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diff --git a/old/1225-h/1225-h.htm b/old/1225-h/1225-h.htm new file mode 100644 index 0000000..d594100 --- /dev/null +++ b/old/1225-h/1225-h.htm @@ -0,0 +1,4849 @@ +<?xml version="1.0" encoding="us-ascii"?> + +<!DOCTYPE html + PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > + +<html xmlns="http://www.w3.org/1999/xhtml" lang="en"> + <head> + <title> + Faraday As a Discoverer, by John Tyndall + </title> + <style type="text/css" xml:space="preserve"> + + body { margin:5%; background:#faebd0; text-align:justify} + P { text-indent: 1em; margin-top: .25em; margin-bottom: .25em; } + H1,H2,H3,H4,H5,H6 { text-align: center; margin-left: 15%; margin-right: 15%; } + hr { width: 50%; text-align: center;} + .foot { margin-left: 20%; margin-right: 20%; text-align: justify; text-indent: -3em; font-size: 90%; } + blockquote {font-size: 97%; font-style: italic; margin-left: 10%; margin-right: 10%;} + .mynote {background-color: #DDE; color: #000; padding: .5em; margin-left: 10%; margin-right: 10%; font-family: sans-serif; font-size: 95%;} + .toc { margin-left: 10%; margin-bottom: .75em;} + .toc2 { margin-left: 20%;} + div.fig { display:block; margin:0 auto; text-align:center; } + div.middle { margin-left: 20%; margin-right: 20%; text-align: justify; } + .figleft {float: left; margin-left: 0%; margin-right: 1%;} + .figright {float: right; margin-right: 0%; margin-left: 1%;} + .pagenum {display:inline; font-size: 70%; font-style:normal; + margin: 0; padding: 0; position: absolute; right: 1%; + text-align: right;} + pre { font-style: italic; font-size: 90%; margin-left: 10%;} + +</style> + </head> + <body> +<pre xml:space="preserve"> + +The Project Gutenberg EBook of Faraday As A Discoverer, by John Tyndall + +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: Faraday As A Discoverer + +Author: John Tyndall + +Release Date: August 20, 2008 [EBook #1225] +Last Updated: February 7, 2013 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK FARADAY AS A DISCOVERER *** + + + + +Produced by An Anonymous Volunteer, and David Widger + + + + + +</pre> + <p> + <br /><br /> + </p> + <h1> + FARADAY AS A DISCOVERER + </h1> + <p> + <br /> + </p> + <h2> + by John Tyndall + </h2> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <blockquote> + <p class="toc"> + <big><b>CONTENTS</b></big> + </p> + <p> + <br /> + </p> + <p class="toc"> + <a href="#link2H_PREF"> Preface to the fifth edition. </a> + </p> + <p class="toc"> + <a href="#link2H_PREF2"> Preface to the fourth edition. </a> + </p> + <p class="toc"> + <a href="#link2H_PREF2"> Preface to the second edition. </a> + </p> + <p> + <br /> + </p> + <p class="toc"> + <a href="#link2H_4_0004"> <b>FARADAY AS A DISCOVERER.</b> </a> + </p> + <p> + <br /> + </p> + <p class="toc"> + <a href="#link2HCH0001"> Chapter 1. </a> + </p> + <p class="toc"> + <a href="#link2HCH0002"> Chapter 2. </a> + </p> + <p class="toc"> + <a href="#link2HCH0003"> Chapter 3. </a> + </p> + <p class="toc"> + <a href="#link2HCH0004"> Chapter 4. </a> + </p> + <p class="toc"> + <a href="#link2HCH0005"> Chapter 5. </a> + </p> + <p class="toc"> + <a href="#link2HCH0006"> Chapter 6. </a> + </p> + <p class="toc"> + <a href="#link2HCH0007"> Chapter 7. </a> + </p> + <p class="toc"> + <a href="#link2HCH0008"> Chapter 8. </a> + </p> + <p class="toc"> + <a href="#link2HCH0009"> Chapter 9. </a> + </p> + <p class="toc"> + <a href="#link2HCH0010"> Chapter 10. </a> + </p> + <p class="toc"> + <a href="#link2HCH0011"> Chapter 11. </a> + </p> + <p class="toc"> + <a href="#link2HCH0012"> Chapter 12. </a> + </p> + <p class="toc"> + <a href="#link2HCH0013"> Chapter 13. </a> + </p> + <p class="toc"> + <a href="#link2HCH0014"> Chapter 14. </a> + </p> + <p class="toc"> + <a href="#link2HCH0015"> Chapter 15. </a> + </p> + <p class="toc"> + <a href="#link2HCH0016"> Chapter 16. </a> + </p> + </blockquote> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a name="link2H_PREF" id="link2H_PREF"> + <!-- H2 anchor --> </a> + </p> + <h2> + Preface to the fifth edition. + </h2> + <p> + Daily and weekly, from all parts of the world, I receive publications + bearing upon the practical applications of electricity. This great + movement, the ultimate outcome of which is not to be foreseen, had its + origin in the discoveries made by Michael Faraday, sixty-two years ago. + From these discoveries have sprung applications of the telephone order, + together with various forms of the electric telegraph. From them have + sprung the extraordinary advances made in electrical illumination. Faraday + could have had but an imperfect notion of the expansions of which his + discoveries were capable. Still he had a vivid and strong imagination, and + I do not doubt that he saw possibilities which did not disclose themselves + to the general scientific mind. He knew that his discoveries had their + practical side, but he steadfastly resisted the seductions of this side, + applying himself to the development of principles; being well aware that + the practical question would receive due development hereafter. + </p> + <p> + During my sojourn in Switzerland this year, I read through the proofs of + this new edition, and by my reading was confirmed in the conviction that + the book ought not to be suffered to go out of print. The memoir was + written under great pressure, but I am not ashamed of it as it stands. + Glimpses of Faraday's character and gleams of his discoveries are there to + be found which will be of interest to humanity to the end of time. + </p> + <p> + John Tyndall. Hind Head, December, 1893. + </p> + <p> + [Note.—It was, I believe, my husband's intention to substitute this + Preface, written a few days before his death, for all former Prefaces. As, + however, he had not the opportunity of revising the old prefatory pages + himself, they have been allowed to remain just as they stood in the last + edition. + </p> + <p> + Louisa C. Tyndall.] + </p> + <p> + <a name="link2H_PREF2" id="link2H_PREF2"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Preface to the fourth edition. + </h2> + <p> + When consulted a short time ago as to the republication of 'Faraday as a + Discoverer,' it seemed to me that the labours, and points of character, of + so great a worker and so good a man should not be allowed to vanish from + the public eye. I therefore willingly fell in with the proposal of my + Publishers to issue a new edition of the little book. + </p> + <p> + Royal Institution, February, 1884. + </p> + <p> + <a name="link2H_PREF3" id="link2H_PREF3"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Preface to the second edition. + </h2> + <p> + The experimental researches of Faraday are so voluminous, their + descriptions are so detailed, and their wealth of illustration is so + great, as to render it a heavy labour to master them. The multiplication + of proofs, necessary and interesting when the new truths had to be + established, are however less needful now when these truths have become + household words in science. I have therefore tried in the following pages + to compress the body, without injury to the spirit, of these imperishable + investigations, and to present them in a form which should be convenient + and useful to the student of the present day. + </p> + <p> + While I write, the volumes of the Life of Faraday by Dr. Bence Jones have + reached my hands. To them the reader must refer for an account of + Faraday's private relations. A hasty glance at the work shows me that the + reverent devotion of the biographer has turned to admirable account the + materials at his command. + </p> + <p> + The work of Dr. Bence Jones enables me to correct a statement regarding + Wollaston's and Faraday's respective relations to the discovery of + Magnetic Rotation. Wollaston's idea was to make the wire carrying a + current rotate round its own axis: an idea afterwards realised by the + celebrated Ampere. Faraday's discovery was to make the wire carrying the + current revolve round the pole of a magnet and the reverse. + </p> + <p> + John Tyndall. Royal Institution: December, 1869. + </p> + <p> + <a name="link2H_4_0004" id="link2H_4_0004"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + FARADAY AS A DISCOVERER. + </h2> + <p> + <a name="link2HCH0001" id="link2HCH0001"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 1. + </h2> +<pre xml:space="preserve"> + Parentage: introduction to the royal institution: earliest + experiments: first royal society paper: marriage. +</pre> + <p> + It has been thought desirable to give you and the world some image of + MICHAEL FARADAY, as a scientific investigator and discoverer. The attempt + to respond to this desire has been to me a labour of difficulty, if also a + labour of love. For however well acquainted I may be with the researches + and discoveries of that great master—however numerous the + illustrations which occur to me of the loftiness of Faraday's character + and the beauty of his life—still to grasp him and his researches as + a whole; to seize upon the ideas which guided him, and connected them; to + gain entrance into that strong and active brain, and read from it the + riddle of the world—this is a work not easy of performance, and all + but impossible amid the distraction of duties of another kind. That I + should at one period or another speak to you regarding Faraday and his + work is natural, if not inevitable; but I did not expect to be called upon + to speak so soon. Still the bare suggestion that this is the fit and + proper time for speech sent me immediately to my task: from it I have + returned with such results as I could gather, and also with the wish that + those results were more worthy than they are of the greatness of my theme. + </p> + <p> + It is not my intention to lay before you a life of Faraday in the ordinary + acceptation of the term. The duty I have to perform is to give you some + notion of what he has done in the world; dwelling incidentally on the + spirit in which his work was executed, and introducing such personal + traits as may be necessary to the completion of your picture of the + philosopher, though by no means adequate to give you a complete idea of + the man. + </p> + <p> + The newspapers have already informed you that Michael Faraday was born at + Newington Butts, on September 22, 1791, and that he died at Hampton Court, + on August 25, 1867. Believing, as I do, in the general truth of the + doctrine of hereditary transmission—sharing the opinion of Mr. + Carlyle, that 'a really able man never proceeded from entirely stupid + parents'—I once used the privilege of my intimacy with Mr. Faraday + to ask him whether his parents showed any signs of unusual ability. He + could remember none. His father, I believe, was a great sufferer during + the latter years of his life, and this might have masked whatever + intellectual power he possessed. When thirteen years old, that is to say + in 1804, Faraday was apprenticed to a bookseller and bookbinder in + Blandford Street, Manchester Square: here he spent eight years of his + life, after which he worked as a journeyman elsewhere. + </p> + <p> + You have also heard the account of Faraday's first contact with the Royal + Institution; that he was introduced by one of the members to Sir Humphry + Davy's last lectures, that he took notes of those lectures; wrote them + fairly out, and sent them to Davy, entreating him at the same time to + enable him to quit trade, which he detested, and to pursue science, which + he loved. Davy was helpful to the young man, and this should never be + forgotten: he at once wrote to Faraday, and afterwards, when an + opportunity occurred, made him his assistant. (1) Mr. Gassiot has lately + favoured me with the following reminiscence of this time:— + </p> + <p> + 'Clapham Common, Surrey, + </p> + <p> + 'November 28, 1867. + </p> + <p> + 'My Dear Tyndall,—Sir H. Davy was accustomed to call on the late Mr. + Pepys, in the Poultry, on his way to the London Institution, of which + Pepys was one of the original managers; the latter told me that on one + occasion Sir H. Davy, showing him a letter, said: "Pepys, what am I to do, + here is a letter from a young man named Faraday; he has been attending my + lectures, and wants me to give him employment at the Royal Institution—what + can I do?" "Do?" replied Pepys, "put him to wash bottles; if he is good + for anything he will do it directly, if he refuses he is good for + nothing." "No, no," replied Davy; "we must try him with something better + than that." The result was, that Davy engaged him to assist in the + Laboratory at weekly wages. + </p> + <p> + 'Davy held the joint office of Professor of Chemistry and Director of the + Laboratory; he ultimately gave up the former to the late Professor Brande, + but he insisted that Faraday should be appointed Director of the + Laboratory, and, as Faraday told me, this enabled him on subsequent + occasions to hold a definite position in the Institution, in which he was + always supported by Davy. I believe he held that office to the last. + </p> + <p> + 'Believe me, my dear Tyndall, yours truly, + </p> + <p> + 'J. P. Gassiot. + </p> + <p> + 'Dr. Tyndall.' + </p> + <p> + From a letter written by Faraday himself soon after his appointment as + Davy's assistant, I extract the following account of his introduction to + the Royal Institution:— + </p> + <p> + 'London, Sept. 13, 1813. + </p> + <p> + 'As for myself, I am absent (from home) nearly day and night, except + occasional calls, and it is likely shall shortly be absent entirely, but + this (having nothing more to say, and at the request of my mother) I will + explain to you. I was formerly a bookseller and binder, but am now turned + philosopher, (2) which happened thus:—Whilst an apprentice, I, for + amusement, learnt a little chemistry and other parts of philosophy, and + felt an eager desire to proceed in that way further. After being a + journeyman for six months, under a disagreeable master, I gave up my + business, and through the interest of a Sir H. Davy, filled the situation + of chemical assistant to the Royal Institution of Great Britain, in which + office I now remain; and where I am constantly employed in observing the + works of nature, and tracing the manner in which she directs the order and + arrangement of the world. I have lately had proposals made to me by Sir + Humphry Davy to accompany him in his travels through Europe and Asia, as + philosophical assistant. If I go at all I expect it will be in October + next—about the end; and my absence from home will perhaps be as long + as three years. But as yet all is uncertain.' + </p> + <p> + This account is supplemented by the following letter, written by Faraday + to his friend De la Rive, (3) on the occasion of the death of Mrs. Marcet. + The letter is dated September 2, 1858:— + </p> + <p> + 'My Dear Friend,—Your subject interested me deeply every way; for + Mrs. Marcet was a good friend to me, as she must have been to many of the + human race. I entered the shop of a bookseller and bookbinder at the age + of thirteen, in the year 1804, remained there eight years, and during the + chief part of my time bound books. Now it was in those books, in the hours + after work, that I found the beginning of my philosophy. + </p> + <p> + There were two that especially helped me, the "Encyclopaedia Britannica," + from which I gained my first notions of electricity, and Mrs. Marcet's + "Conversation on Chemistry," which gave me my foundation in that science. + </p> + <p> + 'Do not suppose that I was a very deep thinker, or was marked as a + precocious person. I was a very lively imaginative person, and could + believe in the "Arabian Nights" as easily as in the "Encyclopaedia." But + facts were important to me, and saved me. I could trust a fact, and always + cross-examined an assertion. So when I questioned Mrs. Marcet's book by + such little experiments as I could find means to perform, and found it + true to the facts as I could understand them, I felt that I had got hold + of an anchor in chemical knowledge, and clung fast to it. Thence my deep + veneration for Mrs. Marcet—first as one who had conferred great + personal good and pleasure on me; and then as one able to convey the truth + and principle of those boundless fields of knowledge which concern natural + things to the young, untaught, and inquiring mind. + </p> + <p> + 'You may imagine my delight when I came to know Mrs. Marcet personally; + how often I cast my thoughts backward, delighting to connect the past and + the present; how often, when sending a paper to her as a thank-offering, I + thought of my first instructress, and such like thoughts will remain with + me. + </p> + <p> + 'I have some such thoughts even as regards your own father; who was, I may + say, the first who personally at Geneva, and afterwards by correspondence, + encouraged, and by that sustained me.' + </p> + <p> + Twelve or thirteen years ago Mr. Faraday and myself quitted the + Institution one evening together, to pay a visit to our friend Grove in + Baker Street. He took my arm at the door, and, pressing it to his side in + his warm genial way, said, 'Come, Tyndall, I will now show you something + that will interest you.' We walked northwards, passed the house of Mr. + Babbage, which drew forth a reference to the famous evening parties once + assembled there. We reached Blandford Street, and after a little looking + about he paused before a stationer's shop, and then went in. On entering + the shop, his usual animation seemed doubled; he looked rapidly at + everything it contained. To the left on entering was a door, through which + he looked down into a little room, with a window in front facing Blandford + Street. Drawing me towards him, he said eagerly, 'Look there, Tyndall, + that was my working-place. I bound books in that little nook.' A + respectable-looking woman stood behind the counter: his conversation with + me was too low to be heard by her, and he now turned to the counter to buy + some cards as an excuse for our being there. He asked the woman her name—her + predecessor's name—his predecessor's name. 'That won't do,' he said, + with good-humoured impatience; 'who was his predecessor?' 'Mr. Riebau,' + she replied, and immediately added, as if suddenly recollecting herself, + 'He, sir, was the master of Sir Charles Faraday.' 'Nonsense!' he + responded, 'there is no such person.' Great was her delight when I told + her the name of her visitor; but she assured me that as soon as she saw + him running about the shop, she felt-though she did not know why—that + it must be 'Sir Charles Faraday.' + </p> + <p> + Faraday did, as you know, accompany Davy to Rome: he was re-engaged by the + managers of the Royal Institution on May 15, 1815. Here he made rapid + progress in chemistry, and after a time was entrusted with easy analyses + by Davy. In those days the Royal Institution published 'The Quarterly + Journal of Science,' the precursor of our own 'Proceedings.' Faraday's + first contribution to science appeared in that journal in 1816. It was an + analysis of some caustic lime from Tuscany, which had been sent to Davy by + the Duchess of Montrose. Between this period and 1818 various notes and + short papers were published by Faraday. In 1818 he experimented upon + 'Sounding Flames.' Professor Auguste De la Rive had investigated those + sounding flames, and had applied to them an explanation which completely + accounted for a class of sounds discovered by himself, but did not account + for those known to his predecessors. By a few simple and conclusive + experiments, Faraday proved the explanation insufficient. It is an epoch + in the life of a young man when he finds himself correcting a person of + eminence, and in Faraday's case, where its effect was to develop a modest + self-trust, such an event could not fail to act profitably. + </p> + <p> + From time to time between 1818 and 1820 Faraday published scientific notes + and notices of minor weight. At this time he was acquiring, not producing; + working hard for his master and storing and strengthening his own mind. He + assisted Mr. Brande in his lectures, and so quietly, skilfully, and + modestly was his work done, that Mr. Brande's vocation at the time was + pronounced 'lecturing on velvet.' In 1820 Faraday published a chemical + paper 'on two new compounds of chlorine and carbon, and on a new compound + of iodine, carbon, and hydrogen.' This paper was read before the Royal + Society on December 21, 1820, and it was the first of his that was + honoured with a place in the 'Philosophical Transactions.' + </p> + <p> + On June 12, 1821, he married, and obtained leave to bring his young wife + into his rooms at the Royal Institution. There for forty-six years they + lived together, occupying the suite of apartments which had been + previously in the successive occupancy of Young, Davy, and Brande. At the + time of her marriage Mrs. Faraday was twenty-one years of age, he being + nearly thirty. Regarding this marriage I will at present limit myself to + quoting an entry written in Faraday's own hand in his book of diplomas, + which caught my eye while in his company some years ago. It ran thus:— + </p> + <p> + '25th January, 1847. 'Amongst these records and events, I here insert the + date of one which, as a source of honour and happiness, far exceeds all + the rest. We were married on June 12, 1821. + </p> + <p> + 'M. Faraday.' + </p> + <p> + Then follows the copy of the minutes, dated May 21, 1821, which gave him + additional rooms, and thus enabled him to bring his wife to the Royal + Institution. A feature of Faraday's character which I have often noticed + makes itself apparent in this entry. In his relations to his wife he added + chivalry to affection. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 1 + </h2> +<pre xml:space="preserve"> + (1) Here is Davy's recommendation of Faraday, presented to + the managers of the Royal Institution, at a meeting on the + 18th of March, 1813, Charles Hatchett, Esq., in the chair:— + + '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. As far as Sir H. Davy has been able to + observe or ascertain, he appears well fitted for the + situation. His habits seem good; his disposition active and + cheerful, and his manner intelligent. He is willing to + engage himself on the same terms as 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.' + + (2) Faraday loved this word and employed it to the last; he + had an intense dislike to the modern term physicist. + + (3) To whom I am indebted for a copy of the original letter. +</pre> + <p> + <a name="link2HCH0002" id="link2HCH0002"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 2. + </h2> +<pre xml:space="preserve"> + Early researches: magnetic rotations: liquefaction of gases: + heavy glass: Charles Anderson: contributions to physics. +</pre> + <p> + Oersted, in 1820, discovered the action of a voltaic current on a magnetic + needle; and immediately afterwards the splendid intellect of Ampere + succeeded in showing that every magnetic phenomenon then known might be + reduced to the mutual action of electric currents. The subject occupied + all men's thoughts: and in this country Dr. Wollaston sought to convert + the deflection of the needle by the current into a permanent rotation of + the needle round the current. He also hoped to produce the reciprocal + effect of causing a current to rotate round a magnet. In the early part of + 1821, Wollaston attempted to realise this idea in the presence of Sir + Humphry Davy in the laboratory of the Royal Institution. (1) This was well + calculated to attract Faraday's attention to the subject. He read much + about it; and in the months of July, August, and September he wrote a + 'history of the progress of electro-magnetism,' which he published in + Thomson's 'Annals of Philosophy.' Soon afterwards he took up the subject + of 'Magnetic Rotations,' and on the morning of Christmas-day, 1821, he + called his wife to witness, for the first time, the revolution of a + magnetic needle round an electric current. Incidental to the 'historic + sketch,' he repeated almost all the experiments there referred to; and + these, added to his own subsequent work, made him practical master of all + that was then known regarding the voltaic current. In 1821, he also + touched upon a subject which subsequently received his closer attention—the + vaporization of mercury at common temperatures; and immediately afterwards + conducted, in company with Mr. Stodart, experiments on the alloys of + steel. He was accustomed in after years to present to his friends razors + formed from one of the alloys then discovered. + </p> + <p> + During Faraday's hours of liberty from other duties, he took up subjects + of inquiry for himself; and in the spring of 1823, thus self-prompted, he + began the examination of a substance which had long been regarded as the + chemical element chlorine, in a solid form, but which Sir Humphry Davy, in + 1810, had proved to be a hydrate of chlorine, that is, a compound of + chlorine and water. Faraday first analysed this hydrate, and wrote out an + account of its composition. This account was looked over by Davy, who + suggested the heating of the hydrate under pressure in a sealed glass + tube. This was done. The hydrate fused at a blood-heat, the tube became + filled with a yellow atmosphere, and was afterwards found to contain two + liquid substances. Dr. Paris happened to enter the laboratory while + Faraday was at work. Seeing the oily liquid in his tube, he rallied the + young chemist for his carelessness in employing soiled vessels. On filing + off the end of the tube, its contents exploded and the oily matter + vanished. Early next morning, Dr. Paris received the following note:— + </p> + <p> + 'Dear Sir,—The oil you noticed yesterday turns out to be liquid + chlorine. + </p> + <p> + 'Yours faithfully, + </p> + <p> + 'M. Faraday.' (2) + </p> + <p> + The gas had been liquefied by its own pressure. Faraday then tried + compression with a syringe, and succeeded thus in liquefying the gas. + </p> + <p> + To the published account of this experiment Davy added the following note:—'In + desiring Mr. Faraday to expose the hydrate of chlorine in a closed glass + tube, it occurred to me that one of three things would happen: that + decomposition of water would occur;... or that the chlorine would separate + in a fluid state.' Davy, moreover, immediately applied the method of + self-compressing atmosphere to the liquefaction of muriatic gas. Faraday + continued the experiments, and succeeded in reducing a number of gases + till then deemed permanent to the liquid condition. In 1844 he returned to + the subject, and considerably expanded its limits. These important + investigations established the fact that gases are but the vapours of + liquids possessing a very low boiling-point, and gave a sure basis to our + views of molecular aggregation. The account of the first investigation was + read before the Royal Society on April 10, 1823, and was published, in + Faraday's name, in the 'Philosophical Transactions.' The second memoir was + sent to the Royal Society on December 19, 1844. I may add that while he + was conducting his first experiments on the liquefaction of gases, + thirteen pieces of glass were on one occasion driven by an explosion into + Faraday's eye. + </p> + <p> + Some small notices and papers, including the observation that glass + readily changes colour in sunlight, follow here. In 1825 and 1826 Faraday + published papers in the 'Philosophical Transactions' on 'new compounds of + carbon and hydrogen,' and on 'sulphonaphthalic acid.' In the former of + these papers he announced the discovery of Benzol, which, in the hands of + modern chemists, has become the foundation of our splendid aniline dyes. + But he swerved incessantly from chemistry into physics; and in 1826 we + find him engaged in investigating the limits of vaporization, and showing, + by exceedingly strong and apparently conclusive arguments, that even in + the case of mercury such a limit exists; much more he conceived it to be + certain that our atmosphere does not contain the vapour of the fixed + constituents of the earth's crust. This question, I may say, is likely to + remain an open one. Dr. Rankine, for example, has lately drawn attention + to the odour of certain metals; whence comes this odour, if it be not from + the vapour of the metal? + </p> + <p> + In 1825 Faraday became a member of a committee, to which Sir John Herschel + and Mr. Dollond also belonged, appointed by the Royal Society to examine, + and if possible improve, the manufacture of glass for optical purposes. + Their experiments continued till 1829, when the account of them + constituted the subject of a 'Bakerian Lecture.' This lectureship, founded + in 1774 by Henry Baker, Esq., of the Strand, London, provides that every + year a lecture shall be given before the Royal Society, the sum of four + pounds being paid to the lecturer. The Bakerian Lecture, however, has long + since passed from the region of pay to that of honour, papers of mark only + being chosen for it by the council of the Society. Faraday's first + Bakerian Lecture, 'On the Manufacture of Glass for Optical Purposes,' was + delivered at the close of 1829. It is a most elaborate and conscientious + description of processes, precautions, and results: the details were so + exact and so minute, and the paper consequently so long, that three + successive sittings of the Royal Society were taken up by the delivery of + the lecture. (3) This glass did not turn out to be of important practical + use, but it happened afterwards to be the foundation of two of Faraday's + greatest discoveries. (4) + </p> + <p> + The experiments here referred to were commenced at the Falcon Glass Works, + on the premises of Messrs. Green and Pellatt, but Faraday could not + conveniently attend to them there. In 1827, therefore, a furnace was + erected in the yard of the Royal Institution; and it was at this time, and + with a view of assisting him at the furnace, that Faraday engaged Sergeant + Anderson, of the Royal Artillery, the respectable, truthful, and + altogether trustworthy man whose appearance here is so fresh in our + memories. Anderson continued to be the reverential helper of Faraday and + the faithful servant of this Institution for nearly forty years. (5) + </p> + <p> + In 1831 Faraday published a paper, 'On a peculiar class of Optical + Deceptions,' to which I believe the beautiful optical toy called the + Chromatrope owes its origin. In the same year he published a paper on + Vibrating Surfaces, in which he solved an acoustical problem which, though + of extreme simplicity when solved, appears to have baffled many eminent + men. The problem was to account for the fact that light bodies, such as + the seed of lycopodium, collected at the vibrating parts of sounding + plates, while sand ran to the nodal lines. Faraday showed that the light + bodies were entangled in the little whirlwinds formed in the air over the + places of vibration, and through which the heavier sand was readily + projected. Faraday's resources as an experimentalist were so wonderful, + and his delight in experiment was so great, that he sometimes almost ran + into excess in this direction. I have heard him say that this paper on + vibrating surfaces was too heavily laden with experiments. