. Jamin, James Clerk Maxwell, +Kirchoff, John Tyndall, A. H. L. Fizeau, Balfour Stewart, A. O. des +Cloiseaux, A. J. Ångström, J. Norman Lockyer, P. J. C. Janssen, W. +Huggins, Captain Abney. + +In the summer of 1796 Rumford and his daughter left England to return +to Munich. On account of the war, they were obliged to go by sea to +Hamburg; whence they drove to Munich, where the count was anxiously +expected, political troubles having compelled the elector to leave the +city. After the battle of Friedburg, the Austrians retired to Munich, +and, finding the gates of the city closed, they fortified +themselves on an eminence overlooking the city, and, through some +misunderstanding with the local authorities, the Austrian general +threatened to attack the city if any Frenchman should be allowed to +enter. Rumford took supreme command of the Bavarian forces, and so +gained the respect of the rival generals that neither the French nor +the Austrians made any attempt to enter the city. The large number of +soldiers now in Munich gave Rumford a good opportunity to exercise his +skill in cooking on a large scale, and this he did, adding to the +comfort of the soldiers and reducing the cost of the commissariat. On +the return of the elector, Miss Sarah was made a countess, and +one-half of her father's pension was secured to her, thus providing +her with an income of about £200 per annum for life. Many of the +details of the home life and social intercourse during this period of +residence at Munich are preserved in the autobiography of the +countess, as well as accounts of excursions, including a trip by river +to Salzburg for the purpose of inspecting the salt-mines. After two +years' stay in Munich, the count was appointed Minister +Plenipotentiary from Bavaria to the Court of Great Britain. After an +unpleasant and perilous journey, he reached London, _viâ_ Hamburg, in +September, 1798, but was terribly disappointed on learning that a +British subject could not be accepted as an envoy from a Foreign +Power. As he did not then wish to return to Bavaria, he purchased a +house in Brompton Row. But he had been too much accustomed to great +enterprises to be content with a quiet life, and was bound to have +some important scheme on hand. Pressing invitations were sent him to +return to America, but he preferred residence in London, and devoted +himself to the foundation of the Royal Institution, though the +countess returned to the States in August, 1799. A letter from Colonel +Baldwin to her father shortly after her return contains the following +passage:-- + + In the cask of fruit which your daughter and Mr. Rolfe have sent + you, there is half a dozen apples of the growth of my farm, + wrapped up in papers, with the name of _Baldwin's apples_ + written upon them.... It is (I believe) a spontaneous production + of this country; that is, it was not originally engrafted fruit. + +The history of the remaining period of Rumford's residence in London +is the early history of the Royal Institution. + +For many years Rumford had had at his disposal for his philanthropic +projects all the resources of the electorate of Bavaria, and he had +done everything on a royal scale. His original plan for the Royal +Institution appears to embody to a very great extent the work of the +Science and Art Department, the City and Guilds Institute for the +Advancement of Technical Education, the National School of Cookery, +the London Society for the Extension of University Teaching, and, in +addition to all this, to have comprehended a sort of perpetual +International Health Exhibition, where every device for domestic +purposes, and especially for the improvement of the condition of the +poor, could be inspected. How all this was to be carried out with the +resources which the count expected to be able to devote to the +purpose, does not appear. Foremost among the objects of the +institution was placed the management of fire; for its promoter was +convinced that more than half the fuel consumed in the country might +be saved by proper arrangements. + +The philanthropic objects with which the institution was started are +apparent from the fact that it was the Society for Bettering the +Condition of the Poor which appointed a committee to confer with +Rumford, to report on the scheme, and to raise the funds necessary for +starting the project; and one of Rumford's hopes in connection with it +was "to make benevolence fashionable." It was arranged that donors of +fifty guineas each should be perpetual proprietors of the institution; +and that subscribers should be admitted at a subscription of two +guineas per annum, or ten guineas for life. The price of a +proprietor's share was raised to sixty guineas from May 1, 1800, and +afterwards increased by ten guineas per annum up to one hundred +guineas. In a very short time there were fifty-eight fifty-guinea +subscribers, and to them Rumford addressed a pamphlet, setting forth +his scheme in detail. The following are specified as some of the +contents of the future institution:--"Cottage fireplaces and kitchen +utensils for cottagers; a farm-house kitchen with its furnishings; a +complete kitchen, with its utensils, for the house of a gentleman of +fortune; a laundry, including boilers, washing, ironing, and drying +rooms, for a gentleman's house, or for a public hospital; the most +improved German, Swedish, and Russian stoves for heating rooms and +passages." As far as possible all these things were to be seen at +work. There were also to be ornamental open stoves with fires in them; +working models of steam-engines, of brewers' boilers, of distillers' +coppers and condensers, of large boilers for hospital kitchens, and of +ships' coppers with the requisite utensils; models of ventilating +apparatus, spinning-wheels and looms "adapted to the circumstances of +the poor;" models of agricultural machinery and bridges, and "of all +such other machines and useful instruments as the managers of the +institution shall deem worthy of public notice." All articles were to +be provided with proper descriptions, with the name and address of the +maker, and the price. + +A lecture-room and laboratory were to be fitted up with all necessary +philosophical apparatus, and the most eminent expounders of science +were to be engaged for the purpose of "teaching the application of +science to the useful purposes of life." + +The lectures were to include warming and ventilation, the preservation +of food, agricultural chemistry, the chemistry of digestion, of +tanning, of bleaching and dyeing, "and, in general, of all the +mechanical arts as they apply to the various branches of manufacture." +The institution was to be governed by nine managers, of whom three +were to be elected each year by the proprietors; and there was also to +be a committee of visitors, the members of which should not be the +managers. The king became patron of the institution, and the first set +of officers was nominated by him. The Earl of Winchelsea and +Nottingham was President; the Earls of Morton and of Egremont and Sir +Joseph Banks, Vice-Presidents; the Earls of Bessborough, of Egremont, +and of Morton, and Count Rumford, were among the Managers; the Duke of +Bridgewater, Viscount Palmerston, and Earl Spencer the Visitors; and +Dr. Thomas Garnett was appointed first Professor of Physics and +Chemistry. The royal charter of the institution was sealed on January +13, 1800. The superintendence of the journals of the institution was +entrusted to Rumford's care. For some time the count resided in the +house in Albemarle Street, which had been purchased by the +institution, and while there he superintended the workmen and +servants. + +Dr. Thomas Garnett, the first professor at the institution, was highly +respected both as a man and a philosopher, and seems to have been +everywhere well spoken of. But Rumford and he could not work together, +and his connection with the institution was consequently a short one. +Rumford was then authorized to engage Dr. Young as Professor of +Natural Philosophy, editor of the journals, and general superintendent +of the house, at a salary of £300 per annum. Shortly before this the +count's attention had been directed to the experiments on heat, made +by Humphry Davy, and on February 16, 1801, it was "resolved that Mr. +Humphry Davy be engaged in the service of the Royal Institution, in +the capacity of Assistant-Lecturer in Chemistry, Director of the +Chemical Laboratory, and Assistant-Editor of the Journals of the +Institution; and that he be allowed to occupy a room in the house, and +be furnished with coals and candles, and that he be paid a salary of +one hundred guineas _per annum_." In his personal appearance, Davy is +said to have been at first somewhat uncouth, and the count was by no +means charmed with him at their first interview. It was not till he +had heard him lecture in private that Rumford would allow Davy to +lecture in the theatre of the institution; but he afterwards showed +his complete confidence in the young chemist by ordering that all the +resources of the institution should be at his service. Davy dined with +Rumford at the count's house in Auteuil, when he visited Paris with +Lady Davy and Faraday, in 1813. He commenced his duties at the +institution on March 11, 1801. It was on June 15, in the same year, +that the managers having objected to the syllabus of his lectures, Dr. +Garnett's resignation was accepted; and on July 6 Dr. Young was +appointed in his stead. Dr. Young resigned after holding the +appointment only two years, as he found the duties incompatible with +his work as a physician. + +Rumford's life in London now became daily more unpleasant to himself. +Accustomed, as he had been in Bavaria, to carry out all his projects +"like an emperor," it was difficult for him to work as one member of a +body of managers. One by one he quarrelled with his colleagues, and at +length left England, in May, 1802, never to return. + +When distinguished men of science are placed at the head of an +institution like that which Rumford founded, there is always a +tendency for the _technical_ teaching of the establishment to become +gradually merged into scientific research; and in this case, after +Rumford's departure, the genius of Davy gradually converted the Royal +Institution into the establishment for scientific research which it +has been for more than three quarters of a century. Probably the man +who has come nearest to realizing all that Count Rumford had planned +for his institution is the late Sir Henry Cole; but he succeeded only +through the resources of the Treasury. + +On leaving England in May, 1802, Rumford went to Paris, where he +stayed till July or August, when he revisited Bavaria and remained +there till the following year, when he returned to Paris. He was again +at Munich in 1805; but under the new elector, though an old friend of +the count, relationships do not seem to have been all that they were +with his uncle, and at length the elector himself was compelled to +leave Munich, and soon after the Bavarian sovereign became a vassal of +Napoleon. On October 24, 1805, Rumford married Madame Lavoisier, a +lady of brilliant talents and ample fortune. That his position might +be nearly equal to hers, the Elector of Bavaria raised his pension to +£1200 per annum. A house, Rue d'Anjou, No. 39, was purchased for six +thousand guineas, and Rumford expended much thought and energy in +making it, with its garden of two acres, all that he could desire. But +the union was not so happy as he anticipated. The count loved quiet; +Madame de Rumford was fond of company: to the former the pleasure of +the table had no charms; the latter took delight in sumptuous +dinner-parties. As time went on, domestic affairs became more and more +unpleasant, and at length a friendly separation was agreed upon, after +they had lived together for about three years and a half. The count +then retired to a small estate which he hired at Auteuil, about four +miles from Paris. The Elector of Bavaria was crowned king on January +1, 1806, and in 1810 Rumford was again at Munich, for the purpose of +forming, at the king's request, an Academy of Arts and Sciences. At +Auteuil the count was joined by his daughter in December, 1811, her +journey having been much delayed through the capture of the vessel in +which she had taken her passage, off Bordeaux. An engraving of the +house at Auteuil, and the room in which Rumford carried on his +experiments, was published in the _Illustrated London News_ of January +22, 1870. + +While resident at Auteuil, Rumford frequently read papers before the +Institute of France, of which he was a member. He complained very much +of the jealousy exhibited by the other members with reference to any +discoveries made by a foreigner. He died in his house at Auteuil, on +August 21, 1814, in the sixty-second year of his age. In 1804 he had +made over, by deed of gift to his mother, the sum of ten thousand +dollars, that she might leave it by will to her younger children. As +before mentioned, Harvard College was his residuary legatee, and the +property so bequeathed founded the Rumford Professorship in that +institution. + +Cuvier, as Secretary of the Institute, pronounced the customary eulogy +over its late member. The following passages throw some light on the +reputation in which the count was held:-- + + He has constructed two singularly ingenious instruments of his + own contriving. One is a new calorimeter for measuring the + amount of heat produced by the combustion of any body. It is a + receptacle containing a given quantity of water, through which + passes, by a serpentine tube, the product of the combustion; and + the heat that is generated is transmitted through the water, + which, being raised by a fixed number of degrees, serves as the + basis of the calculations. The manner in which the exterior heat + is prevented from affecting the experiment is very simple and + very ingenious. He begins the operation at a certain number of + degrees below the outside heat, and terminates it at the same + number of degrees above it. The external air takes back during + the second half of the experiment exactly what it gave up during + the first. The other instrument serves for noting the most + trifling differences in the temperature of bodies, or in the + rapidity of its changes. It consists of two glass bulbs filled + with air, united by a tube, in the middle of which is a pellet + of coloured spirits of wine; the slightest increase of heat in + one of the bulbs drives the pellet towards the other. This + instrument, which he called a thermoscope, was of especial + service in making known to him the varied and powerful influence + of different surfaces in the transmission of heat, and also for + indicating a variety of methods for retarding or hastening at + will the processes of heating and freezing.... + + He thought it was not wise or good to entrust to men, in the + mass, the care of their own well-being. The right, which seems + so natural to them, of judging whether they are wisely governed, + appeared to him to be a fictitious fancy born of false notions + of enlightenment. His views of slavery were nearly the same as + those of a plantation-owner. He regarded the government of China + as coming nearest to perfection, because, in giving over the + people to the absolute control of their only intelligent men, + and in lifting each of those who belonged to this hierarchy on + the scale according to the degree of his intelligence, it made, + so to speak, so many millions of arms the passive organs of the + will of a few sound heads--a notion which I state without + pretending in the slightest degree to approve it, and which, as + we know, would be poorly calculated to find prevalence among + European nations. + + As for the rest, whatever were the sentiments of M. Rumford for + men, they in no way lessened his reverence for God. He never + omitted any opportunity in his works of expressing his religious + admiration of Providence, and of proposing for that admiration + by others, the innumerable and varied provisions which are made + for the preservation of all creatures; indeed, even his + political views came from his firm persuasion that princes ought + to imitate Providence in this respect by taking charge of us + without being amenable to us. + +In front of the new Government offices and the National Museum in the +Maximilian Strasse, in Munich, stand, on granite pedestals, four +bronze figures, ten feet in height. These represent General Deroy, +Fraunhofer, Schelling, and Count Rumford. The statue of Rumford was +erected in 1867, at the king's private expense. In the English garden +which Rumford planned and laid out is the monument erected during his +absence in England in 1796, and bearing allegorical figures of Peace +and Plenty, and a medallion of the count. + +The bare enumeration of Rumford's published papers would occupy +considerable space, but many of them have more to do with philanthropy +and domestic economy than with physics. We have seen that, when guest +of Lord George Germaine, he was engaged in experiments on gunpowder. +The experiments were made in the usual manner by firing bullets into a +ballistic pendulum, and recording the swing of the pendulum. Thompson +suggested a modification of the ballistic pendulum, attaching the +gun-barrel to the pendulum, and observing the recoil, and making +allowance for the recoil due to the discharge from the gun of the +products of combustion of the powder, the excess enabled the velocity +of the bullet to be calculated. Afterwards he made experiments on the +maximum pressure produced by the explosion of powder, and pointed out +that the value of powder in ordnance does not depend simply on the +whole amount of gas produced, but also on the rapidity of combustion. +While superintending the arsenal at Munich, Rumford exploded small +charges of powder in a specially constructed receiver, which was +closed by a plug of well-greased leather, and on this was placed a +hemisphere of steel pressed down by a 24-pounder brass cannon weighing +8081 pounds. He found that the weight of the gun was lifted by the +explosion of quantities of powder varying from twelve to fifteen +grains, and hence concluded that, if the products of combustion of the +powder were confined to the space actually occupied by the solid +powder, the initial pressure would exceed twenty thousand atmospheres. +Rumford's calculation of the pressure, based upon the bursting of a +barrel, which he had previously constructed, is not satisfactory, +inasmuch as he takes no account of the fact that the inner portions of +the metal would give way long before the outer layers exerted anything +like their maximum tension. When a hollow vessel with thick walls, +such as a gun-barrel or shell, is burst by gaseous pressure from +within, the inner layers of material are stretched to their breaking +tension before they receive much support from the outer layers; a rift +is thus made in the interior, into which the gas enters, and the +surface on which the gas presses being thus increased, the rift +deepens till the fracture is complete. In order to gain the full +strength due to the material employed, every portion of that material +should be stretched simultaneously to the extent of its maximum safe +load. This principle was first practically adopted by Sir W. G. +Armstrong, who, by building up the breech of the gun with cylinders +shrunk on, and so arranged that the tension increased towards the +exterior, availed himself of nearly the whole strength of the metal +employed to resist the explosion. Had Rumford's barrel been +constructed on this principle, he would have obtained a much more +satisfactory result. + +These investigations were followed by a very interesting series of +experiments on the conducting power of fluids for heat, and, although +he pushed his conclusions further than his experiments warranted, he +showed conclusively that convection currents are the principal means +by which heat is transferred through the substance of fluids, and +described how, when a vessel of water is heated, there is generally an +ascending current in the centre, and a descending current all round +the periphery. Hence it is only when a liquid expands by increase of +temperature that a large mass can be readily heated from below. Water +below 39° Fahr. contracts when heated. Rumford, in his paper, enlarges +on the bearing of this fact on the economy of the universe, and the +following extracts afford a good specimen of his style, and justify +some of the statements made by Cuvier in his eulogy:-- + + I feel the danger to which a mortal exposes himself who has the + temerity to undertake to explain the designs of Infinite Wisdom. + The enterprise is adventurous, but it cannot surely be improper. + + The wonderful simplicity of the means employed by the Creator of + the world to produce the changes of the seasons, with all the + innumerable advantages to the inhabitants of the earth which + flow from them, cannot fail to make a very deep and lasting + impression on every human being whose mind is not degraded and + quite callous to every ingenuous and noble sentiment; but the + further we pursue our inquiries respecting the constitution of + the universe, and the more attentively we examine the effects + produced by the various modifications of the active powers which + we perceive, the more we shall be disposed to admire, adore, and + love that great First Cause which brought all things into + existence. + + Though winter and summer, spring and autumn, and all the variety + of the seasons are produced in a manner at the same time the + most simple and the most stupendous (by the inclination of the + axis of the earth to the plane of the ecliptic), yet this + mechanical contrivance alone would not have been sufficient (as + I shall endeavour to show) to produce that gradual change of + temperature in the various climates which we find to exist, and + which doubtless is indispensably necessary to the preservation + of animal and vegetable life.... + + But in very cold countries the ground is frozen and covered with + snow, and all the lakes and rivers are frozen over in the very + beginning of winter. The cold then first begins to be extreme, + and there appears to be no source of heat left which is + sufficient to moderate it in any sensible degree. + + Let us see what must have happened if things had been left to + what might be called their natural course--if the condensation + of water, on being deprived of its heat, had followed the law + which we find obtains in other fluids, and even in water itself + in some cases, namely, when it is mixed with certain bodies. + + Had not Providence interfered on this occasion in a manner which + may well be considered _miraculous_, all the fresh water within + the polar circle must inevitably have been frozen to a very + great depth in one winter, and every plant and tree destroyed; + and it is more than probable that the region of eternal frost + would have spread on every side from the poles, and, advancing + towards the equator, would have extended its dreary and solitary + reign over a great part of what are now the most fertile and + most inhabited climates of the world!... + + Let us with becoming diffidence and awe endeavour to see what + the means are which have been employed by an almighty and + benevolent God to protect His fair creation. + +He then goes on to explain how large bodies of water are prevented +from freezing at great depths on account of the expansion which takes +place on cooling below 39° Fahr., and the further expansion which +occurs on freezing, and mentions that in the Lake of Geneva, at a +depth of a thousand feet, M. Pictet found the temperature to be 40° +Fahr. + +"We cannot sufficiently admire the simplicity of the contrivance by +which all this heat is saved. It well deserves to be compared with +that by which the seasons are produced; and I must think that every +candid inquirer who will begin by divesting himself of all +unreasonable prejudice will agree with me in attributing them both TO +THE SAME AUTHOR.... + +"But I must take care not to tire my reader by pursuing these +speculations too far. If I have persisted in them, if I have dwelt on +them with peculiar satisfaction and complacency, it is because I think +them uncommonly interesting, and also because I conceived that they +might be of value in this age of _refinement_ and _scepticism_. + +"If, among barbarous nations, the _fear of a God_, and the practice of +religious duties, tend to soften savage dispositions, and to prepare +the mind for all those sweet enjoyments which result from peace, +order, industry, and friendly intercourse; a _belief in the existence +of a Supreme Intelligence_, who rules and governs the universe with +wisdom and goodness, is not less essential to the happiness of those +who, by cultivating their mental powers, HAVE LEARNED TO KNOW HOW +LITTLE CAN BE KNOWN." + +Rumford, in connection with his experiments on the conducting power of +liquids, tried the effect of increasing the viscosity of water by the +addition of starch, and of impeding its movements by the introduction +of eider-down, on the rate of diffusion of heat through it. Hence he +explained the inequalities of temperature which may obtain in a mass +of thick soup--inequalities which had once caused him to burn his +mouth--and, applying the same principles to air, he at once turned his +conclusions to practical account in the matter of warm clothing. + +After an attempt to determine, if possible, the weight of a definite +quantity of heat--an attempt in which very great precautions were +taken to exclude disturbing causes, while the balance employed was +capable of indicating one-millionth part of the weight of the body +weighed--Rumford, finding no sensible effect on the balance, concluded +that "if the weight of gold is neither augmented nor lessened by +_one-millionth part_, upon being heated from the point of _freezing +water_ to that of a _bright red heat_, I think we may very safely +conclude that ALL ATTEMPTS TO DISCOVER ANY EFFECT OF HEAT UPON THE +APPARENT WEIGHTS OF BODIES WILL BE FRUITLESS." The theoretical +investigations of Principal Hicks, based on the vortex theory of +matter and the dynamical theory of heat, have recently led him to the +conclusion that the attraction of gravitation may depend to some +extent on temperature. + +A series of very valuable experiments on the radiating powers of +different surfaces showed how that power varied with the nature of the +surface, and the effect of a coating of lamp-black in increasing the +radiating power of a body. In order to determine the effect of +radiation in the cooling of bodies, Rumford employed the thermoscope +referred to by Cuvier. The following passage is worthy of attention, +as the truth it expounds in the last thirteen words appears to have +been but very imperfectly recognized many years after it was +written:-- + +"All the heat which a hot body loses when it is exposed in the air to +cool is not given off to the air which comes into contact with it, but +... a large proportion of it escapes in rays, which do not heat the +transparent air through which they pass, but, like light, generate +heat only when and where they are stopped and absorbed." + +Rumford then investigated the absorption of heat by different +surfaces, and established the law that good radiators are good +absorbers; and recommended that vessels in which water is to be heated +should be blackened on the outside. In speculating on the use of the +colouring matter in the skin of the negro, he shows his fondness for +experiment:-- + +"All I will venture to say on the subject is that, were I called to +inhabit a very hot country, nothing should prevent me from making the +experiment of blackening my skin, or at least, of wearing a black +shirt, in the shade, and especially at night, in order to find out if, +by those means, I could contrive to make myself more comfortable." + +In his experiments on the conduction of heat, Rumford employed a +cylinder with one end immersed in boiling water and the other in +melting ice, and determined the temperature at different points in the +length of the cylinder. He found the difficulty which has recently +been forcibly pointed out by Sir Wm. Thomson, in the article "Heat," +in the "Encyclopædia Britannica," viz. that the circulation of the +water was not sufficiently rapid to keep the temperature of the layer +in contact with the metal the same as that of the rest of the water; +and he also called attention to the arbitrary character of +thermometer-scales, and recommended that more attention should be +given to the scale of the air thermometer. It was in his visit to +Edinburgh, in 1800, that, in company with some of the university +professors, the count conducted some experiments in the university +laboratory on the apparent radiation of cold. Rumford's views +respecting _frigorific rays_ have not been generally accepted, and +Prevost's theory of exchanges completely explains the apparent +radiation of cold without supposing that cold is anything else than +the mere absence of heat. + +We must pass over Rumford's papers on the use of steam as a vehicle of +heat, on new boilers and stoves for the purpose of economizing fuel, +and all the papers bearing on the nutritive value of different foods. +The calorimeter with which he determined the amount of heat generated +by the combustion, and the latent heat of evaporation, of various +bodies has been already alluded to. Of the four volumes of Rumford's +works published by the American Academy of Arts and Sciences, the +third is taken up entirely with descriptions of fireplaces and of +cooking utensils. + +Before deciding on the best way to light the military workhouse at +Munich, Rumford made a series of experiments on the relative economy +of different methods, and for this purpose designed his well-known +shadow-photometer. In the final form of this instrument the shadows +were thrown on a plate of ground glass covered with paper, forming the +back of a small box, from which all extraneous light was excluded. Two +rods were placed in front of this screen, and the lights to be +compared were so situated that the shadow of one rod thrown by the +first light might be just in contact with that of the other rod thrown +by the second light. By introducing coloured glasses in front of the +lights, Rumford compared the illuminating powers of different sources +with respect to light of a particular colour. The complementary tints +exhibited by the shadows caused him to devise his theory of the +harmony of complementary colours. One result is worthy of mention: it +is a conclusion to which public attention has since been called in +connection with "duplex" burners. Rumford found that with wax tapers +the amount of light emitted per grain of wax consumed diminished with +the diminution of the consumption, so that a small taper gave out only +one-sixteenth as much light as an ordinary candle for the same +consumption of wax. He says:-- + +"This result can be easily explained if we admit the hypothesis which +supposes light to be analogous to sound.... The particles ... were so +rapidly cooled ... that they had hardly time to shine one instant +before they became too cold to be any longer visible." + +An argand lamp, when compared with a lamp having a flat wick, gave +more light in the ratio of 100 to 85 for the same consumption of oil. + +One of the latest investigations of Rumford was that bearing on the +effect of the width of the wheels on the draught of a carriage. To his +own carriage, weighing, with its passengers, nearly a ton, he fitted a +spring dynamometer by means of a set of pulleys attached to the +under-carriage and the splinter-bar. He used three sets of wheels, +respectively 1-3/4, 2-1/4, and 4 inches wide, and, introducing weights +into the carriage to make up for the difference in the weights of the +wheels, he found a very sensible diminution in the tractive force +required as the width of the wheels was increased, and in a truly +scientific spirit, despising the ridicule cast upon him, he persisted +in riding about Paris in a carriage with four-inch tyres. + +But the piece of work by which Rumford will be best known to future +generations is that described in his paper entitled "An Inquiry +concerning the Source of the Heat which is excited by Friction." It +was while superintending the boring of cannon in the arsenal at Munich +that Rumford was struck with the enormous amount of heat generated by +the friction of the boring-bar against the metal. In order to +determine whether the heat had come from the chips of metal +themselves, he took a quantity of the abraded borings and an equal +weight of chips cut from the metal with a fine saw, and, heating them +to the temperature of boiling water, he immersed them in equal +quantities of water at 59-1/2° Fahr. The change of temperature of the +water was the same in both cases, and Rumford found that there was no +change which he could discover _in regard to its capacity for heat_ +produced in the metal by the action of the borer. + +In order to prevent the honeycombing of the castings by the escaping +gas, the cannon were cast in a vertical position with the breech at +the bottom of the mould and a short cylinder projecting about two feet +beyond the muzzle of the gun, so that any imperfections in the casting +would appear in this projecting cylinder. It was on one of these +pieces of waste metal, while still attached to the gun, that Rumford +conducted his experiments. Having turned the cylinder, he cut away the +metal in front of the muzzle until the projecting piece was connected +with the gun by a narrow cylindrical neck, 2·2 inches in diameter and +3·8 inches long. The external diameter of the cylinder was 7·75 +inches, and its length 9·8 inches, and it was bored to a depth of 7·2 +inches, the diameter of the bore being 3·7 inches. The cannon was +mounted in the boring-lathe, and a blunt borer pressed by a screw +against the bottom of the bore with a force equal to the weight of +10,000 pounds. A small transverse hole was made in the cylinder near +its base for the introduction of a thermometer. The cylinder weighed +113·13 pounds, and, with the gun, was turned at the rate of thirty-two +revolutions per minute by horse-power. To prevent loss of heat, the +cylinder was covered with flannel. After thirty minutes' work, the +thermometer, when introduced into the cylinder, showed a temperature +of 130° Fahr. The loss of heat during the experiment was estimated +from observations of the rate of cooling of the cylinder. The weight +of metal abraded was 837 grains, while the amount of heat produced was +sufficient to raise nearly five pounds of ice-cold water to the +boiling point. + +To exclude the action of the air, the cylinder was closed by an +air-tight piston, but no change was produced in the result. As the air +had access to the metal where it was rubbed by the piston, and Rumford +thought this might possibly affect the result, a deal box was +constructed, with slits at each end closed by sliding shutters, and so +arranged that it could be placed with the boring bar passing through +one slit and the narrow neck connecting the cylinder with the gun +through the other slit, the sliding shutters, with the help of collars +of oiled leather, serving to make the box water-tight. The box was +then filled with water and the lid placed on. After turning for an +hour the temperature was raised from 60° to 107° Fahr., after an hour +and a half it was 142° Fahr., at the end of two hours the temperature +was 178° Fahr., at two hours and twenty minutes it was 200° Fahr., and +at two hours and thirty minutes it ACTUALLY BOILED! + +"It would be difficult to describe the surprise and astonishment +expressed in the countenances of the bystanders on seeing so large a +quantity of cold water heated and actually made to boil without any +fire. + +"Though there was, in fact, nothing that could justly be considered as +surprising in this event, yet I acknowledge fairly that it afforded me +a degree of childish pleasure which, were I ambitious of the +reputation of a _grave philosopher_, I ought most certainly rather to +hide than to discover." + +Rumford estimated the "total quantity of ice-cold water which, with +the heat actually generated by the friction and accumulated in two +hours and thirty minutes, might have been heated 180 degrees, or made +to boil" at 26·58 pounds, and the rate of production he considered +exceeded that of nine wax candles, each consuming ninety-eight grains +of wax per hour, while the work of turning the lathe could easily have +been performed by one horse. This was the first rough attempt ever +made, so far as we know, to determine the mechanical equivalent of +heat. + +In his reflections on these experiments, Rumford writes:-- + + It is hardly necessary to add that anything which any + _insulated_ body or system of bodies can continue to furnish + _without limitation_ cannot possibly be _a material substance_; + and it appears to me to be extremely difficult, if not quite + impossible, to form any distinct idea of anything capable of + being excited and communicated in the manner the heat was + excited and communicated in these experiments, except it be + MOTION. + +It has been stated that, if Rumford had dissolved in acid the borings +and the sawn strips of metal, the capacity for heat of which he +determined, and had shown that the heat developed in the solution was +the same in the two cases, his chain of argument would have been +absolutely complete. Considering the amount of heat produced in the +experiments, there are few minds whose conviction would be +strengthened by this experiment, and it is only those who look for +faultless logic that will refuse to Rumford the credit of having +established the dynamical nature of heat. + +Davy afterwards showed that two pieces of ice could be melted by being +rubbed against one another in a vacuum, but he does not appear to have +made as much as he might of the experiment. Mayer calculated the +mechanical equivalent of heat from the heat developed in the +compression of air, but he _assumed_, what afterwards was shown by +Joule to be nearly true, that the whole of the work done in the +compression was converted into heat. It was Joule, however, who first +showed that heat and mechanical energy are mutually convertible, so +that each may be expressed in terms of the other, a _given_ quantity +of heat always corresponding to the _same amount_ of mechanical +energy, whatever may be the intermediate stages through which it +passes, and that we may therefore define the mechanical equivalent of +heat as _the number of units of energy which, when entirely converted +into heat, will raise unit mass of water one degree from the freezing +point_. + + + + +THOMAS YOUNG. + + +"We here meet with a man altogether beyond the common standard, one in +whom natural endowment and sedulous cultivation rivalled each other in +the production of a true philosopher; nor do we hesitate to state our +belief that, since Newton, Thomas Young stands unrivalled in the +annals of British science." Such was the verdict of Principal Forbes +on one who may not only be regarded as one of the founders of the +undulatory theory of light, but who was among the first to apply the +theory of elasticity to the strength of structures, while it is to him +that we are indebted in the first instance for all we know of Egyptian +hieroglyphics, and for the vast field of antiquarian research which +the interpretation of these symbols has opened up. + +Thomas Young was the son of Thomas and Sarah Young, and the eldest of +ten children. His mother was a niece of the well-known physician, Dr. +Richard Brocklesby, and both his father and mother were members of +the Society of Friends, in whose principles all their children were +very carefully trained. It was to the independence of character thus +developed that Dr. Young attributed very much of the success which he +afterwards attained. He was born at Milverton, in Somersetshire, on +June 13, 1773. For the greater part of the first seven years of his +life he lived with his maternal grandfather, Mr. Robert Davis, at +Minehead, in Somersetshire. According to his own account, he could +read with considerable fluency at the age of _two_, and, under the +instructions of his aunt and a village schoolmistress, he had "read +the Bible twice through, and also Watts's Hymns," before he attained +the age of four. It may with reason be thought that both the +schoolmistress and the aunt should have been severely reprimanded, and +it is certain that their example is not to be commended; but Young's +infantile constitution seems to have been proof against over-pressure, +and before he was five years old he could recite the whole of +Goldsmith's "Deserted Village," with scarcely a mistake. He commenced +learning Latin before he was six, under the guidance of a +Nonconformist minister, who also taught him to write. When not quite +seven years of age he went to boarding-school, where he remained a +year and a half; but he appears to have learned more by independent +effort than under the guidance of his master, for privately he "had +mastered the last rules of Walkinghame's 'Tutor's Assistant'" before +reaching the middle of the book under the master's inspection. After +leaving this school, he lived at home for six months, but frequently +visited a neighbour who was a land surveyor, and at whose house he +amused himself with philosophical instruments and scientific books, +especially a "Dictionary of Arts and Sciences." When nearly nine he +went to the school of Mr. Thompson, at Compton, in Dorsetshire, where +he remained nearly four years, and read several Greek and Latin +authors, as well as the elements of natural philosophy--the latter in +books lent him by Mr. Jeffrey, the assistant-master. This Mr. Jeffrey +appears to have been something of a mechanical genius, and he gave +Young lessons in turning, drawing, bookbinding, and the grinding and +preparation of colours. Before leaving this school, at the age of +thirteen, Young had read six chapters of the Hebrew Bible. + +During the school holidays the construction of a microscope occupied +considerable time, and the reading of "Priestley on Air" turned +Young's attention to the subject of chemistry. Having learned a little +French, he succeeded, with the help of a schoolfellow, in gaining an +elementary knowledge of Italian. After leaving school, he lived at +home for some time, and devoted his energies mainly to Hebrew and to +turning and telescope-making; but Eastern languages received a share +of attention, and by the time he was fourteen he had read most of Sir +William Jones's "Persian Grammar." He then went to Youngsbury, in +Hertfordshire, and resided at the house of Mr. David Barclay, partly +as companion and partly as classical tutor to Mr. Barclay's grandson, +Hudson Gurney. This was the beginning of a friendship which lasted for +life. Gurney was about a year and a half junior to Young, and for five +years the boys studied together, reading the classical works which +Young had previously studied at school. Before the end of these five +years Young had gained more or less acquaintance with fourteen +languages; but his studies were for a time delayed through a serious +illness when he was little more than sixteen. To this illness his +uncle, Dr. Brocklesby, referred in a letter, of which the following +extract is interesting for several reasons:-- + + Recollect that the least slip (as who can be secure against + error?) would in you, who seem in all things to set yourself + above ordinary humanity, seem more monstrous or reprehensible + than it might be in the generality of mankind. Your prudery + about abstaining from the use of sugar on account of the negro + trade, in any one else would be altogether ridiculous, but as + long as the whole of your mind keeps free from spiritual pride + or too much presumption in your facility of acquiring language, + which is no more than the dross of knowledge, you may be + indulged in such whims, till your mind becomes enlightened with + more reason. My late excellent friend, Mr. Day, the author of + 'Sandford and Merton,' abhorred the base traffic in negroes' + lives as much as you can do, and even Mr. Granville Sharp, one + of the earliest writers on the subject, has not done half as + much service in the business as Mr. Day in the above work. And + yet Mr. Day devoured daily as much sugar as I do; for he + reasonably concluded that so great a system as the sugar-culture + in the West Indies, where sixty millions of British property are + employed, could never be affected either way by one or one + hundred in the nation debarring themselves the reasonable use of + it. Reformation must take its rise elsewhere, if ever there is a + general mass of public virtue sufficient to resist such private + interests. Read Locke with care, for he opens the avenues of + knowledge, though he gives too little himself. + +With respect to the sugar, no doubt very much may be said on Young's +side of the question. It appears, however, that in his early manhood +there was a good deal in his conduct which to-day would be regarded as +_priggish_, though it was somewhat more in harmony with the spirit of +his time. + +He left Youngsbury at the age of nineteen, having read, besides his +classical authors, the whole of Newton's "Principia" and "Opticks," +and the systems of chemistry by Lavoisier and Nicholson, besides works +on botany, medicine, mineralogy, and other scientific subjects. One of +Young's peculiarities was the extraordinary neatness of his +handwriting, and a translation in Greek iambics of Wolsey's farewell +to Cromwell, which he sent, written very neatly on vellum, to his +uncle, Dr. Brocklesby, attracted the attention of Mr. Burke, Dr. +Charles Burney, and other classical scholars, so that when, a few +months later, Young went to stay with his uncle in London, and was +thrown into contact with some of the chief literary men of the day, he +found that his fame as a scholar had preceded him. This neatness of +his handwriting and his power of drawing were of great use in his +researches on the Egyptian hieroglyphics. He had little faith in +natural genius, but believed that anything could be accomplished by +persevering application. + + "Thou say'st not only skill is gained, + But genius too may be obtained, + By studious imitation." + +In the autumn of 1792 Young went to London for the purpose of studying +medicine. He lived in lodgings in Westminster, and attended the +Hunterian School of Anatomy. A year afterwards he entered St. +Bartholomew's Hospital as a medical student. The notes which he took +of the lectures were written sometimes in Latin, interspersed with +Greek quotations, and not unfrequently with mathematical calculations, +which may be assumed to have been made before the lecture commenced. +During his school days he had paid some attention to geometrical +optics, and had constructed a microscope and telescope. Now his +attention was attracted to a far more delicate instrument--the eye +itself. Young had learned how a telescope can be "focussed" so as to +give clear images of objects more or less distant. Some such power of +adjustment must be possessed by the eye, or it could never form +distinct images of objects, whether at a distance of a foot or a +mile. The apparently fibrous structure of the crystalline lens of the +eye had been noticed and described by Leuwenhoeck; and Pemberton, a +century before Young took up the subject, had suggested that the +fibres were muscles, by the action of which the eye was "accommodated" +for near or distant vision. In dissecting the eye of an ox Young +thought he had discovered evidence confirmatory of this view, and the +paper which he wrote on the subject was not only published in the +"Philosophical Transactions," but secured his election as a Fellow of +the Royal Society in June, 1794. This paper was important, not simply +because it led to Young's election to the Royal Society, but mainly +because it was his first published paper on optical subjects. Later on +he showed incontestably, by exact measurements, that it is the +crystalline lens which changes its form during adjustment; but he was +wrong in supposing the fibres of the lens to be muscular. By carefully +measuring the distance between the images of two candles formed by +reflection from the cornea, he showed that the cornea experienced no +change of form. His eyes were very prominent; and turning them so as +to look very obliquely, he measured the length of the eye from back to +front with a pair of compasses whose points were protected, pressing +one point against the cornea, and the other between the back of the +eye and the orbit, and showed that, when the eye was focussed for +different distances, there was no change in the length of the axis. +The crystalline lens was the only resource left whereby the +accommodation could be effected. The accommodation is, in fact, +brought about by the action of the ciliary muscle. The natural form of +the lens is more convex than is consistent with distinct vision, +except for very near objects. The tension of the suspensory ligament, +which is attached to the front of the lens all round its edge, renders +the anterior surface of the lens much less curved than it would +naturally be. The ciliary muscle is a ring of muscular fibre attached +to the ciliary process close to the circumference of the suspensory +ligament. By its contraction it forms a smaller ring, and, diminishing +the external diameter, it releases the tension of the suspensory +ligament, thus allowing the crystalline lens to bulge out and adapt +itself for the diverging rays coming from near objects. It is the +exertion of contracting the ciliary muscle that constitutes the effort +of which we are conscious when looking at very near objects. It was +not, however, till long after the time of Dr. Young that this +complicated action was fully made out, though the change of form of +the anterior surface of the crystalline lens was discovered by the +change in the image of a bright object formed by reflection. + +In the spring of 1794 Young took a holiday tour in Cornwall, with +Hudson Gurney, visiting on his way the Duke of Richmond, who was +drinking the waters at Bath, under the advice of Dr. Brocklesby. In +Cornwall, the mining machinery attracted his attention very much more +than the natural beauties of the country. Towards the end of the +summer he visited the Duke of Richmond at Goodwood, when the duke +offered him the appointment of private secretary. He resolved, +however, to continue his medical course, one of the reasons which he +alleged being his regard for the Society of Friends, whose principles +he considered inconsistent with the appointment of Private Secretary +to the Master-General of the Ordnance. + +The following winter he spent as a medical student at Edinburgh. Here +he gave up the costume of the Society of Friends, and in many ways +departed from their rules of conduct. He mingled freely with the +university, attended the theatre, took lessons in dancing and playing +the flute, and generally cultivated the habits of what is technically +known as "society." Throughout this change in his life he retained his +high moral principles as a guide of conduct, and appears to have acted +from a firm conviction of what was right. At the same time, it must be +admitted that the breaking down of barriers, however conventional they +may be, is an operation attended in most cases by not a little danger. +With Young, the progress of his scientific education may have been +delayed on account of the new demands on his time; but besides the +study of German, Spanish, and Italian, he appears to have read a +considerable amount of general literature during his winter session in +Edinburgh. The following summer he took a tour on horseback through +the Highlands, taking with him his flute, drawing materials, spirits +for preserving insects, boards for drying plants, paper and twine for +packing up minerals, and a thermometer; but the geological hammer does +not then appear to have been regarded as an essential to the equipment +of a philosopher. At Aberdeen he stayed for three days, and reported +thus on the university:-- + + Some of the professors are capable of raising a university to + celebrity, especially Copeland and Ogilvie; but the division and + proximity of the two universities (King's College and Marischal + College) is not favourable to the advancement of learning; + besides, the lectures are all, or mostly, given at the same + hour, and the same professor continues to instruct a class for + four years in the different branches. Were the colleges united, + and the internal regulations of the system new modelled, the + cheapness of the place, the number of small bursaries for poor + or distinguished students, and the merit of the instructors, + might make this university a very respectable seminary in some + branches of science. The fee to a professor for a five-months' + session is only a guinea and a half. I was delighted with the + inspection of the rich store of mathematical and philosophical + apparatus belonging to Professor Copeland of Marischal College, + made in his own house, and partly with his own hands, finished + with no less care than elegance; and tending to illustrate every + branch of physics in the course of his lectures, which must be + equally entertaining and instructive. + +Before leaving the Highlands, Young visited Gordon Castle, where he +stayed two days; and appears to have distinguished himself by the +powers of endurance he exhibited in dancing reels. On leaving he +writes: "I could almost have wished to break or dislocate a limb by +chance, that I might be detained against my will; I do not recollect +that I have ever passed my time more agreeably, or with a party that I +thought more congenial to my own dispositions: and what would hardly +be credited by many grave reasoners on life and manners, that a person +who had spent the whole of his earlier years a recluse from the gay +world, and a total stranger to all that was passing in the higher +ranks of society, should feel himself more at home and more at ease in +the most magnificent palace in the country than in the humblest +dwelling with those whose birth was most similar to his own. Without +enlarging on the duke's good sense and sincerity, the duchess's spirit +and powers of conversation, Lady Madeline's liveliness and affability, +Louisa's beauty and sweetness, Georgiana's _naïveté_ and quickness of +parts, young Sandy's good nature, I may say that I was truly sorry to +part with every one of them." + +Young seems not to have known at this time that it is an essential +feature of true gentlefolk to dissipate all sense of constraint or +uneasiness from those with whom they are brought into contact and +that in this they can be readily distinguished from those who have +wealth without breeding. The Duchess of Gordon gave Young an +introduction to the Duke of Argyll, so, while travelling through the +Western Highlands, he paid a visit to Inverary Castle, and "galloped +over" the country with the duke's daughters. Speaking of these ladies, +he says, "Lady Charlotte ... is to Lady Augusta what Venus is to +Minerva; I suppose she wishes for no more. Both are goddesses." + +On his return to the West of England, he visited the Coalbrook Dale +Iron Works, when Mr. Reynolds told him "that before the war he had +agreed with a man to make a flute a hundred and fifty feet long, and +two and a half in diameter, to be blown by a steam-engine and played +on by barrels." + +On the 7th of the following October Young left London, and after +spending six days on the voyage from Yarmouth to Hamburg, he reached +Göttingen on the 27th of the same month; two days afterwards he +matriculated, and on November 3 he commenced his studies as a member +of the university. He continued to take lessons in drawing, dancing, +riding, and music, and commenced learning the clavichord. The English +students at Göttingen, in order to advance their German conversation, +arranged to pay a fine whenever they spoke in English in one another's +company. On Sundays it was usual for the professors to give +entertainments to the students, though they seldom invited them to +dinner or supper. "Indeed, they could not well afford, out of a fee +of a louis or two, to give large entertainments; but the absence of +the hospitality which prevails rather more in Britain, is compensated +by the light in which the students are regarded; they are not the +less, but perhaps the more, respected for being students, and indeed, +they behave in general like gentlemen, much more so than in some other +German universities." + +At Göttingen Young attended, in addition to his medical lectures, +Spithler's lectures on the History and Constitution of the European +States, Heyne on the History of the Ancient Arts, and Lichtenberg's +course on Physics. Speaking of Blumenbach's lectures on Natural +History, Young says, "He showed us yesterday a laborious treatise, +with elegant plates, published in the beginning of this century at +Wurzburg, which is a most singular specimen of credulity in affairs of +natural history. Dr. Behringen used to torment the young men of a +large school by obliging them to go out with him collecting +petrifactions; and the young rogues, in revenge, spent a whole winter +in counterfeiting specimens, which they buried in a hill which the +good man meant to explore, and imposed them upon him for most +wonderful _lusus naturæ_. It is interesting in a metaphysical point of +view to observe how the mind attempts to accommodate itself; in one +case, where the boys had made the figure of a plant thick and clumsy, +the doctor remarks the difference, and says that Nature seems to have +restored to the plant in thickness that which she had taken away from +its other dimensions." + +On April 30, 1796, Young passed the examination for his medical degree +at Göttingen. The examination appears to have been entirely oral. It +lasted between four and five hours. There were four examiners seated +round a table provided "with cakes, sweetmeats, and wine, which helped +to pass the time agreeably." They "were not very severe in exacting +accurate answers." The subject he selected for his public discussion +was the human voice, and he constructed a universal alphabet +consisting of forty-seven letters, of which, however, very little is +known. This study of sound laid the foundation, according to his own +account, of his subsequent researches in the undulatory theory of +light. + +The autumn of 1796 Young spent in travelling in Germany; in the +following February he returned to England, and was admitted a +fellow-commoner of Emmanuel College, Cambridge. It is said that the +Master, in introducing Young to the Tutors and other Fellows, said, "I +have brought you a pupil qualified to read lectures to his tutors." +Young's opinion of Cambridge, as compared with German universities, +was favourable to the former; but as he had complained of the want of +hospitality at Göttingen, so in Cambridge he complained of the want of +social intercourse between the senior members of the university and +persons _in statu pupillari_. At that time there was no system of +medical education in the university, and the statutes required that +six years should elapse between the admission of a medical student and +his taking the degree of M.B. Young appears to have attracted +comparatively little attention as an undergraduate in college. He did +not care to associate with other undergraduates, and had little +opportunity of intercourse with the senior members of the university. +He was still keeping terms at Cambridge when his uncle, Dr. +Brocklesby, died. To Young he left the house in Norfolk Street, Park +Lane, with the furniture, books, pictures, and prints, and about +£10,000. In the summer of 1798 a slight accident at Cambridge +compelled Young to keep to his rooms, and being thus forcibly deprived +of his usual round of social intercourse, he returned to his favourite +studies in physics. The most important result of this study was the +establishment of the principle of interference in sound, which +afforded the explanation of the phenomenon of "beats" in music, and +which afterwards led up to the discovery of the interference of +light--a discovery which Sir John Herschel characterized as "the key +to all the more abstruse and puzzling properties of light, and which +would alone have sufficed to place its author in the highest rank of +scientific immortality, even were his other almost innumerable claims +to such a distinction disregarded." + +The principle of interference is briefly this: When two waves meet +each other, it may happen that their crests coincide; in this case a +wave will be formed equal in height (amplitude) to the sum of the +heights of the two. At another point the crest of one wave may +coincide with the hollow of another, and, as the waves pass, the +height of the wave at this point will be the difference of the two +heights, and if the waves are equal the point will remain stationary. +If a rope be hung from the ceiling of a lofty room, and the lower end +receive a jerk from the hand, a wave will travel up the rope, be +reflected and reversed at the ceiling, and then descend. If another +wave be then sent up, the two will meet, and their passing can be +observed. It will then be seen that, if the waves are exactly equal, +the point at which they meet will remain at rest during the whole time +of transit. If a number of waves in succession be sent up the string, +the motions of the hand being properly timed, the string will appear +to be divided into a number of vibrating segments separated by +stationary points, or nodes. These nodes are simply the points which +remain at rest on account of the upward series of waves crossing the +series which have been reflected at the top and are travelling +downwards. The division of a vibrating string into nodes thus affords +a simple example of the principle of interference. When a tuning-fork +is vibrating there are certain hyperbolic lines along which the +disturbance caused by one prong is exactly neutralized by that due to +the other prong. If a large tuning-fork be struck and then held near +the ear and slowly turned round, the positions of comparative silence +will be readily perceived. If two notes are being sounded side by +side, one consisting of two hundred vibrations per second and the +other of two hundred and two, then, at any distant point, it is clear +that the two sets of waves will arrive in the same condition, or +"phase," twice in each second, and twice they will be in opposite +conditions, and, if of the same intensity, will exactly destroy one +another's effects, thus producing silence. Hence twice in the second +there will be silence and twice there will be sound, the waves of +which have double the amplitude due to either source, and hence the +sound will have four times the intensity of either note by itself. +Thus there will be two "beats" per second due to interference. Later +on this principle was applied by Young to very many optical phenomena +of which it afforded a complete explanation. + +Young completed his last term of residence at Cambridge in December, +1799, and in the early part of 1800 he commenced practice as a +physician at 48, Welbeck Street. In the following year he accepted the +chair of Natural Philosophy in the Royal Institution, which had +shortly before been founded, and soon afterwards, in conjunction with +Davy, the Professor of Chemistry, he undertook the editing of the +journals of the institution. This circumstance has already been +alluded to in connection with Count Rumford, the founder of the +institution. He lectured at the Royal Institution for two years only, +when he resigned the chair in deference to the popular belief that a +physician should give his attention wholly to his professional +practice, whether he has any or not. This fear lest a scientific +reputation should interfere with his success as a physician haunted +him for many years, and sometimes prevented his undertaking scientific +work, while at other times it led him to publish anonymously the +results he obtained. This anonymous publication of scientific papers +caused him great trouble afterwards in order to establish his claim to +his own discoveries. Many of the articles which he contributed to the +supplement to the fourth, fifth, and sixth editions of the +"Encyclopædia Britannica" were anonymous, although the honorarium he +received for this work was increased by 25 per cent. when he would +allow his name to appear. The practical withdrawal of Young from the +scientific world during sixteen years was a great loss to the progress +of natural philosophy, while the absence of that suavity of manner +when dealing with patients which is so essential to the success of a +physician, prevented him from acquiring a valuable private practice. +In fact, Young was too much of a philosopher in his behaviour to +succeed as a physician; he thought too deeply before giving his +opinion on a diagnosis, instead of appearing to know all about the +subject before he commenced his examination, and this habit, which is +essential to the philosopher, does not inspire confidence in the +practitioner. His fondness for society rendered him unwilling to live +within the means which his uncle had left him, supplemented by what +his scientific work might bring, and it was not until his income had +been considerably increased by an appointment under the Admiralty that +he was willing to forego the possible increase of practice which might +accrue by appearing to devote his whole attention to the subject of +medicine. It was this fear of public opinion which caused him, in +1812, to decline the offer of the appointment of Secretary to the +Royal Society, of which, in 1802, he accepted the office of Foreign +Secretary. + +Young's resignation of the chair of Natural Philosophy was, however, +not a great loss to the Royal Institution; for the lecture audience +there was essentially of a popular character, and Young cannot be +considered to have been successful as a popular lecturer. His own +early education had been too much derived from private reading for him +to have become acquainted with the difficulties experienced by +beginners of only average ability, and his lectures, while most +valuable to those who already possessed a fair knowledge of the +subjects, were ill adapted to the requirements of an unscientific +audience. A syllabus of his course of lectures was published by Young +in 1802, but it was not till 1807 that the complete course of sixty +lectures was published in two quarto volumes. They were republished in +1845 in octavo, with references and notes by Professor Kelland. Among +the subjects treated in these lectures are mechanics, including +strength of materials, architecture and carpentry, clocks, drawing and +modelling; hydrostatics and hydraulics; sound and musical instruments; +optics, including vision and the physical nature of light; astronomy; +geography; the essential properties of matter; heat; electricity and +magnetism; climate, winds, and meteorology generally; vegetation and +animal life, and the history of the preceding sciences. The lectures +were followed by a most complete bibliography of the whole subject, +including works in English, French, German, Italian, and Latin. The +following is the syllabus of one lecture, and illustrates the +diversity of the subjects dealt with:-- + + "ON DRAWING, WRITING, AND MEASURING. + + "Subjects preliminary to the study of practical mechanics; + instrumental geometry; statics; passive strength; friction; + drawing; outline; pen; pencil; chalks; crayons; Indian ink; + water-colours; body colours; miniature; distemper; fresco; oil; + encaustic paintings; enamel; mosaic work. Writing; materials + for writing; pens; inks; use of coloured inks for denoting + numbers; polygraph; telegraph; geometrical instruments; rulers; + compasses; flexible rulers; squares; triangular compasses; + parallel rulers; Marquois's scales; pantograph; proportional + compasses; sector. Measurement of angles; theodolites; + quadrants; dividing-engine; vernier; levelling; sines of + angles; Gunter's scale; Nicholson's circle; dendrometer; + arithmetical machines; standard measures; quotation from + Laplace; new measures; decimal divisions; length of the + pendulum and of the meridian of the earth; measures of time; + objections; comparison of measures; instruments for measuring; + micrometrical scales; log-lines." + +This represents an extensive area to cover in a lecture of one hour. + +When Newton, by means of a prism, + + "Unravelled all the shining robe of day," + +he showed that sunlight is made up of light varying in tint from red, +through orange, yellow, green, and blue, to violet, and that by +recombining all these kinds of light, or certain of them selected in +an indefinite number of ways, white light could be produced. +Subsequently Sir Wm. Herschel showed that rays less refrangible than +the red were to be found among the solar radiation; and other rays +more refrangible than the violet, but, like the ultra-red rays, +incapable of exciting vision, were found by Ritter and Wollaston. In +speaking of Newton's experiments, in his thirty-seventh lecture, Young +says:-- + + It is certain that the perfect sensations of yellow and of blue + are produced respectively by mixtures of red and green and of + green and violet light, and there is reason to suspect that + those sensations are always compounded of the separate + sensations combined; at least, this supposition simplifies the + theory of colours. It may, therefore, be adopted with advantage, + until it be found inconsistent with any of the phenomena; and we + may consider white light as composed of a mixture of red, green, + and violet only, ... with respect to the quantity or intensity + of the sensations produced. + +It should be noticed that, in the above quotation, Young speaks only +of the sensations produced. Objectively considered, sunlight consists +of an infinite number of differently coloured lights comprising nearly +all the shades from one end of the spectrum to the other, though white +light may have a much simpler constitution, and may, for example, +consist simply of a mixture of homogeneous red, green, and violet +lights, or of homogeneous yellow and blue lights, properly selected. +But considered subjectively, Young implies that the eye perceives +three, and only three, distinct colour-sensations, corresponding to +pure red, green, and violet; that when these three sensations are +excited in a certain proportion, the complex sensation is that of +white light; but if the relative intensities of the separate +sensations differ from these ratios, the perception is that of some +colour. To exhibit the effects of mixing light of different colours, +Young painted differently coloured sectors on circles of cardboard, +and then made the discs rotate rapidly about their centres, when the +effect was the same as though the lights emitted by the sectors were +mixed in proportion to the breadth of the sectors. This contrivance +had been previously employed by Newton, and will be again referred to +in connection with another memoir. The results of these experiments +were embodied by Young in a diagram of colour, consisting of an +equilateral triangle, in which the colours red, green, and violet, +corresponding to the simple sensations, were placed at the angles, +while those produced by mixing the primary colours in any proportions, +were to be found within the triangle or along its sides; the rule +being that the colour formed by the admixture of the primary colours +in any proportions, was to be found at the centre of gravity of three +heavy particles placed at the angular points of the triangle, with +their masses proportioned to the corresponding amounts of light. Thus +the colours produced by the admixture of red and green only, in +different proportions, were placed along one side of the triangle, +these colours corresponding to various tints of scarlet, orange, +yellow, and yellowish green; another side contained the mixtures of +green and violet representing the various shades of bluish green and +blue; and the third side comprised the admixtures of red and violet +constituting crimsons and purples. The interior of the triangle +contained the colours corresponding to the mixture of all three +primary sensations, the centre being neutral grey, which is a pure +white faintly illuminated. If white light of a certain degree of +intensity fall on white paper, the paper appears white, but if a +stronger light fall on another portion of the same sheet, that which +is less strongly illuminated appears grey by contrast. Shadows thrown +on white paper may possess any degree of intensity, corresponding to +varying shades of neutral grey, up to absolute blackness, which +corresponds to a total absence of light. Thus considered, +chromatically black and white are the same, differing only in the +amount of light they reflect. A piece of white paper in moonlight is +darker than black cloth in full sunlight. + +It must be remembered that Young's diagram of colours corresponds to +the admixture of coloured lights, not of colouring materials or +pigments. The admixture of blue and yellow lights in proper +proportions may make white or pink, but never green. The admixture of +blue and yellow pigments makes a green, because the blue absorbs +nearly all the light except green, blue, and a little violet, while +the yellow absorbs all except orange, yellow, and green. The green +light is the only light common to the two, and therefore the only +light which escapes absorption when the pigments are mixed. Another +point already noticed must also be carefully borne in mind. Young was +quite aware that, physically, there are an infinite number of +different kinds of light differing continuously in wave-length from +the ultra-red to the ultra-violet, though colour can hardly be +regarded as an attribute of the light considered objectively. The +question of colour is essentially one of perception--a physiological, +not a physical, question--and it is only in this sense that Young +maintained the doctrine of three primary colours. In his paper on the +production of colours, read before the Royal Society on July 1, 1802, +he speaks of "the proportions of the sympathetic fibres of the +retina," corresponding to these primary colour-sensations. According +to this doctrine, white light would always be produced when the three +sensations were affected in certain proportions, whether the exciting +cause were simply two kinds of homogeneous light, corresponding to two +pure tones in music, or an infinite number of different kinds, as in +sunlight; and a particular yellow sensation might be excited by +homogeneous yellow light from one part of the spectrum, or by an +infinite number of rays of different wave-lengths, corresponding to +various shades of red, orange, yellow, and green. Subjectively, the +colours would be the same; objectively, the light producing them would +differ exceedingly. + +But Young's greatest service to science was his application of the +principle of interference--of which he had already made good use in +the theory of sound--to the phenomena of light. The results of these +researches were presented to the Royal Society, and two of the papers +were selected as Bakerian lectures in 1801 and 1803 respectively. +Unfavourable criticisms of these papers, which appeared in the +_Edinburgh Review_, and were said to have been written by Mr. +(afterwards Lord) Brougham, seem to have caused their contents to be +neglected by English men of science for many years; and it was to +Arago and Fresnel that we are indebted for recalling public attention +to them. The undulatory theory of light, which maintains that light +consists of waves transmitted through an _ether_, which pervades all +space and all matter, owes its origin to Hooke and Huyghens. Huyghens +showed that this theory explained, in a very beautiful manner, the +laws of reflection and of refraction, if it be allowed that light +travels more slowly the denser the medium. According to the celebrated +principle of Huyghens, every point in the front of a wave at any +instant becomes a centre of disturbance, from which a secondary wave +is propagated. The fronts of these secondary waves all lie on a +surface, which becomes the new surface of the primary wave. When light +enters a denser medium obliquely, the secondary waves which are +propagated within the denser medium extend to a less distance than +those propagated in the rarer medium, and thus the front of the +primary wave becomes bent at the point where it meets the common +surface. Huyghens explained, not only the laws of ordinary refraction +in this manner, but, by supposing the secondary waves to form +spheroids instead of spheres, he obtained the laws of refraction of +the extraordinary ray in Iceland-spar. He did not, however, succeed in +explaining why light should not diverge laterally instead of +proceeding in straight lines. Newton supported the theory that light +consists of particles or corpuscles projected in straight lines from +the luminous body, and sometimes transmitted, sometimes reflected, +when incident on a transparent medium of different density. To account +for the particle being sometimes transmitted and sometimes reflected, +Newton had recourse to the hypothesis of "fits of easy transmission +and of easy reflection," and, to account for the fits themselves, he +supposed the existence of an ether, the vibrations of which affected +the particles. The laws of reflection were readily explained, being +the same as for a perfectly elastic ball; the laws of refraction +admitted of very simple explanation, by supposing that the particles +of the denser medium exert a greater attraction on the particles of +light than those of the rarer medium, but that this attraction acts +only through very short distances, so that when the light-corpuscle is +at a sensible distance from the surface, it is attracted equally all +round, and moves as though there were no force acting upon it. As a +consequence of this hypothesis, it follows that the velocity of light +must be greater the denser the medium, while the undulatory theory +leads to precisely the opposite result. When Foucault directly +measured the velocity of light both in air and water, and found it +less in the denser medium, the result was fatal to the corpuscular +theory. + +Dr. Young called attention to another crucial test between the two +theories. When a piece of plate-glass is pressed against a slightly +convex lens, or a watch-glass, a series of coloured rings is formed by +reflected light, with a black spot in the centre. This was accounted +for by Newton by supposing that the light which was reflected in any +ring was in a fit of easy transmission (from glass to air) when it +reached the first surface of the film of air, and in a fit of easy +reflection when it reached the second surface. By measuring the +thickness of a film of air corresponding to the first ring of any +particular colour, the length of path corresponding to the interval +between two fits for that particular kind of light could be +determined. When water instead of air is placed between the glasses, +according to the corpuscular theory the rings should expand; but +according to the undulatory theory they should contract; for the +wave-length corresponds to the distance between successive fits of the +same kind on the corpuscular hypothesis. On trying the experiment, the +rings were seen to contract. This result seemed to favour the +undulatory theory; but the objection urged by Newton that rays of +light do not bend round obstacles, like waves of sound, still held its +ground. This objection Young completely demolished by his principle of +interference. He showed that when light passes through an aperture in +a screen, whatever the shape of the aperture, provided its width is +large in comparison with the length of a wave of light (one +fifty-thousandth of an inch), no sensible amount of light will reach +any point not directly in front of the aperture; for if any point be +taken to the right or left, the disturbances reaching that point from +different points of the aperture will neutralize one another by +interference, and thus no light will be appreciable. When the breadth +of the aperture is only a small multiple of a wave-length, then there +will be some points outside the direct beam at which the disturbances +from different points of the aperture will not completely destroy one +another, and others at which they will destroy one another; and these +points will be different for light of different wave-lengths. In this +way Young not only explained the rectilinear propagation of light, but +accounted for the coloured bands formed when light diverges from a +point through a very narrow aperture. In a similar way he accounted +for the hyperbolic bands of colour observed by Grimaldi within the +shadow of a square near its corners. With a strip of card +one-thirtieth of an inch in width, Young obtained bands of colour +within the shadow which completely disappeared when the light was cut +off from either side of the strip of card, showing that they were +produced by interference of the two portions of light which had +passed, one to the right, the other to the left, of the strip of card. +Professor Stokes has succeeded in showing a bright spot at the centre +of the shadow of a circular disc of the size of a sovereign. The +narrow bands of colour formed near the edge of the shadow of any +object, which Newton supposed to be due to the "inflection" of the +light by the attraction of the object, Young showed to be independent +of the material or thickness of the edge, and completely accounted for +them by the principle of interference. Newton's rings were explained +with equal facility. They were due to the interference of light +reflected from the first and second surfaces of the film of air or +water between the glasses. The black spot at the centre of the +reflected rings was due to the difference between reflection taking +place from the surface of a denser or a rarer medium, half an +undulation being lost when the reflection takes place in glass at the +surface of air. If a little grease or water be placed between two +pieces of glass which are nearly in contact, but the space between be +not filled with the water or grease, but contain air in some parts, +and water or grease in others, a series of rings will be seen by +transmitted light, which have been called "the colours of mixed +plates." Young showed that these colours could be accounted for by +interference between the light that had passed through the air and +that which had passed through the water, and explained the fact that, +to obtain the same colour, the distance between the plates must be +much greater than in the case of Newton's rings. + +The bands of colour produced by the interference of light proceeding +from a point and passing on each side of a narrow strip of card, have +already been referred to. The bands are broader the narrower the strip +of card. A fine hair gives very broad bands. When a number of hairs +cross one another in all directions, these bands form circular rings +of colour. If the width of the hairs be very variable, the rings +formed will be of different sizes and overlapping one another, no +distinct series will be visible; but when the hairs are of nearly the +same diameter, a series of well-defined circles of colour, resembling +Newton's rings, will be seen, and if the diameter of a particular ring +be measured, the breadth of the hairs can be inferred. Young +practically employed this method for measuring the diameter of the +fibres of different qualities of wool in order to determine their +commercial value. The instrument employed he called the _eriometer_. +It consisted of a plate of brass pierced with a round hole about +one-thirtieth of an inch in diameter in the centre, and around this a +small circle, about one-third of an inch in diameter, of very fine +holes. The plate was placed in front of a lamp, and the specimen of +wool was held on wires at such a distance in front of the brass plate +that the first green ring appeared to coincide with the circle of +small holes. The eye was placed behind the lock of wool, and the +distance to which the wool had to be removed in front of the brass +plate in order that the first green ring might exactly coincide with +the small circle of fine holes, was proportional to the breadth of the +fibres. The same effect is produced if fine particles, such as +lycopodium powder, or blood-corpuscles, scattered on a piece of glass, +be substituted for the lock of wool, and Young employed the instrument +in order to determine the diameter of blood-corpuscles. He determined +the constant of his apparatus by comparison with some of Dr. +Wollaston's micrometric observations. The coloured halos sometimes +seen around the sun Young referred to the existence of small drops of +water of nearly uniform diameter, and calculated the necessary +diameter for halos of different angular magnitudes. + +The same principle of interference afforded explanation of the colours +of striated surfaces, such as mother-of-pearl, which vary with the +direction in which they are seen. Viewed at one angle light of a +particular colour reflected from different ridges will be in a +condition to interfere, and this colour will be absent from the +reflected light. At a different inclination, the light reaching the +eye from all the ridges (within a certain angle) will be in precisely +the same phase, and only then will light of that colour be reflected +in its full intensity. With a micrometer scale engraved on glass by +Coventry, and containing five hundred lines to the inch, Young +obtained interference spectra. Modern gratings, with several thousand +lines to the inch, afford the purest spectra that can be obtained, and +enable the wave-length of any particular kind of light to be measured +with the greatest accuracy. + +Young's dislike of mathematical analysis prevented him from applying +exact calculation to the interference phenomena which he observed, +such as subsequently enabled Fresnel to overcome the prejudice of the +French Academy and to establish the principle on an incontrovertible +footing. Young's papers attracted very little attention, and Fresnel +made for himself many of Young's earlier discoveries, but at once gave +Young the full credit of the work when his priority was pointed out. +The phenomena of polarization, however, still remained unexplained. +Both Young and Fresnel had regarded the vibrations of light as similar +to those of sound, and taking place in the direction in which the wave +is propagated. The fact that light which had passed through a crystal +of Iceland-spar, was differently affected by a second crystal, +according to the direction of that crystal with respect to the former, +showed that light which had been so transmitted was not like common +light, symmetrical in all azimuths, but had acquired sides or poles. +Such want of symmetry could not be accounted for on the hypothesis +that the vibrations of light took place at right angles to the +wave-front, that is, in the direction of propagation of the light. The +polarization of light by reflection was discovered by Malus, in 1809. +In a letter written to Arago, in 1817, Young hinted at the possibility +of the existence of a component vibration at right angles to the +direction of propagation, in light which had passed through +Iceland-spar. In the following year Fresnel arrived independently at +the hypothesis of transverse vibrations, not as constituting a small +component of polarized light, but as representing completely the mode +of vibration of all light, and in the hands of Fresnel this hypothesis +of transverse vibrations led to a theory of polarization and double +refraction both in uniaxal and biaxal crystals which, though it can +hardly be regarded as complete from a mechanical point of view, is +nevertheless one of the most beautiful and successful applications of +mathematics to physics that has ever been made. To Young, however, +belongs the credit of suggesting that the spheroidal form of the waves +in Iceland-spar might be accounted for by supposing the elasticity +different in the direction of the optic axis and at right angles to +that direction; and he illustrated his view by reference to certain +experiments of Chladni, in which it had been shown that the velocity +of sound in the wood of the Scotch fir is different along, and +perpendicular to, the fibre in the ratio of 5 to 4. Young was also the +first to explain the colours exhibited by thin plates of crystals in +polarized light, discovered by Arago in 1811, by the interference of +the ordinary and extraordinary rays, and Fresnel afterwards completed +Young's explanation in 1822. + +It is for his contributions to the undulatory theory of light that +Young will be most honourably remembered. Hooke, in 1664, referred to +light as a "quick, short, vibrating motion;" Huyghens's "Traité de la +Lumière" was published in 1690. From that time the undulatory theory +lost ground, until it was revived by Young and Fresnel. It soon after +received great support from the establishment, by Joule and others, of +the mechanical theory of heat. One remark of Young's respecting the +ether opens up a question which has attracted much attention of late +years. In a letter addressed to the Secretary of the Royal Society, +and read January 16, 1800, he says:-- + + That a medium, resembling in many properties that which has been + denominated ether, does really exist, is undeniably proved by + the phenomena of electricity; and the arguments against the + existence of such an ether throughout the universe have been + pretty sufficiently answered by Euler. The rapid transmission of + the electrical shock shows that the electric medium is possessed + of an elasticity as great as is necessary to be supposed for the + propagation of light. Whether the electric ether is to be + considered as the same with the luminous ether--if such a fluid + exists--may perhaps at some future time be discovered by + experiment. + +Besides his contributions to optics, Young made distinct advances in +connection with elasticity, and with surface-tension, or +"capillarity." It is said that Leonardo da Vinci was the first to +notice the ascent of liquids in fine tubes by so-called capillary +attraction. This, however, is only one of a series of phenomena now +very generally recognized, and all of which are referable to the same +action. The hanging of a drop from the neck of a phial; the pressure +of air required to inflate a soap-bubble; the flotation of a greasy +needle on the surface of water; the manner in which some insects rest +on water, by depressing the surface, without wetting their legs; the +possibility of filling a tumbler with water until the surface stands +above the edge of the glass; the nearly spherical form of rain-drops +and of small drops of mercury, even when they are resting on a +table,--are all examples of the effect of surface-tension. These +phenomena have recently been studied very carefully by Quincke and +Plateau, and they have been explained in accordance with the principle +of energy by Gauss. Hawksbee, however, was the first to notice that +the rise of a liquid in a fine tube did not depend on the thickness of +the walls of the tube, and he therefore inferred that, if the +phenomena were due to the attraction of the glass for the liquid, it +could only be the superficial layers which produced any effect. This +was in 1709. Segner, in 1751, introduced the notion of a +surface-tension; and, according to his view, the surface of a liquid +must be considered as similar to a thin layer of stretched +indiarubber, except that the tension is always the same at the surface +bounding the same media. This idea of surface-tension was taken up by +Young, who showed that it afforded explanation of all the known +phenomena of "capillarity," when combined with the fact, which he was +himself the first to observe, that the angle of contact of the same +liquid-surface with the same solid is constant. This angle he called +the "appropriate angle." But Young went further, and attempted to +explain the existence of surface-tension itself by supposing that the +particles of a liquid not only exert an attractive force on one +another, which is constant, but also a repulsive force which increases +very rapidly when the distance between them is made very small. His +views on this subject were embodied in a paper on the cohesion of +liquids, read before the Royal Society in 1804. He afterwards wrote an +article on the same subject for the supplement of the "Encyclopædia +Britannica." + +The changes which solids undergo under the action of external force, +and their tendency to recover their natural forms, were studied by +Hooke and Gravesande. The experimental fact that, for small changes of +form, the extension of a rod or string is proportional to the tension +to which it is exposed, is known as Hooke's law. The compression and +extension of the fibres of a bent beam were noticed by James +Bernoulli, in 1630, by Duhamel and others. The bending of beams was +also studied by Coulomb and Robison, but Young appears to have been +almost the first to apply the theory of elasticity to the statics of +structures. In a letter to the Secretary of the Admiralty, written in +1811, in reply to an invitation to report on Mr. Steppings's +improvements in naval architecture, Young claimed that he was the only +person who had published "any attempts to improve the _theory_ of +carpentry." It may be here mentioned that Young accepted the +invitation of the Admiralty, and sent in a very exhaustive report, +which their Lordships regarded as "too learned" to be of great +practical value. Young's contributions to this subject will be chiefly +remembered in connection with his "modulus of elasticity." This he +originally defined as follows:-- + +"The modulus of the elasticity of any substance is a column of the +same substance capable of producing a pressure on its base which is to +the weight causing a certain degree of compression as the length of +the substance is to the diminution of its length." + +It is not usual now to express Young's modulus of elasticity in terms +of a length of the substance considered. As now usually defined, +Young's modulus of elasticity is the force which would stretch a rod +or string to double its natural length if Hooke's law were true for so +great an extension. + +So much of Dr. Young's scientific work has been mentioned here because +it was during his early years of professional practice that his most +original scientific work was accomplished. As already stated, after +two years' tenure of the Natural Philosophy chair at the Royal +Institution, Young resigned it because his friends were of opinion +that its tenure militated against his prospects as a physician. In the +summer of 1802 he escorted the great-nephews of the Duke of Richmond +to Rouen, and took the opportunity of visiting Paris. In March, 1803, +he took his degree of M.B. at Cambridge, and on June 14, 1804, he +married Eliza, second daughter of J. P. Maxwell, Esq., whose country +seat was near Farnborough. For sixteen years after his marriage, Young +resided at Worthing during the summer, where he made a very +respectable practice, returning to London in October or November. In +January, 1811, he was elected one of the physicians of St. George's +Hospital, which appointment he retained for the rest of his life. In +this capacity his practice was considerably in advance of the times, +for he regarded medicine as a science rather than an empirical art, +and his careful methods of induction demanded an amount of attention +which medical students, who preferred the more rough-and-ready methods +then in vogue, were slow to give. The apothecary of the hospital +stated that more of Dr. Young's patients went away cured than of those +who were subjected to the more fashionable treatment; but his private +practice, notwithstanding the sacrifices he had made, never became +very valuable. + +In 1816 Young was appointed Secretary to a Commission for determining +the length of the second's pendulum. The reports of this Commission +were drawn up by him, though the experimental work was carried out by +Captain Kater. The result of the work was embodied in an Act of +Parliament, introduced by Sir George Clerk, in 1824, which provided +that if the standard yard should be lost it should "be restored to the +same length," by making it bear to the length of the second's pendulum +at sea-level in London, the ratio of 36 to 39·1393; but before the +standards were destroyed, in 1835, so many sources of possible error +were discovered in the reduction of pendulum observations, that the +Commission appointed to restore the standards recommended that a +material standard yard should be constructed, together with a number +of copies, so that, in the event of the standard being again +destroyed, it might be restored by comparison with its copies. In 1818 +Young was appointed Superintendent of the Nautical Almanac and +Secretary of the Board of Longitude. When this Board was dissolved in +1828, its functions were assumed by the Admiralty, and Young, Faraday, +and Colonel Sabine were appointed a Scientific Committee of Reference +to advise the Admiralty in all matters in which their assistance might +be required. The income from these Government appointments rendered +Young more independent of his practice, and he became less careful to +publish his scientific papers anonymously. In 1820 he left Worthing +and gave up his practice there. The following year, in company with +Mrs. Young, he took a tour through France, Switzerland, and Italy, and +at Paris attended a meeting of the Institute, where he met Arago, who +had called on him in Worthing, in 1816. At the same time he made the +acquaintance of Laplace, Cuvier, Humboldt, and others. In 1824 he +visited Spa, and took a tour through Holland. In the same year Young +was appointed Inspector of Calculations and Medical Referee to the +Palladium Insurance Company. This caused him to turn his attention to +the subject of life assurance and bills of mortality. In 1825, as +Foreign Secretary of the Royal Society, he had the satisfaction of +forwarding to Fresnel the Rumford Medal in acknowledgment of his +researches on polarized light. Fresnel died, in his fortieth year, a +few days after receiving the medal. + +Dr. Young died on May 10, 1829, in the fifty-sixth year of his age, +his excessive mental exertions in early life having apparently led to +a premature old age. He was buried in the parish church of +Farnborough, and a medallion by Sir Francis Chantrey was erected to +his memory in Westminster Abbey. + +But, though Young was essentially a scientific man, his +accomplishments were all but universal, and any memoir of him would be +very incomplete without some sketch of his researches in Egyptian +hieroglyphics. His classical training, his extensive knowledge of +European and Eastern languages, and his neat handwriting and drawing, +have already been referred to. To these attainments must be added his +scientific _method_ and power of careful and systematic observation, +and it will be seen that few persons could come to the task of +deciphering an unknown language with a better chance of success than +Dr. Young. + +The Rosetta Stone was found by the French while excavating at Fort St. +Pierre, near Rosetta, in 1799, and was brought to England in 1802. The +stone bore an inscription in three different kinds of character--the +Hieroglyphic, the Enchorial or Demotic, and the ordinary Greek. +Young's attention was first called to the Egyptian characters by a +manuscript which was submitted to him in 1814. He then obtained copies +of the inscriptions on the Rosetta Stone and subjected them to a +careful analysis. The latter part of the Greek inscription was very +much injured, but was restored by the conjectures of Porson and Heyne, +and read as follows:--"What is here decreed shall be inscribed on a +block of hard stone, in sacred, in enchorial, and in Greek characters, +and placed in each temple, of the first, second, and third gods." + +This indicated that the three inscriptions contained the same decree, +but, unfortunately, the beginnings of the first and second +inscriptions were lost, so that there were no very definitely fixed +points to start upon. The words "Alexander" and "Alexandria," +however, occurred in the Greek, and these words, being so much alike, +might be recognized in each of the other inscriptions. The word +"Ptolemy" appeared eleven times in the Greek inscription, and there +was a word which, from its length and position, seemed to correspond +to it, which, however, appeared fourteen times in the hieroglyphic +inscription. This word, whenever it appeared in the hieroglyphics, was +surrounded by a ring forming what Champollion called a _cartouche_, +which was always employed to denote the names of royal persons. These +words were identified by Baron Sylvestre de Sacy and the Swedish +scholar Akerblad. Young appears to have started with the idea, then +generally current, that hieroglyphic symbols were purely ideographic, +each sign representing a word. His knowledge of Chinese, however, led +him to modify this view. In that language native words are represented +by single symbols, but, when it is necessary to write a foreign word, +a group of word-symbols is employed, each of which then assumes a +phonetic character of the same value as the initial letter of the word +which it represents. The phonetic value of these signs is indicated in +Chinese by a line at the side, or by enclosing them in a square. Young +supposed that the ring surrounding the royal names in the hieroglyphic +inscription had the same value as the phonetic mark in Chinese, and +from the symbols in the name of Ptolemy he commenced to construct a +hieroglyphic alphabet. He made an error, however, in supposing that +some of the symbols might be syllabic instead of alphabetic. It is +true that in the older inscriptions single signs have sometimes a +syllabic value, and sometimes are used ideographically, while in other +cases a single sign representing the whole word is employed in +conjunction with the alphabetic signs, probably to distinguish the +word from others spelt in the same way, but in inscriptions of so late +a date as the Rosetta Stone, the symbols were purely alphabetic. +Another important step made by Young was the discovery of the use of +_homophones_, or different symbols to represent the same letter. +Young's work was closely followed up by Champollion, and afterwards by +Lepsius, Birsch, and others. The greater part of his researches he +never published, though he made careful examinations of several +funeral rolls and other documents. + +It would occupy too much space to give an adequate account of Young's +researches in this subject; some portion of his work he published in a +popular form in the article "Egypt," in the supplement of the +"Encyclopædia Britannica," to which supplement he contributed about +seventy articles on widely different subjects. Perhaps it is not too +much to say that to Young we owe the foundation of all we now know of +hieroglyphics and the Egyptian history which has been learned from +them; and the obelisk on the Thames Embankment should call to mind the +memory of no one more prominently than that of Thomas Young. + + + + +MICHAEL FARADAY. + + +The work of Michael Faraday introduced a new era in the history of +physical science. Unencumbered by pre-existing theories, and +untrammelled by the methods of the mathematician, he set forth on a +line of his own, and, while engaged in the highest branches of +experimental research, he sought to explain his results by reference +to the most elementary mechanical principles only. Hence it was that +those conclusions which had been obtained by mathematicians only by +the help of advanced analytical methods, and which were expressed by +them only in the language of the integral calculus, Faraday achieved +without any such artificial aids to thought, and expressed in simple +language, having reference to the mechanism which he conceived to be +the means by which such results were brought about. For a long time +Faraday's methods were regarded by mathematicians with something more +than suspicion, and, while they could not but admire his experimental +skill and were compelled to admit the accuracy of his conclusions, his +mode of thought differed too widely from that to which they were +accustomed to command their assent. In Sir William Thomson, and in +Clerk Maxwell, Faraday at length found interpreters between him and +the mathematical world, and to the mathematician perhaps the greatest +monument of the genius of Faraday is the "Electricity and Magnetism" +of Clerk Maxwell. + +Michael Faraday was born at Newington, Surrey, on September 22, 1791, +and was the third of four children. His father, James Faraday, was the +son of Robert and Elizabeth Faraday, of Clapham Wood Hall, in the +north-west of Yorkshire, and was brought up as a blacksmith. He was +the third of ten children, and, in 1786, married Margaret Hastwell, a +farmer's daughter. Soon after his marriage he came to London, where +Michael was born. In 1796 James Faraday, with his family, moved from +Newington, and took rooms over a coach-house in Jacob's Well Mews, +Charles Street, Manchester Square. In looking at this humble abode one +can scarcely help thinking that the Yorkshire blacksmith and his +little family would have been far happier in a country "smiddy" near +his native moors than in a crowded London court; but, had he remained +there, it is difficult to see how the genius of young Michael could +have met with the requisites for its development. + +James Faraday was far from enjoying good health, and his illness +often necessitated his absence from work, and, as a consequence, his +family were frequently in very straitened circumstances. The early +education of Michael was, therefore, not of a very high order, and +consisted "of little more than the rudiments of reading, writing, and +arithmetic." Like most boys in a similar position in London, he found +his amusement for the most part in the streets, but, except that in +his games at marbles we may assume that he played with other boys, we +have no evidence whether his time was spent mostly by himself, or +whether he was one of a "set" of street companions. + +In 1804, when thirteen years of age, Michael Faraday went as +errand-boy to Mr. Geo. Riebau, a bookseller in Blandford Street. Part +of his duty in this capacity was to carry round papers lent on hire by +his master, and in his "Life of Faraday," Dr. Bence Jones tells how +anxious the young errand-boy was to collect his papers on Sunday +morning in time to attend the Sandemanian service with the other +members of his family. + +Faraday was apprenticed to Mr. Riebau on October 7, 1805, and learned +the business of a bookbinder. He occasionally occupied his spare time +in reading the scientific books he had to bind, and was particularly +interested in Mrs. Marcet's "Conversations in Chemistry," and in the +article on "Electricity" in the "Encyclopædia Britannica." These were +days before the existence of the London Society for the Extension of +University Teaching, and, though Professor Anderson in Glasgow had +shown how the advantages of a university might be extended to those +whose fortunes prevented them from becoming regular university +students, Professor Stuart had not yet taught the English universities +that they had responsibilities outside their own borders, and that the +national universities of the future must be the teachers of all +classes of the community. But private enterprise supplied in a measure +the neglect of public bodies. Mr. Tatum, of 43, Dorset Street, Fleet +Street, advertised a course of lectures on natural philosophy, to be +delivered at his residence at eight o'clock in the evenings. The price +of admission was high, being a shilling for each lecture, but +Michael's brother Robert frequently supplied him with the money, and +in attending these lectures Faraday made many friendships which were +valuable to him afterwards. + +Faraday appears to have been aware of the value of skill in drawing--a +point to which much attention has recently been called by those +interested in technical education--and he spent some portion of his +time in studying perspective, so as to be better able to illustrate +his notes of Mr. Tatum's lectures, as well as of some of Sir Humphry +Davy's, which he was enabled to hear at the Royal Institution through +the kindness of a customer at Mr. Riebau's shop. + +In 1812, before the end of his apprenticeship, Faraday was engaged in +experiments with voltaic batteries of his own construction. Having +cut out seven discs of zinc the size of halfpence, and covered them +with seven halfpence, he formed a pile by inserting pieces of paper +soaked in common salt between each pair, and found that the pile so +constructed was capable of decomposing Epsom salts. With a somewhat +larger pile he decomposed copper sulphate and lead acetate, and made +some experiments on the decomposition of water. On July 21, 1812, in +writing to his friend Abbott, he mentions the movements of camphor +when floating on water, and adds, "Science may be illustrated by those +minute actions and effects, almost as much as by more evident and +obvious phenomena.... My knife is so bad that I cannot mend my pen +with it; it is now covered with copper, having been employed to +precipitate that metal from the muriatic acid." + +Something of Faraday's disposition, as well as of the results of his +self-education, may be gathered from the following quotations from +letters to Abbott, written at this time:-- + + I have again gone over your letter, but am so blinded that I + cannot see any subject except chlorine to write on; but before + entering on what I intend shall fill up the letter, I will ask + your pardon for having maintained an opinion against one who was + so ready to give his own up. I suspect from that circumstance I + am wrong.... In the present case I conceive that experiments may + be divided into three classes: first, those which are for the + old theory of oxymuriatic acid, and consequently oppose the new + one; second, those which are for the new one, and oppose the old + theory; and third, those which can be explained by both + theories--apparently so only, for in reality a false theory can + never explain a fact. + + It is not for me to affirm that I am right and you wrong; + speaking impartially, I can as well say that I am wrong and you + right, or that we both are wrong and a third right. I am not so + self-opinionated as to suppose that my judgment and perception + in this or other matters is better or clearer than that of other + persons; nor do I mean to affirm that this is the true theory in + reality, but only that my judgment conceives it to be so. + Judgments sometimes oppose each other, as in this case; and as + there cannot be two opposing facts in nature, so there cannot be + two opposing truths in the intellectual world. Consequently, + when judgments oppose, one must be wrong--one must be false; and + mine may be so for aught I can tell. I am not of a superior + nature to estimate exactly the strength and correctness of my + own and other men's understanding, and will assure you, dear + A----, that I am far from being convinced that my own is always + right. I have given you the theory--not as the true one, but as + the one which appeared true to me--and when I perceive errors in + it, I will immediately renounce it, in part or wholly, as my + judgment may direct. From this, dear friend, you will see that I + am very open to conviction; and from the manner in which I + shall answer your letter, you will also perceive that I must be + convinced before I renounce. + +On October 7, 1812, Faraday's apprenticeship terminated, and +immediately afterwards he started life as a journeyman bookbinder. He +now found that he had less time at his disposal for scientific work +than he had enjoyed when an apprentice, and his desire to give up his +trade and enter fully upon scientific pursuits became stronger than +ever. During his apprenticeship he had written to Sir Joseph Banks, +then President of the Royal Society, in the hope of obtaining some +scientific employment; he now applied to Sir Humphry Davy. In a letter +written to Dr. Paris, in 1829, Faraday gave an account of this +application. + +"My desire to escape from trade, which I thought vicious and selfish, +and to enter into the service of science, which I imagined made its +pursuers amiable and liberal, induced me at last to take the bold and +simple step of writing to Sir H. Davy, expressing my wishes, and a +hope that, if an opportunity came in his way, he would favour my +views; at the same time, I sent the notes I had taken of his lectures. + +"The answer, which makes all the point of my communication, I send you +in the original, requesting you to take great care of it, and to let +me have it back, for you may imagine how much I value it. + +"You will observe that this took place at the end of the year 1812; +and early in 1813 he requested to see me, and told me of the situation +of assistant in the laboratory of the Royal Institution, then just +vacant. + +"At the same time that he thus gratified my desires as to scientific +employment, he still advised me not to give up the prospects I had +before me, telling me that Science was a harsh mistress, and, in a +pecuniary point of view, but poorly rewarding those who devoted +themselves to her service. He smiled at my notion of the superior +moral feelings of philosophic men, and said he would leave me to the +experience of a few years to set me right on that matter. + +"Finally, through his good efforts, I went to the Royal Institution, +early in March of 1813, as assistant in the laboratory; and in October +of the same year went with him abroad, as his assistant in experiments +and in writing. I returned with him in April, 1815, resumed my station +in the Royal Institution, and have, as you know, ever since remained +there." + +Sir H. Davy's letter was as follows:-- + + "SIR, + + "I am far from displeased with the proof you have given me of + your confidence, and which displays great zeal, power of + memory, and attention. I am obliged to go out of town, and + shall not be settled in town till the end of January; I will + then see you at any time you wish. It would gratify me to be + of any service to you; I wish it may be in my power. + + "I am, sir, + "Your obedient humble servant, + "H. DAVY." + +The minutes of the meeting of managers of the Royal Institution, on +March 1, 1813, contain the following entry:--"Sir Humphry Davy has the +honour to inform the managers that he has found a person who is +desirous to occupy the situation in the institution lately filled by +William Payne. His name is Michael Faraday. He is a youth of +twenty-two years of age. His habits seem good, his disposition active +and cheerful, and his manner intelligent. He is willing to engage +himself on the same terms as those given to Mr. Payne at the time of +quitting the institution. + +"Resolved, that Michael Faraday be engaged to fill the situation +lately occupied by Mr. Payne, on the same terms." + +About this time Faraday joined the City Philosophical Society, which +had been started at Mr. Tatum's house in 1808. The members met every +Wednesday evening, either for a lecture or discussion; and perhaps the +society did not widely differ from some of the "students' +associations" which have more recently been started in connection with +other educational enterprises. Magrath was secretary of this society, +and from it there sprang a smaller band of students, who, meeting once +a week, either at Magrath's warehouse in Wood Street, or at Faraday's +private rooms in the attics of the Royal Institution, for mutual +improvement, read together, and freely criticized each other's +pronunciation and composition. In a letter to Abbott six weeks after +commencing work at the Royal Institution, Faraday says:-- + + A stranger would certainly think you and I were a couple of very + simple beings, since we find it necessary to write to each + other, though we so often personally meet; but the stranger + would, in so judging, only fall into that error which envelops + all those who decide from the outward appearances of things.... + When writing to you I seek that opportunity of striving to + describe a circumstance or an experiment clearly; so that you + will see I am urged on by selfish motives partly to our mutual + correspondence, but, though selfish, yet not censurable. + +During the summer of 1813 Faraday, in his letters to Abbott, gave his +friend the benefit of his experience "on the subject of lectures and +lecturers in general," in a manner that speaks very highly of his +power of observation of men as well as things. He was of opinion that +a lecture should not last more than an hour, and that the subject +should "fit the audience." + +"A lecturer may consider his audience as being polite or vulgar (terms +I wish you to understand according to Shuffleton's new dictionary), +learned or unlearned (with respect to the subject), listeners or +gazers. Polite company expect to be entertained, not only by the +subject of the lecture, but by the manner of the lecturer; they look +for respect, for language consonant to their dignity, and ideas on a +level with their own. The vulgar--that is to say, in general, those +who will take the trouble of thinking, and the bees of business--wish +for something that they can comprehend. This may be deep and elaborate +for the learned, but for those who are as yet tyros and unacquainted +with the subject, must be simple and plain. Lastly, listeners expect +reason and sense, whilst gazers only require a succession of words." + +In favour of experimental illustration he says:-- + +"I need not point out ... the difference in the perceptive powers of +the eye and the ear, and the facility and clearness with which the +first of these organs conveys ideas to the mind--ideas which, being +thus gained, are held far more retentively and firmly in the memory +than when introduced by the ear.... Apparatus, therefore, is an +essential part of every lecture in which it can be introduced.... When +... apparatus is to be exhibited, some kind of order should be +observed in the arrangement of them on the lecture-table. Every +particular part illustrative of the lecture should be in view, no one +thing should hide another from the audience, nor should anything stand +in the way of or obstruct the lecturer. They should be so placed, too, +as to produce a kind of uniformity in appearance. No one part should +appear naked and another crowded, unless some particular reason +exists and makes it necessary to be so." + +On October 13, 1813, Faraday left the Royal Institution, in order to +accompany Sir Humphry Davy in a tour on the Continent. His journal +gives some interesting details, showing the inconveniences of foreign +travel at that time. Sir Humphry Davy took his carriage with him in +pieces, and these had to be put together after escaping the dangers of +the French custom-house on the quay at Morlaix, two years before the +battle of Waterloo. + +One apparently trivial incident somewhat marred Faraday's pleasure +throughout this journey. It was originally intended that the party +should comprise Sir Humphry and Lady Davy, Faraday, and Sir Humphry's +valet, but at the last moment that most important functionary declined +to leave his native shores. Davy then requested Faraday to undertake +such of the duties of valet as were essential to the well-being of the +party, promising to secure the services of a suitable person in Paris. +But no eligible candidate appeared for the appointment, and thus +Faraday had throughout to take charge of domestic affairs as well as +to assist in experiments. Had there been only Sir Humphry and himself, +this would have been no hardship. Sir Humphry had been accustomed to +humble life in his early days; but the case was different with his +lady, and, apparently, Faraday was more than once on the point of +leaving his patron and returning home alone. A circumstance which +occurred at Geneva illustrates the position of affairs. Professor E. +de la Rive invited Sir Humphry and Lady Davy and Faraday to dinner. +Sir Humphry could not go into society with one who, in some respects, +acted as his valet. When this point was represented to the professor, +he replied that he was sorry, as it would necessitate his giving +another dinner-party. Faraday subsequently kept up a correspondence +with De la Rive, and continued it with his son. In writing to the +latter he says, in speaking of Professor E. de la Rive, that he was +"the first who personally at Geneva, and afterwards by correspondence, +encouraged and by that sustained me." + +At Paris Faraday met many of the most distinguished men of science of +the time. One morning Ampère, Clément, and Desormes called on Davy, to +show him some iodine, a substance which had been discovered only about +two years before, and Davy, while in Paris, and afterwards at +Montpellier, executed a series of experiments upon it. After three +months' stay, the party left Paris for Italy, _viâ_ Montpellier, Aix, +and Nice, whence they crossed the Col de Tende to Turin. The transfer +of the carriage and baggage across the Alps was effected by a party of +sixty-five men, with sledges and a number of mules. The description of +the journey, as recorded in Faraday's diary, makes us respect the +courage of an Englishman who, in the early part of this century, would +attempt the conveyance of a carriage across the Alps in the winter. + +"From Turin we proceeded to Genoa, which place we left afterwards in +an open boat, and proceeded by sea towards Lerici. This place we +reached after a very disagreeable passage, and not without +apprehensions of being overset by the way. As there was nothing there +very enticing, we continued our route to Florence; and, after a stay +of three weeks or a month, left that fine city, and in four days +arrived here at Rome." The foregoing is from Faraday's letter to his +mother. At Florence a good deal of time was spent in the Academia del +Cimento. Here Faraday saw the telescope with which Galileo discovered +Jupiter's satellites, with its tube of wood and paper about three feet +and a half long, and simple object-glass and eye-glass. A red velvet +electric machine with a rubber of gold paper, Leyden jars pierced by +the discharge between their armatures, the first lens constructed by +Galileo, and a number of other objects, were full of interest to the +recently enfranchised bookbinder's apprentice; but it was the great +burning-glass of the grand-duke which was the most serviceable of all +the treasures of the museum. With this glass--which consisted of two +convex lenses about three feet six inches apart, the first lens having +a diameter of about fourteen or fifteen inches, and the second a +diameter of three inches--Davy succeeded in burning several diamonds +in oxygen gas, and in proving that the diamond consists of little else +than carbon. In 1818 Faraday published a paper on this subject in the +_Quarterly Journal of Science_. At Genoa some experiments were made +with the torpedo, but the specimens caught were very small and weak, +and their shocks so feeble that no definite results were obtained. At +Rome Davy attempted to repeat an experiment of Signor Morrichini, +whereby a steel needle was magnetized by causing the concentrated +violet and blue rays from the sun to traverse the needle from the +middle to the north end several times. The experiment did not succeed +in the hands of Davy and Faraday, and it was left to the latter to +discover a relation between magnetism and light. From Rome they +visited Naples and ascended Vesuvius, and shortly afterwards left +Italy for Geneva. In the autumn of 1814 they returned from Switzerland +through Germany, visiting Berne, Zurich, the Tyrol, Padua, Venice, and +Bologne, to Florence, where Davy again carried out some chemical +investigations in the laboratory of the academy. Thence they returned +to Rome, and in the spring went on to Naples, and again visited +Vesuvius, returning to England in April, _viâ_ Rome, the Tyrol, +Stuttgart, Brussels, and Ostend. + +A fortnight after his return from the Continent Faraday was again +assistant at the Royal Institution, but with a salary of thirty +shillings a week. His character will be sufficiently evident from the +quotations which have been given from his diary and letters. +Henceforth we must be mainly occupied with the consideration of his +scientific work. + +In January, 1816, he gave his first lecture to the City Philosophical +Society. In a lecture delivered shortly afterwards before the same +society, the following passage, which gives an idea of one of the +current beliefs of the time, occurs:-- + +"The conclusion that is now generally received appears to be that +light consists of minute atoms of matter of an octahedral form, +possessing polarity, and varying in size or in velocity.... + +"If now we conceive a change as far beyond vaporization as that is +above fluidity, and then take into account also the proportional +increased extent of alteration as the changes rise, we shall, perhaps, +if we can form any conception at all, not fall far short of radiant +matter;[6] and as in the last conversion many qualities were lost, so +here also many more would disappear. + +[Footnote 6: Not Crookes's.] + +"It was the opinion of Newton, and of many other distinguished +philosophers, that this conversion was possible, and continually going +on in the processes of nature, and they found that the idea would bear +without injury the application of mathematical reasoning--as regards +heat, for instance. If assumed, we must also assume the simplicity of +matter; for it would follow that all the variety of substances with +which we are acquainted could be converted into one of three kinds of +radiant matter, which again may differ from one another only in the +size of their particles or their form. The properties of known bodies +would then be supposed to arise from the varied arrangements of their +ultimate atoms, and belong to substances only as long as their +compound nature existed; and thus variety of matter and variety of +properties would be found co-essential. The simplicity of such a +system is singularly beautiful, the idea grand and worthy of Newton's +approbation. It was what the ancients believed, and it may be what a +future race will realize." + +In the closing words of his fifth lecture to the City Philosophical +Society, Faraday said:-- + +"The philosopher should be a man willing to listen to every +suggestion, but determined to judge for himself. He should not be +biassed by any appearances; have no favourite hypothesis; be of no +school; and in doctrine have no master. He should not be a respecter +of persons, but of things. Truth should be his primary object. If to +these qualities be added industry, he may indeed hope to walk within +the veil of the temple of nature." + +Many years afterwards he stated that, of all the suggestions to which +he had patiently listened after his lectures at the Royal Institution, +only one proved on investigation to be of any value, and that led to +the discovery of the "extra current" and the whole subject of +self-induction. + +Faraday always kept a note-book, in which he jotted down any thoughts +which occurred to him in reference to his work, as well as extracts +from books or other publications which attracted his attention. He +called it his "commonplace-book." Many of the queries which he here +took note of he subsequently answered by experiment. For example:-- + +"Query: the nature of sounds produced by flame in tubes." + +"Convert magnetism into electricity." + +"General effects of compression, either in condensing gases or +producing solutions, or even giving combinations at low temperature." + +"Do the pith-balls diverge by the disturbance of electricity through +mutual induction or not?" + +Speaking of this book, he says, "I already owe much to these notes, +and think such a collection worth the making by every scientific man. +I am sure none would think the trouble lost after a year's +experience." + +In a letter dated May 3, 1818, he writes:-- + + I have this evening been busy with an atmospherical electrical + apparatus. It was a very temporary thing, but answered the + purpose completely. A wire, with some small brush-wire rolled + round the top of it, was elevated into the atmosphere by a thin + wood rod having a glass tube at the end, and tied to a + chimney-pot on the housetop; and this wire was continued down + (taking care that it touched nothing in its way) into the + lecture-room; and we succeeded, at intervals, in getting sparks + from it nearly a quarter of an inch in length, and in charging a + Leyden jar, so as to give a strong shock. The electricity was + positive. Now, I think you could easily make an apparatus of + this kind, and it would be a constant source of interesting + matter; only take care you do not kill yourself or knock down + the house. + +On June 12, 1820, he married Miss Sarah Barnard, third daughter of Mr. +Barnard, of Paternoster Row--"an event which," to use his own words, +"more than any other contributed to his earthly happiness and +healthful state of mind." It was his wish that the day should be "just +like any other day"--that there should be "no bustle, no noise, no +hurry occasioned even in one day's proceeding," though in carrying out +this plan he offended some of his relations by not inviting them to +his wedding. + +Up to this time Faraday's experimental researches had been for the +most part in the domain of chemistry, and for two years a great part +of his energy had been expended in investigating, in company with Mr. +Stodart, a surgical instrument-maker, the properties of certain alloys +of steel, with a view to improve its manufacture for special purposes. +It was in 1821 that he commenced his great discoveries in electricity. +In the autumn of that year he wrote an historical sketch of +electro-magnetism for the "Annals of Philosophy," and he repeated for +himself most of the experiments which he described. In the course of +these experiments, in September, 1821, he discovered the rotation of a +wire conveying an electric current around the pole of a magnet. +[OE]rsted had discovered, in 1820, the tendency of a magnetic needle +to set itself at right angles to a wire conveying a current. This +action is due to a tendency on the part of the north pole to revolve +in a right-handed direction around the current, while the south pole +tends to revolve in the opposite direction. The principle that action +and reaction are equal and opposite indicates that, if a magnetic pole +tend to rotate around a conductor conveying a current, there must be +an equal tendency for the conductor to rotate around the pole. It was +this rotation that constituted Faraday's first great discovery in +electro-dynamics. On December 21, in the same year, Faraday showed +that the earth's magnetism was capable of exerting a directive action +on a wire conveying a current. Writing to De la Rive on the subject, +he says:-- + + I find all the usual attractions and repulsions of the magnetic + needle by the conjunctive wire are deceptions, the motions + being, not attractions or repulsions, nor the result of any + attractive or repulsive forces, but the result of a force in the + wire, which, instead of bringing the pole of the needle nearer + to or further from the wire, endeavours to make it move round it + in a never-ending circle and motion whilst the battery remains + in action. I have succeeded, not only in showing the existence + of this motion theoretically, but experimentally, and have been + able to make the wire revolve round a magnetic pole, or a + magnetic pole round the wire, at pleasure. The law of + revolution, and to which all the other motions of the needle are + reducible, is simple and beautiful. + + Conceive a portion of connecting wire north and south, the north + end being attached to the positive pole of a battery, the south + to the negative. A north magnetic pole would then pass round it + continually in the apparent direction of the sun, from east to + west above, and from west to east below. Reverse the connections + with the battery, and the motion of the pole is reversed; or, if + the south pole be made to revolve, the motions will be in the + opposite direction, as with the north pole. + + If the wire be made to revolve round the pole, the motions are + according to those mentioned.... Now, I have been able, + experimentally, to trace this motion into its various forms, as + exhibited by Ampère's helices, etc., and in all cases to show + that the attractions and repulsions are only appearances due to + this circulation of the pole; to show that dissimilar poles + repel as well as attract, and that similar poles attract as well + as repel; and to make, I think, the analogy between the helix + and common bar magnet far stronger than before. But yet I am by + no means decided that there are currents of electricity in the + common magnet. I have no doubt that electricity puts the circles + of the helix into the same state as those circles are in that + may be conceived in the bar magnet; but I am not certain that + this state is directly dependent on the electricity, or that it + cannot be produced by other agencies; and therefore, until the + presence of electric currents be proved in the magnet by other + than magnetical effects, I shall remain in doubt about Ampère's + theory. + +The most convenient rule by which to remember the direction of these +electro-magnetic rotations is probably that given by Clerk Maxwell, +which will be stated in its place.[7] If a circular plate of copper +and another of zinc be connected by a piece (or better, by three +pieces) of insulated wire, so that the zinc is about an inch above the +copper, and the combined plates be suspended by a silk fibre in a +small beaker of dilute sulphuric acid, which is placed on the pole of +a large magnet, the liquid will be seen to rotate about a vertical +axis in one direction, and the two plates with their connecting wires +in the opposite direction. On reversing the polarity of the magnet, +both rotations will be reversed. This is a very simple mode of +exhibiting Faraday's discovery. A little powdered resin renders the +motion of the liquid readily visible. + +[Footnote 7: See p. 302.] + +In 1823 Faraday published his work on the liquefaction of gases, from +which he concluded that there was no difference in kind between gases +and vapours. In the course of this work he met with more than one +serious explosion. On January 8, 1824, he was elected a Fellow of the +Royal Society, and in 1825, on the recommendation of Sir Humphry Davy, +he was appointed Director of the Laboratory of the Royal Institution, +and in this capacity he instituted the laboratory conferences, which +developed into the Friday evening lectures. For five years after +this, the greater part of Faraday's spare time was occupied in some +investigations in connection with optical glass, made at the request +of the Royal Society, and at the expense of the Government. Mr. +Dollond and Sir John Herschel were associated with him on this +committee, but the results obtained were not of much value to +opticians. The silico-borate of lead which Faraday prepared in the +course of these experiments was, however, the substance with which he +first demonstrated the effect of a magnetic field on the plane of +polarization of light, and with which he discovered diamagnetic +action. + +Faraday's experimental researches were generally guided by theoretical +considerations. Frequently these theories were based on very slender +premises, and sometimes were little else than flights of a scientific +imagination, but they served to guide him into fruitful fields of +discovery, and he seldom placed much confidence in his conclusions +till he had succeeded in verifying them experimentally. For many years +he had held the opinion that electric currents should exhibit +phenomena analogous to those of electro-static induction. Again and +again he returned to the investigation, and attempted to obtain an +induced current in one wire through the passage of a powerful current +through a neighbouring conductor; but he looked for a permanent +induced current to be maintained during the whole time that the +primary current was flowing. At length, employing two wires wound +together as a helix on a wooden rod, the first capable of transmitting +a powerful current from a battery, while the second was connected with +a galvanometer, he observed that, when the current started in the +primary, there was a movement of the galvanometer, and when it ceased +there was a movement in the opposite direction, though the +galvanometer remained at zero while the current continued steady. +Hence it was apparent that it is by changes in the primary current +that induced currents may be generated, and not by their steady +continuance; and it was demonstrated that, when a current is started +in a conductor, a temporary current is induced in a neighbouring +conductor in the opposite direction, while a current is induced in the +same direction as the primary when the latter ceases to flow. Before +obtaining this result with the wires on a wooden bobbin, he had +experimented with a wrought-iron ring about six inches in diameter, +and made of 7/8-inch round iron. He wound two sets of coils round it, +one occupying nearly half the ring, and the other filling most of the +other half. One of these he connected with a galvanometer, the other +could be connected at will with a battery. On sending the battery +current through the latter coil, the galvanometer needle swung +completely round four or five times, and a similar action took place, +but in the opposite direction, on stopping the current. Here it was +clearly the magnetism induced in the iron ring which produced so +powerful a current in the galvanometer circuit. Next he wound a +quantity of covered copper wire on a small iron bar, and connecting +the ends to a galvanometer, he placed the little bobbin between the +opposite poles of a pair of bar magnets, whose other ends were in +contact. As soon as the iron core touched the magnets, a current +appeared in the galvanometer. On breaking contact, the current was in +the opposite direction. Then came the experiment above mentioned, in +which no iron was employed. After this, one end of a cylindrical bar +magnet was introduced into a helix of copper wire, and then suddenly +thrust completely in. The galvanometer connected with the coil showed +a transient current. On withdrawing the magnet, the current appeared +in the opposite direction; so that currents were induced merely by the +relative motion of a magnet and a conductor. + +A copper disc was mounted so that it could be made to rotate rapidly. +A wire was placed in connection with the centre of the disc, and the +circuit completed by a rubbing contact on the circumference. A +galvanometer was inserted in the circuit, and the large horseshoe +magnet of the Royal Institution so placed that the portion of the disc +between the centre and the rubbing contact passed between the poles of +the magnet. A current flowed through the galvanometer as long as the +disc was kept spinning. Then he found that the mere passage of a +copper wire between the poles of the magnet was sufficient to induce a +current in it, and concluded that the production of the current was +connected with the cutting of the "magnetic curves," or "lines of +magnetic force" which would be depicted by iron filings. Thus in the +course of ten days' experimental work, in the autumn of 1831, Faraday +so completely investigated the phenomena of electro-magnetic induction +as to leave little, except practical applications, to his successors. +A few weeks later he obtained induction currents by means of the +earth's magnetism only, first with a coil of wire wound upon an iron +bar in which a strong current was produced when it was being quickly +placed in the direction of the magnetic dip or being removed from that +position, and afterwards with a coil of wire without an iron core. On +February 8, 1832, he succeeded in obtaining a spark from the induced +current. Unless the electro-motive force is very great, it is not +possible to obtain a spark between two metallic surfaces which are +separated by a sensible thickness of air. If, however, the circuit of +a wire is broken _while_ the current is passing, a little bridge of +metallic vapour is formed, across which for an instant the spark +leaps. The induced current being of such short duration, the +difficulty was to break the circuit while it was flowing. Faraday +wound a considerable length of fine wire around a short bar of iron; +the ends of the wire were crossed so as just to be in contact with one +another, but free to separate if exposed to a slight shock. The ends +of the iron bar projected beyond the coil, and were held just over the +poles of the magnet. On releasing the bar it fell so as to strike the +magnetic poles and close the circuit of the magnet. An induced current +was generated in the wire, but, while this was passing, the shock +caused by the bar striking the magnet separated the ends of the wire, +thus breaking the circuit of the conductor, and a spark appeared at +the gap. In this little spark was the germ of the electric light of +to-day. Subsequently Faraday improved the apparatus, by attaching a +little disc of amalgamated copper to one end of the wire, and bending +over the other end so as just to press lightly against the surface of +the disc. With this apparatus he showed the "magnetic spark" at the +meeting of the British Association at Oxford. + +Faraday supposed that when a coil of wire was in the neighbourhood of +a magnet, or near to a conductor conveying a current, the coil was +thrown into a peculiar condition, which he called the _electro-tonic +state_, and that the induced currents appeared whenever this state was +assumed or lost by the coil. He frequently reverted to his conception +of the electro-tonic state, though he saw clearly that, when the +currents were induced by the relative motion of a wire and a magnet, +the current induced depended on the rate at which the lines of +magnetic force had been cut by the wire. Of his conception of lines of +force filling the whole of space, we shall have more to say presently. +It is sufficient to remark here that, in the electro-tonic state of +Faraday, Clerk Maxwell recognized the number of lines of magnetic +force enclosed by the circuit, and showed that the electro-motive +force induced is proportional to the rate of change of the number of +lines of force thus enclosed. + +It is seldom that a great discovery is made which has not been +gradually led up to by several observed phenomena which awaited that +discovery for their explanation. In the case of electro-magnetic +induction, however, there appears to have been but one experiment +which had baffled philosophers, and the key to which was found in +Faraday's discovery, while the complete explanation was given by +Faraday himself. Arago had found that, if a copper plate were made +rapidly to rotate beneath a freely suspended magnetic needle, the +needle followed (slowly) the plate in its revolution, though a sheet +of glass were inserted between the two to prevent any air-currents +acting on the magnet. The experiment had been repeated by Sir John +Herschel and Mr. Babbage, but no explanation was forthcoming. Faraday +saw that the revolution of the disc beneath the poles of the magnet +must generate induced currents in the disc, as the different portions +of the metal would be constantly cutting the lines of force of the +magnet. These currents would react upon the magnet, causing a +mechanical stress to act between the two, which, as stated by Lenz, +would be in the direction tending to oppose the _relative_ motion, and +therefore to drag the magnet after the disc in its revolution. In the +above figure the unfledged arrows show the general distribution of the +currents in the disc, while the winged arrows indicate the direction +of the disc's rotation. The currents in the semicircle A will repel +the north pole and attract the south pole. Those in the semicircle B +will produce the opposite effect, and hence there will be a tendency +for the magnet to revolve in the direction of the disc, while the +motion of the disc will be resisted. This resistance to the motion of +a conductor in a magnetic field was noticed by Faraday, and, +independently, by Tyndall, and it is sufficiently obvious in the power +absorbed by dynamos when they are generating large currents. + +Faraday's next series of researches was devoted to the experimental +proof of the identity of frictional and voltaic electricity. He showed +that a magnet could be deflected and iodide of potassium decomposed by +the current from his electrical machine, and came to the conclusion +that the amount of electricity required to decompose a grain of water +was equal to 800,000 charges of his large Leyden battery. The current +from the frictional machine also served to deflect the needle of his +galvanometer. These investigations led on to a complete series of +researches on the laws of electrolysis, wherein Faraday demonstrated +the principle that, however the strength of the current may be varied, +the amount of any compound decomposed is proportional to the whole +quantity of electricity which has passed through the electrolyte. When +the same current is sent through different compounds, there is a +constant relation between the amounts of the several compounds +decomposed. In modern language, Faraday's laws may be thus +expressed:-- + +_If the same current be made to pass through several different +electrolytes, the quantity of each ion produced will be proportional +to its combining weight divided by its valency, and if the current +vary, the quantity of each ion liberated per second will be +proportional to the current._ + +This is the great law of electro-chemical equivalents. The amount of +hydrogen liberated per second by a current of one ampère is about +·00001038 gramme, or nearly one six-thousandth of a grain. This is the +electro-chemical equivalent of hydrogen. That of any other substance +may be found by Faraday's law. + +From Faraday's results it appears that the passage of the same amount +of electricity is required in order to decompose one molecule of any +compound of the same chemical type, but it does not follow that the +same amount of energy is employed in the decomposition. For example, +the combining weights of copper and zinc are nearly equal. Hence it +will require the passage of about the same amount of electricity to +liberate a pound of copper from, say, the copper sulphate as to +liberate a pound of zinc from zinc sulphate; but the work to be done +is much less in the case of the copper. This is made manifest in the +following way:--A battery, which will just decompose the copper salt +slowly, liberating copper, oxygen, and sulphuric acid, will not +decompose the zinc salt at all so as to liberate metallic zinc, but +immediately on sending the current through the electrolyte, +polarization will set in, and the opposing electro-motive force thus +introduced will become equal to that of the battery, and stop the +current before metallic zinc makes its appearance. In the case of the +copper, polarization also sets in, but never attains to equality with +the electro-motive force of the primary battery. In fact, in all cases +of electrolysis, polarization produces an opposing electro-motive +force strictly proportional to the work done in the cell by the +passage of each unit of electricity. If the strength of the battery be +increased, so that it is able to decompose the zinc sulphate, and if +this battery be applied to the copper sulphate solution, the latter +will be _rapidly_ decomposed, and the excess of energy developed by +the battery will be converted into heat in the circuit. + +One important point in connection with electrolysis which Faraday +demonstrated is that the decomposition is the result of the passage of +the current, and is not simply due to the attraction of the +electrodes. Thus he showed that potassium iodide could be decomposed +by a stream of electricity coming from a metallic point on the prime +conductor of his electric machine, though the point did not touch the +test-paper on which the iodide was placed. + +It was in 1834 that Mr. Wm. Jenkin, after one of the Friday evening +lectures at the Royal Institution, called the attention of Faraday to +a shock which he had experienced in breaking the circuit of an +electro-magnet, though the battery employed consisted of only one pair +of plates. Faraday repeated the experiment, and found that, with a +large magnet in circuit, a strong spark could thus be obtained. On +November 14, 1834, he writes, "The phenomenon of increased spark is +merely a case of the induction of electric currents. If a current be +established in a wire, and another wire forming a complete circuit be +placed parallel to it, at the moment the current in the first is +stopped it induces a current in the same direction in the second, +itself then showing but a feeble spark. But if the second be away, it +induces a current in its own wire in the same direction, producing a +strong spark. The strong spark in the current when alone is therefore +the equivalent of the current it can produce in a neighbouring wire +when in company." The strong spark does, in fact, represent the energy +of the current due to the self-induction of its circuit, which energy +would, in part at least, be expended in inducing a current in a +neighbouring wire if such existed. + +His time from 1835 till 1838 was largely taken up with his work on +electro-static induction. Faraday could never be content with any +explanation based on direct action at a distance; he always sought for +the machinery through which the action was communicated. In this +search the lines of magnetic force, which he had so often delineated +in iron filings, came to his aid. Faraday made many pictures in iron +filings of magnetic fields due to various combinations of magnets. He +employed gummed paper, and when the filings were arranged on the hard +gummed surface, he projected a feeble jet of steam on the paper, which +melted the gum and fixed the filings. Several of his diagrams were +exhibited at the Loan Collection at South Kensington. He conceived +electrical action to be transmitted along such lines as these, and to +him the whole electric field was filled with lines passing always from +positive to negative electrification, and in some respects resembling +elastic strings. The action at any place could then be expressed in +terms of the lines of force that existed there, the electrifications +by which these lines were produced being left out of consideration. +The acting bodies were thus replaced by the field of force they +produced. He showed that it was impossible to call into existence a +charge of positive electricity without at the same time producing an +equal negative charge. From every unit of positive electricity he +conceived a line of force to start, and thus, with the origin of the +line, there was created simultaneously a charge of negative +electricity on which the line might terminate. By the famous ice-pail +experiment he showed that, when a charged body is inserted in a closed +or nearly closed hollow conductor, an equal amount of the same kind of +electricity appeared on the outside of the hollow conductor, while an +equal amount of the opposite kind appeared on the interior surface of +the conductor. With the ice-pail and the butterfly-net he showed that +there could be no free electricity on the interior of a conductor. +Lines of force cannot pass through the material of a conductor without +producing electric displacement. Every element of electricity must be +joined to an equal amount of the opposite kind by a line of force. +Such lines cannot pass through the conductor itself; hence the charge +must be entirely on the outside of the conductor, so that every +element of the charge may be associated with an equal amount of the +opposite electricity upon the surfaces of surrounding objects. Thus to +Faraday every electrical action was an exhibition of electric +induction. All this work had been done before by Henry Cavendish, but +neither Faraday nor any one else knew about it at the time. From the +fact that there could be no electricity in the interior of a hollow +conductor, Cavendish deduced, in the best way possible, the truth of +the law of inverse squares as applied to electrical attraction and +repulsion, and thus laid the foundation of the mathematical theory of +electricity. To Cavendish every electrical action was a displacement +of an incompressible fluid which filled the whole of space, producing +no effect in conductors on account of the freedom of its motion, but +producing strains in insulators by displacing the material of the +body. Faraday, in his lines of force, saw, as it were, the lines along +which the displacements of Cavendish's fluid took place. + +Faraday thought that, if he could show that electric induction could +take place along curved lines, it would prove that the action took +place through a medium, and not directly at a distance. He succeeded +in experimentally demonstrating the curvature of these lines; but his +conclusions were not warranted, for if we conceive of two or more +centres of force acting directly at a distance according to the law of +inverse squares, the resultant lines of force will generally be +curved. Of course, this does not prove the possibility of direct +action at a distance, but only shows that the curvature of the lines +is as much a consequence of the one hypothesis as of the other. + +It soon appeared to Faraday that the nature of the dielectric had very +much to do with electric induction. The capacity of a condenser, for +instance, depends on the nature of the dielectric as well as on the +configuration of the conductors. To express this property, Faraday +employed the term "specific inductive capacity." He compared the +electric capacity of condensers, equal in all other respects, but one +possessing air for its dielectric, and the other having other media, +and thus roughly determined the specific inductive capacities of +several insulators. These results turned out afterwards to be of great +value in connection with the insulation of submarine cables. Even now +the student of electricity is sometimes puzzled by the manner in which +specific inductive capacity is introduced to his notice as modifying +the capacity of condensers, after learning that the capacity of any +system of conductors can be calculated from its geometrical +configuration; but the fact is that the intensity of all electrical +actions depends on the nature of the medium through which they take +place, and it will require more electricity to exert upon an equal +charge a unit force at unit distance when the intervening medium has a +high than when it possesses a low specific inductive capacity. + +In 1835 Faraday received a pension from the civil list; in 1836 he was +appointed scientific adviser to the Elder Brethren of the Trinity +House. In the same year he was made a member of the Senate of the +University of London, and in that capacity he has exerted no small +influence on the scientific education of the country, for he was one +of those who drew up the schedules of the various examinations. + +In his early years, Faraday thought that all kinds of matter might +ultimately consist of three materials only, and that as gases and +vapours appeared more nearly to resemble one another than the liquids +or solids to which they corresponded, so each might be subject to a +still higher change in the same direction, and the gas or vapour +become radiant matter--either heat, light, or electricity. Later on, +Faraday clearly recognized the dynamical nature of heat and light; but +his work was always guided by his theoretical conceptions of the +"correlation of the physical forces." For a long time he had tried to +discover relations between electricity and light; at length, on +September 13, 1845, after experimenting on a number of other +substances, he placed a piece of silico-borate of lead, or +heavy-glass, in the field of the magnet, and found that, when a beam +of polarized light was transmitted through the glass in the direction +of the lines of magnetic force, there was a rotation of the plane of +polarization. Afterwards it appeared that all the transparent solids +and liquids experimented on were capable of producing this rotation in +a greater or less degree, and in the case of all non-magnetic +substances the rotation was in the direction of the electric current, +which, passing round the substance, would produce the magnetic field +employed. Abandoning the magnet, and using only a coil of wire with +the transparent substance within it, similar effects were obtained. +Thus at length a relation was found between light and electricity. + +On November 4, employing a piece of heavy-glass and a new horseshoe +magnet, Faraday noticed that the magnet appeared to have a directive +action upon the glass. Further examination showed that the glass was +repelled by the magnetic poles. Three days afterwards he found that +all sorts of substances, including most metals, were acted upon like +the heavy-glass. Small portions of them were repelled, while elongated +cylinders tended to set with their lengths perpendicular to the lines +of magnetic force. Such actions could be imitated by suspending a +feebly magnetic body in a medium more magnetic than itself. Faraday, +therefore, sought for some medium which would be absolutely neutral to +magnetic action. Filling a glass tube with compressed oxygen, and +suspending it in an atmosphere of oxygen at ordinary pressure, the +compressed gas behaved like iron or other magnetic substances. +Faraday compared the intensity of its action with that of ferrous +sulphate, and this led to an explanation of the diurnal variations of +the compass-needle based on the sun's heat diminishing the magnetic +_permeability_ of the oxygen of the air. Repeating the experiment with +nitrogen, he found that the compressed gas behaved in a perfectly +neutral manner when surrounded by the gas at ordinary pressure. Hence +he inferred that in nitrogen he had found the neutral medium required. +Repeating his experiments in an atmosphere of nitrogen, it still +appeared that most bodies were repelled by the magnetic poles, and set +_equatorially_, or at right angles to the lines of force when +elongated portions were tested. To this action Faraday gave the name +of diamagnetism. + +About a month after his marriage, Faraday joined the Sandemanian +Church, to which his family had for several generations belonged, by +confession of sin and profession of faith. Not unfrequently he used to +speak at the meetings of his Church, but in 1840 he was elected an +elder, and then he took his turn regularly in conducting the services. +The notes of his addresses he generally made on small pieces of card. +He had a curious habit of separating his religious belief from his +scientific work, although the spirit of his religion perpetually +pervaded his life. A lecture on mental education, given in 1854, at +the Royal Institution, in the presence of the late Prince Consort, he +commenced as follows:-- + +"Before entering on this subject, I must make one distinction, which, +however it may appear to others, is to me of the utmost importance. +High as man is placed above the creatures around him, there is a +higher and far more exalted position within his view; and the ways are +infinite in which he occupies his thoughts about the fears, or hopes, +or expectations of a future life. I believe that the truth of that +future cannot be brought to his knowledge by any exertion of his +mental powers, however exalted they may be; that it is made known to +him by other teaching than his own, and is received through simple +belief of the testimony given. Let no one suppose for a moment that +the self-education I am about to commend, in respect of the things of +this life, extends to any considerations of the hope set before us, as +if man by reasoning could find out God. It would be improper here to +enter upon this subject further than to claim an absolute distinction +between religious and ordinary belief. I shall be reproached with the +weakness of refusing to apply those mental operations which I think +good in respect of high things to the very highest. I am content to +bear the reproach. Yet even in earthly matters I believe that 'the +invisible things of Him from the creation of the world are clearly +seen, being understood by the things that are made, even His eternal +power and Godhead;' and I have never seen anything incompatible +between those things of man which can be known by the spirit of man +which is within him, and those higher things concerning his future +which he cannot know by that spirit." + +On more than one occasion the late Prince Consort had discussed +physical questions with Faraday, and in 1858 the Queen offered him a +house on Hampton Court Green. This was his home until August 25, 1867. +He saw not only the magnetic spark, which he had first produced, +employed in the lighthouses at the South Foreland and Dungeness, but +he saw also his views respecting lines of electric induction examined +and confirmed by the investigations of Thomson and Clerk Maxwell. + +Of the ninety-five distinctions conferred upon him, we need only +mention that of Commandant of the Legion of Honour, which he received +in January, 1856. + + + + +JAMES CLERK MAXWELL. + + +The story of the life of James Clerk Maxwell has been told so recently +by the able pen of his lifelong friend, Professor Lewis Campbell, that +it is unnecessary, in the few pages which now remain to us, to attempt +to give a repetition of the tale which would not only fail to do +justice to its subject, but must of necessity fall far short of the +merits of the (confessedly imperfect) sketch which has recently been +placed within the reach of all. Looking back on the life of Clerk +Maxwell, he seems to have come amongst us as a light from another +world--to have but partly revealed his message to minds too often +incapable of grasping its full meaning, and all too soon to have +returned to the source from whence he came. There was scarcely any +branch of natural philosophy that he did not grapple with, and upon +which his vivid imagination and far-seeing intelligence did not throw +light. He was born a philosopher, and at every step Nature partly drew +aside the veil and revealed that which was hidden from a gaze less +prophetic. A very brief sketch of the principal incidents in his life +may, however, not be out of place. + +James Clerk Maxwell was born in Edinburgh, on June 13, 1831. His +father, John Clerk Maxwell, was the second son of James Clerk, of +Penicuik, and took the name of Maxwell on inheriting the estate at +Middlesbie. His mother was the daughter of R. H. Cay, Esq., of North +Charlton, Northumberland. James was the only child who survived +infancy. + +Some years before his birth his parents had built a house at Glenlair, +which had been added to their Middlesbie estate, and resided there +during the greater part of the year, though they retained their house +in Edinburgh. Hence it was that James's boyish days were spent almost +entirely in the country, until he entered the Edinburgh Academy in +1841. As a child, he was never content until he had completely +investigated everything which attracted his attention, such as the +hidden courses of bell-wires, water-streams, and the like. His +constant question was "What's the go o' that?" and, if answered in +terms too general for his satisfaction, he would continue, "But what's +the particular go of it?" This desire for the thorough investigation +of every phenomenon was a characteristic of his mind through life. +From a child his knowledge of Scripture was extensive and accurate, +and when eight years old he could repeat the whole of the hundred and +nineteenth psalm. About this time his mother died, and thenceforward +he and his father became constant companions. Together they would +devise all sorts of ingenious mechanical contrivances. Young James was +essentially a child of nature, and free from all conventionality. He +loved every living thing, and took delight in petting young frogs, and +putting them into his mouth to see them jump out. One of his +attainments was to paddle on the duck-pond in a wash-tub, and to make +the vessel go "without spinning"--a recreation which had to be +relinquished on washing-days. He was never without the companionship +of one or two terriers, to whom he taught many tricks, and with whom +he seemed to have complete sympathy. + +As a boy, Maxwell was not one to profit much by the ordinary teaching +of the schools, and experience with a private tutor at home did not +lead to very satisfactory results. At the age of ten, therefore, he +was sent to the Edinburgh Academy, under the care of Archdeacon +Williams, who was then rector. On his first appearance in this +fashionable school, he was naturally a source of amusement to his +companions; but he held his ground, and soon gained more respect than +he had previously provoked ridicule. While at school in Edinburgh, he +resided with his father's sister, Mrs. Wedderburn, and devoted a very +considerable share of his time and attention to relieving the solitude +of the old man at Glenlair, by letters written in quaint styles, +sometimes backwards, sometimes in cypher, sometimes in different +colours, so arranged that the characters written in a particular +colour, when placed consecutively, formed another sentence. All the +details of his school and home life, and the special peculiarities of +the masters at the academy, were thus faithfully transmitted to his +father, by whom the letters were religiously preserved. At thirteen he +had evidently made progress in solid geometry, though he had not +commenced Euclid, for he writes to his father, "I have made a +tetrahedron, a dodecahedron, and two other hedrons whose names I don't +know." In these letters to Glenlair he generally signed himself, "Your +most obedient servant." Sometimes his fun found vent even upon the +envelope; for example:-- + + "Mr. John Clerk Maxwell, + "Postyknowswere, + "Kirkpatrick Durham, + "Dumfries." + +Sometimes he would seal his letters with electrotypes of natural +objects (beetles, etc.), of his own making. In July, 1845, he +writes:-- + + I have got the eleventh prize for scholarship, the first for + English, the prize for English verses, and the mathematical + medal. + +When only fifteen a paper on oval curves was contributed by him to the +_Proceedings of the Royal Society of Edinburgh_. In the spring of 1847 +he accompanied his uncle on a visit to Mr. Nicol, the inventor of the +Nicol prism, and on his return he made a polariscope with glass and a +lucifer-match box, and sketched in water-colours the chromatic +appearances presented by pieces of unannealed glass which he himself +prepared. These sketches he sent to Mr. Nicol, who presented him in +return with a pair of prisms of his own construction. The prisms are +now in the Cavendish Laboratory at Cambridge. Maxwell found that, for +unannealed glass, pieces of window-glass placed in bundles of eight or +nine, one on the other, answered the purpose very well. He cut the +figures, triangles, squares, etc., with a diamond, heated the pieces +of glass on an iron plate to redness in the kitchen fire, and then +dropped them into a plate of iron sparks (scales from the smithy) to +cool. + +In 1847 Maxwell entered the University of Edinburgh, and during his +course of study there he contributed to the Royal Society of Edinburgh +papers upon rolling curves and on the equilibrium of elastic solids. +His attention was mostly devoted to mathematics, physics, chemistry, +and mental and moral philosophy. In 1850 he went to Cambridge, +entering Peterhouse, but at the end of a year he "migrated" to +Trinity; here