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diff --git a/1706-h/1706-h.htm b/1706-h/1706-h.htm new file mode 100644 index 0000000..4844e1b --- /dev/null +++ b/1706-h/1706-h.htm @@ -0,0 +1,9493 @@ +<?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> + A History of Science, Vol. II by Henry Smith Williams + </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 A History of Science, Volume 2(of 5), by +Henry Smith Williams + +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: A History of Science, Volume 2(of 5) + +Author: Henry Smith Williams + +Release Date: November 17, 2009 [EBook #1706] +Last Updated: January 26, 2013 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V2 *** + + + + +Produced by Charles Keller, and David Widger + + + + + + +</pre> + <p> + <br /><br /> + </p> + <h1> + A HISTORY OF SCIENCE + </h1> + <h2> + BY HENRY SMITH WILLIAMS, M.D., LL.D. <br /> <br /> <br /> ASSISTED BY EDWARD + H. WILLIAMS, M.D. <br /> <br /> <br /> IN FIVE VOLUMES <br /> <br /> VOLUME II. + </h2> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <blockquote> + <p class="toc"> + <big><b>CONTENTS</b></big> + </p> + <p> + <br /> <a href="#link2H_4_0001"> <b>A HISTORY OF SCIENCE</b> </a><br /> + <br /> <a href="#link2H_4_0002"> <b>BOOK II. THE BEGINNINGS OF MODERN + SCIENCE</b> </a> + </p> + <p class="toc"> + <a href="#link2H_4_0003"> I. SCIENCE IN THE DARK AGE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0004"> II. MEDIAEVAL SCIENCE AMONG THE ARABIANS </a> + </p> + <p class="toc"> + <a href="#link2H_4_0005"> III. MEDIAEVAL SCIENCE IN THE WEST </a> + </p> + <p class="toc"> + <a href="#link2H_4_0006"> IV. THE NEW COSMOLOGY—COPERNICUS TO + KEPLER AND GALILEO </a> + </p> + <p class="toc"> + <a href="#link2H_4_0007"> V. GALILEO AND THE NEW PHYSICS </a> + </p> + <p class="toc"> + <a href="#link2H_4_0008"> VI. TWO PSEUDO-SCIENCES—ALCHEMY AND + ASTROLOGY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0009"> VII. FROM PARACELSUS TO HARVEY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0010"> VIII. MEDICINE IN THE SIXTEENTH AND + SEVENTEENTH CENTURIES </a> + </p> + <p class="toc"> + <a href="#link2H_4_0011"> IX. PHILOSOPHER-SCIENTISTS AND NEW + INSTITUTIONS OF LEARNING </a> + </p> + <p class="toc"> + <a href="#link2H_4_0012"> X. THE SUCCESSORS OF GALILEO IN PHYSICAL + SCIENCE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0013"> XI. NEWTON AND THE COMPOSITION OF LIGHT </a> + </p> + <p class="toc"> + <a href="#link2H_4_0014"> XII. NEWTON AND THE LAW OF GRAVITATION </a> + </p> + <p class="toc"> + <a href="#link2H_4_0015"> XIII. INSTRUMENTS OF PRECISION IN THE AGE OF + NEWTON </a> + </p> + <p class="toc"> + <a href="#link2H_4_0016"> XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND + VON GUERICKE TO FRANKLIN </a> + </p> + <p class="toc"> + <a href="#link2H_4_0017"> XV. NATURAL HISTORY TO THE TIME OF LINNAEUS + </a> + </p> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <p class="toc2"> + <a href="#link2H_APPE"> APPENDIX </a> + </p> + <p class="toc2"> + <a href="#link2HCH0001"> CHAPTER I </a> + </p> + <p class="toc2"> + <a href="#link2HCH0002"> CHAPTER III </a> + </p> + <p class="toc2"> + <a href="#link2HCH0003"> CHAPTER IV </a> + </p> + <p class="toc2"> + <a href="#link2HCH0004"> CHAPTER V </a> + </p> + <p class="toc2"> + <a href="#link2HCH0005"> CHAPTER VI </a> + </p> + <p class="toc2"> + <a href="#link2HCH0006"> CHAPTER VII </a> + </p> + <p class="toc2"> + <a href="#link2HCH0007"> CHAPTER VIII </a> + </p> + <p class="toc2"> + <a href="#link2HCH0008"> CHAPTER IX </a> + </p> + <p class="toc2"> + <a href="#link2HCH0009"> CHAPTER X </a> + </p> + <p class="toc2"> + <a href="#link2HCH0010"> CHAPTER XI </a> + </p> + <p class="toc2"> + <a href="#link2HCH0011"> CHAPTER XII </a> + </p> + <p class="toc2"> + <a href="#link2HCH0012"> CHAPTER XIV </a> + </p> + </blockquote> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a name="link2H_4_0001" id="link2H_4_0001"> + <!-- H2 anchor --> </a> + </p> + <h1> + A HISTORY OF SCIENCE + </h1> + <p> + <a name="link2H_4_0002" id="link2H_4_0002"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + BOOK II. THE BEGINNINGS OF MODERN SCIENCE + </h2> + <p> + The studies of the present book cover the progress of science from the + close of the Roman period in the fifth century A.D. to about the middle of + the eighteenth century. In tracing the course of events through so long a + period, a difficulty becomes prominent which everywhere besets the + historian in less degree—a difficulty due to the conflict between + the strictly chronological and the topical method of treatment. We must + hold as closely as possible to the actual sequence of events, since, as + already pointed out, one discovery leads on to another. But, on the other + hand, progressive steps are taken contemporaneously in the various fields + of science, and if we were to attempt to introduce these in strict + chronological order we should lose all sense of topical continuity. + </p> + <p> + Our method has been to adopt a compromise, following the course of a + single science in each great epoch to a convenient stopping-point, and + then turning back to bring forward the story of another science. Thus, for + example, we tell the story of Copernicus and Galileo, bringing the record + of cosmical and mechanical progress down to about the middle of the + seventeenth century, before turning back to take up the physiological + progress of the fifteenth and sixteenth centuries. Once the latter stream + is entered, however, we follow it without interruption to the time of + Harvey and his contemporaries in the middle of the seventeenth century, + where we leave it to return to the field of mechanics as exploited by the + successors of Galileo, who were also the predecessors and contemporaries + of Newton. + </p> + <p> + In general, it will aid the reader to recall that, so far as possible, we + hold always to the same sequences of topical treatment of contemporary + events; as a rule we treat first the cosmical, then the physical, then the + biological sciences. The same order of treatment will be held to in + succeeding volumes. + </p> + <p> + Several of the very greatest of scientific generalizations are developed + in the period covered by the present book: for example, the Copernican + theory of the solar system, the true doctrine of planetary motions, the + laws of motion, the theory of the circulation of the blood, and the + Newtonian theory of gravitation. The labors of the investigators of the + early decades of the eighteenth century, terminating with Franklin's + discovery of the nature of lightning and with the Linnaean classification + of plants and animals, bring us to the close of our second great epoch; + or, to put it otherwise, to the threshold of the modern period. + </p> + <p> + <a name="link2H_4_0003" id="link2H_4_0003"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + I. SCIENCE IN THE DARK AGE + </h2> + <p> + An obvious distinction between the classical and mediaeval epochs may be + found in the fact that the former produced, whereas the latter failed to + produce, a few great thinkers in each generation who were imbued with that + scepticism which is the foundation of the investigating spirit; who + thought for themselves and supplied more or less rational explanations of + observed phenomena. Could we eliminate the work of some score or so of + classical observers and thinkers, the classical epoch would seem as much a + dark age as does the epoch that succeeded it. + </p> + <p> + But immediately we are met with the question: Why do no great original + investigators appear during all these later centuries? We have already + offered a part explanation in the fact that the borders of civilization, + where racial mingling naturally took place, were peopled with + semi-barbarians. But we must not forget that in the centres of + civilization all along there were many men of powerful intellect. Indeed, + it would violate the principle of historical continuity to suppose that + there was any sudden change in the level of mentality of the Roman world + at the close of the classical period. We must assume, then, that the + direction in which the great minds turned was for some reason changed. + Newton is said to have alleged that he made his discoveries by "intending" + his mind in a certain direction continuously. It is probable that the same + explanation may be given of almost every great scientific discovery. + Anaxagoras could not have thought out the theory of the moon's phases; + Aristarchus could not have found out the true mechanism of the solar + system; Eratosthenes could not have developed his plan for measuring the + earth, had not each of these investigators "intended" his mind + persistently towards the problems in question. + </p> + <p> + Nor can we doubt that men lived in every generation of the dark age who + were capable of creative thought in the field of science, bad they chosen + similarly to "intend" their minds in the right direction. The difficulty + was that they did not so choose. Their minds had a quite different bent. + They were under the spell of different ideals; all their mental efforts + were directed into different channels. What these different channels were + cannot be in doubt—they were the channels of oriental + ecclesiasticism. One all-significant fact speaks volumes here. It is the + fact that, as Professor Robinson(1) points out, from the time of Boethius + (died 524 or 525 A.D.) to that of Dante (1265-1321 A.D.) there was not a + single writer of renown in western Europe who was not a professional + churchman. All the learning of the time, then, centred in the priesthood. + We know that the same condition of things pertained in Egypt, when science + became static there. But, contrariwise, we have seen that in Greece and + early Rome the scientific workers were largely physicians or professional + teachers; there was scarcely a professional theologian among them. + </p> + <p> + Similarly, as we shall see in the Arabic world, where alone there was + progress in the mediaeval epoch, the learned men were, for the most part, + physicians. Now the meaning of this must be self-evident. The physician + naturally "intends" his mind towards the practicalities. His professional + studies tend to make him an investigator of the operations of nature. He + is usually a sceptic, with a spontaneous interest in practical science. + But the theologian "intends" his mind away from practicalities and towards + mysticism. He is a professional believer in the supernatural; he discounts + the value of merely "natural" phenomena. His whole attitude of mind is + unscientific; the fundamental tenets of his faith are based on alleged + occurrences which inductive science cannot admit—namely, miracles. + And so the minds "intended" towards the supernatural achieved only the + hazy mysticism of mediaeval thought. Instead of investigating natural + laws, they paid heed (as, for example, Thomas Aquinas does in his Summa + Theologia) to the "acts of angels," the "speaking of angels," the + "subordination of angels," the "deeds of guardian angels," and the like. + They disputed such important questions as, How many angels can stand upon + the point of a needle? They argued pro and con as to whether Christ were + coeval with God, or whether he had been merely created "in the beginning," + perhaps ages before the creation of the world. How could it be expected + that science should flourish when the greatest minds of the age could + concern themselves with problems such as these? + </p> + <p> + Despite our preconceptions or prejudices, there can be but one answer to + that question. Oriental superstition cast its blight upon the fair field + of science, whatever compensation it may or may not have brought in other + fields. But we must be on our guard lest we overestimate or incorrectly + estimate this influence. Posterity, in glancing backward, is always prone + to stamp any given age of the past with one idea, and to desire to + characterize it with a single phrase; whereas in reality all ages are + diversified, and any generalization regarding an epoch is sure to do that + epoch something less or something more than justice. We may be sure, then, + that the ideal of ecclesiasticism is not solely responsible for the + scientific stasis of the dark age. Indeed, there was another influence of + a totally different character that is too patent to be overlooked—the + influence, namely, of the economic condition of western Europe during this + period. As I have elsewhere pointed out,(2) Italy, the centre of western + civilization, was at this time impoverished, and hence could not provide + the monetary stimulus so essential to artistic and scientific no less than + to material progress. There were no patrons of science and literature such + as the Ptolemies of that elder Alexandrian day. There were no great + libraries; no colleges to supply opportunities and afford stimuli to the + rising generation. Worst of all, it became increasingly difficult to + secure books. + </p> + <p> + This phase of the subject is often overlooked. Yet a moment's + consideration will show its importance. How should we fare to-day if no + new scientific books were being produced, and if the records of former + generations were destroyed? That is what actually happened in Europe + during the Middle Ages. At an earlier day books were made and distributed + much more abundantly than is sometimes supposed. Bookmaking had, indeed, + been an important profession in Rome, the actual makers of books being + slaves who worked under the direction of a publisher. It was through the + efforts of these workers that the classical works in Greek and Latin were + multiplied and disseminated. Unfortunately the climate of Europe does not + conduce to the indefinite preservation of a book; hence very few remnants + of classical works have come down to us in the original from a remote + period. The rare exceptions are certain papyrus fragments, found in Egypt, + some of which are Greek manuscripts dating from the third century B.C. + Even from these sources the output is meagre; and the only other + repository of classical books is a single room in the buried city of + Herculaneum, which contained several hundred manuscripts, mostly in a + charred condition, a considerable number of which, however, have been + unrolled and found more or less legible. This library in the buried city + was chiefly made up of philosophical works, some of which were quite + unknown to the modern world until discovered there. + </p> + <p> + But this find, interesting as it was from an archaeological stand-point, + had no very important bearing on our knowledge of the literature of + antiquity. Our chief dependence for our knowledge of that literature must + still be placed in such copies of books as were made in the successive + generations. Comparatively few of the extant manuscripts are older than + the tenth century of our era. It requires but a momentary consideration of + the conditions under which ancient books were produced to realize how slow + and difficult the process was before the invention of printing. The taste + of the book-buying public demanded a clearly written text, and in the + Middle Ages it became customary to produce a richly ornamented text as + well. The script employed being the prototype of the modern printed text, + it will be obvious that a scribe could produce but a few pages at best in + a day. A large work would therefore require the labor of a scribe for many + months or even for several years. We may assume, then, that it would be a + very flourishing publisher who could produce a hundred volumes all told + per annum; and probably there were not many publishers at any given time, + even in the period of Rome's greatest glory, who had anything like this + output. + </p> + <p> + As there was a large number of authors in every generation of the + classical period, it follows that most of these authors must have been + obliged to content themselves with editions numbering very few copies; and + it goes without saying that the greater number of books were never + reproduced in what might be called a second edition. Even books that + retained their popularity for several generations would presently fail to + arouse sufficient interest to be copied; and in due course such works + would pass out of existence altogether. Doubtless many hundreds of books + were thus lost before the close of the classical period, the names of + their authors being quite forgotten, or preserved only through a chance + reference; and of course the work of elimination went on much more rapidly + during the Middle Ages, when the interest in classical literature sank to + so low an ebb in the West. Such collections of references and quotations + as the Greek Anthology and the famous anthologies of Stobaeus and + Athanasius and Eusebius give us glimpses of a host of writers—more + than seven hundred are quoted by Stobaeus—a very large proportion of + whom are quite unknown except through these brief excerpts from their lost + works. + </p> + <p> + Quite naturally the scientific works suffered at least as largely as any + others in an age given over to ecclesiastical dreamings. Yet in some + regards there is matter for surprise as to the works preserved. Thus, as + we have seen, the very extensive works of Aristotle on natural history, + and the equally extensive natural history of Pliny, which were preserved + throughout this period, and are still extant, make up relatively bulky + volumes. These works seem to have interested the monks of the Middle Ages, + while many much more important scientific books were allowed to perish. A + considerable bulk of scientific literature was also preserved through the + curious channels of Arabic and Armenian translations. Reference has + already been made to the Almagest of Ptolemy, which, as we have seen, was + translated into Arabic, and which was at a later day brought by the Arabs + into western Europe and (at the instance of Frederick II of Sicily) + translated out of their language into mediaeval Latin. + </p> + <p> + It remains to inquire, however, through what channels the Greek works + reached the Arabs themselves. To gain an answer to this question we must + follow the stream of history from its Roman course eastward to the new + seat of the Roman empire in Byzantium. Here civilization centred from + about the fifth century A.D., and here the European came in contact with + the civilization of the Syrians, the Persians, the Armenians, and finally + of the Arabs. The Byzantines themselves, unlike the inhabitants of western + Europe, did not ignore the literature of old Greece; the Greek language + became the regular speech of the Byzantine people, and their writers made + a strenuous effort to perpetuate the idiom and style of the classical + period. Naturally they also made transcriptions of the classical authors, + and thus a great mass of literature was preserved, while the corresponding + works were quite forgotten in western Europe. + </p> + <p> + Meantime many of these works were translated into Syriac, Armenian, and + Persian, and when later on the Byzantine civilization degenerated, many + works that were no longer to be had in the Greek originals continued to be + widely circulated in Syriac, Persian, Armenian, and, ultimately, in Arabic + translations. When the Arabs started out in their conquests, which carried + them through Egypt and along the southern coast of the Mediterranean, + until they finally invaded Europe from the west by way of Gibraltar, they + carried with them their translations of many a Greek classical author, who + was introduced anew to the western world through this strange channel. + </p> + <p> + We are told, for example, that Averrhoes, the famous commentator of + Aristotle, who lived in Spain in the twelfth century, did not know a word + of Greek and was obliged to gain his knowledge of the master through a + Syriac translation; or, as others alleged (denying that he knew even + Syriac), through an Arabic version translated from the Syriac. We know, + too, that the famous chronology of Eusebius was preserved through an + Armenian translation; and reference has more than once been made to the + Arabic translation of Ptolemy's great work, to which we still apply its + Arabic title of Almagest. + </p> + <p> + The familiar story that when the Arabs invaded Egypt they burned the + Alexandrian library is now regarded as an invention of later times. It + seems much more probable that the library bad been largely scattered + before the coming of the Moslems. Indeed, it has even been suggested that + the Christians of an earlier day removed the records of pagan thought. Be + that as it may, the famous Alexandrian library had disappeared long before + the revival of interest in classical learning. Meanwhile, as we have said, + the Arabs, far from destroying the western literature, were its chief + preservers. Partly at least because of their regard for the records of the + creative work of earlier generations of alien peoples, the Arabs were + enabled to outstrip their contemporaries. For it cannot be in doubt that, + during that long stretch of time when the western world was ignoring + science altogether or at most contenting itself with the casual reading of + Aristotle and Pliny, the Arabs had the unique distinction of attempting + original investigations in science. To them were due all important + progressive steps which were made in any scientific field whatever for + about a thousand years after the time of Ptolemy and Galen. The progress + made even by the Arabs during this long period seems meagre enough, yet it + has some significant features. These will now demand our attention. + </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> + II. MEDIAEVAL SCIENCE AMONG THE ARABIANS + </h2> + <p> + The successors of Mohammed showed themselves curiously receptive of the + ideas of the western people whom they conquered. They came in contact with + the Greeks in western Asia and in Egypt, and, as has been said, became + their virtual successors in carrying forward the torch of learning. It + must not be inferred, however, that the Arabian scholars, as a class, were + comparable to their predecessors in creative genius. On the contrary, they + retained much of the conservative oriental spirit. They were under the + spell of tradition, and, in the main, what they accepted from the Greeks + they regarded as almost final in its teaching. There were, however, a few + notable exceptions among their men of science, and to these must be + ascribed several discoveries of some importance. + </p> + <p> + The chief subjects that excited the interest and exercised the ingenuity + of the Arabian scholars were astronomy, mathematics, and medicine. The + practical phases of all these subjects were given particular attention. + Thus it is well known that our so-called Arabian numerals date from this + period. The revolutionary effect of these characters, as applied to + practical mathematics, can hardly be overestimated; but it is generally + considered, and in fact was admitted by the Arabs themselves, that these + numerals were really borrowed from the Hindoos, with whom the Arabs came + in contact on the east. Certain of the Hindoo alphabets, notably that of + the Battaks of Sumatra, give us clews to the originals of the numerals. It + does not seem certain, however, that the Hindoos employed these characters + according to the decimal system, which is the prime element of their + importance. Knowledge is not forthcoming as to just when or by whom such + application was made. If this was an Arabic innovation, it was perhaps the + most important one with which that nation is to be credited. Another + mathematical improvement was the introduction into trigonometry of the + sine—the half-chord of the double arc—instead of the chord of + the arc itself which the Greek astronomers had employed. This improvement + was due to the famous Albategnius, whose work in other fields we shall + examine in a moment. + </p> + <p> + Another evidence of practicality was shown in the Arabian method of + attempting to advance upon Eratosthenes' measurement of the earth. Instead + of trusting to the measurement of angles, the Arabs decided to measure + directly a degree of the earth's surface—or rather two degrees. + Selecting a level plain in Mesopotamia for the experiment, one party of + the surveyors progressed northward, another party southward, from a given + point to the distance of one degree of arc, as determined by astronomical + observations. The result found was fifty-six miles for the northern + degree, and fifty-six and two-third miles for the southern. Unfortunately, + we do not know the precise length of the mile in question, and therefore + cannot be assured as to the accuracy of the measurement. It is interesting + to note, however, that the two degrees were found of unequal lengths, + suggesting that the earth is not a perfect sphere—a suggestion the + validity of which was not to be put to the test of conclusive measurements + until about the close of the eighteenth century. The Arab measurement was + made in the time of Caliph Abdallah al-Mamun, the son of the famous + Harun-al-Rashid. Both father and son were famous for their interest in + science. Harun-al-Rashid