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT_"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 2 + </h2> +<pre xml:space="preserve"> + (1) The reader's attention is directed to the concluding + paragraph of the 'Preface to the Second Edition written in + December, 1869. Also to the Life of Faraday by Dr. Bence + Jones, vol. i. p. 338 et seq. + + (2) Paris: Life of Davy, p. 391. + + (3) Viz., November 19, December 3 and 10. + + (4) I make the following extract from a letter from Sir John + Herschel, written to me from Collingwood, on the 3rd of + November, 1867:—'I will take this opportunity to mention + that I believe myself to have originated the suggestion of + the employment of borate of lead for optical purposes. It + was somewhere in the year 1822, as well as I can recollect, + that I mentioned it to Sir James (then Mr.) South; and, in + consequence, the trial was made in his laboratory in + Blackman Street, by precipitating and working a large + quantity of borate of lead, and fusing it under a muffle in + a porcelain evaporating dish. A very limpid (though + slightly yellow) glass resulted, the refractive index 1.866! + (which you will find set down in my table of refractive + indices in my article "Light," Encyclopaedia Metropolitana). + It was, however, too soft for optical use as an object- + glass. This Faraday overcame, at least to a considerable + degree, by the introduction of silica.' + + (5) Regarding Anderson, Faraday writes thus in 1845:—'I + cannot resist the occasion that is thus offered to me of + mentioning the name of Mr. Anderson, who came to me as an + assistant in the glass experiments, and has remained ever + since in the laboratory of the Royal Institution. He + assisted me in all the researches into which I have entered + since that time; and to his care, steadiness, exactitude, + and faithfulness in the performance of all that has been + committed to his charge, I am much indebted.—M. F.' (Exp. + Researches, vol. iii. p. 3, footnote.) +</pre> + <p> + <a name="link2HCH0003" id="link2HCH0003"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 3. + </h2> +<pre xml:space="preserve"> + Discovery of Magneto-electricity: Explanation of Argo's + magnetism of rotation: Terrestrial magneto-electric + induction: The extra current. +</pre> + <p> + The work thus referred to, though sufficient of itself to secure no mean + scientific reputation, forms but the vestibule of Faraday's achievements. + He had been engaged within these walls for eighteen years. During part of + the time he had drunk in knowledge from Davy, and during the remainder he + continually exercised his capacity for independent inquiry. In 1831 we + have him at the climax of his intellectual strength, forty years of age, + stored with knowledge and full of original power. Through reading, + lecturing, and experimenting, he had become thoroughly familiar with + electrical science: he saw where light was needed and expansion possible. + The phenomena of ordinary electric induction belonged, as it were, to the + alphabet of his knowledge: he knew that under ordinary circumstances the + presence of an electrified body was sufficient to excite, by induction, an + unelectrified body. He knew that the wire which carried an electric + current was an electrified body, and still that all attempts had failed to + make it excite in other wires a state similar to its own. + </p> + <p> + What was the reason of this failure? Faraday never could work from the + experiments of others, however clearly described. He knew well that from + every experiment issues a kind of radiation, luminous in different degrees + to different minds, and he hardly trusted himself to reason upon an + experiment that he had not seen. In the autumn of 1831 he began to repeat + the experiments with electric currents, which, up to that time, had + produced no positive result. And here, for the sake of younger inquirers, + if not for the sake of us all, it is worth while to dwell for a moment on + a power which Faraday possessed in an extraordinary degree. He united vast + strength with perfect flexibility. His momentum was that of a river, which + combines weight and directness with the ability to yield to the flexures + of its bed. The intentness of his vision in any direction did not + apparently diminish his power of perception in other directions; and when + he attacked a subject, expecting results he had the faculty of keeping his + mind alert, so that results different from those which he expected should + not escape him through preoccupation. + </p> + <p> + He began his experiments 'on the induction of electric currents' by + composing a helix of two insulated wires which were wound side by side + round the same wooden cylinder. One of these wires he connected with a + voltaic battery of ten cells, and the other with a sensitive galvanometer. + When connection with the battery was made, and while the current flowed, + no effect whatever was observed at the galvanometer. But he never accepted + an experimental result, until he had applied to it the utmost power at his + command. He raised his battery from 10 cells to 120 cells, but without + avail. The current flowed calmly through the battery wire without + producing, during its flow, any sensible result upon the galvanometer. + </p> + <p> + 'During its flow,' and this was the time when an effect was expected—but + here Faraday's power of lateral vision, separating, as it were, from the + line of expectation, came into play—he noticed that a feeble + movement of the needle always occurred at the moment when he made contact + with the battery; that the needle would afterwards return to its former + position and remain quietly there unaffected by the flowing current. At + the moment, however, when the circuit was interrupted the needle again + moved, and in a direction opposed to that observed on the completion of + the circuit. + </p> + <p> + This result, and others of a similar kind, led him to the conclusion 'that + the battery current through the one wire did in reality induce a similar + current through the other; but that it continued for an instant only, and + partook more of the nature of the electric wave from a common Leyden jar + than of the current from a voltaic battery.' The momentary currents thus + generated were called induced currents, while the current which generated + them was called the inducing current. It was immediately proved that the + current generated at making the circuit was always opposed in direction to + its generator, while that developed on the rupture of the circuit + coincided in direction with the inducing current. It appeared as if the + current on its first rush through the primary wire sought a purchase in + the secondary one, and, by a kind of kick, impelled backward through the + latter an electric wave, which subsided as soon as the primary current was + fully established. + </p> + <p> + Faraday, for a time, believed that the secondary wire, though quiescent + when the primary current had been once established, was not in its natural + condition, its return to that condition being declared by the current + observed at breaking the circuit. He called this hypothetical state of the + wire the electro-tonic state: he afterwards abandoned this hypothesis, but + seemed to return to it in later life. The term electro-tonic is also + preserved by Professor Du Bois Reymond to express a certain electric + condition of the nerves, and Professor Clerk Maxwell has ably defined and + illustrated the hypothesis in the Tenth Volume of the 'Transactions of the + Cambridge Philosophical Society.' + </p> + <p> + The mere approach of a wire forming a closed curve to a second wire + through which a voltaic current flowed was then shown by Faraday to be + sufficient to arouse in the neutral wire an induced current, opposed in + direction to the inducing current; the withdrawal of the wire also + generated a current having the same direction as the inducing current; + those currents existed only during the time of approach or withdrawal, and + when neither the primary nor the secondary wire was in motion, no matter + how close their proximity might be, no induced current was generated. + </p> + <p> + Faraday has been called a purely inductive philosopher. A great deal of + nonsense is, I fear, uttered in this land of England about induction and + deduction. Some profess to befriend the one, some the other, while the + real vocation of an investigator, like Faraday, consists in the incessant + marriage of both. He was at this time full of the theory of Ampere, and it + cannot be doubted that numbers of his experiments were executed merely to + test his deductions from that theory. Starting from the discovery of + Oersted, the illustrious French philosopher had shown that all the + phenomena of magnetism then known might be reduced to the mutual + attractions and repulsions of electric currents. Magnetism had been + produced from electricity, and Faraday, who all his life long entertained + a strong belief in such reciprocal actions, now attempted to effect the + evolution of electricity from magnetism. Round a welded iron ring he + placed two distinct coils of covered wire, causing the coils to occupy + opposite halves of the ring. Connecting the ends of one of the coils with + a galvanometer, he found that the moment the ring was magnetised, by + sending a current through the other coil, the galvanometer needle whirled + round four or five times in succession. The action, as before, was that of + a pulse, which vanished immediately. On interrupting the circuit, a whirl + of the needle in the opposite direction occurred. It was only during the + time of magnetization or demagnetization that these effects were produced. + The induced currents declared a change of condition only, and they + vanished the moment the act of magnetization or demagnetization was + complete. + </p> + <p> + The effects obtained with the welded ring were also obtained with straight + bars of iron. Whether the bars were magnetised by the electric current, or + were excited by the contact of permanent steel magnets, induced currents + were always generated during the rise, and during the subsidence of the + magnetism. The use of iron was then abandoned, and the same effects were + obtained by merely thrusting a permanent steel magnet into a coil of wire. + A rush of electricity through the coil accompanied the insertion of the + magnet; an equal rush in the opposite direction accompanied its + withdrawal. The precision with which Faraday describes these results, and + the completeness with which he defines the boundaries of his facts, are + wonderful. The magnet, for example, must not be passed quite through the + coil, but only half through; for if passed wholly through, the needle is + stopped as by a blow, and then he shows how this blow results from a + reversal of the electric wave in the helix. He next operated with the + powerful permanent magnet of the Royal Society, and obtained with it, in + an exalted degree, all the foregoing phenomena. + </p> + <p> + And now he turned the light of these discoveries upon the darkest physical + phenomenon of that day. Arago had discovered, in 1824, that a disk of + non-magnetic metal had the power of bringing a vibrating magnetic needle + suspended over it rapidly to rest; and that on causing the disk to rotate + the magnetic needle rotated along with it. When both were quiescent, there + was not the slightest measurable attraction or repulsion exerted between + the needle and the disk; still when in motion the disk was competent to + drag after it, not only a light needle, but a heavy magnet. The question + had been probed and investigated with admirable skill both by Arago and + Ampere, and Poisson had published a theoretic memoir on the subject; but + no cause could be assigned for so extraordinary an action. It had also + been examined in this country by two celebrated men, Mr. Babbage and Sir + John Herschel; but it still remained a mystery. Faraday always recommended + the suspension of judgment in cases of doubt. 'I have always admired,' he + says, 'the prudence and philosophical reserve shown by M. Arago in + resisting the temptation to give a theory of the effect he had discovered, + so long as he could not devise one which was perfect in its application, + and in refusing to assent to the imperfect theories of others.' Now, + however, the time for theory had come. Faraday saw mentally the rotating + disk, under the operation of the magnet, flooded with his induced + currents, and from the known laws of interaction between currents and + magnets he hoped to deduce the motion observed by Arago. That hope he + realised, showing by actual experiment that when his disk rotated currents + passed through it, their position and direction being such as must, in + accordance with the established laws of electro-magnetic action, produce + the observed rotation. + </p> + <p> + Introducing the edge of his disk between the poles of the large horseshoe + magnet of the Royal Society, and connecting the axis and the edge of the + disk, each by a wire with a galvanometer, he obtained, when the disk was + turned round, a constant flow of electricity. The direction of the current + was determined by the direction of the motion, the current being reversed + when the rotation was reversed. He now states the law which rules the + production of currents in both disks and wires, and in so doing uses, for + the first time, a phrase which has since become famous. When iron filings + are scattered over a magnet, the particles of iron arrange themselves in + certain determinate lines called magnetic curves. In 1831, Faraday for the + first time called these curves 'lines of magnetic force'; and he showed + that to produce induced currents neither approach to nor withdrawal from a + magnetic source, or centre, or pole, was essential, but that it was only + necessary to cut appropriately the lines of magnetic force. Faraday's + first paper on Magneto-electric Induction, which I have here endeavoured + to condense, was read before the Royal Society on the 24th of November, + 1831. + </p> + <p> + On January 12, 1832, he communicated to the Royal Society a second paper + on Terrestrial Magneto-electric Induction, which was chosen as the + Bakerian Lecture for the year. He placed a bar of iron in a coil of wire, + and lifting the bar into the direction of the dipping needle, he excited + by this action a current in the coil. On reversing the bar, a current in + the opposite direction rushed through the wire. The same effect was + produced when, on holding the helix in the line of dip, a bar of iron was + thrust into it. Here, however, the earth acted on the coil through the + intermediation of the bar of iron. He abandoned the bar and simply set a + copper plate spinning in a horizontal plane; he knew that the earth's + lines of magnetic force then crossed the plate at an angle of about + 70degrees. When the plate spun round, the lines of force were intersected + and induced currents generated, which produced their proper effect when + carried from the plate to the galvanometer. 'When the plate was in the + magnetic meridian, or in any other plane coinciding with the magnetic dip, + then its rotation produced no effect upon the galvanometer.' + </p> + <p> + At the suggestion of a mind fruitful in suggestions of a profound and + philosophic character—I mean that of Sir John Herschel—Mr. + Barlow, of Woolwich, had experimented with a rotating iron shell. Mr. + Christie had also performed an elaborate series of experiments on a + rotating iron disk. Both of them had found that when in rotation the body + exercised a peculiar action upon the magnetic needle, deflecting it in a + manner which was not observed during quiescence; but neither of them was + aware at the time of the agent which produced this extraordinary + deflection. They ascribed it to some change in the magnetism of the iron + shell and disk. + </p> + <p> + But Faraday at once saw that his induced currents must come into play + here, and he immediately obtained them from an iron disk. With a hollow + brass ball, moreover, he produced the effects obtained by Mr. Barlow. Iron + was in no way necessary: the only condition of success was that the + rotating body should be of a character to admit of the formation of + currents in its substance: it must, in other words, be a conductor of + electricity. The higher the conducting power the more copious were the + currents. He now passes from his little brass globe to the globe of the + earth. He plays like a magician with the earth's magnetism. He sees the + invisible lines along which its magnetic action is exerted, and sweeping + his wand across these lines evokes this new power. Placing a simple loop + of wire round a magnetic needle he bends its upper portion to the west: + the north pole of the needle immediately swerves to the east: he bends his + loop to the east, and the north pole moves to the west. Suspending a + common bar magnet in a vertical position, he causes it to spin round its + own axis. Its pole being connected with one end of a galvanometer wire, + and its equator with the other end, electricity rushes round the + galvanometer from the rotating magnet. He remarks upon the 'singular + independence' of the magnetism and the body of the magnet which carries + it. The steel behaves as if it were isolated from its own magnetism. + </p> + <p> + And then his thoughts suddenly widen, and he asks himself whether the + rotating earth does not generate induced currents as it turns round its + axis from west to east. In his experiment with the twirling magnet the + galvanometer wire remained at rest; one portion of the circuit was in + motion relatively to another portion. But in the case of the twirling + planet the galvanometer wire would necessarily be carried along with the + earth; there would be no relative motion. What must be the consequence? + Take the case of a telegraph wire with its two terminal plates dipped into + the earth, and suppose the wire to lie in the magnetic meridian. The + ground underneath the wire is influenced like the wire itself by the + earth's rotation; if a current from south to north be generated in the + wire, a similar current from south to north would be generated in the + earth under the wire; these currents would run against the same terminal + plate, and thus neutralise each other. + </p> + <p> + This inference appears inevitable, but his profound vision perceived its + possible invalidity. He saw that it was at least possible that the + difference of conducting power between the earth and the wire might give + one an advantage over the other, and that thus a residual or differential + current might be obtained. He combined wires of different materials, and + caused them to act in opposition to each other, but found the combination + ineffectual. The more copious flow in the better conductor was exactly + counterbalanced by the resistance of the worse. Still, though experiment + was thus emphatic, he would clear his mind of all discomfort by operating + on the earth itself. He went to the round lake near Kensington Palace, and + stretched 480 feet of copper wire, north and south, over the lake, causing + plates soldered to the wire at its ends to dip into the water. The copper + wire was severed at the middle, and the severed ends connected with a + galvanometer. No effect whatever was observed. But though quiescent water + gave no effect, moving water might. He therefore worked at London Bridge + for three days during the ebb and flow of the tide, but without any + satisfactory result. Still he urges, 'Theoretically it seems a necessary + consequence, that where water is flowing there electric currents should be + formed. If a line be imagined passing from Dover to Calais through the + sea, and returning through the land, beneath the water, to Dover, it + traces out a circuit of conducting matter one part of which, when the + water moves up or down the channel, is cutting the magnetic curves of the + earth, whilst the other is relatively at rest.... There is every reason to + believe that currents do run in the general direction of the circuit + described, either one way or the other, according as the passage of the + waters is up or down the channel.' This was written before the submarine + cable was thought of, and he once informed me that actual observation upon + that cable had been found to be in accordance with his theoretic + deduction. (1) + </p> + <p> + Three years subsequent to the publication of these researches—that + is to say, on January 29, 1835—Faraday read before the Royal Society + a paper 'On the influence by induction of an electric current upon + itself.' A shock and spark of a peculiar character had been observed by a + young man named William Jenkin, who must have been a youth of some + scientific promise, but who, as Faraday once informed me, was dissuaded by + his own father from having anything to do with science. The investigation + of the fact noticed by Mr. Jenkin led Faraday to the discovery of the + extra current, or the current induced in the primary wire itself at the + moments of making and breaking contact, the phenomena of which he + described and illustrated in the beautiful and exhaustive paper referred + to. + </p> + <p> + Seven-and-thirty years have passed since the discovery of + magneto-electricity; but, if we except the extra current, until quite + recently nothing of moment was added to the subject. Faraday entertained + the opinion that the discoverer of a great law or principle had a right to + the 'spoils'—this was his term—arising from its illustration; + and guided by the principle he had discovered, his wonderful mind, aided + by his wonderful ten fingers, overran in a single autumn this vast domain, + and hardly left behind him the shred of a fact to be gathered by his + successors. + </p> + <p> + And here the question may arise in some minds, What is the use of it all? + The answer is, that if man's intellectual nature thirsts for knowledge, + then knowledge is useful because it satisfies this thirst. If you demand + practical ends, you must, I think, expand your definition of the term + practical, and make it include all that elevates and enlightens the + intellect, as well as all that ministers to the bodily health and comfort + of men. Still, if needed, an answer of another kind might be given to the + question 'What is its use?' As far as electricity has been applied for + medical purposes, it has been almost exclusively Faraday's electricity. + You have noticed those lines of wire which cross the streets of London. It + is Faraday's currents that speed from place to place through these wires. + Approaching the point of Dungeness, the mariner sees an unusually + brilliant light, and from the noble phares of La Heve the same light + flashes across the sea. These are Faraday's sparks exalted by suitable + machinery to sunlike splendour. At the present moment the Board of Trade + and the Brethren of the Trinity House, as well as the Commissioners of + Northern Lights, are contemplating the introduction of the + Magneto-electric Light at numerous points upon our coasts; and future + generations will be able to refer to those guiding stars in answer to the + question. What has been the practical use of the labours of Faraday? But I + would again emphatically say, that his work needs no such justification, + and that if he had allowed his vision to be disturbed by considerations + regarding the practical use of his discoveries, those discoveries would + never have been made by him. 'I have rather,' he writes in 1831, 'been + desirous of discovering new facts and new relations dependent on + magneto-electric induction, than of exalting the force of those already + obtained; being assured that the latter would find their full development + hereafter.' + </p> + <p> + In 1817, when lecturing before a private society in London on the element + chlorine, Faraday thus expressed himself with reference to this question + of utility. 'Before leaving this subject, I will point out the history of + this substance, as an answer to those who are in the habit of saying to + every new fact. "What is its use?" Dr. Franklin says to such, "What is the + use of an infant?" The answer of the experimentalist is, "Endeavour to + make it useful." When Scheele discovered this substance, it appeared to + have no use; it was in its infancy and useless state, but having grown up + to maturity, witness its powers, and see what endeavours to make it useful + have done.' + </p> + <p> + Footnote to Chapter 3 + </p> +<pre xml:space="preserve"> + (1) I am indebted to a friend for the following exquisite + morsel:—'A short time after the publication of Faraday's + first researches in magneto-electricity, he attended the + meeting of the British Association at Oxford, in 1832. On + this occasion he was requested by some of the authorities to + repeat the celebrated experiment of eliciting a spark from a + magnet, employing for this purpose the large magnet in the + Ashmolean Museum. To this he consented, and a large party + assembled to witness the experiments, which, I need not say, + were perfectly successful. Whilst he was repeating them a + dignitary of the University entered the room, and addressing + himself to Professor Daniell, who was standing near Faraday, + inquired what was going on. The Professor explained to him + as popularly as possible this striking result of Faraday's + great discovery. The Dean listened with attention and looked + earnestly at the brilliant spark, but a moment after he + assumed a serious countenance and shook his head; "I am + sorry for it," said he, as he walked away; in the middle of + the room he stopped for a moment and repeated, "I am sorry + for it:" then walking towards the door, when the handle was + in his hand he turned round and said, "Indeed I am sorry for + it; it is putting new arms into the hands of the + incendiary." This occurred a short time after the papers + had been filled with the doings of the hayrick burners. An + erroneous statement of what fell from the Dean's mouth was + printed at the time in one of the Oxford papers. He is there + wrongly stated to have said, "It is putting new arms into + the hands of the infidel."' +</pre> + <p> + <a name="link2HCH0004" id="link2HCH0004"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 4. + </h2> +<pre xml:space="preserve"> + Points of Character. +</pre> + <p> + A point highly illustrative of the character of Faraday now comes into + view. He gave an account of his discovery of Magneto-electricity in a + letter to his friend M. Hachette, of Paris, who communicated the letter to + the Academy of Sciences. The letter was translated and published; and + immediately afterwards two distinguished Italian philosophers took up the + subject, made numerous experiments, and published their results before the + complete memoirs of Faraday had met the public eye. This evidently + irritated him. He reprinted the paper of the learned Italians in the + 'Philosophical Magazine,' accompanied by sharp critical notes from + himself. He also wrote a letter dated Dec. 1, 1832, to Gay Lussac, who was + then one of the editors of the 'Annales de Chimie,' in which he analysed + the results of the Italian philosophers, pointing out their errors, and + defending himself from what he regarded as imputations on his character. + The style of this letter is unexceptionable, for Faraday could not write + otherwise than as a gentleman; but the letter shows that had he willed it + he could have hit hard. We have heard much of Faraday's gentleness and + sweetness and tenderness. It is all true, but it is very incomplete. You + cannot resolve a powerful nature into these elements, and Faraday's + character would have been less admirable than it was had it not embraced + forces and tendencies to which the silky adjectives 'gentle' and 'tender' + would by no means apply. Underneath his sweetness and gentleness was the + heat of a volcano. He was a man of excitable and fiery nature; but through + high self-discipline he had converted the fire into a central glow and + motive power of life, instead of permitting it to waste itself in useless + passion. 'He that is slow to anger,' saith the sage, 'is greater than the + mighty, and he that ruleth his own spirit than he that taketh a city.' + Faraday was not slow to anger, but he completely ruled his own spirit, and + thus, though he took no cities, he captivated all hearts. + </p> + <p> + As already intimated, Faraday had contributed many of his minor papers—including + his first analysis of caustic lime—to the 'Quarterly Journal of + Science.' In 1832, he collected those papers and others together in a + small octavo volume, labelled them, and prefaced them thus:— + </p> + <p> + 'PAPERS, NOTES, NOTICES, &c., &c.,published in octavo, up to 1832. + M. Faraday.' + </p> + <p> + 'Papers of mine, published in octavo, in the "Quarterly Journal of + Science," and elsewhere, since the time that Sir H. Davy encouraged me to + write the analysis of caustic lime. + </p> + <p> + 'Some, I think (at this date), are good; others moderate; and some bad. + But I have put all into the volume, because of the utility they have been + of to me—and none more than the bad—in pointing out to me in + future, or rather, after times, the faults it became me to watch and to + avoid. + </p> + <p> + 'As I never looked over one of my papers a year after it was written + without believing both in philosophy and manner it could have been much + better done, I still hope the collection may be of great use to me. + </p> + <p> + 'M. Faraday. + </p> + <p> + 'Aug. 18, 1832.' + </p> + <p> + 'None more than the bad!' This is a bit of Faraday's innermost nature; and + as I read these words I am almost constrained to retract what I have said + regarding the fire and excitability of his character. But is he not all + the more admirable, through his ability to tone down and subdue that fire + and that excitability, so as to render himself able to write thus as a + little child? I once took the liberty of censuring the conclusion of a + letter of his to the Dean of St. Paul's. He subscribed himself 'humbly + yours,' and I objected to the adverb. 