he was soon surrounded with a circle of friends who +helped to render his Cambridge life a very happy one. His love of +experiment sometimes extended to his own mode of life, and once he +tried sleeping in the evening and working after midnight, but this was +soon given up at the request of his father. One of his friends writes, +"From 2 to 2.30 a.m. he took exercise by running along the upper +corridor, _down_ the stairs, along the lower corridor, then _up_ the +stairs, and so on until the inhabitants of the rooms along his track +got up and laid _perdus_ behind their sporting-doors, to have shots at +him with boots, hair-brushes, etc., as he passed." His love of fun, +his sharp wit, his extensive knowledge, and above all, his complete +unselfishness, rendered him a universal favourite in spite of the +temporary inconveniences which his experiments may have occasionally +caused to his fellow-students. + +An undergraduate friend writes, "Every one who knew him at Trinity can +recall some kindness or some act of his which has left an ineffaceable +impression of his goodness on the memory--for 'good' Maxwell was in +the best sense of the word." The same friend wrote in his diary in +1854, after meeting Maxwell at a social gathering, "Maxwell, as usual, +showing himself acquainted with every subject on which the +conversation turned. I never met a man like him. I do believe there is +not a single subject on which he cannot talk, and talk well too, +displaying always the most curious and out-of-the-way information." +His private tutor, the late well-known Mr. Hopkins, said of him, "It +is not possible for that man to think incorrectly on physical +subjects." + +In 1854 Maxwell took his degree at Cambridge as second wrangler, and +was bracketed with the senior wrangler (Mr. E. J. Routh) for the +Smith's prize. During his undergraduate course, he appears to have +done much of the work which formed the basis of his subsequent papers +on electricity, particularly that on Faraday's lines of force. The +colour-top and colour-box appear also to have been gradually +developing during this time, while the principle of the stereoscope +and the "art of squinting" received their due share of attention. +Shortly after his degree, he devoted a considerable amount of time to +the preparation of a manuscript on geometrical optics, which was +intended to form a university text-book, but was never completed. In +the autumn of 1855 he was elected Fellow of Trinity. About this time +the colour-top was in full swing, and he also constructed an +ophthalmoscope. In May, 1855, he writes:-- + + The colour trick came off on Monday, 7th. I had the proof-sheets + of my paper, and was going to read; but I changed my mind and + talked instead, which was more to the purpose. There were sundry + men who thought that blue and yellow make green, so I had to + undeceive them. I have got Hay's book of colours out of the + University Library, and am working through the specimens, + matching them with the top. + +The "colour trick" came off before the Cambridge Philosophical Society. + +While a Bachelor Fellow, Maxwell gave lectures to working men in +Barnwell, besides lecturing in college. His father died in April, +1856, and shortly afterwards he was appointed Professor of Natural +Philosophy in Marischal College, Aberdeen. This appointment he held +until the fusion of the college with King's College in 1860. These +four years were very productive of valuable work. During them the +dynamical top was constructed, which illustrates the motion of a rigid +body about its axis of greatest, least, or mean moment of inertia; +for, by the movement of certain screws, the axis of the top may be +made to coincide with any one at will. The Adams Prize Essay on the +stability of Saturn's rings belongs also to this period. In this essay +Maxwell showed that the phenomena presented by Saturn's rings can only +be explained on the supposition that they consist of innumerable small +bodies--"a flight of brickbats"--each independent of all the others, +and revolving round Saturn as a satellite. He compared them to a siege +of Sebastopol from a battery of guns measuring thirty thousand miles +in one direction, and a hundred miles in the other, the shots never +stopping, but revolving round a circle of a hundred and seventy +thousand miles radius. A solid ring of such dimensions would be +completely crushed by its own weight, though made of the strongest +material of which we have any knowledge. If revolving at such a rate +as to balance the attraction of the planet at one part, the stress in +other parts would be more than sufficient to crush or tear the ring. +Laplace had shown that a narrow ring might revolve about the planet +and be stable if so loaded that its centre of gravity was at a +considerable distance from its centre, and thought that Saturn's +rings might consist of a number of such unsymmetrical rings--a theory +to which some support was given by the many small divisions observable +in the bright rings. Maxwell showed that, for stability, the mass +required to load each of Laplace's rings must be four and a half times +that of the rest of the ring; and the system would then be far too +artificially balanced to be proof against the action of one ring on +another. He further showed that, in liquid rings, waves would be +produced by the mutual action of the rings, and that before long some +of these waves would be sure to acquire such an amplitude as would +cause the rings to break up into small portions. Finally, he concluded +that the only admissible theory is that of the independent satellites, +and that the _average_ density of the rings so found cannot be much +greater than that of air at ordinary pressure and temperature. + +While he remained at Aberdeen, Maxwell lectured to working men in the +evenings, on the principles of mechanics. On the whole, it is doubtful +whether Aberdeen society was as congenial to him as that of Cambridge +or Edinburgh. He seems not to have been understood even by his +colleagues. On one occasion he wrote:-- + + Gaiety is just beginning here again.... No jokes of any kind are + understood here. I have not made one for two months, and if I + feel one coming I shall bite my tongue. + +But every cloud has its bright side, and, however Maxwell may have +been regarded by his colleagues, he was not long without congenial +companionships. An honoured guest at the home of the Principal, "in +February, 1858, he announced his betrothal to Katherine Mary Dewar, +and they were married early in the following June." Professor Campbell +speaks of his married life as one of unexampled devotion, and those +who enjoyed the great privilege of seeing him at home could more than +endorse the description. + +In 1860 Maxwell accepted the chair of Natural Philosophy at King's +College, London. Here he continued his lectures to working men, and +even kept them up for one session after resigning the chair in 1865. +On May 17, 1861, he gave his first lecture at the Royal Institution, +on "The Theory of the Three Primary Colours." This lecture embodies +many of the results of his work with the colour-top and colour-box, to +be again referred to presently. While at King's College, he was placed +on the Electrical Standards Committee of the British Association, and +most of the work of the committee was carried out in his laboratory. +Here, too, he compared the electro-static repulsion between two discs +of brass with the electro-magnetic attraction of two coils of wire +surrounding them, through which a current of electricity was allowed +to flow, and obtained a result which he afterwards applied to the +electro-magnetic theory of light. The colour-box was perfected, and +his experiments on the viscosity of gases were concluded during his +residence in London. These last were described by him in the Bakerian +Lecture for 1866. + +After resigning the professorship at King's College, Maxwell spent +most of his time at Glenlair, having enlarged the house, in accordance +with his father's original plans. Here he completed his great work on +"Electricity and Magnetism," as well as his "Theory of Heat," an +elementary text-book which may be said to be without a parallel. + +On March 8, 1871, he accepted the chair of Experimental Physics in the +University of Cambridge. This chair was founded in consequence of an +offer made by the Duke of Devonshire, the Chancellor of the +University, to build and equip a physical laboratory for the use of +the university. In this capacity Maxwell's first duty was to prepare +plans for the laboratory. With this view, he inspected the +laboratories of Sir William Thomson at Glasgow, and of Professor +Clifton at Oxford, and endeavoured to embody the best points of both +in the new building. The result was that, in conjunction with Mr. W. +M. Fawcett, the architect, he secured for the university a laboratory +noble in its exterior, and admirably adapted to the purposes for which +it is required. The ground-floor comprises a large battery-room, which +is also used as a storeroom for chemicals; a workshop; a room for +receiving goods, communicating by a lift with the apparatus-room; a +room for experiments on heat; balance-rooms; a room for pendulum +experiments, and other investigations requiring great stability; and a +magnetic observatory. The last two rooms are furnished with stone +supports for instruments, erected on foundations independent of those +of the building, and preserved from contact with the floor. On the +first floor is a handsome lecture-theatre, capable of accommodating +nearly two hundred students. The lecture-table is carried on a wall, +which passes up through the floor without touching it, the joists +being borne by separate brick piers. The lecture-theatre occupies the +height of the first and second floors; its ceiling is of wood, the +panels of which can be removed, thus affording access to the +roof-principals, from which a load of half a ton or more may be safely +suspended over the lecture-table. The panels of the ceiling, adjoining +the wall which is behind the lecturer, can also be readily removed, +and a "window" in this wall communicates with the large +electrical-room on the second floor. Access to the space above the +ceiling of the lecture-theatre is readily obtained from the tower. +Adjoining the lecture-room is the preparation-room, and communicating +with the latter is the apparatus-room. This room is fitted with +mahogany and plate-glass wall and central cases, and at present +contains, besides the more valuable portions of the apparatus +belonging to the laboratory, the marble bust of James Clerk Maxwell, +and many of the home-made pieces of apparatus and other relics of his +early work. The rest of the first floor is occupied by the +professor's private room and the general students' laboratory. +Throughout the building the brick walls have been left bare for +convenience in attaching slats or shelves for the support of +instruments. The second floor contains a large room for electrical +experiments, a dark room for photography, and a number of private +rooms for original work. Water is laid on to every room, including a +small room in the top of the tower, and all the windows are provided +with broad stone ledges without and within the window, the two +portions being in the same horizontal plane, for the support of +heliostats or other instruments. The building is heated with hot +water, but in the magnetic observatory the pipes are all of copper and +the fittings of gun-metal. Open fireplaces for basket fires are also +provided. Over the principal entrance of the laboratory is placed a +stone statue of the present Duke of Devonshire, together with the arms +of the university and of the Cavendish family, and the Cavendish +motto, "Cavendo Tutus." Maxwell presented to the laboratory, in 1874, +all the apparatus in his possession. He usually gave a course of +lectures on heat and the constitution of bodies in the Michaelmas +term; on electricity in the Lent term; and on electro-magnetism in the +Easter term. The following extract from his inaugural lecture, +delivered in October, 1871, is worthy of the attention of all students +of science:-- + + Science appears to us with a very different aspect after we + have found out that it is not in lecture-rooms only, and by + means of the electric light projected on a screen, that we may + witness physical phenomena, but that we may find illustrations + of the highest doctrines of science in games and gymnastics, in + travelling by land and by water, in storms of the air and of the + sea, and wherever there is matter in motion. + + The habit of recognizing principles amid the endless variety of + their action can never degrade our sense of the sublimity of + nature, or mar our enjoyment of its beauty. On the contrary, it + tends to rescue our scientific ideas from that vague condition + in which we too often leave them, buried among the other + products of a lazy credulity, and to raise them into their + proper position among the doctrines in which our faith is so + assured that we are ready at all times to act on them. + Experiments of illustration may be of very different kinds. Some + may be adaptations of the commonest operations of ordinary life; + others may be carefully arranged exhibitions of some phenomenon + which occurs only under peculiar conditions. They all, however, + agree in this, that their aim is to present some phenomenon to + the senses of the student in such a way that he may associate + with it some appropriate scientific idea. When he has grasped + this idea, the experiment which illustrates it has served its + purpose. + + In an experiment of research, on the other hand, this is not the + principal aim.... Experiments of this class--those in which + measurement of some kind is involved--are the proper work of a + physical laboratory. In every experiment we have first to make + our senses familiar with the phenomenon; but we must not stop + here--we must find out which of its features are capable of + measurement, and what measurements are required in order to make + a complete specification of the phenomenon. We must then make + these measurements, and deduce from them the result which we + require to find. + + This characteristic of modern experiments--that they consist + principally of measurements--is so prominent that the opinion + seems to have got abroad that, in a few years, all the great + physical constants will have been approximately estimated, and + that the only occupation which will then be left to men of + science will be to carry these measurements to another place of + decimals. + + If this is really the state of things to which we are + approaching, our laboratory may, perhaps, become celebrated as a + place of conscientious labour and consummate skill; but it will + be out of place in the university, and ought rather to be + classed with the other great workshops of our country, where + equal ability is directed to more useful ends. + + But we have no right to think thus of the unsearchable riches of + creation, or of the untried fertility of those fresh minds into + which these riches will continually be poured.... The history + of Science shows that, even during that phase of her progress + in which she devotes herself to improving the accuracy of the + numerical measurement of quantities with which she has long been + familiar, she is preparing the materials for the subjugation of + new regions, which would have remained unknown if she had been + contented with the rough methods of her early pioneers. + +Maxwell's "Electricity and Magnetism" was published in 1873. Shortly +afterwards there were placed in his hands, by the Duke of Devonshire, +the Cavendish Manuscripts on Electricity, already alluded to. To these +he devoted much of his spare time for several years, and many of +Cavendish's experiments were repeated in the laboratory by Maxwell +himself, or under his direction by his students. The introductory +matter and notes embodied in "The Electrical Researches of the +Honourable Henry Cavendish, F.R.S.," afford sufficient evidence of the +amount of labour he expended over this work. The volume was published +only a few weeks before his death. Another of Maxwell's publications, +which, as a text-book, is unique and beyond praise, is the little book +on "Matter and Motion," published by the S.P.C.K. + +In 1878 Maxwell, at the request of the Vice-Chancellor, delivered the +Rede Lecture in the Senate-House. His subject was the telephone, which +was just then absorbing a considerable amount of public attention. +This was the last lecture which he ever gave to a large public +audience. + +It was during his tenure of the Cambridge chair that one of the +cottages on the Glenlair estate was struck by lightning. The discharge +passed down the damp soot and blew out several stones from the base of +the chimney, apparently making its way to some water in a ditch a few +yards distant. The cottage was built on a granite rock, and this event +set Maxwell thinking about the best way to protect, from lightning, +buildings which are erected on granite or other non-conducting +foundations. He decided that the proper course was to place a strip of +metal upon the ground all round the building, to carry another strip +along the ridge-stay, from which one or more pointed rods should +project upwards, and to unite this strip with that upon the ground by +copper strips passing down each corner of the building, which is thus, +as it were, enclosed in a metal cage. + +After a brief illness, Maxwell passed away on November 5, 1879. His +intellect and memory remained perfect to the last, and his love of fun +scarcely diminished. During his illness he would frequently repeat +hymns, especially some of George Herbert's, and Richard Baxter's hymn +beginning + + "Lord, it belongs not to my care." + +"No man ever met his death more consciously or more calmly." + +It has been stated that Thomas Young propounded a theory of +colour-vision which assumes that there exist three separate +colour-sensations, corresponding to red, green, and violet, each +having its own special organs, the excitement of which causes the +perception of the corresponding colour, other colours being due to the +excitement of two or more of these simple sensations in different +proportions. Maxwell adopted blue instead of violet for the third +sensation, and showed that if a particular red, green, and blue were +selected and placed at the angular points of an equilateral triangle, +the colours formed by mixing them being arranged as in Young's +diagram, all the shades of the spectrum would be ranged along the +sides of this triangle, the centre being neutral grey. For the mixing +of coloured lights, he at first employed the colour-top, but, instead +of painting circles with coloured sectors, the angles of which could +not be changed, he used circular discs of coloured paper slit along +one radius. Any number of such discs can be combined so that each +shows a sector at the top, and the angle of each sector can be varied +at will by sliding the corresponding disc between the others. Maxwell +used discs of two different sizes, the small discs being placed above +the larger on the same pivot, so that one set formed a central circle, +and the other set a ring surrounding it. He found that, with discs of +five different colours, of which one might be white and another black, +it was always possible to combine them so that the inner circle and +the outer ring exactly matched. From this he showed that there could +be only three conditions to be satisfied in the eye, for two +conditions were necessitated by the nature of the top, since the +smaller sectors must exactly fill the circle and so must the larger. +Maxwell's experiments, therefore, confirmed, in general, Young's +theory. They showed, however, that the relative delicacy of the +several colour-sensations is different in different eyes, for the +arrangement which produced an exact match in the case of one observer, +had to be modified for another; but this difference of delicacy proved +to be very conspicuous in colour-blind persons, for in most of the +cases of colour-blindness examined by Maxwell the red sensation was +completely absent, so that only two conditions were required by +colour-blind eyes, and a match could therefore always be made in such +cases with four discs only. Holmgren has since discovered cases of +colour-blindness in which the violet sensation is absent. He agrees +with Young in making the third sensation correspond to violet rather +than blue. Maxwell explained the fact that persons colour-blind to the +red divide colours into blues and yellows by the consideration that, +although yellow is a complex sensation corresponding to a mixture of +red and green, yet in nature yellow tints are so much brighter than +greens that they excite the green sensation more than green objects +themselves can do, and hence greens and yellows are called yellow by +such colour-blind persons, though their perception of yellow is really +the same as perception of green by normal eyes. Later on, by a +combination of adjustable slits, prisms, and lenses arranged in a +"colour-box," Maxwell succeeded in mixing, in any desired proportions, +the light from any three portions of the spectrum, so that he could +deal with pure spectral colours instead of the complex combinations of +differently coloured lights afforded by coloured papers. From these +experiments it appears that no ray of the solar spectrum can affect +one colour-sensation alone, so that there are no colours in nature so +pure as to correspond to the pure simple sensations, and the colours +occupying the angular points of Maxwell's diagram affect all three +colour-sensations, though they influence two of them to a much smaller +extent than the third. A particular colour in the spectrum corresponds +to light which, according to the undulatory theory, physically +consists of waves all of the same period, but it may affect all three +of the colour-sensations of a normal eye, though in different +proportions. Thus, yellow light of a given wave-length affects the red +and green sensations considerably and the blue (or violet) slightly, +and the same effect may be produced by various mixtures of red or +orange and green. For his researches on the perception of colour, the +Royal Society awarded to Clerk Maxwell the Rumford Medal in 1860. + +Another optical contrivance of Maxwell's was a wheel of life, in which +the usual slits were replaced by concave lenses of such focal length +that the picture on the opposite side of the cylinder appeared, when +seen through a lens, at the centre, and thus remained apparently +fixed in position while the cylinder revolved. The same result has +since been secured by a different contrivance in the praxinoscope. + +Another ingenious optical apparatus was a real-image stereoscope, in +which two lenses were placed side by side at a distance apart equal to +half the distance between the pictures on the stereoscopic slide. +These lenses were placed in front of the pictures at a distance equal +to twice their focal length. The real images of the two pictures were +then superposed in front of the lenses at the same distance from them +as the pictures, and these combined images were looked at through a +large convex lens. + +The great difference in the sensibility to different colours of the +eyes of dark and fair persons when the light fell upon the _fovea +centralis_, led Maxwell to the discovery of the extreme want of +sensibility of this portion of the retina to blue light. This he made +manifest by looking through a bottle containing solution of chrome +alum, when the central portion of the field of view appears of a light +red colour for the first second or two. + +A more important discovery was that of double refraction temporarily +produced in viscous liquids. Maxwell found that a quantity of Canada +balsam, if stirred, acquired double-refracting powers, which it +retained for a short period, until the stress temporarily induced had +disappeared. + +But Maxwell's investigations in optics must be regarded as his play; +his real work lay in the domains of electricity and of molecular +physics. + +In 1738 Daniel Bernouilli published an explanation of atmospheric +pressure on the hypothesis that air consists of a number of minute +particles moving in all directions, and impinging on any surface +exposed to their action. In 1847 Herapath explained the diffusion of +gases on the hypothesis that they consisted of perfectly hard +molecules impinging on one another and on surfaces exposed to them, +and pointed out the relation between their motion and the temperature +and pressure of a gas. The present condition of the molecular theory +of gases, and of molecular science generally, is due almost entirely +to the work of Joule, Clausius, Boltzmann, and Maxwell. To Maxwell is +due the general method of solving all problems connected with vast +numbers of individuals--a method which he called the statistical +method, and which consists, in the first place, in separating the +individuals into groups, each fulfilling a particular condition, but +paying no attention to the history of any individual, which may pass +from one group to another in any way and as often as it pleases +without attracting attention. Maxwell was the first to estimate the +average distance through which a particle of gas passes without coming +into collision with another particle. He found that, in the case of +hydrogen, at standard pressure and temperature, it is about 1/250000 +of an inch; for air, about 1/389000 of an inch. These results he +deduced from his experiments on viscosity, and he gave a complete +explanation of the viscosity of gases, showing it to be due to the +"diffusion of momentum" accompanying the diffusion of material +particles between the passing streams of gas. + +One portion of the theory of electricity had been considerably +developed by Cavendish; the application of mathematics to the theory +of attractions, and hence to that of electricity, had been carried to +a great degree of perfection by Laplace, Lagrange, Poisson, Green, and +others. Faraday, however, could not satisfy himself with a +mathematical theory based upon direct action at a distance, and he +filled space, as we have seen, with tubes of force passing from one +body to another whenever there existed any electrical action between +them. These conceptions of Faraday were regarded with suspicion by +mathematicians. Sir William Thomson was the first to look upon them +with favour; and in 1846 he showed that electro-static force might be +treated mathematically in the same way as the flow of heat; so that +there are, at any rate, two methods by which the fundamental formulæ +of electro-statics can be deduced. But it is to Maxwell that +mathematicians are indebted for a complete exposition of Faraday's +views in their own language, and this was given in a paper wherein the +phenomena of electro-statics were deduced as results of a stress in a +medium which, as suggested by Newton and believed by Faraday, might +well be that same medium which serves for the propagation of light; +and "the lines of force" were shown to correspond to an actual +condition of the medium when under electrical stress. Maxwell, in +fact, showed, not only that Faraday's lines formed a consistent system +which would bear the most stringent mathematical analysis, but were +more than a conventional system, and might correspond to a state of +stress actually existing in the medium through which they passed, and +that a tension along these lines, accompanied by an equal pressure in +every direction at right angles to them, would be consistent with the +equilibrium of the medium, and explain, on mechanical principles, the +observed phenomena. The greater part of this work he accomplished +while an undergraduate at Cambridge. He showed, too, that Faraday's +conceptions were equally applicable to the case of electro-magnetism, +and that all the laws of the induction of currents might be concisely +expressed in Faraday's language. Defining the positive direction +through a circuit in which a current flows as the direction in which a +right-handed screw would advance if rotating with the current, and the +positive direction around a wire conveying a current as the direction +in which a right-handed screw would rotate if advancing with the +current, Maxwell pointed out that the lines of magnetic force due to +an electric current always pass round it, or through its circuit, in +the positive direction, and that, _whenever the number of lines of +magnetic force passing through a closed circuit is changed, there is +an electro-motive force round the circuit represented by the rate of +diminution of the number of lines of force which pass through the +circuit in the positive direction_. + +The words in italics form a complete statement of the laws regulating +the production of currents by the motion of magnets or of other +currents, or by the variation of other currents in the neighbourhood. +Maxwell showed, too, that Faraday's electro-tonic state, on the +variation of which induced currents depend, corresponds completely +with the number of lines of magnetic force passing through the +circuit. + +He also showed that, when a conductor conveying a current is free to +move in a magnetic field, or magnets are free to move in the +neighbourhood of such a conductor, _the system will assume that +condition in which the greatest possible number of lines of magnetic +force pass through the circuit in the positive direction_. + +But Maxwell was not content with showing that Faraday's conceptions +were consistent, and had their mathematical equivalents,--he proceeded +to point out how a medium could be imagined so constituted as to be +able to perform all the various duties which were thus thrown upon it. +Assuming a medium to be made up of spherical, or nearly spherical, +cells, and that, when magnetic force is transmitted, these cells are +made to rotate about diameters coinciding in direction with the lines +of force, the tension along those lines, and the pressure at right +angles to them, are accounted for by the tendency of a rotating +elastic sphere to contract along its polar axis and expand +equatorially so as to form an oblate spheroid. By supposing minute +spherical particles to exist between the rotating cells, the motion of +one may be transmitted in the same direction to the next, and these +particles may be supposed to constitute electricity, and roll as +perfectly rough bodies on the cells in contact with them. Maxwell +further imagined the rotating cells, and therefore, _à fortiori_, the +electrical particles, to be extremely small compared with molecules of +matter; and that, in conductors, the electrical particles could pass +from molecule to molecule, though opposed by friction, but that in +insulators no such transference was possible. The machinery was then +complete. If the electric particles were made to flow in a conductor +in one direction, passing between the cells, or _molecular vortices_, +they compelled them to rotate, and the rotation was communicated from +cell to cell in expanding circles by the electric particles, acting as +idle wheels, between them. Thus rings of magnetic force were made to +surround the current, and to continue as long as the current lasted. +If an attempt were made to displace the electric particles in a +dielectric, they would move only within the substance of each +molecule, and not from molecule to molecule, and thus the cells would +be deformed, though no continuous motion would result. The deformation +of the cells would involve elastic stress in the medium. Again, if a +stream of electric particles were started into motion, and if there +were another stream of particles in the neighbourhood free to flow, +though resisted by friction, these particles, instead of at once +transmitting the rotary motion of the cells on one side of them to the +cells on the other side, would at first, on account of the inertia of +the cells, begin to move themselves with a motion of translation +opposite to that of the primary current, and the motion would only +gradually be destroyed by the frictional resistance and the molecular +vortices on the other side made to revolve with their full velocity. A +similar effect, but in the opposite direction, would take place if the +primary current ceased, the vortices not stopping all at once if there +were any possibility of their continuing in motion. The imaginary +medium thus serves for the production of induced currents. + +The mechanical forces between currents and magnets and between +currents and currents, as well as between magnets and currents, were +accounted for by the tension and pressure produced by the molecular +vortices. When currents are flowing in the same direction in +neighbouring conductors, the vortices in the space between them are +urged in opposite directions by the two currents, and remain almost at +rest; the lateral pressure exerted by those on the outside of the +conductors is thus unbalanced, and the conductors are pushed together +as though they attracted each other. When the currents flow in +opposite directions in parallel conductors, they conspire to give a +greater velocity to the vortices in the space between them, than to +those outside them, and are thus pushed apart by the pressure due to +the rotation of the vortices, as though they repelled each other. In a +similar way, the actions of magnets on conductors conveying currents +may be explained. The motion of a conductor across a series of lines +of magnetic force may squeeze together and lengthen the threads of +vortices in front, and thus increase their speed of rotation, while +the vortices behind will move more slowly because allowed to contract +axially and expand transversely. The velocity of the vortices thus +being greater on one side of the wire than the other, a current must +be induced in the wire. Thus the current induced by the motion of a +conductor in a magnetic field may be accounted for. + +This conception of a medium was given by Maxwell, not as a theory, but +to show that it was possible to devise a _mechanism_ capable, in +imagination at least, of producing all the phenomena of electricity +and magnetism. "According to our theory, the particles which form the +partitions between the cells constitute the matter of electricity. The +motion of these particles constitutes an electric current; the +tangential force with which the particles are pressed by the matter of +the cells is electro-motive force; and the pressure of the particles +on each other corresponds to the tension or potential of the +electricity." + +When a current is maintained in a wire, the molecular vortices in the +surrounding space are kept in uniform motion; but if an attempt be +made to stop the current, since this would necessitate the stoppage of +the vortices, it is clear that it cannot take place suddenly, but the +energy of the vortices must be in some way used up. For the same +reason it is impossible for a current to be suddenly started by a +finite force. Thus the phenomena of self-induction are accounted for +by the supposed medium. + +The magnetic permeability of a medium Maxwell identified with the +density of the substance composing the rotating cells, and the +specific inductive capacity he showed to be inversely proportional to +its elasticity. He then proved that the ratio of the electro-magnetic +unit to the electro-static unit must be equal to the velocity of +transmission of a transverse vibration in the medium, and consequently +proportional to the square root of the elasticity, and inversely +proportional to the square root of the density. If the medium is the +same as that engaged in the propagation of light, then this ratio +ought to be equal to the velocity of light, and, moreover, in +non-magnetic media, the refractive index should be proportional to the +square root of the specific inductive capacity. The different +measurements which had been made of the ratio of the electrical units +gave a mean very nearly coinciding with the best determinations of the +velocity of light, and thus the truth underlying Maxwell's speculation +was strikingly confirmed, for the velocity of light was determined by +purely electrical measurements. In the case also of bodies whose +chemical structure was not very complicated, the refractive index was +found to agree fairly well with the square root of the specific +inductive capacity; but the phenomenon of "residual charge" rendered +the accurate measurement of the latter quantity a matter of great +difficulty. It therefore appeared highly probable that light is an +electro-magnetic disturbance due to a motion of the electric particles +in an insulating medium producing a strain in the medium, which +becomes propagated from particle to particle to an indefinite +distance. In the case of a conductor, the electric particles so +displaced would pass from molecule to molecule against a frictional +resistance, and thus dissipate the energy of the disturbance, so that +true (_i.e._ metallic) conductors must be nearly impervious to light; +and this also agrees with experience. + +Maxwell thus furnished a complete theory of electrical and +electro-magnetic action in which all the effects are due to actions +propagated in a medium, and direct action at a distance is dispensed +with, and exposed his theory successfully to most severe tests. In his +great work on electricity and magnetism, he gives the mathematical +theory of all the above actions, without, however, committing himself +to any particular form of mechanism to represent the constitution of +the medium. "This part of that book," Professor Tait says, "is one of +the most splendid monuments ever raised by the genius of a single +individual.... There seems to be no longer any possibility of doubt +that Maxwell has taken the first grand step towards the discovery of +the true nature of electrical phenomena. Had he done nothing but this, +his fame would have been secured for all time. But, striking as it is, +this forms only one small part of the contents of this marvellous +work." + + + + +CONCLUSION. + +SOME OF THE RESULTS OF FARADAY'S DISCOVERIES, AND THE PRINCIPLE OF +ENERGY. + + +In early days, _the spirit of the amber_, when aroused by rubbing, +came forth and took to itself such light objects as it could easily +lift. Later on, and the spirit gave place to the _electric effluvium_, +which proceeded from the excited, or charged, body into the +surrounding space. Still later, and a fluid, or two fluids, acting +directly upon itself, or upon matter, or on one another, through +intervening space without the aid of intermediate mechanism, took the +place of the electric effluvium--a step which in itself was, perhaps, +hardly an advance. Then came the time for accurate measurement. The +simple _observation_ of phenomena and of the results of experiment +must be the first step in science, and its importance cannot be +over-estimated; but before any quantity can be said to be known, we +must have learned how to _measure_ it and to reproduce it in definite +amounts. The great law of electrical action, the same as that of +gravitation--the law of the inverse square--soon followed, as well as +the associated fact that the electrification of a conductor resides +wholly on its surface, and there only in a layer whose thickness is +too small to be discovered. The fundamental laws of electricity having +thus been established, there was no limit to the application of +mathematical methods to the problems of the science, and, in the hands +of the French mathematicians, the theory made rapid advances. George +Green, of Sneinton, Nottingham, introduced the term "potential" in an +essay published by subscription, in Nottingham, in 1828, and to him we +are indebted for some of our most powerful analytical methods of +dealing with the subject; but his work remained unappreciated and +almost unknown until many of his theorems had been rediscovered. But +the idea of a body acting where it is not, and without any conceivable +mechanism to connect it with that upon which it operates, is repulsive +to the minds of most; and, however well such a theory may lend itself +to mathematical treatment and its consequences be borne out by +experiment, we still feel that we have not solved the problem until we +have traced out the hidden mechanism. The pull of the bell-rope is +followed by the tinkling of the distant bell, but the young +philosopher is not satisfied with such knowledge, but must learn "what +is the particular go of that." This universal desire found its +exponent in Faraday, whose imagination beheld "lines" or "tubes of +force" connecting every body with every other body on which it acted. +To his mind these lines or tubes had just as real an existence as the +bell-wire, and were far better adapted to their special purposes. +Maxwell, as we have seen, not only showed that Faraday's system +admitted of the same rigorous mathematical treatment as the older +theory, and stood the test as well, but he gave reality to Faraday's +views by picturing a mechanism capable of doing all that Faraday +required of it, and of transmitting light as well. Thus the problem of +electric, magnetic, and electro-magnetic actions was reduced to that +of strains and stresses in a medium the constitution of which was +pictured to the imagination. Were this theory verified, we might say +that we know at least as much about these actions as we know about the +transmission of pressure or tension through a solid. + +With regard to the _nature_ of electricity, it must be admitted that +our knowledge is chiefly negative; but, before deploring this, it is +worth while to inquire what we mean by saying that we know what a +thing is. A definition describes a thing in terms of other things +simpler, or more familiar to us, than itself. If, for instance, we say +that heat is a form of energy, we know at once its relationship to +matter and to motion, and are content; we have described the +constitution of heat in terms of simpler things, which are more +familiar to us, and of which we _think_ we know the nature. But if we +ask what _matter_ is, we are unable to define it in terms of anything +simpler than itself, and can only trust to daily experience to teach +us more and more of its properties; unless, indeed, we accept the +theory of the vortex atoms of Thomson and Helmholtz. This theory, +which has recently been considerably extended by Professor J. J. +Thomson, the present occupier of Clerk Maxwell's chair in the +University of Cambridge, supposes the existence of a perfect fluid, +filling all space, in which minute whirlpools, or vortices, which in a +perfect fluid can be created or destroyed only by superhuman agency, +form material atoms. These are _atoms_, that is to say, they defy any +attempts to sever them, not because they are infinitely hard, but +because they have an infinite capacity for _wriggling_, and thus avoid +direct contact with any other atoms that come in their way. Perhaps a +theory of electricity consistent with this theory of matter may be +developed in the future; but, setting aside these theories, we may +possibly say that we know as much about electricity as we know about +matter; for while we are conversant with many of the properties of +each, we _know_ nothing of the ultimate nature of either. + +But while the theory of electricity has scarcely advanced beyond the +point at which it was left by Clerk Maxwell, the practical +applications of the science have experienced great developments of +late years. Less than a century ago the lightning-rod was the only +practical outcome of electrical investigations which could be said to +have any real value. [OE]rsted's discovery, in 1820, of the action of +a current on a magnet, led, in the hands of Wheatstone, Cooke, and +others, to the development of the electric telegraph. Sir William +Thomson's employment of a beam of light reflected from a tiny mirror +attached to the magnet of the galvanometer enabled signals to be read +when only extremely feeble currents were available, and thus rendered +submarine telegraphy possible through very great distances. The +discovery by Arago and Davy, that a current of electricity flowing in +a coil surrounding an iron bar would convert the bar into a magnet, at +once rendered possible a variety of contrivances whereby a current of +electricity could be employed to produce small reciprocating +movements, or even continuous rotation, where not much power was +required, at a distance from the battery. An illustration of the +former is found in the common electric bell; it is only necessary that +the vibrating armature should form part of the circuit of the +electro-magnet, and be so arranged that, while it is held away from +the magnet by a spring, it completes the battery circuit, but breaks +the connection as soon as it moves towards the magnet under the +magnetic attraction. To produce continuous rotation, a number of iron +bars may be attached to a fly-wheel, and pass very close to the poles +of the magnet without touching them; when a bar is near the magnet, +and approaching it, contact should be made in the circuit, but should +be broken, so that the magnet may lose its power, as soon as the bar +has passed the poles; or the continuous rotation may be produced from +an oscillating armature by any of the mechanical contrivances usually +adopted for the conversion of reciprocating into continuous circular +motion. But all such motors are extremely wasteful in their employment +of energy. Faraday's discovery of the rotation of a wire around a +magnetic pole laid the foundation for a great variety of +electro-motors, in some of which the efficiency has attained a very +high standard. About ten years ago, Clerk Maxwell said that the +greatest discovery of recent times was the "reversibility" of the +Gramme machine, that is, the possibility of causing the armature to +rotate between the field-magnets by sending a current through the +coils. The electro-motors of to-day differ but little from dynamos in +the principles of their construction. The copper disc spinning between +the poles of a magnet while an electric current was sent from the +centre to the circumference, or _vice versâ_, formed the simplest +electro-motor. All the later motors are simply modifications of this, +designed to increase the efficiency or power of the machine. +Similarly, the earliest machine for the production of an electric +current at the expense of mechanical power only, but through the +intervention of a permanent magnet, was the rotating disc of Faraday, +described on page 262. This contrivance, however, caused a waste of +nearly all the energy employed, for while there was an electro-motive +force from the centre to the circumference, or in the reverse +direction, in that part of the disc which was passing between the +poles of the magnet, the current so generated found its readiest +return path through the other portions of the disc, and very little +traversed the galvanometer or other external circuit. This source of +waste could be, for the most part, got rid of by cutting the disc into +a number of separate rays, or spokes, and filling up the spaces +between them with insulating material. The current then generated in +the disc would be obliged to complete its circuit through the external +conductor. If we can so arrange matters as to employ at once several +turns of a continuous wire in place of one arm, or ray, of the copper +disc, we may multiply in a corresponding manner the electro-motive +force induced by a given speed of rotation. All magneto-electric +generators are simply contrivances with this object. The iron cores +frequently employed within the coils of the armature tend to +concentrate the lines of force of the magnet, causing a greater number +to pass through the coils in certain positions than would pass through +them were no iron present. The electro-motive force of such a +generator depends on the strength of the magnetic field, the length of +wire employed in cutting the lines of force, and the speed with which +the wire moves across these lines. The point to aim at in constructing +an armature is to make the resistance as small as possible consistent +with the electro-motive force required. As there is a limit to the +strength of the magnetic field, it follows that for strong currents, +where thick wire must be employed, the generator must be made of large +dimensions, or the armature must be driven at very high speed to +enable a shorter length of wire to be used. + +The so-called "compound-interest principle," by which a very small +charge of electricity might be employed to develop a very large one by +the help of mechanical power, was first applied about a century ago in +the revolving doubler. Long afterwards, Sir William Thomson availed +himself of the same principle in the construction of the "mouse-mill," +or replenisher. The Holtz machine, the Voss and Wimshurst machines, +and the other induction-machines of the same class, all work on this +principle. It may be illustrated as follows: Take two canisters, call +them A and B, and place them on glass supports. Let a very small +positive charge be given to A, B remaining uncharged. Now take a brass +ball, supported by a silk string. Place it inside A, and let it touch +its interior surface. The ball will, as shown by Franklin, Cavendish, +and Faraday, remain uncharged. Now raise it near the top of the +canister, and, while there, touch it. The ball will become negatively +electrified, because the small positive charge in A will attract +negative electricity from the earth into the ball. Take the ball, with +its negative charge, still hanging by the silk thread, and lower it +into B till it touches the bottom. It will give all its charge to B, +which will thus acquire a slight negative charge. Raise the ball till +it is near the top of B, and then touch it with the finger or a metal +rod. It will receive a positive charge from the earth because of the +attraction of the negative charge on B. Now remove the ball and let it +again touch the interior of A. It will give up all its charge to A; +and then, repeating the whole cycle of operations, the charge carried +on the ball will be greater than before, and increase in each +successive operation, the electrification increasing in geometrical +progression like compound interest. A Leyden jar having one coating +connected to A and the other to B, may thus be highly charged in +course of time. A pair of carrier balls or plates, or a number of +pairs, may be used instead of one. The carriers, just before leaving A +and B, may be put in contact with one another instead of being put to +earth; they may be mounted on a revolving shaft, and the forms of A +and B modified to admit of the revolution of the carriers, and all the +necessary contacts may be made automatically. We thus get various +forms of the continuous electrophorus, and if the carriers are mounted +on glass plates, and rows of points placed alongside the springs or +brushes used for making the contacts, when the charges on the carriers +become very strong, electricity will be radiated from the points on to +the revolving glass plates, which will thus themselves take the place +of the metal carriers. Such is the action in the Voss and other +similar machines. + +But after Faraday had shown how to construct a magneto-electric +machine, the idea of applying the "compound-interest principle," and +thus converting the magneto-electric machine into the "dynamo," +occurred apparently simultaneously and independently to Siemens, +Varley, and Wheatstone. The first dynamo constructed by Wheatstone is +still in the museum of King's College, London. Wilde employed a +magneto-electric machine to generate a current which was used to +excite the electro-magnet of a similar but larger machine, having an +electro-magnet instead of a permanent steel magnet. The electro-magnet +could be made much larger and stronger than the steel magnet, and from +its armature, when made to revolve by steam power, a correspondingly +stronger current could be maintained. The idea which occurred to +Siemens, Varley, and Wheatstone was to use the whole, or a part, of +the current produced by the armature to excite its own electro-magnet, +and thus to dispense with the magneto-electric machine which served as +the separate exciter. When a part only of the current is thus +employed, and is set apart entirely for this duty, the machine is a +"shunt dynamo;" when the whole of the current traverses the +field-magnet coils as well as the external circuit, it is a "series +dynamo." The apparent difficulty lies in starting the current, but a +mass of iron once magnetized always retains a certain amount of +"residual magnetism," unless special means are taken to get rid of +it, and even then the earth's magnetism would generally induce +sufficient in the iron to start the action. Commencing, then, with a +slight trace of residual magnetism, the revolution of the armature +generates a feeble current, which passing round the magnet coils, +strengthens the magnetism, whereupon a stronger current is generated, +which in turn makes the magnet still stronger, and so on until the +magnet becomes saturated or the limit of power of the engine is +reached, and the speed begins to diminish, or a condition of affairs +is reached at which an increased current in the armature injures the +magnetic field as much as the corresponding increase in the +field-magnet coils strengthens it, and then no further increase of +current will take place without increasing the speed of rotation. In a +true dynamo the whole of the energy, both of the current and of the +electro-magnets, is obtained from the source of power employed in +driving the machine. + +But Faraday's discovery of electro-magnetic induction led to practical +developments in other directions. Graham Bell placed a thin iron disc +in front of the pole of a bar magnet, and wound a coil of fine wire +round the bar very near the pole. The ends of the coils of two such +instruments he connected together. When the iron disc of one +instrument approached the pole of the magnet, the lines of force were +disturbed, fewer escaped radially from the bar, and more left it at +the end, so as to go straight to the iron disc; thus the number of +lines of force passing through the coil was altered, and a current was +induced which, passing round the coil of the other instrument, +strengthened or weakened its magnet, and caused the iron disc to +approach it or recede from it, according to the way in which the coils +were coupled. Thus the movements of the first disc were faithfully +repeated by the second, and the minute vibrations set up in the disc +by sound-waves were all faithfully repeated by the second instrument. +This was Graham Bell's telephone, in which the transmitter and +receiver were convertible. + +But another and an earlier application of Faraday's discoveries is +found in the induction coil. A short length of thick wire and a very +great length of thin wire are wound upon an iron bar. The ends of the +long thin wire, or secondary coil, form the terminals of the machine; +the short thick wire, or primary coil, is connected with a battery, +but in the circuit is placed an "interrupter." This is generally a +small piece of iron, or hammer, mounted on a steel spring opposite one +end of the iron core, the spring pressing the hammer back against a +screw the end of which, like the back of the hammer, is tipped with +platinum; and this contact completes the battery circuit. When the +current starts, the iron core becomes a magnet, attracts the hammer, +breaks the contact, stops the current, the magnetism dies away, the +hammer is forced back by the spring, and then the cycle of events is +repeated. But the starting of the current in the primary causes a +great many lines of magnetic force to pass through each of the many +thousand turns of wire in the secondary, especially as the iron core +conducts most of the lines of force of each turn of the primary almost +from end to end of the coil, and thus through nearly all the turns of +the secondary. This action might be further increased by connecting +the ends of the iron core with an iron tube or series of longitudinal +bars placed outside the whole coil. When the primary current ceases, +all these lines of force vanish. Thus during the starting of the +primary current, which, on account of self-induction, occupies a +considerable time, there will be an inverse current in the secondary +proportional to the rate of increase of the primary; and while the +primary is dying away, there will be a direct current in the secondary +proportional to its rate of decrease. The primary current cannot be +increased at a faster rate than corresponds to the power of the +battery, but by making a very sharp break it may be stopped very +rapidly. Still, however rapidly the circuit is broken, self-induction +causes a spark to fly across the gap until the energy of the current +is used up. The introduction of the condenser, consisting of a number +of sheets of tinfoil insulated by paper steeped in paraffin wax, and +connected alternately with one end or the other of the primary coil, +serves to increase the rapidity with which the primary current died +away, by rapidly using up its energy in charging the condenser, and +produces a corresponding diminution in the spark at the +contact-breaker. This rapid destruction of the primary current causes +a correspondingly great electro-motive force in the secondary coil, +and thus very long sparks are produced between the terminals of the +secondary coil when the primary current is broken, though no such +sparks are produced when the primary current starts. If the secondary +coil be connected up with a galvanometer, so that there is a metallic +circuit throughout, it will be found that just as much electricity +flows in one direction through the circuit at the break of the primary +as flows in the other direction at the make, the difference being that +the first is a very strong current of great electro-motive force but +lasting a very short time, the second a feebler current lasting a +correspondingly longer time. + + * * * * * + +But though the recent advances in electrical science have been very +great, the grandest triumph of this century is the establishment of +the principle of the conservation of energy, which has settled for +ever the problem of "the perpetual motion," by showing that it has no +solution. This problem was not simply to find a mechanism which should +for ever move, but one from which energy might be continuously derived +for the performance of external work--in fact, an engine which should +require no fuel. But in spite of all that has been proved, numbers of +patents are annually taken out for contrivances to effect this +object. + +We have seen how Rumford showed that heat was motion, and how he +approximately determined its mechanical equivalent. Séguin, a nephew +of Montgolfier, endeavoured to show that, when a steam-engine was +working, less heat entered the condenser than when the same amount of +steam was blown idly through the engine. This Hirn succeeded in +showing, thus proving that heat was actually used up in doing work. +Mayer, of Heilbronn, measured the work done in compressing air, and +the heat generated by the compression, and assumed that the whole of +the work done in the compression, and no more, was converted into the +heat developed, which was the same thing as assuming that no work was +done in altering the positions of the particles of gas. From these +measurements he deduced a value of the mechanical equivalent of heat. +The assumption which Mayer made was shown experimentally by Joule to +be nearly correct. Joule proved that, when air expands from a high +pressure into a vacuum, no heat is generated or absorbed on the whole. +This he did by compressing air in an iron bottle, which was connected +with another bottle from which the air had been exhausted, the +connecting tube being closed by a stop-cock. The whole apparatus was +immersed in a bath of water, and on allowing the air to rush from one +vessel into the other, and then stirring the water, the temperature +was found to be the same as before. When the iron bottles were in +separate baths of water, that from which the air rushed was cooled, +and that into which it rushed was heated to the same extent. Joule and +Thomson afterwards showed that a very small amount of heat is absorbed +in this experiment. Joule also showed that the heat generated in a +battery circuit is proportional to the product of the electro-motive +force and the current, or to the product of the resistance and the +square of the current, which, in virtue of Ohm's law, is the same +thing. This relation is often known as Joule's law. He also proved +that, for the same amount of chemical action in the battery, the heat +generated was the same, whether it were all generated within the +battery or part in the battery and part in an external wire; and that +in the latter case, if the wire became so hot as to emit light, the +heat measured was less than before, on account of the energy radiated +as light. With a magneto-electric machine he employed mechanical power +to produce a current, and the energy of the current he converted into +heat. In all cases he found that, _whatever transformations the energy +might undergo in its course, a definite amount of mechanical energy, +if entirely converted into heat, always produced the same amount of +heat_; and he thereby proved, not only that heat is essentially +_motion_, but that it corresponds precisely with that particular +dynamical quantity which is called _energy_; and thus justified the +attempt to find a relation between heat and energy, or to express the +mechanical equivalent of heat as so many foot-pounds. + +Joule then set to work to determine, in the most accurate manner +possible, the number of foot-pounds of work which, if entirely +converted into heat, would raise one pound of water through 1° Fahr. +The best known of his experiments is that in which he caused a paddle +to revolve by means of a falling weight, and thereby to churn a +quantity of water contained in a cylindrical vessel, the rotation of +the water being prevented by fixed vanes. In these experiments he +allowed for the work done outside the vessel of water or calorimeter, +for the buoyancy of the air on the descending weight, and for the +energy still retained by the weight when it struck the floor. From the +results obtained he deduced 772 foot-pounds as the mechanical +equivalent of heat. Expressed in terms of the Centigrade scale, +Joule's equivalent, that is, the number of foot-pounds of work in the +latitude of Manchester, which, if entirely converted into heat, will +raise one pound of water 1° C., is 1390. + +Joule's experiments show that the same amount of energy always +corresponds to, and can be converted into, the same amount of heat, +and that no transformations, electrical or other, can ever increase or +diminish this quantity. Maxwell expressed this principle as follows:-- + +_The energy of a system is a quantity which can neither be increased +nor diminished by any actions taking place between the parts of the +system, though it may be transformed into any of the forms of which +energy is susceptible._ + +This is the great principle of the conservation of energy which is +applicable equally to all branches of science. + +Another principle, almost equally general in its applicability, is +that of the dissipation of energy, for which we are indebted in the +first instance to Sir William Thomson. All forms of energy may be +converted into heat, and heat tends so to diffuse itself throughout +all bodies as to bring them to one uniform temperature. This is its +ultimate state of degradation, and from that state no methods with +which we are acquainted can transform any portion of it. When energy +is possessed by a system in consequence of the relative positions or +motions of bodies which we can handle, and whose movements we may +control, the whole of the energy may be employed in doing any work we +please; in fact, it is all _available_ for our purpose, or its +_availability_ may be said to be perfect. Energy in any other form is +limited in its availability by the conditions under which we can place +it. For example, the energy of chemical action in a battery may be +used to produce a current, and this to drive a motor by which +mechanical work is effected, but some of the energy must inevitably be +degraded into the form of heat by the resistance of the battery and of +the conductor, and this portion will be greater as the rate of doing +work is increased. The ratio of the quantity of energy which can be +employed for mechanical purposes with the means at our disposal, to +the whole amount present, is called the _availability_ of the energy. +All forms of energy may be wholly converted into heat, but only a +fraction of any quantity of heat can be transformed into higher forms +of energy, and this depends on the temperature of the source of heat +and of the coldest body which can be employed as a condenser, being +greater the greater the difference between the temperatures of the +source and condenser, and the lower the temperature of the latter. In +every operation which takes place in nature there is a degradation of +energy, and though some portion of the energy may be raised in +availability, another portion is lowered, so that on the whole the +availability is diminished. Thus, in the case of the heat-engine, work +can be obtained from heat only by allowing another portion of the heat +to fall in temperature; and, as originally stated by Sir William +Thomson, "it is impossible, by means of inanimate material agency, to +obtain mechanical effect from any portion of matter by cooling it +below the temperature of the coldest of the surrounding objects," and +to leave the working substance in the same condition in which it was +at the commencement of the operations. Accepting this principle, +Professor James Thomson showed that increase of pressure must lower +the freezing point of water, for otherwise it would be possible to +construct an engine which, working by the expansion of water in +freezing, would continue to do work by cooling a body below the +temperature of any other body available, and he calculated the amount +of pressure necessary to lower the freezing point through one degree. +The conclusion was afterwards experimentally verified by Sir William +Thomson, and served to explain all the phenomena of regelation. Thus, +like the principle of the conservation of energy, the principle of the +dissipation of energy serves as a guide in the search after truth. But +there is this difference between the two principles--no one can +conceive of any method by which to circumvent the conservation of +energy; but Clerk Maxwell showed that the principle of dissipation of +energy might be overridden by the exercise of intelligence on the part +of any creature whose faculties were sufficiently delicate to deal +with individual molecules. In the case of gases, the temperature +depends on the average energy of motion of the individual particles, +and heat consists simply of this motion; but in any mass of gas, +whatever the average energy may be, some of the particles will be +moving with very great, and some with very small, velocities. By +imagining two portions of gas, originally at the same temperature, +separated by a partition containing trap-doors which could be opened +or closed without expenditure of energy, and supposing a "demon" +placed in charge of each door, who would open the door whenever a +particle was approaching very rapidly from one side, or very slowly +from the other, but keep it shut under other circumstances, he showed +that it would be possible to sort the particles, so that those in the +one compartment should have a great velocity, and those in the other a +small one. Hence, out of a mass of gas at uniform temperature, two +portions might be obtained, one at a high temperature and the other at +a low, and, by means of a heat-engine, work could be obtained until +the two portions were again at equal temperatures, when the services +of the "demons" might be again taken advantage of, and the operations +repeated until all the heat was used up. + +Any theory which is brought forward to explain a phenomenon, or any +process which is proposed to effect any operation, must in the first +instance submit to the test of the application of these two principles +of conservation and dissipation of energy; and any proposal which +fails to bear these tests may be at once rejected. The essential +feature of the science of to-day is its quantitative character. We +must, for instance, not only know that radiant energy comes to us from +the sun, but we must learn how much energy is annually received by the +earth in this way; and, in the next place, how much energy is radiated +by the sun in all directions in the same time. When we have learned +this, we want to know what is the source of this energy; and no theory +of the sun which does not enable us to explain how this constant +expenditure of energy is maintained can be accepted. Last century it +was possible to believe, with Sir William Herschel, that the greater +part of the sun's mass is comparatively cool, and that it is +surrounded by only a thin sheet of flame. To-day such a theory would +be rejected at once, simply because the thin shell of flame could not +provide energy for the solar radiation for any considerable time. The +contact theory of the galvanic cell, as originally enunciated, fell to +the ground for a similar reason. The simple contact of dissimilar +metals could afford no continuous supply of energy to sustain the +current. Applied to the steam-engine, the doctrine of energy teaches +us, not only that, corresponding to the combustion of a pound of coal, +there is a definite quantity of work which is the mechanical +equivalent of the heat generated, and is such that no engine of which +we can conceive is capable of deriving from the combustion of the +pound of coal a greater amount of work, but it teaches us that there +is a further limitation fixed to the amount of work obtainable. This +limitation depends upon the range of temperature at our command; and, +when the range is known, we can express the amount of energy +realizable by a perfect engine working through that range as a +definite fraction of the whole energy corresponding to the heat of +combustion of the fuel. Thus, if we find that a particular engine +realizes only 15 per cent. of the energy of its fuel in work done, we +must not suppose that mechanical improvements in the engine would +enable us to realize any considerable portion of the other 85 per +cent.; for it may be that a theoretically perfect engine, working with +its boiler and condenser at the same temperatures as those of the +engine considered, could only realize 25 per cent. of the energy of +the fuel, reducing the margin for improvement from 85 to 10 per cent., +as long as the range of temperature is unaltered. To improve the +efficiency beyond this limit, the range of temperature must be +increased, that is, generally, hotter steam must be used. + +The principles of energy are thus guides, not only to the scientific +theorist, but to the practical engineer, and they have been +established only through careful measurement. The simple observation +of phenomena, and of the conditions under which they occur, could +never have led to the establishment of such principles; and, though +the carrying out of experiments which do not involve measurements is +of great value, it is the careful measurement, however simple, which +affords the highest training to the mind and hand, and without which +any course of instruction in experimental physics is of little value. + +The Hindoos used to regard the earth as a vast dome carried on the +backs of elephants. The elephants themselves, however, required +support, and were represented as standing on the back of a gigantic +tortoise. It does not, however, appear that any support was provided +for the tortoise. In some respects this figure represents the +apparently perpetual condition of scientific knowledge. Phenomena are +investigated, and are shown to depend upon other actions which appear +simpler or more fundamental than the phenomena at first observed. +These, again, are found to obey laws which are of much wider +application, or appear to be still more fundamental; but it may be +that we are as far off as ever from discovering the great secret of +the universe, the ultimate nature of all things. + + + + +INDEX. + + + A. + + Abbott, Faraday's letters to, 241, 246. + + Aberdeen University, Maxwell appointed professor in, 284; + Young's report on, 203. + + Absorption, Rumford's experiments on, 185; + of sun's rays by cloth of different colours, 99. + + Academy of Sciences, Franklin nominated Foreign Associate of, 111. + + Adjustment of the eye, Young's paper on the, 200. + + Æpinus's completion of Franklin's theory, 77. + + Air, Boyle's conception of the constitution of, 19. + + Air-pump, Boyle's experiments with, 19; + constructed by Boyle, 27. + + American Independence, Declaration of, 113. + + American Philosophical Society, foundation of, 61. + + Ampère's theory, Faraday's views on, 257. + + Anchor-ring experiment, Faraday's, 260. + + Arago's experiment, 264. + + Argand lamp, efficiency of, 188. + + Armstrong gun, principle of the, 180. + + Atmospheric electricity, Faraday's experiments on, 254; + obtained by a pointed rod, 84. + + Autobiography of Franklin, 39. + + Availability of energy, 326. + + + B. + + Baily, Francis, repetition of the Cavendish experiment by, 146. + + Beats in music, explanation of, 209. + + Beggary in Bavaria banished by Rumford, 164. + + Bernoulli's, Daniel, molecular theory of gases, 299. + + Boston, blockade of, 110. + + =Boyle=, Hon. Robert, birth, 8; + conversion, 11; + first air-pump, 17; + conception of the constitution of the air, 19; + experiments with the air-pump, 19, _et seq._; + argument on the cause of a vacuum, 23; + experiments establishing his law, 25; + statement of his law, 29; + observations on cold, 32, + and on the expansion of water in freezing, 33; + experiments on induced magnetism, 34; + the province of experimental science, 37. + + Boyle's law, 29. + + Brocklesby, Dr., death of, 208. + + Brougham's criticisms of Thomas Young, 218. + + Bumper, electrical, 80. + + + C. + + Camera obscura, invention of, 2. + + Canada balsam, stresses in, 298. + + Candle-flame, effect of, in discharging electricity, 75. + + Capacity, electrical, 137; + Franklin's experiments on, 81, 89; + Cavendish's unit of, 138; + Cavendish's measures of, 134, 138; + of disc, measured by Cavendish, 134. + + Capillarity, 228. + + Cascade method of charging Leyden jars, 77. + + =Cavendish=, Hon. Henry, F.R.S., birth and parentage, 126; + social habits, 127; + appointed member of the R.S. Committee on Lightning-Conductors, + 131; + elected Foreign Associate of the French Institute, 132; + death, 133; + proof of the law of inverse squares, 135; + experiment with the spheres repeated by MacAlister, 137; + experiments on the torpedo, 140; + experiments on the resistance of conductors, 142; + discovery of Ohm's law, 143; + view of latent heat, 144; + apparatus for determining the melting point of mercury, 145; + the Cavendish experiment, 146. + + Cavendish experiment, 146; + Laboratory, 288; + Manuscripts, 134; + Maxwell's work on the Manuscripts, 293. + + City Philosophical Society, joined by Faraday, 245; + Faraday's lectures to, 251. + + Cold, Boyle's observations on, 32. + + Collinson, Peter, present of, to the Library Company, 72. + + Colour-blindness, Maxwell's experiments on, 296. + + Colour-box, Maxwell's, 297. + + Colours, effect of, on absorption of sun's rays, 99, 186. + + Colours of the spectrum mixed by Boyle, 31. + + Colour-top, Maxwell's, 284, 295; + Young's, 215. + + Colour-vision, Maxwell's theory of, 294; + Young's theory of, 214. + + Commonplace-book, Faraday's, 253. + + Compound-interest principle, 316. + + Condenser, use of, in induction coils, 321. + + Conduction of heat, Rumford's experiments on, 186. + + Conductors, multiple, flow of electricity through, 141. + + Conductors necessarily opaque, 307. + + Conservation of energy, Maxwell's statement of the principle of, + 325. + + Copley Medal awarded to Franklin, 66, 74. + + Cork, Earl of, autobiography of, 5. + + Creeping of electricity on glass, 139. + + Crystalline lens, fibrous structure of, 200; + mode of adjustment of, 201. + + Cuneus's discovery of the Leyden jar, 4. + + + D. + + Davy, Sir Humphry, appointed professor at the Royal Institution, + 174; + letter of, to Faraday, 244. + + Declaration of American Independence signed, 113. + + Defence of the American Colonies against France and Spain, 62. + + Degree of electrification, 137. + + De la Rive's invitation to Faraday, 249. + + Density of the earth, determinations of the mean, 146. + + Desaguliers on electrics and non-electrics, 4. + + Diagram of colour, Young's, 215; + Maxwell's, 295. + + Diamagnetism discovered by Faraday, 274. + + Diamonds burned by Davy, 250. + + Dichroism of _Lignum nephriticum_, 30. + + Discharge, electrical, difference between positive and negative, 87. + + Dissipation of energy, principle of, 326. + + Distilled water, resistance of, 142. + + Double refraction explained by Huyghens, 219. + + Dufay showed that all bodies could be electrified, 4. + + Dynamical nature of heat, suggested by Bacon, 2, 32; + maintained by Boyle, 32; + investigated by Rumford, 189; + established by Joule, 193, 324. + + Dynamical top, Maxwell's, 285. + + Dynamo, constructed by Wheatstone, 318; + action of, 319; + essential feature of, 319. + + + E. + + Effect of points in discharging electricity, 74. + + Electrical picnic, 80. + + Electrical Standards Committee, 287. + + Electric intensity, 137; + potential, 137. + + Electricity, first obtained from clouds, 74; + velocity of, 93. + + Electrics and non-electrics, 3. + + Electrolysis, Faraday's laws of, 266. + + Electro-magnetic induction, discovered by Faraday, 259; + Maxwell's statement of the laws of, 301. + + Electro-magnetic theory of light, 306. + + Electro-motors, 313. + + Electro-tonic state, conceived by Faraday, 264; + explained by Maxwell, 302. + + Energy of Leyden jar resident in the glass, 79. + + Eriometer, Young's, 223. + + Ether, Maxwell's illustration of the possible constitution of, 302. + + Expansion of water on freezing, 33. + + Extra current, 268. + + + F. + + =Faraday=, Michael, birth, 238; + life in Jacob's Well Mews, 238; + becomes an errand-boy, 239; + apprenticeship, 239; + attends lectures at Tatum's, 240; + constructs a voltaic pile, 241; + letters to Abbott, 241, 246; + starts as a journeyman, 243; + application to Davy, 243; + appointed assistant at the Royal Institution, 245; + joins the City Philosophical Society, 245; + opinions respecting lectures, 246, 247; + journey with Davy, 248; + acquaintance with De la Rive, 249; + crosses the Alps, 249; + at the Academia del Cimento, 250; + returns from the Continent, 251; + lectures to the City Philosophical Society, 251; + commonplace-book, 253; + atmospheric electricity apparatus, 254; + marriage, 255; + discovery of electro-magnetic rotation, 255; + of the earth's action on a current, 256; + letter to E. de la Rive, 256; + views on Ampère's theory, 257; + elected F.R.S., 258; + appointed director of the laboratory at the Royal Institution, + 258; + work on optical glass, 259; + discovery of induced currents, 259; + institutes Friday evening lectures, 259; + anchor-ring experiment, 260; + magneto-electric machine, 262; + obtains induced current by action of the earth, 262; + obtains "magnetic spark," 262; + explanation of Arago's experiment, 264; + laws of electrolysis, 266; + proves the identity of frictional and voltaic electricity, 266; + experiments on self-induction, 268; + diagrams of lines of magnetic force, 269; + conception of lines of electric force, 270; + ice-pail experiment, 270; + butterfly-net, 270; + experiments on specific inductive capacity, 272; + appointed scientific adviser to Trinity House, 273; + appointed member of the Senate of the University of London, 273; + discovery of the electro-magnetic rotation of the plane of + polarization, 273; + investigations in diamagnetism, 274; + joins the Sandemanian Church, 275; + lectures before the Prince Consort, 275; + retirement to Hampton Court, 277; + death, 277; + lines of force investigated by Thomson and Maxwell, 300. + + Forbes's, Principal, opinion of Young, 194. + + Foucault's measurement of the velocity of light, 220. + + _Fovea centralis_, insensibility of, to blue light, 298. + + Franciscus Linus, funicular hypothesis of, 25. + + =Franklin=, Benjamin, autobiography of, 39; + birth, 40; + on the disputatious temper, 42; + method of learning prose composition, 43; + tries vegetarianism, 44; + adopts the Socratic method, 44; + first voyage to England, 48; + experience as a journeyman in London, 49; + views on beer as a food, 49; + marriage, 54; + endeavours to attain moral perfection, 56; + method of reconciling an enemy, 60; + elected F.R.S., 66; + second voyage to England, 70; + begins electrical experiments, 72; + electrical papers ridiculed by the Royal Society, 73; + discovers the effect of points, 74; + one-fluid theory of electricity, 76; + theory of the Leyden jar, 78; + invention of the lightning-rod, 83; + golden fish, 85; + view of the nature of light, 86; + kite, 88; + experiments on capacity, 81, 89; + experiments on electrical induction, 90; + proof of the absence of electricity in a hollow conductor, 91; + third voyage to England, 102; + examination before the Parliamentary Committee, 105; + nominated Foreign Associate of the Academy of Sciences, 110; + signs the Declaration of Independence, 113; + sent to Paris, 113; + made Minister Plenipotentiary to the Court of France, 116; + signs the Treaty of Peace, 119; + elected President of Pennsylvania, 120; + death, 122. + + Fresnel, awarded the Rumford Medal, 233. + + Fresnel's repetition of Young's experiments, 225. + + Friction as a source of heat, Rumford's experiments on, 189. + + Friday evening lectures instituted by Faraday, 259. + + + G. + + Galileo and Torricelli on the pressure of the air, 16. + + Garnett, Dr. Thomas, professor at the Royal Institution, 173. + + Gilbert, Dr., founder of electrical science, 3. + + Göttingen, Young's university course at, 206. + + Graham Bell's telephone, 319. + + Gray, Stephen, discovers electric conduction, 3. + + Grimaldi's fringes explained by Young, 222. + + Gunpowder, Rumford's experiments on, 179. + + + H. + + Halos, coloured, Young's explanation of, 224. + + Hawksbee's observations on capillary attraction, 228. + + Heat, a form of energy, 32; + generated by friction in vacuum, 32; + generated by friction, Rumford's experiments on, 189. + + Herapath's explanation of gaseous diffusion, 299. + + Herschel's, Sir John, comments on Young's principle of interference, + 208. + + Hicks's, Principal, investigations on the influence of temperature + on gravitation, 184. + + Hieroglyphics, Young's work on, 234. + + Hobbes, opposition of, to Boyle, 25. + + Hollow conductor, Franklin's experiments on, 91; + Cavendish's experiments on, 135; + Faraday's experiments on, 270. + + Honorary degrees conferred on Franklin, 66, 101. + + Hooke's law, 229. + + Hooke, Theodore, founds the Royal Society, 14. + + Huyghens's explanation of double refraction, 219; + principle, 218. + + Hydrogen, electro-chemical equivalent of, 267. + + + I. + + Ice-pail experiment of Faraday, 270. + + Identity of frictional and voltaic electricity, 266. + + Induced currents, discovered by Faraday, 259; + explained by structure of ether, 304; + from earth's action, 262. + + Induction coil, 320. + + Induction, Franklin's experiments on, 90; + self, 142, 306. + + Induction machines, principle of, 316. + + Insulators for lightning-rods, 96. + + Interference, principle of, discovered by Young, 208; + spectra of, obtained by Young, 225. + + Invisible college, 13. + + + J. + + Jenkin, William, discovery of the "extra current" by, 268. + + Joule and Thomson's determination of the heat absorbed by air in + expanding, 324. + + Joule, Dr., establishment of mechanical theory of heat by, 193, 324. + + Joule's law, 324; + proof that heat and energy are equivalent, 324; + determination of the mechanical equivalent of heat, 325. + + Junto Club, formation of the, 51. + + + K. + + Kelland's, Professor, edition of Young's lectures, 212. + + Kinnersley commences lecturing, 73. + + Kite, Franklin's, 88. + + Knobs _versus_ points, 95. + + + L. + + Laboulaye's comments on Franklin, 38. + + Laplace's theory of Saturn's rings, 285. + + Latent heat, Black's theory of, 144; + Cavendish's views on, 144. + + Leonardo da Vinci's observation of capillary attraction, 228. + + Leyden jar, discovery of, 4; + energy of, resident in the glass, 79. + + Leyden jars charged by cascade, 77. + + Light, Franklin's view of nature of, 86; + Maxwell's electro-magnetic theory of, 306; + rotation of the plane of polarization of, 273. + + Lightning, effects of, on Newbury steeple, 92. + + Lightning-protectors, Maxwell's, 294. + + Lightning-rod, illustrations of the, 83. + + _Lignum nephriticum_, dichroism of, 30. + + Lines of force mathematically investigated by Thomson and Maxwell, + 300. + + Lines of magnetic force fixed by Faraday, 269. + + Luminiferous ether, the vehicle of electrical action, 227; + illustration of the possible constitution of, 302. + + + M. + + Magdeburg hemispheres, experiments with, by Otto von Guericke, 17. + + Magic squares, Franklin's proficiency in, 66. + + "Magnetic spark" obtained by Faraday, 262. + + Magnetization by induction, Boyle's experiments on, 34. + + Magneto-electric machine, Faraday's, 262, 314. + + Magneto-electric machines, Wilde's, 318; + objects to be aimed at in the construction of, 315. + + =Maxwell=, James Clerk, birth and parentage, 279; + enters Edinburgh Academy, 280; + letters to his father, 280; + early papers before the Royal Society of Edinburgh, 281; + visit to Mr. Nicol, 281; + experiments with unannealed glass, 282; + enters the University of Edinburgh, 282; + enters Peterhouse, 282; + migrates to Trinity, 282; + degree in Cambridge, 283; + elected Fellow of Trinity, 284; + appointed Professor at Marischal College, 284; + marriage, 287; + essay on Saturn's rings, 285; + dynamical top, 285; + appointed professor at King's College, 287; + lecture on colour at the Royal Institution, 287; + work on the Electrical Standards Committee, 287; + appointed Professor of Experimental Physics at Cambridge, 288; + plans the Cavendish Laboratory, 288; + lectures at Cambridge, 290; + work on the Cavendish Manuscripts, 134, 293; + delivers the Rede Lecture, 293; + method of protecting buildings from lightning, 294; + death, 294; + colour-top, 295; + experiments on colour-blindness, 296; + colour-box, 297; + awarded the Rumford Medal, 297; + wheel of life, 297; + real-image spectroscope, 298; + discovery of stresses in Canada balsam, 298; + of the insensibility of the _fovea centralis_ to blue light, 298; + statistical method, 299; + explanation of the viscosity of gases, 299; + investigations of Faraday's lines of force, 300; + statement of the laws of electro-magnetic induction, 301; + mechanical illustration of the ether, 302; + explanation of induced currents, 304; + of the mechanical action between currents and currents, and + between magnets and currents, 304; + of self-induction, 306; + electro-magnetic theory of light, 306; + contrivance for overcoming the principle of the dissipation of + energy, 328. + + Maxwell's experiment for showing electro-magnetic rotation, 258. + + Mayer's determination of the mechanical equivalent of heat, 323. + + Mechanical equivalent of heat, definition of, 193; + Rumford's determination of, 192. + + Mercury, melting point of, 145. + + Mirabeau's declamation on Franklin, 123. + + Mixed plates, colours of, 223. + + Moral perfection, Franklin's endeavour to attain, 56. + + Mother-of-pearl, Young's explanation of the colours of, 224. + + + N. + + Nautical Almanack, Young appointed superintendent of the, 232. + + Newton's analysis and synthesis of white light, 213; + rings, Young's explanation of, 222; + theory of light, 219. + + Nicol prisms given to Clerk Maxwell, 282. + + + O. + + [OE]rsted's discovery, 255. + + Ohm's law, discovered by Cavendish, 143; + meaning of, 143. + + Optical glass, Faraday's work on, 259. + + Otto von Guericke, contributions of, to electricity, 3; + experiments of, with the Magdeburg hemispheres, 17. + + + P. + + Paris, Dr., Faraday's letter to, 243. + + Pascal takes a barometer up the Puy de Dome, 17. + + Pennsylvania fireplace invented by Franklin, 63; + _Gazette_ published by Franklin, 53. + + Perpetual motion, Rumford's contrivances for, 150; + impossibility of, 322. + + Philadelphia, Franklin's first arrival in, 46; + Library, foundation of the, 55. + + Photometer, Rumford's, 187. + + Pigments, effects of mixing, 217. + + Points _versus_ knobs, 95, 131. + + Polarization, explained by transverse vibrations, 226; + of light discovered by Malus, 226. + + "Poor Richard's Almanack," 60. + + Pressure of the air the cause of suction, 29. + + + R. + + Radiation, Rumford's experiments on, 184; + of cold, Rumford's experiments on, 186. + + Rede Lecture, delivered by Clerk Maxwell, 293. + + Refraction of light, laws of, 1; + mentioned by Pliny, 1. + + Relative economy of different sources of light, 188. + + Resistance of conductors, Cavendish's experiments on, 142. + + Roemer, measurement of the velocity of light by, 2. + + Rosetta Stone, discovery of the, 234; + inscription on, 234. + + Royal Institution, foundation of the, 169; + Young's lectures at the, 212; + Faraday's appointment at the, 245; + Maxwell's lecture on colour at the, 287. + + Royal Society, origin of the, 13-15. + =Rumford=, Count, birth and parentage, 148; + life as a medical student, 153; + becomes a schoolmaster at Concord, 154; + marriage, 154; + summoned before the Committee of Safety, 156; + imprisoned at Woburn, 156; + first journey to London, 158; + receives an appointment in the Colonial Office, 158; + experiments on the explosion of gunpowder, 158, 179; + elected F.R.S., 158; + made lieutenant-colonel in the British army, 159; + promoted to colonel, 160; + visits Elector of Bavaria, 160; + cured of martial ambition, 160; + enters the service of the Elector of Bavaria, 161; + knighted by George III., 161; + reforms in the Bavarian army, 162; + attack on the beggars, 163; + made Count of the Holy Roman Empire, 165; + robbed of his manuscripts, 166; + visited by his daughter, 166; + his roaster, 166; + experiments on fire-places, 166; + founds the Rumford Medal, 167; + appointed Minister Plenipotentiary to the Court of Great Britain, + 169; + founds the Royal institution, 169; + plans for the Institution, 169; + residence in Paris, 175; + marriage with Madame Lavoisier, 175; + death; 176; + Cuvier's _éloge_ on, 176; + statue at Munich, 178; + experiments on the conduction of heat in fluids, 181; + on the convection of heat in viscous liquids, 184; + on the weight of heat, 185; + on radiation, 185; + on the conduction of heat, 186; + on the apparent radiation of cold, 187; + shadow-photometer, 188; + experiments on the relative economy of candles and tapers, 188; + on the traction of carriages, 189; + on friction as a source of heat, 189; + determination of the mechanical equivalent of heat, 192. + + Rumford Medal, foundation of the, 167; + recipients of the, 167; + awarded to Fresnel, 233; + awarded to Clerk Maxwell, 297. + + Rumford roaster, 166. + + + S. + + "Sandford and Merton," influence of, on the negro traffic, 197. + + Saturn's rings, Maxwell's essay on, 285. + + Sea-water, resistance of, 142. + + Séguin's attempt to measure loss of heat in the steam-engine, 323. + + Self-induction, effect of, on sudden discharge, 142; + of electro-magnet, 268; + effect of, in induction coil, 321. + + Sensation of heat, cause of, 33. + + Seraphic love, Boyle's essay on, 15. + + Shaw's, Dr., comments on Boyle, 37. + + Snellius's laws of refraction, 1. + + Socratic method adopted by Franklin, 44. + + Specific inductive capacity, discovered by Cavendish, 139; + rediscovered by Faraday, 272. + + Spectral colours, mixed by Boyle, 31; + mixed by Maxwell, 297. + + S.P.G., foundation of the, 30. + + Spheroidal waves in Iceland-spar explained by Young, 226. + + Stamp Act, 112. + + Standards Commission, report of, 232. + + Statistical method, Maxwell's, 299. + + Steeple struck by lightning at Newbury, 92. + + Stereoscope, Maxwell's real-image, 298. + + Stokes's, Professor G. G., exhibition of the bright centre in the + shadow of a disc, 222. + + Suction caused by atmospheric pressure, 29. + + Surface-tension, 228; + suggested by Segner, 229; + Young's investigations on, 229. + + + T. + + Table of results of experiments on Boyle's law, 27. + + Tatum's lectures on natural philosophy, 240. + + Telephone, Graham Bell's, 319. + + Temperature, its nature, 33. + + Thermometers first hermetically sealed, 2. + + Thomson's, Professor James, application of the principle of + dissipation of energy to the freezing of water under pressure, + 327. + + Thomson's, Sir William, statement of the principle of dissipation of + energy, 327; + vortex theory of matter, 312; + mirror galvanometer, 313; + replenisher, 316. + + Thunder-storms, Franklin's theory of, 81. + + Torpedo, Cavendish's experiments on the, 140; + Davy's experiments on the, 251. + + Traction of carriages, Rumford's experiments on, 189. + + Trial plate used by Cavendish, 139. + + Tyres, relative advantages of broad and narrow, 189. + + + U. + + Undulatory theory founded by Hooke and Huyghens, 218. + + Union of the American States, Franklin's plan for, 68. + + University of Philadelphia, foundation of the, 64. + + + V. + + Vacuum, Boyle's argument on the cause of a, 23. + + Velocity of electricity, 93; + of light measured by Roemer, 2; + of light deduced from electro-magnetic theory, 306. + + Viscosity of gases explained by Maxwell, 299. + + Voltaic pile constructed by Faraday, 241. + + Vortex theory of matter, 312. + + Voss machine, 316. + + + W. + + Wallis, Dr., account of the Royal Society by, 14. + + Wealth, ways to acquire, 100. + + Wheel of life, Clerk Maxwell's, 297. + + Wilson, Dr., account of Cavendish by, 132, 147. + + + Y. + + =Young=, Thomas, Principal Forbes's opinion of, 194; + birth and parentage, 194; + early education, 195; + becomes a London medical student, 199; + paper on the power of adjustment of the eye, 199; + elected F.R.S., 200; + visit to Cornwall, 201; + first visit to the Duke of Richmond, 201; + enters the Medical School at Edinburgh, 202; + declines secretaryship to the Duke of Richmond, 202; + visits Gordon Castle, 204; + visits Inverary Castle, 205; + enters the University of Göttingen, 206; + examination in medicine at Göttingen, 207; + enters Emmanuel College, 207; + discovers the principle of interference, 208; + appointed Professor of Natural Philosophy at the Royal + Institution, 174, 210; + lectures at the Royal Institution, 212; + theory of colour-vision, 214; + his colour-top, 215; + colour-diagram, 215; + his Bakerian lectures, 218; + explanation of the rectilinear propagation of light, 221; + of Newton's rings, 222; + eriometer, 223; + explanation of coloured halos, 224; + of the colours exhibited by mother-of-pearl, 224; + interference spectra, 225; + explanation of spheroidal waves in Iceland-spar, 226; + of the colours of thin plates, 227; + hypothesis of an electric ether, 227; + investigations on surface-tension, 229; + modulus of elasticity, 230; + his marriage, 231; + appointed physician in St. George's Hospital, 231; + superintendent of the Nautical Almanack, 232; + death, 233. + +PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, + +LONDON AND BECCLES. + + + + + +End of Project Gutenberg's Heroes of Science: Physicists, by William Garnett + +*** END OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: PHYSICISTS *** + +***** This file should be named 38583-8.txt or 38583-8.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/8/5/8/38583/ + +Produced by Albert László, P. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Heroes of Science: Physicists + +Author: William Garnett + +Release Date: January 15, 2012 [EBook #38583] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: PHYSICISTS *** + + + + +Produced by Albert László, P. G. Máté, Matthew Wheaton and +the Online Distributed Proofreading Team at +http://www.pgdp.net (This file was produced from images +generously made available by The Internet Archive) + + + + + + +</pre> + + +<h1 class="booktitle">HEROES OF SCIENCE.</h1> + +<p class="h4">PHYSICISTS.</p> + +<p class="h5">BY</p> + +<p class="h3">WILLIAM GARNETT, M.A., D.C.L.,</p> + +<blockquote><p><small> +FORMERLY FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE; PRINCIPAL OF +THE DURHAM COLLEGE OF SCIENCE, NEWCASTLE-UPON-TYNE; +HON. MEMBER OF THE NORTH OF ENGLAND INSTITUTE OF MINING AND +MECHANICAL ENGINEERS.</small></p></blockquote> +<p class="spacer"> </p> + +<blockquote><p><small> +PUBLISHED UNDER THE DIRECTION OF THE COMMITTEE +OF GENERAL LITERATURE AND EDUCATION APPOINTED BY THE +SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE.</small></p></blockquote> +<p class="spacer"> </p> + +<p class="h3">LONDON:</p> + +<p class="h4"> +SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE,<br /> +NORTHUMBERLAND AVENUE, CHARING CROSS, W.C.;</p> + +<p class="h5"> +43, QUEEN VICTORIA STREET, E.C.;<br /> +26, ST. GEORGE'S PLACE, HYDE PARK CORNER, S.W.<br /> +BRIGHTON: 135, NORTH STREET.<br /> +<span class="smcap">New York</span>: E. & J. B. YOUNG AND CO.</p> + +<p class="spacer"> </p> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_v">[v]</a></span></p> + +<div class="figcenter"> +<img src="images/i005.jpg" width="476" height="122" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="PREFACE">PREFACE.</h2> + +<p>The following pages claim no originality, and no merits beyond that of +bringing within reach of every boy and girl material which would +otherwise be available only to those who had extensive libraries at +their command, and much time at their disposal. In the schools and +colleges in which the principles of physical science are well taught, +the history of the discoveries whereby those principles have been +established has been too much neglected. The series to which the +present volume belongs is intended, in some measure, to meet this +deficiency.</p> + +<p>A complete history of physical science would, if it could be written, +form a library of considerable dimensions. The following pages deal +only with<span class="pagenum"><a id="Page_vi">[vi]</a></span> the biographies of a few distinguished men, who, by birth, +were British subjects, and incidental allusions only are made to +living philosophers; but, notwithstanding these narrow restrictions, +the foundations of the Royal Society of London, of the American +Philosophical Society, of the great Library of Pennsylvania, and of +the Royal Institution, are events, some account of which comes within +the compass of the volume. The gradual development of our knowledge of +electricity, of the mechanical theory of heat, and of the undulatory +theory of optics, will be found delineated in the biographies +selected, though no continuous history is traced in the case of any +one of these branches of physics.</p> + +<p>The sources from which the matter contained in the following pages has +been derived have been, in addition to the published works of the +subjects of the several sketches, the following:—</p> + +<p>"The Encyclopædia Britannica."</p> + +<p>"Memoir of the Honourable Robert Boyle," by Thomas Birch, M.A., +prefixed to the folio edition of his works, which was published in +London in 1743.</p> + +<p>"Life of Benjamin Franklin," from his own writings, by John Bigelow.</p> + +<p>Dr. G. Wilson's "Life of Cavendish," which<span class="pagenum"><a id="Page_vii">[vii]</a></span> forms the first volume of +the publications of the Cavendish Society; and the "Electrical +Researches of the Hon. Henry Cavendish, F.R.S.," edited by the late +Professor James Clerk Maxwell.</p> + +<p>"The Life of Sir Benjamin Thompson, Count Rumford," by George E. +Ellis, published by the American Academy of Arts and Sciences, in +connection with the complete edition of his works.</p> + +<p>"Memoir of Thomas Young," by the late Dean Peacock.</p> + +<p>Dr. Bence Jones's "Life of Faraday;" and Professor Tyndall's "Faraday +as a Discoverer."</p> + +<p>"Life of James Clerk Maxwell," by Professor Lewis Campbell and William +Garnett.</p> + +<p>It is hoped that the perusal of the following sketches may prove as +instructive to the reader as their preparation has been to the writer.</p> + +<p class="author">WM. GARNETT.</p> + +<p><span class="smcap">Newcastle-upon-Tyne</span>,<br /> +<span class="in2"><i>December, 1885</i>.</span> +</p> + +<div class="figcenter"> +<img src="images/i007.jpg" width="205" height="73" alt="" /> +</div> + +<p class="spacer"> </p> + +<hr class="chap" /> + +<div class="figcenter"> +<img src="images/i009-1.jpg" width="472" height="118" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="CONTENTS">CONTENTS.</h2> + +<div class="center600"> +<p> +<a href="#INTRODUCTION">INTRODUCTION.</a> +<span class="right">1</span><br /> +<a href="#ROBERT_BOYLE">ROBERT BOYLE.</a> +<span class="right">5</span><br /> +<a href="#BENJAMIN_FRANKLIN">BENJAMIN FRANKLIN.</a> +<span class="right">38</span><br /> +<a href="#HENRY_CAVENDISH">HENRY CAVENDISH.</a> +<span class="right">125</span><br /> +<a href="#COUNT_RUMFORD">COUNT RUMFORD.</a> +<span class="right">148</span><br /> +<a href="#THOMAS_YOUNG">THOMAS YOUNG.</a> +<span class="right">194</span><br /> +<a href="#MICHAEL_FARADAY">MICHAEL FARADAY.</a> +<span class="right">237</span><br /> +<a href="#JAMES_CLERK_MAXWELL">JAMES CLERK MAXWELL.</a> +<span class="right">278</span><br /> +<a href="#CONCLUSION">CONCLUSION.</a> +<span class="right">309</span><br /> +</p> +</div> + +<div class="figcenter"> +<img src="images/i009-2.jpg" width="190" height="157" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_1">[1]</a></span></p> + +<div class="figcenter"> +<img src="images/i011.jpg" width="468" height="101" alt="" /> +</div> + +<p class="spacer"> </p> + +<p class="h1">HEROES OF SCIENCE.</p> + +<h2 id="INTRODUCTION">INTRODUCTION.</h2> + +<p>The dawn of true ideas respecting mechanics has been described in the +volume of this series devoted to astronomers. At the time when the +first of the following biographies opens there were a few men who held +sound views respecting the laws of motion and the principles of +hydrostatics. Considerable advance had been made in the subject of +geometrical optics; the rectilinear propagation of light and the laws +of reflection having been known to the Greeks and Arabians, whilst +Willebrod Snellius, Professor of Mathematics at Leyden, had correctly +enunciated the laws of refraction very early in the seventeenth +century. Pliny mentions the action of a sphere of rock-crystal and of +a glass globe filled with water in bringing light to a focus. Roger +Bacon used segments of<span class="pagenum"><a id="Page_2">[2]</a></span> a glass sphere as lenses; and in the eleventh +century Alhazen made many measurements of the angles of incidence and +refraction, though he did not succeed in discovering the law. Huyghens +developed to a great extent the undulatory theory; while Newton at the +same time made great contributions to the subject of geometrical +optics, decomposed white light by means of a prism, investigated the +colours of thin plates, and some cases of diffraction, and speculated +on the nature, properties, and functions of the ether, which was +equally necessary to the corpuscular as to the undulatory theory of +light, if any of the phenomena of interference were to be explained. +The velocity of light was first measured by Roemer, in 1676. The +camera obscura was invented by Baptista Porta, a wealthy Neapolitan, +in 1560; and Kepler explained the action of the eye as an optical +instrument, in 1604. Antonio de Dominis, Archbishop of Spalatro, +discovered the fringe of colours produced by sunlight once reflected +from the interior of a globe of water, and this led, in Newton's +hands, to the complete explanation of the rainbow.</p> + +<p>The germ of the mechanical theory of heat is to be found in the +writings of Lord Bacon. The first thermometers which were blown in +glass with a bulb and tube hermetically sealed, were made by a +craftsman in Florence, in the time of Torricelli. The graduations on +these thermometers were made by attaching little beads of<span class="pagenum"><a id="Page_3">[3]</a></span> coloured +glass to their stems, and they were carried about Europe by members of +the Florentine Academy, in order to learn whether ice melted at the +same temperature in all latitudes.</p> + +<p>In electricity the attraction of light bodies by amber when rubbed, +was known at least six hundred years before the Christian era, and the +shocks of the torpedo were described by Pliny and by Aristotle; but +the phenomena were not associated in men's minds until recent times. +Dr. Gilbert, of Colchester, Physician to Queen Elizabeth, may be +regarded as the founder of the modern science. He distinguished two +classes of bodies, viz. electrics, or those which would attract light +bodies when rubbed; and non-electrics, or those which could not be so +excited. The first electric machine was constructed by Otto von +Guericke, the inventor of the Magdeburg hemispheres, who mounted a +ball of sulphur so that it could be made rapidly to rotate while it +was excited by the friction of the hand. He observed the repulsion +which generally follows the attraction of a light body by an +electrified object after the two have come in contact. He also noticed +that certain bodies placed near to electrified bodies possessed +similar powers of attraction to those of the electrified bodies +themselves. Newton replaced the sulphur globe of Otto von Guericke by +a globe of glass. Stephen Gray discovered the conduction of +electricity, in 1729, when he succeeded in transmitting a charge to a +distance of 886 feet along<span class="pagenum"><a id="Page_4">[4]</a></span> a pack-thread suspended by silk strings so +as to insulate it from the earth. Desaguliers showed that Gilbert's +"electrics" were simply those bodies which could not conduct +electricity, while all conductors were "non-electrics;" and Dufay +showed that all bodies could be electrified by friction if supported +on insulating stands. He also showed that there were two kinds of +electrification, and called one <i>vitreous</i>, the other <i>resinous</i>. +Gray, Hawksbee, and Dr. Wall all noticed the similarity between +lightning and the electric discharge. The prime conductor was first +added to the electric machine by Boze, of Wittenberg; and Winkler, of +Leipsic, employed a cushion instead of the hand to produce friction +against the glass. The accumulation of electricity in the Leyden jar +was discovered accidentally by Cuneus, a pupil of Muschenbroeck, of +Leyden, about 1745, while attempting to electrify water in a bottle +held in his hand. A nail passed through the cork, by which the +electricity was communicated to the water. On touching the nail after +charging the water, he received the shock of the Leyden jar. This +brings the history of electrical discovery down to the time of +Franklin.</p> + +<div class="figcenter"> +<img src="images/i014.jpg" width="159" height="138" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_5">[5]</a></span></p> + +<div class="figcenter"> +<img src="images/i015.jpg" width="470" height="110" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="ROBERT_BOYLE">ROBERT BOYLE.</h2> + +<p>Robert Boyle was descended from a family who, in Saxon times, held +land in the county of Hereford, and whose name in the Doomsday Book is +written Biuvile. His father was Richard Boyle, Earl of Cork, to whom +the fortunes of the family were largely due. Richard Boyle was born in +the city of Canterbury, October 3, 1566. He was educated at Bene't +College (now Corpus Christi College), Cambridge, and afterwards became +a member of the Middle Temple. Finding his means insufficient for the +prosecution of his legal studies, he determined to seek his fortune +abroad. In 1595 he married, at Limerick, one of the daughters of +William Apsley, who brought him land of the value of £500 per annum. +In his autobiography the Earl of Cork writes:—</p> + +<blockquote> +<p>When first I arrived at Dublin, in Ireland, the 23rd of June 1588, +all my wealth then was twenty-seven pounds three shillings in money, +and two<span class="pagenum"><a id="Page_6">[6]</a></span> tokens which my mother had given me, viz. a diamond ring, +which I have ever since and still do wear, and a bracelet of gold +worth about ten pounds; a taffety doublet cut with and upon taffety, a +pair of black velvet breeches laced, a new Milan fustian suit laced +and cut upon taffety, two cloaks, competent linen, and necessaries, +with my rapier and dagger. And since, the blessing of God, whose +heavenly providence guided me hither, hath enriched my weak estate, in +beginning with such a fortune, as I need not envy any of my +neighbours, and added no care or burthen of my conscience thereunto. +And the 23rd of June, 1632, I have served my God, Queen Elizabeth, +King James, and King Charles, full forty-four years, and so long after +as it shall please God to enable me.</p> +</blockquote> + +<p>Richard Boyle's property in Ireland increased so rapidly that he was +accused to Queen Elizabeth of receiving pay from some foreign power. +When about to visit England in order to clear himself of this charge, +the rebellion in Munster broke out; his lands were wasted, and his +income for the time destroyed. Reaching London, he returned to his old +chambers in the Middle Temple, until he entered the service of the +Earl of Essex, to whom the government of Ireland had been entrusted. +The charges against him were then resumed, and he was made a prisoner, +and kept in confinement until the Earl of Essex had gone over to +Ireland. At length he obtained a hearing before the queen, who fully +acquitted him of the charges, gave him her hand<span class="pagenum"><a id="Page_7">[7]</a></span> to kiss, and promised +to employ him in her own service; at the same time she dismissed Sir +Henry Wallop, who was Treasurer for Ireland, and prominent among +Boyle's accusers, from his office.</p> + +<p>A few days afterwards, Richard Boyle was appointed by the queen Clerk +to the Council of Munster, and having purchased a ship of Sir Walter +Raleigh, he returned to Ireland with ammunition and provisions.</p> + +<p>"Then, as Clerk of the Council, I attended the Lord President in all +his employments, and waited upon him at the siege of Kingsale, and was +employed by his Lordship to her Majesty, with the news of that happy +victory; in which employment I made a speedy expedition to the court; +for I left my Lord President at Shannon Castle, near Corke, on the +Monday morning, about two of the clock, and the next day, being +Tuesday, I delivered my packet, and supped with Sir Robert Cecil, +being then principal Secretary of State, at his house in the Strand; +who, after supper, held me in discourse till two of the clock in the +morning; and by seven that morning called upon me to attend him to the +court, where he presented me to her Majesty in her bed-chamber, who +remembered me, calling me by my name, and giving me her hand to kiss, +telling me that she was glad that I was the happy man to bring the +first news of that glorious victory ... and so I was dismissed with +grace and favour."</p> + +<p>In reading of this journey from Cork to London, it is almost necessary +to be reminded that it took<span class="pagenum"><a id="Page_8">[8]</a></span> place two hundred and fifty years before +the introduction of steam-boats and railways. At the close of the +rebellion, Richard Boyle purchased from Sir Walter Raleigh all his +lands in Munster; and on July 25, 1603, he married his second wife, +Catharine, the only daughter of Sir Geoffrey Fenton, principal +Secretary of State, and Privy Councillor in Ireland, "with whom I +never demanded any marriage portion, neither promise of any, it not +being in my consideration; yet her father, after my marriage, gave me +one thousand pounds in gold with her. But that gift of his daughter +unto me I must ever thankfully acknowledge as the crown of all my +blessings; for she was a most religious, virtuous, loving, and +obedient wife unto me all the days of her life." He was knighted by +the Lord Deputy of Ireland, Sir George Carew, on his wedding-day; was +sworn Privy Councillor of State of the Kingdom of Ireland in 1612; +created Lord Boyle, Baron of Youghall, September 29, 1616; Lord +Viscount of Dungarvon and Earl of Cork, October 26, 1620; one of the +Lords Justices of Ireland, with a salary of £1200 per annum, in 1629; +and Lord High Treasurer of Ireland, November 9, 1631.</p> + +<p>Robert Boyle, the seventh son of the Earl of Cork, was born January +25, 1627. His mother died February 16, 1630. The earl lived in +prosperity in Ireland till the breaking out of the rebellion in 1641, +and died at Youghall in September, 1643. It is said that when Cromwell +saw<span class="pagenum"><a id="Page_9">[9]</a></span> the vast improvements which the earl had made on his estate in +Munster, he declared that "if there had been an Earl of Cork in every +province, it would have been impossible for the Irish to have raised a +rebellion."</p> + +<p>At a very early age Robert was sent by his father to a country nurse, +"who, by early inuring him, by slow degrees, to a coarse but cleanly +diet, and to the usual passion of the air, gave him so vigorous a +complexion that both hardships were made easy to him by custom, and +the delights of conveniences and ease were endeared to him by their +rarity." Making the acquaintance of some children who stuttered in +their speech, he, by imitation, acquired the same habit, "so +contagious and catching are men's faults, and so dangerous is the +familiar commerce of those condemnable customs, that, being imitated +but in jest, come to be learned and acquired in earnest." Before going +to school he studied French and Latin, and showed considerable +aptitude for scholarship. He was then sent to Eton, where his master +took much notice of him, and "would sometimes give him unasked +play-days, and oft bestow upon him such balls and tops and other +implements of idleness as he had taken away from others that had +unduly used them."</p> + +<p>While at school, in the early morning, a part of the wall of the +bedroom, with the bed, chairs, books, and furniture of the room above, +fell on him and his brother. "His brother had his band torn about his +neck, and his coat upon his back, and his chair<span class="pagenum"><a id="Page_10">[10]</a></span> crushed and broken +under him; but by a lusty youth, then accidentally in the room, was +snatched from out the ruins, by which [Robert] had, in all +probability, been immediately oppressed, had not his bed been +curtained by a watchful Providence, which kept all heavy things from +falling on it; but the dust of the crumbled rubbish raised was so +thick that he might there have been stifled had not he remembered to +wrap his head in the sheet, which served him as a strainer, through +which none but the purer air could find a passage." At Eton he spent +nearly four years, "in the last of which he forgot much of that Latin +he had got, for he was so addicted to more solid parts of knowledge +that he hated the study of bare words naturally, as something that +relished too much of pedantry to consort with his disposition and +designs." On leaving Eton he joined his father at Stalbridge, in +Dorsetshire, and was sent to reside with "Mr. W. Douch, then parson of +that place," who took the supervision of his studies. Here he renewed +his acquaintance with Latin, and devoted some attention to English +verse, spending some of his idle hours in composing verses, "most of +which, the day he came of age, he sacrificed to Vulcan, with a design +to make the rest perish by the same fate." A little later he returned +to his father's house in Stalbridge, and was placed under the tutelage +of a French gentleman, who had been tutor to two of his brothers.</p> + +<p>In October, 1638, Robert Boyle and his brother<span class="pagenum"><a id="Page_11">[11]</a></span> were sent into France. +After a short stay at Lyons, they reached Geneva, where Robert +remained with his tutor for about a year and three quarters. During +his residence here an incident occurred which he regarded as the most +important event of his life, and which we therefore give in his own +words.</p> + +<p>"To frame a right apprehension of this, you must understand that, +though his inclinations were ever virtuous, and his life free from +scandal and inoffensive, yet had the piety he was master of already so +diverted him from aspiring unto more, that Christ, who long had lain +asleep in his conscience (as He once did in the ship), must now, as +then, be waked by a storm. For at a time which (being the very heat of +summer) promised nothing less, about the dead of night, that adds most +terror to such accidents, [he] was suddenly waked in a fright with +such loud claps of thunder (which are oftentimes very terrible in +those hot climes and seasons), that he thought the earth would owe an +ague to the air, and every clap was both preceded and attended with +flashes of lightning, so frequent and so dazzling that [he] began to +imagine them the sallies of that fire that must consume the world. The +long continuance of that dismal tempest, where the winds were so loud +as almost drowned the noise of the very thunder, and the showers so +hideous as almost quenched the lightning ere it could reach his eyes, +confirmed him in his apprehensions of the day of judgment's being at +hand.<span class="pagenum"><a id="Page_12">[12]</a></span> Whereupon the consideration of his unpreparedness to welcome +it, and the hideousness of being surprised by it in an unfit +condition, made him resolve and vow that, if his fears were that night +disappointed, all his further additions to his life should be more +religiously and watchfully employed. The morning came, and a serene, +cloudless sky returned, when he ratified his determinations so +solemnly, that from that day he dated his conversion, renewing, now he +was past danger, the vow he had made whilst he believed himself to be +in it; and though his fear was (and he blushed it was so) the occasion +of his resolution of amendment, yet at least he might not owe his more +deliberate consecration of himself to piety to any less noble motive +than that of its own excellence."</p> + +<p>After leaving Geneva, he crossed the Alps and travelled through +Northern Italy. Here he spent much time in learning Italian; "the rest +of his spare hours he spent in reading the modern history in Italian, +and the new paradoxes of the great stargazer Galileo, whose ingenious +books, perhaps because they could not be so otherwise, were confuted +by a decree from Rome; his highness the Pope, it seems, presuming, and +that justly, that the infallibility of his chair extended equally to +determine points in philosophy as in religion, and loth to have the +stability of that earth questioned in which he had established his +kingdom."</p> + +<p>Having visited Rome, he at length returned to France, and was detained +at Marseilles, awaiting<span class="pagenum"><a id="Page_13">[13]</a></span> a remittance from the earl to enable him to +continue his travels. Through some miscarriage, the money which the +earl sent did not arrive, and Robert and his brother had to depend on +the credit of the tutor to procure the means to enable them to return +home. They reached England in the summer of 1644, "where we found +things in such confusion that, although the manor of Stalbridge were, +by my father's decease, descended unto me, yet it was near four months +before I could get thither." On reaching London, Robert Boyle resided +for some time with his sister, Lady Ranelagh, and was thus prevented +from entering the Royalist Army. Later on he returned for a short time +to France; visited Cambridge in December, 1645, and then took up his +residence at Stalbridge till May, 1650, where he commenced the study +of chemistry and natural philosophy.</p> + +<p>It was in October, 1646, that Boyle first made mention of the +"<i>invisible college</i>," which afterwards developed into the Royal +Society. Writing to a Fellow of Magdalen College, Cambridge, in +February, 1647, he says, "The corner-stones of the <i>invisible</i>, or, as +they term themselves, the <i>philosophical college</i>, do now and then +honour me with their company." It appears that a desire to escape from +the troubles of the times had induced several persons to take refuge +in philosophical pursuits, and, meeting together to discuss the +subjects of their study, they formed the "invisible college." Boyle +says, "I will conclude their praises with<span class="pagenum"><a id="Page_14">[14]</a></span> the recital of their +chiefest fault, which is very incident to almost all good things, and +that is, that there is not enough of them." Dr. Wallis, one of the +first members of the society, states that Mr. Theodore Hooke, a German +of the Palatinate, then resident in London, "gave the first occasion +and first suggested those meetings and many others. These meetings we +held sometimes at Dr. Goddard's lodging, in Wood Street (or some +convenient place near), on occasion of his keeping an operator in his +house, for grinding glasses for telescopes and microscopes, and +sometimes at a convenient place in Cheapside; sometimes at Gresham +College, or some place near adjoining. Our business was (precluding +theology and State affairs) to discourse and consider of philosophical +inquiries, and such as related thereunto; as physic, anatomy, +geometry, astronomy, navigation, statics, magnetics, chemics, +mechanics, and natural experiments, with the state of these studies as +then cultivated at home and abroad. About the year 1648-49 some of us +being removed to Oxford, first Dr. Wilkins, then I, and soon after Dr. +Goddard, our company divided. Those in London continued to meet there +as before, and we with them when we had occasion to be there. And +those of us at Oxford, with Dr. Ward, since Bishop of Salisbury, Dr. +Ralph Bathurst, now President of Trinity College in Oxford, Dr. Petty, +since Sir William Petty, Dr. Willis, then an eminent physician in +Oxford, and divers others, continued such meetings in Oxford, and +brought<span class="pagenum"><a id="Page_15">[15]</a></span> those studies into fashion there; meeting first at Dr. +Petty's lodgings, in an apothecary's house, because of the convenience +of inspecting drugs and the like, as there was occasion; and after his +remove to Ireland (though not so constantly) at the lodgings of Dr. +Wilkins, then Warden of Wadham College; and after his removal to +Trinity College in Cambridge, at the lodgings of the Honourable Mr. +Robert Boyle, then resident for divers years in Oxford. These meetings +in London continued, and after the king's return, in 1660, were +increased with the accession of divers worthy and honourable persons, +and were afterwards incorporated by the name of the <i>Royal Society</i>, +and so continue to this day."</p> + +<p>Boyle was only about twenty years of age when he wrote his "Free +Discourse against Swearing;" his "Seraphic Love; or, Some Motives and +Incentives to the Love of God;" and his "Essay on Mistaken Modesty." +"Seraphic Love" was the last of a series of treatises on love, but the +only one of the series that he published, as he considered the others +too trifling to be published alone or in conjunction with it. In a +letter to Lady Ranelagh, he refers to his laboratory as "a kind of +Elysium," and there were few things which gave him so much pleasure as +his furnaces and philosophical experiments. In 1652 he visited +Ireland, returning in the following summer. In the autumn he was again +obliged to visit Ireland, and remained there till the summer of 1654, +though residence in that country was far<span class="pagenum"><a id="Page_16">[16]</a></span> from agreeable to him. He +styled it "a barbarous country, where chemical spirits were so +misunderstood, and chemical instruments so unprocurable, that it was +hard to have any hermetic thoughts in it." On his return he settled in +Oxford, and there his lodgings soon became the centre of the +scientific life of the university. Boyle and his friends may be +regarded as the pioneers of experimental philosophy in this country. +To Boyle the methods of Aristotle appeared little more than +discussions on words; for a long time he refused to study the +philosophy of Descartes, lest he should be turned aside from reasoning +based strictly on the results of experiment. The method pursued by +these philosophers had been fully discussed by Lord Bacon, but at best +his experimental methods, though most complete and systematic, existed +only upon paper, and it was reserved for Boyle and his friends to put +the Baconian philosophy into actual practice.</p> + +<p>It was during his residence at Oxford that he invented the air-pump, +which was afterwards improved for him by Hooke, and with which he +conducted most of those experiments on the "spring" and weight of the +air, which led up to the investigations that have rendered his name +inseparably connected with "the gaseous laws." The experiments of +Galileo and of Torricelli had shown that the pressure of the air was +capable of supporting a column of water about thirty-four feet in +height, or a column of mercury nearly thirty<span class="pagenum"><a id="Page_17">[17]</a></span> inches high. The younger +Pascal, at the request of Torricelli, had carried a barometer to the +summit of the Puy de Dome, and demonstrated that the height of the +column of mercury supported by the air diminishes as the altitude is +increased. Otto von Guericke had constructed the Magdeburg +hemispheres, and shown that, when exhausted, they could not be +separated by sixteen horses, eight pulling one way and eight the +other. He was aware that the same traction could have been produced by +eight horses if one of the hemispheres had been attached to a fixed +obstacle; but, with the instincts of a popular lecturer, he considered +that the spectacle would thus be rendered less striking, and it was +prepared for the king's entertainment. Boyle wished for an air-pump +with an aperture in the receiver sufficiently large for the +introduction of various objects, and an arrangement for exhausting it +without filling the receiver with water or otherwise interfering with +the objects placed therein. His apparatus consisted of a large glass +globe capable of containing about three gallons or thereabouts, +terminating in an open tube below, and with an aperture of about four +inches diameter at the top. Around this aperture was cemented a turned +brass ring, the inner surface being conical, and into this conical +seat was fitted a brass plate with a thick rim, but drilled with a +small hole in the centre. To this hole, which was also conical, was +fitted a brass stopper, which could be turned round when the receiver +was exhausted. By<span class="pagenum"><a id="Page_18">[18]</a></span> attaching a string to this stopper, which was so +long as to enter the receiver to the depth of two or three inches, and +turning the stopper in its seat, the string could be wound up, and +thus objects could be moved within the receiver. The tube at the +bottom of the receiver communicated with a stop-cock, and this with +the upper end of the pumpbarrel, which was inverted, so that this +stop-cock, which was at the top of the barrel, took the place of the +foot-valve. The piston was solid, made of wood, and surrounded with +sole leather, which was kept well greased. There being no valve in the +piston, it was necessary to place an exhaust-valve in the upper end of +the cylinder. This consisted of a small brass plug closing a conical +hole so that it could be removed at pleasure. The construction of the +cylinder was, therefore, similar to that of an ordinary force-pump, +except that the valves had to be moved by hand (as in the early forms +of the steam-engine). The piston was raised and depressed by means of +a rack and pinion. The pumps could be used either for exhausting the +receiver or for forcing air into it, according to the order in which +the "valves" were opened. If the stop-cock communicating with the +receiver were open while the piston was being drawn down, and the +brass plug removed so as to open the exhaust-valve when the piston was +being forced up, the receiver would gradually be exhausted. If the +brass plug were removed during the descent of the piston, and the +stop-cock opened during its ascent,<span class="pagenum"><a id="Page_19">[19]</a></span> air would be forced into the +receiver. In the latter case it was necessary to take special +precautions to prevent the brass plate at the top of the receiver +being raised from its seat. All joints were made air-tight with +"diachylon," and when, through the bursting of a glass bulb within it, +the receiver became cracked, the crack was rendered air-tight by the +same means. Other receivers of smaller capacity were also provided, on +account of the greater readiness with which they could be exhausted.</p> + +<p>With this apparatus Boyle carried out a long series of experiments. He +could reduce the pressure in the large receiver to somewhat less than +that corresponding to an inch of mercury, or about a foot of water. +Squeezing a bladder so as to expel nearly all the air, tying the neck, +and then introducing it into the receiver, he found, on working the +pump, that the bladder swelled so that at length it became completely +distended. In order to account for this great expansibility, Boyle +pictured the constitution of the air in the following way. He supposed +the air to consist of separate particles, each resembling a spiral +spring, which became tightly wound when exposed to great pressure, but +which expanded so as to occupy a larger circle when the pressure was +diminished. Each of these little spirals he supposed to rotate about a +diameter so as to exclude every other body from the sphere in which it +moved. Increasing the length of the diameter tenfold would increase +the volume of one of these spheres, and therefore the volume of the +gas,<span class="pagenum"><a id="Page_20">[20]</a></span> a thousandfold. Possibly this was only intended as a mental +illustration, exhibiting a mechanism by which very great expansion +might conceivably be produced, and scarcely pretending to be +considered a <i>theory</i> of the constitution of the air. Boyle's first +idea seems to have been derived from a lock of wool in which the +elasticity of each fibre caused the lock to expand after it had been +compressed in the hand. In another passage he speaks of the air as +consisting of a number of bodies capable of striking against a surface +exposed to them. He demonstrated the weight of the air by placing a +delicate balance within the receiver, suspending from one arm a +bladder half filled with water, and balancing it with brass weights. +On exhausting the air, the bladder preponderated, and, by repeating +the experiment with additional weights on the other arm until a +balance was effected in the exhausted receiver, he determined the +amount of the preponderance. In another experiment he compressed air +in a bladder by tying a pack-thread round it, balanced it from one arm +of his balance in the open air; then, pricking the bladder so as to +relieve the pressure, he found that with the escape of the compressed +air the weight diminished.</p> + +<p>One of the most important of his experiments with the air-pump was the +following. He placed within the receiver the cistern of a mercurial +barometer, the tube of which was made to pass through the central hole +in the brass plate, from which the stopper had been removed. The space +around the tube was<span class="pagenum"><a id="Page_21">[21]</a></span> filled up with cement, and the receiver +exhausted. At each stroke of the pump the mercury in the barometer +tube descended, but through successively diminishing distances, until +at length it stood only an inch above the mercury in the cistern. The +experiment was then repeated with a tube four feet long and filled +with water. This constituted the nineteenth experiment referred to +later on. A great many strokes of the pump had to be made before the +water began to descend. At length it fell till the surface in the tube +stood only about a foot above that in the tank. Placing vessels of +ordinary spring-water and of distilled rain-water in the receiver, he +found that, after the exhaustion had reached a certain stage, bubbles +of gas were copiously evolved from the spring-water, but not from the +distilled water. On another occasion he caused warm water to boil by a +few strokes of the pump; and, continuing the exhaustion, the water was +made to boil at intervals until it became only lukewarm. The +experiment was repeated with several volatile liquids. He also noticed +the cloud formed in the receiver when the air was allowed rapidly to +expand; but the mechanical theory of heat had not then made sufficient +progress to enable him to account for the condensation by the loss of +heat due to the work done by the expanding air. The very minute +accuracy of his observations is conspicuous in the descriptions of +most of his experiments. That the air is the usual medium for the +conveyance of sound was shown by suspending a watch<span class="pagenum"><a id="Page_22">[22]</a></span> by a linen thread +within the receiver. On exhausting the air, the ticking of the watch +ceased to be heard. A pretty experiment consisted in placing a bottle +of a certain fuming liquid within the receiver; on exhausting the air, +the fumes fell over the neck of the bottle and poured over the stand +on which it was placed like a stream of water. Another experiment, the +thirty-second, is worthy of mention on account of the use to which it +was afterwards applied in the controversy respecting the cause of +suction. The receiver, having been exhausted, was removed from the +cylinder, the stop-cock being turned off, and a small brass valve, to +which a scale-pan was attached, was placed just under the aperture of +the tube below the stop-cock. On turning the latter, the stream of air +raised the valve, closing the aperture, and the atmospheric pressure +supported it until a considerable weight had been placed in the +scale-pan. Because the receiver could not be exhausted so thoroughly +as the pump-cylinder, Boyle attempted to measure the pressure of the +air by determining what weight could be supported by the piston. He +found first that a weight of twenty-eight pounds suspended directly +from the piston was sufficient to overcome friction when air was +admitted above the piston. When the access of air to the top of the +piston was prevented, more than one hundred pounds additional weight +was required to draw down the piston. The diameter of the cylinder was +about three inches.</p><p><span class="pagenum"><a id="Page_23">[23]</a></span></p> + +<p>Boyle's style of reasoning is well illustrated by the following from +his paper on "The Spring of the Air:"—</p> + +<p>"In the next place, these experiments may teach us what to judge of +the vulgar axiom received for so many ages as an undoubted truth in +the peripatetick schools, that Nature abhors and flieth a vacuum, and +that to such a degree that no human power (to go no higher) is able to +make one in the universe; wherein heaven and earth would change +places, and all its other bodies rather act contrary to their own +nature than suffer it.... It will not easily, then, be intelligibly +made out how hatred or aversation, which is a passion of the soul, can +either for a vacuum or any other object be supposed to be in water, or +such like inanimate body, which cannot be presumed to know when a +vacuum would ensue, if they did not bestir themselves to prevent it; +nor to be so generous as to act contrary to what is most conducive to +their own particular preservation for the public good of the universe. +As much, then, of intelligible and probable truth as is contained in +this metaphorical expression seems to amount but to this—that by the +wise Author of nature (who is justly said to have made all things in +number, weight, and measure) the universe, and the parts of it, are so +contrived that it is hard to make a vacuum in it, as if they +studiously conspired to prevent it. And how far this itself may be +granted deserves to be further considered.</p><p><span class="pagenum"><a id="Page_24">[24]</a></span></p> + +<p>"For, in the next place, our experiments seem to teach that the +supposed aversation of Nature to a vacuum is but accidental, or in +consequence, partly of the weight and fluidity, or, at least, +fluxility of the bodies here below; and partly, and perhaps +principally, of the air, whose restless endeavour to expand itself +every way makes it either rush in itself or compel the interposed +bodies into all spaces where it finds no greater resistance than it +can surmount. And that in those motions which are made <i>ob fugam +vacui</i> (as the common phrase is), bodies act without such generosity +and consideration as is wont to be ascribed to them, is apparent +enough in our thirty-second experiment, where the torrent of air, that +seemed to strive to get into the emptied receiver, did plainly prevent +its own design, by so impelling the valve as to make it shut the only +orifice the air was to get [in] at. And if afterwards either Nature or +the internal air had a design the external air should be attracted, +they seemed to prosecute it very unwisely by continuing to suck the +valve so strongly, when they found that by that suction the valve +itself could not be drawn in; whereas, by forbearing to suck, the +valve would, by its own weight, have fallen down and suffered the +excluded air to return freely, and to fill again the exhausted +vessel....</p> + +<p>"And as for the care of the public good of the universe ascribed to +dead and stupid bodies, we shall only demand why, in our nineteenth +experiment, upon the exsuction of the ambient air,<span class="pagenum"><a id="Page_25">[25]</a></span> the water deserted +the upper half of the glass tube, and did not ascend to fill it up +till the external air was let in upon it. Whereas, by its easy and +sudden rejoining that upper part of the tube, it appeared both that +there was then much space devoid of air, and that the water might, +with small or no resistance, have ascended into it, if it could have +done so without the impulsion of the readmitted air; which, it seems, +was necessary to mind the water of its formerly neglected duty to the +universe."</p> + +<p>Boyle then goes on to explain the phenomena correctly by the pressure +of the air. Elsewhere he accounts for the diminished pressure on the +top of a mountain by the diminished weight of the superincumbent +column of air.</p> + +<p>The treatise on "The Spring of the Air" met with much opposition, and +Boyle considered it necessary to defend his doctrine against the +objections of Franciscus Linus and Hobbes. In this defence he +described the experiment in connection with which he is most generally +remembered. Linus had admitted that the air might possess a certain +small amount of elasticity, but maintained that the force with which +mercury rose in a barometer tube was due mainly to a totally different +action, as though a string were pulling upon it from above. This was +his funicular hypothesis. Boyle undertook to show that the pressure of +the air might be made to support a much higher column of mercury than +that of the barometer.<span class="pagenum"><a id="Page_26">[26]</a></span> To this end he took a glass tube several feet +in length, and bent so as to form two vertical legs connected below. +The shorter leg was little more than a foot long, and hermetically +closed at the top. The longer leg was nearly eight feet in length, and +open at the top. The tube was suspended by strings upon the staircase, +the bend at the bottom pressing lightly against the bottom of a box +placed to receive the mercury employed in case of accident. Each leg +of the tube was provided with a paper scale. Mercury was poured in at +the open end, the tube being tilted so as to allow some of the air to +escape from the shorter limb until the mercury stood at the same level +in both legs when the tube was vertical. The length of the closed tube +occupied by the air was then just twelve inches. The height of the +barometer was about 29-1/8 inches. Mercury was gently poured into the +open limb by one operator, while another watched its height in the +closed limb. The results of the experiments are given in the table on +the opposite page.</p> + +<p>In this table the third column gives the result of adding to the +second column the height of the barometer, which expresses in inches +of mercury the pressure of the air on the free surface of the mercury +in the longer limb. The fourth column gives the total pressure, in +inches of mercury, on the hypothesis that the pressure of the air +varies inversely as the volume. The agreement between the third and +fourth columns is very close, considering<span class="pagenum"><a id="Page_27">[27]</a></span> the roughness of the +experiment and that no trouble appears to have been taken to +<i>calibrate</i> the shorter limb of the tube, and justified Boyle in +concluding that the hypothesis referred to expresses the relation +between the volume and pressure of a given mass of air.</p><p><span class="pagenum"><a id="Page_28">[28]</a></span></p> + +<div class="center"> +<table border="0" cellpadding="4" cellspacing="0" summary="Boyle hypothesis"> +<tr><td class="tdc">Length of closed tube occupied by air.</td><td class="tdc">Height of mercury in open tube above that in closed tube.</td><td class="tdc">Total pressure on air in inches of mercury.</td><td class="tdc">Total pressure according to Boyle's law.</td></tr> +<tr><td class="tdc">12</td><td class="tdc">0</td><td class="tdc">29-2/16</td><td class="tdc">29-2/16</td></tr> +<tr><td class="tdc">11-1/2</td><td class="tdc">1-7/16</td><td class="tdc">30-9/16</td><td class="tdc">30-6/16</td></tr> +<tr><td class="tdc">11</td><td class="tdc">2-13/16</td><td class="tdc">31-15/16</td><td class="tdc">31-12/16</td></tr> +<tr><td class="tdc">10-1/2</td><td class="tdc">4-6/16</td><td class="tdc">33-8/16</td><td class="tdc">33-1/7</td></tr> +<tr><td class="tdc">10</td><td class="tdc">6-3/16</td><td class="tdc">35-5/16</td><td class="tdc">35</td></tr> +<tr><td class="tdc">9-1/2</td><td class="tdc">7-14/16</td><td class="tdc">37</td><td class="tdc">36-15/19</td></tr> +<tr><td class="tdc">9</td><td class="tdc">10-1/16</td><td class="tdc">39-3/16</td><td class="tdc">38-7/8</td></tr> +<tr><td class="tdc">8-1/2</td><td class="tdc">12-8/16</td><td class="tdc">41-10/16</td><td class="tdc">41-2/17</td></tr> +<tr><td class="tdc">8</td><td class="tdc">15-1/16</td><td class="tdc">44-3/16</td><td class="tdc">43-11/16</td></tr> +<tr><td class="tdc">7-1/2</td><td class="tdc">17-15/16</td><td class="tdc">47-1/16</td><td class="tdc">46-3/5</td></tr> +<tr><td class="tdc">7</td><td class="tdc">21-3/16</td><td class="tdc">50-5/16</td><td class="tdc">50</td></tr> +<tr><td class="tdc">6-1/2</td><td class="tdc">25-3/16</td><td class="tdc">54-5/16</td><td class="tdc">53-10/13</td></tr> +<tr><td class="tdc">6</td><td class="tdc">29-11/16</td><td class="tdc">58-13/16</td><td class="tdc">58-2/8</td></tr> +<tr><td class="tdc">5-3/4</td><td class="tdc">32-3/16</td><td class="tdc">61-5/16</td><td class="tdc">60-13/23</td></tr> +<tr><td class="tdc">5-1/2</td><td class="tdc">34-15/16</td><td class="tdc">64-1/16</td><td class="tdc">63-6/11</td></tr> +<tr><td class="tdc">5-1/4</td><td class="tdc">37-15/16</td><td class="tdc">67-1/16</td><td class="tdc">66-4/7</td></tr> +<tr><td class="tdc">5</td><td class="tdc">41-9/16</td><td class="tdc">70-11/16</td><td class="tdc">70</td></tr> +<tr><td class="tdc">4-3/4</td><td class="tdc">45</td><td class="tdc">74-2/16</td><td class="tdc">73-11/19</td></tr> +<tr><td class="tdc">4-1/2</td><td class="tdc">48-12/16</td><td class="tdc">77-14/16</td><td class="tdc">77-2/3</td></tr> +<tr><td class="tdc">4-1/4</td><td class="tdc">53-11/16</td><td class="tdc">82-13/16</td><td class="tdc">82-4/17</td></tr> +<tr><td class="tdc">4</td><td class="tdc">58-2/16</td><td class="tdc">87-14/16</td><td class="tdc">87-1/8</td></tr> +<tr><td class="tdc">3-3/4</td><td class="tdc">63-15/16</td><td class="tdc">93-1/16</td><td class="tdc">93-1/5</td></tr> +<tr><td class="tdc">3-1/2</td><td class="tdc">71-5/16</td><td class="tdc">100-7/16</td><td class="tdc">99-6/7</td></tr> +<tr><td class="tdc">3-1/4</td><td class="tdc">78-11/16</td><td class="tdc">107-13/16</td><td class="tdc">107-7/13</td></tr> +<tr><td class="tdc">3</td><td class="tdc">88-7/16</td><td class="tdc">117-9/16</td><td class="tdc">116-4/8</td></tr> +</table></div> +<p>To extend the investigation so as to include expansion below +atmospheric pressure, a different apparatus was employed. It consisted +of a glass tube about six feet in length, closed at the lower end and +filled with mercury. Into this bath of mercury was plunged a length of +quill tube, and the upper end was sealed with wax. When the wax and +air in the tube had cooled, a hot pin was passed through the wax, +making a small orifice by which the amount of air in the tube was +adjusted so as to occupy exactly one inch of its length as measured by +a paper scale attached thereto, after again sealing the wax. The quill +tube was then raised, and the height of the surface of the mercury in +the tube above that in the bath noticed, together with the length of +the tube occupied by the air. The difference between the height of the +barometer and the height of the mercury in the tube above that in the +bath gave the pressure on the imprisoned air in inches of mercury. The +result showed that the volume varied very nearly in the inverse ratio +of the pressure. A certain amount of air, however, clung to the sides +of the quill tube when immersed in the mercury, and no care was taken +to remove it by boiling the mercury or otherwise; in consequence of +this, as the mercury descended, this air escaped and joined the rest +of the air in the tube. This made the pressure rather greater than it +should have been towards the end of the experiment, and when the tube +was again pressed down into the bath it was found that, when the +surfaces of the mercury within<span class="pagenum"><a id="Page_29">[29]</a></span> and without the tube were at the same +level, the air occupied nearly 1-1/8 inch instead of one inch of the +tube. These experiments first established the truth of the great law +known as "Boyle's law," which states that <i>the volume of a given mass +of a perfect gas varies inversely as the pressure to which it is +exposed</i>.</p> + +<p>Another experiment, to show that the pressure of the air was the cause +of suction, Boyle succeeded in carrying out at a later date. Two discs +of marble were carefully polished, so that when a little spirit of +turpentine was placed between them the lower disc, with a pound weight +suspended from it, was supported by the upper one. The apparatus was +introduced into the air-pump, and a considerable amount of shaking +proved insufficient to separate the discs. After sixteen strokes of +the pump, on opening the communication between the receiver and +cylinder, when no mechanical vibration occurred, the discs separated.</p> + +<p>Upon the Restoration in 1660, the Earl of Clarendon, who was Lord +Chancellor of England, endeavoured to persuade Boyle to enter holy +orders, urging the interest of the Church as the chief motive for the +proceeding. This made some impression upon Boyle, but he declined for +two reasons—first, because he thought that he would have a greater +influence for good if he had no share in the patrimony of the Church; +and next, because he had never felt "an inward motion to it by the +Holy Ghost."</p><p><span class="pagenum"><a id="Page_30">[30]</a></span></p> + +<p>In 1649 an association was incorporated by Parliament, to be called +"the President and Society for the Propagation of the Gospel in New +England," whose object should be "to receive and dispose of moneys in +such manner as shall best and principally conduce to the preaching and +propagating the gospel among the natives, and for the maintenance of +schools and nurseries of learning for the education of the children of +the natives; for which purpose a general collection was appointed to +be made in and through all the counties, cities, towns, and parishes +of England and Wales, for a charitable contribution, to be as the +foundation of so pious and great an undertaking." The society was +revived by special charter in 1661, and Boyle was appointed president, +an office he continued to hold until shortly before his death. The +society afterwards enlarged its sphere of operations, and became the +Society for the Propagation of the Gospel in Foreign Parts.</p> + +<p>In the same year (1661) Boyle published "Some Considerations on the +Usefulness of Experimental Natural Philosophy," etc., and in 1663 an +extremely interesting paper on "Experiments and Considerations +touching Colours." In the course of this paper he describes some very +beautiful experiments with a tincture of <i>Lignum nephriticum</i>, wherein +the dichroism of the extract is made apparent. Boyle found that by +transmitted light it appeared of a bright golden colour, but when +viewed from the side from which it was illuminated<span class="pagenum"><a id="Page_31">[31]</a></span> the light emitted +was sky blue, and in some cases bright green. By arranging experiments +so that some parts of the liquid were seen by the transmitted light +and some by the scattered light, very beautiful effects were produced. +Boyle endeavoured to learn something of the nature of colours by +projecting spectra on differently coloured papers, and observing the +appearance of the papers when illuminated by the several spectral +rays. He also passed sunlight, concentrated by a lens, through plates +of differently coloured glass superposed, allowing the light to fall +on a white paper screen, and observing the tint of the light which +passed through each combination. But the most interesting of these +experiments was the actual mixture of light of different colours by +forming two spectra, one by means of a fixed prism, the other by a +prism held in the hand, and superposing the latter on the former so +that different colours were made to coincide. This experiment was +repeated in a modified form, nearly two hundred years later, by +Helmholtz, who found that the mixture of blue and yellow lights +produced pink. Unfortunately, Boyle's spectra were far from pure, for, +the source of light being of considerable dimensions, the different +colours overlapped one another, as in Newton's experiments, and in +consequence some of his conclusions were inaccurate. Thus blue paper +in the yellow part of the spectrum appeared to Boyle green instead of +black, but this was due to the admixture of green light with the +yellow. He concluded that bodies<span class="pagenum"><a id="Page_32">[32]</a></span> appear black because they damp the +light so as to reflect very little to the eye, but that the surfaces +of white bodies consist of innumerable little facets which reflect the +light in all directions. In the same year he published some +"Observations on a Diamond, which shines in the Dark;" and an +extensive treatise on "Some Considerations touching the Style of the +Holy Scriptures." Next year appeared several papers from his pen, the +most important being "Occasional Reflections upon Several Subjects," +the wide scope of which may be gathered from the title. His "New +Experiments and Observations touching Cold" were printed in 1665. In +this paper he discussed the cause of the force exerted by water in +freezing, methods of measuring degrees of cold, the action of +freezing-mixtures, and many other questions. He contended that cold +was probably only privative, and not a positive existence.</p> + +<p>Lord Bacon had asserted that the "essential self" of heat was probably +motion and nothing more, and had adduced several experiments and +observations in support of this opinion. In his paper on the +mechanical origin of heat and cold, Boyle maintained that heat was +motion, but motion of the very small particles of bodies, very +intense, and taking place in all directions; and that heat could be +produced by any means whatever by which the particles of bodies could +be agitated. On one occasion he caused two pieces of brass, one convex +and the other concave, to be pressed against each other by<span class="pagenum"><a id="Page_33">[33]</a></span> a spring, +and then rubbed together in a vacuum by a rotary motion communicated +by a shaft which passed air-tight through the hole in the cover of the +receiver, a little emery being inserted between them. In the second +experiment the brasses became so hot that he "could not endure to hold +[his] hand on either of them." This experiment was intended, like the +rubbing of the blocks of ice in vacuo by Davy, to meet the objection +that the heat developed by friction was due to the action of the air. +The following extract from a paper intended to show that the sense of +touch cannot be relied upon for the estimation of temperature, shows +that Boyle possessed a very clear insight into the question:—"The +account upon which we judge a body to be cold seems to be that we feel +its particles less vehemently agitated than those of our fingers or +other parts of the organ of touching; and, consequently, if the temper +of that organ be changed, the object will appear more or less cold to +us, though itself continue of one and the same temperature." To +determine the expansion of water in freezing, he filled the bulb and +part of the stem of a "bulb tube," or, as it was then generally +called, "a philosophical egg," with water, and applying a +freezing-mixture, at first to the bottom of the bulb, he succeeded in +freezing the water without injury to the glass, and found that 82 +volumes of water expanded to 91-1/8 volumes of ice—an expansion of +about 11-1/8 per cent. Probably air-bubbles caused the ice to appear +to have a greater volume than it<span class="pagenum"><a id="Page_34">[34]</a></span> really possessed, the true expansion +being about nine per cent. of the volume of the water at 4°C. The +expansion of water in freezing he employed in order to compress air to +a greater extent than he had been able otherwise to compress it. +Having nearly filled a tube with water, but left a little air above, +and then having sealed the top of the tube, he froze the water from +the bottom upwards, so that in expanding it compressed the air to +one-tenth of its former volume.</p> + +<p>Magnetism and electricity came in for some share of Boyle's attention. +He carried out a number of experiments on magnetic induction, and +found that lodestones, as well as pieces of iron, when heated and +allowed to cool, became magnetized by the induction of the earth. His +later experiments with exhausted receivers were not made with his +first pump, but with a two-barrelled pump, in which the pistons were +connected by a cord passing over a large fixed pulley, so that, when +the receiver was nearly exhausted, the pressure of the air on the +descending piston during the greater part of the stroke nearly +balanced that on the ascending piston. In this respect the pump +differed only from Hawksbee's in having the pulley and cord instead of +the pinion and two racks. It also resembled Hawksbee's pump in having +self-closing valves in the pistons and at the bottom of the cylinders, +which, in this pump, had their open ends at the top. The pistons were +alternately raised and lowered by the feet of the operator, which were +placed in stirrups, of which one<span class="pagenum"><a id="Page_35">[35]</a></span> was fixed on each piston. The lower +portions of the barrels were filled with water, through which the air +bubbled, and this, occupying the clearance, enabled a much higher +degree of exhaustion to be produced than could be obtained without its +employment.</p> + +<p>In 1665 Boyle was nominated Provost of Eton, but declined to accept +the appointment. His "Hydrostatical Paradoxes," published about this +time, contain all the ordinary theorems respecting the pressure of +fluids under the action of gravity demonstrated experimentally.</p> + +<p>In 1677 Boyle printed, at his own expense, five hundred copies of the +four Gospels and the Acts of the Apostles in the Malayan tongue. This +was but one of his many contributions towards similar objects.</p> + +<p>On November 30, 1680, the Royal Society chose Boyle for President. He, +however, declined to accept the appointment, because he had +conscientious objections to taking the oath required of the President +by the charter of the Society.</p> + +<p>It appears that very many of Boyle's manuscripts, which were written +in bound books, were taken away, and others mutilated by "corrosive +liquors." In May, 1688, he made this known to his friends, but, though +these losses put him on his guard, he complained afterwards that all +his care and circumspection had not prevented the loss of "six +centuries of matters of fact in one parcel," besides many other +smaller papers. His works, however, which have been published<span class="pagenum"><a id="Page_36">[36]</a></span> are so +numerous that it would take several pages for the bare enumeration of +their titles, many of them being devoted to medical subjects. The +edition published in London in 1743 comprises nearly three thousand +pages of folio. Boyle always suffered from weak eyes, and in +consequence he declined to revise his proofs. In the advertisement to +the original edition of his works the publisher mentioned this, and at +the same time pleaded his own business engagements as an excuse for +not revising the proofs himself! It was partly on account of the +injury to his manuscripts, and partly through failing health, that in +1689 he set apart two days in the week, during which he declined to +receive visitors, that he might devote himself to his work, and +especially to the reparation of the injured writings. About this time +he succeeded in procuring the repeal of an Act passed in the fifth +year of Henry IV. to the effect "that none from thenceforth should use +to multiply gold or silver, or use the craft of multiplication; and if +any the same do, they should incur the pain of felony." By this repeal +it was made legal to extract gold and silver from ores, or from their +mixtures with other metals, in this country provided that the gold and +silver so procured should be put to no other use than "the increase of +moneys." It is curious that Boyle seems always to have believed in the +possibility of transmuting other metals into gold.</p> + +<p>His sister, Lady Ranelagh, died on December 23, 1691, and Boyle +survived her but a few days, for he<span class="pagenum"><a id="Page_37">[37]</a></span> died on December 30, and his body +was interred near his sister's grave in the chancel of St. +Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works, +writes, "The men of wit and learning have, in all ages, busied +themselves in explaining nature by words; but it is Mr. Boyle alone +who has wholly laid himself out in showing philosophy in action. The +single point he perpetually keeps in view is to render his reader, not +a talkative or a speculative, but an actual and practical philosopher. +Himself sets the example; he made all the experiments he possibly +could upon natural bodies, and communicated them with all desirable +candour and fidelity." The second part of his treatise on "The +Christian Virtuoso," Boyle concluded with a number of aphorisms, of +which the following well represent his views respecting science:—</p> + +<p>"I think it becomes Christian philosophers rather to try whether they +can investigate the final causes of things than, without trial, to +take it for granted that they are undiscoverable."</p> + +<p>"The book of Nature is a fine and large piece of tapestry rolled up, +which we are not able to see all at once, but must be content to wait +for the discovery of its beauty and symmetry, little by little, as it +gradually comes to be more unfolded or displayed."</p> + +<div class="figcenter"> +<img src="images/i047.jpg" width="316" height="78" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_38">[Pg 38]</a></span></p> + +<div class="figcenter"> +<img src="images/i048.jpg" width="472" height="110" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="BENJAMIN_FRANKLIN">BENJAMIN FRANKLIN.</h2> + +<p>Among those whose contributions to physics have immortalized their +names in the annals of science, there is none that holds a more +prominent position in the history of the world than Benjamin Franklin. +At one time a journeyman printer, living in obscure lodgings in +London, he became, during the American War of Independence, one of the +most conspicuous figures in Europe, and among Americans his reputation +was probably second to none, General Washington not excepted.</p> + +<p>Professor Laboulaye says of Franklin: "No one ever started from a +lower point than the poor apprentice of Boston. No one ever raised +himself higher by his own unaided forces than the inventor of the +lightning-rod. No one has rendered greater service to his country than +the diplomatist who signed the treaty of 1783, and assured the +independence of the United States. Better than the biographies of +Plutarch, this life, so long and so<span class="pagenum"><a id="Page_39">[39]</a></span> well filled, is a source of +perpetual instruction to all men. Every one can there find counsel and +example."</p> + +<p>A great part of the history of his life was written by Franklin +himself, at first for the edification of the members of his own +family, and afterwards at the pressing request of some of his friends +in London and Paris. His autobiography does not, however, comprise +much more than the first fifty years of his life. The first part was +written while he was the guest of the Bishop of St. Asaph, at Twyford; +the second portion at Passy, in the house of M. de Chaumont; and the +last part in Philadelphia, when he was retiring from public life at +the age of eighty-two. The former part of this autobiography was +translated into French, and published in Paris, in 1793, though it is +not known how the manuscript came into the publisher's hands. The +French version was translated into English, and published in England +and America, together with such other of Franklin's works as could be +collected, before the latter part was given to the world by Franklin's +grandson, to whom he had bequeathed his papers, and who first +published them in America in 1817.</p> + +<p>For a period of three hundred years at least Franklin's family lived +on a small freehold of about thirty acres, in the village of Ecton, in +Northamptonshire, the eldest son, who inherited the property, being +always brought up to the trade of a smith. Franklin himself "was the +youngest son of the<span class="pagenum"><a id="Page_40">[40]</a></span> youngest son for five generations back." His +grandfather lived at Ecton till he was too old to follow his business, +when he went to live with his second son, John, who was a dyer at +Banbury. To this business Franklin's father, Josiah, was apprenticed. +The eldest son, Thomas, was brought up a smith, but afterwards became +a solicitor; the other son, Benjamin, was a silk-dyer, and followed +Josiah to America. He was fond of writing poetry and sermons. The +latter he wrote in a shorthand of his own inventing, which he taught +to his nephew and namesake, in order that he might utilize the sermons +if, as was proposed, he became a Presbyterian minister. Franklin's +father, Josiah, took his wife and three children to New England, in +1682, where he practised the trade of a tallow-chandler and +soap-boiler. Franklin was born in Boston on January 6 (O.S.), 1706, +and was the youngest of seventeen children, of whom thirteen grew up +and married.</p> + +<p>Benjamin being the youngest of ten sons, his father intended him for +the service of the Church, and sent him to the grammar school when +eight years of age, where he continued only a year, although he made +very rapid progress in the school; for his father concluded that he +could not afford the expense of a college education, and at the end of +the year removed him to a private commercial school. At the age of ten +young Benjamin was taken home to assist in cutting the wicks of +candles, and otherwise to make himself useful in<span class="pagenum"><a id="Page_41">[41]</a></span> his father's +business. His enterprising character as a boy is shown by the +following story, which is in his own words:—</p> + +<blockquote> +<p>There was a salt marsh that bounded part of the mill-pond, on the +edge of which, at high-water, we used to stand to fish for minnows. By +much trampling we had made it a mere quagmire. My proposal was to +build a wharf there fit for us to stand upon, and I showed my comrades +a large heap of stones, which were intended for a new house near the +marsh, and which would very well suit our purpose. Accordingly, in the +evening, when the workmen were gone, I assembled a number of my +play-fellows, and working with them diligently, like so many emmets, +sometimes two or three to a stone, we brought them all away and built +our little wharf. The next morning the workmen were surprised at +missing the stones, which were found in our wharf. Inquiry was made +after the removers; we were discovered and complained of; several of +us were corrected by our fathers; and, though I pleaded the usefulness +of the work, mine convinced me that nothing was useful which was not +honest.</p> +</blockquote> + +<p>Until twelve years of age Benjamin continued in his father's business, +but as he manifested a great dislike for it, and his parents feared +that he might one day run away to sea, they set about finding some +trade which would be more congenial to his tastes. With this view his +father took him to see various artificers at their work, that he +might<span class="pagenum"><a id="Page_42">[42]</a></span> observe the tastes of the boy. This experience was very +valuable to him, as it taught him to do many little jobs for himself +when workmen could not readily be procured. During this time Benjamin +spent most of his pocket-money in purchasing books, some of which he +sold when he had read them, in order to buy others. He read through +most of the books in his father's very limited library. These mainly +consisted of works on theological controversy, which Franklin +afterwards considered to have been not very profitable to him.</p> + +<p>"There was another bookish lad in the town, John Collins by name, with +whom I was intimately acquainted. We sometimes disputed, and very fond +we were of argument, and very desirous of confuting one another, which +disputatious turn, by the way, is apt to become a very bad habit, +making people often very disagreeable in company by the contradiction +that is necessary to bring it into practice; and thence, besides +souring and spoiling the conversation, is productive of disgusts and +perhaps enmities when you may have occasion for friendship. I had +caught it by reading my father's books of dispute about religion. +Persons of good sense, I have since observed, seldom fall into it, +except lawyers, university men, and men of all sorts that have been +bred at Edinburgh."</p> + +<p>At length Franklin's fondness for books caused his father to decide to +make him a printer. His brother James had already entered that +business, and had set up in Boston with a new press and<span class="pagenum"><a id="Page_43">[43]</a></span> types which +he had brought from England. He signed his indentures when only twelve +years old, thereby apprenticing himself to his brother until he should +attain the age of twenty-one. The acquaintance which he formed with +booksellers through the printing business enabled him to borrow a +better class of books than he had been accustomed to, and he +frequently sat up the greater part of the night to read a book which +he had to return in the morning.