was, it will be recalled, the friend of + Charlemagne. It is said that he sent that ruler, as a token of friendship, + a marvellous clock which let fall a metal ball to mark the hours. This + mechanism, which is alleged to have excited great wonder in the West, + furnishes yet another instance of Arabian practicality. + </p> + <p> + Perhaps the greatest of the Arabian astronomers was Mohammed ben Jabir + Albategnius, or El-batani, who was born at Batan, in Mesopotamia, about + the year 850 A.D., and died in 929. Albategnius was a student of the + Ptolemaic astronomy, but he was also a practical observer. He made the + important discovery of the motion of the solar apogee. That is to say, he + found that the position of the sun among the stars, at the time of its + greatest distance from the earth, was not what it had been in the time of + Ptolemy. The Greek astronomer placed the sun in longitude 65 degrees, but + Albategnius found it in longitude 82 degrees, a distance too great to be + accounted for by inaccuracy of measurement. The modern inference from this + observation is that the solar system is moving through space; but of + course this inference could not well be drawn while the earth was regarded + as the fixed centre of the universe. + </p> + <p> + In the eleventh century another Arabian discoverer, Arzachel, observing + the sun to be less advanced than Albategnius had found it, inferred + incorrectly that the sun had receded in the mean time. The modern + explanation of this observation is that the measurement of Albategnius was + somewhat in error, since we know that the sun's motion is steadily + progressive. Arzachel, however, accepting the measurement of his + predecessor, drew the false inference of an oscillatory motion of the + stars, the idea of the motion of the solar system not being permissible. + This assumed phenomenon, which really has no existence in point of fact, + was named the "trepidation of the fixed stars," and was for centuries + accepted as an actual phenomenon. Arzachel explained this supposed + phenomenon by assuming that the equinoctial points, or the points of + intersection of the equator and the ecliptic, revolve in circles of eight + degrees' radius. The first points of Aries and Libra were supposed to + describe the circumference of these circles in about eight hundred years. + All of which illustrates how a difficult and false explanation may take + the place of a simple and correct one. The observations of later + generations have shown conclusively that the sun's shift of position is + regularly progressive, hence that there is no "trepidation" of the stars + and no revolution of the equinoctial points. + </p> + <p> + If the Arabs were wrong as regards this supposed motion of the fixed + stars, they made at least one correct observation as to the inequality of + motion of the moon. Two inequalities of the motion of this body were + already known. A third, called the moon's variation, was discovered by an + Arabian astronomer who lived at Cairo and observed at Bagdad in 975, and + who bore the formidable name of Mohammed Aboul Wefaal-Bouzdjani. The + inequality of motion in question, in virtue of which the moon moves + quickest when she is at new or full, and slowest at the first and third + quarter, was rediscovered by Tycho Brahe six centuries later; a fact which + in itself evidences the neglect of the Arabian astronomer's discovery by + his immediate successors. + </p> + <p> + In the ninth and tenth centuries the Arabian city of Cordova, in Spain, + was another important centre of scientific influence. There was a library + of several hundred thousand volumes here, and a college where mathematics + and astronomy were taught. Granada, Toledo, and Salamanca were also + important centres, to which students flocked from western Europe. It was + the proximity of these Arabian centres that stimulated the scientific + interests of Alfonso X. of Castile, at whose instance the celebrated + Alfonsine tables were constructed. A familiar story records that Alfonso, + pondering the complications of the Ptolemaic cycles and epicycles, was led + to remark that, had he been consulted at the time of creation, he could + have suggested a much better and simpler plan for the universe. Some + centuries were to elapse before Copernicus was to show that it was not the + plan of the universe, but man's interpretation of it, that was at fault. + </p> + <p> + Another royal personage who came under Arabian influence was Frederick II. + of Sicily—the "Wonder of the World," as he was called by his + contemporaries. The Almagest of Ptolemy was translated into Latin at his + instance, being introduced to the Western world through this curious + channel. At this time it became quite usual for the Italian and Spanish + scholars to understand Arabic although they were totally ignorant of + Greek. + </p> + <p> + In the field of physical science one of the most important of the Arabian + scientists was Alhazen. His work, published about the year 1100 A.D., had + great celebrity throughout the mediaeval period. The original + investigations of Alhazen had to do largely with optics. He made + particular studies of the eye itself, and the names given by him to + various parts of the eye, as the vitreous humor, the cornea, and the + retina, are still retained by anatomists. It is known that Ptolemy had + studied the refraction of light, and that he, in common with his immediate + predecessors, was aware that atmospheric refraction affects the apparent + position of stars near the horizon. Alhazen carried forward these studies, + and was led through them to make the first recorded scientific estimate of + the phenomena of twilight and of the height of the atmosphere. The + persistence of a glow in the atmosphere after the sun has disappeared + beneath the horizon is so familiar a phenomenon that the ancient + philosophers seem not to have thought of it as requiring an explanation. + Yet a moment's consideration makes it clear that, if light travels in + straight lines and the rays of the sun were in no wise deflected, the + complete darkness of night should instantly succeed to day when the sun + passes below the horizon. That this sudden change does not occur, Alhazen + explained as due to the reflection of light by the earth's atmosphere. + </p> + <p> + Alhazen appears to have conceived the atmosphere as a sharply defined + layer, and, assuming that twilight continues only so long as rays of the + sun reflected from the outer surface of this layer can reach the spectator + at any given point, he hit upon a means of measurement that seemed to + solve the hitherto inscrutable problem as to the atmospheric depth. Like + the measurements of Aristarchus and Eratosthenes, this calculation of + Alhazen is simple enough in theory. Its defect consists largely in the + difficulty of fixing its terms with precision, combined with the further + fact that the rays of the sun, in taking the slanting course through the + earth's atmosphere, are really deflected from a straight line in virtue of + the constantly increasing density of the air near the earth's surface. + Alhazen must have been aware of this latter fact, since it was known to + the later Alexandrian astronomers, but he takes no account of it in the + present measurement. The diagram will make the method of Alhazen clear. + </p> + <p> + His important premises are two: first, the well-recognized fact that, when + light is reflected from any surface, the angle of incidence is equal to + the angle of reflection; and, second, the much more doubtful observation + that twilight continues until such time as the sun, according to a simple + calculation, is nineteen degrees below the horizon. Referring to the + diagram, let the inner circle represent the earth's surface, the outer + circle the limits of the atmosphere, C being the earth's centre, and RR + radii of the earth. Then the observer at the point A will continue to + receive the reflected rays of the sun until that body reaches the point S, + which is, according to the hypothesis, nineteen degrees below the horizon + line of the observer at A. This horizon line, being represented by AH, and + the sun's ray by SM, the angle HMS is an angle of nineteen degrees. The + complementary angle SMA is, obviously, an angle of (180-19) one hundred + and sixty-one degrees. But since M is the reflecting surface and the angle + of incidence equals the angle of reflection, the angle AMC is an angle of + one-half of one hundred and sixty-one degrees, or eighty degrees and + thirty minutes. Now this angle AMC, being known, the right-angled triangle + MAC is easily resolved, since the side AC of that triangle, being the + radius of the earth, is a known dimension. Resolution of this triangle + gives us the length of the hypotenuse MC, and the difference between this + and the radius (AC), or CD, is obviously the height of the atmosphere (h), + which was the measurement desired. According to the calculation of + Alhazen, this h, or the height of the atmosphere, represents from twenty + to thirty miles. The modern computation extends this to about fifty miles. + But, considering the various ambiguities that necessarily attended the + experiment, the result was a remarkably close approximation to the truth. + </p> + <p> + Turning from physics to chemistry, we find as perhaps the greatest Arabian + name that of Geber, who taught in the College of Seville in the first half + of the eighth century. The most important researches of this really + remarkable experimenter had to do with the acids. The ancient world had + had no knowledge of any acid more powerful than acetic. Geber, however, + vastly increased the possibilities of chemical experiment by the discovery + of sulphuric, nitric, and nitromuriatic acids. He made use also of the + processes of sublimation and filtration, and his works describe the water + bath and the chemical oven. Among the important chemicals which he first + differentiated is oxide of mercury, and his studies of sulphur in its + various compounds have peculiar interest. In particular is this true of + his observation that, tinder certain conditions of oxidation, the weight + of a metal was lessened. + </p> + <p> + From the record of these studies in the fields of astronomy, physics, and + chemistry, we turn to a somewhat extended survey of the Arabian advances + in the field of medicine. + </p> + <p> + ARABIAN MEDICINE + </p> + <p> + The influence of Arabian physicians rested chiefly upon their use of drugs + rather than upon anatomical knowledge. Like the mediaeval Christians, they + looked with horror on dissection of the human body; yet there were always + among them investigators who turned constantly to nature herself for + hidden truths, and were ready to uphold the superiority of actual + observation to mere reading. Thus the physician Abd el-Letif, while in + Egypt, made careful studies of a mound of bones containing more than + twenty thousand skeletons. While examining these bones he discovered that + the lower jaw consists of a single bone, not of two, as had been taught by + Galen. He also discovered several other important mistakes in Galenic + anatomy, and was so impressed with his discoveries that he contemplated + writing a work on anatomy which should correct the great classical + authority's mistakes. + </p> + <p> + It was the Arabs who invented the apothecary, and their pharmacopoeia, + issued from the hospital at Gondisapor, and elaborated from time to time, + formed the basis for Western pharmacopoeias. Just how many drugs + originated with them, and how many were borrowed from the Hindoos, Jews, + Syrians, and Persians, cannot be determined. It is certain, however, that + through them various new and useful drugs, such as senna, aconite, + rhubarb, camphor, and mercury, were handed down through the Middle Ages, + and that they are responsible for the introduction of alcohol in the field + of therapeutics. + </p> + <p> + In mediaeval Europe, Arabian science came to be regarded with + superstitious awe, and the works of certain Arabian physicians were + exalted to a position above all the ancient writers. In modern times, + however, there has been a reaction and a tendency to depreciation of their + work. By some they are held to be mere copyists or translators of Greek + books, and in no sense original investigators in medicine. Yet there can + be little doubt that while the Arabians did copy and translate freely, + they also originated and added considerably to medical knowledge. It is + certain that in the time when Christian monarchs in western Europe were + paying little attention to science or education, the caliphs and vizirs + were encouraging physicians and philosophers, building schools, and + erecting libraries and hospitals. They made at least a creditable effort + to uphold and advance upon the scientific standards of an earlier age. + </p> + <p> + The first distinguished Arabian physician was Harets ben Kaladah, who + received his education in the Nestonian school at Gondisapor, about the + beginning of the seventh century. Notwithstanding the fact that Harets was + a Christian, he was chosen by Mohammed as his chief medical adviser, and + recommended as such to his successor, the Caliph Abu Bekr. Thus, at the + very outset, the science of medicine was divorced from religion among the + Arabians; for if the prophet himself could employ the services of an + unbeliever, surely others might follow his example. And that this example + was followed is shown in the fact that many Christian physicians were + raised to honorable positions by succeeding generations of Arabian + monarchs. This broad-minded view of medicine taken by the Arabs + undoubtedly assisted as much as any one single factor in upbuilding the + science, just as the narrow and superstitious view taken by Western + nations helped to destroy it. + </p> + <p> + The education of the Arabians made it natural for them to associate + medicine with the natural sciences, rather than with religion. An Arabian + savant was supposed to be equally well educated in philosophy, + jurisprudence, theology, mathematics, and medicine, and to practise law, + theology, and medicine with equal skill upon occasion. It is easy to + understand, therefore, why these religious fanatics were willing to employ + unbelieving physicians, and their physicians themselves to turn to the + scientific works of Hippocrates and Galen for medical instruction, rather + than to religious works. Even Mohammed himself professed some knowledge of + medicine, and often relied upon this knowledge in treating ailments rather + than upon prayers or incantations. He is said, for example, to have + recommended and applied the cautery in the case of a friend who, when + suffering from angina, had sought his aid. + </p> + <p> + The list of eminent Arabian physicians is too long to be given here, but + some of them are of such importance in their influence upon later medicine + that they cannot be entirely ignored. One of the first of these was Honain + ben Isaac (809-873 A.D.), a Christian Arab of Bagdad. He made translations + of the works of Hippocrates, and practised the art along the lines + indicated by his teachings and those of Galen. He is considered the + greatest translator of the ninth century and one of the greatest + philosophers of that period. + </p> + <p> + Another great Arabian physician, whose work was just beginning as Honain's + was drawing to a close, was Rhazes (850-923 A.D.), who during his life was + no less noted as a philosopher and musician than as a physician. He + continued the work of Honain, and advanced therapeutics by introducing + more extensive use of chemical remedies, such as mercurial ointments, + sulphuric acid, and aqua vitae. He is also credited with being the first + physician to describe small-pox and measles accurately. + </p> + <p> + While Rhazes was still alive another Arabian, Haly Abbas (died about 994), + was writing his famous encyclopaedia of medicine, called The Royal Book. + But the names of all these great physicians have been considerably + obscured by the reputation of Avicenna (980-1037), the Arabian "Prince of + Physicians," the greatest name in Arabic medicine, and one of the most + remarkable men in history. Leclerc says that "he was perhaps never + surpassed by any man in brilliancy of intellect and indefatigable + activity." His career was a most varied one. He was at all times a + boisterous reveller, but whether flaunting gayly among the guests of an + emir or biding in some obscure apothecary cellar, his work of + philosophical writing was carried on steadily. When a friendly emir was in + power, he taught and wrote and caroused at court; but between times, when + some unfriendly ruler was supreme, he was hiding away obscurely, still + pouring out his great mass of manuscripts. In this way his entire life was + spent. + </p> + <p> + By his extensive writings he revived and kept alive the best of the + teachings of the Greek physicians, adding to them such observations as he + had made in anatomy, physiology, and materia medica. Among his discoveries + is that of the contagiousness of pulmonary tuberculosis. His works for + several centuries continued to be looked upon as the highest standard by + physicians, and he should undoubtedly be credited with having at least + retarded the decline of mediaeval medicine. + </p> + <p> + But it was not the Eastern Arabs alone who were active in the field of + medicine. Cordova, the capital of the western caliphate, became also a + great centre of learning and produced several great physicians. One of + these, Albucasis (died in 1013 A.D.), is credited with having published + the first illustrated work on surgery, this book being remarkable in still + another way, in that it was also the first book, since classical times, + written from the practical experience of the physician, and not a mere + compilation of ancient authors. A century after Albucasis came the great + physician Avenzoar (1113-1196), with whom he divides about equally the + medical honors of the western caliphate. Among Avenzoar's discoveries was + that of the cause of "itch"—a little parasite, "so small that he is + hardly visible." The discovery of the cause of this common disease seems + of minor importance now, but it is of interest in medical history because, + had Avenzoar's discovery been remembered a hundred years ago, "itch struck + in" could hardly have been considered the cause of three-fourths of all + diseases, as it was by the famous Hahnemann. + </p> + <p> + The illustrious pupil of Avenzoar, Averrhoes, who died in 1198 A.D., was + the last of the great Arabian physicians who, by rational conception of + medicine, attempted to stem the flood of superstition that was + overwhelming medicine. For a time he succeeded; but at last the Moslem + theologians prevailed, and he was degraded and banished to a town + inhabited only by the despised Jews. + </p> + <p> + ARABIAN HOSPITALS + </p> + <p> + To early Christians belong the credit of having established the first + charitable institutions for caring for the sick; but their efforts were + soon eclipsed by both Eastern and Western Mohammedans. As early as the + eighth century the Arabs had begun building hospitals, but the flourishing + time of hospital building seems to have begun early in the tenth century. + Lady Seidel, in 918 A.D., opened a hospital at Bagdad, endowed with an + amount corresponding to about three hundred pounds sterling a month. Other + similar hospitals were erected in the years immediately following, and in + 977 the Emir Adad-adaula established an enormous institution with a staff + of twenty-four medical officers. The great physician Rhazes is said to + have selected the site for one of these hospitals by hanging pieces of + meat in various places about the city, selecting the site near the place + at which putrefaction was slowest in making its appearance. By the middle + of the twelfth century there were something like sixty medical + institutions in Bagdad alone, and these institutions were free to all + patients and supported by official charity. + </p> + <p> + The Emir Nureddin, about the year 1160, founded a great hospital at + Damascus, as a thank-offering for his victories over the Crusaders. This + great institution completely overshadowed all the earlier Moslem hospitals + in size and in the completeness of its equipment. It was furnished with + facilities for teaching, and was conducted for several centuries in a + lavish manner, regardless of expense. But little over a century after its + foundation the fame of its methods of treatment led to the establishment + of a larger and still more luxurious institution—the Mansuri + hospital at Cairo. It seems that a certain sultan, having been cured by + medicines from the Damascene hospital, determined to build one of his own + at Cairo which should eclipse even the great Damascene institution. + </p> + <p> + In a single year (1283-1284) this hospital was begun and completed. No + efforts were spared in hurrying on the good work, and no one was exempt + from performing labor on the building if he chanced to pass one of the + adjoining streets. It was the order of the sultan that any person passing + near could be impressed into the work, and this order was carried out to + the letter, noblemen and beggars alike being forced to lend a hand. Very + naturally, the adjacent thoroughfares became unpopular and practically + deserted, but still the holy work progressed rapidly and was shortly + completed. + </p> + <p> + This immense structure is said to have contained four courts, each having + a fountain in the centre; lecture-halls, wards for isolating certain + diseases, and a department that corresponded to the modern hospital's + "out-patient" department. The yearly endowment amounted to something like + the equivalent of one hundred and twenty-five thousand dollars. A novel + feature was a hall where musicians played day and night, and another where + story-tellers were employed, so that persons troubled with insomnia were + amused and melancholiacs cheered. Those of a religious turn of mind could + listen to readings of the Koran, conducted continuously by a staff of some + fifty chaplains. Each patient on leaving the hospital received some gold + pieces, that he need not be obliged to attempt hard labor at once. + </p> + <p> + In considering the astonishing tales of these sumptuous Arabian + institutions, it should be borne in mind that our accounts of them are, + for the most part, from Mohammedan sources. Nevertheless, there can be + little question that they were enormous institutions, far surpassing any + similar institutions in western Europe. The so-called hospitals in the + West were, at this time, branches of monasteries under supervision of the + monks, and did not compare favorably with the Arabian hospitals. + </p> + <p> + But while the medical science of the Mohammedans greatly overshadowed that + of the Christians during this period, it did not completely obliterate it. + About the year 1000 A.D. came into prominence the Christian medical school + at Salerno, situated on the Italian coast, some thirty miles southeast of + Naples. Just how long this school had been in existence, or by whom it was + founded, cannot be determined, but its period of greatest influence was + the eleventh, twelfth, and thirteenth centuries. The members of this + school gradually adopted Arabic medicine, making use of many drugs from + the Arabic pharmacopoeia, and this formed one of the stepping-stones to + the introduction of Arabian medicine all through western Europe. + </p> + <p> + It was not the adoption of Arabian medicines, however, that has made the + school at Salerno famous both in rhyme and prose, but rather the fact that + women there practised the healing art. Greatest among them was Trotula, + who lived in the eleventh century, and whose learning is reputed to have + equalled that of the greatest physicians of the day. She is accredited + with a work on Diseases of Women, still extant, and many of her writings + on general medical subjects were quoted through two succeeding centuries. + If we may judge from these writings, she seemed to have had many excellent + ideas as to the proper methods of treating diseases, but it is difficult + to determine just which of the writings credited to her are in reality + hers. Indeed, the uncertainty is even greater than this implies, for, + according to some writers, "Trotula" is merely the title of a book. Such + an authority as Malgaigne, however, believed that such a woman existed, + and that the works accredited to her are authentic. The truth of the + matter may perhaps never be fully established, but this at least is + certain—the tradition in regard to Trotula could never have arisen + had not women held a far different position among the Arabians of this + period from that accorded them in contemporary Christendom. + </p> + <p> + <a name="link2H_4_0005" id="link2H_4_0005"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + III. MEDIAEVAL SCIENCE IN THE WEST + </h2> + <p> + We have previously referred to the influence of the Byzantine civilization + in transmitting the learning of antiquity across the abysm of the dark + age. It must be admitted, however, that the importance of that + civilization