'Well, but, Tyndall,' he said, 'I am + humble; and still it would be a great mistake to think that I am not also + proud.' This duality ran through his character. A democrat in his defiance + of all authority which unfairly limited his freedom of thought, and still + ready to stoop in reverence to all that was really worthy of reverence, in + the customs of the world or the characters of men. + </p> + <p> + And here, as well as elsewhere, may be introduced a letter which bears + upon this question of self-control, written long years subsequent to the + period at which we have now arrived. I had been at Glasgow in 1855, at a + meeting of the British Association. On a certain day, I communicated a + paper to the physical section, which was followed by a brisk discussion. + Men of great distinction took part in it, the late Dr. Whewell among the + number, and it waxed warm on both sides. I was by no means content with + this discussion; and least of all, with my own part in it. This discontent + affected me for some days, during which I wrote to Faraday, giving him no + details, but expressing, in a general way, my dissatisfaction. I give the + following extract from his reply:— + </p> + <p> + 'Sydenham, Oct. 6, 1855. + </p> + <p> + 'My Dear Tyndall,—These great meetings, of which I think very well + altogether, advance science chiefly by bringing scientific men together + and making them to know and be friends with each other; and I am sorry + when that is not the effect in every part of their course. I know nothing + except from what you tell me, for I have not yet looked at the reports of + the proceedings; but let me, as an old man, who ought by this time to have + profited by experience, say that when I was younger I found I often + misinterpreted the intentions of people, and found they did not mean what + at the time I supposed they meant; and, further, that as a general rule, + it was better to be a little dull of apprehension where phrases seemed to + imply pique, and quick in perception when, on the contrary, they seemed to + imply kindly feeling. The real truth never fails ultimately to appear; and + opposing parties, if wrong, are sooner convinced when replied to + forbearingly, than when overwhelmed. All I mean to say is, that it is + better to be blind to the results of partisanship, and quick to see good + will. One has more happiness in oneself in endeavouring to follow the + things that make for peace. You can hardly imagine how often I have been + heated in private when opposed, as I have thought, unjustly and + superciliously, and yet I have striven, and succeeded, I hope, in keeping + down replies of the like kind. And I know I have never lost by it. I would + not say all this to you did I not esteem you as a true philosopher and + friend. (1) + </p> + <p> + 'Yours, very truly, + </p> + <p> + 'M. Faraday.' + </p> + <p> + Footnote to Chapter 4 + </p> +<pre xml:space="preserve"> + (1) Faraday would have been rejoiced to learn that, during + its last meeting at Dundee, the British Association + illustrated in a striking manner the function which he here + describes as its principal one. In my own case, a brotherly + welcome was everywhere manifested. In fact, the differences + of really honourable and sane men are never beyond healing. +</pre> + <p> + <a name="link2HCH0005" id="link2HCH0005"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 5. + </h2> +<pre xml:space="preserve"> + Identity of electricities; first researches on + electro-chemistry. +</pre> + <p> + I have already once used the word 'discomfort' in reference to the + occasional state of Faraday's mind when experimenting. It was to him a + discomfort to reason upon data which admitted of doubt. He hated what he + called 'doubtful knowledge,' and ever tended either to transfer it into + the region of undoubtful knowledge, or of certain and definite ignorance. + Pretence of all kinds, whether in life or in philosophy, was hateful to + him. He wished to know the reality of our nescience as well as of our + science. 'Be one thing or the other,' he seemed to say to an unproved + hypothesis; 'come out as a solid truth, or disappear as a convicted lie.' + After making the great discovery which I have attempted to describe, a + doubt seemed to beset him as regards the identity of electricities. 'Is it + right,' he seemed to ask, 'to call this agency which I have discovered + electricity at all? Are there perfectly conclusive grounds for believing + that the electricity of the machine, the pile, the gymnotus and torpedo, + magneto-electricity and thermo-electricity, are merely different + manifestations of one and the same agent?' To answer this question to his + own satisfaction he formally reviewed the knowledge of that day. He added + to it new experiments of his own, and finally decided in favour of the + 'Identity of Electricities.' His paper upon this subject was read before + the Royal Society on January 10 and 17, 1833. + </p> + <p> + After he had proved to his own satisfaction the identity of electricities, + he tried to compare them quantitatively together. The terms quantity and + intensity, which Faraday constantly used, need a word of explanation here. + He might charge a single Leyden jar by twenty turns of his machine, or he + might charge a battery of ten jars by the same number of turns. The + quantity in both cases would be sensibly the same, but the intensity of + the single jar would be the greatest, for here the electricity would be + less diffused. Faraday first satisfied himself that the needle of his + galvanometer was caused to swing through the same arc by the same quantity + of machine electricity, whether it was condensed in a small battery or + diffused over a large one. Thus the electricity developed by thirty turns + of his machine produced, under very variable conditions of battery + surface, the same deflection. Hence he inferred the possibility of + comparing, as regards quantity, electricities which differ greatly from + each other in intensity. His object now is to compare frictional with + voltaic electricity. Moistening bibulous paper with the iodide of + potassium—a favourite test of his—and subjecting it to the + action of machine electricity, he decomposed the iodide, and formed a + brown spot where the iodine was liberated. Then he immersed two wires, one + of zinc, the other of platinum, each 1/13th of an inch in diameter, to a + depth of 5/8ths of an inch in acidulated water during eight beats of his + watch, or 3/20ths of a second; and found that the needle of his + galvanometer swung through the same arc, and coloured his moistened paper + to the same extent, as thirty turns of his large electrical machine. + Twenty-eight turns of the machine produced an effect distinctly less than + that produced by his two wires. Now, the quantity of water decomposed by + the wires in this experiment totally eluded observation; it was + immeasurably small; and still that amount of decomposition involved the + development of a quantity of electric force which, if applied in a proper + form, would kill a rat, and no man would like to bear it. + </p> + <p> + In his subsequent researches 'On the absolute Quantity of Electricity + associated with the Particles or Atoms of matter,' he endeavours to give + an idea of the amount of electrical force involved in the decomposition of + a single grain of water. He is almost afraid to mention it, for he + estimates it at 800,000 discharges of his large Leyden battery. This, if + concentrated in a single discharge, would be equal to a very great flash + of lightning; while the chemical action of a single grain of water on four + grains of zinc would yield electricity equal in quantity to a powerful + thunderstorm. Thus his mind rises from the minute to the vast, expanding + involuntarily from the smallest laboratory fact till it embraces the + largest and grandest natural phenomena. (1) + </p> + <p> + In reality, however, he is at this time only clearing his way, and he + continues laboriously to clear it for some time afterwards. He is digging + the shaft, guided by that instinct towards the mineral lode which was to + him a rod of divination. 'Er riecht die Wahrheit,' said the lamented + Kohlrausch, an eminent German, once in my hearing:—'He smells the + truth.' His eyes are now steadily fixed on this wonderful voltaic current, + and he must learn more of its mode of transmission. + </p> + <p> + On May 23, 1833, he read a paper before the Royal Society 'On a new Law of + Electric Conduction.' He found that, though the current passed through + water, it did not pass through ice:—why not, since they are one and + the same substance? Some years subsequently he answered this question by + saying that the liquid condition enables the molecule of water to turn + round so as to place itself in the proper line of polarization, while the + rigidity of the solid condition prevents this arrangement. This polar + arrangement must precede decomposition, and decomposition is an + accompaniment of conduction. He then passed on to other substances; to + oxides and chlorides, and iodides, and salts, and sulphurets, and found + them all insulators when solid, and conductors when fused. In all cases, + moreover, except one—and this exception he thought might be apparent + only—he found the passage of the current across the fused compound + to be accompanied by its decomposition. Is then the act of decomposition + essential to the act of conduction in these bodies? Even recently this + question was warmly contested. Faraday was very cautious latterly in + expressing himself upon this subject; but as a matter of fact he held that + an infinitesimal quantity of electricity might pass through a compound + liquid without producing its decomposition. De la Rive, who has been a + great worker on the chemical phenomena of the pile, is very emphatic on + the other side. Experiment, according to him and others, establishes in + the most conclusive manner that no trace of electricity can pass through a + liquid compound without producing its equivalent decomposition. (2) + </p> + <p> + Faraday has now got fairly entangled amid the chemical phenomena of the + pile, and here his previous training under Davy must have been of the most + important service to him. Why, he asks, should decomposition thus take + place?—what force is it that wrenches the locked constituents of + these compounds asunder? On the 20th of June, 1833, he read a paper before + the Royal Society 'On Electro-chemical Decomposition,' in which he seeks + to answer these questions. The notion had been entertained that the poles, + as they are called, of the decomposing cell, or in other words the + surfaces by which the current enters and quits the liquid, exercised + electric attractions upon the constituents of the liquid and tore them + asunder. Faraday combats this notion with extreme vigour. Litmus reveals, + as you know, the action of an acid by turning red, turmeric reveals the + action of an alkali by turning brown. Sulphate of soda, you know, is a + salt compounded of the alkali soda and sulphuric acid. The voltaic current + passing through a solution of this salt so decomposes it, that sulphuric + acid appears at one pole of the decomposing cell and alkali at the other. + Faraday steeped a piece of litmus paper and a piece of turmeric paper in a + solution of sulphate of soda: placing each of them upon a separate plate + of glass, he connected them together by means of a string moistened with + the same solution. He then attached one of them to the positive conductor + of an electric machine, and the other to the gas-pipes of this building. + These he called his 'discharging train.' On turning the machine the + electricity passed from paper to paper through the string, which might be + varied in length from a few inches to seventy feet without changing the + result. The first paper was reddened, declaring the presence of sulphuric + acid; the second was browned, declaring the presence of the alkali soda. + The dissolved salt, therefore, arranged in this fashion, was decomposed by + the machine, exactly as it would have been by the voltaic current. When + instead of using the positive conductor he used the negative, the + positions of the acid and alkali were reversed. Thus he satisfied himself + that chemical decomposition by the machine is obedient to the laws which + rule decomposition by the pile. + </p> + <p> + And now he gradually abolishes those so-called poles, to the attraction of + which electric decomposition had been ascribed. He connected a piece of + turmeric paper moistened with the sulphate of soda with the positive + conductor of his machine; then he placed a metallic point in connection + with his discharging train opposite the moist paper, so that the + electricity should discharge through the air towards the point. The + turning of the machine caused the corners of the piece of turmeric paper + opposite to the point to turn brown, thus declaring the presence of + alkali. He changed the turmeric for litmus paper, and placed it, not in + connection with his conductor, but with his discharging train, a metallic + point connected with the conductor being fixed at a couple of inches from + the paper; on turning the machine, acid was liberated at the edges and + corners of the litmus. He then placed a series of pointed pieces of paper, + each separate piece being composed of two halves, one of litmus and the + other of turmeric paper, and all moistened with sulphate of soda, in the + line of the current from the machine. The pieces of paper were separated + from each other by spaces of air. The machine was turned; and it was + always found that at the point where the electricity entered the paper, + litmus was reddened, and at the point where it quitted the paper, turmeric + was browned. 'Here,' he urges, 'the poles are entirely abandoned, but we + have still electrochemical decomposition.' It is evident to him that + instead of being attracted by the poles, the bodies separated are ejected + by the current. The effects thus obtained with poles of air he also + succeeded in obtaining with poles of water. The advance in Faraday's own + ideas made at this time is indicated by the word 'ejected.' He afterwards + reiterates this view: the evolved substances are expelled from the + decomposing body, and 'not drawn out by an attraction. + </p> + <p> + Having abolished this idea of polar attraction, he proceeds to enunciate + and develop a theory of his own. He refers to Davy's celebrated Bakerian + Lecture, given in 1806, which he says 'is almost entirely occupied in the + consideration of electrochemical decompositions.' The facts recorded in + that lecture Faraday regards as of the utmost value. But 'the mode of + action by which the effects take place is stated very generally; so + generally, indeed, that probably a dozen precise schemes of + electrochemical action might be drawn up, differing essentially from each + other, yet all agreeing with the statement there given.' + </p> + <p> + It appears to me that these words might with justice be applied to + Faraday's own researches at this time. They furnish us with results of + permanent value; but little help can be found in the theory advanced to + account for them. It would, perhaps, be more correct to say that the + theory itself is hardly presentable in any tangible form to the intellect. + Faraday looks, and rightly looks, into the heart of the decomposing body + itself; he sees, and rightly sees, active within it the forces which + produce the decomposition, and he rejects, and rightly rejects, the notion + of external attraction; but beyond the hypothesis of decompositions and + recompositions, enunciated and developed by Grothuss and Davy, he does + not, I think, help us to any definite conception as to how the force + reaches the decomposing mass and acts within it. Nor, indeed, can this be + done, until we know the true physical process which underlies what we call + an electric current. + </p> + <p> + Faraday conceives of that current as 'an axis of power having contrary + forces exactly equal in amount in opposite directions'; but this + definition, though much quoted and circulated, teaches us nothing + regarding the current. An 'axis' here can only mean a direction; and what + we want to be able to conceive of is, not the axis along which the power + acts, but the nature and mode of action of the power itself. He objects to + the vagueness of De la Rive; but the fact is, that both he and De la Rive + labour under the same difficulty. Neither wishes to commit himself to the + notion of a current compounded of two electricities flowing in two + opposite directions: but the time had not come, nor is it yet come, for + the displacement of this provisional fiction by the true mechanical + conception. Still, however indistinct the theoretic notions of Faraday at + this time may be, the facts which are rising before him and around him are + leading him gradually, but surely, to results of incalculable importance + in relation to the philosophy of the voltaic pile. + </p> + <p> + He had always some great object of research in view, but in the pursuit of + it he frequently alighted on facts of collateral interest, to examine + which he sometimes turned aside from his direct course. Thus we find the + series of his researches on electrochemical decomposition interrupted by + an inquiry into 'the power of metals and other solids, to induce the + combination of gaseous bodies.' This inquiry, which was received by the + Royal Society on Nov. 30, 1833, though not so important as those which + precede and follow it, illustrates throughout his strength as an + experimenter. The power of spongy platinum to cause the combination of + oxygen and hydrogen had been discovered by Dobereiner in 1823, and had + been applied by him in the construction of his well-known philosophic + lamp. It was shown subsequently by Dulong and Thenard that even a platinum + wire, when perfectly cleansed, may be raised to incandescence by its + action on a jet of cold hydrogen. + </p> + <p> + In his experiments on the decomposition of water, Faraday found that the + positive platinum plate of the decomposing cell possessed in an + extraordinary degree the power of causing oxygen and hydrogen to combine. + He traced the cause of this to the perfect cleanness of the positive + plate. Against it was liberated oxygen, which, with the powerful affinity + of the 'nascent state,' swept away all impurity from the surface against + which it was liberated. The bubbles of gas liberated on one of the + platinum plates or wires of a decomposing cell are always much smaller, + and they rise in much more rapid succession than those from the other. + Knowing that oxygen is sixteen times heavier than hydrogen, I have more + than once concluded, and, I fear, led others into the error of concluding, + that the smaller and more quickly rising bubbles must belong to the + lighter gas. The thing appeared so obvious that I did not give myself the + trouble of looking at the battery, which would at once have told me the + nature of the gas. But Faraday would never have been satisfied with a + deduction if he could have reduced it to a fact. And he has taught me that + the fact here is the direct reverse of what I supposed it to be. The small + bubbles are oxygen, and their smallness is due to the perfect cleanness of + the surface on which they are liberated. The hydrogen adhering to the + other electrode swells into large bubbles, which rise in much slower + succession; but when the current is reversed, the hydrogen is liberated + upon the cleansed wire, and then its bubbles also become small. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT__"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 5 + </h2> +<pre xml:space="preserve"> + (1) Buff finds the quantity of electricity associated with + one milligramme of hydrogen in water to be equal to 45,480 + charges of a Leyden jar, with a height of 480 millimetres, + and a diameter of 160 millimetres. Weber and Kohlrausch + have calculated that, if the quantity of electricity + associated with one milligramme of hydrogen in water were + diffused over a cloud at a height of 1000 metres above the + earth, it would exert upon an equal quantity of the opposite + electricity at the earth's surface an attractive force of + 2,268,000 kilogrammes. (Electrolytische Maasbestimmungen, + 1856, p. 262.) + + (2) Faraday, sa Vie et ses Travaux, p. 20. +</pre> + <p> + <a name="link2HCH0006" id="link2HCH0006"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 6. + </h2> +<pre xml:space="preserve"> + Laws of electro-chemical decomposition. +</pre> + <p> + In our conceptions and reasonings regarding the forces of nature, we + perpetually make use of symbols which, when they possess a high + representative value, we dignify with the name of theories. Thus, prompted + by certain analogies, we ascribe electrical phenomena to the action of a + peculiar fluid, sometimes flowing, sometimes at rest. Such conceptions + have their advantages and their disadvantages; they afford peaceful + lodging to the intellect for a time, but they also circumscribe it, and + by-and-by, when the mind has grown too large for its lodging, it often + finds difficulty in breaking down the walls of what has become its prison + instead of its home. (1) + </p> + <p> + No man ever felt this tyranny of symbols more deeply than Faraday, and no + man was ever more assiduous than he to liberate himself from them, and the + terms which suggested them. Calling Dr. Whewell to his aid in 1833, he + endeavoured to displace by others all terms tainted by a foregone + conclusion. His paper on Electro-chemical Decomposition, received by the + Royal Society on January 9, 1834, opens with the proposal of a new + terminology. He would avoid the word 'current' if he could. (2) He does + abandon the word 'poles' as applied to the ends of a decomposing cell, + because it suggests the idea of attraction, substituting for it the + perfectly natural term Electrodes. He applied the term Electrolyte to + every substance which can be decomposed by the current, and the act of + decomposition he called Electrolysis. All these terms have become current + in science. He called the positive electrode the Anode, and the negative + one the Cathode, but these terms, though frequently used, have not enjoyed + the same currency as the others. The terms Anion and Cation, which he + applied to the constituents of the decomposed electrolyte, and the term + Ion, which included both anions and cations, are still less frequently + employed. + </p> + <p> + Faraday now passes from terminology to research; he sees the necessity of + quantitative determinations, and seeks to supply himself with a measure of + voltaic electricity. This he finds in the quantity of water decomposed by + the current. He tests this measure in all possible ways, to assure himself + that no error can arise from its employment. He places in the course of + one and the same current a series of cells with electrodes of different + sizes, some of them plates of platinum, others merely platinum wires, and + collects the gas liberated on each distinct pair of electrodes. He finds + the quantity of gas to be the same for all. Thus he concludes that when + the same quantity of electricity is caused to pass through a series of + cells containing acidulated water, the electro-chemical action is + independent of the size of the electrodes. (3) He next proves that + variations in intensity do not interfere with this equality of action. + Whether his battery is charged with strong acid or with weak; whether it + consists of five pairs or of fifty pairs; in short, whatever be its + source, when the same current is sent through his series of cells the same + amount of decomposition takes place in all. He next assures himself that + the strength or weakness of his dilute acid does not interfere with this + law. Sending the same current through a series of cells containing + mixtures of sulphuric acid and water of different strengths, he finds, + however the proportion of acid to water might vary, the same amount of gas + to be collected in all the cells. A crowd of facts of this character + forced upon Faraday's mind the conclusion that the amount of + electro-chemical decomposition depends, not upon the size of the + electrodes, not upon the intensity of the current, not upon the strength + of the solution, but solely upon the quantity of electricity which passes + through the cell. The quantity of electricity he concludes is proportional + to the amount of chemical action. On this law Faraday based the + construction of his celebrated Voltameter, or Measure of Voltaic + electricity. + </p> + <p> + But before he can apply this measure he must clear his ground of numerous + possible sources of error. The decomposition of his acidulated water is + certainly a direct result of the current; but as the varied and important + researches of MM. Becquerel, De la Rive, and others had shown, there are + also secondary actions which may materially interfere with and complicate + the pure action of the current. These actions may occur in two ways: + either the liberated ion may seize upon the electrode against which it is + set free, forming a chemical compound with that electrode; or it may seize + upon the substance of the electrolyte itself, and thus introduce into the + circuit chemical actions over and above those due to the current. Faraday + subjected these secondary actions to an exhaustive examination. Instructed + by his experiments, and rendered competent by them to distinguish between + primary and secondary results, he proceeds to establish the doctrine of + 'Definite Electro-chemical Decomposition.' + </p> + <p> + Into the same circuit he introduced his voltameter, which consisted of a + graduated tube filled with acidulated water and provided with platinum + plates for the decomposition of the water, and also a cell containing + chloride of tin. Experiments already referred to had taught him that this + substance, though an insulator when solid, is a conductor when fused, the + passage of the current being always accompanied by the decomposition of + the chloride. He wished to ascertain what relation this decomposition bore + to that of the water in his voltameter. + </p> + <p> + Completing his circuit, he permitted the current to continue until 'a + reasonable quantity of gas' was collected in the voltameter. The circuit + was then broken, and the quantity of tin liberated compared with the + quantity of gas. The weight of the former was 3.2 grains, that of the + latter 0.49742 of a grain. Oxygen, as you know, unites with hydrogen in + the proportion of 8 to 1, to form water. Calling the equivalent, or as it + is sometimes called, the atomic weight of hydrogen 1, that of oxygen is 8; + that of water is consequently 8 + 1 or 9. Now if the quantity of water + decomposed in Faraday's experiment be represented by the number 9, or in + other words by the equivalent of water, then the quantity of tin liberated + from the fused chloride is found by an easy calculation to be 57.9, which + is almost exactly the chemical equivalent of tin. Thus both the water and + the chloride were broken up in proportions expressed by their respective + equivalents. The amount of electric force which wrenched asunder the + constituents of the molecule of water was competent, and neither more nor + less than competent, to wrench asunder the constituents of the molecules + of the chloride of tin. The fact is typical. With the indications of his + voltameter he compared the decompositions of other substances, both singly + and in series. He submitted his conclusions to numberless tests. He + purposely introduced secondary actions. He endeavoured to hamper the + fulfilment of those laws which it was the intense desire of his mind to + see established. But from all these difficulties emerged the golden truth, + that under every variety of circumstances the decompositions of the + voltaic current are as definite in their character as those chemical + combinations which gave birth to the atomic theory. This law of + Electro-chemical Decomposition ranks, in point of importance, with that of + Definite Combining Proportions in chemistry. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT___"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 6 + </h2> +<pre xml:space="preserve"> + (1) I copy these words from the printed abstract of a Friday + evening lecture, given by myself, because they remind me of + Faraday's voice, responding to the utterance by an emphatic + 'hear! hear!'—Proceedings of the Royal Institution, vol. + ii. p. 132. + + (2) In 1838 he expresses himself thus:—'The word current is + so expressive in common language that when applied in the + consideration of electrical phenomena, we can hardly divest + it sufficiently of its meaning, or prevent our minds from + being prejudiced by it.'