</p> + +<p>While working with his brother, the young apprentice wrote two +ballads, which he printed and sold in the streets of Boston. His +father, however, ridiculed the performance; so he "escaped being a +poet." He adopted at this time a somewhat original method to improve +his prose writing. Meeting with an odd volume of the <i>Spectator</i>, he +purchased it and read it "over and over," and wished to imitate the +style. "Making short notes of the sentiment in each sentence," he laid +them by, and afterwards tried to write out the papers without looking +at the original. Then on comparison he discovered his faults and +corrected them. Finding his vocabulary deficient, he turned some of +the tales into verse, then retranslated them into prose, believing +that the attempt to make verses would necessitate a search for several +words of the same meaning. "I also sometimes jumbled my collection of +hints into confusion, and after some weeks endeavoured to reduce them +into the best order, before I began to form the full sentence and<span class="pagenum"><a id="Page_44">[44]</a></span> +complete the paper. This was to teach me method in the arrangement of +my thoughts."</p> + +<p>Meeting with a book on vegetarianism, Franklin determined to give the +system a trial. This led to some inconvenience in his brother's +house-keeping, so Franklin proposed to board himself if his brother +would give him half the sum he paid for his board, and out of this he +was able to save a considerable amount for the purpose of buying +books. Moreover, the time required for meals was so short that the +dinner hour afforded considerable leisure for reading. It was on his +journey from Boston to Philadelphia that he first violated vegetarian +principles; for, a large cod having been caught by the sailors, some +small fishes were found in its stomach, whereupon Franklin argued that +if fishes ate one another, there could be no reason against eating +them, so he dined on cod during the rest of the journey.</p> + +<p>After reading Xenophon's "Memorabilia," Franklin took up strongly with +the Socratic method of discussion, and became so "artful and expert in +drawing people, even of superior knowledge, into concessions, the +consequence of which they did not foresee," that some time afterwards +one of his employers, before answering the most simple question, would +frequently ask what he intended to infer from the answer. This +practice he gradually gave up, retaining only the habit of expressing +his opinions with "modest diffidence."</p> + +<p>In 1720 or 1721 James Franklin began to print<span class="pagenum"><a id="Page_45">[45]</a></span> a newspaper, the <i>New +England Courant</i>. To this paper, which he helped to compose and print, +Benjamin became an anonymous contributor. The members of the staff +spoke highly of his contributions, but when the authorship became +known, James appears to have conceived a jealousy of his younger +brother, which ultimately led to their separation. An article in the +paper having offended the Assembly, James was imprisoned for a month +and forbidden to print the paper. He then freed Benjamin from his +indentures, in order that the paper might be published in his name. At +length, some disagreement arising, Benjamin took advantage of the +cancelling of his indentures to quit his brother's service. As he +could get no employment in Boston, he obtained a passage to New York, +whence he was recommended to go to Philadelphia, which he reached +after a very troublesome journey. His whole stock of cash then +consisted of a Dutch dollar and about a shilling's worth of coppers. +The coppers he gave to the boatmen with whom he came across from +Burlington. His first appearance in Philadelphia, about eight o'clock +on a Sunday morning, was certainly striking. A youth between seventeen +and eighteen years of age, dressed in his working clothes, which were +dirty through his journey, with his pockets stuffed out with stockings +and shirts, his aspect was not calculated to command respect.</p> + +<p>"Then I walked up the street, gazing about till near the market-house +I met a boy with bread.<span class="pagenum"><a id="Page_46">[46]</a></span> I had made many a meal on bread, and, +inquiring where he got it, I went immediately to the baker's he +directed me to, in Second Street, and ask'd for bisket, intending such +as we had in Boston; but they, it seems, were not made in +Philadelphia. Then I asked for a threepenny loaf, and was told they +had none such. So, not considering or knowing the difference of money, +and the greater cheapness, nor the name of his bread, I bad him give +me three-penny-worth of any sort. He gave me, accordingly, three great +puffy rolls. I was surpriz'd at the quantity, but took it, and having +no room in my pockets, walk'd off with a roll under each arm, and +eating the other. Thus I went up Market Street as far as Fourth +Street, passing by the door of Mr. Read, my future wife's father; when +she, standing at the door, saw me, and thought I made, as I certainly +did, a most awkward, ridiculous appearance. Then I turned and went +down Chestnut Street and part of Walnut Street, eating my roll all the +way, and, coming round, found myself again at Market Street Wharf, +near the boat I came in, to which I went for a draught of the river +water; and, being filled out with one of my rolls, gave the other two +to a woman and her child that came down the river in the boat with us, +and were waiting to go further."</p> + +<p>In Philadelphia Franklin obtained an introduction, through a gentleman +he had met at New York, to a printer, named Keimer, who had just set +up business with an old press which he appeared<span class="pagenum"><a id="Page_47">[47]</a></span> not to know how to +use, and one pair of cases of English type. Here Franklin obtained +employment when the business on hand would permit, and he put the +press in order and worked it. Keimer obtained lodgings for him at the +house of Mr. Read, and, by industry and economical living, Franklin +found himself in easy circumstances. Sir William Keith was then +Governor of Pennsylvania, and hearing of Franklin, he called upon him +at Keimer's printing-office, invited him to take wine at a +neighbouring tavern, and promised to obtain for him the Government +printing if he would set up for himself. It was then arranged that +Franklin should return to Boston by the first ship, in order to see +what help his father would give towards setting him up in business. In +the mean while he was frequently invited to dine at the governor's +house. Notwithstanding Sir William Keith's recommendation, Josiah +Franklin thought his son too young to take the responsibility of a +business, and would only promise to assist him if, when he was +twenty-one, he had himself saved sufficient to purchase most of the +requisite plant. On his return to Philadelphia, he delivered his +father's letter to Sir William Keith, whereon the governor, stating +that he was determined to have a good printer there, promised to find +the means of equipping the printing-office himself, and suggested the +desirability of Franklin's making a journey to England in order to +purchase the plant. He promised letters of introduction to various +persons<span class="pagenum"><a id="Page_48">[48]</a></span> in England, as well as a letter of credit to furnish the +money for the purchase of the printing-plant. These letters Franklin +was to call for, but there was always some excuse for their not being +ready. At last they were to be sent on board the ship, and Franklin, +having gone on board, awaited the letters. When the governor's +despatches came, they were all put into a bag together, and the +captain promised to let Franklin have his letters before landing. On +opening the bag off Plymouth, there were no letters of the kind +promised, and Franklin was left without introductions and almost +without money, to make his own way in the world. In London he learned +that Governor Keith was well known as a man in whom no dependence +could be placed, and as to his giving a letter of credit, "he had no +credit to give."</p> + +<p>A friend of Franklin's, named Ralph, accompanied him from America, and +the two took lodgings together in Little Britain at three shillings +and sixpence per week. Franklin immediately obtained employment at +Palmer's printing-office, in Bartholomew Close; but Ralph, who knew no +trade, but aimed at literature, was unable to get any work. He could +not obtain employment, even among the law stationers as a copying +clerk, so for some time the wages which Franklin earned had to support +the two. At Palmer's Franklin was employed in composing Wollaston's +"Religion of Nature." On this he wrote a short critique, which he +printed. it was entitled "A Dissertation on Liberty and<span class="pagenum"><a id="Page_49">[49]</a></span> Necessity, +Pleasure and Pain." The publication of this he afterwards regretted, +but it obtained for him introductions to some literary persons in +London. Subsequently he left Palmer's and obtained work at Watts's +printing-office, where he remained during the rest of his stay in +London. The beer-drinking capabilities of some of his fellow-workmen +excited his astonishment. He says:—</p> + +<blockquote> +<p>We had an alehouse boy who attended always in the house to supply the +workmen. My companion at the press drank every day a pint before +breakfast, a pint at breakfast with his bread and cheese, a pint +between breakfast and dinner, a pint at dinner, a pint in the +afternoon about six o'clock, and another when he had done his day's +work. I thought it a detestable custom, but it was necessary, he +suppos'd, to drink <i>strong</i> beer, that he might be <i>strong</i> to labour. +I endeavoured to convince him that the bodily strength afforded by +beer could only be in proportion to the grain or flour of the barley +dissolved in the water of which it was made; that there was more flour +in a pennyworth of bread; and therefore, if he would eat that with a +pint of water, it would give him more strength than a quart of beer. +He drank on, however, and had four or five shillings to pay out of his +wages every Saturday night for that muddling liquor; an expense I was +free from. And thus these poor devils keep themselves always under.</p> +</blockquote> + +<p>Afterwards Franklin succeeded in persuading several of the compositors +to give up "their muddling<span class="pagenum"><a id="Page_50">[50]</a></span> breakfast of beer and bread and cheese," +for a porringer of hot-water gruel, with pepper, breadcrumbs, and +butter, which they obtained from a neighbouring house at a cost of +three halfpence.</p> + +<p>Among Franklin's fellow-passengers from Philadelphia to England was an +American merchant, a Mr. Denham, who had formerly been in business in +Bristol, but failed and compounded with his creditors. He then went to +America, where he soon acquired a fortune, and returned in Franklin's +ship. He invited all his old creditors to dine with him. At the dinner +each guest found under his plate a cheque for the balance which had +been due to him, with interest to date. This gentleman always remained +a firm friend to Franklin, who, during his stay in London, sought his +advice when any important questions arose. When Mr. Denham returned to +Philadelphia with a quantity of merchandise, he offered Franklin an +appointment as clerk, which was afterwards to develop into a +commission agency. The offer was accepted, and, after a voyage of +nearly three months, Franklin reached Philadelphia on October 11, +1726. Here he found Governor Keith had been superseded by Major +Gordon, and, what was of more importance to him, that Miss Read, to +whom he had become engaged before leaving for England, and to whom he +had written only once during his absence, had married. Shortly after +starting in business, Mr. Denham died, and thus left Franklin to +commence life again for himself. Keimer had by this time<span class="pagenum"><a id="Page_51">[51]</a></span> obtained a +fairly extensive establishment, and employed a number of hands, but +none of them were of much value; and he made overtures to Franklin to +take the management of his printing-office, apparently with the +intention of getting his men taught their business, so that he might +afterwards be able to dispense with the manager. Franklin set the +printing-house in order, started type-founding, made the ink, and, +when necessary, executed engravings. As the other hands improved under +his superintendence, Keimer began to treat his manager less civilly, +and apparently desired to curtail his stipend. At length, through an +outbreak of temper on the part of Keimer, Franklin left, but was +afterwards induced to return in order to prepare copper-plates and a +press for printing paper money for New Jersey.</p> + +<p>While working for Keimer, Franklin formed a club, which was destined +to exert considerable influence on American politics. The club met on +Friday evenings, and was called the Junto. It was essentially a +debating society, the subject for each evening's discussion being +proposed at the preceding meeting. One of the rules was that the +existence of the club should remain a secret, and that its members +should be limited to twelve. Afterwards other similar clubs were +formed by its members; but the existence of the Junto was kept a +secret from them. The club lasted for about forty years, and became +the nucleus of the American Philosophical Society, of which Franklin +was the first<span class="pagenum"><a id="Page_52">[52]</a></span> president. This, and the fact that many of the great +questions that arose previously to the Declaration of Independence +were discussed in the Junto in the first instance, give to the club a +special importance. The following are specimens of subjects discussed +by the club:—</p> + +<p>"Is sound an entity or body?"</p> + +<p>"How may the phenomena of vapours be explained?"</p> + +<p>"Is self-interest the rudder that steers mankind, the universal +monarch to whom all are tributaries?"</p> + +<p>"Which is the best form of government? and what was that form which +first prevailed among mankind?"</p> + +<p>"Can any one particular form of government suit all mankind?"</p> + +<p>"What is the reason that the tides rise higher in the Bay of Fundy +than the Bay of Delaware?"</p> + +<p>"Is the emission of paper money safe?"</p> + +<p>"What is the reason that men of the greatest knowledge are not the +most happy?"</p> + +<p>"How may the possessions of the Lakes be improved to our advantage?"</p> + +<p>"Why are tumultuous, uneasy sensations united with our desires?"</p> + +<p>"Whether it ought to be the aim of philosophy to eradicate the +passions."</p> + +<p>"How may smoky chimneys be best cured?"</p> + +<p>"Why does the flame of a candle tend upwards in a spire?"</p> + +<p>"Which is least criminal—a bad action joined<span class="pagenum"><a id="Page_53">[53]</a></span> with a good intention, +or a good action with a bad intention?"</p> + +<p>"Is it consistent with the principles of liberty in a free government +to punish a man as a libeller when he speaks the truth?"</p> + +<p>On leaving Keimer's, Franklin went into partnership with one of his +fellow-workmen, Hugh Meredith, whose father found the necessary +capital, and a printing-office was started which soon excelled its two +rivals in Philadelphia. Franklin's industry attracted the attention of +the townsfolk, and inspired the merchants with confidence in the +prospects of the new concern. Keimer started a newspaper, which he had +not the ability to carry on; Franklin purchased it from him for a +trifle, remodelled it, and continued it in a very spirited manner +under the title of the <i>Pennsylvania Gazette</i>. His political articles +soon attracted the attention of the principal men of the state; the +number of subscribers increased rapidly, and the paper became a source +of considerable profit. Soon after, the printing for the House of +Representatives came into the hands of the firm. Meredith never took +to the business, and was seldom sober, and at length was bought out by +his partner, on July 14, 1730. The discussion in the Junto on paper +currency induced Franklin to publish a paper entitled "The Nature and +Necessity of a Paper Currency." This was a prominent subject before +the House, but the introduction of paper money was opposed by the +capitalists. They were unable, however, to answer<span class="pagenum"><a id="Page_54">[54]</a></span> Franklin's +arguments; the point was carried in the House, and Franklin was +employed to print the money. The amount of paper money in Pennsylvania +in 1739 amounted to £80,000; during the war it rose to more than +£350,000.</p> + +<p>"In order to secure my credit and character as a tradesman, I took +care not only to be in <i>reality</i> industrious and frugal, but to avoid +all appearances to the contrary. I drest plainly; I was seen at no +places of idle diversion. I never went out a-fishing or shooting; a +book, indeed, sometimes debauch'd me from my work, but that was +seldom, snug, and gave no scandal; and, to show that I was not above +my business, I sometimes brought home the paper I purchas'd at the +stores thro' the streets on a wheelbarrow. Thus being esteem'd an +industrious, thriving young man, and paying duly for what I bought, +the merchants who imported stationery solicited my custom; others +proposed supplying me with books, and I went on swimmingly. In the +mean time, Keimer's credit and business declining daily, he was at +last forc'd to sell his printing-house to satisfy his creditors."</p> + +<p>On September 1, 1730, Franklin married his former <i>fiancée</i>, whose +previous husband had left her and was reported to have died in the +West Indies. The marriage was a very happy one, and continued over +forty years, Mrs. Franklin living until the end of 1774. Industry and +frugality reigned in the household of the young printer. Mrs. Franklin +not only managed the house, but assisted<span class="pagenum"><a id="Page_55">[55]</a></span> in the business, folding and +stitching pamphlets, and in other ways making herself useful. The +first part of Franklin's autobiography concludes with an account of +the foundation of the first subscription library. By the co-operation +of the members of the Junto, fifty subscribers were obtained, who each +paid in the first instance forty shillings, and afterwards ten +shillings per annum. "We afterwards obtained a charter, the company +being increased to one hundred. This was the mother of all the North +American subscription libraries, now so numerous. It is become a great +thing itself, and continually increasing. These libraries have +improved the general conversation of the Americans, made the common +tradesmen and farmers as intelligent as most gentlemen from other +countries, and perhaps have contributed in some degree to the stand so +generally made throughout the colonies in defence of their +privileges."</p> + +<p>Ten years ago this library contained between seventy and eighty +thousand volumes.</p> + +<p>Franklin's success in business was attributed by him largely to his +early training. "My circumstances, however, grew daily easier. My +original habits of frugality continuing, and my father having, among +his instructions to me when a boy, frequently repeated a proverb of +Solomon, 'Seest thou a man diligent in his business? he shall stand +before kings; he shall not stand before mean men,' I from thence +considered industry as a means of obtaining wealth and distinction, +which encourag'd<span class="pagenum"><a id="Page_56">[56]</a></span> me, tho' I did not think that I should ever +literally <i>stand before kings</i>, which, however, has since happened; +for I have stood before <i>five</i>, and even had the honour of sitting +down with one, the King of Denmark, to dinner."</p> + +<p>After his marriage, Franklin conceived the idea of obtaining moral +perfection. He was not altogether satisfied with the result, but +thought his method worthy of imitation. Assuming that he possessed +complete knowledge of what was right or wrong, he saw no reason why he +should not always act in accordance therewith. His principle was to +devote his attention to one virtue only at first for a week, at the +end of which time he expected the practice of that virtue to have +become a habit. He then added another virtue to his list, and devoted +his attention to the same for the next week, and so on, until he had +exhausted his list of virtues. He then commenced again at the +beginning. As his moral code comprised thirteen virtues, it was +possible to go through the complete curriculum four times in a year. +Afterwards he occupied a year in going once through the list, and +subsequently employed several years in one course. A little book was +ruled, with a column for each day and a line for each virtue, and in +this a mark was made for every failure which could be remembered on +examination at the end of the day. It is easy to believe his +statement: "I am surprised to find myself so much fuller of faults +than I had imagined; but I had the satisfaction of seeing them +diminish."</p><p><span class="pagenum"><a id="Page_57">[57]</a></span></p> + +<p>"This my little book had for its motto these lines from Addison's +'Cato':—</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"'Here will I hold. If there's a Power above us<br /></span> +<span class="i0">(And that there is, all Nature cries aloud<br /></span> +<span class="i0">Thro' all her work), He must delight in virtue;<br /></span> +<span class="i0">And that which He delights in must be happy.'<br /></span> +</div></div> + +<p>"Another from Cicero:—</p> + +<p>"'O vitæ Philosophia dux! O virtutum indagatrix expultrixque vitiorum! +Unus dies ex præceptis tuis actus, peccanti immortalitati est +anteponendus.'</p> + +<p>"Another from the Proverbs of Solomon, speaking of wisdom and virtue:—</p> + +<p>"'Length of days is in her right hand; and in her left hand riches and +honour. Her ways are ways of pleasantness, and all her paths are +peace.'</p> + +<p>"And conceiving God to be the fountain of wisdom, I thought it right +and necessary to solicit His assistance for obtaining it; to this end +I formed the following little prayer, which was prefixed to my tables +of examination, for daily use:—</p> + +<p>"'O powerful Goodness! bountiful Father! merciful Guide! increase in +me that wisdom which discovers my truest interest. Strengthen my +resolutions to perform what that wisdom dictates. Accept my kind +offices to Thy other children as the only return in my power for Thy +continual favours to me.'</p> + +<p>"I used also sometimes a little prayer which I took from Thomson's +Poems, viz.:<span class="pagenum"><a id="Page_58">[58]</a></span>—</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"'Father of light and life, Thou Good Supreme!<br /></span> +<span class="i0">Oh teach me what is good; teach me Thyself!<br /></span> +<span class="i0">Save me from folly, vanity, and vice,<br /></span> +<span class="i0">From every low pursuit; and fill my soul<br /></span> +<span class="i0">With knowledge, conscious peace, and virtue pure;<br /></span> +<span class="i0">Sacred, substantial, never-failing bliss!'"<br /></span> +</div></div> + +<p>The senses in which Franklin's thirteen virtues were to be understood +were explained by short precepts which followed them in his list. The +list was as follows:—</p> + +<div class="center600"> +<p class="h5">"<span class="smcap">1. Temperance.</span></p> + +<p>"Eat not to dulness; drink not to elevation.</p> + +<p class="h5">"<span class="smcap">2. Silence.</span></p> + +<p>"Speak not but what may benefit others or yourself; avoid trifling +conversation.</p> + +<p class="h5">"<span class="smcap">3. Order.</span></p> + +<p>"Let all your things have their places; let each part of your business +have its time.</p> + +<p class="h5">"<span class="smcap">4. Resolution.</span></p> + +<p>"Resolve to perform what you ought; perform without fail what you +resolve.</p> + +<p class="h5">"<span class="smcap">5. Frugality.</span></p> + +<p>"Make no expense but to do good to others or yourself; <i>i.e.</i> waste +nothing.</p><p><span class="pagenum"><a id="Page_59">[59]</a></span></p> + +<p class="h5">"<span class="smcap">6. Industry.</span></p> + +<p>"Lose no time; be always employed in something useful; cut off all +unnecessary actions.</p> + +<p class="h5">"<span class="smcap">7. Sincerity.</span></p> + +<p>"Use no hurtful deceit; think innocently and justly; and, if you +speak, speak accordingly.</p> + +<p class="h5">"<span class="smcap">8. Justice.</span></p> + +<p>"Wrong none by doing injuries, or omitting the benefits that are your +duty.</p> + +<p class="h5">"<span class="smcap">9. Moderation.</span></p> + +<p>"Avoid extremes; forbear resenting injuries so much as you think they +deserve.</p> + +<p class="h5">"<span class="smcap">10. Cleanliness.</span></p> + +<p>"Tolerate no uncleanness in body, clothes, or habitation.</p> + +<p class="h5">"<span class="smcap">11. Tranquillity.</span></p> + +<p>"Be not disturbed at trifles, or accidents common or unavoidable.</p> + +<p class="h5">"<span class="smcap">12. Chastity.</span></p> + +<p class="h5">"<span class="smcap">13. Humility.</span></p> +</div> + +<p>"Imitate Jesus and Socrates."</p> + +<p>The last of these was added to the list at the suggestion of a Quaker +friend. Franklin claims to<span class="pagenum"><a id="Page_60">[60]</a></span> have acquired a good deal of the +<i>appearance</i> of it, but concluded that in reality there was no passion +so hard to subdue as <i>pride</i>. "For even if I could conceive that I had +completely overcome it, I should probably be proud of my humility." +The virtue which gave him most trouble, however, was order, and this +he never acquired.</p> + +<p>In 1732 appeared the first copy of "Poor Richard's Almanack." This was +prepared, printed, and published by Franklin for about twenty-five +years in succession, and nearly ten thousand copies were sold +annually. Besides the usual astronomical information, it contained a +collection of entertaining anecdotes, verses, jests, etc., while the +"little spaces that occurred between the remarkable events in the +calendar" were filled with proverbial sayings, inculcating industry +and frugality as helps to virtue. These sayings were collected and +prefixed to the almanack of 1757, whence they were copied into the +American newspapers, and afterwards reprinted as a broad-sheet in +England and in France.</p> + +<p>In 1733 Franklin commenced studying modern languages, and acquired +sufficient knowledge of French, Italian, and Spanish to be able to +read books in those languages. In 1736 he was chosen Clerk to the +General Assembly, an office to which he was annually re-elected until +he became a member of the Assembly about 1750. There was one member +who, on the second occasion of his election, made a long speech +against him. Franklin determined to secure the friendship of this +member.<span class="pagenum"><a id="Page_61">[61]</a></span> Accordingly he wrote to him to request the loan of a very +scarce and curious book which was in his library. The book was lent +and returned in about a week, with a note of thanks. The member ever +after manifested a readiness to serve Franklin, and they became great +friends—"Another instance of the truth of an old maxim I had learned, +which says, '<i>He that has once done you a kindness will be more ready +to do you another than he whom you yourself have obliged</i>.' And it +shows how much more profitable it is prudently to remove, than to +resent, return, and continue inimical proceedings."</p> + +<p>In 1737 Franklin was appointed Deputy-Postmaster-General for +Pennsylvania. He was afterwards made Postmaster-General of the +Colonies. He read a paper in the Junto on the organization of the City +watch, and the propriety of rating the inhabitants on the value of +their premises in order to support the same. The subject was also +discussed in the other clubs which had sprung from the Junto, and thus +the way was prepared for the law which a few years afterwards carried +Franklin's proposals into effect. His next scheme was the formation of +a fire brigade, in which he met with his usual success, and other +clubs followed, until most of the men of property in the city were +members of one club or another. The original brigade, known as the +Union Fire Company, was formed December 7, 1736. It was in active +service in 1791.</p> + +<p>Franklin founded the American Philosophical<span class="pagenum"><a id="Page_62">[62]</a></span> Society in 1743. The +head-quarters of the society were fixed in Philadelphia, where it was +arranged that there should always be at least seven members, viz. a +physician, a botanist, a mathematician, a chemist, a mechanician, a +geographer, and a general natural philosopher, besides a president, +treasurer, and secretary. The other members might be resident in any +part of America. Correspondence was to be kept up with the Royal +Society of London and the Dublin Society, and abstracts of the +communications were to be sent quarterly to all the members. Franklin +became the first secretary.</p> + +<p>Spain, having been for some years at war with England, was joined at +length by France. This threatened danger to the American colonies, as +France then held Canada, and no organization for their defence +existed. Franklin published a pamphlet entitled "Plain Truth," setting +forth the unarmed condition of the colonies, and recommending the +formation of a volunteer force for defensive purposes. The pamphlet +excited much attention. A public meeting was held and addressed by +Franklin; at this meeting twelve hundred joined the association. At +length the number of members enrolled exceeded ten thousand. These all +provided themselves with arms, formed regiments and companies, elected +their own officers, and attended once a week for military drill. +Franklin was elected colonel of the Philadelphia Regiment, but +declined the appointment, and served as a private soldier.<span class="pagenum"><a id="Page_63">[63]</a></span> The +provision of war material was a difficulty with the Assembly, which +consisted largely of Quakers, who, though they appeared privately to +be willing that the country should be put in a state of defence, +hesitated to vote in opposition to their peace principles. Hence it +was that, when the Government of New England asked a grant of +gunpowder from Pennsylvania, the Assembly voted £3000 "for the +purchasing of bread, flour, wheat, or <i>other grain</i>." Pebble-powder +was not then in use. When it was proposed to devote £60, which was a +balance in the hands of the Union Fire Company, as a contribution +towards the erection of a battery below the town, Franklin suggested +that it should be proposed that a fire-engine be purchased with the +money, and that the committee should "buy a great gun, which is +certainly a <i>fire-engine</i>."</p> + +<p>The "Pennsylvania fireplace" was invented in 1742. A patent was +offered to Franklin by the Governor of Pennsylvania, but he declined +it on the principle "<i>that, as we enjoy great advantages from the +inventions of others, we should be glad of an opportunity to serve +others by any invention of ours; and this we should do freely and +generously</i>." An ironmonger in London made slight alterations, which +were not improvements, in the design, and took out a patent for the +fireplace, whereby he made a "small fortune." Franklin never contested +the patent, "having no desire of profiting by patents himself," and +"hating disputes." This fireplace was designed to burn wood, but, +unlike the German<span class="pagenum"><a id="Page_64">[64]</a></span> stoves, it was completely open in front, though +enclosed at the sides and top. An air-chamber was formed in the middle +of the stove, so arranged that, while the burning wood was in contact +with the front of the chamber, the flame passed above and behind it on +its way to the flue. Through this chamber a constant current of air +passed, entering the room heated, but not contaminated, by the +products of combustion. In this way the stove furnished a constant +supply of fresh warm air to the room, while it possessed all the +advantages of an open fireplace. Subsequently Franklin contrived a +special fireplace for the combustion of coal. In the scientific +thought which he devoted to the requirements of the domestic +economist, as in very many other particulars, Franklin strongly +reminds us of Count Rumford.</p> + +<p>The next important enterprise which Franklin undertook, partly through +the medium of the Junto, was to establish an academy which soon +developed into the University of Philadelphia. The members of the club +having taken up the subject, the next step was to enlist the sympathy +of a wider constituency, and this Franklin effected, in his usual way, +by the publication of a pamphlet. He then set on foot a subscription, +the payments to extend over five years, and thereby obtained about +£5000. A house was taken and schools opened in 1749. The classes soon +became too large for the house, and the trustees of the academy then +took over a large building, or "tabernacle," which<span class="pagenum"><a id="Page_65">[65]</a></span> had been erected +for George Whitefield when he was preaching in Philadelphia. The hall +was divided into stories, and at a very small expense adapted to the +requirements of the classes. Franklin, having taken a partner in his +printing business, took the oversight of the work. Afterwards the +funds were increased by English subscriptions, by a grant from the +Assembly, and by gifts of land from the proprietaries; and thus was +established the University of Philadelphia.</p> + +<p>Having practically retired from business, Franklin intended to devote +himself to philosophical studies, having commenced his electrical +researches some time before in conjunction with the other members of +the Library Company. Public business, however, crowded upon him. He +was elected a member of the Assembly, a councillor and afterwards an +alderman of the city, and by the governor was made a justice of the +peace. As a member of the Assembly, he was largely concerned in +providing the means for the erection of a hospital, and in arranging +for the paving and cleansing of the streets of the city. In 1753 he +was appointed, in conjunction with Mr. Hunter, Postmaster-General of +America. The post-office of the colonies had previously been conducted +at a loss. In a few years, under Franklin's management, it not only +paid the stipends of himself and Mr. Hunter, but yielded a +considerable revenue to the Crown. But it was not only in the conduct +of public business that Franklin's merits were<span class="pagenum"><a id="Page_66">[66]</a></span> recognized. By this +time he had secured his reputation as an electrician, and both Yale +College and Cambridge University (New England) conferred on him the +honorary degree of Master of Arts. In the same year that he was made +Postmaster-General of America he was awarded the Copley Medal and +elected a Fellow of the Royal Society of London, the usual fees being +remitted in his case.</p> + +<p>Before his election as member, Franklin had for several years held the +appointment of Clerk to the Assembly, and he used to relieve the +dulness of the debates by amusing himself in the construction of magic +circles and squares, and "acquired such a knack at it" that he could +"fill the cells of any magic square of reasonable size with a series +of numbers as fast as" he "could write them." Many years afterwards +Mr. Logan showed Franklin a French folio volume filled with magic +squares, and afterwards a magic "square of 16," which Mr. Logan +thought must have been a work of great labour, though it possessed +only the common properties of making 2056 in every row, horizontal, +vertical, and diagonal. During the evening Franklin made the square +shown on the opposite page. "This I sent to our friend the next +morning, who, after some days, sent it back in a letter, with these +words: 'I return to thee thy astonishing and most stupendous piece of +the magical square, in which——;' but the compliment is too +extravagant, and therefore, for his sake as well as my own,<span class="pagenum"><a id="Page_67">[67]</a></span> I ought +not to repeat it. Nor is it necessary; for I make no question that you +will readily allow this square of 16 to be the most magically magical +of any magic square ever made by any magician."</p> + +<p>The square has the following properties:—Every straight row of +sixteen numbers, whether vertical, horizontal, or diagonal, makes +2056.</p> + +<p>Every bent row of sixteen numbers, as shown by the diagonal lines in +the figure, makes 2056.</p> + +<p>If a square hole be cut in a piece of paper, so as to show through it +just sixteen of the little squares, and the paper be laid on the magic +square, then, wherever the paper is placed, the sum of the sixteen +numbers visible through the hole will be 2056.</p> + +<div class="figcenter"> +<img src="images/i077.jpg" width="600" height="539" alt="" /> +</div> + +<div class="center"> +<table border="0" cellpadding="4" cellspacing="0" summary="Magic-16 Square"> +<tr><td class="tdc">200</td><td class="tdc">217</td><td class="tdc">232</td><td class="tdc">249</td><td class="tdc">8</td><td class="tdc">25</td><td class="tdc">40</td><td class="tdc">57</td><td class="tdc">72</td><td class="tdc">89</td><td class="tdc">104</td><td class="tdc">121</td><td class="tdc">136</td><td class="tdc">153</td><td class="tdc">168</td><td class="tdc">185</td></tr> +<tr><td class="tdc">58</td><td class="tdc">39</td><td class="tdc">26</td><td class="tdc">7</td><td class="tdc">250</td><td class="tdc">231</td><td class="tdc">218</td><td class="tdc">199</td><td class="tdc">186</td><td class="tdc">167</td><td class="tdc">154</td><td class="tdc">135</td><td class="tdc">122</td><td class="tdc">103</td><td class="tdc">90</td><td class="tdc">71</td></tr> +<tr><td class="tdc">198</td><td class="tdc">219</td><td class="tdc">230</td><td class="tdc">251</td><td class="tdc">6</td><td class="tdc">27</td><td class="tdc">38</td><td class="tdc">59</td><td class="tdc">70</td><td class="tdc">91</td><td class="tdc">102</td><td class="tdc">123</td><td class="tdc">134</td><td class="tdc">155</td><td class="tdc">166</td><td class="tdc">187</td></tr> +<tr><td class="tdc">60</td><td class="tdc">37</td><td class="tdc">28</td><td class="tdc">5</td><td class="tdc">252</td><td class="tdc">229</td><td class="tdc">220</td><td class="tdc">197</td><td class="tdc">188</td><td class="tdc">165</td><td class="tdc">156</td><td class="tdc">133</td><td class="tdc">124</td><td class="tdc">101</td><td class="tdc">92</td><td class="tdc">69</td></tr> +<tr><td class="tdc">201</td><td class="tdc">216</td><td class="tdc">233</td><td class="tdc">248</td><td class="tdc">9</td><td class="tdc">24</td><td class="tdc">41</td><td class="tdc">56</td><td class="tdc">73</td><td class="tdc">88</td><td class="tdc">105</td><td class="tdc">120</td><td class="tdc">137</td><td class="tdc">152</td><td class="tdc">169</td><td class="tdc">184</td></tr> +<tr><td class="tdc">55</td><td class="tdc">42</td><td class="tdc">23</td><td class="tdc">10</td><td class="tdc">247</td><td class="tdc">234</td><td 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class="tdc">76</td></tr> +<tr><td class="tdc">205</td><td class="tdc">212</td><td class="tdc">237</td><td class="tdc">244</td><td class="tdc">13</td><td class="tdc">20</td><td class="tdc">45</td><td class="tdc">52</td><td class="tdc">77</td><td class="tdc">84</td><td class="tdc">109</td><td class="tdc">116</td><td class="tdc">141</td><td class="tdc">148</td><td class="tdc">173</td><td class="tdc">180</td></tr> +<tr><td class="tdc">51</td><td class="tdc">46</td><td class="tdc">19</td><td class="tdc">14</td><td class="tdc">243</td><td class="tdc">238</td><td class="tdc">211</td><td class="tdc">206</td><td class="tdc">179</td><td class="tdc">174</td><td class="tdc">147</td><td class="tdc">142</td><td class="tdc">115</td><td class="tdc">110</td><td class="tdc">83</td><td class="tdc">78</td></tr> +<tr><td class="tdc">207</td><td class="tdc">210</td><td class="tdc">239</td><td class="tdc">242</td><td class="tdc">15</td><td class="tdc">18</td><td class="tdc">47</td><td class="tdc">50</td><td class="tdc">79</td><td class="tdc">82</td><td class="tdc">111</td><td class="tdc">114</td><td class="tdc">143</td><td class="tdc">146</td><td class="tdc">175</td><td class="tdc">178</td></tr> +<tr><td class="tdc">49</td><td class="tdc">48</td><td class="tdc">17</td><td class="tdc">16</td><td class="tdc">241</td><td class="tdc">240</td><td class="tdc">209</td><td class="tdc">208</td><td class="tdc">177</td><td class="tdc">176</td><td class="tdc">145</td><td class="tdc">144</td><td class="tdc">113</td><td class="tdc">112</td><td class="tdc">81</td><td class="tdc">80</td></tr> +<tr><td class="tdc">196</td><td class="tdc">221</td><td class="tdc">228</td><td class="tdc">253</td><td class="tdc">4</td><td class="tdc">29</td><td class="tdc">36</td><td class="tdc">61</td><td class="tdc">68</td><td class="tdc">93</td><td class="tdc">100</td><td class="tdc">125</td><td class="tdc">132</td><td class="tdc">157</td><td class="tdc">164</td><td class="tdc">189</td></tr> +<tr><td class="tdc">62</td><td class="tdc">35</td><td class="tdc">30</td><td class="tdc">3</td><td class="tdc">254</td><td class="tdc">227</td><td class="tdc">222</td><td class="tdc">195</td><td class="tdc">190</td><td class="tdc">163</td><td class="tdc">158</td><td class="tdc">131</td><td class="tdc">126</td><td class="tdc">99</td><td class="tdc">94</td><td class="tdc">67</td></tr> +<tr><td class="tdc">194</td><td class="tdc">223</td><td class="tdc">226</td><td class="tdc">255</td><td class="tdc">2</td><td class="tdc">31</td><td class="tdc">34</td><td class="tdc">63</td><td class="tdc">66</td><td class="tdc">95</td><td class="tdc">98</td><td class="tdc">127</td><td class="tdc">130</td><td class="tdc">159</td><td class="tdc">162</td><td class="tdc">191</td></tr> +<tr><td class="tdc">64</td><td class="tdc">33</td><td class="tdc">32</td><td class="tdc">1</td><td class="tdc">256</td><td class="tdc">225</td><td class="tdc">224</td><td class="tdc">193</td><td class="tdc">192</td><td class="tdc">161</td><td class="tdc">160</td><td class="tdc">129</td><td class="tdc">128</td><td class="tdc">97</td><td class="tdc">96</td><td class="tdc">65</td></tr> +</table></div> + +<p><span class="pagenum"><a id="Page_68">[68]</a></span></p> + +<p>In 1754 war with France appeared to be again imminent, and a Congress +of Commissioners from the several colonies was arranged for. Of +course, Franklin was one of the representatives of Pennsylvania, and +was also one of the members who independently drew up a plan for the +union of all the colonies under one government, for defensive and +other general purposes, and his was the plan finally approved by +Congress for the union, though it was not accepted by the Assemblies +or by the English Government, being regarded by the former as having +too much of the <i>prerogative</i> in it, by the latter as being too +<i>democratic</i>. Franklin wrote respecting this scheme: "The different +and contrary reasons of dislike to my plan makes me suspect that it +was really the true medium; and I am still of opinion that it would +have been happy for both sides of the water if it had been adopted. The +colonies, so united, would have been sufficiently strong to have +defended themselves; there would then have been no need of troops from +England; of course, the subsequent pretence for taxing America, and +the bloody contest it occasioned, would have been avoided."</p> + +<p>With this war against France began the struggle of the Assemblies and +the proprietaries on the question of taxing the estates of the latter. +The governors received strict instructions to approve no bills for the +raising of money for the purposes of defence, unless the estates of +the proprietaries were specially exempted from the tax. The<span class="pagenum"><a id="Page_69">[69]</a></span> Assembly +of Pennsylvania resolved to contribute £10,000 to assist the +Government of Massachusetts Bay in an attack upon Crown Point, but the +governor refused his assent to the bill for raising the money. At this +juncture Franklin proposed a scheme by which the money could be raised +without the consent of the governor. His plan was successful, and the +difficulty was surmounted for the time, but was destined to recur +again and again during the progress of the war.</p> + +<p>The British Government, not approving of the scheme of union, whereby +the colonies might have defended themselves, sent General Braddock to +Virginia, with two regiments of regular troops. On their arrival they +found it impossible to obtain waggons for the conveyance of their +baggage, and the general commissioned Franklin to provide them in +Pennsylvania. By giving his private bond for their safety, Franklin +succeeded in engaging one hundred and fifty four-horse waggons, and +two hundred and fifty-nine pack-horses. His modest warnings against +Indian ambuscades were disregarded by the general, the little army was +cut to pieces, and the remainder took to flight, sacrificing the whole +of their baggage and stores. Franklin was never fully recouped by the +British Government for the payments he had to make on account of +provisions which the general had instructed him to procure for the use +of the army.</p> + +<p>After this, Franklin appeared for some time in a purely military +capacity, having yielded to the<span class="pagenum"><a id="Page_70">[70]</a></span> governor's persuasions to undertake +the defence of the north-western frontier, to raise troops, and to +build a line of forts. After building and manning three wooden forts, +he was recalled by the Assembly, whose relations with the governor had +become more and more strained. At length the Assembly determined to +send Franklin to England, to present a petition to the king respecting +the conduct of the proprietaries, viz. Richard and Thomas Penn, the +successors of William Penn. A bill had been framed by the House to +provide £60,000 for the king's use in the defence of the province. +This the governor refused to pass, because the proprietary estates +were not exempted from the taxation. The petition to the king was +drawn up, and Franklin's baggage was on board the ship which was to +convey him to England, when General Lord Loudon endeavoured to make an +arrangement between the parties. The governor pleaded his +instructions, and the bond he had given for carrying them out, and the +Assembly was prevailed upon to reconstruct the bill in accordance with +the governor's wishes. This was done under protest; in the mean time +Franklin's ship had sailed, carrying his baggage. After a great deal +of unnecessary delay on account of the general's inability to decide +upon the despatch of the packet-boats, Franklin at last got away from +New York, and, having narrowly escaped shipwreck off Falmouth, he +reached London on July 27, 1757.</p> + +<p>On arriving in London, Franklin was introduced<span class="pagenum"><a id="Page_71">[71]</a></span> to Lord Granville, who +told him that the king's instructions were laws in the colonies. +Franklin replied that he had always understood that the Assemblies +made the laws, which then only required the king's consent. "I +recollected that, about twenty years before, a clause in a bill +brought into Parliament by the Ministry had proposed to make the +king's instructions laws in the colonies, but the clause was thrown +out by the Commons, for which we adored them as our friends and the +friends of liberty, till, by their conduct towards us in 1765, it +seem'd that they had refus'd that point of sovereignty to the king +only that they might reserve it for themselves." A meeting was shortly +afterwards arranged between Franklin and the proprietaries at Mr. T. +Penn's house; but their views were so discordant that, after some +discussion, Franklin was requested to give them in writing the heads +of his complaints, and the whole question was submitted to the opinion +of the attorney- and solicitor-general. It was nearly a year before +this opinion was given. The proprietaries then communicated directly +with the Assembly, but in the mean while Governor Denny had consented +to a bill for raising £100,000 for the king's use, in which it was +provided that the proprietary estates should be taxed with the others. +When this bill reached England, the proprietaries determined to oppose +its receiving the royal assent. Franklin engaged counsel on behalf of +the Assembly, and on his undertaking that the<span class="pagenum"><a id="Page_72">[72]</a></span> assessment should be +fairly made between the estates of the proprietaries and others, the +bill was allowed to pass.</p> + +<p>By this time Franklin's career as a scientific investigator was +practically at an end. Political business almost completely occupied +his attention, and in one sense the diplomatist replaced the +philosopher. His public scientific career was of short duration. It +may be said to have begun in 1746, when Mr. Peter Collinson presented +an "electrical tube" to the Library Company in Philadelphia, which was +some time after followed by a present of a complete set of electrical +apparatus from the proprietaries, but by 1755 Franklin's time was so +much taken up by public business that there was very little +opportunity for experimental work. Throughout his life he frequently +expressed in his letters his strong desire to return to philosophy, +but the opportunity never came, and when, at the age of eighty-two, he +was liberated from public duty, his strength was insufficient to +enable him to complete even his autobiography.</p> + +<p>It was on a visit to Boston in 1746 that Franklin met with Dr. Spence, +a Scotchman, who exhibited some electrical experiments. Soon after his +return to Philadelphia the tube arrived from Mr. Collinson, and +Franklin acquired considerable dexterity in its use. His house was +continually full of visitors, who came to see the experiments, and, to +relieve the pressure upon his time, he had a number of similar tubes +blown at the glass-house, and these<span class="pagenum"><a id="Page_73">[73]</a></span> he distributed to his friends, so +that there were soon a number of "performers" in Philadelphia. One of +these was Mr. Kinnersley, who, having no other employment, was induced +by Franklin to become an itinerant lecturer. Franklin drew up a scheme +for the lectures, and Kinnersley obtained several well-constructed +instruments from Franklin's rough and home-made models. Kinnersley and +Franklin appear to have worked together a good deal, and when +Kinnersley was travelling on his lecture tour, each communicated to +the other the results of his experiments. Franklin sent his papers to +Mr. Collinson, who presented them to the Royal Society, but they were +not at first judged worthy of a place in the "Transactions." The paper +on the identity of lightning and electricity was sent to Dr. Mitchell, +who read it before the Royal Society, when it "was laughed at by the +connoisseurs." The papers were subsequently published in a pamphlet, +but did not at first receive much attention in England. On the +recommendation of Count de Buffon, they were translated into French. +The Abbé Nollet, who had previously published a theory of his own +respecting electricity, wrote and published a volume of letters +defending his theory, and denying the accuracy of some of Franklin's +experimental results. To these letters Franklin made no reply, but +they were answered by M. le Roy. M. de Lor undertook to repeat in +Paris all Franklin's experiments, and they were performed before the +king and court. Not content<span class="pagenum"><a id="Page_74">[74]</a></span> with the experiments which Franklin had +actually performed, he tried those which had been only suggested, and +so was the first to obtain electricity from the clouds by means of the +pointed rod. This experiment produced a great sensation everywhere, +and was afterwards repeated by Franklin at Philadelphia. Franklin's +papers were translated into Italian, German, and Latin; his theory met +with all but universal acceptance, and great surprise was expressed +that his papers had excited so little interest in England. Dr. Watson +then drew up a summary of all Franklin's papers, and this was +published in the "Philosophical Transactions;" Mr. Canton verified the +experiment of procuring electricity from the clouds by means of a +pointed rod, and the Royal Society awarded to Franklin the Copley +Medal for 1753, which was conveyed to him by Governor Denny.</p> + +<p>We must now give a short account of Franklin's contributions to +electrical science.</p> + +<p>"The first is the wonderful effect of pointed bodies, both in <i>drawing +off</i> and <i>throwing off</i> the electrical fire."</p> + +<p>It will be observed that this statement is made in the language of the +<i>one</i>-fluid theory, of which Franklin may be regarded as the author. +This theory will be again referred to presently. Franklin electrified +a cannon-ball so that it repelled a cork. On bringing near it the +point of a bodkin, the repulsion disappeared. A blunt body had to be +brought near enough for a spark to pass in order to produce<span class="pagenum"><a id="Page_75">[75]</a></span> the same +effect. "To prove that the electrical fire is <i>drawn off</i> by the +point, if you take the blade of the bodkin out of the wooden handle, +and fix it in a stick of sealing-wax, and then present it at the +distance aforesaid, or if you bring it very near, no such effect +follows; but sliding one finger along the wax till you touch the +blade, and the ball flies to the shot immediately. If you present the +point in the dark, you will see, sometimes at a foot distance or more, +a light gather upon it like that of a fire-fly or glow-worm; the less +sharp the point, the nearer you must bring it to observe the light; +and at whatever distance you see the light, you may draw off the +electrical fire, and destroy the repelling."</p> + +<p>By laying a needle upon the shot, Franklin showed "that points will +<i>throw off</i> as well as <i>draw off</i> the electrical fire." A candle-flame +was found to be equally efficient with a sharp point in drawing off +the electricity from a charged conductor. The effect of the +candle-flame Franklin accounted for by supposing the particles +separated from the candle to be first "attracted and then repelled, +carrying off the electric matter with them." The effect of points is a +direct consequence of the law of electrical repulsion. When a +conductor is electrified, the density of the electricity is greatest +where the curvature is greatest. Thus, if a number of spheres are +electrified from the same source, the density of the electricity on +the different spheres will vary inversely as their diameters. The +force tending to<span class="pagenum"><a id="Page_76">[76]</a></span> drive the electricity off a conductor is everywhere +proportional to the density, and hence in the case of the spheres will +be greatest for the smallest sphere. On this principle, the density of +electricity on a perfectly sharp point, if such could exist, on a +charged conductor, would be infinite and the force tending to drive it +off would be infinite also. Hence a moderately sharp point is +sufficient to dissipate the electricity from a highly charged +conductor, or to neutralize it if the point is connected to earth and +brought near the conductor so as to be electrified by induction.</p> + +<p>Franklin next found that, if the person rubbing the electric tube +stood upon a cake of resin, and the person taking the charge from the +tube stood also on an insulating stand, a stronger spark would pass +between these two persons than between either of them and the earth; +that, after the spark had passed, neither person was electrified, +though each had appeared electrified before. These experiments +suggested the idea of <i>positive</i> and <i>negative</i> electrification; and +Franklin, regarding the electric fluid as corresponding to positive +electrification, remarked that "you may circulate it as Mr. Watson has +shown; you may also accumulate or subtract it upon or from any body, +as you connect that body with the rubber or with the receiver, the +common stock being cut off." Thus Franklin regarded electricity as a +fluid, of which everything in its normal state possesses a certain +amount; that, by appropriate means, some of the fluid may<span class="pagenum"><a id="Page_77">[77]</a></span> be removed +from one body and given to another. The former is then electrified +negatively, the latter positively, and all processes by which bodies +are electrified consist in the removal of electricity from one body or +system and giving it to another. He regarded the electric fluid as +repelling itself and attracting matter. Æpinus afterwards added the +supposition that matter, when devoid of electricity, is +self-repulsive, and thus completed the "one-fluid theory," and +accounted for the repulsion observed between negatively electrified +bodies.</p> + +<p>It had been usual to employ water for the interior armatures of Leyden +jars, or phials, as they were then generally called. Franklin +substituted granulated lead for the water, thereby improving the +insulation by keeping the glass dry. With these phials he contrived +many ingenious experiments, and imitated lightning by discharging them +through the gilding of a mirror or the gold lines on the cover of a +book. He found that the inner and outer armatures of his Leyden jars +were oppositely electrified. "Here we have a bottle containing at the +same time a <i>plenum</i> of electrical fire and a <i>vacuum</i> of the same +fire; and yet the equilibrium cannot be restored between them but by a +communication <i>without</i>! though the plenum presses violently to +expand, and the hungry vacuum seems to attract as violently in order +to be filled." The charging of Leyden jars by cascade, that is by +insulating all the jars except the last, connecting the outer armature +of the first with the inner<span class="pagenum"><a id="Page_78">[78]</a></span> armature of the second, and so on +throughout the series, was well understood by Franklin, and he knew +too that by this method the extent to which each jar could be charged +from a given source varied inversely as the number of jars. The +discharge of the Leyden jar by alternate contacts was also carried out +by him; and he found that, if the jar is first placed on an insulating +stand, it may be held by the hook (or knob) without discharging it. +Franklin, in fact, appears to have known almost as much about the +Leyden jar as is known to-day. He found that, when the armatures were +removed from a jar, no discharge would pass between them, but when a +fresh pair of armatures were supplied to the glass, the jar could be +discharged. "We are of opinion that there is really no more electrical +fire in the phial after what is called its <i>charging</i> than before, nor +less after its <i>discharging</i>; excepting only the small spark that +might be given to and taken from the non-electric matter, if separated +from the bottle, which spark may not be equal to a five-hundredth part +of what is called the explosion.</p> + +<p>"The phial will not suffer what is called a <i>charging</i> unless as much +fire can go out of it one way as is thrown in by another.</p> + +<p>"When a bottle is charged in the common way, its <i>inside</i> and +<i>outside</i> surfaces stand ready, the one to give fire by the hook, the +other to receive it by the coating; the one is full and ready to throw +out, the other empty and extremely hungry; yet, as the<span class="pagenum"><a id="Page_79">[79]</a></span> first will not +<i>give out</i> unless the other can at the same time <i>receive in</i>, so +neither will the latter receive in unless the first can at the same +time give out. When both can be done at once, it is done with +inconceivable quickness and violence."</p> + +<p>Then follows a very beautiful illustration of the condition of the +glass in the Leyden jar.</p> + +<p>"So a straight spring (though the comparison does not agree in every +particular), when forcibly bent, must, to restore itself, contract +that side which in the bending was extended, and extend that which was +contracted; if either of these two operations be hindered, the other +cannot be done.</p> + +<p>"Glass, in like manner, has, within its substance, always the same +quantity of electrical fire, and that a very great quantity in +proportion to the mass of the glass, as shall be shown hereafter.</p> + +<p>"This quantity proportioned to the glass it strongly and obstinately +retains, and will have neither more nor less, though it will suffer a +change to be made in its parts and situation; <i>i.e.</i> we may take away +part of it from one of the sides, provided we throw an equal quantity +into the other."</p> + +<p>"The whole force of the bottle, and power of giving a shock, is in the +<span class="smcap">glass itself</span>; the non-electrics in contact with the two surfaces +serving only to <i>give</i> and <i>receive</i> to and from the several parts of +the glass, that is, to give on one side and take away from the other."</p> + +<p>All these statements were, as far as possible, fully substantiated by +experiment. They are perfectly<span class="pagenum"><a id="Page_80">[80]</a></span> consistent with the views held by +Cavendish and by Clerk Maxwell, and, though the phraseology is not +that of the modern text-books, the statements themselves can hardly be +improved upon to-day.</p> + +<p>One of Franklin's early contrivances was an electro-motor, which was +driven by the alternate electrical attraction and repulsion of leaden +bullets which discharged Leyden jars by alternate contacts. Franklin +concluded his account of these experiments as follows:—</p> + +<blockquote> +<p>Chagrined a little that we have been hitherto able to produce nothing +in this way of use to mankind, and the hot weather coming on, when +electrical experiments are not so agreeable, it is proposed to put an +end to them for this season, somewhat humorously, in a party of +pleasure, on the banks of Skuylkil. Spirits, at the same time, are to +be fired by a spark sent from side to side through the river, without +any other conductor than the water—an experiment which we some time +since performed, to the amazement of many. A turkey is to be killed +for our dinner by the <i>electrical shock</i>, and roasted by the +<i>electrical jack</i> before a fire kindled by the <i>electrified bottle</i>, +when the healths of all the famous electricians in England, Holland, +France, and Germany, are to be drunk in <i>electrified bumpers</i>, under +the discharge of guns from the <i>electrical battery</i>.</p> +</blockquote> + +<p>Franklin's electrical battery consisted of eleven large panes of glass +coated on each side with sheet lead. The electrified bumper was a thin +tumbler<span class="pagenum"><a id="Page_81">[81]</a></span> nearly filled with wine and electrified as a Leyden jar, so +as to give a shock through the lips.</p> + +<p>Franklin's theory of the manner in which thunder-clouds become +electrified he found to be not consistent with his subsequent +experiments. In the paper which he wrote explaining this theory, +however, he shows some knowledge of the effects of bringing conductors +into contact in diminishing their capacity. He states that two +gun-barrels electrified equally and then united, will give a spark at +a greater distance than one alone. Hence he asks, "To what a great +distance may ten thousand acres of electrified cloud strike and give +its fire, and how loud must be that crack?</p> + +<p>"An electrical spark, drawn from an irregular body at some distance, +is scarcely ever straight, but shows crooked and waving in the air. So +do the flashes of lightning, the clouds being very irregular bodies.</p> + +<p>"As electrified clouds pass over a country, high hills and high trees, +lofty towers, spires, masts of ships, chimneys, etc., as so many +prominences and points, draw the electrical fire, and the whole cloud +discharges there.</p> + +<p>"Dangerous, therefore, is it to take shelter under a tree during a +thunder-gust. It has been fatal to many, both men and beasts.</p> + +<p>"It is safer to be in the open field for another reason. When the +clothes are wet, if a flash in its way to the ground should strike +your head, it may run in the water over the surface of your body;<span class="pagenum"><a id="Page_82">[82]</a></span> +whereas, if your clothes were dry, it would go through the body, +because the blood and other humours, containing so much water, are +more ready conductors.</p> + +<p>"Hence a wet rat cannot be killed by the exploding electrical bottle +[a quart jar], while a dry rat may."</p> + +<p>In the above quotations we see, so to speak, the germ of the +lightning-rod. This was developed in a letter addressed to Mr. +Collinson, and dated July 29, 1750. The following quotations will give +an idea of its contents:—</p> + +<p>"The electrical matter consists of particles extremely subtile, since +it can permeate common matter, even the densest metals, with such ease +and freedom as not to receive any perceptible resistance.<a id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a></p> + +<div class="footnote"><p><a id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> Franklin was aware of the resistance of conductors (see +p. <a href="#Page_96">96</a>).</p></div> + +<p>"If any one should doubt whether the electrical matter passes through +the substance of bodies or only over and along their surfaces, a shock +from an electrified large glass jar, taken through his own body, will +probably convince him.</p> + +<p>"Common matter is a kind of sponge to the electrical fluid.</p> + +<p>"We know that the electrical fluid is <i>in</i> common matter, because we +can pump it <i>out</i> by the globe or tube. We know that common matter has +near as much as it can contain, because when we add a little more to +any portion of it, the additional <span class="pagenum"><a id="Page_83">[83]</a></span>quantity does not enter, but forms +an electrical atmosphere."</p> + +<p>To illustrate the action of a lightning-conductor on a thunder-cloud, +Franklin suspended from the ceiling a pair of scales by a twisted +string so that the beam revolved. Upon the floor, in such a position +that the scale-pans passed over it, he placed a blunt steel punch. The +scale-pans were suspended by silk threads, and one of them +electrified. When this passed over the punch it dipped towards it, and +sometimes discharged into it by a spark. When a needle was placed with +its point uppermost by the side of the punch, no attraction was +apparent, for the needle discharged the scale-pan before it came near.</p> + +<p>"Now, if the fire of electricity and that of lightning be the same, as +I have endeavoured to show at large in a former paper ... these scales +may represent electrified clouds.... The horizontal motion of the +scales over the floor may represent the motion of the clouds over the +earth, and the erect iron punch a hill or high building; and then we +see how electrified clouds, passing over hills or high buildings at +too great a height to strike, may be attracted lower till within their +striking distance; and lastly, if a needle fixed on the punch, with +its point upright, or even on the floor below the punch, will draw the +fire from the scale silently at a much greater than the striking +distance, and so prevent its descending towards the punch; or if in +its course it would have come nigh enough<span class="pagenum"><a id="Page_84">[84]</a></span> to strike, yet, being first +deprived of its fire, it cannot, and the punch is thereby secured from +its stroke;—I say, if these things are so, may not the knowledge of +this power of points be of use to mankind, in preserving houses, +churches, ships, etc., from the stroke of the lightning, by directing +us to fix, on the highest parts of those edifices, upright rods of +iron made sharp as a needle, and gilt to prevent rusting, and from the +foot of those rods a wire down the outside of the building into the +ground, or down round one of the shrouds of a ship, and down her side +till it reaches the water? Would not these pointed rods probably draw +the electrical fire silently out of a cloud before it came nigh enough +to strike, and thereby secure us from that most sudden and terrible +mischief?"</p> + +<p>Franklin goes on to suggest the possibility of obtaining electricity +from the clouds by means of a pointed rod fixed on the top of a high +building and insulated. Such a rod he afterwards erected in his own +house. Another rod connected to the earth he brought within six inches +of it, and, attaching a small bell to each rod, he suspended a little +ball or clapper by a silk thread, so that it could strike either bell +when attracted to it. On the approach of a thunder-cloud, and +occasionally when no clouds were near, the bells would ring, +indicating that the rod had become strongly electrified. On one +occasion Franklin was disturbed by a loud noise, and, coming out of +his bedroom, he<span class="pagenum"><a id="Page_85">[85]</a></span> found an apparently continuous and very luminous +discharge taking place between the bells, forming a stream of fire +about as large as a pencil.</p> + +<p>A very pretty experiment of Franklin's was that of the <i>golden fish</i>. +A small piece of gold-leaf is cut into a quadrilateral having one of +its angles about 150°, the opposite angle about 30°, and the other two +right angles. "If you take it by the tail, and hold it at a foot or +greater horizontal distance from the prime conductor, it will, when +let go, fly to it with a brisk but wavering motion, like that of an +eel through the water; it will then take place under the prime +conductor, at perhaps a quarter or half an inch distance, and keep a +continual shaking of its tail like a fish, so that it seems animated. +Turn its tail towards the prime conductor, and then it flies to your +finger, and seems to nibble it. And if you hold a [pewter] plate under +it at six or eight inches distance, and cease turning the globe, when +the electrical atmosphere of the conductor grows small it will descend +to the plate and swim back again several times with the same fish-like +motion; greatly to the entertainment of spectators. By a little +practice in blunting or sharpening the heads or tails of these +figures, you may make them take place as desired, nearer or further +from the electrified plate."</p> + +<p>By the discharge of the battery, Franklin succeeded in melting and +volatilizing gold-leaf, thin strips of tinfoil, etc. His views on the +nature of light are best given in his own words.</p><p><span class="pagenum"><a id="Page_86">[86]</a></span></p> + +<p>"I am not satisfied with the doctrine that supposes particles of +matter called light, continually driven off from the sun's surface, +with a swiftness so prodigious! Must not the smallest particle +conceivable have, with such a motion, a force exceeding that of a +twenty-four pounder discharged from a cannon?... Yet these particles, +with this amazing motion, will not drive before them, or remove, the +least and lightest dust they meet with.</p> + +<p>"May not all the phenomena of light be more conveniently solved by +supposing universal space filled with a subtile elastic fluid, which, +when at rest, is not visible, but whose vibrations affect that fine +sense in the eye, as those of air do the grosser organs of the ear? We +do not, in the case of sound, imagine that any sonorous particles are +thrown off from a bell, for instance, and fly in straight lines to the +ear; why must we believe that luminous particles leave the sun and +proceed to the eye? Some diamonds, if rubbed, shine in the dark +without losing any part of their matter. I can make an electrical +spark as big as the flame of a candle, much brighter, and therefore +visible further; yet this is without fuel; and I am persuaded no part +of the electrical fluid flies off in such case to distant places, but +all goes directly and is to be found in the place to which I destine +it. May not different degrees of the vibration of the abovementioned +universal medium occasion the appearances of different colours? I +think the electric fluid is always the same; yet I find that weaker<span class="pagenum"><a id="Page_87">[87]</a></span> +and stronger sparks differ in apparent colour, some white, blue, +purple, red: the strongest, white; weak ones, red. Thus different +degrees of vibration given to the air produce the seven different +sounds in music, analogous to the seven colours, yet the medium, air, +is the same."</p> + +<p>Mr. Kinnersley having called Franklin's attention to the fact that a +sulphur globe when rubbed produced electrification of an opposite kind +from that produced by a glass globe, Franklin repeated the experiment, +and noticed that the discharge from the end of a wire connected with +the conductor was different in the two cases, being "long, large, and +much diverging when the glass globe is used, and makes a snapping (or +rattling) noise; but when the sulphur one is used it is short, small, +and makes a hissing noise; and just the reverse of both happens when +you hold the same wire in your hand and the globes are worked +alternately.... When the brush is long, large, and much diverging, the +body to which it is joined seems to be throwing the fire out; and when +the contrary appears it seems to be drinking in."</p> + +<p>On October 19, 1752, Franklin wrote to Mr. Peter Collinson as +follows:—</p> + +<blockquote> +<p>As frequent mention is made in public papers from Europe of the +success of the Philadelphia experiment for drawing the electric fire +from clouds by means of pointed rods of iron erected on high +buildings, etc., it may be agreeable to the curious to be informed +that the same experiment<span class="pagenum"><a id="Page_88">[88]</a></span> has succeeded in Philadelphia, though made +in a different and more easy manner, which is as follows:—</p> + +<p>Make a small cross of two light strips of cedar, the arms so long as +to reach to the four corners of a large thin silk handkerchief when +extended. Tie the corners of the handkerchief to the extremities of +the cross, so you have the body of a kite; which, being properly +accommodated with a tail, loop, and string, will rise in the air like +those made of paper; but this being of silk is fitter to bear the wet +and wind of a thunder-gust without tearing. To the top of the upright +stick of the cross is to be fixed a very sharp-pointed wire, rising a +foot or more above the wood. To the end of the twine, next the hand, +is to be tied a silk ribbon, and, where the silk and twine join, a key +may be fastened. This kite is to be raised when a thunder-gust appears +to be coming on, and the person who holds the string must stand within +a door or window, or under some cover so that the silk ribbon may not +be wet, and care must be taken that the twine does not touch the frame +of the door or window. As soon as any of the thunder-clouds come over +the kite, the pointed wire will draw the electric fire from them, and +the kite, with all the twine, will be electrified, and the loose +filaments of the twine will stand out every way, and be attracted by +an approaching finger. And when the rain has wetted the kite and twine +so that it can conduct the electric fire freely, you will find it +stream out plentifully from<span class="pagenum"><a id="Page_89">[89]</a></span> the key on the approach of your knuckle. +At this key the phial may be charged, and from electric fire there +obtained spirits may be kindled, and all the other electric +experiments be performed which are usually done by the help of a +rubbed glass globe or tube, and thereby the sameness of the electric +matter with that of lightning completely demonstrated.</p> +</blockquote> + +<p>Having, in September, 1752, erected the iron rod and bells in his own +house, as previously mentioned, Franklin succeeded, in April, 1753, in +charging a Leyden jar from the rod, and found its charge was negative. +On June 6, however, he obtained a positive charge from a cloud. The +results of his observations led him to the conclusion "<i>That the +clouds of a thunder-gust are most commonly in a negative state of +electricity, but sometimes in a positive state.</i>"</p> + +<p>In order to illustrate a theory respecting the electrification of +clouds, Franklin placed a silver can on a wine-glass. Inside the can +was placed a considerable length of chain, which could be drawn out by +means of a silk thread. He electrified the can from a Leyden jar until +it would receive no more electricity. Then raising the silk thread, he +gradually drew the chain out of the can, and found that the greater +the length of chain drawn out the greater was the charge which the jar +would give to the system, and as the chain was raised, spark after +spark passed from the jar to the silver can, thus showing that the +capacity of the system<span class="pagenum"><a id="Page_90">[90]</a></span> was increased by increasing the amount of +chain exposed.</p> + +<p>In 1755 Franklin observed the effects of induction; for, having +attached to his prime conductor a tassel made of damp threads and +electrified the conductor, he found that the threads repelled each +other and stood out. Bringing an excited glass tube near the other end +of the conductor, the threads were found to diverge more, "because the +atmosphere of the prime conductor is pressed by the atmosphere of the +excited tube, and driven towards the end where the threads are, by +which each thread acquires more atmosphere." When the excited tube was +brought near the threads, they closed a little, "because the +atmosphere of the glass tube repels their atmospheres, and drives part +of them back on the prime conductor." A number of other experiments +illustrating electrical induction were also carried out.</p> + +<p>In writing to Dr. Living, of Charlestown, under date March 18, 1755, +Franklin gave the following extracts of the minutes of his experiments +as explaining the train of thought which led him to attempt to obtain +electricity from the clouds:—</p> + +<p>"<i>November 7, 1749.</i> Electrical fluid agrees with lightning in these +particulars: 1. Giving light. 2. Colour of the light. 3. Crooked +direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or +noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies +it passes through. 9. Destroying animals. 10. Melting metals. 11.<span class="pagenum"><a id="Page_91">[91]</a></span> +Firing inflammable substances. 12. Sulphureous smell. The electric +fluid is attracted by points. We do not know whether this property is +in lightning. But since they agree in all the particulars wherein we +can already compare them, is it not probable they agree likewise in +this? Let the experiment be made."</p> + +<p>Another experiment very important in its bearing on the theory of +electricity was described by Franklin in the same letter to Dr. +Living. It was afterwards repeated in a much more complete form by +Cavendish, who deduced from it the great law that electrical repulsion +varies inversely as the square of the distance between the charges. +The same experiment was repeated in other forms by Faraday, who had no +means of knowing what Cavendish had done. Franklin writes:—</p> + +<blockquote> +<p>I electrified a silver fruit-can on an electric stand, and then +lowered into it a cork ball of about an inch in diameter, hanging by a +silk string, till the cork touched the bottom of the can. The cork was +not attracted to the inside of the can, as it would have been to the +outside, and though it touched the bottom, yet, when drawn out, it was +not found to be electrified by that touch, as it would have been by +touching the outside. The fact is singular. You require the reason? I +do not know it. Perhaps you may discover it, and then you will be so +good as to communicate it to me. I find a frank acknowledgment of +one's ignorance is not only the easiest way to get rid of a +difficulty,<span class="pagenum"><a id="Page_92">[92]</a></span> but the likeliest way to obtain information, and +therefore I practise it. I think it is an honest policy.</p> +</blockquote> + +<p>A note appended to this letter runs as follows:—</p> + +<blockquote> +<p>Mr. F. has since thought that, possibly, the mutual repulsion of the +inner opposite sides of the electrized can may prevent the +accumulating an electric atmosphere upon them, and occasion it to +stand chiefly on the outside. But recommends it to the further +examination of the curious.</p> +</blockquote> + +<p>The explanation in this note is the correct one, and from the fact +that in the case of a completely closed hollow conductor the charge is +not only <i>chiefly</i> but <i>wholly</i> on the outside, the law of inverse +squares above referred to follows as a mathematical consequence.</p> + +<p>On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin +complained that, though he always (except once) assigned to +lightning-rods the alternative duty of either <i>preventing</i> a stroke or +of <i>conducting</i> the lightning with safety to the ground, yet in Europe +attention was paid only to the <i>prevention</i> of the stroke, which was +only a <i>part</i> of the duty assigned to the conductors. This is followed +by the description of the effect of a stroke upon a church-steeple at +Newbury, in New England. The spire was split all to pieces, so that +nothing remained above the bell. The lightning then passed down a wire +to the clock, then down the pendulum, without injury to the building. +"From the end of the pendulum, down quite to the ground, the<span class="pagenum"><a id="Page_93">[93]</a></span> building +was exceedingly rent and damaged, and some stones in the +foundation-wall torn out and thrown to the distance of twenty or +thirty feet." The pendulum-rod was uninjured, but the fine wire +leading from the bell to the clock was vaporized except for about two +inches at each end.</p> + +<p>Mr. James Alexander, of New York, having proposed to Franklin that the +velocity of the electric discharge might be measured by discharging a +jar through a long circuit of river-water, Franklin, in his reply, +explained that such an experiment, if successful, would not determine +the actual velocity of electricity in the conductor. He compared the +electricity in conductors to an incompressible fluid, so that when a +little additional fluid is injected at one end of a conductor, an +equal amount must be extruded at the other end—his view apparently +being identical with that of Maxwell, who held that all electric +displacements must take place <i>in closed circuits</i>.</p> + +<p>"Suppose a tube of any length open at both ends.... If the tube be +filled with water, and I inject an additional inch of water at one +end, I force out an equal quantity at the other in the very same +instant.</p> + +<p>"And the water forced out at one end of the tube is not the very same +water that was forced in at the other end at the same time; it was +only one motion at the same time.</p> + +<p>"The long wire, made use of in the experiment to discover the velocity +of the electric fluid, is itself<span class="pagenum"><a id="Page_94">[94]</a></span> filled with what we call its natural +quantity of that fluid, before the hook of the Leyden bottle is +applied at one end of it.</p> + +<p>"The outside of the bottle being at the time of such application in +contact with the other end of the wire, the whole quantity of electric +fluid contained in the wire is, probably, put in motion at once.</p> + +<p>"For at the instant the hook, connected with the inside of the bottle, +<i>gives out</i>, the coating or outside of the bottle <i>draws in</i>, a +portion of that fluid....</p> + +<p>"So that this experiment only shows the extreme facility with which +the electric fluid moves in metal; it can never determine the +velocity.</p> + +<p>"And, therefore, the proposed experiment (though well imagined and +very ingenious) of sending the spark round through a vast length of +space, by the waters of Susquehannah, or Potowmack, and Ohio, would +not afford the satisfaction desired, though we could be sure that the +motion of the electric fluid would be in that tract, and not +underground in the wet earth by the shortest way."</p> + +<p>In his investigations of the source of electricity in thunder-clouds, +Franklin tried an experiment which has been frequently repeated with +various modifications. Having insulated a large brass plate which had +been previously heated, he sprinkled water upon it, in order, if +possible, to obtain electricity by the evaporation of the water, but +no trace of electrification could be detected.</p><p><span class="pagenum"><a id="Page_95">[95]</a></span></p> + +<p>During his visit to England, Franklin wrote many letters to Mr. +Kinnersley and others on philosophical questions, but they consisted +mainly of accounts of the work done by other experimenters in England, +his public business occupying too much of his attention to allow him +to conduct investigations for himself. In one of his letters, speaking +of Lord Charles Cavendish, he says:—</p> + +<blockquote> +<p>It were to be wished that this noble philosopher would communicate +more of his experiments to the world, as he makes many, and with great +accuracy.</p> +</blockquote> + +<p>When the controversy between the relative merits of points and knobs +for the terminals of lightning-conductors arose, Franklin wrote to Mr. +Kinnersley:—</p> + +<blockquote> +<p>Here are some electricians that recommend knobs instead of points on +the upper end of the rods, from a supposition that the points invite +the stroke. It is true that points draw electricity at greater +distances in the gradual silent way; but knobs will draw at the +greatest distance a stroke. There is an experiment which will settle +this. Take a crooked wire of the thickness of a quill, and of such a +length as that, one end of it being applied to the lower part of a +charged bottle, the upper may be brought near the ball on the top of +the wire that is in the bottle. Let one end of this wire be furnished +with a knob, and the other may be gradually tapered to a fine point. +When the point is presented to discharge the bottle, it must be +brought much nearer before it will receive the<span class="pagenum"><a id="Page_96">[96]</a></span> stroke than the knob +requires to be. Points, besides, tend to repel the fragments of an +electrical cloud; knobs draw them nearer. An experiment, which I +believe I have shown you, of cotton fleece hanging from an electrized +body, shows this clearly when a point or a knob is presented under +it.</p> +</blockquote> + +<p>The following quotation from Franklin's paper on the method of +securing buildings and persons from the effects of lightning is worthy +of attention, for of late years a good deal of money has been wasted +in providing insulators for lightning-rods. A few years ago the vicar +and churchwardens of a Lincolnshire parish were strongly urged to go +to the expense of insulating the conductor throughout the whole height +of the very lofty tower and spire of their parish church. Happily they +were wise enough to send the lightning-rod man about his business. But +this is not the only case which has come under the writer's notice, +showing that there is still a widespread impression that +lightning-conductors should be carefully insulated. Franklin says:—</p> + +<p>"The rod may be fastened to the wall, chimney, etc., with staples of +iron. The lightning will not leave the rod (a good conductor) to pass +into the wall (a bad conductor) through these staples. It would +rather, if any were in the wall, pass out of it into the rod, to get +more readily by that conductor into the earth."<a id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a></p> + +<div class="footnote"><p><a id="Footnote_2_2"></a><a href="#FNanchor_2_2"> +<span class="label">[2]</span></a> See p. <a href="#Page_141">141</a>.</p></div> + +<p>The conditions to be secured in a lightning-con<span class="pagenum"><a id="Page_97">[97]</a></span>ductor are, firstly, a +sharp point projecting above the highest part of the building, and +gilded to prevent corrosion; secondly, metallic continuity from the +point to the lower end of the conductor; and, thirdly, a good +earth-contact. The last can frequently be secured by soldering the +conductor to iron water-pipes underground. Where these are not +available, a copper plate, two or three feet square, imbedded in clay +or other damp earth, will serve the purpose. The method of securing a +building which is erected on granite or other foundation affording no +good earth-connection, will be referred to in a subsequent +biographical sketch.</p> + +<p>The controversy of points <i>versus</i> knobs was again revived in London +when Franklin was in Paris, and the War of Independence had begun. +Franklin was consulted on the subject, the question having arisen in +connection with the conductor at the palace. His reply was +characteristic.</p> + +<p>"As to my writing anything on the subject, which you seem to desire, I +think it not necessary, especially as I have nothing to add to what I +have already said upon it in a paper read to the committee who ordered +the conductors at Purfleet, which paper is printed in the last French +edition of my writings.</p> + +<p>"I have never entered into any controversy in defence of my +philosophical opinions. I leave them to take their chance in the +world. If they are <i>right</i>, truth and experience will support them; if +<i>wrong</i>, they ought to be refuted and rejected.<span class="pagenum"><a id="Page_98">[98]</a></span> Disputes are apt to +sour one's temper and disturb one's quiet. I have no private interest +in the reception of my inventions by the world, having never made, nor +proposed to make, the least profit by any of them. The king's changing +his <i>pointed</i> conductors for <i>blunt</i> ones is, therefore, a matter of +small importance to me. If I had a wish about it, it would be that he +had rejected them altogether as ineffectual. For it is only since he +thought himself and family safe from the thunder of Heaven, that he +dared to use his own thunder in destroying his innocent subjects."</p> + +<p>The paper referred to was read before "the committee appointed to +consider the erecting conductors to secure the magazines at Purfleet," +on August 27, 1772. It described a variety of experiments clearly +demonstrating the effect of points in discharging a conductor. This +was a committee of the Royal Society, to whom the question had been +referred on account of Dr. Wilson's recommendation of a blunt +conductor. The committee decided in favour of Franklin's view, and +when, in 1777, the question was again raised and again referred to a +committee of the Royal Society, the decision of the former committee +was confirmed, "conceiving that the experiments and reasons made and +alleged to the contrary by Mr. Wilson are inconclusive."</p> + +<p>Though Franklin's scientific reputation rests mainly on his electrical +researches, he did not leave other branches of science untouched. +Besides<span class="pagenum"><a id="Page_99">[99]</a></span> his work on atmospheric electricity, he devoted a great deal +of thought to meteorology, especially to the vortical motion of +waterspouts. The Gulf-stream received a share of his attention. His +improvements in fireplaces have already been noticed; the cure of +smoky chimneys was the subject of a long paper addressed to Dr. +Ingenhousz, and of some other letters. One of his experiments on the +absorption of radiant energy has been deservedly remembered.</p> + +<p>"My experiment was this: I took a number of little square pieces of +broad-cloth from a tailor's pattern-card, of various colours. There +were black, deep blue, lighter blue, green, purple, red, yellow, +white, and other colours or shades of colours. I laid them all out +upon the snow in a bright, sun-shiny morning. In a few hours (I cannot +now be exact as to the time) the black, being warmed most by the sun, +was sunk so low as to be below the stroke of the sun's rays; the dark +blue almost as low, the lighter blue not quite so much as the dark, +the other colours less as they were lighter; and the quite white +remained on the surface of the snow, not having entered it at all.</p> + +<p>"What signifies philosophy that does not apply to some use? May we not +learn from hence that black clothes are not so fit to wear in a hot, +sunny climate or season, as white ones?"</p> + +<p>Franklin knew much about electricity, but his knowledge of human +nature was deeper still. This appears in all his transactions. His +political<span class="pagenum"><a id="Page_100">[100]</a></span> economy was, perhaps, not always sound, but his judgment of +men was seldom at fault.</p> + +<p>"Finally, there seem to be but three ways for a nation to acquire +wealth. The first is by <i>war</i>, as the Romans did, in plundering their +conquered neighbour: this is <i>robbery</i>. The second by <i>commerce</i>, +which is generally <i>cheating</i>. The third by <i>agriculture</i>, the only +<i>honest way</i>, wherein man receives a real increase of the seed thrown +into the ground, in a kind of continual miracle wrought by the hand of +God in his favour, as a reward for his innocent life and his virtuous +industry."</p> + +<p>When Franklin reached London in 1757 he took up his abode with Mrs. +Margaret Stevenson, in Craven Street, Strand. For Mrs. Stevenson and +her daughter Mary, then a young lady of eighteen, he acquired a +sincere affection, which continued throughout their lives. Miss +Stevenson spent much of her time with an aunt in the country, and some +of Franklin's letters to her respecting the conduct of her "higher +education" are among the most interesting of his writings. Miss +Stevenson treated him as a father, and consulted him on every question +of importance in her life. When she was a widow and Franklin eighty +years of age, he urged upon her to come to Philadelphia, for the sake +of the better prospects which the new country offered her boys. In +coming to England, Franklin brought with him his son William, who +entered the Middle Temple, but he left behind his only daughter, +Sarah, in charge of her mother. To his wife and<span class="pagenum"><a id="Page_101">[101]</a></span> daughter he +frequently sent presents from London, and his letters to Mrs. Franklin +give a pretty full account of all his doings while in England. During +his visit he received the honorary degrees of D.C.L. from the +University of Oxford, and LL.D. from that of Edinburgh. At Cambridge +he was sumptuously entertained. In August, 1762, he started again for +America, and reached Philadelphia on November 1, after an absence of +five years. His son William had shortly before been appointed Governor +of New Jersey. From this time William Franklin became very much the +servant of the proprietaries and of the English Government, but no +offer of patronage produced any effect on the father.</p> + +<p>Franklin's stay in America was of short duration, but while there he +was mainly instrumental in quelling an insurrection in Pennsylvania. +He made a tour of inspection through the northern colonies in the +summer of 1763, to regulate the post-offices. The disorder just +referred to in the province caused the governor, as well as the +Assembly, to determine on the formation of a militia. A committee, of +which Franklin was a member, drew up the necessary bill. The governor +claimed the sole power of appointing officers, and required that +trials should be by court-martial, some offences being punishable with +death. The Assembly refused to agree to these considerations. The ill +feeling was increased by the governor insisting on taxing all +proprietary lands at the same rate as uncultivated<span class="pagenum"><a id="Page_102">[102]</a></span> land belonging to +other persons, whether the proprietary lands were cultivated or not. +The Assembly, before adjourning, expressed an opinion that peace and +happiness would not be secured until the government was lodged +directly in the Crown. When the Assembly again met, petitions to the +king came in from more than three thousand inhabitants. In the mean +while the British Ministry had proposed the Stamp Act, which was +similar in principle to the English Stamp Act, which requires that all +agreements, receipts, bills of exchange, marriage and birth +certificates, and all other legal documents should be provided with an +inland revenue stamp of a particular value, in order that they might +be valid. As soon as the Assembly was convened, it determined to send +Franklin to England, to take charge of a petition for a change of +government. The merchants subscribed £1100 towards his expenses in a +few hours, and in twelve days he was on his journey, being accompanied +to the ship, a distance of sixteen miles, by a cavalcade of three +hundred of his friends, and in thirty days he reached London. Arrived +in London, he at once took up his abode in his old lodgings with Mrs. +Stevenson. He was a master of satire, equalled only by Swift, and +during the quarrels which preceded the War of Independence, as well as +during the war, he made good use of his powers in this respect. +Articles appeared in some of the English papers tending to raise an +alarm respecting the competition of the colonies with English +manufacturers.<span class="pagenum"><a id="Page_103">[103]</a></span> Franklin's contribution to the discussion was a +caricature of the English press writers.</p> + +<p>"It is objected by superficial readers, who yet pretend to some +knowledge of those countries, that such establishments [manufactories +for woollen goods, etc.] are not only improbable, but impossible, for +that their sheep have but little wool, not in the whole sufficient for +a pair of stockings a year to each inhabitant; that, from the +universal dearness of labour among them, the working of iron and other +materials, except in a few coarse instances, is impracticable to any +advantage.</p> + +<p>"Dear sir, do not let us suffer ourselves to be amused with such +groundless objections. The very tails of the American sheep are so +laden with wool that each has a little car or waggon on four little +wheels to support and keep it from trailing on the ground. Would they +caulk their ships, would they even litter their horses with wool, if +it were not both plenty and cheap? And what signifies the dearness of +labour, when an English shilling passes for five and twenty? Their +engaging three hundred silk throwsters here in one week for New York +was treated as a fable, because, forsooth, they have 'no silk there to +throw!' Those who make this objection perhaps do not know that, at the +same time, the agents for the King of Spain were at Quebec, to +contract for one thousand pieces of cannon to be made there for the +fortification of Mexico, and at New York engaging the usual supply of +woollen floor-carpets for their West India houses. Other<span class="pagenum"><a id="Page_104">[104]</a></span> agents from +the Emperor of China were at Boston, treating about an exchange of raw +silk for wool, to be carried in Chinese junks through the Straits of +Magellan.</p> + +<p>"And yet all this is as certainly true as the account said to be from +Quebec in all the papers of last week, that the inhabitants of Canada +are making preparations for a cod and whale fishery this summer in the +upper Lakes. Ignorant people may object that the upper Lakes are +fresh, and that cod and whales are salt-water fish; but let them know, +sir, that cod, like other fish when attacked by their enemies, fly +into any water where they can be safest; that whales, when they have a +mind to eat cod, pursue them wherever they fly; and that the grand +leap of the whale in the chase up the Falls of Niagara is esteemed, by +all who have seen it, as one of the finest spectacles in nature."</p> + +<p>One of Franklin's chief objects in coming to England was to prevent +the passing of Mr. Grenville's bill, previously referred to as the +Stamp Act. The colonists urged that they had always been liberal in +their votes, whenever money was required by the Crown, and that +taxation and representation must, in accordance with the British +constitution, go hand-in-hand, so that the English Parliament had no +right to raise taxes in America, so long as the colonists were +unrepresented in Parliament. "Had Mr. Grenville, instead of that act, +applied to the king in Council for such requisitional letters<span class="pagenum"><a id="Page_105">[105]</a></span> [<i>i.e.</i> +requests to the Assemblies for voluntary grants], to be circulated by +the Secretary of State, I am sure he would have obtained more money +from the colonies by their voluntary grants than he himself expected +from the sale of stamps. But he chose compulsion rather than +persuasion, and would not receive from their good will what he thought +he could obtain without it." The Stamp Act was passed, stamps were +printed, distributors were appointed, but the colonists would have +nothing to do with the stamps. The distributors were compelled to +resign their commissions, and the captains of vessels were forbidden +to land the stamped paper. The cost of printing and distributing +amounted to £12,000; the whole return was about £1500, from Canada and +the West Indies.</p> + +<p>The passing of the Stamp Act was soon followed by a change of +Ministry, when the question again came before Parliament. Franklin +submitted to a long examination before a Committee of the whole House. +The feeling prevalent in America respecting the Stamp Act may be +inferred from some of his answers.</p> + +<p>"31. <i>Q.</i> Do you think the people of America would submit to pay the +stamp duty if it was moderated?</p> + +<p>"<i>A.</i> No, never, unless compelled by force of arms.</p> + +<p>"36. <i>Q.</i> What was the temper of America towards Great Britain before +the year 1763?<a id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a></p> + +<div class="footnote"><p><a id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> The date of the Sugar Act.</p><p><span class="pagenum"><a id="Page_106">[106]</a></span></p></div> + +<p>"<i>A.</i> The best in the world. They submitted willingly to the +government of the Crown, and paid, in their courts, obedience to the +Acts of Parliament. Numerous as the people are in the several old +provinces, they cost you nothing in forts, citadels, garrisons, or +armies to keep them in subjection. They were governed by this country +at the expense only of a little pen, ink, and paper; they were led by +a thread. They had not only a respect, but an affection, for Great +Britain—for its laws, its customs and manners, and even a fondness +for its fashions, that greatly increased the commerce. Natives of +Britain were always treated with particular regard; to be an +<i>Old-Englandman</i> was, of itself, a character of some respect, and gave +a kind of rank among us.</p> + +<p>"37. <i>Q.</i> And what is their temper now?</p> + +<p>"<i>A.</i> Oh, very much altered.</p> + +<p>"50. <i>Q.</i> Was it an opinion in America before 1763 that the Parliament +had no right to lay taxes and duties there?</p> + +<p>"<i>A.</i> I never heard any objection to the right of laying duties to +regulate commerce; but a right to lay internal taxes was never +supposed to be in Parliament, as we are not represented there.</p> + +<p>"59. <i>Q.</i> You say the colonies have always submitted to external +taxes, and object to the right of Parliament only in laying internal +taxes; now, can you show that there is any kind of difference between +the two taxes to the colony on which they may be laid?</p><p><span class="pagenum"><a id="Page_107">[107]</a></span></p> + +<p>"<i>A.</i> I think the difference is very great. An <i>external</i> tax is a +duty laid on commodities imported; that duty is added to the first +cost and other charges on the commodity, and, when it is offered to +sale, makes a part of the price. If the people do not like it at that +price, they refuse it; they are not obliged to pay it. But an +<i>internal</i> tax is forced upon the people without their consent, if not +laid by their own representatives. The Stamp Act says we shall have no +commerce, make no exchange of property with each other, neither +purchase, nor grant, nor recover debts; we shall neither marry nor +make our wills, unless we pay such and such sums; and thus it is +intended to extort our money from us, or ruin us by the consequences +of refusing to pay it.</p> + +<p>"61. <i>Q.</i> Don't you think cloth from England absolutely necessary to +them?</p> + +<p>"<i>A.</i> No, by no means absolutely necessary; with industry and good +management they may very well supply themselves with all they want.</p> + +<p>"62. <i>Q.</i> Will it not take a long time to establish that manufacture +among them? and must they not in the mean while suffer greatly?</p> + +<p>"<i>A.</i> I think not. They have made a surprising progress already. And I +am of opinion that, before their old clothes are worn out, they will +have new ones of their own making.</p> + +<p>"84. <i>Q.</i> If the Act is not repealed, what do you think will be the +consequence?</p><p><span class="pagenum"><a id="Page_108">[108]</a></span></p> + +<p>"<i>A.</i> A total loss of the respect and affection the people of America +bear to this country, and of all the commerce that depends on that +respect and affection.</p> + +<p>"85. <i>Q.</i> How can the commerce be affected?</p> + +<p>"<i>A.</i> You will find that, if the Act is not repealed, they will take a +very little of your manufactures in a short time.</p> + +<p>"86. <i>Q.</i> Is it in their power to do without them?</p> + +<p>"<i>A.</i> I think they may very well do without them.</p> + +<p>"87. <i>Q.</i> Is it their interest not to take them?</p> + +<p>"<i>A.</i> The goods they take from Britain are either necessaries, mere +conveniences, or superfluities. The first, as cloth, etc., with a +little industry they can make at home; the second they can do without +till they are able to provide them among themselves; and the last, +which are much the greatest part, they will strike off immediately. +They are mere articles of fashion, purchased and consumed because the +fashion in a respected country; but will now be detested and rejected. +The people have already struck off, by general agreement, the use of +all goods fashionable in mournings, and many thousand pounds' worth +are sent back as unsaleable.</p> + +<p>"173. <i>Q.</i> What used to be the pride of the Americans?</p> + +<p>"<i>A.</i> To indulge in the fashions and manufactures of Great Britain.</p> + +<p>"174. <i>Q.</i> What is now their pride?</p><p><span class="pagenum"><a id="Page_109">[109]</a></span></p> + +<p>"<i>A.</i> To wear their old clothes over again till they can make new +ones."</p> + +<p>The month following Franklin's examination, the repeal of the Stamp +Act received the royal assent. Thereupon Franklin sent his wife and +daughter new dresses, and a number of other little luxuries (or toilet +necessaries).</p> + +<p>In 1767 Franklin visited Paris. In the same year his daughter married +Mr. Richard Bache. Though Parliament had repealed the Stamp Act, it +nevertheless insisted on its right to tax the colonies. The Duty Act +was scarcely less objectionable than its predecessor. On Franklin's +return from the Continent, he heard of the retaliatory measures of the +Boston people, who had assembled in town-meetings, formally resolved +to encourage home manufactures, to abandon superfluities, and, after a +certain time, to give up the use of some articles of foreign +manufacture. These <i>associations</i> afterwards became very general in +the colonies, so that in one year the importations by the colonists of +New York fell from £482,000 to £74,000, and in Pennsylvania from +£432,000 to £119,000.</p> + +<p>The effect of the Duty Act was to encourage the Dutch and other +nations to smuggle tea and probably other India produce into America. +The exclusion from the American markets of tea sent from England +placed the East India Company in great difficulties; for while they +were unable to meet their bills, they had in stock two million pounds' +worth of tea and other goods. The balance<span class="pagenum"><a id="Page_110">[110]</a></span> of the revenue collected +under the Duty Act, after paying salaries, etc., amounted to only £85 +for the year, and for this a fleet had to be maintained, to guard the +fifteen hundred miles of American coast; while the fall in East India +Stock deprived the revenue of £400,000 per annum, which the East India +Company would otherwise have paid. At length a licence was granted to +the East India Company to carry tea into America, duty free. This, of +course, excluded all other merchants from the American tea-trade. A +quantity of tea sent by the East India Company to Boston was destroyed +by the people. The British Government then blockaded the port. This +soon led to open hostilities. Franklin worked hard to effect a +reconciliation. He drew up a scheme, setting forth the conditions +under which he conceived a reconciliation might be brought about, and +discussed it fully with Mr. Daniel Barclay and Dr. Fothergill. This +scheme was shown to Lord Howe, and afterwards brought before the +Ministry, but was rejected. Other plans were considered, and Franklin +offered to pay for the tea which had been destroyed at Boston. All his +negotiations were, however, fruitless. At last he addressed a memorial +to the Earl of Dartmouth, Secretary of State, complaining of the +blockade of Boston, which had then continued for nine months, and had +"during every week of its continuance done damage to that town, equal +to what was suffered there by the India Company;" and claiming +reparation for such injury beyond the value of<span class="pagenum"><a id="Page_111">[111]</a></span> the tea which had been +destroyed. The memorial also complained of the exclusion of the +colonists from the Newfoundland fisheries, for which reparation would +one day be required. This memorial was returned to Franklin by Mr. +Walpole, and Franklin shortly afterwards returned to Philadelphia.</p> + +<p>During this visit to England he had lost his wife, who died on +December 19, 1774; and his friend Miss Stevenson had married and been +left a widow.</p> + +<p>In April, 1768, Franklin was appointed Agent for Georgia, in the +following year for New Jersey, and in 1770 for Massachusetts, so that +he was then the representative in England of four colonies, with an +income of £1200 per annum.</p> + +<p>In 1771 he spent three weeks at Twyford, with the Bishop of St. Asaph, +who remained a fast friend of Franklin's until his death. In 1772 he +was nominated by the King of France as Foreign Associate of the +Academy of Sciences.</p> + +<p>During his negotiations with the British Government Franklin wrote two +satirical pieces, setting forth the treatment which the American +colonists were receiving. The first was entitled "Rules for Reducing a +Great Empire to a Small One," the rules being precisely those which, +in Franklin's opinion, had been followed by the British Government in +its dealings with America. The other was "An Edict by the King of +Prussia," in which the king claimed the right of taxing the British +nation; of forbidding<span class="pagenum"><a id="Page_112">[112]</a></span> English manufacture, and compelling Englishmen +to purchase Prussian goods; of transporting prisoners to Britain, and +generally of exercising all such controls over the English people as +had been claimed over America by various Acts of the English +Parliament, on the ground that England was originally colonized by +emigrants from Prussia.</p> + +<p>Before Franklin reached America, the War of Independence, though not +formally declared, had fairly begun. He was appointed a member of the +second Continental Congress, and one of a committee of three to confer +with General Washington respecting the support and regulation of the +Continental Army. This latter office necessitated his spending some +time in the camp. On October 3, 1775, he wrote to Priestley:—</p> + +<blockquote> +<p>Tell our dear good friend, Dr. Price, who sometimes has his doubts +and despondencies about our firmness, that America is determined and +unanimous; a very few Tories and placemen excepted, who will probably +soon export themselves. Britain, at the expense of three millions, has +killed a hundred and fifty Yankees this campaign, which is £20,000 a +head; and at Bunker's Hill she gained a mile of ground, half of which +she lost again by our taking the post on Ploughed Hill. During the +same time sixty thousand children have been born in America. From +these <i>data</i> his mathematical head will easily calculate the time and +expense necessary to kill us all and conquer our whole territory.</p> +<p><span class="pagenum"><a id="Page_113">[113]</a></span></p> +</blockquote> + +<p>In 1776 Franklin, then seventy years old, was appointed one of three +Commissioners to visit Canada, in order, if possible, to promote a +union between it and the States. Finding that only one Canadian in +five hundred could read, and that the state of feeling in Canada was +fatal to the success of the Commissioners, they returned, and Franklin +suggested that the next Commission sent to Canada should consist of +schoolmasters. On the 4th of July Franklin took part in the signing of +the Declaration of Independence. When the document was about to be +signed, Mr. Hancock remarked, "We must be unanimous; there must be no +pulling different ways; we must all hang together." Franklin replied, +"Yes, we must indeed all hang together, or most assuredly we shall all +hang separately."</p> + +<p>In the autumn of 1776 Franklin was unanimously chosen a Special +Commissioner to the French Court. He took with him his two grandsons, +William Temple Franklin and Benjamin Franklin Bache, and leaving +Marcus Hook on October 28, crossed the Atlantic in a sloop of sixteen +guns. In Paris he met with an enthusiastic reception. M. de Chaumont +placed at his disposal his house at Passy, then about a mile from +Paris, but now within the city. Here he resided for nine years, being +a constant visitor at the French Court, and certainly one of the most +conspicuous figures in Paris. He was obliged to serve in many +capacities, and was very much burdened with work. Not only were there<span class="pagenum"><a id="Page_114">[114]</a></span> +his duties as Commissioner at the French Court, but he was also made +Admiralty Judge and Financial Agent, so that all the coupons for the +payment of interest on the money borrowed for the prosecution of the +war, as well as all financial negotiations, either with the French +Government or contractors, had to pass through his hands. Perhaps the +most unpleasant part of his work was his continued applications to the +French Court for monetary advances. The French Government, as is well +known, warmly espoused the cause of the Americans, and to the utmost +of its ability assisted them with money, material, and men. Franklin +was worried a good deal by applications from French officers for +introductions to General Washington, that they might obtain employment +in the American Army. At last he framed a model letter of +recommendation, which may be useful to many in this country in the +present day. It was as follows:—</p> + +<blockquote> +<p>"<span class="smcap">Sir</span>,</p> + +<p>The bearer of this, who is going to America, presses me to give him a +letter of recommendation, though I know nothing of him, not even his +name. This may seem extraordinary, but I assure you it is not uncommon +here. Sometimes, indeed, one unknown person brings another equally +unknown, to recommend him; and sometimes they recommend one another! +As to this gentleman, I must refer you to himself for his character +and merits, with which he is certainly<span class="pagenum"><a id="Page_115">[115]</a></span> better acquainted than I can +possibly be. I recommend him, however, to those civilities which every +stranger, of whom one knows no harm, has a right to; and I request you +will do him all the good offices and show him all the favour that, on +further acquaintance, you shall find him to deserve.</p> + +<p class="author">I have the honour to be, etc.</p> +</blockquote> + +<p>Captain Wickes, of the <i>Refusal</i>, having taken about a hundred British +seamen prisoners, Franklin and Silas Deane, one of the other +Commissioners, wrote to Lord Stormont, the British ambassador, +respecting an exchange. Receiving no answer, they wrote again, and +ventured to complain of the treatment which the American prisoners +were receiving in the English prisons, and in being compelled to fight +against their own countrymen. To this communication Lord Stormont +replied:—</p> + +<blockquote> +<p>The king's ambassador receives no applications from rebels, unless +they come to implore his Majesty's mercy.</p> +</blockquote> + +<p>To this the Commissioners rejoined:—</p> + +<blockquote> +<p>In answer to a letter, which concerns some of the most material +interests of humanity, and of the two nations, Great Britain and the +United States of America, now at war, we received the enclosed +<i>indecent</i> paper, as coming from your Lordship, which we return for +your Lordship's more mature consideration.</p> +</blockquote> + +<p>At first the British Government, regarding the<span class="pagenum"><a id="Page_116">[116]</a></span> Americans as rebels, +did not treat their prisoners as prisoners of war, but threatened to +try them for high treason. Their sufferings in the English prisons +were very great. Mr. David Hartley did much to relieve them, and +Franklin transmitted money for the purpose. When a treaty had been +formed between France and the States, and France had engaged in the +war, and when fortune began to turn in favour of the united armies, +the American prisoners received better treatment from the English +Government, and exchanges took place freely. In April, 1778, Mr. +Hartley visited Franklin at Passy, apparently for the purpose of +preventing, if possible, the offensive and defensive alliance between +America and France. Very many attempts were made to produce a rupture +between the French Government and the American Commissioners, but +Franklin insisted that no treaty of peace could be made between +England and America in which France was not included. In 1779 the +other Commissioners were recalled, and Franklin was made Minister +Plenipotentiary to the Court of France.</p> + +<p>In a letter to Mr. David Hartley, dated February 2, 1780, Franklin +showed something of the feelings of the Americans with respect to the +English at that time:—</p> + +<blockquote> +<p>You may have heard that accounts upon oath have been taken in +America, by order of Congress, of the British barbarities committed +there. It is expected of me to make a school-book of them,<span class="pagenum"><a id="Page_117">[117]</a></span> and to +have thirty-five prints designed here by good artists, and engraved, +each expressing one or more of the horrid facts, in order to impress +the minds of children and posterity with a deep sense of your bloody +and insatiable malice and wickedness. Every kindness I hear of done by +an Englishman to an American prisoner makes me resolve not to proceed +in the work.</p> +</blockquote> + +<p>While at Passy, Franklin addressed to the <i>Journal of Paris</i> a paper +on an economical project for diminishing the cost of light. The +proposal was to utilize the sunlight instead of candles, and thereby +save to the city of Paris the sum of 96,075,000 livres per annum. His +reputation in Paris is shown by the following quotation from a +contemporary writer:—</p> + +<blockquote> +<p>I do not often speak of Mr. Franklin, because the gazettes tell you +enough of him. However, I will say to you that our Parisians are no +more sensible in their attentions to him than they were towards +Voltaire, of whom they have not spoken since the day following his +death. Mr. Franklin is besieged, followed, admired, adored, wherever +he shows himself, with a fury, a fanaticism, capable no doubt of +flattering him and of doing him honour, but which at the same time +proves that we shall never be reasonable, and that the virtues and +better qualities of our nation will always be balanced by a levity, an +inconsequence, and an enthusiasm too excessive to be durable.</p> +</blockquote> + +<p>Franklin always advocated free trade, even in<span class="pagenum"><a id="Page_118">[118]</a></span> time of war. He was of +opinion that the merchant, the agriculturist, and the fisherman were +benefactors to mankind. He condemned privateering in every form, and +endeavoured to bring about an agreement between all the civilized +powers against the fitting out of privateers. He held that no +merchantmen should be interfered with unless carrying war material. He +greatly lamented the horrors of the war, but preferred anything to a +dishonourable peace. To Priestley he wrote:—</p> + +<blockquote> +<p>Perhaps as you grow older you may ... repent of having murdered in +mephitic air so many honest, harmless mice, and wish that, to prevent +mischief, you had used boys and girls instead of them. In what light +we are viewed by superior beings may be gathered from a piece of late +West India news, which possibly has not yet reached you. A young angel +of distinction, being sent down to this world on some business for the +first time, had an old courier-spirit assigned him as a guide. They +arrived over the seas of Martinico, in the middle of the long day of +obstinate fight between the fleets of Rodney and De Grasse. When, +through the clouds of smoke, he saw the fire of the guns, the decks +covered with mangled limbs and bodies dead or dying; the ships +sinking, burning, or blown into the air; and the quantity of pain, +misery, and destruction the crews yet alive were thus with so much +eagerness dealing round to one another,—he turned angrily to his +guide, and said, 'You blundering blockhead, you<span class="pagenum"><a id="Page_119">[119]</a></span> are ignorant of your +business; you undertook to conduct me to the earth, and you have +brought me into hell!' 'No, sir,' says the guide, 'I have made no +mistake; this is really the earth, and these are men. Devils never +treat one another in this cruel manner; they have more sense and more +of what men (vainly) call humanity.'</p> +</blockquote> + +<p>Franklin maintained that it would be far cheaper for a nation to +extend its possessions by purchase from other nations than to pay the +cost of war for the sake of conquest.</p> + +<p>Two British armies, under General Burgoyne and Lord Cornwallis, having +been wholly taken prisoners during the war, at last, after two years' +negotiations, a definitive treaty of peace was signed on September 3, +1782, between Great Britain and the United States, Franklin being one +of the Commissioners for the latter, and Mr. Hartley for the former. +On the same day a treaty of peace between Great Britain and France was +signed at Versailles. The United States Treaty was ratified by the +king on April 9, and therewith terminated the seven years' War of +Independence. Franklin celebrated the surrender of the armies of +Burgoyne and Cornwallis by a medal, on which the infant Hercules +appears strangling two serpents.</p> + +<p>When peace was at length realized, a scheme was proposed for an +hereditary knighthood of the order of Cincinnatus, to be bestowed upon +the American officers who had distinguished themselves<span class="pagenum"><a id="Page_120">[120]</a></span> in the war. +Franklin condemned the hereditary principle. He pointed out that, in +the ninth generation, the "young noble" would be only "one five +hundred and twelfth part of the present knight," 1022 men and women +being counted among his ancestors, reckoning only from the foundation +of the knighthood. "Posterity will have much reason to boast of the +noble blood of the then existing set of Chevaliers of Cincinnatus."</p> + +<p>On May 2, 1785, Franklin received from Congress permission to return +to America. He was then in his eightieth year. On July 12 he left +Passy for Havre, whence he crossed to Southampton, and there saw for +the last time his old friend, the Bishop of St. Asaph, and his family. +He reached his home in Philadelphia early in September, and the day +after his arrival he received a congratulatory address from the +Assembly of Pennsylvania. In the following month he was elected +President of the State, and was twice re-elected to the same office, +it being contrary to the constitution for any president to be elected +for more than three years in succession.</p> + +<p>The following extract from a letter, written most probably to Tom +Paine, is worthy of the attention of some writers:—</p> + +<blockquote> +<p>I have read your manuscript with some attention. By the argument it +contains against a particular Providence, though you allow a general +Providence, you strike at the foundations of all religion. For without +the belief of a Providence<span class="pagenum"><a id="Page_121">[121]</a></span> that takes cognizance of, guards, and +guides, and may favour particular persons, there is no motive to +worship a Deity, to fear His displeasure, or to pray for His +protection. I will not enter into any discussion of your principles, +though you seem to desire it. At present I shall only give you my +opinion, that, though your reasonings are subtle, and may prevail with +some readers, you will not succeed so as to change the general +sentiments of mankind on that subject, and the consequence of printing +this piece will be a great deal of odium drawn upon yourself, mischief +to you, and no benefit to others. He that spits against the wind spits +in his own face.</p> + +<p>But were you to succeed, do you imagine any good would be done by it? +You yourself may find it easy to live a virtuous life without the +assistance afforded by religion; you having a clear perception of the +advantages of virtue and the disadvantages of vice, and possessing +strength of resolution sufficient to enable you to resist common +temptations. But think how great a portion of mankind consists of weak +and ignorant men and women, and of inexperienced, inconsiderate youth +of both sexes, who have need of the motives of religion to restrain +them from vice, to support their virtue, and retain them in the +practice of it till it becomes <i>habitual</i>, which is the great point +for its security. And perhaps you are indebted to her originally, that +is, to your religious education, for the habits of virtue upon which +you now justly value yourself. You might<span class="pagenum"><a id="Page_122">[122]</a></span> easily display your +excellent talents of reasoning upon a less hazardous subject, and +thereby obtain a rank with our most distinguished authors. For among +us it is not necessary, as among the Hottentots, that a youth, to be +raised into the company of men, should prove his manhood by beating +his mother.</p> + +<p>I would advise you, therefore, not to attempt unchaining the tiger, +but to burn this piece before it is seen by any other person; whereby +you will save yourself a great deal of mortification by the enemies it +may raise against you, and perhaps a good deal of regret and +repentance. If men are so wicked <i>with religion</i>, what would they be +<i>if without</i> it? I intend this letter itself as a <i>proof</i> of my +friendship, and therefore add no <i>professions</i> to it; but subscribe +simply yours.</p> +</blockquote> + +<p>During the last few years of his life Franklin suffered from a painful +disease, which confined him to his bed and seriously interfered with +his literary work, preventing him from completing his biography. +During this time he was cared for by his daughter, Mrs. Bache, who +resided in the same house with him. He died on April 17, 1790, the +immediate cause of death being an affection of the lungs. He was +buried beside his wife in the cemetery of Christ Church, Philadelphia, +the marble slab upon the grave bearing no other inscription than the +name and date of death. In his early days (1728) he had written the +following epitaph for himself:<span class="pagenum"><a id="Page_123">[123]</a></span>—</p> + +<p class="h4 smcap">The Body</p> + +<p class="h4 smcap">of</p> + +<p class="h3">BENJAMIN FRANKLIN,</p> + +<p class="h4 smcap">Printer,<br /> +(like the cover of an old book,<br /> +its contents torn out<br /> +and stript of its lettering and gilding,)<br /> +lies here, food for worms.<br /> +but the work shall not be lost,<br /> +for it will (as he believed) appear once more<br /> +in a new and more elegant edition,<br /> +revised and corrected<br /> +by<br /> +THE AUTHOR. +</p> + +<p>When the news of his death reached the National Assembly of France, +Mirabeau rose and said:—</p> + +<p>"Franklin is dead!</p> + +<p>"The genius, which gave freedom to America, and scattered torrents of +light upon Europe, is returned to the bosom of the Divinity.</p> + +<p>"The sage, whom two worlds claim; the man, disputed by the history of +the sciences and the history of empires, holds, most undoubtedly, an +elevated rank among the human species.</p> + +<p>"Political cabinets have but too long notified the death of those who +were never great but in their funeral orations; the etiquette of +courts has but too long sanctioned hypocritical grief. Nations ought +only to mourn for their benefactors; the representatives of free men +ought never to recommend<span class="pagenum"><a id="Page_124">[124]</a></span> any other than the heroes of humanity to +their homage.</p> + +<p>"The Congress hath ordered a general mourning for one month throughout +the fourteen confederated States on account of the death of Franklin; +and America hath thus acquitted her tribute of admiration in behalf of +one of the fathers of her constitution.</p> + +<p>"Would it not be worthy of you, fellow-legislators, to unite +yourselves in this religious act, to participate in this homage +rendered in the face of the universe to the rights of man, and to the +philosopher who has so eminently propagated the conquest of them +throughout the world?</p> + +<p>"Antiquity would have elevated altars to that mortal who, for the +advantage of the human race, embracing both heaven and earth in his +vast and extensive mind, knew how to subdue thunder and tyranny.</p> + +<p>"Enlightened and free, Europe at least owes its remembrance and its +regret to one of the greatest men who has ever served the cause of +philosophy and liberty.</p> + +<p>"I propose, therefore, that a decree do now pass, enacting that the +National Assembly shall wear mourning during three days for Benjamin +Franklin."</p> + +<div class="figcenter"> +<img src="images/i134.jpg" width="188" height="50" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_125">[125]</a></span></p> + +<div class="figcenter"> +<img src="images/i135.jpg" width="466" height="99" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="HENRY_CAVENDISH">HENRY CAVENDISH.</h2> + +<p>It would not be easy to mention two men between whom there was a +greater contrast, both in respect of their characters and lives, than +that which existed between Benjamin Franklin and the Honourable Henry +Cavendish. The former of humble birth, but of great public spirit, +possessed social qualities which were on a par with his scientific +attainments, and toward the close of his life was more renowned as a +statesman than as a philosopher; the latter, a member of one of the +most noble families of England, and possessed of wealth far exceeding +his own capacity for the enjoyment of it, was known to very few, was +intimate with no one, and devoted himself to scientific pursuits +rather for the sake of the satisfaction which his results afforded to +himself than from any hope that they might be useful to mankind, or +from any desire to secure a reputation by making them known, and +passed a long life, the most uneventful that can be imagined.</p> + +<p>Though the records of his family may be<span class="pagenum"><a id="Page_126">[126]</a></span> traced to the Norman +Conquest, the famous Elizabeth Hardwicke, the foundress of two ducal +families and the builder of Hardwicke Hall and of Chatsworth as it was +before the erection of the present mansion, was the most remarkable +person in the genealogy. Her second son, William, was raised to the +peerage by James I., thus becoming Baron Cavendish, and was +subsequently created first Earl of Devonshire by the same monarch. His +great-grandson, the fourth earl, was created first Duke of Devonshire +by William III., to whom he had rendered valuable services. He was +succeeded by his eldest son in 1707, and the third son of the second +duke was Lord Charles Cavendish, the father of Henry and Frederick, of +whom Henry was the elder, having been born at Nice, October 13, 1731. +His mother died when he was two years old, and very little indeed is +known respecting his early life. In 1742 he entered Dr. Newcome's +school at Hackney, where he remained until he entered Peterhouse, in +1749. He remained at Cambridge until February, 1753, when he left the +university without taking his degree, objecting, most probably, to the +religious tests which were then required of all graduates. In this +respect his brother Frederick followed his example. On leaving +Cambridge Cavendish appears to have resided with his father in +Marlborough Street, and to have occasionally assisted him in his +scientific experiments, but the investigations of the son soon +eclipsed those of the father. It is said that the rooms allotted to<span class="pagenum"><a id="Page_127">[127]</a></span> +Henry Cavendish "were a set of stables, fitted up for his +accommodation," and here he carried out many of his experiments, +including all those electrical investigations in which he forestalled +so much of the work of the present century.</p> + +<p>During his father's life, or, at any rate, till within a few years of +its close, Henry Cavendish appears to have enjoyed a very narrow +income. He frequently dined at the Royal Society Club, and on these +occasions would come provided with the five shillings to be paid for +the dinner, but no more. Upon his father's death, which took place in +1783, when Henry was more than fifty years of age, his circumstances +were very much changed, but it seems that the greater part of his +wealth was left him by an uncle who had been an Indian officer, and +this legacy may have come into his possession before his father's +death. He appears to have been very liberal when it was suggested to +him that his assistance would be of service, but it never occurred to +him to offer a contribution towards any scientific or public +undertaking, and though at the time of his death he is said to have +had more money in the funds than any other person in the country, +besides a balance of £50,000 on his current account at his bank, and +various other property, he bequeathed none to scientific societies or +similar institutions. Throughout the latter part of his life he seems +to have been quite careless about money, and to have been satisfied if +he could only avoid the trouble of attending to his own financial +affairs. Hence he<span class="pagenum"><a id="Page_128">[128]</a></span> would allow enormous sums to accumulate at his +banker's, and on one occasion, being present at a christening, and +hearing that it was customary for guests to give something to the +nurse, he drew from his pocket a handful of guineas, and handed them +to her without counting them. After his father's death, Cavendish +resided in his own house on Clapham Common. Here a few rooms at the +top of the house were made habitable; the rest were filled with +apparatus of all descriptions, among which the most numerous examples +were thermometers of every kind. He seldom entertained visitors, but +when, on rare occasions, a guest had to be entertained, the repast +invariably consisted of a leg of mutton. His extreme shyness caused +him to dislike all kinds of company, and he had a special aversion to +being addressed by a stranger. On one occasion, at a reception given +by Sir Joseph Banks, Dr. Ingenhousz introduced to him a distinguished +Austrian philosopher, who professed that his main object in coming to +England was to obtain a sight of so distinguished a man. Cavendish +listened with his gaze fixed on the floor; then, observing a gap in +the crowd, he made a rush to the door, nor did he pause till he had +reached his carriage. His aversion to women was still greater; his +orders for the day he would write out and leave at a stated time on +the hall-table, where his house-keeper, at another stated time, would +find them. Servants were allowed access to the portion of the house +which he occupied only at fixed times when<span class="pagenum"><a id="Page_129">[129]</a></span> he was away; and having +once met a servant on the stairs, a back staircase was immediately +erected. His regular walk was down Nightingale Lane to Wandsworth +Common, and home by another route. On one occasion, as he was crossing +a stile, he saw that he was watched, and thenceforth he took his walks +in the evening, but never along the same road. There were only two +occasions on which it is recorded that scientific men were admitted to +Cavendish's laboratory. The first was in 1775, when Hunter, Priestley, +Romayne, Lane, and Nairne were invited to see the experiments with the +artificial torpedo. The second was when his experiment on the +formation of nitric acid by electric sparks in air had been +unsuccessfully attempted by Van Marum, Lavoisier, and Monge, and he +"thought it right to take some measures to authenticate the truth of +it."</p> + +<p>Besides his house at Clapham, Cavendish occupied (by his instruments) +a house in Bloomsbury, near the British Museum, while a "mansion" in +Dean Street, Soho, was set apart as a library. To this library a +number of persons were admitted, who could take out the books on +depositing a receipt for them. Cavendish was perfectly methodical in +all his actions, and whenever he borrowed one of his own books he duly +left the receipt in its place. The only relief to his solitary life +was afforded by the meetings of the Royal Society, of which he was +elected a Fellow in 1760; by the occasional receptions at the +residence of Sir Joseph Banks, P.R.S.;<span class="pagenum"><a id="Page_130">[130]</a></span> and by his not infrequent +dinners with the Royal Society Club at the Crown and Anchor; and he +may sometimes have joined the social gatherings of another club which +met at the Cat and Bagpipes, in Downing Street. It was to his visits +to the Royal Society Club that we are indebted for the only portrait +that exists of him. Alexander, the draughtsman to the China Embassy, +was bent upon procuring a portrait of Cavendish, and induced a friend +to invite him to the club dinner, "where he could easily succeed, by +taking his seat near the end of the table, from whence he could sketch +the peculiar great-coat of a greyish-green colour, and the remarkable +three-cornered hat, invariably worn by Cavendish, and obtain, +unobserved, such an outline of the face as, when inserted between the +hat and coat, would make, he was quite sure, a full-length portrait +that no one could mistake. It was so contrived, and every one who saw +it recognized it at once." Another incident is recorded of the Royal +Society Club which, perhaps, reflects as much credit upon Cavendish as +upon the Society. "One evening we observed a very pretty girl looking +out from an upper window on the opposite side of the street, watching +the philosophers at dinner. She attracted notice, and one by one we +got up and mustered round the window to admire the fair one. +Cavendish, who thought we were looking at the moon, hustled up to us +in his odd way, and when he saw the real object of our study, turned +away with intense disgust, and grunted out, 'Pshaw!'"</p><p><span class="pagenum"><a id="Page_131">[131]</a></span></p> + +<p>In the spring and autumn of 1785, 1786, 1787, and 1793, Cavendish made +tours through most of the southern, midland, and western counties, and +reached as far north as Whitby. The most memorable of these journeys +was that undertaken in 1785, since during its course he visited James +Watt at the Soho Works, and manifested great interest in Watt's +inventions. This was only two years after the great controversy as to +the discovery of the composition of water, but the meeting of the +philosophers was of the most friendly character. On all these journeys +considerable attention was paid to the geology of the country.</p> + +<p>Allusion has already been made to the two committees of the Royal +Society to which the questions of the lightning-conductors at +Purfleet, and of points <i>versus</i> knobs for the terminals of +conductors, were referred. Cavendish served on each of these +committees, and supported Franklin's view against the recommendation +of Mr. Wilson. On the first committee he probably came into personal +communication with Franklin himself.</p> + +<p>Cavendish's life consisted almost entirely of his philosophical +experiments. In other respects it was nearly without incident. He +appears to have been so constituted that he must subject everything to +accurate measurement. He rarely made experiments which were not +<i>quantitative</i>; and he may be regarded as the founder of "quantitative +philosophy." The labour which he expended over some of his +measurements must have been very great, and the<span class="pagenum"><a id="Page_132">[132]</a></span> accuracy of many of +his results is marvellous considering the appliances he had at +disposal. When he had satisfied himself with the result of an +experiment, he wrote out a full account and preserved it, but very +seldom gave it to the public, and when he did publish accounts of any +of his investigations it was usually a long time after the experiments +had been completed. One of the consequences of his reluctance to +publish anything was the long controversy on the discovery of the +composition of water, which was revived many years afterwards by +Arago's <i>éloge</i> on James Watt; but a much more serious result was the +loss to the world for so many years of discoveries and measurements +which had to be made over again by Faraday, Kohlrausch, and others. +The papers he published appeared in the <i>Philosophical Transactions of +the Royal Society</i>, to which he began to communicate them in 1766. On +March 25, 1803, he was elected one of the eight Foreign Associates of +the Institute of France. His <i>éloge</i> was pronounced by Cuvier, in +1812, who said, "His demeanour and the modest tone of his writings +procured him the uncommon distinction of never having his repose +disturbed either by jealousy or by criticism." Dr. Wilson says, "He +was almost passionless. All that needed for its apprehension more than +the pure intellect, or required the exercise of fancy, imagination, +affection, or faith, was distasteful to Cavendish. An intellectual +head thinking, a pair of wonderfully acute eyes observing, and a pair +of very skilful hands experimenting or<span class="pagenum"><a id="Page_133">[133]</a></span> recording, are all that I +realize in reading his memorials." He appeared to have no eye for +beauty; he cared nothing for natural scenery, and his apparatus, +provided it were efficient, might be clumsy in appearance and of the +cheapest materials; but he was extremely particular about accuracy of +construction in all essential details. He reminds us of one of our +foremost men of science, who, when his attention was directed to the +beautiful lantern tower of a cathedral, behind which the full moon was +shining, remarked, "I see form and colour, but I don't know what you +mean by beauty."</p> + +<p>The accounts of Cavendish's death differ to some extent in their +details, but otherwise are very similar. It appears that he requested +his servant, "as he had something particular to engage his thoughts, +and did not wish to be disturbed by any one," to leave him and not to +return until a certain hour. When the servant came back, at the time +appointed, he found his master dead. This was on February 24, 1810, +after an illness of only two or three days.</p> + +<p>It is mainly on account of his researches in electricity that the +biography of Cavendish finds a place in this volume. These +investigations took place between the years 1760 and 1783, and, as +already stated, were all conducted in the stables attached to his +father's house in Marlborough Street. It was by these experiments that +electricity was first brought within the domain of measurement, and +many of the numerical results<span class="pagenum"><a id="Page_134">[134]</a></span> obtained far exceeded in accuracy those +of any other observer until the instruments of Sir W. Thomson rendered +many electrical measurements a comparatively easy matter. The near +agreement of Cavendish's results with those of the best modern +electricians has made them a perpetual monument to the genius of their +author. It was at the request of Sir W. Thomson, Mr. Charles +Tomlinson, and others, that Cavendish's electrical researches might be +given to the public, that the Duke of Devonshire, in 1874, entrusted +the manuscripts to the care of the late Professor Clerk Maxwell. They +had previously been in the hands of Sir William Snow Harris, who +reported upon them, but after his death, in 1867, the report could not +be found. The papers, with an introduction and a number of very +valuable notes by the editor, were published by the Cambridge +University Press, just before the death of Clerk Maxwell, in 1879. Sir +W. Thomson quotes the following illustration of the accuracy of +Cavendish's work:—"I find already that the capacity of a disc was +determined experimentally by Cavendish as 1/1·57 of that of a sphere +of the same radius. Now we have capacity of disc = (2/π)<i>a</i> = +<i>a</i>/1·571!"</p> + +<p>Cavendish adopted Franklin's theory of electricity, treating it as an +incompressible fluid pervading all bodies, and admitting of +displacement only in a closed circuit, unless, indeed, the disturbance +might extend to infinity. This fluid he supposed, with Franklin, to be +self-repulsive, but to attract<span class="pagenum"><a id="Page_135">[135]</a></span> matter, while matter devoid of +electricity, and therefore in the highest possible condition of +negative electrification, he supposed, with Æpinus, to be, like +electricity, self-repulsive. One of Cavendish's earliest experiments +was the determination of the precise law according to which electrical +action varies with the distance between the charges. Franklin had +shown that there was no sensible amount of electricity on the interior +of a deep hollow vessel, however its exterior surface might be +charged. Cavendish mounted a sphere of 12·1 inches in diameter, so +that it could be completely enclosed (except where its insulating +support passed through) within two hemispheres of 13·3 inches +diameter, which were carried by hinged frames, and could thus be +allowed to close completely over the sphere, or opened and removed +altogether from its neighbourhood. A piece of wire passed through one +of the hemispheres so as to touch the inner sphere, but could be +removed at pleasure by means of a silk string. The hemispheres being +closed with the globe within them, and the wire inserted so as to make +communication between the inner and outer spheres, the whole apparatus +was electrified by a wire from a charged Leyden jar. This wire was +then removed by means of a silken string and "the same motion of the +hand which drew away the wire by which the hemispheres were +electrified, immediately after that was done, drew out the wire which +made the communication between the hemispheres and the inner globe, +and,<span class="pagenum"><a id="Page_136">[136]</a></span> immediately after that was drawn out, separated the hemispheres +from each other," and applied the electrometer to the inner globe. "It +was also contrived so that the electricity of the hemispheres and of +the wire by which they were electrified was discharged as soon as they +were separated from each other.... The inner globe and hemispheres +were also both coated with tinfoil to make them the more perfect +conductors of electricity." The electrometer consisted of a pair of +pith-balls; but, though the experiment was several times repeated, +they shewed no signs of electrification. From this it was clear that, +as there could have been no communication between the globe and +hemispheres when the connecting wire was withdrawn, there must have +been no electrification on the globe while the hemispheres, though +themselves highly charged, surrounded it. To test the delicacy of the +experiment, a charge was given to the globe less than one-sixtieth of +that previously given to the hemispheres, and this was readily +detected by the electrometer. From the result Cavendish inferred that +there is no reason to think the inner globe to be at all charged +during the experiment. "Hence it follows that the electric attraction +and repulsion must be inversely as the square of the distance, and +that, when a globe is positively electrified, the redundant fluid in +it is lodged entirely on its surface." This conclusion Cavendish +showed to be a mathematical consequence of the absence of +electrification from the inner sphere; for, were the law<span class="pagenum"><a id="Page_137">[137]</a></span> otherwise, +the inner sphere must be electrified positively or negatively, +according as the inverse power were higher or lower than the second, +and that the accuracy of the experiment showed the law must lie +between the 2 1/50 and the 1 49/50 power of the distance. With his +torsion-balance, Coulomb obtained the same law, but Cavendish's method +is much easier to carry out, and admits of much greater accuracy than +that of Coulomb. Cavendish's experiment was repeated by Dr. +MacAlister, under the superintendence of Clerk Maxwell, in the +Cavendish Laboratory, the absence of electrification being tested by +Thomson's quadrant electrometer, and it was shown that the deviation +from the law of inverse squares could not exceed one in 72,000.</p> + +<p>The distinction between <i>electrical charge</i> or <i>quantity of +electricity</i> and "<i>degree of electrification</i>" was first clearly made +by Cavendish. The latter phrase was subsequently replaced by +<i>intensity</i>, but <i>electric intensity</i> is now used in another sense. +Cavendish's phrase, <i>degree of electrification</i>, corresponds precisely +with our notion of electric <i>potential</i>, and is measured by the work +done on a unit of electricity by the electric forces in removing it +from the point in question to the earth or to infinity. Along with +this notion Cavendish introduced the further conception of the amount +of electricity required to raise a conductor to a given degree of +electrification, that is, the capacity of the conductor. In modern +language, the <i>capacity</i> of a conductor is<span class="pagenum"><a id="Page_138">[138]</a></span> defined as "the number of +units of electricity required to raise it to unit potential;" and this +definition is in precise accordance with the notion of Cavendish, who +may be regarded as the founder of the mathematical theory of +electricity. Finding that the capacities of similar conductors are +proportional to their linear dimensions, he adopted a sphere of one +inch diameter as the unit of capacity, and when he speaks of a +capacity of so many "inches of electricity," he means a capacity so +many times that of his one-inch sphere, or equal to that of a sphere +whose diameter is so many inches. The modern unit of capacity in the +electro-static system is that of a sphere of <i>one centimetre radius</i>, +and the capacity of any sphere is numerically equal to its radius +expressed in centimetres. Cavendish determined the capacities of +nearly all the pieces of apparatus he employed. For this purpose he +prepared plates of glass, coated on each side with circles of tinfoil, +and arranged in three sets of three, each plate of a set having the +same capacity, but each set having three times the capacity of the +preceding. There was also a tenth plate, having a capacity equal to +the whole of the largest set. The capacity of the ten plates was thus +sixty-six times that of one of the smallest set. With these as +standards of comparison, he measured the capacities of his other +apparatus, and, when possible, modified his conductors so as to make +them equal to one of his standards. His large Leyden battery he found +to have a capacity of about 321,000<span class="pagenum"><a id="Page_139">[139]</a></span> "inches of electricity," so that +it was equivalent to a sphere more than five miles in diameter. One of +his instruments employed in the measurement of capacities was a "trial +plate," consisting of a sheet of metal, with a second sheet which +could be made to slide upon it and to lie entirely on the top of the +larger plate, or to rest with any portion of its area extending over +the edge of the former. This was a conductor whose capacity could be +varied at will within certain limits. Finding the capacity of two +plates of tinfoil on glass much greater than his calculations led him +to expect, Cavendish compared them with two equal plates having air +between, and found their capacity very much to exceed that of the air +condenser. The same was the case, though in a less degree, with +condensers having shellac or bee's-wax for their dielectrics, and thus +Cavendish not only discovered the property to which Faraday afterwards +gave the name of "specific inductive capacity," but determined its +measure in these dielectrics. He also discovered that the apparent +capacity of a Leyden jar increases at first for some time after it has +been charged—a phenomenon connected with the so-called residual +charge of the Leyden jar. Another feature on which he laid some +stress, and which was brought to his notice by the comparison of his +coated panes, was the creeping of electricity over the surface of the +glass beyond the edge of the tinfoil, which had the same effect on the +capacity as an increase in the dimensions of the tinfoil. The +electricity appeared to<span class="pagenum"><a id="Page_140">[140]</a></span> spread to a distance of 0·07 inch all round +the tinfoil on glass plates whose thickness was 0·21 inch, and 0·09 +inch in the case of plates 0·08 inch thick.</p> + +<p>His paper on the torpedo was read before the Royal Society in 1776. +The experiments were undertaken in order to determine whether the +phenomena observed by Mr. John Walsh in connection with the torpedo +could be so far imitated by electricity as to justify the conclusion +that the shock of the torpedo is an electric discharge. For this +purpose Cavendish constructed a wooden torpedo with electrical organs, +consisting of a pewter plate on each side, covered with leather. The +plates were connected with a charged Leyden battery, by means of wires +carried in glass tubes, and thus the battery was discharged through +the water in which the torpedo was immersed, and which was rendered of +about the same degree of saltness as the sea. Cavendish compared the +shock given through the water with that given by the model fish in +air, and found the difference much greater than in the case of the +real torpedo, but, by increasing the capacity of the battery and +diminishing the potential to which it was charged, this discrepancy +was diminished, and it was found to be very much less in the case of a +second model having a leather, instead of a wooden, body, so that the +body of the fish itself offered less resistance to the discharge. One +of the chief difficulties lay in the fact that no one had succeeded in +obtaining<span class="pagenum"><a id="Page_141">[141]</a></span> a visible spark from the discharge of the torpedo, which +will not pass through the smallest thickness of air. Cavendish +accounted for this by supposing the quantity of electricity discharged +to be very great, and its potential very small, and showed that the +more the charge was increased and the potential diminished in his +model, the more closely did it imitate the behaviour of the torpedo.</p> + +<p>But the main interest in this paper lies in the indications which it +gives that Cavendish was aware of the laws which regulate the flow of +electricity through multiple conductors, and in the comparisons of +electrical resistance which are introduced. It had been formerly +believed that electricity would always select the shortest or best +path, and that the whole of the discharge would take place along that +route. Franklin seems to have assumed this in the passage quoted<a id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">[4]</a> +respecting the discharge of the lightning down the uninsulated +conductor instead of through the building. The truth, however, is +that, when a number of paths are open to an electric current, it will +divide itself between them in the inverse ratios of their resistances, +or directly as their conductivities, so that, however great the +resistance of one of the conductors, some portion, though it may be a +very small fraction, of the discharge will take place through it. But +this law does not hold in the case of insulators like the air, through +which electricity passes only by disruptive discharges, and which +completely prevent <span class="pagenum"><a id="Page_142">[142]</a></span>its passage unless the electro-motive force is +sufficient to break through their substance. In the case of the +lightning-conductor, however, its resistance is generally so small in +comparison with that of the building it is used to protect, that +Franklin's conclusion is practically correct.</p> + +<div class="footnote"><p><a id="Footnote_4_4"></a><a href="#FNanchor_4_4"> +<span class="label">[4]</span></a> Page <a href="#Page_96">96</a>.</p></div> + +<p>In his paper on the torpedo Cavendish stated that some experiments had +shown that iron wire conducted 400,000,000 times better than rain or +distilled water, sea-water 100 times, and saturated solution of +sea-salt about 720 times, better than rain-water. Maxwell pointed out +that this comparison of iron wire with sea-water would agree almost +precisely with the measurements of Matthiesen and Kohlrausch at 11°C. +The records of the experiments which led to these results were found +among Cavendish's unpublished papers, and the experiments also showed +that the conductivity of saline solutions was very nearly proportional +to the percentage of salt contained, when this was not very large—a +result also obtained long afterwards by Kohlrausch. In making these +measurements Cavendish was his own galvanometer. The solutions were +contained in glass tubes more than three feet long, and a wire +inserted to different distances into the solution; thus the discharge +could be made to pass through any length of the liquid column less +than that of the tube itself. From the Leyden battery of forty-nine +jars, six jars of nearly equal capacity were selected and charged +together, and the charge of one jar only was employed for<span class="pagenum"><a id="Page_143">[143]</a></span> each shock. +The discharge passed through the column of liquid contained in the +tube, from a wire inserted at the further end, until it reached the +sliding wire, when nearly the whole current betook itself to the wire +on account of its smaller resistance, and thence passed through the +galvanometer, which was Cavendish himself. Two tubes were generally +compared together, and the jars discharged alternately through the +tubes, and the tube which gave the greatest shock was assumed to +possess the least resistance. The wires were then adjusted till the +shocks were nearly equal, and positions determined which made the +first tube possess a greater and then a less resistance than the +second. From these positions the length of the column of liquid was +estimated which would make the resistances of the two tubes exactly +equal. But the result which has the greatest theoretical interest was +obtained by discharging the Leyden jars through wide and narrow tubes +containing the same solutions. By these experiments Cavendish found +that the resistances of the conductors were independent of the +strengths of the currents flowing in them; that is to say, he +established Ohm's law for electrolytes in a form which carried with it +its full explanation. This was in January, 1781. Ohm's law was first +formally stated in 1827. The physical fact which is expressed by it is +that the ratio of the electro-motive force to the current produced is +the same for the same conductor, otherwise under the same<span class="pagenum"><a id="Page_144">[144]</a></span> physical +conditions, however great or small that electro-motive force may be.</p> + +<p>Cavendish devoted considerable attention to the subject of heat, +especially thermometry. In many of his investigations on latent and +specific heat he worked on the same lines as Black, and at about the +same time; but it is difficult to determine the exact date of some of +Cavendish's work, as he frequently did not publish it for a long time +after its completion, and most of Black's results were made public +only to his lecture audience. Cavendish, however, improved upon Black +in his mode of stating some of his results. The heat, for instance, +which is absorbed by a body in passing from the solid to the liquid, +or from the liquid to the gaseous, condition, Black called "latent +heat," and supposed it to become latent within the substance, ready to +reveal itself when the body returned to its original condition. This +heat Cavendish spoke of as being <i>destroyed</i> or <i>generated</i>, and this +is in accordance with what we now know respecting the nature of heat, +for when a body passes from the solid to the liquid, or from the +liquid or solid to the gaseous, condition, a certain amount of work +has to be done, and a corresponding amount of heat is used up in the +doing of it. When the body returns to its original condition, the heat +is restored, as when a heavy body falls to the ground, or a bent +spring returns to its original form. Cavendish's determination of the +so-called latent heat of steam was very slightly in error.</p><p><span class="pagenum"><a id="Page_145">[145]</a></span></p> + +<p>About 1760 very extraordinary beliefs were current respecting the +excessive degree of cold and the rapid variations of temperature which +take place in the Arctic regions. Braun, of St. Petersburg, had +observed that mercury, in solidifying in the tube of a thermometer, +descended through more than four hundred degrees, and it was assumed +that the melting point of mercury was about 400° below Fahrenheit's +zero. It then became necessary to suppose that, while the mercury in a +thermometer was freezing, there was a variation of temperature to this +extent, and thus these wild reports became current. Cavendish and +Black independently explained the anomaly, and each suggested the same +method of determining the freezing point of mercury. Cavendish, +however, had a piece of apparatus prepared which he sent to Governor +Hutchins, at Albany Fort, Hudson's Bay. It consisted of an outer +vessel, in which the mercury was allowed to freeze, but not throughout +the whole of its mass, and the bulb of the thermometer was kept +immersed in the liquid metal in the interior. In this way the mercury +in the thermometer was cooled down to the melting point without +commencing to solidify, and the temperature was found to be between +39° and 40° below Fahrenheit's zero.</p> + +<p>As a chemist, Cavendish is renowned for his eudiometric analysis, +whereby he determined the percentage of oxygen in air with an amount +of accuracy that would be creditable to a chemist of to-day, and for +his discovery of the composition<span class="pagenum"><a id="Page_146">[146]</a></span> of water; but to the world generally +he is perhaps best known by the famous "Cavendish experiment" for +determining the mass, and hence the mean density, of the earth. The +apparatus was originally suggested by the Rev. John Michell, but was +first employed by Cavendish, who thereby determined the mean density +of the earth to be 5·45. At the request of the Astronomical Society, +the investigation was afterwards taken up by Mr. Francis Baily, who, +after much labour, discovered that the principal sources of error were +due to radiation of heat, and consequent variation of temperature of +parts of the apparatus during the experiment. To minimize the +radiation and absorption, he gilded the principal portions of the +apparatus and the interior of the case in which it was contained, and +his results then became consistent. Cavendish had himself suggested +the cause of the discrepancy, but the gilding was proposed by +Principal Forbes. As a mean of many hundreds of experiments, Mr. Baily +deduced for the mean density of the earth 5·6604. Cavendish's +apparatus was a delicate torsion-balance, whereby two leaden balls +were supported upon the extremities of a wooden rod, which was +suspended by a thin wire. These balls were about two inches in +diameter, and the experiment consisted in determining the deflection +of the wooden arm by the attraction of two large solid spheres of lead +brought very near the balls, and so situated that the attraction of +each tended to twist the rod horizontally in the same direction.<span class="pagenum"><a id="Page_147">[147]</a></span> The +force required to produce the observed deflection was calculated from +the time of swing of the rod and balls when left to themselves. The +force exerted upon either ball by a known spherical mass of metal, +with its centre at a known distance, being thus determined, it was +easy to calculate what mass, having its centre at the centre of the +earth, would be required to attract one of the balls with the force +with which the earth was known to attract it.</p> + +<p>Dr. Wilson sums up Cavendish's view of life in these words:—</p> + +<blockquote> +<p>His theory of the universe seems to have been that it consisted +<i>solely</i> of a multitude of objects which could be weighed, numbered, +and measured; and the vocation to which he considered himself called +was to weigh, number, and measure as many of these objects as his +allotted three score years and ten would permit. This conviction +biased all his doings—alike his great scientific enterprises and the +petty details of his daily life. +Πάντα +μέτρῳ, +καὶ +ἀριθμῷ, +καὶ +σταθμῷ +was his motto; and in the microcosm of his own nature +he tried to reflect and repeat the subjection to inflexible rule and +the necessitated harmony which are the appointed conditions of the +macrocosm of God's universe.</p> +</blockquote> + +<div class="figcenter"> +<img src="images/i157.jpg" width="197" height="66" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_148">[148]</a></span></p> + +<div class="figcenter"> +<img src="images/i158.jpg" width="478" height="103" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="COUNT_RUMFORD">COUNT RUMFORD.</h2> + +<p>Benjamin Thompson, like Franklin, was a native of Massachusetts, his +ancestors for several generations having been yeomen in that province, +and descendants of the first colonists of the Bay. In the diploma of +arms granted him when he was knighted by George III., he is described +as "son of Benjamin Thompson, late of the province of Massachusetts +Bay, in New England, gent." He was born in the house of his +grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26, +1753. His father died at the age of twenty-six, on November 7, 1754, +leaving the infant Benjamin and his mother to the care of the +grandparents. The widow married Josiah Pierce, junior, in March, 1756, +and with her child, now a boy of three, went to live in a house but a +short distance from her former residence.