did not extend much beyond the task of the common carrier. + There were no great creative scientists in the later Roman empire of the + East any more than in the corresponding empire of the West. There was, + however, one field in which the Byzantine made respectable progress and + regarding which their efforts require a few words of special comment. This + was the field of medicine. + </p> + <p> + The Byzantines of this time could boast of two great medical men, Aetius + of Amida (about 502-575 A.D.) and Paul of Aegina (about 620-690). The + works of Aetius were of value largely because they recorded the teachings + of many of his eminent predecessors, but he was not entirely lacking in + originality, and was perhaps the first physician to mention diphtheria, + with an allusion to some observations of the paralysis of the palate which + sometimes follows this disease. + </p> + <p> + Paul of Aegina, who came from the Alexandrian school about a century + later, was one of those remarkable men whose ideas are centuries ahead of + their time. This was particularly true of Paul in regard to surgery, and + his attitude towards the supernatural in the causation and treatment of + diseases. He was essentially a surgeon, being particularly familiar with + military surgery, and some of his descriptions of complicated and + difficult operations have been little improved upon even in modern times. + In his books he describes such operations as the removal of foreign bodies + from the nose, ear, and esophagus; and he recognizes foreign growths such + as polypi in the air-passages, and gives the method of their removal. Such + operations as tracheotomy, tonsillotomy, bronchotomy, staphylotomy, etc., + were performed by him, and he even advocated and described puncture of the + abdominal cavity, giving careful directions as to the location in which + such punctures should be made. He advocated amputation of the breast for + the cure of cancer, and described extirpation of the uterus. Just how + successful this last operation may have been as performed by him does not + appear; but he would hardly have recommended it if it had not been + sometimes, at least, successful. That he mentions it at all, however, is + significant, as this difficult operation is considered one of the great + triumphs of modern surgery. + </p> + <p> + But Paul of Aegina is a striking exception to the rule among Byzantine + surgeons, and as he was their greatest, so he was also their last + important surgeon. The energies of all Byzantium were so expended in + religious controversies that medicine, like the other sciences, was soon + relegated to a place among the other superstitions, and the influence of + the Byzantine school was presently replaced by that of the conquering + Arabians. + </p> + <p> + THIRTEENTH-CENTURY MEDICINE + </p> + <p> + The thirteenth century marks the beginning of a gradual change in + medicine, and a tendency to leave the time-worn rut of superstitious + dogmas that so long retarded the progress of science. It is thought that + the great epidemics which raged during the Middle Ages acted powerfully in + diverting the medical thought of the times into new and entirely different + channels. It will be remembered that the teachings of Galen were handed + through mediaeval times as the highest and best authority on the subject + of all diseases. When, however, the great epidemics made their appearance, + the medical men appealed to the works of Galen in vain for enlightenment, + as these works, having been written several centuries before the time of + the plagues, naturally contained no information concerning them. It was + evident, therefore, that on this subject, at least, Galen was not + infallible; and it would naturally follow that, one fallible point having + been revealed, others would be sought for. In other words, scepticism in + regard to accepted methods would be aroused, and would lead naturally, as + such scepticism usually does, to progress. The devastating effects of + these plagues, despite prayers and incantations, would arouse doubt in the + minds of many as to the efficacy of superstitious rites and ceremonies in + curing diseases. They had seen thousands and tens of thousands of their + fellow-beings swept away by these awful scourges. They had seen the + ravages of these epidemics continue for months or even years, + notwithstanding the fact that multitudes of God-fearing people prayed + hourly that such ravages might be checked. And they must have observed + also that when even very simple rules of cleanliness and hygiene were + followed there was a diminution in the ravages of the plague, even without + the aid of incantations. Such observations as these would have a tendency + to awaken a suspicion in the minds of many of the physicians that disease + was not a manifestation of the supernatural, but a natural phenomenon, to + be treated by natural methods. + </p> + <p> + But, be the causes what they may, it is a fact that the thirteenth century + marks a turning-point, or the beginning of an attitude of mind which + resulted in bringing medicine to a much more rational position. Among the + thirteenth-century physicians, two men are deserving of special mention. + These are Arnald of Villanova (1235-1312) and Peter of Abano (1250-1315). + Both these men suffered persecution for expressing their belief in + natural, as against the supernatural, causes of disease, and at one time + Arnald was obliged to flee from Barcelona for declaring that the "bulls" + of popes were human works, and that "acts of charity were dearer to God + than hecatombs." He was also accused of alchemy. Fleeing from persecution, + he finally perished by shipwreck. + </p> + <p> + Arnald was the first great representative of the school of Montpellier. He + devoted much time to the study of chemicals, and was active in attempting + to re-establish the teachings of Hippocrates and Galen. He was one of the + first of a long line of alchemists who, for several succeeding centuries, + expended so much time and energy in attempting to find the "elixir of + life." The Arab discovery of alcohol first deluded him into the belief + that the "elixir" had at last been found; but later he discarded it and + made extensive experiments with brandy, employing it in the treatment of + certain diseases—the first record of the administration of this + liquor as a medicine. Arnald also revived the search for some anaesthetic + that would produce insensibility to pain in surgical operations. This idea + was not original with him, for since very early times physicians had + attempted to discover such an anaesthetic, and even so early a writer as + Herodotus tells how the Scythians, by inhalation of the vapors of some + kind of hemp, produced complete insensibility. It may have been these + writings that stimulated Arnald to search for such an anaesthetic. In a + book usually credited to him, medicines are named and methods of + administration described which will make the patient insensible to pain, + so that "he may be cut and feel nothing, as though he were dead." For this + purpose a mixture of opium, mandragora, and henbane is to be used. This + mixture was held at the patient's nostrils much as ether and chloroform + are administered by the modern surgeon. The method was modified by Hugo of + Lucca (died in 1252 or 1268), who added certain other narcotics, such as + hemlock, to the mixture, and boiled a new sponge in this decoction. After + boiling for a certain time, this sponge was dried, and when wanted for use + was dipped in hot water and applied to the nostrils. + </p> + <p> + Just how frequently patients recovered from the administration of such a + combination of powerful poisons does not appear, but the percentage of + deaths must have been very high, as the practice was generally condemned. + Insensibility could have been produced only by swallowing large quantities + of the liquid, which dripped into the nose and mouth when the sponge was + applied, and a lethal quantity might thus be swallowed. The method was + revived, with various modifications, from time to time, but as often fell + into disuse. As late as 1782 it was sometimes attempted, and in that year + the King of Poland is said to have been completely anaesthetized and to + have recovered, after a painless amputation had been performed by the + surgeons. + </p> + <p> + Peter of Abano was one of the first great men produced by the University + of Padua. His fate would have been even more tragic than that of the + shipwrecked Arnald had he not cheated the purifying fagots of the church + by dying opportunely on the eve of his execution for heresy. But if his + spirit had cheated the fanatics, his body could not, and his bones were + burned for his heresy. He had dared to deny the existence of a devil, and + had suggested that the case of a patient who lay in a trance for three + days might help to explain some miracles, like the raising of Lazarus. + </p> + <p> + His great work was Conciliator Differentiarum, an attempt to reconcile + physicians and philosophers. But his researches were not confined to + medicine, for he seems to have had an inkling of the hitherto unknown fact + that air possesses weight, and his calculation of the length of the year + at three hundred and sixty-five days, six hours, and four minutes, is + exceptionally accurate for the age in which he lived. He was probably the + first of the Western writers to teach that the brain is the source of the + nerves, and the heart the source of the vessels. From this it is seen that + he was groping in the direction of an explanation of the circulation of + the blood, as demonstrated by Harvey three centuries later. + </p> + <p> + The work of Arnald and Peter of Abano in "reviving" medicine was continued + actively by Mondino (1276-1326) of Bologna, the "restorer of anatomy," and + by Guy of Chauliac: (born about 1300), the "restorer of surgery." All + through the early Middle Ages dissections of human bodies had been + forbidden, and even dissection of the lower animals gradually fell into + disrepute because physicians detected in such practices were sometimes + accused of sorcery. Before the close of the thirteenth century, however, a + reaction had begun, physicians were protected, and dissections were + occasionally sanctioned by the ruling monarch. Thus Emperor Frederick H. + (1194-1250 A.D.)—whose services to science we have already had + occasion to mention—ordered that at least one human body should be + dissected by physicians in his kingdom every five years. By the time of + Mondino dissections were becoming more frequent, and he himself is known + to have dissected and demonstrated several bodies. His writings on anatomy + have been called merely plagiarisms of Galen, but in all probability be + made many discoveries independently, and on the whole, his work may be + taken as more advanced than Galen's. His description of the heart is + particularly accurate, and he seems to have come nearer to determining the + course of the blood in its circulation than any of his predecessors. In + this quest he was greatly handicapped by the prevailing belief in the idea + that blood-vessels must contain air as well as blood, and this led him to + assume that one of the cavities of the heart contained "spirits," or air. + It is probable, however, that his accurate observations, so far as they + went, were helpful stepping-stones to Harvey in his discovery of the + circulation. + </p> + <p> + Guy of Chauliac, whose innovations in surgery reestablished that science + on a firm basis, was not only one of the most cultured, but also the most + practical surgeon of his time. He had great reverence for the works of + Galen, Albucasis, and others of his noted predecessors; but this reverence + did not blind him to their mistakes nor prevent him from using rational + methods of treatment far in advance of theirs. His practicality is shown + in some of his simple but useful inventions for the sick-room, such as the + device of a rope, suspended from the ceiling over the bed, by which a + patient may move himself about more easily; and in some of his + improvements in surgical dressings, such as stiffening bandages by dipping + them in the white of an egg so that they are held firmly. He treated + broken limbs in the suspended cradle still in use, and introduced the + method of making "traction" on a broken limb by means of a weight and + pulley, to prevent deformity through shortening of the member. He was one + of the first physicians to recognize the utility of spectacles, and + recommended them in cases not amenable to treatment with lotions and + eye-waters. In some of his surgical operations, such as trephining for + fracture of the skull, his technique has been little improved upon even in + modern times. In one of these operations he successfully removed a portion + of a man's brain. + </p> + <p> + Surgery was undoubtedly stimulated greatly at this period by the constant + wars. Lay physicians, as a class, had been looked down upon during the + Dark Ages; but with the beginning of the return to rationalism, the + services of surgeons on the battle-field, to remove missiles from wounds, + and to care for wounds and apply dressings, came to be more fully + appreciated. In return for his labors the surgeon was thus afforded better + opportunities for observing wounds and diseases, which led naturally to a + gradual improvement in surgical methods. + </p> + <p> + FIFTEENTH-CENTURY MEDICINE + </p> + <p> + The thirteenth and fourteenth centuries had seen some slight advancement + in the science of medicine; at least, certain surgeons and physicians, if + not the generality, had made advances; but it was not until the fifteenth + century that the general revival of medical learning became assured. In + this movement, naturally, the printing-press played an all-important part. + Medical books, hitherto practically inaccessible to the great mass of + physicians, now became common, and this output of reprints of Greek and + Arabic treatises revealed the fact that many of the supposed true copies + were spurious. These discoveries very naturally aroused all manner of + doubt and criticism, which in turn helped in the development of + independent thought. + </p> + <p> + A certain manuscript of the great Cornelius Celsus, the De Medicine, which + had been lost for many centuries, was found in the church of St. Ambrose, + at Milan, in 1443, and was at once put into print. The effect of the + publication of this book, which had lain in hiding for so many centuries, + was a revelation, showing the medical profession how far most of their + supposed true copies of Celsus had drifted away from the original. The + indisputable authenticity of this manuscript, discovered and vouched for + by the man who shortly after became Pope Nicholas V., made its publication + the more impressive. The output in book form of other authorities followed + rapidly, and the manifest discrepancies between such teachers as Celsus, + Hippocrates, Galen, and Pliny heightened still more the growing spirit of + criticism. + </p> + <p> + These doubts resulted in great controversies as to the proper treatment of + certain diseases, some physicians following Hippocrates, others Galen or + Celsus, still others the Arabian masters. One of the most bitter of these + contests was over the question of "revulsion," and "derivation"—that + is, whether in cases of pleurisy treated by bleeding, the venesection + should be made at a point distant from the seat of the disease, as held by + the "revulsionists," or at a point nearer and on the same side of the + body, as practised by the "derivationists." That any great point for + discussion could be raised in the fifteenth or sixteenth centuries on so + simple a matter as it seems to-day shows how necessary to the progress of + medicine was the discovery of the circulation of the blood made by Harvey + two centuries later. After Harvey's discovery no such discussion could + have been possible, because this discovery made it evident that as far as + the general effect upon the circulation is concerned, it made little + difference whether the bleeding was done near a diseased part or remote + from it. But in the sixteenth century this question was the all-absorbing + one among the doctors. At one time the faculty of Paris condemned + "derivation"; but the supporters of this method carried the war still + higher, and Emperor Charles V. himself was appealed to. He reversed the + decision of the Paris faculty, and decided in favor of "derivation." His + decision was further supported by Pope Clement VII., although the + discussion dragged on until cut short by Harvey's discovery. + </p> + <p> + But a new form of injury now claimed the attention of the surgeons, + something that could be decided by neither Greek nor Arabian authors, as + the treatment of gun-shot wounds was, for obvious reasons, not given in + their writings. About this time, also, came the great epidemics, "the + sweating sickness" and scurvy; and upon these subjects, also, the Greeks + and Arabians were silent. John of Vigo, in his book, the Practica Copiosa, + published in 1514, and repeated in many editions, became the standard + authority on all these subjects, and thus supplanted the works of the + ancient writers. + </p> + <p> + According to Vigo, gun-shot wounds differed from the wounds made by + ordinary weapons—that is, spear, arrow, sword, or axe—in that + the bullet, being round, bruised rather than cut its way through the + tissues; it burned the flesh; and, worst of all, it poisoned it. Vigo laid + especial stress upon treating this last condition, recommending the use of + the cautery or the oil of elder, boiling hot. It is little wonder that + gun-shot wounds were so likely to prove fatal. Yet, after all, here was + the germ of the idea of antisepsis. + </p> + <p> + NEW BEGINNINGS IN GENERAL SCIENCE + </p> + <p> + We have dwelt thus at length on the subject of medical science, because it + was chiefly in this field that progress was made in the Western world + during the mediaeval period, and because these studies furnished the point + of departure for the revival all along the line. It will be understood, + however, from what was stated in the preceding chapter, that the Arabian + influences in particular were to some extent making themselves felt along + other lines. The opportunity afforded a portion of the Western world—notably + Spain and Sicily—to gain access to the scientific ideas of antiquity + through Arabic translations could not fail of influence. Of like + character, and perhaps even more pronounced in degree, was the influence + wrought by the Byzantine refugees, who, when Constantinople began to be + threatened by the Turks, migrated to the West in considerable numbers, + bringing with them a knowledge of Greek literature and a large number of + precious works which for centuries had been quite forgotten or absolutely + ignored in Italy. Now Western scholars began to take an interest in the + Greek language, which had been utterly neglected since the beginning of + the Middle Ages. Interesting stories are told of the efforts made by such + men as Cosmo de' Medici to gain possession of classical manuscripts. The + revival of learning thus brought about had its first permanent influence + in the fields of literature and art, but its effect on science could not + be long delayed. Quite independently of the Byzantine influence, however, + the striving for better intellectual things had manifested itself in many + ways before the close of the thirteenth century. An illustration of this + is found in the almost simultaneous development of centres of teaching, + which developed into the universities of Italy, France, England, and, a + little later, of Germany. + </p> + <p> + The regular list of studies that came to be adopted everywhere comprised + seven nominal branches, divided into two groups—the so-called + quadrivium, comprising music, arithmetic, geometry, and astronomy; and the + trivium comprising grammar, rhetoric, and logic. The vagueness of + implication of some of these branches gave opportunity to the teacher for + the promulgation of almost any knowledge of which he might be possessed, + but there can be no doubt that, in general, science had but meagre share + in the curriculum. In so far as it was given representation, its chief + field must have been Ptolemaic astronomy. The utter lack of scientific + thought and scientific method is illustrated most vividly in the works of + the greatest men of that period—such men as Albertus Magnus, Thomas + Aquinas, Bonaventura, and the hosts of other scholastics of lesser rank. + Yet the mental awakening implied in their efforts was sure to extend to + other fields, and in point of fact there was at least one contemporary of + these great scholastics whose mind was intended towards scientific + subjects, and who produced writings strangely at variance in tone and in + content with the others. This anachronistic thinker was the English monk, + Roger Bacon. + </p> + <p> + ROGER BACON + </p> + <p> + Bacon was born in 1214 and died in 1292. By some it is held that he was + not appreciated in his own time because he was really a modern scientist + living in an age two centuries before modern science or methods of modern + scientific thinking were known. Such an estimate, however, is a manifest + exaggeration of the facts, although there is probably a grain of truth in + it withal. His learning certainly brought him into contact with the great + thinkers of the time, and his writings caused him to be imprisoned by his + fellow-churchmen at different times, from which circumstances we may + gather that he was advanced thinker, even if not a modern scientist. + </p> + <p> + Although Bacon was at various times in durance, or under surveillance, and + forbidden to write, he was nevertheless a marvellously prolific writer, as + is shown by the numerous books and unpublished manuscripts of his still + extant. His master-production was the Opus Majus. In Part IV. of this work + he attempts to show that all sciences rest ultimately on mathematics; but + Part V., which treats of perspective, is of particular interest to modern + scientists, because in this he discusses reflection and refraction, and + the properties of mirrors and lenses. In this part, also, it is evident + that he is making use of such Arabian writers as Alkindi and Alhazen, and + this is of especial interest, since it has been used by his detractors, + who accuse him of lack of originality, to prove that his seeming + inventions and discoveries were in reality adaptations of the Arab + scientists. It is difficult to determine just how fully such criticisms + are justified. It is certain, however, that in this part he describes the + anatomy of the eye with great accuracy, and discusses mirrors and lenses. + </p> + <p> + The magnifying power of the segment of a glass sphere had been noted by + Alhazen, who had observed also that the magnification was increased by + increasing the size of the segment used. Bacon took up the discussion of + the comparative advantages of segments, and in this discussion seems to + show that he understood how to trace the progress of the rays of light + through a spherical transparent body, and how to determine the place of + the image. He also described a method of constructing a telescope, but it + is by no means clear that he had ever actually constructed such an + instrument. It is also a mooted question as to whether his instructions as + to the construction of such an instrument would have enabled any one to + construct one. The vagaries of the names of terms as he uses them allow + such latitude in interpretation that modern scientists are not agreed as + to the practicability of Bacon's suggestions. For example, he constantly + refers to force under such names as virtus, species, imago, agentis, and a + score of other names, and this naturally gives rise to the great + differences in the interpretations of his writings, with corresponding + differences in estimates of them. + </p> + <p> + The claim that Bacon originated the use of lenses, in the form of + spectacles, cannot be proven. Smith has determined that as early as the + opening years of the fourteenth century such lenses were in use, but this + proves nothing as regards Bacon's connection with their invention. The + knowledge of lenses seems to be very ancient, if we may judge from the + convex lens of rock crystal found by Layard in his excavations at Nimrud. + There is nothing to show, however, that the ancients ever thought of using + them to correct defects of vision. Neither, apparently, is it feasible to + determine whether the idea of such an application originated with Bacon. + </p> + <p> + Another mechanical discovery about which there has been a great deal of + discussion is Bacon's supposed invention of gunpowder. It appears that in + a certain passage of his work he describes the process of making a + substance that is, in effect, ordinary gunpowder; but it is more than + doubtful whether he understood the properties of the substance he + describes. It is fairly well established, however, that in Bacon's time + gunpowder was known to the Arabs, so that it should not be surprising to + find references made to it in Bacon's work, since there is reason to + believe that he constantly consulted Arabian writings. + </p> + <p> + The great merit of Bacon's work, however, depends on the principles taught + as regards experiment and the observation of nature, rather than on any + single invention. He had the all-important idea of breaking with + tradition. He championed unfettered inquiry in every field of thought. He + had the instinct of a scientific worker—a rare instinct indeed in + that age. Nor need we doubt that to the best of his opportunities he was + himself an original investigator. + </p> + <p> + LEONARDO DA VINCI + </p> + <p> + The relative infertility of Bacon's thought is shown by the fact that he + founded no school and left no trace of discipleship. The entire century + after his death shows no single European name that need claim the + attention of the historian of science. In the latter part of the fifteenth + century, however, there is evidence of a renaissance of science no less + than of art. The German Muller became famous under the latinized named of + Regio Montanus (1437-1472), although his actual scientific attainments + would appear to have been important only in comparison with the utter + ignorance of his contemporaries. The most distinguished worker of the new + era was the famous Italian Leonardo da Vinci—a man who has been + called by Hamerton the most universal genius that ever lived. Leonardo's + position in the history of art is known to every one. With that, of + course, we have no present concern; but it is worth our while to inquire + at some length as to the famous painter's accomplishments as a scientist. + </p> + <p> + From a passage in the works of Leonardo, first brought to light by + Venturi,(1) it would seem that the great painter anticipated Copernicus in + determining the movement of the earth. He made mathematical calculations + to prove this, and appears to have reached the definite conclusion that + the earth does move—or what amounts to the same thing, that the sun + does not move. Muntz is authority for the statement that in one of his + writings he declares, "Il sole non si mouve"—the sun does not + move.