—Exp. Resear., vol. i. p. 515. ($ + 1617.) + + (3) This conclusion needs qualification. Faraday overlooked + the part played by ozone. +</pre> + <p> + <a name="link2HCH0007" id="link2HCH0007"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 7. + </h2> +<pre xml:space="preserve"> + Origin of power in the voltaic pile. +</pre> + <p> + In one of the public areas of the town of Como stands a statue with no + inscription on its pedestal, save that of a single name, 'Volta.' The + bearer of that name occupies a place for ever memorable in the history of + science. To him we owe the discovery of the voltaic pile, to which for a + brief interval we must now turn our attention. + </p> + <p> + The objects of scientific thought being the passionless laws and phenomena + of external nature, one might suppose that their investigation and + discussion would be completely withdrawn from the region of the feelings, + and pursued by the cold dry light of the intellect alone. This, however, + is not always the case. Man carries his heart with him into all his works. + You cannot separate the moral and emotional from the intellectual; and + thus it is that the discussion of a point of science may rise to the heat + of a battle-field. The fight between the rival optical theories of + Emission and Undulation was of this fierce character; and scarcely less + fierce for many years was the contest as to the origin and maintenance of + the power of the voltaic pile. Volta himself supposed it to reside in the + Contact of different metals. Here was exerted his 'Electro-motive force,' + which tore the combined electricities asunder and drove them as currents + in opposite directions. To render the circulation of the current possible, + it was necessary to connect the metals by a moist conductor; for when any + two metals were connected by a third, their relation to each other was + such that a complete neutralisation of the electric motion was the result. + Volta's theory of metallic contact was so clear, so beautiful, and + apparently so complete, that the best intellects of Europe accepted it as + the expression of natural law. + </p> + <p> + Volta himself knew nothing of the chemical phenomena of the pile; but as + soon as these became known, suggestions and intimations appeared that + chemical action, and not metallic contact, might be the real source of + voltaic electricity. This idea was expressed by Fabroni in Italy, and by + Wollaston in England. It was developed and maintained by those 'admirable + electricians,' Becquerel, of Paris, and De la Rive, of Geneva. The Contact + Theory, on the other hand, received its chief development and illustration + in Germany. It was long the scientific creed of the great chemists and + natural philosophers of that country, and to the present hour there may be + some of them unable to liberate themselves from the fascination of their + first-love. + </p> + <p> + After the researches which I have endeavoured to place before you, it was + impossible for Faraday to avoid taking a side in this controversy. He did + so in a paper 'On the Electricity of the Voltaic Pile,' received by the + Royal Society on the 7th of April, 1834. His position in the controversy + might have been predicted. He saw chemical effects going hand in hand with + electrical effects, the one being proportional to the other; and, in the + paper now before us, he proved that when the former was excluded, the + latter were sought for in vain. He produced a current without metallic + contact; he discovered liquids which, though competent to transmit the + feeblest currents—competent therefore to allow the electricity of + contact to flow through them if it were able to form a current—were + absolutely powerless when chemically inactive. + </p> + <p> + One of the very few experimental mistakes of Faraday occurred in this + investigation. He thought that with a single voltaic cell he had obtained + the spark before the metals touched, but he subsequently discovered his + error. To enable the voltaic spark to pass through air before the + terminals of the battery were united, it was necessary to exalt the + electro-motive force of the battery by multiplying its elements; but all + the elements Faraday possessed were unequal to the task of urging the + spark across the shortest measurable space of air. Nor, indeed, could the + action of the battery, the different metals of which were in contact with + each other, decide the point in question. Still, as regards the identity + of electricities from various sources, it was at that day of great + importance to determine whether or not the voltaic current could jump, as + a spark, across an interval before contact. Faraday's friend, Mr. Gassiot, + solved this problem. He erected a battery of 4000 cells, and with it urged + a stream of sparks from terminal to terminal, when separated from each + other by a measurable space of air. + </p> + <p> + The memoir on the 'Electricity of the Voltaic Pile,' published in 1834, + appears to have produced but little impression upon the supporters of the + contact theory. These indeed were men of too great intellectual weight and + insight lightly to take up, or lightly to abandon a theory. Faraday + therefore resumed the attack in a paper, communicated to the Royal Society + on the 6th of February, 1840. In this paper he hampered his antagonists by + a crowd of adverse experiments. He hung difficulty after difficulty about + the neck of the contact theory, until in its efforts to escape from his + assaults it so changed its character as to become a thing totally + different from the theory proposed by Volta. The more persistently it was + defended, however, the more clearly did it show itself to be a congeries + of devices, bearing the stamp of dialectic skill rather than of natural + truth. + </p> + <p> + In conclusion, Faraday brought to bear upon it an argument which, had its + full weight and purport been understood at the time, would have instantly + decided the controversy. 'The contact theory,' he urged, 'assumed that a + force which is able to overcome powerful resistance, as for instance that + of the conductors, good or bad, through which the current passes, and that + again of the electrolytic action where bodies are decomposed by it, can + arise out of nothing; that, without any change in the acting matter, or + the consumption of any generating force, a current shall be produced which + shall go on for ever against a constant resistance, or only be stopped, as + in the voltaic trough, by the ruins which its exertion has heaped up in + its own course. This would indeed be a creation of power, and is like no + other force in nature. We have many processes by which the form of the + power may be so changed, that an apparent conversion of one into the other + takes place. So we can change chemical force into the electric current, or + the current into chemical force. The beautiful experiments of Seebeck and + Peltier show the convertibility of heat and electricity; and others by + Oersted and myself show the convertibility of electricity and magnetism. + But in no case, not even in those of the Gymnotus and Torpedo, is there a + pure creation or a production of power without a corresponding exhaustion + of something to supply it.' + </p> + <p> + These words were published more than two years before either Mayer printed + his brief but celebrated essay on the Forces of Inorganic Nature, or Mr. + Joule published his first famous experiments on the Mechanical Value of + Heat. They illustrate the fact that before any great scientific principle + receives distinct enunciation by individuals, it dwells more or less + clearly in the general scientific mind. The intellectual plateau is + already high, and our discoverers are those who, like peaks above the + plateau, rise a little above the general level of thought at the time. + </p> + <p> + But many years prior even to the foregoing utterance of Faraday, a similar + argument had been employed. I quote here with equal pleasure and + admiration the following passage written by Dr. Roget so far back as 1829. + Speaking of the contact theory, he says:—'If there could exist a + power having the property ascribed to it by the hypothesis, namely, that + of giving continual impulse to a fluid in one constant direction, without + being exhausted by its own action, it would differ essentially from all + the known powers in nature. All the powers and sources of motion with the + operation of which we are acquainted, when producing these peculiar + effects, are expended in the same proportion as those effects are + produced; and hence arises the impossibility of obtaining by their agency + a perpetual effect; or in other words a perpetual motion. But the + electro-motive force, ascribed by Volta to the metals, when in contact, is + a force which, as long as a free course is allowed to the electricity it + sets in motion, is never expended, and continues to be excited with + undiminished power in the production of a never-ceasing effect. Against + the truth of such a supposition the probabilities are all but infinite.' + When this argument, which he employed independently, had clearly fixed + itself in his mind, Faraday never cared to experiment further on the + source of electricity in the voltaic pile. The argument appeared to him + 'to remove the foundation itself of the contact theory,' and he afterwards + let it crumble down in peace. (1) + </p> + <p> + Footnote to Chapter 7 + </p> +<pre xml:space="preserve"> + (1) To account for the electric current, which was really + the core of the whole discussion, Faraday demonstrated the + impotence of the Contact Theory as then enunciated and + defended. Still, it is certain that two different metals, + when brought into contact, charge themselves, the one with + positive and the other with negative electricity. I had the + pleasure of going over this ground with Kohlrausch in 1849, + and his experiments left no doubt upon my mind that the + contact electricity of Volta was a reality, though it could + produce no current. With one of the beautiful instruments + devised by himself, Sir William Thomson has rendered this + point capable of sure and easy demonstration; and he and + others now hold what may be called a contact theory, which, + while it takes into account the action of the metals, also + embraces the chemical phenomena of the circuit. Helmholtz, + I believe, was the first to give the contact theory this new + form, in his celebrated essay, Ueber die Erhaltung der + Kraft, p. 45. +</pre> + <p> + <a name="link2HCH0008" id="link2HCH0008"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 8. + </h2> +<pre xml:space="preserve"> + Researches on frictional electricity: induction: conduction: + specific inductive capacity: theory of contiguous particles. +</pre> + <p> + The burst of power which had filled the four preceding years with an + amount of experimental work unparalleled in the history of science + partially subsided in 1835, and the only scientific paper contributed by + Faraday in that year was a comparatively unimportant one, 'On an improved + Form of the Voltaic Battery.' He brooded for a time: his experiments on + electrolysis had long filled his mind; he looked, as already stated, into + the very heart of the electrolyte, endeavouring to render the play of its + atoms visible to his mental eye. He had no doubt that in this case what is + called 'the electric current' was propagated from particle to particle of + the electrolyte; he accepted the doctrine of decomposition and + recomposition which, according to Grothuss and Davy, ran from electrode to + electrode. And the thought impressed him more and more that ordinary + electric induction was also transmitted and sustained by the action of + 'contiguous particles.' + </p> + <p> + His first great paper on frictional electricity was sent to the Royal + Society on November 30, 1837. We here find him face to face with an idea + which beset his mind throughout his whole subsequent life,—the idea + of action at a distance. It perplexed and bewildered him. In his attempts + to get rid of this perplexity, he was often unconsciously rebelling + against the limitations of the intellect itself. He loved to quote Newton + upon this point; over and over again he introduces his memorable words, + 'That gravity should be innate, inherent, and essential to matter, so that + one body may act upon another at a distance through a vacuum and without + the mediation of anything else, by and through which this action and force + may be conveyed from one to another, is to me so great an absurdity, that + I believe no man who has in philosophical matters a competent faculty of + thinking, can ever fall into it. Gravity must be caused by an agent acting + constantly according to certain laws; but whether this agent be material + or immaterial, I have left to the consideration of my readers.' (1) + </p> + <p> + Faraday does not see the same difficulty in his contiguous particles. And + yet, by transferring the conception from masses to particles, we simply + lessen size and distance, but we do not alter the quality of the + conception. Whatever difficulty the mind experiences in conceiving of + action at sensible distances, besets it also when it attempts to conceive + of action at insensible distances. Still the investigation of the point + whether electric and magnetic effects were wrought out through the + intervention of contiguous particles or not, had a physical interest + altogether apart from the metaphysical difficulty. Faraday grapples with + the subject experimentally. By simple intuition he sees that action at a + distance must be exerted in straight lines. Gravity, he knows, will not + turn a corner, but exerts its pull along a right line; hence his aim and + effort to ascertain whether electric action ever takes place in curved + lines. This once proved, it would follow that the action is carried on by + means of a medium surrounding the electrified bodies. His experiments in + 1837 reduced, in his opinion, this point of demonstration. He then found + that he could electrify, by induction, an insulated sphere placed + completely in the shadow of a body which screened it from direct action. + He pictured the lines of electric force bending round the edges of the + screen, and reuniting on the other side of it; and he proved that in many + cases the augmentation of the distance between his insulated sphere and + the inducing body, instead of lessening, increased the charge of the + sphere. This he ascribed to the coalescence of the lines of electric force + at some distance behind the screen. + </p> + <p> + Faraday's theoretic views on this subject have not received general + acceptance, but they drove him to experiment, and experiment with him was + always prolific of results. By suitable arrangements he placed a metallic + sphere in the middle of a large hollow sphere, leaving a space of + something more than half an inch between them. The interior sphere was + insulated, the external one uninsulated. To the former he communicated a + definite charge of electricity. It acted by induction upon the concave + surface of the latter, and he examined how this act of induction was + effected by placing insulators of various kinds between the two spheres. + He tried gases, liquids, and solids, but the solids alone gave him + positive results. He constructed two instruments of the foregoing + description, equal in size and similar in form. The interior sphere of + each communicated with the external air by a brass stem ending in a knob. + The apparatus was virtually a Leyden jar, the two coatings of which were + the two spheres, with a thick and variable insulator between them. The + amount of charge in each jar was determined by bringing a proof-plane into + contact with its knob and measuring by a torsion balance the charge taken + away. He first charged one of his instruments, and then dividing the + charge with the other, found that when air intervened in both cases the + charge was equally divided. But when shellac, sulphur, or spermaceti was + interposed between the two spheres of one jar, while air occupied this + interval in the other, then he found that the instrument occupied by the + 'solid dielectric' takes more than half the original charge. A portion of + the charge was absorbed by the dielectric itself. The electricity took + time to penetrate the dielectric. Immediately after the discharge of the + apparatus, no trace of electricity was found upon its knob. But after a + time electricity was found there, the charge having gradually returned + from the dielectric in which it had been lodged. Different insulators + possess this power of permitting the charge to enter them in different + degrees. Faraday figured their particles as polarized, and he concluded + that the force of induction is propagated from particle to particle of the + dielectric from the inner sphere to the outer one. This power of + propagation possessed by insulators he called their 'Specific Inductive + Capacity.' + </p> + <p> + Faraday visualizes with the utmost clearness the state of his contiguous + particles; one after another they become charged, each succeeding particle + depending for its charge upon its predecessor. And now he seeks to break + down the wall of partition between conductors and insulators. 'Can we + not,' he says, 'by a gradual chain of association carry up discharge from + its occurrence in air through spermaceti and water, to solutions, and then + on to chlorides, oxides, and metals, without any essential change in its + character?' Even copper, he urges, offers a resistance to the transmission + of electricity. The action of its particles differs from those of an + insulator only in degree. They are charged like the particles of the + insulator, but they discharge with greater ease and rapidity; and this + rapidity of molecular discharge is what we call conduction. Conduction + then is always preceded by atomic induction; and when, through some + quality of the body which Faraday does not define, the atomic discharge is + rendered slow and difficult, conduction passes into insulation. + </p> + <p> + Though they are often obscure, a fine vein of philosophic thought runs + through those investigations. The mind of the philosopher dwells amid + those agencies which underlie the visible phenomena of Induction and + Conduction; and he tries by the strong light of his imagination to see the + very molecules of his dielectrics. It would, however, be easy to criticise + these researches, easy to show the looseness, and sometimes the + inaccuracy, of the phraseology employed; but this critical spirit will get + little good out of Faraday. Rather let those who ponder his works seek to + realise the object he set before him, not permitting his occasional + vagueness to interfere with their appreciation of his speculations. We may + see the ripples, and eddies, and vortices of a flowing stream, without + being able to resolve all these motions into their constituent elements; + and so it sometimes strikes me that Faraday clearly saw the play of fluids + and ethers and atoms, though his previous training did not enable him to + resolve what he saw into its constituents, or describe it in a manner + satisfactory to a mind versed in mechanics. And then again occur, I + confess, dark sayings, difficult to be understood, which disturb my + confidence in this conclusion. It must, however, always be remembered that + he works at the very boundaries of our knowledge, and that his mind + habitually dwells in the 'boundless contiguity of shade' by which that + knowledge is surrounded. + </p> + <p> + In the researches now under review the ratio of speculation and reasoning + to experiment is far higher than in any of Faraday's previous works. Amid + much that is entangled and dark we have flashes of wondrous insight and + utterances which seem less the product of reasoning than of revelation. I + will confine myself here to one example of this divining power. By his + most ingenious device of a rapidly rotating mirror, Wheatstone had proved + that electricity required time to pass through a wire, the current + reaching the middle of the wire later than its two ends. 'If,' says + Faraday, 'the two ends of the wire in Professor Wheatstone's experiments + were immediately connected with two large insulated metallic surfaces + exposed to the air, so that the primary act of induction, after making the + contact for discharge, might be in part removed from the internal portion + of the wire at the first instance, and disposed for the moment on its + surface jointly with the air and surrounding conductors, then I venture to + anticipate that the middle spark would be more retarded than before. And + if those two plates were the inner and outer coatings of a large jar or + Leyden battery, then the retardation of the spark would be much greater.' + This was only a prediction, for the experiment was not made. (2) Sixteen + years subsequently, however, the proper conditions came into play, and + Faraday was able to show that the observations of Werner Siemens, and + Latimer Clark, on subterraneous and submarine wires were illustrations, on + a grand scale, of the principle which he had enunciated in 1838. The wires + and the surrounding water act as a Leyden jar, and the retardation of the + current predicted by Faraday manifests itself in every message sent by + such cables. + </p> + <p> + The meaning of Faraday in these memoirs on Induction and Conduction is, as + I have said, by no means always clear; and the difficulty will be most + felt by those who are best trained in ordinary theoretic conceptions. He + does not know the reader's needs, and he therefore does not meet them. For + instance he speaks over and over again of the impossibility of charging a + body with one electricity, though the impossibility is by no means + evident. The key to the difficulty is this. He looks upon every insulated + conductor as the inner coating of a Leyden jar. An insulated sphere in the + middle of a room is to his mind such a coating; the walls are the outer + coating, while the air between both is the insulator, across which the + charge acts by induction. Without this reaction of the walls upon the + sphere you could no more, according to Faraday, charge it with electricity + than you could charge a Leyden jar, if its outer coating were removed. + Distance with him is immaterial. His strength as a generalizer enables him + to dissolve the idea of magnitude; and if you abolish the walls of the + room—even the earth itself—he would make the sun and planets + the outer coating of his jar. I dare not contend that Faraday in these + memoirs made all his theoretic positions good. But a pure vein of + philosophy runs through these writings; while his experiments and + reasonings on the forms and phenomena of electrical discharge are of + imperishable importance. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT____"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 8 + </h2> +<pre xml:space="preserve"> + (1) Newton's third letter to Bentley. + + (2) Had Sir Charles Wheatstone been induced to resume his + measurements, varying the substances through which, and the + conditions under which, the current is propagated, he might + have rendered great service to science, both theoretic and + experimental. +</pre> + <p> + <a name="link2HCH0009" id="link2HCH0009"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 9. + </h2> +<pre xml:space="preserve"> + Rest needed—visit to Switzerland. +</pre> + <p> + The last of these memoirs was dated from the Royal Institution in June, + 1838. It concludes the first volume of his 'Experimental Researches on + Electricity.' In 1840, as already stated, he made his final assault on the + Contact Theory, from which it never recovered. (1) He was now feeling the + effects of the mental strain to which he had been subjected for so many + years. During these years he repeatedly broke down. His wife alone + witnessed the extent of his prostration, and to her loving care we, and + the world, are indebted for the enjoyment of his presence here so long. He + found occasional relief in a theatre. He frequently quitted London and + went to Brighton and elsewhere, always choosing a situation which + commanded a view of the sea, or of some other pleasant horizon, where he + could sit and gaze and feel the gradual revival of the faith that + </p> +<pre xml:space="preserve"> + 'Nature never did betray + The heart that loved her.' +</pre> + <p> + But very often for some days after his removal to the country, he would be + unable to do more than sit at a window and look out upon the sea and sky. + </p> + <p> + In 1841, his state became more serious than it had ever been before. A + published letter to Mr. Richard Taylor, dated March 11, 1843, contains an + allusion to his previous condition. 'You are aware,' he says, 'that + considerations regarding health have prevented me from working or reading + on science for the last two years.' This, at one period or another of + their lives, seems to be the fate of most great investigators. They do not + know the limits of their constitutional strength until they have + transgressed them. It is, perhaps, right that they should transgress them, + in order to ascertain where they lie. Faraday, however, though he went far + towards it, did not push his transgression beyond his power of + restitution. In 1841 Mrs. Faraday and he went to Switzerland, under the + affectionate charge of her brother, Mr. George Barnard, the artist. This + time of suffering throws fresh light upon his character. I have said that + sweetness and gentleness were not its only constituents; that he was also + fiery and strong. At the time now referred to, his fire was low and his + strength distilled away; but the residue of his life was neither + irritability nor discontent. He was unfit to mingle in society, for + conversation was a pain to him; but let us observe the great Man-child + when alone. He is at the village of Interlaken, enjoying Jungfrau sunsets, + and at times watching the Swiss nailers making their nails. He keeps a + little journal, in which he describes the process of nailmaking, and + incidentally throws a luminous beam upon himself. + </p> + <p> + 'August 2, 1841.—Clout nailmaking goes on here rather considerably, + and is a very neat and pretty operation to observe. I love a smith's shop + and anything relating to smithery. My father was a smith.' + </p> + <p> + From Interlaken he went to the Falls of the Giessbach, on the pleasant + lake of Brientz. And here we have him watching the shoot of the cataract + down its series of precipices. It is shattered into foam at the base of + each, and tossed by its own recoil as water-dust through the air. The sun + is at his back, shining on the drifting spray, and he thus describes and + muses on what he sees:— + </p> + <p> + 'August 12, 1841.—To-day every fall was foaming from the abundance + of water, and the current of wind brought down by it was in some places + too strong to stand against. The sun shone brightly, and the rainbows seen + from various points were very beautiful. One at the bottom of a fine but + furious fall was very pleasant,—there it remained motionless, whilst + the gusts and clouds of spray swept furiously across its place and were + dashed against the rock. It looked like a spirit strong in faith and + steadfast in the midst of the storm of passions sweeping across it, and + though it might fade and revive, still it held on to the rock as in hope + and giving hope. And the very drops, which in the whirlwind of their fury + seemed as if they would carry all away, were made to revive it and give it + greater beauty.' + </p> + <p> + Footnote to Chapter 9 + </p> +<pre xml:space="preserve"> + (1) See note, p. 77. +</pre> + <p> + <a name="link2HCH0010" id="link2HCH0010"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 10. + </h2> +<pre xml:space="preserve"> + Magnetization of light. +</pre> + <p> + But we must quit the man and go on to the discoverer: we shall return for + a brief space to his company by-and-by. Carry your thoughts back to his + last experiments, and see him endeavouring to prove that induction is due + to the action of contiguous particles. He knew that polarized light was a + most subtle and delicate investigator of molecular condition. He used it + in 1834 in exploring his electrolytes, and he tried it in 1838 upon his + dielectrics. At that time he coated two opposite faces of a glass cube + with tinfoil, connected one coating with his powerful electric machine and + the other with the earth, and examined by polarized light the condition of + the glass when thus subjected to strong electric influence. He failed to + obtain any effect; still he was persuaded an action existed, and required + only suitable means to call it forth. + </p> + <p> + After his return from Switzerland he was beset by these thoughts; they + were more inspired than logical: but he resorted to magnets and proved his + inspiration true. His dislike of 'doubtful knowledge' and his efforts to + liberate his mind from the thraldom of hypotheses have been already + referred to. Still this rebel against theory was incessantly theorising + himself. His principal researches are all connected by an undercurrent of + speculation. Theoretic ideas were the very sap of his intellect—the + source from which all his strength as an experimenter was derived. While + once sauntering with him through the Crystal Palace, at Sydenham, I asked + him what directed his attention to the magnetization of light. It was his + theoretic notions. He had certain views regarding the unity and + convertibility of natural forces; certain ideas regarding the vibrations + of light and their relations to the lines of magnetic force; these views + and ideas drove him to investigation. And so it must always be: the great + experimentalist must ever be the habitual theorist, whether or not he + gives to his theories formal enunciation. + </p> + <p> + Faraday, you have been informed, endeavoured to improve the manufacture of + glass for optical purposes. But though he produced a heavy glass of great + refractive power, its value to optics did not repay him for the pains and + labour bestowed on it. Now, however, we reach a result established by + means of this same heavy glass, which made ample amends for all. + </p> + <p> + In November, 1845, he announced his discovery of the 'Magnetization of + Light and the Illumination of the Lines of Magnetic Force.' This title + provoked comment at the time, and caused misapprehension. He therefore + added an explanatory note; but the note left his meaning as entangled as + before. In fact Faraday had notions regarding the magnetization of light + which were peculiar to himself, and untranslatable into the scientific + language of the time. Probably no other philosopher of his day would have + employed the phrases just quoted as appropriate to the discovery announced + in 1845. But Faraday was more than a philosopher; he was a prophet, and + often wrought by an inspiration to be understood by sympathy alone. The + prophetic element in his character occasionally coloured, and even + injured, the utterance of the man of science; but subtracting that + element, though you might have conferred on him intellectual symmetry, you + would have destroyed his motive force. + </p> + <p> + But let us pass from the label of this casket to the jewel it contains. 