</p> + +<p>Young Thompson appears to have received a sound elementary education +at the village school. From some remarks made by him in after years<span class="pagenum"><a id="Page_149">[149]</a></span> +to his friend, M. Pictet, it has been inferred that he did not receive +very kind treatment at the hands of his stepfather. It is clear, +however, that the most affectionate relationships always obtained +between him and his mother, and the latter appears to have had no +cause to complain of the treatment she received from her second +husband, with whom she lived to a very good old age. That Thompson in +early boyhood developed some tendencies which did not meet with ready +sympathy from those around him is, however, equally clear. His +guardians destined him for a farmer, like his ancestors, and his +experiments in mechanics, which took up much of his playtime and in +all probability not a few hours which should have been devoted to less +interesting work, were not regarded as tending towards the end in +view. Hence he was probably looked upon as "indolent, flighty, and +unpromising." Later on he was sent to school in Byfield, and in 1764, +at the age of eleven, "was put under the tuition of Mr. Hill, an able +teacher in Medford, a town adjoining Woburn." At length, his friends +having given up all hope of ever making a farmer of the boy, he was +apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an +importer of British goods and dealer in miscellaneous articles. He +lived with his master, and seems to have done his work in a manner +satisfactory on the whole, but there is evidence that he would, during +business hours, occupy his spare moments with mechanical contrivances, +which he used to hide under the<span class="pagenum"><a id="Page_150">[150]</a></span> counter, and even ventured +occasionally to practise on his fiddle in the store. He stayed with +Mr. Appleton till the autumn of 1769, and during this time he attended +the ministry of the Rev. Thomas Barnard. This gentleman seems to have +taken great interest in the boy, and to have taught him mathematics, +so that at the age of fifteen he was able "to calculate an eclipse," +and was delighted when the eclipse commenced within six seconds of his +calculated time. Thompson, while an apprentice, showed a great faculty +for drawing and designing, and used to carve devices for his friends +on the handles of their knives or other implements. It was at this +time he constructed an elaborate contrivance to produce perpetual +motion, and on one evening it is said that he walked from Salem to +Woburn, to show it to Loammi Baldwin, who was nine years older than +himself, but his most intimate friend. Like many other devices +designed for the same purpose, it had only one fault—it wouldn't go.</p> + +<p>It was in 1769, while preparing fireworks for the illumination on the +abolition of the Stamp Act, that Thompson was injured by a severe +explosion as he was grinding his materials in a mortar. His note-book +contained many directions for the manufacture of fireworks.</p> + +<p>During Thompson's apprenticeship those questions were agitating the +public mind which finally had their outcome in the War of +Independence. Mr. Appleton was one of those who signed the agreement +refusing to import British goods, and<span class="pagenum"><a id="Page_151">[151]</a></span> this so affected the trade of +the store that he had no further need for the apprentice. Hence it was +that, in the autumn of 1769, Thompson went to Boston as +apprentice-clerk in a dry goods store, but had to leave after a few +months, through the depression in trade consequent on the +non-importation agreement.</p> + +<p>His note-book, containing the entries made at this time, comprised +several comic sketches very well drawn, and a quantity of business +memoranda which show that he was very systematic in keeping his +accounts. His chief method of earning money, or rather of making up +the "Cr." side of his accounts, was by cutting and cording wood. A +series of entries made in July and August, 1771, show the expense he +incurred in constructing an electrical machine. It is not easy to +determine, from the list of items purchased, the character of the +machine he constructed; but it is interesting to note that the price +in America at that time of nitric acid was <i>2s. 6d.</i> per ounce; of +lacquer, <i>40s.</i> per pint; of shellac, <i>5s.</i> per ounce; brass wire, +<i>40s.</i> per pound; and iron wire, <i>1s. 3d.</i> per yard. The nature of the +problems which occupied his thoughts during the last year or two of +his business life are apparent in the following letters:—</p> + +<blockquote> +<p class="right">Woburn, August 16, 1769.</p> +<p>Mr. Loammi Baldwin,<br /> +<br /> +<span class="smcap">Sir</span>, +</p> + +<p>Please to inform me in what manner fire operates upon clay to change +the colour from the<span class="pagenum"><a id="Page_152">[152]</a></span> natural colour to red, and from red to black, +etc.; and how it operates upon silver to change it to blue.</p> + +<p> +I am your most humble and obedient servant,</p> + +<p class="author smcap">Benjamin Thompson</p> + +<p>God save the king.</p> + +<p class="right"><br />Woburn, August, 1769.</p> + +<p>Mr. Loammi Baldwin,<br /> +<span class="smcap">Sir</span>,</p> + +<p>Please to give the nature, essence, beginning of existence, and rise +of the wind in general, with the whole theory thereof, so as to be +able to answer all questions relative thereto.</p> + +<p class="right2">Yours,</p> + +<p class="author smcap">Benjamin Thompson.</p> +</blockquote> + +<p>This was an extensive request, and the reply was probably not +altogether satisfactory to the inquirer. On the back of the above +letter was written:—</p> + +<blockquote> +<p>Woburn, August 15, 1769.</p> + +<p class="smcap">Sir</p> + +<p>There was but few beings (for inhabitants of this world) created +before the airy element was; so it has not been transmitted down to us +how the Great Creator formed the matter thereof. So I shall leave it +till I am asked only the Natural Cause, and why it blows so many ways +in so short a time as it does.</p> +</blockquote> + +<p>Thompson appears now to have given up business and commenced the study +of medicine under<span class="pagenum"><a id="Page_153">[153]</a></span> Dr. Hay, to whom for a year and a half he paid +forty shillings per week for his board. During this time he paid part +of his expenses by keeping school for a few weeks consecutively at +Wilmington and Bradford, and another part was paid by cords of wood. +His business capacity, as well as his dislike of ordinary work, is +shown by some arrangements which he made for getting wood cut and +corded at prices considerably below those at which he was himself paid +for it. His note-book made at this time contains, besides business +entries, several receipts for medicines and descriptions of surgical +operations, in some cases illustrated by sketches. In his work he was +methodical and industrious, and the life of a medical student suited +his genius far better than that of a clerk in a dry goods store. When +teaching at Wilmington he seems to have attracted attention by the +gymnastic performances with which he exercised both himself and his +pupils. While a student with Dr. Hay, he attended some of the +scientific lectures at Harvard College. The pleasure and profit which +he derived from these lectures are sufficiently indicated by the fact +that forty years afterwards he made the college his residuary legatee.</p> + +<p>Thompson won such a reputation as a teacher during the few weeks that +he taught in village schools in the course of his student life, that +he received an invitation from Colonel Timothy Walker to come to +Concord, in New Hampshire, on the Merrimack, and accept a permanent +situation<span class="pagenum"><a id="Page_154">[154]</a></span> in a higher grade school. It was from this place that he +afterwards took his title, for the early name of Concord was Rumford, +and the name was changed to Concord "to mark the restoration of +harmony after a long period of agitation as to its provincial +jurisdiction and its relation with its neighbours."</p> + +<p>The young schoolmaster of Concord was soon on very intimate terms with +the minister of the town, the Rev. Timothy Walker,<a id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a> a man who was so +much respected that he had thrice been sent to Britain on diplomatic +business. Mr. Walker's daughter had been married to Colonel Rolfe, a +man of wealth and position, and, with the exception of the Governor of +Portsmouth, said to have been the first man in New Hampshire to drive +a curricle and pair of horses. Thompson soon married—or, as he told +Pictet, was married to—the young widow. Whatever may have been +implied by this other way of putting the question, there is no doubt +that Thompson always had the greatest possible respect for his +father-in-law, and ever remembered him with sincere gratitude. The +fortunes of the gallant young schoolmaster now appeared to be made; +when the engagement was settled, the carriage and pair were brought +out again, and the youth was attired in his favourite scarlet as a man +of wealth and position. In this garb he drove to Woburn, and +introduced his future wife to his mother, whose surprise can be better +imagined than described.</p> + +<div class="footnote"><p><a id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> Father of the colonel.</p><p><span class="pagenum"><a id="Page_155">[155]</a></span></p></div> + +<p>The exact date of Thompson's marriage is not known. His daughter +Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion +on October 18, 1774. It is needless to say that the engagement to Mrs. +Rolfe terminated the teaching at the school.</p> + +<p>Thompson now had a large estate and ample means to improve it. He gave +much attention to gardening, and sent to England for garden seeds. In +some way he attracted the attention of Governor Wentworth, the +Governor of Portsmouth, who invited him to the Government House, and +was so taken with the former apprentice, medical student, and +schoolmaster, that he gave him at once a commission as major. This +appointment was the cause of the misfortunes which almost immediately +began to overtake him. He incurred the jealousy of his +fellow-officers, over whom he had been appointed, and he failed to +secure the confidence of the civilians of Concord.</p> + +<p>Public feeling in New England was very much excited against the mother +country. Representations were sent to the British Government, but +appeared to be treated with contempt. Very many of these documents +were found, after the war was over, unopened in drawers at the +Colonial Office. British ministers appeared to know little about the +needs of their American dependencies, and relations rapidly became +more and more strained. The patriots appointed committees to watch +over the patriotism of their fellow-townsmen, and thus the<span class="pagenum"><a id="Page_156">[156]</a></span> freedom of +a free country was inaugurated by an institution bordering in +character very closely upon the Inquisition; and the Committees of +Correspondence and Safety accepted evidence from every spy or +eavesdropper who came before them with reports of suspected persons. +Thompson was accused of "Toryism;" the only definite charge against +him being that he had secured remission of punishment for some +deserters from Boston who had for some time worked upon his estate. He +was summoned before the Committee of Safety, but refused to make any +confession of acts injurious to his country, on the ground that he had +nothing to confess. His whole after-life shows that his sympathies +were very much on the side of monarchy and centralization, but at this +time there appears to have been no evidence that could be brought +against him. The populace, however, stormed his house, and he owed his +safety to the fact that he had received notice of their intentions, +and had made his escape a few hours before. This was in November, +1774. Thompson then took refuge at Woburn, with his mother, but the +popular ill feeling troubled him here, so that his life was one of +great anxiety.</p> + +<p>While at Woburn, his wife and child joined him, and stayed there for +some months. At length he was arrested and confined in the town upon +suspicion of being inimical to the interests of his country. When he +was brought before the Committee of Inquiry, there was no evidence +brought against him. Major Thompson then petitioned to<span class="pagenum"><a id="Page_157">[157]</a></span> be heard +before the Committee of the Provincial Congress at Washington. This +petition he entrusted to his friend Colonel Baldwin to present. The +petition was referred by the committee to Congress, by whom it was +deferred for the sake of more pressing business. At length he secured +a hearing in his native town, but the result was indecisive, and he +did not obtain the public acquittal that he desired, though the +Committee of Correspondence found that the "said Thompson" had not "in +any one instance shown a disposition unfriendly to American liberty; +but that his general behaviour has evinced the direct contrary; and as +he has now given us the strongest assurances of his good intentions, +we recommend him to the friendship, confidence, and protection of all +good people in this and the neighbouring provinces." This decision, +however, does not appear to have been made public; and Thompson, on +his release, retired to Charlestown, near Boston. When the buildings +of Harvard College were converted into barracks, Major Thompson +assisted in the transfer of the books to Concord. It is said that, +after the battle of Charlestown, Thompson was introduced to General +Washington, and would probably have received a commission under him +but for the opposition of some of the New Hampshire officers. He +afterwards took refuge in Boston, and it does not appear that he ever +again saw his wife or her father. His daughter he did not see again +till 1796, when she was twenty-two years of age. On March 24,<span class="pagenum"><a id="Page_158">[158]</a></span> 1776, +General Washington obliged the British troops to evacuate Boston; +Thompson was the first official bearer of this intelligence to London. +Of course, his property at Concord was confiscated to the commonwealth +of Massachusetts, and he himself was proscribed in the Alienation Act +of New Hampshire, in 1778.</p> + +<p>When Thompson reached London with the intelligence of the evacuation +of Boston, Lord George Germaine, the Secretary for War, saw that he +could afford much information which would be of value to the +Government. An appointment was soon found for him in the Colonial +Office, and afterwards he was made Secretary of the Province of +Georgia, in which latter capacity, however, he had no duties to +fulfil. Throughout his career in the Colonial Office he remained on +very intimate terms with Lord George Germaine, and generally +breakfasted with him. In July, 1778, he was guest of Lord George at +Stoneland Lodge, and here, in company with Mr. Ball, the Rector of +Withyham, he undertook experiments "to determine the most advantageous +situation for the vent in firearms, and to measure the velocities of +bullets and the recoil under various circumstances."</p> + +<p>The results of these investigations procured for him the friendship of +Sir Joseph Banks, the President of the Royal Society, and Thompson was +not the man to lose opportunities for want of making use of them. In +1779 he was elected a Fellow of the Royal Society, "as a gentleman +well versed<span class="pagenum"><a id="Page_159">[159]</a></span> in natural knowledge and many branches of polite +learning." In the same year he went for a cruise in the <i>Victory</i> with +Sir Charles Hardy, in order to pursue his experiments on gunpowder +with heavy guns. Here he studied the principles of naval artillery, +and devised a new code of marine signals. In 1780 he was made +Under-Secretary of State for the Northern Department, and in that +capacity had the oversight of the transport and commissariat +arrangements for the British forces.</p> + +<p>On the defeat of Cornwallis, Lord George Germaine and his department +had to bear the brunt of Parliamentary dissatisfaction. Lord George +resigned his position in the Government, and was created Viscount +Sackville. He had, however, previously conferred on Thompson a +commission as lieutenant-colonel in the British army, and Thompson, +probably foreseeing the outcome of events and its effect on the +Ministry, was already in America when Lord George resigned. He had +intended landing at New York, but contrary winds drove him to +Charlestown. It is needless to trace the sad events which preceded the +end of the war. It was to be expected that many bitter statements +would be made by his countrymen respecting Thompson's own actions as +colonel commanding a British garrison, for at length he succeeded in +reaching Long Island, and taking the command of the King's American +Dragoons, who were there awaiting him. The spirit of war always acts +injuriously on those exposed to its<span class="pagenum"><a id="Page_160">[160]</a></span> influence, and Lieutenant-Colonel +Thompson in Long Island was doubtless a very different man from that +which we find him to have been before and after; nor were the months +so spent very fruitful in scientific work.</p> + +<p>In 1783, before the final disbanding of the British forces, Thompson +returned to England, and was promoted to the rank of colonel, with +half-pay for the rest of his life. Still anxious for military service, +he obtained permission to travel on the Continent, in hopes of serving +in the Austrian army against the Turks. He took with him three English +horses, which rendered themselves very objectionable to his +fellow-travellers while crossing the Channel in a small boat. Thompson +went to Strasbourg, where he attracted the attention of the Prince +Maximilian, then Field-Marshal of France, but afterwards Elector of +Bavaria. On leaving Strasbourg, the prince gave him an introduction to +his uncle, the Elector of Bavaria. He stayed some days at Munich, but +on reaching Vienna learned that the war against the Turks would not be +carried on, so he returned to Munich, and thence to England.</p> + +<p>M. Pictet gives the following as Rumford's account of the manner in +which he was cured of his passion for war:—</p> + +<p>"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I +was cured in season of this martial folly. I met, at the house of the +Prince de Kaunitz, a lady, aged seventy years, of<span class="pagenum"><a id="Page_161">[161]</a></span> infinite spirit and +full of information. She was the wife of General Bourghausen. The +emperor, Joseph II., came often to pass the evening with her. This +excellent person conceived a regard for me; she gave me the wisest +advice, made my ideas take a new direction, and opened my eyes to +other kinds of glory than that of victory in battle.'"</p> + +<p>If the course in life which Colonel Thompson afterwards took was due +to the advice of this lady, she deserves a European reputation. The +Elector of Bavaria, Charles Theodore, gave Thompson a pressing +invitation to enter his service in a sort of semi-military and +semi-civil capacity, to assist in reorganizing his dominions and +removing the abuses which had crept in. Before accepting this +appointment, it was necessary to obtain the permission of George III. +The king not only approved of the arrangement, but on February 23, +1784, conferred on the colonel the honour of knighthood. Sir Benjamin +then returned to Bavaria, and was appointed by the elector colonel of +a regiment of cavalry and general aide-de-camp. A palatial residence +in Munich was furnished for him, and here he lived more as a prince +than a soldier. It was eleven years before he returned, even on a +visit, to England, and these years were spent by him in works of +philanthropy and statesmanship, to which it is difficult to find a +parallel. At one time he is found reorganizing the military system of +the country, arranging a complete<span class="pagenum"><a id="Page_162">[162]</a></span> system of military police, erecting +arsenals at Mannheim and Munich; at another time he is carrying out +scientific investigations in one of these arsenals; and then he is +cooking cheap dinners for the poor of the country.</p> + +<p>One great evil of a standing army is the idleness which it develops in +its members, unfitting them for the business of life when their +military service is ended. Thompson commenced by attacking this evil. +In 1788 he was made major-general of cavalry and Privy Councillor of +State, and was put at the head of the War Department, with +instructions to carry out any schemes which he had developed for the +reform of the army and the removal of mendicity. Four years after his +arrival in Munich he began to put some of his plans into operation. +The pay of the soldiers was only threepence per day, and their +quarters extremely uncomfortable, while their drill and discipline +were unnecessarily irksome. Thompson set to work to make "soldiers +citizens and citizens soldiers." The soldier's pay, uniform, and +quarters were improved; the discipline rendered less irksome; and +schools in which the three R's were taught were connected with all the +regiments,—and here not only the soldiers, but their children as well +as other children, were taught gratuitously. Not only were the +soldiers employed in public works, and thus accustomed to habits of +industry, while they were enlivened in their work by the strains of +their own military bands, but they were supplied with raw material of +various kinds, and<span class="pagenum"><a id="Page_163">[163]</a></span> allowed, when not on duty, to manufacture various +articles and sell them for their own benefit—an arrangement which in +this country to-day would probably raise a storm of opposition from +the various trades. The garrisons were made permanent, so that +soldiers might all be near their homes and remain there, and in time +of peace only a small portion of the force was required to be in +garrison at any time, so that the great part of his life was spent by +each soldier at home. Each soldier had a small garden appropriated to +his use, and its produce was his sole property. Garden seeds, and +especially seed potatoes, were provided for the men, for at that time +the potato was almost unknown in Bavaria. Under these circumstances a +reform was quickly effected; idle men began to take interest in their +gardens, and all looked on Sir Benjamin as a benefactor.</p> + +<p>Having thus secured the co-operation of the army, Thompson determined +to attack the mendicants. The number of beggars may be estimated from +the fact that in Munich, with a population of sixty thousand, no less +than two thousand six hundred beggars were seized in a week. In the +towns, they possessed a complete organization, and positions of +advantage were assigned in regular order, or inherited according to +definite customs. In the country, farm labourers begged of travellers, +and children were brought up to beggary from their infancy. Of course, +the evils did not cease with simple begging. Children were stolen<span class="pagenum"><a id="Page_164">[164]</a></span> and +ill treated, for the purpose of assisting in enlisting sympathy, and +the people had come to regard these evils as inevitable. Thompson +organized a regular system of military patrol through every village of +the country, four regiments of cavalry being set apart for this work. +Then on January 1, 1790, when the beggars were out in full force to +keep their annual holiday, Thompson, with the other field officers and +the magistrates of the city, gave the signal, and all the beggars in +Munich were seized upon by the three regiments of infantry then in +garrison. The beggars were taken to the town hall, and their names and +addresses entered on lists prepared for the purpose. They were ordered +to present themselves next day at the "military workhouse," and a +committee was appointed to inquire into the condition of each, the +city being divided into sixteen districts for that purpose. Relieved +of an evil which they had regarded as inevitable, the townspeople +readily subscribed for the purpose of affording systematic relief, +while tradesmen sent articles of food and other requisites to "the +relief committee." In the military workhouse the former mendicants +made all the uniforms for the troops, besides a great deal of clothes +for sale in Bavaria and other countries. Thompson himself fitted up +and superintended the kitchen, where food was daily cooked for between +a thousand and fifteen hundred persons; and, under Sir Benjamin's +management, a dinner for a thousand was cooked at a cost for fuel of +fourpence<span class="pagenum"><a id="Page_165">[165]</a></span> halfpenny—a result which has scarcely been surpassed in +modern times, even at Gateshead.</p> + +<p>That Thompson's work was appreciated by those in whose interest it was +undertaken is shown by the fact that when, on one occasion, he was +dangerously ill, the poor of Munich went in public procession to the +cathedral to pray for him, though he was a foreigner and a Protestant. +Perhaps it may appear that his philanthropic work has little to do +with physical science; but with Thompson everything was a scientific +experiment, conducted in a truly scientific manner. For example, the +lighting of the military workhouse afforded matter for a long series +of experiments, described in his papers on photometry, coloured +shadows, etc. The investigations on the best methods of employing fuel +for culinary purposes led to some of his most elaborate essays; and +his essay on food was welcomed alike in London and Bavaria at a time +of great scarcity, and when famine seemed impending.</p> + +<p>The Emperor Joseph was succeeded by Leopold II., but during the +interregnum the Elector of Bavaria was Vicar of the Empire, and he +employed the power thus temporarily placed in his hands in raising Sir +Benjamin to the dignity of Count of the Holy Roman Empire, with the +order of the White Eagle, and the title which the new count selected +was the old name of the village in New England where he had spent the +two or three years of his wedded life.</p> + +<p>In 1795 Count Rumford returned to England,<span class="pagenum"><a id="Page_166">[166]</a></span> in order to publish his +essays, and to make known in this country something of the work in +which he had been engaged. Soon after his arrival he was robbed of +most of his manuscripts, the trunk containing them being stolen from +his carriage in St. Paul's Churchyard. On the invitation of Lord +Pelham, he visited Dublin, and carried out some of his improvements in +the hospitals and other institutions of that city. On his return to +London he fitted up the kitchen of the Foundling Hospital.</p> + +<p>Lady Thompson lived to hear of her husband's high position in Bavaria, +but died on January 29, 1792. When Rumford came to London in 1795, he +wrote to his daughter, who was then twenty-one years of age, to meet +him there, and on January 29, 1796, she started in the <i>Charlestown</i>, +from Boston. She remained with her father for more than three years, +and her autobiography gives much information respecting the count's +doings during this time.</p> + +<p>While in London, Count Rumford attained a high reputation as a curer +of smoky chimneys. One firm of builders found full employment in +carrying out work in accordance with his instructions; and in his +hotel at Pall Mall he conducted experiments on fireplaces. He +concluded that the sides of a fireplace ought to make an angle of 135° +with the back, so as to throw the heat straight to the front; and that +the width of the back should be one-third of that of the front +opening, and be carried up perpendicularly till it joins the breast. +The "Rumford<span class="pagenum"><a id="Page_167">[167]</a></span> roaster" gained a reputation not less than that earned +by his open fireplace.</p> + +<p>It was during this stay in London that Rumford presented to the Royal +Society of London, and to the American Academy of Sciences £1000 Three +per Cent. Stock, for the purpose of endowing a medal to be called the +Rumford Medal, and to be given each alternate year for the best work +done during the preceding two years in the subjects of heat and light. +He directed that two medals, one in gold and the other in silver, +should be struck from the same die, the value of the two together to +amount to £60. Whenever no award was made, the interest was to be +added to the principal, and the excess of the income for two years +over £60 was to be presented in cash to the recipient of the medal. At +present the amount thus presented is sufficient to pay the composition +fee for life membership of the Royal Society. The first award of the +medal was made in 1802, to Rumford himself. The other recipients have +been John Leslie, William Murdock, Étienne-Louis Malus, William +Charles Wells, Humphry Davy, David Brewster, Augustin Jean Fresnel, +Macedonio Melloni, James David Forbes, Jean Baptiste Biot, Henry Fox +Talbot, Michael Faraday, M. Regnault, F. J. D. Arago, George Gabriel +Stokes, Neil Arnott, M. Pasteur, M. Jamin, James Clerk Maxwell, +Kirchoff, John Tyndall, A. H. L. Fizeau, Balfour Stewart, A. O. des +Cloiseaux, A. J. Ångström, J. Norman Lockyer, P. J. C. Janssen, W. +Huggins, Captain Abney.</p><p><span class="pagenum"><a id="Page_168">[168]</a></span></p> + +<p>In the summer of 1796 Rumford and his daughter left England to return +to Munich. On account of the war, they were obliged to go by sea to +Hamburg; whence they drove to Munich, where the count was anxiously +expected, political troubles having compelled the elector to leave the +city. After the battle of Friedburg, the Austrians retired to Munich, +and, finding the gates of the city closed, they fortified themselves +on an eminence overlooking the city, and, through some +misunderstanding with the local authorities, the Austrian general +threatened to attack the city if any Frenchman should be allowed to +enter. Rumford took supreme command of the Bavarian forces, and so +gained the respect of the rival generals that neither the French nor +the Austrians made any attempt to enter the city. The large number of +soldiers now in Munich gave Rumford a good opportunity to exercise his +skill in cooking on a large scale, and this he did, adding to the +comfort of the soldiers and reducing the cost of the commissariat. On +the return of the elector, Miss Sarah was made a countess, and +one-half of her father's pension was secured to her, thus providing +her with an income of about £200 per annum for life. Many of the +details of the home life and social intercourse during this period of +residence at Munich are preserved in the autobiography of the +countess, as well as accounts of excursions, including a trip by river +to Salzburg for the purpose of inspecting the salt-mines. After two +years' stay in Munich, the count was appointed<span class="pagenum"><a id="Page_169">[169]</a></span> Minister +Plenipotentiary from Bavaria to the Court of Great Britain. After an +unpleasant and perilous journey, he reached London, <i>viâ</i> Hamburg, in +September, 1798, but was terribly disappointed on learning that a +British subject could not be accepted as an envoy from a Foreign +Power. As he did not then wish to return to Bavaria, he purchased a +house in Brompton Row. But he had been too much accustomed to great +enterprises to be content with a quiet life, and was bound to have +some important scheme on hand. Pressing invitations were sent him to +return to America, but he preferred residence in London, and devoted +himself to the foundation of the Royal Institution, though the +countess returned to the States in August, 1799. A letter from Colonel +Baldwin to her father shortly after her return contains the following +passage:—</p> + +<blockquote> +<p>In the cask of fruit which your daughter and Mr. Rolfe have sent you, +there is half a dozen apples of the growth of my farm, wrapped up in +papers, with the name of <i>Baldwin's apples</i> written upon them.... It +is (I believe) a spontaneous production of this country; that is, it +was not originally engrafted fruit.</p> +</blockquote> + +<p>The history of the remaining period of Rumford's residence in London +is the early history of the Royal Institution.</p> + +<p>For many years Rumford had had at his disposal for his philanthropic +projects all the resources of the electorate of Bavaria, and he had +done everything on a royal scale. His original plan for the<span class="pagenum"><a id="Page_170">[170]</a></span> Royal +Institution appears to embody to a very great extent the work of the +Science and Art Department, the City and Guilds Institute for the +Advancement of Technical Education, the National School of Cookery, +the London Society for the Extension of University Teaching, and, in +addition to all this, to have comprehended a sort of perpetual +International Health Exhibition, where every device for domestic +purposes, and especially for the improvement of the condition of the +poor, could be inspected. How all this was to be carried out with the +resources which the count expected to be able to devote to the +purpose, does not appear. Foremost among the objects of the +institution was placed the management of fire; for its promoter was +convinced that more than half the fuel consumed in the country might +be saved by proper arrangements.</p> + +<p>The philanthropic objects with which the institution was started are +apparent from the fact that it was the Society for Bettering the +Condition of the Poor which appointed a committee to confer with +Rumford, to report on the scheme, and to raise the funds necessary for +starting the project; and one of Rumford's hopes in connection with it +was "to make benevolence fashionable." It was arranged that donors of +fifty guineas each should be perpetual proprietors of the institution; +and that subscribers should be admitted at a subscription of two +guineas per annum, or ten guineas for life. The price of a +proprietor's share was<span class="pagenum"><a id="Page_171">[171]</a></span> raised to sixty guineas from May 1, 1800, and +afterwards increased by ten guineas per annum up to one hundred +guineas. In a very short time there were fifty-eight fifty-guinea +subscribers, and to them Rumford addressed a pamphlet, setting forth +his scheme in detail. The following are specified as some of the +contents of the future institution:—"Cottage fireplaces and kitchen +utensils for cottagers; a farm-house kitchen with its furnishings; a +complete kitchen, with its utensils, for the house of a gentleman of +fortune; a laundry, including boilers, washing, ironing, and drying +rooms, for a gentleman's house, or for a public hospital; the most +improved German, Swedish, and Russian stoves for heating rooms and +passages." As far as possible all these things were to be seen at +work. There were also to be ornamental open stoves with fires in them; +working models of steam-engines, of brewers' boilers, of distillers' +coppers and condensers, of large boilers for hospital kitchens, and of +ships' coppers with the requisite utensils; models of ventilating +apparatus, spinning-wheels and looms "adapted to the circumstances of +the poor;" models of agricultural machinery and bridges, and "of all +such other machines and useful instruments as the managers of the +institution shall deem worthy of public notice." All articles were to +be provided with proper descriptions, with the name and address of the +maker, and the price.</p> + +<p>A lecture-room and laboratory were to be fitted<span class="pagenum"><a id="Page_172">[172]</a></span> up with all necessary +philosophical apparatus, and the most eminent expounders of science +were to be engaged for the purpose of "teaching the application of +science to the useful purposes of life."</p> + +<p>The lectures were to include warming and ventilation, the preservation +of food, agricultural chemistry, the chemistry of digestion, of +tanning, of bleaching and dyeing, "and, in general, of all the +mechanical arts as they apply to the various branches of manufacture." +The institution was to be governed by nine managers, of whom three +were to be elected each year by the proprietors; and there was also to +be a committee of visitors, the members of which should not be the +managers. The king became patron of the institution, and the first set +of officers was nominated by him. The Earl of Winchelsea and +Nottingham was President; the Earls of Morton and of Egremont and Sir +Joseph Banks, Vice-Presidents; the Earls of Bessborough, of Egremont, +and of Morton, and Count Rumford, were among the Managers; the Duke of +Bridgewater, Viscount Palmerston, and Earl Spencer the Visitors; and +Dr. Thomas Garnett was appointed first Professor of Physics and +Chemistry. The royal charter of the institution was sealed on January +13, 1800. The superintendence of the journals of the institution was +entrusted to Rumford's care. For some time the count resided in the +house in Albemarle Street, which had been purchased by the +institution, and while there he superintended the workmen and +servants.</p><p><span class="pagenum"><a id="Page_173">[173]</a></span></p> + +<p>Dr. Thomas Garnett, the first professor at the institution, was highly +respected both as a man and a philosopher, and seems to have been +everywhere well spoken of. But Rumford and he could not work together, +and his connection with the institution was consequently a short one. +Rumford was then authorized to engage Dr. Young as Professor of +Natural Philosophy, editor of the journals, and general superintendent +of the house, at a salary of £300 per annum. Shortly before this the +count's attention had been directed to the experiments on heat, made +by Humphry Davy, and on February 16, 1801, it was "resolved that Mr. +Humphry Davy be engaged in the service of the Royal Institution, in +the capacity of Assistant-Lecturer in Chemistry, Director of the +Chemical Laboratory, and Assistant-Editor of the Journals of the +Institution; and that he be allowed to occupy a room in the house, and +be furnished with coals and candles, and that he be paid a salary of +one hundred guineas <i>per annum</i>." In his personal appearance, Davy is +said to have been at first somewhat uncouth, and the count was by no +means charmed with him at their first interview. It was not till he +had heard him lecture in private that Rumford would allow Davy to +lecture in the theatre of the institution; but he afterwards showed +his complete confidence in the young chemist by ordering that all the +resources of the institution should be at his service. Davy dined with +Rumford at the count's house in Auteuil,<span class="pagenum"><a id="Page_174">[174]</a></span> when he visited Paris with +Lady Davy and Faraday, in 1813. He commenced his duties at the +institution on March 11, 1801. It was on June 15, in the same year, +that the managers having objected to the syllabus of his lectures, Dr. +Garnett's resignation was accepted; and on July 6 Dr. Young was +appointed in his stead. Dr. Young resigned after holding the +appointment only two years, as he found the duties incompatible with +his work as a physician.</p> + +<p>Rumford's life in London now became daily more unpleasant to himself. +Accustomed, as he had been in Bavaria, to carry out all his projects +"like an emperor," it was difficult for him to work as one member of a +body of managers. One by one he quarrelled with his colleagues, and at +length left England, in May, 1802, never to return.</p> + +<p>When distinguished men of science are placed at the head of an +institution like that which Rumford founded, there is always a +tendency for the <i>technical</i> teaching of the establishment to become +gradually merged into scientific research; and in this case, after +Rumford's departure, the genius of Davy gradually converted the Royal +Institution into the establishment for scientific research which it +has been for more than three quarters of a century. Probably the man +who has come nearest to realizing all that Count Rumford had planned +for his institution is the late Sir Henry Cole; but he succeeded only +through the resources of the Treasury.</p><p><span class="pagenum"><a id="Page_175">[175]</a></span></p> + +<p>On leaving England in May, 1802, Rumford went to Paris, where he +stayed till July or August, when he revisited Bavaria and remained +there till the following year, when he returned to Paris. He was again +at Munich in 1805; but under the new elector, though an old friend of +the count, relationships do not seem to have been all that they were +with his uncle, and at length the elector himself was compelled to +leave Munich, and soon after the Bavarian sovereign became a vassal of +Napoleon. On October 24, 1805, Rumford married Madame Lavoisier, a +lady of brilliant talents and ample fortune. That his position might +be nearly equal to hers, the Elector of Bavaria raised his pension to +£1200 per annum. A house, Rue d'Anjou, No. 39, was purchased for six +thousand guineas, and Rumford expended much thought and energy in +making it, with its garden of two acres, all that he could desire. But +the union was not so happy as he anticipated. The count loved quiet; +Madame de Rumford was fond of company: to the former the pleasure of +the table had no charms; the latter took delight in sumptuous +dinner-parties. As time went on, domestic affairs became more and more +unpleasant, and at length a friendly separation was agreed upon, after +they had lived together for about three years and a half. The count +then retired to a small estate which he hired at Auteuil, about four +miles from Paris. The Elector of Bavaria was crowned king on January +1, 1806, and in 1810 Rumford was again at Munich, for the purpose of<span class="pagenum"><a id="Page_176">[176]</a></span> +forming, at the king's request, an Academy of Arts and Sciences. At +Auteuil the count was joined by his daughter in December, 1811, her +journey having been much delayed through the capture of the vessel in +which she had taken her passage, off Bordeaux. An engraving of the +house at Auteuil, and the room in which Rumford carried on his +experiments, was published in the <i>Illustrated London News</i> of January +22, 1870.</p> + +<p>While resident at Auteuil, Rumford frequently read papers before the +Institute of France, of which he was a member. He complained very much +of the jealousy exhibited by the other members with reference to any +discoveries made by a foreigner. He died in his house at Auteuil, on +August 21, 1814, in the sixty-second year of his age. In 1804 he had +made over, by deed of gift to his mother, the sum of ten thousand +dollars, that she might leave it by will to her younger children. As +before mentioned, Harvard College was his residuary legatee, and the +property so bequeathed founded the Rumford Professorship in that +institution.</p> + +<p>Cuvier, as Secretary of the Institute, pronounced the customary eulogy +over its late member. The following passages throw some light on the +reputation in which the count was held:—</p> + +<blockquote> +<p>He has constructed two singularly ingenious instruments of his own +contriving. One is a new calorimeter for measuring the amount of heat +produced by the combustion of any body. It is a receptacle containing +a given quantity of water,<span class="pagenum"><a id="Page_177">[177]</a></span> through which passes, by a serpentine +tube, the product of the combustion; and the heat that is generated is +transmitted through the water, which, being raised by a fixed number +of degrees, serves as the basis of the calculations. The manner in +which the exterior heat is prevented from affecting the experiment is +very simple and very ingenious. He begins the operation at a certain +number of degrees below the outside heat, and terminates it at the +same number of degrees above it. The external air takes back during +the second half of the experiment exactly what it gave up during the +first. The other instrument serves for noting the most trifling +differences in the temperature of bodies, or in the rapidity of its +changes. It consists of two glass bulbs filled with air, united by a +tube, in the middle of which is a pellet of coloured spirits of wine; +the slightest increase of heat in one of the bulbs drives the pellet +towards the other. This instrument, which he called a thermoscope, was +of especial service in making known to him the varied and powerful +influence of different surfaces in the transmission of heat, and also +for indicating a variety of methods for retarding or hastening at will +the processes of heating and freezing....</p> + +<p>He thought it was not wise or good to entrust to men, in the mass, +the care of their own well-being. The right, which seems so natural to +them, of judging whether they are wisely governed, appeared to him to +be a fictitious fancy born of<span class="pagenum"><a id="Page_178">[178]</a></span> false notions of enlightenment. His +views of slavery were nearly the same as those of a plantation-owner. +He regarded the government of China as coming nearest to perfection, +because, in giving over the people to the absolute control of their +only intelligent men, and in lifting each of those who belonged to +this hierarchy on the scale according to the degree of his +intelligence, it made, so to speak, so many millions of arms the +passive organs of the will of a few sound heads—a notion which I +state without pretending in the slightest degree to approve it, and +which, as we know, would be poorly calculated to find prevalence among +European nations.</p> + +<p>As for the rest, whatever were the sentiments of M. Rumford for men, +they in no way lessened his reverence for God. He never omitted any +opportunity in his works of expressing his religious admiration of +Providence, and of proposing for that admiration by others, the +innumerable and varied provisions which are made for the preservation +of all creatures; indeed, even his political views came from his firm +persuasion that princes ought to imitate Providence in this respect by +taking charge of us without being amenable to us.</p> +</blockquote> + +<p>In front of the new Government offices and the National Museum in the +Maximilian Strasse, in Munich, stand, on granite pedestals, four +bronze figures, ten feet in height. These represent General Deroy, +Fraunhofer, Schelling, and Count Rumford. The statue of Rumford was +erected in<span class="pagenum"><a id="Page_179">[179]</a></span> 1867, at the king's private expense. In the English garden +which Rumford planned and laid out is the monument erected during his +absence in England in 1796, and bearing allegorical figures of Peace +and Plenty, and a medallion of the count.</p> + +<p>The bare enumeration of Rumford's published papers would occupy +considerable space, but many of them have more to do with philanthropy +and domestic economy than with physics. We have seen that, when guest +of Lord George Germaine, he was engaged in experiments on gunpowder. +The experiments were made in the usual manner by firing bullets into a +ballistic pendulum, and recording the swing of the pendulum. Thompson +suggested a modification of the ballistic pendulum, attaching the +gun-barrel to the pendulum, and observing the recoil, and making +allowance for the recoil due to the discharge from the gun of the +products of combustion of the powder, the excess enabled the velocity +of the bullet to be calculated. Afterwards he made experiments on the +maximum pressure produced by the explosion of powder, and pointed out +that the value of powder in ordnance does not depend simply on the +whole amount of gas produced, but also on the rapidity of combustion. +While superintending the arsenal at Munich, Rumford exploded small +charges of powder in a specially constructed receiver, which was +closed by a plug of well-greased leather, and on this was placed a +hemisphere of steel pressed down by a 24-pounder brass cannon weighing +8081 pounds.<span class="pagenum"><a id="Page_180">[180]</a></span> He found that the weight of the gun was lifted by the +explosion of quantities of powder varying from twelve to fifteen +grains, and hence concluded that, if the products of combustion of the +powder were confined to the space actually occupied by the solid +powder, the initial pressure would exceed twenty thousand atmospheres. +Rumford's calculation of the pressure, based upon the bursting of a +barrel, which he had previously constructed, is not satisfactory, +inasmuch as he takes no account of the fact that the inner portions of +the metal would give way long before the outer layers exerted anything +like their maximum tension. When a hollow vessel with thick walls, +such as a gun-barrel or shell, is burst by gaseous pressure from +within, the inner layers of material are stretched to their breaking +tension before they receive much support from the outer layers; a rift +is thus made in the interior, into which the gas enters, and the +surface on which the gas presses being thus increased, the rift +deepens till the fracture is complete. In order to gain the full +strength due to the material employed, every portion of that material +should be stretched simultaneously to the extent of its maximum safe +load. This principle was first practically adopted by Sir W. G. +Armstrong, who, by building up the breech of the gun with cylinders +shrunk on, and so arranged that the tension increased towards the +exterior, availed himself of nearly the whole strength of the metal +employed to resist the explosion. Had Rumford's barrel been +constructed on this principle,<span class="pagenum"><a id="Page_181">[181]</a></span> he would have obtained a much more +satisfactory result.</p> + +<p>These investigations were followed by a very interesting series of +experiments on the conducting power of fluids for heat, and, although +he pushed his conclusions further than his experiments warranted, he +showed conclusively that convection currents are the principal means +by which heat is transferred through the substance of fluids, and +described how, when a vessel of water is heated, there is generally an +ascending current in the centre, and a descending current all round +the periphery. Hence it is only when a liquid expands by increase of +temperature that a large mass can be readily heated from below. Water +below 39° Fahr. contracts when heated. Rumford, in his paper, enlarges +on the bearing of this fact on the economy of the universe, and the +following extracts afford a good specimen of his style, and justify +some of the statements made by Cuvier in his eulogy:—</p> + +<blockquote> +<p>I feel the danger to which a mortal exposes himself who has the +temerity to undertake to explain the designs of Infinite Wisdom. The +enterprise is adventurous, but it cannot surely be improper.</p> + +<p>The wonderful simplicity of the means employed by the Creator of the +world to produce the changes of the seasons, with all the innumerable +advantages to the inhabitants of the earth which flow from them, +cannot fail to make a very deep and lasting impression on every human +being<span class="pagenum"><a id="Page_182">[182]</a></span> whose mind is not degraded and quite callous to every ingenuous +and noble sentiment; but the further we pursue our inquiries +respecting the constitution of the universe, and the more attentively +we examine the effects produced by the various modifications of the +active powers which we perceive, the more we shall be disposed to +admire, adore, and love that great First Cause which brought all +things into existence.</p> + +<p>Though winter and summer, spring and autumn, and all the variety of +the seasons are produced in a manner at the same time the most simple +and the most stupendous (by the inclination of the axis of the earth +to the plane of the ecliptic), yet this mechanical contrivance alone +would not have been sufficient (as I shall endeavour to show) to +produce that gradual change of temperature in the various climates +which we find to exist, and which doubtless is indispensably necessary +to the preservation of animal and vegetable life....</p> + +<p>But in very cold countries the ground is frozen and covered with +snow, and all the lakes and rivers are frozen over in the very +beginning of winter. The cold then first begins to be extreme, and +there appears to be no source of heat left which is sufficient to +moderate it in any sensible degree.</p> + +<p>Let us see what must have happened if things had been left to what +might be called their natural course—if the condensation of water, on +being deprived of its heat, had followed the law which we find obtains +in other fluids, and even in water itself<span class="pagenum"><a id="Page_183">[183]</a></span> in some cases, namely, when +it is mixed with certain bodies.</p> + +<p>Had not Providence interfered on this occasion in a manner which may +well be considered <i>miraculous</i>, all the fresh water within the polar +circle must inevitably have been frozen to a very great depth in one +winter, and every plant and tree destroyed; and it is more than +probable that the region of eternal frost would have spread on every +side from the poles, and, advancing towards the equator, would have +extended its dreary and solitary reign over a great part of what are +now the most fertile and most inhabited climates of the world!...</p> + +<p>Let us with becoming diffidence and awe endeavour to see what the +means are which have been employed by an almighty and benevolent God +to protect His fair creation.</p> +</blockquote> + +<p>He then goes on to explain how large bodies of water are prevented +from freezing at great depths on account of the expansion which takes +place on cooling below 39° Fahr., and the further expansion which +occurs on freezing, and mentions that in the Lake of Geneva, at a +depth of a thousand feet, M. Pictet found the temperature to be 40° +Fahr.</p> + +<p>"We cannot sufficiently admire the simplicity of the contrivance by +which all this heat is saved. It well deserves to be compared with +that by which the seasons are produced; and I must think that every +candid inquirer who will begin by divesting himself of all +unreasonable prejudice will agree<span class="pagenum"><a id="Page_184">[184]</a></span> with me in attributing them both <span class="smcap">to +the same Author</span>....</p> + +<p>"But I must take care not to tire my reader by pursuing these +speculations too far. If I have persisted in them, if I have dwelt on +them with peculiar satisfaction and complacency, it is because I think +them uncommonly interesting, and also because I conceived that they +might be of value in this age of <i>refinement</i> and <i>scepticism</i>.</p> + +<p>"If, among barbarous nations, the <i>fear of a God</i>, and the practice of +religious duties, tend to soften savage dispositions, and to prepare +the mind for all those sweet enjoyments which result from peace, +order, industry, and friendly intercourse; a <i>belief in the existence +of a Supreme Intelligence</i>, who rules and governs the universe with +wisdom and goodness, is not less essential to the happiness of those +who, by cultivating their mental powers, HAVE LEARNED TO KNOW HOW +LITTLE CAN BE KNOWN."</p> + +<p>Rumford, in connection with his experiments on the conducting power of +liquids, tried the effect of increasing the viscosity of water by the +addition of starch, and of impeding its movements by the introduction +of eider-down, on the rate of diffusion of heat through it. Hence he +explained the inequalities of temperature which may obtain in a mass +of thick soup—inequalities which had once caused him to burn his +mouth—and, applying the same principles to air, he at once turned his +conclusions to practical account in the matter of warm clothing.</p><p><span class="pagenum"><a id="Page_185">[185]</a></span></p> + +<p>After an attempt to determine, if possible, the weight of a definite +quantity of heat—an attempt in which very great precautions were +taken to exclude disturbing causes, while the balance employed was +capable of indicating one-millionth part of the weight of the body +weighed—Rumford, finding no sensible effect on the balance, concluded +that "if the weight of gold is neither augmented nor lessened by +<i>one-millionth part</i>, upon being heated from the point of <i>freezing +water</i> to that of a <i>bright red heat</i>, I think we may very safely +conclude that ALL ATTEMPTS TO DISCOVER ANY EFFECT OF HEAT UPON THE +APPARENT WEIGHTS OF BODIES WILL BE FRUITLESS." The theoretical +investigations of Principal Hicks, based on the vortex theory of +matter and the dynamical theory of heat, have recently led him to the +conclusion that the attraction of gravitation may depend to some +extent on temperature.</p> + +<p>A series of very valuable experiments on the radiating powers of +different surfaces showed how that power varied with the nature of the +surface, and the effect of a coating of lamp-black in increasing the +radiating power of a body. In order to determine the effect of +radiation in the cooling of bodies, Rumford employed the thermoscope +referred to by Cuvier. The following passage is worthy of attention, +as the truth it expounds in the last thirteen words appears to have +been but very imperfectly recognized many years after it was +written:<span class="pagenum"><a id="Page_186">[186]</a></span>—</p> + +<p>"All the heat which a hot body loses when it is exposed in the air to +cool is not given off to the air which comes into contact with it, but +... a large proportion of it escapes in rays, which do not heat the +transparent air through which they pass, but, like light, generate +heat only when and where they are stopped and absorbed."</p> + +<p>Rumford then investigated the absorption of heat by different +surfaces, and established the law that good radiators are good +absorbers; and recommended that vessels in which water is to be heated +should be blackened on the outside. In speculating on the use of the +colouring matter in the skin of the negro, he shows his fondness for +experiment:—</p> + +<p>"All I will venture to say on the subject is that, were I called to +inhabit a very hot country, nothing should prevent me from making the +experiment of blackening my skin, or at least, of wearing a black +shirt, in the shade, and especially at night, in order to find out if, +by those means, I could contrive to make myself more comfortable."</p> + +<p>In his experiments on the conduction of heat, Rumford employed a +cylinder with one end immersed in boiling water and the other in +melting ice, and determined the temperature at different points in the +length of the cylinder. He found the difficulty which has recently +been forcibly pointed out by Sir Wm. Thomson, in the article "Heat," +in the "Encyclopædia Britannica," viz. that the circulation of the +water was not sufficiently rapid<span class="pagenum"><a id="Page_187">[187]</a></span> to keep the temperature of the layer +in contact with the metal the same as that of the rest of the water; +and he also called attention to the arbitrary character of +thermometer-scales, and recommended that more attention should be +given to the scale of the air thermometer. It was in his visit to +Edinburgh, in 1800, that, in company with some of the university +professors, the count conducted some experiments in the university +laboratory on the apparent radiation of cold. Rumford's views +respecting <i>frigorific rays</i> have not been generally accepted, and +Prevost's theory of exchanges completely explains the apparent +radiation of cold without supposing that cold is anything else than +the mere absence of heat.</p> + +<p>We must pass over Rumford's papers on the use of steam as a vehicle of +heat, on new boilers and stoves for the purpose of economizing fuel, +and all the papers bearing on the nutritive value of different foods. +The calorimeter with which he determined the amount of heat generated +by the combustion, and the latent heat of evaporation, of various +bodies has been already alluded to. Of the four volumes of Rumford's +works published by the American Academy of Arts and Sciences, the +third is taken up entirely with descriptions of fireplaces and of +cooking utensils.</p> + +<p>Before deciding on the best way to light the military workhouse at +Munich, Rumford made a series of experiments on the relative economy +of different methods, and for this purpose designed<span class="pagenum"><a id="Page_188">[188]</a></span> his well-known +shadow-photometer. In the final form of this instrument the shadows +were thrown on a plate of ground glass covered with paper, forming the +back of a small box, from which all extraneous light was excluded. Two +rods were placed in front of this screen, and the lights to be +compared were so situated that the shadow of one rod thrown by the +first light might be just in contact with that of the other rod thrown +by the second light. By introducing coloured glasses in front of the +lights, Rumford compared the illuminating powers of different sources +with respect to light of a particular colour. The complementary tints +exhibited by the shadows caused him to devise his theory of the +harmony of complementary colours. One result is worthy of mention: it +is a conclusion to which public attention has since been called in +connection with "duplex" burners. Rumford found that with wax tapers +the amount of light emitted per grain of wax consumed diminished with +the diminution of the consumption, so that a small taper gave out only +one-sixteenth as much light as an ordinary candle for the same +consumption of wax. He says:—</p> + +<p>"This result can be easily explained if we admit the hypothesis which +supposes light to be analogous to sound.... The particles ... were so +rapidly cooled ... that they had hardly time to shine one instant +before they became too cold to be any longer visible."</p> + +<p>An argand lamp, when compared with a lamp<span class="pagenum"><a id="Page_189">[189]</a></span> having a flat wick, gave +more light in the ratio of 100 to 85 for the same consumption of oil.</p> + +<p>One of the latest investigations of Rumford was that bearing on the +effect of the width of the wheels on the draught of a carriage. To his +own carriage, weighing, with its passengers, nearly a ton, he fitted a +spring dynamometer by means of a set of pulleys attached to the +under-carriage and the splinter-bar. He used three sets of wheels, +respectively 1-3/4, 2-1/4, and 4 inches wide, and, introducing weights +into the carriage to make up for the difference in the weights of the +wheels, he found a very sensible diminution in the tractive force +required as the width of the wheels was increased, and in a truly +scientific spirit, despising the ridicule cast upon him, he persisted +in riding about Paris in a carriage with four-inch tyres.</p> + +<p>But the piece of work by which Rumford will be best known to future +generations is that described in his paper entitled "An Inquiry +concerning the Source of the Heat which is excited by Friction." It +was while superintending the boring of cannon in the arsenal at Munich +that Rumford was struck with the enormous amount of heat generated by +the friction of the boring-bar against the metal. In order to +determine whether the heat had come from the chips of metal +themselves, he took a quantity of the abraded borings and an equal +weight of chips cut from the metal with a fine saw, and, heating them +to the temperature of boiling water, he immersed them in equal +quantities of water at 59-1/2° Fahr. The<span class="pagenum"><a id="Page_190">[190]</a></span> change of temperature of the +water was the same in both cases, and Rumford found that there was no +change which he could discover <i>in regard to its capacity for heat</i> +produced in the metal by the action of the borer.</p> + +<p>In order to prevent the honeycombing of the castings by the escaping +gas, the cannon were cast in a vertical position with the breech at +the bottom of the mould and a short cylinder projecting about two feet +beyond the muzzle of the gun, so that any imperfections in the casting +would appear in this projecting cylinder. It was on one of these +pieces of waste metal, while still attached to the gun, that Rumford +conducted his experiments. Having turned the cylinder, he cut away the +metal in front of the muzzle until the projecting piece was connected +with the gun by a narrow cylindrical neck, 2·2 inches in diameter and +3·8 inches long. The external diameter of the cylinder was 7·75 +inches, and its length 9·8 inches, and it was bored to a depth of 7·2 +inches, the diameter of the bore being 3·7 inches. The cannon was +mounted in the boring-lathe, and a blunt borer pressed by a screw +against the bottom of the bore with a force equal to the weight of +10,000 pounds. A small transverse hole was made in the cylinder near +its base for the introduction of a thermometer. The cylinder weighed +113·13 pounds, and, with the gun, was turned at the rate of thirty-two +revolutions per minute by horse-power. To prevent loss of heat, the +cylinder was covered with flannel. After thirty minutes'<span class="pagenum"><a id="Page_191">[191]</a></span> work, the +thermometer, when introduced into the cylinder, showed a temperature +of 130° Fahr. The loss of heat during the experiment was estimated +from observations of the rate of cooling of the cylinder. The weight +of metal abraded was 837 grains, while the amount of heat produced was +sufficient to raise nearly five pounds of ice-cold water to the +boiling point.</p> + +<p>To exclude the action of the air, the cylinder was closed by an +air-tight piston, but no change was produced in the result. As the air +had access to the metal where it was rubbed by the piston, and Rumford +thought this might possibly affect the result, a deal box was +constructed, with slits at each end closed by sliding shutters, and so +arranged that it could be placed with the boring bar passing through +one slit and the narrow neck connecting the cylinder with the gun +through the other slit, the sliding shutters, with the help of collars +of oiled leather, serving to make the box water-tight. The box was +then filled with water and the lid placed on. After turning for an +hour the temperature was raised from 60° to 107° Fahr., after an hour +and a half it was 142° Fahr., at the end of two hours the temperature +was 178° Fahr., at two hours and twenty minutes it was 200° Fahr., and +at two hours and thirty minutes it ACTUALLY BOILED!</p> + +<p>"It would be difficult to describe the surprise and astonishment +expressed in the countenances of the bystanders on seeing so large a +quantity of cold<span class="pagenum"><a id="Page_192">[192]</a></span> water heated and actually made to boil without any +fire.</p> + +<p>"Though there was, in fact, nothing that could justly be considered as +surprising in this event, yet I acknowledge fairly that it afforded me +a degree of childish pleasure which, were I ambitious of the +reputation of a <i>grave philosopher</i>, I ought most certainly rather to +hide than to discover."</p> + +<p>Rumford estimated the "total quantity of ice-cold water which, with +the heat actually generated by the friction and accumulated in two +hours and thirty minutes, might have been heated 180 degrees, or made +to boil" at 26·58 pounds, and the rate of production he considered +exceeded that of nine wax candles, each consuming ninety-eight grains +of wax per hour, while the work of turning the lathe could easily have +been performed by one horse. This was the first rough attempt ever +made, so far as we know, to determine the mechanical equivalent of +heat.</p> + +<p>In his reflections on these experiments, Rumford writes:—</p> + +<blockquote> +<p>It is hardly necessary to add that anything which any <i>insulated</i> +body or system of bodies can continue to furnish <i>without limitation</i> +cannot possibly be <i>a material substance</i>; and it appears to me to be +extremely difficult, if not quite impossible, to form any distinct +idea of anything capable of being excited and communicated in the +manner the heat was excited and communicated in these experiments, +except it be MOTION.</p> +</blockquote> + +<p><span class="pagenum"><a id="Page_193">[193]</a></span></p> + +<p>It has been stated that, if Rumford had dissolved in acid the borings +and the sawn strips of metal, the capacity for heat of which he +determined, and had shown that the heat developed in the solution was +the same in the two cases, his chain of argument would have been +absolutely complete. Considering the amount of heat produced in the +experiments, there are few minds whose conviction would be +strengthened by this experiment, and it is only those who look for +faultless logic that will refuse to Rumford the credit of having +established the dynamical nature of heat.</p> + +<p>Davy afterwards showed that two pieces of ice could be melted by being +rubbed against one another in a vacuum, but he does not appear to have +made as much as he might of the experiment. Mayer calculated the +mechanical equivalent of heat from the heat developed in the +compression of air, but he <i>assumed</i>, what afterwards was shown by +Joule to be nearly true, that the whole of the work done in the +compression was converted into heat. It was Joule, however, who first +showed that heat and mechanical energy are mutually convertible, so +that each may be expressed in terms of the other, a <i>given</i> quantity +of heat always corresponding to the <i>same amount</i> of mechanical +energy, whatever may be the intermediate stages through which it +passes, and that we may therefore define the mechanical equivalent of +heat as <i>the number of units of energy which, when entirely converted +into heat, will raise unit mass of water one degree from the freezing +point</i>.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_194">[194]</a></span></p> + +<div class="figcenter"> +<img src="images/i204.jpg" width="476" height="103" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="THOMAS_YOUNG">THOMAS YOUNG.</h2> + +<p>"We here meet with a man altogether beyond the common standard, one in +whom natural endowment and sedulous cultivation rivalled each other in +the production of a true philosopher; nor do we hesitate to state our +belief that, since Newton, Thomas Young stands unrivalled in the +annals of British science." Such was the verdict of Principal Forbes +on one who may not only be regarded as one of the founders of the +undulatory theory of light, but who was among the first to apply the +theory of elasticity to the strength of structures, while it is to him +that we are indebted in the first instance for all we know of Egyptian +hieroglyphics, and for the vast field of antiquarian research which +the interpretation of these symbols has opened up.</p> + +<p>Thomas Young was the son of Thomas and Sarah Young, and the eldest of +ten children. His mother was a niece of the well-known physician, Dr. +Richard Brocklesby, and both his father and mother were<span class="pagenum"><a id="Page_195">[195]</a></span> members of +the Society of Friends, in whose principles all their children were +very carefully trained. It was to the independence of character thus +developed that Dr. Young attributed very much of the success which he +afterwards attained. He was born at Milverton, in Somersetshire, on +June 13, 1773. For the greater part of the first seven years of his +life he lived with his maternal grandfather, Mr. Robert Davis, at +Minehead, in Somersetshire. According to his own account, he could +read with considerable fluency at the age of <i>two</i>, and, under the +instructions of his aunt and a village schoolmistress, he had "read +the Bible twice through, and also Watts's Hymns," before he attained +the age of four. It may with reason be thought that both the +schoolmistress and the aunt should have been severely reprimanded, and +it is certain that their example is not to be commended; but Young's +infantile constitution seems to have been proof against over-pressure, +and before he was five years old he could recite the whole of +Goldsmith's "Deserted Village," with scarcely a mistake. He commenced +learning Latin before he was six, under the guidance of a +Nonconformist minister, who also taught him to write. When not quite +seven years of age he went to boarding-school, where he remained a +year and a half; but he appears to have learned more by independent +effort than under the guidance of his master, for privately he "had +mastered the last rules of Walkinghame's 'Tutor's Assistant'" before +reaching the middle of the book<span class="pagenum"><a id="Page_196">[196]</a></span> under the master's inspection. After +leaving this school, he lived at home for six months, but frequently +visited a neighbour who was a land surveyor, and at whose house he +amused himself with philosophical instruments and scientific books, +especially a "Dictionary of Arts and Sciences." When nearly nine he +went to the school of Mr. Thompson, at Compton, in Dorsetshire, where +he remained nearly four years, and read several Greek and Latin +authors, as well as the elements of natural philosophy—the latter in +books lent him by Mr. Jeffrey, the assistant-master. This Mr. Jeffrey +appears to have been something of a mechanical genius, and he gave +Young lessons in turning, drawing, bookbinding, and the grinding and +preparation of colours. Before leaving this school, at the age of +thirteen, Young had read six chapters of the Hebrew Bible.</p> + +<p>During the school holidays the construction of a microscope occupied +considerable time, and the reading of "Priestley on Air" turned +Young's attention to the subject of chemistry. Having learned a little +French, he succeeded, with the help of a schoolfellow, in gaining an +elementary knowledge of Italian. After leaving school, he lived at +home for some time, and devoted his energies mainly to Hebrew and to +turning and telescope-making; but Eastern languages received a share +of attention, and by the time he was fourteen he had read most of Sir +William Jones's "Persian Grammar." He then went to Youngsbury, in +Hertfordshire, and resided at the house of Mr. David Barclay, partly +as companion<span class="pagenum"><a id="Page_197">[197]</a></span> and partly as classical tutor to Mr. Barclay's grandson, +Hudson Gurney. This was the beginning of a friendship which lasted for +life. Gurney was about a year and a half junior to Young, and for five +years the boys studied together, reading the classical works which +Young had previously studied at school. Before the end of these five +years Young had gained more or less acquaintance with fourteen +languages; but his studies were for a time delayed through a serious +illness when he was little more than sixteen. To this illness his +uncle, Dr. Brocklesby, referred in a letter, of which the following +extract is interesting for several reasons:—</p> + +<blockquote> +<p>Recollect that the least slip (as who can be secure against error?) +would in you, who seem in all things to set yourself above ordinary +humanity, seem more monstrous or reprehensible than it might be in the +generality of mankind. Your prudery about abstaining from the use of +sugar on account of the negro trade, in any one else would be +altogether ridiculous, but as long as the whole of your mind keeps +free from spiritual pride or too much presumption in your facility of +acquiring language, which is no more than the dross of knowledge, you +may be indulged in such whims, till your mind becomes enlightened with +more reason. My late excellent friend, Mr. Day, the author of +'Sandford and Merton,' abhorred the base traffic in negroes' lives as +much as you can do, and even Mr. Granville Sharp, one of the earliest +writers on the subject, has not done half as much service in the +business<span class="pagenum"><a id="Page_198">[198]</a></span> as Mr. Day in the above work. And yet Mr. Day devoured daily +as much sugar as I do; for he reasonably concluded that so great a +system as the sugar-culture in the West Indies, where sixty millions +of British property are employed, could never be affected either way +by one or one hundred in the nation debarring themselves the +reasonable use of it. Reformation must take its rise elsewhere, if +ever there is a general mass of public virtue sufficient to resist +such private interests. Read Locke with care, for he opens the avenues +of knowledge, though he gives too little himself.</p> +</blockquote> + +<p>With respect to the sugar, no doubt very much may be said on Young's +side of the question. It appears, however, that in his early manhood +there was a good deal in his conduct which to-day would be regarded as +<i>priggish</i>, though it was somewhat more in harmony with the spirit of +his time.</p> + +<p>He left Youngsbury at the age of nineteen, having read, besides his +classical authors, the whole of Newton's "Principia" and "Opticks," +and the systems of chemistry by Lavoisier and Nicholson, besides works +on botany, medicine, mineralogy, and other scientific subjects. One of +Young's peculiarities was the extraordinary neatness of his +handwriting, and a translation in Greek iambics of Wolsey's farewell +to Cromwell, which he sent, written very neatly on vellum, to his +uncle, Dr. Brocklesby, attracted the attention of Mr. Burke, Dr. +Charles Burney, and other classical scholars, so that when, a few +months later, Young went to stay<span class="pagenum"><a id="Page_199">[199]</a></span> with his uncle in London, and was +thrown into contact with some of the chief literary men of the day, he +found that his fame as a scholar had preceded him. This neatness of +his handwriting and his power of drawing were of great use in his +researches on the Egyptian hieroglyphics. He had little faith in +natural genius, but believed that anything could be accomplished by +persevering application.</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"Thou say'st not only skill is gained,<br /></span> +<span class="i0">But genius too may be obtained,<br /></span> +<span class="i2">By studious imitation."<br /></span> +</div></div> + +<p>In the autumn of 1792 Young went to London for the purpose of studying +medicine. He lived in lodgings in Westminster, and attended the +Hunterian School of Anatomy. A year afterwards he entered St. +Bartholomew's Hospital as a medical student. The notes which he took +of the lectures were written sometimes in Latin, interspersed with +Greek quotations, and not unfrequently with mathematical calculations, +which may be assumed to have been made before the lecture commenced. +During his school days he had paid some attention to geometrical +optics, and had constructed a microscope and telescope. Now his +attention was attracted to a far more delicate instrument—the eye +itself. Young had learned how a telescope can be "focussed" so as to +give clear images of objects more or less distant. Some such power of +adjustment must be possessed by the eye, or it could never form +distinct<span class="pagenum"><a id="Page_200">[200]</a></span> images of objects, whether at a distance of a foot or a +mile. The apparently fibrous structure of the crystalline lens of the +eye had been noticed and described by Leuwenhoeck; and Pemberton, a +century before Young took up the subject, had suggested that the +fibres were muscles, by the action of which the eye was "accommodated" +for near or distant vision. In dissecting the eye of an ox Young +thought he had discovered evidence confirmatory of this view, and the +paper which he wrote on the subject was not only published in the +"Philosophical Transactions," but secured his election as a Fellow of +the Royal Society in June, 1794. This paper was important, not simply +because it led to Young's election to the Royal Society, but mainly +because it was his first published paper on optical subjects. Later on +he showed incontestably, by exact measurements, that it is the +crystalline lens which changes its form during adjustment; but he was +wrong in supposing the fibres of the lens to be muscular. By carefully +measuring the distance between the images of two candles formed by +reflection from the cornea, he showed that the cornea experienced no +change of form. His eyes were very prominent; and turning them so as +to look very obliquely, he measured the length of the eye from back to +front with a pair of compasses whose points were protected, pressing +one point against the cornea, and the other between the back of the +eye and the orbit, and showed that, when the eye was focussed for +different distances, there was<span class="pagenum"><a id="Page_201">[201]</a></span> no change in the length of the axis. +The crystalline lens was the only resource left whereby the +accommodation could be effected. The accommodation is, in fact, +brought about by the action of the ciliary muscle. The natural form of +the lens is more convex than is consistent with distinct vision, +except for very near objects. The tension of the suspensory ligament, +which is attached to the front of the lens all round its edge, renders +the anterior surface of the lens much less curved than it would +naturally be. The ciliary muscle is a ring of muscular fibre attached +to the ciliary process close to the circumference of the suspensory +ligament. By its contraction it forms a smaller ring, and, diminishing +the external diameter, it releases the tension of the suspensory +ligament, thus allowing the crystalline lens to bulge out and adapt +itself for the diverging rays coming from near objects. It is the +exertion of contracting the ciliary muscle that constitutes the effort +of which we are conscious when looking at very near objects. It was +not, however, till long after the time of Dr. Young that this +complicated action was fully made out, though the change of form of +the anterior surface of the crystalline lens was discovered by the +change in the image of a bright object formed by reflection.</p> + +<p>In the spring of 1794 Young took a holiday tour in Cornwall, with +Hudson Gurney, visiting on his way the Duke of Richmond, who was +drinking the waters at Bath, under the advice of Dr. Brocklesby. In +Cornwall, the mining machinery attracted his<span class="pagenum"><a id="Page_202">[202]</a></span> attention very much more +than the natural beauties of the country. Towards the end of the +summer he visited the Duke of Richmond at Goodwood, when the duke +offered him the appointment of private secretary. He resolved, +however, to continue his medical course, one of the reasons which he +alleged being his regard for the Society of Friends, whose principles +he considered inconsistent with the appointment of Private Secretary +to the Master-General of the Ordnance.</p> + +<p>The following winter he spent as a medical student at Edinburgh. Here +he gave up the costume of the Society of Friends, and in many ways +departed from their rules of conduct. He mingled freely with the +university, attended the theatre, took lessons in dancing and playing +the flute, and generally cultivated the habits of what is technically +known as "society." Throughout this change in his life he retained his +high moral principles as a guide of conduct, and appears to have acted +from a firm conviction of what was right. At the same time, it must be +admitted that the breaking down of barriers, however conventional they +may be, is an operation attended in most cases by not a little danger. +With Young, the progress of his scientific education may have been +delayed on account of the new demands on his time; but besides the +study of German, Spanish, and Italian, he appears to have read a +considerable amount of general literature during his winter session in +Edinburgh. The following summer he took a tour on horseback<span class="pagenum"><a id="Page_203">[203]</a></span> through +the Highlands, taking with him his flute, drawing materials, spirits +for preserving insects, boards for drying plants, paper and twine for +packing up minerals, and a thermometer; but the geological hammer does +not then appear to have been regarded as an essential to the equipment +of a philosopher. At Aberdeen he stayed for three days, and reported +thus on the university:—</p> + +<blockquote> +<p>Some of the professors are capable of raising a university to +celebrity, especially Copeland and Ogilvie; but the division and +proximity of the two universities (King's College and Marischal +College) is not favourable to the advancement of learning; besides, +the lectures are all, or mostly, given at the same hour, and the same +professor continues to instruct a class for four years in the +different branches. Were the colleges united, and the internal +regulations of the system new modelled, the cheapness of the place, +the number of small bursaries for poor or distinguished students, and +the merit of the instructors, might make this university a very +respectable seminary in some branches of science. The fee to a +professor for a five-months' session is only a guinea and a half. I +was delighted with the inspection of the rich store of mathematical +and philosophical apparatus belonging to Professor Copeland of +Marischal College, made in his own house, and partly with his own +hands, finished with no less care than elegance; and tending to +illustrate every branch of physics in the course of his<span class="pagenum"><a id="Page_204">[204]</a></span> lectures, +which must be equally entertaining and instructive.</p> +</blockquote> + +<p>Before leaving the Highlands, Young visited Gordon Castle, where he +stayed two days; and appears to have distinguished himself by the +powers of endurance he exhibited in dancing reels. On leaving he +writes: "I could almost have wished to break or dislocate a limb by +chance, that I might be detained against my will; I do not recollect +that I have ever passed my time more agreeably, or with a party that I +thought more congenial to my own dispositions: and what would hardly +be credited by many grave reasoners on life and manners, that a person +who had spent the whole of his earlier years a recluse from the gay +world, and a total stranger to all that was passing in the higher +ranks of society, should feel himself more at home and more at ease in +the most magnificent palace in the country than in the humblest +dwelling with those whose birth was most similar to his own. Without +enlarging on the duke's good sense and sincerity, the duchess's spirit +and powers of conversation, Lady Madeline's liveliness and affability, +Louisa's beauty and sweetness, Georgiana's <i>naïveté</i> and quickness of +parts, young Sandy's good nature, I may say that I was truly sorry to +part with every one of them."</p> + +<p>Young seems not to have known at this time that it is an essential +feature of true gentlefolk to dissipate all sense of constraint or +uneasiness from those with whom they are brought into contact<span class="pagenum"><a id="Page_205">[205]</a></span> and +that in this they can be readily distinguished from those who have +wealth without breeding. The Duchess of Gordon gave Young an +introduction to the Duke of Argyll, so, while travelling through the +Western Highlands, he paid a visit to Inverary Castle, and "galloped +over" the country with the duke's daughters. Speaking of these ladies, +he says, "Lady Charlotte ... is to Lady Augusta what Venus is to +Minerva; I suppose she wishes for no more. Both are goddesses."</p> + +<p>On his return to the West of England, he visited the Coalbrook Dale +Iron Works, when Mr. Reynolds told him "that before the war he had +agreed with a man to make a flute a hundred and fifty feet long, and +two and a half in diameter, to be blown by a steam-engine and played +on by barrels."</p> + +<p>On the 7th of the following October Young left London, and after +spending six days on the voyage from Yarmouth to Hamburg, he reached +Göttingen on the 27th of the same month; two days afterwards he +matriculated, and on November 3 he commenced his studies as a member +of the university. He continued to take lessons in drawing, dancing, +riding, and music, and commenced learning the clavichord. The English +students at Göttingen, in order to advance their German conversation, +arranged to pay a fine whenever they spoke in English in one another's +company. On Sundays it was usual for the professors to give +entertainments to the students, though they seldom invited them to +dinner or supper. "Indeed, they<span class="pagenum"><a id="Page_206">[206]</a></span> could not well afford, out of a fee +of a louis or two, to give large entertainments; but the absence of +the hospitality which prevails rather more in Britain, is compensated +by the light in which the students are regarded; they are not the +less, but perhaps the more, respected for being students, and indeed, +they behave in general like gentlemen, much more so than in some other +German universities."</p> + +<p>At Göttingen Young attended, in addition to his medical lectures, +Spithler's lectures on the History and Constitution of the European +States, Heyne on the History of the Ancient Arts, and Lichtenberg's +course on Physics. Speaking of Blumenbach's lectures on Natural +History, Young says, "He showed us yesterday a laborious treatise, +with elegant plates, published in the beginning of this century at +Wurzburg, which is a most singular specimen of credulity in affairs of +natural history. Dr. Behringen used to torment the young men of a +large school by obliging them to go out with him collecting +petrifactions; and the young rogues, in revenge, spent a whole winter +in counterfeiting specimens, which they buried in a hill which the +good man meant to explore, and imposed them upon him for most +wonderful <i>lusus naturæ</i>. It is interesting in a metaphysical point of +view to observe how the mind attempts to accommodate itself; in one +case, where the boys had made the figure of a plant thick and clumsy, +the doctor remarks the difference, and says that Nature seems<span class="pagenum"><a id="Page_207">[207]</a></span> to have +restored to the plant in thickness that which she had taken away from +its other dimensions."</p> + +<p>On April 30, 1796, Young passed the examination for his medical degree +at Göttingen. The examination appears to have been entirely oral. It +lasted between four and five hours. There were four examiners seated +round a table provided "with cakes, sweetmeats, and wine, which helped +to pass the time agreeably." They "were not very severe in exacting +accurate answers." The subject he selected for his public discussion +was the human voice, and he constructed a universal alphabet +consisting of forty-seven letters, of which, however, very little is +known. This study of sound laid the foundation, according to his own +account, of his subsequent researches in the undulatory theory of +light.</p> + +<p>The autumn of 1796 Young spent in travelling in Germany; in the +following February he returned to England, and was admitted a +fellow-commoner of Emmanuel College, Cambridge. It is said that the +Master, in introducing Young to the Tutors and other Fellows, said, "I +have brought you a pupil qualified to read lectures to his tutors." +Young's opinion of Cambridge, as compared with German universities, +was favourable to the former; but as he had complained of the want of +hospitality at Göttingen, so in Cambridge he complained of the want of +social intercourse between the senior members of the university and +persons <i>in statu pupillari</i>. At that time there was no system of<span class="pagenum"><a id="Page_208">[208]</a></span> +medical education in the university, and the statutes required that +six years should elapse between the admission of a medical student and +his taking the degree of M.B. Young appears to have attracted +comparatively little attention as an undergraduate in college. He did +not care to associate with other undergraduates, and had little +opportunity of intercourse with the senior members of the university. +He was still keeping terms at Cambridge when his uncle, Dr. +Brocklesby, died. To Young he left the house in Norfolk Street, Park +Lane, with the furniture, books, pictures, and prints, and about +£10,000. In the summer of 1798 a slight accident at Cambridge +compelled Young to keep to his rooms, and being thus forcibly deprived +of his usual round of social intercourse, he returned to his favourite +studies in physics. The most important result of this study was the +establishment of the principle of interference in sound, which +afforded the explanation of the phenomenon of "beats" in music, and +which afterwards led up to the discovery of the interference of +light—a discovery which Sir John Herschel characterized as "the key +to all the more abstruse and puzzling properties of light, and which +would alone have sufficed to place its author in the highest rank of +scientific immortality, even were his other almost innumerable claims +to such a distinction disregarded."</p> + +<p>The principle of interference is briefly this: When two waves meet +each other, it may happen that their crests coincide; in this case a +wave will<span class="pagenum"><a id="Page_209">[209]</a></span> be formed equal in height (amplitude) to the sum of the +heights of the two. At another point the crest of one wave may +coincide with the hollow of another, and, as the waves pass, the +height of the wave at this point will be the difference of the two +heights, and if the waves are equal the point will remain stationary. +If a rope be hung from the ceiling of a lofty room, and the lower end +receive a jerk from the hand, a wave will travel up the rope, be +reflected and reversed at the ceiling, and then descend. If another +wave be then sent up, the two will meet, and their passing can be +observed. It will then be seen that, if the waves are exactly equal, +the point at which they meet will remain at rest during the whole time +of transit. If a number of waves in succession be sent up the string, +the motions of the hand being properly timed, the string will appear +to be divided into a number of vibrating segments separated by +stationary points, or nodes. These nodes are simply the points which +remain at rest on account of the upward series of waves crossing the +series which have been reflected at the top and are travelling +downwards. The division of a vibrating string into nodes thus affords +a simple example of the principle of interference. When a tuning-fork +is vibrating there are certain hyperbolic lines along which the +disturbance caused by one prong is exactly neutralized by that due to +the other prong. If a large tuning-fork be struck and then held near +the ear and slowly turned round, the positions of comparative silence +will be readily perceived.<span class="pagenum"><a id="Page_210">[210]</a></span> If two notes are being sounded side by +side, one consisting of two hundred vibrations per second and the +other of two hundred and two, then, at any distant point, it is clear +that the two sets of waves will arrive in the same condition, or +"phase," twice in each second, and twice they will be in opposite +conditions, and, if of the same intensity, will exactly destroy one +another's effects, thus producing silence. Hence twice in the second +there will be silence and twice there will be sound, the waves of +which have double the amplitude due to either source, and hence the +sound will have four times the intensity of either note by itself. +Thus there will be two "beats" per second due to interference. Later +on this principle was applied by Young to very many optical phenomena +of which it afforded a complete explanation.</p> + +<p>Young completed his last term of residence at Cambridge in December, +1799, and in the early part of 1800 he commenced practice as a +physician at 48, Welbeck Street. In the following year he accepted the +chair of Natural Philosophy in the Royal Institution, which had +shortly before been founded, and soon afterwards, in conjunction with +Davy, the Professor of Chemistry, he undertook the editing of the +journals of the institution. This circumstance has already been +alluded to in connection with Count Rumford, the founder of the +institution. He lectured at the Royal Institution for two years only, +when he resigned the chair in deference to the popular belief that a +physician should give his<span class="pagenum"><a id="Page_211">[211]</a></span> attention wholly to his professional +practice, whether he has any or not. This fear lest a scientific +reputation should interfere with his success as a physician haunted +him for many years, and sometimes prevented his undertaking scientific +work, while at other times it led him to publish anonymously the +results he obtained. This anonymous publication of scientific papers +caused him great trouble afterwards in order to establish his claim to +his own discoveries. Many of the articles which he contributed to the +supplement to the fourth, fifth, and sixth editions of the +"Encyclopædia Britannica" were anonymous, although the honorarium he +received for this work was increased by 25 per cent. when he would +allow his name to appear. The practical withdrawal of Young from the +scientific world during sixteen years was a great loss to the progress +of natural philosophy, while the absence of that suavity of manner +when dealing with patients which is so essential to the success of a +physician, prevented him from acquiring a valuable private practice. +In fact, Young was too much of a philosopher in his behaviour to +succeed as a physician; he thought too deeply before giving his +opinion on a diagnosis, instead of appearing to know all about the +subject before he commenced his examination, and this habit, which is +essential to the philosopher, does not inspire confidence in the +practitioner. His fondness for society rendered him unwilling to live +within the means which his uncle had left him, supplemented by what +his scientific work might bring, and<span class="pagenum"><a id="Page_212">[212]</a></span> it was not until his income had +been considerably increased by an appointment under the Admiralty that +he was willing to forego the possible increase of practice which might +accrue by appearing to devote his whole attention to the subject of +medicine. It was this fear of public opinion which caused him, in +1812, to decline the offer of the appointment of Secretary to the +Royal Society, of which, in 1802, he accepted the office of Foreign +Secretary.</p> + +<p>Young's resignation of the chair of Natural Philosophy was, however, +not a great loss to the Royal Institution; for the lecture audience +there was essentially of a popular character, and Young cannot be +considered to have been successful as a popular lecturer. His own +early education had been too much derived from private reading for him +to have become acquainted with the difficulties experienced by +beginners of only average ability, and his lectures, while most +valuable to those who already possessed a fair knowledge of the +subjects, were ill adapted to the requirements of an unscientific +audience. A syllabus of his course of lectures was published by Young +in 1802, but it was not till 1807 that the complete course of sixty +lectures was published in two quarto volumes. They were republished in +1845 in octavo, with references and notes by Professor Kelland. Among +the subjects treated in these lectures are mechanics, including +strength of materials, architecture and carpentry, clocks, drawing and +modelling; hydrostatics and hydraulics; sound and musical instruments; +optics,<span class="pagenum"><a id="Page_213">[213]</a></span> including vision and the physical nature of light; astronomy; +geography; the essential properties of matter; heat; electricity and +magnetism; climate, winds, and meteorology generally; vegetation and +animal life, and the history of the preceding sciences. The lectures +were followed by a most complete bibliography of the whole subject, +including works in English, French, German, Italian, and Latin. The +following is the syllabus of one lecture, and illustrates the +diversity of the subjects dealt with:—</p> + +<blockquote> +<p>"<span class="smcap">On Drawing, Writing, and Measuring</span>.</p> + +<p>"Subjects preliminary to the study of practical mechanics; +instrumental geometry; statics; passive strength; friction; +drawing; outline; pen; pencil; chalks; crayons; Indian ink; +water-colours; body colours; miniature; distemper; fresco; oil; +encaustic paintings; enamel; mosaic work. Writing; materials +for writing; pens; inks; use of coloured inks for denoting +numbers; polygraph; telegraph; geometrical instruments; rulers; +compasses; flexible rulers; squares; triangular compasses; +parallel rulers; Marquois's scales; pantograph; proportional +compasses; sector. Measurement of angles; theodolites; +quadrants; dividing-engine; vernier; levelling; sines of +angles; Gunter's scale; Nicholson's circle; dendrometer; +arithmetical machines; standard measures; quotation from +Laplace; new measures; decimal divisions; length of the +pendulum and of the meridian of the earth; measures of time; +objections; comparison of measures; instruments for measuring; +micrometrical scales; log-lines."</p> +</blockquote> + +<p>This represents an extensive area to cover in a lecture of one hour.</p> + +<p>When Newton, by means of a prism,</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"Unravelled all the shining robe of day,"<br /></span> +</div></div> + +<p>he showed that sunlight is made up of light<span class="pagenum"><a id="Page_214">[214]</a></span> varying in tint from red, +through orange, yellow, green, and blue, to violet, and that by +recombining all these kinds of light, or certain of them selected in +an indefinite number of ways, white light could be produced. +Subsequently Sir Wm. Herschel showed that rays less refrangible than +the red were to be found among the solar radiation; and other rays +more refrangible than the violet, but, like the ultra-red rays, +incapable of exciting vision, were found by Ritter and Wollaston. In +speaking of Newton's experiments, in his thirty-seventh lecture, Young +says:—</p> + +<blockquote> +<p>It is certain that the perfect sensations of yellow and of blue are +produced respectively by mixtures of red and green and of green and +violet light, and there is reason to suspect that those sensations are +always compounded of the separate sensations combined; at least, this +supposition simplifies the theory of colours. It may, therefore, be +adopted with advantage, until it be found inconsistent with any of the +phenomena; and we may consider white light as composed of a mixture of +red, green, and violet only, ... with respect to the quantity or +intensity of the sensations produced.</p> +</blockquote> + +<p>It should be noticed that, in the above quotation, Young speaks only +of the sensations produced. Objectively considered, sunlight consists +of an infinite number of differently coloured lights comprising nearly +all the shades from one end of the spectrum to the other, though white +light may<span class="pagenum"><a id="Page_215">[215]</a></span> have a much simpler constitution, and may, for example, +consist simply of a mixture of homogeneous red, green, and violet +lights, or of homogeneous yellow and blue lights, properly selected. +But considered subjectively, Young implies that the eye perceives +three, and only three, distinct colour-sensations, corresponding to +pure red, green, and violet; that when these three sensations are +excited in a certain proportion, the complex sensation is that of +white light; but if the relative intensities of the separate +sensations differ from these ratios, the perception is that of some +colour. To exhibit the effects of mixing light of different colours, +Young painted differently coloured sectors on circles of cardboard, +and then made the discs rotate rapidly about their centres, when the +effect was the same as though the lights emitted by the sectors were +mixed in proportion to the breadth of the sectors. This contrivance +had been previously employed by Newton, and will be again referred to +in connection with another memoir. The results of these experiments +were embodied by Young in a diagram of colour, consisting of an +equilateral triangle, in which the colours red, green, and violet, +corresponding to the simple sensations, were placed at the angles, +while those produced by mixing the primary colours in any proportions, +were to be found within the triangle or along its sides; the rule +being that the colour formed by the admixture of the primary colours +in any proportions, was to be found at the centre<span class="pagenum"><a id="Page_216">[216]</a></span> of gravity of three +heavy particles placed at the angular points of the triangle, with +their masses proportioned to the corresponding amounts of light. Thus +the colours produced by the admixture of red and green only, in +different proportions, were placed along one side of the triangle, +these colours corresponding to various tints of scarlet, orange, +yellow, and yellowish green; another side contained the mixtures of +green and violet representing the various shades of bluish green and +blue; and the third side comprised the admixtures of red and violet +constituting crimsons and purples. The interior of the triangle +contained the colours corresponding to the mixture of all three +primary sensations, the centre being neutral grey, which is a pure +white faintly illuminated. If white light of a certain degree of +intensity fall on white paper, the paper appears white, but if a +stronger light fall on another portion of the same sheet, that which +is less strongly illuminated appears grey by contrast. Shadows thrown +on white paper may possess any degree of intensity, corresponding to +varying shades of neutral grey, up to absolute blackness, which +corresponds to a total absence of light. Thus considered, +chromatically black and white are the same, differing only in the +amount of light they reflect. A piece of white paper in moonlight is +darker than black cloth in full sunlight.</p> + +<p>It must be remembered that Young's diagram of colours corresponds to +the admixture of coloured<span class="pagenum"><a id="Page_217">[217]</a></span> lights, not of colouring materials or +pigments. The admixture of blue and yellow lights in proper +proportions may make white or pink, but never green. The admixture of +blue and yellow pigments makes a green, because the blue absorbs +nearly all the light except green, blue, and a little violet, while +the yellow absorbs all except orange, yellow, and green. The green +light is the only light common to the two, and therefore the only +light which escapes absorption when the pigments are mixed. Another +point already noticed must also be carefully borne in mind. Young was +quite aware that, physically, there are an infinite number of +different kinds of light differing continuously in wave-length from +the ultra-red to the ultra-violet, though colour can hardly be +regarded as an attribute of the light considered objectively. The +question of colour is essentially one of perception—a physiological, +not a physical, question—and it is only in this sense that Young +maintained the doctrine of three primary colours. In his paper on the +production of colours, read before the Royal Society on July 1, 1802, +he speaks of "the proportions of the sympathetic fibres of the +retina," corresponding to these primary colour-sensations. According +to this doctrine, white light would always be produced when the three +sensations were affected in certain proportions, whether the exciting +cause were simply two kinds of homogeneous light, corresponding to two +pure tones in music, or an infinite number of different kinds, as in +sunlight;<span class="pagenum"><a id="Page_218">[218]</a></span> and a particular yellow sensation might be excited by +homogeneous yellow light from one part of the spectrum, or by an +infinite number of rays of different wave-lengths, corresponding to +various shades of red, orange, yellow, and green. Subjectively, the +colours would be the same; objectively, the light producing them would +differ exceedingly.</p> + +<p>But Young's greatest service to science was his application of the +principle of interference—of which he had already made good use in +the theory of sound—to the phenomena of light. The results of these +researches were presented to the Royal Society, and two of the papers +were selected as Bakerian lectures in 1801 and 1803 respectively. +Unfavourable criticisms of these papers, which appeared in the +<i>Edinburgh Review</i>, and were said to have been written by Mr. +(afterwards Lord) Brougham, seem to have caused their contents to be +neglected by English men of science for many years; and it was to +Arago and Fresnel that we are indebted for recalling public attention +to them. The undulatory theory of light, which maintains that light +consists of waves transmitted through an <i>ether</i>, which pervades all +space and all matter, owes its origin to Hooke and Huyghens. Huyghens +showed that this theory explained, in a very beautiful manner, the +laws of reflection and of refraction, if it be allowed that light +travels more slowly the denser the medium. According to the celebrated +principle of Huyghens, every point in the front of a wave at any +instant becomes a centre<span class="pagenum"><a id="Page_219">[219]</a></span> of disturbance, from which a secondary wave +is propagated. The fronts of these secondary waves all lie on a +surface, which becomes the new surface of the primary wave. When light +enters a denser medium obliquely, the secondary waves which are +propagated within the denser medium extend to a less distance than +those propagated in the rarer medium, and thus the front of the +primary wave becomes bent at the point where it meets the common +surface. Huyghens explained, not only the laws of ordinary refraction +in this manner, but, by supposing the secondary waves to form +spheroids instead of spheres, he obtained the laws of refraction of +the extraordinary ray in Iceland-spar. He did not, however, succeed in +explaining why light should not diverge laterally instead of +proceeding in straight lines. Newton supported the theory that light +consists of particles or corpuscles projected in straight lines from +the luminous body, and sometimes transmitted, sometimes reflected, +when incident on a transparent medium of different density. To account +for the particle being sometimes transmitted and sometimes reflected, +Newton had recourse to the hypothesis of "fits of easy transmission +and of easy reflection," and, to account for the fits themselves, he +supposed the existence of an ether, the vibrations of which affected +the particles. The laws of reflection were readily explained, being +the same as for a perfectly elastic ball; the laws of refraction +admitted of very simple explanation, by supposing that the particles<span class="pagenum"><a id="Page_220">[220]</a></span> +of the denser medium exert a greater attraction on the particles of +light than those of the rarer medium, but that this attraction acts +only through very short distances, so that when the light-corpuscle is +at a sensible distance from the surface, it is attracted equally all +round, and moves as though there were no force acting upon it. As a +consequence of this hypothesis, it follows that the velocity of light +must be greater the denser the medium, while the undulatory theory +leads to precisely the opposite result. When Foucault directly +measured the velocity of light both in air and water, and found it +less in the denser medium, the result was fatal to the corpuscular +theory.</p> + +<p>Dr. Young called attention to another crucial test between the two +theories. When a piece of plate-glass is pressed against a slightly +convex lens, or a watch-glass, a series of coloured rings is formed by +reflected light, with a black spot in the centre. This was accounted +for by Newton by supposing that the light which was reflected in any +ring was in a fit of easy transmission (from glass to air) when it +reached the first surface of the film of air, and in a fit of easy +reflection when it reached the second surface. By measuring the +thickness of a film of air corresponding to the first ring of any +particular colour, the length of path corresponding to the interval +between two fits for that particular kind of light could be +determined. When water instead of air is placed between the glasses, +according to the corpuscular theory the rings should<span class="pagenum"><a id="Page_221">[221]</a></span> expand; but +according to the undulatory theory they should contract; for the +wave-length corresponds to the distance between successive fits of the +same kind on the corpuscular hypothesis. On trying the experiment, the +rings were seen to contract. This result seemed to favour the +undulatory theory; but the objection urged by Newton that rays of +light do not bend round obstacles, like waves of sound, still held its +ground. This objection Young completely demolished by his principle of +interference. He showed that when light passes through an aperture in +a screen, whatever the shape of the aperture, provided its width is +large in comparison with the length of a wave of light (one +fifty-thousandth of an inch), no sensible amount of light will reach +any point not directly in front of the aperture; for if any point be +taken to the right or left, the disturbances reaching that point from +different points of the aperture will neutralize one another by +interference, and thus no light will be appreciable. When the breadth +of the aperture is only a small multiple of a wave-length, then there +will be some points outside the direct beam at which the disturbances +from different points of the aperture will not completely destroy one +another, and others at which they will destroy one another; and these +points will be different for light of different wave-lengths. In this +way Young not only explained the rectilinear propagation of light, but +accounted for the coloured bands formed when light diverges<span class="pagenum"><a id="Page_222">[222]</a></span> from a +point through a very narrow aperture. In a similar way he accounted +for the hyperbolic bands of colour observed by Grimaldi within the +shadow of a square near its corners. With a strip of card +one-thirtieth of an inch in width, Young obtained bands of colour +within the shadow which completely disappeared when the light was cut +off from either side of the strip of card, showing that they were +produced by interference of the two portions of light which had +passed, one to the right, the other to the left, of the strip of card. +Professor Stokes has succeeded in showing a bright spot at the centre +of the shadow of a circular disc of the size of a sovereign. The +narrow bands of colour formed near the edge of the shadow of any +object, which Newton supposed to be due to the "inflection" of the +light by the attraction of the object, Young showed to be independent +of the material or thickness of the edge, and completely accounted for +them by the principle of interference. Newton's rings were explained +with equal facility. They were due to the interference of light +reflected from the first and second surfaces of the film of air or +water between the glasses. The black spot at the centre of the +reflected rings was due to the difference between reflection taking +place from the surface of a denser or a rarer medium, half an +undulation being lost when the reflection takes place in glass at the +surface of air. If a little grease or water be placed between two +pieces of glass which are nearly in contact, but the space<span class="pagenum"><a id="Page_223">[223]</a></span> between be +not filled with the water or grease, but contain air in some parts, +and water or grease in others, a series of rings will be seen by +transmitted light, which have been called "the colours of mixed +plates." Young showed that these colours could be accounted for by +interference between the light that had passed through the air and +that which had passed through the water, and explained the fact that, +to obtain the same colour, the distance between the plates must be +much greater than in the case of Newton's rings.</p> + +<p>The bands of colour produced by the interference of light proceeding +from a point and passing on each side of a narrow strip of card, have +already been referred to. The bands are broader the narrower the strip +of card. A fine hair gives very broad bands. When a number of hairs +cross one another in all directions, these bands form circular rings +of colour. If the width of the hairs be very variable, the rings +formed will be of different sizes and overlapping one another, no +distinct series will be visible; but when the hairs are of nearly the +same diameter, a series of well-defined circles of colour, resembling +Newton's rings, will be seen, and if the diameter of a particular ring +be measured, the breadth of the hairs can be inferred. Young +practically employed this method for measuring the diameter of the +fibres of different qualities of wool in order to determine their +commercial value. The instrument employed he called the <i>eriometer</i>. +It consisted of a plate of brass pierced with a round hole<span class="pagenum"><a id="Page_224">[224]</a></span> about +one-thirtieth of an inch in diameter in the centre, and around this a +small circle, about one-third of an inch in diameter, of very fine +holes. The plate was placed in front of a lamp, and the specimen of +wool was held on wires at such a distance in front of the brass plate +that the first green ring appeared to coincide with the circle of +small holes. The eye was placed behind the lock of wool, and the +distance to which the wool had to be removed in front of the brass +plate in order that the first green ring might exactly coincide with +the small circle of fine holes, was proportional to the breadth of the +fibres. The same effect is produced if fine particles, such as +lycopodium powder, or blood-corpuscles, scattered on a piece of glass, +be substituted for the lock of wool, and Young employed the instrument +in order to determine the diameter of blood-corpuscles. He determined +the constant of his apparatus by comparison with some of Dr. +Wollaston's micrometric observations. The coloured halos sometimes +seen around the sun Young referred to the existence of small drops of +water of nearly uniform diameter, and calculated the necessary +diameter for halos of different angular magnitudes.</p> + +<p>The same principle of interference afforded explanation of the colours +of striated surfaces, such as mother-of-pearl, which vary with the +direction in which they are seen. Viewed at one angle light of a +particular colour reflected from different ridges will be in a +condition to interfere, and this<span class="pagenum"><a id="Page_225">[225]</a></span> colour will be absent from the +reflected light. At a different inclination, the light reaching the +eye from all the ridges (within a certain angle) will be in precisely +the same phase, and only then will light of that colour be reflected +in its full intensity. With a micrometer scale engraved on glass by +Coventry, and containing five hundred lines to the inch, Young +obtained interference spectra. Modern gratings, with several thousand +lines to the inch, afford the purest spectra that can be obtained, and +enable the wave-length of any particular kind of light to be measured +with the greatest accuracy.</p> + +<p>Young's dislike of mathematical analysis prevented him from applying +exact calculation to the interference phenomena which he observed, +such as subsequently enabled Fresnel to overcome the prejudice of the +French Academy and to establish the principle on an incontrovertible +footing. Young's papers attracted very little attention, and Fresnel +made for himself many of Young's earlier discoveries, but at once gave +Young the full credit of the work when his priority was pointed out. +The phenomena of polarization, however, still remained unexplained. +Both Young and Fresnel had regarded the vibrations of light as similar +to those of sound, and taking place in the direction in which the wave +is propagated. The fact that light which had passed through a crystal +of Iceland-spar, was differently affected by a second crystal, +according to the direction of that crystal with respect to the former, +showed that light which had been so<span class="pagenum"><a id="Page_226">[226]</a></span> transmitted was not like common +light, symmetrical in all azimuths, but had acquired sides or poles. +Such want of symmetry could not be accounted for on the hypothesis +that the vibrations of light took place at right angles to the +wave-front, that is, in the direction of propagation of the light. The +polarization of light by reflection was discovered by Malus, in 1809. +In a letter written to Arago, in 1817, Young hinted at the possibility +of the existence of a component vibration at right angles to the +direction of propagation, in light which had passed through +Iceland-spar. In the following year Fresnel arrived independently at +the hypothesis of transverse vibrations, not as constituting a small +component of polarized light, but as representing completely the mode +of vibration of all light, and in the hands of Fresnel this hypothesis +of transverse vibrations led to a theory of polarization and double +refraction both in uniaxal and biaxal crystals which, though it can +hardly be regarded as complete from a mechanical point of view, is +nevertheless one of the most beautiful and successful applications of +mathematics to physics that has ever been made. To Young, however, +belongs the credit of suggesting that the spheroidal form of the waves +in Iceland-spar might be accounted for by supposing the elasticity +different in the direction of the optic axis and at right angles to +that direction; and he illustrated his view by reference to certain +experiments of Chladni, in which it had been shown that the velocity +of sound in the wood of the<span class="pagenum"><a id="Page_227">[227]</a></span> Scotch fir is different along, and +perpendicular to, the fibre in the ratio of 5 to 4. Young was also the +first to explain the colours exhibited by thin plates of crystals in +polarized light, discovered by Arago in 1811, by the interference of +the ordinary and extraordinary rays, and Fresnel afterwards completed +Young's explanation in 1822.</p> + +<p>It is for his contributions to the undulatory theory of light that +Young will be most honourably remembered. Hooke, in 1664, referred to +light as a "quick, short, vibrating motion;" Huyghens's "Traité de la +Lumière" was published in 1690. From that time the undulatory theory +lost ground, until it was revived by Young and Fresnel. It soon after +received great support from the establishment, by Joule and others, of +the mechanical theory of heat. One remark of Young's respecting the +ether opens up a question which has attracted much attention of late +years. In a letter addressed to the Secretary of the Royal Society, +and read January 16, 1800, he says:—</p> + +<blockquote> +<p>That a medium, resembling in many properties that which has been +denominated ether, does really exist, is undeniably proved by the +phenomena of electricity; and the arguments against the existence of +such an ether throughout the universe have been pretty sufficiently +answered by Euler. The rapid transmission of the electrical shock +shows that the electric medium is possessed of an elasticity as great +as is necessary to be supposed for the propagation of light. Whether +the electric<span class="pagenum"><a id="Page_228">[228]</a></span> ether is to be considered as the same with the luminous +ether—if such a fluid exists—may perhaps at some future time be +discovered by experiment.</p> +</blockquote> + +<p>Besides his contributions to optics, Young made distinct advances in +connection with elasticity, and with surface-tension, or +"capillarity." It is said that Leonardo da Vinci was the first to +notice the ascent of liquids in fine tubes by so-called capillary +attraction. This, however, is only one of a series of phenomena now +very generally recognized, and all of which are referable to the same +action. The hanging of a drop from the neck of a phial; the pressure +of air required to inflate a soap-bubble; the flotation of a greasy +needle on the surface of water; the manner in which some insects rest +on water, by depressing the surface, without wetting their legs; the +possibility of filling a tumbler with water until the surface stands +above the edge of the glass; the nearly spherical form of rain-drops +and of small drops of mercury, even when they are resting on a +table,—are all examples of the effect of surface-tension. These +phenomena have recently been studied very carefully by Quincke and +Plateau, and they have been explained in accordance with the principle +of energy by Gauss. Hawksbee, however, was the first to notice that +the rise of a liquid in a fine tube did not depend on the thickness of +the walls of the tube, and he therefore inferred that, if the +phenomena were due to the attraction of the glass for the liquid, it +could only be the superficial layers which produced any effect. This +was in 1709.<span class="pagenum"><a id="Page_229">[229]</a></span> Segner, in 1751, introduced the notion of a +surface-tension; and, according to his view, the surface of a liquid +must be considered as similar to a thin layer of stretched +indiarubber, except that the tension is always the same at the surface +bounding the same media. This idea of surface-tension was taken up by +Young, who showed that it afforded explanation of all the known +phenomena of "capillarity," when combined with the fact, which he was +himself the first to observe, that the angle of contact of the same +liquid-surface with the same solid is constant. This angle he called +the "appropriate angle." But Young went further, and attempted to +explain the existence of surface-tension itself by supposing that the +particles of a liquid not only exert an attractive force on one +another, which is constant, but also a repulsive force which increases +very rapidly when the distance between them is made very small. His +views on this subject were embodied in a paper on the cohesion of +liquids, read before the Royal Society in 1804. He afterwards wrote an +article on the same subject for the supplement of the "Encyclopædia +Britannica."</p> + +<p>The changes which solids undergo under the action of external force, +and their tendency to recover their natural forms, were studied by +Hooke and Gravesande. The experimental fact that, for small changes of +form, the extension of a rod or string is proportional to the tension +to which it is exposed, is known as Hooke's law. The compression<span class="pagenum"><a id="Page_230">[230]</a></span> and +extension of the fibres of a bent beam were noticed by James +Bernoulli, in 1630, by Duhamel and others. The bending of beams was +also studied by Coulomb and Robison, but Young appears to have been +almost the first to apply the theory of elasticity to the statics of +structures. In a letter to the Secretary of the Admiralty, written in +1811, in reply to an invitation to report on Mr. Steppings's +improvements in naval architecture, Young claimed that he was the only +person who had published "any attempts to improve the <i>theory</i> of +carpentry." It may be here mentioned that Young accepted the +invitation of the Admiralty, and sent in a very exhaustive report, +which their Lordships regarded as "too learned" to be of great +practical value. Young's contributions to this subject will be chiefly +remembered in connection with his "modulus of elasticity." This he +originally defined as follows:—</p> + +<p>"The modulus of the elasticity of any substance is a column of the +same substance capable of producing a pressure on its base which is to +the weight causing a certain degree of compression as the length of +the substance is to the diminution of its length."</p> + +<p>It is not usual now to express Young's modulus of elasticity in terms +of a length of the substance considered. As now usually defined, +Young's modulus of elasticity is the force which would stretch a rod +or string to double its natural length if Hooke's law were true for so +great an extension.</p><p><span class="pagenum"><a id="Page_231">[231]</a></span></p> + +<p>So much of Dr. Young's scientific work has been mentioned here because +it was during his early years of professional practice that his most +original scientific work was accomplished. As already stated, after +two years' tenure of the Natural Philosophy chair at the Royal +Institution, Young resigned it because his friends were of opinion +that its tenure militated against his prospects as a physician. In the +summer of 1802 he escorted the great-nephews of the Duke of Richmond +to Rouen, and took the opportunity of visiting Paris. In March, 1803, +he took his degree of M.B. at Cambridge, and on June 14, 1804, he +married Eliza, second daughter of J. P. Maxwell, Esq., whose country +seat was near Farnborough. For sixteen years after his marriage, Young +resided at Worthing during the summer, where he made a very +respectable practice, returning to London in October or November. In +January, 1811, he was elected one of the physicians of St. George's +Hospital, which appointment he retained for the rest of his life. In +this capacity his practice was considerably in advance of the times, +for he regarded medicine as a science rather than an empirical art, +and his careful methods of induction demanded an amount of attention +which medical students, who preferred the more rough-and-ready methods +then in vogue, were slow to give. The apothecary of the hospital +stated that more of Dr. Young's patients went away cured than of those +who were subjected to the more fashionable treatment; but his private<span class="pagenum"><a id="Page_232">[232]</a></span> +practice, notwithstanding the sacrifices he had made, never became +very valuable.</p> + +<p>In 1816 Young was appointed Secretary to a Commission for determining +the length of the second's pendulum. The reports of this Commission +were drawn up by him, though the experimental work was carried out by +Captain Kater. The result of the work was embodied in an Act of +Parliament, introduced by Sir George Clerk, in 1824, which provided +that if the standard yard should be lost it should "be restored to the +same length," by making it bear to the length of the second's pendulum +at sea-level in London, the ratio of 36 to 39·1393; but before the +standards were destroyed, in 1835, so many sources of possible error +were discovered in the reduction of pendulum observations, that the +Commission appointed to restore the standards recommended that a +material standard yard should be constructed, together with a number +of copies, so that, in the event of the standard being again +destroyed, it might be restored by comparison with its copies. In 1818 +Young was appointed Superintendent of the Nautical Almanac and +Secretary of the Board of Longitude. When this Board was dissolved in +1828, its functions were assumed by the Admiralty, and Young, Faraday, +and Colonel Sabine were appointed a Scientific Committee of Reference +to advise the Admiralty in all matters in which their assistance might +be required. The income from these Government appointments rendered +Young<span class="pagenum"><a id="Page_233">[233]</a></span> more independent of his practice, and he became less careful to +publish his scientific papers anonymously. In 1820 he left Worthing +and gave up his practice there. The following year, in company with +Mrs. Young, he took a tour through France, Switzerland, and Italy, and +at Paris attended a meeting of the Institute, where he met Arago, who +had called on him in Worthing, in 1816. At the same time he made the +acquaintance of Laplace, Cuvier, Humboldt, and others. In 1824 he +visited Spa, and took a tour through Holland. In the same year Young +was appointed Inspector of Calculations and Medical Referee to the +Palladium Insurance Company. This caused him to turn his attention to +the subject of life assurance and bills of mortality. In 1825, as +Foreign Secretary of the Royal Society, he had the satisfaction of +forwarding to Fresnel the Rumford Medal in acknowledgment of his +researches on polarized light. Fresnel died, in his fortieth year, a +few days after receiving the medal.</p> + +<p>Dr. Young died on May 10, 1829, in the fifty-sixth year of his age, +his excessive mental exertions in early life having apparently led to +a premature old age. He was buried in the parish church of +Farnborough, and a medallion by Sir Francis Chantrey was erected to +his memory in Westminster Abbey.</p> + +<p>But, though Young was essentially a scientific man, his +accomplishments were all but universal, and any memoir of him would be +very incomplete<span class="pagenum"><a id="Page_234">[234]</a></span> without some sketch of his researches in Egyptian +hieroglyphics. His classical training, his extensive knowledge of +European and Eastern languages, and his neat handwriting and drawing, +have already been referred to. To these attainments must be added his +scientific <i>method</i> and power of careful and systematic observation, +and it will be seen that few persons could come to the task of +deciphering an unknown language with a better chance of success than +Dr. Young.</p> + +<p>The Rosetta Stone was found by the French while excavating at Fort St. +Pierre, near Rosetta, in 1799, and was brought to England in 1802. The +stone bore an inscription in three different kinds of character—the +Hieroglyphic, the Enchorial or Demotic, and the ordinary Greek. +Young's attention was first called to the Egyptian characters by a +manuscript which was submitted to him in 1814. He then obtained copies +of the inscriptions on the Rosetta Stone and subjected them to a +careful analysis. The latter part of the Greek inscription was very +much injured, but was restored by the conjectures of Porson and Heyne, +and read as follows:—"What is here decreed shall be inscribed on a +block of hard stone, in sacred, in enchorial, and in Greek characters, +and placed in each temple, of the first, second, and third gods."</p> + +<p>This indicated that the three inscriptions contained the same decree, +but, unfortunately, the beginnings of the first and second +inscriptions were lost, so that there were no very definitely fixed +points<span class="pagenum"><a id="Page_235">[235]</a></span> to start upon. The words "Alexander" and "Alexandria," +however, occurred in the Greek, and these words, being so much alike, +might be recognized in each of the other inscriptions. The word +"Ptolemy" appeared eleven times in the Greek inscription, and there +was a word which, from its length and position, seemed to correspond +to it, which, however, appeared fourteen times in the hieroglyphic +inscription. This word, whenever it appeared in the hieroglyphics, was +surrounded by a ring forming what Champollion called a <i>cartouche</i>, +which was always employed to denote the names of royal persons. These +words were identified by Baron Sylvestre de Sacy and the Swedish +scholar Akerblad. Young appears to have started with the idea, then +generally current, that hieroglyphic symbols were purely ideographic, +each sign representing a word. His knowledge of Chinese, however, led +him to modify this view. In that language native words are represented +by single symbols, but, when it is necessary to write a foreign word, +a group of word-symbols is employed, each of which then assumes a +phonetic character of the same value as the initial letter of the word +which it represents. The phonetic value of these signs is indicated in +Chinese by a line at the side, or by enclosing them in a square. Young +supposed that the ring surrounding the royal names in the hieroglyphic +inscription had the same value as the phonetic mark in Chinese, and +from the symbols in the name of Ptolemy he commenced to construct a +hieroglyphic alphabet. He made an error, however,<span class="pagenum"><a id="Page_236">[236]</a></span> in supposing that +some of the symbols might be syllabic instead of alphabetic. It is +true that in the older inscriptions single signs have sometimes a +syllabic value, and sometimes are used ideographically, while in other +cases a single sign representing the whole word is employed in +conjunction with the alphabetic signs, probably to distinguish the +word from others spelt in the same way, but in inscriptions of so late +a date as the Rosetta Stone, the symbols were purely alphabetic. +Another important step made by Young was the discovery of the use of +<i>homophones</i>, or different symbols to represent the same letter. +Young's work was closely followed up by Champollion, and afterwards by +Lepsius, Birsch, and others. The greater part of his researches he +never published, though he made careful examinations of several +funeral rolls and other documents.</p> + +<p>It would occupy too much space to give an adequate account of Young's +researches in this subject; some portion of his work he published in a +popular form in the article "Egypt," in the supplement of the +"Encyclopædia Britannica," to which supplement he contributed about +seventy articles on widely different subjects. Perhaps it is not too +much to say that to Young we owe the foundation of all we now know of +hieroglyphics and the Egyptian history which has been learned from +them; and the obelisk on the Thames Embankment should call to mind the +memory of no one more prominently than that of Thomas Young.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_237">[237]</a></span></p> + +<div class="figcenter"> +<img src="images/i247.jpg" width="480" height="104" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="MICHAEL_FARADAY">MICHAEL FARADAY.</h2> + +<p>The work of Michael Faraday introduced a new era in the history of +physical science. Unencumbered by pre-existing theories, and +untrammelled by the methods of the mathematician, he set forth on a +line of his own, and, while engaged in the highest branches of +experimental research, he sought to explain his results by reference +to the most elementary mechanical principles only. Hence it was that +those conclusions which had been obtained by mathematicians only by +the help of advanced analytical methods, and which were expressed by +them only in the language of the integral calculus, Faraday achieved +without any such artificial aids to thought, and expressed in simple +language, having reference to the mechanism which he conceived to be +the means by which such results were brought about. For a long time +Faraday's methods were regarded by mathematicians with something more +than suspicion, and, while they could not but admire<span class="pagenum"><a id="Page_238">[238]</a></span> his experimental +skill and were compelled to admit the accuracy of his conclusions, his +mode of thought differed too widely from that to which they were +accustomed to command their assent. In Sir William Thomson, and in +Clerk Maxwell, Faraday at length found interpreters between him and +the mathematical world, and to the mathematician perhaps the greatest +monument of the genius of Faraday is the "Electricity and Magnetism" +of Clerk Maxwell.</p> + +<p>Michael Faraday was born at Newington, Surrey, on September 22, 1791, +and was the third of four children. His father, James Faraday, was the +son of Robert and Elizabeth Faraday, of Clapham Wood Hall, in the +north-west of Yorkshire, and was brought up as a blacksmith. He was +the third of ten children, and, in 1786, married Margaret Hastwell, a +farmer's daughter. Soon after his marriage he came to London, where +Michael was born. In 1796 James Faraday, with his family, moved from +Newington, and took rooms over a coach-house in Jacob's Well Mews, +Charles Street, Manchester Square. In looking at this humble abode one +can scarcely help thinking that the Yorkshire blacksmith and his +little family would have been far happier in a country "smiddy" near +his native moors than in a crowded London court; but, had he remained +there, it is difficult to see how the genius of young Michael could +have met with the requisites for its development.</p> + +<p>James Faraday was far from enjoying good health,<span class="pagenum"><a id="Page_239">[239]</a></span> and his illness +often necessitated his absence from work, and, as a consequence, his +family were frequently in very straitened circumstances. The early +education of Michael was, therefore, not of a very high order, and +consisted "of little more than the rudiments of reading, writing, and +arithmetic." Like most boys in a similar position in London, he found +his amusement for the most part in the streets, but, except that in +his games at marbles we may assume that he played with other boys, we +have no evidence whether his time was spent mostly by himself, or +whether he was one of a "set" of street companions.</p> + +<p>In 1804, when thirteen years of age, Michael Faraday went as +errand-boy to Mr. Geo. Riebau, a bookseller in Blandford Street. Part +of his duty in this capacity was to carry round papers lent on hire by +his master, and in his "Life of Faraday," Dr. Bence Jones tells how +anxious the young errand-boy was to collect his papers on Sunday +morning in time to attend the Sandemanian service with the other +members of his family.</p> + +<p>Faraday was apprenticed to Mr. Riebau on October 7, 1805, and learned +the business of a bookbinder. He occasionally occupied his spare time +in reading the scientific books he had to bind, and was particularly +interested in Mrs. Marcet's "Conversations in Chemistry," and in the +article on "Electricity" in the "Encyclopædia Britannica." These were +days before the existence of the London Society for the Extension of +University Teaching,<span class="pagenum"><a id="Page_240">[240]</a></span> and, though Professor Anderson in Glasgow had +shown how the advantages of a university might be extended to those +whose fortunes prevented them from becoming regular university +students, Professor Stuart had not yet taught the English universities +that they had responsibilities outside their own borders, and that the +national universities of the future must be the teachers of all +classes of the community. But private enterprise supplied in a measure +the neglect of public bodies. Mr. Tatum, of 43, Dorset Street, Fleet +Street, advertised a course of lectures on natural philosophy, to be +delivered at his residence at eight o'clock in the evenings. The price +of admission was high, being a shilling for each lecture, but +Michael's brother Robert frequently supplied him with the money, and +in attending these lectures Faraday made many friendships which were +valuable to him afterwards.</p> + +<p>Faraday appears to have been aware of the value of skill in drawing—a +point to which much attention has recently been called by those +interested in technical education—and he spent some portion of his +time in studying perspective, so as to be better able to illustrate +his notes of Mr. Tatum's lectures, as well as of some of Sir Humphry +Davy's, which he was enabled to hear at the Royal Institution through +the kindness of a customer at Mr. Riebau's shop.</p> + +<p>In 1812, before the end of his apprenticeship, Faraday was engaged in +experiments with voltaic<span class="pagenum"><a id="Page_241">[241]</a></span> batteries of his own construction. Having +cut out seven discs of zinc the size of halfpence, and covered them +with seven halfpence, he formed a pile by inserting pieces of paper +soaked in common salt between each pair, and found that the pile so +constructed was capable of decomposing Epsom salts. With a somewhat +larger pile he decomposed copper sulphate and lead acetate, and made +some experiments on the decomposition of water. On July 21, 1812, in +writing to his friend Abbott, he mentions the movements of camphor +when floating on water, and adds, "Science may be illustrated by those +minute actions and effects, almost as much as by more evident and +obvious phenomena.... My knife is so bad that I cannot mend my pen +with it; it is now covered with copper, having been employed to +precipitate that metal from the muriatic acid."</p> + +<p>Something of Faraday's disposition, as well as of the results of his +self-education, may be gathered from the following quotations from +letters to Abbott, written at this time:—</p> + +<blockquote> +<p>I have again gone over your letter, but am so blinded that I cannot +see any subject except chlorine to write on; but before entering on +what I intend shall fill up the letter, I will ask your pardon for +having maintained an opinion against one who was so ready to give his +own up. I suspect from that circumstance I am wrong.... In the present +case I conceive that experiments may be divided into three classes: +first, those which are<span class="pagenum"><a id="Page_242">[242]</a></span> for the old theory of oxymuriatic acid, and +consequently oppose the new one; second, those which are for the new +one, and oppose the old theory; and third, those which can be +explained by both theories—apparently so only, for in reality a false +theory can never explain a fact."</p> + +<p>It is not for me to affirm that I am right and you wrong; speaking +impartially, I can as well say that I am wrong and you right, or that +we both are wrong and a third right. I am not so self-opinionated as +to suppose that my judgment and perception in this or other matters is +better or clearer than that of other persons; nor do I mean to affirm +that this is the true theory in reality, but only that my judgment +conceives it to be so. Judgments sometimes oppose each other, as in +this case; and as there cannot be two opposing facts in nature, so +there cannot be two opposing truths in the intellectual world. +Consequently, when judgments oppose, one must be wrong—one must be +false; and mine may be so for aught I can tell. I am not of a superior +nature to estimate exactly the strength and correctness of my own and +other men's understanding, and will assure you, dear A——, that I am +far from being convinced that my own is always right. I have given you +the theory—not as the true one, but as the one which appeared true to +me—and when I perceive errors in it, I will immediately renounce it, +in part or wholly, as my judgment may direct. From this, dear friend, +you will see that I am very open to conviction; and from<span class="pagenum"><a id="Page_243">[243]</a></span> the manner +in which I shall answer your letter, you will also perceive that I +must be convinced before I renounce.</p> +</blockquote> + +<p>On October 7, 1812, Faraday's apprenticeship terminated, and +immediately afterwards he started life as a journeyman bookbinder. He +now found that he had less time at his disposal for scientific work +than he had enjoyed when an apprentice, and his desire to give up his +trade and enter fully upon scientific pursuits became stronger than +ever. During his apprenticeship he had written to Sir Joseph Banks, +then President of the Royal Society, in the hope of obtaining some +scientific employment; he now applied to Sir Humphry Davy. In a letter +written to Dr. Paris, in 1829, Faraday gave an account of this +application.</p> + +<p>"My desire to escape from trade, which I thought vicious and selfish, +and to enter into the service of science, which I imagined made its +pursuers amiable and liberal, induced me at last to take the bold and +simple step of writing to Sir H. Davy, expressing my wishes, and a +hope that, if an opportunity came in his way, he would favour my +views; at the same time, I sent the notes I had taken of his lectures.</p> + +<p>"The answer, which makes all the point of my communication, I send you +in the original, requesting you to take great care of it, and to let +me have it back, for you may imagine how much I value it.</p> + +<p>"You will observe that this took place at the end<span class="pagenum"><a id="Page_244">[244]</a></span> of the year 1812; +and early in 1813 he requested to see me, and told me of the situation +of assistant in the laboratory of the Royal Institution, then just +vacant.</p> + +<p>"At the same time that he thus gratified my desires as to scientific +employment, he still advised me not to give up the prospects I had +before me, telling me that Science was a harsh mistress, and, in a +pecuniary point of view, but poorly rewarding those who devoted +themselves to her service. He smiled at my notion of the superior +moral feelings of philosophic men, and said he would leave me to the +experience of a few years to set me right on that matter.</p> + +<p>"Finally, through his good efforts, I went to the Royal Institution, +early in March of 1813, as assistant in the laboratory; and in October +of the same year went with him abroad, as his assistant in experiments +and in writing. I returned with him in April, 1815, resumed my station +in the Royal Institution, and have, as you know, ever since remained +there."</p> + +<p>Sir H. Davy's letter was as follows:—</p> + +<blockquote><p> +"<span class="smcap">Sir</span>,<br /> +</p> + +<p>"I am far from displeased with the proof you have given me of +your confidence, and which displays great zeal, power of +memory, and attention. I am obliged to go out of town, and +shall not be settled in town till the end of January; I will +then see you at any time you wish. It would gratify<span class="pagenum"><a id="Page_245">[245]</a></span> me to be +of any service to you; I wish it may be in my power.</p> + +<p class="right1">"I am, sir,</p> + +<p class="right">Your obedient humble servant,</p> +<p class="author smcap">H. Davy.</p> +</blockquote> + +<p>The minutes of the meeting of managers of the Royal Institution, on +March 1, 1813, contain the following entry:—"Sir Humphry Davy has the +honour to inform the managers that he has found a person who is +desirous to occupy the situation in the institution lately filled by +William Payne. His name is Michael Faraday. He is a youth of +twenty-two years of age. His habits seem good, his disposition active +and cheerful, and his manner intelligent. He is willing to engage +himself on the same terms as those given to Mr. Payne at the time of +quitting the institution.</p> + +<p>"Resolved, that Michael Faraday be engaged to fill the situation +lately occupied by Mr. Payne, on the same terms."</p> + +<p>About this time Faraday joined the City Philosophical Society, which +had been started at Mr. Tatum's house in 1808. The members met every +Wednesday evening, either for a lecture or discussion; and perhaps the +society did not widely differ from some of the "students' +associations" which have more recently been started in connection with +other educational enterprises. Magrath was secretary of this society, +and from it there sprang a smaller band of students, who, meeting once +a week,<span class="pagenum"><a id="Page_246">[246]</a></span> either at Magrath's warehouse in Wood Street, or at Faraday's +private rooms in the attics of the Royal Institution, for mutual +improvement, read together, and freely criticized each other's +pronunciation and composition. In a letter to Abbott six weeks after +commencing work at the Royal Institution, Faraday says:—</p> + +<blockquote> +<p>A stranger would certainly think you and I were a couple of very +simple beings, since we find it necessary to write to each other, +though we so often personally meet; but the stranger would, in so +judging, only fall into that error which envelops all those who decide +from the outward appearances of things.... When writing to you I seek +that opportunity of striving to describe a circumstance or an +experiment clearly; so that you will see I am urged on by selfish +motives partly to our mutual correspondence, but, though selfish, yet +not censurable.</p> +</blockquote> + +<p>During the summer of 1813 Faraday, in his letters to Abbott, gave his +friend the benefit of his experience "on the subject of lectures and +lecturers in general," in a manner that speaks very highly of his +power of observation of men as well as things. He was of opinion that +a lecture should not last more than an hour, and that the subject +should "fit the audience."</p> + +<p>"A lecturer may consider his audience as being polite or vulgar (terms +I wish you to understand according to Shuffleton's new dictionary), +learned or unlearned (with respect to the subject), listeners<span class="pagenum"><a id="Page_247">[247]</a></span> or +gazers. Polite company expect to be entertained, not only by the +subject of the lecture, but by the manner of the lecturer; they look +for respect, for language consonant to their dignity, and ideas on a +level with their own. The vulgar—that is to say, in general, those +who will take the trouble of thinking, and the bees of business—wish +for something that they can comprehend. This may be deep and elaborate +for the learned, but for those who are as yet tyros and unacquainted +with the subject, must be simple and plain. Lastly, listeners expect +reason and sense, whilst gazers only require a succession of words."</p> + +<p>In favour of experimental illustration he says:—</p> + +<p>"I need not point out ... the difference in the perceptive powers of +the eye and the ear, and the facility and clearness with which the +first of these organs conveys ideas to the mind—ideas which, being +thus gained, are held far more retentively and firmly in the memory +than when introduced by the ear.... Apparatus, therefore, is an +essential part of every lecture in which it can be introduced.... When +... apparatus is to be exhibited, some kind of order should be +observed in the arrangement of them on the lecture-table. Every +particular part illustrative of the lecture should be in view, no one +thing should hide another from the audience, nor should anything stand +in the way of or obstruct the lecturer. They should be so placed, too, +as to produce a kind of uniformity in appearance. No one part should +appear naked and another crowded,<span class="pagenum"><a id="Page_248">[248]</a></span> unless some particular reason +exists and makes it necessary to be so."</p> + +<p>On October 13, 1813, Faraday left the Royal Institution, in order to +accompany Sir Humphry Davy in a tour on the Continent. His journal +gives some interesting details, showing the inconveniences of foreign +travel at that time. Sir Humphry Davy took his carriage with him in +pieces, and these had to be put together after escaping the dangers of +the French custom-house on the quay at Morlaix, two years before the +battle of Waterloo.</p> + +<p>One apparently trivial incident somewhat marred Faraday's pleasure +throughout this journey. It was originally intended that the party +should comprise Sir Humphry and Lady Davy, Faraday, and Sir Humphry's +valet, but at the last moment that most important functionary declined +to leave his native shores. Davy then requested Faraday to undertake +such of the duties of valet as were essential to the well-being of the +party, promising to secure the services of a suitable person in Paris. +But no eligible candidate appeared for the appointment, and thus +Faraday had throughout to take charge of domestic affairs as well as +to assist in experiments. Had there been only Sir Humphry and himself, +this would have been no hardship. Sir Humphry had been accustomed to +humble life in his early days; but the case was different with his +lady, and, apparently, Faraday was more than once on the point of +leaving his patron and returning home alone. A circumstance which<span class="pagenum"><a id="Page_249">[249]</a></span> +occurred at Geneva illustrates the position of affairs. Professor E. +de la Rive invited Sir Humphry and Lady Davy and Faraday to dinner. +Sir Humphry could not go into society with one who, in some respects, +acted as his valet. When this point was represented to the professor, +he replied that he was sorry, as it would necessitate his giving +another dinner-party. Faraday subsequently kept up a correspondence +with De la Rive, and continued it with his son. In writing to the +latter he says, in speaking of Professor E. de la Rive, that he was +"the first who personally at Geneva, and afterwards by correspondence, +encouraged and by that sustained me."</p> + +<p>At Paris Faraday met many of the most distinguished men of science of +the time. One morning Ampère, Clément, and Desormes called on Davy, to +show him some iodine, a substance which had been discovered only about +two years before, and Davy, while in Paris, and afterwards at +Montpellier, executed a series of experiments upon it. After three +months' stay, the party left Paris for Italy, <i>viâ</i> Montpellier, Aix, +and Nice, whence they crossed the Col de Tende to Turin. The transfer +of the carriage and baggage across the Alps was effected by a party of +sixty-five men, with sledges and a number of mules. The description of +the journey, as recorded in Faraday's diary, makes us respect the +courage of an Englishman who, in the early part of this century, would +attempt the conveyance of a carriage across the Alps in the winter.</p><p><span class="pagenum"><a id="Page_250">[250]</a></span></p> + +<p>"From Turin we proceeded to Genoa, which place we left afterwards in +an open boat, and proceeded by sea towards Lerici. This place we +reached after a very disagreeable passage, and not without +apprehensions of being overset by the way. As there was nothing there +very enticing, we continued our route to Florence; and, after a stay +of three weeks or a month, left that fine city, and in four days +arrived here at Rome." The foregoing is from Faraday's letter to his +mother. At Florence a good deal of time was spent in the Academia del +Cimento. Here Faraday saw the telescope with which Galileo discovered +Jupiter's satellites, with its tube of wood and paper about three feet +and a half long, and simple object-glass and eye-glass. A red velvet +electric machine with a rubber of gold paper, Leyden jars pierced by +the discharge between their armatures, the first lens constructed by +Galileo, and a number of other objects, were full of interest to the +recently enfranchised bookbinder's apprentice; but it was the great +burning-glass of the grand-duke which was the most serviceable of all +the treasures of the museum. With this glass—which consisted of two +convex lenses about three feet six inches apart, the first lens having +a diameter of about fourteen or fifteen inches, and the second a +diameter of three inches—Davy succeeded in burning several diamonds +in oxygen gas, and in proving that the diamond consists of little else +than carbon. In 1818 Faraday published a paper on this subject in the +<i>Quarterly Journal of Science</i>. At Genoa some<span class="pagenum"><a id="Page_251">[251]</a></span> experiments were made +with the torpedo, but the specimens caught were very small and weak, +and their shocks so feeble that no definite results were obtained. At +Rome Davy attempted to repeat an experiment of Signor Morrichini, +whereby a steel needle was magnetized by causing the concentrated +violet and blue rays from the sun to traverse the needle from the +middle to the north end several times. The experiment did not succeed +in the hands of Davy and Faraday, and it was left to the latter to +discover a relation between magnetism and light. From Rome they +visited Naples and ascended Vesuvius, and shortly afterwards left +Italy for Geneva. In the autumn of 1814 they returned from Switzerland +through Germany, visiting Berne, Zurich, the Tyrol, Padua, Venice, and +Bologne, to Florence, where Davy again carried out some chemical +investigations in the laboratory of the academy. Thence they returned +to Rome, and in the spring went on to Naples, and again visited +Vesuvius, returning to England in April, <i>viâ</i> Rome, the Tyrol, +Stuttgart, Brussels, and Ostend.</p> + +<p>A fortnight after his return from the Continent Faraday was again +assistant at the Royal Institution, but with a salary of thirty +shillings a week. His character will be sufficiently evident from the +quotations which have been given from his diary and letters. +Henceforth we must be mainly occupied with the consideration of his +scientific work.</p> + +<p>In January, 1816, he gave his first lecture to the City Philosophical +Society. In a lecture delivered<span class="pagenum"><a id="Page_252">[252]</a></span> shortly afterwards before the same +society, the following passage, which gives an idea of one of the +current beliefs of the time, occurs:—</p> + +<p>"The conclusion that is now generally received appears to be that +light consists of minute atoms of matter of an octahedral form, +possessing polarity, and varying in size or in velocity....</p> + +<p>"If now we conceive a change as far beyond vaporization as that is +above fluidity, and then take into account also the proportional +increased extent of alteration as the changes rise, we shall, perhaps, +if we can form any conception at all, not fall far short of radiant +matter;<a id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a> and as in the last conversion many qualities were lost, so +here also many more would disappear.</p> + +<div class="footnote"><p><a id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> Not Crookes's.</p></div> + +<p>"It was the opinion of Newton, and of many other distinguished +philosophers, that this conversion was possible, and continually going +on in the processes of nature, and they found that the idea would bear +without injury the application of mathematical reasoning—as regards +heat, for instance. If assumed, we must also assume the simplicity of +matter; for it would follow that all the variety of substances with +which we are acquainted could be converted into one of three kinds of +radiant matter, which again may differ from one another only in the +size of their particles or their form. The properties of known bodies +would then be supposed to arise from the varied arrangements of their +ultimate atoms, and belong to substances <span class="pagenum"><a id="Page_253">[253]</a></span>only as long as their +compound nature existed; and thus variety of matter and variety of +properties would be found co-essential. The simplicity of such a +system is singularly beautiful, the idea grand and worthy of Newton's +approbation. It was what the ancients believed, and it may be what a +future race will realize."</p> + +<p>In the closing words of his fifth lecture to the City Philosophical +Society, Faraday said:—</p> + +<p>"The philosopher should be a man willing to listen to every +suggestion, but determined to judge for himself. He should not be +biassed by any appearances; have no favourite hypothesis; be of no +school; and in doctrine have no master. He should not be a respecter +of persons, but of things. Truth should be his primary object. If to +these qualities be added industry, he may indeed hope to walk within +the veil of the temple of nature."</p> + +<p>Many years afterwards he stated that, of all the suggestions to which +he had patiently listened after his lectures at the Royal Institution, +only one proved on investigation to be of any value, and that led to +the discovery of the "extra current" and the whole subject of +self-induction.</p> + +<p>Faraday always kept a note-book, in which he jotted down any thoughts +which occurred to him in reference to his work, as well as extracts +from books or other publications which attracted his attention. He +called it his "commonplace-book." Many of the queries which he here +took note of he<span class="pagenum"><a id="Page_254">[254]</a></span> subsequently answered by experiment. For example:—</p> + +<p>"Query: the nature of sounds produced by flame in tubes."</p> + +<p>"Convert magnetism into electricity."</p> + +<p>"General effects of compression, either in condensing gases or +producing solutions, or even giving combinations at low temperature."</p> + +<p>"Do the pith-balls diverge by the disturbance of electricity through +mutual induction or not?"</p> + +<p>Speaking of this book, he says, "I already owe much to these notes, +and think such a collection worth the making by every scientific man. +I am sure none would think the trouble lost after a year's +experience."</p> + +<p>In a letter dated May 3, 1818, he writes:—</p> + +<blockquote> +<p>I have this evening been busy with an atmospherical electrical +apparatus. It was a very temporary thing, but answered the purpose +completely. A wire, with some small brush-wire rolled round the top of +it, was elevated into the atmosphere by a thin wood rod having a glass +tube at the end, and tied to a chimney-pot on the housetop; and this +wire was continued down (taking care that it touched nothing in its +way) into the lecture-room; and we succeeded, at intervals, in getting +sparks from it nearly a quarter of an inch in length, and in charging +a Leyden jar, so as to give a strong shock. The electricity was +positive. Now, I think you could easily make an apparatus of this +kind, and it would be a constant source of<span class="pagenum"><a id="Page_255">[255]</a></span> interesting matter; only +take care you do not kill yourself or knock down the house.</p> +</blockquote> + +<p>On June 12, 1820, he married Miss Sarah Barnard, third daughter of Mr. +Barnard, of Paternoster Row—"an event which," to use his own words, +"more than any other contributed to his earthly happiness and +healthful state of mind." It was his wish that the day should be "just +like any other day"—that there should be "no bustle, no noise, no +hurry occasioned even in one day's proceeding," though in carrying out +this plan he offended some of his relations by not inviting them to +his wedding.</p> + +<p>Up to this time Faraday's experimental researches had been for the +most part in the domain of chemistry, and for two years a great part +of his energy had been expended in investigating, in company with Mr. +Stodart, a surgical instrument-maker, the properties of certain alloys +of steel, with a view to improve its manufacture for special purposes. +It was in 1821 that he commenced his great discoveries in electricity. +In the autumn of that year he wrote an historical sketch of +electro-magnetism for the "Annals of Philosophy," and he repeated for +himself most of the experiments which he described. In the course of +these experiments, in September, 1821, he discovered the rotation of a +wire conveying an electric current around the pole of a magnet. +Œrsted had discovered, in 1820, the tendency of a magnetic needle +to set itself at right angles to a wire conveying a current. This<span class="pagenum"><a id="Page_256">[256]</a></span> +action is due to a tendency on the part of the north pole to revolve +in a right-handed direction around the current, while the south pole +tends to revolve in the opposite direction. The principle that action +and reaction are equal and opposite indicates that, if a magnetic pole +tend to rotate around a conductor conveying a current, there must be +an equal tendency for the conductor to rotate around the pole. It was +this rotation that constituted Faraday's first great discovery in +electro-dynamics. On December 21, in the same year, Faraday showed +that the earth's magnetism was capable of exerting a directive action +on a wire conveying a current. Writing to De la Rive on the subject, +he says:—</p> + +<blockquote> +<p>I find all the usual attractions and repulsions of the magnetic +needle by the conjunctive wire are deceptions, the motions being, not +attractions or repulsions, nor the result of any attractive or +repulsive forces, but the result of a force in the wire, which, +instead of bringing the pole of the needle nearer to or further from +the wire, endeavours to make it move round it in a never-ending circle +and motion whilst the battery remains in action. I have succeeded, not +only in showing the existence of this motion theoretically, but +experimentally, and have been able to make the wire revolve round a +magnetic pole, or a magnetic pole round the wire, at pleasure. The law +of revolution, and to which all the other motions of the needle are +reducible, is simple and beautiful.</p><p><span class="pagenum"><a id="Page_257">[257]</a></span></p> + +<p>Conceive a portion of connecting wire north and south, the north end +being attached to the positive pole of a battery, the south to the +negative. A north magnetic pole would then pass round it continually +in the apparent direction of the sun, from east to west above, and +from west to east below. Reverse the connections with the battery, and +the motion of the pole is reversed; or, if the south pole be made to +revolve, the motions will be in the opposite direction, as with the +north pole.