(2) + </p> + <p> + Among his inventions is a dynamometer for determining the traction power + of machines and animals, and his experiments with steam have led some of + his enthusiastic partisans to claim for him priority to Watt in the + invention of the steam-engine. In these experiments, however, Leonardo + seems to have advanced little beyond Hero of Alexandria and his steam toy. + Hero's steam-engine did nothing but rotate itself by virtue of escaping + jets of steam forced from the bent tubes, while Leonardo's "steam-engine" + "drove a ball weighing one talent over a distance of six stadia." In a + manuscript now in the library of the Institut de France, Da Vinci + describes this engine minutely. The action of this machine was due to the + sudden conversion of small quantities of water into steam ("smoke," as he + called it) by coming suddenly in contact with a heated surface in a proper + receptacle, the rapidly formed steam acting as a propulsive force after + the manner of an explosive. It is really a steam-gun, rather than a + steam-engine, and it is not unlikely that the study of the action of + gunpowder may have suggested it to Leonardo. + </p> + <p> + It is believed that Leonardo is the true discoverer of the camera-obscura, + although the Neapolitan philosopher, Giambattista Porta, who was not born + until some twenty years after the death of Leonardo, is usually credited + with first describing this device. There is little doubt, however, that Da + Vinci understood the principle of this mechanism, for he describes how + such a camera can be made by cutting a small, round hole through the + shutter of a darkened room, the reversed image of objects outside being + shown on the opposite wall. + </p> + <p> + Like other philosophers in all ages, he had observed a great number of + facts which he was unable to explain correctly. But such accumulations of + scientific observations are always interesting, as showing how many + centuries of observation frequently precede correct explanation. He + observed many facts about sounds, among others that blows struck upon a + bell produced sympathetic sounds in a bell of the same kind; and that + striking the string of a lute produced vibration in corresponding strings + of lutes strung to the same pitch. He knew, also, that sounds could be + heard at a distance at sea by listening at one end of a tube, the other + end of which was placed in the water; and that the same expedient worked + successfully on land, the end of the tube being placed against the ground. + </p> + <p> + The knowledge of this great number of unexplained facts is often + interpreted by the admirers of Da Vinci, as showing an almost occult + insight into science many centuries in advance of his time. Such + interpretations, however, are illusive. The observation, for example, that + a tube placed against the ground enables one to hear movements on the + earth at a distance, is not in itself evidence of anything more than acute + scientific observation, as a similar method is in use among almost every + race of savages, notably the American Indians. On the other hand, one is + inclined to give credence to almost any story of the breadth of knowledge + of the man who came so near anticipating Hutton, Lyell, and Darwin in his + interpretation of the geological records as he found them written on the + rocks. + </p> + <p> + It is in this field of geology that Leonardo is entitled to the greatest + admiration by modern scientists. He had observed the deposit of fossil + shells in various strata of rocks, even on the tops of mountains, and he + rejected once for all the theory that they had been deposited there by the + Deluge. He rightly interpreted their presence as evidence that they had + once been deposited at the bottom of the sea. This process he assumed bad + taken hundreds and thousands of centuries, thus tacitly rejecting the + biblical tradition as to the date of the creation. + </p> + <p> + Notwithstanding the obvious interest that attaches to the investigations + of Leonardo, it must be admitted that his work in science remained almost + as infertile as that of his great precursor, Bacon. The really stimulative + work of this generation was done by a man of affairs, who knew little of + theoretical science except in one line, but who pursued that one practical + line until he achieved a wonderful result. This man was Christopher + Columbus. It is not necessary here to tell the trite story of his + accomplishment. Suffice it that his practical demonstration of the + rotundity of the earth is regarded by most modern writers as marking an + epoch in history. With the year of his voyage the epoch of the Middle Ages + is usually regarded as coming to an end. It must not be supposed that any + very sudden change came over the aspect of scholarship of the time, but + the preliminaries of great things had been achieved, and when Columbus + made his famous voyage in 1492, the man was already alive who was to bring + forward the first great vitalizing thought in the field of pure science + that the Western world had originated for more than a thousand years. This + man bore the name of Kopernik, or in its familiar Anglicized form, + Copernicus. His life work and that of his disciples will claim our + attention in the succeeding chapter. + </p> + <p> + <a name="link2H_4_0006" id="link2H_4_0006"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + IV. THE NEW COSMOLOGY—COPERNICUS TO KEPLER AND GALILEO + </h2> + <p> + We have seen that the Ptolemaic astronomy, which was the accepted doctrine + throughout the Middle Ages, taught that the earth is round. Doubtless + there was a popular opinion current which regarded the earth as flat, but + it must be understood that this opinion had no champions among men of + science during the Middle Ages. When, in the year 1492, Columbus sailed + out to the west on his memorable voyage, his expectation of reaching India + had full scientific warrant, however much it may have been scouted by + certain ecclesiastics and by the average man of the period. Nevertheless, + we may well suppose that the successful voyage of Columbus, and the still + more demonstrative one made about thirty years later by Magellan, gave the + theory of the earth's rotundity a certainty it could never previously have + had. Alexandrian geographers had measured the size of the earth, and had + not hesitated to assert that by sailing westward one might reach India. + But there is a wide gap between theory and practice, and it required the + voyages of Columbus and his successors to bridge that gap. + </p> + <p> + After the companions of Magellan completed the circumnavigation of the + globe, the general shape of our earth would, obviously, never again be + called in question. But demonstration of the sphericity of the earth had, + of course, no direct bearing upon the question of the earth's position in + the universe. Therefore the voyage of Magellan served to fortify, rather + than to dispute, the Ptolemaic theory. According to that theory, as we + have seen, the earth was supposed to lie immovable at the centre of the + universe; the various heavenly bodies, including the sun, revolving about + it in eccentric circles. We have seen that several of the ancient Greeks, + notably Aristarchus, disputed this conception, declaring for the central + position of the sun in the universe, and the motion of the earth and other + planets about that body. But this revolutionary theory seemed so opposed + to the ordinary observation that, having been discountenanced by + Hipparchus and Ptolemy, it did not find a single important champion for + more than a thousand years after the time of the last great Alexandrian + astronomer. + </p> + <p> + The first man, seemingly, to hark back to the Aristarchian conception in + the new scientific era that was now dawning was the noted cardinal, + Nikolaus of Cusa, who lived in the first half of the fifteenth century, + and was distinguished as a philosophical writer and mathematician. His De + Docta Ignorantia expressly propounds the doctrine of the earth's motion. + No one, however, paid the slightest attention to his suggestion, which, + therefore, merely serves to furnish us with another interesting + illustration of the futility of propounding even a correct hypothesis + before the time is ripe to receive it—particularly if the hypothesis + is not fully fortified by reasoning based on experiment or observation. + </p> + <p> + The man who was destined to put forward the theory of the earth's motion + in a way to command attention was born in 1473, at the village of Thorn, + in eastern Prussia. His name was Nicholas Copernicus. There is no more + famous name in the entire annals of science than this, yet posterity has + never been able fully to establish the lineage of the famous expositor of + the true doctrine of the solar system. The city of Thorn lies in a + province of that border territory which was then under control of Poland, + but which subsequently became a part of Prussia. It is claimed that the + aspects of the city were essentially German, and it is admitted that the + mother of Copernicus belonged to that race. The nationality of the father + is more in doubt, but it is urged that Copernicus used German as his + mother-tongue. His great work was, of course, written in Latin, according + to the custom of the time; but it is said that, when not employing that + language, he always wrote in German. The disputed nationality of + Copernicus strongly suggests that he came of a mixed racial lineage, and + we are reminded again of the influences of those ethnical minglings to + which we have previously more than once referred. The acknowledged centres + of civilization towards the close of the fifteenth century were Italy and + Spain. Therefore, the birthplace of Copernicus lay almost at the confines + of civilization, reminding us of that earlier period when Greece was the + centre of culture, but when the great Greek thinkers were born in Asia + Minor and in Italy. + </p> + <p> + As a young man, Copernicus made his way to Vienna to study medicine, and + subsequently he journeyed into Italy and remained there many years, About + the year 1500 he held the chair of mathematics in a college at Rome. + Subsequently he returned to his native land and passed his remaining years + there, dying at Domkerr, in Frauenburg, East Prussia, in the year 1543. + </p> + <p> + It would appear that Copernicus conceived the idea of the heliocentric + system of the universe while he was a comparatively young man, since in + the introduction to his great work, which he addressed to Pope Paul III., + he states that he has pondered his system not merely nine years, in + accordance with the maxim of Horace, but well into the fourth period of + nine years. Throughout a considerable portion of this period the great + work of Copernicus was in manuscript, but it was not published until the + year of his death. The reasons for the delay are not very fully + established. Copernicus undoubtedly taught his system throughout the later + decades of his life. He himself tells us that he had even questioned + whether it were not better for him to confine himself to such verbal + teaching, following thus the example of Pythagoras. Just as his life was + drawing to a close, he decided to pursue the opposite course, and the + first copy of his work is said to have been placed in his hands as he lay + on his deathbed. + </p> + <p> + The violent opposition which the new system met from ecclesiastical + sources led subsequent commentators to suppose that Copernicus had delayed + publication of his work through fear of the church authorities. There + seems, however, to be no direct evidence for this opinion. It has been + thought significant that Copernicus addressed his work to the pope. It is, + of course, quite conceivable that the aged astronomer might wish by this + means to demonstrate that he wrote in no spirit of hostility to the + church. His address to the pope might have been considered as a desirable + shield precisely because the author recognized that his work must needs + meet with ecclesiastical criticism. Be that as it may, Copernicus was + removed by death from the danger of attack, and it remained for his + disciples of a later generation to run the gauntlet of criticism and + suffer the charges of heresy. + </p> + <p> + The work of Copernicus, published thus in the year 1543 at Nuremberg, + bears the title De Orbium Coelestium Revolutionibus. + </p> + <p> + It is not necessary to go into details as to the cosmological system which + Copernicus advocated, since it is familiar to every one. In a word, he + supposed the sun to be the centre of all the planetary motions, the earth + taking its place among the other planets, the list of which, as known at + that time, comprised Mercury, Venus, the Earth, Mars, Jupiter, and Saturn. + The fixed stars were alleged to be stationary, and it was necessary to + suppose that they are almost infinitely distant, inasmuch as they showed + to the observers of that time no parallax; that is to say, they preserved + the same apparent position when viewed from the opposite points of the + earth's orbit. + </p> + <p> + But let us allow Copernicus to speak for himself regarding his system, His + exposition is full of interest. We quote first the introduction just + referred to, in which appeal is made directly to the pope. + </p> + <p> + "I can well believe, most holy father, that certain people, when they hear + of my attributing motion to the earth in these books of mine, will at once + declare that such an opinion ought to be rejected. Now, my own theories do + not please me so much as not to consider what others may judge of them. + Accordingly, when I began to reflect upon what those persons who accept + the stability of the earth, as confirmed by the opinion of many centuries, + would say when I claimed that the earth moves, I hesitated for a long time + as to whether I should publish that which I have written to demonstrate + its motion, or whether it would not be better to follow the example of the + Pythagoreans, who used to hand down the secrets of philosophy to their + relatives and friends only in oral form. As I well considered all this, I + was almost impelled to put the finished work wholly aside, through the + scorn I had reason to anticipate on account of the newness and apparent + contrariness to reason of my theory. + </p> + <p> + "My friends, however, dissuaded me from such a course and admonished me + that I ought to publish my book, which had lain concealed in my possession + not only nine years, but already into four times the ninth year. Not a few + other distinguished and very learned men asked me to do the same thing, + and told me that I ought not, on account of my anxiety, to delay any + longer in consecrating my work to the general service of mathematicians. + </p> + <p> + "But your holiness will perhaps not so much wonder that I have dared to + bring the results of my night labors to the light of day, after having + taken so much care in elaborating them, but is waiting instead to hear how + it entered my mind to imagine that the earth moved, contrary to the + accepted opinion of mathematicians—nay, almost contrary to ordinary + human understanding. Therefore I will not conceal from your holiness that + what moved me to consider another way of reckoning the motions of the + heavenly bodies was nothing else than the fact that the mathematicians do + not agree with one another in their investigations. In the first place, + they are so uncertain about the motions of the sun and moon that they + cannot find out the length of a full year. In the second place, they apply + neither the same laws of cause and effect, in determining the motions of + the sun and moon and of the five planets, nor the same proofs. Some employ + only concentric circles, others use eccentric and epicyclic ones, with + which, however, they do not fully attain the desired end. They could not + even discover nor compute the main thing—namely, the form of the + universe and the symmetry of its parts. It was with them as if some + should, from different places, take hands, feet, head, and other parts of + the body, which, although very beautiful, were not drawn in their proper + relations, and, without making them in any way correspond, should + construct a monster instead of a human being. + </p> + <p> + "Accordingly, when I had long reflected on this uncertainty of + mathematical tradition, I took the trouble to read again the books of all + the philosophers I could get hold of, to see if some one of them had not + once believed that there were other motions of the heavenly bodies. First + I found in Cicero that Niceties had believed in the motion of the earth. + Afterwards I found in Plutarch, likewise, that some others had held the + same opinion. This induced me also to begin to consider the movability of + the earth, and, although the theory appeared contrary to reason, I did so + because I knew that others before me had been allowed to assume rotary + movements at will, in order to explain the phenomena of these celestial + bodies. I was of the opinion that I, too, might be permitted to see + whether, by presupposing motion in the earth, more reliable conclusions + than hitherto reached could not be discovered for the rotary motions of + the spheres. And thus, acting on the hypothesis of the motion which, in + the following book, I ascribe to the earth, and by long and continued + observations, I have finally discovered that if the motion of the other + planets be carried over to the relation of the earth and this is made the + basis for the rotation of every star, not only will the phenomena of the + planets be explained thereby, but also the laws and the size of the stars; + all their spheres and the heavens themselves will appear so harmoniously + connected that nothing could be changed in any part of them without + confusion in the remaining parts and in the whole universe. I do not doubt + that clever and learned men will agree with me if they are willing fully + to comprehend and to consider the proofs which I advance in the book + before us. In order, however, that both the learned and the unlearned may + see that I fear no man's judgment, I wanted to dedicate these, my night + labors, to your holiness, rather than to any one else, because you, even + in this remote corner of the earth where I live, are held to be the + greatest in dignity of station and in love for all sciences and for + mathematics, so that you, through your position and judgment, can easily + suppress the bites of slanderers, although the proverb says that there is + no remedy against the bite of calumny." + </p> + <p> + In chapter X. of book I., "On the Order of the Spheres," occurs a more + detailed presentation of the system, as follows: + </p> + <p> + "That which Martianus Capella, and a few other Latins, very well knew, + appears to me extremely noteworthy. He believed that Venus and Mercury + revolve about the sun as their centre and that they cannot go farther away + from it than the circles of their orbits permit, since they do not revolve + about the earth like the other planets. According to this theory, then, + Mercury's orbit would be included within that of Venus, which is more than + twice as great, and would find room enough within it for its revolution. + </p> + <p> + "If, acting upon this supposition, we connect Saturn, Jupiter, and Mars + with the same centre, keeping in mind the greater extent of their orbits, + which include the earth's sphere besides those of Mercury and Venus, we + cannot fail to see the explanation of the regular order of their motions. + He is certain that Saturn, Jupiter, and Mars are always nearest the earth + when they rise in the evening—that is, when they appear over against + the sun, or the earth stands between them and the sun—but that they + are farthest from the earth when they set in the evening—that is, + when we have the sun between them and the earth. This proves sufficiently + that their centre belongs to the sun and is the same about which the + orbits of Venus and Mercury circle. Since, however, all have one centre, + it is necessary for the space intervening between the orbits of Venus and + Mars to include the earth with her accompanying moon and all that is + beneath the moon; for the moon, which stands unquestionably nearest the + earth, can in no way be separated from her, especially as there is + sufficient room for the moon in the aforesaid space. Hence we do not + hesitate to claim that the whole system, which includes the moon with the + earth for its centre, makes the round of that great circle between the + planets, in yearly motion about the sun, and revolves about the centre of + the universe, in which the sun rests motionless, and that all which looks + like motion in the sun is explained by the motion of the earth. The extent + of the universe, however, is so great that, whereas the distance of the + earth from the sun is considerable in comparison with the size of the + other planetary orbits, it disappears when compared with the sphere of the + fixed stars. I hold this to be more easily comprehensible than when the + mind is confused by an almost endless number of circles, which is + necessarily the case with those who keep the earth in the middle of the + universe. Although this may appear incomprehensible and contrary to the + opinion of many, I shall, if God wills, make it clearer than the sun, at + least to those who are not ignorant of mathematics. + </p> + <p> + "The order of the spheres is as follows: The first and lightest of all the + spheres is that of the fixed stars, which includes itself and all others, + and hence is motionless as the place in the universe to which the motion + and position of all other stars is referred. + </p> + <p> + "Then follows the outermost planet, Saturn, which completes its revolution + around the sun in thirty years; next comes Jupiter with a twelve years' + revolution; then Mars, which completes its course in two years. The fourth + one in order is the yearly revolution which includes the earth with the + moon's orbit as an epicycle. In the fifth place is Venus with a revolution + of nine months. The sixth place is taken by Mercury, which completes its + course in eighty days. In the middle of all stands the sun, and who could + wish to place the lamp of this most beautiful temple in another or better + place. Thus, in fact, the sun, seated upon the royal throne, controls the + family of the stars which circle around him. We find in their order a + harmonious connection which cannot be found elsewhere. Here the attentive + observer can see why the waxing and waning of Jupiter seems greater than + with Saturn and smaller than with Mars, and again greater with Venus than + with Mercury. Also, why Saturn, Jupiter, and Mars are nearer to the earth + when they rise in the evening than when they disappear in the rays of the + sun. More prominently, however, is it seen in the case of Mars, which when + it appears in the heavens at night, seems to equal Jupiter in size, but + soon afterwards is found among the stars of second magnitude. All of this + results from the same cause—namely, from the earth's motion. The + fact that nothing of this is to be seen in the case of the fixed stars is + a proof of their immeasurable distance, which makes even the orbit of + yearly motion or its counterpart invisible to us."