'I + have long,' he says, 'held an opinion, almost amounting to conviction, in + common, I believe, with many other lovers of natural knowledge, that the + various forms under which the forces of matter are made manifest have one + common origin; in other words, are so directly related and mutually + dependent, that they are convertible, as it were, into one another, and + possess equivalents of power in their action.... This strong persuasion,' + he adds, 'extended to the powers of light.' And then he examines the + action of magnets upon light. From conversation with him and Anderson, I + should infer that the labour preceding this discovery was very great. The + world knows little of the toil of the discoverer. It sees the climber + jubilant on the mountain top, but does not know the labour expended in + reaching it. Probably hundreds of experiments had been made on transparent + crystals before he thought of testing his heavy glass. Here is his own + clear and simple description of the result of his first experiment with + this substance:—'A piece of this glass, about two inches square, and + 0.5 of an inch thick, having flat and polished edges, was placed as a + diamagnetic (1) between the poles (not as yet magnetized by the electric + current), so that the polarized ray should pass through its length; the + glass acted as air, water, or any other transparent substance would do; + and if the eye-piece were previously turned into such a position that the + polarized ray was extinguished, or rather the image produced by it + rendered invisible, then the introduction of the glass made no alteration + in this respect. In this state of circumstances, the force of the + electro-magnet was developed by sending an electric current through its + coils, and immediately the image of the lamp-flame became visible and + continued so as long as the arrangement continued magnetic. On stopping + the electric current, and so causing the magnetic force to cease, the + light instantly disappeared. These phenomena could be renewed at pleasure, + at any instant of time, and upon any occasion, showing a perfect + dependence of cause and effect.' + </p> + <p> + In a beam of ordinary light the particles of the luminiferous ether + vibrate in all directions perpendicular to the line of progression; by the + act of polarization, performed here by Faraday, all oscillations but those + parallel to a certain plane are eliminated. When the plane of vibration of + the polarizer coincides with that of the analyzer, a portion of the beam + passes through both; but when these two planes are at right angles to each + other, the beam is extinguished. If by any means, while the polarizer and + analyzer remain thus crossed, the plane of vibration of the polarized beam + between them could be changed, then the light would be, in part at least, + transmitted. In Faraday's experiment this was accomplished. His magnet + turned the plane of polarization of the beam through a certain angle, and + thus enabled it to get through the analyzer; so that 'the magnetization of + light and the illumination of the magnetic lines of force' becomes, when + expressed in the language of modern theory, the rotation of the plane of + polarization. + </p> + <p> + To him, as to all true philosophers, the main value of a fact was its + position and suggestiveness in the general sequence of scientific truth. + Hence, having established the existence of a phenomenon, his habit was to + look at it from all possible points of view, and to develop its + relationship to other phenomena. He proved that the direction of the + rotation depends upon the polarity of his magnet; being reversed when the + magnetic poles are reversed. He showed that when a polarized ray passed + through his heavy glass in a direction parallel to the magnetic lines of + force, the rotation is a maximum, and that when the direction of the ray + is at right angles to the lines of force, there is no rotation at all. He + also proved that the amount of the rotation is proportional to the length + of the diamagnetic through which the ray passes. He operated with liquids + and solutions. Of aqueous solutions he tried 150 and more, and found the + power in all of them. He then examined gases; but here all his efforts to + produce any sensible action upon the polarized beam were ineffectual. He + then passed from magnets to currents, enclosing bars of heavy glass, and + tubes containing liquids and aqueous solutions within an electro-magnetic + helix. A current sent through the helix caused the plane of polarization + to rotate, and always in the direction of the current. The rotation was + reversed when the current was reversed. In the case of magnets, he + observed a gradual, though quick, ascent of the transmitted beam from a + state of darkness to its maximum brilliancy, when the magnet was excited. + In the case of currents, the beam attained at once its maximum. This he + showed to be due to the time required by the iron of the electro-magnet to + assume its full magnetic power, which time vanishes when a current, + without iron, is employed. 'In this experiment,' he says, 'we may, I + think, justly say that a ray of light is electrified, and the electric + forces illuminated.' In the helix, as with the magnets, he submitted air + to magnetic influence 'carefully and anxiously,' but could not discover + any trace of action on the polarized ray. + </p> + <p> + Many substances possess the power of turning the plane of polarization + without the intervention of magnetism. Oil of turpentine and quartz are + examples; but Faraday showed that, while in one direction, that is, across + the lines of magnetic force, his rotation is zero, augmenting gradually + from this until it attains its maximum, when the direction of the ray is + parallel to the lines of force; in the oil of turpentine the rotation is + independent of the direction of the ray. But he showed that a still more + profound distinction exists between the magnetic rotation and the natural + one. I will try to explain how. Suppose a tube with glass ends containing + oil of turpentine to be placed north and south. Fixing the eye at the + south end of the tube, let a polarized beam be sent through it from the + north. To the observer in this position the rotation of the plane of + polarization, by the turpentine, is right-handed. Let the eye be placed at + the north end of the tube, and a beam be sent through it from the south; + the rotation is still right-handed. Not so, however, when a bar of heavy + glass is subjected to the action of an electric current. In this case if, + in the first position of the eye, the rotation be right-handed, in the + second position it is left-handed. These considerations make it manifest + that if a polarized beam, after having passed through the oil of + turpentine in its natural state, could by any means be reflected back + through the liquid, the rotation impressed upon the direct beam would be + exactly neutralized by that impressed upon the reflected one. Not so with + the induced magnetic effect. Here it is manifest that the rotation would + be doubled by the act of reflection. Hence Faraday concludes that the + particles of the oil of turpentine which rotate by virtue of their natural + force, and those which rotate in virtue of the induced force, cannot be in + the same condition. The same remark applies to all bodies which possess a + natural power of rotating the plane of polarization. + </p> + <p> + And then he proceeded with exquisite skill and insight to take advantage + of this conclusion. He silvered the ends of his piece of heavy glass, + leaving, however, a narrow portion parallel to two edges diagonally + opposed to each other unsilvered. He then sent his beam through this + uncovered portion, and by suitably inclining his glass caused the beam + within it to reach his eye first direct, and then after two, four, and six + reflections. These corresponded to the passage of the ray once, three + times, five times, and seven times through the glass. He thus established + with numerical accuracy the exact proportionality of the rotation to the + distance traversed by the polarized beam. Thus in one series of + experiments where the rotation required by the direct beam was 12degrees, + that acquired by three passages through the glass was 36degrees, while + that acquired by five passages was 60degrees. But even when this method of + magnifying was applied, he failed with various solid substances to obtain + any effect; and in the case of air, though he employed to the utmost the + power which these repeated reflections placed in his hands, he failed to + produce the slightest sensible rotation. + </p> + <p> + These failures of Faraday to obtain the effect with gases seem to indicate + the true seat of the phenomenon. The luminiferous ether surrounds and is + influenced by the ultimate particles of matter. The symmetry of the one + involves that of the other. Thus, if the molecules of a crystal be + perfectly symmetrical round any line through the crystal, we may safely + conclude that a ray will pass along this line as through ordinary glass. + It will not be doubly refracted. From the symmetry of the liquid figures, + known to be produced in the planes of freezing, when radiant heat is sent + through ice, we may safely infer symmetry of aggregation, and hence + conclude that the line perpendicular to the planes of freezing is a line + of no double refraction; that it is, in fact, the optic axis of the + crystal. The same remark applies to the line joining the opposite blunt + angles of a crystal of Iceland spar. The arrangement of the molecules + round this line being symmetrical, the condition of the ether depending + upon these molecules shares their symmetry; and there is, therefore, no + reason why the wavelength should alter with the alteration of the azimuth + round this line. Annealed glass has its molecules symmetrically arranged + round every line that can be drawn through it; hence it is not doubly + refractive. But let the substance be either squeezed or strained in one + direction, the molecular symmetry, and with it the symmetry of the ether, + is immediately destroyed and the glass becomes doubly refractive. Unequal + heating produces the same effect. Thus mechanical strains reveal + themselves by optical effects; and there is little doubt that in Faraday's + experiment it is the magnetic strain that produces the rotation of the + plane of polarization. (2) + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT_____"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 10 + </h2> +<pre xml:space="preserve"> + (1) 'By a diamagnetic,' says Faraday, 'I mean a body through + which lines of magnetic force are passing, and which does + not by their action assume the usual magnetic state of iron + or loadstone.' Faraday subsequently used this term in a + different sense from that here given, as will immediately + appear. + + (2) The power of double refraction conferred on the centre + of a glass rod, when it is caused to sound the fundamental + note due to its longitudinal vibration, and the absence of + the same power in the case of vibrating air (enclosed in a + glass organ-pipe), seems to be analogous to the presence and + absence of Faraday's effect in the same two substances. + Faraday never, to my knowledge, attempted to give, even in + conversation, a picture of the molecular condition of his + heavy glass when subjected to magnetic influence. In a + mathematical investigation of the subject, published in the + Proceedings of the Royal Society for 1856, Sir William + Thomson arrives at the conclusion that the 'diamagnetic' is + in a state of molecular rotation. +</pre> + <p> + <a name="link2HCH0011" id="link2HCH0011"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 11. + </h2> +<pre xml:space="preserve"> + Discovery of diamagnetism—researches on magne-crystallic + action. +</pre> + <p> + Faraday's next great step in discovery was announced in a memoir on the + 'Magnetic Condition of all matter,' communicated to the Royal Society on + December 18, 1845. One great source of his success was the employment of + extraordinary power. As already stated, he never accepted a negative + answer to an experiment until he had brought to bear upon it all the force + at his command. He had over and over again tried steel magnets and + ordinary electro-magnets on various substances, but without detecting + anything different from the ordinary attraction exhibited by a few of + them. Stronger coercion, however, developed a new action. Before the pole + of an electro-magnet, he suspended a fragment of his famous heavy glass; + and observed that when the magnet was powerfully excited the glass fairly + retreated from the pole. It was a clear case of magnetic repulsion. He + then suspended a bar of the glass between two poles; the bar retreated + when the poles were excited, and set its length equatorially or at right + angles to the line joining them. When an ordinary magnetic body was + similarly suspended, it always set axially, that is, from pole to pole. + </p> + <p> + Faraday called those bodies which were repelled by the poles of a magnet, + diamagnetic bodies; using this term in a sense different from that in + which he employed it in his memoir on the magnetization of light. The term + magnetic he reserved for bodies which exhibited the ordinary attraction. + He afterwards employed the term magnetic to cover the whole phenomena of + attraction and repulsion, and used the word paramagnetic to designate such + magnetic action as is exhibited by iron. + </p> + <p> + Isolated observations by Brugmanns, Becquerel, Le Baillif, Saigy, and + Seebeck had indicated the existence of a repulsive force exercised by the + magnet on two or three substances; but these observations, which were + unknown to Faraday, had been permitted to remain without extension or + examination. Having laid hold of the fact of repulsion, Faraday + immediately expanded and multiplied it. He subjected bodies of the most + varied qualities to the action of his magnet:—mineral salts, acids, + alkalis, ethers, alcohols, aqueous solutions, glass, phosphorus, resins, + oils, essences, vegetable and animal tissues, and found them all amenable + to magnetic influence. No known solid or liquid proved insensible to the + magnetic power when developed in sufficient strength. All the tissues of + the human body, the blood—though it contains iron—included, + were proved to be diamagnetic. So that if you could suspend a man between + the poles of a magnet, his extremities would retreat from the poles until + his length became equatorial. + </p> + <p> + Soon after he had commenced his researches on diamagnetism, Faraday + noticed a remarkable phenomenon which first crossed my own path in the + following way: In the year 1849, while working in the cabinet of my + friend, Professor Knoblauch, of Marburg, I suspended a small copper coin + between the poles of an electro-magnet. On exciting the magnet, the coin + moved towards the poles and then suddenly stopped, as if it had struck + against a cushion. On breaking the circuit, the coin was repelled, the + revulsion being so violent as to cause it to spin several times round its + axis of suspension. A Silber-groschen similarly suspended exhibited the + same deportment. For a moment I thought this a new discovery; but on + looking over the literature of the subject, it appeared that Faraday had + observed, multiplied, and explained the same effect during his researches + on diamagnetism. His explanation was based upon his own great discovery of + magneto-electric currents. The effect is a most singular one. A weight of + several pounds of copper may be set spinning between the electro-magnetic + poles; the excitement of the magnet instantly stops the rotation. Though + nothing is apparent to the eye, the copper, if moved in the excited + magnetic field, appears to move through a viscous fluid; while, when a + flat piece of the metal is caused to pass to and fro like a saw between + the poles, the sawing of the magnetic field resembles the cutting through + of cheese or butter. (1) This virtual friction of the magnetic field is so + strong, that copper, by its rapid rotation between the poles, might + probably be fused. We may easily dismiss this experiment by saying that + the heat is due to the electric currents excited in the copper. But so + long as we are unable to reply to the question, 'What is an electric + current?' the explanation is only provisional. For my own part, I look + with profound interest and hope on the strange action here referred to. + </p> + <p> + Faraday's thoughts ran intuitively into experimental combinations, so that + subjects whose capacity for experimental treatment would, to ordinary + minds, seem to be exhausted in a moment, were shown by him to be all but + inexhaustible. He has now an object in view, the first step towards which + is the proof that the principle of Archimedes is true of magnetism. He + forms magnetic solutions of various degrees of strength, places them + between the poles of his magnet, and suspends in the solutions various + magnetic bodies. He proves that when the solution is stronger than the + body plunged in it, the body, though magnetic, is repelled; and when an + elongated piece of it is surrounded by the solution, it sets, like a + diamagnetic body, equatorially between the excited poles. The same body + when suspended in a solution of weaker magnetic power than itself, is + attracted as a whole, while an elongated portion of it sets axially. + </p> + <p> + And now theoretic questions rush in upon him. Is this new force a true + repulsion, or is it merely a differential attraction? Might not the + apparent repulsion of diamagnetic bodies be really due to the greater + attraction of the medium by which they are surrounded? He tries the + rarefaction of air, but finds the effect insensible. He is averse to + ascribing a capacity of attraction to space, or to any hypothetical medium + supposed to fill space. He therefore inclines, but still with caution, to + the opinion that the action of a magnet upon bismuth is a true and + absolute repulsion, and not merely the result of differential attraction. + And then he clearly states a theoretic view sufficient to account for the + phenomena. 'Theoretically,' he says, 'an explanation of the movements of + the diamagnetic bodies, and all the dynamic phenomena consequent upon the + action of magnets upon them, might be offered in the supposition that + magnetic induction caused in them a contrary state to that which it + produced in ordinary matter.' That is to say, while in ordinary magnetic + influence the exciting pole excites adjacent to itself the contrary + magnetism, in diamagnetic bodies the adjacent magnetism is the same as + that of the exciting pole. This theory of reversed polarity, however, does + not appear to have ever laid deep hold of Faraday's mind; and his own + experiments failed to give any evidence of its truth. He therefore + subsequently abandoned it, and maintained the non-polarity of the + diamagnetic force. + </p> + <p> + He then entered a new, though related field of inquiry. Having dealt with + the metals and their compounds, and having classified all of them that + came within the range of his observation under the two heads magnetic and + diamagnetic, he began the investigation of the phenomena presented by + crystals when subjected to magnetic power. This action of crystals had + been in part theoretically predicted by Poisson, (2) and actually + discovered by Plucker, whose beautiful results, at the period which we + have now reached, profoundly interested all scientific men. Faraday had + been frequently puzzled by the deportment of bismuth, a highly crystalline + metal. Sometimes elongated masses of the substance refused to set + equatorially, sometimes they set persistently oblique, and sometimes even, + like a magnetic body, from pole to pole. + </p> + <p> + 'The effect,' he says, 'occurs at a single pole; and it is then striking + to observe a long piece of a substance so diamagnetic as bismuth repelled, + and yet at the same moment set round with force, axially, or end on, as a + piece of magnetic substance would do.' The effect perplexed him; and in + his efforts to release himself from this perplexity, no feature of this + new manifestation of force escaped his attention. His experiments are + described in a memoir communicated to the Royal Society on December 7, + 1848. + </p> + <p> + I have worked long myself at magne-crystallic action, amid all the light + of Faraday's and Plucker's researches. The papers now before me were + objects of daily and nightly study with me eighteen or nineteen years ago; + but even now, though their perusal is but the last of a series of + repetitions, they astonish me. Every circumstance connected with the + subject; every shade of deportment; every variation in the energy of the + action; almost every application which could possibly be made of magnetism + to bring out in detail the character of this new force, is minutely + described. The field is swept clean, and hardly anything experimental is + left for the gleaner. The phenomena, he concludes, are altogether + different from those of magnetism or diamagnetism: they would appear, in + fact, to present to us 'a new force, or a new form of force, in the + molecules of matter,' which, for convenience sake, he designates by a new + word, as 'the magne-crystallic force.' + </p> + <p> + He looks at the crystal acted upon by the magnet. From its mass he passes, + in idea, to its atoms, and he asks himself whether the power which can + thus seize upon the crystalline molecules, after they have been fixed in + their proper positions by crystallizing force, may not, when they are + free, be able to determine their arrangement? He, therefore, liberates the + atoms by fusing the bismuth. He places the fused substance between the + poles of an electro-magnet, powerfully excited; but he fails to detect any + action. I think it cannot be doubted that an action is exerted here, that + a true cause comes into play; but its magnitude is not such as sensibly to + interfere with the force of crystallization, which, in comparison with the + diamagnetic force, is enormous. 'Perhaps,' adds Faraday, 'if a longer time + were allowed, and a permanent magnet used, a better result might be + obtained. I had built many hopes upon the process.' This expression, and + his writings abound in such, illustrates what has been already said + regarding his experiments being suggested and guided by his theoretic + conceptions. His mind was full of hopes and hypotheses, but he always + brought them to an experimental test. The record of his planned and + executed experiments would, I doubt not, show a high ratio of hopes + disappointed to hopes fulfilled; but every case of fulfilment abolished + all memory of defeat; disappointment was swallowed up in victory. + </p> + <p> + After the description of the general character of this new force, Faraday + states with the emphasis here reproduced its mode of action: 'The law of + action appears to be that the line or axis of MAGNE-CRYSTALLIC force + (being the resultant of the action of all the molecules) tends to place + itself parallel, or as a tangent, to the magnetic curve, or line of + magnetic force, passing through the place where the crystal is situated.' + The magne-crystallic force, moreover, appears to him 'to be clearly + distinguished from the magnetic or diamagnetic forces, in that it causes + neither approach nor recession, consisting not in attraction or repulsion, + but in giving a certain determinate position to the mass under its + influence.' And then he goes on 'very carefully to examine and prove the + conclusion that there was no connection of the force with attractive or + repulsive influences.' With the most refined ingenuity he shows that, + under certain circumstances, the magne-crystallic force can cause the + centre of gravity of a highly magnetic body to retreat from the poles, and + the centre of gravity of a highly diamagnetic body to approach them. His + experiments root his mind more and more firmly in the conclusion that + 'neither attraction nor repulsion causes the set, or governs the final + position' of the crystal in the magnetic field. That the force which does + so is therefore 'distinct in its character and effects from the magnetic + and diamagnetic forms of force. On the other hand,' he continues, 'it has + a most manifest relation to the crystalline structure of bismuth and other + bodies, and therefore to the power by which their molecules are able to + build up the crystalline masses.' + </p> + <p> + And here follows one of those expressions which characterize the + conceptions of Faraday in regard to force generally:—'It appears to + me impossible to conceive of the results in any other way than by a mutual + reaction of the magnetic force, and the force of the particles of the + crystals upon each other.' He proves that the action of the force, though + thus molecular, is an action at a distance; he shows that a bismuth + crystal can cause a freely suspended magnetic needle to set parallel to + its magne-crystallic axis. Few living men are aware of the difficulty of + obtaining results like this, or of the delicacy necessary to their + attainment. 'But though it thus takes up the character of a force acting + at a distance, still it is due to that power of the particles which makes + them cohere in regular order and gives the mass its crystalline + aggregation, which we call at other times the attraction of aggregation, + and so often speak of as acting at insensible distances.' Thus he broods + over this new force, and looks at it from all possible points of + inspection. Experiment follows experiment, as thought follows thought. He + will not relinquish the subject as long as a hope exists of throwing more + light upon it. He knows full well the anomalous nature of the conclusion + to which his experiments lead him. But experiment to him is final, and he + will not shrink from the conclusion. 'This force,' he says, 'appears to me + to be very strange and striking in its character. It is not polar, for + there is no attraction or repulsion.' And then, as if startled by his own + utterance, he asks—'What is the nature of the mechanical force which + turns the crystal round, and makes it affect a magnet?'... 'I do not + remember,' he continues 'heretofore such a case of force as the present + one, where a body is brought into position only, without attraction or + repulsion.' + </p> + <p> + Plucker, the celebrated geometer already mentioned, who pursued + experimental physics for many years of his life with singular devotion and + success, visited Faraday in those days, and repeated before him his + beautiful experiments on magneto-optic action. Faraday repeated and + verified Plucker's observations, and concluded, what he at first seemed to + doubt, that Plucker's results and magne-crystallic action had the same + origin. + </p> + <p> + At the end of his papers, when he takes a last look along the line of + research, and then turns his eyes to the future, utterances quite as much + emotional as scientific escape from Faraday. 'I cannot,' he says, at the + end of his first paper on magne-crystallic action, 'conclude this series + of researches without remarking how rapidly the knowledge of molecular + forces grows upon us, and how strikingly every investigation tends to + develop more and more their importance, and their extreme attraction as an + object of study. A few years ago magnetism was to us an occult power, + affecting only a few bodies, now it is found to influence all bodies, and + to possess the most intimate relations with electricity, heat, chemical + action, light, crystallization, and through it, with the forces concerned + in cohesion; and we may, in the present state of things, well feel urged + to continue in our labours, encouraged by the hope of bringing it into a + bond of union with gravity itself.' + </p> + <p> + Supplementary remarks + </p> + <p> + A brief space will, perhaps, be granted me here to state the further + progress of an investigation which interested Faraday so much. Drawn by + the fame of Bunsen as a teacher, in the year 1848 I became a student in + the University of Marburg, in Hesse Cassel. Bunsen's behaviour to me was + that of a brother as well as that of a teacher, and it was also my + happiness to make the acquaintance and gain the friendship of Professor + Knoblauch, so highly distinguished by his researches on Radiant Heat. + Plucker's and Faraday's investigations filled all minds at the time, and + towards the end of 1849, Professor Knoblauch and myself commenced a joint + investigation of the entire question. Long discipline was necessary to + give us due mastery over it. Employing a method proposed by Dove, we + examined the optical properties of our crystals ourselves; and these + optical observations went hand in hand with our magnetic experiments. The + number of these experiments was very great, but for a considerable time no + fact of importance was added to those already published. At length, + however, it was our fortune to meet with various crystals whose deportment + could not be brought under the laws of magne-crystallic action enunciated + by Plucker. We also discovered instances which led us to suppose that the + magne-crystallic force was by no means independent, as alleged, of the + magnetism or diamagnetism of the mass of the crystal. Indeed, the more we + worked at the subject, the more clearly did it appear to us that the + deportment of crystals in the magnetic field was due, not to a force + previously unknown, but to the modification of the known forces of + magnetism and diamagnetism by crystalline aggregation. + </p> + <p> + An eminent example of magne-crystallic action adduced by Plucker, and + experimented on by Faraday, was Iceland spar. It is what in optics is + called a negative crystal, and according to the law of Plucker, the axis + of such a crystal was always repelled by a magnet. But we showed that it + was only necessary to substitute, in whole or in part, carbonate of iron + for carbonate of lime, thus changing the magnetic but not the optical + character of the crystal, to cause the axis to be attracted. That the + deportment of magnetic crystals is exactly antithetical to that of + diamagnetic crystals isomorphous with the magnetic ones, was proved to be + a general law of action. In all cases, the line which in a diamagnetic + crystal set equatorially, always set itself in an isomorphous magnetic + crystal axially. By mechanical compression other bodies were also made to + imitate the Iceland spar. + </p> + <p> + These and numerous other results bearing upon the question were published + at the time in the 'Philosophical Magazine' and in 'Poggendorff's + Annalen'; and the investigation of diamagnetism and magne-crystallic + action was subsequently continued by me in the laboratory of Professor + Magnus of Berlin. In December, 1851, after I had quitted Germany, Dr. + Bence Jones went to the Prussian capital to see the celebrated experiments + of Du Bois Reymond. Influenced, I suppose, by what he there heard, he + afterwards invited me to give a Friday evening discourse at the Royal + Institution. I consented, not without fear and trembling. For the Royal + Institution was to me a kind of dragon's den, where tact and strength + would be necessary to save me from destruction. On February 11, 1853, the + discourse was given, and it ended happily. I allude to these things, that + I may mention that, though my aim and object in that lecture was to + subvert the notions both of Faraday and Plucker, and to establish in + opposition to their views what I regarded as the truth, it was very far + from producing in Faraday either enmity or anger. At the conclusion of the + lecture, he quitted his accustomed seat, crossed the theatre to the corner + into which I had shrunk, shook me by the hand, and brought me back to the + table. Once more, subsequently, and in connection with a related question, + I ventured to differ from him still more