</p> + +<p>If the wire be made to revolve round the pole, the motions are +according to those mentioned.... Now, I have been able, +experimentally, to trace this motion into its various forms, as +exhibited by Ampère's helices, etc., and in all cases to show that the +attractions and repulsions are only appearances due to this +circulation of the pole; to show that dissimilar poles repel as well +as attract, and that similar poles attract as well as repel; and to +make, I think, the analogy between the helix and common bar magnet far +stronger than before. But yet I am by no means decided that there are +currents of electricity in the common magnet. I have no doubt that +electricity puts the circles of the helix into the same state as those +circles are in that may be conceived in the bar magnet; but I am not +certain that this state is directly dependent on the electricity, or +that it cannot be produced by other agencies; and therefore, until the +presence of electric currents be proved in the magnet by<span class="pagenum"><a id="Page_258">[258]</a></span> other than +magnetical effects, I shall remain in doubt about Ampère's theory.</p> +</blockquote> + +<p>The most convenient rule by which to remember the direction of these +electro-magnetic rotations is probably that given by Clerk Maxwell, +which will be stated in its place.<a id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a> If a circular plate of copper +and another of zinc be connected by a piece (or better, by three +pieces) of insulated wire, so that the zinc is about an inch above the +copper, and the combined plates be suspended by a silk fibre in a +small beaker of dilute sulphuric acid, which is placed on the pole of +a large magnet, the liquid will be seen to rotate about a vertical +axis in one direction, and the two plates with their connecting wires +in the opposite direction. On reversing the polarity of the magnet, +both rotations will be reversed. This is a very simple mode of +exhibiting Faraday's discovery. A little powdered resin renders the +motion of the liquid readily visible.</p> + +<div class="footnote"><p><a id="Footnote_7_7"></a><a href="#FNanchor_7_7"> +<span class="label">[7]</span></a> See p. <a href="#Page_302">302</a>.</p></div> + +<p>In 1823 Faraday published his work on the liquefaction of gases, from +which he concluded that there was no difference in kind between gases +and vapours. In the course of this work he met with more than one +serious explosion. On January 8, 1824, he was elected a Fellow of the +Royal Society, and in 1825, on the recommendation of Sir Humphry Davy, +he was appointed Director of the Laboratory of the Royal Institution, +and in this capacity he instituted the laboratory conferences, which +developed into the Friday evening <span class="pagenum"><a id="Page_259">[259]</a></span>lectures. For five years after +this, the greater part of Faraday's spare time was occupied in some +investigations in connection with optical glass, made at the request +of the Royal Society, and at the expense of the Government. Mr. +Dollond and Sir John Herschel were associated with him on this +committee, but the results obtained were not of much value to +opticians. The silico-borate of lead which Faraday prepared in the +course of these experiments was, however, the substance with which he +first demonstrated the effect of a magnetic field on the plane of +polarization of light, and with which he discovered diamagnetic +action.</p> + +<p>Faraday's experimental researches were generally guided by theoretical +considerations. Frequently these theories were based on very slender +premises, and sometimes were little else than flights of a scientific +imagination, but they served to guide him into fruitful fields of +discovery, and he seldom placed much confidence in his conclusions +till he had succeeded in verifying them experimentally. For many years +he had held the opinion that electric currents should exhibit +phenomena analogous to those of electro-static induction. Again and +again he returned to the investigation, and attempted to obtain an +induced current in one wire through the passage of a powerful current +through a neighbouring conductor; but he looked for a permanent +induced current to be maintained during the whole time that the +primary current was flowing. At length, employing two wires<span class="pagenum"><a id="Page_260">[260]</a></span> wound +together as a helix on a wooden rod, the first capable of transmitting +a powerful current from a battery, while the second was connected with +a galvanometer, he observed that, when the current started in the +primary, there was a movement of the galvanometer, and when it ceased +there was a movement in the opposite direction, though the +galvanometer remained at zero while the current continued steady. +Hence it was apparent that it is by changes in the primary current +that induced currents may be generated, and not by their steady +continuance; and it was demonstrated that, when a current is started +in a conductor, a temporary current is induced in a neighbouring +conductor in the opposite direction, while a current is induced in the +same direction as the primary when the latter ceases to flow. Before +obtaining this result with the wires on a wooden bobbin, he had +experimented with a wrought-iron ring about six inches in diameter, +and made of 7/8-inch round iron. He wound two sets of coils round it, +one occupying nearly half the ring, and the other filling most of the +other half. One of these he connected with a galvanometer, the other +could be connected at will with a battery. On sending the battery +current through the latter coil, the galvanometer needle swung +completely round four or five times, and a similar action took place, +but in the opposite direction, on stopping the current. Here it was +clearly the magnetism induced in the iron ring<span class="pagenum"><a id="Page_261">[261]</a></span> which produced so +powerful a current in the galvanometer circuit. Next he wound a +quantity of covered copper wire on a small iron bar, and connecting +the ends to a galvanometer, he placed the little bobbin between the +opposite poles of a pair of bar magnets, whose other ends were in +contact. As soon as the iron core touched the magnets, a current +appeared in the galvanometer. On breaking contact, the current was in +the opposite direction. Then came the experiment above mentioned, in +which no iron was employed. After this, one end of a cylindrical bar +magnet was introduced into a helix of copper wire, and then suddenly +thrust completely in. The galvanometer connected with the coil showed +a transient current. On withdrawing the magnet, the current appeared +in the opposite direction; so that currents were induced merely by the +relative motion of a magnet and a conductor.</p> + +<div class="figcenter"> +<img src="images/i271.jpg" width="325" height="207" alt="" /> +</div> + +<p>A copper disc was mounted so that it could be made to rotate rapidly. +A wire was placed in connection with the centre of the disc, and<span class="pagenum"><a id="Page_262">[262]</a></span> the +circuit completed by a rubbing contact on the circumference. A +galvanometer was inserted in the circuit, and the large horseshoe +magnet of the Royal Institution so placed that the portion of the disc +between the centre and the rubbing contact passed between the poles of +the magnet. A current flowed through the galvanometer as long as the +disc was kept spinning. Then he found that the mere passage of a +copper wire between the poles of the magnet was sufficient to induce a +current in it, and concluded that the production of the current was +connected with the cutting of the "magnetic curves," or "lines of +magnetic force" which would be depicted by iron filings. Thus in the +course of ten days' experimental work, in the autumn of 1831, Faraday +so completely investigated the phenomena of electro-magnetic induction +as to leave little, except practical applications, to his successors. +A few weeks later he obtained induction currents by means of the +earth's magnetism only, first with a coil of wire wound upon an iron +bar in which a strong current was produced when it was being quickly +placed in the direction of the magnetic dip or being removed from that +position, and afterwards with a coil of wire without an iron core. On +February 8, 1832, he succeeded in obtaining a spark from the induced +current. Unless the electro-motive force is very great, it is not +possible to obtain a spark between two metallic surfaces which are +separated by a sensible thickness of air. If, however, the<span class="pagenum"><a id="Page_263">[263]</a></span> circuit of +a wire is broken <i>while</i> the current is passing, a little bridge of +metallic vapour is formed, across which for an instant the spark +leaps. The induced current being of such short duration, the +difficulty was to break the circuit while it was flowing. Faraday +wound a considerable length of fine wire around a short bar of iron; +the ends of the wire were crossed so as just to be in contact with one +another, but free to separate if exposed to a slight shock. The ends +of the iron bar projected beyond the coil, and were held just over the +poles of the magnet. On releasing the bar it fell so as to strike the +magnetic poles and close the circuit of the magnet. An induced current +was generated in the wire, but, while this was passing, the shock +caused by the bar striking the magnet separated the ends of the wire, +thus breaking the circuit of the conductor, and a spark appeared at +the gap. In this little spark was the germ of the electric light of +to-day. Subsequently Faraday improved the apparatus, by attaching a +little disc of amalgamated copper to one end of the wire, and bending +over the other end so as just to press lightly against the surface of +the disc. With this apparatus he showed the "magnetic spark" at the +meeting of the British Association at Oxford.</p> + +<p>Faraday supposed that when a coil of wire was in the neighbourhood of +a magnet, or near to a conductor conveying a current, the coil was +thrown into a peculiar condition, which he called the <i>electro-tonic<span class="pagenum"><a id="Page_264">[264]</a></span> +state</i>, and that the induced currents appeared whenever this state was +assumed or lost by the coil. He frequently reverted to his conception +of the electro-tonic state, though he saw clearly that, when the +currents were induced by the relative motion of a wire and a magnet, +the current induced depended on the rate at which the lines of +magnetic force had been cut by the wire. Of his conception of lines of +force filling the whole of space, we shall have more to say presently. +It is sufficient to remark here that, in the electro-tonic state of +Faraday, Clerk Maxwell recognized the number of lines of magnetic +force enclosed by the circuit, and showed that the electro-motive +force induced is proportional to the rate of change of the number of +lines of force thus enclosed.</p> + +<div class="figcenter"> +<img src="images/i275.jpg" width="318" height="252" alt="" /> +</div> + +<p>It is seldom that a great discovery is made which has not been +gradually led up to by several observed phenomena which awaited that +discovery for their explanation. In the case of electro-magnetic +induction, however, there appears to have been but one experiment +which had baffled philosophers, and the key to which was found in +Faraday's discovery, while the complete explanation was given by +Faraday himself. Arago had found that, if a copper plate were made +rapidly to rotate beneath a freely suspended magnetic needle, the +needle followed (slowly) the plate in its revolution, though a sheet +of glass were inserted between the two to prevent any air-currents +acting on the magnet. The experiment had been repeated by<span class="pagenum"><a id="Page_265">[265]</a></span> Sir John +Herschel and Mr. Babbage, but no explanation was forthcoming. Faraday +saw that the revolution of the disc beneath the poles of the magnet +must generate induced currents in the disc, as the different portions +of the metal would be constantly cutting the lines of force of the +magnet. These currents would react upon the magnet, causing a +mechanical stress to act between the two, which, as stated by Lenz, +would be in the direction tending to oppose the <i>relative</i> motion, and +therefore to drag the magnet after the disc in its revolution. In the +above figure the unfledged arrows show the general distribution of the +currents in the disc, while the winged arrows indicate the direction +of the disc's rotation. The currents in the semicircle A will repel +the north pole and attract the south pole. Those in the semicircle B +will produce the opposite effect, and hence there will be a tendency +for the magnet to revolve in the direction of the disc, while the +motion of the disc will be resisted. This resistance<span class="pagenum"><a id="Page_266">[266]</a></span> to the motion of +a conductor in a magnetic field was noticed by Faraday, and, +independently, by Tyndall, and it is sufficiently obvious in the power +absorbed by dynamos when they are generating large currents.</p> + +<p>Faraday's next series of researches was devoted to the experimental +proof of the identity of frictional and voltaic electricity. He showed +that a magnet could be deflected and iodide of potassium decomposed by +the current from his electrical machine, and came to the conclusion +that the amount of electricity required to decompose a grain of water +was equal to 800,000 charges of his large Leyden battery. The current +from the frictional machine also served to deflect the needle of his +galvanometer. These investigations led on to a complete series of +researches on the laws of electrolysis, wherein Faraday demonstrated +the principle that, however the strength of the current may be varied, +the amount of any compound decomposed is proportional to the whole +quantity of electricity which has passed through the electrolyte. When +the same current is sent through different compounds, there is a +constant relation between the amounts of the several compounds +decomposed. In modern language, Faraday's laws may be thus +expressed:—</p> + +<p><i>If the same current be made to pass through several different +electrolytes, the quantity of each ion produced will be proportional +to its combining weight divided by its valency, and if the current +vary, the quantity<span class="pagenum"><a id="Page_267">[267]</a></span> of each ion liberated per second will be +proportional to the current.</i></p> + +<p>This is the great law of electro-chemical equivalents. The amount of +hydrogen liberated per second by a current of one ampère is about +·00001038 gramme, or nearly one six-thousandth of a grain. This is the +electro-chemical equivalent of hydrogen. That of any other substance +may be found by Faraday's law.</p> + +<p>From Faraday's results it appears that the passage of the same amount +of electricity is required in order to decompose one molecule of any +compound of the same chemical type, but it does not follow that the +same amount of energy is employed in the decomposition. For example, +the combining weights of copper and zinc are nearly equal. Hence it +will require the passage of about the same amount of electricity to +liberate a pound of copper from, say, the copper sulphate as to +liberate a pound of zinc from zinc sulphate; but the work to be done +is much less in the case of the copper. This is made manifest in the +following way:—A battery, which will just decompose the copper salt +slowly, liberating copper, oxygen, and sulphuric acid, will not +decompose the zinc salt at all so as to liberate metallic zinc, but +immediately on sending the current through the electrolyte, +polarization will set in, and the opposing electro-motive force thus +introduced will become equal to that of the battery, and stop the +current before metallic zinc makes its appearance. In the<span class="pagenum"><a id="Page_268">[268]</a></span> case of the +copper, polarization also sets in, but never attains to equality with +the electro-motive force of the primary battery. In fact, in all cases +of electrolysis, polarization produces an opposing electro-motive +force strictly proportional to the work done in the cell by the +passage of each unit of electricity. If the strength of the battery be +increased, so that it is able to decompose the zinc sulphate, and if +this battery be applied to the copper sulphate solution, the latter +will be <i>rapidly</i> decomposed, and the excess of energy developed by +the battery will be converted into heat in the circuit.</p> + +<p>One important point in connection with electrolysis which Faraday +demonstrated is that the decomposition is the result of the passage of +the current, and is not simply due to the attraction of the +electrodes. Thus he showed that potassium iodide could be decomposed +by a stream of electricity coming from a metallic point on the prime +conductor of his electric machine, though the point did not touch the +test-paper on which the iodide was placed.</p> + +<p>It was in 1834 that Mr. Wm. Jenkin, after one of the Friday evening +lectures at the Royal Institution, called the attention of Faraday to +a shock which he had experienced in breaking the circuit of an +electro-magnet, though the battery employed consisted of only one pair +of plates. Faraday repeated the experiment, and found that, with a +large magnet in circuit, a strong spark could thus<span class="pagenum"><a id="Page_269">[269]</a></span> be obtained. On +November 14, 1834, he writes, "The phenomenon of increased spark is +merely a case of the induction of electric currents. If a current be +established in a wire, and another wire forming a complete circuit be +placed parallel to it, at the moment the current in the first is +stopped it induces a current in the same direction in the second, +itself then showing but a feeble spark. But if the second be away, it +induces a current in its own wire in the same direction, producing a +strong spark. The strong spark in the current when alone is therefore +the equivalent of the current it can produce in a neighbouring wire +when in company." The strong spark does, in fact, represent the energy +of the current due to the self-induction of its circuit, which energy +would, in part at least, be expended in inducing a current in a +neighbouring wire if such existed.</p> + +<p>His time from 1835 till 1838 was largely taken up with his work on +electro-static induction. Faraday could never be content with any +explanation based on direct action at a distance; he always sought for +the machinery through which the action was communicated. In this +search the lines of magnetic force, which he had so often delineated +in iron filings, came to his aid. Faraday made many pictures in iron +filings of magnetic fields due to various combinations of magnets. He +employed gummed paper, and when the filings were arranged on the hard +gummed surface, he projected a feeble jet of steam on the paper, which +melted the gum<span class="pagenum"><a id="Page_270">[270]</a></span> and fixed the filings. Several of his diagrams were +exhibited at the Loan Collection at South Kensington. He conceived +electrical action to be transmitted along such lines as these, and to +him the whole electric field was filled with lines passing always from +positive to negative electrification, and in some respects resembling +elastic strings. The action at any place could then be expressed in +terms of the lines of force that existed there, the electrifications +by which these lines were produced being left out of consideration. +The acting bodies were thus replaced by the field of force they +produced. He showed that it was impossible to call into existence a +charge of positive electricity without at the same time producing an +equal negative charge. From every unit of positive electricity he +conceived a line of force to start, and thus, with the origin of the +line, there was created simultaneously a charge of negative +electricity on which the line might terminate. By the famous ice-pail +experiment he showed that, when a charged body is inserted in a closed +or nearly closed hollow conductor, an equal amount of the same kind of +electricity appeared on the outside of the hollow conductor, while an +equal amount of the opposite kind appeared on the interior surface of +the conductor. With the ice-pail and the butterfly-net he showed that +there could be no free electricity on the interior of a conductor. +Lines of force cannot pass through the material of a conductor without +producing electric displacement. Every element<span class="pagenum"><a id="Page_271">[271]</a></span> of electricity must be +joined to an equal amount of the opposite kind by a line of force. +Such lines cannot pass through the conductor itself; hence the charge +must be entirely on the outside of the conductor, so that every +element of the charge may be associated with an equal amount of the +opposite electricity upon the surfaces of surrounding objects. Thus to +Faraday every electrical action was an exhibition of electric +induction. All this work had been done before by Henry Cavendish, but +neither Faraday nor any one else knew about it at the time. From the +fact that there could be no electricity in the interior of a hollow +conductor, Cavendish deduced, in the best way possible, the truth of +the law of inverse squares as applied to electrical attraction and +repulsion, and thus laid the foundation of the mathematical theory of +electricity. To Cavendish every electrical action was a displacement +of an incompressible fluid which filled the whole of space, producing +no effect in conductors on account of the freedom of its motion, but +producing strains in insulators by displacing the material of the +body. Faraday, in his lines of force, saw, as it were, the lines along +which the displacements of Cavendish's fluid took place.</p> + +<p>Faraday thought that, if he could show that electric induction could +take place along curved lines, it would prove that the action took +place through a medium, and not directly at a distance. He succeeded +in experimentally demonstrating the curvature of these lines; but his +conclusions were<span class="pagenum"><a id="Page_272">[272]</a></span> not warranted, for if we conceive of two or more +centres of force acting directly at a distance according to the law of +inverse squares, the resultant lines of force will generally be +curved. Of course, this does not prove the possibility of direct +action at a distance, but only shows that the curvature of the lines +is as much a consequence of the one hypothesis as of the other.</p> + +<p>It soon appeared to Faraday that the nature of the dielectric had very +much to do with electric induction. The capacity of a condenser, for +instance, depends on the nature of the dielectric as well as on the +configuration of the conductors. To express this property, Faraday +employed the term "specific inductive capacity." He compared the +electric capacity of condensers, equal in all other respects, but one +possessing air for its dielectric, and the other having other media, +and thus roughly determined the specific inductive capacities of +several insulators. These results turned out afterwards to be of great +value in connection with the insulation of submarine cables. Even now +the student of electricity is sometimes puzzled by the manner in which +specific inductive capacity is introduced to his notice as modifying +the capacity of condensers, after learning that the capacity of any +system of conductors can be calculated from its geometrical +configuration; but the fact is that the intensity of all electrical +actions depends on the nature of the medium through which they take +place, and it will require more electricity to exert<span class="pagenum"><a id="Page_273">[273]</a></span> upon an equal +charge a unit force at unit distance when the intervening medium has a +high than when it possesses a low specific inductive capacity.</p> + +<p>In 1835 Faraday received a pension from the civil list; in 1836 he was +appointed scientific adviser to the Elder Brethren of the Trinity +House. In the same year he was made a member of the Senate of the +University of London, and in that capacity he has exerted no small +influence on the scientific education of the country, for he was one +of those who drew up the schedules of the various examinations.</p> + +<p>In his early years, Faraday thought that all kinds of matter might +ultimately consist of three materials only, and that as gases and +vapours appeared more nearly to resemble one another than the liquids +or solids to which they corresponded, so each might be subject to a +still higher change in the same direction, and the gas or vapour +become radiant matter—either heat, light, or electricity. Later on, +Faraday clearly recognized the dynamical nature of heat and light; but +his work was always guided by his theoretical conceptions of the +"correlation of the physical forces." For a long time he had tried to +discover relations between electricity and light; at length, on +September 13, 1845, after experimenting on a number of other +substances, he placed a piece of silico-borate of lead, or +heavy-glass, in the field of the magnet, and found that, when a beam +of polarized light was transmitted through the glass in the direction +of<span class="pagenum"><a id="Page_274">[274]</a></span> the lines of magnetic force, there was a rotation of the plane of +polarization. Afterwards it appeared that all the transparent solids +and liquids experimented on were capable of producing this rotation in +a greater or less degree, and in the case of all non-magnetic +substances the rotation was in the direction of the electric current, +which, passing round the substance, would produce the magnetic field +employed. Abandoning the magnet, and using only a coil of wire with +the transparent substance within it, similar effects were obtained. +Thus at length a relation was found between light and electricity.</p> + +<p>On November 4, employing a piece of heavy-glass and a new horseshoe +magnet, Faraday noticed that the magnet appeared to have a directive +action upon the glass. Further examination showed that the glass was +repelled by the magnetic poles. Three days afterwards he found that +all sorts of substances, including most metals, were acted upon like +the heavy-glass. Small portions of them were repelled, while elongated +cylinders tended to set with their lengths perpendicular to the lines +of magnetic force. Such actions could be imitated by suspending a +feebly magnetic body in a medium more magnetic than itself. Faraday, +therefore, sought for some medium which would be absolutely neutral to +magnetic action. Filling a glass tube with compressed oxygen, and +suspending it in an atmosphere of oxygen at ordinary pressure, the +compressed gas<span class="pagenum"><a id="Page_275">[275]</a></span> behaved like iron or other magnetic substances. +Faraday compared the intensity of its action with that of ferrous +sulphate, and this led to an explanation of the diurnal variations of +the compass-needle based on the sun's heat diminishing the magnetic +<i>permeability</i> of the oxygen of the air. Repeating the experiment with +nitrogen, he found that the compressed gas behaved in a perfectly +neutral manner when surrounded by the gas at ordinary pressure. Hence +he inferred that in nitrogen he had found the neutral medium required. +Repeating his experiments in an atmosphere of nitrogen, it still +appeared that most bodies were repelled by the magnetic poles, and set +<i>equatorially</i>, or at right angles to the lines of force when +elongated portions were tested. To this action Faraday gave the name +of diamagnetism.</p> + +<p>About a month after his marriage, Faraday joined the Sandemanian +Church, to which his family had for several generations belonged, by +confession of sin and profession of faith. Not unfrequently he used to +speak at the meetings of his Church, but in 1840 he was elected an +elder, and then he took his turn regularly in conducting the services. +The notes of his addresses he generally made on small pieces of card. +He had a curious habit of separating his religious belief from his +scientific work, although the spirit of his religion perpetually +pervaded his life. A lecture on mental education, given in 1854, at +the Royal Institution, in the presence of the late Prince Consort, he +commenced as follows:<span class="pagenum"><a id="Page_276">[276]</a></span>—</p> + +<p>"Before entering on this subject, I must make one distinction, which, +however it may appear to others, is to me of the utmost importance. +High as man is placed above the creatures around him, there is a +higher and far more exalted position within his view; and the ways are +infinite in which he occupies his thoughts about the fears, or hopes, +or expectations of a future life. I believe that the truth of that +future cannot be brought to his knowledge by any exertion of his +mental powers, however exalted they may be; that it is made known to +him by other teaching than his own, and is received through simple +belief of the testimony given. Let no one suppose for a moment that +the self-education I am about to commend, in respect of the things of +this life, extends to any considerations of the hope set before us, as +if man by reasoning could find out God. It would be improper here to +enter upon this subject further than to claim an absolute distinction +between religious and ordinary belief. I shall be reproached with the +weakness of refusing to apply those mental operations which I think +good in respect of high things to the very highest. I am content to +bear the reproach. Yet even in earthly matters I believe that 'the +invisible things of Him from the creation of the world are clearly +seen, being understood by the things that are made, even His eternal +power and Godhead;' and I have never seen anything incompatible +between those things of man which can be known by the spirit of man +which is within him, and those<span class="pagenum"><a id="Page_277">[277]</a></span> higher things concerning his future +which he cannot know by that spirit."</p> + +<p>On more than one occasion the late Prince Consort had discussed +physical questions with Faraday, and in 1858 the Queen offered him a +house on Hampton Court Green. This was his home until August 25, 1867. +He saw not only the magnetic spark, which he had first produced, +employed in the lighthouses at the South Foreland and Dungeness, but +he saw also his views respecting lines of electric induction examined +and confirmed by the investigations of Thomson and Clerk Maxwell.</p> + +<p>Of the ninety-five distinctions conferred upon him, we need only +mention that of Commandant of the Legion of Honour, which he received +in January, 1856.</p> + +<div class="figcenter"> +<img src="images/i287.jpg" width="182" height="157" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_278">[278]</a></span></p> + +<div class="figcenter"> +<img src="images/i288.jpg" width="486" height="120" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="JAMES_CLERK_MAXWELL">JAMES CLERK MAXWELL.</h2> + +<p>The story of the life of James Clerk Maxwell has been told so recently +by the able pen of his lifelong friend, Professor Lewis Campbell, that +it is unnecessary, in the few pages which now remain to us, to attempt +to give a repetition of the tale which would not only fail to do +justice to its subject, but must of necessity fall far short of the +merits of the (confessedly imperfect) sketch which has recently been +placed within the reach of all. Looking back on the life of Clerk +Maxwell, he seems to have come amongst us as a light from another +world—to have but partly revealed his message to minds too often +incapable of grasping its full meaning, and all too soon to have +returned to the source from whence he came. There was scarcely any +branch of natural philosophy that he did not grapple with, and upon +which his vivid imagination and far-seeing intelligence did not throw +light. He was born a philosopher, and at every step Nature partly drew +aside<span class="pagenum"><a id="Page_279">[279]</a></span> the veil and revealed that which was hidden from a gaze less +prophetic. A very brief sketch of the principal incidents in his life +may, however, not be out of place.</p> + +<p>James Clerk Maxwell was born in Edinburgh, on June 13, 1831. His +father, John Clerk Maxwell, was the second son of James Clerk, of +Penicuik, and took the name of Maxwell on inheriting the estate at +Middlesbie. His mother was the daughter of R. H. Cay, Esq., of North +Charlton, Northumberland. James was the only child who survived +infancy.</p> + +<p>Some years before his birth his parents had built a house at Glenlair, +which had been added to their Middlesbie estate, and resided there +during the greater part of the year, though they retained their house +in Edinburgh. Hence it was that James's boyish days were spent almost +entirely in the country, until he entered the Edinburgh Academy in +1841. As a child, he was never content until he had completely +investigated everything which attracted his attention, such as the +hidden courses of bell-wires, water-streams, and the like. His +constant question was "What's the go o' that?" and, if answered in +terms too general for his satisfaction, he would continue, "But what's +the particular go of it?" This desire for the thorough investigation +of every phenomenon was a characteristic of his mind through life. +From a child his knowledge of Scripture was extensive and accurate, +and when eight years old he could<span class="pagenum"><a id="Page_280">[280]</a></span> repeat the whole of the hundred and +nineteenth psalm. About this time his mother died, and thenceforward +he and his father became constant companions. Together they would +devise all sorts of ingenious mechanical contrivances. Young James was +essentially a child of nature, and free from all conventionality. He +loved every living thing, and took delight in petting young frogs, and +putting them into his mouth to see them jump out. One of his +attainments was to paddle on the duck-pond in a wash-tub, and to make +the vessel go "without spinning"—a recreation which had to be +relinquished on washing-days. He was never without the companionship +of one or two terriers, to whom he taught many tricks, and with whom +he seemed to have complete sympathy.</p> + +<p>As a boy, Maxwell was not one to profit much by the ordinary teaching +of the schools, and experience with a private tutor at home did not +lead to very satisfactory results. At the age of ten, therefore, he +was sent to the Edinburgh Academy, under the care of Archdeacon +Williams, who was then rector. On his first appearance in this +fashionable school, he was naturally a source of amusement to his +companions; but he held his ground, and soon gained more respect than +he had previously provoked ridicule. While at school in Edinburgh, he +resided with his father's sister, Mrs. Wedderburn, and devoted a very +considerable share of his time and attention to relieving the solitude +of the old man at Glenlair, by letters written in quaint styles,<span class="pagenum"><a id="Page_281">[281]</a></span> +sometimes backwards, sometimes in cypher, sometimes in different +colours, so arranged that the characters written in a particular +colour, when placed consecutively, formed another sentence. All the +details of his school and home life, and the special peculiarities of +the masters at the academy, were thus faithfully transmitted to his +father, by whom the letters were religiously preserved. At thirteen he +had evidently made progress in solid geometry, though he had not +commenced Euclid, for he writes to his father, "I have made a +tetrahedron, a dodecahedron, and two other hedrons whose names I don't +know." In these letters to Glenlair he generally signed himself, "Your +most obedient servant." Sometimes his fun found vent even upon the +envelope; for example:—</p> + +<p class="right3">Mr. John Clerk Maxwell,</p> +<p class="right2">"Postyknowswere,</p> +<p class="right1">"Kirkpatrick Durham,</p> +<p class="right1">"Dumfries."</p> + +<p><br />Sometimes he would seal his letters with electrotypes of natural +objects (beetles, etc.), of his own making. In July, 1845, he +writes:—</p> + +<blockquote> +<p>I have got the eleventh prize for scholarship, the first for English, +the prize for English verses, and the mathematical medal.</p> +</blockquote> + +<p>When only fifteen a paper on oval curves was contributed by him to the +<i>Proceedings of the Royal Society of Edinburgh</i>. In the spring of 1847 +he accompanied his uncle on a visit to Mr. Nicol, the inventor of the +Nicol prism, and on his return he<span class="pagenum"><a id="Page_282">[282]</a></span> made a polariscope with glass and a +lucifer-match box, and sketched in water-colours the chromatic +appearances presented by pieces of unannealed glass which he himself +prepared. These sketches he sent to Mr. Nicol, who presented him in +return with a pair of prisms of his own construction. The prisms are +now in the Cavendish Laboratory at Cambridge. Maxwell found that, for +unannealed glass, pieces of window-glass placed in bundles of eight or +nine, one on the other, answered the purpose very well. He cut the +figures, triangles, squares, etc., with a diamond, heated the pieces +of glass on an iron plate to redness in the kitchen fire, and then +dropped them into a plate of iron sparks (scales from the smithy) to +cool.</p> + +<p>In 1847 Maxwell entered the University of Edinburgh, and during his +course of study there he contributed to the Royal Society of Edinburgh +papers upon rolling curves and on the equilibrium of elastic solids. +His attention was mostly devoted to mathematics, physics, chemistry, +and mental and moral philosophy. In 1850 he went to Cambridge, +entering Peterhouse, but at the end of a year he "migrated" to +Trinity; here he was soon surrounded with a circle of friends who +helped to render his Cambridge life a very happy one. His love of +experiment sometimes extended to his own mode of life, and once he +tried sleeping in the evening and working after midnight, but this was +soon given up at the request of his father. One of his friends writes, +"From 2 to 2.30 a.m. he<span class="pagenum"><a id="Page_283">[283]</a></span> took exercise by running along the upper +corridor, <i>down</i> the stairs, along the lower corridor, then <i>up</i> the +stairs, and so on until the inhabitants of the rooms along his track +got up and laid <i>perdus</i> behind their sporting-doors, to have shots at +him with boots, hair-brushes, etc., as he passed." His love of fun, +his sharp wit, his extensive knowledge, and above all, his complete +unselfishness, rendered him a universal favourite in spite of the +temporary inconveniences which his experiments may have occasionally +caused to his fellow-students.</p> + +<p>An undergraduate friend writes, "Every one who knew him at Trinity can +recall some kindness or some act of his which has left an ineffaceable +impression of his goodness on the memory—for 'good' Maxwell was in +the best sense of the word." The same friend wrote in his diary in +1854, after meeting Maxwell at a social gathering, "Maxwell, as usual, +showing himself acquainted with every subject on which the +conversation turned. I never met a man like him. I do believe there is +not a single subject on which he cannot talk, and talk well too, +displaying always the most curious and out-of-the-way information." +His private tutor, the late well-known Mr. Hopkins, said of him, "It +is not possible for that man to think incorrectly on physical +subjects."</p> + +<p>In 1854 Maxwell took his degree at Cambridge as second wrangler, and +was bracketed with the senior wrangler (Mr. E. J. Routh) for the +Smith's prize. During his undergraduate course, he appears<span class="pagenum"><a id="Page_284">[284]</a></span> to have +done much of the work which formed the basis of his subsequent papers +on electricity, particularly that on Faraday's lines of force. The +colour-top and colour-box appear also to have been gradually +developing during this time, while the principle of the stereoscope +and the "art of squinting" received their due share of attention. +Shortly after his degree, he devoted a considerable amount of time to +the preparation of a manuscript on geometrical optics, which was +intended to form a university text-book, but was never completed. In +the autumn of 1855 he was elected Fellow of Trinity. About this time +the colour-top was in full swing, and he also constructed an +ophthalmoscope. In May, 1855, he writes:—</p> + +<blockquote> +<p>The colour trick came off on Monday, 7th. I had the proof-sheets of +my paper, and was going to read; but I changed my mind and talked +instead, which was more to the purpose. There were sundry men who +thought that blue and yellow make green, so I had to undeceive them. I +have got Hay's book of colours out of the University Library, and am +working through the specimens, matching them with the top.</p> +</blockquote> + +<p>The "colour trick" came off before the Cambridge Philosophical Society.</p> + +<p>While a Bachelor Fellow, Maxwell gave lectures to working men in +Barnwell, besides lecturing in college. His father died in April, +1856, and shortly afterwards he was appointed Professor of Natural +Philosophy in Marischal College, Aberdeen. This<span class="pagenum"><a id="Page_285">[285]</a></span> appointment he held +until the fusion of the college with King's College in 1860. These +four years were very productive of valuable work. During them the +dynamical top was constructed, which illustrates the motion of a rigid +body about its axis of greatest, least, or mean moment of inertia; +for, by the movement of certain screws, the axis of the top may be +made to coincide with any one at will. The Adams Prize Essay on the +stability of Saturn's rings belongs also to this period. In this essay +Maxwell showed that the phenomena presented by Saturn's rings can only +be explained on the supposition that they consist of innumerable small +bodies—"a flight of brickbats"—each independent of all the others, +and revolving round Saturn as a satellite. He compared them to a siege +of Sebastopol from a battery of guns measuring thirty thousand miles +in one direction, and a hundred miles in the other, the shots never +stopping, but revolving round a circle of a hundred and seventy +thousand miles radius. A solid ring of such dimensions would be +completely crushed by its own weight, though made of the strongest +material of which we have any knowledge. If revolving at such a rate +as to balance the attraction of the planet at one part, the stress in +other parts would be more than sufficient to crush or tear the ring. +Laplace had shown that a narrow ring might revolve about the planet +and be stable if so loaded that its centre of gravity was at a +considerable distance from its centre, and thought that<span class="pagenum"><a id="Page_286">[286]</a></span> Saturn's +rings might consist of a number of such unsymmetrical rings—a theory +to which some support was given by the many small divisions observable +in the bright rings. Maxwell showed that, for stability, the mass +required to load each of Laplace's rings must be four and a half times +that of the rest of the ring; and the system would then be far too +artificially balanced to be proof against the action of one ring on +another. He further showed that, in liquid rings, waves would be +produced by the mutual action of the rings, and that before long some +of these waves would be sure to acquire such an amplitude as would +cause the rings to break up into small portions. Finally, he concluded +that the only admissible theory is that of the independent satellites, +and that the <i>average</i> density of the rings so found cannot be much +greater than that of air at ordinary pressure and temperature.</p> + +<p>While he remained at Aberdeen, Maxwell lectured to working men in the +evenings, on the principles of mechanics. On the whole, it is doubtful +whether Aberdeen society was as congenial to him as that of Cambridge +or Edinburgh. He seems not to have been understood even by his +colleagues. On one occasion he wrote:—</p> + +<blockquote> +<p>Gaiety is just beginning here again.... No jokes of any kind are +understood here. I have not made one for two months, and if I feel one +coming I shall bite my tongue.</p> +</blockquote> + +<p>But every cloud has its bright side, and, however<span class="pagenum"><a id="Page_287">[287]</a></span> Maxwell may have +been regarded by his colleagues, he was not long without congenial +companionships. An honoured guest at the home of the Principal, "in +February, 1858, he announced his betrothal to Katherine Mary Dewar, +and they were married early in the following June." Professor Campbell +speaks of his married life as one of unexampled devotion, and those +who enjoyed the great privilege of seeing him at home could more than +endorse the description.</p> + +<p>In 1860 Maxwell accepted the chair of Natural Philosophy at King's +College, London. Here he continued his lectures to working men, and +even kept them up for one session after resigning the chair in 1865. +On May 17, 1861, he gave his first lecture at the Royal Institution, +on "The Theory of the Three Primary Colours." This lecture embodies +many of the results of his work with the colour-top and colour-box, to +be again referred to presently. While at King's College, he was placed +on the Electrical Standards Committee of the British Association, and +most of the work of the committee was carried out in his laboratory. +Here, too, he compared the electro-static repulsion between two discs +of brass with the electro-magnetic attraction of two coils of wire +surrounding them, through which a current of electricity was allowed +to flow, and obtained a result which he afterwards applied to the +electro-magnetic theory of light. The colour-box was perfected, and +his experiments on the viscosity of gases were concluded<span class="pagenum"><a id="Page_288">[288]</a></span> during his +residence in London. These last were described by him in the Bakerian +Lecture for 1866.</p> + +<p>After resigning the professorship at King's College, Maxwell spent +most of his time at Glenlair, having enlarged the house, in accordance +with his father's original plans. Here he completed his great work on +"Electricity and Magnetism," as well as his "Theory of Heat," an +elementary text-book which may be said to be without a parallel.</p> + +<p>On March 8, 1871, he accepted the chair of Experimental Physics in the +University of Cambridge. This chair was founded in consequence of an +offer made by the Duke of Devonshire, the Chancellor of the +University, to build and equip a physical laboratory for the use of +the university. In this capacity Maxwell's first duty was to prepare +plans for the laboratory. With this view, he inspected the +laboratories of Sir William Thomson at Glasgow, and of Professor +Clifton at Oxford, and endeavoured to embody the best points of both +in the new building. The result was that, in conjunction with Mr. W. +M. Fawcett, the architect, he secured for the university a laboratory +noble in its exterior, and admirably adapted to the purposes for which +it is required. The ground-floor comprises a large battery-room, which +is also used as a storeroom for chemicals; a workshop; a room for +receiving goods, communicating by a lift with the apparatus-room; a +room for experiments on heat; balance-rooms; a room for pendulum<span class="pagenum"><a id="Page_289">[289]</a></span> +experiments, and other investigations requiring great stability; and a +magnetic observatory. The last two rooms are furnished with stone +supports for instruments, erected on foundations independent of those +of the building, and preserved from contact with the floor. On the +first floor is a handsome lecture-theatre, capable of accommodating +nearly two hundred students. The lecture-table is carried on a wall, +which passes up through the floor without touching it, the joists +being borne by separate brick piers. The lecture-theatre occupies the +height of the first and second floors; its ceiling is of wood, the +panels of which can be removed, thus affording access to the +roof-principals, from which a load of half a ton or more may be safely +suspended over the lecture-table. The panels of the ceiling, adjoining +the wall which is behind the lecturer, can also be readily removed, +and a "window" in this wall communicates with the large +electrical-room on the second floor. Access to the space above the +ceiling of the lecture-theatre is readily obtained from the tower. +Adjoining the lecture-room is the preparation-room, and communicating +with the latter is the apparatus-room. This room is fitted with +mahogany and plate-glass wall and central cases, and at present +contains, besides the more valuable portions of the apparatus +belonging to the laboratory, the marble bust of James Clerk Maxwell, +and many of the home-made pieces of apparatus and other relics of his +early work. The rest of the first floor is<span class="pagenum"><a id="Page_290">[290]</a></span> occupied by the +professor's private room and the general students' laboratory. +Throughout the building the brick walls have been left bare for +convenience in attaching slats or shelves for the support of +instruments. The second floor contains a large room for electrical +experiments, a dark room for photography, and a number of private +rooms for original work. Water is laid on to every room, including a +small room in the top of the tower, and all the windows are provided +with broad stone ledges without and within the window, the two +portions being in the same horizontal plane, for the support of +heliostats or other instruments. The building is heated with hot +water, but in the magnetic observatory the pipes are all of copper and +the fittings of gun-metal. Open fireplaces for basket fires are also +provided. Over the principal entrance of the laboratory is placed a +stone statue of the present Duke of Devonshire, together with the arms +of the university and of the Cavendish family, and the Cavendish +motto, "Cavendo Tutus." Maxwell presented to the laboratory, in 1874, +all the apparatus in his possession. He usually gave a course of +lectures on heat and the constitution of bodies in the Michaelmas +term; on electricity in the Lent term; and on electro-magnetism in the +Easter term. The following extract from his inaugural lecture, +delivered in October, 1871, is worthy of the attention of all students +of science:—</p> + +<blockquote> +<p>Science appears to us with a very different<span class="pagenum"><a id="Page_291">[291]</a></span> aspect after we have +found out that it is not in lecture-rooms only, and by means of the +electric light projected on a screen, that we may witness physical +phenomena, but that we may find illustrations of the highest doctrines +of science in games and gymnastics, in travelling by land and by +water, in storms of the air and of the sea, and wherever there is +matter in motion.</p> + +<p>The habit of recognizing principles amid the endless variety of their +action can never degrade our sense of the sublimity of nature, or mar +our enjoyment of its beauty. On the contrary, it tends to rescue our +scientific ideas from that vague condition in which we too often leave +them, buried among the other products of a lazy credulity, and to +raise them into their proper position among the doctrines in which our +faith is so assured that we are ready at all times to act on them. +Experiments of illustration may be of very different kinds. Some may +be adaptations of the commonest operations of ordinary life; others +may be carefully arranged exhibitions of some phenomenon which occurs +only under peculiar conditions. They all, however, agree in this, that +their aim is to present some phenomenon to the senses of the student +in such a way that he may associate with it some appropriate +scientific idea. When he has grasped this idea, the experiment which +illustrates it has served its purpose.</p> + +<p>In an experiment of research, on the other hand, this is not the +principal aim.... Experiments<span class="pagenum"><a id="Page_292">[292]</a></span> of this class—those in which +measurement of some kind is involved—are the proper work of a +physical laboratory. In every experiment we have first to make our +senses familiar with the phenomenon; but we must not stop here—we +must find out which of its features are capable of measurement, and +what measurements are required in order to make a complete +specification of the phenomenon. We must then make these measurements, +and deduce from them the result which we require to find.</p> + +<p>This characteristic of modern experiments—that they consist +principally of measurements—is so prominent that the opinion seems to +have got abroad that, in a few years, all the great physical constants +will have been approximately estimated, and that the only occupation +which will then be left to men of science will be to carry these +measurements to another place of decimals.</p> + +<p>If this is really the state of things to which we are approaching, +our laboratory may, perhaps, become celebrated as a place of +conscientious labour and consummate skill; but it will be out of place +in the university, and ought rather to be classed with the other great +workshops of our country, where equal ability is directed to more +useful ends.</p> + +<p>But we have no right to think thus of the unsearchable riches of +creation, or of the untried fertility of those fresh minds into which +these riches will continually be poured.... The history of<span class="pagenum"><a id="Page_293">[293]</a></span> Science +shows that, even during that phase of her progress in which she +devotes herself to improving the accuracy of the numerical measurement +of quantities with which she has long been familiar, she is preparing +the materials for the subjugation of new regions, which would have +remained unknown if she had been contented with the rough methods of +her early pioneers.</p> +</blockquote> + +<p>Maxwell's "Electricity and Magnetism" was published in 1873. Shortly +afterwards there were placed in his hands, by the Duke of Devonshire, +the Cavendish Manuscripts on Electricity, already alluded to. To these +he devoted much of his spare time for several years, and many of +Cavendish's experiments were repeated in the laboratory by Maxwell +himself, or under his direction by his students. The introductory +matter and notes embodied in "The Electrical Researches of the +Honourable Henry Cavendish, F.R.S.," afford sufficient evidence of the +amount of labour he expended over this work. The volume was published +only a few weeks before his death. Another of Maxwell's publications, +which, as a text-book, is unique and beyond praise, is the little book +on "Matter and Motion," published by the S.P.C.K.</p> + +<p>In 1878 Maxwell, at the request of the Vice-Chancellor, delivered the +Rede Lecture in the Senate-House. His subject was the telephone, which +was just then absorbing a considerable amount of public attention. +This was the last<span class="pagenum"><a id="Page_294">[294]</a></span> lecture which he ever gave to a large public +audience.</p> + +<p>It was during his tenure of the Cambridge chair that one of the +cottages on the Glenlair estate was struck by lightning. The discharge +passed down the damp soot and blew out several stones from the base of +the chimney, apparently making its way to some water in a ditch a few +yards distant. The cottage was built on a granite rock, and this event +set Maxwell thinking about the best way to protect, from lightning, +buildings which are erected on granite or other non-conducting +foundations. He decided that the proper course was to place a strip of +metal upon the ground all round the building, to carry another strip +along the ridge-stay, from which one or more pointed rods should +project upwards, and to unite this strip with that upon the ground by +copper strips passing down each corner of the building, which is thus, +as it were, enclosed in a metal cage.</p> + +<p>After a brief illness, Maxwell passed away on November 5, 1879. His +intellect and memory remained perfect to the last, and his love of fun +scarcely diminished. During his illness he would frequently repeat +hymns, especially some of George Herbert's, and Richard Baxter's hymn +beginning</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"Lord, it belongs not to my care."<br /></span> +</div></div> + +<p>"No man ever met his death more consciously or more calmly."</p> + +<p>It has been stated that Thomas Young propounded<span class="pagenum"><a id="Page_295">[295]</a></span> a theory of +colour-vision which assumes that there exist three separate +colour-sensations, corresponding to red, green, and violet, each +having its own special organs, the excitement of which causes the +perception of the corresponding colour, other colours being due to the +excitement of two or more of these simple sensations in different +proportions. Maxwell adopted blue instead of violet for the third +sensation, and showed that if a particular red, green, and blue were +selected and placed at the angular points of an equilateral triangle, +the colours formed by mixing them being arranged as in Young's +diagram, all the shades of the spectrum would be ranged along the +sides of this triangle, the centre being neutral grey. For the mixing +of coloured lights, he at first employed the colour-top, but, instead +of painting circles with coloured sectors, the angles of which could +not be changed, he used circular discs of coloured paper slit along +one radius. Any number of such discs can be combined so that each +shows a sector at the top, and the angle of each sector can be varied +at will by sliding the corresponding disc between the others. Maxwell +used discs of two different sizes, the small discs being placed above +the larger on the same pivot, so that one set formed a central circle, +and the other set a ring surrounding it. He found that, with discs of +five different colours, of which one might be white and another black, +it was always possible to combine them so that the inner circle and +the outer ring exactly matched. From this he showed that there<span class="pagenum"><a id="Page_296">[296]</a></span> could +be only three conditions to be satisfied in the eye, for two +conditions were necessitated by the nature of the top, since the +smaller sectors must exactly fill the circle and so must the larger. +Maxwell's experiments, therefore, confirmed, in general, Young's +theory. They showed, however, that the relative delicacy of the +several colour-sensations is different in different eyes, for the +arrangement which produced an exact match in the case of one observer, +had to be modified for another; but this difference of delicacy proved +to be very conspicuous in colour-blind persons, for in most of the +cases of colour-blindness examined by Maxwell the red sensation was +completely absent, so that only two conditions were required by +colour-blind eyes, and a match could therefore always be made in such +cases with four discs only. Holmgren has since discovered cases of +colour-blindness in which the violet sensation is absent. He agrees +with Young in making the third sensation correspond to violet rather +than blue. Maxwell explained the fact that persons colour-blind to the +red divide colours into blues and yellows by the consideration that, +although yellow is a complex sensation corresponding to a mixture of +red and green, yet in nature yellow tints are so much brighter than +greens that they excite the green sensation more than green objects +themselves can do, and hence greens and yellows are called yellow by +such colour-blind persons, though their perception of yellow is really +the same as perception of green by normal eyes. Later on, by a +combination<span class="pagenum"><a id="Page_297">[297]</a></span> of adjustable slits, prisms, and lenses arranged in a +"colour-box," Maxwell succeeded in mixing, in any desired proportions, +the light from any three portions of the spectrum, so that he could +deal with pure spectral colours instead of the complex combinations of +differently coloured lights afforded by coloured papers. From these +experiments it appears that no ray of the solar spectrum can affect +one colour-sensation alone, so that there are no colours in nature so +pure as to correspond to the pure simple sensations, and the colours +occupying the angular points of Maxwell's diagram affect all three +colour-sensations, though they influence two of them to a much smaller +extent than the third. A particular colour in the spectrum corresponds +to light which, according to the undulatory theory, physically +consists of waves all of the same period, but it may affect all three +of the colour-sensations of a normal eye, though in different +proportions. Thus, yellow light of a given wave-length affects the red +and green sensations considerably and the blue (or violet) slightly, +and the same effect may be produced by various mixtures of red or +orange and green. For his researches on the perception of colour, the +Royal Society awarded to Clerk Maxwell the Rumford Medal in 1860.</p> + +<p>Another optical contrivance of Maxwell's was a wheel of life, in which +the usual slits were replaced by concave lenses of such focal length +that the picture on the opposite side of the cylinder appeared, when +seen through a lens, at the centre, and thus<span class="pagenum"><a id="Page_298">[298]</a></span> remained apparently +fixed in position while the cylinder revolved. The same result has +since been secured by a different contrivance in the praxinoscope.</p> + +<p>Another ingenious optical apparatus was a real-image stereoscope, in +which two lenses were placed side by side at a distance apart equal to +half the distance between the pictures on the stereoscopic slide. +These lenses were placed in front of the pictures at a distance equal +to twice their focal length. The real images of the two pictures were +then superposed in front of the lenses at the same distance from them +as the pictures, and these combined images were looked at through a +large convex lens.</p> + +<p>The great difference in the sensibility to different colours of the +eyes of dark and fair persons when the light fell upon the <i>fovea +centralis</i>, led Maxwell to the discovery of the extreme want of +sensibility of this portion of the retina to blue light. This he made +manifest by looking through a bottle containing solution of chrome +alum, when the central portion of the field of view appears of a light +red colour for the first second or two.</p> + +<p>A more important discovery was that of double refraction temporarily +produced in viscous liquids. Maxwell found that a quantity of Canada +balsam, if stirred, acquired double-refracting powers, which it +retained for a short period, until the stress temporarily induced had +disappeared.</p> + +<p>But Maxwell's investigations in optics must be<span class="pagenum"><a id="Page_299">[299]</a></span> regarded as his play; +his real work lay in the domains of electricity and of molecular +physics.</p> + +<p>In 1738 Daniel Bernouilli published an explanation of atmospheric +pressure on the hypothesis that air consists of a number of minute +particles moving in all directions, and impinging on any surface +exposed to their action. In 1847 Herapath explained the diffusion of +gases on the hypothesis that they consisted of perfectly hard +molecules impinging on one another and on surfaces exposed to them, +and pointed out the relation between their motion and the temperature +and pressure of a gas. The present condition of the molecular theory +of gases, and of molecular science generally, is due almost entirely +to the work of Joule, Clausius, Boltzmann, and Maxwell. To Maxwell is +due the general method of solving all problems connected with vast +numbers of individuals—a method which he called the statistical +method, and which consists, in the first place, in separating the +individuals into groups, each fulfilling a particular condition, but +paying no attention to the history of any individual, which may pass +from one group to another in any way and as often as it pleases +without attracting attention. Maxwell was the first to estimate the +average distance through which a particle of gas passes without coming +into collision with another particle. He found that, in the case of +hydrogen, at standard pressure and temperature, it is about 1/250000 +of an inch; for air, about 1/389000 of an inch. These results he +deduced from his experiments on viscosity, and he gave a<span class="pagenum"><a id="Page_300">[300]</a></span> complete +explanation of the viscosity of gases, showing it to be due to the +"diffusion of momentum" accompanying the diffusion of material +particles between the passing streams of gas.</p> + +<p>One portion of the theory of electricity had been considerably +developed by Cavendish; the application of mathematics to the theory +of attractions, and hence to that of electricity, had been carried to +a great degree of perfection by Laplace, Lagrange, Poisson, Green, and +others. Faraday, however, could not satisfy himself with a +mathematical theory based upon direct action at a distance, and he +filled space, as we have seen, with tubes of force passing from one +body to another whenever there existed any electrical action between +them. These conceptions of Faraday were regarded with suspicion by +mathematicians. Sir William Thomson was the first to look upon them +with favour; and in 1846 he showed that electro-static force might be +treated mathematically in the same way as the flow of heat; so that +there are, at any rate, two methods by which the fundamental formulæ +of electro-statics can be deduced. But it is to Maxwell that +mathematicians are indebted for a complete exposition of Faraday's +views in their own language, and this was given in a paper wherein the +phenomena of electro-statics were deduced as results of a stress in a +medium which, as suggested by Newton and believed by Faraday, might +well be that same medium which serves for the propagation of light; +and "the lines of force" were shown to correspond to an actual<span class="pagenum"><a id="Page_301">[301]</a></span> +condition of the medium when under electrical stress. Maxwell, in +fact, showed, not only that Faraday's lines formed a consistent system +which would bear the most stringent mathematical analysis, but were +more than a conventional system, and might correspond to a state of +stress actually existing in the medium through which they passed, and +that a tension along these lines, accompanied by an equal pressure in +every direction at right angles to them, would be consistent with the +equilibrium of the medium, and explain, on mechanical principles, the +observed phenomena. The greater part of this work he accomplished +while an undergraduate at Cambridge. He showed, too, that Faraday's +conceptions were equally applicable to the case of electro-magnetism, +and that all the laws of the induction of currents might be concisely +expressed in Faraday's language. Defining the positive direction +through a circuit in which a current flows as the direction in which a +right-handed screw would advance if rotating with the current, and the +positive direction around a wire conveying a current as the direction +in which a right-handed screw would rotate if advancing with the +current, Maxwell pointed out that the lines of magnetic force due to +an electric current always pass round it, or through its circuit, in +the positive direction, and that, <i>whenever the number of lines of +magnetic force passing through a closed circuit is changed, there is +an electro-motive force round the circuit represented by the rate of +diminution of the<span class="pagenum"><a id="Page_302">[302]</a></span> number of lines of force which pass through the +circuit in the positive direction</i>.</p> + +<p>The words in italics form a complete statement of the laws regulating +the production of currents by the motion of magnets or of other +currents, or by the variation of other currents in the neighbourhood. +Maxwell showed, too, that Faraday's electro-tonic state, on the +variation of which induced currents depend, corresponds completely +with the number of lines of magnetic force passing through the +circuit.</p> + +<p>He also showed that, when a conductor conveying a current is free to +move in a magnetic field, or magnets are free to move in the +neighbourhood of such a conductor, <i>the system will assume that +condition in which the greatest possible number of lines of magnetic +force pass through the circuit in the positive direction</i>.</p> + +<p>But Maxwell was not content with showing that Faraday's conceptions +were consistent, and had their mathematical equivalents,—he proceeded +to point out how a medium could be imagined so constituted as to be +able to perform all the various duties which were thus thrown upon it. +Assuming a medium to be made up of spherical, or nearly spherical, +cells, and that, when magnetic force is transmitted, these cells are +made to rotate about diameters coinciding in direction with the lines +of force, the tension along those lines, and the pressure at right +angles to them, are accounted for by the tendency of a rotating +elastic sphere<span class="pagenum"><a id="Page_303">[303]</a></span> to contract along its polar axis and expand +equatorially so as to form an oblate spheroid. By supposing minute +spherical particles to exist between the rotating cells, the motion of +one may be transmitted in the same direction to the next, and these +particles may be supposed to constitute electricity, and roll as +perfectly rough bodies on the cells in contact with them. Maxwell +further imagined the rotating cells, and therefore, <i>à fortiori</i>, the +electrical particles, to be extremely small compared with molecules of +matter; and that, in conductors, the electrical particles could pass +from molecule to molecule, though opposed by friction, but that in +insulators no such transference was possible. The machinery was then +complete. If the electric particles were made to flow in a conductor +in one direction, passing between the cells, or <i>molecular vortices</i>, +they compelled them to rotate, and the rotation was communicated from +cell to cell in expanding circles by the electric particles, acting as +idle wheels, between them. Thus rings of magnetic force were made to +surround the current, and to continue as long as the current lasted. +If an attempt were made to displace the electric particles in a +dielectric, they would move only within the substance of each +molecule, and not from molecule to molecule, and thus the cells would +be deformed, though no continuous motion would result. The deformation +of the cells would involve elastic stress in the medium. Again, if a +stream of electric particles were started<span class="pagenum"><a id="Page_304">[304]</a></span> into motion, and if there +were another stream of particles in the neighbourhood free to flow, +though resisted by friction, these particles, instead of at once +transmitting the rotary motion of the cells on one side of them to the +cells on the other side, would at first, on account of the inertia of +the cells, begin to move themselves with a motion of translation +opposite to that of the primary current, and the motion would only +gradually be destroyed by the frictional resistance and the molecular +vortices on the other side made to revolve with their full velocity. A +similar effect, but in the opposite direction, would take place if the +primary current ceased, the vortices not stopping all at once if there +were any possibility of their continuing in motion. The imaginary +medium thus serves for the production of induced currents.</p> + +<p>The mechanical forces between currents and magnets and between +currents and currents, as well as between magnets and currents, were +accounted for by the tension and pressure produced by the molecular +vortices. When currents are flowing in the same direction in +neighbouring conductors, the vortices in the space between them are +urged in opposite directions by the two currents, and remain almost at +rest; the lateral pressure exerted by those on the outside of the +conductors is thus unbalanced, and the conductors are pushed together +as though they attracted each other. When the currents flow in +opposite directions in parallel conductors, they conspire to give a +greater velocity to the vortices in the space<span class="pagenum"><a id="Page_305">[305]</a></span> between them, than to +those outside them, and are thus pushed apart by the pressure due to +the rotation of the vortices, as though they repelled each other. In a +similar way, the actions of magnets on conductors conveying currents +may be explained. The motion of a conductor across a series of lines +of magnetic force may squeeze together and lengthen the threads of +vortices in front, and thus increase their speed of rotation, while +the vortices behind will move more slowly because allowed to contract +axially and expand transversely. The velocity of the vortices thus +being greater on one side of the wire than the other, a current must +be induced in the wire. Thus the current induced by the motion of a +conductor in a magnetic field may be accounted for.</p> + +<p>This conception of a medium was given by Maxwell, not as a theory, but +to show that it was possible to devise a <i>mechanism</i> capable, in +imagination at least, of producing all the phenomena of electricity +and magnetism. "According to our theory, the particles which form the +partitions between the cells constitute the matter of electricity. The +motion of these particles constitutes an electric current; the +tangential force with which the particles are pressed by the matter of +the cells is electro-motive force; and the pressure of the particles +on each other corresponds to the tension or potential of the +electricity."</p> + +<p>When a current is maintained in a wire, the molecular vortices in the +surrounding space are<span class="pagenum"><a id="Page_306">[306]</a></span> kept in uniform motion; but if an attempt be +made to stop the current, since this would necessitate the stoppage of +the vortices, it is clear that it cannot take place suddenly, but the +energy of the vortices must be in some way used up. For the same +reason it is impossible for a current to be suddenly started by a +finite force. Thus the phenomena of self-induction are accounted for +by the supposed medium.</p> + +<p>The magnetic permeability of a medium Maxwell identified with the +density of the substance composing the rotating cells, and the +specific inductive capacity he showed to be inversely proportional to +its elasticity. He then proved that the ratio of the electro-magnetic +unit to the electro-static unit must be equal to the velocity of +transmission of a transverse vibration in the medium, and consequently +proportional to the square root of the elasticity, and inversely +proportional to the square root of the density. If the medium is the +same as that engaged in the propagation of light, then this ratio +ought to be equal to the velocity of light, and, moreover, in +non-magnetic media, the refractive index should be proportional to the +square root of the specific inductive capacity. The different +measurements which had been made of the ratio of the electrical units +gave a mean very nearly coinciding with the best determinations of the +velocity of light, and thus the truth underlying Maxwell's speculation +was strikingly confirmed, for the velocity of light was determined by +purely electrical measurements. In the case also of bodies whose +chemical structure was not<span class="pagenum"><a id="Page_307">[307]</a></span> very complicated, the refractive index was +found to agree fairly well with the square root of the specific +inductive capacity; but the phenomenon of "residual charge" rendered +the accurate measurement of the latter quantity a matter of great +difficulty. It therefore appeared highly probable that light is an +electro-magnetic disturbance due to a motion of the electric particles +in an insulating medium producing a strain in the medium, which +becomes propagated from particle to particle to an indefinite +distance. In the case of a conductor, the electric particles so +displaced would pass from molecule to molecule against a frictional +resistance, and thus dissipate the energy of the disturbance, so that +true (<i>i.e.</i> metallic) conductors must be nearly impervious to light; +and this also agrees with experience.</p> + +<p>Maxwell thus furnished a complete theory of electrical and +electro-magnetic action in which all the effects are due to actions +propagated in a medium, and direct action at a distance is dispensed +with, and exposed his theory successfully to most severe tests. In his +great work on electricity and magnetism, he gives the mathematical +theory of all the above actions, without, however, committing himself +to any particular form of mechanism to represent the constitution of +the medium. "This part of that book," Professor Tait says, "is one of +the most splendid monuments ever raised by the genius of a single +individual.... There seems to be no longer any possibility of doubt +that Maxwell has<span class="pagenum"><a id="Page_308">[308]</a></span> taken the first grand step towards the discovery of +the true nature of electrical phenomena. Had he done nothing but this, +his fame would have been secured for all time. But, striking as it is, +this forms only one small part of the contents of this marvellous +work."</p> + +<div class="figcenter"> +<img src="images/i318.jpg" width="209" height="85" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_309">[309]</a></span></p> + +<div class="figcenter"> +<img src="images/i319.jpg" width="447" height="103" alt="" /> +</div> + +<p class="spacer"> </p> + +<h2 id="CONCLUSION">CONCLUSION.</h2> + +<p>SOME OF THE RESULTS OF FARADAY'S DISCOVERIES, AND THE PRINCIPLE OF +ENERGY.</p> + +<p>In early days, <i>the spirit of the amber</i>, when aroused by rubbing, +came forth and took to itself such light objects as it could easily +lift. Later on, and the spirit gave place to the <i>electric effluvium</i>, +which proceeded from the excited, or charged, body into the +surrounding space. Still later, and a fluid, or two fluids, acting +directly upon itself, or upon matter, or on one another, through +intervening space without the aid of intermediate mechanism, took the +place of the electric effluvium—a step which in itself was, perhaps, +hardly an advance. Then came the time for accurate measurement. The +simple <i>observation</i> of phenomena and of the results of experiment +must be the first step in science, and its importance cannot be +over-estimated; but before any quantity can be said to be known, we +must have learned how to <i>measure</i> it and to reproduce it in definite +amounts. The great law of electrical<span class="pagenum"><a id="Page_310">[310]</a></span> action, the same as that of +gravitation—the law of the inverse square—soon followed, as well as +the associated fact that the electrification of a conductor resides +wholly on its surface, and there only in a layer whose thickness is +too small to be discovered. The fundamental laws of electricity having +thus been established, there was no limit to the application of +mathematical methods to the problems of the science, and, in the hands +of the French mathematicians, the theory made rapid advances. George +Green, of Sneinton, Nottingham, introduced the term "potential" in an +essay published by subscription, in Nottingham, in 1828, and to him we +are indebted for some of our most powerful analytical methods of +dealing with the subject; but his work remained unappreciated and +almost unknown until many of his theorems had been rediscovered. But +the idea of a body acting where it is not, and without any conceivable +mechanism to connect it with that upon which it operates, is repulsive +to the minds of most; and, however well such a theory may lend itself +to mathematical treatment and its consequences be borne out by +experiment, we still feel that we have not solved the problem until we +have traced out the hidden mechanism. The pull of the bell-rope is +followed by the tinkling of the distant bell, but the young +philosopher is not satisfied with such knowledge, but must learn "what +is the particular go of that." This universal desire found its +exponent in Faraday, whose<span class="pagenum"><a id="Page_311">[311]</a></span> imagination beheld "lines" or "tubes of +force" connecting every body with every other body on which it acted. +To his mind these lines or tubes had just as real an existence as the +bell-wire, and were far better adapted to their special purposes. +Maxwell, as we have seen, not only showed that Faraday's system +admitted of the same rigorous mathematical treatment as the older +theory, and stood the test as well, but he gave reality to Faraday's +views by picturing a mechanism capable of doing all that Faraday +required of it, and of transmitting light as well. Thus the problem of +electric, magnetic, and electro-magnetic actions was reduced to that +of strains and stresses in a medium the constitution of which was +pictured to the imagination. Were this theory verified, we might say +that we know at least as much about these actions as we know about the +transmission of pressure or tension through a solid.</p> + +<p>With regard to the <i>nature</i> of electricity, it must be admitted that +our knowledge is chiefly negative; but, before deploring this, it is +worth while to inquire what we mean by saying that we know what a +thing is. A definition describes a thing in terms of other things +simpler, or more familiar to us, than itself. If, for instance, we say +that heat is a form of energy, we know at once its relationship to +matter and to motion, and are content; we have described the +constitution of heat in terms of simpler things, which are more +familiar to us, and of which we <i>think</i> we know the nature. But if<span class="pagenum"><a id="Page_312">[312]</a></span> we +ask what <i>matter</i> is, we are unable to define it in terms of anything +simpler than itself, and can only trust to daily experience to teach +us more and more of its properties; unless, indeed, we accept the +theory of the vortex atoms of Thomson and Helmholtz. This theory, +which has recently been considerably extended by Professor J. J. +Thomson, the present occupier of Clerk Maxwell's chair in the +University of Cambridge, supposes the existence of a perfect fluid, +filling all space, in which minute whirlpools, or vortices, which in a +perfect fluid can be created or destroyed only by superhuman agency, +form material atoms. These are <i>atoms</i>, that is to say, they defy any +attempts to sever them, not because they are infinitely hard, but +because they have an infinite capacity for <i>wriggling</i>, and thus avoid +direct contact with any other atoms that come in their way. Perhaps a +theory of electricity consistent with this theory of matter may be +developed in the future; but, setting aside these theories, we may +possibly say that we know as much about electricity as we know about +matter; for while we are conversant with many of the properties of +each, we <i>know</i> nothing of the ultimate nature of either.</p> + +<p>But while the theory of electricity has scarcely advanced beyond the +point at which it was left by Clerk Maxwell, the practical +applications of the science have experienced great developments of +late years. Less than a century ago the lightning-rod was the only +practical outcome of electrical investigations<span class="pagenum"><a id="Page_313">[313]</a></span> which could be said to +have any real value. Œrsted's discovery, in 1820, of the action of +a current on a magnet, led, in the hands of Wheatstone, Cooke, and +others, to the development of the electric telegraph. Sir William +Thomson's employment of a beam of light reflected from a tiny mirror +attached to the magnet of the galvanometer enabled signals to be read +when only extremely feeble currents were available, and thus rendered +submarine telegraphy possible through very great distances. The +discovery by Arago and Davy, that a current of electricity flowing in +a coil surrounding an iron bar would convert the bar into a magnet, at +once rendered possible a variety of contrivances whereby a current of +electricity could be employed to produce small reciprocating +movements, or even continuous rotation, where not much power was +required, at a distance from the battery. An illustration of the +former is found in the common electric bell; it is only necessary that +the vibrating armature should form part of the circuit of the +electro-magnet, and be so arranged that, while it is held away from +the magnet by a spring, it completes the battery circuit, but breaks +the connection as soon as it moves towards the magnet under the +magnetic attraction. To produce continuous rotation, a number of iron +bars may be attached to a fly-wheel, and pass very close to the poles +of the magnet without touching them; when a bar is near the magnet, +and approaching it, contact should be made in the circuit, but should +be<span class="pagenum"><a id="Page_314">[314]</a></span> broken, so that the magnet may lose its power, as soon as the bar +has passed the poles; or the continuous rotation may be produced from +an oscillating armature by any of the mechanical contrivances usually +adopted for the conversion of reciprocating into continuous circular +motion. But all such motors are extremely wasteful in their employment +of energy. Faraday's discovery of the rotation of a wire around a +magnetic pole laid the foundation for a great variety of +electro-motors, in some of which the efficiency has attained a very +high standard. About ten years ago, Clerk Maxwell said that the +greatest discovery of recent times was the "reversibility" of the +Gramme machine, that is, the possibility of causing the armature to +rotate between the field-magnets by sending a current through the +coils. The electro-motors of to-day differ but little from dynamos in +the principles of their construction. The copper disc spinning between +the poles of a magnet while an electric current was sent from the +centre to the circumference, or <i>vice versâ</i>, formed the simplest +electro-motor. All the later motors are simply modifications of this, +designed to increase the efficiency or power of the machine. +Similarly, the earliest machine for the production of an electric +current at the expense of mechanical power only, but through the +intervention of a permanent magnet, was the rotating disc of Faraday, +described on page 262. This contrivance, however, caused a waste of +nearly all the energy employed,<span class="pagenum"><a id="Page_315">[315]</a></span> for while there was an electro-motive +force from the centre to the circumference, or in the reverse +direction, in that part of the disc which was passing between the +poles of the magnet, the current so generated found its readiest +return path through the other portions of the disc, and very little +traversed the galvanometer or other external circuit. This source of +waste could be, for the most part, got rid of by cutting the disc into +a number of separate rays, or spokes, and filling up the spaces +between them with insulating material. The current then generated in +the disc would be obliged to complete its circuit through the external +conductor. If we can so arrange matters as to employ at once several +turns of a continuous wire in place of one arm, or ray, of the copper +disc, we may multiply in a corresponding manner the electro-motive +force induced by a given speed of rotation. All magneto-electric +generators are simply contrivances with this object. The iron cores +frequently employed within the coils of the armature tend to +concentrate the lines of force of the magnet, causing a greater number +to pass through the coils in certain positions than would pass through +them were no iron present. The electro-motive force of such a +generator depends on the strength of the magnetic field, the length of +wire employed in cutting the lines of force, and the speed with which +the wire moves across these lines. The point to aim at in constructing +an armature is to make the resistance as small as possible consistent<span class="pagenum"><a id="Page_316">[316]</a></span> +with the electro-motive force required. As there is a limit to the +strength of the magnetic field, it follows that for strong currents, +where thick wire must be employed, the generator must be made of large +dimensions, or the armature must be driven at very high speed to +enable a shorter length of wire to be used.</p> + +<p>The so-called "compound-interest principle," by which a very small +charge of electricity might be employed to develop a very large one by +the help of mechanical power, was first applied about a century ago in +the revolving doubler. Long afterwards, Sir William Thomson availed +himself of the same principle in the construction of the "mouse-mill," +or replenisher. The Holtz machine, the Voss and Wimshurst machines, +and the other induction-machines of the same class, all work on this +principle. It may be illustrated as follows: Take two canisters, call +them A and B, and place them on glass supports. Let a very small +positive charge be given to A, B remaining uncharged. Now take a brass +ball, supported by a silk string. Place it inside A, and let it touch +its interior surface. The ball will, as shown by Franklin, Cavendish, +and Faraday, remain uncharged. Now raise it near the top of the +canister, and, while there, touch it. The ball will become negatively +electrified, because the small positive charge in A will attract +negative electricity from the earth into the ball. Take the ball, with +its negative charge, still hanging by the silk thread, and lower it +into<span class="pagenum"><a id="Page_317">[317]</a></span> B till it touches the bottom. It will give all its charge to B, +which will thus acquire a slight negative charge. Raise the ball till +it is near the top of B, and then touch it with the finger or a metal +rod. It will receive a positive charge from the earth because of the +attraction of the negative charge on B. Now remove the ball and let it +again touch the interior of A. It will give up all its charge to A; +and then, repeating the whole cycle of operations, the charge carried +on the ball will be greater than before, and increase in each +successive operation, the electrification increasing in geometrical +progression like compound interest. A Leyden jar having one coating +connected to A and the other to B, may thus be highly charged in +course of time. A pair of carrier balls or plates, or a number of +pairs, may be used instead of one. The carriers, just before leaving A +and B, may be put in contact with one another instead of being put to +earth; they may be mounted on a revolving shaft, and the forms of A +and B modified to admit of the revolution of the carriers, and all the +necessary contacts may be made automatically. We thus get various +forms of the continuous electrophorus, and if the carriers are mounted +on glass plates, and rows of points placed alongside the springs or +brushes used for making the contacts, when the charges on the carriers +become very strong, electricity will be radiated from the points on to +the revolving glass plates, which will thus themselves take the place +of the metal carriers.<span class="pagenum"><a id="Page_318">[318]</a></span> Such is the action in the Voss and other +similar machines.</p> + +<p>But after Faraday had shown how to construct a magneto-electric +machine, the idea of applying the "compound-interest principle," and +thus converting the magneto-electric machine into the "dynamo," +occurred apparently simultaneously and independently to Siemens, +Varley, and Wheatstone. The first dynamo constructed by Wheatstone is +still in the museum of King's College, London. Wilde employed a +magneto-electric machine to generate a current which was used to +excite the electro-magnet of a similar but larger machine, having an +electro-magnet instead of a permanent steel magnet. The electro-magnet +could be made much larger and stronger than the steel magnet, and from +its armature, when made to revolve by steam power, a correspondingly +stronger current could be maintained. The idea which occurred to +Siemens, Varley, and Wheatstone was to use the whole, or a part, of +the current produced by the armature to excite its own electro-magnet, +and thus to dispense with the magneto-electric machine which served as +the separate exciter. When a part only of the current is thus +employed, and is set apart entirely for this duty, the machine is a +"shunt dynamo;" when the whole of the current traverses the +field-magnet coils as well as the external circuit, it is a "series +dynamo." The apparent difficulty lies in starting the current, but a +mass of iron once magnetized always retains a certain amount of +"residual<span class="pagenum"><a id="Page_319">[319]</a></span> magnetism," unless special means are taken to get rid of +it, and even then the earth's magnetism would generally induce +sufficient in the iron to start the action. Commencing, then, with a +slight trace of residual magnetism, the revolution of the armature +generates a feeble current, which passing round the magnet coils, +strengthens the magnetism, whereupon a stronger current is generated, +which in turn makes the magnet still stronger, and so on until the +magnet becomes saturated or the limit of power of the engine is +reached, and the speed begins to diminish, or a condition of affairs +is reached at which an increased current in the armature injures the +magnetic field as much as the corresponding increase in the +field-magnet coils strengthens it, and then no further increase of +current will take place without increasing the speed of rotation. In a +true dynamo the whole of the energy, both of the current and of the +electro-magnets, is obtained from the source of power employed in +driving the machine.</p> + +<p>But Faraday's discovery of electro-magnetic induction led to practical +developments in other directions. Graham Bell placed a thin iron disc +in front of the pole of a bar magnet, and wound a coil of fine wire +round the bar very near the pole. The ends of the coils of two such +instruments he connected together. When the iron disc of one +instrument approached the pole of the magnet, the lines of force were +disturbed, fewer escaped radially from the bar, and more left it at +the end, so as to<span class="pagenum"><a id="Page_320">[320]</a></span> go straight to the iron disc; thus the number of +lines of force passing through the coil was altered, and a current was +induced which, passing round the coil of the other instrument, +strengthened or weakened its magnet, and caused the iron disc to +approach it or recede from it, according to the way in which the coils +were coupled. Thus the movements of the first disc were faithfully +repeated by the second, and the minute vibrations set up in the disc +by sound-waves were all faithfully repeated by the second instrument. +This was Graham Bell's telephone, in which the transmitter and +receiver were convertible.</p> + +<p>But another and an earlier application of Faraday's discoveries is +found in the induction coil. A short length of thick wire and a very +great length of thin wire are wound upon an iron bar. The ends of the +long thin wire, or secondary coil, form the terminals of the machine; +the short thick wire, or primary coil, is connected with a battery, +but in the circuit is placed an "interrupter." This is generally a +small piece of iron, or hammer, mounted on a steel spring opposite one +end of the iron core, the spring pressing the hammer back against a +screw the end of which, like the back of the hammer, is tipped with +platinum; and this contact completes the battery circuit. When the +current starts, the iron core becomes a magnet, attracts the hammer, +breaks the contact, stops the current, the magnetism dies away, the +hammer is forced back by the spring, and then the cycle of events is +repeated. But the<span class="pagenum"><a id="Page_321">[321]</a></span> starting of the current in the primary causes a +great many lines of magnetic force to pass through each of the many +thousand turns of wire in the secondary, especially as the iron core +conducts most of the lines of force of each turn of the primary almost +from end to end of the coil, and thus through nearly all the turns of +the secondary. This action might be further increased by connecting +the ends of the iron core with an iron tube or series of longitudinal +bars placed outside the whole coil. When the primary current ceases, +all these lines of force vanish. Thus during the starting of the +primary current, which, on account of self-induction, occupies a +considerable time, there will be an inverse current in the secondary +proportional to the rate of increase of the primary; and while the +primary is dying away, there will be a direct current in the secondary +proportional to its rate of decrease. The primary current cannot be +increased at a faster rate than corresponds to the power of the +battery, but by making a very sharp break it may be stopped very +rapidly. Still, however rapidly the circuit is broken, self-induction +causes a spark to fly across the gap until the energy of the current +is used up. The introduction of the condenser, consisting of a number +of sheets of tinfoil insulated by paper steeped in paraffin wax, and +connected alternately with one end or the other of the primary coil, +serves to increase the rapidity with which the primary current died +away, by rapidly using up its energy<span class="pagenum"><a id="Page_322">[322]</a></span> in charging the condenser, and +produces a corresponding diminution in the spark at the +contact-breaker. This rapid destruction of the primary current causes +a correspondingly great electro-motive force in the secondary coil, +and thus very long sparks are produced between the terminals of the +secondary coil when the primary current is broken, though no such +sparks are produced when the primary current starts. If the secondary +coil be connected up with a galvanometer, so that there is a metallic +circuit throughout, it will be found that just as much electricity +flows in one direction through the circuit at the break of the primary +as flows in the other direction at the make, the difference being that +the first is a very strong current of great electro-motive force but +lasting a very short time, the second a feebler current lasting a +correspondingly longer time.</p> + +<hr class="tb" /> + +<p>But though the recent advances in electrical science have been very +great, the grandest triumph of this century is the establishment of +the principle of the conservation of energy, which has settled for +ever the problem of "the perpetual motion," by showing that it has no +solution. This problem was not simply to find a mechanism which should +for ever move, but one from which energy might be continuously derived +for the performance of external work—in fact, an engine which should +require no fuel. But in spite of all that has been proved, numbers of +patents are annually taken out for contrivances to effect this +object.</p><p><span class="pagenum"><a id="Page_323">[323]</a></span></p> + +<p>We have seen how Rumford showed that heat was motion, and how he +approximately determined its mechanical equivalent. Séguin, a nephew +of Montgolfier, endeavoured to show that, when a steam-engine was +working, less heat entered the condenser than when the same amount of +steam was blown idly through the engine. This Hirn succeeded in +showing, thus proving that heat was actually used up in doing work. +Mayer, of Heilbronn, measured the work done in compressing air, and +the heat generated by the compression, and assumed that the whole of +the work done in the compression, and no more, was converted into the +heat developed, which was the same thing as assuming that no work was +done in altering the positions of the particles of gas. From these +measurements he deduced a value of the mechanical equivalent of heat. +The assumption which Mayer made was shown experimentally by Joule to +be nearly correct. Joule proved that, when air expands from a high +pressure into a vacuum, no heat is generated or absorbed on the whole. +This he did by compressing air in an iron bottle, which was connected +with another bottle from which the air had been exhausted, the +connecting tube being closed by a stop-cock. The whole apparatus was +immersed in a bath of water, and on allowing the air to rush from one +vessel into the other, and then stirring the water, the temperature +was found to be the same as before. When the iron bottles were in +separate baths of<span class="pagenum"><a id="Page_324">[324]</a></span> water, that from which the air rushed was cooled, +and that into which it rushed was heated to the same extent. Joule and +Thomson afterwards showed that a very small amount of heat is absorbed +in this experiment. Joule also showed that the heat generated in a +battery circuit is proportional to the product of the electro-motive +force and the current, or to the product of the resistance and the +square of the current, which, in virtue of Ohm's law, is the same +thing. This relation is often known as Joule's law. He also proved +that, for the same amount of chemical action in the battery, the heat +generated was the same, whether it were all generated within the +battery or part in the battery and part in an external wire; and that +in the latter case, if the wire became so hot as to emit light, the +heat measured was less than before, on account of the energy radiated +as light. With a magneto-electric machine he employed mechanical power +to produce a current, and the energy of the current he converted into +heat. In all cases he found that, <i>whatever transformations the energy +might undergo in its course, a definite amount of mechanical energy, +if entirely converted into heat, always produced the same amount of +heat</i>; and he thereby proved, not only that heat is essentially +<i>motion</i>, but that it corresponds precisely with that particular +dynamical quantity which is called <i>energy</i>; and thus justified the +attempt to find a relation between heat and energy, or to express the +mechanical equivalent of heat as so many foot-pounds.</p><p><span class="pagenum"><a id="Page_325">[325]</a></span></p> + +<p>Joule then set to work to determine, in the most accurate manner +possible, the number of foot-pounds of work which, if entirely +converted into heat, would raise one pound of water through 1° Fahr. +The best known of his experiments is that in which he caused a paddle +to revolve by means of a falling weight, and thereby to churn a +quantity of water contained in a cylindrical vessel, the rotation of +the water being prevented by fixed vanes. In these experiments he +allowed for the work done outside the vessel of water or calorimeter, +for the buoyancy of the air on the descending weight, and for the +energy still retained by the weight when it struck the floor. From the +results obtained he deduced 772 foot-pounds as the mechanical +equivalent of heat. Expressed in terms of the Centigrade scale, +Joule's equivalent, that is, the number of foot-pounds of work in the +latitude of Manchester, which, if entirely converted into heat, will +raise one pound of water 1° C., is 1390.</p> + +<p>Joule's experiments show that the same amount of energy always +corresponds to, and can be converted into, the same amount of heat, +and that no transformations, electrical or other, can ever increase or +diminish this quantity. Maxwell expressed this principle as follows:—</p> + +<p><i>The energy of a system is a quantity which can neither be increased +nor diminished by any actions taking place between the parts of the +system, though it may be transformed into any of the forms of which +energy is susceptible.</i></p><p><span class="pagenum"><a id="Page_326">[326]</a></span></p> + +<p>This is the great principle of the conservation of energy which is +applicable equally to all branches of science.</p> + +<p>Another principle, almost equally general in its applicability, is +that of the dissipation of energy, for which we are indebted in the +first instance to Sir William Thomson. All forms of energy may be +converted into heat, and heat tends so to diffuse itself throughout +all bodies as to bring them to one uniform temperature. This is its +ultimate state of degradation, and from that state no methods with +which we are acquainted can transform any portion of it. When energy +is possessed by a system in consequence of the relative positions or +motions of bodies which we can handle, and whose movements we may +control, the whole of the energy may be employed in doing any work we +please; in fact, it is all <i>available</i> for our purpose, or its +<i>availability</i> may be said to be perfect. Energy in any other form is +limited in its availability by the conditions under which we can place +it. For example, the energy of chemical action in a battery may be +used to produce a current, and this to drive a motor by which +mechanical work is effected, but some of the energy must inevitably be +degraded into the form of heat by the resistance of the battery and of +the conductor, and this portion will be greater as the rate of doing +work is increased. The ratio of the quantity of energy which can be +employed for mechanical purposes with the means at our disposal, to +the whole<span class="pagenum"><a id="Page_327">[327]</a></span> amount present, is called the <i>availability</i> of the energy. +All forms of energy may be wholly converted into heat, but only a +fraction of any quantity of heat can be transformed into higher forms +of energy, and this depends on the temperature of the source of heat +and of the coldest body which can be employed as a condenser, being +greater the greater the difference between the temperatures of the +source and condenser, and the lower the temperature of the latter. In +every operation which takes place in nature there is a degradation of +energy, and though some portion of the energy may be raised in +availability, another portion is lowered, so that on the whole the +availability is diminished. Thus, in the case of the heat-engine, work +can be obtained from heat only by allowing another portion of the heat +to fall in temperature; and, as originally stated by Sir William +Thomson, "it is impossible, by means of inanimate material agency, to +obtain mechanical effect from any portion of matter by cooling it +below the temperature of the coldest of the surrounding objects," and +to leave the working substance in the same condition in which it was +at the commencement of the operations. Accepting this principle, +Professor James Thomson showed that increase of pressure must lower +the freezing point of water, for otherwise it would be possible to +construct an engine which, working by the expansion of water in +freezing, would continue to do work by cooling a body below the +temperature of any other body available,<span class="pagenum"><a id="Page_328">[328]</a></span> and he calculated the amount +of pressure necessary to lower the freezing point through one degree. +The conclusion was afterwards experimentally verified by Sir William +Thomson, and served to explain all the phenomena of regelation. Thus, +like the principle of the conservation of energy, the principle of the +dissipation of energy serves as a guide in the search after truth. But +there is this difference between the two principles—no one can +conceive of any method by which to circumvent the conservation of +energy; but Clerk Maxwell showed that the principle of dissipation of +energy might be overridden by the exercise of intelligence on the part +of any creature whose faculties were sufficiently delicate to deal +with individual molecules. In the case of gases, the temperature +depends on the average energy of motion of the individual particles, +and heat consists simply of this motion; but in any mass of gas, +whatever the average energy may be, some of the particles will be +moving with very great, and some with very small, velocities. By +imagining two portions of gas, originally at the same temperature, +separated by a partition containing trap-doors which could be opened +or closed without expenditure of energy, and supposing a "demon" +placed in charge of each door, who would open the door whenever a +particle was approaching very rapidly from one side, or very slowly +from the other, but keep it shut under other circumstances, he showed +that it would be possible to sort the<span class="pagenum"><a id="Page_329">[329]</a></span> particles, so that those in the +one compartment should have a great velocity, and those in the other a +small one. Hence, out of a mass of gas at uniform temperature, two +portions might be obtained, one at a high temperature and the other at +a low, and, by means of a heat-engine, work could be obtained until +the two portions were again at equal temperatures, when the services +of the "demons" might be again taken advantage of, and the operations +repeated until all the heat was used up.</p> + +<p>Any theory which is brought forward to explain a phenomenon, or any +process which is proposed to effect any operation, must in the first +instance submit to the test of the application of these two principles +of conservation and dissipation of energy; and any proposal which +fails to bear these tests may be at once rejected. The essential +feature of the science of to-day is its quantitative character. We +must, for instance, not only know that radiant energy comes to us from +the sun, but we must learn how much energy is annually received by the +earth in this way; and, in the next place, how much energy is radiated +by the sun in all directions in the same time. When we have learned +this, we want to know what is the source of this energy; and no theory +of the sun which does not enable us to explain how this constant +expenditure of energy is maintained can be accepted. Last century it +was possible to believe, with Sir William Herschel, that the greater +part of the sun's mass is comparatively cool, and that it is +surrounded by only a thin<span class="pagenum"><a id="Page_330">[330]</a></span> sheet of flame. To-day such a theory would +be rejected at once, simply because the thin shell of flame could not +provide energy for the solar radiation for any considerable time. The +contact theory of the galvanic cell, as originally enunciated, fell to +the ground for a similar reason. The simple contact of dissimilar +metals could afford no continuous supply of energy to sustain the +current. Applied to the steam-engine, the doctrine of energy teaches +us, not only that, corresponding to the combustion of a pound of coal, +there is a definite quantity of work which is the mechanical +equivalent of the heat generated, and is such that no engine of which +we can conceive is capable of deriving from the combustion of the +pound of coal a greater amount of work, but it teaches us that there +is a further limitation fixed to the amount of work obtainable. This +limitation depends upon the range of temperature at our command; and, +when the range is known, we can express the amount of energy +realizable by a perfect engine working through that range as a +definite fraction of the whole energy corresponding to the heat of +combustion of the fuel. Thus, if we find that a particular engine +realizes only 15 per cent. of the energy of its fuel in work done, we +must not suppose that mechanical improvements in the engine would +enable us to realize any considerable portion of the other 85 per +cent.; for it may be that a theoretically perfect engine, working with +its boiler and condenser at the same<span class="pagenum"><a id="Page_331">[331]</a></span> temperatures as those of the +engine considered, could only realize 25 per cent. of the energy of +the fuel, reducing the margin for improvement from 85 to 10 per cent., +as long as the range of temperature is unaltered. To improve the +efficiency beyond this limit, the range of temperature must be +increased, that is, generally, hotter steam must be used.</p> + +<p>The principles of energy are thus guides, not only to the scientific +theorist, but to the practical engineer, and they have been +established only through careful measurement. The simple observation +of phenomena, and of the conditions under which they occur, could +never have led to the establishment of such principles; and, though +the carrying out of experiments which do not involve measurements is +of great value, it is the careful measurement, however simple, which +affords the highest training to the mind and hand, and without which +any course of instruction in experimental physics is of little value.</p> + +<p>The Hindoos used to regard the earth as a vast dome carried on the +backs of elephants. The elephants themselves, however, required +support, and were represented as standing on the back of a gigantic +tortoise. It does not, however, appear that any support was provided +for the tortoise. In some respects this figure represents the +apparently perpetual condition of scientific knowledge. Phenomena are +investigated, and are shown to depend upon other actions which appear +simpler or more<span class="pagenum"><a id="Page_332">[332]</a></span> fundamental than the phenomena at first observed. +These, again, are found to obey laws which are of much wider +application, or appear to be still more fundamental; but it may be +that we are as far off as ever from discovering the great secret of +the universe, the ultimate nature of all things.</p> + +<div class="figcenter"> +<img src="images/i342.jpg" width="187" height="227" alt="" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a id="Page_333">[333]</a></span></p> + +<h2 id="INDEX">INDEX.</h2> + +<ul class="index"> +<li class="ifrst">A.</li> +<li class="indx">Abbott, Faraday's letters to, <a href="#Page_241">241</a>, <a href="#Page_246">246</a>.</li> +<li class="indx">Aberdeen University, Maxwell appointed professor in, <a href="#Page_284">284</a>;</li> +<li class="isub1">Young's report on, <a href="#Page_203">203</a>.</li> +<li class="indx">Absorption, Rumford's experiments on, <a href="#Page_185">185</a>;</li> +<li class="isub1">of sun's rays by cloth of different colours, <a href="#Page_99">99</a>.</li> +<li class="indx">Academy of Sciences, Franklin nominated Foreign Associate of, <a href="#Page_111">111</a>.</li> +<li class="indx">Adjustment of the eye, Young's paper on the, <a href="#Page_200">200</a>.</li> +<li class="indx">Æpinus's completion of Franklin's theory, <a href="#Page_77">77</a>.</li> +<li class="indx">Air, Boyle's conception of the constitution of, <a href="#Page_19">19</a>.</li> +<li class="indx">Air-pump, Boyle's experiments with, <a href="#Page_19">19</a>;</li> +<li class="isub1">constructed by Boyle, <a href="#Page_27">27</a>.</li> +<li class="indx">American Independence, Declaration of, <a href="#Page_113">113</a>.</li> +<li class="indx">American Philosophical Society, foundation of, <a href="#Page_61">61</a>.</li> +<li class="indx">Ampère's theory, Faraday's views on, <a href="#Page_257">257</a>.</li> +<li class="indx">Anchor-ring experiment, Faraday's, <a href="#Page_260">260</a>.</li> +<li class="indx">Arago's experiment, <a href="#Page_264">264</a>.</li> +<li class="indx">Argand lamp, efficiency of, <a href="#Page_188">188</a>.</li> +<li class="indx">Armstrong gun, principle of the, <a href="#Page_180">180</a>.</li> +<li class="indx">Atmospheric electricity, Faraday's experiments on, <a href="#Page_254">254</a>;</li> +<li class="isub1">obtained by a pointed rod, <a href="#Page_84">84</a>.</li> +<li class="indx">Autobiography of Franklin, <a href="#Page_39">39</a>.</li> +<li class="indx">Availability of energy, <a href="#Page_326">326</a>.</li> +<li class="ifrst">B.</li> +<li class="indx">Baily, Francis, repetition of the Cavendish experiment by, <a href="#Page_146">146</a>.</li> +<li class="indx">Beats in music, explanation of, <a href="#Page_209">209</a>.</li> +<li class="indx">Beggary in Bavaria banished by Rumford, <a href="#Page_164">164</a>.</li> +<li class="indx">Bernoulli's, Daniel, molecular theory of gases, <a href="#Page_299">299</a>.</li> +<li class="indx">Boston, blockade of, <a href="#Page_110">110</a>.</li> +<li class="indx"><b>Boyle</b>, Hon. Robert, birth, <a href="#Page_8">8</a>;</li> +<li class="isub1">conversion, <a href="#Page_11">11</a>;</li> +<li class="isub1">first air-pump, <a href="#Page_17">17</a>;</li> +<li class="isub1">conception of the constitution of the air, <a href="#Page_19">19</a>;</li> +<li class="isub1">experiments with the air-pump, <a href="#Page_19">19</a>, <i>et seq.</i>;</li> +<li class="isub1">argument on the cause of a vacuum, <a href="#Page_23">23</a>;</li> +<li class="isub1">experiments establishing his law, <a href="#Page_25">25</a>;</li> +<li class="isub1">statement of his law, <a href="#Page_29">29</a>;</li> +<li class="isub1">observations on cold, <a href="#Page_32">32</a>,</li> +<li class="isub1">and on the expansion of water in freezing, <a href="#Page_33">33</a>;</li> +<li class="isub1">experiments on induced magnetism, <a href="#Page_34">34</a>;</li> +<li class="isub1">the province of experimental science, <a href="#Page_37">37</a>.</li> +<li class="indx">Boyle's law, <a href="#Page_29">29</a>.</li> +<li class="indx">Brocklesby, Dr., death of, <a href="#Page_208">208</a>.</li> +<li class="indx">Brougham's criticisms of Thomas Young, <a href="#Page_218">218</a>.</li> +<li class="indx">Bumper, electrical, <a href="#Page_80">80</a>.</li> +<li class="ifrst">C.</li> +<li class="indx">Camera obscura, invention of, <a href="#Page_2">2</a>.</li> +<li class="indx">Canada balsam, stresses in, <a href="#Page_298">298</a>.</li> +<li class="indx">Candle-flame, effect of, in discharging electricity, <a href="#Page_75">75</a>.</li> +<li class="indx">Capacity, electrical, <a href="#Page_137">137</a>;</li> +<li class="isub1">Franklin's experiments on, <a href="#Page_81">81</a>, <a href="#Page_89">89</a>;</li> +<li class="isub1">Cavendish's unit of, <a href="#Page_138">138</a>;</li> +<li class="isub1">Cavendish's measures of, <a href="#Page_134">134</a>, <a href="#Page_138">138</a>;</li> +<li class="isub1">of disc, measured by Cavendish, <a href="#Page_134">134</a>.</li> +<li class="indx">Capillarity, <a href="#Page_228">228</a>.</li> +<li class="indx">Cascade method of charging Leyden jars, <a href="#Page_77">77</a>.</li> +<li class="indx"><b>Cavendish</b>, Hon. Henry, F.R.S., birth and parentage, <a href="#Page_126">126</a>;</li> +<li class="isub1">social habits, <a href="#Page_127">127</a>;</li> +<li class="isub1">appointed member of the R.S. Committee on Lightning-Conductors, <a href="#Page_131">131</a>;</li> +<li class="isub1">elected Foreign Associate of the French Institute, <a href="#Page_132">132</a>;</li> +<li class="isub1">death, <a href="#Page_133">133</a>;</li> +<li class="isub1">proof of the law of inverse squares, <a href="#Page_135">135</a>;</li> +<li class="isub1">experiment with the spheres repeated by MacAlister, <a href="#Page_137">137</a>;</li> +<li class="isub1">experiments on the torpedo, <a href="#Page_140">140</a>; +<span class="pagenum"><a id="Page_334">[334]</a></span></li> +<li class="isub1">experiments on the resistance of conductors, <a href="#Page_142">142</a>;</li> +<li class="isub1">discovery of Ohm's law, <a href="#Page_143">143</a>;</li> +<li class="isub1">view of latent heat, <a href="#Page_144">144</a>;</li> +<li class="isub1">apparatus for determining the melting point of mercury, <a href="#Page_145">145</a>;</li> +<li class="isub1">the Cavendish experiment, <a href="#Page_146">146</a>.</li> +<li class="indx">Cavendish experiment, <a href="#Page_146">146</a>;</li> +<li class="isub1">Laboratory, <a href="#Page_288">288</a>;</li> +<li class="isub1">Manuscripts, <a href="#Page_134">134</a>;</li> +<li class="isub1">Maxwell's work on the Manuscripts, <a href="#Page_293">293</a>.</li> +<li class="indx">City Philosophical Society, joined by Faraday, <a href="#Page_245">245</a>;</li> +<li class="isub1">Faraday's lectures to, <a href="#Page_251">251</a>.</li> +<li class="indx">Cold, Boyle's observations on, <a href="#Page_32">32</a>.</li> +<li class="indx">Collinson, Peter, present of, to the Library Company, <a href="#Page_72">72</a>.</li> +<li class="indx">Colour-blindness, Maxwell's experiments on, <a href="#Page_296">296</a>.</li> +<li class="indx">Colour-box, Maxwell's, <a href="#Page_297">297</a>.</li> +<li class="indx">Colours, effect of, on absorption of sun's rays, <a href="#Page_99">99</a>, <a href="#Page_186">186</a>.</li> +<li class="indx">Colours of the spectrum mixed by Boyle, <a href="#Page_31">31</a>.</li> +<li class="indx">Colour-top, Maxwell's, <a href="#Page_284">284</a>, <a href="#Page_295">295</a>;</li> +<li class="isub1">Young's, <a href="#Page_215">215</a>.</li> +<li class="indx">Colour-vision, Maxwell's theory of, <a href="#Page_294">294</a>;</li> +<li class="isub1">Young's theory of, <a href="#Page_214">214</a>.</li> +<li class="indx">Commonplace-book, Faraday's, <a href="#Page_253">253</a>.</li> +<li class="indx">Compound-interest principle, <a href="#Page_316">316</a>.</li> +<li class="indx">Condenser, use of, in induction coils, <a href="#Page_321">321</a>.</li> +<li class="indx">Conduction of heat, Rumford's experiments on, <a href="#Page_186">186</a>.</li> +<li class="indx">Conductors, multiple, flow of electricity through, <a href="#Page_141">141</a>.</li> +<li class="indx">Conductors necessarily opaque, <a href="#Page_307">307</a>.</li> +<li class="indx">Conservation of energy, Maxwell's statement of the principle of, <a href="#Page_325">325</a>.</li> +<li class="indx">Copley Medal awarded to Franklin, <a href="#Page_66">66</a>, <a href="#Page_74">74</a>.</li> +<li class="indx">Cork, Earl of, autobiography of, <a href="#Page_5">5</a>.</li> +<li class="indx">Creeping of electricity on glass, <a href="#Page_139">139</a>.</li> +<li class="indx">Crystalline lens, fibrous structure of, <a href="#Page_200">200</a>;</li> +<li class="isub1">mode of adjustment of, <a href="#Page_201">201</a>.</li> +<li class="indx">Cuneus's discovery of the Leyden jar, <a href="#Page_4">4</a>.</li> +<li class="ifrst">D.</li> +<li class="indx">Davy, Sir Humphry, appointed professor at the Royal Institution, <a href="#Page_174">174</a>;</li> +<li class="isub1">letter of, to Faraday, <a href="#Page_244">244</a>.</li> +<li class="indx">Declaration of American Independence signed, <a href="#Page_113">113</a>.</li> +<li class="indx">Defence of the American Colonies against France and Spain, <a href="#Page_62">62</a>.</li> +<li class="indx">Degree of electrification, <a href="#Page_137">137</a>.</li> +<li class="indx">De la Rive's invitation to Faraday, <a href="#Page_249">249</a>.</li> +<li class="indx">Density of the earth, determinations of the mean, <a href="#Page_146">146</a>.</li> +<li class="indx">Desaguliers on electrics and non-electrics, <a href="#Page_4">4</a>.</li> +<li class="indx">Diagram of colour, Young's, <a href="#Page_215">215</a>;</li> +<li class="isub1">Maxwell's, <a href="#Page_295">295</a>.</li> +<li class="indx">Diamagnetism discovered by Faraday, <a href="#Page_274">274</a>.</li> +<li class="indx">Diamonds burned by Davy, <a href="#Page_250">250</a>.</li> +<li class="indx">Dichroism of <i>Lignum nephriticum</i>, <a href="#Page_30">30</a>.</li> +<li class="indx">Discharge, electrical, difference between positive and negative, <a href="#Page_87">87</a>.</li> +<li class="indx">Dissipation of energy, principle of, <a href="#Page_326">326</a>.</li> +<li class="indx">Distilled water, resistance of, <a href="#Page_142">142</a>.</li> +<li class="indx">Double refraction explained by Huyghens, <a href="#Page_219">219</a>.</li> +<li class="indx">Dufay showed that all bodies could be electrified, <a href="#Page_4">4</a>.</li> +<li class="indx">Dynamical nature of heat, suggested by Bacon, <a href="#Page_2">2</a>, <a href="#Page_32">32</a>;</li> +<li class="isub1">maintained by Boyle, <a href="#Page_32">32</a>;</li> +<li class="isub1">investigated by Rumford, <a href="#Page_189">189</a>;</li> +<li class="isub1">established by Joule, <a href="#Page_193">193</a>, <a href="#Page_324">324</a>.</li> +<li class="indx">Dynamical top, Maxwell's, <a href="#Page_285">285</a>.</li> +<li class="indx">Dynamo, constructed by Wheatstone, <a href="#Page_318">318</a>;</li> +<li class="isub1">action of, <a href="#Page_319">319</a>;</li> +<li class="isub1">essential feature of, <a href="#Page_319">319</a>.</li> +<li class="ifrst">E.</li> +<li class="indx">Effect of points in discharging electricity, <a href="#Page_74">74</a>.</li> +<li class="indx">Electrical picnic, <a href="#Page_80">80</a>.</li> +<li class="indx">Electrical Standards Committee, <a href="#Page_287">287</a>.</li> +<li class="indx">Electric intensity, <a href="#Page_137">137</a>;</li> +<li class="isub1">potential, <a href="#Page_137">137</a>.</li> +<li class="indx">Electricity, first obtained from clouds, <a href="#Page_74">74</a>;</li> +<li class="isub1">velocity of, <a href="#Page_93">93</a>.</li> +<li class="indx">Electrics and non-electrics, <a href="#Page_3">3</a>.</li> +<li class="indx">Electrolysis, Faraday's laws of, <a href="#Page_266">266</a>.</li> +<li class="indx">Electro-magnetic induction, discovered by Faraday, <a href="#Page_259">259</a>;</li> +<li class="isub1">Maxwell's statement of the laws of, <a href="#Page_301">301</a>.</li> +<li class="indx">Electro-magnetic theory of light, <a href="#Page_306">306</a>.</li> +<li class="indx">Electro-motors, <a href="#Page_313">313</a>.</li> +<li class="indx">Electro-tonic state, conceived by Faraday, <a href="#Page_264">264</a>;</li> +<li class="isub1">explained by Maxwell, <a href="#Page_302">302</a>.</li> +<li class="indx">Energy of Leyden jar resident in the glass, <a href="#Page_79">79</a>.</li> +<li class="indx">Eriometer, Young's, <a href="#Page_223">223</a>.</li> +<li class="indx">Ether, Maxwell's illustration of the possible constitution of, <a href="#Page_302">302</a>.</li> +<li class="indx">Expansion of water on freezing, <a href="#Page_33">33</a>.</li> +<li class="indx">Extra current, <a href="#Page_268">268</a>.</li> +<li class="ifrst">F.</li> +<li class="indx"><b>Faraday</b>, Michael, birth, <a href="#Page_238">238</a>;</li> +<li class="isub1">life in Jacob's Well Mews, <a href="#Page_238">238</a>;</li> +<li class="isub1">becomes an errand-boy, <a href="#Page_239">239</a>;</li> +<li class="isub1">apprenticeship, <a href="#Page_239">239</a>; +<span class="pagenum"><a id="Page_335">[335]</a></span></li> +<li class="isub1">attends lectures at Tatum's, <a href="#Page_240">240</a>;</li> +<li class="isub1">constructs a voltaic pile, <a href="#Page_241">241</a>;</li> +<li class="isub1">letters to Abbott, <a href="#Page_241">241</a>, <a href="#Page_246">246</a>;</li> +<li class="isub1">starts as a journeyman, <a href="#Page_243">243</a>;</li> +<li class="isub1">application to Davy, <a href="#Page_243">243</a>;</li> +<li class="isub1">appointed assistant at the Royal Institution, <a href="#Page_245">245</a>;</li> +<li class="isub1">joins the City Philosophical Society, <a href="#Page_245">245</a>;</li> +<li class="isub1">opinions respecting lectures, <a href="#Page_246">246</a>, <a href="#Page_247">247</a>;</li> +<li class="isub1">journey with Davy, <a href="#Page_248">248</a>;</li> +<li class="isub1">acquaintance with De la Rive, <a href="#Page_249">249</a>;</li> +<li class="isub1">crosses the Alps, <a href="#Page_249">249</a>;</li> +<li class="isub1">at the Academia del Cimento, <a href="#Page_250">250</a>;</li> +<li class="isub1">returns from the Continent, <a href="#Page_251">251</a>;</li> +<li class="isub1">lectures to the City Philosophical Society, <a href="#Page_251">251</a>;</li> +<li class="isub1">commonplace-book, <a href="#Page_253">253</a>;</li> +<li class="isub1">atmospheric electricity apparatus, <a href="#Page_254">254</a>;</li> +<li class="isub1">marriage, <a href="#Page_255">255</a>;</li> +<li class="isub1">discovery of electro-magnetic rotation, <a href="#Page_255">255</a>;</li> +<li class="isub1">of the earth's action on a current, <a href="#Page_256">256</a>;</li> +<li class="isub1">letter to E. de la Rive, <a href="#Page_256">256</a>;</li> +<li class="isub1">views on Ampère's theory, <a href="#Page_257">257</a>;</li> +<li class="isub1">elected F.R.S., <a href="#Page_258">258</a>;</li> +<li class="isub1">appointed director of the laboratory at the Royal Institution, <a href="#Page_258">258</a>;</li> +<li class="isub1">work on optical glass, <a href="#Page_259">259</a>;</li> +<li class="isub1">discovery of induced currents, <a href="#Page_259">259</a>;</li> +<li class="isub1">institutes Friday evening lectures, <a href="#Page_259">259</a>;</li> +<li class="isub1">anchor-ring experiment, <a href="#Page_260">260</a>;</li> +<li class="isub1">magneto-electric machine, <a href="#Page_262">262</a>;</li> +<li class="isub1">obtains induced current by action of the earth, <a href="#Page_262">262</a>;</li> +<li class="isub1">obtains "magnetic spark," <a href="#Page_262">262</a>;</li> +<li class="isub1">explanation of Arago's experiment, <a href="#Page_264">264</a>;</li> +<li class="isub1">laws of electrolysis, <a href="#Page_266">266</a>;</li> +<li class="isub1">proves the identity of frictional and voltaic electricity, <a href="#Page_266">266</a>;</li> +<li class="isub1">experiments on self-induction, <a href="#Page_268">268</a>;</li> +<li class="isub1">diagrams of lines of magnetic force, <a href="#Page_269">269</a>;</li> +<li class="isub1">conception of lines of electric force, <a href="#Page_270">270</a>;</li> +<li class="isub1">ice-pail experiment, <a href="#Page_270">270</a>;</li> +<li class="isub1">butterfly-net, <a href="#Page_270">270</a>;</li> +<li class="isub1">experiments on specific inductive capacity, <a href="#Page_272">272</a>;</li> +<li class="isub1">appointed scientific adviser to Trinity House, <a href="#Page_273">273</a>;</li> +<li class="isub1">appointed member of the Senate of the University of London, <a href="#Page_273">273</a>;</li> +<li class="isub1">discovery of the electro-magnetic rotation of the plane of polarization, <a href="#Page_273">273</a>;</li> +<li class="isub1">investigations in diamagnetism, <a href="#Page_274">274</a>;</li> +<li class="isub1">joins the Sandemanian Church, <a href="#Page_275">275</a>;</li> +<li class="isub1">lectures before the Prince Consort, <a href="#Page_275">275</a>;</li> +<li class="isub1">retirement to Hampton Court, <a href="#Page_277">277</a>;</li> +<li class="isub1">death, <a href="#Page_277">277</a>;</li> +<li class="isub1">lines of force investigated by Thomson and Maxwell, <a href="#Page_300">300</a>.</li> +<li class="indx">Forbes's, Principal, opinion of Young, <a href="#Page_194">194</a>.</li> +<li class="indx">Foucault's measurement of the velocity of light, <a href="#Page_220">220</a>.</li> +<li class="indx"><i>Fovea centralis</i>, insensibility of, to blue light, <a href="#Page_298">298</a>.</li> +<li class="indx">Franciscus Linus, funicular hypothesis of, <a href="#Page_25">25</a>.</li> +<li class="indx"><b>Franklin</b>, Benjamin, autobiography of, <a href="#Page_39">39</a>;</li> +<li class="isub1">birth, <a href="#Page_40">40</a>;</li> +<li class="isub1">on the disputatious temper, <a href="#Page_42">42</a>;</li> +<li class="isub1">method of learning prose composition, <a href="#Page_43">43</a>;</li> +<li class="isub1">tries vegetarianism, <a href="#Page_44">44</a>;</li> +<li class="isub1">adopts the Socratic method, <a href="#Page_44">44</a>;</li> +<li class="isub1">first voyage to England, <a href="#Page_48">48</a>;</li> +<li class="isub1">experience as a journeyman in London, <a href="#Page_49">49</a>;</li> +<li class="isub1">views on beer as a food, <a href="#Page_49">49</a>;</li> +<li class="isub1">marriage, <a href="#Page_54">54</a>;</li> +<li class="isub1">endeavours to attain moral perfection, <a href="#Page_56">56</a>;</li> +<li class="isub1">method of reconciling an enemy, <a href="#Page_60">60</a>;</li> +<li class="isub1">elected F.R.S., <a href="#Page_66">66</a>;</li> +<li class="isub1">second voyage to England, <a href="#Page_70">70</a>;</li> +<li class="isub1">begins electrical experiments, <a href="#Page_72">72</a>;</li> +<li class="isub1">electrical papers ridiculed by the Royal Society, <a href="#Page_73">73</a>;</li> +<li class="isub1">discovers the effect of points, <a href="#Page_74">74</a>;</li> +<li class="isub1">one-fluid theory of electricity, <a href="#Page_76">76</a>;</li> +<li class="isub1">theory of the Leyden jar, <a href="#Page_78">78</a>;</li> +<li class="isub1">invention of the lightning-rod, <a href="#Page_83">83</a>;</li> +<li class="isub1">golden fish, <a href="#Page_85">85</a>;</li> +<li class="isub1">view of the nature of light, <a href="#Page_86">86</a>;</li> +<li class="isub1">kite, <a href="#Page_88">88</a>;</li> +<li class="isub1">experiments on capacity, <a href="#Page_81">81</a>, <a href="#Page_89">89</a>;</li> +<li class="isub1">experiments on electrical induction, <a href="#Page_90">90</a>;</li> +<li class="isub1">proof of the absence of electricity in a hollow conductor, <a href="#Page_91">91</a>;</li> +<li class="isub1">third voyage to England, <a href="#Page_102">102</a>;</li> +<li class="isub1">examination before the Parliamentary Committee, <a href="#Page_105">105</a>;</li> +<li class="isub1">nominated Foreign Associate of the Academy of Sciences, <a href="#Page_110">110</a>;</li> +<li class="isub1">signs the Declaration of Independence, <a href="#Page_113">113</a>;</li> +<li class="isub1">sent to Paris, <a href="#Page_113">113</a>;</li> +<li class="isub1">made Minister Plenipotentiary to the Court of France, <a href="#Page_116">116</a>;</li> +<li class="isub1">signs the Treaty of Peace, <a href="#Page_119">119</a>;</li> +<li class="isub1">elected President of Pennsylvania, <a href="#Page_120">120</a>;</li> +<li class="isub1">death, <a href="#Page_122">122</a>.</li> +<li class="indx">Fresnel, awarded the Rumford Medal, <a href="#Page_233">233</a>.</li> +<li class="indx">Fresnel's repetition of Young's experiments, <a href="#Page_225">225</a>.</li> +<li class="indx">Friction as a source of heat, Rumford's experiments on, <a href="#Page_189">189</a>.</li> +<li class="indx">Friday evening lectures instituted by Faraday, <a href="#Page_259">259</a>.</li> +<li class="ifrst">G.</li> +<li class="indx">Galileo and Torricelli on the pressure of the air, <a href="#Page_16">16</a>.</li> +<li class="indx">Garnett, Dr. Thomas, professor at the Royal Institution, <a href="#Page_173">173</a>.</li> +<li class="indx">Gilbert, Dr., founder of electrical science, <a href="#Page_3">3</a>.</li> +<li class="indx">Göttingen, Young's university course at, <a href="#Page_206">206</a>.</li> +<li class="indx">Graham Bell's telephone, <a href="#Page_319">319</a>.</li> +<li class="indx">Gray, Stephen, discovers electric conduction, <a href="#Page_3">3</a>.</li> +<li class="indx">Grimaldi's fringes explained by Young, <a href="#Page_222">222</a>.</li> +<li class="indx">Gunpowder, Rumford's experiments on, <a href="#Page_179">179</a>. +<span class="pagenum"><a id="Page_336">[336]</a></span></li> +<li class="ifrst">H.</li> +<li class="indx">Halos, coloured, Young's explanation of, <a href="#Page_224">224</a>.</li> +<li class="indx">Hawksbee's observations on capillary attraction, <a href="#Page_228">228</a>.</li> +<li class="indx">Heat, a form of energy, <a href="#Page_32">32</a>;</li> +<li class="isub1">generated by friction in vacuum, <a href="#Page_32">32</a>;</li> +<li class="isub1">generated by friction, Rumford's experiments on, <a href="#Page_189">189</a>.</li> +<li class="indx">Herapath's explanation of gaseous diffusion, <a href="#Page_299">299</a>.</li> +<li class="indx">Herschel's, Sir John, comments on Young's principle of interference, <a href="#Page_208">208</a>.</li> +<li class="indx">Hicks's, Principal, investigations on the influence of temperature on gravitation, <a href="#Page_184">184</a>.</li> +<li class="indx">Hieroglyphics, Young's work on, <a href="#Page_234">234</a>.</li> +<li class="indx">Hobbes, opposition of, to Boyle, <a href="#Page_25">25</a>.</li> +<li class="indx">Hollow conductor, Franklin's experiments on, <a href="#Page_91">91</a>;</li> +<li class="isub1">Cavendish's experiments on, <a href="#Page_135">135</a>;</li> +<li class="isub1">Faraday's experiments on, <a href="#Page_270">270</a>.</li> +<li class="indx">Honorary degrees conferred on Franklin, <a href="#Page_66">66</a>, <a href="#Page_101">101</a>.</li> +<li class="indx">Hooke's law, <a href="#Page_229">229</a>.</li> +<li class="indx">Hooke, Theodore, founds the Royal Society, <a href="#Page_14">14</a>.</li> +<li class="indx">Huyghens's explanation of double refraction, <a href="#Page_219">219</a>;</li> +<li class="isub1">principle, <a href="#Page_218">218</a>.</li> +<li class="indx">Hydrogen, electro-chemical equivalent of, <a href="#Page_267">267</a>.</li> +<li class="ifrst">I.</li> +<li class="indx">Ice-pail experiment of Faraday, <a href="#Page_270">270</a>.</li> +<li class="indx">Identity of frictional and voltaic electricity, <a href="#Page_266">266</a>.</li> +<li class="indx">Induced currents, discovered by Faraday, <a href="#Page_259">259</a>;</li> +<li class="isub1">explained by structure of ether, <a href="#Page_304">304</a>;</li> +<li class="isub1">from earth's action, <a href="#Page_262">262</a>.</li> +<li class="indx">Induction coil, <a href="#Page_320">320</a>.</li> +<li class="indx">Induction, Franklin's experiments on, <a href="#Page_90">90</a>;</li> +<li class="isub1">self, <a href="#Page_142">142</a>, <a href="#Page_306">306</a>.</li> +<li class="indx">Induction machines, principle of, <a href="#Page_316">316</a>.</li> +<li class="indx">Insulators for lightning-rods, <a href="#Page_96">96</a>.</li> +<li class="indx">Interference, principle of, discovered by Young, <a href="#Page_208">208</a>;</li> +<li class="isub1">spectra of, obtained by Young, <a href="#Page_225">225</a>.</li> +<li class="indx">Invisible college, <a href="#Page_13">13</a>.</li> +<li class="ifrst">J.</li> +<li class="indx">Jenkin, William, discovery of the "extra current" by, <a href="#Page_268">268</a>.</li> +<li class="indx">Joule and Thomson's determination of the heat absorbed by air in expanding, <a href="#Page_324">324</a>.</li> +<li class="indx">Joule, Dr., establishment of mechanical theory of heat by, <a href="#Page_193">193</a>, <a href="#Page_324">324</a>.</li> +<li class="indx">Joule's law, <a href="#Page_324">324</a>;</li> +<li class="isub1">proof that heat and energy are equivalent, <a href="#Page_324">324</a>;</li> +<li class="isub1">determination of the mechanical equivalent of heat, <a href="#Page_325">325</a>.</li> +<li class="indx">Junto Club, formation of the, <a href="#Page_51">51</a>.</li> +<li class="ifrst">K.</li> +<li class="indx">Kelland's, Professor, edition of Young's lectures, <a href="#Page_212">212</a>.</li> +<li class="indx">Kinnersley commences lecturing, <a href="#Page_73">73</a>.</li> +<li class="indx">Kite, Franklin's, <a href="#Page_88">88</a>.</li> +<li class="indx">Knobs <i>versus</i> points, <a href="#Page_95">95</a>.</li> +<li class="ifrst">L.</li> +<li class="indx">Laboulaye's comments on Franklin, <a href="#Page_38">38</a>.</li> +<li class="indx">Laplace's theory of Saturn's rings, <a href="#Page_285">285</a>.</li> +<li class="indx">Latent heat, Black's theory of, <a href="#Page_144">144</a>;</li> +<li class="isub1">Cavendish's views on, <a href="#Page_144">144</a>.</li> +<li class="indx">Leonardo da Vinci's observation of capillary attraction, <a href="#Page_228">228</a>.</li> +<li class="indx">Leyden jar, discovery of, <a href="#Page_4">4</a>;</li> +<li class="isub1">energy of, resident in the glass, <a href="#Page_79">79</a>.</li> +<li class="indx">Leyden jars charged by cascade, <a href="#Page_77">77</a>.</li> +<li class="indx">Light, Franklin's view of nature of, <a href="#Page_86">86</a>;</li> +<li class="isub1">Maxwell's electro-magnetic theory of, <a href="#Page_306">306</a>;</li> +<li class="isub1">rotation of the plane of polarization of, <a href="#Page_273">273</a>.</li> +<li class="indx">Lightning, effects of, on Newbury steeple, <a href="#Page_92">92</a>.</li> +<li class="indx">Lightning-protectors, Maxwell's, <a href="#Page_294">294</a>.</li> +<li class="indx">Lightning-rod, illustrations of the, <a href="#Page_83">83</a>.</li> +<li class="indx"><i>Lignum nephriticum</i>, dichroism of, <a href="#Page_30">30</a>.</li> +<li class="indx">Lines of force mathematically investigated by Thomson and Maxwell, <a href="#Page_300">300</a>.</li> +<li class="indx">Lines of magnetic force fixed by Faraday, <a href="#Page_269">269</a>.</li> +<li class="indx">Luminiferous ether, the vehicle of electrical action, <a href="#Page_227">227</a>;</li> +<li class="isub1">illustration of the possible constitution of, <a href="#Page_302">302</a>.</li> +<li class="ifrst">M.</li> +<li class="indx">Magdeburg hemispheres, experiments with, by Otto von Guericke, <a href="#Page_17">17</a>.</li> +<li class="indx">Magic squares, Franklin's proficiency in, <a href="#Page_66">66</a>.</li> +<li class="indx">"Magnetic spark" obtained by Faraday, <a href="#Page_262">262</a>.</li> +<li class="indx">Magnetization by induction, Boyle's experiments on, <a href="#Page_34">34</a>.</li> +<li class="indx">Magneto-electric machine, Faraday's, <a href="#Page_262">262</a>, <a href="#Page_314">314</a>.</li> +<li class="indx">Magneto-electric machines, Wilde's, <a href="#Page_318">318</a>;</li> +<li class="isub1">objects to be aimed at in the construction of, <a href="#Page_315">315</a>.</li> +<li class="indx"><b>Maxwell</b>, James Clerk, birth and parentage, <a href="#Page_279">279</a>; +<span class="pagenum"><a id="Page_337">[337]</a></span></li> +<li class="isub1">enters Edinburgh Academy, <a href="#Page_280">280</a>;</li> +<li class="isub1">letters to his father, <a href="#Page_280">280</a>;</li> +<li class="isub1">early papers before the Royal Society of Edinburgh, <a href="#Page_281">281</a>;</li> +<li class="isub1">visit to Mr. Nicol, <a href="#Page_281">281</a>;</li> +<li class="isub1">experiments with unannealed glass, <a href="#Page_282">282</a>;</li> +<li class="isub1">enters the University of Edinburgh, <a href="#Page_282">282</a>;</li> +<li class="isub1">enters Peterhouse, <a href="#Page_282">282</a>;</li> +<li class="isub1">migrates to Trinity, <a href="#Page_282">282</a>;</li> +<li class="isub1">degree in Cambridge, <a href="#Page_283">283</a>;</li> +<li class="isub1">elected Fellow of Trinity, <a href="#Page_284">284</a>;</li> +<li class="isub1">appointed Professor at Marischal College, <a href="#Page_284">284</a>;</li> +<li class="isub1">marriage, <a href="#Page_287">287</a>;</li> +<li class="isub1">essay on Saturn's rings, <a href="#Page_285">285</a>;</li> +<li class="isub1">dynamical top, <a href="#Page_285">285</a>;</li> +<li class="isub1">appointed professor at King's College, <a href="#Page_287">287</a>;</li> +<li class="isub1">lecture on colour at the Royal Institution, <a href="#Page_287">287</a>;</li> +<li class="isub1">work on the Electrical Standards Committee, <a href="#Page_287">287</a>;</li> +<li class="isub1">appointed Professor of Experimental Physics at Cambridge, <a href="#Page_288">288</a>;</li> +<li class="isub1">plans the Cavendish Laboratory, <a href="#Page_288">288</a>;</li> +<li class="isub1">lectures at Cambridge, <a href="#Page_290">290</a>;</li> +<li class="isub1">work on the Cavendish Manuscripts, <a href="#Page_134">134</a>, <a href="#Page_293">293</a>;</li> +<li class="isub1">delivers the Rede Lecture, <a href="#Page_293">293</a>;</li> +<li class="isub1">method of protecting buildings from lightning, <a href="#Page_294">294</a>;</li> +<li class="isub1">death, <a href="#Page_294">294</a>;</li> +<li class="isub1">colour-top, <a href="#Page_295">295</a>;</li> +<li class="isub1">experiments on colour-blindness, <a href="#Page_296">296</a>;</li> +<li class="isub1">colour-box, <a href="#Page_297">297</a>;</li> +<li class="isub1">awarded the Rumford Medal, <a href="#Page_297">297</a>;</li> +<li class="isub1">wheel of life, <a href="#Page_297">297</a>;</li> +<li class="isub1">real-image spectroscope, <a href="#Page_298">298</a>;</li> +<li class="isub1">discovery of stresses in Canada balsam, <a href="#Page_298">298</a>;</li> +<li class="isub1">of the insensibility of the <i>fovea centralis</i> to blue light, <a href="#Page_298">298</a>;</li> +<li class="isub1">statistical method, <a href="#Page_299">299</a>;</li> +<li class="isub1">explanation of the viscosity of gases, <a href="#Page_299">299</a>;</li> +<li class="isub1">investigations of Faraday's lines of force, <a href="#Page_300">300</a>;</li> +<li class="isub1">statement of the laws of electro-magnetic induction, <a href="#Page_301">301</a>;</li> +<li class="isub1">mechanical illustration of the ether, <a href="#Page_302">302</a>;</li> +<li class="isub1">explanation of induced currents, <a href="#Page_304">304</a>;</li> +<li class="isub1">of the mechanical action between currents and currents, and between magnets and currents, <a href="#Page_304">304</a>;</li> +<li class="isub1">of self-induction, <a href="#Page_306">306</a>;</li> +<li class="isub1">electro-magnetic theory of light, <a href="#Page_306">306</a>;</li> +<li class="isub1">contrivance for overcoming the principle of the dissipation of energy, <a href="#Page_328">328</a>.</li> +<li class="indx">Maxwell's experiment for showing electro-magnetic rotation, <a href="#Page_258">258</a>.</li> +<li class="indx">Mayer's determination of the mechanical equivalent of heat, <a href="#Page_323">323</a>.</li> +<li class="indx">Mechanical equivalent of heat, definition of, <a href="#Page_193">193</a>;</li> +<li class="isub1">Rumford's determination of, <a href="#Page_192">192</a>.</li> +<li class="indx">Mercury, melting point of, <a href="#Page_145">145</a>.</li> +<li class="indx">Mirabeau's declamation on Franklin, <a href="#Page_123">123</a>.</li> +<li class="indx">Mixed plates, colours of, <a href="#Page_223">223</a>.</li> +<li class="indx">Moral perfection, Franklin's endeavour to attain, <a href="#Page_56">56</a>.</li> +<li class="indx">Mother-of-pearl, Young's explanation of the colours of, <a href="#Page_224">224</a>.</li> +<li class="ifrst">N.</li> +<li class="indx">Nautical Almanack, Young appointed superintendent of the, <a href="#Page_232">232</a>.</li> +<li class="indx">Newton's analysis and synthesis of white light, <a href="#Page_213">213</a>;</li> +<li class="isub1">rings, Young's explanation of, <a href="#Page_222">222</a>;</li> +<li class="isub1">theory of light, <a href="#Page_219">219</a>.</li> +<li class="indx">Nicol prisms given to Clerk Maxwell, <a href="#Page_282">282</a>.</li> +<li class="ifrst">O.</li> +<li class="indx">Œrsted's discovery, <a href="#Page_255">255</a>.</li> +<li class="indx">Ohm's law, discovered by Cavendish, <a href="#Page_143">143</a>;</li> +<li class="isub1">meaning of, <a href="#Page_143">143</a>.</li> +<li class="indx">Optical glass, Faraday's work on, <a href="#Page_259">259</a>.</li> +<li class="indx">Otto von Guericke, contributions of, to electricity, <a href="#Page_3">3</a>;</li> +<li class="isub1">experiments of, with the Magdeburg hemispheres, <a href="#Page_17">17</a>.</li> +<li class="ifrst">P.</li> +<li class="indx">Paris, Dr., Faraday's letter to, <a href="#Page_243">243</a>.</li> +<li class="indx">Pascal takes a barometer up the Puy de Dome, <a href="#Page_17">17</a>.</li> +<li class="indx">Pennsylvania fireplace invented by Franklin, <a href="#Page_63">63</a>;</li> +<li class="isub1"><i>Gazette</i> published by Franklin, <a href="#Page_53">53</a>.</li> +<li class="indx">Perpetual motion, Rumford's contrivances for, <a href="#Page_150">150</a>;</li> +<li class="isub1">impossibility of, <a href="#Page_322">322</a>.</li> +<li class="indx">Philadelphia, Franklin's first arrival in, <a href="#Page_46">46</a>;</li> +<li class="isub1">Library, foundation of the, <a href="#Page_55">55</a>.</li> +<li class="indx">Photometer, Rumford's, <a href="#Page_187">187</a>.</li> +<li class="indx">Pigments, effects of mixing, <a href="#Page_217">217</a>.</li> +<li class="indx">Points <i>versus</i> knobs, <a href="#Page_95">95</a>, <a href="#Page_131">131</a>.</li> +<li class="indx">Polarization, explained by transverse vibrations, <a href="#Page_226">226</a>;</li> +<li class="isub1">of light discovered by Malus, <a href="#Page_226">226</a>.</li> +<li class="indx">"Poor Richard's Almanack," <a href="#Page_60">60</a>.</li> +<li class="indx">Pressure of the air the cause of suction, <a href="#Page_29">29</a>.</li> +<li class="ifrst">R.</li> +<li class="indx">Radiation, Rumford's experiments on, <a href="#Page_184">184</a>;</li> +<li class="isub1">of cold, Rumford's experiments on, <a href="#Page_186">186</a>.</li> +<li class="indx">Rede Lecture, delivered by Clerk Maxwell, <a href="#Page_293">293</a>.</li> +<li class="indx">Refraction of light, laws of, <a href="#Page_1">1</a>;</li> +<li class="isub1">mentioned by Pliny, <a href="#Page_1">1</a>.</li> +<li class="indx">Relative economy of different sources of light, <a href="#Page_188">188</a>.</li> +<li class="indx">Resistance of conductors, Cavendish's experiments on, <a href="#Page_142">142</a>.</li> +<li class="indx">Roemer, measurement of the velocity of light by, <a href="#Page_2">2</a>.</li> +<li class="indx">Rosetta Stone, discovery of the, <a href="#Page_234">234</a>;</li> +<li class="isub1">inscription on, <a href="#Page_234">234</a>. +<span class="pagenum"><a id="Page_338">[338]</a></span></li> +<li class="indx">Royal Institution, foundation of the, <a href="#Page_169">169</a>;</li> +<li class="isub1">Young's lectures at the, <a href="#Page_212">212</a>;</li> +<li class="isub1">Faraday's appointment at the, <a href="#Page_245">245</a>;</li> +<li class="isub1">Maxwell's lecture on colour at the, <a href="#Page_287">287</a>.</li> +<li class="indx">Royal Society, origin of the, <a href="#Page_13">13-15</a>.</li> +<li class="indx"><b>Rumford</b>, Count, birth and parentage, <a href="#Page_148">148</a>;</li> +<li class="isub1">life as a medical student, <a href="#Page_153">153</a>;</li> +<li class="isub1">becomes a schoolmaster at Concord, <a href="#Page_154">154</a>;</li> +<li class="isub1">marriage, <a href="#Page_154">154</a>;</li> +<li class="isub1">summoned before the Committee of Safety, <a href="#Page_156">156</a>;</li> +<li class="isub1">imprisoned at Woburn, <a href="#Page_156">156</a>;</li> +<li class="isub1">first journey to London, <a href="#Page_158">158</a>;</li> +<li class="isub1">receives an appointment in the Colonial Office, <a href="#Page_158">158</a>;</li> +<li class="isub1">experiments on the explosion of gunpowder, <a href="#Page_158">158</a>, <a href="#Page_179">179</a>;</li> +<li class="isub1">elected F.R.S., <a href="#Page_158">158</a>;</li> +<li class="isub1">made lieutenant-colonel in the British army, <a href="#Page_159">159</a>;</li> +<li class="isub1">promoted to colonel, <a href="#Page_160">160</a>;</li> +<li class="isub1">visits Elector of Bavaria, <a href="#Page_160">160</a>;</li> +<li class="isub1">cured of martial ambition, <a href="#Page_160">160</a>;</li> +<li class="isub1">enters the service of the Elector of Bavaria, <a href="#Page_161">161</a>;</li> +<li class="isub1">knighted by George III., <a href="#Page_161">161</a>;</li> +<li class="isub1">reforms in the Bavarian army, <a href="#Page_162">162</a>;</li> +<li class="isub1">attack on the beggars, <a href="#Page_163">163</a>;</li> +<li class="isub1">made Count of the Holy Roman Empire, <a href="#Page_165">165</a>;</li> +<li class="isub1">robbed of his manuscripts, <a href="#Page_166">166</a>;</li> +<li class="isub1">visited by his daughter, <a href="#Page_166">166</a>;</li> +<li class="isub1">his roaster, <a href="#Page_166">166</a>;</li> +<li class="isub1">experiments on fire-places, <a href="#Page_166">166</a>;</li> +<li class="isub1">founds the Rumford Medal, <a href="#Page_167">167</a>;</li> +<li class="isub1">appointed Minister Plenipotentiary to the Court of Great Britain, <a href="#Page_169">169</a>;</li> +<li class="isub1">founds the Royal institution, <a href="#Page_169">169</a>;</li> +<li class="isub1">plans for the Institution, <a href="#Page_169">169</a>;</li> +<li class="isub1">residence in Paris, <a href="#Page_175">175</a>;</li> +<li class="isub1">marriage with Madame Lavoisier, <a href="#Page_175">175</a>;</li> +<li class="isub1">death; <a href="#Page_176">176</a>;</li> +<li class="isub1">Cuvier's <i>éloge</i> on, <a href="#Page_176">176</a>;</li> +<li class="isub1">statue at Munich, <a href="#Page_178">178</a>;</li> +<li class="isub1">experiments on the conduction of heat in fluids, <a href="#Page_181">181</a>;</li> +<li class="isub1">on the convection of heat in viscous liquids, <a href="#Page_184">184</a>;</li> +<li class="isub1">on the weight of heat, <a href="#Page_185">185</a>;</li> +<li class="isub1">on radiation, <a href="#Page_185">185</a>;</li> +<li class="isub1">on the conduction of heat, <a href="#Page_186">186</a>;</li> +<li class="isub1">on the apparent radiation of cold, <a href="#Page_187">187</a>;</li> +<li class="isub1">shadow-photometer, <a href="#Page_188">188</a>;</li> +<li class="isub1">experiments on the relative economy of candles and tapers, <a href="#Page_188">188</a>;</li> +<li class="isub1">on the traction of carriages, <a href="#Page_189">189</a>;</li> +<li class="isub1">on friction as a source of heat, <a href="#Page_189">189</a>;</li> +<li class="isub1">determination of the mechanical equivalent of heat, <a href="#Page_192">192</a>.</li> +<li class="indx">Rumford Medal, foundation of the, <a href="#Page_167">167</a>;</li> +<li class="isub1">recipients of the, <a href="#Page_167">167</a>;</li> +<li class="isub1">awarded to Fresnel, <a href="#Page_233">233</a>;</li> +<li class="isub1">awarded to Clerk Maxwell, <a href="#Page_297">297</a>.</li> +<li class="indx">Rumford roaster, <a href="#Page_166">166</a>.</li> +<li class="ifrst">S.</li> +<li class="indx">"Sandford and Merton," influence of, on the negro traffic, <a href="#Page_197">197</a>.</li> +<li class="indx">Saturn's rings, Maxwell's essay on, <a href="#Page_285">285</a>.</li> +<li class="indx">Sea-water, resistance of, <a href="#Page_142">142</a>.</li> +<li class="indx">Séguin's attempt to measure loss of heat in the steam-engine, <a href="#Page_323">323</a>.</li> +<li class="indx">Self-induction, effect of, on sudden discharge, <a href="#Page_142">142</a>;</li> +<li class="isub1">of electro-magnet, <a href="#Page_268">268</a>;</li> +<li class="isub1">effect of, in induction coil, <a href="#Page_321">321</a>.</li> +<li class="indx">Sensation of heat, cause of, <a href="#Page_33">33</a>.</li> +<li class="indx">Seraphic love, Boyle's essay on, <a href="#Page_15">15</a>.</li> +<li class="indx">Shaw's, Dr., comments on Boyle, <a href="#Page_37">37</a>.</li> +<li class="indx">Snellius's laws of refraction, <a href="#Page_1">1</a>.</li> +<li class="indx">Socratic method adopted by Franklin, <a href="#Page_44">44</a>.</li> +<li class="indx">Specific inductive capacity, discovered by Cavendish, <a href="#Page_139">139</a>;</li> +<li class="isub1">rediscovered by Faraday, <a href="#Page_272">272</a>.</li> +<li class="indx">Spectral colours, mixed by Boyle, <a href="#Page_31">31</a>;</li> +<li class="isub1">mixed by Maxwell, <a href="#Page_297">297</a>.</li> +<li class="indx">S.P.G., foundation of the, <a href="#Page_30">30</a>.</li> +<li class="indx">Spheroidal waves in Iceland-spar explained by Young, <a href="#Page_226">226</a>.</li> +<li class="indx">Stamp Act, <a href="#Page_112">112</a>.</li> +<li class="indx">Standards Commission, report of, <a href="#Page_232">232</a>.</li> +<li class="indx">Statistical method, Maxwell's, <a href="#Page_299">299</a>.</li> +<li class="indx">Steeple struck by lightning at Newbury, <a href="#Page_92">92</a>.</li> +<li class="indx">Stereoscope, Maxwell's real-image, <a href="#Page_298">298</a>.</li> +<li class="indx">Stokes's, Professor G. G., exhibition of the bright centre in the shadow of a disc, <a href="#Page_222">222</a>.</li> +<li class="indx">Suction caused by atmospheric pressure, <a href="#Page_29">29</a>.</li> +<li class="indx">Surface-tension, <a href="#Page_228">228</a>;</li> +<li class="isub1">suggested by Segner, <a href="#Page_229">229</a>;</li> +<li class="isub1">Young's investigations on, <a href="#Page_229">229</a>.</li> +<li class="ifrst">T.</li> +<li class="indx">Table of results of experiments on Boyle's law, <a href="#Page_27">27</a>.</li> +<li class="indx">Tatum's lectures on natural philosophy, <a href="#Page_240">240</a>.</li> +<li class="indx">Telephone, Graham Bell's, <a href="#Page_319">319</a>.</li> +<li class="indx">Temperature, its nature, <a href="#Page_33">33</a>.</li> +<li class="indx">Thermometers first hermetically sealed, <a href="#Page_2">2</a>.</li> +<li class="indx">Thomson's, Professor James, application of the principle of dissipation of energy to the freezing of water under pressure, <a href="#Page_327">327</a>.</li> +<li class="indx">Thomson's, Sir William, statement of the principle of dissipation of energy, <a href="#Page_327">327</a>;</li> +<li class="isub1">vortex theory of matter, <a href="#Page_312">312</a>;</li> +<li class="isub1">mirror galvanometer, <a href="#Page_313">313</a>;</li> +<li class="isub1">replenisher, <a href="#Page_316">316</a>.</li> +<li class="indx">Thunder-storms, Franklin's theory of, <a href="#Page_81">81</a>.</li> +<li class="indx">Torpedo, Cavendish's experiments on the, <a href="#Page_140">140</a>;</li> +<li class="isub1">Davy's experiments on the, <a href="#Page_251">251</a>. +<span class="pagenum"><a id="Page_339">[339]</a></span></li> +<li class="indx">Traction of carriages, Rumford's experiments on, <a href="#Page_189">189</a>.</li> +<li class="indx">Trial plate used by Cavendish, <a href="#Page_139">139</a>.</li> +<li class="indx">Tyres, relative advantages of broad and narrow, <a href="#Page_189">189</a>.</li> +<li class="ifrst">U.</li> +<li class="indx">Undulatory theory founded by Hooke and Huyghens, <a href="#Page_218">218</a>.</li> +<li class="indx">Union of the American States, Franklin's plan for, <a href="#Page_68">68</a>.</li> +<li class="indx">University of Philadelphia, foundation of the, <a href="#Page_64">64</a>.</li> +<li class="ifrst">V.</li> +<li class="indx">Vacuum, Boyle's argument on the cause of a, <a href="#Page_23">23</a>.</li> +<li class="indx">Velocity of electricity, <a href="#Page_93">93</a>;</li> +<li class="isub1">of light measured by Roemer, <a href="#Page_2">2</a>;</li> +<li class="isub1">of light deduced from electro-magnetic theory, <a href="#Page_306">306</a>.</li> +<li class="indx">Viscosity of gases explained by Maxwell, <a href="#Page_299">299</a>.</li> +<li class="indx">Voltaic pile constructed by Faraday, <a href="#Page_241">241</a>.</li> +<li class="indx">Vortex theory of matter, <a href="#Page_312">312</a>.</li> +<li class="indx">Voss machine, <a href="#Page_316">316</a>.</li> +<li class="ifrst">W.</li> +<li class="indx">Wallis, Dr., account of the Royal Society by, <a href="#Page_14">14</a>.</li> +<li class="indx">Wealth, ways to acquire, <a href="#Page_100">100</a>.</li> +<li class="indx">Wheel of life, Clerk Maxwell's, <a href="#Page_297">297</a>.</li> +<li class="indx">Wilson, Dr., account of Cavendish by, <a href="#Page_132">132</a>, <a href="#Page_147">147</a>.</li> +<li class="ifrst">Y.</li> +<li class="indx"><b>Young</b>, Thomas, Principal Forbes's opinion of, <a href="#Page_194">194</a>;</li> +<li class="isub1">birth and parentage, <a href="#Page_194">194</a>;</li> +<li class="isub1">early education, <a href="#Page_195">195</a>;</li> +<li class="isub1">becomes a London medical student, <a href="#Page_199">199</a>;</li> +<li class="isub1">paper on the power of adjustment of the eye, <a href="#Page_199">199</a>;</li> +<li class="isub1">elected F.R.S., <a href="#Page_200">200</a>;</li> +<li class="isub1">visit to Cornwall, <a href="#Page_201">201</a>;</li> +<li class="isub1">first visit to the Duke of Richmond, <a href="#Page_201">201</a>;</li> +<li class="isub1">enters the Medical School at Edinburgh, <a href="#Page_202">202</a>;</li> +<li class="isub1">declines secretaryship to the Duke of Richmond, <a href="#Page_202">202</a>;</li> +<li class="isub1">visits Gordon Castle, <a href="#Page_204">204</a>;</li> +<li class="isub1">visits Inverary Castle, <a href="#Page_205">205</a>;</li> +<li class="isub1">enters the University of Göttingen, <a href="#Page_206">206</a>;</li> +<li class="isub1">examination in medicine at Göttingen, <a href="#Page_207">207</a>;</li> +<li class="isub1">enters Emmanuel College, <a href="#Page_207">207</a>;</li> +<li class="isub1">discovers the principle of interference, <a href="#Page_208">208</a>;</li> +<li class="isub1">appointed Professor of Natural Philosophy at the Royal Institution, <a href="#Page_174">174</a>, <a href="#Page_210">210</a>;</li> +<li class="isub1">lectures at the Royal Institution, <a href="#Page_212">212</a>;</li> +<li class="isub1">theory of colour-vision, <a href="#Page_214">214</a>;</li> +<li class="isub1">his colour-top, <a href="#Page_215">215</a>;</li> +<li class="isub1">colour-diagram, <a href="#Page_215">215</a>;</li> +<li class="isub1">his Bakerian lectures, <a href="#Page_218">218</a>;</li> +<li class="isub1">explanation of the rectilinear propagation of light, <a href="#Page_221">221</a>;</li> +<li class="isub1">of Newton's rings, <a href="#Page_222">222</a>;</li> +<li class="isub1">eriometer, <a href="#Page_223">223</a>;</li> +<li class="isub1">explanation of coloured halos, <a href="#Page_224">224</a>;</li> +<li class="isub1">of the colours exhibited by mother-of-pearl, <a href="#Page_224">224</a>;</li> +<li class="isub1">interference spectra, <a href="#Page_225">225</a>;</li> +<li class="isub1">explanation of spheroidal waves in Iceland-spar, <a href="#Page_226">226</a>;</li> +<li class="isub1">of the colours of thin plates, <a href="#Page_227">227</a>;</li> +<li class="isub1">hypothesis of an electric ether, <a href="#Page_227">227</a>;</li> +<li class="isub1">investigations on surface-tension, <a href="#Page_229">229</a>;</li> +<li class="isub1">modulus of elasticity, <a href="#Page_230">230</a>;</li> +<li class="isub1">his marriage, <a href="#Page_231">231</a>;</li> +<li class="isub1">appointed physician in St. George's Hospital, <a href="#Page_231">231</a>;</li> +<li class="isub1">superintendent of the Nautical Almanack, <a href="#Page_232">232</a>;</li> +<li class="isub1">death, <a href="#Page_233">233</a>.</li> +</ul> + +<p class="spacer"> </p> + +<p><span class="pagenum"><a id="Page_340">[340]</a></span></p> + +<p class="h5">PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,<br /> +LONDON AND BECCLES.