(1) + </p> + <p> + The fact that the stars show no parallax had been regarded as an important + argument against the motion of the earth, and it was still so considered + by the opponents of the system of Copernicus. It had, indeed, been + necessary for Aristarchus to explain the fact as due to the extreme + distance of the stars; a perfectly correct explanation, but one that + implies distances that are altogether inconceivable. It remained for + nineteenth-century astronomers to show, with the aid of instruments of + greater precision, that certain of the stars have a parallax. But long + before this demonstration had been brought forward, the system of + Copernicus had been accepted as a part of common knowledge. + </p> + <p> + While Copernicus postulated a cosmical scheme that was correct as to its + main features, he did not altogether break away from certain defects of + the Ptolemaic hypothesis. Indeed, he seems to have retained as much of + this as practicable, in deference to the prejudice of his time. Thus he + records the planetary orbits as circular, and explains their + eccentricities by resorting to the theory of epicycles, quite after the + Ptolemaic method. But now, of course, a much more simple mechanism + sufficed to explain the planetary motions, since the orbits were correctly + referred to the central sun and not to the earth. + </p> + <p> + Needless to say, the revolutionary conception of Copernicus did not meet + with immediate acceptance. A number of prominent astronomers, however, + took it up almost at once, among these being Rhaeticus, who wrote a + commentary on the evolutions; Erasmus Reinhold, the author of the Prutenic + tables; Rothmann, astronomer to the Landgrave of Hesse, and Maestlin, the + instructor of Kepler. The Prutenic tables, just referred to, so called + because of their Prussian origin, were considered an improvement on the + tables of Copernicus, and were highly esteemed by the astronomers of the + time. The commentary of Rhaeticus gives us the interesting information + that it was the observation of the orbit of Mars and of the very great + difference between his apparent diameters at different times which first + led Copernicus to conceive the heliocentric idea. Of Reinhold it is + recorded that he considered the orbit of Mercury elliptical, and that he + advocated a theory of the moon, according to which her epicycle revolved + on an elliptical orbit, thus in a measure anticipating one of the great + discoveries of Kepler to which we shall refer presently. The Landgrave of + Hesse was a practical astronomer, who produced a catalogue of fixed stars + which has been compared with that of Tycho Brahe. He was assisted by + Rothmann and by Justus Byrgius. Maestlin, the preceptor of Kepler, is + reputed to have been the first modern observer to give a correct + explanation of the light seen on portions of the moon not directly + illumined by the sun. He explained this as not due to any proper light of + the moon itself, but as light reflected from the earth. Certain of the + Greek philosophers, however, are said to have given the same explanation, + and it is alleged also that Leonardo da Vinci anticipated Maestlin in this + regard.(2) + </p> + <p> + While, various astronomers of some eminence thus gave support to the + Copernican system, almost from the beginning, it unfortunately chanced + that by far the most famous of the immediate successors of Copernicus + declined to accept the theory of the earth's motion. This was Tycho Brahe, + one of the greatest observing astronomers of any age. Tycho Brahe was a + Dane, born at Knudstrup in the year 1546. He died in 1601 at Prague, in + Bohemia. During a considerable portion of his life he found a patron in + Frederick, King of Denmark, who assisted him to build a splendid + observatory on the Island of Huene. On the death of his patron Tycho moved + to Germany, where, as good luck would have it, he came in contact with the + youthful Kepler, and thus, no doubt, was instrumental in stimulating the + ambitions of one who in later years was to be known as a far greater + theorist than himself. As has been said, Tycho rejected the Copernican + theory of the earth's motion. It should be added, however, that he + accepted that part of the Copernican theory which makes the sun the centre + of all the planetary motions, the earth being excepted. He thus developed + a system of his own, which was in some sort a compromise between the + Ptolemaic and the Copernican systems. As Tycho conceived it, the sun + revolves about the earth, carrying with it the planets-Mercury, Venus, + Mars, Jupiter, and Saturn, which planets have the sun and not the earth as + the centre of their orbits. This cosmical scheme, it should be added, may + be made to explain the observed motions of the heavenly bodies, but it + involves a much more complex mechanism than is postulated by the + Copernican theory. + </p> + <p> + Various explanations have been offered of the conservatism which held the + great Danish astronomer back from full acceptance of the relatively simple + and, as we now know, correct Copernican doctrine. From our latter-day + point of view, it seems so much more natural to accept than to reject the + Copernican system, that we find it difficult to put ourselves in the place + of a sixteenth-century observer. Yet if we recall that the traditional + view, having warrant of acceptance by nearly all thinkers of every age, + recorded the earth as a fixed, immovable body, we shall see that our + surprise should be excited rather by the thinker who can break away from + this view than by the one who still tends to cling to it. + </p> + <p> + Moreover, it is useless to attempt to disguise the fact that something + more than a mere vague tradition was supposed to support the idea of the + earth's overshadowing importance in the cosmical scheme. The + sixteenth-century mind was overmastered by the tenets of ecclesiasticism, + and it was a dangerous heresy to doubt that the Hebrew writings, upon + which ecclesiasticism based its claim, contained the last word regarding + matters of science. But the writers of the Hebrew text had been under the + influence of that Babylonian conception of the universe which accepted the + earth as unqualifiedly central—which, indeed, had never so much as + conceived a contradictory hypothesis; and so the Western world, which had + come to accept these writings as actually supernatural in origin, lay + under the spell of Oriental ideas of a pre-scientific era. In our own day, + no one speaking with authority thinks of these Hebrew writings as having + any scientific weight whatever. Their interest in this regard is purely + antiquarian; hence from our changed point of view it seems scarcely + credible that Tycho Brahe can have been in earnest when he quotes the + Hebrew traditions as proof that the sun revolves about the earth. Yet we + shall see that for almost three centuries after the time of Tycho, these + same dreamings continued to be cited in opposition to those scientific + advances which new observations made necessary; and this notwithstanding + the fact that the Oriental phrasing is, for the most part, poetically + ambiguous and susceptible of shifting interpretations, as the criticism of + successive generations has amply testified. + </p> + <p> + As we have said, Tycho Brahe, great observer as he was, could not shake + himself free from the Oriental incubus. He began his objections, then, to + the Copernican system by quoting the adverse testimony of a Hebrew prophet + who lived more than a thousand years B.C. All of this shows sufficiently + that Tycho Brahe was not a great theorist. He was essentially an observer, + but in this regard he won a secure place in the very first rank. Indeed, + he was easily the greatest observing astronomer since Hipparchus, between + whom and himself there were many points of resemblance. Hipparchus, it + will be recalled, rejected the Aristarchian conception of the universe + just as Tycho rejected the conception of Copernicus. + </p> + <p> + But if Tycho propounded no great generalizations, the list of specific + advances due to him is a long one, and some of these were to prove + important aids in the hands of later workers to the secure demonstration + of the Copernican idea. One of his most important series of studies had to + do with comets. Regarding these bodies there had been the greatest + uncertainty in the minds of astronomers. The greatest variety of opinions + regarding them prevailed; they were thought on the one hand to be divine + messengers, and on the other to be merely igneous phenomena of the earth's + atmosphere. Tycho Brahe declared that a comet which he observed in the + year 1577 had no parallax, proving its extreme distance. The observed + course of the comet intersected the planetary orbits, which fact gave a + quietus to the long-mooted question as to whether the Ptolemaic spheres + were transparent solids or merely imaginary; since the comet was seen to + intersect these alleged spheres, it was obvious that they could not be the + solid substance that they were commonly imagined to be, and this fact in + itself went far towards discrediting the Ptolemaic system. It should be + recalled, however, that this supposition of tangible spheres for the + various planetary and stellar orbits was a mediaeval interpretation of + Ptolemy's theory rather than an interpretation of Ptolemy himself, there + being nothing to show that the Alexandrian astronomer regarded his cycles + and epicycles as other than theoretical. + </p> + <p> + An interesting practical discovery made by Tycho was his method of + determining the latitude of a place by means of two observations made at + an interval of twelve hours. Hitherto it had been necessary to observe the + sun's angle on the equinoctial days, a period of six months being + therefore required. Tycho measured the angle of elevation of some star + situated near the pole, when on the meridian, and then, twelve hours + later, measured the angle of elevation of the same star when it again came + to the meridian at the opposite point of its apparent circle about the + polestar. Half the sum of these angles gives the latitude of the place of + observation. + </p> + <p> + As illustrating the accuracy of Tycho's observations, it may be noted that + he rediscovered a third inequality of the moon's motion at its variation, + he, in common with other European astronomers, being then quite unaware + that this inequality had been observed by an Arabian astronomer. Tycho + proved also that the angle of inclination of the moon's orbit to the + ecliptic is subject to slight variation. + </p> + <p> + The very brilliant new star which shone forth suddenly in the + constellation of Cassiopeia in the year 1572, was made the object of + special studies by Tycho, who proved that the star had no sensible + parallax and consequently was far beyond the planetary regions. The + appearance of a new star was a phenomenon not unknown to the ancients, + since Pliny records that Hipparchus was led by such an appearance to make + his catalogue of the fixed stars. But the phenomenon is sufficiently + uncommon to attract unusual attention. A similar phenomenon occurred in + the year 1604, when the new star—in this case appearing in the + constellation of Serpentarius—was explained by Kepler as probably + proceeding from a vast combustion. This explanation—in which Kepler + is said to have followed. Tycho—is fully in accord with the most + recent theories on the subject, as we shall see in due course. It is + surprising to hear Tycho credited with so startling a theory, but, on the + other hand, such an explanation is precisely what should be expected from + the other astronomer named. For Johann Kepler, or, as he was originally + named, Johann von Kappel, was one of the most speculative astronomers of + any age. He was forever theorizing, but such was the peculiar quality of + his mind that his theories never satisfied him for long unless he could + put them to the test of observation. Thanks to this happy combination of + qualities, Kepler became the discoverer of three famous laws of planetary + motion which lie at the very foundation of modern astronomy, and which + were to be largely instrumental in guiding Newton to his still greater + generalization. These laws of planetary motion were vastly important as + corroborating the Copernican theory of the universe, though their position + in this regard was not immediately recognized by contemporary thinkers. + Let us examine with some detail into their discovery, meantime catching a + glimpse of the life history of the remarkable man whose name they bear. + </p> + <p> + JOHANN KEPLER AND THE LAWS OF PLANETARY MOTION + </p> + <p> + Johann Kepler was born the 27th of December, 1571, in the little town of + Weil, in Wurtemburg. He was a weak, sickly child, further enfeebled by a + severe attack of small-pox. It would seem paradoxical to assert that the + parents of such a genius were mismated, but their home was not a happy + one, the mother being of a nervous temperament, which perhaps in some + measure accounted for the genius of the child. The father led the life of + a soldier, and finally perished in the campaign against the Turks. Young + Kepler's studies were directed with an eye to the ministry. After a + preliminary training he attended the university at Tubingen, where he came + under the influence of the celebrated Maestlin and became his life-long + friend. + </p> + <p> + Curiously enough, it is recorded that at first Kepler had no taste for + astronomy or for mathematics. But the doors of the ministry being + presently barred to him, he turned with enthusiasm to the study of + astronomy, being from the first an ardent advocate of the Copernican + system. His teacher, Maestlin, accepted the same doctrine, though he was + obliged, for theological reasons, to teach the Ptolemaic system, as also + to oppose the Gregorian reform of the calendar. + </p> + <p> + The Gregorian calendar, it should be explained, is so called because it + was instituted by Pope Gregory XIII., who put it into effect in the year + 1582, up to which time the so-called Julian calendar, as introduced by + Julius Caesar, had been everywhere accepted in Christendom. This Julian + calendar, as we have seen, was a great improvement on preceding ones, but + still lacked something of perfection inasmuch as its theoretical day + differed appreciably from the actual day. In the course of fifteen hundred + years, since the time of Caesar, this defect amounted to a discrepancy of + about eleven days. Pope Gregory proposed to correct this by omitting ten + days from the calendar, which was done in September, 1582. To prevent + similar inaccuracies in the future, the Gregorian calendar provided that + once in four centuries the additional day to make a leap-year should be + omitted, the date selected for such omission being the last year of every + fourth century. Thus the years 1500, 1900, and 2300, A.D., would not be + leap-years. By this arrangement an approximate rectification of the + calendar was effected, though even this does not make it absolutely exact. + </p> + <p> + Such a rectification as this was obviously desirable, but there was really + no necessity for the omission of the ten days from the calendar. The + equinoctial day had shifted so that in the year 1582 it fell on the 10th + of March and September. There was no reason why it should not have + remained there. It would greatly have simplified the task of future + historians had Gregory contented himself with providing for the future + stability of the calendar without making the needless shift in question. + We are so accustomed to think of the 21st of March and 21st of September + as the natural periods of the equinox, that we are likely to forget that + these are purely arbitrary dates for which the 10th might have been + substituted without any inconvenience or inconsistency. + </p> + <p> + But the opposition to the new calendar, to which reference has been made, + was not based on any such considerations as these. It was due, largely at + any rate, to the fact that Germany at this time was under sway of the + Lutheran revolt against the papacy. So effective was the opposition that + the Gregorian calendar did not come into vogue in Germany until the year + 1699. It may be added that England, under stress of the same manner of + prejudice, held out against the new reckoning until the year 1751, while + Russia does not accept it even now. + </p> + <p> + As the Protestant leaders thus opposed the papal attitude in a matter of + so practical a character as the calendar, it might perhaps have been + expected that the Lutherans would have had a leaning towards the + Copernican theory of the universe, since this theory was opposed by the + papacy. Such, however, was not the case. Luther himself pointed out with + great strenuousness, as a final and demonstrative argument, the fact that + Joshua commanded the sun and not the earth to stand still; and his + followers were quite as intolerant towards the new teaching as were their + ultramontane opponents. Kepler himself was, at various times, to feel the + restraint of ecclesiastical opposition, though he was never subjected to + direct persecution, as was his friend and contemporary, Galileo. At the + very outset of Kepler's career there was, indeed, question as to the + publication of a work he had written, because that work took for granted + the truth of the Copernican doctrine. This work appeared, however, in the + year 1596. It bore the title Mysterium Cosmographium, and it attempted to + explain the positions of the various planetary bodies. Copernicus had + devoted much time to observation of the planets with reference to + measuring their distance, and his efforts had been attended with + considerable success. He did not, indeed, know the actual distance of the + sun, and, therefore, was quite unable to fix the distance of any planet; + but, on the other hand, he determined the relative distance of all the + planets then known, as measured in terms of the sun's distance, with + remarkable accuracy. + </p> + <p> + With these measurements as a guide, Kepler was led to a very fanciful + theory, according to which the orbits of the five principal planets + sustain a peculiar relation to the five regular solids of geometry. His + theory was this: "Around the orbit of the earth describe a dodecahedron—the + circle comprising it will be that of Mars; around Mars describe a + tetrahedron—the circle comprising it will be that of Jupiter; around + Jupiter describe a cube—the circle comprising it will be that of + Saturn; now within the earth's orbit inscribe an icosahedron—the + inscribed circle will be that of Venus; in the orbit of Venus inscribe an + octahedron—the circle inscribed will be that of Mercury."(3) + </p> + <p> + Though this arrangement was a fanciful one, which no one would now recall + had not the theorizer obtained subsequent fame on more substantial + grounds, yet it evidenced a philosophical spirit on the part of the + astronomer which, misdirected as it was in this instance, promised well + for the future. Tycho Brahe, to whom a copy of the work was sent, had the + acumen to recognize it as a work of genius. He summoned the young + astronomer to be his assistant at Prague, and no doubt the association + thus begun was instrumental in determining the character of Kepler's + future work. It was precisely the training in minute observation that + could avail most for a mind which, like Kepler's, tended instinctively to + the formulation of theories. When Tycho Brahe died, in 1601, Kepler became + his successor. In due time he secured access to all the unpublished + observations of his great predecessor, and these were of inestimable value + to him in the progress of his own studies. + </p> + <p> + Kepler was not only an ardent worker and an enthusiastic theorizer, but he + was an indefatigable writer, and it pleased him to take the public fully + into his confidence, not merely as to his successes, but as to his + failures. Thus his works elaborate false theories as well as correct ones, + and detail the observations through which the incorrect guesses were + refuted by their originator. Some of these accounts are highly + interesting, but they must not detain us here. For our present purpose it + must suffice to point out the three important theories, which, as culled + from among a score or so of incorrect ones, Kepler was able to demonstrate + to his own satisfaction and to that of subsequent observers. Stated in a + few words, these theories, which have come to bear the name of Kepler's + Laws, are the following: + </p> + <p> + 1. That the planetary orbits are not circular, but elliptical, the sun + occupying one focus of the ellipses. + </p> + <p> + 2. That the speed of planetary motion varies in different parts of the + orbit in such a way that an imaginary line drawn from the sun to the + planet—that is to say, the radius vector of the planet's orbit—always + sweeps the same area in a given time. + </p> + <p> + These two laws Kepler published as early as 1609. Many years more of + patient investigation were required before he found out the secret of the + relation between planetary distances and times of revolution which his + third law expresses. In 1618, however, he was able to formulate this + relation also, as follows: + </p> + <p> + 3. The squares of the distance of the various planets from the sun are + proportional to the cubes of their periods of revolution about the sun. + </p> + <p> + All these laws, it will be observed, take for granted the fact that the + sun is the centre of the planetary orbits. It must be understood, too, + that the earth is constantly regarded, in accordance with the Copernican + system, as being itself a member of the planetary system, subject to + precisely the same laws as the other planets. Long familiarity has made + these wonderful laws of Kepler seem such a matter of course that it is + difficult now to appreciate them at their full value. Yet, as has been + already pointed out, it was the knowledge of these marvellously simple + relations between the planetary orbits that laid the foundation for the + Newtonian law of universal gravitation. Contemporary judgment could not, + of course, anticipate this culmination of a later generation. What it + could understand was that the first law of Kepler attacked one of the most + time-honored of metaphysical conceptions—namely, the Aristotelian + idea that the circle is the perfect figure, and hence that the planetary + orbits must be circular. Not even Copernicus had doubted the validity of + this assumption. That Kepler dared dispute so firmly fixed a belief, and + one that seemingly had so sound a philosophical basis, evidenced the + iconoclastic nature of his genius. That he did not rest content until he + had demonstrated the validity of his revolutionary assumption shows how + truly this great theorizer made his hypotheses subservient to the most + rigid inductions. + </p> + <p> + GALILEO GALILEI + </p> + <p> + While Kepler was solving these riddles of planetary motion, there was an + even more famous man in Italy whose championship of the Copernican + doctrine was destined to give the greatest possible publicity to the new + ideas. This was Galileo Galilei, one of the most extraordinary scientific + observers of any age. Galileo was born at Pisa, on the 18th of February + (old style), 1564. The day of his birth is doubly memorable, since on the + same day the greatest Italian of the preceding epoch, Michael Angelo, + breathed his last. Persons fond of symbolism have found in the coincidence + a forecast of the transit from the artistic to the scientific epoch of the + later Renaissance. Galileo came of an impoverished noble family. He was + educated for the profession of medicine, but did not progress far before + his natural proclivities directed him towards the physical sciences. + Meeting with opposition in Pisa, he early accepted a call to the chair of + natural philosophy in the University of Padua, and later in life he made + his home at Florence. The mechanical and physical discoveries of Galileo + will claim our attention in another chapter. Our present concern is with + his contribution to the Copernican theory. + </p> + <p> + Galileo himself records in a letter to Kepler that he became a convert to + this theory at an early day. He was not enabled, however, to make any + marked contribution to the subject, beyond the influence of his general + teachings, until about the year 1610. The brilliant contributions which he + made were due largely to a single discovery—namely, that of the + telescope. Hitherto the astronomical observations had been made with the + unaided eye. Glass lenses had been known since the thirteenth century, + but, until now, no one had thought of their possible use as aids to + distant vision. The question of priority of discovery has never been + settled. It is admitted, however, that