emphatically. It was done out of + trust in the greatness of his character; nor was the trust misplaced. He + felt my public dissent from him; and it pained me afterwards to the quick + to think that I had given him even momentary annoyance. It was, however, + only momentary. His soul was above all littleness and proof to all + egotism. He was the same to me afterwards that he had been before; the + very chance expression which led me to conclude that he felt my dissent + being one of kindness and affection. + </p> + <p> + It required long subsequent effort to subdue the complications of + magne-crystallic action, and to bring under the dominion of elementary + principles the vast mass of facts which the experiments of Faraday and + Plucker had brought to light. It was proved by Reich, Edmond Becquerel, + and myself, that the condition of diamagnetic bodies, in virtue of which + they were repelled by the poles of a magnet, was excited in them by those + poles; that the strength of this condition rose and fell with, and was + proportional to, the strength of the acting magnet. It was not then any + property possessed permanently by the bismuth, and which merely required + the development of magnetism to act upon it, that caused the repulsion; + for then the repulsion would have been simply proportional to the strength + of the influencing magnet, whereas experiment proved it to augment as the + square of the strength. The capacity to be repelled was therefore not + inherent in the bismuth, but induced. So far an identity of action was + established between magnetic and diamagnetic bodies. After this the + deportment of magnetic bodies, 'normal' and 'abnormal'; crystalline, + amorphous, and compressed, was compared with that of crystalline, + amorphous, and compressed diamagnetic bodies; and by a series of + experiments, executed in the laboratory of this Institution, the most + complete antithesis was established between magnetism and diamagnetism. + This antithesis embraced the quality of polarity,—the theory of + reversed polarity, first propounded by Faraday, being proved to be true. + The discussion of the question was very brisk. On the Continent Professor + Wilhelm Weber was the ablest and most successful supporter of the doctrine + of diamagnetic polarity; and it was with an apparatus, devised by him and + constructed under his own superintendence, by Leyser of Leipzig, that the + last demands of the opponents of diamagnetic polarity were satisfied. The + establishment of this point was absolutely necessary to the explanation of + magne-crystallic action. + </p> + <p> + With that admirable instinct which always guided him, Faraday had seen + that it was possible, if not probable, that the diamagnetic force acts + with different degrees of intensity in different directions, through the + mass of a crystal. In his studies on electricity, he had sought an + experimental reply to the question whether crystalline bodies had not + different specific inductive capacities in different directions, but he + failed to establish any difference of the kind. His first attempt to + establish differences of diamagnetic action in different directions + through bismuth, was also a failure; but he must have felt this to be a + point of cardinal importance, for he returned to the subject in 1850, and + proved that bismuth was repelled with different degrees of force in + different directions. It seemed as if the crystal were compounded of two + diamagnetic bodies of different strengths, the substance being more + strongly repelled across the magne-crystallic axis than along it. The same + result was obtained independently, and extended to various other bodies, + magnetic as well as diamagnetic, and also to compressed substances, a + little subsequently by myself. + </p> + <p> + The law of action in relation to this point is, that in diamagnetic + crystals, the line along which the repulsion is a maximum, sets + equatorially in the magnetic field; while in magnetic crystals the line + along which the attraction is a maximum sets from pole to pole. Faraday + had said that the magne-crystallic force was neither attraction nor + repulsion. Thus far he was right. It was neither taken singly, but it was + both. By the combination of the doctrine of diamagnetic polarity with + these differential attractions and repulsions, and by paying due regard to + the character of the magnetic field, every fact brought to light in the + domain of magne-crystallic action received complete explanation. The most + perplexing of those facts were shown to result from the action of + mechanical couples, which the proved polarity both of magnetism and + diamagnetism brought into play. Indeed the thoroughness with which the + experiments of Faraday were thus explained, is the most striking possible + demonstration of the marvellous precision with which they were executed. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT______"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 11 + </h2> +<pre xml:space="preserve"> + (1) See Heat as a Mode of Motion, ninth edition, p. 75. + + (2) See Sir Wm. Thomson on Magne-crystallic Action. Phil. + Mag., 1851. +</pre> + <p> + <a name="link2HCH0012" id="link2HCH0012"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 12. + </h2> +<pre xml:space="preserve"> + Magnetism of flame and gases—atmospheric magnetism +</pre> + <p> + When an experimental result was obtained by Faraday it was instantly + enlarged by his imagination. I am acquainted with no mind whose power and + suddenness of expansion at the touch of new physical truth could be ranked + with his. Sometimes I have compared the action of his experiments on his + mind to that of highly combustible matter thrown into a furnace; every + fresh entry of fact was accompanied by the immediate development of light + and heat. The light, which was intellectual, enabled him to see far beyond + the boundaries of the fact itself, and the heat, which was emotional, + urged him to the conquest of this newly-revealed domain. But though the + force of his imagination was enormous, he bridled it like a mighty rider, + and never permitted his intellect to be overthrown. + </p> + <p> + In virtue of the expansive power which his vivid imagination conferred + upon him, he rose from the smallest beginnings to the grandest ends. + Having heard from Zantedeschi that Bancalari had established the magnetism + of flame, he repeated the experiments and augmented the results. He passed + from flames to gases, examining and revealing their magnetic and + diamagnetic powers; and then he suddenly rose from his bubbles of oxygen + and nitrogen to the atmospheric envelope of the earth itself, and its + relations to the great question of terrestrial magnetism. The rapidity + with which these ever-augmenting thoughts assumed the form of experiments + is unparalleled. His power in this respect is often best illustrated by + his minor investigations, and, perhaps, by none more strikingly than by + his paper 'On the Diamagnetic Condition of Flame and Gases,' published as + a letter to Mr. Richard Taylor, in the 'Philosophical Magazine' for + December, 1847. After verifying, varying, and expanding the results of + Bancalari, he submitted to examination heated air-currents, produced by + platinum spirals placed in the magnetic field, and raised to incandescence + by electricity. He then examined the magnetic deportment of gases + generally. Almost all of these gases are invisible; but he must, + nevertheless, track them in their unseen courses. He could not effect this + by mingling smoke with his gases, for the action of his magnet upon the + smoke would have troubled his conclusions. He, therefore, 'caught' his + gases in tubes, carried them out of the magnetic field, and made them + reveal themselves at a distance from the magnet. + </p> + <p> + Immersing one gas in another, he determined their differential action; + results of the utmost beauty being thus arrived at. Perhaps the most + important are those obtained with atmospheric air and its two + constituents. Oxygen, in various media, was strongly attracted by the + magnet; in coal-gas, for example, it was powerfully magnetic, whereas + nitrogen was diamagnetic. Some of the effects obtained with oxygen in + coal-gas were strikingly beautiful. When the fumes of chloride of ammonium + (a diamagnetic substance) were mingled with the oxygen, the cloud of + chloride behaved in a most singular manner,—'The attraction of iron + filings,' says Faraday, 'to a magnetic pole is not more striking than the + appearance presented by the oxygen under these circumstances.' + </p> + <p> + On observing this deportment the question immediately occurs to him,—Can + we not separate the oxygen of the atmosphere from its nitrogen by magnetic + analysis? It is the perpetual occurrence of such questions that marks the + great experimenter. The attempt to analyze atmospheric air by magnetic + force proved a failure, like the previous attempt to influence + crystallization by the magnet. The enormous comparative power of the force + of crystallization I have already assigned as a reason for the + incompetence of the magnet to determine molecular arrangement; in the + present instance the magnetic analysis is opposed by the force of + diffusion, which is also very strong comparatively. The same remark + applies to, and is illustrated by, another experiment subsequently + executed by Faraday. Water is diamagnetic, sulphate of iron is strongly + magnetic. He enclosed 'a dilute solution of sulphate of iron in a tube, + and placed the lower end of the tube between the poles of a powerful + horseshoe magnet for days together,' but he could produce 'no + concentration of the solution in the part near the magnet.' Here also the + diffusibility of the salt was too powerful for the force brought against + it. + </p> + <p> + The experiment last referred to is recorded in a paper presented to the + Royal Society on the 2nd August, 1850, in which he pursues the + investigation of the magnetism of gases. Newton's observations on + soap-bubbles were often referred to by Faraday. His delight in a + soap-bubble was like that of a boy, and he often introduced them into his + lectures, causing them, when filled with air, to float on invisible seas + of carbonic acid, and otherwise employing them as a means of illustration. + He now finds them exceedingly useful in his experiments on the magnetic + condition of gases. A bubble of air in a magnetic field occupied by air + was unaffected, save through the feeble repulsion of its envelope. A + bubble of nitrogen, on the contrary, was repelled from the magnetic axis + with a force far surpassing that of a bubble of air. The deportment of + oxygen in air 'was very impressive, the bubble being pulled inward or + towards the axial line, sharply and suddenly, as if the oxygen were highly + magnetic.' + </p> + <p> + He next labours to establish the true magnetic zero, a problem not so easy + as might at first sight be imagined. For the action of the magnet upon any + gas, while surrounded by air or any other gas, can only be differential; + and if the experiment were made in vacuo, the action of the envelope, in + this case necessarily of a certain thickness, would trouble the result. + While dealing with this subject, Faraday makes some noteworthy + observations regarding space. In reference to the Torricellian vacuum, he + says, 'Perhaps it is hardly necessary for me to state that I find both + iron and bismuth in such vacua perfectly obedient to the magnet. From such + experiments, and also from general observations and knowledge, it seems + manifest that the lines of magnetic force can traverse pure space, just as + gravitating force does, and as statical electrical forces do, and + therefore space has a magnetic relation of its own, and one that we shall + probably find hereafter to be of the utmost importance in natural + phenomena. But this character of space is not of the same kind as that + which, in relation to matter, we endeavour to express by the terms + magnetic and diamagnetic. To confuse these together would be to confound + space with matter, and to trouble all the conceptions by which we + endeavour to understand and work out a progressively clearer view of the + mode of action, and the laws of natural forces. It would be as if in + gravitation or electric forces, one were to confound the particles acting + on each other with the space across which they are acting, and would, I + think, shut the door to advancement. Mere space cannot act as matter acts, + even though the utmost latitude be allowed to the hypothesis of an ether; + and admitting that hypothesis, it would be a large additional assumption + to suppose that the lines of magnetic force are vibrations carried on by + it, whilst as yet we have no proof that time is required for their + propagation, or in what respect they may, in general character, assimilate + to or differ from their respective lines of gravitating, luminiferous, or + electric forces.' + </p> + <p> + Pure space he assumes to be the true magnetic zero, but he pushes his + inquiries to ascertain whether among material substances there may not be + some which resemble space. If you follow his experiments, you will soon + emerge into the light of his results. A torsion-beam was suspended by a + skein of cocoon silk; at one end of the beam was fixed a cross-piece 1 1/2 + inch long. Tubes of exceedingly thin glass, filled with various gases, and + hermetically sealed, were suspended in pairs from the two ends of the + cross-piece. The position of the rotating torsion-head was such that the + two tubes were at opposite sides of, and equidistant from, the magnetic + axis, that is to say from the line joining the two closely approximated + polar points of an electro-magnet. His object was to compare the magnetic + action of the gases in the two tubes. When one tube was filled with + oxygen, and the other with nitrogen, on the supervention of the magnetic + force, the oxygen was pulled towards the axis, the nitrogen being pushed + out. By turning the torsion-head they could be restored to their primitive + position of equidistance, where it is evident the action of the glass + envelopes was annulled. The amount of torsion necessary to re-establish + equidistance expressed the magnetic difference of the substances compared. + </p> + <p> + And then he compared oxygen with oxygen at different pressures. One of his + tubes contained the gas at the pressure of 30 inches of mercury, another + at a pressure of 15 inches of mercury, a third at a pressure of 10 inches, + while a fourth was exhausted as far as a good air-pump renders exhaustion + possible. 'When the first of these was compared with the other three, the + effect was most striking.' It was drawn towards the axis when the magnet + was excited, the tube containing the rarer gas being apparently driven + away, and the greater the difference between the densities of the two + gases, the greater was the energy of this action. + </p> + <p> + And now observe his mode of reaching a material magnetic zero. When a + bubble of nitrogen was exposed in air in the magnetic field, on the + supervention of the power, the bubble retreated from the magnet. A less + acute observer would have set nitrogen down as diamagnetic; but Faraday + knew that retreat, in a medium composed in part of oxygen, might be due to + the attraction of the latter gas, instead of to the repulsion of the gas + immersed in it. But if nitrogen be really diamagnetic, then a bubble or + bulb filled with the dense gas will overcome one filled with the rarer + gas. From the cross-piece of his torsion-balance he suspended his bulbs of + nitrogen, at equal distances from the magnetic axis, and found that the + rarefaction, or the condensation of the gas in either of the bulbs had not + the slightest influence. When the magnetic force was developed, the bulbs + remained in their first position, even when one was filled with nitrogen, + and the other as far as possible exhausted. Nitrogen, in fact, acted 'like + space itself'; it was neither magnetic nor diamagnetic. + </p> + <p> + He cannot conveniently compare the paramagnetic force of oxygen with iron, + in consequence of the exceeding magnetic intensity of the latter + substance; but he does compare it with the sulphate of iron, and finds + that, bulk for bulk, oxygen is equally magnetic with a solution of this + substance in water 'containing seventeen times the weight of the oxygen in + crystallized proto-sulphate of iron, or 3.4 times its weight of metallic + iron in that state of combination.' By its capability to deflect a fine + glass fibre, he finds that the attraction of this bulb of oxygen, + containing only 0.117 of a grain of the gas, at an average distance of + more than an inch from the magnetic axis, is about equal to the + gravitating force of the same amount of oxygen as expressed by its weight. + </p> + <p> + These facts could not rest for an instant in the mind of Faraday without + receiving that expansion to which I have already referred. 'It is hardly + necessary,' he writes, 'for me to say here that this oxygen cannot exist + in the atmosphere exerting such a remarkable and high amount of magnetic + force, without having a most important influence on the disposition of the + magnetism of the earth, as a planet; especially if it be remembered that + its magnetic condition is greatly altered by variations of its density and + by variations of its temperature. I think I see here the real cause of + many of the variations of that force, which have been, and are now so + carefully watched on different parts of the surface of the globe. The + daily variation, and the annual variation, both seem likely to come under + it; also very many of the irregular continual variations, which the + photographic process of record renders so beautifully manifest. If such + expectations be confirmed, and the influence of the atmosphere be found + able to produce results like these, then we shall probably find a new + relation between the aurora borealis and the magnetism of the earth, + namely, a relation established, more or less, through the air itself in + connection with the space above it; and even magnetic relations and + variations, which are not as yet suspected, may be suggested and rendered + manifest and measurable, in the further development of what I will venture + to call Atmospheric Magnetism. I may be over-sanguine in these + expectations, but as yet I am sustained in them by the apparent reality, + simplicity, and sufficiency of the cause assumed, as it at present appears + to my mind. As soon as I have submitted these views to a close + consideration, and the test of accordance with observation, and, where + applicable, with experiments also, I will do myself the honour to bring + them before the Royal Society.' + </p> + <p> + Two elaborate memoirs are then devoted to the subject of Atmospheric + Magnetism; the first sent to the Royal Society on the 9th of October, and + the second on the 19th of November, 1850. In these memoirs he discusses + the effects of heat and cold upon the magnetism of the air, and the action + on the magnetic needle, which must result from thermal changes. By the + convergence and divergence of the lines of terrestrial magnetic force, he + shows how the distribution of magnetism, in the earth's atmosphere, is + effected. He applies his results to the explanation of the Annual and of + the Diurnal Variation: he also considers irregular variations, including + the action of magnetic storms. He discusses, at length, the observations + at St. Petersburg, Greenwich, Hobarton, St. Helena, Toronto, and the Cape + of Good Hope; believing that the facts, revealed by his experiments, + furnish the key to the variations observed at all these places. + </p> + <p> + In the year 1851, I had the honour of an interview with Humboldt, in + Berlin, and his parting words to me then were, 'Tell Faraday that I + entirely agree with him, and that he has, in my opinion, completely + explained the variation of the declination.' Eminent men have since + informed me that Humboldt was hasty in expressing this opinion. In fact, + Faraday's memoirs on atmospheric magnetism lost much of their force—perhaps + too much—through the important discovery of the relation of the + variation of the declination to the number of the solar spots. But I agree + with him and M. Edmond Becquerel, who worked independently at this + subject, in thinking, that a body so magnetic as oxygen, swathing the + earth, and subject to variations of temperature, diurnal and annual, must + affect the manifestations of terrestrial magnetism. (1) The air that + stands upon a single square foot of the earth's surface is, according to + Faraday, equivalent in magnetic force to 8160 lbs. of crystallized + protosulphate of iron. Such a substance cannot be absolutely neutral as + regards the deportment of the magnetic needle. But Faraday's writings on + this subject are so voluminous, and the theoretic points are so novel and + intricate, that I shall postpone the complete analysis of these researches + to a time when I can lay hold of them more completely than my other duties + allow me to do now. + </p> + <p> + Footnote to Chapter 12 + </p> +<pre xml:space="preserve"> + (1) This persuasion has been greatly strengthened by the + recent perusal of a paper by Mr. Baxendell. +</pre> + <p> + <a name="link2HCH0013" id="link2HCH0013"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 13. + </h2> +<pre xml:space="preserve"> + Speculations: nature of matter: lines of force +</pre> + <p> + The scientific picture of Faraday would not be complete without a + reference to his speculative writings. On Friday, January 19, 1844, he + opened the weekly evening-meetings of the Royal Institution by a discourse + entitled 'A speculation touching Electric Conduction and the nature of + Matter.' In this discourse he not only attempts the overthrow of Dalton's + Theory of Atoms, but also the subversion of all ordinary scientific ideas + regarding the nature and relations of Matter and Force. He objected to the + use of the term atom:—'I have not yet found a mind,' he says, 'that + did habitually separate it from its accompanying temptations; and there + can be no doubt that the words definite proportions, equivalent, primes, + &c., which did and do fully express all the facts of what is usually + called the atomic theory in chemistry, were dismissed because they were + not expressive enough, and did not say all that was in the mind of him who + used the word atom in their stead.' + </p> + <p> + A moment will be granted me to indicate my own view of Faraday's position + here. The word 'atom' was not used in the stead of definite proportions, + equivalents, or primes. These terms represented facts that followed from, + but were not equivalent to, the atomic theory. Facts cannot satisfy the + mind: and the law of definite combining proportions being once + established, the question 'why should combination take place according to + that law?' is inevitable. Dalton answered this question by the enunciation + of the Atomic Theory, the fundamental idea of which is, in my opinion, + perfectly secure. The objection of Faraday to Dalton might be urged with + the same substantial force against Newton: it might be stated with regard + to the planetary motions that the laws of Kepler revealed the facts; that + the introduction of the principle of gravitation was an addition to the + facts. But this is the essence of all theory. The theory is the backward + guess from fact to principle; the conjecture, or divination regarding + something, which lies behind the facts, and from which they flow in + necessary sequence. If Dalton's theory, then, account for the definite + proportions observed in the combinations of chemistry, its justification + rests upon the same basis as that of the principle of gravitation. All + that can in strictness be said in either case is that the facts occur as + if the principle existed. + </p> + <p> + The manner in which Faraday himself habitually deals with his hypotheses + is revealed in this lecture. He incessantly employed them to gain + experimental ends, but he incessantly took them down, as an architect + removes the scaffolding when the edifice is complete. 'I cannot but + doubt,' he says, 'that he who as a mere philosopher has most power of + penetrating the secrets of nature, and guessing by hypothesis at her mode + of working, will also be most careful for his own safe progress and that + of others, to distinguish the knowledge which consists of assumption, by + which I mean theory and hypothesis, from that which is the knowledge of + facts and laws.' Faraday himself, in fact, was always 'guessing by + hypothesis,' and making theoretic divination the stepping-stone to his + experimental results. + </p> + <p> + I have already more than once dwelt on the vividness with which he + realised molecular conditions; we have a fine example of this strength and + brightness of imagination in the present 'speculation.' He grapples with + the notion that matter is made up of particles, not in absolute contact, + but surrounded by interatomic space. 'Space,' he observes, 'must be taken + as the only continuous part of a body so constituted. Space will permeate + all masses of matter in every direction like a net, except that in place + of meshes it will form cells, isolating each atom from its neighbours, + itself only being continuous.' + </p> + <p> + Let us follow out this notion; consider, he argues, the case of a + non-conductor of electricity, such for example as shell-lac, with its + molecules, and intermolecular spaces running through the mass. In its case + space must be an insulator; for if it were a conductor it would resemble + 'a fine metallic web,' penetrating the lac in every direction. But the + fact is that it resembles the wax of black sealing-wax, which surrounds + and insulates the particles of conducting carbon, interspersed throughout + its mass. In the case of shell-lac, therefore, space is an insulator. + </p> + <p> + But now, take the case of a conducting metal. Here we have, as before, the + swathing of space round every atom. If space be an insulator there can be + no transmission of electricity from atom to atom. But there is + transmission; hence space is a conductor. Thus he endeavours to hamper the + atomic theory. 'The reasoning,' he says, 'ends in a subversion of that + theory altogether; for if space be an insulator it cannot exist in + conducting bodies, and if it be a conductor it cannot exist in insulating + bodies. Any ground of reasoning,' he adds, as if carried away by the + ardour of argument, 'which tends to such conclusions as these must in + itself be false.' + </p> + <p> + He then tosses the atomic theory from horn to horn of his dilemmas. What + do we know, he asks, of the atom apart from its force? You imagine a + nucleus which may be called a, and surround it by forces which may be + called m; 'to my mind the a or nucleus vanishes, and the substance + consists in the powers of m. And indeed what notion can we form of the + nucleus independent of its powers? What thought remains on which to hang + the imagination of an a independent of the acknowledged forces?' Like + Boscovich, he abolishes the atom, and puts a 'centre of force' in its + place. + </p> + <p> + With his usual courage and sincerity he pushes his view to its utmost + consequences. 'This view of the constitution of matter,' he continues, + 'would seem to involve necessarily the conclusion that matter fills all + space, or at least all space to which gravitation extends; for gravitation + is a property of matter dependent on a certain force, and it is this force + which constitutes the matter. In that view matter is not merely mutually + penetrable; (1) but each atom extends, so to say, throughout the whole of + the solar system, yet always retaining its own centre of force.' + </p> + <p> + It is the operation of a mind filled with thoughts of this profound, + strange, and subtle character that we have to take into account in dealing + with Faraday's later researches. A similar cast of thought pervades a + letter addressed by Faraday to Mr. Richard Phillips, and published in the + 'Philosophical Magazine' for May, 1846. It is entitled 'Thoughts on + Ray-vibrations,' and it contains one of the most singular speculations + that ever emanated from a scientific mind. It must be remembered here, + that though Faraday lived amid such speculations he did not rate them + highly, and that he was prepared at any moment to change them or let them + go. They spurred him on, but they did not hamper him. His theoretic + notions were fluent; and when minds less plastic than his own attempted to + render those fluxional images rigid, he rebelled. He warns Phillips + moreover, that from first to last, 'he merely threw out as matter for + speculation the vague impressions of his mind; for he gave nothing as the + result of sufficient consideration, or as the settled conviction, or even + probable conclusion at which he had arrived.' + </p> + <p> + The gist of this communication is that gravitating force acts in lines + across space, and that the vibrations of light and radiant heat consist in + the tremors of these lines of force. 'This notion,' he says, 'as far as it + is admitted, will dispense with the ether, which, in another view is + supposed to be the medium in which these vibrations take place.' And he + adds further on, that his view 'endeavours to dismiss the ether but not + the vibrations.' The idea here set forth is the natural supplement of his + previous notion, that it is gravitating force which constitutes matter, + each atom extending, so to say, throughout the whole of the solar system. + </p> + <p> + The letter to Mr. Phillips winds up with this beautiful conclusion:— + </p> + <p> + 'I think it likely that I have made many mistakes in the preceding pages, + for even to myself my ideas on this point appear only as the shadow of a + speculation, or as one of those impressions upon the mind which are + allowable for a time as guides to thought and research. He who labours in + experimental inquiries, knows how numerous these are, and how often their + apparent fitness and beauty vanish before the progress and development of + real natural truth.' + </p> + <p> + Let it then be remembered that Faraday entertained notions regarding + matter and force altogether distinct from the views generally held by + scientific men. Force seemed to him an entity dwelling along the line in + which it is exerted. The lines along which gravity acts between the sun + and earth seem figured in his mind as so many elastic strings; indeed he + accepts the assumed instantaneity of gravity as the expression of the + enormous elasticity of the 'lines of weight.' Such views, fruitful in the + case of magnetism, barren, as yet, in the case of gravity, explain his + efforts to transform this latter force. When he goes into the open air and + permits his helices to fall, to his mind's eye they are tearing through + the lines of gravitating power, and hence his hope and conviction that an + effect would and ought to be produced. It must ever be borne in mind that + Faraday's difficulty in dealing with these conceptions was at bottom the + same as that of Newton; that he is in fact trying to overleap this + difficulty, and with it probably the limits prescribed to the intellect + itself. + </p> + <p> + The idea of lines of magnetic force was suggested to Faraday by the linear + arrangement of iron filings when scattered over a magnet. He speaks of and + illustrates by sketches, the deflection, both convergent and divergent, of + the lines of force, when they pass respectively through magnetic and + diamagnetic bodies. These notions of concentration and divergence are also + based on the direct observation of his filings. So long did he brood upon + these lines; so habitually did he associate them with his experiments on + induced currents, that the association became 'indissoluble,' and he could + not think without them. 