</p> + + + + + + + + +<pre> + + + + + +End of Project Gutenberg's Heroes of Science: Physicists, by William Garnett + +*** END OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Heroes of Science: Physicists + +Author: William Garnett + +Release Date: January 15, 2012 [EBook #38583] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: PHYSICISTS *** + + + + +Produced by Albert Laszlo, P. G. Mate, Matthew Wheaton and +the Online Distributed Proofreading Team at +http://www.pgdp.net (This file was produced from images +generously made available by The Internet Archive) + + + + + + + + + + HEROES OF SCIENCE. + + + + + HEROES OF SCIENCE. + + PHYSICISTS. + + BY + + WILLIAM GARNETT, M.A., D.C.L., + + + FORMERLY FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE; PRINCIPAL OF + THE DURHAM COLLEGE OF SCIENCE, NEWCASTLE-UPON-TYNE; HON. MEMBER + OF THE NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL + ENGINEERS. + + PUBLISHED UNDER THE DIRECTION OF THE COMMITTEE OF GENERAL + LITERATURE AND EDUCATION APPOINTED BY THE SOCIETY FOR PROMOTING + CHRISTIAN KNOWLEDGE. + + LONDON: + SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE, + NORTHUMBERLAND AVENUE, CHARING CROSS, W.C.; + + 43, QUEEN VICTORIA STREET, E.C.; + 26, ST. GEORGE'S PLACE, HYDE PARK CORNER, S.W. + BRIGHTON: 135, NORTH STREET. + + NEW YORK: E. & J. B. YOUNG AND CO. + + + + +PREFACE. + + +The following pages claim no originality, and no merits beyond that of +bringing within reach of every boy and girl material which would +otherwise be available only to those who had extensive libraries at +their command, and much time at their disposal. In the schools and +colleges in which the principles of physical science are well taught, +the history of the discoveries whereby those principles have been +established has been too much neglected. The series to which the +present volume belongs is intended, in some measure, to meet this +deficiency. + +A complete history of physical science would, if it could be written, +form a library of considerable dimensions. The following pages deal +only with the biographies of a few distinguished men, who, by birth, +were British subjects, and incidental allusions only are made to +living philosophers; but, notwithstanding these narrow restrictions, +the foundations of the Royal Society of London, of the American +Philosophical Society, of the great Library of Pennsylvania, and of +the Royal Institution, are events, some account of which comes within +the compass of the volume. The gradual development of our knowledge of +electricity, of the mechanical theory of heat, and of the undulatory +theory of optics, will be found delineated in the biographies +selected, though no continuous history is traced in the case of any +one of these branches of physics. + +The sources from which the matter contained in the following pages has +been derived have been, in addition to the published works of the +subjects of the several sketches, the following:-- + +"The Encyclopaedia Britannica." + +"Memoir of the Honourable Robert Boyle," by Thomas Birch, M.A., +prefixed to the folio edition of his works, which was published in +London in 1743. + +"Life of Benjamin Franklin," from his own writings, by John Bigelow. + +Dr. G. Wilson's "Life of Cavendish," which forms the first volume of +the publications of the Cavendish Society; and the "Electrical +Researches of the Hon. Henry Cavendish, F.R.S.," edited by the late +Professor James Clerk Maxwell. + +"The Life of Sir Benjamin Thompson, Count Rumford," by George E. +Ellis, published by the American Academy of Arts and Sciences, in +connection with the complete edition of his works. + +"Memoir of Thomas Young," by the late Dean Peacock. + +Dr. Bence Jones's "Life of Faraday;" and Professor Tyndall's "Faraday +as a Discoverer." + +"Life of James Clerk Maxwell," by Professor Lewis Campbell and William +Garnett. + +It is hoped that the perusal of the following sketches may prove as +instructive to the reader as their preparation has been to the writer. + + WM. GARNETT. + + NEWCASTLE-UPON-TYNE, + _December, 1885_. + + + + +CONTENTS. + + + PAGE +INTRODUCTION 1 +ROBERT BOYLE 5 +BENJAMIN FRANKLIN 38 +HENRY CAVENDISH 125 +COUNT RUMFORD 148 +THOMAS YOUNG 194 +MICHAEL FARADAY 237 +JAMES CLERK MAXWELL 278 +CONCLUSION 309 + + + + +HEROES OF SCIENCE. + + + + +INTRODUCTION. + + +The dawn of true ideas respecting mechanics has been described in the +volume of this series devoted to astronomers. At the time when the +first of the following biographies opens there were a few men who held +sound views respecting the laws of motion and the principles of +hydrostatics. Considerable advance had been made in the subject of +geometrical optics; the rectilinear propagation of light and the laws +of reflection having been known to the Greeks and Arabians, whilst +Willebrod Snellius, Professor of Mathematics at Leyden, had correctly +enunciated the laws of refraction very early in the seventeenth +century. Pliny mentions the action of a sphere of rock-crystal and of +a glass globe filled with water in bringing light to a focus. Roger +Bacon used segments of a glass sphere as lenses; and in the eleventh +century Alhazen made many measurements of the angles of incidence and +refraction, though he did not succeed in discovering the law. Huyghens +developed to a great extent the undulatory theory; while Newton at the +same time made great contributions to the subject of geometrical +optics, decomposed white light by means of a prism, investigated the +colours of thin plates, and some cases of diffraction, and speculated +on the nature, properties, and functions of the ether, which was +equally necessary to the corpuscular as to the undulatory theory of +light, if any of the phenomena of interference were to be explained. +The velocity of light was first measured by Roemer, in 1676. The +camera obscura was invented by Baptista Porta, a wealthy Neapolitan, +in 1560; and Kepler explained the action of the eye as an optical +instrument, in 1604. Antonio de Dominis, Archbishop of Spalatro, +discovered the fringe of colours produced by sunlight once reflected +from the interior of a globe of water, and this led, in Newton's +hands, to the complete explanation of the rainbow. + +The germ of the mechanical theory of heat is to be found in the +writings of Lord Bacon. The first thermometers which were blown in +glass with a bulb and tube hermetically sealed, were made by a +craftsman in Florence, in the time of Torricelli. The graduations on +these thermometers were made by attaching little beads of coloured +glass to their stems, and they were carried about Europe by members of +the Florentine Academy, in order to learn whether ice melted at the +same temperature in all latitudes. + +In electricity the attraction of light bodies by amber when rubbed, +was known at least six hundred years before the Christian era, and the +shocks of the torpedo were described by Pliny and by Aristotle; but +the phenomena were not associated in men's minds until recent times. +Dr. Gilbert, of Colchester, Physician to Queen Elizabeth, may be +regarded as the founder of the modern science. He distinguished two +classes of bodies, viz. electrics, or those which would attract light +bodies when rubbed; and non-electrics, or those which could not be so +excited. The first electric machine was constructed by Otto von +Guericke, the inventor of the Magdeburg hemispheres, who mounted a +ball of sulphur so that it could be made rapidly to rotate while it +was excited by the friction of the hand. He observed the repulsion +which generally follows the attraction of a light body by an +electrified object after the two have come in contact. He also noticed +that certain bodies placed near to electrified bodies possessed +similar powers of attraction to those of the electrified bodies +themselves. Newton replaced the sulphur globe of Otto von Guericke by +a globe of glass. Stephen Gray discovered the conduction of +electricity, in 1729, when he succeeded in transmitting a charge to a +distance of 886 feet along a pack-thread suspended by silk strings so +as to insulate it from the earth. Desaguliers showed that Gilbert's +"electrics" were simply those bodies which could not conduct +electricity, while all conductors were "non-electrics;" and Dufay +showed that all bodies could be electrified by friction if supported +on insulating stands. He also showed that there were two kinds of +electrification, and called one _vitreous_, the other _resinous_. +Gray, Hawksbee, and Dr. Wall all noticed the similarity between +lightning and the electric discharge. The prime conductor was first +added to the electric machine by Boze, of Wittenberg; and Winkler, of +Leipsic, employed a cushion instead of the hand to produce friction +against the glass. The accumulation of electricity in the Leyden jar +was discovered accidentally by Cuneus, a pupil of Muschenbroeck, of +Leyden, about 1745, while attempting to electrify water in a bottle +held in his hand. A nail passed through the cork, by which the +electricity was communicated to the water. On touching the nail after +charging the water, he received the shock of the Leyden jar. This +brings the history of electrical discovery down to the time of +Franklin. + + + + +ROBERT BOYLE. + + +Robert Boyle was descended from a family who, in Saxon times, held +land in the county of Hereford, and whose name in the Doomsday Book is +written Biuvile. His father was Richard Boyle, Earl of Cork, to whom +the fortunes of the family were largely due. Richard Boyle was born in +the city of Canterbury, October 3, 1566. He was educated at Bene't +College (now Corpus Christi College), Cambridge, and afterwards became +a member of the Middle Temple. Finding his means insufficient for the +prosecution of his legal studies, he determined to seek his fortune +abroad. In 1595 he married, at Limerick, one of the daughters of +William Apsley, who brought him land of the value of L500 per annum. +In his autobiography the Earl of Cork writes:-- + + When first I arrived at Dublin, in Ireland, the 23rd of June + 1588, all my wealth then was twenty-seven pounds three shillings + in money, and two tokens which my mother had given me, viz. a + diamond ring, which I have ever since and still do wear, and a + bracelet of gold worth about ten pounds; a taffety doublet cut + with and upon taffety, a pair of black velvet breeches laced, a + new Milan fustian suit laced and cut upon taffety, two cloaks, + competent linen, and necessaries, with my rapier and dagger. And + since, the blessing of God, whose heavenly providence guided me + hither, hath enriched my weak estate, in beginning with such a + fortune, as I need not envy any of my neighbours, and added no + care or burthen of my conscience thereunto. And the 23rd of + June, 1632, I have served my God, Queen Elizabeth, King James, + and King Charles, full forty-four years, and so long after as it + shall please God to enable me. + +Richard Boyle's property in Ireland increased so rapidly that he was +accused to Queen Elizabeth of receiving pay from some foreign power. +When about to visit England in order to clear himself of this charge, +the rebellion in Munster broke out; his lands were wasted, and his +income for the time destroyed. Reaching London, he returned to his old +chambers in the Middle Temple, until he entered the service of the +Earl of Essex, to whom the government of Ireland had been entrusted. +The charges against him were then resumed, and he was made a prisoner, +and kept in confinement until the Earl of Essex had gone over to +Ireland. At length he obtained a hearing before the queen, who fully +acquitted him of the charges, gave him her hand to kiss, and promised +to employ him in her own service; at the same time she dismissed Sir +Henry Wallop, who was Treasurer for Ireland, and prominent among +Boyle's accusers, from his office. + +A few days afterwards, Richard Boyle was appointed by the queen Clerk +to the Council of Munster, and having purchased a ship of Sir Walter +Raleigh, he returned to Ireland with ammunition and provisions. + +"Then, as Clerk of the Council, I attended the Lord President in all +his employments, and waited upon him at the siege of Kingsale, and was +employed by his Lordship to her Majesty, with the news of that happy +victory; in which employment I made a speedy expedition to the court; +for I left my Lord President at Shannon Castle, near Corke, on the +Monday morning, about two of the clock, and the next day, being +Tuesday, I delivered my packet, and supped with Sir Robert Cecil, +being then principal Secretary of State, at his house in the Strand; +who, after supper, held me in discourse till two of the clock in the +morning; and by seven that morning called upon me to attend him to the +court, where he presented me to her Majesty in her bed-chamber, who +remembered me, calling me by my name, and giving me her hand to kiss, +telling me that she was glad that I was the happy man to bring the +first news of that glorious victory ... and so I was dismissed with +grace and favour." + +In reading of this journey from Cork to London, it is almost necessary +to be reminded that it took place two hundred and fifty years before +the introduction of steam-boats and railways. At the close of the +rebellion, Richard Boyle purchased from Sir Walter Raleigh all his +lands in Munster; and on July 25, 1603, he married his second wife, +Catharine, the only daughter of Sir Geoffrey Fenton, principal +Secretary of State, and Privy Councillor in Ireland, "with whom I +never demanded any marriage portion, neither promise of any, it not +being in my consideration; yet her father, after my marriage, gave me +one thousand pounds in gold with her. But that gift of his daughter +unto me I must ever thankfully acknowledge as the crown of all my +blessings; for she was a most religious, virtuous, loving, and +obedient wife unto me all the days of her life." He was knighted by +the Lord Deputy of Ireland, Sir George Carew, on his wedding-day; was +sworn Privy Councillor of State of the Kingdom of Ireland in 1612; +created Lord Boyle, Baron of Youghall, September 29, 1616; Lord +Viscount of Dungarvon and Earl of Cork, October 26, 1620; one of the +Lords Justices of Ireland, with a salary of L1200 per annum, in 1629; +and Lord High Treasurer of Ireland, November 9, 1631. + +Robert Boyle, the seventh son of the Earl of Cork, was born January +25, 1627. His mother died February 16, 1630. The earl lived in +prosperity in Ireland till the breaking out of the rebellion in 1641, +and died at Youghall in September, 1643. It is said that when Cromwell +saw the vast improvements which the earl had made on his estate in +Munster, he declared that "if there had been an Earl of Cork in every +province, it would have been impossible for the Irish to have raised a +rebellion." + +At a very early age Robert was sent by his father to a country nurse, +"who, by early inuring him, by slow degrees, to a coarse but cleanly +diet, and to the usual passion of the air, gave him so vigorous a +complexion that both hardships were made easy to him by custom, and +the delights of conveniences and ease were endeared to him by their +rarity." Making the acquaintance of some children who stuttered in +their speech, he, by imitation, acquired the same habit, "so +contagious and catching are men's faults, and so dangerous is the +familiar commerce of those condemnable customs, that, being imitated +but in jest, come to be learned and acquired in earnest." Before going +to school he studied French and Latin, and showed considerable +aptitude for scholarship. He was then sent to Eton, where his master +took much notice of him, and "would sometimes give him unasked +play-days, and oft bestow upon him such balls and tops and other +implements of idleness as he had taken away from others that had +unduly used them." + +While at school, in the early morning, a part of the wall of the +bedroom, with the bed, chairs, books, and furniture of the room above, +fell on him and his brother. "His brother had his band torn about his +neck, and his coat upon his back, and his chair crushed and broken +under him; but by a lusty youth, then accidentally in the room, was +snatched from out the ruins, by which [Robert] had, in all +probability, been immediately oppressed, had not his bed been +curtained by a watchful Providence, which kept all heavy things from +falling on it; but the dust of the crumbled rubbish raised was so +thick that he might there have been stifled had not he remembered to +wrap his head in the sheet, which served him as a strainer, through +which none but the purer air could find a passage." At Eton he spent +nearly four years, "in the last of which he forgot much of that Latin +he had got, for he was so addicted to more solid parts of knowledge +that he hated the study of bare words naturally, as something that +relished too much of pedantry to consort with his disposition and +designs." On leaving Eton he joined his father at Stalbridge, in +Dorsetshire, and was sent to reside with "Mr. W. Douch, then parson of +that place," who took the supervision of his studies. Here he renewed +his acquaintance with Latin, and devoted some attention to English +verse, spending some of his idle hours in composing verses, "most of +which, the day he came of age, he sacrificed to Vulcan, with a design +to make the rest perish by the same fate." A little later he returned +to his father's house in Stalbridge, and was placed under the tutelage +of a French gentleman, who had been tutor to two of his brothers. + +In October, 1638, Robert Boyle and his brother were sent into France. +After a short stay at Lyons, they reached Geneva, where Robert +remained with his tutor for about a year and three quarters. During +his residence here an incident occurred which he regarded as the most +important event of his life, and which we therefore give in his own +words. + +"To frame a right apprehension of this, you must understand that, +though his inclinations were ever virtuous, and his life free from +scandal and inoffensive, yet had the piety he was master of already so +diverted him from aspiring unto more, that Christ, who long had lain +asleep in his conscience (as He once did in the ship), must now, as +then, be waked by a storm. For at a time which (being the very heat of +summer) promised nothing less, about the dead of night, that adds most +terror to such accidents, [he] was suddenly waked in a fright with +such loud claps of thunder (which are oftentimes very terrible in +those hot climes and seasons), that he thought the earth would owe an +ague to the air, and every clap was both preceded and attended with +flashes of lightning, so frequent and so dazzling that [he] began to +imagine them the sallies of that fire that must consume the world. The +long continuance of that dismal tempest, where the winds were so loud +as almost drowned the noise of the very thunder, and the showers so +hideous as almost quenched the lightning ere it could reach his eyes, +confirmed him in his apprehensions of the day of judgment's being at +hand. Whereupon the consideration of his unpreparedness to welcome +it, and the hideousness of being surprised by it in an unfit +condition, made him resolve and vow that, if his fears were that night +disappointed, all his further additions to his life should be more +religiously and watchfully employed. The morning came, and a serene, +cloudless sky returned, when he ratified his determinations so +solemnly, that from that day he dated his conversion, renewing, now he +was past danger, the vow he had made whilst he believed himself to be +in it; and though his fear was (and he blushed it was so) the occasion +of his resolution of amendment, yet at least he might not owe his more +deliberate consecration of himself to piety to any less noble motive +than that of its own excellence." + +After leaving Geneva, he crossed the Alps and travelled through +Northern Italy. Here he spent much time in learning Italian; "the rest +of his spare hours he spent in reading the modern history in Italian, +and the new paradoxes of the great stargazer Galileo, whose ingenious +books, perhaps because they could not be so otherwise, were confuted +by a decree from Rome; his highness the Pope, it seems, presuming, and +that justly, that the infallibility of his chair extended equally to +determine points in philosophy as in religion, and loth to have the +stability of that earth questioned in which he had established his +kingdom." + +Having visited Rome, he at length returned to France, and was detained +at Marseilles, awaiting a remittance from the earl to enable him to +continue his travels. Through some miscarriage, the money which the +earl sent did not arrive, and Robert and his brother had to depend on +the credit of the tutor to procure the means to enable them to return +home. They reached England in the summer of 1644, "where we found +things in such confusion that, although the manor of Stalbridge were, +by my father's decease, descended unto me, yet it was near four months +before I could get thither." On reaching London, Robert Boyle resided +for some time with his sister, Lady Ranelagh, and was thus prevented +from entering the Royalist Army. Later on he returned for a short time +to France; visited Cambridge in December, 1645, and then took up his +residence at Stalbridge till May, 1650, where he commenced the study +of chemistry and natural philosophy. + +It was in October, 1646, that Boyle first made mention of the +"_invisible college_," which afterwards developed into the Royal +Society. Writing to a Fellow of Magdalen College, Cambridge, in +February, 1647, he says, "The corner-stones of the _invisible_, or, as +they term themselves, the _philosophical college_, do now and then +honour me with their company." It appears that a desire to escape from +the troubles of the times had induced several persons to take refuge +in philosophical pursuits, and, meeting together to discuss the +subjects of their study, they formed the "invisible college." Boyle +says, "I will conclude their praises with the recital of their +chiefest fault, which is very incident to almost all good things, and +that is, that there is not enough of them." Dr. Wallis, one of the +first members of the society, states that Mr. Theodore Hooke, a German +of the Palatinate, then resident in London, "gave the first occasion +and first suggested those meetings and many others. These meetings we +held sometimes at Dr. Goddard's lodging, in Wood Street (or some +convenient place near), on occasion of his keeping an operator in his +house, for grinding glasses for telescopes and microscopes, and +sometimes at a convenient place in Cheapside; sometimes at Gresham +College, or some place near adjoining. Our business was (precluding +theology and State affairs) to discourse and consider of philosophical +inquiries, and such as related thereunto; as physic, anatomy, +geometry, astronomy, navigation, statics, magnetics, chemics, +mechanics, and natural experiments, with the state of these studies as +then cultivated at home and abroad. About the year 1648-49 some of us +being removed to Oxford, first Dr. Wilkins, then I, and soon after Dr. +Goddard, our company divided. Those in London continued to meet there +as before, and we with them when we had occasion to be there. And +those of us at Oxford, with Dr. Ward, since Bishop of Salisbury, Dr. +Ralph Bathurst, now President of Trinity College in Oxford, Dr. Petty, +since Sir William Petty, Dr. Willis, then an eminent physician in +Oxford, and divers others, continued such meetings in Oxford, and +brought those studies into fashion there; meeting first at Dr. +Petty's lodgings, in an apothecary's house, because of the convenience +of inspecting drugs and the like, as there was occasion; and after his +remove to Ireland (though not so constantly) at the lodgings of Dr. +Wilkins, then Warden of Wadham College; and after his removal to +Trinity College in Cambridge, at the lodgings of the Honourable Mr. +Robert Boyle, then resident for divers years in Oxford. These meetings +in London continued, and after the king's return, in 1660, were +increased with the accession of divers worthy and honourable persons, +and were afterwards incorporated by the name of the _Royal Society_, +and so continue to this day." + +Boyle was only about twenty years of age when he wrote his "Free +Discourse against Swearing;" his "Seraphic Love; or, Some Motives and +Incentives to the Love of God;" and his "Essay on Mistaken Modesty." +"Seraphic Love" was the last of a series of treatises on love, but the +only one of the series that he published, as he considered the others +too trifling to be published alone or in conjunction with it. In a +letter to Lady Ranelagh, he refers to his laboratory as "a kind of +Elysium," and there were few things which gave him so much pleasure as +his furnaces and philosophical experiments. In 1652 he visited +Ireland, returning in the following summer. In the autumn he was again +obliged to visit Ireland, and remained there till the summer of 1654, +though residence in that country was far from agreeable to him. He +styled it "a barbarous country, where chemical spirits were so +misunderstood, and chemical instruments so unprocurable, that it was +hard to have any hermetic thoughts in it." On his return he settled in +Oxford, and there his lodgings soon became the centre of the +scientific life of the university. Boyle and his friends may be +regarded as the pioneers of experimental philosophy in this country. +To Boyle the methods of Aristotle appeared little more than +discussions on words; for a long time he refused to study the +philosophy of Descartes, lest he should be turned aside from reasoning +based strictly on the results of experiment. The method pursued by +these philosophers had been fully discussed by Lord Bacon, but at best +his experimental methods, though most complete and systematic, existed +only upon paper, and it was reserved for Boyle and his friends to put +the Baconian philosophy into actual practice. + +It was during his residence at Oxford that he invented the air-pump, +which was afterwards improved for him by Hooke, and with which he +conducted most of those experiments on the "spring" and weight of the +air, which led up to the investigations that have rendered his name +inseparably connected with "the gaseous laws." The experiments of +Galileo and of Torricelli had shown that the pressure of the air was +capable of supporting a column of water about thirty-four feet in +height, or a column of mercury nearly thirty inches high. The younger +Pascal, at the request of Torricelli, had carried a barometer to the +summit of the Puy de Dome, and demonstrated that the height of the +column of mercury supported by the air diminishes as the altitude is +increased. Otto von Guericke had constructed the Magdeburg +hemispheres, and shown that, when exhausted, they could not be +separated by sixteen horses, eight pulling one way and eight the +other. He was aware that the same traction could have been produced by +eight horses if one of the hemispheres had been attached to a fixed +obstacle; but, with the instincts of a popular lecturer, he considered +that the spectacle would thus be rendered less striking, and it was +prepared for the king's entertainment. Boyle wished for an air-pump +with an aperture in the receiver sufficiently large for the +introduction of various objects, and an arrangement for exhausting it +without filling the receiver with water or otherwise interfering with +the objects placed therein. His apparatus consisted of a large glass +globe capable of containing about three gallons or thereabouts, +terminating in an open tube below, and with an aperture of about four +inches diameter at the top. Around this aperture was cemented a turned +brass ring, the inner surface being conical, and into this conical +seat was fitted a brass plate with a thick rim, but drilled with a +small hole in the centre. To this hole, which was also conical, was +fitted a brass stopper, which could be turned round when the receiver +was exhausted. By attaching a string to this stopper, which was so +long as to enter the receiver to the depth of two or three inches, and +turning the stopper in its seat, the string could be wound up, and +thus objects could be moved within the receiver. The tube at the +bottom of the receiver communicated with a stop-cock, and this with +the upper end of the pumpbarrel, which was inverted, so that this +stop-cock, which was at the top of the barrel, took the place of the +foot-valve. The piston was solid, made of wood, and surrounded with +sole leather, which was kept well greased. There being no valve in the +piston, it was necessary to place an exhaust-valve in the upper end of +the cylinder. This consisted of a small brass plug closing a conical +hole so that it could be removed at pleasure. The construction of the +cylinder was, therefore, similar to that of an ordinary force-pump, +except that the valves had to be moved by hand (as in the early forms +of the steam-engine). The piston was raised and depressed by means of +a rack and pinion. The pumps could be used either for exhausting the +receiver or for forcing air into it, according to the order in which +the "valves" were opened. If the stop-cock communicating with the +receiver were open while the piston was being drawn down, and the +brass plug removed so as to open the exhaust-valve when the piston was +being forced up, the receiver would gradually be exhausted. If the +brass plug were removed during the descent of the piston, and the +stop-cock opened during its ascent, air would be forced into the +receiver. In the latter case it was necessary to take special +precautions to prevent the brass plate at the top of the receiver +being raised from its seat. All joints were made air-tight with +"diachylon," and when, through the bursting of a glass bulb within it, +the receiver became cracked, the crack was rendered air-tight by the +same means. Other receivers of smaller capacity were also provided, on +account of the greater readiness with which they could be exhausted. + +With this apparatus Boyle carried out a long series of experiments. He +could reduce the pressure in the large receiver to somewhat less than +that corresponding to an inch of mercury, or about a foot of water. +Squeezing a bladder so as to expel nearly all the air, tying the neck, +and then introducing it into the receiver, he found, on working the +pump, that the bladder swelled so that at length it became completely +distended. In order to account for this great expansibility, Boyle +pictured the constitution of the air in the following way. He supposed +the air to consist of separate particles, each resembling a spiral +spring, which became tightly wound when exposed to great pressure, but +which expanded so as to occupy a larger circle when the pressure was +diminished. Each of these little spirals he supposed to rotate about a +diameter so as to exclude every other body from the sphere in which it +moved. Increasing the length of the diameter tenfold would increase +the volume of one of these spheres, and therefore the volume of the +gas, a thousandfold. Possibly this was only intended as a mental +illustration, exhibiting a mechanism by which very great expansion +might conceivably be produced, and scarcely pretending to be +considered a _theory_ of the constitution of the air. Boyle's first +idea seems to have been derived from a lock of wool in which the +elasticity of each fibre caused the lock to expand after it had been +compressed in the hand. In another passage he speaks of the air as +consisting of a number of bodies capable of striking against a surface +exposed to them. He demonstrated the weight of the air by placing a +delicate balance within the receiver, suspending from one arm a +bladder half filled with water, and balancing it with brass weights. +On exhausting the air, the bladder preponderated, and, by repeating +the experiment with additional weights on the other arm until a +balance was effected in the exhausted receiver, he determined the +amount of the preponderance. In another experiment he compressed air +in a bladder by tying a pack-thread round it, balanced it from one arm +of his balance in the open air; then, pricking the bladder so as to +relieve the pressure, he found that with the escape of the compressed +air the weight diminished. + +One of the most important of his experiments with the air-pump was the +following. He placed within the receiver the cistern of a mercurial +barometer, the tube of which was made to pass through the central hole +in the brass plate, from which the stopper had been removed. The space +around the tube was filled up with cement, and the receiver +exhausted. At each stroke of the pump the mercury in the barometer +tube descended, but through successively diminishing distances, until +at length it stood only an inch above the mercury in the cistern. The +experiment was then repeated with a tube four feet long and filled +with water. This constituted the nineteenth experiment referred to +later on. A great many strokes of the pump had to be made before the +water began to descend. At length it fell till the surface in the tube +stood only about a foot above that in the tank. Placing vessels of +ordinary spring-water and of distilled rain-water in the receiver, he +found that, after the exhaustion had reached a certain stage, bubbles +of gas were copiously evolved from the spring-water, but not from the +distilled water. On another occasion he caused warm water to boil by a +few strokes of the pump; and, continuing the exhaustion, the water was +made to boil at intervals until it became only lukewarm. The +experiment was repeated with several volatile liquids. He also noticed +the cloud formed in the receiver when the air was allowed rapidly to +expand; but the mechanical theory of heat had not then made sufficient +progress to enable him to account for the condensation by the loss of +heat due to the work done by the expanding air. The very minute +accuracy of his observations is conspicuous in the descriptions of +most of his experiments. That the air is the usual medium for the +conveyance of sound was shown by suspending a watch by a linen thread +within the receiver. On exhausting the air, the ticking of the watch +ceased to be heard. A pretty experiment consisted in placing a bottle +of a certain fuming liquid within the receiver; on exhausting the air, +the fumes fell over the neck of the bottle and poured over the stand +on which it was placed like a stream of water. Another experiment, the +thirty-second, is worthy of mention on account of the use to which it +was afterwards applied in the controversy respecting the cause of +suction. The receiver, having been exhausted, was removed from the +cylinder, the stop-cock being turned off, and a small brass valve, to +which a scale-pan was attached, was placed just under the aperture of +the tube below the stop-cock. On turning the latter, the stream of air +raised the valve, closing the aperture, and the atmospheric pressure +supported it until a considerable weight had been placed in the +scale-pan. Because the receiver could not be exhausted so thoroughly +as the pump-cylinder, Boyle attempted to measure the pressure of the +air by determining what weight could be supported by the piston. He +found first that a weight of twenty-eight pounds suspended directly +from the piston was sufficient to overcome friction when air was +admitted above the piston. When the access of air to the top of the +piston was prevented, more than one hundred pounds additional weight +was required to draw down the piston. The diameter of the cylinder was +about three inches. + +Boyle's style of reasoning is well illustrated by the following from +his paper on "The Spring of the Air:"-- + +"In the next place, these experiments may teach us what to judge of +the vulgar axiom received for so many ages as an undoubted truth in +the peripatetick schools, that Nature abhors and flieth a vacuum, and +that to such a degree that no human power (to go no higher) is able to +make one in the universe; wherein heaven and earth would change +places, and all its other bodies rather act contrary to their own +nature than suffer it.... It will not easily, then, be intelligibly +made out how hatred or aversation, which is a passion of the soul, can +either for a vacuum or any other object be supposed to be in water, or +such like inanimate body, which cannot be presumed to know when a +vacuum would ensue, if they did not bestir themselves to prevent it; +nor to be so generous as to act contrary to what is most conducive to +their own particular preservation for the public good of the universe. +As much, then, of intelligible and probable truth as is contained in +this metaphorical expression seems to amount but to this--that by the +wise Author of nature (who is justly said to have made all things in +number, weight, and measure) the universe, and the parts of it, are so +contrived that it is hard to make a vacuum in it, as if they +studiously conspired to prevent it. And how far this itself may be +granted deserves to be further considered. + +"For, in the next place, our experiments seem to teach that the +supposed aversation of Nature to a vacuum is but accidental, or in +consequence, partly of the weight and fluidity, or, at least, +fluxility of the bodies here below; and partly, and perhaps +principally, of the air, whose restless endeavour to expand itself +every way makes it either rush in itself or compel the interposed +bodies into all spaces where it finds no greater resistance than it +can surmount. And that in those motions which are made _ob fugam +vacui_ (as the common phrase is), bodies act without such generosity +and consideration as is wont to be ascribed to them, is apparent +enough in our thirty-second experiment, where the torrent of air, that +seemed to strive to get into the emptied receiver, did plainly prevent +its own design, by so impelling the valve as to make it shut the only +orifice the air was to get [in] at. And if afterwards either Nature or +the internal air had a design the external air should be attracted, +they seemed to prosecute it very unwisely by continuing to suck the +valve so strongly, when they found that by that suction the valve +itself could not be drawn in; whereas, by forbearing to suck, the +valve would, by its own weight, have fallen down and suffered the +excluded air to return freely, and to fill again the exhausted +vessel.... + +"And as for the care of the public good of the universe ascribed to +dead and stupid bodies, we shall only demand why, in our nineteenth +experiment, upon the exsuction of the ambient air, the water deserted +the upper half of the glass tube, and did not ascend to fill it up +till the external air was let in upon it. Whereas, by its easy and +sudden rejoining that upper part of the tube, it appeared both that +there was then much space devoid of air, and that the water might, +with small or no resistance, have ascended into it, if it could have +done so without the impulsion of the readmitted air; which, it seems, +was necessary to mind the water of its formerly neglected duty to the +universe." + +Boyle then goes on to explain the phenomena correctly by the pressure +of the air. Elsewhere he accounts for the diminished pressure on the +top of a mountain by the diminished weight of the superincumbent +column of air. + +The treatise on "The Spring of the Air" met with much opposition, and +Boyle considered it necessary to defend his doctrine against the +objections of Franciscus Linus and Hobbes. In this defence he +described the experiment in connection with which he is most generally +remembered. Linus had admitted that the air might possess a certain +small amount of elasticity, but maintained that the force with which +mercury rose in a barometer tube was due mainly to a totally different +action, as though a string were pulling upon it from above. This was +his funicular hypothesis. Boyle undertook to show that the pressure of +the air might be made to support a much higher column of mercury than +that of the barometer. To this end he took a glass tube several feet +in length, and bent so as to form two vertical legs connected below. +The shorter leg was little more than a foot long, and hermetically +closed at the top. The longer leg was nearly eight feet in length, and +open at the top. The tube was suspended by strings upon the staircase, +the bend at the bottom pressing lightly against the bottom of a box +placed to receive the mercury employed in case of accident. Each leg +of the tube was provided with a paper scale. Mercury was poured in at +the open end, the tube being tilted so as to allow some of the air to +escape from the shorter limb until the mercury stood at the same level +in both legs when the tube was vertical. The length of the closed tube +occupied by the air was then just twelve inches. The height of the +barometer was about 29-1/8 inches. Mercury was gently poured into the +open limb by one operator, while another watched its height in the +closed limb. The results of the experiments are given in the table on +the opposite page. + +In this table the third column gives the result of adding to the +second column the height of the barometer, which expresses in inches +of mercury the pressure of the air on the free surface of the mercury +in the longer limb. The fourth column gives the total pressure, in +inches of mercury, on the hypothesis that the pressure of the air +varies inversely as the volume. The agreement between the third and +fourth columns is very close, considering the roughness of the +experiment and that no trouble appears to have been taken to +_calibrate_ the shorter limb of the tube, and justified Boyle in +concluding that the hypothesis referred to expresses the relation +between the volume and pressure of a given mass of air. + + +-----------+---------------+----------------+--------------+ + |Length of |Height of |Total pressure |Total pressure| + |closed tube|mercury in open|on air in inches|according to | + |occupied |tube above that|of mercury. |Boyle's law. | + |by air. |in closed tube.| | | + +-----------+---------------+----------------+--------------+ + | 12 | 0 | 29-2/16 | 29-2/16 | + | 11-1/2 | 1-7/16 | 30-9/16 | 30-6/16 | + | 11 | 2-13/16 | 31-15/16 | 31-12/16 | + | 10-1/2 | 4-6/16 | 33-8/16 | 33-1/7 | + | 10 | 6-3/16 | 35-5/16 | 35 | + | 9-1/2 | 7-14/16 | 37 | 36-15/19 | + | 9 | 10-1/16 | 39-3/16 | 38-7/8 | + | 8-1/2 | 12-8/16 | 41-10/16 | 41-2/17 | + | 8 | 15-1/16 | 44-3/16 | 43-11/16 | + | 7-1/2 | 17-15/16 | 47-1/16 | 46-3/5 | + | 7 | 21-3/16 | 50-5/16 | 50 | + | 6-1/2 | 25-3/16 | 54-5/16 | 53-10/13 | + | 6 | 29-11/16 | 58-13/16 | 58-2/8 | + | 5-3/4 | 32-3/16 | 61-5/16 | 60-13/23 | + | 5-1/2 | 34-15/16 | 64-1/16 | 63-6/11 | + | 5-1/4 | 37-15/16 | 67-1/16 | 66-4/7 | + | 5 | 41-9/16 | 70-11/16 | 70 | + | 4-3/4 | 45 | 74-2/16 | 73-11/19 | + | 4-1/2 | 48-12/16 | 77-14/16 | 77-2/3 | + | 4-1/4 | 53-11/16 | 82-13/16 | 82-4/17 | + | 4 | 58-2/16 | 87-14/16 | 87-1/8 | + | 3-3/4 | 63-15/16 | 93-1/16 | 93-1/5 | + | 3-1/2 | 71-5/16 | 100-7/16 | 99-6/7 | + | 3-1/4 | 78-11/16 | 107-13/16 | 107-7/13 | + | 3 | 88-7/16 | 117-9/16 | 116-4/8 | + +-----------+---------------+----------------+--------------+ + +To extend the investigation so as to include expansion below +atmospheric pressure, a different apparatus was employed. It consisted +of a glass tube about six feet in length, closed at the lower end and +filled with mercury. Into this bath of mercury was plunged a length of +quill tube, and the upper end was sealed with wax. When the wax and +air in the tube had cooled, a hot pin was passed through the wax, +making a small orifice by which the amount of air in the tube was +adjusted so as to occupy exactly one inch of its length as measured by +a paper scale attached thereto, after again sealing the wax. The quill +tube was then raised, and the height of the surface of the mercury in +the tube above that in the bath noticed, together with the length of +the tube occupied by the air. The difference between the height of the +barometer and the height of the mercury in the tube above that in the +bath gave the pressure on the imprisoned air in inches of mercury. The +result showed that the volume varied very nearly in the inverse ratio +of the pressure. A certain amount of air, however, clung to the sides +of the quill tube when immersed in the mercury, and no care was taken +to remove it by boiling the mercury or otherwise; in consequence of +this, as the mercury descended, this air escaped and joined the rest +of the air in the tube. This made the pressure rather greater than it +should have been towards the end of the experiment, and when the tube +was again pressed down into the bath it was found that, when the +surfaces of the mercury within and without the tube were at the same +level, the air occupied nearly 1-1/8 inch instead of one inch of the +tube. These experiments first established the truth of the great law +known as "Boyle's law," which states that _the volume of a given mass +of a perfect gas varies inversely as the pressure to which it is +exposed_. + +Another experiment, to show that the pressure of the air was the cause +of suction, Boyle succeeded in carrying out at a later date. Two discs +of marble were carefully polished, so that when a little spirit of +turpentine was placed between them the lower disc, with a pound weight +suspended from it, was supported by the upper one. The apparatus was +introduced into the air-pump, and a considerable amount of shaking +proved insufficient to separate the discs. After sixteen strokes of +the pump, on opening the communication between the receiver and +cylinder, when no mechanical vibration occurred, the discs separated. + +Upon the Restoration in 1660, the Earl of Clarendon, who was Lord +Chancellor of England, endeavoured to persuade Boyle to enter holy +orders, urging the interest of the Church as the chief motive for the +proceeding. This made some impression upon Boyle, but he declined for +two reasons--first, because he thought that he would have a greater +influence for good if he had no share in the patrimony of the Church; +and next, because he had never felt "an inward motion to it by the +Holy Ghost." + +In 1649 an association was incorporated by Parliament, to be called +"the President and Society for the Propagation of the Gospel in New +England," whose object should be "to receive and dispose of moneys in +such manner as shall best and principally conduce to the preaching and +propagating the gospel among the natives, and for the maintenance of +schools and nurseries of learning for the education of the children of +the natives; for which purpose a general collection was appointed to +be made in and through all the counties, cities, towns, and parishes +of England and Wales, for a charitable contribution, to be as the +foundation of so pious and great an undertaking." The society was +revived by special charter in 1661, and Boyle was appointed president, +an office he continued to hold until shortly before his death. The +society afterwards enlarged its sphere of operations, and became the +Society for the Propagation of the Gospel in Foreign Parts. + +In the same year (1661) Boyle published "Some Considerations on the +Usefulness of Experimental Natural Philosophy," etc., and in 1663 an +extremely interesting paper on "Experiments and Considerations +touching Colours." In the course of this paper he describes some very +beautiful experiments with a tincture of _Lignum nephriticum_, wherein +the dichroism of the extract is made apparent. Boyle found that by +transmitted light it appeared of a bright golden colour, but when +viewed from the side from which it was illuminated the light emitted +was sky blue, and in some cases bright green. By arranging experiments +so that some parts of the liquid were seen by the transmitted light +and some by the scattered light, very beautiful effects were produced. +Boyle endeavoured to learn something of the nature of colours by +projecting spectra on differently coloured papers, and observing the +appearance of the papers when illuminated by the several spectral +rays. He also passed sunlight, concentrated by a lens, through plates +of differently coloured glass superposed, allowing the light to fall +on a white paper screen, and observing the tint of the light which +passed through each combination. But the most interesting of these +experiments was the actual mixture of light of different colours by +forming two spectra, one by means of a fixed prism, the other by a +prism held in the hand, and superposing the latter on the former so +that different colours were made to coincide. This experiment was +repeated in a modified form, nearly two hundred years later, by +Helmholtz, who found that the mixture of blue and yellow lights +produced pink. Unfortunately, Boyle's spectra were far from pure, for, +the source of light being of considerable dimensions, the different +colours overlapped one another, as in Newton's experiments, and in +consequence some of his conclusions were inaccurate. Thus blue paper +in the yellow part of the spectrum appeared to Boyle green instead of +black, but this was due to the admixture of green light with the +yellow. He concluded that bodies appear black because they damp the +light so as to reflect very little to the eye, but that the surfaces +of white bodies consist of innumerable little facets which reflect the +light in all directions. In the same year he published some +"Observations on a Diamond, which shines in the Dark;" and an +extensive treatise on "Some Considerations touching the Style of the +Holy Scriptures." Next year appeared several papers from his pen, the +most important being "Occasional Reflections upon Several Subjects," +the wide scope of which may be gathered from the title. His "New +Experiments and Observations touching Cold" were printed in 1665. In +this paper he discussed the cause of the force exerted by water in +freezing, methods of measuring degrees of cold, the action of +freezing-mixtures, and many other questions. He contended that cold +was probably only privative, and not a positive existence. + +Lord Bacon had asserted that the "essential self" of heat was probably +motion and nothing more, and had adduced several experiments and +observations in support of this opinion. In his paper on the +mechanical origin of heat and cold, Boyle maintained that heat was +motion, but motion of the very small particles of bodies, very +intense, and taking place in all directions; and that heat could be +produced by any means whatever by which the particles of bodies could +be agitated. On one occasion he caused two pieces of brass, one convex +and the other concave, to be pressed against each other by a spring, +and then rubbed together in a vacuum by a rotary motion communicated +by a shaft which passed air-tight through the hole in the cover of the +receiver, a little emery being inserted between them. In the second +experiment the brasses became so hot that he "could not endure to hold +[his] hand on either of them." This experiment was intended, like the +rubbing of the blocks of ice in vacuo by Davy, to meet the objection +that the heat developed by friction was due to the action of the air. +The following extract from a paper intended to show that the sense of +touch cannot be relied upon for the estimation of temperature, shows +that Boyle possessed a very clear insight into the question:--"The +account upon which we judge a body to be cold seems to be that we feel +its particles less vehemently agitated than those of our fingers or +other parts of the organ of touching; and, consequently, if the temper +of that organ be changed, the object will appear more or less cold to +us, though itself continue of one and the same temperature." To +determine the expansion of water in freezing, he filled the bulb and +part of the stem of a "bulb tube," or, as it was then generally +called, "a philosophical egg," with water, and applying a +freezing-mixture, at first to the bottom of the bulb, he succeeded in +freezing the water without injury to the glass, and found that 82 +volumes of water expanded to 91-1/8 volumes of ice--an expansion of +about 11-1/8 per cent. Probably air-bubbles caused the ice to appear +to have a greater volume than it really possessed, the true expansion +being about nine per cent. of the volume of the water at 4 deg.C. The +expansion of water in freezing he employed in order to compress air to +a greater extent than he had been able otherwise to compress it. +Having nearly filled a tube with water, but left a little air above, +and then having sealed the top of the tube, he froze the water from +the bottom upwards, so that in expanding it compressed the air to +one-tenth of its former volume. + +Magnetism and electricity came in for some share of Boyle's attention. +He carried out a number of experiments on magnetic induction, and +found that lodestones, as well as pieces of iron, when heated and +allowed to cool, became magnetized by the induction of the earth. His +later experiments with exhausted receivers were not made with his +first pump, but with a two-barrelled pump, in which the pistons were +connected by a cord passing over a large fixed pulley, so that, when +the receiver was nearly exhausted, the pressure of the air on the +descending piston during the greater part of the stroke nearly +balanced that on the ascending piston. In this respect the pump +differed only from Hawksbee's in having the pulley and cord instead of +the pinion and two racks. It also resembled Hawksbee's pump in having +self-closing valves in the pistons and at the bottom of the cylinders, +which, in this pump, had their open ends at the top. The pistons were +alternately raised and lowered by the feet of the operator, which were +placed in stirrups, of which one was fixed on each piston. The lower +portions of the barrels were filled with water, through which the air +bubbled, and this, occupying the clearance, enabled a much higher +degree of exhaustion to be produced than could be obtained without its +employment. + +In 1665 Boyle was nominated Provost of Eton, but declined to accept +the appointment. His "Hydrostatical Paradoxes," published about this +time, contain all the ordinary theorems respecting the pressure of +fluids under the action of gravity demonstrated experimentally. + +In 1677 Boyle printed, at his own expense, five hundred copies of the +four Gospels and the Acts of the Apostles in the Malayan tongue. This +was but one of his many contributions towards similar objects. + +On November 30, 1680, the Royal Society chose Boyle for President. He, +however, declined to accept the appointment, because he had +conscientious objections to taking the oath required of the President +by the charter of the Society. + +It appears that very many of Boyle's manuscripts, which were written +in bound books, were taken away, and others mutilated by "corrosive +liquors." In May, 1688, he made this known to his friends, but, though +these losses put him on his guard, he complained afterwards that all +his care and circumspection had not prevented the loss of "six +centuries of matters of fact in one parcel," besides many other +smaller papers. His works, however, which have been published are so +numerous that it would take several pages for the bare enumeration of +their titles, many of them being devoted to medical subjects. The +edition published in London in 1743 comprises nearly three thousand +pages of folio. Boyle always suffered from weak eyes, and in +consequence he declined to revise his proofs. In the advertisement to +the original edition of his works the publisher mentioned this, and at +the same time pleaded his own business engagements as an excuse for +not revising the proofs himself! It was partly on account of the +injury to his manuscripts, and partly through failing health, that in +1689 he set apart two days in the week, during which he declined to +receive visitors, that he might devote himself to his work, and +especially to the reparation of the injured writings. About this time +he succeeded in procuring the repeal of an Act passed in the fifth +year of Henry IV. to the effect "that none from thenceforth should use +to multiply gold or silver, or use the craft of multiplication; and if +any the same do, they should incur the pain of felony." By this repeal +it was made legal to extract gold and silver from ores, or from their +mixtures with other metals, in this country provided that the gold and +silver so procured should be put to no other use than "the increase of +moneys." It is curious that Boyle seems always to have believed in the +possibility of transmuting other metals into gold. + +His sister, Lady Ranelagh, died on December 23, 1691, and Boyle +survived her but a few days, for he died on December 30, and his body +was interred near his sister's grave in the chancel of St. +Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works, +writes, "The men of wit and learning have, in all ages, busied +themselves in explaining nature by words; but it is Mr. Boyle alone +who has wholly laid himself out in showing philosophy in action. The +single point he perpetually keeps in view is to render his reader, not +a talkative or a speculative, but an actual and practical philosopher. +Himself sets the example; he made all the experiments he possibly +could upon natural bodies, and communicated them with all desirable +candour and fidelity." The second part of his treatise on "The +Christian Virtuoso," Boyle concluded with a number of aphorisms, of +which the following well represent his views respecting science:-- + +"I think it becomes Christian philosophers rather to try whether they +can investigate the final causes of things than, without trial, to +take it for granted that they are undiscoverable." + +"The book of Nature is a fine and large piece of tapestry rolled up, +which we are not able to see all at once, but must be content to wait +for the discovery of its beauty and symmetry, little by little, as it +gradually comes to be more unfolded or displayed." + + + + +BENJAMIN FRANKLIN. + + +Among those whose contributions to physics have immortalized their +names in the annals of science, there is none that holds a more +prominent position in the history of the world than Benjamin Franklin. +At one time a journeyman printer, living in obscure lodgings in +London, he became, during the American War of Independence, one of the +most conspicuous figures in Europe, and among Americans his reputation +was probably second to none, General Washington not excepted. + +Professor Laboulaye says of Franklin: "No one ever started from a +lower point than the poor apprentice of Boston. No one ever raised +himself higher by his own unaided forces than the inventor of the +lightning-rod. No one has rendered greater service to his country than +the diplomatist who signed the treaty of 1783, and assured the +independence of the United States. Better than the biographies of +Plutarch, this life, so long and so well filled, is a source of +perpetual instruction to all men. Every one can there find counsel and +example." + +A great part of the history of his life was written by Franklin +himself, at first for the edification of the members of his own +family, and afterwards at the pressing request of some of his friends +in London and Paris. His autobiography does not, however, comprise +much more than the first fifty years of his life. The first part was +written while he was the guest of the Bishop of St. Asaph, at Twyford; +the second portion at Passy, in the house of M. de Chaumont; and the +last part in Philadelphia, when he was retiring from public life at +the age of eighty-two. The former part of this autobiography was +translated into French, and published in Paris, in 1793, though it is +not known how the manuscript came into the publisher's hands. The +French version was translated into English, and published in England +and America, together with such other of Franklin's works as could be +collected, before the latter part was given to the world by Franklin's +grandson, to whom he had bequeathed his papers, and who first +published them in America in 1817. + +For a period of three hundred years at least Franklin's family lived +on a small freehold of about thirty acres, in the village of Ecton, in +Northamptonshire, the eldest son, who inherited the property, being +always brought up to the trade of a smith. Franklin himself "was the +youngest son of the youngest son for five generations back." His +grandfather lived at Ecton till he was too old to follow his business, +when he went to live with his second son, John, who was a dyer at +Banbury. To this business Franklin's father, Josiah, was apprenticed. +The eldest son, Thomas, was brought up a smith, but afterwards became +a solicitor; the other son, Benjamin, was a silk-dyer, and followed +Josiah to America. He was fond of writing poetry and sermons. The +latter he wrote in a shorthand of his own inventing, which he taught +to his nephew and namesake, in order that he might utilize the sermons +if, as was proposed, he became a Presbyterian minister. Franklin's +father, Josiah, took his wife and three children to New England, in +1682, where he practised the trade of a tallow-chandler and +soap-boiler. Franklin was born in Boston on January 6 (O.S.), 1706, +and was the youngest of seventeen children, of whom thirteen grew up +and married. + +Benjamin being the youngest of ten sons, his father intended him for +the service of the Church, and sent him to the grammar school when +eight years of age, where he continued only a year, although he made +very rapid progress in the school; for his father concluded that he +could not afford the expense of a college education, and at the end of +the year removed him to a private commercial school. At the age of ten +young Benjamin was taken home to assist in cutting the wicks of +candles, and otherwise to make himself useful in his father's +business. His enterprising character as a boy is shown by the +following story, which is in his own words:-- + + There was a salt marsh that bounded part of the mill-pond, on + the edge of which, at high-water, we used to stand to fish for + minnows. By much trampling we had made it a mere quagmire. My + proposal was to build a wharf there fit for us to stand upon, + and I showed my comrades a large heap of stones, which were + intended for a new house near the marsh, and which would very + well suit our purpose. Accordingly, in the evening, when the + workmen were gone, I assembled a number of my play-fellows, and + working with them diligently, like so many emmets, sometimes two + or three to a stone, we brought them all away and built our + little wharf. The next morning the workmen were surprised at + missing the stones, which were found in our wharf. Inquiry was + made after the removers; we were discovered and complained of; + several of us were corrected by our fathers; and, though I + pleaded the usefulness of the work, mine convinced me that + nothing was useful which was not honest. + +Until twelve years of age Benjamin continued in his father's business, +but as he manifested a great dislike for it, and his parents feared +that he might one day run away to sea, they set about finding some +trade which would be more congenial to his tastes. With this view his +father took him to see various artificers at their work, that he +might observe the tastes of the boy. This experience was very +valuable to him, as it taught him to do many little jobs for himself +when workmen could not readily be procured. During this time Benjamin +spent most of his pocket-money in purchasing books, some of which he +sold when he had read them, in order to buy others. He read through +most of the books in his father's very limited library. These mainly +consisted of works on theological controversy, which Franklin +afterwards considered to have been not very profitable to him. + +"There was another bookish lad in the town, John Collins by name, with +whom I was intimately acquainted. We sometimes disputed, and very fond +we were of argument, and very desirous of confuting one another, which +disputatious turn, by the way, is apt to become a very bad habit, +making people often very disagreeable in company by the contradiction +that is necessary to bring it into practice; and thence, besides +souring and spoiling the conversation, is productive of disgusts and +perhaps enmities when you may have occasion for friendship. I had +caught it by reading my father's books of dispute about religion. +Persons of good sense, I have since observed, seldom fall into it, +except lawyers, university men, and men of all sorts that have been +bred at Edinburgh." + +At length Franklin's fondness for books caused his father to decide to +make him a printer. His brother James had already entered that +business, and had set up in Boston with a new press and types which +he had brought from England. He signed his indentures when only twelve +years old, thereby apprenticing himself to his brother until he should +attain the age of twenty-one. The acquaintance which he formed with +booksellers through the printing business enabled him to borrow a +better class of books than he had been accustomed to, and he +frequently sat up the greater part of the night to read a book which +he had to return in the morning. + +While working with his brother, the young apprentice wrote two +ballads, which he printed and sold in the streets of Boston. His +father, however, ridiculed the performance; so he "escaped being a +poet." He adopted at this time a somewhat original method to improve +his prose writing. Meeting with an odd volume of the _Spectator_, he +purchased it and read it "over and over," and wished to imitate the +style. "Making short notes of the sentiment in each sentence," he laid +them by, and afterwards tried to write out the papers without looking +at the original. Then on comparison he discovered his faults and +corrected them. Finding his vocabulary deficient, he turned some of +the tales into verse, then retranslated them into prose, believing +that the attempt to make verses would necessitate a search for several +words of the same meaning. "I also sometimes jumbled my collection of +hints into confusion, and after some weeks endeavoured to reduce them +into the best order, before I began to form the full sentence and +complete the paper. This was to teach me method in the arrangement of +my thoughts." + +Meeting with a book on vegetarianism, Franklin determined to give the +system a trial. This led to some inconvenience in his brother's +house-keeping, so Franklin proposed to board himself if his brother +would give him half the sum he paid for his board, and out of this he +was able to save a considerable amount for the purpose of buying +books. Moreover, the time required for meals was so short that the +dinner hour afforded considerable leisure for reading. It was on his +journey from Boston to Philadelphia that he first violated vegetarian +principles; for, a large cod having been caught by the sailors, some +small fishes were found in its stomach, whereupon Franklin argued that +if fishes ate one another, there could be no reason against eating +them, so he dined on cod during the rest of the journey. + +After reading Xenophon's "Memorabilia," Franklin took up strongly with +the Socratic method of discussion, and became so "artful and expert in +drawing people, even of superior knowledge, into concessions, the +consequence of which they did not foresee," that some time afterwards +one of his employers, before answering the most simple question, would +frequently ask what he intended to infer from the answer. This +practice he gradually gave up, retaining only the habit of expressing +his opinions with "modest diffidence." + +In 1720 or 1721 James Franklin began to print a newspaper, the _New +England Courant_. To this paper, which he helped to compose and print, +Benjamin became an anonymous contributor. The members of the staff +spoke highly of his contributions, but when the authorship became +known, James appears to have conceived a jealousy of his younger +brother, which ultimately led to their separation. An article in the +paper having offended the Assembly, James was imprisoned for a month +and forbidden to print the paper. He then freed Benjamin from his +indentures, in order that the paper might be published in his name. At +length, some disagreement arising, Benjamin took advantage of the +cancelling of his indentures to quit his brother's service. As he +could get no employment in Boston, he obtained a passage to New York, +whence he was recommended to go to Philadelphia, which he reached +after a very troublesome journey. His whole stock of cash then +consisted of a Dutch dollar and about a shilling's worth of coppers. +The coppers he gave to the boatmen with whom he came across from +Burlington. His first appearance in Philadelphia, about eight o'clock +on a Sunday morning, was certainly striking. A youth between seventeen +and eighteen years of age, dressed in his working clothes, which were +dirty through his journey, with his pockets stuffed out with stockings +and shirts, his aspect was not calculated to command respect. + +"Then I walked up the street, gazing about till near the market-house +I met a boy with bread. I had made many a meal on bread, and, +inquiring where he got it, I went immediately to the baker's he +directed me to, in Second Street, and ask'd for bisket, intending such +as we had in Boston; but they, it seems, were not made in +Philadelphia. Then I asked for a threepenny loaf, and was told they +had none such. So, not considering or knowing the difference of money, +and the greater cheapness, nor the name of his bread, I bad him give +me three-penny-worth of any sort. He gave me, accordingly, three great +puffy rolls. I was surpriz'd at the quantity, but took it, and having +no room in my pockets, walk'd off with a roll under each arm, and +eating the other. Thus I went up Market Street as far as Fourth +Street, passing by the door of Mr. Read, my future wife's father; when +she, standing at the door, saw me, and thought I made, as I certainly +did, a most awkward, ridiculous appearance. Then I turned and went +down Chestnut Street and part of Walnut Street, eating my roll all the +way, and, coming round, found myself again at Market Street Wharf, +near the boat I came in, to which I went for a draught of the river +water; and, being filled out with one of my rolls, gave the other two +to a woman and her child that came down the river in the boat with us, +and were waiting to go further." + +In Philadelphia Franklin obtained an introduction, through a gentleman +he had met at New York, to a printer, named Keimer, who had just set +up business with an old press which he appeared not to know how to +use, and one pair of cases of English type. Here Franklin obtained +employment when the business on hand would permit, and he put the +press in order and worked it. Keimer obtained lodgings for him at the +house of Mr. Read, and, by industry and economical living, Franklin +found himself in easy circumstances. Sir William Keith was then +Governor of Pennsylvania, and hearing of Franklin, he called upon him +at Keimer's printing-office, invited him to take wine at a +neighbouring tavern, and promised to obtain for him the Government +printing if he would set up for himself. It was then arranged that +Franklin should return to Boston by the first ship, in order to see +what help his father would give towards setting him up in business. In +the mean while he was frequently invited to dine at the governor's +house. Notwithstanding Sir William Keith's recommendation, Josiah +Franklin thought his son too young to take the responsibility of a +business, and would only promise to assist him if, when he was +twenty-one, he had himself saved sufficient to purchase most of the +requisite plant. On his return to Philadelphia, he delivered his +father's letter to Sir William Keith, whereon the governor, stating +that he was determined to have a good printer there, promised to find +the means of equipping the printing-office himself, and suggested the +desirability of Franklin's making a journey to England in order to +purchase the plant. He promised letters of introduction to various +persons in England, as well as a letter of credit to furnish the +money for the purchase of the printing-plant. These letters Franklin +was to call for, but there was always some excuse for their not being +ready. At last they were to be sent on board the ship, and Franklin, +having gone on board, awaited the letters. When the governor's +despatches came, they were all put into a bag together, and the +captain promised to let Franklin have his letters before landing. On +opening the bag off Plymouth, there were no letters of the kind +promised, and Franklin was left without introductions and almost +without money, to make his own way in the world. In London he learned +that Governor Keith was well known as a man in whom no dependence +could be placed, and as to his giving a letter of credit, "he had no +credit to give." + +A friend of Franklin's, named Ralph, accompanied him from America, and +the two took lodgings together in Little Britain at three shillings +and sixpence per week. Franklin immediately obtained employment at +Palmer's printing-office, in Bartholomew Close; but Ralph, who knew no +trade, but aimed at literature, was unable to get any work. He could +not obtain employment, even among the law stationers as a copying +clerk, so for some time the wages which Franklin earned had to support +the two. At Palmer's Franklin was employed in composing Wollaston's +"Religion of Nature." On this he wrote a short critique, which he +printed. it was entitled "A Dissertation on Liberty and Necessity, +Pleasure and Pain." The publication of this he afterwards regretted, +but it obtained for him introductions to some literary persons in +London. Subsequently he left Palmer's and obtained work at Watts's +printing-office, where he remained during the rest of his stay in +London. The beer-drinking capabilities of some of his fellow-workmen +excited his astonishment. He says:-- + + We had an alehouse boy who attended always in the house to + supply the workmen. My companion at the press drank every day a + pint before breakfast, a pint at breakfast with his bread and + cheese, a pint between breakfast and dinner, a pint at dinner, a + pint in the afternoon about six o'clock, and another when he had + done his day's work. I thought it a detestable custom, but it + was necessary, he suppos'd, to drink _strong_ beer, that he + might be _strong_ to labour. I endeavoured to convince him that + the bodily strength afforded by beer could only be in proportion + to the grain or flour of the barley dissolved in the water of + which it was made; that there was more flour in a pennyworth of + bread; and therefore, if he would eat that with a pint of water, + it would give him more strength than a quart of beer. He drank + on, however, and had four or five shillings to pay out of his + wages every Saturday night for that muddling liquor; an expense + I was free from. And thus these poor devils keep themselves + always under. + +Afterwards Franklin succeeded in persuading several of the compositors +to give up "their muddling breakfast of beer and bread and cheese," +for a porringer of hot-water gruel, with pepper, breadcrumbs, and +butter, which they obtained from a neighbouring house at a cost of +three halfpence. + +Among Franklin's fellow-passengers from Philadelphia to England was an +American merchant, a Mr. Denham, who had formerly been in business in +Bristol, but failed and compounded with his creditors. He then went to +America, where he soon acquired a fortune, and returned in Franklin's +ship. He invited all his old creditors to dine with him. At the dinner +each guest found under his plate a cheque for the balance which had +been due to him, with interest to date. This gentleman always remained +a firm friend to Franklin, who, during his stay in London, sought his +advice when any important questions arose. When Mr. Denham returned to +Philadelphia with a quantity of merchandise, he offered Franklin an +appointment as clerk, which was afterwards to develop into a +commission agency. The offer was accepted, and, after a voyage of +nearly three months, Franklin reached Philadelphia on October 11, +1726. Here he found Governor Keith had been superseded by Major +Gordon, and, what was of more importance to him, that Miss Read, to +whom he had become engaged before leaving for England, and to whom he +had written only once during his absence, had married. Shortly after +starting in business, Mr. Denham died, and thus left Franklin to +commence life again for himself. Keimer had by this time obtained a +fairly extensive establishment, and employed a number of hands, but +none of them were of much value; and he made overtures to Franklin to +take the management of his printing-office, apparently with the +intention of getting his men taught their business, so that he might +afterwards be able to dispense with the manager. Franklin set the +printing-house in order, started type-founding, made the ink, and, +when necessary, executed engravings. As the other hands improved under +his superintendence, Keimer began to treat his manager less civilly, +and apparently desired to curtail his stipend. At length, through an +outbreak of temper on the part of Keimer, Franklin left, but was +afterwards induced to return in order to prepare copper-plates and a +press for printing paper money for New Jersey. + +While working for Keimer, Franklin formed a club, which was destined +to exert considerable influence on American politics. The club met on +Friday evenings, and was called the Junto. It was essentially a +debating society, the subject for each evening's discussion being +proposed at the preceding meeting. One of the rules was that the +existence of the club should remain a secret, and that its members +should be limited to twelve. Afterwards other similar clubs were +formed by its members; but the existence of the Junto was kept a +secret from them. The club lasted for about forty years, and became +the nucleus of the American Philosophical Society, of which Franklin +was the first president. This, and the fact that many of the great +questions that arose previously to the Declaration of Independence +were discussed in the Junto in the first instance, give to the club a +special importance. The following are specimens of subjects discussed +by the club:-- + +"Is sound an entity or body?" + +"How may the phenomena of vapours be explained?" + +"Is self-interest the rudder that steers mankind, the universal +monarch to whom all are tributaries?" + +"Which is the best form of government? and what was that form which +first prevailed among mankind?" + +"Can any one particular form of government suit all mankind?" + +"What is the reason that the tides rise higher in the Bay of Fundy +than the Bay of Delaware?" + +"Is the emission of paper money safe?" + +"What is the reason that men of the greatest knowledge are not the +most happy?" + +"How may the possessions of the Lakes be improved to our advantage?" + +"Why are tumultuous, uneasy sensations united with our desires?" + +"Whether it ought to be the aim of philosophy to eradicate the +passions." + +"How may smoky chimneys be best cured?" + +"Why does the flame of a candle tend upwards in a spire?" + +"Which is least criminal--a bad action joined with a good intention, +or a good action with a bad intention?" + +"Is it consistent with the principles of liberty in a free government +to punish a man as a libeller when he speaks the truth?" + +On leaving Keimer's, Franklin went into partnership with one of his +fellow-workmen, Hugh Meredith, whose father found the necessary +capital, and a printing-office was started which soon excelled its two +rivals in Philadelphia. Franklin's industry attracted the attention of +the townsfolk, and inspired the merchants with confidence in the +prospects of the new concern. Keimer started a newspaper, which he had +not the ability to carry on; Franklin purchased it from him for a +trifle, remodelled it, and continued it in a very spirited manner +under the title of the _Pennsylvania Gazette_. His political articles +soon attracted the attention of the principal men of the state; the +number of subscribers increased rapidly, and the paper became a source +of considerable profit. Soon after, the printing for the House of +Representatives came into the hands of the firm. Meredith never took +to the business, and was seldom sober, and at length was bought out by +his partner, on July 14, 1730. The discussion in the Junto on paper +currency induced Franklin to publish a paper entitled "The Nature and +Necessity of a Paper Currency." This was a prominent subject before +the House, but the introduction of paper money was opposed by the +capitalists. They were unable, however, to answer Franklin's +arguments; the point was carried in the House, and Franklin was +employed to print the money. The amount of paper money in Pennsylvania +in 1739 amounted to L80,000; during the war it rose to more than +L350,000. + +"In order to secure my credit and character as a tradesman, I took +care not only to be in _reality_ industrious and frugal, but to avoid +all appearances to the contrary. I drest plainly; I was seen at no +places of idle diversion. I never went out a-fishing or shooting; a +book, indeed, sometimes debauch'd me from my work, but that was +seldom, snug, and gave no scandal; and, to show that I was not above +my business, I sometimes brought home the paper I purchas'd at the +stores thro' the streets on a wheelbarrow. Thus being esteem'd an +industrious, thriving young man, and paying duly for what I bought, +the merchants who imported stationery solicited my custom; others +proposed supplying me with books, and I went on swimmingly. In the +mean time, Keimer's credit and business declining daily, he was at +last forc'd to sell his printing-house to satisfy his creditors." + +On September 1, 1730, Franklin married his former _fiancee_, whose +previous husband had left her and was reported to have died in the +West Indies. The marriage was a very happy one, and continued over +forty years, Mrs. Franklin living until the end of 1774. Industry and +frugality reigned in the household of the young printer. Mrs. Franklin +not only managed the house, but assisted in the business, folding and +stitching pamphlets, and in other ways making herself useful. The +first part of Franklin's autobiography concludes with an account of +the foundation of the first subscription library. By the co-operation +of the members of the Junto, fifty subscribers were obtained, who each +paid in the first instance forty shillings, and afterwards ten +shillings per annum. "We afterwards obtained a charter, the company +being increased to one hundred. This was the mother of all the North +American subscription libraries, now so numerous. It is become a great +thing itself, and continually increasing. These libraries have +improved the general conversation of the Americans, made the common +tradesmen and farmers as intelligent as most gentlemen from other +countries, and perhaps have contributed in some degree to the stand so +generally made throughout the colonies in defence of their +privileges." + +Ten years ago this library contained between seventy and eighty +thousand volumes. + +Franklin's success in business was attributed by him largely to his +early training. "My circumstances, however, grew daily easier. My +original habits of frugality continuing, and my father having, among +his instructions to me when a boy, frequently repeated a proverb of +Solomon, 'Seest thou a man diligent in his business? he shall stand +before kings; he shall not stand before mean men,' I from thence +considered industry as a means of obtaining wealth and distinction, +which encourag'd me, tho' I did not think that I should ever +literally _stand before kings_, which, however, has since happened; +for I have stood before _five_, and even had the honour of sitting +down with one, the King of Denmark, to dinner." + +After his marriage, Franklin conceived the idea of obtaining moral +perfection. He was not altogether satisfied with the result, but +thought his method worthy of imitation. Assuming that he possessed +complete knowledge of what was right or wrong, he saw no reason why he +should not always act in accordance therewith. His principle was to +devote his attention to one virtue only at first for a week, at the +end of which time he expected the practice of that virtue to have +become a habit. He then added another virtue to his list, and devoted +his attention to the same for the next week, and so on, until he had +exhausted his list of virtues. He then commenced again at the +beginning. As his moral code comprised thirteen virtues, it was +possible to go through the complete curriculum four times in a year. +Afterwards he occupied a year in going once through the list, and +subsequently employed several years in one course. A little book was +ruled, with a column for each day and a line for each virtue, and in +this a mark was made for every failure which could be remembered on +examination at the end of the day. It is easy to believe his +statement: "I am surprised to find myself so much fuller of faults +than I had imagined; but I had the satisfaction of seeing them +diminish." + +"This my little book had for its motto these lines from Addison's +'Cato':-- + + "'Here will I hold. If there's a Power above us + (And that there is, all Nature cries aloud + Thro' all her work), He must delight in virtue; + And that which He delights in must be happy.' + +"Another from Cicero:-- + +"'O vitae Philosophia dux! O virtutum indagatrix expultrixque vitiorum! +Unus dies ex praeceptis tuis actus, peccanti immortalitati est +anteponendus.' + +"Another from the Proverbs of Solomon, speaking of wisdom and virtue:-- + +"'Length of days is in her right hand; and in her left hand riches and +honour. Her ways are ways of pleasantness, and all her paths are +peace.' + +"And conceiving God to be the fountain of wisdom, I thought it right +and necessary to solicit His assistance for obtaining it; to this end +I formed the following little prayer, which was prefixed to my tables +of examination, for daily use:-- + +"'O powerful Goodness! bountiful Father! merciful Guide! increase in +me that wisdom which discovers my truest interest. Strengthen my +resolutions to perform what that wisdom dictates. Accept my kind +offices to Thy other children as the only return in my power for Thy +continual favours to me.' + +"I used also sometimes a little prayer which I took from Thomson's +Poems, viz.:-- + + "'Father of light and life, Thou Good Supreme! + Oh teach me what is good; teach me Thyself! + Save me from folly, vanity, and vice, + From every low pursuit; and fill my soul + With knowledge, conscious peace, and virtue pure; + Sacred, substantial, never-failing bliss!'" + +The senses in which Franklin's thirteen virtues were to be understood +were explained by short precepts which followed them in his list. The +list was as follows:-- + +"1. TEMPERANCE. + +"Eat not to dulness; drink not to elevation. + +"2. SILENCE. + +"Speak not but what may benefit others or yourself; avoid trifling +conversation. + +"3. ORDER. + +"Let all your things have their places; let each part of your business +have its time. + +"4. RESOLUTION. + +"Resolve to perform what you ought; perform without fail what you +resolve. + +"5. FRUGALITY. + +"Make no expense but to do good to others or yourself; _i.e._ waste +nothing. + +"6. INDUSTRY. + +"Lose no time; be always employed in something useful; cut off all +unnecessary actions. + +"7. SINCERITY. + +"Use no hurtful deceit; think innocently and justly; and, if you +speak, speak accordingly. + +"8. JUSTICE. + +"Wrong none by doing injuries, or omitting the benefits that are your +duty. + +"9. MODERATION. + +"Avoid extremes; forbear resenting injuries so much as you think they +deserve. + +"10. CLEANLINESS. + +"Tolerate no uncleanness in body, clothes, or habitation. + +"11. TRANQUILLITY. + +"Be not disturbed at trifles, or accidents common or unavoidable. + +"12. CHASTITY. + +"13. HUMILITY. + +"Imitate Jesus and Socrates." + +The last of these was added to the list at the suggestion of a Quaker +friend. Franklin claims to have acquired a good deal of the +_appearance_ of it, but concluded that in reality there was no passion +so hard to subdue as _pride_. "For even if I could conceive that I had +completely overcome it, I should probably be proud of my humility." +The virtue which gave him most trouble, however, was order, and this +he never acquired. + +In 1732 appeared the first copy of "Poor Richard's Almanack." This was +prepared, printed, and published by Franklin for about twenty-five +years in succession, and nearly ten thousand copies were sold +annually. Besides the usual astronomical information, it contained a +collection of entertaining anecdotes, verses, jests, etc., while the +"little spaces that occurred between the remarkable events in the +calendar" were filled with proverbial sayings, inculcating industry +and frugality as helps to virtue. These sayings were collected and +prefixed to the almanack of 1757, whence they were copied into the +American newspapers, and afterwards reprinted as a broad-sheet in +England and in France. + +In 1733 Franklin commenced studying modern languages, and acquired +sufficient knowledge of French, Italian, and Spanish to be able to +read books in those languages. In 1736 he was chosen Clerk to the +General Assembly, an office to which he was annually re-elected until +he became a member of the Assembly about 1750. There was one member +who, on the second occasion of his election, made a long speech +against him. Franklin determined to secure the friendship of this +member. Accordingly he wrote to him to request the loan of a very +scarce and curious book which was in his library. The book was lent +and returned in about a week, with a note of thanks. The member ever +after manifested a readiness to serve Franklin, and they became great +friends--"Another instance of the truth of an old maxim I had learned, +which says, '_He that has once done you a kindness will be more ready +to do you another than he whom you yourself have obliged_.' And it +shows how much more profitable it is prudently to remove, than to +resent, return, and continue inimical proceedings." + +In 1737 Franklin was appointed Deputy-Postmaster-General for +Pennsylvania. He was afterwards made Postmaster-General of the +Colonies. He read a paper in the Junto on the organization of the City +watch, and the propriety of rating the inhabitants on the value of +their premises in order to support the same. The subject was also +discussed in the other clubs which had sprung from the Junto, and thus +the way was prepared for the law which a few years afterwards carried +Franklin's proposals into effect. His next scheme was the formation of +a fire brigade, in which he met with his usual success, and other +clubs followed, until most of the men of property in the city were +members of one club or another. The original brigade, known as the +Union Fire Company, was formed December 7, 1736. It was in active +service in 1791. + +Franklin founded the American Philosophical Society in 1743. The +head-quarters of the society were fixed in Philadelphia, where it was +arranged that there should always be at least seven members, viz. a +physician, a botanist, a mathematician, a chemist, a mechanician, a +geographer, and a general natural philosopher, besides a president, +treasurer, and secretary. The other members might be resident in any +part of America. Correspondence was to be kept up with the Royal +Society of London and the Dublin Society, and abstracts of the +communications were to be sent quarterly to all the members. Franklin +became the first secretary. + +Spain, having been for some years at war with England, was joined at +length by France. This threatened danger to the American colonies, as +France then held Canada, and no organization for their defence +existed. Franklin published a pamphlet entitled "Plain Truth," setting +forth the unarmed condition of the colonies, and recommending the +formation of a volunteer force for defensive purposes. The pamphlet +excited much attention. A public meeting was held and addressed by +Franklin; at this meeting twelve hundred joined the association. At +length the number of members enrolled exceeded ten thousand. These all +provided themselves with arms, formed regiments and companies, elected +their own officers, and attended once a week for military drill. +Franklin was elected colonel of the Philadelphia Regiment, but +declined the appointment, and served as a private soldier. The +provision of war material was a difficulty with the Assembly, which +consisted largely of Quakers, who, though they appeared privately to +be willing that the country should be put in a state of defence, +hesitated to vote in opposition to their peace principles. Hence it +was that, when the Government of New England asked a grant of +gunpowder from Pennsylvania, the Assembly voted L3000 "for the +purchasing of bread, flour, wheat, or _other grain_." Pebble-powder +was not then in use. When it was proposed to devote L60, which was a +balance in the hands of the Union Fire Company, as a contribution +towards the erection of a battery below the town, Franklin suggested +that it should be proposed that a fire-engine be purchased with the +money, and that the committee should "buy a great gun, which is +certainly a _fire-engine_." + +The "Pennsylvania fireplace" was invented in 1742. A patent was +offered to Franklin by the Governor of Pennsylvania, but he declined +it on the principle "_that, as we enjoy great advantages from the +inventions of others, we should be glad of an opportunity to serve +others by any invention of ours; and this we should do freely and +generously_." An ironmonger in London made slight alterations, which +were not improvements, in the design, and took out a patent for the +fireplace, whereby he made a "small fortune." Franklin never contested +the patent, "having no desire of profiting by patents himself," and +"hating disputes." This fireplace was designed to burn wood, but, +unlike the German stoves, it was completely open in front, though +enclosed at the sides and top. An air-chamber was formed in the middle +of the stove, so arranged that, while the burning wood was in contact +with the front of the chamber, the flame passed above and behind it on +its way to the flue. Through this chamber a constant current of air +passed, entering the room heated, but not contaminated, by the +products of combustion. In this way the stove furnished a constant +supply of fresh warm air to the room, while it possessed all the +advantages of an open fireplace. Subsequently Franklin contrived a +special fireplace for the combustion of coal. In the scientific +thought which he devoted to the requirements of the domestic +economist, as in very many other particulars, Franklin strongly +reminds us of Count Rumford. + +The next important enterprise which Franklin undertook, partly through +the medium of the Junto, was to establish an academy which soon +developed into the University of Philadelphia. The members of the club +having taken up the subject, the next step was to enlist the sympathy +of a wider constituency, and this Franklin effected, in his usual way, +by the publication of a pamphlet. He then set on foot a subscription, +the payments to extend over five years, and thereby obtained about +L5000. A house was taken and schools opened in 1749. The classes soon +became too large for the house, and the trustees of the academy then +took over a large building, or "tabernacle," which had been erected +for George Whitefield when he was preaching in Philadelphia. The hall +was divided into stories, and at a very small expense adapted to the +requirements of the classes. Franklin, having taken a partner in his +printing business, took the oversight of the work. Afterwards the +funds were increased by English subscriptions, by a grant from the +Assembly, and by gifts of land from the proprietaries; and thus was +established the University of Philadelphia. + +Having practically retired from business, Franklin intended to devote +himself to philosophical studies, having commenced his electrical +researches some time before in conjunction with the other members of +the Library Company. Public business, however, crowded upon him. He +was elected a member of the Assembly, a councillor and afterwards an +alderman of the city, and by the governor was made a justice of the +peace. As a member of the Assembly, he was largely concerned in +providing the means for the erection of a hospital, and in arranging +for the paving and cleansing of the streets of the city. In 1753 he +was appointed, in conjunction with Mr. Hunter, Postmaster-General of +America. The post-office of the colonies had previously been conducted +at a loss. In a few years, under Franklin's management, it not only +paid the stipends of himself and Mr. Hunter, but yielded a +considerable revenue to the Crown. But it was not only in the conduct +of public business that Franklin's merits were recognized. By this +time he had secured his reputation as an electrician, and both Yale +College and Cambridge University (New England) conferred on him the +honorary degree of Master of Arts. In the same year that he was made +Postmaster-General of America he was awarded the Copley Medal and +elected a Fellow of the Royal Society of London, the usual fees being +remitted in his case. + +Before his election as member, Franklin had for several years held the +appointment of Clerk to the Assembly, and he used to relieve the +dulness of the debates by amusing himself in the construction of magic +circles and squares, and "acquired such a knack at it" that he could +"fill the cells of any magic square of reasonable size with a series +of numbers as fast as" he "could write them." Many years afterwards +Mr. Logan showed Franklin a French folio volume filled with magic +squares, and afterwards a magic "square of 16," which Mr. Logan +thought must have been a work of great labour, though it possessed +only the common properties of making 2056 in every row, horizontal, +vertical, and diagonal. During the evening Franklin made the square +shown on the opposite page. "This I sent to our friend the next +morning, who, after some days, sent it back in a letter, with these +words: 'I return to thee thy astonishing and most stupendous piece of +the magical square, in which----;' but the compliment is too +extravagant, and therefore, for his sake as well as my own, I ought +not to repeat it. Nor is it necessary; for I make no question that you +will readily allow this square of 16 to be the most magically magical +of any magic square ever made by any magician." + +The square has the following properties:--Every straight row of +sixteen numbers, whether vertical, horizontal, or diagonal, makes +2056. + +Every bent row of sixteen numbers, as shown by the diagonal lines in +the figure, makes 2056. + +If a square hole be cut in a piece of paper, so as to show through it +just sixteen of the little squares, and the paper be laid on the magic +square, then, wherever the paper is placed, the sum of the sixteen +numbers visible through the hole will be 2056. + +[Illustration: + + 200 217 232 249 8 25 40 57 72 89 104 121 136 153 168 185 + 58 39 26 7 250 231 218 199 186 167 154 135 122 103 90 71 + 198 219 230 251 6 27 38 59 70 91 102 123 134 155 166 187 + 60 37 28 5 252 229 220 197 188 165 156 133 124 101 92 69 + 201 216 233 248 9 24 41 56 73 88 105 120 137 152 169 184 + 55 42 23 10 247 234 215 202 183 170 151 138 119 106 87 74 + 203 214 235 246 11 22 43 54 75 86 107 118 139 150 171 182 + 53 44 21 12 245 236 213 204 181 172 149 140 117 108 85 76 + 205 212 237 244 13 20 45 52 77 84 109 116 141 148 173 180 + 51 46 19 14 243 238 211 206 179 174 147 142 115 110 83 78 + 207 210 239 242 15 18 47 50 79 82 111 114 143 146 175 178 + 49 48 17 16 241 240 209 208 177 176 145 144 113 112 81 80 + 196 221 228 253 4 29 36 61 68 93 100 125 132 157 164 189 + 62 35 30 3 254 227 222 195 190 163 158 131 126 99 94 67 + 194 223 226 255 2 31 34 63 66 95 98 127 130 159 162 191 + 64 33 32 1 256 225 224 193 192 161 160 129 128 97 96 65 +] + +In 1754 war with France appeared to be again imminent, and a Congress +of Commissioners from the several colonies was arranged for. Of +course, Franklin was one of the representatives of Pennsylvania, and +was also one of the members who independently drew up a plan for the +union of all the colonies under one government, for defensive and +other general purposes, and his was the plan finally approved by +Congress for the union, though it was not accepted by the Assemblies +or by the English Government, being regarded by the former as having +too much of the _prerogative_ in it, by the latter as being too +_democratic_. Franklin wrote respecting this scheme: "The different +and contrary reasons of dislike to my plan makes me suspect that it +was really the true medium; and I am still of opinion that it would +have been happy for both sides of the water if it had been adopted. The +colonies, so united, would have been sufficiently strong to have +defended themselves; there would then have been no need of troops from +England; of course, the subsequent pretence for taxing America, and +the bloody contest it occasioned, would have been avoided." + +With this war against France began the struggle of the Assemblies and +the proprietaries on the question of taxing the estates of the latter. +The governors received strict instructions to approve no bills for the +raising of money for the purposes of defence, unless the estates of +the proprietaries were specially exempted from the tax. The Assembly +of Pennsylvania resolved to contribute L10,000 to assist the +Government of Massachusetts Bay in an attack upon Crown Point, but the +governor refused his assent to the bill for raising the money. At this +juncture Franklin proposed a scheme by which the money could be raised +without the consent of the governor. His plan was successful, and the +difficulty was surmounted for the time, but was destined to recur +again and again during the progress of the war. + +The British Government, not approving of the scheme of union, whereby +the colonies might have defended themselves, sent General Braddock to +Virginia, with two regiments of regular troops. On their arrival they +found it impossible to obtain waggons for the conveyance of their +baggage, and the general commissioned Franklin to provide them in +Pennsylvania. By giving his private bond for their safety, Franklin +succeeded in engaging one hundred and fifty four-horse waggons, and +two hundred and fifty-nine pack-horses. His modest warnings against +Indian ambuscades were disregarded by the general, the little army was +cut to pieces, and the remainder took to flight, sacrificing the whole +of their baggage and stores. Franklin was never fully recouped by the +British Government for the payments he had to make on account of +provisions which the general had instructed him to procure for the use +of the army. + +After this, Franklin appeared for some time in a purely military +capacity, having yielded to the governor's persuasions to undertake +the defence of the north-western frontier, to raise troops, and to +build a line of forts. After building and manning three wooden forts, +he was recalled by the Assembly, whose relations with the governor had +become more and more strained. At length the Assembly determined to +send Franklin to England, to present a petition to the king respecting +the conduct of the proprietaries, viz. Richard and Thomas Penn, the +successors of William Penn. A bill had been framed by the House to +provide L60,000 for the king's use in the defence of the province. +This the governor refused to pass, because the proprietary estates +were not exempted from the taxation. The petition to the king was +drawn up, and Franklin's baggage was on board the ship which was to +convey him to England, when General Lord Loudon endeavoured to make an +arrangement between the parties. The governor pleaded his +instructions, and the bond he had given for carrying them out, and the +Assembly was prevailed upon to reconstruct the bill in accordance with +the governor's wishes. This was done under protest; in the mean time +Franklin's ship had sailed, carrying his baggage. After a great deal +of unnecessary delay on account of the general's inability to decide +upon the despatch of the packet-boats, Franklin at last got away from +New York, and, having narrowly escaped shipwreck off Falmouth, he +reached London on July 27, 1757. + +On arriving in London, Franklin was introduced to Lord Granville, who +told him that the king's instructions were laws in the colonies. +Franklin replied that he had always understood that the Assemblies +made the laws, which then only required the king's consent. "I +recollected that, about twenty years before, a clause in a bill +brought into Parliament by the Ministry had proposed to make the +king's instructions laws in the colonies, but the clause was thrown +out by the Commons, for which we adored them as our friends and the +friends of liberty, till, by their conduct towards us in 1765, it +seem'd that they had refus'd that point of sovereignty to the king +only that they might reserve it for themselves." A meeting was shortly +afterwards arranged between Franklin and the proprietaries at Mr. T. +Penn's house; but their views were so discordant that, after some +discussion, Franklin was requested to give them in writing the heads +of his complaints, and the whole question was submitted to the opinion +of the attorney- and solicitor-general. It was nearly a year before +this opinion was given. The proprietaries then communicated directly +with the Assembly, but in the mean while Governor Denny had consented +to a bill for raising L100,000 for the king's use, in which it was +provided that the proprietary estates should be taxed with the others. +When this bill reached England, the proprietaries determined to oppose +its receiving the royal assent. Franklin engaged counsel on behalf of +the Assembly, and on his undertaking that the assessment should be +fairly made between the estates of the proprietaries and others, the +bill was allowed to pass. + +By this time Franklin's career as a scientific investigator was +practically at an end. Political business almost completely occupied +his attention, and in one sense the diplomatist replaced the +philosopher. His public scientific career was of short duration. It +may be said to have begun in 1746, when Mr. Peter Collinson presented +an "electrical tube" to the Library Company in Philadelphia, which was +some time after followed by a present of a complete set of electrical +apparatus from the proprietaries, but by 1755 Franklin's time was so +much taken up by public business that there was very little +opportunity for experimental work. Throughout his life he frequently +expressed in his letters his strong desire to return to philosophy, +but the opportunity never came, and when, at the age of eighty-two, he +was liberated from public duty, his strength was insufficient to +enable him to complete even his autobiography. + +It was on a visit to Boston in 1746 that Franklin met with Dr. Spence, +a Scotchman, who exhibited some electrical experiments. Soon after his +return to Philadelphia the tube arrived from Mr. Collinson, and +Franklin acquired considerable dexterity in its use. His house was +continually full of visitors, who came to see the experiments, and, to +relieve the pressure upon his time, he had a number of similar tubes +blown at the glass-house, and these he distributed to his friends, so +that there were soon a number of "performers" in Philadelphia. One of +these was Mr. Kinnersley, who, having no other employment, was induced +by Franklin to become an itinerant lecturer. Franklin drew up a scheme +for the lectures, and Kinnersley obtained several well-constructed +instruments from Franklin's rough and home-made models. Kinnersley and +Franklin appear to have worked together a good deal, and when +Kinnersley was travelling on his lecture tour, each communicated to +the other the results of his experiments. Franklin sent his papers to +Mr. Collinson, who presented them to the Royal Society, but they were +not at first judged worthy of a place in the "Transactions." The paper +on the identity of lightning and electricity was sent to Dr. Mitchell, +who read it before the Royal Society, when it "was laughed at by the +connoisseurs." The papers were subsequently published in a pamphlet, +but did not at first receive much attention in England. On the +recommendation of Count de Buffon, they were translated into French. +The Abbe Nollet, who had previously published a theory of his own +respecting electricity, wrote and published a volume of letters +defending his theory, and denying the accuracy of some of Franklin's +experimental results. To these letters Franklin made no reply, but +they were answered by M. le Roy. M. de Lor undertook to repeat in +Paris all Franklin's experiments, and they were performed before the +king and court. Not content with the experiments which Franklin had +actually performed, he tried those which had been only suggested, and +so was the first to obtain electricity from the clouds by means of the +pointed rod. This experiment produced a great sensation everywhere, +and was afterwards repeated by Franklin at Philadelphia. Franklin's +papers were translated into Italian, German, and Latin; his theory met +with all but universal acceptance, and great surprise was expressed +that his papers had excited so little interest in England. Dr. Watson +then drew up a summary of all Franklin's papers, and this was +published in the "Philosophical Transactions;" Mr. Canton verified the +experiment of procuring electricity from the clouds by means of a +pointed rod, and the Royal Society awarded to Franklin the Copley +Medal for 1753, which was conveyed to him by Governor Denny. + +We must now give a short account of Franklin's contributions to +electrical science. + +"The first is the wonderful effect of pointed bodies, both in _drawing +off_ and _throwing off_ the electrical fire." + +It will be observed that this statement is made in the language of the +_one_-fluid theory, of which Franklin may be regarded as the author. +This theory will be again referred to presently. Franklin electrified +a cannon-ball so that it repelled a cork. On bringing near it the +point of a bodkin, the repulsion disappeared. A blunt body had to be +brought near enough for a spark to pass in order to produce the same +effect. "To prove that the electrical fire is _drawn off_ by the +point, if you take the blade of the bodkin out of the wooden handle, +and fix it in a stick of sealing-wax, and then present it at the +distance aforesaid, or if you bring it very near, no such effect +follows; but sliding one finger along the wax till you touch the +blade, and the ball flies to the shot immediately. If you present the +point in the dark, you will see, sometimes at a foot distance or more, +a light gather upon it like that of a fire-fly or glow-worm; the less +sharp the point, the nearer you must bring it to observe the light; +and at whatever distance you see the light, you may draw off the +electrical fire, and destroy the repelling." + +By laying a needle upon the shot, Franklin showed "that points will +_throw off_ as well as _draw off_ the electrical fire." A candle-flame +was found to be equally efficient with a sharp point in drawing off +the electricity from a charged conductor. The effect of the +candle-flame Franklin accounted for by supposing the particles +separated from the candle to be first "attracted and then repelled, +carrying off the electric matter with them." The effect of points is a +direct consequence of the law of electrical repulsion. When a +conductor is electrified, the density of the electricity is greatest +where the curvature is greatest. Thus, if a number of spheres are +electrified from the same source, the density of the electricity on +the different spheres will vary inversely as their diameters. The +force tending to drive the electricity off a conductor is everywhere +proportional to the density, and hence in the case of the spheres will +be greatest for the smallest sphere. On this principle, the density of +electricity on a perfectly sharp point, if such could exist, on a +charged conductor, would be infinite and the force tending to drive it +off would be infinite also. Hence a moderately sharp point is +sufficient to dissipate the electricity from a highly charged +conductor, or to neutralize it if the point is connected to earth and +brought near the conductor so as to be electrified by induction. + +Franklin next found that, if the person rubbing the electric tube +stood upon a cake of resin, and the person taking the charge from the +tube stood also on an insulating stand, a stronger spark would pass +between these two persons than between either of them and the earth; +that, after the spark had passed, neither person was electrified, +though each had appeared electrified before. These experiments +suggested the idea of _positive_ and _negative_ electrification; and +Franklin, regarding the electric fluid as corresponding to positive +electrification, remarked that "you may circulate it as Mr. Watson has +shown; you may also accumulate or subtract it upon or from any body, +as you connect that body with the rubber or with the receiver, the +common stock being cut off." Thus Franklin regarded electricity as a +fluid, of which everything in its normal state possesses a certain +amount; that, by appropriate means, some of the fluid may be removed +from one body and given to another. The former is then electrified +negatively, the latter positively, and all processes by which bodies +are electrified consist in the removal of electricity from one body or +system and giving it to another. He regarded the electric fluid as +repelling itself and attracting matter. AEpinus afterwards added the +supposition that matter, when devoid of electricity, is +self-repulsive, and thus completed the "one-fluid theory," and +accounted for the repulsion observed between negatively electrified +bodies. + +It had been usual to employ water for the interior armatures of Leyden +jars, or phials, as they were then generally called. Franklin +substituted granulated lead for the water, thereby improving the +insulation by keeping the glass dry. With these phials he contrived +many ingenious experiments, and imitated lightning by discharging them +through the gilding of a mirror or the gold lines on the cover of a +book. He found that the inner and outer armatures of his Leyden jars +were oppositely electrified. "Here we have a bottle containing at the +same time a _plenum_ of electrical fire and a _vacuum_ of the same +fire; and yet the equilibrium cannot be restored between them but by a +communication _without_! though the plenum presses violently to +expand, and the hungry vacuum seems to attract as violently in order +to be filled." The charging of Leyden jars by cascade, that is by +insulating all the jars except the last, connecting the outer armature +of the first with the inner armature of the second, and so on +throughout the series, was well understood by Franklin, and he knew +too that by this method the extent to which each jar could be charged +from a given source varied inversely as the number of jars. The +discharge of the Leyden jar by alternate contacts was also carried out +by him; and he found that, if the jar is first placed on an insulating +stand, it may be held by the hook (or knob) without discharging it. +Franklin, in fact, appears to have known almost as much about the +Leyden jar as is known to-day. He found that, when the armatures were +removed from a jar, no discharge would pass between them, but when a +fresh pair of armatures were supplied to the glass, the jar could be +discharged. "We are of opinion that there is really no more electrical +fire in the phial after what is called its _charging_ than before, nor +less after its _discharging_; excepting only the small spark that +might be given to and taken from the non-electric matter, if separated +from the bottle, which spark may not be equal to a five-hundredth part +of what is called the explosion. + +"The phial will not suffer what is called a _charging_ unless as much +fire can go out of it one way as is thrown in by another. + +"When a bottle is charged in the common way, its _inside_ and +_outside_ surfaces stand ready, the one to give fire by the hook, the +other to receive it by the coating; the one is full and ready to throw +out, the other empty and extremely hungry; yet, as the first will not +_give out_ unless the other can at the same time _receive in_, so +neither will the latter receive in unless the first can at the same +time give out. When both can be done at once, it is done with +inconceivable quickness and violence." + +Then follows a very beautiful illustration of the condition of the +glass in the Leyden jar. + +"So a straight spring (though the comparison does not agree in every +particular), when forcibly bent, must, to restore itself, contract +that side which in the bending was extended, and extend that which was +contracted; if either of these two operations be hindered, the other +cannot be done. + +"Glass, in like manner, has, within its substance, always the same +quantity of electrical fire, and that a very great quantity in +proportion to the mass of the glass, as shall be shown hereafter. + +"This quantity proportioned to the glass it strongly and obstinately +retains, and will have neither more nor less, though it will suffer a +change to be made in its parts and situation; _i.e._ we may take away +part of it from one of the sides, provided we throw an equal quantity +into the other." + +"The whole force of the bottle, and power of giving a shock, is in the +GLASS ITSELF; the non-electrics in contact with the two surfaces +serving only to _give_ and _receive_ to and from the several parts of +the glass, that is, to give on one side and take away from the other." + +All these statements were, as far as possible, fully substantiated by +experiment. They are perfectly consistent with the views held by +Cavendish and by Clerk Maxwell, and, though the phraseology is not +that of the modern text-books, the statements themselves can hardly be +improved upon to-day. + +One of Franklin's early contrivances was an electro-motor, which was +driven by the alternate electrical attraction and repulsion of leaden +bullets which discharged Leyden jars by alternate contacts. Franklin +concluded his account of these experiments as follows:-- + + Chagrined a little that we have been hitherto able to produce + nothing in this way of use to mankind, and the hot weather + coming on, when electrical experiments are not so agreeable, it + is proposed to put an end to them for this season, somewhat + humorously, in a party of pleasure, on the banks of Skuylkil. + Spirits, at the same time, are to be fired by a spark sent from + side to side through the river, without any other conductor than + the water--an experiment which we some time since performed, to + the amazement of many. A turkey is to be killed for our dinner + by the _electrical shock_, and roasted by the _electrical jack_ + before a fire kindled by the _electrified bottle_, when the + healths of all the famous electricians in England, Holland, + France, and Germany, are to be drunk in _electrified bumpers_, + under the discharge of guns from the _electrical battery_. + +Franklin's electrical battery consisted of eleven large panes of glass +coated on each side with sheet lead. The electrified bumper was a thin +tumbler nearly filled with wine and electrified as a Leyden jar, so +as to give a shock through the lips. + +Franklin's theory of the manner in which thunder-clouds become +electrified he found to be not consistent with his subsequent +experiments. In the paper which he wrote explaining this theory, +however, he shows some knowledge of the effects of bringing conductors +into contact in diminishing their capacity. He states that two +gun-barrels electrified equally and then united, will give a spark at +a greater distance than one alone. Hence he asks, "To what a great +distance may ten thousand acres of electrified cloud strike and give +its fire, and how loud must be that crack? + +"An electrical spark, drawn from an irregular body at some distance, +is scarcely ever straight, but shows crooked and waving in the air. So +do the flashes of lightning, the clouds being very irregular bodies. + +"As electrified clouds pass over a country, high hills and high trees, +lofty towers, spires, masts of ships, chimneys, etc., as so many +prominences and points, draw the electrical fire, and the whole cloud +discharges there. + +"Dangerous, therefore, is it to take shelter under a tree during a +thunder-gust. It has been fatal to many, both men and beasts. + +"It is safer to be in the open field for another reason. When the +clothes are wet, if a flash in its way to the ground should strike +your head, it may run in the water over the surface of your body; +whereas, if your clothes were dry, it would go through the body, +because the blood and other humours, containing so much water, are +more ready conductors. + +"Hence a wet rat cannot be killed by the exploding electrical bottle +[a quart jar], while a dry rat may." + +In the above quotations we see, so to speak, the germ of the +lightning-rod. This was developed in a letter addressed to Mr. +Collinson, and dated July 29, 1750. The following quotations will give +an idea of its contents:-- + +"The electrical matter consists of particles extremely subtile, since +it can permeate common matter, even the densest metals, with such ease +and freedom as not to receive any perceptible resistance.[1] + +[Footnote 1: Franklin was aware of the resistance of conductors (see +p. 96).] + +"If any one should doubt whether the electrical matter passes through +the substance of bodies or only over and along their surfaces, a shock +from an electrified large glass jar, taken through his own body, will +probably convince him. + +"Common matter is a kind of sponge to the electrical fluid. + +"We know that the electrical fluid is _in_ common matter, because we +can pump it _out_ by the globe or tube. We know that common matter has +near as much as it can contain, because when we add a little more to +any portion of it, the additional quantity does not enter, but forms +an electrical atmosphere." + +To illustrate the action of a lightning-conductor on a thunder-cloud, +Franklin suspended from the ceiling a pair of scales by a twisted +string so that the beam revolved. Upon the floor, in such a position +that the scale-pans passed over it, he placed a blunt steel punch. The +scale-pans were suspended by silk threads, and one of them +electrified. When this passed over the punch it dipped towards it, and +sometimes discharged into it by a spark. When a needle was placed with +its point uppermost by the side of the punch, no attraction was +apparent, for the needle discharged the scale-pan before it came near. + +"Now, if the fire of electricity and that of lightning be the same, as +I have endeavoured to show at large in a former paper ... these scales +may represent electrified clouds.... The horizontal motion of the +scales over the floor may represent the motion of the clouds over the +earth, and the erect iron punch a hill or high building; and then we +see how electrified clouds, passing over hills or high buildings at +too great a height to strike, may be attracted lower till within their +striking distance; and lastly, if a needle fixed on the punch, with +its point upright, or even on the floor below the punch, will draw the +fire from the scale silently at a much greater than the striking +distance, and so prevent its descending towards the punch; or if in +its course it would have come nigh enough to strike, yet, being first +deprived of its fire, it cannot, and the punch is thereby secured from +its stroke;--I say, if these things are so, may not the knowledge of +this power of points be of use to mankind, in preserving houses, +churches, ships, etc., from the stroke of the lightning, by directing +us to fix, on the highest parts of those edifices, upright rods of +iron made sharp as a needle, and gilt to prevent rusting, and from the +foot of those rods a wire down the outside of the building into the +ground, or down round one of the shrouds of a ship, and down her side +till it reaches the water? Would not these pointed rods probably draw +the electrical fire silently out of a cloud before it came nigh enough +to strike, and thereby secure us from that most sudden and terrible +mischief?" + +Franklin goes on to suggest the possibility of obtaining electricity +from the clouds by means of a pointed rod fixed on the top of a high +building and insulated. Such a rod he afterwards erected in his own +house. Another rod connected to the earth he brought within six inches +of it, and, attaching a small bell to each rod, he suspended a little +ball or clapper by a silk thread, so that it could strike either bell +when attracted to it. On the approach of a thunder-cloud, and +occasionally when no clouds were near, the bells would ring, +indicating that the rod had become strongly electrified. On one +occasion Franklin was disturbed by a loud noise, and, coming out of +his bedroom, he found an apparently continuous and very luminous +discharge taking place between the bells, forming a stream of fire +about as large as a pencil. + +A very pretty experiment of Franklin's was that of the _golden fish_. +A small piece of gold-leaf is cut into a quadrilateral having one of +its angles about 150 deg., the opposite angle about 30 deg., and the other two +right angles. "If you take it by the tail, and hold it at a foot or +greater horizontal distance from the prime conductor, it will, when +let go, fly to it with a brisk but wavering motion, like that of an +eel through the water; it will then take place under the prime +conductor, at perhaps a quarter or half an inch distance, and keep a +continual shaking of its tail like a fish, so that it seems animated. +Turn its tail towards the prime conductor, and then it flies to your +finger, and seems to nibble it. And if you hold a [pewter] plate under +it at six or eight inches distance, and cease turning the globe, when +the electrical atmosphere of the conductor grows small it will descend +to the plate and swim back again several times with the same fish-like +motion; greatly to the entertainment of spectators. By a little +practice in blunting or sharpening the heads or tails of these +figures, you may make them take place as desired, nearer or further +from the electrified plate." + +By the discharge of the battery, Franklin succeeded in melting and +volatilizing gold-leaf, thin strips of tinfoil, etc. His views on the +nature of light are best given in his own words. + +"I am not satisfied with the doctrine that supposes particles of +matter called light, continually driven off from the sun's surface, +with a swiftness so prodigious! Must not the smallest particle +conceivable have, with such a motion, a force exceeding that of a +twenty-four pounder discharged from a cannon?... Yet these particles, +with this amazing motion, will not drive before them, or remove, the +least and lightest dust they meet with. + +"May not all the phenomena of light be more conveniently solved by +supposing universal space filled with a subtile elastic fluid, which, +when at rest, is not visible, but whose vibrations affect that fine +sense in the eye, as those of air do the grosser organs of the ear? We +do not, in the case of sound, imagine that any sonorous particles are +thrown off from a bell, for instance, and fly in straight lines to the +ear; why must we believe that luminous particles leave the sun and +proceed to the eye? Some diamonds, if rubbed, shine in the dark +without losing any part of their matter. I can make an electrical +spark as big as the flame of a candle, much brighter, and therefore +visible further; yet this is without fuel; and I am persuaded no part +of the electrical fluid flies off in such case to distant places, but +all goes directly and is to be found in the place to which I destine +it. May not different degrees of the vibration of the abovementioned +universal medium occasion the appearances of different colours? I +think the electric fluid is always the same; yet I find that weaker +and stronger sparks differ in apparent colour, some white, blue, +purple, red: the strongest, white; weak ones, red. Thus different +degrees of vibration given to the air produce the seven different +sounds in music, analogous to the seven colours, yet the medium, air, +is the same." + +Mr. Kinnersley having called Franklin's attention to the fact that a +sulphur globe when rubbed produced electrification of an opposite kind +from that produced by a glass globe, Franklin repeated the experiment, +and noticed that the discharge from the end of a wire connected with +the conductor was different in the two cases, being "long, large, and +much diverging when the glass globe is used, and makes a snapping (or +rattling) noise; but when the sulphur one is used it is short, small, +and makes a hissing noise; and just the reverse of both happens when +you hold the same wire in your hand and the globes are worked +alternately.... When the brush is long, large, and much diverging, the +body to which it is joined seems to be throwing the fire out; and when +the contrary appears it seems to be drinking in." + +On October 19, 1752, Franklin wrote to Mr. Peter Collinson as +follows:-- + + As frequent mention is made in public papers from Europe of the + success of the Philadelphia experiment for drawing the electric + fire from clouds by means of pointed rods of iron erected on + high buildings, etc., it may be agreeable to the curious to be + informed that the same experiment has succeeded in + Philadelphia, though made in a different and more easy manner, + which is as follows:-- + + Make a small cross of two light strips of cedar, the arms so + long as to reach to the four corners of a large thin silk + handkerchief when extended. Tie the corners of the handkerchief + to the extremities of the cross, so you have the body of a kite; + which, being properly accommodated with a tail, loop, and + string, will rise in the air like those made of paper; but this + being of silk is fitter to bear the wet and wind of a + thunder-gust without tearing. To the top of the upright stick of + the cross is to be fixed a very sharp-pointed wire, rising a + foot or more above the wood. To the end of the twine, next the + hand, is to be tied a silk ribbon, and, where the silk and twine + join, a key may be fastened. This kite is to be raised when a + thunder-gust appears to be coming on, and the person who holds + the string must stand within a door or window, or under some + cover so that the silk ribbon may not be wet, and care must be + taken that the twine does not touch the frame of the door or + window. As soon as any of the thunder-clouds come over the kite, + the pointed wire will draw the electric fire from them, and the + kite, with all the twine, will be electrified, and the loose + filaments of the twine will stand out every way, and be + attracted by an approaching finger. And when the rain has wetted + the kite and twine so that it can conduct the electric fire + freely, you will find it stream out plentifully from the key on + the approach of your knuckle. At this key the phial may be + charged, and from electric fire there obtained spirits may be + kindled, and all the other electric experiments be performed + which are usually done by the help of a rubbed glass globe or + tube, and thereby the sameness of the electric matter with that + of lightning completely demonstrated. + +Having, in September, 1752, erected the iron rod and bells in his own +house, as previously mentioned, Franklin succeeded, in April, 1753, in +charging a Leyden jar from the rod, and found its charge was negative. +On June 6, however, he obtained a positive charge from a cloud. The +results of his observations led him to the conclusion "_That the +clouds of a thunder-gust are most commonly in a negative state of +electricity, but sometimes in a positive state._" + +In order to illustrate a theory respecting the electrification of +clouds, Franklin placed a silver can on a wine-glass. Inside the can +was placed a considerable length of chain, which could be drawn out by +means of a silk thread. He electrified the can from a Leyden jar until +it would receive no more electricity. Then raising the silk thread, he +gradually drew the chain out of the can, and found that the greater +the length of chain drawn out the greater was the charge which the jar +would give to the system, and as the chain was raised, spark after +spark passed from the jar to the silver can, thus showing that the +capacity of the system was increased by increasing the amount of +chain exposed. + +In 1755 Franklin observed the effects of induction; for, having +attached to his prime conductor a tassel made of damp threads and +electrified the conductor, he found that the threads repelled each +other and stood out. Bringing an excited glass tube near the other end +of the conductor, the threads were found to diverge more, "because the +atmosphere of the prime conductor is pressed by the atmosphere of the +excited tube, and driven towards the end where the threads are, by +which each thread acquires more atmosphere." When the excited tube was +brought near the threads, they closed a little, "because the +atmosphere of the glass tube repels their atmospheres, and drives part +of them back on the prime conductor." A number of other experiments +illustrating electrical induction were also carried out. + +In writing to Dr. Living, of Charlestown, under date March 18, 1755, +Franklin gave the following extracts of the minutes of his experiments +as explaining the train of thought which led him to attempt to obtain +electricity from the clouds:-- + +"_November 7, 1749._ Electrical fluid agrees with lightning in these +particulars: 1. Giving light. 2. Colour of the light. 3. Crooked +direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or +noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies +it passes through. 9. Destroying animals. 10. Melting metals. 11. +Firing inflammable substances. 12. Sulphureous smell. The electric +fluid is attracted by points. We do not know whether this property is +in lightning. But since they agree in all the particulars wherein we +can already compare them, is it not probable they agree likewise in +this? Let the experiment be made." + +Another experiment very important in its bearing on the theory of +electricity was described by Franklin in the same letter to Dr. +Living. It was afterwards repeated in a much more complete form by +Cavendish, who deduced from it the great law that electrical repulsion +varies inversely as the square of the distance between the charges. +The same experiment was repeated in other forms by Faraday, who had no +means of knowing what Cavendish had done. Franklin writes:-- + + I electrified a silver fruit-can on an electric stand, and then + lowered into it a cork ball of about an inch in diameter, + hanging by a silk string, till the cork touched the bottom of + the can. The cork was not attracted to the inside of the can, as + it would have been to the outside, and though it touched the + bottom, yet, when drawn out, it was not found to be electrified + by that touch, as it would have been by touching the outside. + The fact is singular. You require the reason? I do not know it. + Perhaps you may discover it, and then you will be so good as to + communicate it to me. I find a frank acknowledgment of one's + ignorance is not only the easiest way to get rid of a + difficulty, but the likeliest way to obtain information, and + therefore I practise it. I think it is an honest policy. + +A note appended to this letter runs as follows:-- + + Mr. F. has since thought that, possibly, the mutual repulsion of + the inner opposite sides of the electrized can may prevent the + accumulating an electric atmosphere upon them, and occasion it + to stand chiefly on the outside. But recommends it to the + further examination of the curious. + +The explanation in this note is the correct one, and from the fact +that in the case of a completely closed hollow conductor the charge is +not only _chiefly_ but _wholly_ on the outside, the law of inverse +squares above referred to follows as a mathematical consequence. + +On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin +complained that, though he always (except once) assigned to +lightning-rods the alternative duty of either _preventing_ a stroke or +of _conducting_ the lightning with safety to the ground, yet in Europe +attention was paid only to the _prevention_ of the stroke, which was +only a _part_ of the duty assigned to the conductors. This is followed +by the description of the effect of a stroke upon a church-steeple at +Newbury, in New England. The spire was split all to pieces, so that +nothing remained above the bell. The lightning then passed down a wire +to the clock, then down the pendulum, without injury to the building. +"From the end of the pendulum, down quite to the ground, the building +was exceedingly rent and damaged, and some stones in the +foundation-wall torn out and thrown to the distance of twenty or +thirty feet." The pendulum-rod was uninjured, but the fine wire +leading from the bell to the clock was vaporized except for about two +inches at each end. + +Mr. James Alexander, of New York, having proposed to Franklin that the +velocity of the electric discharge might be measured by discharging a +jar through a long circuit of river-water, Franklin, in his reply, +explained that such an experiment, if successful, would not determine +the actual velocity of electricity in the conductor. He compared the +electricity in conductors to an incompressible fluid, so that when a +little additional fluid is injected at one end of a conductor, an +equal amount must be extruded at the other end--his view apparently +being identical with that of Maxwell, who held that all electric +displacements must take place _in closed circuits_. + +"Suppose a tube of any length open at both ends.... If the tube be +filled with water, and I inject an additional inch of water at one +end, I force out an equal quantity at the other in the very same +instant. + +"And the water forced out at one end of the tube is not the very same +water that was forced in at the other end at the same time; it was +only one motion at the same time. + +"The long wire, made use of in the experiment to discover the velocity +of the electric fluid, is itself filled with what we call its natural +quantity of that fluid, before the hook of the Leyden bottle is +applied at one end of it. + +"The outside of the bottle being at the time of such application in +contact with the other end of the wire, the whole quantity of electric +fluid contained in the wire is, probably, put in motion at once. + +"For at the instant the hook, connected with the inside of the bottle, +_gives out_, the coating or outside of the bottle _draws in_, a +portion of that fluid.... + +"So that this experiment only shows the extreme facility with which +the electric fluid moves in metal; it can never determine the +velocity. + +"And, therefore, the proposed experiment (though well imagined and +very ingenious) of sending the spark round through a vast length of +space, by the waters of Susquehannah, or Potowmack, and Ohio, would +not afford the satisfaction desired, though we could be sure that the +motion of the electric fluid would be in that tract, and not +underground in the wet earth by the shortest way." + +In his investigations of the source of electricity in thunder-clouds, +Franklin tried an experiment which has been frequently repeated with +various modifications. Having insulated a large brass plate which had +been previously heated, he sprinkled water upon it, in order, if +possible, to obtain electricity by the evaporation of the water, but +no trace of electrification could be detected. + +During his visit to England, Franklin wrote many letters to Mr. +Kinnersley and others on philosophical questions, but they consisted +mainly of accounts of the work done by other experimenters in England, +his public business occupying too much of his attention to allow him +to conduct investigations for himself. In one of his letters, speaking +of Lord Charles Cavendish, he says:-- + + It were to be wished that this noble philosopher would + communicate more of his experiments to the world, as he makes + many, and with great accuracy. + +When the controversy between the relative merits of points and knobs +for the terminals of lightning-conductors arose, Franklin wrote to Mr. +Kinnersley:-- + + Here are some electricians that recommend knobs instead of + points on the upper end of the rods, from a supposition that the + points invite the stroke. It is true that points draw + electricity at greater distances in the gradual silent way; but + knobs will draw at the greatest distance a stroke. There is an + experiment which will settle this. Take a crooked wire of the + thickness of a quill, and of such a length as that, one end of + it being applied to the lower part of a charged bottle, the + upper may be brought near the ball on the top of the wire that + is in the bottle. Let one end of this wire be furnished with a + knob, and the other may be gradually tapered to a fine point. + When the point is presented to discharge the bottle, it must be + brought much nearer before it will receive the stroke than the + knob requires to be. Points, besides, tend to repel the + fragments of an electrical cloud; knobs draw them nearer. An + experiment, which I believe I have shown you, of cotton fleece + hanging from an electrized body, shows this clearly when a point + or a knob is presented under it. + +The following quotation from Franklin's paper on the method of +securing buildings and persons from the effects of lightning is worthy +of attention, for of late years a good deal of money has been wasted +in providing insulators for lightning-rods. A few years ago the vicar +and churchwardens of a Lincolnshire parish were strongly urged to go +to the expense of insulating the conductor throughout the whole height +of the very lofty tower and spire of their parish church. Happily they +were wise enough to send the lightning-rod man about his business. But +this is not the only case which has come under the writer's notice, +showing that there is still a widespread impression that +lightning-conductors should be carefully insulated. Franklin says:-- + +"The rod may be fastened to the wall, chimney, etc., with staples of +iron. The lightning will not leave the rod (a good conductor) to pass +into the wall (a bad conductor) through these staples. It would +rather, if any were in the wall, pass out of it into the rod, to get +more readily by that conductor into the earth."[2] + +[Footnote 2: See p. 141.] + +The conditions to be secured in a lightning-conductor are, firstly, a +sharp point projecting above the highest part of the building, and +gilded to prevent corrosion; secondly, metallic continuity from the +point to the lower end of the conductor; and, thirdly, a good +earth-contact. The last can frequently be secured by soldering the +conductor to iron water-pipes underground. Where these are not +available, a copper plate, two or three feet square, imbedded in clay +or other damp earth, will serve the purpose. The method of securing a +building which is erected on granite or other foundation affording no +good earth-connection, will be referred to in a subsequent +biographical sketch. + +The controversy of points _versus_ knobs was again revived in London +when Franklin was in Paris, and the War of Independence had begun. +Franklin was consulted on the subject, the question having arisen in +connection with the conductor at the palace. His reply was +characteristic. + +"As to my writing anything on the subject, which you seem to desire, I +think it not necessary, especially as I have nothing to add to what I +have already said upon it in a paper read to the committee who ordered +the conductors at Purfleet, which paper is printed in the last French +edition of my writings. + +"I have never entered into any controversy in defence of my +philosophical opinions. I leave them to take their chance in the +world. If they are _right_, truth and experience will support them; if +_wrong_, they ought to be refuted and rejected. Disputes are apt to +sour one's temper and disturb one's quiet. I have no private interest +in the reception of my inventions by the world, having never made, nor +proposed to make, the least profit by any of them. The king's changing +his _pointed_ conductors for _blunt_ ones is, therefore, a matter of +small importance to me. If I had a wish about it, it would be that he +had rejected them altogether as ineffectual. For it is only since he +thought himself and family safe from the thunder of Heaven, that he +dared to use his own thunder in destroying his innocent subjects." + +The paper referred to was read before "the committee appointed to +consider the erecting conductors to secure the magazines at Purfleet," +on August 27, 1772. It described a variety of experiments clearly +demonstrating the effect of points in discharging a conductor. This +was a committee of the Royal Society, to whom the question had been +referred on account of Dr. Wilson's recommendation of a blunt +conductor. The committee decided in favour of Franklin's view, and +when, in 1777, the question was again raised and again referred to a +committee of the Royal Society, the decision of the former committee +was confirmed, "conceiving that the experiments and reasons made and +alleged to the contrary by Mr. Wilson are inconclusive." + +Though Franklin's scientific reputation rests mainly on his electrical +researches, he did not leave other branches of science untouched. +Besides his work on atmospheric electricity, he devoted a great deal +of thought to meteorology, especially to the vortical motion of +waterspouts. The Gulf-stream received a share of his attention. His +improvements in fireplaces have already been noticed; the cure of +smoky chimneys was the subject of a long paper addressed to Dr. +Ingenhousz, and of some other letters. One of his experiments on the +absorption of radiant energy has been deservedly remembered. + +"My experiment was this: I took a number of little square pieces of +broad-cloth from a tailor's pattern-card, of various colours. There +were black, deep blue, lighter blue, green, purple, red, yellow, +white, and other colours or shades of colours. I laid them all out +upon the snow in a bright, sun-shiny morning. In a few hours (I cannot +now be exact as to the time) the black, being warmed most by the sun, +was sunk so low as to be below the stroke of the sun's rays; the dark +blue almost as low, the lighter blue not quite so much as the dark, +the other colours less as they were lighter; and the quite white +remained on the surface of the snow, not having entered it at all. + +"What signifies philosophy that does not apply to some use? May we not +learn from hence that black clothes are not so fit to wear in a hot, +sunny climate or season, as white ones?" + +Franklin knew much about electricity, but his knowledge of human +nature was deeper still. This appears in all his transactions. His +political economy was, perhaps, not always sound, but his judgment of +men was seldom at fault. + +"Finally, there seem to be but three ways for a nation to acquire +wealth. The first is by _war_, as the Romans did, in plundering their +conquered neighbour: this is _robbery_. The second by _commerce_, +which is generally _cheating_. The third by _agriculture_, the only +_honest way_, wherein man receives a real increase of the seed thrown +into the ground, in a kind of continual miracle wrought by the hand of +God in his favour, as a reward for his innocent life and his virtuous +industry." + +When Franklin reached London in 1757 he took up his abode with Mrs. +Margaret Stevenson, in Craven Street, Strand. For Mrs. Stevenson and +her daughter Mary, then a young lady of eighteen, he acquired a +sincere affection, which continued throughout their lives. Miss +Stevenson spent much of her time with an aunt in the country, and some +of Franklin's letters to her respecting the conduct of her "higher +education" are among the most interesting of his writings. Miss +Stevenson treated him as a father, and consulted him on every question +of importance in her life. When she was a widow and Franklin eighty +years of age, he urged upon her to come to Philadelphia, for the sake +of the better prospects which the new country offered her boys. In +coming to England, Franklin brought with him his son William, who +entered the Middle Temple, but he left behind his only daughter, +Sarah, in charge of her mother. To his wife and daughter he +frequently sent presents from London, and his letters to Mrs. Franklin +give a pretty full account of all his doings while in England. During +his visit he received the honorary degrees of D.C.L. from the +University of Oxford, and LL.D. from that of Edinburgh. At Cambridge +he was sumptuously entertained. In August, 1762, he started again for +America, and reached Philadelphia on November 1, after an absence of +five years. His son William had shortly before been appointed Governor +of New Jersey. From this time William Franklin became very much the +servant of the proprietaries and of the English Government, but no +offer of patronage produced any effect on the father. + +Franklin's stay in America was of short duration, but while there he +was mainly instrumental in quelling an insurrection in Pennsylvania. +He made a tour of inspection through the northern colonies in the +summer of 1763, to regulate the post-offices. The disorder just +referred to in the province caused the governor, as well as the +Assembly, to determine on the formation of a militia. A committee, of +which Franklin was a member, drew up the necessary bill. The governor +claimed the sole power of appointing officers, and required that +trials should be by court-martial, some offences being punishable with +death. The Assembly refused to agree to these considerations. The ill +feeling was increased by the governor insisting on taxing all +proprietary lands at the same rate as uncultivated land belonging to +other persons, whether the proprietary lands were cultivated or not. +The Assembly, before adjourning, expressed an opinion that peace and +happiness would not be secured until the government was lodged +directly in the Crown. When the Assembly again met, petitions to the +king came in from more than three thousand inhabitants. In the mean +while the British Ministry had proposed the Stamp Act, which was +similar in principle to the English Stamp Act, which requires that all +agreements, receipts, bills of exchange, marriage and birth +certificates, and all other legal documents should be provided with an +inland revenue stamp of a particular value, in order that they might +be valid. As soon as the Assembly was convened, it determined to send +Franklin to England, to take charge of a petition for a change of +government. The merchants subscribed L1100 towards his expenses in a +few hours, and in twelve days he was on his journey, being accompanied +to the ship, a distance of sixteen miles, by a cavalcade of three +hundred of his friends, and in thirty days he reached London. Arrived +in London, he at once took up his abode in his old lodgings with Mrs. +Stevenson. He was a master of satire, equalled only by Swift, and +during the quarrels which preceded the War of Independence, as well as +during the war, he made good use of his powers in this respect. +Articles appeared in some of the English papers tending to raise an +alarm respecting the competition of the colonies with English +manufacturers. Franklin's contribution to the discussion was a +caricature of the English press writers. + +"It is objected by superficial readers, who yet pretend to some +knowledge of those countries, that such establishments [manufactories +for woollen goods, etc.] are not only improbable, but impossible, for +that their sheep have but little wool, not in the whole sufficient for +a pair of stockings a year to each inhabitant; that, from the +universal dearness of labour among them, the working of iron and other +materials, except in a few coarse instances, is impracticable to any +advantage. + +"Dear sir, do not let us suffer ourselves to be amused with such +groundless objections. The very tails of the American sheep are so +laden with wool that each has a little car or waggon on four little +wheels to support and keep it from trailing on the ground. Would they +caulk their ships, would they even litter their horses with wool, if +it were not both plenty and cheap? And what signifies the dearness of +labour, when an English shilling passes for five and twenty? Their +engaging three hundred silk throwsters here in one week for New York +was treated as a fable, because, forsooth, they have 'no silk there to +throw!' Those who make this objection perhaps do not know that, at the +same time, the agents for the King of Spain were at Quebec, to +contract for one thousand pieces of cannon to be made there for the +fortification of Mexico, and at New York engaging the usual supply of +woollen floor-carpets for their West India houses. Other agents from +the Emperor of China were at Boston, treating about an exchange of raw +silk for wool, to be carried in Chinese junks through the Straits of +Magellan. + +"And yet all this is as certainly true as the account said to be from +Quebec in all the papers of last week, that the inhabitants of Canada +are making preparations for a cod and whale fishery this summer in the +upper Lakes. Ignorant people may object that the upper Lakes are +fresh, and that cod and whales are salt-water fish; but let them know, +sir, that cod, like other fish when attacked by their enemies, fly +into any water where they can be safest; that whales, when they have a +mind to eat cod, pursue them wherever they fly; and that the grand +leap of the whale in the chase up the Falls of Niagara is esteemed, by +all who have seen it, as one of the finest spectacles in nature." + +One of Franklin's chief objects in coming to England was to prevent +the passing of Mr. Grenville's bill, previously referred to as the +Stamp Act. The colonists urged that they had always been liberal in +their votes, whenever money was required by the Crown, and that +taxation and representation must, in accordance with the British +constitution, go hand-in-hand, so that the English Parliament had no +right to raise taxes in America, so long as the colonists were +unrepresented in Parliament. "Had Mr. Grenville, instead of that act, +applied to the king in Council for such requisitional letters [_i.e._ +requests to the Assemblies for voluntary grants], to be circulated by +the Secretary of State, I am sure he would have obtained more money +from the colonies by their voluntary grants than he himself expected +from the sale of stamps. But he chose compulsion rather than +persuasion, and would not receive from their good will what he thought +he could obtain without it." The Stamp Act was passed, stamps were +printed, distributors were appointed, but the colonists would have +nothing to do with the stamps. The distributors were compelled to +resign their commissions, and the captains of vessels were forbidden +to land the stamped paper. The cost of printing and distributing +amounted to L12,000; the whole return was about L1500, from Canada and +the West Indies. + +The passing of the Stamp Act was soon followed by a change of +Ministry, when the question again came before Parliament. Franklin +submitted to a long examination before a Committee of the whole House. +The feeling prevalent in America respecting the Stamp Act may be +inferred from some of his answers. + +"31. _Q._ Do you think the people of America would submit to pay the +stamp duty if it was moderated? + +"_A._ No, never, unless compelled by force of arms. + +"36. _Q._ What was the temper of America towards Great Britain before +the year 1763?[3] + +[Footnote 3: The date of the Sugar Act.] + +"_A._ The best in the world. They submitted willingly to the +government of the Crown, and paid, in their courts, obedience to the +Acts of Parliament. Numerous as the people are in the several old +provinces, they cost you nothing in forts, citadels, garrisons, or +armies to keep them in subjection. They were governed by this country +at the expense only of a little pen, ink, and paper; they were led by +a thread. They had not only a respect, but an affection, for Great +Britain--for its laws, its customs and manners, and even a fondness +for its fashions, that greatly increased the commerce. Natives of +Britain were always treated with particular regard; to be an +_Old-Englandman_ was, of itself, a character of some respect, and gave +a kind of rank among us. + +"37. _Q._ And what is their temper now? + +"_A._ Oh, very much altered. + +"50. _Q._ Was it an opinion in America before 1763 that the Parliament +had no right to lay taxes and duties there? + +"_A._ I never heard any objection to the right of laying duties to +regulate commerce; but a right to lay internal taxes was never +supposed to be in Parliament, as we are not represented there. + +"59. _Q._ You say the colonies have always submitted to external +taxes, and object to the right of Parliament only in laying internal +taxes; now, can you show that there is any kind of difference between +the two taxes to the colony on which they may be laid? + +"_A._ I think the difference is very great. An _external_ tax is a +duty laid on commodities imported; that duty is added to the first +cost and other charges on the commodity, and, when it is offered to +sale, makes a part of the price. If the people do not like it at that +price, they refuse it; they are not obliged to pay it. But an +_internal_ tax is forced upon the people without their consent, if not +laid by their own representatives. The Stamp Act says we shall have no +commerce, make no exchange of property with each other, neither +purchase, nor grant, nor recover debts; we shall neither marry nor +make our wills, unless we pay such and such sums; and thus it is +intended to extort our money from us, or ruin us by the consequences +of refusing to pay it. + +"61. _Q._ Don't you think cloth from England absolutely necessary to +them? + +"_A._ No, by no means absolutely necessary; with industry and good +management they may very well supply themselves with all they want. + +"62. _Q._ Will it not take a long time to establish that manufacture +among them? and must they not in the mean while suffer greatly? + +"_A._ I think not. They have made a surprising progress already. And I +am of opinion that, before their old clothes are worn out, they will +have new ones of their own making. + +"84. _Q._ If the Act is not repealed, what do you think will be the +consequence? + +"_A._ A total loss of the respect and affection the people of America +bear to this country, and of all the commerce that depends on that +respect and affection. + +"85. _Q._ How can the commerce be affected? + +"_A._ You will find that, if the Act is not repealed, they will take a +very little of your manufactures in a short time. + +"86. _Q._ Is it in their power to do without them? + +"_A._ I think they may very well do without them. + +"87. _Q._ Is it their interest not to take them? + +"_A._ The goods they take from Britain are either necessaries, mere +conveniences, or superfluities. The first, as cloth, etc., with a +little industry they can make at home; the second they can do without +till they are able to provide them among themselves; and the last, +which are much the greatest part, they will strike off immediately. +They are mere articles of fashion, purchased and consumed because the +fashion in a respected country; but will now be detested and rejected. +The people have already struck off, by general agreement, the use of +all goods fashionable in mournings, and many thousand pounds' worth +are sent back as unsaleable. + +"173. _Q._ What used to be the pride of the Americans? + +"_A._ To indulge in the fashions and manufactures of Great Britain. + +"174. _Q._ What is now their pride? + +"_A._ To wear their old clothes over again till they can make new +ones." + +The month following Franklin's examination, the repeal of the Stamp +Act received the royal assent. Thereupon Franklin sent his wife and +daughter new dresses, and a number of other little luxuries (or toilet +necessaries). + +In 1767 Franklin visited Paris. In the same year his daughter married +Mr. Richard Bache. Though Parliament had repealed the Stamp Act, it +nevertheless insisted on its right to tax the colonies. The Duty Act +was scarcely less objectionable than its predecessor. On Franklin's +return from the Continent, he heard of the retaliatory measures of the +Boston people, who had assembled in town-meetings, formally resolved +to encourage home manufactures, to abandon superfluities, and, after a +certain time, to give up the use of some articles of foreign +manufacture. These _associations_ afterwards became very general in +the colonies, so that in one year the importations by the colonists of +New York fell from L482,000 to L74,000, and in Pennsylvania from +L432,000 to L119,000. + +The effect of the Duty Act was to encourage the Dutch and other +nations to smuggle tea and probably other India produce into America. +The exclusion from the American markets of tea sent from England +placed the East India Company in great difficulties; for while they +were unable to meet their bills, they had in stock two million pounds' +worth of tea and other goods. The balance of the revenue collected +under the Duty Act, after paying salaries, etc., amounted to only L85 +for the year, and for this a fleet had to be maintained, to guard the +fifteen hundred miles of American coast; while the fall in East India +Stock deprived the revenue of L400,000 per annum, which the East India +Company would otherwise have paid. At length a licence was granted to +the East India Company to carry tea into America, duty free. This, of +course, excluded all other merchants from the American tea-trade. A +quantity of tea sent by the East India Company to Boston was destroyed +by the people. The British Government then blockaded the port. This +soon led to open hostilities. Franklin worked hard to effect a +reconciliation. He drew up a scheme, setting forth the conditions +under which he conceived a reconciliation might be brought about, and +discussed it fully with Mr. Daniel Barclay and Dr. Fothergill. This +scheme was shown to Lord Howe, and afterwards brought before the +Ministry, but was rejected. Other plans were considered, and Franklin +offered to pay for the tea which had been destroyed at Boston. All his +negotiations were, however, fruitless. At last he addressed a memorial +to the Earl of Dartmouth, Secretary of State, complaining of the +blockade of Boston, which had then continued for nine months, and had +"during every week of its continuance done damage to that town, equal +to what was suffered there by the India Company;" and claiming +reparation for such injury beyond the value of the tea which had been +destroyed. The memorial also complained of the exclusion of the +colonists from the Newfoundland fisheries, for which reparation would +one day be required. This memorial was returned to Franklin by Mr. +Walpole, and Franklin shortly afterwards returned to Philadelphia. + +During this visit to England he had lost his wife, who died on +December 19, 1774; and his friend Miss Stevenson had married and been +left a widow. + +In April, 1768, Franklin was appointed Agent for Georgia, in the +following year for New Jersey, and in 1770 for Massachusetts, so that +he was then the representative in England of four colonies, with an +income of L1200 per annum. + +In 1771 he spent three weeks at Twyford, with the Bishop of St. Asaph, +who remained a fast friend of Franklin's until his death. In 1772 he +was nominated by the King of France as Foreign Associate of the +Academy of Sciences. + +During his negotiations with the British Government Franklin wrote two +satirical pieces, setting forth the treatment which the American +colonists were receiving. The first was entitled "Rules for Reducing a +Great Empire to a Small One," the rules being precisely those which, +in Franklin's opinion, had been followed by the British Government in +its dealings with America. The other was "An Edict by the King of +Prussia," in which the king claimed the right of taxing the British +nation; of forbidding English manufacture, and compelling Englishmen +to purchase Prussian goods; of transporting prisoners to Britain, and +generally of exercising all such controls over the English people as +had been claimed over America by various Acts of the English +Parliament, on the ground that England was originally colonized by +emigrants from Prussia. + +Before Franklin reached America, the War of Independence, though not +formally declared, had fairly begun. He was appointed a member of the +second Continental Congress, and one of a committee of three to confer +with General Washington respecting the support and regulation of the +Continental Army. This latter office necessitated his spending some +time in the camp. On October 3, 1775, he wrote to Priestley:-- + + Tell our dear good friend, Dr. Price, who sometimes has his + doubts and despondencies about our firmness, that America is + determined and unanimous; a very few Tories and placemen + excepted, who will probably soon export themselves. Britain, at + the expense of three millions, has killed a hundred and fifty + Yankees this campaign, which is L20,000 a head; and at Bunker's + Hill she gained a mile of ground, half of which she lost again + by our taking the post on Ploughed Hill. During the same time + sixty thousand children have been born in America. From these + _data_ his mathematical head will easily calculate the time and + expense necessary to kill us all and conquer our whole + territory. + +In 1776 Franklin, then seventy years old, was appointed one of three +Commissioners to visit Canada, in order, if possible, to promote a +union between it and the States. Finding that only one Canadian in +five hundred could read, and that the state of feeling in Canada was +fatal to the success of the Commissioners, they returned, and Franklin +suggested that the next Commission sent to Canada should consist of +schoolmasters. On the 4th of July Franklin took part in the signing of +the Declaration of Independence. When the document was about to be +signed, Mr. Hancock remarked, "We must be unanimous; there must be no +pulling different ways; we must all hang together." Franklin replied, +"Yes, we must indeed all hang together, or most assuredly we shall all +hang separately." + +In the autumn of 1776 Franklin was unanimously chosen a Special +Commissioner to the French Court. He took with him his two grandsons, +William Temple Franklin and Benjamin Franklin Bache, and leaving +Marcus Hook on October 28, crossed the Atlantic in a sloop of sixteen +guns. In Paris he met with an enthusiastic reception. M. de Chaumont +placed at his disposal his house at Passy, then about a mile from +Paris, but now within the city. Here he resided for nine years, being +a constant visitor at the French Court, and certainly one of the most +conspicuous figures in Paris. He was obliged to serve in many +capacities, and was very much burdened with work. Not only were there +his duties as Commissioner at the French Court, but he was also made +Admiralty Judge and Financial Agent, so that all the coupons for the +payment of interest on the money borrowed for the prosecution of the +war, as well as all financial negotiations, either with the French +Government or contractors, had to pass through his hands. Perhaps the +most unpleasant part of his work was his continued applications to the +French Court for monetary advances. The French Government, as is well +known, warmly espoused the cause of the Americans, and to the utmost +of its ability assisted them with money, material, and men. Franklin +was worried a good deal by applications from French officers for +introductions to General Washington, that they might obtain employment +in the American Army. At last he framed a model letter of +recommendation, which may be useful to many in this country in the +present day. It was as follows:-- + + SIR, + + The bearer of this, who is going to America, presses me to give + him a letter of recommendation, though I know nothing of him, + not even his name. This may seem extraordinary, but I assure you + it is not uncommon here. Sometimes, indeed, one unknown person + brings another equally unknown, to recommend him; and sometimes + they recommend one another! As to this gentleman, I must refer + you to himself for his character and merits, with which he is + certainly better acquainted than I can possibly be. I recommend + him, however, to those civilities which every stranger, of whom + one knows no harm, has a right to; and I request you will do him + all the good offices and show him all the favour that, on + further acquaintance, you shall find him to deserve. + + "I have the honour to be," etc. + +Captain Wickes, of the _Refusal_, having taken about a hundred British +seamen prisoners, Franklin and Silas Deane, one of the other +Commissioners, wrote to Lord Stormont, the British ambassador, +respecting an exchange. Receiving no answer, they wrote again, and +ventured to complain of the treatment which the American prisoners +were receiving in the English prisons, and in being compelled to fight +against their own countrymen. To this communication Lord Stormont +replied:-- + + The king's ambassador receives no applications from rebels, + unless they come to implore his Majesty's mercy. + +To this the Commissioners rejoined:-- + + In answer to a letter, which concerns some of the most material + interests of humanity, and of the two nations, Great Britain and + the United States of America, now at war, we received the + enclosed _indecent_ paper, as coming from your Lordship, which + we return for your Lordship's more mature consideration. + +At first the British Government, regarding the Americans as rebels, +did not treat their prisoners as prisoners of war, but threatened to +try them for high treason. Their sufferings in the English prisons +were very great. Mr. David Hartley did much to relieve them, and +Franklin transmitted money for the purpose. When a treaty had been +formed between France and the States, and France had engaged in the +war, and when fortune began to turn in favour of the united armies, +the American prisoners received better treatment from the English +Government, and exchanges took place freely. In April, 1778, Mr. +Hartley visited Franklin at Passy, apparently for the purpose of +preventing, if possible, the offensive and defensive alliance between +America and France. Very many attempts were made to produce a rupture +between the French Government and the American Commissioners, but +Franklin insisted that no treaty of peace could be made between +England and America in which France was not included. In 1779 the +other Commissioners were recalled, and Franklin was made Minister +Plenipotentiary to the Court of France. + +In a letter to Mr. David Hartley, dated February 2, 1780, Franklin +showed something of the feelings of the Americans with respect to the +English at that time:-- + + You may have heard that accounts upon oath have been taken in + America, by order of Congress, of the British barbarities + committed there. It is expected of me to make a school-book of + them, and to have thirty-five prints designed here by good + artists, and engraved, each expressing one or more of the horrid + facts, in order to impress the minds of children and posterity + with a deep sense of your bloody and insatiable malice and + wickedness. Every kindness I hear of done by an Englishman to an + American prisoner makes me resolve not to proceed in the work. + +While at Passy, Franklin addressed to the _Journal of Paris_ a paper +on an economical project for diminishing the cost of light. The +proposal was to utilize the sunlight instead of candles, and thereby +save to the city of Paris the sum of 96,075,000 livres per annum. His +reputation in Paris is shown by the following quotation from a +contemporary writer:-- + + I do not often speak of Mr. Franklin, because the gazettes tell + you enough of him. However, I will say to you that our Parisians + are no more sensible in their attentions to him than they were + towards Voltaire, of whom they have not spoken since the day + following his death. Mr. Franklin is besieged, followed, + admired, adored, wherever he shows himself, with a fury, a + fanaticism, capable no doubt of flattering him and of doing him + honour, but which at the same time proves that we shall never be + reasonable, and that the virtues and better qualities of our + nation will always be balanced by a levity, an inconsequence, + and an enthusiasm too excessive to be durable. + +Franklin always advocated free trade, even in time of war. He was of +opinion that the merchant, the agriculturist, and the fisherman were +benefactors to mankind. He condemned privateering in every form, and +endeavoured to bring about an agreement between all the civilized +powers against the fitting out of privateers. He held that no +merchantmen should be interfered with unless carrying war material. He +greatly lamented the horrors of the war, but preferred anything to a +dishonourable peace. To Priestley he wrote:-- + + Perhaps as you grow older you may ... repent of having murdered + in mephitic air so many honest, harmless mice, and wish that, to + prevent mischief, you had used boys and girls instead of them. + In what light we are viewed by superior beings may be gathered + from a piece of late West India news, which possibly has not yet + reached you. A young angel of distinction, being sent down to + this world on some business for the first time, had an old + courier-spirit assigned him as a guide. They arrived over the + seas of Martinico, in the middle of the long day of obstinate + fight between the fleets of Rodney and De Grasse. When, through + the clouds of smoke, he saw the fire of the guns, the decks + covered with mangled limbs and bodies dead or dying; the ships + sinking, burning, or blown into the air; and the quantity of + pain, misery, and destruction the crews yet alive were thus with + so much eagerness dealing round to one another,--he turned + angrily to his guide, and said, 'You blundering blockhead, you + are ignorant of your business; you undertook to conduct me to + the earth, and you have brought me into hell!' 