the chief honors belong to the + opticians of the Netherlands. + </p> + <p> + As early as the year 1590 the Dutch optician Zacharias Jensen placed a + concave and a convex lens respectively at the ends of a tube about + eighteen inches long, and used this instrument for the purpose of + magnifying small objects—producing, in short, a crude microscope. + Some years later, Johannes Lippershey, of whom not much is known except + that he died in 1619, experimented with a somewhat similar combination of + lenses, and made the startling observation that the weather-vane on a + distant church-steeple seemed to be brought much nearer when viewed + through the lens. The combination of lenses he employed is that still used + in the construction of opera-glasses; the Germans still call such a + combination a Dutch telescope. + </p> + <p> + Doubtless a large number of experimenters took the matter up and the fame + of the new instrument spread rapidly abroad. Galileo, down in Italy, heard + rumors of this remarkable contrivance, through the use of which it was + said "distant objects might be seen as clearly as those near at hand." He + at once set to work to construct for himself a similar instrument, and his + efforts were so far successful that at first he "saw objects three times + as near and nine times enlarged." Continuing his efforts, he presently so + improved his glass that objects were enlarged almost a thousand times and + made to appear thirty times nearer than when seen with the naked eye. + Naturally enough, Galileo turned this fascinating instrument towards the + skies, and he was almost immediately rewarded by several startling + discoveries. At the very outset, his magnifying-glass brought to view a + vast number of stars that are invisible to the naked eye, and enabled the + observer to reach the conclusion that the hazy light of the Milky Way is + merely due to the aggregation of a vast number of tiny stars. + </p> + <p> + Turning his telescope towards the moon, Galileo found that body rough and + earth-like in contour, its surface covered with mountains, whose height + could be approximately measured through study of their shadows. This was + disquieting, because the current Aristotelian doctrine supposed the moon, + in common with the planets, to be a perfectly spherical, smooth body. The + metaphysical idea of a perfect universe was sure to be disturbed by this + seemingly rough workmanship of the moon. Thus far, however, there was + nothing in the observations of Galileo to bear directly upon the + Copernican theory; but when an inspection was made of the planets the case + was quite different. With the aid of his telescope, Galileo saw that + Venus, for example, passes through phases precisely similar to those of + the moon, due, of course, to the same cause. Here, then, was demonstrative + evidence that the planets are dark bodies reflecting the light of the sun, + and an explanation was given of the fact, hitherto urged in opposition to + the Copernican theory, that the inferior planets do not seem many times + brighter when nearer the earth than when in the most distant parts of + their orbits; the explanation being, of course, that when the planets are + between the earth and the sun only a small portion of their illumined + surfaces is visible from the earth. + </p> + <p> + On inspecting the planet Jupiter, a still more striking revelation was + made, as four tiny stars were observed to occupy an equatorial position + near that planet, and were seen, when watched night after night, to be + circling about the planet, precisely as the moon circles about the earth. + Here, obviously, was a miniature solar system—a tangible + object-lesson in the Copernican theory. In honor of the ruling Florentine + house of the period, Galileo named these moons of Jupiter, Medicean stars. + </p> + <p> + Turning attention to the sun itself, Galileo observed on the surface of + that luminary a spot or blemish which gradually changed its shape, + suggesting that changes were taking place in the substance of the sun—changes + obviously incompatible with the perfect condition demanded by the + metaphysical theorists. But however disquieting for the conservative, the + sun's spots served a most useful purpose in enabling Galileo to + demonstrate that the sun itself revolves on its axis, since a given spot + was seen to pass across the disk and after disappearing to reappear in due + course. The period of rotation was found to be about twenty-four days. + </p> + <p> + It must be added that various observers disputed priority of discovery of + the sun's spots with Galileo. Unquestionably a sun-spot had been seen by + earlier observers, and by them mistaken for the transit of an inferior + planet. Kepler himself had made this mistake. Before the day of the + telescope, he had viewed the image of the sun as thrown on a screen in a + camera-obscura, and had observed a spot on the disk which be interpreted + as representing the planet Mercury, but which, as is now known, must have + been a sun-spot, since the planetary disk is too small to have been + revealed by this method. Such observations as these, however interesting, + cannot be claimed as discoveries of the sun-spots. It is probable, + however, that several discoverers (notably Johann Fabricius) made the + telescopic observation of the spots, and recognized them as having to do + with the sun's surface, almost simultaneously with Galileo. One of these + claimants was a Jesuit named Scheiner, and the jealousy of this man is + said to have had a share in bringing about that persecution to which we + must now refer. + </p> + <p> + There is no more famous incident in the history of science than the heresy + trial through which Galileo was led to the nominal renunciation of his + cherished doctrines. There is scarcely another incident that has been + commented upon so variously. Each succeeding generation has put its own + interpretation on it. The facts, however, have been but little questioned. + It appears that in the year 1616 the church became at last aroused to the + implications of the heliocentric doctrine of the universe. Apparently it + seemed clear to the church authorities that the authors of the Bible + believed the world to be immovably fixed at the centre of the universe. + Such, indeed, would seem to be the natural inference from various familiar + phrases of the Hebrew text, and what we now know of the status of Oriental + science in antiquity gives full warrant to this interpretation. There is + no reason to suppose that the conception of the subordinate place of the + world in the solar system had ever so much as occurred, even as a vague + speculation, to the authors of Genesis. In common with their + contemporaries, they believed the earth to be the all-important body in + the universe, and the sun a luminary placed in the sky for the sole + purpose of giving light to the earth. There is nothing strange, nothing + anomalous, in this view; it merely reflects the current notions of + Oriental peoples in antiquity. What is strange and anomalous is the fact + that the Oriental dreamings thus expressed could have been supposed to + represent the acme of scientific knowledge. Yet such a hold had these + writings taken upon the Western world that not even a Galileo dared + contradict them openly; and when the church fathers gravely declared the + heliocentric theory necessarily false, because contradictory to Scripture, + there were probably few people in Christendom whose mental attitude would + permit them justly to appreciate the humor of such a pronouncement. And, + indeed, if here and there a man might have risen to such an appreciation, + there were abundant reasons for the repression of the impulse, for there + was nothing humorous about the response with which the authorities of the + time were wont to meet the expression of iconoclastic opinions. The + burning at the stake of Giordano Bruno, in the year 1600, was, for + example, an object-lesson well calculated to restrain the enthusiasm of + other similarly minded teachers. + </p> + <p> + Doubtless it was such considerations that explained the relative silence + of the champions of the Copernican theory, accounting for the otherwise + inexplicable fact that about eighty years elapsed after the death of + Copernicus himself before a single text-book expounded his theory. The + text-book which then appeared, under date of 1622, was written by the + famous Kepler, who perhaps was shielded in a measure from the papal + consequences of such hardihood by the fact of residence in a Protestant + country. Not that the Protestants of the time favored the heliocentric + doctrine—we have already quoted Luther in an adverse sense—but + of course it was characteristic of the Reformation temper to oppose any + papal pronouncement, hence the ultramontane declaration of 1616 may + indirectly have aided the doctrine which it attacked, by making that + doctrine less obnoxious to Lutheran eyes. Be that as it may, the work of + Kepler brought its author into no direct conflict with the authorities. + But the result was quite different when, in 1632, Galileo at last broke + silence and gave the world, under cover of the form of dialogue, an + elaborate exposition of the Copernican theory. Galileo, it must be + explained, had previously been warned to keep silent on the subject, hence + his publication doubly offended the authorities. To be sure, he could + reply that his dialogue introduced a champion of the Ptolemaic system to + dispute with the upholder of the opposite view, and that, both views being + presented with full array of argument, the reader was left to reach a + verdict for himself, the author having nowhere pointedly expressed an + opinion. But such an argument, of course, was specious, for no one who + read the dialogue could be in doubt as to the opinion of the author. + Moreover, it was hinted that Simplicio, the character who upheld the + Ptolemaic doctrine and who was everywhere worsted in the argument, was + intended to represent the pope himself—a suggestion which probably + did no good to Galileo's cause. + </p> + <p> + The character of Galileo's artistic presentation may best be judged from + an example, illustrating the vigorous assault of Salviati, the champion of + the new theory, and the feeble retorts of his conservative antagonist: + </p> + <p> + "Salviati. Let us then begin our discussion with the consideration that, + whatever motion may be attributed to the earth, yet we, as dwellers upon + it, and hence as participators in its motion, cannot possibly perceive + anything of it, presupposing that we are to consider only earthly things. + On the other hand, it is just as necessary that this same motion belong + apparently to all other bodies and visible objects, which, being separated + from the earth, do not take part in its motion. The correct method to + discover whether one can ascribe motion to the earth, and what kind of + motion, is, therefore, to investigate and observe whether in bodies + outside the earth a perceptible motion may be discovered which belongs to + all alike. Because a movement which is perceptible only in the moon, for + instance, and has nothing to do with Venus or Jupiter or other stars, + cannot possibly be peculiar to the earth, nor can its seat be anywhere + else than in the moon. Now there is one such universal movement which + controls all others—namely, that which the sun, moon, the other + planets, the fixed stars—in short, the whole universe, with the + single exception of the earth—appears to execute from east to west + in the space of twenty-four hours. This now, as it appears at the first + glance anyway, might just as well be a motion of the earth alone as of all + the rest of the universe with the exception of the earth, for the same + phenomena would result from either hypothesis. Beginning with the most + general, I will enumerate the reasons which seem to speak in favor of the + earth's motion. When we merely consider the immensity of the starry sphere + in comparison with the smallness of the terrestrial ball, which is + contained many million times in the former, and then think of the rapidity + of the motion which completes a whole rotation in one day and night, I + cannot persuade myself how any one can hold it to be more reasonable and + credible that it is the heavenly sphere which rotates, while the earth + stands still. + </p> + <p> + "Simplicio. I do not well understand how that powerful motion may be said + to as good as not exist for the sun, the moon, the other planets, and the + innumerable host of fixed stars. Do you call that nothing when the sun + goes from one meridian to another, rises up over this horizon and sinks + behind that one, brings now day, and now night; when the moon goes through + similar changes, and the other planets and fixed stars in the same way? + </p> + <p> + "Salviati. All the changes you mention are such only in respect to the + earth. To convince yourself of it, only imagine the earth out of + existence. There would then be no rising and setting of the sun or of the + moon, no horizon, no meridian, no day, no night—in short, the said + motion causes no change of any sort in the relation of the sun to the moon + or to any of the other heavenly bodies, be they planets or fixed stars. + All changes are rather in respect to the earth; they may all be reduced to + the simple fact that the sun is first visible in China, then in Persia, + afterwards in Egypt, Greece, France, Spain, America, etc., and that the + same thing happens with the moon and the other heavenly bodies. Exactly + the same thing happens and in exactly the same way if, instead of + disturbing so large a part of the universe, you let the earth revolve + about itself. The difficulty is, however, doubled, inasmuch as a second + very important problem presents itself. If, namely, that powerful motion + is ascribed to the heavens, it is absolutely necessary to regard it as + opposed to the individual motion of all the planets, every one of which + indubitably has its own very leisurely and moderate movement from west to + east. If, on the other hand, you let the earth move about itself, this + opposition of motion disappears. + </p> + <p> + "The improbability is tripled by the complete overthrow of that order + which rules all the heavenly bodies in which the revolving motion is + definitely established. The greater the sphere is in such a case, so much + longer is the time required for its revolution; the smaller the sphere the + shorter the time. Saturn, whose orbit surpasses those of all the planets + in size, traverses it in thirty years. Jupiter(4) completes its smaller + course in twelve years, Mars in two; the moon performs its much smaller + revolution within a month. Just as clearly in the Medicean stars, we see + that the one nearest Jupiter completes its revolution in a very short time—about + forty-two hours; the next in about three and one-half days, the third in + seven, and the most distant one in sixteen days. This rule, which is + followed throughout, will still remain if we ascribe the + twenty-four-hourly motion to a rotation of the earth. If, however, the + earth is left motionless, we must go first from the very short rule of the + moon to ever greater ones—to the two-yearly rule of Mars, from that + to the twelve-yearly one of Jupiter, from here to the thirty-yearly one of + Saturn, and then suddenly to an incomparably greater sphere, to which also + we must ascribe a complete rotation in twenty-four hours. If, however, we + assume a motion of the earth, the rapidity of the periods is very well + preserved; from the slowest sphere of Saturn we come to the wholly + motionless fixed stars. We also escape thereby a fourth difficulty, which + arises as soon as we assume that there is motion in the sphere of the + stars. I mean the great unevenness in the movement of these very stars, + some of which would have to revolve with extraordinary rapidity in immense + circles, while others moved very slowly in small circles, since some of + them are at a greater, others at a less, distance from the pole. That is + likewise an inconvenience, for, on the one hand, we see all those stars, + the motion of which is indubitable, revolve in great circles, while, on + the other hand, there seems to be little object in placing bodies, which + are to move in circles, at an enormous distance from the centre and then + let them move in very small circles. And not only are the size of the + different circles and therewith the rapidity of the movement very + different in the different fixed stars, but the same stars also change + their orbits and their rapidity of motion. Therein consists the fifth + inconvenience. Those stars, namely, which were at the equator two thousand + years ago, and hence described great circles in their revolutions, must + to-day move more slowly and in smaller circles, because they are many + degrees removed from it. It will even happen, after not so very long a + time, that one of those which have hitherto been continually in motion + will finally coincide with the pole and stand still, but after a period of + repose will again begin to move. The other stars in the mean while, which + unquestionably move, all have, as was said, a great circle for an orbit + and keep this unchangeably. + </p> + <p> + "The improbability is further increased—this may be considered the + sixth inconvenience—by the fact that it is impossible to conceive + what degree of solidity those immense spheres must have, in the depths of + which so many stars are fixed so enduringly that they are kept revolving + evenly in spite of such difference of motion without changing their + respective positions. Or if, according to the much more probable theory, + the heavens are fluid, and every star describes an orbit of its own, + according to what law then, or for what reason, are their orbits so + arranged that, when looked at from the earth, they appear to be contained + in one single sphere? To attain this it seems to me much easier and more + convenient to make them motionless instead of moving, just as the + paving-stones on the market-place, for instance, remain in order more + easily than the swarms of children running about on them. + </p> + <p> + "Finally, the seventh difficulty: If we attribute the daily rotation to + the higher region of the heavens, we should have to endow it with force + and power sufficient to carry with it the innumerable host of the fixed + stars—every one a body of very great compass and much larger than + the earth—and all the planets, although the latter, like the earth, + move naturally in an opposite direction. In the midst of all this the + little earth, single and alone, would obstinately and wilfully withstand + such force—a supposition which, it appears to me, has much against + it. I could also not explain why the earth, a freely poised body, + balancing itself about its centre, and surrounded on all sides by a fluid + medium, should not be affected by the universal rotation. Such + difficulties, however, do not confront us if we attribute motion to the + earth—such a small, insignificant body in comparison with the whole + universe, and which for that very reason cannot exercise any power over + the latter. + </p> + <p> + "Simplicio. You support your arguments throughout, it seems to me, on the + greater ease and simplicity with which the said effects are produced. You + mean that as a cause the motion of the earth alone is just as satisfactory + as the motion of all the rest of the universe with the exception of the + earth; you hold the actual event to be much easier in the former case than + in the latter. For the ruler of the universe, however, whose might is + infinite, it is no less easy to move the universe than the earth or a + straw balm. But if his power is infinite, why should not a greater, rather + than a very small, part of it be revealed to me? + </p> + <p> + "Salviati. If I had said that the universe does not move on account of the + impotence of its ruler, I should have been wrong and your rebuke would + have been in order. I admit that it is just as easy for an infinite power + to move a hundred thousand as to move one. What I said, however, does not + refer to him who causes the motion, but to that which is moved. In answer + to your remark that it is more fitting for an infinite power to reveal a + large part of itself rather than a little, I answer that, in relation to + the infinite, one part is not greater than another, if both are finite. + Hence it is unallowable to say that a hundred thousand is a larger part of + an infinite number than two, although the former is fifty thousand times + greater than the latter. If, therefore, we consider the moving bodies, we + must unquestionably regard the motion of the earth as a much simpler + process than that of the universe; if, furthermore, we direct our + attention to so many other simplifications which may be reached only by + this theory, the daily movement of the earth must appear much more + probable than the motion of the universe without the earth, for, according + to Aristotle's just axiom, 'Frustra fit per plura, quod potest fieri per p + auciora' (It is vain to expend many means where a few are sufficient)."(2) + </p> + <p> + The work was widely circulated, and it was received with an interest which + bespeaks a wide-spread undercurrent of belief in the Copernican doctrine. + Naturally enough, it attracted immediate attention from the church + authorities. Galileo was summoned to appear at Rome to defend his conduct. + The philosopher, who was now in his seventieth year, pleaded age and + infirmity. He had no desire for personal experience of the tribunal of the + Inquisition; but the mandate was repeated, and Galileo went to Rome. + There, as every one knows, he disavowed any intention to oppose the + teachings of Scripture, and formally renounced the heretical doctrine of + the earth's motion. According to a tale which so long passed current that + every historian must still repeat it though no one now believes it + authentic, Galileo qualified his renunciation by muttering to himself, "E + pur si muove" (It does move, none the less), as he rose to his feet and + retired from the presence of his persecutors. The tale is one of those + fictions which the dramatic sense of humanity is wont to impose upon + history, but, like most such fictions, it expresses the spirit if not the + letter of truth; for just as no one believes that Galileo's lips uttered + the phrase, so no one doubts that the rebellious words were in his mind. + </p> + <p> + After his formal renunciation, Galileo was allowed to depart, but with the + injunction that he abstain in future from heretical teaching. The + remaining ten years of his life were devoted chiefly to mechanics, where + his experiments fortunately opposed the Aristotelian rather than the + Hebrew teachings. Galileo's death occurred in 1642, a hundred years after + the death of Copernicus. Kepler had died thirteen years before, and there + remained no astronomer in the field who is conspicuous in the history of + science as a champion of the Copernican doctrine. But in truth it might be + said that the theory no longer needed a champion. The researches of Kepler + and Galileo had produced a mass of evidence for the Copernican theory + which amounted to demonstration. A generation or two might be required for + this evidence to make itself everywhere known among men of science, and of + course the ecclesiastical authorities must be expected to stand by their + guns for a somewhat longer period. In point of fact, the ecclesiastical + ban was not technically removed by the striking of the Copernican books + from the list of the Index Expurgatorius until the year 1822, almost two + hundred years after the date of Galileo's dialogue. But this, of course, + is in no sense a guide to the state of general opinion regarding the + theory. We shall gain a true gauge as to this if we assume that the + greater number of important thinkers had accepted the heliocentric + doctrine before the middle of the seventeenth century, and that before the + close of that century the old Ptolemaic idea had been quite abandoned. A + wonderful revolution in man's estimate of the universe had thus been + effected within about two centuries after the birth of Copernicus. + </p> + <p> + <a name="link2H_4_0007" id="link2H_4_0007"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + V. GALILEO AND THE NEW PHYSICS + </h2> + <p> + After Galileo had felt the strong hand of the Inquisition, in 1632, he was + careful to confine his researches, or at least his publications, to topics + that seemed free from theological implications. In doing so he reverted to + the field of his earliest studies—namely, the field of mechanics; + and the Dialoghi delle Nuove Scienze, which he finished in 1636, and which + was printed two years later, attained a celebrity no less than that of the + heretical dialogue that had preceded it. The later work was free from all + apparent heresies, yet perhaps it did more towards the establishment of + the Copernican doctrine, through the teaching of correct mechanical + principles, than the other work had accomplished by a more direct method. + </p> + <p> + Galileo's astronomical discoveries were, as we have