'I have been so accustomed,' he writes, 'to employ + them, and especially in my last researches, that I may have unwittingly + become prejudiced in their favour, and ceased to be a clear-sighted judge. + Still, I have always endeavoured to make experiment the test and + controller of theory and opinion; but neither by that nor by close + cross-examination in principle, have I been made aware of any error + involved in their use.' + </p> + <p> + In his later researches on magne-crystallic action, the idea of lines of + force is extensively employed; it indeed led him to an experiment which + lies at the root of the whole question. In his subsequent researches on + Atmospheric Magnetism the idea receives still wider application, showing + itself to be wonderfully flexible and convenient. Indeed without this + conception the attempt to seize upon the magnetic actions, possible or + actual, of the atmosphere would be difficult in the extreme; but the + notion of lines of force, and of their divergence and convergence, guides + Faraday without perplexity through all the intricacies of the question. + After the completion of those researches, and in a paper forwarded to the + Royal Society on October 22, 1851, he devotes himself to the formal + development and illustration of his favourite idea. The paper bears the + title, 'On lines of magnetic force, their definite character, and their + distribution within a magnet and through space.' A deep reflectiveness is + the characteristic of this memoir. In his experiments, which are perfectly + beautiful and profoundly suggestive, he takes but a secondary delight. His + object is to illustrate the utility of his conception of lines of force. + 'The study of these lines,' he says, 'has at different times been greatly + influential in leading me to various results which I think prove their + utility as well as fertility.' + </p> + <p> + Faraday for a long period used the lines of force merely as 'a + representative idea.' He seemed for a time averse to going further in + expression than the lines themselves, however much further he may have + gone in idea. That he believed them to exist at all times round a magnet, + and irrespective of the existence of magnetic matter, such as iron + filings, external to the magnet, is certain. No doubt the space round + every magnet presented itself to his imagination as traversed by loops of + magnetic power; but he was chary in speaking of the physical substratum of + those loops. Indeed it may be doubted whether the physical theory of lines + of force presented itself with any distinctness to his own mind. The + possible complicity of the luminiferous ether in magnetic phenomena was + certainly in his thoughts. 'How the magnetic force,' he writes, 'is + transferred through bodies or through space we know not; whether the + result is merely action at a distance, as in the case of gravity; or by + some intermediate agency, as in the case of light, heat, the electric + current, and (as I believe) static electric action. The idea of magnetic + fluids, as applied by some, or of Magnetic centres of action, does not + include that of the latter kind of transmission, but the idea of lines of + force does.' And he continues thus:—'I am more inclined to the + notion that in the transmission of the (magnetic) force there is such an + action (an intermediate agency) external to the magnet, than that the + effects are merely attraction and repulsion at a distance. Such an + affection may be a function of the ether; for it is not at all unlikely + that, if there be an ether, it should have other uses than simply the + conveyance of radiations.' When he speaks of the magnet in certain cases, + 'revolving amongst its own forces,' he appears to have some conception of + this kind in view. + </p> + <p> + A great part of the investigation completed in October, 1851, was taken up + with the motions of wires round the poles of a magnet and the converse. He + carried an insulated wire along the axis of a bar magnet from its pole to + its equator, where it issued from the magnet, and was bent up so as to + connect its two ends. A complete circuit, no part of which was in contact + with the magnet, was thus obtained. He found that when the magnet and the + external wire were rotated together no current was produced; whereas, when + either of them was rotated and the other left at rest currents were + evolved. He then abandoned the axial wire, and allowed the magnet itself + to take its place; the result was the same. (2) It was the relative motion + of the magnet and the loop that was effectual in producing a current. + </p> + <p> + The lines of force have their roots in the magnet, and though they may + expand into infinite space, they eventually return to the magnet. Now + these lines may be intersected close to the magnet or at a distance from + it. Faraday finds distance to be perfectly immaterial so long as the + number of lines intersected is the same. For example, when the loop + connecting the equator and the pole of his barmagnet performs one complete + revolution round the magnet, it is manifest that all the lines of force + issuing from the magnet are once intersected. Now it matters not whether + the loop be ten feet or ten inches in length, it matters not how it may be + twisted and contorted, it matters not how near to the magnet or how + distant from it the loop may be, one revolution always produces the same + amount of current electricity, because in all these cases all the lines of + force issuing from the magnet are once intersected and no more. + </p> + <p> + From the external portion of the circuit he passes in idea to the + internal, and follows the lines of force into the body of the magnet + itself. His conclusion is that there exist lines of force within the + magnet of the same nature as those without. What is more, they are exactly + equal in amount to those without. They have a relation in direction to + those without; and in fact are continuations of them.... 'Every line of + force, therefore, at whatever distance it may be taken from the magnet, + must be considered as a closed circuit, passing in some part of its course + through the magnet, and having an equal amount of force in every part of + its course.' + </p> + <p> + All the results here described were obtained with moving metals. 'But,' he + continues with profound sagacity, 'mere motion would not generate a + relation, which had not a foundation in the existence of some previous + state; and therefore the quiescent metals must be in some relation to the + active centre of force,' that is to the magnet. He here touches the core + of the whole question, and when we can state the condition into which the + conducting wire is thrown before it is moved, we shall then be in a + position to understand the physical constitution of the electric current + generated by its motion. + </p> + <p> + In this inquiry Faraday worked with steel magnets, the force of which + varies with the distance from the magnet. He then sought a uniform field + of magnetic force, and found it in space as affected by the magnetism of + the earth. His next memoir, sent to the Royal Society, December 31, 1851, + is 'on the employment of the Induced Magnetoelectro Current as a test and + measure of magnetic forces.' He forms rectangles and rings, and by + ingenious and simple devices collects the opposed currents which are + developed in them by rotation across the terrestrial lines of magnetic + force. He varies the shapes of his rectangles while preserving their areas + constant, and finds that the constant area produces always the same amount + of current per revolution. The current depends solely on the number of + lines of force intersected, and when this number is kept constant the + current remains constant too. Thus the lines of magnetic force are + continually before his eyes, by their aid he colligates his facts, and + through the inspirations derived from them he vastly expands the + boundaries of our experimental knowledge. The beauty and exactitude of the + results of this investigation are extraordinary. I cannot help thinking + while I dwell upon them, that this discovery of magneto-electricity is the + greatest experimental result ever obtained by an investigator. It is the + Mont Blanc of Faraday's own achievements. He always worked at great + elevations, but a higher than this he never subsequently attained. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT_______"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 13 + </h2> +<pre xml:space="preserve"> + (1) He compares the interpenetration of two atoms to the + coalescence of two distinct waves, which though for a moment + blended to a single mass, preserve their individuality, and + afterwards separate. + + (2) In this form the experiment is identical with one made + twenty years earlier. See page 34. +</pre> + <p> + <a name="link2HCH0014" id="link2HCH0014"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 14. + </h2> +<pre xml:space="preserve"> + Unity and convertibility of natural forces: theory of the + electric current. +</pre> + <p> + The terms unity and convertibility, as applied to natural forces, are + often employed in these investigations, many profound and beautiful + thoughts respecting these subjects being expressed in Faraday's memoirs. + Modern inquiry has, however, much augmented our knowledge of the + relationship of natural forces, and it seems worth while to say a few + words here, tending to clear up certain misconceptions which appear to + exist among philosophic writers regarding this relationship. + </p> + <p> + The whole stock of energy or working-power in the world consists of + attractions, repulsions, and motions. If the attractions and repulsions + are so circumstanced as to be able to produce motion, they are sources of + working-power, but not otherwise. Let us for the sake of simplicity + confine our attention to the case of attraction. The attraction exerted + between the earth and a body at a distance from the earth's surface is a + source of working-power; because the body can be moved by the attraction, + and in falling to the earth can perform work. When it rests upon the + earth's surface it is not a source of power or energy, because it can fall + no further. But though it has ceased to be a source of energy, the + attraction of gravity still acts as a force, which holds the earth and + weight together. + </p> + <p> + The same remarks apply to attracting atoms and molecules. As long as + distance separates them, they can move across it in obedience to the + attraction, and the motion thus produced may, by proper appliances, be + caused to perform mechanical work. When, for example, two atoms of + hydrogen unite with one of oxygen, to form water the atoms are first drawn + towards each other—they move, they clash, and then by virtue of + their resiliency, they recoil and quiver. To this quivering motion we give + the name of heat. Now this quivering motion is merely the redistribution + of the motion produced by the chemical affinity; and this is the only + sense in which chemical affinity can be said to be converted into heat. We + must not imagine the chemical attraction destroyed, or converted into + anything else. For the atoms, when mutually clasped to form a molecule of + water, are held together by the very attraction which first drew them + towards each other. That which has really been expended is the pull + exerted through the space by which the distance between the atoms has been + diminished. + </p> + <p> + If this be understood, it will be at once seen that gravity may in this + sense be said to be convertible into heat; that it is in reality no more + an outstanding and inconvertible agent, as it is sometimes stated to be, + than chemical affinity. By the exertion of a certain pull, through a + certain space, a body is caused to clash with a certain definite velocity + against the earth. Heat is thereby developed, and this is the only sense + in which gravity can be said to be converted into heat. In no case is the + force which produces the motion annihilated or changed into anything else. + The mutual attraction of the earth and weight exists when they are in + contact as when they were separate; but the ability of that attraction to + employ itself in the production of motion does not exist. + </p> + <p> + The transformation, in this case, is easily followed by the mind's eye. + First, the weight as a whole is set in motion by the attraction of + gravity. This motion of the mass is arrested by collision with the earth; + being broken up into molecular tremors, to which we give the name of heat. + </p> + <p> + And when we reverse the process, and employ those tremors of heat to raise + a weight, as is done through the intermediation of an elastic fluid in the + steam-engine, a certain definite portion of the molecular motion is + destroyed in raising the weight. In this sense, and this sense only, can + the heat be said to be converted into gravity, or more correctly, into + potential energy of gravity. It is not that the destruction of the heat + has created any new attraction, but simply that the old attraction has now + a power conferred upon it, of exerting a certain definite pull in the + interval between the starting-point of the falling weight and its + collision with the earth. + </p> + <p> + So also as regards magnetic attraction: when a sphere of iron placed at + some distance from a magnet rushes towards the magnet, and has its motion + stopped by collision, an effect mechanically the same as that produced by + the attraction of gravity occurs. The magnetic attraction generates the + motion of the mass, and the stoppage of that motion produces heat. In this + sense, and in this sense only, is there a transformation of magnetic work + into heat. And if by the mechanical action of heat, brought to bear by + means of a suitable machine, the sphere be torn from the magnet and again + placed at a distance, a power of exerting a pull through that distance, + and producing a new motion of the sphere, is thereby conferred upon the + magnet; in this sense, and in this sense only, is the heat converted into + magnetic potential energy. + </p> + <p> + When, therefore, writers on the conservation of energy speak of tensions + being 'consumed' and 'generated,' they do not mean thereby that old + attractions have been annihilated and new ones brought into existence, but + that, in the one case, the power of the attraction to produce motion has + been diminished by the shortening of the distance between the attracting + bodies, and that in the other case the power of producing motion has been + augmented by the increase of the distance. These remarks apply to all + bodies, whether they be sensible masses or molecules. + </p> + <p> + Of the inner quality that enables matter to attract matter we know + nothing; and the law of conservation makes no statement regarding that + quality. It takes the facts of attraction as they stand, and affirms only + the constancy of working-power. That power may exist in the form of + MOTION; or it may exist in the form of FORCE, with distance to act + through. The former is dynamic energy, the latter is potential energy, the + constancy of the sum of both being affirmed by the law of conservation. + The convertibility of natural forces consists solely in transformations of + dynamic into potential, and of potential into dynamic, energy, which are + incessantly going on. In no other sense has the convertibility of force, + at present, any scientific meaning. + </p> + <p> + By the contraction of a muscle a man lifts a weight from the earth. But + the muscle can contract only through the oxidation of its own tissue or of + the blood passing through it. Molecular motion is thus converted into + mechanical motion. Supposing the muscle to contract without raising the + weight, oxidation would also occur, but the whole of the heat produced by + this oxidation would be liberated in the muscle itself. Not so when it + performs external work; to do that work a certain definite portion of the + heat of oxidation must be expended. It is so expended in pulling the + weight away from the earth. If the weight be permitted to fall, the heat + generated by its collision with the earth would exactly make up for that + lacking in the muscle during the lifting of the weight. In the case here + supposed, we have a conversion of molecular muscular action into potential + energy of gravity; and a conversion of that potential energy into heat; + the heat, however, appearing at a distance from its real origin in the + muscle. The whole process consists of a transference of molecular motion + from the muscle to the weight, and gravitating force is the mere + go-between, by means of which the transference is effected. + </p> + <p> + These considerations will help to clear our way to the conception of the + transformations which occur when a wire is moved across the lines of force + in a magnetic field. In this case it is commonly said we have a conversion + of magnetism into electricity. But let us endeavour to understand what + really occurs. For the sake of simplicity, and with a view to its + translation into a different one subsequently, let us adopt for a moment + the provisional conception of a mixed fluid in the wire, composed of + positive and negative electricities in equal quantities, and therefore + perfectly neutralizing each other when the wire is still. By the motion of + the wire, say with the hand, towards the magnet, what the Germans call a + Scheidungs-Kraft—a separating force—is brought into play. This + force tears the mixed fluids asunder, and drives them in two currents, the + one positive and the other negative, in two opposite directions through + the wire. The presence of these currents evokes a force of repulsion + between the magnet and the wire; and to cause the one to approach the + other, this repulsion must be overcome. The overcoming of this repulsion + is, in fact, the work done in separating and impelling the two + electricities. When the wire is moved away from the magnet, a + Scheidungs-Kraft, or separating force, also comes into play; but now it is + an attraction that has to be surmounted. In surmounting it, currents are + developed in directions opposed to the former; positive takes the place of + negative, and negative the place of positive; the overcoming of the + attraction being the work done in separating and impelling the two + electricities. + </p> + <p> + The mechanical action occurring here is different from that occurring + where a sphere of soft iron is withdrawn from a magnet, and again + attracted. In this case muscular force is expended during the act of + separation; but the attraction of the magnet effects the reunion. In the + case of the moving wire also we overcome a resistance in separating it + from the magnet, and thus far the action is mechanically the same as the + separation of the sphere of iron. But after the wire has ceased moving, + the attraction ceases; and so far from any action occurring similar to + that which draws the iron sphere back to the magnet, we have to overcome a + repulsion to bring them together. + </p> + <p> + There is no potential energy conferred either by the removal or by the + approach of the wire, and the only power really transformed or converted, + in the experiment, is muscular power. Nothing that could in strictness be + called a conversion of magnetism into electricity occurs. The muscular + oxidation that moves the wire fails to produce within the muscle its due + amount of heat, a portion of that heat, equivalent to the resistance + overcome, appearing in the moving wire instead. + </p> + <p> + Is this effect an attraction and a repulsion at a distance? If so, why + should both cease when the wire ceases to move? In fact, the deportment of + the wire resembles far more that of a body moving in a resisting medium + than anything else; the resistance ceasing when the motion is suspended. + Let us imagine the case of a liquid so mobile that the hand may be passed + through it to and fro, without encountering any sensible resistance. It + resembles the motion of a conductor in the unexcited field of an + electro-magnet. Now, let us suppose a body placed in the liquid, or acting + on it, which confers upon it the property of viscosity; the hand would no + longer move freely. During its motion, but then only, resistance would be + encountered and overcome. Here we have rudely represented the case of the + excited magnetic field, and the result in both cases would be + substantially the same. In both cases heat would, in the end, be generated + outside of the muscle, its amount being exactly equivalent to the + resistance overcome. + </p> + <p> + Let us push the analogy a little further; suppose in the case of the fluid + rendered viscous, as assumed a moment ago, the viscosity not to be so + great as to prevent the formation of ripples when the hand is passed + through the liquid. Then the motion of the hand, before its final + conversion into heat, would exist for a time as wave-motion, which, on + subsiding, would generate its due equivalent of heat. This intermediate + stage, in the case of our moving wire, is represented by the period during + which the electric current is flowing through it; but that current, like + the ripples of our liquid, soon subsides, being, like them, converted into + heat. + </p> + <p> + Do these words shadow forth anything like the reality? Such speculations + cannot be injurious if they are enunciated without dogmatism. I do confess + that ideas such as these here indicated exercise a strong fascination on + my mind. Is then the magnetic field really viscous, and if so, what + substance exists in it and the wire to produce the viscosity? Let us first + look at the proved effects, and afterwards turn our thoughts back upon + their cause. When the wire approaches the magnet, an action is evoked + within it, which travels through it with a velocity comparable to that of + light. One substance only in the universe has been hitherto proved + competent to transmit power at this velocity; the luminiferous ether. Not + only its rapidity of progression, but its ability to produce the motion of + light and heat, indicates that the electric current is also motion. (1) + Further, there is a striking resemblance between the action of good and + bad conductors as regards electricity, and the action of diathermanous and + adiathermanous bodies as regards radiant heat. The good conductor is + diathermanous to the electric current; it allows free transmission without + the development of heat. The bad conductor is adiathermanous to the + electric current, and hence the passage of the latter is accompanied by + the development of heat. I am strongly inclined to hold the electric + current, pure and simple, to be a motion of the ether alone; good + conductors being so constituted that the motion may be propagated through + their ether without sensible transfer to their atoms, while in the case of + bad conductors this transfer is effected, the transferred motion appearing + as heat. (2) + </p> + <p> + I do not know whether Faraday would have subscribed to what is here + written; probably his habitual caution would have prevented him from + committing himself to anything so definite. But some such idea filled his + mind and coloured his language through all the later years of his life. I + dare not say that he has been always successful in the treatment of these + theoretic notions. In his speculations he mixes together light and + darkness in varying proportions, and carries us along with him through + strong alternations of both. It is impossible to say how a certain amount + of mathematical training would have affected his work. We cannot say what + its influence would have been upon that force of inspiration that urged + him on; whether it would have daunted him, and prevented him from driving + his adits into places where no theory pointed to a lode. If so, then we + may rejoice that this strong delver at the mine of natural knowledge was + left free to wield his mattock in his own way. It must be admitted, that + Faraday's purely speculative writings often lack that precision which the + mathematical habit of thought confers. Still across them flash frequent + gleams of prescient wisdom which will excite admiration throughout all + time; while the facts, relations, principles, and laws which his + experiments have established are sure to form the body of grand theories + yet to come. + </p> + <p> + <a name="link2H_FOOT" id="link2H_FOOT________"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Footnotes to Chapter 14 + </h2> +<pre xml:space="preserve"> + (1) Mr. Clerk Maxwell has recently published an exceedingly + important investigation connected with this question. Even + in the non-mathematical portions of the memoirs of Mr. + Maxwell, the admirable spirit of his philosophy is + sufficiently revealed. As regards the employment of + scientific imagery, I hardly know his equal in power of + conception and clearness of definition. + + (2) One important difference, of course, exists between the + effect of motion in the magnetic field, and motion in a + resisting medium. In the former case the heat is generated + in the moving conductor, in the latter it is in part + generated in the medium. +</pre> + <p> + <a name="link2HCH0015" id="link2HCH0015"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 15. + </h2> +<pre xml:space="preserve"> + Summary. +</pre> + <p> + When from an Alpine height the eye of the climber ranges over the + mountains, he finds that for the most part they resolve themselves into + distinct groups, each consisting of a dominant mass surrounded by peaks of + lesser elevation. The power which lifted the mightier eminences, in nearly + all cases lifted others to an almost equal height. And so it is with the + discoveries of Faraday. As a general rule, the dominant result does not + stand alone, but forms the culminating point of a vast and varied mass of + inquiry. In this way, round about his great discovery of Magneto-electric + Induction, other weighty labours group themselves. His investigations on + the Extra Current; on the Polar and other Condition of Diamagnetic Bodies; + on Lines of Magnetic Force, their definite character and distribution; on + the employment of the Induced Magneto-electric Current as a measure and + test of Magnetic Action; on the Revulsive Phenomena of the magnetic field, + are all, notwithstanding the diversity of title, researches in the domain + of Magneto-electric Induction. + </p> + <p> + Faraday's second group of researches and discoveries embrace the chemical + phenomena of the current. The dominant result here is the great law of + definite Electro-chemical Decomposition, around which are massed various + researches on Electro-chemical Conduction and on Electrolysis both with + the Machine and with the Pile. To this group also belongs his analysis of + the Contact Theory, his inquiries as to the Source of Voltaic Electricity, + and his final development of the Chemical Theory of the pile. + </p> + <p> + His third great discovery is the Magnetization of Light, which I should + liken to the Weisshorn among mountains—high, beautiful, and alone. + </p> + <p> + The dominant result of his fourth group of researches is the discovery of + Diamagnetism, announced in his memoir as the Magnetic Condition of all + Matter, round which are grouped his inquiries on the Magnetism of Flame + and Gases; on Magne-crystallic action, and on Atmospheric Magnetism, in + its relations to the annual and diurnal variation of the needle, the full + significance of which is still to be shown. + </p> + <p> + These are Faraday's most massive discoveries, and upon them his fame must + mainly rest. But even without them, sufficient would remain to secure for + him a high and lasting scientific reputation. We should still have his + researches on the Liquefaction of Gases; on Frictional Electricity; on the + Electricity of the Gymnotus; on the source of Power in the Hydro-electric + machine, the last two investigations being untouched in the foregoing + memoir; on Electro-magnetic Rotations; on Regelation; all his more purely + Chemical Researches, including his discovery of Benzol. Besides these he + published a multitude of minor papers, most of which, in some way or + other, illustrate his genius. I have made no allusion to his power and + sweetness as a lecturer. Taking him for all in all, I think it will be + conceded that Michael Faraday was the greatest experimental philosopher + the world has ever seen; and I will add the opinion, that the progress of + future research will tend, not to dim or to diminish, but to enhance and + glorify the labours of this mighty investigator. + </p> + <p> + <a name="link2HCH0016" id="link2HCH0016"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + Chapter 16. + </h2> +<pre xml:space="preserve"> + Illustrations of Character. +</pre> + <p> + Thus far I have confined myself to topics mainly interesting to the man of + science, endeavouring, however, to treat them in a manner unrepellent to + the general reader who might wish to obtain a notion of Faraday as a + worker. On others will fall the duty of presenting to the world a picture + of the man. But I know you will permit me to add to the foregoing analysis + a few personal reminiscences and remarks, tending to connect Faraday with + a wider world than that of science—namely, with the general human + heart. + </p> + <p> + One word in reference to his married life, in addition