'No, sir,' says + the guide, 'I have made no mistake; this is really the earth, + and these are men. Devils never treat one another in this cruel + manner; they have more sense and more of what men (vainly) call + humanity.' + +Franklin maintained that it would be far cheaper for a nation to +extend its possessions by purchase from other nations than to pay the +cost of war for the sake of conquest. + +Two British armies, under General Burgoyne and Lord Cornwallis, having +been wholly taken prisoners during the war, at last, after two years' +negotiations, a definitive treaty of peace was signed on September 3, +1782, between Great Britain and the United States, Franklin being one +of the Commissioners for the latter, and Mr. Hartley for the former. +On the same day a treaty of peace between Great Britain and France was +signed at Versailles. The United States Treaty was ratified by the +king on April 9, and therewith terminated the seven years' War of +Independence. Franklin celebrated the surrender of the armies of +Burgoyne and Cornwallis by a medal, on which the infant Hercules +appears strangling two serpents. + +When peace was at length realized, a scheme was proposed for an +hereditary knighthood of the order of Cincinnatus, to be bestowed upon +the American officers who had distinguished themselves in the war. +Franklin condemned the hereditary principle. He pointed out that, in +the ninth generation, the "young noble" would be only "one five +hundred and twelfth part of the present knight," 1022 men and women +being counted among his ancestors, reckoning only from the foundation +of the knighthood. "Posterity will have much reason to boast of the +noble blood of the then existing set of Chevaliers of Cincinnatus." + +On May 2, 1785, Franklin received from Congress permission to return +to America. He was then in his eightieth year. On July 12 he left +Passy for Havre, whence he crossed to Southampton, and there saw for +the last time his old friend, the Bishop of St. Asaph, and his family. +He reached his home in Philadelphia early in September, and the day +after his arrival he received a congratulatory address from the +Assembly of Pennsylvania. In the following month he was elected +President of the State, and was twice re-elected to the same office, +it being contrary to the constitution for any president to be elected +for more than three years in succession. + +The following extract from a letter, written most probably to Tom +Paine, is worthy of the attention of some writers:-- + + I have read your manuscript with some attention. By the argument + it contains against a particular Providence, though you allow a + general Providence, you strike at the foundations of all + religion. For without the belief of a Providence that takes + cognizance of, guards, and guides, and may favour particular + persons, there is no motive to worship a Deity, to fear His + displeasure, or to pray for His protection. I will not enter + into any discussion of your principles, though you seem to + desire it. At present I shall only give you my opinion, that, + though your reasonings are subtle, and may prevail with some + readers, you will not succeed so as to change the general + sentiments of mankind on that subject, and the consequence of + printing this piece will be a great deal of odium drawn upon + yourself, mischief to you, and no benefit to others. He that + spits against the wind spits in his own face. + + But were you to succeed, do you imagine any good would be done + by it? You yourself may find it easy to live a virtuous life + without the assistance afforded by religion; you having a clear + perception of the advantages of virtue and the disadvantages of + vice, and possessing strength of resolution sufficient to enable + you to resist common temptations. But think how great a portion + of mankind consists of weak and ignorant men and women, and of + inexperienced, inconsiderate youth of both sexes, who have need + of the motives of religion to restrain them from vice, to + support their virtue, and retain them in the practice of it till + it becomes _habitual_, which is the great point for its + security. And perhaps you are indebted to her originally, that + is, to your religious education, for the habits of virtue upon + which you now justly value yourself. You might easily display + your excellent talents of reasoning upon a less hazardous + subject, and thereby obtain a rank with our most distinguished + authors. For among us it is not necessary, as among the + Hottentots, that a youth, to be raised into the company of men, + should prove his manhood by beating his mother. + + I would advise you, therefore, not to attempt unchaining the + tiger, but to burn this piece before it is seen by any other + person; whereby you will save yourself a great deal of + mortification by the enemies it may raise against you, and + perhaps a good deal of regret and repentance. If men are so + wicked _with religion_, what would they be _if without_ it? I + intend this letter itself as a _proof_ of my friendship, and + therefore add no _professions_ to it; but subscribe simply + yours. + +During the last few years of his life Franklin suffered from a painful +disease, which confined him to his bed and seriously interfered with +his literary work, preventing him from completing his biography. +During this time he was cared for by his daughter, Mrs. Bache, who +resided in the same house with him. He died on April 17, 1790, the +immediate cause of death being an affection of the lungs. He was +buried beside his wife in the cemetery of Christ Church, Philadelphia, +the marble slab upon the grave bearing no other inscription than the +name and date of death. In his early days (1728) he had written the +following epitaph for himself:-- + + THE BODY + + OF + + BENJAMIN FRANKLIN, + + PRINTER, + + (LIKE THE COVER OF AN OLD BOOK, + ITS CONTENTS TORN OUT + AND STRIPT OF ITS LETTERING AND GILDING,) + LIES HERE, FOOD FOR WORMS. + BUT THE WORK SHALL NOT BE LOST, + FOR IT WILL (AS HE BELIEVED) APPEAR ONCE MORE + IN A NEW AND MORE ELEGANT EDITION, + REVISED AND CORRECTED + BY + + THE AUTHOR. + +When the news of his death reached the National Assembly of France, +Mirabeau rose and said:-- + +"Franklin is dead! + +"The genius, which gave freedom to America, and scattered torrents of +light upon Europe, is returned to the bosom of the Divinity. + +"The sage, whom two worlds claim; the man, disputed by the history of +the sciences and the history of empires, holds, most undoubtedly, an +elevated rank among the human species. + +"Political cabinets have but too long notified the death of those who +were never great but in their funeral orations; the etiquette of +courts has but too long sanctioned hypocritical grief. Nations ought +only to mourn for their benefactors; the representatives of free men +ought never to recommend any other than the heroes of humanity to +their homage. + +"The Congress hath ordered a general mourning for one month throughout +the fourteen confederated States on account of the death of Franklin; +and America hath thus acquitted her tribute of admiration in behalf of +one of the fathers of her constitution. + +"Would it not be worthy of you, fellow-legislators, to unite +yourselves in this religious act, to participate in this homage +rendered in the face of the universe to the rights of man, and to the +philosopher who has so eminently propagated the conquest of them +throughout the world? + +"Antiquity would have elevated altars to that mortal who, for the +advantage of the human race, embracing both heaven and earth in his +vast and extensive mind, knew how to subdue thunder and tyranny. + +"Enlightened and free, Europe at least owes its remembrance and its +regret to one of the greatest men who has ever served the cause of +philosophy and liberty. + +"I propose, therefore, that a decree do now pass, enacting that the +National Assembly shall wear mourning during three days for Benjamin +Franklin." + + + + +HENRY CAVENDISH. + + +It would not be easy to mention two men between whom there was a +greater contrast, both in respect of their characters and lives, than +that which existed between Benjamin Franklin and the Honourable Henry +Cavendish. The former of humble birth, but of great public spirit, +possessed social qualities which were on a par with his scientific +attainments, and toward the close of his life was more renowned as a +statesman than as a philosopher; the latter, a member of one of the +most noble families of England, and possessed of wealth far exceeding +his own capacity for the enjoyment of it, was known to very few, was +intimate with no one, and devoted himself to scientific pursuits +rather for the sake of the satisfaction which his results afforded to +himself than from any hope that they might be useful to mankind, or +from any desire to secure a reputation by making them known, and +passed a long life, the most uneventful that can be imagined. + +Though the records of his family may be traced to the Norman +Conquest, the famous Elizabeth Hardwicke, the foundress of two ducal +families and the builder of Hardwicke Hall and of Chatsworth as it was +before the erection of the present mansion, was the most remarkable +person in the genealogy. Her second son, William, was raised to the +peerage by James I., thus becoming Baron Cavendish, and was +subsequently created first Earl of Devonshire by the same monarch. His +great-grandson, the fourth earl, was created first Duke of Devonshire +by William III., to whom he had rendered valuable services. He was +succeeded by his eldest son in 1707, and the third son of the second +duke was Lord Charles Cavendish, the father of Henry and Frederick, of +whom Henry was the elder, having been born at Nice, October 13, 1731. +His mother died when he was two years old, and very little indeed is +known respecting his early life. In 1742 he entered Dr. Newcome's +school at Hackney, where he remained until he entered Peterhouse, in +1749. He remained at Cambridge until February, 1753, when he left the +university without taking his degree, objecting, most probably, to the +religious tests which were then required of all graduates. In this +respect his brother Frederick followed his example. On leaving +Cambridge Cavendish appears to have resided with his father in +Marlborough Street, and to have occasionally assisted him in his +scientific experiments, but the investigations of the son soon +eclipsed those of the father. It is said that the rooms allotted to +Henry Cavendish "were a set of stables, fitted up for his +accommodation," and here he carried out many of his experiments, +including all those electrical investigations in which he forestalled +so much of the work of the present century. + +During his father's life, or, at any rate, till within a few years of +its close, Henry Cavendish appears to have enjoyed a very narrow +income. He frequently dined at the Royal Society Club, and on these +occasions would come provided with the five shillings to be paid for +the dinner, but no more. Upon his father's death, which took place in +1783, when Henry was more than fifty years of age, his circumstances +were very much changed, but it seems that the greater part of his +wealth was left him by an uncle who had been an Indian officer, and +this legacy may have come into his possession before his father's +death. He appears to have been very liberal when it was suggested to +him that his assistance would be of service, but it never occurred to +him to offer a contribution towards any scientific or public +undertaking, and though at the time of his death he is said to have +had more money in the funds than any other person in the country, +besides a balance of L50,000 on his current account at his bank, and +various other property, he bequeathed none to scientific societies or +similar institutions. Throughout the latter part of his life he seems +to have been quite careless about money, and to have been satisfied if +he could only avoid the trouble of attending to his own financial +affairs. Hence he would allow enormous sums to accumulate at his +banker's, and on one occasion, being present at a christening, and +hearing that it was customary for guests to give something to the +nurse, he drew from his pocket a handful of guineas, and handed them +to her without counting them. After his father's death, Cavendish +resided in his own house on Clapham Common. Here a few rooms at the +top of the house were made habitable; the rest were filled with +apparatus of all descriptions, among which the most numerous examples +were thermometers of every kind. He seldom entertained visitors, but +when, on rare occasions, a guest had to be entertained, the repast +invariably consisted of a leg of mutton. His extreme shyness caused +him to dislike all kinds of company, and he had a special aversion to +being addressed by a stranger. On one occasion, at a reception given +by Sir Joseph Banks, Dr. Ingenhousz introduced to him a distinguished +Austrian philosopher, who professed that his main object in coming to +England was to obtain a sight of so distinguished a man. Cavendish +listened with his gaze fixed on the floor; then, observing a gap in +the crowd, he made a rush to the door, nor did he pause till he had +reached his carriage. His aversion to women was still greater; his +orders for the day he would write out and leave at a stated time on +the hall-table, where his house-keeper, at another stated time, would +find them. Servants were allowed access to the portion of the house +which he occupied only at fixed times when he was away; and having +once met a servant on the stairs, a back staircase was immediately +erected. His regular walk was down Nightingale Lane to Wandsworth +Common, and home by another route. On one occasion, as he was crossing +a stile, he saw that he was watched, and thenceforth he took his walks +in the evening, but never along the same road. There were only two +occasions on which it is recorded that scientific men were admitted to +Cavendish's laboratory. The first was in 1775, when Hunter, Priestley, +Romayne, Lane, and Nairne were invited to see the experiments with the +artificial torpedo. The second was when his experiment on the +formation of nitric acid by electric sparks in air had been +unsuccessfully attempted by Van Marum, Lavoisier, and Monge, and he +"thought it right to take some measures to authenticate the truth of +it." + +Besides his house at Clapham, Cavendish occupied (by his instruments) +a house in Bloomsbury, near the British Museum, while a "mansion" in +Dean Street, Soho, was set apart as a library. To this library a +number of persons were admitted, who could take out the books on +depositing a receipt for them. Cavendish was perfectly methodical in +all his actions, and whenever he borrowed one of his own books he duly +left the receipt in its place. The only relief to his solitary life +was afforded by the meetings of the Royal Society, of which he was +elected a Fellow in 1760; by the occasional receptions at the +residence of Sir Joseph Banks, P.R.S.; and by his not infrequent +dinners with the Royal Society Club at the Crown and Anchor; and he +may sometimes have joined the social gatherings of another club which +met at the Cat and Bagpipes, in Downing Street. It was to his visits +to the Royal Society Club that we are indebted for the only portrait +that exists of him. Alexander, the draughtsman to the China Embassy, +was bent upon procuring a portrait of Cavendish, and induced a friend +to invite him to the club dinner, "where he could easily succeed, by +taking his seat near the end of the table, from whence he could sketch +the peculiar great-coat of a greyish-green colour, and the remarkable +three-cornered hat, invariably worn by Cavendish, and obtain, +unobserved, such an outline of the face as, when inserted between the +hat and coat, would make, he was quite sure, a full-length portrait +that no one could mistake. It was so contrived, and every one who saw +it recognized it at once." Another incident is recorded of the Royal +Society Club which, perhaps, reflects as much credit upon Cavendish as +upon the Society. "One evening we observed a very pretty girl looking +out from an upper window on the opposite side of the street, watching +the philosophers at dinner. She attracted notice, and one by one we +got up and mustered round the window to admire the fair one. +Cavendish, who thought we were looking at the moon, hustled up to us +in his odd way, and when he saw the real object of our study, turned +away with intense disgust, and grunted out, 'Pshaw!'" + +In the spring and autumn of 1785, 1786, 1787, and 1793, Cavendish made +tours through most of the southern, midland, and western counties, and +reached as far north as Whitby. The most memorable of these journeys +was that undertaken in 1785, since during its course he visited James +Watt at the Soho Works, and manifested great interest in Watt's +inventions. This was only two years after the great controversy as to +the discovery of the composition of water, but the meeting of the +philosophers was of the most friendly character. On all these journeys +considerable attention was paid to the geology of the country. + +Allusion has already been made to the two committees of the Royal +Society to which the questions of the lightning-conductors at +Purfleet, and of points _versus_ knobs for the terminals of +conductors, were referred. Cavendish served on each of these +committees, and supported Franklin's view against the recommendation +of Mr. Wilson. On the first committee he probably came into personal +communication with Franklin himself. + +Cavendish's life consisted almost entirely of his philosophical +experiments. In other respects it was nearly without incident. He +appears to have been so constituted that he must subject everything to +accurate measurement. He rarely made experiments which were not +_quantitative_; and he may be regarded as the founder of "quantitative +philosophy." The labour which he expended over some of his +measurements must have been very great, and the accuracy of many of +his results is marvellous considering the appliances he had at +disposal. When he had satisfied himself with the result of an +experiment, he wrote out a full account and preserved it, but very +seldom gave it to the public, and when he did publish accounts of any +of his investigations it was usually a long time after the experiments +had been completed. One of the consequences of his reluctance to +publish anything was the long controversy on the discovery of the +composition of water, which was revived many years afterwards by +Arago's _eloge_ on James Watt; but a much more serious result was the +loss to the world for so many years of discoveries and measurements +which had to be made over again by Faraday, Kohlrausch, and others. +The papers he published appeared in the _Philosophical Transactions of +the Royal Society_, to which he began to communicate them in 1766. On +March 25, 1803, he was elected one of the eight Foreign Associates of +the Institute of France. His _eloge_ was pronounced by Cuvier, in +1812, who said, "His demeanour and the modest tone of his writings +procured him the uncommon distinction of never having his repose +disturbed either by jealousy or by criticism." Dr. Wilson says, "He +was almost passionless. All that needed for its apprehension more than +the pure intellect, or required the exercise of fancy, imagination, +affection, or faith, was distasteful to Cavendish. An intellectual +head thinking, a pair of wonderfully acute eyes observing, and a pair +of very skilful hands experimenting or recording, are all that I +realize in reading his memorials." He appeared to have no eye for +beauty; he cared nothing for natural scenery, and his apparatus, +provided it were efficient, might be clumsy in appearance and of the +cheapest materials; but he was extremely particular about accuracy of +construction in all essential details. He reminds us of one of our +foremost men of science, who, when his attention was directed to the +beautiful lantern tower of a cathedral, behind which the full moon was +shining, remarked, "I see form and colour, but I don't know what you +mean by beauty." + +The accounts of Cavendish's death differ to some extent in their +details, but otherwise are very similar. It appears that he requested +his servant, "as he had something particular to engage his thoughts, +and did not wish to be disturbed by any one," to leave him and not to +return until a certain hour. When the servant came back, at the time +appointed, he found his master dead. This was on February 24, 1810, +after an illness of only two or three days. + +It is mainly on account of his researches in electricity that the +biography of Cavendish finds a place in this volume. These +investigations took place between the years 1760 and 1783, and, as +already stated, were all conducted in the stables attached to his +father's house in Marlborough Street. It was by these experiments that +electricity was first brought within the domain of measurement, and +many of the numerical results obtained far exceeded in accuracy those +of any other observer until the instruments of Sir W. Thomson rendered +many electrical measurements a comparatively easy matter. The near +agreement of Cavendish's results with those of the best modern +electricians has made them a perpetual monument to the genius of their +author. It was at the request of Sir W. Thomson, Mr. Charles +Tomlinson, and others, that Cavendish's electrical researches might be +given to the public, that the Duke of Devonshire, in 1874, entrusted +the manuscripts to the care of the late Professor Clerk Maxwell. They +had previously been in the hands of Sir William Snow Harris, who +reported upon them, but after his death, in 1867, the report could not +be found. The papers, with an introduction and a number of very +valuable notes by the editor, were published by the Cambridge +University Press, just before the death of Clerk Maxwell, in 1879. Sir +W. Thomson quotes the following illustration of the accuracy of +Cavendish's work:--"I find already that the capacity of a disc was +determined experimentally by Cavendish as 1/1.57 of that of a sphere +of the same radius. Now we have capacity of disc = (2/[pi])_a_ = +_a_/1.571!" + +Cavendish adopted Franklin's theory of electricity, treating it as an +incompressible fluid pervading all bodies, and admitting of +displacement only in a closed circuit, unless, indeed, the disturbance +might extend to infinity. This fluid he supposed, with Franklin, to be +self-repulsive, but to attract matter, while matter devoid of +electricity, and therefore in the highest possible condition of +negative electrification, he supposed, with AEpinus, to be, like +electricity, self-repulsive. One of Cavendish's earliest experiments +was the determination of the precise law according to which electrical +action varies with the distance between the charges. Franklin had +shown that there was no sensible amount of electricity on the interior +of a deep hollow vessel, however its exterior surface might be +charged. Cavendish mounted a sphere of 12.1 inches in diameter, so +that it could be completely enclosed (except where its insulating +support passed through) within two hemispheres of 13.3 inches +diameter, which were carried by hinged frames, and could thus be +allowed to close completely over the sphere, or opened and removed +altogether from its neighbourhood. A piece of wire passed through one +of the hemispheres so as to touch the inner sphere, but could be +removed at pleasure by means of a silk string. The hemispheres being +closed with the globe within them, and the wire inserted so as to make +communication between the inner and outer spheres, the whole apparatus +was electrified by a wire from a charged Leyden jar. This wire was +then removed by means of a silken string and "the same motion of the +hand which drew away the wire by which the hemispheres were +electrified, immediately after that was done, drew out the wire which +made the communication between the hemispheres and the inner globe, +and, immediately after that was drawn out, separated the hemispheres +from each other," and applied the electrometer to the inner globe. "It +was also contrived so that the electricity of the hemispheres and of +the wire by which they were electrified was discharged as soon as they +were separated from each other.... The inner globe and hemispheres +were also both coated with tinfoil to make them the more perfect +conductors of electricity." The electrometer consisted of a pair of +pith-balls; but, though the experiment was several times repeated, +they shewed no signs of electrification. From this it was clear that, +as there could have been no communication between the globe and +hemispheres when the connecting wire was withdrawn, there must have +been no electrification on the globe while the hemispheres, though +themselves highly charged, surrounded it. To test the delicacy of the +experiment, a charge was given to the globe less than one-sixtieth of +that previously given to the hemispheres, and this was readily +detected by the electrometer. From the result Cavendish inferred that +there is no reason to think the inner globe to be at all charged +during the experiment. "Hence it follows that the electric attraction +and repulsion must be inversely as the square of the distance, and +that, when a globe is positively electrified, the redundant fluid in +it is lodged entirely on its surface." This conclusion Cavendish +showed to be a mathematical consequence of the absence of +electrification from the inner sphere; for, were the law otherwise, +the inner sphere must be electrified positively or negatively, +according as the inverse power were higher or lower than the second, +and that the accuracy of the experiment showed the law must lie +between the 2-1/50 and the 1-49/50 power of the distance. With his +torsion-balance, Coulomb obtained the same law, but Cavendish's method +is much easier to carry out, and admits of much greater accuracy than +that of Coulomb. Cavendish's experiment was repeated by Dr. +MacAlister, under the superintendence of Clerk Maxwell, in the +Cavendish Laboratory, the absence of electrification being tested by +Thomson's quadrant electrometer, and it was shown that the deviation +from the law of inverse squares could not exceed one in 72,000. + +The distinction between _electrical charge_ or _quantity of +electricity_ and "_degree of electrification_" was first clearly made +by Cavendish. The latter phrase was subsequently replaced by +_intensity_, but _electric intensity_ is now used in another sense. +Cavendish's phrase, _degree of electrification_, corresponds precisely +with our notion of electric _potential_, and is measured by the work +done on a unit of electricity by the electric forces in removing it +from the point in question to the earth or to infinity. Along with +this notion Cavendish introduced the further conception of the amount +of electricity required to raise a conductor to a given degree of +electrification, that is, the capacity of the conductor. In modern +language, the _capacity_ of a conductor is defined as "the number of +units of electricity required to raise it to unit potential;" and this +definition is in precise accordance with the notion of Cavendish, who +may be regarded as the founder of the mathematical theory of +electricity. Finding that the capacities of similar conductors are +proportional to their linear dimensions, he adopted a sphere of one +inch diameter as the unit of capacity, and when he speaks of a +capacity of so many "inches of electricity," he means a capacity so +many times that of his one-inch sphere, or equal to that of a sphere +whose diameter is so many inches. The modern unit of capacity in the +electro-static system is that of a sphere of _one centimetre radius_, +and the capacity of any sphere is numerically equal to its radius +expressed in centimetres. Cavendish determined the capacities of +nearly all the pieces of apparatus he employed. For this purpose he +prepared plates of glass, coated on each side with circles of tinfoil, +and arranged in three sets of three, each plate of a set having the +same capacity, but each set having three times the capacity of the +preceding. There was also a tenth plate, having a capacity equal to +the whole of the largest set. The capacity of the ten plates was thus +sixty-six times that of one of the smallest set. With these as +standards of comparison, he measured the capacities of his other +apparatus, and, when possible, modified his conductors so as to make +them equal to one of his standards. His large Leyden battery he found +to have a capacity of about 321,000 "inches of electricity," so that +it was equivalent to a sphere more than five miles in diameter. One of +his instruments employed in the measurement of capacities was a "trial +plate," consisting of a sheet of metal, with a second sheet which +could be made to slide upon it and to lie entirely on the top of the +larger plate, or to rest with any portion of its area extending over +the edge of the former. This was a conductor whose capacity could be +varied at will within certain limits. Finding the capacity of two +plates of tinfoil on glass much greater than his calculations led him +to expect, Cavendish compared them with two equal plates having air +between, and found their capacity very much to exceed that of the air +condenser. The same was the case, though in a less degree, with +condensers having shellac or bee's-wax for their dielectrics, and thus +Cavendish not only discovered the property to which Faraday afterwards +gave the name of "specific inductive capacity," but determined its +measure in these dielectrics. He also discovered that the apparent +capacity of a Leyden jar increases at first for some time after it has +been charged--a phenomenon connected with the so-called residual +charge of the Leyden jar. Another feature on which he laid some +stress, and which was brought to his notice by the comparison of his +coated panes, was the creeping of electricity over the surface of the +glass beyond the edge of the tinfoil, which had the same effect on the +capacity as an increase in the dimensions of the tinfoil. The +electricity appeared to spread to a distance of 0.07 inch all round +the tinfoil on glass plates whose thickness was 0.21 inch, and 0.09 +inch in the case of plates 0.08 inch thick. + +His paper on the torpedo was read before the Royal Society in 1776. +The experiments were undertaken in order to determine whether the +phenomena observed by Mr. John Walsh in connection with the torpedo +could be so far imitated by electricity as to justify the conclusion +that the shock of the torpedo is an electric discharge. For this +purpose Cavendish constructed a wooden torpedo with electrical organs, +consisting of a pewter plate on each side, covered with leather. The +plates were connected with a charged Leyden battery, by means of wires +carried in glass tubes, and thus the battery was discharged through +the water in which the torpedo was immersed, and which was rendered of +about the same degree of saltness as the sea. Cavendish compared the +shock given through the water with that given by the model fish in +air, and found the difference much greater than in the case of the +real torpedo, but, by increasing the capacity of the battery and +diminishing the potential to which it was charged, this discrepancy +was diminished, and it was found to be very much less in the case of a +second model having a leather, instead of a wooden, body, so that the +body of the fish itself offered less resistance to the discharge. One +of the chief difficulties lay in the fact that no one had succeeded in +obtaining a visible spark from the discharge of the torpedo, which +will not pass through the smallest thickness of air. Cavendish +accounted for this by supposing the quantity of electricity discharged +to be very great, and its potential very small, and showed that the +more the charge was increased and the potential diminished in his +model, the more closely did it imitate the behaviour of the torpedo. + +But the main interest in this paper lies in the indications which it +gives that Cavendish was aware of the laws which regulate the flow of +electricity through multiple conductors, and in the comparisons of +electrical resistance which are introduced. It had been formerly +believed that electricity would always select the shortest or best +path, and that the whole of the discharge would take place along that +route. Franklin seems to have assumed this in the passage quoted[4] +respecting the discharge of the lightning down the uninsulated +conductor instead of through the building. The truth, however, is +that, when a number of paths are open to an electric current, it will +divide itself between them in the inverse ratios of their resistances, +or directly as their conductivities, so that, however great the +resistance of one of the conductors, some portion, though it may be a +very small fraction, of the discharge will take place through it. But +this law does not hold in the case of insulators like the air, through +which electricity passes only by disruptive discharges, and which +completely prevent its passage unless the electro-motive force is +sufficient to break through their substance. In the case of the +lightning-conductor, however, its resistance is generally so small in +comparison with that of the building it is used to protect, that +Franklin's conclusion is practically correct. + +[Footnote 4: Page 96.] + +In his paper on the torpedo Cavendish stated that some experiments had +shown that iron wire conducted 400,000,000 times better than rain or +distilled water, sea-water 100 times, and saturated solution of +sea-salt about 720 times, better than rain-water. Maxwell pointed out +that this comparison of iron wire with sea-water would agree almost +precisely with the measurements of Matthiesen and Kohlrausch at 11 deg.C. +The records of the experiments which led to these results were found +among Cavendish's unpublished papers, and the experiments also showed +that the conductivity of saline solutions was very nearly proportional +to the percentage of salt contained, when this was not very large--a +result also obtained long afterwards by Kohlrausch. In making these +measurements Cavendish was his own galvanometer. The solutions were +contained in glass tubes more than three feet long, and a wire +inserted to different distances into the solution; thus the discharge +could be made to pass through any length of the liquid column less +than that of the tube itself. From the Leyden battery of forty-nine +jars, six jars of nearly equal capacity were selected and charged +together, and the charge of one jar only was employed for each shock. +The discharge passed through the column of liquid contained in the +tube, from a wire inserted at the further end, until it reached the +sliding wire, when nearly the whole current betook itself to the wire +on account of its smaller resistance, and thence passed through the +galvanometer, which was Cavendish himself. Two tubes were generally +compared together, and the jars discharged alternately through the +tubes, and the tube which gave the greatest shock was assumed to +possess the least resistance. The wires were then adjusted till the +shocks were nearly equal, and positions determined which made the +first tube possess a greater and then a less resistance than the +second. From these positions the length of the column of liquid was +estimated which would make the resistances of the two tubes exactly +equal. But the result which has the greatest theoretical interest was +obtained by discharging the Leyden jars through wide and narrow tubes +containing the same solutions. By these experiments Cavendish found +that the resistances of the conductors were independent of the +strengths of the currents flowing in them; that is to say, he +established Ohm's law for electrolytes in a form which carried with it +its full explanation. This was in January, 1781. Ohm's law was first +formally stated in 1827. The physical fact which is expressed by it is +that the ratio of the electro-motive force to the current produced is +the same for the same conductor, otherwise under the same physical +conditions, however great or small that electro-motive force may be. + +Cavendish devoted considerable attention to the subject of heat, +especially thermometry. In many of his investigations on latent and +specific heat he worked on the same lines as Black, and at about the +same time; but it is difficult to determine the exact date of some of +Cavendish's work, as he frequently did not publish it for a long time +after its completion, and most of Black's results were made public +only to his lecture audience. Cavendish, however, improved upon Black +in his mode of stating some of his results. The heat, for instance, +which is absorbed by a body in passing from the solid to the liquid, +or from the liquid to the gaseous, condition, Black called "latent +heat," and supposed it to become latent within the substance, ready to +reveal itself when the body returned to its original condition. This +heat Cavendish spoke of as being _destroyed_ or _generated_, and this +is in accordance with what we now know respecting the nature of heat, +for when a body passes from the solid to the liquid, or from the +liquid or solid to the gaseous, condition, a certain amount of work +has to be done, and a corresponding amount of heat is used up in the +doing of it. When the body returns to its original condition, the heat +is restored, as when a heavy body falls to the ground, or a bent +spring returns to its original form. Cavendish's determination of the +so-called latent heat of steam was very slightly in error. + +About 1760 very extraordinary beliefs were current respecting the +excessive degree of cold and the rapid variations of temperature which +take place in the Arctic regions. Braun, of St. Petersburg, had +observed that mercury, in solidifying in the tube of a thermometer, +descended through more than four hundred degrees, and it was assumed +that the melting point of mercury was about 400 deg. below Fahrenheit's +zero. It then became necessary to suppose that, while the mercury in a +thermometer was freezing, there was a variation of temperature to this +extent, and thus these wild reports became current. Cavendish and +Black independently explained the anomaly, and each suggested the same +method of determining the freezing point of mercury. Cavendish, +however, had a piece of apparatus prepared which he sent to Governor +Hutchins, at Albany Fort, Hudson's Bay. It consisted of an outer +vessel, in which the mercury was allowed to freeze, but not throughout +the whole of its mass, and the bulb of the thermometer was kept +immersed in the liquid metal in the interior. In this way the mercury +in the thermometer was cooled down to the melting point without +commencing to solidify, and the temperature was found to be between +39 deg. and 40 deg. below Fahrenheit's zero. + +As a chemist, Cavendish is renowned for his eudiometric analysis, +whereby he determined the percentage of oxygen in air with an amount +of accuracy that would be creditable to a chemist of to-day, and for +his discovery of the composition of water; but to the world generally +he is perhaps best known by the famous "Cavendish experiment" for +determining the mass, and hence the mean density, of the earth. The +apparatus was originally suggested by the Rev. John Michell, but was +first employed by Cavendish, who thereby determined the mean density +of the earth to be 5.45. At the request of the Astronomical Society, +the investigation was afterwards taken up by Mr. Francis Baily, who, +after much labour, discovered that the principal sources of error were +due to radiation of heat, and consequent variation of temperature of +parts of the apparatus during the experiment. To minimize the +radiation and absorption, he gilded the principal portions of the +apparatus and the interior of the case in which it was contained, and +his results then became consistent. Cavendish had himself suggested +the cause of the discrepancy, but the gilding was proposed by +Principal Forbes. As a mean of many hundreds of experiments, Mr. Baily +deduced for the mean density of the earth 5.6604. Cavendish's +apparatus was a delicate torsion-balance, whereby two leaden balls +were supported upon the extremities of a wooden rod, which was +suspended by a thin wire. These balls were about two inches in +diameter, and the experiment consisted in determining the deflection +of the wooden arm by the attraction of two large solid spheres of lead +brought very near the balls, and so situated that the attraction of +each tended to twist the rod horizontally in the same direction. The +force required to produce the observed deflection was calculated from +the time of swing of the rod and balls when left to themselves. The +force exerted upon either ball by a known spherical mass of metal, +with its centre at a known distance, being thus determined, it was +easy to calculate what mass, having its centre at the centre of the +earth, would be required to attract one of the balls with the force +with which the earth was known to attract it. + +Dr. Wilson sums up Cavendish's view of life in these words:-- + + His theory of the universe seems to have been that it consisted + _solely_ of a multitude of objects which could be weighed, + numbered, and measured; and the vocation to which he considered + himself called was to weigh, number, and measure as many of + these objects as his allotted three score years and ten would + permit. This conviction biased all his doings--alike his great + scientific enterprises and the petty details of his daily life. + [Greek: _Panta metro, kai arithmo, kai stathmo_], was his motto; + and in the microcosm of his own nature he tried to reflect and + repeat the subjection to inflexible rule and the necessitated + harmony which are the appointed conditions of the macrocosm of + God's universe. + + + + +COUNT RUMFORD. + + +Benjamin Thompson, like Franklin, was a native of Massachusetts, his +ancestors for several generations having been yeomen in that province, +and descendants of the first colonists of the Bay. In the diploma of +arms granted him when he was knighted by George III., he is described +as "son of Benjamin Thompson, late of the province of Massachusetts +Bay, in New England, gent." He was born in the house of his +grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26, +1753. His father died at the age of twenty-six, on November 7, 1754, +leaving the infant Benjamin and his mother to the care of the +grandparents. The widow married Josiah Pierce, junior, in March, 1756, +and with her child, now a boy of three, went to live in a house but a +short distance from her former residence. + +Young Thompson appears to have received a sound elementary education +at the village school. From some remarks made by him in after years +to his friend, M. Pictet, it has been inferred that he did not receive +very kind treatment at the hands of his stepfather. It is clear, +however, that the most affectionate relationships always obtained +between him and his mother, and the latter appears to have had no +cause to complain of the treatment she received from her second +husband, with whom she lived to a very good old age. That Thompson in +early boyhood developed some tendencies which did not meet with ready +sympathy from those around him is, however, equally clear. His +guardians destined him for a farmer, like his ancestors, and his +experiments in mechanics, which took up much of his playtime and in +all probability not a few hours which should have been devoted to less +interesting work, were not regarded as tending towards the end in +view. Hence he was probably looked upon as "indolent, flighty, and +unpromising." Later on he was sent to school in Byfield, and in 1764, +at the age of eleven, "was put under the tuition of Mr. Hill, an able +teacher in Medford, a town adjoining Woburn." At length, his friends +having given up all hope of ever making a farmer of the boy, he was +apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an +importer of British goods and dealer in miscellaneous articles. He +lived with his master, and seems to have done his work in a manner +satisfactory on the whole, but there is evidence that he would, during +business hours, occupy his spare moments with mechanical contrivances, +which he used to hide under the counter, and even ventured +occasionally to practise on his fiddle in the store. He stayed with +Mr. Appleton till the autumn of 1769, and during this time he attended +the ministry of the Rev. Thomas Barnard. This gentleman seems to have +taken great interest in the boy, and to have taught him mathematics, +so that at the age of fifteen he was able "to calculate an eclipse," +and was delighted when the eclipse commenced within six seconds of his +calculated time. Thompson, while an apprentice, showed a great faculty +for drawing and designing, and used to carve devices for his friends +on the handles of their knives or other implements. It was at this +time he constructed an elaborate contrivance to produce perpetual +motion, and on one evening it is said that he walked from Salem to +Woburn, to show it to Loammi Baldwin, who was nine years older than +himself, but his most intimate friend. Like many other devices +designed for the same purpose, it had only one fault--it wouldn't go. + +It was in 1769, while preparing fireworks for the illumination on the +abolition of the Stamp Act, that Thompson was injured by a severe +explosion as he was grinding his materials in a mortar. His note-book +contained many directions for the manufacture of fireworks. + +During Thompson's apprenticeship those questions were agitating the +public mind which finally had their outcome in the War of +Independence. Mr. Appleton was one of those who signed the agreement +refusing to import British goods, and this so affected the trade of +the store that he had no further need for the apprentice. Hence it was +that, in the autumn of 1769, Thompson went to Boston as +apprentice-clerk in a dry goods store, but had to leave after a few +months, through the depression in trade consequent on the +non-importation agreement. + +His note-book, containing the entries made at this time, comprised +several comic sketches very well drawn, and a quantity of business +memoranda which show that he was very systematic in keeping his +accounts. His chief method of earning money, or rather of making up +the "Cr." side of his accounts, was by cutting and cording wood. A +series of entries made in July and August, 1771, show the expense he +incurred in constructing an electrical machine. It is not easy to +determine, from the list of items purchased, the character of the +machine he constructed; but it is interesting to note that the price +in America at that time of nitric acid was _2s. 6d._ per ounce; of +lacquer, _40s._ per pint; of shellac, _5s._ per ounce; brass wire, +_40s._ per pound; and iron wire, _1s. 3d._ per yard. The nature of the +problems which occupied his thoughts during the last year or two of +his business life are apparent in the following letters:-- + + Woburn, August 16, 1769. + + Mr. Loammi Baldwin, + + SIR, + + Please to inform me in what manner fire operates upon clay to + change the colour from the natural colour to red, and from red + to black, etc.; and how it operates upon silver to change it to + blue. + + I am your most humble and obedient servant, + + BENJAMIN THOMPSON + + God save the king. + + + Woburn, August, 1769. + + Mr. Loammi Baldwin, + + SIR, + + Please to give the nature, essence, beginning of existence, and + rise of the wind in general, with the whole theory thereof, so + as to be able to answer all questions relative thereto. + + Yours, + + BENJAMIN THOMPSON. + +This was an extensive request, and the reply was probably not +altogether satisfactory to the inquirer. On the back of the above +letter was written:-- + + Woburn, August 15, 1769. + + SIR, + + There was but few beings (for inhabitants of this world) created + before the airy element was; so it has not been transmitted down + to us how the Great Creator formed the matter thereof. So I + shall leave it till I am asked only the Natural Cause, and why + it blows so many ways in so short a time as it does. + +Thompson appears now to have given up business and commenced the study +of medicine under Dr. Hay, to whom for a year and a half he paid +forty shillings per week for his board. During this time he paid part +of his expenses by keeping school for a few weeks consecutively at +Wilmington and Bradford, and another part was paid by cords of wood. +His business capacity, as well as his dislike of ordinary work, is +shown by some arrangements which he made for getting wood cut and +corded at prices considerably below those at which he was himself paid +for it. His note-book made at this time contains, besides business +entries, several receipts for medicines and descriptions of surgical +operations, in some cases illustrated by sketches. In his work he was +methodical and industrious, and the life of a medical student suited +his genius far better than that of a clerk in a dry goods store. When +teaching at Wilmington he seems to have attracted attention by the +gymnastic performances with which he exercised both himself and his +pupils. While a student with Dr. Hay, he attended some of the +scientific lectures at Harvard College. The pleasure and profit which +he derived from these lectures are sufficiently indicated by the fact +that forty years afterwards he made the college his residuary legatee. + +Thompson won such a reputation as a teacher during the few weeks that +he taught in village schools in the course of his student life, that +he received an invitation from Colonel Timothy Walker to come to +Concord, in New Hampshire, on the Merrimack, and accept a permanent +situation in a higher grade school. It was from this place that he +afterwards took his title, for the early name of Concord was Rumford, +and the name was changed to Concord "to mark the restoration of +harmony after a long period of agitation as to its provincial +jurisdiction and its relation with its neighbours." + +The young schoolmaster of Concord was soon on very intimate terms with +the minister of the town, the Rev. Timothy Walker,[5] a man who was so +much respected that he had thrice been sent to Britain on diplomatic +business. Mr. Walker's daughter had been married to Colonel Rolfe, a +man of wealth and position, and, with the exception of the Governor of +Portsmouth, said to have been the first man in New Hampshire to drive +a curricle and pair of horses. Thompson soon married--or, as he told +Pictet, was married to--the young widow. Whatever may have been +implied by this other way of putting the question, there is no doubt +that Thompson always had the greatest possible respect for his +father-in-law, and ever remembered him with sincere gratitude. The +fortunes of the gallant young schoolmaster now appeared to be made; +when the engagement was settled, the carriage and pair were brought +out again, and the youth was attired in his favourite scarlet as a man +of wealth and position. In this garb he drove to Woburn, and +introduced his future wife to his mother, whose surprise can be better +imagined than described. + +[Footnote 5: Father of the colonel.] + +The exact date of Thompson's marriage is not known. His daughter +Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion +on October 18, 1774. It is needless to say that the engagement to Mrs. +Rolfe terminated the teaching at the school. + +Thompson now had a large estate and ample means to improve it. He gave +much attention to gardening, and sent to England for garden seeds. In +some way he attracted the attention of Governor Wentworth, the +Governor of Portsmouth, who invited him to the Government House, and +was so taken with the former apprentice, medical student, and +schoolmaster, that he gave him at once a commission as major. This +appointment was the cause of the misfortunes which almost +immediately began to overtake him. He incurred the jealousy of his +fellow-officers, over whom he had been appointed, and he failed to +secure the confidence of the civilians of Concord. + +Public feeling in New England was very much excited against the mother +country. Representations were sent to the British Government, but +appeared to be treated with contempt. Very many of these documents +were found, after the war was over, unopened in drawers at the +Colonial Office. British ministers appeared to know little about the +needs of their American dependencies, and relations rapidly became +more and more strained. The patriots appointed committees to watch +over the patriotism of their fellow-townsmen, and thus the freedom of +a free country was inaugurated by an institution bordering in +character very closely upon the Inquisition; and the Committees of +Correspondence and Safety accepted evidence from every spy or +eavesdropper who came before them with reports of suspected persons. +Thompson was accused of "Toryism;" the only definite charge against +him being that he had secured remission of punishment for some +deserters from Boston who had for some time worked upon his estate. He +was summoned before the Committee of Safety, but refused to make any +confession of acts injurious to his country, on the ground that he had +nothing to confess. His whole after-life shows that his sympathies +were very much on the side of monarchy and centralization, but at this +time there appears to have been no evidence that could be brought +against him. The populace, however, stormed his house, and he owed his +safety to the fact that he had received notice of their intentions, +and had made his escape a few hours before. This was in November, +1774. Thompson then took refuge at Woburn, with his mother, but the +popular ill feeling troubled him here, so that his life was one of +great anxiety. + +While at Woburn, his wife and child joined him, and stayed there for +some months. At length he was arrested and confined in the town upon +suspicion of being inimical to the interests of his country. When he +was brought before the Committee of Inquiry, there was no evidence +brought against him. Major Thompson then petitioned to be heard +before the Committee of the Provincial Congress at Washington. This +petition he entrusted to his friend Colonel Baldwin to present. The +petition was referred by the committee to Congress, by whom it was +deferred for the sake of more pressing business. At length he secured +a hearing in his native town, but the result was indecisive, and he +did not obtain the public acquittal that he desired, though the +Committee of Correspondence found that the "said Thompson" had not "in +any one instance shown a disposition unfriendly to American liberty; +but that his general behaviour has evinced the direct contrary; and as +he has now given us the strongest assurances of his good intentions, +we recommend him to the friendship, confidence, and protection of all +good people in this and the neighbouring provinces." This decision, +however, does not appear to have been made public; and Thompson, on +his release, retired to Charlestown, near Boston. When the buildings +of Harvard College were converted into barracks, Major Thompson +assisted in the transfer of the books to Concord. It is said that, +after the battle of Charlestown, Thompson was introduced to General +Washington, and would probably have received a commission under him +but for the opposition of some of the New Hampshire officers. He +afterwards took refuge in Boston, and it does not appear that he ever +again saw his wife or her father. His daughter he did not see again +till 1796, when she was twenty-two years of age. On March 24, 1776, +General Washington obliged the British troops to evacuate Boston; +Thompson was the first official bearer of this intelligence to London. +Of course, his property at Concord was confiscated to the commonwealth +of Massachusetts, and he himself was proscribed in the Alienation Act +of New Hampshire, in 1778. + +When Thompson reached London with the intelligence of the evacuation +of Boston, Lord George Germaine, the Secretary for War, saw that he +could afford much information which would be of value to the +Government. An appointment was soon found for him in the Colonial +Office, and afterwards he was made Secretary of the Province of +Georgia, in which latter capacity, however, he had no duties to +fulfil. Throughout his career in the Colonial Office he remained on +very intimate terms with Lord George Germaine, and generally +breakfasted with him. In July, 1778, he was guest of Lord George at +Stoneland Lodge, and here, in company with Mr. Ball, the Rector of +Withyham, he undertook experiments "to determine the most advantageous +situation for the vent in firearms, and to measure the velocities of +bullets and the recoil under various circumstances." + +The results of these investigations procured for him the friendship of +Sir Joseph Banks, the President of the Royal Society, and Thompson was +not the man to lose opportunities for want of making use of them. In +1779 he was elected a Fellow of the Royal Society, "as a gentleman +well versed in natural knowledge and many branches of polite +learning." In the same year he went for a cruise in the _Victory_ with +Sir Charles Hardy, in order to pursue his experiments on gunpowder +with heavy guns. Here he studied the principles of naval artillery, +and devised a new code of marine signals. In 1780 he was made +Under-Secretary of State for the Northern Department, and in that +capacity had the oversight of the transport and commissariat +arrangements for the British forces. + +On the defeat of Cornwallis, Lord George Germaine and his department +had to bear the brunt of Parliamentary dissatisfaction. Lord George +resigned his position in the Government, and was created Viscount +Sackville. He had, however, previously conferred on Thompson a +commission as lieutenant-colonel in the British army, and Thompson, +probably foreseeing the outcome of events and its effect on the +Ministry, was already in America when Lord George resigned. He had +intended landing at New York, but contrary winds drove him to +Charlestown. It is needless to trace the sad events which preceded the +end of the war. It was to be expected that many bitter statements +would be made by his countrymen respecting Thompson's own actions as +colonel commanding a British garrison, for at length he succeeded in +reaching Long Island, and taking the command of the King's American +Dragoons, who were there awaiting him. The spirit of war always acts +injuriously on those exposed to its influence, and Lieutenant-Colonel +Thompson in Long Island was doubtless a very different man from that +which we find him to have been before and after; nor were the months +so spent very fruitful in scientific work. + +In 1783, before the final disbanding of the British forces, Thompson +returned to England, and was promoted to the rank of colonel, with +half-pay for the rest of his life. Still anxious for military service, +he obtained permission to travel on the Continent, in hopes of serving +in the Austrian army against the Turks. He took with him three English +horses, which rendered themselves very objectionable to his +fellow-travellers while crossing the Channel in a small boat. Thompson +went to Strasbourg, where he attracted the attention of the Prince +Maximilian, then Field-Marshal of France, but afterwards Elector of +Bavaria. On leaving Strasbourg, the prince gave him an introduction to +his uncle, the Elector of Bavaria. He stayed some days at Munich, but +on reaching Vienna learned that the war against the Turks would not be +carried on, so he returned to Munich, and thence to England. + +M. Pictet gives the following as Rumford's account of the manner in +which he was cured of his passion for war:-- + +"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I +was cured in season of this martial folly. I met, at the house of the +Prince de Kaunitz, a lady, aged seventy years, of infinite spirit and +full of information. She was the wife of General Bourghausen. The +emperor, Joseph II., came often to pass the evening with her. This +excellent person conceived a regard for me; she gave me the wisest +advice, made my ideas take a new direction, and opened my eyes to +other kinds of glory than that of victory in battle.'" + +If the course in life which Colonel Thompson afterwards took was due +to the advice of this lady, she deserves a European reputation. The +Elector of Bavaria, Charles Theodore, gave Thompson a pressing +invitation to enter his service in a sort of semi-military and +semi-civil capacity, to assist in reorganizing his dominions and +removing the abuses which had crept in. Before accepting this +appointment, it was necessary to obtain the permission of George III. +The king not only approved of the arrangement, but on February 23, +1784, conferred on the colonel the honour of knighthood. Sir Benjamin +then returned to Bavaria, and was appointed by the elector colonel of +a regiment of cavalry and general aide-de-camp. A palatial residence +in Munich was furnished for him, and here he lived more as a prince +than a soldier. It was eleven years before he returned, even on a +visit, to England, and these years were spent by him in works of +philanthropy and statesmanship, to which it is difficult to find a +parallel. At one time he is found reorganizing the military system of +the country, arranging a complete system of military police, erecting +arsenals at Mannheim and Munich; at another time he is carrying out +scientific investigations in one of these arsenals; and then he is +cooking cheap dinners for the poor of the country. + +One great evil of a standing army is the idleness which it develops in +its members, unfitting them for the business of life when their +military service is ended. Thompson commenced by attacking this evil. +In 1788 he was made major-general of cavalry and Privy Councillor of +State, and was put at the head of the War Department, with +instructions to carry out any schemes which he had developed for the +reform of the army and the removal of mendicity. Four years after his +arrival in Munich he began to put some of his plans into operation. +The pay of the soldiers was only threepence per day, and their +quarters extremely uncomfortable, while their drill and discipline +were unnecessarily irksome. Thompson set to work to make "soldiers +citizens and citizens soldiers." The soldier's pay, uniform, and +quarters were improved; the discipline rendered less irksome; and +schools in which the three R's were taught were connected with all the +regiments,--and here not only the soldiers, but their children as well +as other children, were taught gratuitously. Not only were the +soldiers employed in public works, and thus accustomed to habits of +industry, while they were enlivened in their work by the strains of +their own military bands, but they were supplied with raw material of +various kinds, and allowed, when not on duty, to manufacture various +articles and sell them for their own benefit--an arrangement which in +this country to-day would probably raise a storm of opposition from +the various trades. The garrisons were made permanent, so that +soldiers might all be near their homes and remain there, and in time +of peace only a small portion of the force was required to be in +garrison at any time, so that the great part of his life was spent by +each soldier at home. Each soldier had a small garden appropriated to +his use, and its produce was his sole property. Garden seeds, and +especially seed potatoes, were provided for the men, for at that time +the potato was almost unknown in Bavaria. Under these circumstances a +reform was quickly effected; idle men began to take interest in their +gardens, and all looked on Sir Benjamin as a benefactor. + +Having thus secured the co-operation of the army, Thompson determined +to attack the mendicants. The number of beggars may be estimated from +the fact that in Munich, with a population of sixty thousand, no less +than two thousand six hundred beggars were seized in a week. In the +towns, they possessed a complete organization, and positions of +advantage were assigned in regular order, or inherited according to +definite customs. In the country, farm labourers begged of travellers, +and children were brought up to beggary from their infancy. Of course, +the evils did not cease with simple begging. Children were stolen and +ill treated, for the purpose of assisting in enlisting sympathy, and +the people had come to regard these evils as inevitable. Thompson +organized a regular system of military patrol through every village of +the country, four regiments of cavalry being set apart for this work. +Then on January 1, 1790, when the beggars were out in full force to +keep their annual holiday, Thompson, with the other field officers and +the magistrates of the city, gave the signal, and all the beggars in +Munich were seized upon by the three regiments of infantry then in +garrison. The beggars were taken to the town hall, and their names and +addresses entered on lists prepared for the purpose. They were ordered +to present themselves next day at the "military workhouse," and a +committee was appointed to inquire into the condition of each, the +city being divided into sixteen districts for that purpose. Relieved +of an evil which they had regarded as inevitable, the townspeople +readily subscribed for the purpose of affording systematic relief, +while tradesmen sent articles of food and other requisites to "the +relief committee." In the military workhouse the former mendicants +made all the uniforms for the troops, besides a great deal of clothes +for sale in Bavaria and other countries. Thompson himself fitted up +and superintended the kitchen, where food was daily cooked for between +a thousand and fifteen hundred persons; and, under Sir Benjamin's +management, a dinner for a thousand was cooked at a cost for fuel of +fourpence halfpenny--a result which has scarcely been surpassed in +modern times, even at Gateshead. + +That Thompson's work was appreciated by those in whose interest it was +undertaken is shown by the fact that when, on one occasion, he was +dangerously ill, the poor of Munich went in public procession to the +cathedral to pray for him, though he was a foreigner and a Protestant. +Perhaps it may appear that his philanthropic work has little to do +with physical science; but with Thompson everything was a scientific +experiment, conducted in a truly scientific manner. For example, the +lighting of the military workhouse afforded matter for a long series +of experiments, described in his papers on photometry, coloured +shadows, etc. The investigations on the best methods of employing fuel +for culinary purposes led to some of his most elaborate essays; and +his essay on food was welcomed alike in London and Bavaria at a time +of great scarcity, and when famine seemed impending. + +The Emperor Joseph was succeeded by Leopold II., but during the +interregnum the Elector of Bavaria was Vicar of the Empire, and he +employed the power thus temporarily placed in his hands in raising Sir +Benjamin to the dignity of Count of the Holy Roman Empire, with the +order of the White Eagle, and the title which the new count selected +was the old name of the village in New England where he had spent the +two or three years of his wedded life. + +In 1795 Count Rumford returned to England, in order to publish his +essays, and to make known in this country something of the work in +which he had been engaged. Soon after his arrival he was robbed of +most of his manuscripts, the trunk containing them being stolen from +his carriage in St. Paul's Churchyard. On the invitation of Lord +Pelham, he visited Dublin, and carried out some of his improvements in +the hospitals and other institutions of that city. On his return to +London he fitted up the kitchen of the Foundling Hospital. + +Lady Thompson lived to hear of her husband's high position in Bavaria, +but died on January 29, 1792. When Rumford came to London in 1795, he +wrote to his daughter, who was then twenty-one years of age, to meet +him there, and on January 29, 1796, she started in the _Charlestown_, +from Boston. She remained with her father for more than three years, +and her autobiography gives much information respecting the count's +doings during this time. + +While in London, Count Rumford attained a high reputation as a curer +of smoky chimneys. One firm of builders found full employment in +carrying out work in accordance with his instructions; and in his +hotel at Pall Mall he conducted experiments on fireplaces. He +concluded that the sides of a fireplace ought to make an angle of 135 deg. +with the back, so as to throw the heat straight to the front; and that +the width of the back should be one-third of that of the front +opening, and be carried up perpendicularly till it joins the breast. +The "Rumford roaster" gained a reputation not less than that earned +by his open fireplace. + +It was during this stay in London that Rumford presented to the Royal +Society of London, and to the American Academy of Sciences L1000 Three +per Cent. Stock, for the purpose of endowing a medal to be called the +Rumford Medal, and to be given each alternate year for the best work +done during the preceding two years in the subjects of heat and light. +He directed that two medals, one in gold and the other in silver, +should be struck from the same die, the value of the two together to +amount to L60. Whenever no award was made, the interest was to be +added to the principal, and the excess of the income for two years +over L60 was to be presented in cash to the recipient of the medal. At +present the amount thus presented is sufficient to pay the composition +fee for life membership of the Royal Society. The first award of the +medal was made in 1802, to Rumford himself. The other recipients have +been John Leslie, William Murdock, Etienne-Louis Malus, William +Charles Wells, Humphry Davy, David Brewster, Augustin Jean Fresnel, +Macedonio Melloni, James David Forbes, Jean Baptiste Biot, Henry Fox +Talbot, Michael Faraday, M. Regnault, F. J. D. Arago, George Gabriel +Stokes, Neil Arnott, M. Pasteur, M. Jamin, James Clerk Maxwell, +Kirchoff, John Tyndall, A. H. L. Fizeau, Balfour Stewart, A. O. des +Cloiseaux, A. J. Angstroem, J. Norman Lockyer, P. J. C. Janssen, W. +Huggins, Captain Abney. + +In the summer of 1796 Rumford and his daughter left England to return +to Munich. On account of the war, they were obliged to go by sea to +Hamburg; whence they drove to Munich, where the count was anxiously +expected, political troubles having compelled the elector to leave the +city. After the battle of Friedburg, the Austrians retired to Munich, +and, finding the gates of the city closed, they fortified +themselves on an eminence overlooking the city, and, through some +misunderstanding with the local authorities, the Austrian general +threatened to attack the city if any Frenchman should be allowed to +enter. Rumford took supreme command of the Bavarian forces, and so +gained the respect of the rival generals that neither the French nor +the Austrians made any attempt to enter the city. The large number of +soldiers now in Munich gave Rumford a good opportunity to exercise his +skill in cooking on a large scale, and this he did, adding to the +comfort of the soldiers and reducing the cost of the commissariat. On +the return of the elector, Miss Sarah was made a countess, and +one-half of her father's pension was secured to her, thus providing +her with an income of about L200 per annum for life. Many of the +details of the home life and social intercourse during this period of +residence at Munich are preserved in the autobiography of the +countess, as well as accounts of excursions, including a trip by river +to Salzburg for the purpose of inspecting the salt-mines. After two +years' stay in Munich, the count was appointed Minister +Plenipotentiary from Bavaria to the Court of Great Britain. After an +unpleasant and perilous journey, he reached London, _via_ Hamburg, in +September, 1798, but was terribly disappointed on learning that a +British subject could not be accepted as an envoy from a Foreign +Power. As he did not then wish to return to Bavaria, he purchased a +house in Brompton Row. But he had been too much accustomed to great +enterprises to be content with a quiet life, and was bound to have +some important scheme on hand. Pressing invitations were sent him to +return to America, but he preferred residence in London, and devoted +himself to the foundation of the Royal Institution, though the +countess returned to the States in August, 1799. A letter from Colonel +Baldwin to her father shortly after her return contains the following +passage:-- + + In the cask of fruit which your daughter and Mr. Rolfe have sent + you, there is half a dozen apples of the growth of my farm, + wrapped up in papers, with the name of _Baldwin's apples_ + written upon them.... It is (I believe) a spontaneous production + of this country; that is, it was not originally engrafted fruit. + +The history of the remaining period of Rumford's residence in London +is the early history of the Royal Institution. + +For many years Rumford had had at his disposal for his philanthropic +projects all the resources of the electorate of Bavaria, and he had +done everything on a royal scale. His original plan for the Royal +Institution appears to embody to a very great extent the work of the +Science and Art Department, the City and Guilds Institute for the +Advancement of Technical Education, the National School of Cookery, +the London Society for the Extension of University Teaching, and, in +addition to all this, to have comprehended a sort of perpetual +International Health Exhibition, where every device for domestic +purposes, and especially for the improvement of the condition of the +poor, could be inspected. How all this was to be carried out with the +resources which the count expected to be able to devote to the +purpose, does not appear. Foremost among the objects of the +institution was placed the management of fire; for its promoter was +convinced that more than half the fuel consumed in the country might +be saved by proper arrangements. + +The philanthropic objects with which the institution was started are +apparent from the fact that it was the Society for Bettering the +Condition of the Poor which appointed a committee to confer with +Rumford, to report on the scheme, and to raise the funds necessary for +starting the project; and one of Rumford's hopes in connection with it +was "to make benevolence fashionable." It was arranged that donors of +fifty guineas each should be perpetual proprietors of the institution; +and that subscribers should be admitted at a subscription of two +guineas per annum, or ten guineas for life. The price of a +proprietor's share was raised to sixty guineas from May 1, 1800, and +afterwards increased by ten guineas per annum up to one hundred +guineas. In a very short time there were fifty-eight fifty-guinea +subscribers, and to them Rumford addressed a pamphlet, setting forth +his scheme in detail. The following are specified as some of the +contents of the future institution:--"Cottage fireplaces and kitchen +utensils for cottagers; a farm-house kitchen with its furnishings; a +complete kitchen, with its utensils, for the house of a gentleman of +fortune; a laundry, including boilers, washing, ironing, and drying +rooms, for a gentleman's house, or for a public hospital; the most +improved German, Swedish, and Russian stoves for heating rooms and +passages." As far as possible all these things were to be seen at +work. There were also to be ornamental open stoves with fires in them; +working models of steam-engines, of brewers' boilers, of distillers' +coppers and condensers, of large boilers for hospital kitchens, and of +ships' coppers with the requisite utensils; models of ventilating +apparatus, spinning-wheels and looms "adapted to the circumstances of +the poor;" models of agricultural machinery and bridges, and "of all +such other machines and useful instruments as the managers of the +institution shall deem worthy of public notice." All articles were to +be provided with proper descriptions, with the name and address of the +maker, and the price. + +A lecture-room and laboratory were to be fitted up with all necessary +philosophical apparatus, and the most eminent expounders of science +were to be engaged for the purpose of "teaching the application of +science to the useful purposes of life." + +The lectures were to include warming and ventilation, the preservation +of food, agricultural chemistry, the chemistry of digestion, of +tanning, of bleaching and dyeing, "and, in general, of all the +mechanical arts as they apply to the various branches of manufacture." +The institution was to be governed by nine managers, of whom three +were to be elected each year by the proprietors; and there was also to +be a committee of visitors, the members of which should not be the +managers. The king became patron of the institution, and the first set +of officers was nominated by him. The Earl of Winchelsea and +Nottingham was President; the Earls of Morton and of Egremont and Sir +Joseph Banks, Vice-Presidents; the Earls of Bessborough, of Egremont, +and of Morton, and Count Rumford, were among the Managers; the Duke of +Bridgewater, Viscount Palmerston, and Earl Spencer the Visitors; and +Dr. Thomas Garnett was appointed first Professor of Physics and +Chemistry. The royal charter of the institution was sealed on January +13, 1800. The superintendence of the journals of the institution was +entrusted to Rumford's care. For some time the count resided in the +house in Albemarle Street, which had been purchased by the +institution, and while there he superintended the workmen and +servants. + +Dr. Thomas Garnett, the first professor at the institution, was highly +respected both as a man and a philosopher, and seems to have been +everywhere well spoken of. But Rumford and he could not work together, +and his connection with the institution was consequently a short one. +Rumford was then authorized to engage Dr. Young as Professor of +Natural Philosophy, editor of the journals, and general superintendent +of the house, at a salary of L300 per annum. Shortly before this the +count's attention had been directed to the experiments on heat, made +by Humphry Davy, and on February 16, 1801, it was "resolved that Mr. +Humphry Davy be engaged in the service of the Royal Institution, in +the capacity of Assistant-Lecturer in Chemistry, Director of the +Chemical Laboratory, and Assistant-Editor of the Journals of the +Institution; and that he be allowed to occupy a room in the house, and +be furnished with coals and candles, and that he be paid a salary of +one hundred guineas _per annum_." In his personal appearance, Davy is +said to have been at first somewhat uncouth, and the count was by no +means charmed with him at their first interview. It was not till he +had heard him lecture in private that Rumford would allow Davy to +lecture in the theatre of the institution; but he afterwards showed +his complete confidence in the young chemist by ordering that all the +resources of the institution should be at his service. Davy dined with +Rumford at the count's house in Auteuil, when he visited Paris with +Lady Davy and Faraday, in 1813. He commenced his duties at the +institution on March 11, 1801. It was on June 15, in the same year, +that the managers having objected to the syllabus of his lectures, Dr. +Garnett's resignation was accepted; and on July 6 Dr. Young was +appointed in his stead. Dr. Young resigned after holding the +appointment only two years, as he found the duties incompatible with +his work as a physician. + +Rumford's life in London now became daily more unpleasant to himself. +Accustomed, as he had been in Bavaria, to carry out all his projects +"like an emperor," it was difficult for him to work as one member of a +body of managers. One by one he quarrelled with his colleagues, and at +length left England, in May, 1802, never to return. + +When distinguished men of science are placed at the head of an +institution like that which Rumford founded, there is always a +tendency for the _technical_ teaching of the establishment to become +gradually merged into scientific research; and in this case, after +Rumford's departure, the genius of Davy gradually converted the Royal +Institution into the establishment for scientific research which it +has been for more than three quarters of a century. Probably the man +who has come nearest to realizing all that Count Rumford had planned +for his institution is the late Sir Henry Cole; but he succeeded only +through the resources of the Treasury. + +On leaving England in May, 1802, Rumford went to Paris, where he +stayed till July or August, when he revisited Bavaria and remained +there till the following year, when he returned to Paris. He was again +at Munich in 1805; but under the new elector, though an old friend of +the count, relationships do not seem to have been all that they were +with his uncle, and at length the elector himself was compelled to +leave Munich, and soon after the Bavarian sovereign became a vassal of +Napoleon. On October 24, 1805, Rumford married Madame Lavoisier, a +lady of brilliant talents and ample fortune. That his position might +be nearly equal to hers, the Elector of Bavaria raised his pension to +L1200 per annum. A house, Rue d'Anjou, No. 39, was purchased for six +thousand guineas, and Rumford expended much thought and energy in +making it, with its garden of two acres, all that he could desire. But +the union was not so happy as he anticipated. The count loved quiet; +Madame de Rumford was fond of company: to the former the pleasure of +the table had no charms; the latter took delight in sumptuous +dinner-parties. As time went on, domestic affairs became more and more +unpleasant, and at length a friendly separation was agreed upon, after +they had lived together for about three years and a half. The count +then retired to a small estate which he hired at Auteuil, about four +miles from Paris. The Elector of Bavaria was crowned king on January +1, 1806, and in 1810 Rumford was again at Munich, for the purpose of +forming, at the king's request, an Academy of Arts and Sciences. At +Auteuil the count was joined by his daughter in December, 1811, her +journey having been much delayed through the capture of the vessel in +which she had taken her passage, off Bordeaux. An engraving of the +house at Auteuil, and the room in which Rumford carried on his +experiments, was published in the _Illustrated London News_ of January +22, 1870. + +While resident at Auteuil, Rumford frequently read papers before the +Institute of France, of which he was a member. He complained very much +of the jealousy exhibited by the other members with reference to any +discoveries made by a foreigner. He died in his house at Auteuil, on +August 21, 1814, in the sixty-second year of his age. In 1804 he had +made over, by deed of gift to his mother, the sum of ten thousand +dollars, that she might leave it by will to her younger children. As +before mentioned, Harvard College was his residuary legatee, and the +property so bequeathed founded the Rumford Professorship in that +institution. + +Cuvier, as Secretary of the Institute, pronounced the customary eulogy +over its late member. The following passages throw some light on the +reputation in which the count was held:-- + + He has constructed two singularly ingenious instruments of his + own contriving. One is a new calorimeter for measuring the + amount of heat produced by the combustion of any body. It is a + receptacle containing a given quantity of water, through which + passes, by a serpentine tube, the product of the combustion; and + the heat that is generated is transmitted through the water, + which, being raised by a fixed number of degrees, serves as the + basis of the calculations. The manner in which the exterior heat + is prevented from affecting the experiment is very simple and + very ingenious. He begins the operation at a certain number of + degrees below the outside heat, and terminates it at the same + number of degrees above it. The external air takes back during + the second half of the experiment exactly what it gave up during + the first. The other instrument serves for noting the most + trifling differences in the temperature of bodies, or in the + rapidity of its changes. It consists of two glass bulbs filled + with air, united by a tube, in the middle of which is a pellet + of coloured spirits of wine; the slightest increase of heat in + one of the bulbs drives the pellet towards the other. This + instrument, which he called a thermoscope, was of especial + service in making known to him the varied and powerful influence + of different surfaces in the transmission of heat, and also for + indicating a variety of methods for retarding or hastening at + will the processes of heating and freezing.... + + He thought it was not wise or good to entrust to men, in the + mass, the care of their own well-being. The right, which seems + so natural to them, of judging whether they are wisely governed, + appeared to him to be a fictitious fancy born of false notions + of enlightenment. His views of slavery were nearly the same as + those of a plantation-owner. He regarded the government of China + as coming nearest to perfection, because, in giving over the + people to the absolute control of their only intelligent men, + and in lifting each of those who belonged to this hierarchy on + the scale according to the degree of his intelligence, it made, + so to speak, so many millions of arms the passive organs of the + will of a few sound heads--a notion which I state without + pretending in the slightest degree to approve it, and which, as + we know, would be poorly calculated to find prevalence among + European nations. + + As for the rest, whatever were the sentiments of M. Rumford for + men, they in no way lessened his reverence for God. He never + omitted any opportunity in his works of expressing his religious + admiration of Providence, and of proposing for that admiration + by others, the innumerable and varied provisions which are made + for the preservation of all creatures; indeed, even his + political views came from his firm persuasion that princes ought + to imitate Providence in this respect by taking charge of us + without being amenable to us. + +In front of the new Government offices and the National Museum in the +Maximilian Strasse, in Munich, stand, on granite pedestals, four +bronze figures, ten feet in height. These represent General Deroy, +Fraunhofer, Schelling, and Count Rumford. The statue of Rumford was +erected in 1867, at the king's private expense. In the English garden +which Rumford planned and laid out is the monument erected during his +absence in England in 1796, and bearing allegorical figures of Peace +and Plenty, and a medallion of the count. + +The bare enumeration of Rumford's published papers would occupy +considerable space, but many of them have more to do with philanthropy +and domestic economy than with physics. We have seen that, when guest +of Lord George Germaine, he was engaged in experiments on gunpowder. +The experiments were made in the usual manner by firing bullets into a +ballistic pendulum, and recording the swing of the pendulum. Thompson +suggested a modification of the ballistic pendulum, attaching the +gun-barrel to the pendulum, and observing the recoil, and making +allowance for the recoil due to the discharge from the gun of the +products of combustion of the powder, the excess enabled the velocity +of the bullet to be calculated. Afterwards he made experiments on the +maximum pressure produced by the explosion of powder, and pointed out +that the value of powder in ordnance does not depend simply on the +whole amount of gas produced, but also on the rapidity of combustion. +While superintending the arsenal at Munich, Rumford exploded small +charges of powder in a specially constructed receiver, which was +closed by a plug of well-greased leather, and on this was placed a +hemisphere of steel pressed down by a 24-pounder brass cannon weighing +8081 pounds. He found that the weight of the gun was lifted by the +explosion of quantities of powder varying from twelve to fifteen +grains, and hence concluded that, if the products of combustion of the +powder were confined to the space actually occupied by the solid +powder, the initial pressure would exceed twenty thousand atmospheres. +Rumford's calculation of the pressure, based upon the bursting of a +barrel, which he had previously constructed, is not satisfactory, +inasmuch as he takes no account of the fact that the inner portions of +the metal would give way long before the outer layers exerted anything +like their maximum tension. When a hollow vessel with thick walls, +such as a gun-barrel or shell, is burst by gaseous pressure from +within, the inner layers of material are stretched to their breaking +tension before they receive much support from the outer layers; a rift +is thus made in the interior, into which the gas enters, and the +surface on which the gas presses being thus increased, the rift +deepens till the fracture is complete. In order to gain the full +strength due to the material employed, every portion of that material +should be stretched simultaneously to the extent of its maximum safe +load. This principle was first practically adopted by Sir W. G. +Armstrong, who, by building up the breech of the gun with cylinders +shrunk on, and so arranged that the tension increased towards the +exterior, availed himself of nearly the whole strength of the metal +employed to resist the explosion. Had Rumford's barrel been +constructed on this principle, he would have obtained a much more +satisfactory result. + +These investigations were followed by a very interesting series of +experiments on the conducting power of fluids for heat, and, although +he pushed his conclusions further than his experiments warranted, he +showed conclusively that convection currents are the principal means +by which heat is transferred through the substance of fluids, and +described how, when a vessel of water is heated, there is generally an +ascending current in the centre, and a descending current all round +the periphery. Hence it is only when a liquid expands by increase of +temperature that a large mass can be readily heated from below. Water +below 39 deg. Fahr. contracts when heated. Rumford, in his paper, enlarges +on the bearing of this fact on the economy of the universe, and the +following extracts afford a good specimen of his style, and justify +some of the statements made by Cuvier in his eulogy:-- + + I feel the danger to which a mortal exposes himself who has the + temerity to undertake to explain the designs of Infinite Wisdom. + The enterprise is adventurous, but it cannot surely be improper. + + The wonderful simplicity of the means employed by the Creator of + the world to produce the changes of the seasons, with all the + innumerable advantages to the inhabitants of the earth which + flow from them, cannot fail to make a very deep and lasting + impression on every human being whose mind is not degraded and + quite callous to every ingenuous and noble sentiment; but the + further we pursue our inquiries respecting the constitution of + the universe, and the more attentively we examine the effects + produced by the various modifications of the active powers which + we perceive, the more we shall be disposed to admire, adore, and + love that great First Cause which brought all things into + existence. + + Though winter and summer, spring and autumn, and all the variety + of the seasons are produced in a manner at the same time the + most simple and the most stupendous (by the inclination of the + axis of the earth to the plane of the ecliptic), yet this + mechanical contrivance alone would not have been sufficient (as + I shall endeavour to show) to produce that gradual change of + temperature in the various climates which we find to exist, and + which doubtless is indispensably necessary to the preservation + of animal and vegetable life.... + + But in very cold countries the ground is frozen and covered with + snow, and all the lakes and rivers are frozen over in the very + beginning of winter. The cold then first begins to be extreme, + and there appears to be no source of heat left which is + sufficient to moderate it in any sensible degree. + + Let us see what must have happened if things had been left to + what might be called their natural course--if the condensation + of water, on being deprived of its heat, had followed the law + which we find obtains in other fluids, and even in water itself + in some cases, namely, when it is mixed with certain bodies. + + Had not Providence interfered on this occasion in a manner which + may well be considered _miraculous_, all the fresh water within + the polar circle must inevitably have been frozen to a very + great depth in one winter, and every plant and tree destroyed; + and it is more than probable that the region of eternal frost + would have spread on every side from the poles, and, advancing + towards the equator, would have extended its dreary and solitary + reign over a great part of what are now the most fertile and + most inhabited climates of the world!... + + Let us with becoming diffidence and awe endeavour to see what + the means are which have been employed by an almighty and + benevolent God to protect His fair creation. + +He then goes on to explain how large bodies of water are prevented +from freezing at great depths on account of the expansion which takes +place on cooling below 39 deg. Fahr., and the further expansion which +occurs on freezing, and mentions that in the Lake of Geneva, at a +depth of a thousand feet, M. Pictet found the temperature to be 40 deg. +Fahr. + +"We cannot sufficiently admire the simplicity of the contrivance by +which all this heat is saved. It well deserves to be compared with +that by which the seasons are produced; and I must think that every +candid inquirer who will begin by divesting himself of all +unreasonable prejudice will agree with me in attributing them both TO +THE SAME AUTHOR.... + +"But I must take care not to tire my reader by pursuing these +speculations too far. If I have persisted in them, if I have dwelt on +them with peculiar satisfaction and complacency, it is because I think +them uncommonly interesting, and also because I conceived that they +might be of value in this age of _refinement_ and _scepticism_. + +"If, among barbarous nations, the _fear of a God_, and the practice of +religious duties, tend to soften savage dispositions, and to prepare +the mind for all those sweet enjoyments which result from peace, +order, industry, and friendly intercourse; a _belief in the existence +of a Supreme Intelligence_, who rules and governs the universe with +wisdom and goodness, is not less essential to the happiness of those +who, by cultivating their mental powers, HAVE LEARNED TO KNOW HOW +LITTLE CAN BE KNOWN." + +Rumford, in connection with his experiments on the conducting power of +liquids, tried the effect of increasing the viscosity of water by the +addition of starch, and of impeding its movements by the introduction +of eider-down, on the rate of diffusion of heat through it. Hence he +explained the inequalities of temperature which may obtain in a mass +of thick soup--inequalities which had once caused him to burn his +mouth--and, applying the same principles to air, he at once turned his +conclusions to practical account in the matter of warm clothing. + +After an attempt to determine, if possible, the weight of a definite +quantity of heat--an attempt in which very great precautions were +taken to exclude disturbing causes, while the balance employed was +capable of indicating one-millionth part of the weight of the body +weighed--Rumford, finding no sensible effect on the balance, concluded +that "if the weight of gold is neither augmented nor lessened by +_one-millionth part_, upon being heated from the point of _freezing +water_ to that of a _bright red heat_, I think we may very safely +conclude that ALL ATTEMPTS TO DISCOVER ANY EFFECT OF HEAT UPON THE +APPARENT WEIGHTS OF BODIES WILL BE FRUITLESS." The theoretical +investigations of Principal Hicks, based on the vortex theory of +matter and the dynamical theory of heat, have recently led him to the +conclusion that the attraction of gravitation may depend to some +extent on temperature. + +A series of very valuable experiments on the radiating powers of +different surfaces showed how that power varied with the nature of the +surface, and the effect of a coating of lamp-black in increasing the +radiating power of a body. In order to determine the effect of +radiation in the cooling of bodies, Rumford employed the thermoscope +referred to by Cuvier. The following passage is worthy of attention, +as the truth it expounds in the last thirteen words appears to have +been but very imperfectly recognized many years after it was +written:-- + +"All the heat which a hot body loses when it is exposed in the air to +cool is not given off to the air which comes into contact with it, but +... a large proportion of it escapes in rays, which do not heat the +transparent air through which they pass, but, like light, generate +heat only when and where they are stopped and absorbed." + +Rumford then investigated the absorption of heat by different +surfaces, and established the law that good radiators are good +absorbers; and recommended that vessels in which water is to be heated +should be blackened on the outside. In speculating on the use of the +colouring matter in the skin of the negro, he shows his fondness for +experiment:-- + +"All I will venture to say on the subject is that, were I called to +inhabit a very hot country, nothing should prevent me from making the +experiment of blackening my skin, or at least, of wearing a black +shirt, in the shade, and especially at night, in order to find out if, +by those means, I could contrive to make myself more comfortable." + +In his experiments on the conduction of heat, Rumford employed a +cylinder with one end immersed in boiling water and the other in +melting ice, and determined the temperature at different points in the +length of the cylinder. He found the difficulty which has recently +been forcibly pointed out by Sir Wm. Thomson, in the article "Heat," +in the "Encyclopaedia Britannica," viz. that the circulation of the +water was not sufficiently rapid to keep the temperature of the layer +in contact with the metal the same as that of the rest of the water; +and he also called attention to the arbitrary character of +thermometer-scales, and recommended that more attention should be +given to the scale of the air thermometer. It was in his visit to +Edinburgh, in 1800, that, in company with some of the university +professors, the count conducted some experiments in the university +laboratory on the apparent radiation of cold. Rumford's views +respecting _frigorific rays_ have not been generally accepted, and +Prevost's theory of exchanges completely explains the apparent +radiation of cold without supposing that cold is anything else than +the mere absence of heat. + +We must pass over Rumford's papers on the use of steam as a vehicle of +heat, on new boilers and stoves for the purpose of economizing fuel, +and all the papers bearing on the nutritive value of different foods. +The calorimeter with which he determined the amount of heat generated +by the combustion, and the latent heat of evaporation, of various +bodies has been already alluded to. Of the four volumes of Rumford's +works published by the American Academy of Arts and Sciences, the +third is taken up entirely with descriptions of fireplaces and of +cooking utensils. + +Before deciding on the best way to light the military workhouse at +Munich, Rumford made a series of experiments on the relative economy +of different methods, and for this purpose designed his well-known +shadow-photometer. In the final form of this instrument the shadows +were thrown on a plate of ground glass covered with paper, forming the +back of a small box, from which all extraneous light was excluded. Two +rods were placed in front of this screen, and the lights to be +compared were so situated that the shadow of one rod thrown by the +first light might be just in contact with that of the other rod thrown +by the second light. By introducing coloured glasses in front of the +lights, Rumford compared the illuminating powers of different sources +with respect to light of a particular colour. The complementary tints +exhibited by the shadows caused him to devise his theory of the +harmony of complementary colours. One result is worthy of mention: it +is a conclusion to which public attention has since been called in +connection with "duplex" burners. Rumford found that with wax tapers +the amount of light emitted per grain of wax consumed diminished with +the diminution of the consumption, so that a small taper gave out only +one-sixteenth as much light as an ordinary candle for the same +consumption of wax. He says:-- + +"This result can be easily explained if we admit the hypothesis which +supposes light to be analogous to sound.... The particles ... were so +rapidly cooled ... that they had hardly time to shine one instant +before they became too cold to be any longer visible." + +An argand lamp, when compared with a lamp having a flat wick, gave +more light in the ratio of 100 to 85 for the same consumption of oil. + +One of the latest investigations of Rumford was that bearing on the +effect of the width of the wheels on the draught of a carriage. To his +own carriage, weighing, with its passengers, nearly a ton, he fitted a +spring dynamometer by means of a set of pulleys attached to the +under-carriage and the splinter-bar. He used three sets of wheels, +respectively 1-3/4, 2-1/4, and 4 inches wide, and, introducing weights +into the carriage to make up for the difference in the weights of the +wheels, he found a very sensible diminution in the tractive force +required as the width of the wheels was increased, and in a truly +scientific spirit, despising the ridicule cast upon him, he persisted +in riding about Paris in a carriage with four-inch tyres. + +But the piece of work by which Rumford will be best known to future +generations is that described in his paper entitled "An Inquiry +concerning the Source of the Heat which is excited by Friction." It +was while superintending the boring of cannon in the arsenal at Munich +that Rumford was struck with the enormous amount of heat generated by +the friction of the boring-bar against the metal. In order to +determine whether the heat had come from the chips of metal +themselves, he took a quantity of the abraded borings and an equal +weight of chips cut from the metal with a fine saw, and, heating them +to the temperature of boiling water, he immersed them in equal +quantities of water at 59-1/2 deg. Fahr. The change of temperature of the +water was the same in both cases, and Rumford found that there was no +change which he could discover _in regard to its capacity for heat_ +produced in the metal by the action of the borer. + +In order to prevent the honeycombing of the castings by the escaping +gas, the cannon were cast in a vertical position with the breech at +the bottom of the mould and a short cylinder projecting about two feet +beyond the muzzle of the gun, so that any imperfections in the casting +would appear in this projecting cylinder. It was on one of these +pieces of waste metal, while still attached to the gun, that Rumford +conducted his experiments. Having turned the cylinder, he cut away the +metal in front of the muzzle until the projecting piece was connected +with the gun by a narrow cylindrical neck, 2.2 inches in diameter and +3.8 inches long. The external diameter of the cylinder was 7.75 +inches, and its length 9.8 inches, and it was bored to a depth of 7.2 +inches, the diameter of the bore being 3.7 inches. The cannon was +mounted in the boring-lathe, and a blunt borer pressed by a screw +against the bottom of the bore with a force equal to the weight of +10,000 pounds. A small transverse hole was made in the cylinder near +its base for the introduction of a thermometer. The cylinder weighed +113.13 pounds, and, with the gun, was turned at the rate of thirty-two +revolutions per minute by horse-power. To prevent loss of heat, the +cylinder was covered with flannel. After thirty minutes' work, the +thermometer, when introduced into the cylinder, showed a temperature +of 130 deg. Fahr. The loss of heat during the experiment was estimated +from observations of the rate of cooling of the cylinder. The weight +of metal abraded was 837 grains, while the amount of heat produced was +sufficient to raise nearly five pounds of ice-cold water to the +boiling point. + +To exclude the action of the air, the cylinder was closed by an +air-tight piston, but no change was produced in the result. As the air +had access to the metal where it was rubbed by the piston, and Rumford +thought this might possibly affect the result, a deal box was +constructed, with slits at each end closed by sliding shutters, and so +arranged that it could be placed with the boring bar passing through +one slit and the narrow neck connecting the cylinder with the gun +through the other slit, the sliding shutters, with the help of collars +of oiled leather, serving to make the box water-tight. The box was +then filled with water and the lid placed on. After turning for an +hour the temperature was raised from 60 deg. to 107 deg. Fahr., after an hour +and a half it was 142 deg. Fahr., at the end of two hours the temperature +was 178 deg. Fahr., at two hours and twenty minutes it was 200 deg. Fahr., and +at two hours and thirty minutes it ACTUALLY BOILED! + +"It would be difficult to describe the surprise and astonishment +expressed in the countenances of the bystanders on seeing so large a +quantity of cold water heated and actually made to boil without any +fire. + +"Though there was, in fact, nothing that could justly be considered as +surprising in this event, yet I acknowledge fairly that it afforded me +a degree of childish pleasure which, were I ambitious of the +reputation of a _grave philosopher_, I ought most certainly rather to +hide than to discover." + +Rumford estimated the "total quantity of ice-cold water which, with +the heat actually generated by the friction and accumulated in two +hours and thirty minutes, might have been heated 180 degrees, or made +to boil" at 26.58 pounds, and the rate of production he considered +exceeded that of nine wax candles, each consuming ninety-eight grains +of wax per hour, while the work of turning the lathe could easily have +been performed by one horse. This was the first rough attempt ever +made, so far as we know, to determine the mechanical equivalent of +heat. + +In his reflections on these experiments, Rumford writes:-- + + It is hardly necessary to add that anything which any + _insulated_ body or system of bodies can continue to furnish + _without limitation_ cannot possibly be _a material substance_; + and it appears to me to be extremely difficult, if not quite + impossible, to form any distinct idea of anything capable of + being excited and communicated in the manner the heat was + excited and communicated in these experiments, except it be + MOTION. + +It has been stated that, if Rumford had dissolved in acid the borings +and the sawn strips of metal, the capacity for heat of which he +determined, and had shown that the heat developed in the solution was +the same in the two cases, his chain of argument would have been +absolutely complete. Considering the amount of heat produced in the +experiments, there are few minds whose conviction would be +strengthened by this experiment, and it is only those who look for +faultless logic that will refuse to Rumford the credit of having +established the dynamical nature of heat. + +Davy afterwards showed that two pieces of ice could be melted by being +rubbed against one another in a vacuum, but he does not appear to have +made as much as he might of the experiment. Mayer calculated the +mechanical equivalent of heat from the heat developed in the +compression of air, but he _assumed_, what afterwards was shown by +Joule to be nearly true, that the whole of the work done in the +compression was converted into heat. It was Joule, however, who first +showed that heat and mechanical energy are mutually convertible, so +that each may be expressed in terms of the other, a _given_ quantity +of heat always corresponding to the _same amount_ of mechanical +energy, whatever may be the intermediate stages through which it +passes, and that we may therefore define the mechanical equivalent of +heat as _the number of units of energy which, when entirely converted +into heat, will raise unit mass of water one degree from the freezing +point_. + + + + +THOMAS YOUNG. + + +"We here meet with a man altogether beyond the common standard, one in +whom natural endowment and sedulous cultivation rivalled each other in +the production of a true philosopher; nor do we hesitate to state our +belief that, since Newton, Thomas Young stands unrivalled in the +annals of British science." Such was the verdict of Principal Forbes +on one who may not only be regarded as one of the founders of the +undulatory theory of light, but who was among the first to apply the +theory of elasticity to the strength of structures, while it is to him +that we are indebted in the first instance for all we know of Egyptian +hieroglyphics, and for the vast field of antiquarian research which +the interpretation of these symbols has opened up. + +Thomas Young was the son of Thomas and Sarah Young, and the eldest of +ten children. His mother was a niece of the well-known physician, Dr. +Richard Brocklesby, and both his father and mother were members of +the Society of Friends, in whose principles all their children were +very carefully trained. It was to the independence of character thus +developed that Dr. Young attributed very much of the success which he +afterwards attained. He was born at Milverton, in Somersetshire, on +June 13, 1773. For the greater part of the first seven years of his +life he lived with his maternal grandfather, Mr. Robert Davis, at +Minehead, in Somersetshire. According to his own account, he could +read with considerable fluency at the age of _two_, and, under the +instructions of his aunt and a village schoolmistress, he had "read +the Bible twice through, and also Watts's Hymns," before he attained +the age of four. It may with reason be thought that both the +schoolmistress and the aunt should have been severely reprimanded, and +it is certain that their example is not to be commended; but Young's +infantile constitution seems to have been proof against over-pressure, +and before he was five years old he could recite the whole of +Goldsmith's "Deserted Village," with scarcely a mistake. He commenced +learning Latin before he was six, under the guidance of a +Nonconformist minister, who also taught him to write. When not quite +seven years of age he went to boarding-school, where he remained a +year and a half; but he appears to have learned more by independent +effort than under the guidance of his master, for privately he "had +mastered the last rules of Walkinghame's 'Tutor's Assistant'" before +reaching the middle of the book under the master's inspection. After +leaving this school, he lived at home for six months, but frequently +visited a neighbour who was a land surveyor, and at whose house he +amused himself with philosophical instruments and scientific books, +especially a "Dictionary of Arts and Sciences." When nearly nine he +went to the school of Mr. Thompson, at Compton, in Dorsetshire, where +he remained nearly four years, and read several Greek and Latin +authors, as well as the elements of natural philosophy--the latter in +books lent him by Mr. Jeffrey, the assistant-master. This Mr. Jeffrey +appears to have been something of a mechanical genius, and he gave +Young lessons in turning, drawing, bookbinding, and the grinding and +preparation of colours. Before leaving this school, at the age of +thirteen, Young had read six chapters of the Hebrew Bible. + +During the school holidays the construction of a microscope occupied +considerable time, and the reading of "Priestley on Air" turned +Young's attention to the subject of chemistry. Having learned a little +French, he succeeded, with the help of a schoolfellow, in gaining an +elementary knowledge of Italian. After leaving school, he lived at +home for some time, and devoted his energies mainly to Hebrew and to +turning and telescope-making; but Eastern languages received a share +of attention, and by the time he was fourteen he had read most of Sir +William Jones's "Persian Grammar." He then went to Youngsbury, in +Hertfordshire, and resided at the house of Mr. David Barclay, partly +as companion and partly as classical tutor to Mr. Barclay's grandson, +Hudson Gurney. This was the beginning of a friendship which lasted for +life. Gurney was about a year and a half junior to Young, and for five +years the boys studied together, reading the classical works which +Young had previously studied at school. Before the end of these five +years Young had gained more or less acquaintance with fourteen +languages; but his studies were for a time delayed through a serious +illness when he was little more than sixteen. To this illness his +uncle, Dr. Brocklesby, referred in a letter, of which the following +extract is interesting for several reasons:-- + + Recollect that the least slip (as who can be secure against + error?) would in you, who seem in all things to set yourself + above ordinary humanity, seem more monstrous or reprehensible + than it might be in the generality of mankind. Your prudery + about abstaining from the use of sugar on account of the negro + trade, in any one else would be altogether ridiculous, but as + long as the whole of your mind keeps free from spiritual pride + or too much presumption in your facility of acquiring language, + which is no more than the dross of knowledge, you may be + indulged in such whims, till your mind becomes enlightened with + more reason. My late excellent friend, Mr. Day, the author of + 'Sandford and Merton,' abhorred the base traffic in negroes' + lives as much as you can do, and even Mr. Granville Sharp, one + of the earliest writers on the subject, has not done half as + much service in the business as Mr. Day in the above work. And + yet Mr. Day devoured daily as much sugar as I do; for he + reasonably concluded that so great a system as the sugar-culture + in the West Indies, where sixty millions of British property are + employed, could never be affected either way by one or one + hundred in the nation debarring themselves the reasonable use of + it. Reformation must take its rise elsewhere, if ever there is a + general mass of public virtue sufficient to resist such private + interests. Read Locke with care, for he opens the avenues of + knowledge, though he gives too little himself. + +With respect to the sugar, no doubt very much may be said on Young's +side of the question. It appears, however, that in his early manhood +there was a good deal in his conduct which to-day would be regarded as +_priggish_, though it was somewhat more in harmony with the spirit of +his time. + +He left Youngsbury at the age of nineteen, having read, besides his +classical authors, the whole of Newton's "Principia" and "Opticks," +and the systems of chemistry by Lavoisier and Nicholson, besides works +on botany, medicine, mineralogy, and other scientific subjects. One of +Young's peculiarities was the extraordinary neatness of his +handwriting, and a translation in Greek iambics of Wolsey's farewell +to Cromwell, which he sent, written very neatly on vellum, to his +uncle, Dr. Brocklesby, attracted the attention of Mr. Burke, Dr. +Charles Burney, and other classical scholars, so that when, a few +months later, Young went to stay with his uncle in London, and was +thrown into contact with some of the chief literary men of the day, he +found that his fame as a scholar had preceded him. This neatness of +his handwriting and his power of drawing were of great use in his +researches on the Egyptian hieroglyphics. He had little faith in +natural genius, but believed that anything could be accomplished by +persevering application. + + "Thou say'st not only skill is gained, + But genius too may be obtained, + By studious imitation." + +In the autumn of 1792 Young went to London for the purpose of studying +medicine. He lived in lodgings in Westminster, and attended the +Hunterian School of Anatomy. A year afterwards he entered St. +Bartholomew's Hospital as a medical student. The notes which he took +of the lectures were written sometimes in Latin, interspersed with +Greek quotations, and not unfrequently with mathematical calculations, +which may be assumed to have been made before the lecture commenced. +During his school days he had paid some attention to geometrical +optics, and had constructed a microscope and telescope. Now his +attention was attracted to a far more delicate instrument--the eye +itself. Young had learned how a telescope can be "focussed" so as to +give clear images of objects more or less distant. Some such power of +adjustment must be possessed by the eye, or it could never form +distinct images of objects, whether at a distance of a foot or a +mile. The apparently fibrous structure of the crystalline lens of the +eye had been noticed and described by Leuwenhoeck; and Pemberton, a +century before Young took up the subject, had suggested that the +fibres were muscles, by the action of which the eye was "accommodated" +for near or distant vision. In dissecting the eye of an ox Young +thought he had discovered evidence confirmatory of this view, and the +paper which he wrote on the subject was not only published in the +"Philosophical Transactions," but secured his election as a Fellow of +the Royal Society in June, 1794. This paper was important, not simply +because it led to Young's election to the Royal Society, but mainly +because it was his first published paper on optical subjects. Later on +he showed incontestably, by exact measurements, that it is the +crystalline lens which changes its form during adjustment; but he was +wrong in supposing the fibres of the lens to be muscular. By carefully +measuring the distance between the images of two candles formed by +reflection from the cornea, he showed that the cornea experienced no +change of form. His eyes were very prominent; and turning them so as +to look very obliquely, he measured the length of the eye from back to +front with a pair of compasses whose points were protected, pressing +one point against the cornea, and the other between the back of the +eye and the orbit, and showed that, when the eye was focussed for +different distances, there was no change in the length of the axis. +The crystalline lens was the only resource left whereby the +accommodation could be effected. The accommodation is, in fact, +brought about by the action of the ciliary muscle. The natural form of +the lens is more convex than is consistent with distinct vision, +except for very near objects. The tension of the suspensory ligament, +which is attached to the front of the lens all round its edge, renders +the anterior surface of the lens much less curved than it would +naturally be. The ciliary muscle is a ring of muscular fibre attached +to the ciliary process close to the circumference of the suspensory +ligament. By its contraction it forms a smaller ring, and, diminishing +the external diameter, it releases the tension of the suspensory +ligament, thus allowing the crystalline lens to bulge out and adapt +itself for the diverging rays coming from near objects. It is the +exertion of contracting the ciliary muscle that constitutes the effort +of which we are conscious when looking at very near objects. It was +not, however, till long after the time of Dr. Young that this +complicated action was fully made out, though the change of form of +the anterior surface of the crystalline lens was discovered by the +change in the image of a bright object formed by reflection. + +In the spring of 1794 Young took a holiday tour in Cornwall, with +Hudson Gurney, visiting on his way the Duke of Richmond, who was +drinking the waters at Bath, under the advice of Dr. Brocklesby. In +Cornwall, the mining machinery attracted his attention very much more +than the natural beauties of the country. Towards the end of the +summer he visited the Duke of Richmond at Goodwood, when the duke +offered him the appointment of private secretary. He resolved, +however, to continue his medical course, one of the reasons which he +alleged being his regard for the Society of Friends, whose principles +he considered inconsistent with the appointment of Private Secretary +to the Master-General of the Ordnance. + +The following winter he spent as a medical student at Edinburgh. Here +he gave up the costume of the Society of Friends, and in many ways +departed from their rules of conduct. He mingled freely with the +university, attended the theatre, took lessons in dancing and playing +the flute, and generally cultivated the habits of what is technically +known as "society." Throughout this change in his life he retained his +high moral principles as a guide of conduct, and appears to have acted +from a firm conviction of what was right. At the same time, it must be +admitted that the breaking down of barriers, however conventional they +may be, is an operation attended in most cases by not a little danger. +With Young, the progress of his scientific education may have been +delayed on account of the new demands on his time; but besides the +study of German, Spanish, and Italian, he appears to have read a +considerable amount of general literature during his winter session in +Edinburgh. The following summer he took a tour on horseback through +the Highlands, taking with him his flute, drawing materials, spirits +for preserving insects, boards for drying plants, paper and twine for +packing up minerals, and a thermometer; but the geological hammer does +not then appear to have been regarded as an essential to the equipment +of a philosopher. At Aberdeen he stayed for three days, and reported +thus on the university:-- + + Some of the professors are capable of raising a university to + celebrity, especially Copeland and Ogilvie; but the division and + proximity of the two universities (King's College and Marischal + College) is not favourable to the advancement of learning; + besides, the lectures are all, or mostly, given at the same + hour, and the same professor continues to instruct a class for + four years in the different branches. Were the colleges united, + and the internal regulations of the system new modelled, the + cheapness of the place, the number of small bursaries for poor + or distinguished students, and the merit of the instructors, + might make this university a very respectable seminary in some + branches of science. The fee to a professor for a five-months' + session is only a guinea and a half. I was delighted with the + inspection of the rich store of mathematical and philosophical + apparatus belonging to Professor Copeland of Marischal College, + made in his own house, and partly with his own hands, finished + with no less care than elegance; and tending to illustrate every + branch of physics in the course of his lectures, which must be + equally entertaining and instructive. + +Before leaving the Highlands, Young visited Gordon Castle, where he +stayed two days; and appears to have distinguished himself by the +powers of endurance he exhibited in dancing reels. On leaving he +writes: "I could almost have wished to break or dislocate a limb by +chance, that I might be detained against my will; I do not recollect +that I have ever passed my time more agreeably, or with a party that I +thought more congenial to my own dispositions: and what would hardly +be credited by many grave reasoners on life and manners, that a person +who had spent the whole of his earlier years a recluse from the gay +world, and a total stranger to all that was passing in the higher +ranks of society, should feel himself more at home and more at ease in +the most magnificent palace in the country than in the humblest +dwelling with those whose birth was most similar to his own. Without +enlarging on the duke's good sense and sincerity, the duchess's spirit +and powers of conversation, Lady Madeline's liveliness and affability, +Louisa's beauty and sweetness, Georgiana's _naivete_ and quickness of +parts, young Sandy's good nature, I may say that I was truly sorry to +part with every one of them." + +Young seems not to have known at this time that it is an essential +feature of true gentlefolk to dissipate all sense of constraint or +uneasiness from those with whom they are brought into contact and +that in this they can be readily distinguished from those who have +wealth without breeding. The Duchess of Gordon gave Young an +introduction to the Duke of Argyll, so, while travelling through the +Western Highlands, he paid a visit to Inverary Castle, and "galloped +over" the country with the duke's daughters. Speaking of these ladies, +he says, "Lady Charlotte ... is to Lady Augusta what Venus is to +Minerva; I suppose she wishes for no more. Both are goddesses." + +On his return to the West of England, he visited the Coalbrook Dale +Iron Works, when Mr. Reynolds told him "that before the war he had +agreed with a man to make a flute a hundred and fifty feet long, and +two and a half in diameter, to be blown by a steam-engine and played +on by barrels." + +On the 7th of the following October Young left London, and after +spending six days on the voyage from Yarmouth to Hamburg, he reached +Goettingen on the 27th of the same month; two days afterwards he +matriculated, and on November 3 he commenced his studies as a member +of the university. He continued to take lessons in drawing, dancing, +riding, and music, and commenced learning the clavichord. The English +students at Goettingen, in order to advance their German conversation, +arranged to pay a fine whenever they spoke in English in one another's +company. On Sundays it was usual for the professors to give +entertainments to the students, though they seldom invited them to +dinner or supper. "Indeed, they could not well afford, out of a fee +of a louis or two, to give large entertainments; but the absence of +the hospitality which prevails rather more in Britain, is compensated +by the light in which the students are regarded; they are not the +less, but perhaps the more, respected for being students, and indeed, +they behave in general like gentlemen, much more so than in some other +German universities." + +At Goettingen Young attended, in addition to his medical lectures, +Spithler's lectures on the History and Constitution of the European +States, Heyne on the History of the Ancient Arts, and Lichtenberg's +course on Physics. Speaking of Blumenbach's lectures on Natural +History, Young says, "He showed us yesterday a laborious treatise, +with elegant plates, published in the beginning of this century at +Wurzburg, which is a most singular specimen of credulity in affairs of +natural history. Dr. Behringen used to torment the young men of a +large school by obliging them to go out with him collecting +petrifactions; and the young rogues, in revenge, spent a whole winter +in counterfeiting specimens, which they buried in a hill which the +good man meant to explore, and imposed them upon him for most +wonderful _lusus naturae_. It is interesting in a metaphysical point of +view to observe how the mind attempts to accommodate itself; in one +case, where the boys had made the figure of a plant thick and clumsy, +the doctor remarks the difference, and says that Nature seems to have +restored to the plant in thickness that which she had taken away from +its other dimensions." + +On April 30, 1796, Young passed the examination for his medical degree +at Goettingen. The examination appears to have been entirely oral. It +lasted between four and five hours. There were four examiners seated +round a table provided "with cakes, sweetmeats, and wine, which helped +to pass the time agreeably." They "were not very severe in exacting +accurate answers." The subject he selected for his public discussion +was the human voice, and he constructed a universal alphabet +consisting of forty-seven letters, of which, however, very little is +known. This study of sound laid the foundation, according to his own +account, of his subsequent researches in the undulatory theory of +light. + +The autumn of 1796 Young spent in travelling in Germany; in the +following February he returned to England, and was admitted a +fellow-commoner of Emmanuel College, Cambridge. It is said that the +Master, in introducing Young to the Tutors and other Fellows, said, "I +have brought you a pupil qualified to read lectures to his tutors." +Young's opinion of Cambridge, as compared with German universities, +was favourable to the former; but as he had complained of the want of +hospitality at Goettingen, so in Cambridge he complained of the want of +social intercourse between the senior members of the university and +persons _in statu pupillari_. At that time there was no system of +medical education in the university, and the statutes required that +six years should elapse between the admission of a medical student and +his taking the degree of M.B. Young appears to have attracted +comparatively little attention as an undergraduate in college. He did +not care to associate with other undergraduates, and had little +opportunity of intercourse with the senior members of the university. +He was still keeping terms at Cambridge when his uncle, Dr. +Brocklesby, died. To Young he left the house in Norfolk Street, Park +Lane, with the furniture, books, pictures, and prints, and about +L10,000. In the summer of 1798 a slight accident at Cambridge +compelled Young to keep to his rooms, and being thus forcibly deprived +of his usual round of social intercourse, he returned to his favourite +studies in physics. The most important result of this study was the +establishment of the principle of interference in sound, which +afforded the explanation of the phenomenon of "beats" in music, and +which afterwards led up to the discovery of the interference of +light--a discovery which Sir John Herschel characterized as "the key +to all the more abstruse and puzzling properties of light, and which +would alone have sufficed to place its author in the highest rank of +scientific immortality, even were his other almost innumerable claims +to such a distinction disregarded." + +The principle of interference is briefly this: When two waves meet +each other, it may happen that their crests coincide; in this case a +wave will be formed equal in height (amplitude) to the sum of the +heights of the two. At another point the crest of one wave may +coincide with the hollow of another, and, as the waves pass, the +height of the wave at this point will be the difference of the two +heights, and if the waves are equal the point will remain stationary. +If a rope be hung from the ceiling of a lofty room, and the lower end +receive a jerk from the hand, a wave will travel up the rope, be +reflected and reversed at the ceiling, and then descend. If another +wave be then sent up, the two will meet, and their passing can be +observed. It will then be seen that, if the waves are exactly equal, +the point at which they meet will remain at rest during the whole time +of transit. If a number of waves in succession be sent up the string, +the motions of the hand being properly timed, the string will appear +to be divided into a number of vibrating segments separated by +stationary points, or nodes. These nodes are simply the points which +remain at rest on account of the upward series of waves crossing the +series which have been reflected at the top and are travelling +downwards. The division of a vibrating string into nodes thus affords +a simple example of the principle of interference. When a tuning-fork +is vibrating there are certain hyperbolic lines along which the +disturbance caused by one prong is exactly neutralized by that due to +the other prong. If a large tuning-fork be struck and then held near +the ear and slowly turned round, the positions of comparative silence +will be readily perceived. If two notes are being sounded side by +side, one consisting of two hundred vibrations per second and the +other of two hundred and two, then, at any distant point, it is clear +that the two sets of waves will arrive in the same condition, or +"phase," twice in each second, and twice they will be in opposite +conditions, and, if of the same intensity, will exactly destroy one +another's effects, thus producing silence. Hence twice in the second +there will be silence and twice there will be sound, the waves of +which have double the amplitude due to either source, and hence the +sound will have four times the intensity of either note by itself. +Thus there will be two "beats" per second due to interference. Later +on this principle was applied by Young to very many optical phenomena +of which it afforded a complete explanation. + +Young completed his last term of residence at Cambridge in December, +1799, and in the early part of 1800 he commenced practice as a +physician at 48, Welbeck Street. In the following year he accepted the +chair of Natural Philosophy in the Royal Institution, which had +shortly before been founded, and soon afterwards, in conjunction with +Davy, the Professor of Chemistry, he undertook the editing of the +journals of the institution. This circumstance has already been +alluded to in connection with Count Rumford, the founder of the +institution. He lectured at the Royal Institution for two years only, +when he resigned the chair in deference to the popular belief that a +physician should give his attention wholly to his professional +practice, whether he has any or not. This fear lest a scientific +reputation should interfere with his success as a physician haunted +him for many years, and sometimes prevented his undertaking scientific +work, while at other times it led him to publish anonymously the +results he obtained. This anonymous publication of scientific papers +caused him great trouble afterwards in order to establish his claim to +his own discoveries. Many of the articles which he contributed to the +supplement to the fourth, fifth, and sixth editions of the +"Encyclopaedia Britannica" were anonymous, although the honorarium he +received for this work was increased by 25 per cent. when he would +allow his name to appear. The practical withdrawal of Young from the +scientific world during sixteen years was a great loss to the progress +of natural philosophy, while the absence of that suavity of manner +when dealing with patients which is so essential to the success of a +physician, prevented him from acquiring a valuable private practice. +In fact, Young was too much of a philosopher in his behaviour to +succeed as a physician; he thought too deeply before giving his +opinion on a diagnosis, instead of appearing to know all about the +subject before he commenced his examination, and this habit, which is +essential to the philosopher, does not inspire confidence in the +practitioner. His fondness for society rendered him unwilling to live +within the means which his uncle had left him, supplemented by what +his scientific work might bring, and it was not until his income had +been considerably increased by an appointment under the Admiralty that +he was willing to forego the possible increase of practice which might +accrue by appearing to devote his whole attention to the subject of +medicine. It was this fear of public opinion which caused him, in +1812, to decline the offer of the appointment of Secretary to the +Royal Society, of which, in 1802, he accepted the office of Foreign +Secretary. + +Young's resignation of the chair of Natural Philosophy was, however, +not a great loss to the Royal Institution; for the lecture audience +there was essentially of a popular character, and Young cannot be +considered to have been successful as a popular lecturer. His own +early education had been too much derived from private reading for him +to have become acquainted with the difficulties experienced by +beginners of only average ability, and his lectures, while most +valuable to those who already possessed a fair knowledge of the +subjects, were ill adapted to the requirements of an unscientific +audience. A syllabus of his course of lectures was published by Young +in 1802, but it was not till 1807 that the complete course of sixty +lectures was published in two quarto volumes. They were republished in +1845 in octavo, with references and notes by Professor Kelland. Among +the subjects treated in these lectures are mechanics, including +strength of materials, architecture and carpentry, clocks, drawing and +modelling; hydrostatics and hydraulics; sound and musical instruments; +optics, including vision and the physical nature of light; astronomy; +geography; the essential properties of matter; heat; electricity and +magnetism; climate, winds, and meteorology generally; vegetation and +animal life, and the history of the preceding sciences. The lectures +were followed by a most complete bibliography of the whole subject, +including works in English, French, German, Italian, and Latin. The +following is the syllabus of one lecture, and illustrates the +diversity of the subjects dealt with:-- + + "ON DRAWING, WRITING, AND MEASURING. + + "Subjects preliminary to the study of practical mechanics; + instrumental geometry; statics; passive strength; friction; + drawing; outline; pen; pencil; chalks; crayons; Indian ink; + water-colours; body colours; miniature; distemper; fresco; oil; + encaustic paintings; enamel; mosaic work. Writing; materials + for writing; pens; inks; use of coloured inks for denoting + numbers; polygraph; telegraph; geometrical instruments; rulers; + compasses; flexible rulers; squares; triangular compasses; + parallel rulers; Marquois's scales; pantograph; proportional + compasses; sector. Measurement of angles; theodolites; + quadrants; dividing-engine; vernier; levelling; sines of + angles; Gunter's scale; Nicholson's circle; dendrometer; + arithmetical machines; standard measures; quotation from + Laplace; new measures; decimal divisions; length of the + pendulum and of the meridian of the earth; measures of time; + objections; comparison of measures; instruments for measuring; + micrometrical scales; log-lines." + +This represents an extensive area to cover in a lecture of one hour. + +When Newton, by means of a prism, + + "Unravelled all the shining robe of day," + +he showed that sunlight is made up of light varying in tint from red, +through orange, yellow, green, and blue, to violet, and that by +recombining all these kinds of light, or certain of them selected in +an indefinite number of ways, white light could be produced. +Subsequently Sir Wm. Herschel showed that rays less refrangible than +the red were to be found among the solar radiation; and other rays +more refrangible than the violet, but, like the ultra-red rays, +incapable of exciting vision, were found by Ritter and Wollaston. In +speaking of Newton's experiments, in his thirty-seventh lecture, Young +says:-- + + It is certain that the perfect sensations of yellow and of blue + are produced respectively by mixtures of red and green and of + green and violet light, and there is reason to suspect that + those sensations are always compounded of the separate + sensations combined; at least, this supposition simplifies the + theory of colours. It may, therefore, be adopted with advantage, + until it be found inconsistent with any of the phenomena; and we + may consider white light as composed of a mixture of red, green, + and violet only, ... with respect to the quantity or intensity + of the sensations produced. + +It should be noticed that, in the above quotation, Young speaks only +of the sensations produced. Objectively considered, sunlight consists +of an infinite number of differently coloured lights comprising nearly +all the shades from one end of the spectrum to the other, though white +light may have a much simpler constitution, and may, for example, +consist simply of a mixture of homogeneous red, green, and violet +lights, or of homogeneous yellow and blue lights, properly selected. +But considered subjectively, Young implies that the eye perceives +three, and only three, distinct colour-sensations, corresponding to +pure red, green, and violet; that when these three sensations are +excited in a certain proportion, the complex sensation is that of +white light; but if the relative intensities of the separate +sensations differ from these ratios, the perception is that of some +colour. To exhibit the effects of mixing light of different colours, +Young painted differently coloured sectors on circles of cardboard, +and then made the discs rotate rapidly about their centres, when the +effect was the same as though the lights emitted by the sectors were +mixed in proportion to the breadth of the sectors. This contrivance +had been previously employed by Newton, and will be again referred to +in connection with another memoir. The results of these experiments +were embodied by Young in a diagram of colour, consisting of an +equilateral triangle, in which the colours red, green, and violet, +corresponding to the simple sensations, were placed at the angles, +while those produced by mixing the primary colours in any proportions, +were to be found within the triangle or along its sides; the rule +being that the colour formed by the admixture of the primary colours +in any proportions, was to be found at the centre of gravity of three +heavy particles placed at the angular points of the triangle, with +their masses proportioned to the corresponding amounts of light. Thus +the colours produced by the admixture of red and green only, in +different proportions, were placed along one side of the triangle, +these colours corresponding to various tints of scarlet, orange, +yellow, and yellowish green; another side contained the mixtures of +green and violet representing the various shades of bluish green and +blue; and the third side comprised the admixtures of red and violet +constituting crimsons and purples. The interior of the triangle +contained the colours corresponding to the mixture of all three +primary sensations, the centre being neutral grey, which is a pure +white faintly illuminated. If white light of a certain degree of +intensity fall on white paper, the paper appears white, but if a +stronger light fall on another portion of the same sheet, that which +is less strongly illuminated appears grey by contrast. Shadows thrown +on white paper may possess any degree of intensity, corresponding to +varying shades of neutral grey, up to absolute blackness, which +corresponds to a total absence of light. Thus considered, +chromatically black and white are the same, differing only in the +amount of light they reflect. A piece of white paper in moonlight is +darker than black cloth in full sunlight. + +It must be remembered that Young's diagram of colours corresponds to +the admixture of coloured lights, not of colouring materials or +pigments. The admixture of blue and yellow lights in proper +proportions may make white or pink, but never green. The admixture of +blue and yellow pigments makes a green, because the blue absorbs +nearly all the light except green, blue, and a little violet, while +the yellow absorbs all except orange, yellow, and green. The green +light is the only light common to the two, and therefore the only +light which escapes absorption when the pigments are mixed. Another +point already noticed must also be carefully borne in mind. Young was +quite aware that, physically, there are an infinite number of +different kinds of light differing continuously in wave-length from +the ultra-red to the ultra-violet, though colour can hardly be +regarded as an attribute of the light considered objectively. The +question of colour is essentially one of perception--a physiological, +not a physical, question--and it is only in this sense that Young +maintained the doctrine of three primary colours. In his paper on the +production of colours, read before the Royal Society on July 1, 1802, +he speaks of "the proportions of the sympathetic fibres of the +retina," corresponding to these primary colour-sensations. According +to this doctrine, white light would always be produced when the three +sensations were affected in certain proportions, whether the exciting +cause were simply two kinds of homogeneous light, corresponding to two +pure tones in music, or an infinite number of different kinds, as in +sunlight; and a particular yellow sensation might be excited by +homogeneous yellow light from one part of the spectrum, or by an +infinite number of rays of different wave-lengths, corresponding to +various shades of red, orange, yellow, and green. Subjectively, the +colours would be the same; objectively, the light producing them would +differ exceedingly. + +But Young's greatest service to science was his application of the +principle of interference--of which he had already made good use in +the theory of sound--to the phenomena of light. The results of these +researches were presented to the Royal Society, and two of the papers +were selected as Bakerian lectures in 1801 and 1803 respectively. +Unfavourable criticisms of these papers, which appeared in the +_Edinburgh Review_, and were said to have been written by Mr. +(afterwards Lord) Brougham, seem to have caused their contents to be +neglected by English men of science for many years; and it was to +Arago and Fresnel that we are indebted for recalling public attention +to them. The undulatory theory of light, which maintains that light +consists of waves transmitted through an _ether_, which pervades all +space and all matter, owes its origin to Hooke and Huyghens. Huyghens +showed that this theory explained, in a very beautiful manner, the +laws of reflection and of refraction, if it be allowed that light +travels more slowly the denser the medium. According to the celebrated +principle of Huyghens, every point in the front of a wave at any +instant becomes a centre of disturbance, from which a secondary wave +is propagated. The fronts of these secondary waves all lie on a +surface, which becomes the new surface of the primary wave. When light +enters a denser medium obliquely, the secondary waves which are +propagated within the denser medium extend to a less distance than +those propagated in the rarer medium, and thus the front of the +primary wave becomes bent at the point where it meets the common +surface. Huyghens explained, not only the laws of ordinary refraction +in this manner, but, by supposing the secondary waves to form +spheroids instead of spheres, he obtained the laws of refraction of +the extraordinary ray in Iceland-spar. He did not, however, succeed in +explaining why light should not diverge laterally instead of +proceeding in straight lines. Newton supported the theory that light +consists of particles or corpuscles projected in straight lines from +the luminous body, and sometimes transmitted, sometimes reflected, +when incident on a transparent medium of different density. To account +for the particle being sometimes transmitted and sometimes reflected, +Newton had recourse to the hypothesis of "fits of easy transmission +and of easy reflection," and, to account for the fits themselves, he +supposed the existence of an ether, the vibrations of which affected +the particles. The laws of reflection were readily explained, being +the same as for a perfectly elastic ball; the laws of refraction +admitted of very simple explanation, by supposing that the particles +of the denser medium exert a greater attraction on the particles of +light than those of the rarer medium, but that this attraction acts +only through very short distances, so that when the light-corpuscle is +at a sensible distance from the surface, it is attracted equally all +round, and moves as though there were no force acting upon it. As a +consequence of this hypothesis, it follows that the velocity of light +must be greater the denser the medium, while the undulatory theory +leads to precisely the opposite result. When Foucault directly +measured the velocity of light both in air and water, and found it +less in the denser medium, the result was fatal to the corpuscular +theory. + +Dr. Young called attention to another crucial test between the two +theories. When a piece of plate-glass is pressed against a slightly +convex lens, or a watch-glass, a series of coloured rings is formed by +reflected light, with a black spot in the centre. This was accounted +for by Newton by supposing that the light which was reflected in any +ring was in a fit of easy transmission (from glass to air) when it +reached the first surface of the film of air, and in a fit of easy +reflection when it reached the second surface. By measuring the +thickness of a film of air corresponding to the first ring of any +particular colour, the length of path corresponding to the interval +between two fits for that particular kind of light could be +determined. When water instead of air is placed between the glasses, +according to the corpuscular theory the rings should expand; but +according to the undulatory theory they should contract; for the +wave-length corresponds to the distance between successive fits of the +same kind on the corpuscular hypothesis. On trying the experiment, the +rings were seen to contract. This result seemed to favour the +undulatory theory; but the objection urged by Newton that rays of +light do not bend round obstacles, like waves of sound, still held its +ground. This objection Young completely demolished by his principle of +interference. He showed that when light passes through an aperture in +a screen, whatever the shape of the aperture, provided its width is +large in comparison with the length of a wave of light (one +fifty-thousandth of an inch), no sensible amount of light will reach +any point not directly in front of the aperture; for if any point be +taken to the right or left, the disturbances reaching that point from +different points of the aperture will neutralize one another by +interference, and thus no light will be appreciable. When the breadth +of the aperture is only a small multiple of a wave-length, then there +will be some points outside the direct beam at which the disturbances +from different points of the aperture will not completely destroy one +another, and others at which they will destroy one another; and these +points will be different for light of different wave-lengths. In this +way Young not only explained the rectilinear propagation of light, but +accounted for the coloured bands formed when light diverges from a +point through a very narrow aperture. In a similar way he accounted +for the hyperbolic bands of colour observed by Grimaldi within the +shadow of a square near its corners. With a strip of card +one-thirtieth of an inch in width, Young obtained bands of colour +within the shadow which completely disappeared when the light was cut +off from either side of the strip of card, showing that they were +produced by interference of the two portions of light which had +passed, one to the right, the other to the left, of the strip of card. +Professor Stokes has succeeded in showing a bright spot at the centre +of the shadow of a circular disc of the size of a sovereign. The +narrow bands of colour formed near the edge of the shadow of any +object, which Newton supposed to be due to the "inflection" of the +light by the attraction of the object, Young showed to be independent +of the material or thickness of the edge, and completely accounted for +them by the principle of interference. Newton's rings were explained +with equal facility. They were due to the interference of light +reflected from the first and second surfaces of the film of air or +water between the glasses. The black spot at the centre of the +reflected rings was due to the difference between reflection taking +place from the surface of a denser or a rarer medium, half an +undulation being lost when the reflection takes place in glass at the +surface of air. If a little grease or water be placed between two +pieces of glass which are nearly in contact, but the space between be +not filled with the water or grease, but contain air in some parts, +and water or grease in others, a series of rings will be seen by +transmitted light, which have been called "the colours of mixed +plates." Young showed that these colours could be accounted for by +interference between the light that had passed through the air and +that which had passed through the water, and explained the fact that, +to obtain the same colour, the distance between the plates must be +much greater than in the case of Newton's rings. + +The bands of colour produced by the interference of light proceeding +from a point and passing on each side of a narrow strip of card, have +already been referred to. The bands are broader the narrower the strip +of card. A fine hair gives very broad bands. When a number of hairs +cross one another in all directions, these bands form circular rings +of colour. If the width of the hairs be very variable, the rings +formed will be of different sizes and overlapping one another, no +distinct series will be visible; but when the hairs are of nearly the +same diameter, a series of well-defined circles of colour, resembling +Newton's rings, will be seen, and if the diameter of a particular ring +be measured, the breadth of the hairs can be inferred. Young +practically employed this method for measuring the diameter of the +fibres of different qualities of wool in order to determine their +commercial value. The instrument employed he called the _eriometer_. +It consisted of a plate of brass pierced with a round hole about +one-thirtieth of an inch in diameter in the centre, and around this a +small circle, about one-third of an inch in diameter, of very fine +holes. The plate was placed in front of a lamp, and the specimen of +wool was held on wires at such a distance in front of the brass plate +that the first green ring appeared to coincide with the circle of +small holes. The eye was placed behind the lock of wool, and the +distance to which the wool had to be removed in front of the brass +plate in order that the first green ring might exactly coincide with +the small circle of fine holes, was proportional to the breadth of the +fibres. The same effect is produced if fine particles, such as +lycopodium powder, or blood-corpuscles, scattered on a piece of glass, +be substituted for the lock of wool, and Young employed the instrument +in order to determine the diameter of blood-corpuscles. He determined +the constant of his apparatus by comparison with some of Dr. +Wollaston's micrometric observations. The coloured halos sometimes +seen around the sun Young referred to the existence of small drops of +water of nearly uniform diameter, and calculated the necessary +diameter for halos of different angular magnitudes. + +The same principle of interference afforded explanation of the colours +of striated surfaces, such as mother-of-pearl, which vary with the +direction in which they are seen. Viewed at one angle light of a +particular colour reflected from different ridges will be in a +condition to interfere, and this colour will be absent from the +reflected light. At a different inclination, the light reaching the +eye from all the ridges (within a certain angle) will be in precisely +the same phase, and only then will light of that colour be reflected +in its full intensity. With a micrometer scale engraved on glass by +Coventry, and containing five hundred lines to the inch, Young +obtained interference spectra. Modern gratings, with several thousand +lines to the inch, afford the purest spectra that can be obtained, and +enable the wave-length of any particular kind of light to be measured +with the greatest accuracy. + +Young's dislike of mathematical analysis prevented him from applying +exact calculation to the interference phenomena which he observed, +such as subsequently enabled Fresnel to overcome the prejudice of the +French Academy and to establish the principle on an incontrovertible +footing. Young's papers attracted very little attention, and Fresnel +made for himself many of Young's earlier discoveries, but at once gave +Young the full credit of the work when his priority was pointed out. +The phenomena of polarization, however, still remained unexplained. +Both Young and Fresnel had regarded the vibrations of light as similar +to those of sound, and taking place in the direction in which the wave +is propagated. The fact that light which had passed through a crystal +of Iceland-spar, was differently affected by a second crystal, +according to the direction of that crystal with respect to the former, +showed that light which had been so transmitted was not like common +light, symmetrical in all azimuths, but had acquired sides or poles. +Such want of symmetry could not be accounted for on the hypothesis +that the vibrations of light took place at right angles to the +wave-front, that is, in the direction of propagation of the light. The +polarization of light by reflection was discovered by Malus, in 1809. +In a letter written to Arago, in 1817, Young hinted at the possibility +of the existence of a component vibration at right angles to the +direction of propagation, in light which had passed through +Iceland-spar. In the following year Fresnel arrived independently at +the hypothesis of transverse vibrations, not as constituting a small +component of polarized light, but as representing completely the mode +of vibration of all light, and in the hands of Fresnel this hypothesis +of transverse vibrations led to a theory of polarization and double +refraction both in uniaxal and biaxal crystals which, though it can +hardly be regarded as complete from a mechanical point of view, is +nevertheless one of the most beautiful and successful applications of +mathematics to physics that has ever been made. To Young, however, +belongs the credit of suggesting that the spheroidal form of the waves +in Iceland-spar might be accounted for by supposing the elasticity +different in the direction of the optic axis and at right angles to +that direction; and he illustrated his view by reference to certain +experiments of Chladni, in which it had been shown that the velocity +of sound in the wood of the Scotch fir is different along, and +perpendicular to, the fibre in the ratio of 5 to 4. Young was also the +first to explain the colours exhibited by thin plates of crystals in +polarized light, discovered by Arago in 1811, by the interference of +the ordinary and extraordinary rays, and Fresnel afterwards completed +Young's explanation in 1822. + +It is for his contributions to the undulatory theory of light that +Young will be most honourably remembered. Hooke, in 1664, referred to +light as a "quick, short, vibrating motion;" Huyghens's "Traite de la +Lumiere" was published in 1690. From that time the undulatory theory +lost ground, until it was revived by Young and Fresnel. It soon after +received great support from the establishment, by Joule and others, of +the mechanical theory of heat. One remark of Young's respecting the +ether opens up a question which has attracted much attention of late +years. In a letter addressed to the Secretary of the Royal Society, +and read January 16, 1800, he says:-- + + That a medium, resembling in many properties that which has been + denominated ether, does really exist, is undeniably proved by + the phenomena of electricity; and the arguments against the + existence of such an ether throughout the universe have been + pretty sufficiently answered by Euler. The rapid transmission of + the electrical shock shows that the electric medium is possessed + of an elasticity as great as is necessary to be supposed for the + propagation of light. Whether the electric ether is to be + considered as the same with the luminous ether--if such a fluid + exists--may perhaps at some future time be discovered by + experiment. + +Besides his contributions to optics, Young made distinct advances in +connection with elasticity, and with surface-tension, or +"capillarity." It is said that Leonardo da Vinci was the first to +notice the ascent of liquids in fine tubes by so-called capillary +attraction. This, however, is only one of a series of phenomena now +very generally recognized, and all of which are referable to the same +action. The hanging of a drop from the neck of a phial; the pressure +of air required to inflate a soap-bubble; the flotation of a greasy +needle on the surface of water; the manner in which some insects rest +on water, by depressing the surface, without wetting their legs; the +possibility of filling a tumbler with water until the surface stands +above the edge of the glass; the nearly spherical form of rain-drops +and of small drops of mercury, even when they are resting on a +table,--are all examples of the effect of surface-tension. These +phenomena have recently been studied very carefully by Quincke and +Plateau, and they have been explained in accordance with the principle +of energy by Gauss. Hawksbee, however, was the first to notice that +the rise of a liquid in a fine tube did not depend on the thickness of +the walls of the tube, and he therefore inferred that, if the +phenomena were due to the attraction of the glass for the liquid, it +could only be the superficial layers which produced any effect. This +was in 1709. Segner, in 1751, introduced the notion of a +surface-tension; and, according to his view, the surface of a liquid +must be considered as similar to a thin layer of stretched +indiarubber, except that the tension is always the same at the surface +bounding the same media. This idea of surface-tension was taken up by +Young, who showed that it afforded explanation of all the known +phenomena of "capillarity," when combined with the fact, which he was +himself the first to observe, that the angle of contact of the same +liquid-surface with the same solid is constant. This angle he called +the "appropriate angle." But Young went further, and attempted to +explain the existence of surface-tension itself by supposing that the +particles of a liquid not only exert an attractive force on one +another, which is constant, but also a repulsive force which increases +very rapidly when the distance between them is made very small. His +views on this subject were embodied in a paper on the cohesion of +liquids, read before the Royal Society in 1804. He afterwards wrote an +article on the same subject for the supplement of the "Encyclopaedia +Britannica." + +The changes which solids undergo under the action of external force, +and their tendency to recover their natural forms, were studied by +Hooke and Gravesande. The experimental fact that, for small changes of +form, the extension of a rod or string is proportional to the tension +to which it is exposed, is known as Hooke's law. The compression and +extension of the fibres of a bent beam were noticed by James +Bernoulli, in 1630, by Duhamel and others. The bending of beams was +also studied by Coulomb and Robison, but Young appears to have been +almost the first to apply the theory of elasticity to the statics of +structures. In a letter to the Secretary of the Admiralty, written in +1811, in reply to an invitation to report on Mr. Steppings's +improvements in naval architecture, Young claimed that he was the only +person who had published "any attempts to improve the _theory_ of +carpentry." It may be here mentioned that Young accepted the +invitation of the Admiralty, and sent in a very exhaustive report, +which their Lordships regarded as "too learned" to be of great +practical value. Young's contributions to this subject will be chiefly +remembered in connection with his "modulus of elasticity." This he +originally defined as follows:-- + +"The modulus of the elasticity of any substance is a column of the +same substance capable of producing a pressure on its base which is to +the weight causing a certain degree of compression as the length of +the substance is to the diminution of its length." + +It is not usual now to express Young's modulus of elasticity in terms +of a length of the substance considered. As now usually defined, +Young's modulus of elasticity is the force which would stretch a rod +or string to double its natural length if Hooke's law were true for so +great an extension. + +So much of Dr. Young's scientific work has been mentioned here because +it was during his early years of professional practice that his most +original scientific work was accomplished. As already stated, after +two years' tenure of the Natural Philosophy chair at the Royal +Institution, Young resigned it because his friends were of opinion +that its tenure militated against his prospects as a physician. In the +summer of 1802 he escorted the great-nephews of the Duke of Richmond +to Rouen, and took the opportunity of visiting Paris. In March, 1803, +he took his degree of M.B. at Cambridge, and on June 14, 1804, he +married Eliza, second daughter of J. P. Maxwell, Esq., whose country +seat was near Farnborough. For sixteen years after his marriage, Young +resided at Worthing during the summer, where he made a very +respectable practice, returning to London in October or November. In +January, 1811, he was elected one of the physicians of St. George's +Hospital, which appointment he retained for the rest of his life. In +this capacity his practice was considerably in advance of the times, +for he regarded medicine as a science rather than an empirical art, +and his careful methods of induction demanded an amount of attention +which medical students, who preferred the more rough-and-ready methods +then in vogue, were slow to give. The apothecary of the hospital +stated that more of Dr. Young's patients went away cured than of those +who were subjected to the more fashionable treatment; but his private +practice, notwithstanding