to what has been + already said, may find a place here. As in the former case, Faraday shall + be his own spokesman. The following paragraph, though written in the third + person, is from his hand:—'On June 12, 1821, he married, an event + which more than any other contributed to his earthly happiness and + healthful state of mind. The union has continued for twenty-eight years + and has in no wise changed, except in the depth and strength of its + character.' + </p> + <p> + Faraday's immediate forefathers lived in a little place called Clapham + Wood Hall, in Yorkshire. Here dwelt Robert Faraday and Elizabeth his wife, + who had ten children, one of them, James Faraday, born in 1761, being + father to the philosopher. A family tradition exists that the Faradays + came originally from Ireland. Faraday himself has more than once expressed + to me his belief that his blood was in part Celtic, but how much of it was + so, or when the infusion took place, he was unable to say. He could + imitate the Irish brogue, and his wonderful vivacity may have been in part + due to his extraction. But there were other qualities which we should + hardly think of deriving from Ireland. The most prominent of these was his + sense of order, which ran like a luminous beam through all the + transactions of his life. The most entangled and complicated matters fell + into harmony in his hands. His mode of keeping accounts excited the + admiration of the managing board of this Institution. And his science was + similarly ordered. In his Experimental Researches, he numbered every + paragraph, and welded their various parts together by incessant reference. + His private notes of the Experimental Researches, which are happily + preserved, are similarly numbered: their last paragraph bears the figure + 16,041. His working qualities, moreover, showed the tenacity of the + Teuton. His nature was impulsive, but there was a force behind the impulse + which did not permit it to retreat. If in his warm moments he formed a + resolution, in his cool ones he made that resolution good. Thus his fire + was that of a solid combustible, not that of a gas, which blazes suddenly, + and dies as suddenly away. + </p> + <p> + And here I must claim your tolerance for the limits by which I am + confined. No materials for a life of Faraday are in my hands, and what I + have now to say has arisen almost wholly out of our close personal + relationship. + </p> + <p> + Letters of his, covering a period of sixteen years, are before me, each + one of which contains some characteristic utterance;—strong, yet + delicate in counsel, joyful in encouragement, and warm in affection. + References which would be pleasant to such of them as still live are made + to Humboldt, Biot, Dumas, Chevreul, Magnus, and Arago. Accident brought + these names prominently forward; but many others would be required to + complete his list of continental friends. He prized the love and sympathy + of men—prized it almost more than the renown which his science + brought him. Nearly a dozen years ago it fell to my lot to write a review + of his 'Experimental Researches' for the 'Philosophical Magazine.' After + he had read it, he took me by the hand, and said, 'Tyndall, the sweetest + reward of my work is the sympathy and good will which it has caused to + flow in upon me from all quarters of the world.' Among his letters I find + little sparks of kindness, precious to no one but myself, but more + precious to me than all. He would peep into the laboratory when he thought + me weary, and take me upstairs with him to rest. And if I happened to be + absent, he would leave a little note for me, couched in this or some other + similar form:—'Dear Tyndall,—I was looking for you, because we + were at tea—we have not yet done—will you come up?' I + frequently shared his early dinner; almost always, in fact, while my + lectures were going on. There was no trace of asceticism in his nature. He + preferred the meat and wine of life to its locusts and wild honey. Never + once during an intimacy of fifteen years did he mention religion to me, + save when I drew him on to the subject. He then spoke to me without + hesitation or reluctance; not with any apparent desire to 'improve the + occasion,' but to give me such information as I sought. He believed the + human heart to be swayed by a power to which science or logic opened no + approach, and, right or wrong, this faith, held in perfect tolerance of + the faiths of others, strengthened and beautified his life. + </p> + <p> + From the letters just referred to, I will select three for publication + here. I choose the first, because it contains a passage revealing the + feelings with which Faraday regarded his vocation, and also because it + contains an allusion which will give pleasure to a friend. + </p> + <p> + 'Royal Institution. ( this is crossed out by Faraday ) + </p> + <p> + 'Ventnor, Isle of Wight, June 28, 1854. + </p> + <p> + 'My Dear Tyndall,—You see by the top of this letter how much habit + prevails over me; I have just read yours from thence, and yet I think + myself there. However, I have left its science in very good keeping, and I + am glad to learn that you are at experiment once more. But how is the + health? Not well, I fear. I wish you would get yourself strong first and + work afterwards. As for the fruits, I am sure they will be good, for + though I sometimes despond as regards myself, I do not as regards you. You + are young, I am old.... But then our subjects are so glorious, that to + work at them rejoices and encourages the feeblest; delights and enchants + the strongest. + </p> + <p> + 'I have not yet seen anything from Magnus. Thoughts of him always delight + me. We shall look at his black sulphur together. I heard from Schonbein + the other day. He tells me that Liebig is full of ozone, i.e., of + allotropic oxygen. + </p> + <p> + 'Good-bye for the present. + </p> + <p> + 'Ever, my dear Tyndall, + </p> + <p> + 'Yours truly, + </p> + <p> + 'M. Faraday.' + </p> + <p> + The contemplation of Nature, and his own relation to her, produced in + Faraday a kind of spiritual exaltation which makes itself manifest here. + His religious feeling and his philosophy could not be kept apart; there + was an habitual overflow of the one into the other. + </p> + <p> + Whether he or another was its exponent, he appeared to take equal delight + in science. A good experiment would make him almost dance with delight. In + November, 1850, he wrote to me thus:—'I hope some day to take up the + point respecting the magnetism of associated particles. In the meantime I + rejoice at every addition to the facts and reasoning connected with the + subject. When science is a republic, then it gains: and though I am no + republican in other matters, I am in that.' All his letters illustrate + this catholicity of feeling. Ten years ago, when going down to Brighton, + he carried with him a little paper I had just completed, and afterwards + wrote to me. His letter is a mere sample of the sympathy which he always + showed to me and my work. + </p> + <p> + 'Brighton, December 9, 1857. + </p> + <p> + 'My Dear Tyndall,—I cannot resist the pleasure of saying how very + much I have enjoyed your paper. Every part has given me delight. It goes + on from point to point beautifully. You will find many pencil marks, for I + made them as I read. I let them stand, for though many of them receive + their answer as the story proceeds, yet they show how the wording + impresses a mind fresh to the subject, and perhaps here and there you may + like to alter it slightly, if you wish the full idea, i.e., not an + inaccurate one, to be suggested at first; and yet after all I believe it + is not your exposition, but the natural jumping to a conclusion that + affects or has affected my pencil. + </p> + <p> + 'We return on Friday, when I will return you the paper. + </p> + <p> + 'Ever truly yours, + </p> + <p> + 'M. Faraday.' + </p> + <p> + The third letter will come in its proper place towards the end. + </p> + <p> + While once conversing with Faraday on science, in its relations to + commerce and litigation, he said to me, that at a certain period of his + career, he was forced definitely to ask himself, and finally to decide + whether he should make wealth or science the pursuit of his life. He could + not serve both masters, and he was therefore compelled to choose between + them. After the discovery of magneto-electricity his fame was so noised + abroad, that the commercial world would hardly have considered any + remuneration too high for the aid of abilities like his. Even before he + became so famous, he had done a little 'professional business.' This was + the phrase he applied to his purely commercial work. His friend, Richard + Phillips, for example, had induced him to undertake a number of analyses, + which produced, in the year 1830, an addition to his income of more than a + thousand pounds; and in 1831 a still greater addition. He had only to will + it to raise in 1832 his professional business income to 5000L. a year. + Indeed double this sum would be a wholly insufficient estimate of what he + might, with ease, have realised annually during the last thirty years of + his life. + </p> + <p> + While restudying the Experimental Researches with reference to the present + memoir, the conversation with Faraday here alluded to came to my + recollection, and I sought to ascertain the period when the question, + 'wealth or science,' had presented itself with such emphasis to his mind. + I fixed upon the year 1831 or 1832, for it seemed beyond the range of + human power to pursue science as he had done during the subsequent years, + and to pursue commercial work at the same time. To test this conclusion I + asked permission to see his accounts, and on my own responsibility, I will + state the result. In 1832, his professional business income, instead of + rising to 5000L., or more, fell from 1090L. 4s. to 155L. 9s. From this it + fell with slight oscillations to 92L. in 1837, and to zero in 1838. + Between 1839 and 1845, it never, except in one instance, exceeded 22L.; + being for the most part much under this. The exceptional year referred to + was that in which he and Sir Charles Lyell were engaged by Government to + write a report on the Haswell Colliery explosion, and then his business + income rose to 112L. From the end of 1845 to the day of his death, + Faraday's annual professional business income was exactly zero. Taking the + duration of his life into account, this son of a blacksmith, and + apprentice to a bookbinder, had to decide between a fortune of 150,000L. + on the one side, and his undowered science on the other. He chose the + latter, and died a poor man. But his was the glory of holding aloft among + the nations the scientific name of England for a period of forty years. + </p> + <p> + The outward and visible signs of fame were also of less account to him + than to most men. He had been loaded with scientific honours from all + parts of the world. Without, I imagine, a dissentient voice, he was + regarded as the prince of the physical investigators of the present age. + The highest scientific position in this country he had, however, never + filled. When the late excellent and lamented Lord Wrottesley resigned the + presidency of the Royal Society, a deputation from the council, consisting + of his Lordship, Mr. Grove, and Mr. Gassiot, waited upon Faraday, to urge + him to accept the president's chair. All that argument or friendly + persuasion could do was done to induce him to yield to the wishes of the + council, which was also the unanimous wish of scientific men. A knowledge + of the quickness of his own nature had induced in Faraday the habit of + requiring an interval of reflection, before he decided upon any question + of importance. In the present instance he followed his usual habit, and + begged for a little time. + </p> + <p> + On the following morning, I went up to his room and said on entering that + I had come to him with some anxiety of mind. He demanded its cause, and I + responded:—'Lest you should have decided against the wishes of the + deputation that waited on you yesterday.' 'You would not urge me to + undertake this responsibility,' he said. 'I not only urge you,' was my + reply, 'but I consider it your bounden duty to accept it.' He spoke of the + labour that it would involve; urged that it was not in his nature to take + things easy; and that if he became president, he would surely have to stir + many new questions, and agitate for some changes. I said that in such + cases he would find himself supported by the youth and strength of the + Royal Society. This, however, did not seem to satisfy him. Mrs. Faraday + came into the room, and he appealed to her. Her decision was adverse, and + I deprecated her decision. 'Tyndall,' he said at length, 'I must remain + plain Michael Faraday to the last; and let me now tell you, that if I + accepted the honour which the Royal Society desires to confer upon me, I + would not answer for the integrity of my intellect for a single year.' I + urged him no more, and Lord Wrottesley had a most worthy successor in Sir + Benjamin Brodie. + </p> + <p> + After the death of the Duke of Northumberland, our Board of Managers + wished to see Mr. Faraday finish his career as President of the + Institution, which he had entered on weekly wages more than half a century + before. But he would have nothing to do with the presidency. He wished for + rest, and the reverent affection of his friends was to him infinitely more + precious than all the honours of official life. + </p> + <p> + The first requisite of the intellectual life of Faraday was the + independence of his mind; and though prompt to urge obedience where + obedience was due, with every right assertion of manhood he intensely + sympathized. Even rashness on the side of honour found from him ready + forgiveness, if not open applause. The wisdom of years, tempered by a + character of this kind, rendered his counsel peculiarly precious to men + sensitive like himself. I often sought that counsel, and, with your + permission, will illustrate its character by one or two typical instances. + </p> + <p> + In 1855, I was appointed examiner under the Council for Military + Education. At that time, as indeed now, I entertained strong convictions + as to the enormous utility of physical science to officers of artillery + and engineers, and whenever opportunity offered, I expressed this + conviction without reserve. I did not think the recognition, though + considerable, accorded to physical science in those examinations at all + proportionate to its importance; and this probably rendered me more + jealous than I otherwise should have been of its claims. + </p> + <p> + In Trinity College, Dublin, a school had been organized with reference to + the Woolwich examinations, and a large number of exceedingly + well-instructed young gentlemen were sent over from Dublin, to compete for + appointments in the artillery and the engineers. The result of one + examination was particularly satisfactory to me; indeed the marks obtained + appeared so eloquent that I forbore saying a word about them. My + colleagues, however, followed the usual custom of sending in brief reports + with their returns of marks. After the results were published, a leading + article appeared in 'The Times,' in which the reports were largely quoted, + praise being bestowed on all the candidates, except the excellent young + fellows who had passed through my hands. + </p> + <p> + A letter from Trinity College drew my attention to this article, bitterly + complaining that whereas the marks proved them to be the best of all, the + science candidates were wholly ignored. I tried to set matters right by + publishing, on my own responsibility, a letter in 'The Times.' The act, I + knew, could not bear justification from the War Office point of view; and + I expected and risked the displeasure of my superiors. The merited + reprimand promptly came. 'Highly as the Secretary of State for War might + value the expression of Professor Tyndall's opinion, he begged to say that + an examiner, appointed by His Royal Highness the Commander-in-Chief, had + no right to appear in the public papers as Professor Tyndall has done, + without the sanction of the War Office.' Nothing could be more just than + this reproof, but I did not like to rest under it. I wrote a reply, and + previous to sending it took it up to Faraday. We sat together before his + fire, and he looked very earnest as he rubbed his hands and pondered. The + following conversation then passed between us:— + </p> + <p> + F. You certainly have received a reprimand, Tyndall; but the matter is + over, and if you wish to accept the reproof, you will hear no more about + it. + </p> + <p> + T. But I do not wish to accept it. + </p> + <p> + F. Then you know what the consequence of sending that letter will be? + </p> + <p> + T. I do. + </p> + <p> + F. They will dismiss you. + </p> + <p> + T. I know it. + </p> + <p> + F. Then send the letter! + </p> + <p> + The letter was firm, but respectful; it acknowledged the justice of the + censure, but expressed neither repentance nor regret. Faraday, in his + gracious way, slightly altered a sentence or two to make it more + respectful still. It was duly sent, and on the following day I entered the + Institution with the conviction that my dismissal was there before me. + Weeks, however, passed. At length the well-known envelope appeared, and I + broke the seal, not doubting the contents. They were very different from + what I expected. 'The Secretary of State for War has received Professor + Tyndall's letter, and deems the explanation therein given perfectly + satisfactory.' I have often wished for an opportunity of publicly + acknowledging this liberal treatment, proving, as it did, that Lord + Panmure could discern and make allowance for a good intention, though it + involved an offence against routine. For many years subsequently it was my + privilege to act under that excellent body, the Council for Military + Education. + </p> + <p> + On another occasion of this kind, having encouraged me in a somewhat hardy + resolution I had formed, Faraday backed his encouragement by an + illustration drawn from his own life. The subject will interest you, and + it is so sure to be talked about in the world, that no avoidable harm can + rise from its introduction here. + </p> + <p> + In the year 1835, Sir Robert Peel wished to offer Faraday a pension, but + that great statesman quitted office before he was able to realise his + wish. The Minister who founded these pensions intended them, I believe, to + be marks of honour which even proud men might accept without compromise of + independence. When, however, the intimation first reached Faraday in an + unofficial way, he wrote a letter announcing his determination to decline + the pension; and stating that he was quite competent to earn his + livelihood himself. That letter still exists, but it was never sent, + Faraday's repugnance having been overruled by his friends. When Lord + Melbourne came into office, he desired to see Faraday; and probably in + utter ignorance of the man—for unhappily for them and us, Ministers + of State in England are only too often ignorant of great Englishmen—his + Lordship said something that must have deeply displeased his visitor. All + the circumstances were once communicated to me, but I have forgotten the + details. The term 'humbug,' I think, was incautiously employed by his + Lordship, and other expressions were used of a similar kind. Faraday + quitted the Minister with his own resolves, and that evening he left his + card and a short and decisive note at the residence of Lord Melbourne, + stating that he had manifestly mistaken his Lordship's intention of + honouring science in his person, and declining to have anything whatever + to do with the proposed pension. The good-humoured nobleman at first + considered the matter a capital joke; but he was afterwards led to look at + it more seriously. An excellent lady, who was a friend both to Faraday and + the Minister, tried to arrange matters between them; but she found Faraday + very difficult to move from the position he had assumed. After many + fruitless efforts, she at length begged of him to state what he would + require of Lord Melbourne to induce him to change his mind. He replied, 'I + should require from his Lordship what I have no right or reason to expect + that he would grant—a written apology for the words he permitted + himself to use to me.' The required apology came, frank and full, + creditable, I thought, alike to the Prime Minister and the philosopher. + </p> + <p> + Considering the enormous strain imposed on Faraday's intellect, the + boy-like buoyancy even of his later years was astonishing. He was often + prostrate, but he had immense resiliency, which he brought into action by + getting away from London whenever his health failed. I have already + indicated the thoughts which filled his mind during the evening of his + life. He brooded on magnetic media and lines of force; and the great + object of the last investigation he ever undertook was the decision of the + question whether magnetic force requires time for its propagation. How he + proposed to attack this subject we may never know. But he has left some + beautiful apparatus behind; delicate wheels and pinions, and associated + mirrors, which were to have been employed in the investigation. The mere + conception of such an inquiry is an illustration of his strength and + hopefulness, and it is impossible to say to what results it might have led + him. But the work was too heavy for his tired brain. It was long before he + could bring himself to relinquish it and during this struggle he often + suffered from fatigue of mind. It was at this period, and before he + resigned himself to the repose which marked the last two years of his + life, that he wrote to me the following letter—one of many priceless + letters now before me—which reveals, more than anything another pen + could express, the state of his mind at the time. I was sometimes censured + in his presence for my doings in the Alps, but his constant reply was, + 'Let him alone, he knows how to take care of himself.' In this letter, + anxiety on this score reveals itself for the first time. + </p> + <p> + 'Hampton Court, August 1, 1864. + </p> + <p> + 'My Dear Tyndall,—I do not know whether my letter will catch you, + but I will risk it, though feeling very unfit to communicate with a man + whose life is as vivid and active as yours; but the receipt of your kind + letter makes me to know that, though I forget, I am not forgotten, and + though I am not able to remember at the end of a line what was said at the + beginning of it, the imperfect marks will convey to you some sense of what + I long to say. We had heard of your illness through Miss Moore, and I was + therefore very glad to learn that you are now quite well; do not run too + many risks or make your happiness depend too much upon dangers, or the + hunting of them. Sometimes the very thinking of you, and what you may be + about, wearies me with fears, and then the cogitations pause and change, + but without giving me rest. I know that much of this depends upon my own + worn-out nature, and I do not know why I write it, save that when I write + to you I cannot help thinking it, and the thoughts stand in the way of + other matter. + </p> + <hr /> + <p> + 'See what a strange desultory epistle I am writing to you, and yet I feel + so weary that I long to leave my desk and go to the couch. + </p> + <p> + 'My dear wife and Jane desire their kindest remembrances: I hear them in + the next room:... I forget—but not you, my dear Tyndall, for I am + </p> + <p> + 'Ever yours, + </p> + <p> + 'M. Faraday.' + </p> + <p> + This weariness subsided when he relinquished his work, and I have a + cheerful letter from him, written in the autumn of 1865. But towards the + close of that year he had an attack of illness, from which he never + completely rallied. He continued to attend the Friday Evening Meetings, + but the advance of infirmity was apparent to us all. Complete rest became + finally essential to him, and he ceased to appear among us. There was no + pain in his decline to trouble the memory of those who loved him. Slowly + and peacefully he sank towards his final rest, and when it came, his death + was a falling asleep. In the fulness of his honours and of his age he + quitted us; the good fight fought, the work of duty—shall I not say + of glory?—done. The 'Jane' referred to in the foregoing letter is + Faraday's niece, Miss Jane Barnard, who with an affection raised almost to + religious devotion watched him and tended him to the end. + </p> + <p> + I saw Mr. Faraday for the first time on my return from Marburg in 1850. I + came to the Royal Institution, and sent up my card, with a copy of the + paper which Knoblauch and myself had just completed. He came down and + conversed with me for half an hour. I could not fail to remark the + wonderful play of intellect and kindly feeling exhibited by his + countenance. When he was in good health the question of his age would + never occur to you. In the light and laughter of his eyes you never + thought of his grey hairs. He was then on the point of publishing one of + his papers on Magnecrystallic action, and he had time to refer in a + flattering Note to the memoir I placed in his hands. I returned to + Germany, worked there for nearly another year, and in June, 1851, came + back finally from Berlin to England. Then, for the first time, and on my + way to the meeting of the British Association, at Ipswich, I met a man who + has since made his mark upon the intellect of his time; who has long been, + and who by the strong law of natural affinity must continue to be, a + brother to me. We were both without definite outlook at the time, needing + proper work, and only anxious to have it to perform. The chairs of Natural + History and of Physics being advertised as vacant in the University of + Toronto, we applied for them, he for the one, I for the other; but, + possibly guided by a prophetic instinct, the University authorities + declined having anything to do with either of us. If I remember aright, we + were equally unlucky elsewhere. + </p> + <p> + One of Faraday's earliest letters to me had reference to this Toronto + business, which he thought it unwise in me to neglect. But Toronto had its + own notions, and in 1853, at the instance of Dr. Bence Jones, and on the + recommendation of Faraday himself, a chair of Physics at the Royal + Institution was offered to me. I was tempted at the same time to go + elsewhere, but a strong attraction drew me to his side. Let me say that it + was mainly his and other friendships, precious to me beyond all + expression, that caused me to value my position here more highly than any + other that could be offered to me in this land. Nor is it for its honour, + though surely that is great, but for the strong personal ties that bind me + to it, that I now chiefly prize this place. You might not credit me were I + to tell you how lightly I value the honour of being Faraday's successor + compared with the honour of having been Faraday's friend. His friendship + was energy and inspiration; his 'mantle' is a burden almost too heavy to + be borne. + </p> + <p> + Sometimes during the last year of his life, by the permission or + invitation of Mrs. Faraday, I went up to his rooms to see him. The deep + radiance, which in his time of strength flashed with such extraordinary + power from his countenance, had subsided to a calm and kindly light, by + which my latest memory of him is warmed and illuminated. I knelt one day + beside him on the carpet and placed my hand upon his knee; he stroked it + affectionately, smiled, and murmured, in a low soft voice, the last words + that I remember as having been spoken to me by Michael Faraday. + </p> + <p> + It was my wish and aspiration to play the part of Schiller to this Goethe: + and he was at times so strong and joyful—his body so active, and his + intellect so clear—as to suggest to me the thought that he, like + Goethe, would see the younger man laid low. Destiny ruled otherwise, and + now he is but a memory to us all. Surely no memory could be more + beautiful. He was equally rich in mind and heart. The fairest traits of a + character sketched by Paul, found in him perfect illustration. For he was + 'blameless, vigilant, sober, of good behaviour, apt to teach, not given to + filthy lucre.' He had not a trace of worldly ambition; he declared his + duty to his Sovereign by going to the levee once a year, but beyond this + he never sought contact with the great. The life of his spirit and of his + intellect was so full, that the things which men most strive after were + absolutely indifferent to him. 'Give me health and a day,' says the brave + Emerson, 'and I will make the pomp of emperors ridiculous.' In an eminent + degree Faraday could say the same. What to him was the splendour of a + palace compared with a thunderstorm upon Brighton Downs?—what among + all the appliances of royalty to compare with the setting sun? I refer to + a thunderstorm and a sunset, because these things excited a kind of + ecstasy in his mind, and to a mind open to such ecstasy the pomps and + pleasures of the world are usually of small account. Nature, not + education, rendered Faraday strong and refined. A favourite experiment of + his own was representative of himself. He loved to show that water in + crystallizing excluded all foreign ingredients, however intimately they + might be mixed with it. Out of acids, alkalis, or saline solutions, the + crystal came sweet and pure. By some such natural process in the formation + of this man, beauty and nobleness coalesced, to the exclusion of + everything vulgar and low. He did not learn his gentleness in the world, + for he withdrew himself from its culture; and still this land of England + contained no truer gentleman than he. Not half his greatness was + incorporate in his science, for science could not reveal the bravery and + delicacy of his heart. + </p> + <p> + But it is time that I should end these weak words, and lay my poor garland + on the grave of this + </p> +<pre xml:space="preserve"> + Just and faithful knight of God. +</pre> + <p> + <br /><br /><br /><br /> + </p> +<pre xml:space="preserve"> + + + + + +End of the Project Gutenberg EBook of Faraday As A Discoverer, by John Tyndall + +*** END OF THIS PROJECT GUTENBERG EBOOK FARADAY AS A DISCOVERER *** + +***** This file should be named 1225-h.htm or 1225-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/2/2/1225/ + +Produced by An Anonymous Volunteer, and David Widger + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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