the sacrifices he had made, never became +very valuable. + +In 1816 Young was appointed Secretary to a Commission for determining +the length of the second's pendulum. The reports of this Commission +were drawn up by him, though the experimental work was carried out by +Captain Kater. The result of the work was embodied in an Act of +Parliament, introduced by Sir George Clerk, in 1824, which provided +that if the standard yard should be lost it should "be restored to the +same length," by making it bear to the length of the second's pendulum +at sea-level in London, the ratio of 36 to 39.1393; but before the +standards were destroyed, in 1835, so many sources of possible error +were discovered in the reduction of pendulum observations, that the +Commission appointed to restore the standards recommended that a +material standard yard should be constructed, together with a number +of copies, so that, in the event of the standard being again +destroyed, it might be restored by comparison with its copies. In 1818 +Young was appointed Superintendent of the Nautical Almanac and +Secretary of the Board of Longitude. When this Board was dissolved in +1828, its functions were assumed by the Admiralty, and Young, Faraday, +and Colonel Sabine were appointed a Scientific Committee of Reference +to advise the Admiralty in all matters in which their assistance might +be required. The income from these Government appointments rendered +Young more independent of his practice, and he became less careful to +publish his scientific papers anonymously. In 1820 he left Worthing +and gave up his practice there. The following year, in company with +Mrs. Young, he took a tour through France, Switzerland, and Italy, and +at Paris attended a meeting of the Institute, where he met Arago, who +had called on him in Worthing, in 1816. At the same time he made the +acquaintance of Laplace, Cuvier, Humboldt, and others. In 1824 he +visited Spa, and took a tour through Holland. In the same year Young +was appointed Inspector of Calculations and Medical Referee to the +Palladium Insurance Company. This caused him to turn his attention to +the subject of life assurance and bills of mortality. In 1825, as +Foreign Secretary of the Royal Society, he had the satisfaction of +forwarding to Fresnel the Rumford Medal in acknowledgment of his +researches on polarized light. Fresnel died, in his fortieth year, a +few days after receiving the medal. + +Dr. Young died on May 10, 1829, in the fifty-sixth year of his age, +his excessive mental exertions in early life having apparently led to +a premature old age. He was buried in the parish church of +Farnborough, and a medallion by Sir Francis Chantrey was erected to +his memory in Westminster Abbey. + +But, though Young was essentially a scientific man, his +accomplishments were all but universal, and any memoir of him would be +very incomplete without some sketch of his researches in Egyptian +hieroglyphics. His classical training, his extensive knowledge of +European and Eastern languages, and his neat handwriting and drawing, +have already been referred to. To these attainments must be added his +scientific _method_ and power of careful and systematic observation, +and it will be seen that few persons could come to the task of +deciphering an unknown language with a better chance of success than +Dr. Young. + +The Rosetta Stone was found by the French while excavating at Fort St. +Pierre, near Rosetta, in 1799, and was brought to England in 1802. The +stone bore an inscription in three different kinds of character--the +Hieroglyphic, the Enchorial or Demotic, and the ordinary Greek. +Young's attention was first called to the Egyptian characters by a +manuscript which was submitted to him in 1814. He then obtained copies +of the inscriptions on the Rosetta Stone and subjected them to a +careful analysis. The latter part of the Greek inscription was very +much injured, but was restored by the conjectures of Porson and Heyne, +and read as follows:--"What is here decreed shall be inscribed on a +block of hard stone, in sacred, in enchorial, and in Greek characters, +and placed in each temple, of the first, second, and third gods." + +This indicated that the three inscriptions contained the same decree, +but, unfortunately, the beginnings of the first and second +inscriptions were lost, so that there were no very definitely fixed +points to start upon. The words "Alexander" and "Alexandria," +however, occurred in the Greek, and these words, being so much alike, +might be recognized in each of the other inscriptions. The word +"Ptolemy" appeared eleven times in the Greek inscription, and there +was a word which, from its length and position, seemed to correspond +to it, which, however, appeared fourteen times in the hieroglyphic +inscription. This word, whenever it appeared in the hieroglyphics, was +surrounded by a ring forming what Champollion called a _cartouche_, +which was always employed to denote the names of royal persons. These +words were identified by Baron Sylvestre de Sacy and the Swedish +scholar Akerblad. Young appears to have started with the idea, then +generally current, that hieroglyphic symbols were purely ideographic, +each sign representing a word. His knowledge of Chinese, however, led +him to modify this view. In that language native words are represented +by single symbols, but, when it is necessary to write a foreign word, +a group of word-symbols is employed, each of which then assumes a +phonetic character of the same value as the initial letter of the word +which it represents. The phonetic value of these signs is indicated in +Chinese by a line at the side, or by enclosing them in a square. Young +supposed that the ring surrounding the royal names in the hieroglyphic +inscription had the same value as the phonetic mark in Chinese, and +from the symbols in the name of Ptolemy he commenced to construct a +hieroglyphic alphabet. He made an error, however, in supposing that +some of the symbols might be syllabic instead of alphabetic. It is +true that in the older inscriptions single signs have sometimes a +syllabic value, and sometimes are used ideographically, while in other +cases a single sign representing the whole word is employed in +conjunction with the alphabetic signs, probably to distinguish the +word from others spelt in the same way, but in inscriptions of so late +a date as the Rosetta Stone, the symbols were purely alphabetic. +Another important step made by Young was the discovery of the use of +_homophones_, or different symbols to represent the same letter. +Young's work was closely followed up by Champollion, and afterwards by +Lepsius, Birsch, and others. The greater part of his researches he +never published, though he made careful examinations of several +funeral rolls and other documents. + +It would occupy too much space to give an adequate account of Young's +researches in this subject; some portion of his work he published in a +popular form in the article "Egypt," in the supplement of the +"Encyclopaedia Britannica," to which supplement he contributed about +seventy articles on widely different subjects. Perhaps it is not too +much to say that to Young we owe the foundation of all we now know of +hieroglyphics and the Egyptian history which has been learned from +them; and the obelisk on the Thames Embankment should call to mind the +memory of no one more prominently than that of Thomas Young. + + + + +MICHAEL FARADAY. + + +The work of Michael Faraday introduced a new era in the history of +physical science. Unencumbered by pre-existing theories, and +untrammelled by the methods of the mathematician, he set forth on a +line of his own, and, while engaged in the highest branches of +experimental research, he sought to explain his results by reference +to the most elementary mechanical principles only. Hence it was that +those conclusions which had been obtained by mathematicians only by +the help of advanced analytical methods, and which were expressed by +them only in the language of the integral calculus, Faraday achieved +without any such artificial aids to thought, and expressed in simple +language, having reference to the mechanism which he conceived to be +the means by which such results were brought about. For a long time +Faraday's methods were regarded by mathematicians with something more +than suspicion, and, while they could not but admire his experimental +skill and were compelled to admit the accuracy of his conclusions, his +mode of thought differed too widely from that to which they were +accustomed to command their assent. In Sir William Thomson, and in +Clerk Maxwell, Faraday at length found interpreters between him and +the mathematical world, and to the mathematician perhaps the greatest +monument of the genius of Faraday is the "Electricity and Magnetism" +of Clerk Maxwell. + +Michael Faraday was born at Newington, Surrey, on September 22, 1791, +and was the third of four children. His father, James Faraday, was the +son of Robert and Elizabeth Faraday, of Clapham Wood Hall, in the +north-west of Yorkshire, and was brought up as a blacksmith. He was +the third of ten children, and, in 1786, married Margaret Hastwell, a +farmer's daughter. Soon after his marriage he came to London, where +Michael was born. In 1796 James Faraday, with his family, moved from +Newington, and took rooms over a coach-house in Jacob's Well Mews, +Charles Street, Manchester Square. In looking at this humble abode one +can scarcely help thinking that the Yorkshire blacksmith and his +little family would have been far happier in a country "smiddy" near +his native moors than in a crowded London court; but, had he remained +there, it is difficult to see how the genius of young Michael could +have met with the requisites for its development. + +James Faraday was far from enjoying good health, and his illness +often necessitated his absence from work, and, as a consequence, his +family were frequently in very straitened circumstances. The early +education of Michael was, therefore, not of a very high order, and +consisted "of little more than the rudiments of reading, writing, and +arithmetic." Like most boys in a similar position in London, he found +his amusement for the most part in the streets, but, except that in +his games at marbles we may assume that he played with other boys, we +have no evidence whether his time was spent mostly by himself, or +whether he was one of a "set" of street companions. + +In 1804, when thirteen years of age, Michael Faraday went as +errand-boy to Mr. Geo. Riebau, a bookseller in Blandford Street. Part +of his duty in this capacity was to carry round papers lent on hire by +his master, and in his "Life of Faraday," Dr. Bence Jones tells how +anxious the young errand-boy was to collect his papers on Sunday +morning in time to attend the Sandemanian service with the other +members of his family. + +Faraday was apprenticed to Mr. Riebau on October 7, 1805, and learned +the business of a bookbinder. He occasionally occupied his spare time +in reading the scientific books he had to bind, and was particularly +interested in Mrs. Marcet's "Conversations in Chemistry," and in the +article on "Electricity" in the "Encyclopaedia Britannica." These were +days before the existence of the London Society for the Extension of +University Teaching, and, though Professor Anderson in Glasgow had +shown how the advantages of a university might be extended to those +whose fortunes prevented them from becoming regular university +students, Professor Stuart had not yet taught the English universities +that they had responsibilities outside their own borders, and that the +national universities of the future must be the teachers of all +classes of the community. But private enterprise supplied in a measure +the neglect of public bodies. Mr. Tatum, of 43, Dorset Street, Fleet +Street, advertised a course of lectures on natural philosophy, to be +delivered at his residence at eight o'clock in the evenings. The price +of admission was high, being a shilling for each lecture, but +Michael's brother Robert frequently supplied him with the money, and +in attending these lectures Faraday made many friendships which were +valuable to him afterwards. + +Faraday appears to have been aware of the value of skill in drawing--a +point to which much attention has recently been called by those +interested in technical education--and he spent some portion of his +time in studying perspective, so as to be better able to illustrate +his notes of Mr. Tatum's lectures, as well as of some of Sir Humphry +Davy's, which he was enabled to hear at the Royal Institution through +the kindness of a customer at Mr. Riebau's shop. + +In 1812, before the end of his apprenticeship, Faraday was engaged in +experiments with voltaic batteries of his own construction. Having +cut out seven discs of zinc the size of halfpence, and covered them +with seven halfpence, he formed a pile by inserting pieces of paper +soaked in common salt between each pair, and found that the pile so +constructed was capable of decomposing Epsom salts. With a somewhat +larger pile he decomposed copper sulphate and lead acetate, and made +some experiments on the decomposition of water. On July 21, 1812, in +writing to his friend Abbott, he mentions the movements of camphor +when floating on water, and adds, "Science may be illustrated by those +minute actions and effects, almost as much as by more evident and +obvious phenomena.... My knife is so bad that I cannot mend my pen +with it; it is now covered with copper, having been employed to +precipitate that metal from the muriatic acid." + +Something of Faraday's disposition, as well as of the results of his +self-education, may be gathered from the following quotations from +letters to Abbott, written at this time:-- + + I have again gone over your letter, but am so blinded that I + cannot see any subject except chlorine to write on; but before + entering on what I intend shall fill up the letter, I will ask + your pardon for having maintained an opinion against one who was + so ready to give his own up. I suspect from that circumstance I + am wrong.... In the present case I conceive that experiments may + be divided into three classes: first, those which are for the + old theory of oxymuriatic acid, and consequently oppose the new + one; second, those which are for the new one, and oppose the old + theory; and third, those which can be explained by both + theories--apparently so only, for in reality a false theory can + never explain a fact. + + It is not for me to affirm that I am right and you wrong; + speaking impartially, I can as well say that I am wrong and you + right, or that we both are wrong and a third right. I am not so + self-opinionated as to suppose that my judgment and perception + in this or other matters is better or clearer than that of other + persons; nor do I mean to affirm that this is the true theory in + reality, but only that my judgment conceives it to be so. + Judgments sometimes oppose each other, as in this case; and as + there cannot be two opposing facts in nature, so there cannot be + two opposing truths in the intellectual world. Consequently, + when judgments oppose, one must be wrong--one must be false; and + mine may be so for aught I can tell. I am not of a superior + nature to estimate exactly the strength and correctness of my + own and other men's understanding, and will assure you, dear + A----, that I am far from being convinced that my own is always + right. I have given you the theory--not as the true one, but as + the one which appeared true to me--and when I perceive errors in + it, I will immediately renounce it, in part or wholly, as my + judgment may direct. From this, dear friend, you will see that I + am very open to conviction; and from the manner in which I + shall answer your letter, you will also perceive that I must be + convinced before I renounce. + +On October 7, 1812, Faraday's apprenticeship terminated, and +immediately afterwards he started life as a journeyman bookbinder. He +now found that he had less time at his disposal for scientific work +than he had enjoyed when an apprentice, and his desire to give up his +trade and enter fully upon scientific pursuits became stronger than +ever. During his apprenticeship he had written to Sir Joseph Banks, +then President of the Royal Society, in the hope of obtaining some +scientific employment; he now applied to Sir Humphry Davy. In a letter +written to Dr. Paris, in 1829, Faraday gave an account of this +application. + +"My desire to escape from trade, which I thought vicious and selfish, +and to enter into the service of science, which I imagined made its +pursuers amiable and liberal, induced me at last to take the bold and +simple step of writing to Sir H. Davy, expressing my wishes, and a +hope that, if an opportunity came in his way, he would favour my +views; at the same time, I sent the notes I had taken of his lectures. + +"The answer, which makes all the point of my communication, I send you +in the original, requesting you to take great care of it, and to let +me have it back, for you may imagine how much I value it. + +"You will observe that this took place at the end of the year 1812; +and early in 1813 he requested to see me, and told me of the situation +of assistant in the laboratory of the Royal Institution, then just +vacant. + +"At the same time that he thus gratified my desires as to scientific +employment, he still advised me not to give up the prospects I had +before me, telling me that Science was a harsh mistress, and, in a +pecuniary point of view, but poorly rewarding those who devoted +themselves to her service. He smiled at my notion of the superior +moral feelings of philosophic men, and said he would leave me to the +experience of a few years to set me right on that matter. + +"Finally, through his good efforts, I went to the Royal Institution, +early in March of 1813, as assistant in the laboratory; and in October +of the same year went with him abroad, as his assistant in experiments +and in writing. I returned with him in April, 1815, resumed my station +in the Royal Institution, and have, as you know, ever since remained +there." + +Sir H. Davy's letter was as follows:-- + + "SIR, + + "I am far from displeased with the proof you have given me of + your confidence, and which displays great zeal, power of + memory, and attention. I am obliged to go out of town, and + shall not be settled in town till the end of January; I will + then see you at any time you wish. It would gratify me to be + of any service to you; I wish it may be in my power. + + "I am, sir, + "Your obedient humble servant, + "H. DAVY." + +The minutes of the meeting of managers of the Royal Institution, on +March 1, 1813, contain the following entry:--"Sir Humphry Davy has the +honour to inform the managers that he has found a person who is +desirous to occupy the situation in the institution lately filled by +William Payne. His name is Michael Faraday. He is a youth of +twenty-two years of age. His habits seem good, his disposition active +and cheerful, and his manner intelligent. He is willing to engage +himself on the same terms as those given to Mr. Payne at the time of +quitting the institution. + +"Resolved, that Michael Faraday be engaged to fill the situation +lately occupied by Mr. Payne, on the same terms." + +About this time Faraday joined the City Philosophical Society, which +had been started at Mr. Tatum's house in 1808. The members met every +Wednesday evening, either for a lecture or discussion; and perhaps the +society did not widely differ from some of the "students' +associations" which have more recently been started in connection with +other educational enterprises. Magrath was secretary of this society, +and from it there sprang a smaller band of students, who, meeting once +a week, either at Magrath's warehouse in Wood Street, or at Faraday's +private rooms in the attics of the Royal Institution, for mutual +improvement, read together, and freely criticized each other's +pronunciation and composition. In a letter to Abbott six weeks after +commencing work at the Royal Institution, Faraday says:-- + + A stranger would certainly think you and I were a couple of very + simple beings, since we find it necessary to write to each + other, though we so often personally meet; but the stranger + would, in so judging, only fall into that error which envelops + all those who decide from the outward appearances of things.... + When writing to you I seek that opportunity of striving to + describe a circumstance or an experiment clearly; so that you + will see I am urged on by selfish motives partly to our mutual + correspondence, but, though selfish, yet not censurable. + +During the summer of 1813 Faraday, in his letters to Abbott, gave his +friend the benefit of his experience "on the subject of lectures and +lecturers in general," in a manner that speaks very highly of his +power of observation of men as well as things. He was of opinion that +a lecture should not last more than an hour, and that the subject +should "fit the audience." + +"A lecturer may consider his audience as being polite or vulgar (terms +I wish you to understand according to Shuffleton's new dictionary), +learned or unlearned (with respect to the subject), listeners or +gazers. Polite company expect to be entertained, not only by the +subject of the lecture, but by the manner of the lecturer; they look +for respect, for language consonant to their dignity, and ideas on a +level with their own. The vulgar--that is to say, in general, those +who will take the trouble of thinking, and the bees of business--wish +for something that they can comprehend. This may be deep and elaborate +for the learned, but for those who are as yet tyros and unacquainted +with the subject, must be simple and plain. Lastly, listeners expect +reason and sense, whilst gazers only require a succession of words." + +In favour of experimental illustration he says:-- + +"I need not point out ... the difference in the perceptive powers of +the eye and the ear, and the facility and clearness with which the +first of these organs conveys ideas to the mind--ideas which, being +thus gained, are held far more retentively and firmly in the memory +than when introduced by the ear.... Apparatus, therefore, is an +essential part of every lecture in which it can be introduced.... When +... apparatus is to be exhibited, some kind of order should be +observed in the arrangement of them on the lecture-table. Every +particular part illustrative of the lecture should be in view, no one +thing should hide another from the audience, nor should anything stand +in the way of or obstruct the lecturer. They should be so placed, too, +as to produce a kind of uniformity in appearance. No one part should +appear naked and another crowded, unless some particular reason +exists and makes it necessary to be so." + +On October 13, 1813, Faraday left the Royal Institution, in order to +accompany Sir Humphry Davy in a tour on the Continent. His journal +gives some interesting details, showing the inconveniences of foreign +travel at that time. Sir Humphry Davy took his carriage with him in +pieces, and these had to be put together after escaping the dangers of +the French custom-house on the quay at Morlaix, two years before the +battle of Waterloo. + +One apparently trivial incident somewhat marred Faraday's pleasure +throughout this journey. It was originally intended that the party +should comprise Sir Humphry and Lady Davy, Faraday, and Sir Humphry's +valet, but at the last moment that most important functionary declined +to leave his native shores. Davy then requested Faraday to undertake +such of the duties of valet as were essential to the well-being of the +party, promising to secure the services of a suitable person in Paris. +But no eligible candidate appeared for the appointment, and thus +Faraday had throughout to take charge of domestic affairs as well as +to assist in experiments. Had there been only Sir Humphry and himself, +this would have been no hardship. Sir Humphry had been accustomed to +humble life in his early days; but the case was different with his +lady, and, apparently, Faraday was more than once on the point of +leaving his patron and returning home alone. A circumstance which +occurred at Geneva illustrates the position of affairs. Professor E. +de la Rive invited Sir Humphry and Lady Davy and Faraday to dinner. +Sir Humphry could not go into society with one who, in some respects, +acted as his valet. When this point was represented to the professor, +he replied that he was sorry, as it would necessitate his giving +another dinner-party. Faraday subsequently kept up a correspondence +with De la Rive, and continued it with his son. In writing to the +latter he says, in speaking of Professor E. de la Rive, that he was +"the first who personally at Geneva, and afterwards by correspondence, +encouraged and by that sustained me." + +At Paris Faraday met many of the most distinguished men of science of +the time. One morning Ampere, Clement, and Desormes called on Davy, to +show him some iodine, a substance which had been discovered only about +two years before, and Davy, while in Paris, and afterwards at +Montpellier, executed a series of experiments upon it. After three +months' stay, the party left Paris for Italy, _via_ Montpellier, Aix, +and Nice, whence they crossed the Col de Tende to Turin. The transfer +of the carriage and baggage across the Alps was effected by a party of +sixty-five men, with sledges and a number of mules. The description of +the journey, as recorded in Faraday's diary, makes us respect the +courage of an Englishman who, in the early part of this century, would +attempt the conveyance of a carriage across the Alps in the winter. + +"From Turin we proceeded to Genoa, which place we left afterwards in +an open boat, and proceeded by sea towards Lerici. This place we +reached after a very disagreeable passage, and not without +apprehensions of being overset by the way. As there was nothing there +very enticing, we continued our route to Florence; and, after a stay +of three weeks or a month, left that fine city, and in four days +arrived here at Rome." The foregoing is from Faraday's letter to his +mother. At Florence a good deal of time was spent in the Academia del +Cimento. Here Faraday saw the telescope with which Galileo discovered +Jupiter's satellites, with its tube of wood and paper about three feet +and a half long, and simple object-glass and eye-glass. A red velvet +electric machine with a rubber of gold paper, Leyden jars pierced by +the discharge between their armatures, the first lens constructed by +Galileo, and a number of other objects, were full of interest to the +recently enfranchised bookbinder's apprentice; but it was the great +burning-glass of the grand-duke which was the most serviceable of all +the treasures of the museum. With this glass--which consisted of two +convex lenses about three feet six inches apart, the first lens having +a diameter of about fourteen or fifteen inches, and the second a +diameter of three inches--Davy succeeded in burning several diamonds +in oxygen gas, and in proving that the diamond consists of little else +than carbon. In 1818 Faraday published a paper on this subject in the +_Quarterly Journal of Science_. At Genoa some experiments were made +with the torpedo, but the specimens caught were very small and weak, +and their shocks so feeble that no definite results were obtained. At +Rome Davy attempted to repeat an experiment of Signor Morrichini, +whereby a steel needle was magnetized by causing the concentrated +violet and blue rays from the sun to traverse the needle from the +middle to the north end several times. The experiment did not succeed +in the hands of Davy and Faraday, and it was left to the latter to +discover a relation between magnetism and light. From Rome they +visited Naples and ascended Vesuvius, and shortly afterwards left +Italy for Geneva. In the autumn of 1814 they returned from Switzerland +through Germany, visiting Berne, Zurich, the Tyrol, Padua, Venice, and +Bologne, to Florence, where Davy again carried out some chemical +investigations in the laboratory of the academy. Thence they returned +to Rome, and in the spring went on to Naples, and again visited +Vesuvius, returning to England in April, _via_ Rome, the Tyrol, +Stuttgart, Brussels, and Ostend. + +A fortnight after his return from the Continent Faraday was again +assistant at the Royal Institution, but with a salary of thirty +shillings a week. His character will be sufficiently evident from the +quotations which have been given from his diary and letters. +Henceforth we must be mainly occupied with the consideration of his +scientific work. + +In January, 1816, he gave his first lecture to the City Philosophical +Society. In a lecture delivered shortly afterwards before the same +society, the following passage, which gives an idea of one of the +current beliefs of the time, occurs:-- + +"The conclusion that is now generally received appears to be that +light consists of minute atoms of matter of an octahedral form, +possessing polarity, and varying in size or in velocity.... + +"If now we conceive a change as far beyond vaporization as that is +above fluidity, and then take into account also the proportional +increased extent of alteration as the changes rise, we shall, perhaps, +if we can form any conception at all, not fall far short of radiant +matter;[6] and as in the last conversion many qualities were lost, so +here also many more would disappear. + +[Footnote 6: Not Crookes's.] + +"It was the opinion of Newton, and of many other distinguished +philosophers, that this conversion was possible, and continually going +on in the processes of nature, and they found that the idea would bear +without injury the application of mathematical reasoning--as regards +heat, for instance. If assumed, we must also assume the simplicity of +matter; for it would follow that all the variety of substances with +which we are acquainted could be converted into one of three kinds of +radiant matter, which again may differ from one another only in the +size of their particles or their form. The properties of known bodies +would then be supposed to arise from the varied arrangements of their +ultimate atoms, and belong to substances only as long as their +compound nature existed; and thus variety of matter and variety of +properties would be found co-essential. The simplicity of such a +system is singularly beautiful, the idea grand and worthy of Newton's +approbation. It was what the ancients believed, and it may be what a +future race will realize." + +In the closing words of his fifth lecture to the City Philosophical +Society, Faraday said:-- + +"The philosopher should be a man willing to listen to every +suggestion, but determined to judge for himself. He should not be +biassed by any appearances; have no favourite hypothesis; be of no +school; and in doctrine have no master. He should not be a respecter +of persons, but of things. Truth should be his primary object. If to +these qualities be added industry, he may indeed hope to walk within +the veil of the temple of nature." + +Many years afterwards he stated that, of all the suggestions to which +he had patiently listened after his lectures at the Royal Institution, +only one proved on investigation to be of any value, and that led to +the discovery of the "extra current" and the whole subject of +self-induction. + +Faraday always kept a note-book, in which he jotted down any thoughts +which occurred to him in reference to his work, as well as extracts +from books or other publications which attracted his attention. He +called it his "commonplace-book." Many of the queries which he here +took note of he subsequently answered by experiment. For example:-- + +"Query: the nature of sounds produced by flame in tubes." + +"Convert magnetism into electricity." + +"General effects of compression, either in condensing gases or +producing solutions, or even giving combinations at low temperature." + +"Do the pith-balls diverge by the disturbance of electricity through +mutual induction or not?" + +Speaking of this book, he says, "I already owe much to these notes, +and think such a collection worth the making by every scientific man. +I am sure none would think the trouble lost after a year's +experience." + +In a letter dated May 3, 1818, he writes:-- + + I have this evening been busy with an atmospherical electrical + apparatus. It was a very temporary thing, but answered the + purpose completely. A wire, with some small brush-wire rolled + round the top of it, was elevated into the atmosphere by a thin + wood rod having a glass tube at the end, and tied to a + chimney-pot on the housetop; and this wire was continued down + (taking care that it touched nothing in its way) into the + lecture-room; and we succeeded, at intervals, in getting sparks + from it nearly a quarter of an inch in length, and in charging a + Leyden jar, so as to give a strong shock. The electricity was + positive. Now, I think you could easily make an apparatus of + this kind, and it would be a constant source of interesting + matter; only take care you do not kill yourself or knock down + the house. + +On June 12, 1820, he married Miss Sarah Barnard, third daughter of Mr. +Barnard, of Paternoster Row--"an event which," to use his own words, +"more than any other contributed to his earthly happiness and +healthful state of mind." It was his wish that the day should be "just +like any other day"--that there should be "no bustle, no noise, no +hurry occasioned even in one day's proceeding," though in carrying out +this plan he offended some of his relations by not inviting them to +his wedding. + +Up to this time Faraday's experimental researches had been for the +most part in the domain of chemistry, and for two years a great part +of his energy had been expended in investigating, in company with Mr. +Stodart, a surgical instrument-maker, the properties of certain alloys +of steel, with a view to improve its manufacture for special purposes. +It was in 1821 that he commenced his great discoveries in electricity. +In the autumn of that year he wrote an historical sketch of +electro-magnetism for the "Annals of Philosophy," and he repeated for +himself most of the experiments which he described. In the course of +these experiments, in September, 1821, he discovered the rotation of a +wire conveying an electric current around the pole of a magnet. +[OE]rsted had discovered, in 1820, the tendency of a magnetic needle +to set itself at right angles to a wire conveying a current. This +action is due to a tendency on the part of the north pole to revolve +in a right-handed direction around the current, while the south pole +tends to revolve in the opposite direction. The principle that action +and reaction are equal and opposite indicates that, if a magnetic pole +tend to rotate around a conductor conveying a current, there must be +an equal tendency for the conductor to rotate around the pole. It was +this rotation that constituted Faraday's first great discovery in +electro-dynamics. On December 21, in the same year, Faraday showed +that the earth's magnetism was capable of exerting a directive action +on a wire conveying a current. Writing to De la Rive on the subject, +he says:-- + + I find all the usual attractions and repulsions of the magnetic + needle by the conjunctive wire are deceptions, the motions + being, not attractions or repulsions, nor the result of any + attractive or repulsive forces, but the result of a force in the + wire, which, instead of bringing the pole of the needle nearer + to or further from the wire, endeavours to make it move round it + in a never-ending circle and motion whilst the battery remains + in action. I have succeeded, not only in showing the existence + of this motion theoretically, but experimentally, and have been + able to make the wire revolve round a magnetic pole, or a + magnetic pole round the wire, at pleasure. The law of + revolution, and to which all the other motions of the needle are + reducible, is simple and beautiful. + + Conceive a portion of connecting wire north and south, the north + end being attached to the positive pole of a battery, the south + to the negative. A north magnetic pole would then pass round it + continually in the apparent direction of the sun, from east to + west above, and from west to east below. Reverse the connections + with the battery, and the motion of the pole is reversed; or, if + the south pole be made to revolve, the motions will be in the + opposite direction, as with the north pole. + + If the wire be made to revolve round the pole, the motions are + according to those mentioned.... Now, I have been able, + experimentally, to trace this motion into its various forms, as + exhibited by Ampere's helices, etc., and in all cases to show + that the attractions and repulsions are only appearances due to + this circulation of the pole; to show that dissimilar poles + repel as well as attract, and that similar poles attract as well + as repel; and to make, I think, the analogy between the helix + and common bar magnet far stronger than before. But yet I am by + no means decided that there are currents of electricity in the + common magnet. I have no doubt that electricity puts the circles + of the helix into the same state as those circles are in that + may be conceived in the bar magnet; but I am not certain that + this state is directly dependent on the electricity, or that it + cannot be produced by other agencies; and therefore, until the + presence of electric currents be proved in the magnet by other + than magnetical effects, I shall remain in doubt about Ampere's + theory. + +The most convenient rule by which to remember the direction of these +electro-magnetic rotations is probably that given by Clerk Maxwell, +which will be stated in its place.[7] If a circular plate of copper +and another of zinc be connected by a piece (or better, by three +pieces) of insulated wire, so that the zinc is about an inch above the +copper, and the combined plates be suspended by a silk fibre in a +small beaker of dilute sulphuric acid, which is placed on the pole of +a large magnet, the liquid will be seen to rotate about a vertical +axis in one direction, and the two plates with their connecting wires +in the opposite direction. On reversing the polarity of the magnet, +both rotations will be reversed. This is a very simple mode of +exhibiting Faraday's discovery. A little powdered resin renders the +motion of the liquid readily visible. + +[Footnote 7: See p. 302.] + +In 1823 Faraday published his work on the liquefaction of gases, from +which he concluded that there was no difference in kind between gases +and vapours. In the course of this work he met with more than one +serious explosion. On January 8, 1824, he was elected a Fellow of the +Royal Society, and in 1825, on the recommendation of Sir Humphry Davy, +he was appointed Director of the Laboratory of the Royal Institution, +and in this capacity he instituted the laboratory conferences, which +developed into the Friday evening lectures. For five years after +this, the greater part of Faraday's spare time was occupied in some +investigations in connection with optical glass, made at the request +of the Royal Society, and at the expense of the Government. Mr. +Dollond and Sir John Herschel were associated with him on this +committee, but the results obtained were not of much value to +opticians. The silico-borate of lead which Faraday prepared in the +course of these experiments was, however, the substance with which he +first demonstrated the effect of a magnetic field on the plane of +polarization of light, and with which he discovered diamagnetic +action. + +Faraday's experimental researches were generally guided by theoretical +considerations. Frequently these theories were based on very slender +premises, and sometimes were little else than flights of a scientific +imagination, but they served to guide him into fruitful fields of +discovery, and he seldom placed much confidence in his conclusions +till he had succeeded in verifying them experimentally. For many years +he had held the opinion that electric currents should exhibit +phenomena analogous to those of electro-static induction. Again and +again he returned to the investigation, and attempted to obtain an +induced current in one wire through the passage of a powerful current +through a neighbouring conductor; but he looked for a permanent +induced current to be maintained during the whole time that the +primary current was flowing. At length, employing two wires wound +together as a helix on a wooden rod, the first capable of transmitting +a powerful current from a battery, while the second was connected with +a galvanometer, he observed that, when the current started in the +primary, there was a movement of the galvanometer, and when it ceased +there was a movement in the opposite direction, though the +galvanometer remained at zero while the current continued steady. +Hence it was apparent that it is by changes in the primary current +that induced currents may be generated, and not by their steady +continuance; and it was demonstrated that, when a current is started +in a conductor, a temporary current is induced in a neighbouring +conductor in the opposite direction, while a current is induced in the +same direction as the primary when the latter ceases to flow. Before +obtaining this result with the wires on a wooden bobbin, he had +experimented with a wrought-iron ring about six inches in diameter, +and made of 7/8-inch round iron. He wound two sets of coils round it, +one occupying nearly half the ring, and the other filling most of the +other half. One of these he connected with a galvanometer, the other +could be connected at will with a battery. On sending the battery +current through the latter coil, the galvanometer needle swung +completely round four or five times, and a similar action took place, +but in the opposite direction, on stopping the current. Here it was +clearly the magnetism induced in the iron ring which produced so +powerful a current in the galvanometer circuit. Next he wound a +quantity of covered copper wire on a small iron bar, and connecting +the ends to a galvanometer, he placed the little bobbin between the +opposite poles of a pair of bar magnets, whose other ends were in +contact. As soon as the iron core touched the magnets, a current +appeared in the galvanometer. On breaking contact, the current was in +the opposite direction. Then came the experiment above mentioned, in +which no iron was employed. After this, one end of a cylindrical bar +magnet was introduced into a helix of copper wire, and then suddenly +thrust completely in. The galvanometer connected with the coil showed +a transient current. On withdrawing the magnet, the current appeared +in the opposite direction; so that currents were induced merely by the +relative motion of a magnet and a conductor. + +A copper disc was mounted so that it could be made to rotate rapidly. +A wire was placed in connection with the centre of the disc, and the +circuit completed by a rubbing contact on the circumference. A +galvanometer was inserted in the circuit, and the large horseshoe +magnet of the Royal Institution so placed that the portion of the disc +between the centre and the rubbing contact passed between the poles of +the magnet. A current flowed through the galvanometer as long as the +disc was kept spinning. Then he found that the mere passage of a +copper wire between the poles of the magnet was sufficient to induce a +current in it, and concluded that the production of the current was +connected with the cutting of the "magnetic curves," or "lines of +magnetic force" which would be depicted by iron filings. Thus in the +course of ten days' experimental work, in the autumn of 1831, Faraday +so completely investigated the phenomena of electro-magnetic induction +as to leave little, except practical applications, to his successors. +A few weeks later he obtained induction currents by means of the +earth's magnetism only, first with a coil of wire wound upon an iron +bar in which a strong current was produced when it was being quickly +placed in the direction of the magnetic dip or being removed from that +position, and afterwards with a coil of wire without an iron core. On +February 8, 1832, he succeeded in obtaining a spark from the induced +current. Unless the electro-motive force is very great, it is not +possible to obtain a spark between two metallic surfaces which are +separated by a sensible thickness of air. If, however, the circuit of +a wire is broken _while_ the current is passing, a little bridge of +metallic vapour is formed, across which for an instant the spark +leaps. The induced current being of such short duration, the +difficulty was to break the circuit while it was flowing. Faraday +wound a considerable length of fine wire around a short bar of iron; +the ends of the wire were crossed so as just to be in contact with one +another, but free to separate if exposed to a slight shock. The ends +of the iron bar projected beyond the coil, and were held just over the +poles of the magnet. On releasing the bar it fell so as to strike the +magnetic poles and close the circuit of the magnet. An induced current +was generated in the wire, but, while this was passing, the shock +caused by the bar striking the magnet separated the ends of the wire, +thus breaking the circuit of the conductor, and a spark appeared at +the gap. In this little spark was the germ of the electric light of +to-day. Subsequently Faraday improved the apparatus, by attaching a +little disc of amalgamated copper to one end of the wire, and bending +over the other end so as just to press lightly against the surface of +the disc. With this apparatus he showed the "magnetic spark" at the +meeting of the British Association at Oxford. + +Faraday supposed that when a coil of wire was in the neighbourhood of +a magnet, or near to a conductor conveying a current, the coil was +thrown into a peculiar condition, which he called the _electro-tonic +state_, and that the induced currents appeared whenever this state was +assumed or lost by the coil. He frequently reverted to his conception +of the electro-tonic state, though he saw clearly that, when the +currents were induced by the relative motion of a wire and a magnet, +the current induced depended on the rate at which the lines of +magnetic force had been cut by the wire. Of his conception of lines of +force filling the whole of space, we shall have more to say presently. +It is sufficient to remark here that, in the electro-tonic state of +Faraday, Clerk Maxwell recognized the number of lines of magnetic +force enclosed by the circuit, and showed that the electro-motive +force induced is proportional to the rate of change of the number of +lines of force thus enclosed. + +It is seldom that a great discovery is made which has not been +gradually led up to by several observed phenomena which awaited that +discovery for their explanation. In the case of electro-magnetic +induction, however, there appears to have been but one experiment +which had baffled philosophers, and the key to which was found in +Faraday's discovery, while the complete explanation was given by +Faraday himself. Arago had found that, if a copper plate were made +rapidly to rotate beneath a freely suspended magnetic needle, the +needle followed (slowly) the plate in its revolution, though a sheet +of glass were inserted between the two to prevent any air-currents +acting on the magnet. The experiment had been repeated by Sir John +Herschel and Mr. Babbage, but no explanation was forthcoming. Faraday +saw that the revolution of the disc beneath the poles of the magnet +must generate induced currents in the disc, as the different portions +of the metal would be constantly cutting the lines of force of the +magnet. These currents would react upon the magnet, causing a +mechanical stress to act between the two, which, as stated by Lenz, +would be in the direction tending to oppose the _relative_ motion, and +therefore to drag the magnet after the disc in its revolution. In the +above figure the unfledged arrows show the general distribution of the +currents in the disc, while the winged arrows indicate the direction +of the disc's rotation. The currents in the semicircle A will repel +the north pole and attract the south pole. Those in the semicircle B +will produce the opposite effect, and hence there will be a tendency +for the magnet to revolve in the direction of the disc, while the +motion of the disc will be resisted. This resistance to the motion of +a conductor in a magnetic field was noticed by Faraday, and, +independently, by Tyndall, and it is sufficiently obvious in the power +absorbed by dynamos when they are generating large currents. + +Faraday's next series of researches was devoted to the experimental +proof of the identity of frictional and voltaic electricity. He showed +that a magnet could be deflected and iodide of potassium decomposed by +the current from his electrical machine, and came to the conclusion +that the amount of electricity required to decompose a grain of water +was equal to 800,000 charges of his large Leyden battery. The current +from the frictional machine also served to deflect the needle of his +galvanometer. These investigations led on to a complete series of +researches on the laws of electrolysis, wherein Faraday demonstrated +the principle that, however the strength of the current may be varied, +the amount of any compound decomposed is proportional to the whole +quantity of electricity which has passed through the electrolyte. When +the same current is sent through different compounds, there is a +constant relation between the amounts of the several compounds +decomposed. In modern language, Faraday's laws may be thus +expressed:-- + +_If the same current be made to pass through several different +electrolytes, the quantity of each ion produced will be proportional +to its combining weight divided by its valency, and if the current +vary, the quantity of each ion liberated per second will be +proportional to the current._ + +This is the great law of electro-chemical equivalents. The amount of +hydrogen liberated per second by a current of one ampere is about +.00001038 gramme, or nearly one six-thousandth of a grain. This is the +electro-chemical equivalent of hydrogen. That of any other substance +may be found by Faraday's law. + +From Faraday's results it appears that the passage of the same amount +of electricity is required in order to decompose one molecule of any +compound of the same chemical type, but it does not follow that the +same amount of energy is employed in the decomposition. For example, +the combining weights of copper and zinc are nearly equal. Hence it +will require the passage of about the same amount of electricity to +liberate a pound of copper from, say, the copper sulphate as to +liberate a pound of zinc from zinc sulphate; but the work to be done +is much less in the case of the copper. This is made manifest in the +following way:--A battery, which will just decompose the copper salt +slowly, liberating copper, oxygen, and sulphuric acid, will not +decompose the zinc salt at all so as to liberate metallic zinc, but +immediately on sending the current through the electrolyte, +polarization will set in, and the opposing electro-motive force thus +introduced will become equal to that of the battery, and stop the +current before metallic zinc makes its appearance. In the case of the +copper, polarization also sets in, but never attains to equality with +the electro-motive force of the primary battery. In fact, in all cases +of electrolysis, polarization produces an opposing electro-motive +force strictly proportional to the work done in the cell by the +passage of each unit of electricity. If the strength of the battery be +increased, so that it is able to decompose the zinc sulphate, and if +this battery be applied to the copper sulphate solution, the latter +will be _rapidly_ decomposed, and the excess of energy developed by +the battery will be converted into heat in the circuit. + +One important point in connection with electrolysis which Faraday +demonstrated is that the decomposition is the result of the passage of +the current, and is not simply due to the attraction of the +electrodes. Thus he showed that potassium iodide could be decomposed +by a stream of electricity coming from a metallic point on the prime +conductor of his electric machine, though the point did not touch the +test-paper on which the iodide was placed. + +It was in 1834 that Mr. Wm. Jenkin, after one of the Friday evening +lectures at the Royal Institution, called the attention of Faraday to +a shock which he had experienced in breaking the circuit of an +electro-magnet, though the battery employed consisted of only one pair +of plates. Faraday repeated the experiment, and found that, with a +large magnet in circuit, a strong spark could thus be obtained. On +November 14, 1834, he writes, "The phenomenon of increased spark is +merely a case of the induction of electric currents. If a current be +established in a wire, and another wire forming a complete circuit be +placed parallel to it, at the moment the current in the first is +stopped it induces a current in the same direction in the second, +itself then showing but a feeble spark. But if the second be away, it +induces a current in its own wire in the same direction, producing a +strong spark. The strong spark in the current when alone is therefore +the equivalent of the current it can produce in a neighbouring wire +when in company." The strong spark does, in fact, represent the energy +of the current due to the self-induction of its circuit, which energy +would, in part at least, be expended in inducing a current in a +neighbouring wire if such existed. + +His time from 1835 till 1838 was largely taken up with his work on +electro-static induction. Faraday could never be content with any +explanation based on direct action at a distance; he always sought for +the machinery through which the action was communicated. In this +search the lines of magnetic force, which he had so often delineated +in iron filings, came to his aid. Faraday made many pictures in iron +filings of magnetic fields due to various combinations of magnets. He +employed gummed paper, and when the filings were arranged on the hard +gummed surface, he projected a feeble jet of steam on the paper, which +melted the gum and fixed the filings. Several of his diagrams were +exhibited at the Loan Collection at South Kensington. He conceived +electrical action to be transmitted along such lines as these, and to +him the whole electric field was filled with lines passing always from +positive to negative electrification, and in some respects resembling +elastic strings. The action at any place could then be expressed in +terms of the lines of force that existed there, the electrifications +by which these lines were produced being left out of consideration. +The acting bodies were thus replaced by the field of force they +produced. He showed that it was impossible to call into existence a +charge of positive electricity without at the same time producing an +equal negative charge. From every unit of positive electricity he +conceived a line of force to start, and thus, with the origin of the +line, there was created simultaneously a charge of negative +electricity on which the line might terminate. By the famous ice-pail +experiment he showed that, when a charged body is inserted in a closed +or nearly closed hollow conductor, an equal amount of the same kind of +electricity appeared on the outside of the hollow conductor, while an +equal amount of the opposite kind appeared on the interior surface of +the conductor. With the ice-pail and the butterfly-net he showed that +there could be no free electricity on the interior of a conductor. +Lines of force cannot pass through the material of a conductor without +producing electric displacement. Every element of electricity must be +joined to an equal amount of the opposite kind by a line of force. +Such lines cannot pass through the conductor itself; hence the charge +must be entirely on the outside of the conductor, so that every +element of the charge may be associated with an equal amount of the +opposite electricity upon the surfaces of surrounding objects. Thus to +Faraday every electrical action was an exhibition of electric +induction. All this work had been done before by Henry Cavendish, but +neither Faraday nor any one else knew about it at the time. From the +fact that there could be no electricity in the interior of a hollow +conductor, Cavendish deduced, in the best way possible, the truth of +the law of inverse squares as applied to electrical attraction and +repulsion, and thus laid the foundation of the mathematical theory of +electricity. To Cavendish every electrical action was a displacement +of an incompressible fluid which filled the whole of space, producing +no effect in conductors on account of the freedom of its motion, but +producing strains in insulators by displacing the material of the +body. Faraday, in his lines of force, saw, as it were, the lines along +which the displacements of Cavendish's fluid took place. + +Faraday thought that, if he could show that electric induction could +take place along curved lines, it would prove that the action took +place through a medium, and not directly at a distance. He succeeded +in experimentally demonstrating the curvature of these lines; but his +conclusions were not warranted, for if we conceive of two or more +centres of force acting directly at a distance according to the law of +inverse squares, the resultant lines of force will generally be +curved. Of course, this does not prove the possibility of direct +action at a distance, but only shows that the curvature of the lines +is as much a consequence of the one hypothesis as of the other. + +It soon appeared to Faraday that the nature of the dielectric had very +much to do with electric induction. The capacity of a condenser, for +instance, depends on the nature of the dielectric as well as on the +configuration of the conductors. To express this property, Faraday +employed the term "specific inductive capacity." He compared the +electric capacity of condensers, equal in all other respects, but one +possessing air for its dielectric, and the other having other media, +and thus roughly determined the specific inductive capacities of +several insulators. These results turned out afterwards to be of great +value in connection with the insulation of submarine cables. Even now +the student of electricity is sometimes puzzled by the manner in which +specific inductive capacity is introduced to his notice as modifying +the capacity of condensers, after learning that the capacity of any +system of conductors can be calculated from its geometrical +configuration; but the fact is that the intensity of all electrical +actions depends on the nature of the medium through which they take +place, and it will require more electricity to exert upon an equal +charge a unit force at unit distance when the intervening medium has a +high than when it possesses a low specific inductive capacity. + +In 1835 Faraday received a pension from the civil list; in 1836 he was +appointed scientific adviser to the Elder Brethren of the Trinity +House. In the same year he was made a member of the Senate of the +University of London, and in that capacity he has exerted no small +influence on the scientific education of the country, for he was one +of those who drew up the schedules of the various examinations. + +In his early years, Faraday thought that all kinds of matter might +ultimately consist of three materials only, and that as gases and +vapours appeared more nearly to resemble one another than the liquids +or solids to which they corresponded, so each might be subject to a +still higher change in the same direction, and the gas or vapour +become radiant matter--either heat, light, or electricity. Later on, +Faraday clearly recognized the dynamical nature of heat and light; but +his work was always guided by his theoretical conceptions of the +"correlation of the physical forces." For a long time he had tried to +discover relations between electricity and light; at length, on +September 13, 1845, after experimenting on a number of other +substances, he placed a piece of silico-borate of lead, or +heavy-glass, in the field of the magnet, and found that, when a beam +of polarized light was transmitted through the glass in the direction +of the lines of magnetic force, there was a rotation of the plane of +polarization. Afterwards it appeared that all the transparent solids +and liquids experimented on were capable of producing this rotation in +a greater or less degree, and in the case of all non-magnetic +substances the rotation was in the direction of the electric current, +which, passing round the substance, would produce the magnetic field +employed. Abandoning the magnet, and using only a coil of wire with +the transparent substance within it, similar effects were obtained. +Thus at length a relation was found between light and electricity. + +On November 4, employing a piece of heavy-glass and a new horseshoe +magnet, Faraday noticed that the magnet appeared to have a directive +action upon the glass. Further examination showed that the glass was +repelled by the magnetic poles. Three days afterwards he found that +all sorts of substances, including most metals, were acted upon like +the heavy-glass. Small portions of them were repelled, while elongated +cylinders tended to set with their lengths perpendicular to the lines +of magnetic force. Such actions could be imitated by suspending a +feebly magnetic body in a medium more magnetic than itself. Faraday, +therefore, sought for some medium which would be absolutely neutral to +magnetic action. Filling a glass tube with compressed oxygen, and +suspending it in an atmosphere of oxygen at ordinary pressure, the +compressed gas behaved like iron or other magnetic substances. +Faraday compared the intensity of its action with that of ferrous +sulphate, and this led to an explanation of the diurnal variations of +the compass-needle based on the sun's heat diminishing the magnetic +_permeability_ of the oxygen of the air. Repeating the experiment with +nitrogen, he found that the compressed gas behaved in a perfectly +neutral manner when surrounded by the gas at ordinary pressure. Hence +he inferred that in nitrogen he had found the neutral medium required. +Repeating his experiments in an atmosphere of nitrogen, it still +appeared that most bodies were repelled by the magnetic poles, and set +_equatorially_, or at right angles to the lines of force when +elongated portions were tested. To this action Faraday gave the name +of diamagnetism. + +About a month after his marriage, Faraday joined the Sandemanian +Church, to which his family had for several generations belonged, by +confession of sin and profession of faith. Not unfrequently he used to +speak at the meetings of his Church, but in 1840 he was elected an +elder, and then he took his turn regularly in conducting the services. +The notes of his addresses he generally made on small pieces of card. +He had a curious habit of separating his religious belief from his +scientific work, although the spirit of his religion perpetually +pervaded his life. A lecture on mental education, given in 1854, at +the Royal Institution, in the presence of the late Prince Consort, he +commenced as follows:-- + +"Before entering on this subject, I must make one distinction, which, +however it may appear to others, is to me of the utmost importance. +High as man is placed above the creatures around him, there is a +higher and far more exalted position within his view; and the ways are +infinite in which he occupies his thoughts about the fears, or hopes, +or expectations of a future life. I believe that the truth of that +future cannot be brought to his knowledge by any exertion of his +mental powers, however exalted they may be; that it is made known to +him by other teaching than his own, and is received through simple +belief of the testimony given. Let no one suppose for a moment that +the self-education I am about to commend, in respect of the things of +this life, extends to any considerations of the hope set before us, as +if man by reasoning could find out God. It would be improper here to +enter upon this subject further than to claim an absolute distinction +between religious and ordinary belief. I shall be reproached with the +weakness of refusing to apply those mental operations which I think +good in respect of high things to the very highest. I am content to +bear the reproach. Yet even in earthly matters I believe that 'the +invisible things of Him from the creation of the world are clearly +seen, being understood by the things that are made, even His eternal +power and Godhead;' and I have never seen anything incompatible +between those things of man which can be known by the spirit of man +which is within him, and those higher things concerning his future +which he cannot know by that spirit." + +On more than one occasion the late Prince Consort had discussed +physical questions with Faraday, and in 1858 the Queen offered him a +house on Hampton Court Green. This was his home until August 25, 1867. +He saw not only the magnetic spark, which he had first produced, +employed in the lighthouses at the South Foreland and Dungeness, but +he saw also his views respecting lines of electric induction examined +and confirmed by the investigations of Thomson and Clerk Maxwell. + +Of the ninety-five distinctions conferred upon him, we need only +mention that of Commandant of the Legion of Honour, which he received +in January, 1856. + + + + +JAMES CLERK MAXWELL. + + +The story of the life of James Clerk Maxwell has been told so recently +by the able pen of his lifelong friend, Professor Lewis Campbell, that +it is unnecessary, in the few pages which now remain to us, to attempt +to give a repetition of the tale which would not only fail to do +justice to its subject, but must of necessity fall far short of the +merits of the (confessedly imperfect) sketch which has recently been +placed within the reach of all. Looking back on the life of Clerk +Maxwell, he seems to have come amongst us as a light from another +world--to have but partly revealed his message to minds too often +incapable of grasping its full meaning, and all too soon to have +returned to the source from whence he came. There was scarcely any +branch of natural philosophy that he did not grapple with, and upon +which his vivid imagination and far-seeing intelligence did not throw +light. He was born a philosopher, and at every step Nature partly drew +aside the veil and revealed that which was hidden from a gaze less +prophetic. A very brief sketch of the principal incidents in his life +may, however, not be out of place. + +James Clerk Maxwell was born in Edinburgh, on June 13, 1831. His +father, John Clerk Maxwell, was the second son of James Clerk, of +Penicuik, and took the name of Maxwell on inheriting the estate at +Middlesbie. His mother was the daughter of R. H. Cay, Esq., of North +Charlton, Northumberland. James was the only child who survived +infancy. + +Some years before his birth his parents had built a house at Glenlair, +which had been added to their Middlesbie estate, and resided there +during the greater part of the year, though they retained their house +in Edinburgh. Hence it was that James's boyish days were spent almost +entirely in the country, until he entered the Edinburgh Academy in +1841. As a child, he was never content until he had completely +investigated everything which attracted his attention, such as the +hidden courses of bell-wires, water-streams, and the like. His +constant question was "What's the go o' that?" and, if answered in +terms too general for his satisfaction, he would continue, "But what's +the particular go of it?" This desire for the thorough investigation +of every phenomenon was a characteristic of his mind through life. +From a child his knowledge of Scripture was extensive and accurate, +and when eight years old he could repeat the whole of the hundred and +nineteenth psalm. About this time his mother died, and thenceforward +he and his father became constant companions. Together they would +devise all sorts of ingenious mechanical contrivances. Young James was +essentially a child of nature, and free from all conventionality. He +loved every living thing, and took delight in petting young frogs, and +putting them into his mouth to see them jump out. One of his +attainments was to paddle on the duck-pond in a wash-tub, and to make +the vessel go "without spinning"--a recreation which had to be +relinquished on washing-days. He was never without the companionship +of one or two terriers, to whom he taught many tricks, and with whom +he seemed to have complete sympathy. + +As a boy, Maxwell was not one to profit much by the ordinary teaching +of the schools, and experience with a private tutor at home did not +lead to very satisfactory results. At the age of ten, therefore, he +was sent to the Edinburgh Academy, under the care of Archdeacon +Williams, who was then rector. On his first appearance in this +fashionable school, he was naturally a source of amusement to his +companions; but he held his ground, and soon gained more respect than +he had previously provoked ridicule. While at school in Edinburgh, he +resided with his father's sister, Mrs. Wedderburn, and devoted a very +considerable share of his time and attention to relieving the solitude +of the old man at Glenlair, by letters written in quaint styles, +sometimes backwards, sometimes in cypher, sometimes in different +colours, so arranged that the characters written in a particular +colour, when placed consecutively, formed another sentence. All the +details of his school and home life, and the special peculiarities of +the masters at the academy, were thus faithfully transmitted to his +father, by whom the letters were religiously preserved. At thirteen he +had evidently made progress in solid geometry, though he had not +commenced Euclid, for he writes to his father, "I have made a +tetrahedron, a dodecahedron, and two other hedrons whose names I don't +know." In these letters to Glenlair he generally signed himself, "Your +most obedient servant." Sometimes his fun found vent even upon the +envelope; for example:-- + + "Mr. John Clerk Maxwell, + "Postyknowswere, + "Kirkpatrick Durham, + "Dumfries." + +Sometimes he would seal his letters with electrotypes of natural +objects (beetles, etc.), of his own making. In July, 1845, he +writes:-- + + I have got the eleventh prize for scholarship, the first for + English, the prize for English verses, and the mathematical + medal. + +When only fifteen a paper on oval curves was contributed by him to the +_Proceedings of the Royal Society of Edinburgh_. In the spring of 1847 +he accompanied his uncle on a visit to Mr. Nicol, the inventor of the +Nicol prism, and on his return he made a polariscope with glass and a +lucifer-match box, and sketched in water-colours the chromatic +appearances presented by pieces of unannealed glass which he himself +prepared. These sketches he sent to Mr. Nicol, who presented him in +return with a pair of prisms of his own construction. The prisms are +now in the Cavendish Laboratory at Cambridge. Maxwell found that, for +unannealed glass, pieces of window-glass placed in bundles of eight or +nine, one on the other, answered the purpose very well. He cut the +figures, triangles, squares, etc., with a diamond, heated the pieces +of glass on an iron plate to redness in the kitchen fire, and then +dropped them into a plate of iron sparks (scales from the smithy) to +cool. + +In 1847 Maxwell entered the University of Edinburgh, and during his +course of study there he contributed to the Royal Society of Edinburgh +papers upon rolling curves and on the equilibrium of elastic solids. +His attention was mostly devoted to mathematics, physics, chemistry, +and mental and moral philosophy. In 1850 he went to Cambridge, +entering Peterhouse, but at the end of a year he "migrated" to +Trinity; here he was soon surrounded with a circle of friends who +helped to render his Cambridge life a very happy one. His love of +experiment sometimes extended to his own mode of life, and once he +tried sleeping in the evening and working after midnight, but this was +soon given up at the request of his father. One of his friends writes, +"From 2 to 2.30 a.m. he took exercise by running along the upper +corridor, _down_ the stairs, along the lower corridor, then _up_ the +stairs, and so on until the inhabitants of the rooms along his track +got up and laid _perdus_ behind their sporting-doors, to have shots at +him with boots, hair-brushes, etc., as he passed." His love of fun, +his sharp wit, his extensive knowledge, and above all, his complete +unselfishness, rendered him a universal favourite in spite of the +temporary inconveniences which his experiments may have occasionally +caused to his fellow-students. + +An undergraduate friend writes, "Every one who knew him at Trinity can +recall some kindness or some act of his which has left an ineffaceable +impression of his goodness on the memory--for 'good' Maxwell was in +the best sense of the word." The same friend wrote in his diary in +1854, after meeting Maxwell at a social gathering, "Maxwell, as usual, +showing himself acquainted with every subject on which the +conversation turned. I never met a man like him. I do believe there is +not a single subject on which he cannot talk, and talk well too, +displaying always the most curious and out-of-the-way information." +His private tutor, the late well-known Mr. Hopkins, said of him, "It +is not possible for that man to think incorrectly on physical +subjects." + +In 1854 Maxwell took his degree at Cambridge as second wrangler, and +was bracketed with the senior wrangler (Mr. E. J. Routh) for the +Smith's prize. During his undergraduate course, he appears to have +done much of the work which formed the basis of his subsequent papers +on electricity, particularly that on Faraday's lines of force. The +colour-top and colour-box appear also to have been gradually +developing during this time, while the principle of the stereoscope +and the "art of squinting" received their due share of attention. +Shortly after his degree, he devoted a considerable amount of time to +the preparation of a manuscript on geometrical optics, which was +intended to form a university text-book, but was never completed. In +the autumn of 1855 he was elected Fellow of Trinity. About this time +the colour-top was in full swing, and he also constructed an +ophthalmoscope. In May, 1855, he writes:-- + + The colour trick came off on Monday, 7th. I had the proof-sheets + of my paper, and was going to read; but I changed my mind and + talked instead, which was more to the purpose. There were sundry + men who thought that blue and yellow make green, so I had to + undeceive them. I have got Hay's book of colours out of the + University Library, and am working through the specimens, + matching them with the top. + +The "colour trick" came off before the Cambridge Philosophical Society. + +While a Bachelor Fellow, Maxwell gave lectures to working men in +Barnwell, besides lecturing in college. His father died in April, +1856, and shortly afterwards he was appointed Professor of Natural +Philosophy in Marischal College, Aberdeen. This appointment he held +until the fusion of the college with King's College in 1860. These +four years were very productive of valuable work. During them the +dynamical top was constructed, which illustrates the motion of a rigid +body about its axis of greatest, least, or mean moment of inertia; +for, by the movement of certain screws, the axis of the top may be +made to coincide with any one at will. The Adams Prize Essay on the +stability of Saturn's rings belongs also to this period. In this essay +Maxwell showed that the phenomena presented by Saturn's rings can only +be explained on the supposition that they consist of innumerable small +bodies--"a flight of brickbats"--each independent of all the others, +and revolving round Saturn as a satellite. He compared them to a siege +of Sebastopol from a battery of guns measuring thirty thousand miles +in one direction, and a hundred miles in the other, the shots never +stopping, but revolving round a circle of a hundred and seventy +thousand miles radius. A solid ring of such dimensions would be +completely crushed by its own weight, though made of the strongest +material of which we have any knowledge. If revolving at such a rate +as to balance the attraction of the planet at one part, the stress in +other parts would be more than sufficient to crush or tear the ring. +Laplace had shown that a narrow ring might revolve about the planet +and be stable if so loaded that its centre of gravity was at a +considerable distance from its centre, and thought that Saturn's +rings might consist of a number of such unsymmetrical rings--a theory +to which some support was given by the many small divisions observable +in the bright rings. Maxwell showed that, for stability, the mass +required to load each of Laplace's rings must be four and a half times +that of the rest of the ring; and the system would then be far too +artificially balanced to be proof against the action of one ring on +another. He further showed that, in liquid rings, waves would be +produced by the mutual action of the rings, and that before long some +of these waves would be sure to acquire such an amplitude as would +cause the rings to break up into small portions. Finally, he concluded +that the only admissible theory is that of the independent satellites, +and that the _average_ density of the rings so found cannot be much +greater than that of air at ordinary pressure and temperature. + +While he remained at Aberdeen, Maxwell lectured to working men in the +evenings, on the principles of mechanics. On the whole, it is doubtful +whether Aberdeen society was as congenial to him as that of Cambridge +or Edinburgh. He seems not to have been understood even by his +colleagues. On one occasion he wrote:-- + + Gaiety is just beginning here again.... No jokes of any kind are + understood here. I have not made one for two months, and if I + feel one coming I shall bite my tongue. + +But every cloud has its bright side, and, however Maxwell may have +been regarded by his colleagues, he was not long without congenial +companionships. An honoured guest at the home of the Principal, "in +February, 1858, he announced his betrothal to Katherine Mary Dewar, +and they were married early in the following June." Professor Campbell +speaks of his married life as one of unexampled devotion, and those +who enjoyed the great privilege of seeing him at home could more than +endorse the description. + +In 1860 Maxwell accepted the chair of Natural Philosophy at King's +College, London. Here he continued his lectures to working men, and +even kept them up for one session after resigning the chair in 1865. +On May 17, 1861, he gave his first lecture at the Royal Institution, +on "The Theory of the Three Primary Colours." This lecture embodies +many of the results of his work with the colour-top and colour-box, to +be again referred to presently. While at King's College, he was placed +on the Electrical Standards Committee of the British Association, and +most of the work of the committee was carried out in his laboratory. +Here, too, he compared the electro-static repulsion between two discs +of brass with the electro-magnetic attraction of two coils of wire +surrounding them, through which a current of electricity was allowed +to flow, and obtained a result which he afterwards applied to the +electro-magnetic theory of light. The colour-box was perfected, and +his experiments on the viscosity of gases were concluded during his +residence in London. These last were described by him in the Bakerian +Lecture for 1866. + +After resigning the professorship at King's College, Maxwell spent +most of his time at Glenlair, having enlarged the house, in accordance +with his father's original plans. Here he completed his great work on +"Electricity and Magnetism," as well as his "Theory of Heat," an +elementary text-book which may be said to be without a parallel. + +On March 8, 1871, he accepted the chair of Experimental Physics in the +University of Cambridge. This chair was founded in consequence of an +offer made by the Duke of Devonshire, the Chancellor of the +University, to build and equip a physical laboratory for the use of +the university. In this capacity Maxwell's first duty was to prepare +plans for the laboratory. With this view, he inspected the +laboratories of Sir William Thomson at Glasgow, and of Professor +Clifton at Oxford, and endeavoured to embody the best points of both +in the new building. The result was that, in conjunction with Mr. W. +M. Fawcett, the architect, he secured for the university a laboratory +noble in its exterior, and admirably adapted to the purposes for which +it is required. The ground-floor comprises a large battery-room, which +is also used as a storeroom for chemicals; a workshop; a room for +receiving goods, communicating by a lift with the apparatus-room; a +room for experiments on heat; balance-rooms; a room for pendulum +experiments, and other investigations requiring great stability; and a +magnetic observatory. The last two rooms are furnished with stone +supports for instruments, erected on foundations independent of those +of the building, and preserved from contact with the floor. On the +first floor is a handsome lecture-theatre, capable of accommodating +nearly two hundred students. The lecture-table is carried on a wall, +which passes up through the floor without touching it, the joists +being borne by separate brick piers. The lecture-theatre occupies the +height of the first and second floors; its ceiling is of wood, the +panels of which can be removed, thus affording access to the +roof-principals, from which a load of half a ton or more may be safely +suspended over the lecture-table. The panels of the ceiling, adjoining +the wall which is behind the lecturer, can also be readily removed, +and a "window" in this wall communicates with the large +electrical-room on the second floor. Access to the space above the +ceiling of the lecture-theatre is readily obtained from the tower. +Adjoining the lecture-room is the preparation-room, and communicating +with the latter is the apparatus-room. This room is fitted with +mahogany and plate-glass wall and central cases, and at present +contains, besides the more valuable portions of the apparatus +belonging to the laboratory, the marble bust of James Clerk Maxwell, +and many of the home-made pieces of apparatus and other relics of his +early work. The rest of the first floor is occupied by the +professor's private room and the general students' laboratory. +Throughout the building the brick walls have been left bare for +convenience in attaching slats or shelves for the support of +instruments. The second floor contains a large room for electrical +experiments, a dark room for photography, and a number of private +rooms for original work. Water is laid on to every room, including a +small room in the top of the tower, and all the windows are provided +with broad stone ledges without and within the window, the two +portions being in the same horizontal plane, for the support of +heliostats or other instruments. The building is heated with hot +water, but in the magnetic observatory the pipes are all of copper and +the fittings of gun-metal. Open fireplaces for basket fires are also +provided. Over the principal entrance of the laboratory is placed a +stone statue of the present Duke of Devonshire, together with the arms +of the university and of the Cavendish family, and the Cavendish +motto, "Cavendo Tutus." Maxwell presented to the laboratory, in 1874, +all the apparatus in his possession. He usually gave a course of +lectures on heat and the constitution of bodies in the Michaelmas +term; on electricity in the Lent term; and on electro-magnetism in the +Easter term. The following extract from his inaugural lecture, +delivered in October, 1871, is worthy of the attention of all students +of science:-- + + Science appears to us with a very different aspect after we + have found out that it is not in lecture-rooms only, and by + means of the electric light projected on a screen, that we may + witness physical phenomena, but that we may find illustrations + of the highest doctrines of science in games and gymnastics, in + travelling by land and by water, in storms of the air and of the + sea, and wherever there is matter in motion. + + The habit of recognizing principles amid the endless variety of + their action can never degrade our sense of the sublimity of + nature, or mar our enjoyment of its beauty. On the contrary, it + tends to rescue our scientific ideas from that vague condition + in which we too often leave them, buried among the other + products of a lazy credulity, and to raise them into their + proper position among the doctrines in which our faith is so + assured that we are ready at all times to act on them. + Experiments of illustration may be of very different kinds. Some + may be adaptations of the commonest operations of ordinary life; + others may be carefully arranged exhibitions of some phenomenon + which occurs only under peculiar conditions. They all, however, + agree in this, that their aim is to present some phenomenon to + the senses of the student in such a way that he may associate + with it some appropriate scientific idea. When he has grasped + this idea, the experiment which illustrates it has served its + purpose. + + In an experiment of research, on the other hand, this is not the + principal aim.... Experiments of this class--those in which + measurement of some kind is involved--are the proper work of a + physical laboratory. In every experiment we have first to make + our senses familiar with the phenomenon; but we must not stop + here--we must find out which of its features are capable of + measurement, and what measurements are required in order to make + a complete specification of the phenomenon. We must then make + these measurements, and deduce from them the result which we + require to find. + + This characteristic of modern experiments--that they consist + principally of measurements--is so prominent that the opinion + seems to have got abroad that, in a few years, all the great + physical constants will have been approximately estimated, and + that the only occupation which will then be left to men of + science will be to carry these measurements to another place of + decimals. + + If this is really the state of things to which we are + approaching, our laboratory may, perhaps, become celebrated as a + place of conscientious labour and consummate skill; but it will + be out of place in the university, and ought rather to be + classed with the other great workshops of our country, where + equal ability is directed to more useful ends. + + But we have no right to think thus of the unsearchable riches of + creation, or of the untried fertility of those fresh minds into + which these riches will continually be poured.... The history + of Science shows that, even during that phase of her progress + in which she devotes herself to improving the accuracy of the + numerical measurement of quantities with which she has long been + familiar, she is preparing the materials for the subjugation of + new regions, which would have remained unknown if she had been + contented with the rough methods of her early pioneers. + +Maxwell's "Electricity and Magnetism" was published in 1873. Shortly +afterwards there were placed in his hands, by the Duke of Devonshire, +the Cavendish Manuscripts on Electricity, already alluded to. To these +he devoted much of his spare time for several years, and many of +Cavendish's experiments were repeated in the laboratory by Maxwell +himself, or under his direction by his students. The introductory +matter and notes embodied in "The Electrical Researches of the +Honourable Henry Cavendish, F.R.S.," afford sufficient evidence of the +amount of labour he expended over this work. The volume was published +only a few weeks before his death. Another of Maxwell's publications, +which, as a text-book, is unique and beyond praise, is the little book +on "Matter and Motion," published by the S.P.C.K. + +In 1878 Maxwell, at the request of the Vice-Chancellor, delivered the +Rede Lecture in the Senate-House. His subject was the telephone, which +was just then absorbing a considerable amount of public attention. +This was the last lecture which he ever gave to a large public +audience. + +It was during his tenure of the Cambridge chair that one of the +cottages on the Glenlair estate was struck by lightning. The discharge +passed down the damp soot and blew out several stones from the base of +the chimney, apparently making its way to some water in a ditch a few +yards distant. The cottage was built on a granite rock, and this event +set Maxwell thinking about the best way to protect, from lightning, +buildings which are erected on granite or other non-conducting +foundations. He decided that the proper course was to place a strip of +metal upon the ground all round the building, to carry another strip +along the ridge-stay, from which one or more pointed rods should +project upwards, and to unite this strip with that upon the ground by +copper strips passing down each corner of the building, which is thus, +as it were, enclosed in a metal cage. + +After a brief illness, Maxwell passed away on November 5, 1879. His +intellect and memory remained perfect to the last, and his love of fun +scarcely diminished. During his illness he would frequently repeat +hymns, especially some of George Herbert's, and Richard Baxter's hymn +beginning + + "Lord, it belongs not to my care." + +"No man ever met his death more consciously or more calmly." + +It has been stated that Thomas Young propounded a theory of +colour-vision which assumes that there exist three separate +colour-sensations, corresponding to red, green, and violet, each +having its own special organs, the excitement of which causes the +perception of the corresponding colour, other colours being due to the +excitement of two or more of these simple sensations in different +proportions. Maxwell adopted blue instead of violet for the third +sensation, and showed that if a particular red, green, and blue were +selected and placed at the angular points of an equilateral triangle, +the colours formed by mixing them being arranged as in Young's +diagram, all the shades of the spectrum would be ranged along the +sides of this triangle, the centre being neutral grey. For the mixing +of coloured lights, he at first employed the colour-top, but, instead +of painting circles with coloured sectors, the angles of which could +not be changed, he used circular discs of coloured paper slit along +one radius. Any number of such discs can be combined so that each +shows a sector at the top, and the angle of each sector can be varied +at will by sliding the corresponding disc between the others. Maxwell +used discs of two different sizes, the small discs being placed above +the larger on the same pivot, so that one set formed a central circle, +and the other set a ring surrounding it. He found that, with discs of +five different colours, of which one might be white and another black, +it was always possible to combine them so that the inner circle and +the outer ring exactly matched. From this he showed that there could +be only three conditions to be satisfied in the eye, for two +conditions were necessitated by the nature of the top, since the +smaller sectors must exactly fill the circle and so must the larger. +Maxwell's experiments, therefore, confirmed, in general, Young's +theory. They showed, however, that the relative delicacy of the +several colour-sensations is different in different eyes, for the +arrangement which produced an exact match in the case of one observer, +had to be modified for another; but this difference of delicacy proved +to be very conspicuous in colour-blind persons, for in most of the +cases of colour-blindness examined by Maxwell the red sensation was +completely absent, so that only two conditions were required by +colour-blind eyes, and a match could therefore always be made in such +cases with four discs only. Holmgren has since discovered cases of +colour-blindness in which the violet sensation is absent. He agrees +with Young in making the third sensation correspond to violet rather +than blue. Maxwell explained the fact that persons colour-blind to the +red divide colours into blues and yellows by the consideration that, +although yellow is a complex sensation corresponding to a mixture of +red and green, yet in nature yellow tints are so much brighter than +greens that they excite the green sensation more than green objects +themselves can do, and hence greens and yellows are called yellow by +such colour-blind persons, though their perception of yellow is really +the same as perception of green by normal eyes. Later on, by a +combination of adjustable slits, prisms, and lenses arranged in a +"colour-box," Maxwell succeeded in mixing, in any desired proportions, +the light from any three portions of the spectrum, so that he could +deal with pure spectral colours instead of the complex combinations of +differently coloured lights afforded by coloured papers. From these +experiments it appears that no ray of the solar spectrum can affect +one colour-sensation alone, so that there are no colours in nature so +pure as to correspond to the pure simple sensations, and the colours +occupying the angular points of Maxwell's diagram affect all three +colour-sensations, though they influence two of them to a much smaller +extent than the third. A particular colour in the spectrum corresponds +to light which, according to the undulatory theory, physically +consists of waves all of the same period, but it may affect all three +of the colour-sensations of a normal eye, though in different +proportions. Thus, yellow light of a given wave-length affects the red +and green sensations considerably and the blue (or violet) slightly, +and the same effect may be produced by various mixtures of red or +orange and green. For his researches on the perception of colour, the +Royal Society awarded to Clerk Maxwell the Rumford Medal in 1860. + +Another optical contrivance of Maxwell's was a wheel of life, in which +the usual slits were replaced by concave lenses of such focal length +that the picture on the opposite side of the cylinder appeared, when +seen through a lens, at the centre, and thus remained apparently +fixed in position while the cylinder revolved. The same result has +since been secured by a different contrivance in the praxinoscope. + +Another ingenious optical apparatus was a real-image stereoscope, in +which two lenses were placed side by side at a distance apart equal to +half the distance between the pictures on the stereoscopic slide. +These lenses were placed in front of the pictures at a distance equal +to twice their focal length. The real images of the two pictures were +then superposed in front of the lenses at the same distance from them +as the pictures, and these combined images were looked at through a +large convex lens. + +The great difference in the sensibility to different colours of the +eyes of dark and fair persons when the light fell upon the _fovea +centralis_, led Maxwell to the discovery of the extreme want of +sensibility of this portion of the retina to blue light. This he made +manifest by looking through a bottle containing solution of chrome +alum, when the central portion of the field of view appears of a light +red colour for the first second or two. + +A more important discovery was that of double refraction temporarily +produced in viscous liquids. Maxwell found that a quantity of Canada +balsam, if stirred, acquired double-refracting powers, which it +retained for a short period, until the stress temporarily induced had +disappeared. + +But Maxwell's investigations in optics must be regarded as his play; +his real work lay in the domains of electricity and of molecular +physics. + +In 1738 Daniel Bernouilli published an explanation of atmospheric +pressure on the hypothesis that air consists of a number of minute +particles moving in all directions, and impinging on any surface +exposed to their action. In 1847 Herapath explained the diffusion of +gases on the hypothesis that they consisted of perfectly hard +molecules impinging on one another and on surfaces exposed to them, +and pointed out the relation between their motion and the temperature +and pressure of a gas. The present condition of the molecular theory +of gases, and of molecular science generally, is due almost entirely +to the work of Joule, Clausius, Boltzmann, and Maxwell. To Maxwell is +due the general method of solving all problems connected with vast +numbers of individuals--a method which he called the statistical +method, and which consists, in the first place, in separating the +individuals into groups, each fulfilling a particular condition, but +paying no attention to the history of any individual, which may pass +from one group to another in any way and as often as it pleases +without attracting attention. Maxwell was the first to estimate the +average distance through which a particle of gas passes without coming +into collision with another particle. He found that, in the case of +hydrogen, at standard pressure and temperature, it is about 1/250000 +of an inch; for air, about 1/389000 of an inch. These results he +deduced from his experiments on viscosity, and he gave a complete +explanation of the viscosity of gases, showing it to be due to the +"diffusion of momentum" accompanying the diffusion of material +particles between the passing streams of gas. + +One portion of the theory of electricity had been considerably +developed by Cavendish; the application of mathematics to the theory +of attractions, and hence to that of electricity, had been carried to +a great degree of perfection by Laplace, Lagrange, Poisson, Green, and +others. Faraday, however, could not satisfy himself with a +mathematical theory based upon direct action at a distance, and he +filled space, as we have seen, with tubes of force passing from one +body to another whenever there existed any electrical action between +them. These conceptions of Faraday were regarded with suspicion by +mathematicians. Sir William Thomson was the first to look upon them +with favour; and in 1846 he showed that electro-static force might be +treated mathematically in the same way as the flow of heat; so that +there are, at any rate, two methods by which the fundamental formulae +of electro-statics can be deduced. But it is to Maxwell that +mathematicians are indebted for a complete exposition of Faraday's +views in their own language, and this was given in a paper wherein the +phenomena of electro-statics were deduced as results of a stress in a +medium which, as suggested by Newton and believed by Faraday, might +well be that same medium which serves for the propagation of light; +and "the lines of force" were shown to correspond to an actual +condition of the medium when under electrical stress. Maxwell, in +fact, showed, not only that Faraday's lines formed a consistent system +which would bear the most stringent mathematical analysis, but were +more than a conventional system, and might correspond to a state of +stress actually existing in the medium through which they passed, and +that a tension along these lines, accompanied by an equal pressure in +every direction at right angles to them, would be consistent with the +equilibrium of the medium, and explain, on mechanical principles, the +observed phenomena. The greater part of this work he accomplished +while an undergraduate at Cambridge. He showed, too, that Faraday's +conceptions were equally applicable to the case of electro-magnetism, +and that all the laws of the induction of currents might be concisely +expressed in Faraday's language. Defining the positive direction +through a circuit in which a current flows as the direction in which a +right-handed screw would advance if rotating with the current, and the +positive direction around a wire conveying a current as the direction +in which a right-handed screw would rotate if advancing with the +current, Maxwell pointed out that the lines of magnetic force due to +an electric current always pass round it, or through its circuit, in +the positive direction, and that, _whenever the number of lines of +magnetic force passing through a closed circuit is changed, there is +an electro-motive force round the circuit represented by the rate of +diminution of the number of lines of force which pass through the +circuit in the positive direction_. + +The words in italics form a complete statement of the laws regulating +the production of currents by the motion of magnets or of other +currents, or by the variation of other currents in the neighbourhood. +Maxwell showed, too, that Faraday's electro-tonic state, on the +variation of which induced currents depend, corresponds completely +with the number of lines of magnetic force passing through the +circuit. + +He also showed that, when a conductor conveying a current is free to +move in a magnetic field, or magnets are free to move in the +neighbourhood of such a conductor, _the system will assume that +condition in which the greatest possible number of lines of magnetic +force pass through the circuit in the positive direction_. + +But Maxwell was not content with showing that Faraday's conceptions +were consistent, and had their mathematical equivalents,--he proceeded +to point out how a medium could be imagined so constituted as to be +able to perform all the various duties which were thus thrown upon it. +Assuming a medium to be made up of spherical, or nearly spherical, +cells, and that, when magnetic force is transmitted, these cells are +made to rotate about diameters coinciding in direction with the lines +of force, the tension along those lines, and the pressure at right +angles to them, are accounted for by the tendency of a rotating +elastic sphere to contract along its polar axis and expand +equatorially so as to form an oblate spheroid. By supposing minute +spherical particles to exist between the rotating cells, the motion of +one may be transmitted in the same direction to the next, and these +particles may be supposed to constitute electricity, and roll as +perfectly rough bodies on the cells in contact with them. Maxwell +further imagined the rotating cells, and therefore, _a fortiori_, the +electrical particles, to be extremely small compared with molecules of +matter; and that, in conductors, the electrical particles could pass +from molecule to molecule, though opposed by friction, but that in +insulators no such transference was possible. The machinery was then +complete. If the electric particles were made to flow in a conductor +in one direction, passing between the cells, or _molecular vortices_, +they compelled them to rotate, and the rotation was communicated from +cell to cell in expanding circles by the electric particles, acting as +idle wheels, between them. Thus rings of magnetic force were made to +surround the current, and to continue as long as the current lasted. +If an attempt were made to displace the electric particles in a +dielectric, they would move only within the substance of each +molecule, and not from molecule to molecule, and thus the cells would +be deformed, though no continuous motion would result. The deformation +of the cells would involve elastic stress in the medium. Again, if a +stream of electric particles were started into motion, and if there +were another stream of particles in the neighbourhood free to flow, +though resisted by friction, these particles, instead of at once +transmitting the rotary motion of the cells on one side of them to the +cells on the other side, would at first, on account of the inertia of +the cells, begin to move themselves with a motion of translation +opposite to that of the primary current, and the motion would only +gradually be destroyed by the frictional resistance and the molecular +vortices on the other side made to revolve with their full velocity. A +similar effect, but in the opposite direction, would take place if the +primary current ceased, the vortices not stopping all at once if there +were any possibility of their continuing in motion. The imaginary +medium thus serves for the production of induced currents. + +The mechanical forces between currents and magnets and between +currents and currents, as well as between magnets and currents, were +accounted for by the tension and pressure produced by the molecular +vortices. When currents are flowing in the same direction in +neighbouring conductors, the vortices in the space between them are +urged in opposite directions by the two currents, and remain almost at +rest; the lateral pressure exerted by those on the outside of the +conductors is thus unbalanced, and the conductors are pushed together +as though they attracted each other. When the currents flow in +opposite directions in parallel conductors, they conspire to give a +greater velocity to the vortices in the space between them, than to +those outside them, and are thus pushed apart by the pressure due to +the rotation of the vortices, as though they repelled each other. In a +similar way, the actions of magnets on conductors conveying currents +may be explained. The motion of a conductor across a series of lines +of magnetic force may squeeze together and lengthen the threads of +vortices in front, and thus increase their speed of rotation, while +the vortices behind will move more slowly because allowed to contract +axially and expand transversely. The velocity of the vortices thus +being greater on one side of the wire than the other, a current must +be induced in the wire. Thus the current induced by the motion of a +conductor in a magnetic field may be accounted for. + +This conception of a medium was given by Maxwell, not as a theory, but +to show that it was possible to devise a _mechanism_ capable, in +imagination at least, of producing all the phenomena of electricity +and magnetism. "According to our theory, the particles which form the +partitions between the cells constitute the matter of electricity. The +motion of these particles constitutes an electric current; the +tangential force with which the particles are pressed by the matter of +the cells is electro-motive force; and the pressure of the particles +on each other corresponds to the tension or potential of the +electricity." + +When a current is maintained in a wire, the molecular vortices in the +surrounding space are kept in uniform motion; but if an attempt be +made to stop the current, since this would necessitate the stoppage of +the vortices, it is clear that it cannot take place suddenly, but the +energy of the vortices must be in some way used up. For the same +reason it is impossible for a current to be suddenly started by a +finite force. Thus the phenomena of self-induction are accounted for +by the supposed medium. + +The magnetic permeability of a medium Maxwell identified with the +density of the substance composing the rotating cells, and the +specific inductive capacity he showed to be inversely proportional to +its elasticity. He then proved that the ratio of the electro-magnetic +unit to the electro-static unit must be equal to the velocity of +transmission of a transverse vibration in the medium, and consequently +proportional to the square root of the elasticity, and inversely +proportional to the square root of the density. If the medium is the +same as that engaged in the propagation of light, then this ratio +ought to be equal to the velocity of light, and, moreover, in +non-magnetic media, the refractive index should be proportional to the +square root of the specific inductive capacity. The different +measurements which had been made of the ratio of the electrical units +gave a mean very nearly coinciding with the best determinations of the +velocity of light, and thus the truth underlying Maxwell's speculation +was strikingly confirmed, for the velocity of light was determined by +purely electrical measurements. In the case also of bodies whose +chemical structure was not very complicated, the refractive index was +found to agree fairly well with the square root of the specific +inductive capacity; but the phenomenon of "residual charge" rendered +the accurate measurement of the latter quantity a matter of great +difficulty. It therefore appeared highly probable that light is an +electro-magnetic disturbance due to a motion of the electric particles +in an insulating medium producing a strain in the medium, which +becomes propagated from particle to particle to an indefinite +distance. In the case of a conductor, the electric particles so +displaced would pass from molecule to molecule against a frictional +resistance, and thus dissipate the energy of the disturbance, so that +true (_i.e._ metallic) conductors must be nearly impervious to light; +and this also agrees with experience. + +Maxwell thus furnished a complete theory of electrical and +electro-magnetic action in which all the effects are due to actions +propagated in a medium, and direct action at a distance is dispensed +with, and exposed his theory successfully to most severe tests. In his +great work on electricity and magnetism, he gives the mathematical +theory of all the above actions, without, however, committing himself +to any particular form of mechanism to represent the constitution of +the medium. "This part of that book," Professor Tait says, "is one of +the most splendid monuments ever raised by the genius of a single +individual.... There seems to be no longer any possibility of doubt +that Maxwell has taken the first grand step towards the discovery of +the true nature of electrical phenomena. Had he done nothing but this, +his fame would have been secured for all time. But, striking as it is, +this forms only one small part of the contents of this marvellous +work." + + + + +CONCLUSION. + +SOME OF THE RESULTS OF FARADAY'S DISCOVERIES, AND THE PRINCIPLE OF +ENERGY. + + +In early days, _the spirit of the amber_, when aroused by rubbing, +came forth and took to itself such light objects as it could easily +lift. Later on, and the spirit gave place to the _electric effluvium_, +which proceeded from the excited, or charged, body into the +surrounding space. Still later, and a fluid, or two fluids, acting +directly upon itself, or upon matter, or on one another, through +intervening space without the aid of intermediate mechanism, took the +place of the electric effluvium--a step which in itself was, perhaps, +hardly an advance. Then came the time for accurate measurement. The +simple _observation_ of phenomena and of the results of experiment +must be the first step in science, and its importance cannot be +over-estimated; but before any quantity can be said to be known, we +must have learned how to _measure_ it and to reproduce it in definite +amounts. The great law of electrical action, the same as that of +gravitation--the law of the inverse square--soon followed, as well as +the associated fact that the electrification of a conductor resides +wholly on its surface, and there only in a layer whose thickness is +too small to be discovered. The fundamental laws of electricity having +thus been established, there was no limit to the application of +mathematical methods to the problems of the science, and, in the hands +of the French mathematicians, the theory made rapid advances. George +Green, of Sneinton, Nottingham, introduced the term "potential" in an +essay published by subscription, in Nottingham, in 1828, and to him we +are indebted for some of our most powerful analytical methods of +dealing with the subject; but his work remained unappreciated and +almost unknown until many of his theorems had been rediscovered. But +the idea of a body acting where it is not, and without any conceivable +mechanism to connect it with that upon which it operates, is repulsive +to the minds of most; and, however well such a theory may lend itself +to mathematical treatment and its consequences be borne out by +experiment, we still feel that we have not solved the problem until we +have traced out the hidden mechanism. The pull of the bell-rope is +followed by the tinkling of the distant bell, but the young +philosopher is not satisfied with such knowledge, but must learn "what +is the particular go of that." This universal desire found its +exponent in Faraday, whose imagination beheld "lines" or "tubes of +force" connecting every body with every other body on which it acted. +To his mind these lines or tubes had just as real an existence as the +bell-wire, and were far better adapted to their special purposes. +Maxwell, as we have seen, not only showed that Faraday's system +admitted of the same rigorous mathematical treatment as the older +theory, and stood the test as well, but he gave reality to Faraday's +views by picturing a mechanism capable of doing all that Faraday +required of it, and of transmitting light as well. Thus the problem of +electric, magnetic, and electro-magnetic actions was reduced to that +of strains and stresses in a medium the constitution of which was +pictured to the imagination. Were this theory verified, we might say +that we know at least as much about these actions as we know about the +transmission of pressure or tension through a solid. + +With regard to the _nature_ of electricity, it must be admitted that +our knowledge is chiefly negative; but, before deploring this, it is +worth while to inquire what we mean by saying that we know what a +thing is. A definition describes a thing in terms of other things +simpler, or more familiar to us, than itself. If, for instance, we say +that heat is a form of energy, we know at once its relationship to +matter and to motion, and are content; we have described the +constitution of heat in terms of simpler things, which are more +familiar to us, and of which we _think_ we know the nature. But if we +ask what _matter_ is, we are unable to define it in terms of anything +simpler than itself, and can only trust to daily experience to teach +us more and more of its properties; unless, indeed, we accept the +theory of the vortex atoms of Thomson and Helmholtz. This theory, +which has recently been considerably extended by Professor J. J. +Thomson, the present occupier of Clerk Maxwell's chair in the +University of Cambridge, supposes the existence of a perfect fluid, +filling all space, in which minute whirlpools, or vortices, which in a +perfect fluid can be created or destroyed only by superhuman agency, +form material atoms. These are _atoms_, that is to say, they defy any +attempts to sever them, not because they are infinitely hard, but +because they have an infinite capacity for _wriggling_, and thus avoid +direct contact with any other atoms that come in their way. Perhaps a +theory of electricity consistent with this theory of matter may be +developed in the future; but, setting aside these theories, we may +possibly say that we know as much about electricity as we know about +matter; for while we are conversant with many of the properties of +each, we _know_ nothing of the ultimate nature of either. + +But while the theory of electricity has scarcely advanced beyond the +point at which it was left by Clerk Maxwell, the practical +applications of the science have experienced great developments of +late years. Less than a century ago the lightning-rod was the only +practical outcome of electrical investigations which could be said to +have any real value. [OE]rsted's discovery, in 1820, of the action of +a current on a magnet, led, in the hands of Wheatstone, Cooke, and +others, to the development of the electric telegraph. Sir William +Thomson's employment of a beam of light reflected from a tiny mirror +attached to the magnet of the galvanometer enabled signals to be read +when only extremely feeble currents were available, and thus rendered +submarine telegraphy possible through very great distances. The +discovery by Arago and Davy, that a current of electricity flowing in +a coil surrounding an iron bar would convert the bar into a magnet, at +once rendered possible a variety of contrivances whereby a current of +electricity could be employed to produce small reciprocating +movements, or even continuous rotation, where not much power was +required, at a distance from the battery. An illustration of the +former is found in the common electric bell; it is only necessary that +the vibrating armature should form part of the circuit of the +electro-magnet, and be so arranged that, while it is held away from +the magnet by a spring, it completes the battery circuit, but breaks +the connection as soon as it moves towards the magnet under the +magnetic attraction. To produce continuous rotation, a number of iron +bars may be attached to a fly-wheel, and pass very close to the poles +of the magnet without touching them; when a bar is near the magnet, +and approaching it, contact should be made in the circuit, but should +be broken, so that the magnet may lose its power, as soon as the bar +has passed the poles; or the continuous rotation may be produced from +an oscillating armature by any of the mechanical contrivances usually +adopted for the conversion of reciprocating into continuous circular +motion. But all such motors are extremely wasteful in their employment +of energy. Faraday's discovery of the rotation of a wire around a +magnetic pole laid the foundation for a great variety of +electro-motors, in some of which the efficiency has attained a very +high standard. About ten years ago, Clerk Maxwell said that the +greatest discovery of recent times was the "reversibility" of the +Gramme machine, that is, the possibility of causing the armature to +rotate between the field-magnets by sending a current through the +coils. The electro-motors of to-day differ but little from dynamos in +the principles of their construction. The copper disc spinning between +the poles of a magnet while an electric current was sent from the +centre to the circumference, or _vice versa_, formed the simplest +electro-motor. All the later motors are simply modifications of this, +designed to increase the efficiency or power of the machine. +Similarly, the earliest machine for the production of an electric +current at the expense of mechanical power only, but through the +intervention of a permanent magnet, was the rotating disc of Faraday, +described on page 262. This contrivance, however, caused a waste of +nearly all the energy employed, for while there was an electro-motive +force from the centre to the circumference, or in the reverse +direction, in that part of the disc which was passing between the +poles of the magnet, the current so generated found its readiest +return path through the other portions of the disc, and very little +traversed the galvanometer or other external circuit. This source of +waste could be, for the most part, got rid of by cutting the disc into +a number of separate rays, or spokes, and filling up the spaces +between them with insulating material. The current then generated in +the disc would be obliged to complete its circuit through the external +conductor. If we can so arrange matters as to employ at once several +turns of a continuous wire in place of one arm, or ray, of the copper +disc, we may multiply in a corresponding manner the electro-motive +force induced by a given speed of rotation. All magneto-electric +generators are simply contrivances with this object. The iron cores +frequently employed within the coils of the armature tend to +concentrate the lines of force of the magnet, causing a greater number +to pass through the coils in certain positions than would pass through +them were no iron present. The electro-motive force of such a +generator depends on the strength of the magnetic field, the length of +wire employed in cutting the lines of force, and the speed with which +the wire moves across these lines. The point to aim at in constructing +an armature is to make the resistance as small as possible consistent +with the electro-motive force required. As there is a limit to the +strength of the magnetic field, it follows that for strong currents, +where thick wire must be employed, the generator must be made of large +dimensions, or the armature must be driven at very high speed to +enable a shorter length of wire to be used. + +The so-called "compound-interest principle," by which a very small +charge of electricity might be employed to develop a very large one by +the help of mechanical power, was first applied about a century ago in +the revolving doubler. Long afterwards, Sir William Thomson availed +himself of the same principle in the construction of the "mouse-mill," +or replenisher. The Holtz machine, the Voss and Wimshurst machines, +and the other induction-machines of the same class, all work on this +principle. It may be illustrated as follows: Take two canisters, call +them A and B, and place them on glass supports. Let a very small +positive charge be given to A, B remaining uncharged. Now take a brass +ball, supported by a silk string. Place it inside A, and let it touch +its interior surface. The ball will, as shown by Franklin, Cavendish, +and Faraday, remain uncharged. Now raise it near the top of the +canister, and, while there, touch it. The ball will become negatively +electrified, because the small positive charge in A will attract +negative electricity from the earth into the ball. Take the ball, with +its negative charge, still hanging by the silk thread, and lower it +into B till it touches the bottom. It will give all its charge to B, +which will thus acquire a slight negative charge. Raise the ball till +it is near the top of B, and then touch it with the finger or a metal +rod. It will receive a positive charge from the earth because of the +attraction of the negative charge on B. Now remove the ball and let it +again touch the interior of A. It will give up all its charge to A; +and then, repeating the whole cycle of operations, the charge carried +on the ball will be greater than before, and increase in each +successive operation, the electrification increasing in geometrical +progression like compound interest. A Leyden jar having one coating +connected to A and the other to B, may thus be highly charged in +course of time. A pair of carrier balls or plates, or a number of +pairs, may be used instead of one. The carriers, just before leaving A +and B, may be put in contact with one another instead of being put to +earth; they may be mounted on a revolving shaft, and the forms of A +and B modified to admit of the revolution of the carriers, and all the +necessary contacts may be made automatically. We thus get various +forms of the continuous electrophorus, and if the carriers are mounted +on glass plates, and rows of points placed alongside the springs or +brushes used for making the contacts, when the charges on the carriers +become very strong, electricity will be radiated from the points on to +the revolving glass plates, which will thus themselves take the place +of the metal carriers. Such is the action in the Voss and other +similar machines. + +But after Faraday had shown how to construct a magneto-electric +machine, the idea of applying the "compound-interest principle," and +thus converting the magneto-electric machine into the "dynamo," +occurred apparently simultaneously and independently to Siemens, +Varley, and Wheatstone. The first dynamo constructed by Wheatstone is +still in the museum of King's College, London. Wilde employed a +magneto-electric machine to generate a current which was used to +excite the electro-magnet of a similar but larger machine, having an +electro-magnet instead of a permanent steel magnet. The electro-magnet +could be made much larger and stronger than the steel magnet, and from +its armature, when made to revolve by steam power, a correspondingly +stronger current could be maintained. The idea which occurred to +Siemens, Varley, and Wheatstone was to use the whole, or a part, of +the current produced by the armature to excite its own electro-magnet, +and thus to dispense with the magneto-electric machine which served as +the separate exciter. When a part only of the current is thus +employed, and is set apart entirely for this duty, the machine is a +"shunt dynamo;" when the whole of the current traverses the +field-magnet coils as well as the external circuit, it is a "series +dynamo." The apparent difficulty lies in starting the current, but a +mass of iron once magnetized always retains a certain amount of +"residual magnetism," unless special means are taken to get rid of +it, and even then the earth's magnetism would generally induce +sufficient in the iron to start the action. Commencing, then, with a +slight trace of residual magnetism, the revolution of the armature +generates a feeble current, which passing round the magnet coils, +strengthens the magnetism, whereupon a stronger current is generated, +which in turn makes the magnet still stronger, and so on until the +magnet becomes saturated or the limit of power of the engine is +reached, and the speed begins to diminish, or a condition of affairs +is reached at which an increased current in the armature injures the +magnetic field as much as the corresponding increase in the +field-magnet coils strengthens it, and then no further increase of +current will take place without increasing the speed of rotation. In a +true dynamo the whole of the energy, both of the current and of the +electro-magnets, is obtained from the source of power employed in +driving the machine. + +But Faraday's discovery of electro-magnetic induction led to practical +developments in other directions. Graham Bell placed a thin iron disc +in front of the pole of a bar magnet, and wound a coil of fine wire +round the bar very near the pole. The ends of the coils of two such +instruments he connected together. When the iron disc of one +instrument approached the pole of the magnet, the lines of force were +disturbed, fewer escaped radially from the bar, and more left it at +the end, so as to go straight to the iron disc; thus the number of +lines of force passing through the coil was altered, and a current was +induced which, passing round the coil of the other instrument, +strengthened or weakened its magnet, and caused the iron disc to +approach it or recede from it, according to the way in which the coils +were coupled. Thus the movements of the first disc were faithfully +repeated by the second, and the minute vibrations set up in the disc +by sound-waves were all faithfully repeated by the second instrument. +This was Graham Bell's telephone, in which the transmitter and +receiver were convertible. + +But another and an earlier application of Faraday's discoveries is +found in the induction coil. A short length of thick wire and a very +great length of thin wire are wound upon an iron bar. The ends of the +long thin wire, or secondary coil, form the terminals of the machine; +the short thick wire, or primary coil, is connected with a battery, +but in the circuit is placed an "interrupter." This is generally a +small piece of iron, or hammer, mounted on a steel spring opposite one +end of the iron core, the spring pressing the hammer back against a +screw the end of which, like the back of the hammer, is tipped with +platinum; and this contact completes the battery circuit. When the +current starts, the iron core becomes a magnet, attracts the hammer, +breaks the contact, stops the current, the magnetism dies away, the +hammer is forced back by the spring, and then the cycle of events is +repeated. But the starting of the current in the primary causes a +great many lines of magnetic force to pass through each of the many +thousand turns of wire in the secondary, especially as the iron core +conducts most of the lines of force of each turn of the primary almost +from end to end of the coil, and thus through nearly all the turns of +the secondary. This action might be further increased by connecting +the ends of the iron core with an iron tube or series of longitudinal +bars placed outside the whole coil. When the primary current ceases, +all these lines of force vanish. Thus during the starting of the +primary current, which, on account of self-induction, occupies a +considerable time, there will be an inverse current in the secondary +proportional to the rate of increase of the primary; and while the +primary is dying away, there will be a direct current in the secondary +proportional to its rate of decrease. The primary current cannot be +increased at a faster rate than corresponds to the power of the +battery, but by making a very sharp break it may be stopped very +rapidly. Still, however rapidly the circuit is broken, self-induction +causes a spark to fly across the gap until the energy of the current +is used up. The introduction of the condenser, consisting of a number +of sheets of tinfoil insulated by paper steeped in paraffin wax, and +connected alternately with one end or the other of the primary coil, +serves to increase the rapidity with which the primary current died +away, by rapidly using up its energy in charging the condenser, and +produces a corresponding diminution in the spark at the +contact-breaker. This rapid destruction of the primary current causes +a correspondingly great electro-motive force in the secondary coil, +and thus very long sparks are produced between the terminals of the +secondary coil when the primary current is broken, though no such +sparks are produced when the primary current starts. If the secondary +coil be connected up with a galvanometer, so that there is a metallic +circuit throughout, it will be found that just as much electricity +flows in one direction through the circuit at the break of the primary +as flows in the other direction at the make, the difference being that +the first is a very strong current of great electro-motive force but +lasting a very short time, the second a feebler current lasting a +correspondingly longer time. + + * * * * * + +But though the recent advances in electrical science have been very +great, the grandest triumph of this century is the establishment of +the principle of the conservation of energy, which has settled for +ever the problem of "the perpetual motion," by showing that it has no +solution. This problem was not simply to find a mechanism which should +for ever move, but one from which energy might be continuously derived +for the performance of external work--in fact, an engine which should +require no fuel. But in spite of all that has been proved, numbers of +patents are annually taken out for contrivances to effect this +object. + +We have seen how Rumford showed that heat was motion, and how he +approximately determined its mechanical equivalent. Seguin, a nephew +of Montgolfier, endeavoured to show that, when a steam-engine was +working, less heat entered the condenser than when the same amount of +steam was blown idly through the engine. This Hirn succeeded in +showing, thus proving that heat was actually used up in doing work. +Mayer, of Heilbronn, measured the work done in compressing air, and +the heat generated by the compression, and assumed that the whole of +the work done in the compression, and no more, was converted into the +heat developed, which was the same thing as assuming that no work was +done in altering the positions of the particles of gas. From these +measurements he deduced a value of the mechanical equivalent of heat. +The assumption which Mayer made was shown experimentally by Joule to +be nearly correct. Joule proved that, when air expands from a high +pressure into a vacuum, no heat is generated or absorbed on the whole. +This he did by compressing air in an iron bottle, which was connected +with another bottle from which the air had been exhausted, the +connecting tube being closed by a stop-cock. The whole apparatus was +immersed in a bath of water, and on allowing the air to rush from one +vessel into the other, and then stirring the water, the temperature +was found to be the same as before. When the iron bottles were in +separate baths of water, that from which the air rushed was cooled, +and that into which it rushed was heated to the same extent. Joule and +Thomson afterwards showed that a very small amount of heat is absorbed +in this experiment. Joule also showed that the heat generated in a +battery circuit is proportional to the product of the electro-motive +force and the current, or to the product of the resistance and the +square of the current, which, in virtue of Ohm's law, is the same +thing. This relation is often known as Joule's law. He also proved +that, for the same amount of chemical action in the battery, the heat +generated was the same, whether it were all generated within the +battery or part in the battery and part in an external wire; and that +in the latter case, if the wire became so hot as to emit light, the +heat measured was less than before, on account of the energy radiated +as light. With a magneto-electric machine he employed mechanical power +to produce a current, and the energy of the current he converted into +heat. In all cases he found that, _whatever transformations the energy +might undergo in its course, a definite amount of mechanical energy, +if entirely converted into heat, always produced the same amount of +heat_; and he thereby proved, not only that heat is essentially +_motion_, but that it corresponds precisely with that particular +dynamical quantity which is called _energy_; and thus justified the +attempt to find a relation between heat and energy, or to express the +mechanical equivalent of heat as so many foot-pounds. + +Joule then set to work to determine, in the most accurate manner +possible, the number of foot-pounds of work which, if entirely +converted into heat, would raise one pound of water through 1 deg. Fahr. +The best known of his experiments is that in which he caused a paddle +to revolve by means of a falling weight, and thereby to churn a +quantity of water contained in a cylindrical vessel, the rotation of +the water being prevented by fixed vanes. In these experiments he +allowed for the work done outside the vessel of water or calorimeter, +for the buoyancy of the air on the descending weight, and for the +energy still retained by the weight when it struck the floor. From the +results obtained he deduced 772 foot-pounds as the mechanical +equivalent of heat. Expressed in terms of the Centigrade scale, +Joule's equivalent, that is, the number of foot-pounds of work in the +latitude of Manchester, which, if entirely converted into heat, will +raise one pound of water 1 deg. C., is 1390. + +Joule's experiments show that the same amount of energy always +corresponds to, and can be converted into, the same amount of heat, +and that no transformations, electrical or other, can ever increase or +diminish this quantity. Maxwell expressed this principle as follows:-- + +_The energy of a system is a quantity which can neither be increased +nor diminished by any actions taking place between the parts of the +system, though it may be transformed into any of the forms of which +energy is susceptible._ + +This is the great principle of the conservation of energy which is +applicable equally to all branches of science. + +Another principle, almost equally general in its applicability, is +that of the dissipation of energy, for which we are indebted in the +first instance to Sir William Thomson. All forms of energy may be +converted into heat, and heat tends so to diffuse itself throughout +all bodies as to bring them to one uniform temperature. This is its +ultimate state of degradation, and from that state no methods with +which we are acquainted can transform any portion of it. When energy +is possessed by a system in consequence of the relative positions or +motions of bodies which we can handle, and whose movements we may +control, the whole of the energy may be employed in doing any work we +please; in fact, it is all _available_ for our purpose, or its +_availability_ may be said to be perfect. Energy in any other form is +limited in its availability by the conditions under which we can place +it. For example, the energy of chemical action in a battery may be +used to produce a current, and this to drive a motor by which +mechanical work is effected, but some of the energy must inevitably be +degraded into the form of heat by the resistance of the battery and of +the conductor, and this portion will be greater as the rate of doing +work is increased. The ratio of the quantity of energy which can be +employed for mechanical purposes with the means at our disposal, to +the whole amount present, is called the _availability_ of the energy. +All forms of energy may be wholly converted into heat, but only a +fraction of any quantity of heat can be transformed into higher forms +of energy, and this depends on the temperature of the source of heat +and of the coldest body which can be employed as a condenser, being +greater the greater the difference between the temperatures of the +source and condenser, and the lower the temperature of the latter. In +every operation which takes place in nature there is a degradation of +energy, and though some portion of the energy may be raised in +availability, another portion is lowered, so that on the whole the +availability is diminished. Thus, in the case of the heat-engine, work +can be obtained from heat only by allowing another portion of the heat +to fall in temperature; and, as originally stated by Sir William +Thomson, "it is impossible, by means of inanimate material agency, to +obtain mechanical effect from any portion of matter by cooling it +below the temperature of the coldest of the surrounding objects," and +to leave the working substance in the same condition in which it was +at the commencement of the operations. Accepting this principle, +Professor James Thomson showed that increase of pressure must lower +the freezing point of water, for otherwise it would be possible to +construct an engine which, working by the expansion of water in +freezing, would continue to do work by cooling a body below the +temperature of any other body available, and he calculated the amount +of pressure necessary to lower the freezing point through one degree. +The conclusion was afterwards experimentally verified by Sir William +Thomson, and served to explain all the phenomena of regelation. Thus, +like the principle of the conservation of energy, the principle of the +dissipation of energy serves as a guide in the search after truth. But +there is this difference between the two principles--no one can +conceive of any method by which to circumvent the conservation of +energy; but Clerk Maxwell showed that the principle of dissipation of +energy might be overridden by the exercise of intelligence on the part +of any creature whose faculties were sufficiently delicate to deal +with individual molecules. In the case of gases, the temperature +depends on the average energy of motion of the individual particles, +and heat consists simply of this motion; but in any mass of gas, +whatever the average energy may be, some of the particles will be +moving with very great, and some with very small, velocities. By +imagining two portions of gas, originally at the same temperature, +separated by a partition containing trap-doors which could be opened +or closed without expenditure of energy, and supposing a "demon" +placed in charge of each door, who would open the door whenever a +particle was approaching very rapidly from one side, or very slowly +from the other, but keep it shut under other circumstances, he showed +that it would be possible to sort the particles, so that those in the +one compartment should have a great velocity, and those in the other a +small one. Hence, out of a mass of gas at uniform temperature, two +portions might be obtained, one at a high temperature and the other at +a low, and, by means of a heat-engine, work could be obtained until +the two portions were again at equal temperatures, when the services +of the "demons" might be again taken advantage of, and the operations +repeated until all the heat was used up. + +Any theory which is brought forward to explain a phenomenon, or any +process which is proposed to effect any operation, must in the first +instance submit to the test of the application of these two principles +of conservation and dissipation of energy; and any proposal which +fails to bear these tests may be at once rejected. The essential +feature of the science of to-day is its quantitative character. We +must, for instance, not only know that radiant energy comes to us from +the sun, but we must learn how much energy is annually received by the +earth in this way; and, in the next place, how much energy is radiated +by the sun in all directions in the same time. When we have learned +this, we want to know what is the source of this energy; and no theory +of the sun which does not enable us to explain how this constant +expenditure of energy is maintained can be accepted. Last century it +was possible to believe, with Sir William Herschel, that the greater +part of the sun's mass is comparatively cool, and that it is +surrounded by only a thin sheet of flame. To-day such a theory would +be rejected at once, simply because the thin shell of flame could not +provide energy for the solar radiation for any considerable time. The +contact theory of the galvanic cell, as originally enunciated, fell to +the ground for a similar reason. The simple contact of dissimilar +metals could afford no continuous supply of energy to sustain the +current. Applied to the steam-engine, the doctrine of energy teaches +us, not only that, corresponding to the combustion of a pound of coal, +there is a definite quantity of work which is the mechanical +equivalent of the heat generated, and is such that no engine of which +we can conceive is capable of deriving from the combustion of the +pound of coal a greater amount of work, but it teaches us that there +is a further limitation fixed to the amount of work obtainable. This +limitation depends upon the range of temperature at our command; and, +when the range is known, we can express the amount of energy +realizable by a perfect engine working through that range as a +definite fraction of the whole energy corresponding to the heat of +combustion of the fuel. Thus, if we find that a particular engine +realizes only 15 per cent. of the energy of its fuel in work done, we +must not suppose that mechanical improvements in the engine would +enable us to realize any considerable portion of the other 85 per +cent.; for it may be that a theoretically perfect engine, working with +its boiler and condenser at the same temperatures as those of the +engine considered, could only realize 25 per cent. of the energy of +the fuel, reducing the margin for improvement from 85 to 10 per cent., +as long as the range of temperature is unaltered. To improve the +efficiency beyond this limit, the range of temperature must be +increased, that is, generally, hotter steam must be used. + +The principles of energy are thus guides, not only to the scientific +theorist, but to the practical engineer, and they have been +established only through careful measurement. The simple observation +of phenomena, and of the conditions under which they occur, could +never have led to the establishment of such principles; and, though +the carrying out of experiments which do not involve measurements is +of great value, it is the careful measurement, however simple, which +affords the highest training to the mind and hand, and without which +any course of instruction in experimental physics is of little value. + +The Hindoos used to regard the earth as a vast dome carried on the +backs of elephants. The elephants themselves, however, required +support, and were represented as standing on the back of a gigantic +tortoise. It does not, however, appear that any support was provided +for the tortoise. In some respects this figure represents the +apparently perpetual condition of scientific knowledge. Phenomena are +investigated, and are shown to depend upon other actions which appear +simpler or more fundamental than the phenomena at first observed. +These, again, are found to obey laws which are of much wider +application, or appear to be still more fundamental; but it may be +that we are as far off as ever from discovering the great secret of +the universe, the ultimate nature of all things. + + + + +INDEX. + + + A. + + Abbott, Faraday's letters to, 241, 246. + + Aberdeen University, Maxwell appointed professor in, 284; + Young's report on, 203. + + Absorption, Rumford's experiments on, 185; + of sun's rays by cloth of different colours, 99. + + Academy of Sciences, Franklin nominated Foreign Associate of, 111. + + Adjustment of the eye, Young's paper on the, 200. + + AEpinus's completion of Franklin's theory, 77. + + Air, Boyle's conception of the constitution of, 19. + + Air-pump, Boyle's experiments with, 19; + constructed by Boyle, 27. + + American Independence, Declaration of, 113. + + American Philosophical Society, foundation of, 61. + + Ampere's theory, Faraday's views on, 257. + + Anchor-ring experiment, Faraday's, 260. + + Arago's experiment, 264. + + Argand lamp, efficiency of, 188. + + Armstrong gun, principle of the, 180. + + Atmospheric electricity, Faraday's experiments on, 254; + obtained by a pointed rod, 84. + + Autobiography of Franklin, 39. + + Availability of energy, 326. + + + B. + + Baily, Francis, repetition of the Cavendish experiment by, 146. + + Beats in music, explanation of, 209. + + Beggary in Bavaria banished by Rumford, 164. + + Bernoulli's, Daniel, molecular theory of gases, 299. + + Boston, blockade of, 110. + + =Boyle=, Hon. Robert, birth, 8; + conversion, 11; + first air-pump, 17; + conception of the constitution of the air, 19; + experiments with the air-pump, 19, _et seq._; + argument on the cause of a vacuum, 23; + experiments establishing his law, 25; + statement of his law, 29; + observations on cold, 32, + and on the expansion of water in freezing, 33; + experiments on induced magnetism, 34; + the province of experimental science, 37. + + Boyle's law, 29. + + Brocklesby, Dr., death of, 208. + + Brougham's criticisms of Thomas Young, 218. + + Bumper, electrical, 80. + + + C. + + Camera obscura, invention of, 2. + + Canada balsam, stresses in, 298. + + Candle-flame, effect of, in discharging electricity, 75. + + Capacity, electrical, 137; + Franklin's experiments on, 81, 89; + Cavendish's unit of, 138; + Cavendish's measures of, 134, 138; + of disc, measured by Cavendish, 134. + + Capillarity, 228. + + Cascade method of charging Leyden jars, 77. + + =Cavendish=, Hon. Henry, F.R.S., birth and parentage, 126; + social habits, 127; + appointed member of the R.S. Committee on Lightning-Conductors, + 131; + elected Foreign Associate of the French Institute, 132; + death, 133; + proof of the law of inverse squares, 135; + experiment with the spheres repeated by MacAlister, 137; + experiments on the torpedo, 140; + experiments on the resistance of conductors, 142; + discovery of Ohm's law, 143; + view of latent heat, 144; + apparatus for determining the melting point of mercury, 145; + the Cavendish experiment, 146. + + Cavendish experiment, 146; + Laboratory, 288; + Manuscripts, 134; + Maxwell's work on the Manuscripts, 293. + + City Philosophical Society, joined by Faraday, 245; + Faraday's lectures to, 251. + + Cold, Boyle's observations on, 32. + + Collinson, Peter, present of, to the Library Company, 72. + + Colour-blindness, Maxwell's experiments on, 296. + + Colour-box, Maxwell's, 297. + + Colours, effect of, on absorption of sun's rays, 99, 186. + + Colours of the spectrum mixed by Boyle, 31. + + Colour-top, Maxwell's, 284, 295; + Young's, 215. + + Colour-vision, Maxwell's theory of, 294; + Young's theory of, 214. + + Commonplace-book, Faraday's, 253. + + Compound-interest principle, 316. + + Condenser, use of, in induction coils, 321. + + Conduction of heat, Rumford's experiments on, 186. + + Conductors, multiple, flow of electricity through, 141. + + Conductors necessarily opaque, 307. + + Conservation of energy, Maxwell's statement of the principle of, + 325. + + Copley Medal awarded to Franklin, 66, 74. + + Cork, Earl of, autobiography of, 5. + + Creeping of electricity on glass, 139. + + Crystalline lens, fibrous structure of, 200; + mode of adjustment of, 201. + + Cuneus's discovery of the Leyden jar, 4. + + + D. + + Davy, Sir Humphry, appointed professor at the Royal Institution, + 174; + letter of, to Faraday, 244. + + Declaration of American Independence signed, 113. + + Defence of the American Colonies against France and Spain, 62. + + Degree of electrification, 137. + + De la Rive's invitation to Faraday, 249. + + Density of the earth, determinations of the mean, 146. + + Desaguliers on electrics and non-electrics, 4. + + Diagram of colour, Young's, 215; + Maxwell's, 295. + + Diamagnetism discovered by Faraday, 274. + + Diamonds burned by Davy, 250. + + Dichroism of _Lignum nephriticum_, 30. + + Discharge, electrical, difference between positive and negative, 87. + + Dissipation of energy, principle of, 326. + + Distilled water, resistance of, 142. + + Double refraction explained by Huyghens, 219. + + Dufay showed that all bodies could be electrified, 4. + + Dynamical nature of heat, suggested by Bacon, 2, 32; + maintained by Boyle, 32; + investigated by Rumford, 189; + established by Joule, 193, 324. + + Dynamical top, Maxwell's, 285. + + Dynamo, constructed by Wheatstone, 318; + action of, 319; + essential feature of, 319. + + + E. + + Effect of points in discharging electricity, 74. + + Electrical picnic, 80. + + Electrical Standards Committee, 287. + + Electric intensity, 137; + potential, 137. + + Electricity, first obtained from clouds, 74; + velocity of, 93. + + Electrics and non-electrics, 3. + + Electrolysis, Faraday's laws of, 266. + + Electro-magnetic induction, discovered by Faraday, 259; + Maxwell's statement of the laws of, 301. + + Electro-magnetic theory of light, 306. + + Electro-motors, 313. + + Electro-tonic state, conceived by Faraday, 264; + explained by Maxwell, 302. + + Energy of Leyden jar resident in the glass, 79. + + Eriometer, Young's, 223. + + Ether, Maxwell's illustration of the possible constitution of, 302. + + Expansion of water on freezing, 33. + + Extra current, 268. + + + F. + + =Faraday=, Michael, birth, 238; + life in Jacob's Well Mews, 238; + becomes an errand-boy, 239; + apprenticeship, 239; + attends lectures at Tatum's, 240; + constructs a voltaic pile, 241; + letters to Abbott, 241, 246; + starts as a journeyman, 243; + application to Davy, 243; + appointed assistant at the Royal Institution, 245; + joins the City Philosophical Society, 245; + opinions respecting lectures, 246, 247; + journey with Davy, 248; + acquaintance with De la Rive, 249; + crosses the Alps, 249; + at the Academia del Cimento, 250; + returns from the Continent, 251; + lectures to the City Philosophical Society, 251; + commonplace-book, 253; + atmospheric electricity apparatus, 254; + marriage, 255; + discovery of electro-magnetic rotation, 255; + of the earth's action on a current, 256; + letter to E. de la Rive, 256; + views on Ampere's theory, 257; + elected F.R.S., 258; + appointed director of the laboratory at the Royal Institution, + 258; + work on optical glass, 259; + discovery of induced currents, 259; + institutes Friday evening lectures, 259; + anchor-ring experiment, 260; + magneto-electric machine, 262; + obtains induced current by action of the earth, 262; + obtains "magnetic spark," 262; + explanation of Arago's experiment, 264; + laws of electrolysis, 266; + proves the identity of frictional and voltaic electricity, 266; + experiments on self-induction, 268; + diagrams of lines of magnetic force, 269; + conception of lines of electric force, 270; + ice-pail experiment, 270; + butterfly-net, 270; + experiments on specific inductive capacity, 272; + appointed scientific adviser to Trinity House, 273; + appointed member of the Senate of the University of London, 273; + discovery of the electro-magnetic rotation of the plane of + polarization, 273; + investigations in diamagnetism, 274; + joins the Sandemanian Church, 275; + lectures before the Prince Consort, 275; + retirement to Hampton Court, 277; + death, 277; + lines of force investigated by Thomson and Maxwell, 300. + + Forbes's, Principal, opinion of Young, 194. + + Foucault's measurement of the velocity of light, 220. + + _Fovea centralis_, insensibility of, to blue light, 298. + + Franciscus Linus, funicular hypothesis of, 25. + + =Franklin=, Benjamin, autobiography of, 39; + birth, 40; + on the disputatious temper, 42; + method of learning prose composition, 43; + tries vegetarianism, 44; + adopts the Socratic method, 44; + first voyage to England, 48; + experience as a journeyman in London, 49; + views on beer as a food, 49; + marriage, 54; + endeavours to attain moral perfection, 56; + method of reconciling an enemy, 60; + elected F.R.S., 66; + second voyage to England, 70; + begins electrical experiments, 72; + electrical papers ridiculed by the Royal Society, 73; + discovers the effect of points, 74; + one-fluid theory of electricity, 76; + theory of the Leyden jar, 78; + invention of the lightning-rod, 83; + golden fish, 85; + view of the nature of light, 86; + kite, 88; + experiments on capacity, 81, 89; + experiments on electrical induction, 90; + proof of the absence of electricity in a hollow conductor, 91; + third voyage to England, 102; + examination before the Parliamentary Committee, 105; + nominated Foreign Associate of the Academy of Sciences, 110; + signs the Declaration of Independence, 113; + sent to Paris, 113; + made Minister Plenipotentiary to the Court of France, 116; + signs the Treaty of Peace, 119; + elected President of Pennsylvania, 120; + death, 122. + + Fresnel, awarded the Rumford Medal, 233. + + Fresnel's repetition of Young's experiments, 225. + + Friction as a source of heat, Rumford's experiments on, 189. + + Friday evening lectures instituted by Faraday, 259. + + + G. + + Galileo and Torricelli on the pressure of the air, 16. + + Garnett, Dr. Thomas, professor at the Royal Institution, 173. + + Gilbert, Dr., founder of electrical science, 3. + + Goettingen, Young's university course at, 206. + + Graham Bell's telephone, 319. + + Gray, Stephen, discovers electric conduction, 3. + + Grimaldi's fringes explained by Young, 222. + + Gunpowder, Rumford's experiments on, 179. + + + H. + + Halos, coloured, Young's explanation of, 224. + + Hawksbee's observations on capillary attraction, 228. + + Heat, a form of energy, 32; + generated by friction in vacuum, 32; + generated by friction, Rumford's experiments on, 189. + + Herapath's explanation of gaseous diffusion, 299. + + Herschel's, Sir John, comments on Young's principle of interference, + 208. + + Hicks's, Principal, investigations on the influence of temperature + on gravitation, 184. + + Hieroglyphics, Young's work on, 234. + + Hobbes, opposition of, to Boyle, 25. + + Hollow conductor, Franklin's experiments on, 91; + Cavendish's experiments on, 135; + Faraday's experiments on, 270. + + Honorary degrees conferred on Franklin, 66, 101. + + Hooke's law, 229. + + Hooke, Theodore, founds the Royal Society, 14. + + Huyghens's explanation of double refraction, 219; + principle, 218. + + Hydrogen, electro-chemical equivalent of, 267. + + + I. + + Ice-pail experiment of Faraday, 270. + + Identity of frictional and voltaic electricity, 266. + + Induced currents, discovered by Faraday, 259; + explained by structure of ether, 304; + from earth's action, 262. + + Induction coil, 320. + + Induction, Franklin's experiments on, 90; + self, 142, 306. + + Induction machines, principle of, 316. + + Insulators for lightning-rods, 96. + + Interference, principle of, discovered by Young, 208; + spectra of, obtained by Young, 225. + + Invisible college, 13. + + + J. + + Jenkin, William, discovery of the "extra current" by, 268. + + Joule and Thomson's determination of the heat absorbed by air in + expanding, 324. + + Joule, Dr., establishment of mechanical theory of heat by, 193, 324. + + Joule's law, 324; + proof that heat and energy are equivalent, 324; + determination of the mechanical equivalent of heat, 325. + + Junto Club, formation of the, 51. + + + K. + + Kelland's, Professor, edition of Young's lectures, 212. + + Kinnersley commences lecturing, 73. + + Kite, Franklin's, 88. + + Knobs _versus_ points, 95. + + + L. + + Laboulaye's comments on Franklin, 38. + + Laplace's theory of Saturn's rings, 285. + + Latent heat, Black's theory of, 144; + Cavendish's views on, 144. + + Leonardo da Vinci's observation of capillary attraction, 228. + + Leyden jar, discovery of, 4; + energy of, resident in the glass, 79. + + Leyden jars charged by cascade, 77. + + Light, Franklin's view of nature of, 86; + Maxwell's electro-magnetic theory of, 306; + rotation of the plane of polarization of, 273. + + Lightning, effects of, on Newbury steeple, 92. + + Lightning-protectors, Maxwell's, 294. + + Lightning-rod, illustrations of the, 83. + + _Lignum nephriticum_, dichroism of, 30. + + Lines of force mathematically investigated by Thomson and Maxwell, + 300. + + Lines of magnetic force fixed by Faraday, 269. + + Luminiferous ether, the vehicle of electrical action, 227; + illustration of the possible constitution of, 302. + + + M. + + Magdeburg hemispheres, experiments with, by Otto von Guericke, 17. + + Magic squares, Franklin's proficiency in, 66. + + "Magnetic spark" obtained by Faraday, 262. + + Magnetization by induction, Boyle's experiments on, 34. + + Magneto-electric machine, Faraday's, 262, 314. + + Magneto-electric machines, Wilde's, 318; + objects to be aimed at in the construction of, 315. + + =Maxwell=, James Clerk, birth and parentage, 279; + enters Edinburgh Academy, 280; + letters to his father, 280; + early papers before the Royal Society of Edinburgh, 281; + visit to Mr. Nicol, 281; + experiments with unannealed glass, 282; + enters the University of Edinburgh, 282; + enters Peterhouse, 282; + migrates to Trinity, 282; + degree in Cambridge, 283; + elected Fellow of Trinity, 284; + appointed Professor at Marischal College, 284; + marriage, 287; + essay on Saturn's rings, 285; + dynamical top, 285; + appointed professor at King's College, 287; + lecture on colour at the Royal Institution, 287; + work on the Electrical Standards Committee, 287; + appointed Professor of Experimental Physics at Cambridge, 288; + plans the Cavendish Laboratory, 288; + lectures at Cambridge, 290; + work on the Cavendish Manuscripts, 134, 293; + delivers the Rede Lecture, 293; + method of protecting buildings from lightning, 294; + death, 294; + colour-top, 295; + experiments on colour-blindness, 296; + colour-box, 297; + awarded the Rumford Medal, 297; + wheel of life, 297; + real-image spectroscope, 298; + discovery of stresses in Canada balsam, 298; + of the insensibility of the _fovea centralis_ to blue light, 298; + statistical method, 299; + explanation of the viscosity of gases, 299; + investigations of Faraday's lines of force, 300; + statement of the laws of electro-magnetic induction, 301; + mechanical illustration of the ether, 302; + explanation of induced currents, 304; + of the mechanical action between currents and currents, and + between magnets and currents, 304; + of self-induction, 306; + electro-magnetic theory of light, 306; + contrivance for overcoming the principle of the dissipation of + energy, 328. + + Maxwell's experiment for showing electro-magnetic rotation, 258. + + Mayer's determination of the mechanical equivalent of heat, 323. + + Mechanical equivalent of heat, definition of, 193; + Rumford's determination of, 192. + + Mercury, melting point of, 145. + + Mirabeau's declamation on Franklin, 123. + + Mixed plates, colours of, 223. + + Moral perfection, Franklin's endeavour to attain, 56. + + Mother-of-pearl, Young's explanation of the colours of, 224. + + + N. + + Nautical Almanack, Young appointed superintendent of the, 232. + + Newton's analysis and synthesis of white light, 213; + rings, Young's explanation of, 222; + theory of light, 219. + + Nicol prisms given to Clerk Maxwell, 282. + + + O. + + [OE]rsted's discovery, 255. + + Ohm's law, discovered by Cavendish, 143; + meaning of, 143. + + Optical glass, Faraday's work on, 259. + + Otto von Guericke, contributions of, to electricity, 3; + experiments of, with the Magdeburg hemispheres, 17. + + + P. + + Paris, Dr., Faraday's letter to, 243. + + Pascal takes a barometer up the Puy de Dome, 17. + + Pennsylvania fireplace invented by Franklin, 63; + _Gazette_ published by Franklin, 53. + + Perpetual motion, Rumford's contrivances for, 150; + impossibility of, 322. + + Philadelphia, Franklin's first arrival in, 46; + Library, foundation of the, 55. + + Photometer, Rumford's, 187. + + Pigments, effects of mixing, 217. + + Points _versus_ knobs, 95, 131. + + Polarization, explained by transverse vibrations, 226; + of light discovered by Malus, 226. + + "Poor Richard's Almanack," 60. + + Pressure of the air the cause of suction, 29. + + + R. + + Radiation, Rumford's experiments on, 184; + of cold, Rumford's experiments on, 186. + + Rede Lecture, delivered by Clerk Maxwell, 293. + + Refraction of light, laws of, 1; + mentioned by Pliny, 1. + + Relative economy of different sources of light, 188. + + Resistance of conductors, Cavendish's experiments on, 142. + + Roemer, measurement of the velocity of light by, 2. + + Rosetta Stone, discovery of the, 234; + inscription on, 234. + + Royal Institution, foundation of the, 169; + Young's lectures at the, 212; + Faraday's appointment at the, 245; + Maxwell's lecture on colour at the, 287. + + Royal Society, origin of the, 13-15. + =Rumford=, Count, birth and parentage, 148; + life as a medical student, 153; + becomes a schoolmaster at Concord, 154; + marriage, 154; + summoned before the Committee of Safety, 156; + imprisoned at Woburn, 156; + first journey to London, 158; + receives an appointment in the Colonial Office, 158; + experiments on the explosion of gunpowder, 158, 179; + elected F.R.S., 158; + made lieutenant-colonel in the British army, 159; + promoted to colonel, 160; + visits Elector of Bavaria, 160; + cured of martial ambition, 160; + enters the service of the Elector of Bavaria, 161; + knighted by George III., 161; + reforms in the Bavarian army, 162; + attack on the beggars, 163; + made Count of the Holy Roman Empire, 165; + robbed of his manuscripts, 166; + visited by his daughter, 166; + his roaster, 166; + experiments on fire-places, 166; + founds the Rumford Medal, 167; + appointed Minister Plenipotentiary to the Court of Great Britain, + 169; + founds the Royal institution, 169; + plans for the Institution, 169; + residence in Paris, 175; + marriage with Madame Lavoisier, 175; + death; 176; + Cuvier's _eloge_ on, 176; + statue at Munich, 178; + experiments on the conduction of heat in fluids, 181; + on the convection of heat in viscous liquids, 184; + on the weight of heat, 185; + on radiation, 185; + on the conduction of heat, 186; + on the apparent radiation of cold, 187; + shadow-photometer, 188; + experiments on the relative economy of candles and tapers, 188; + on the traction of carriages, 189; + on friction as a source of heat, 189; + determination of the mechanical equivalent of heat, 192. + + Rumford Medal, foundation of the, 167; + recipients of the, 167; + awarded to Fresnel, 233; + awarded to Clerk Maxwell, 297. + + Rumford roaster, 166. + + + S. + + "Sandford and Merton," influence of, on the negro traffic, 197. + + Saturn's rings, Maxwell's essay on, 285. + + Sea-water, resistance of, 142. + + Seguin's attempt to measure loss of heat in the steam-engine, 323. + + Self-induction, effect of, on sudden discharge, 142; + of electro-magnet, 268; + effect of, in induction coil, 321. + + Sensation of heat, cause of, 33. + + Seraphic love, Boyle's essay on, 15. + + Shaw's, Dr., comments on Boyle, 37. + + Snellius's laws of refraction, 1. + + Socratic method adopted by Franklin, 44. + + Specific inductive capacity, discovered by Cavendish, 139; + rediscovered by Faraday, 272. + + Spectral colours, mixed by Boyle, 31; + mixed by Maxwell, 297. + + S.P.G., foundation of the, 30. + + Spheroidal waves in Iceland-spar explained by Young, 226. + + Stamp Act, 112. + + Standards Commission, report of, 232. + + Statistical method, Maxwell's, 299. + + Steeple struck by lightning at Newbury, 92. + + Stereoscope, Maxwell's real-image, 298. + + Stokes's, Professor G. G., exhibition of the bright centre in the + shadow of a disc, 222. + + Suction caused by atmospheric pressure, 29. + + Surface-tension, 228; + suggested by Segner, 229; + Young's investigations on, 229. + + + T. + + Table of results of experiments on Boyle's law, 27. + + Tatum's lectures on natural philosophy, 240. + + Telephone, Graham Bell's, 319. + + Temperature, its nature, 33. + + Thermometers first hermetically sealed, 2. + + Thomson's, Professor James, application of the principle of + dissipation of energy to the freezing of water under pressure, + 327. + + Thomson's, Sir William, statement of the principle of dissipation of + energy, 327; + vortex theory of matter, 312; + mirror galvanometer, 313; + replenisher, 316. + + Thunder-storms, Franklin's theory of, 81. + + Torpedo, Cavendish's experiments on the, 140; + Davy's experiments on the, 251. + + Traction of carriages, Rumford's experiments on, 189. + + Trial plate used by Cavendish, 139. + + Tyres, relative advantages of broad and narrow, 189. + + + U. + + Undulatory theory founded by Hooke and Huyghens, 218. + + Union of the American States, Franklin's plan for, 68. + + University of Philadelphia, foundation of the, 64. + + + V. + + Vacuum, Boyle's argument on the cause of a, 23. + + Velocity of electricity, 93; + of light measured by Roemer, 2; + of light deduced from electro-magnetic theory, 306. + + Viscosity of gases explained by Maxwell, 299. + + Voltaic pile constructed by Faraday, 241. + + Vortex theory of matter, 312. + + Voss machine, 316. + + + W. + + Wallis, Dr., account of the Royal Society by, 14. + + Wealth, ways to acquire, 100. + + Wheel of life, Clerk Maxwell's, 297. + + Wilson, Dr., account of Cavendish by, 132, 147. + + + Y. + + =Young=, Thomas, Principal Forbes's opinion of, 194; + birth and parentage, 194; + early education, 195; + becomes a London medical student, 199; + paper on the power of adjustment of the eye, 199; + elected F.R.S., 200; + visit to Cornwall, 201; + first visit to the Duke of Richmond, 201; + enters the Medical School at Edinburgh, 202; + declines secretaryship to the Duke of Richmond, 202; + visits Gordon Castle, 204; + visits Inverary Castle, 205; + enters the University of Goettingen, 206; + examination in medicine at Goettingen, 207; + enters Emmanuel College, 207; + discovers the principle of interference, 208; + appointed Professor of Natural Philosophy at the Royal + Institution, 174, 210; + lectures at the Royal Institution, 212; + theory of colour-vision, 214; + his colour-top, 215; + colour-diagram, 215; + his Bakerian lectures, 218; + explanation of the rectilinear propagation of light, 221; + of Newton's rings, 222; + eriometer, 223; + explanation of coloured halos, 224; + of the colours exhibited by mother-of-pearl, 224; + interference spectra, 225; + explanation of spheroidal waves in Iceland-spar, 226; + of the colours of thin plates, 227; + hypothesis of an electric ether, 227; + investigations on surface-tension, 229; + modulus of elasticity, 230; + his marriage, 231; + appointed physician in St. George's Hospital, 231; + superintendent of the Nautical Almanack, 232; + death, 233. + +PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, + +LONDON AND BECCLES. + + + + + +End of Project Gutenberg's Heroes of Science: Physicists, by William Garnett + +*** END OF THIS PROJECT GUTENBERG EBOOK HEROES OF SCIENCE: PHYSICISTS *** + +***** This file should be named 38583.txt or 38583.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/8/5/8/38583/ + +Produced by Albert Laszlo, P. 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