seen, in a sense + accidental; at least, they received their inception through the inventive + genius of another. His mechanical discoveries, on the other hand, were the + natural output of his own creative genius. At the very beginning of his + career, while yet a very young man, though a professor of mathematics at + Pisa, he had begun that onslaught upon the old Aristotelian ideas which he + was to continue throughout his life. At the famous leaning tower in Pisa, + the young iconoclast performed, in the year 1590, one of the most + theatrical demonstrations in the history of science. Assembling a + multitude of champions of the old ideas, he proposed to demonstrate the + falsity of the Aristotelian doctrine that the velocity of falling bodies + is proportionate to their weight. There is perhaps no fact more strongly + illustrative of the temper of the Middle Ages than the fact that this + doctrine, as taught by the Aristotelian philosopher, should so long have + gone unchallenged. Now, however, it was put to the test; Galileo released + a half-pound weight and a hundred-pound cannon-ball from near the top of + the tower, and, needless to say, they reached the ground together. Of + course, the spectators were but little pleased with what they saw. They + could not doubt the evidence of their own senses as to the particular + experiment in question; they could suggest, however, that the experiment + involved a violation of the laws of nature through the practice of magic. + To controvert so firmly established an idea savored of heresy. The young + man guilty of such iconoclasm was naturally looked at askance by the + scholarship of his time. Instead of being applauded, he was hissed, and he + found it expedient presently to retire from Pisa. + </p> + <p> + Fortunately, however, the new spirit of progress had made itself felt more + effectively in some other portions of Italy, and so Galileo found a refuge + and a following in Padua, and afterwards in Florence; and while, as we + have seen, he was obliged to curb his enthusiasm regarding the subject + that was perhaps nearest his heart—the promulgation of the + Copernican theory—yet he was permitted in the main to carry on his + experimental observations unrestrained. These experiments gave him a place + of unquestioned authority among his contemporaries, and they have + transmitted his name to posterity as that of one of the greatest of + experimenters and the virtual founder of modern mechanical science. The + experiments in question range over a wide field; but for the most part + they have to do with moving bodies and with questions of force, or, as we + should now say, of energy. The experiment at the leaning tower showed that + the velocity of falling bodies is independent of the weight of the bodies, + provided the weight is sufficient to overcome the resistance of the + atmosphere. Later experiments with falling bodies led to the discovery of + laws regarding the accelerated velocity of fall. Such velocities were + found to bear a simple relation to the period of time from the beginning + of the fall. Other experiments, in which balls were allowed to roll down + inclined planes, corroborated the observation that the pull of gravitation + gave a velocity proportionate to the length of fall, whether such fall + were direct or in a slanting direction. + </p> + <p> + These studies were associated with observations on projectiles, regarding + which Galileo was the first to entertain correct notions. According to the + current idea, a projectile fired, for example, from a cannon, moved in a + straight horizontal line until the propulsive force was exhausted, and + then fell to the ground in a perpendicular line. Galileo taught that the + projectile begins to fall at once on leaving the mouth of the cannon and + traverses a parabolic course. According to his idea, which is now familiar + to every one, a cannon-ball dropped from the level of the cannon's muzzle + will strike the ground simultaneously with a ball fired horizontally from + the cannon. As to the paraboloid course pursued by the projectile, the + resistance of the air is a factor which Galileo could not accurately + compute, and which interferes with the practical realization of his + theory. But this is a minor consideration. The great importance of his + idea consists in the recognition that such a force as that of gravitation + acts in precisely the same way upon all unsupported bodies, whether or not + such bodies be at the same time acted upon by a force of translation. + </p> + <p> + Out of these studies of moving bodies was gradually developed a correct + notion of several important general laws of mechanics—laws a + knowledge of which was absolutely essential to the progress of physical + science. The belief in the rotation of the earth made necessary a clear + conception that all bodies at the surface of the earth partake of that + motion quite independently of their various observed motions in relation + to one another. This idea was hard to grasp, as an oft-repeated argument + shows. It was asserted again and again that, if the earth rotates, a stone + dropped from the top of a tower could not fall at the foot of the tower, + since the earth's motion would sweep the tower far away from its original + position while the stone is in transit. + </p> + <p> + This was one of the stock arguments against the earth's motion, yet it was + one that could be refuted with the greatest ease by reasoning from + strictly analogous experiments. It might readily be observed, for example, + that a stone dropped from a moving cart does not strike the ground + directly below the point from which it is dropped, but partakes of the + forward motion of the cart. If any one doubt this he has but to jump from + a moving cart to be given a practical demonstration of the fact that his + entire body was in some way influenced by the motion of translation. + Similarly, the simple experiment of tossing a ball from the deck of a + moving ship will convince any one that the ball partakes of the motion of + the ship, so that it can be manipulated precisely as if the manipulator + were standing on the earth. In short, every-day experience gives us + illustrations of what might be called compound motion, which makes it seem + altogether plausible that, if the earth is in motion, objects at its + surface will partake of that motion in a way that does not interfere with + any other movements to which they may be subjected. As the Copernican + doctrine made its way, this idea of compound motion naturally received + more and more attention, and such experiments as those of Galileo prepared + the way for a new interpretation of the mechanical principles involved. + </p> + <p> + The great difficulty was that the subject of moving bodies had all along + been contemplated from a wrong point of view. Since force must be applied + to an object to put it in motion, it was perhaps not unnaturally assumed + that similar force must continue to be applied to keep the object in + motion. When, for example, a stone is thrown from the hand, the direct + force applied necessarily ceases as soon as the projectile leaves the + hand. The stone, nevertheless, flies on for a certain distance and then + falls to the ground. How is this flight of the stone to be explained? The + ancient philosophers puzzled more than a little over this problem, and the + Aristotelians reached the conclusion that the motion of the hand had + imparted a propulsive motion to the air, and that this propulsive motion + was transmitted to the stone, pushing it on. Just how the air took on this + propulsive property was not explained, and the vagueness of thought that + characterized the time did not demand an explanation. Possibly the dying + away of ripples in water may have furnished, by analogy, an explanation of + the gradual dying out of the impulse which propels the stone. + </p> + <p> + All of this was, of course, an unfortunate maladjustment of the point of + view. As every one nowadays knows, the air retards the progress of the + stone, enabling the pull of gravitation to drag it to the earth earlier + than it otherwise could. Were the resistance of the air and the pull of + gravitation removed, the stone as projected from the hand would fly on in + a straight line, at an unchanged velocity, forever. But this fact, which + is expressed in what we now term the first law of motion, was extremely + difficult to grasp. The first important step towards it was perhaps + implied in Galileo's study of falling bodies. These studies, as we have + seen, demonstrated that a half-pound weight and a hundred-pound weight + fall with the same velocity. It is, however, matter of common experience + that certain bodies, as, for example, feathers, do not fall at the same + rate of speed with these heavier bodies. This anomaly demands an + explanation, and the explanation is found in the resistance offered the + relatively light object by the air. Once the idea that the air may thus + act as an impeding force was grasped, the investigator of mechanical + principles had entered on a new and promising course. + </p> + <p> + Galileo could not demonstrate the retarding influence of air in the way + which became familiar a generation or two later; he could not put a + feather and a coin in a vacuum tube and prove that the two would there + fall with equal velocity, because, in his day, the air-pump had not yet + been invented. The experiment was made only a generation after the time of + Galileo, as we shall see; but, meantime, the great Italian had fully + grasped the idea that atmospheric resistance plays a most important part + in regard to the motion of falling and projected bodies. Thanks largely to + his own experiments, but partly also to the efforts of others, he had + come, before the end of his life, pretty definitely to realize that the + motion of a projectile, for example, must be thought of as inherent in the + projectile itself, and that the retardation or ultimate cessation of that + motion is due to the action of antagonistic forces. In other words, he had + come to grasp the meaning of the first law of motion. It remained, + however, for the great Frenchman Descartes to give precise expression to + this law two years after Galileo's death. As Descartes expressed it in his + Principia Philosophiae, published in 1644, any body once in motion tends + to go on in a straight line, at a uniform rate of speed, forever. + Contrariwise, a stationary body will remain forever at rest unless acted + on by some disturbing force. + </p> + <p> + This all-important law, which lies at the very foundation of all true + conceptions of mechanics, was thus worked out during the first half of the + seventeenth century, as the outcome of numberless experiments for which + Galileo's experiments with failing bodies furnished the foundation. So + numerous and so gradual were the steps by which the reversal of view + regarding moving bodies was effected that it is impossible to trace them + in detail. We must be content to reflect that at the beginning of the + Galilean epoch utterly false notions regarding the subject were + entertained by the very greatest philosophers—by Galileo himself, + for example, and by Kepler—whereas at the close of that epoch the + correct and highly illuminative view had been attained. + </p> + <p> + We must now consider some other experiments of Galileo which led to + scarcely less-important results. The experiments in question had to do + with the movements of bodies passing down an inclined plane, and with the + allied subject of the motion of a pendulum. The elaborate experiments of + Galileo regarding the former subject were made by measuring the velocity + of a ball rolling down a plane inclined at various angles. He found that + the velocity acquired by a ball was proportional to the height from which + the ball descended regardless of the steepness of the incline. Experiments + were made also with a ball rolling down a curved gutter, the curve + representing the are of a circle. These experiments led to the study of + the curvilinear motions of a weight suspended by a cord; in other words, + of the pendulum. + </p> + <p> + Regarding the motion of the pendulum, some very curious facts were soon + ascertained. Galileo found, for example, that a pendulum of a given length + performs its oscillations with the same frequency though the arc described + by the pendulum be varied greatly.(1) He found, also, that the rate of + oscillation for pendulums of different lengths varies according to a + simple law. In order that one pendulum shall oscillate one-half as fast as + another, the length of the pendulums must be as four to one. Similarly, by + lengthening the pendulums nine times, the oscillation is reduced to + one-third, In other words, the rate of oscillation of pendulums varies + inversely as the square of their length. Here, then, is a simple relation + between the motions of swinging bodies which suggests the relation which + Kepler bad discovered between the relative motions of the planets. Every + such discovery coming in this age of the rejuvenation of experimental + science had a peculiar force in teaching men the all-important lesson that + simple laws lie back of most of the diverse phenomena of nature, if only + these laws can be discovered. + </p> + <p> + Galileo further observed that his pendulum might be constructed of any + weight sufficiently heavy readily to overcome the atmospheric resistance, + and that, with this qualification, neither the weight nor the material had + any influence upon the time of oscillation, this being solely determined + by the length of the cord. Naturally, the practical utility of these + discoveries was not overlooked by Galileo. Since a pendulum of a given + length oscillates with unvarying rapidity, here is an obvious means of + measuring time. Galileo, however, appears not to have met with any great + measure of success in putting this idea into practice. It remained for the + mechanical ingenuity of Huyghens to construct a satisfactory pendulum + clock. + </p> + <p> + As a theoretical result of the studies of rolling and oscillating bodies, + there was developed what is usually spoken of as the third law of motion—namely, + the law that a given force operates upon a moving body with an effect + proportionate to its effect upon the same body when at rest. Or, as + Whewell states the law: "The dynamical effect of force is as the statical + effect; that is, the velocity which any force generates in a given time, + when it puts the body in motion, is proportional to the pressure which + this same force produces in a body at rest."(2) According to the second + law of motion, each one of the different forces, operating at the same + time upon a moving body, produces the same effect as if it operated upon + the body while at rest. + </p> + <p> + STEVINUS AND THE LAW OF EQUILIBRIUM + </p> + <p> + It appears, then, that the mechanical studies of Galileo, taken as a + whole, were nothing less than revolutionary. They constituted the first + great advance upon the dynamic studies of Archimedes, and then led to the + secure foundation for one of the most important of modern sciences. We + shall see that an important company of students entered the field + immediately after the time of Galileo, and carried forward the work he had + so well begun. But before passing on to the consideration of their labors, + we must consider work in allied fields of two men who were contemporaries + of Galileo and whose original labors were in some respects scarcely less + important than his own. These men are the Dutchman Stevinus, who must + always be remembered as a co-laborer with Galileo in the foundation of the + science of dynamics, and the Englishman Gilbert, to whom is due the + unqualified praise of first subjecting the phenomenon of magnetism to a + strictly scientific investigation. + </p> + <p> + Stevinus was born in the year 1548, and died in 1620. He was a man of a + practical genius, and he attracted the attention of his non-scientific + contemporaries, among other ways, by the construction of a curious + land-craft, which, mounted on wheels, was to be propelled by sails like a + boat. Not only did he write a book on this curious horseless carriage, but + he put his idea into practical application, producing a vehicle which + actually traversed the distance between Scheveningen and Petton, with no + fewer than twenty-seven passengers, one of them being Prince Maurice of + Orange. This demonstration was made about the year 1600. It does not + appear, however, that any important use was made of the strange vehicle; + but the man who invented it put his mechanical ingenuity to other use with + better effect. It was he who solved the problem of oblique forces, and who + discovered the important hydrostatic principle that the pressure of fluids + is proportionate to their depth, without regard to the shape of the + including vessel. + </p> + <p> + The study of oblique forces was made by Stevinus with the aid of inclined + planes. His most demonstrative experiment was a very simple one, in which + a chain of balls of equal weight was hung from a triangle; the triangle + being so constructed as to rest on a horizontal base, the oblique sides + bearing the relation to each other of two to one. Stevinus found that his + chain of balls just balanced when four balls were on the longer side and + two on the shorter and steeper side. The balancing of force thus brought + about constituted a stable equilibrium, Stevinus being the first to + discriminate between such a condition and the unbalanced condition called + unstable equilibrium. By this simple experiment was laid the foundation of + the science of statics. Stevinus had a full grasp of the principle which + his experiment involved, and he applied it to the solution of oblique + forces in all directions. Earlier investigations of Stevinus were + published in 1608. His collected works were published at Leyden in 1634. + </p> + <p> + This study of the equilibrium of pressure of bodies at rest led Stevinus, + not unnaturally, to consider the allied subject of the pressure of + liquids. He is to be credited with the explanation of the so-called + hydrostatic paradox. The familiar modern experiment which illustrates this + paradox is made by inserting a long perpendicular tube of small caliber + into the top of a tight barrel. On filling the barrel and tube with water, + it is possible to produce a pressure which will burst the barrel, though + it be a strong one, and though the actual weight of water in the tube is + comparatively insignificant. This illustrates the fact that the pressure + at the bottom of a column of liquid is proportionate to the height of the + column, and not to its bulk, this being the hydrostatic paradox in + question. The explanation is that an enclosed fluid under pressure exerts + an equal force upon all parts of the circumscribing wall; the aggregate + pressure may, therefore, be increased indefinitely by increasing the + surface. It is this principle, of course, which is utilized in the + familiar hydrostatic press. Theoretical explanations of the pressure of + liquids were supplied a generation or two later by numerous investigators, + including Newton, but the practical refoundation of the science of + hydrostatics in modern times dates from the experiments of Stevinus. + </p> + <p> + GALILEO AND THE EQUILIBRIUM OF FLUIDS + </p> + <p> + Experiments of an allied character, having to do with the equilibrium of + fluids, exercised the ingenuity of Galileo. Some of his most interesting + experiments have to do with the subject of floating bodies. It will be + recalled that Archimedes, away back in the Alexandrian epoch, had solved + the most important problems of hydrostatic equilibrium. Now, however, his + experiments were overlooked or forgotten, and Galileo was obliged to make + experiments anew, and to combat fallacious views that ought long since to + have been abandoned. Perhaps the most illuminative view of the spirit of + the times can be gained by quoting at length a paper of Galileo's, in + which he details his own experiments with floating bodies and controverts + the views of his opponents. The paper has further value as illustrating + Galileo's methods both as experimenter and as speculative reasoner. + </p> + <p> + The current view, which Galileo here undertakes to refute, asserts that + water offers resistance to penetration, and that this resistance is + instrumental in determining whether a body placed in water will float or + sink. Galileo contends that water is non-resistant, and that bodies float + or sink in virtue of their respective weights. This, of course, is merely + a restatement of the law of Archimedes. But it remains to explain the fact + that bodies of a certain shape will float, while bodies of the same + material and weight, but of a different shape, will sink. We shall see + what explanation Galileo finds of this anomaly as we proceed. + </p> + <p> + In the first place, Galileo makes a cone of wood or of wax, and shows that + when it floats with either its point or its base in the water, it + displaces exactly the same amount of fluid, although the apex is by its + shape better adapted to overcome the resistance of the water, if that were + the cause of buoyancy. Again, the experiment may be varied by tempering + the wax with filings of lead till it sinks in the water, when it will be + found that in any figure the same quantity of cork must be added to it to + raise the surface. + </p> + <p> + "But," says Galileo, "this silences not my antagonists; they say that all + the discourse hitherto made by me imports little to them, and that it + serves their turn; that they have demonstrated in one instance, and in + such manner and figure as pleases them best—namely, in a board and + in a ball of ebony—that one when put into the water sinks to the + bottom, and that the other stays to swim on the top; and the matter being + the same, and the two bodies differing in nothing but in figure, they + affirm that with all perspicuity they have demonstrated and sensibly + manifested what they undertook. Nevertheless, I believe, and think I can + prove, that this very experiment proves nothing against my theory. And + first, it is false that the ball sinks and the board not; for the board + will sink, too, if you do to both the figures as the words of our question + require; that is, if you put them both in the water; for to be in the + water implies to be placed in the water, and by Aristotle's own definition + of place, to be placed imports to be environed by the surface of the + ambient body; but when my antagonists show the floating board of ebony, + they put it not into the water, but upon the water; where, being detained + by a certain impediment (of which more anon), it is surrounded, partly + with water, partly with air, which is contrary to our agreement, for that + was that bodies should be in the water, and not part in the water, part in + the air. + </p> + <p> + "I will not omit another reason, founded also upon experience, and, if I + deceive not myself, conclusive against the notion that figure, and the + resistance of the water to penetration, have anything to do with the + buoyancy of bodies. Choose a piece of wood or other matter, as, for + instance, walnut-wood, of which a ball rises from the bottom of the water + to the surface more slowly than a ball of ebony of the same size sinks, so + that, clearly, the ball of ebony divides the water more readily in sinking + than the ball of wood does in rising. Then take a board of walnut-tree + equal to and like the floating one of my antagonists; and if it be true + that this latter floats by reason of the figure being unable to penetrate + the water, the other of walnut-tree, without a question, if thrust to the + bottom, ought to stay there, as having the same impeding figure, and being + less apt to overcome the said resistance of the water. But if we find by + experience that not only the thin board, but every other figure of the + same walnut-tree, will return to float, as unquestionably we shall, then I + must desire my opponents to forbear to attribute the floating of the ebony + to the figure of the board, since the resistance of the water is the same + in rising as in sinking, and the force of ascension of the walnut-tree is + less than the ebony's force for going to the bottom. + </p> + <p> + "Now let us return to the thin plate of gold or silver, or the thin board + of ebony, and let us lay it lightly upon the water, so that it may stay + there without sinking, and carefully observe the effect. It will appear + clearly that the plates are a considerable matter lower than the surface + of the water, which rises up and makes a kind of rampart round them on + every side. But if it has already penetrated and overcome the continuity + of the water, and is of its own nature heavier than the water, why does it + not continue to sink, but stop and suspend itself in that little dimple + that its weight has made in the water? My answer is, because in sinking + till its surface is below the water, which rises up in a bank round it, it + draws after and carries along with it the air above it, so that that + which, in this case, descends in the water is not only the board of ebony + or the plate of iron, but a compound of ebony and air, from which + composition results a solid no longer specifically heavier than the water, + as was the ebony or gold alone. But, gentlemen, we want the same matter; + you are to alter nothing but the shape, and, therefore, have the goodness + to remove this air, which may be done simply by washing the surface of the + board, for the water having once got between the board and the air will + run together, and the ebony will go to the bottom; and if it does not, you + have won the day. + </p> + <p> + "But methinks I hear some of my antagonists cunningly opposing this, and + telling me that they will not on any account allow their boards to be + wetted, because the weight of the water so added, by making it heavier + than it was before, draws it to the bottom, and that the addition of new + weight is contrary to our agreement, which was that the matter should be + the same. + </p> + <p> + "To this I answer, first, that nobody can suppose bodies to be put into + the water without their being wet, nor do I wish to do more to the board + than you may do to the ball. Moreover, it is not true that the board sinks + on account of the weight of the water added in the washing; for I will put + ten or twenty drops on the floating board, and so long as they stand + separate it shall not sink; but if the board be taken out and all that + water wiped off, and the whole surface bathed with one single drop, and + put it again upon the water, there is no question but it will sink, the + other water running to cover it, being no longer hindered by the air. In + the next place, it is altogether false that water can in any way increase + the weight of bodies immersed in it, for water has no weight in water, + since it does not sink. Now just as he who should say that brass by its + own nature sinks, but that when formed into the shape of a kettle it + acquires from that figure the virtue of lying in water without sinking, + would say what is false, because that is not purely brass which then is + put into the water, but a compound of brass and air; so is it neither more + nor less false that a thin plate of brass or ebony swims by virtue of its + dilated and broad figure. Also, I cannot omit to tell my opponents that + this conceit of refusing to bathe the surface of the board might beget an + opinion in a third person of a poverty of argument on their side, + especially as the conversation began about flakes of ice, in which it + would be simple to require that the surfaces should be kept dry; not to + mention that such pieces of ice, whether wet or dry, always float, and so + my antagonists say, because of their shape. + </p> + <p> + "Some may wonder that I affirm this power to be in the air of keeping + plate of brass or silver above water, as if in a certain sense I would + attribute to the air a kind of magnetic virtue for sustaining heavy bodies + with which it is in contact. To satisfy all these doubts I have contrived + the following experiment to demonstrate how truly the air does support + these bodies; for I have found, when one of these bodies which floats when + placed lightly on the water is thoroughly bathed and sunk to the bottom, + that by carrying down to it a little air without otherwise touching it in + the least, I am able to raise and carry it back to the top, where it + floats as before. To this effect, I take a ball of wax, and with a little + lead make it just heavy enough to sink very slowly to the bottom, taking + care that its surface be quite smooth and even. This, if put gently into + the water, submerges almost entirely, there remaining visible only a + little of the very top, which, so long as it is joined to the air, keeps + the ball afloat; but if we take away the contact of the air by wetting + this top, the ball sinks to the bottom and remains there. Now to make it + return to the surface by virtue of the air which before sustained it, + thrust into the water a glass with the mouth downward, which will carry + with it the air it contains, and move this down towards the ball until you + see, by the transparency of the glass, that the air has reached the top of + it; then gently draw the glass upward, and you will see the ball rise, and + afterwards stay on the top of the water, if you carefully part the glass + and water without too much disturbing it."(3) + </p> + <p> + It will be seen that Galileo, while holding in the main to a correct + thesis, yet mingles with it some false ideas. At the very outset, of + course, it is not true that water has no resistance to penetration; it is + true, however, in the sense in which Galileo uses the term—that is + to say, the resistance of the water to penetration is not the determining + factor ordinarily in deciding whether a body sinks or floats. Yet in the + case of the flat body it is not altogether inappropriate to say that the + water resists penetration and thus supports the body. The modern physicist + explains the phenomenon as due to surface-tension of the fluid. Of course, + Galileo's disquisition on the mixing of air with the floating body is + utterly fanciful. His experiments were beautifully exact; his theorizing + from them was, in this instance, altogether fallacious. Thus, as already + intimated, his paper is admirably adapted to convey a double lesson to the + student of science. + </p> + <p> + WILLIAM GILBERT AND THE STUDY OF MAGNETISM + </p> + <p> + It will be observed that the studies of Galileo and Stevinus were chiefly + concerned with the force of gravitation. Meanwhile, there was an English + philosopher of corresponding genius, whose attention was directed towards + investigation of the equally mysterious force of terrestrial magnetism. + With the doubtful exception of Bacon, Gilbert was the most distinguished + man of science in England during the reign of Queen Elizabeth. He was for + many years court physician, and Queen Elizabeth ultimately settled upon + him a pension that enabled him to continue his researches in pure science. + </p> + <p> + His investigations in chemistry, although supposed to be of great + importance, are mostly lost; but his great work, De Magnete, on which he + labored for upwards of eighteen years, is a work of sufficient importance, + as Hallam says, "to raise a lasting reputation for its author." From its + first appearance it created a profound impression upon the learned men of + the continent, although in England Gilbert's theories seem to have been + somewhat less favorably received. Galileo freely expressed his admiration + for the work and its author; Bacon, who admired the author, did not + express the same admiration for his theories; but Dr. Priestley, later, + declared him to be "the father of modern electricity." + </p> + <p> + Strangely enough, Gilbert's book had never been translated into English, + or apparently into any other language, until recent years, although at the + time of its publication certain learned men, unable to read the book in + the original, had asked that it should be. By this neglect, or oversight, + a great number of general readers as well as many scientists, through + succeeding centuries, have been deprived of the benefit of writings that + contained a good share of the fundamental facts about magnetism as known + to-day. + </p> + <p> + Gilbert was the first to discover that the earth is a great magnet, and he + not only gave the name of "pole" to the extremities of the magnetic + needle, but also spoke of these "poles" as north and south pole, although + he used these names in the opposite sense from that in which we now use + them, his south pole being the extremity which pointed towards the north, + and vice versa. He was also first to make use of the terms "electric + force," "electric emanations," and "electric attractions." + </p> + <p> + It is hardly necessary to say that some of the views taken by Gilbert, + many of his theories, and the accuracy of some of his experiments have in + recent times been found to be erroneous. As a pioneer in an unexplored + field of science, however, his work is remarkably accurate. "On the + whole," says Dr. John Robinson, "this performance contains more real + information than any writing of the age in which he lived, and is scarcely + exceeded by any that has appeared since."(4) + </p> + <p> + In the preface to his work Gilbert says: "Since in the discovery of secret + things, and in the investigation of hidden causes, stronger reasons are + obtained from sure experiments and demonstrated arguments than from + probable conjectures and the opinions of philosophical speculators of the + common sort, therefore, to the end of that noble substance of that great + loadstone, our common mother (the earth), still quite unknown, and also + that the forces extraordinary and exalted of this globe may the better be + understood, we have decided, first, to begin with the common stony and + ferruginous matter, and magnetic bodies, and the part of the earth that we + may handle and may perceive with senses, and then to proceed with plain + magnetic experiments, and to penetrate to the inner parts of the + earth."(5) + </p> + <p> + Before taking up the demonstration that the earth is simply a giant + loadstone, Gilbert demonstrated in an ingenious way that every loadstone, + of whatever size, has definite and fixed poles. He did this by placing the + stone in a metal lathe and converting it into a sphere, and upon this + sphere demonstrated how the poles can be found. To this round loadstone he + gave the name of terrella—that is, little earth. + </p> + <p> + "To find, then, poles answering to the earth," he says, "take in your hand + the round stone, and lay on it a needle or a piece of iron wire: the ends + of the wire move round their middle point, and suddenly come to a + standstill. Now, with ochre or with chalk, mark where the wire lies still + and sticks. Then move the middle or centre of the wire to another spot, + and so to a third and fourth, always marking the stone along the length of + the wire where it stands still; the lines so marked will exhibit meridian + circles, or circles like meridians, on the stone or terrella; and + manifestly they will all come together at the poles of the stone. The + circle being continued in this way, the poles appear, both the north and + the south, and betwixt these, midway, we may draw a large circle for an + equator, as is done by the astronomer in the heavens and on his spheres, + and by the geographer on the terrestrial globe."(6) + </p> + <p> + Gilbert had tried the familiar experiment of placing the loadstone on a + float in water, and observed that the poles always revolved until they + pointed north and south, which he explained as due to the earth's magnetic + attraction. In this same connection he noticed that a piece of wrought + iron mounted on a cork float was attracted by other metals to a slight + degree, and he observed also that an ordinary iron bar, if suspended + horizontally by a thread, assumes invariably a north and south direction. + These, with many other experiments of a similar nature, convinced him that + the earth "is a magnet and a loadstone," which he says is a "new and till + now unheard-of view of the earth." + </p> + <p> + Fully to appreciate Gilbert's revolutionary views concerning the earth as + a magnet, it should be remembered that numberless theories to explain the + action of the electric needle had been advanced. Columbus and Paracelsus, + for example, believed that the magnet was attracted by some point in the + heavens, such as a magnetic star. Gilbert himself tells of some of the + beliefs that had been held by his predecessors, many of whom he declares + "wilfully falsify." One of his first steps was to refute by experiment + such assertions as that of Cardan, that "a wound by a magnetized needle + was painless"; and also the assertion of Fracastoni that loadstone + attracts silver; or that of Scalinger, that the diamond will attract iron; + and the statement of Matthiolus that "iron rubbed with garlic is no longer + attracted to the loadstone." + </p> + <p> + Gilbert made extensive experiments to explain the dipping of the needle, + which had been first noticed by William Norman. His deduction as to this + phenomenon led him to believe that this was also explained by the magnetic + attraction of the earth, and to predict where the vertical dip would be + found. These deductions seem the more wonderful because at the time he + made them the dip had just been discovered, and had not been studied + except at London. His theory of the dip was, therefore, a scientific + prediction, based on a preconceived hypothesis. Gilbert found the dip to + be 72 degrees at London; eight years later Hudson found the dip at 75 + degrees 22' north latitude to be 89 degrees 30'; but it was not until over + two hundred years later, in 1831, that the vertical dip was first observed + by Sir James Ross at about 70 degrees 5' north latitude, and 96 degrees + 43' west longitude. This was not the exact point assumed by Gilbert, and + his scientific predictions, therefore, were not quite correct; but such + comparatively slight and excusable errors mar but little the excellence of + his work as a whole. + </p> + <p> + A brief epitome of some of his other important discoveries suffices to + show that the exalted position in science accorded him by contemporaries, + as well as succeeding generations of scientists, was well merited. He was + first to distinguish between magnetism and electricity, giving the latter + its name. He discovered also the "electrical charge," and pointed the way + to the discovery of insulation by showing that the charge could be + retained some time in the excited body by covering it with some + non-conducting substance, such as silk; although, of course, electrical + conduction can hardly be said to have been more than vaguely surmised, if + understood at all by him. The first electrical instrument ever made, and + known as such, was invented by him, as was also the first magnetometer, + and the first electrical indicating device. Although three centuries have + elapsed since his death, the method of magnetizing iron first introduced + by him is in common use to-day. + </p> + <p> + He made exhaustive experiments with a needle balanced on a pivot to see + how many substances he could find which, like amber, on being rubbed + affected the needle. In this way he discovered that light substances were + attracted by alum, mica, arsenic, sealing-wax, lac sulphur, slags, beryl, + amethyst, rock-crystal, sapphire, jet, carbuncle, diamond, opal, Bristol + stone, glass, glass of antimony, gum-mastic, hard resin, rock-salt, and, + of course, amber. He discovered also that atmospheric conditions affected + the production of electricity, dryness being unfavorable and moisture + favorable. + </p> + <p> + Galileo's estimate of this first electrician is the verdict of succeeding + generations. "I extremely admire and envy this author," he said. "I think + him worthy of the greatest praise for the many new and true observations + which he has made, to the disgrace of so many vain and fabling authors." + </p> + <p> + STUDIES OF LIGHT, HEAT, AND ATMOSPHERIC PRESSURE + </p> + <p> + We have seen that Gilbert was by no means lacking in versatility, yet the + investigations upon which his fame is founded were all pursued along one + line, so that the father of magnetism may be considered one of the + earliest of specialists in physical science. Most workers of the time, on + the other band, extended their investigations in many directions. The sum + total of scientific knowledge of that day had not bulked so large as to + exclude the possibility that one man might master it all. So we find a + Galileo, for example, making revolutionary discoveries in astronomy, and + performing fundamental experiments in various fields of physics. Galileo's + great contemporary, Kepler, was almost equally versatile, though his + astronomical studies were of such pre-eminent importance that his other + investigations sink into relative insignificance. Yet he performed some + notable experiments in at least one department of physics. These + experiments had to do with the refraction of light, a subject which Kepler + was led to investigate, in part at least, through his interest in the + telescope. + </p> + <p> + We have seen that Ptolemy in the Alexandrian time, and Alhazen, the Arab, + made studies of refraction. Kepler repeated their experiments, and, + striving as always to generalize his observations, he attempted to find + the law that governed the observed change of direction which a ray of + light assumes in passing from one medium to another. Kepler measured the + angle of refraction by means of a simple yet ingenious trough-like + apparatus which enabled him to compare readily the direct and refracted + rays. He discovered that when a ray of light passes through a glass plate, + if it strikes the farther surface of the glass at an angle greater than 45 + degrees it will be totally refracted instead of passing through into the + air. He could not well fail to know that different mediums refract light + differently, and that for the same medium the amount of light valies with + the change in the angle of incidence. He was not able, however, to + generalize his observations as he desired, and to the last the law that + governs refraction escaped him. It remained for Willebrord Snell, a + Dutchman, about the year 1621, to discover the law in question, and for + Descartes, a little later, to formulate it. Descartes, indeed, has + sometimes been supposed to be the discoverer of the law. There is reason + to believe that he based his generalizations on the experiment of Snell, + though he did not openly acknowledge his indebtedness. The law, as + Descartes expressed it, states that the sine of the angle of incidence + bears a fixed ratio to the sine of the angle of refraction for any given + medium. Here, then, was another illustration of the fact that almost + infinitely varied phenomena may be brought within the scope of a simple + law. Once the law had been expressed, it could be tested and verified with + the greatest ease; and, as usual, the discovery being made, it seems + surprising that earlier investigators—in particular so sagacious a + guesser as Kepler—should have missed it. + </p> + <p> + Galileo himself must have been to some extent a student of light, since, + as we have seen, he made such notable contributions to practical optics + through perfecting the telescope; but he seems not to have added anything + to the theory of light. The subject of heat, however, attracted his + attention in a somewhat different way, and he was led to the invention of + the first contrivance for measuring temperatures. His thermometer was + based on the afterwards familiar principle of the expansion of a liquid + under the influence of heat; but as a practical means of measuring + temperature it was a very crude affair, because the tube that contained + the measuring liquid was exposed to the air, hence barometric changes of + pressure vitiated the experiment. It remained for Galileo's Italian + successors of the Accademia del Cimento of Florence to improve upon the + apparatus, after the experiments of Torricelli—to which we shall + refer in a moment—had thrown new light on the question of + atmospheric pressure. Still later the celebrated Huygens hit upon the idea + of using the melting and the boiling point of water as fixed points in a + scale of measurements, which first gave definiteness to thermometric + tests. + </p> + <p> + TORRICELLI + </p> + <p> + In the closing years of his life Galileo took into his family, as his + adopted disciple in science, a young man, Evangelista Torricelli + (1608-1647), who proved himself, during his short lifetime, to be a worthy + follower of his great master. Not only worthy on account of his great + scientific discoveries, but grateful as well, for when he had made the + great discovery that the "suction" made by a vacuum was really nothing but + air pressure, and not suction at all, he regretted that so important a + step in science might not have been made by his great teacher, Galileo, + instead of by himself. "This generosity of Torricelli," says Playfair, + "was, perhaps, rarer than his genius: there are more who might have + discovered the suspension of mercury in the barometer than who would have + been willing to part with the honor of the discovery to a master or a + friend." + </p> + <p> + Torricelli's discovery was made in 1643, less than two years after the + death of his master. Galileo had observed that water will not rise in an + exhausted tube, such as a pump, to a height greater than thirty-three + feet, but he was never able to offer a satisfactory explanation of the + principle. Torricelli was able to demonstrate that the height at which the + water stood depended upon nothing but its weight as compared with the + weight of air. If this be true, it is evident that any fluid will be + supported at a definite height, according to its relative weight as + compared with air. Thus mercury, which is about thirteen times more dense + than water, should only rise to one-thirteenth the height of a column of + water—that is, about thirty inches. Reasoning in this way, + Torricelli proceeded to prove that his theory was correct. Filling a long + tube, closed at one end, with mercury, he inverted the tube with its open + orifice in a vessel of mercury. The column of mercury fell at once, but at + a height of about thirty inches it stopped and remained stationary, the + pressure of the air on the mercury in the vessel maintaining it at that + height. This discovery was a shattering blow to the old theory that had + dominated that field of physics for so many centuries. It was completely + revolutionary to prove that, instead of a mysterious something within the + tube being responsible for the suspension of liquids at certain heights, + it was simply the ordinary atmospheric pressure mysterious enough, it is + true—pushing upon them from without. The pressure exerted by the + atmosphere was but little understood at that time, but Torricelli's + discovery aided materially in solving the mystery. The whole class of + similar phenomena of air pressure, which had been held in the trammel of + long-established but false doctrines, was now reduced to one simple law, + and the door to a solution of a host of unsolved problems thrown open. + </p> + <p> + It had long been suspected and believed that the density of the atmosphere + varies at certain times. That the air is sometimes "heavy" and at other + times "light" is apparent to the senses without scientific apparatus for + demonstration. It is evident, then, that Torricelli's column of mercury + should rise and fall just in proportion to the lightness or heaviness of + the air. A short series of observations proved that it did so, and with + those observations went naturally the observations as to changes in the + weather. It was only necessary, therefore, to scratch a scale on the glass + tube, indicating relative atmospheric pressures, and the Torricellian + barometer was complete. + </p> + <p> + Such a revolutionary theory and such an important discovery were, of + course, not to be accepted without controversy, but the feeble arguments + of the opponents showed how untenable the old theory had become. In 1648 + Pascal suggested that if the theory of the pressure of air upon the + mercury was correct, it could be demonstrated by ascending a mountain with + the mercury tube. As the air was known to get progressively lighter from + base to summit, the height of the column should be progressively lessened + as the ascent was made, and increase again on the descent into the denser + air. The experiment was made on the mountain called the Puy-de-Dome, in + Auvergne, and the column of mercury fell and rose progressively through a + space of about three inches as the ascent and descent were made. + </p> + <p> + This experiment practically sealed the verdict on the new theory, but it + also suggested something more. If the mercury descended to a certain mark + on the scale on a mountain-top whose height was known, why was not this a + means of measuring the heights of all other elevations? And so the + beginning was made which, with certain modifications and corrections in + details, is now the basis of barometrical measurements of heights. + </p> + <p> + In hydraulics, also, Torricelli seems to have taken one of the first + steps. He did this by showing that the water which issues from a hole in + the side or bottom of a vessel does so at the same velocity as that which + a body would acquire by falling from the level of the surface of the water + to that of the orifice. This discovery was of the greatest importance to a + correct understanding of the science of the motions of fluids. He also + discovered the valuable mechanical principle that if any number of bodies + be connected so that by their motion there is neither ascent nor descent + of their centre of gravity, these bodies are in equilibrium. + </p> + <p> + Besides making these discoveries, he greatly improved the microscope and + the telescope, and invented a simple microscope made of a globule of + glass. In 1644 he published a tract on the properties of the cycloid in + which he suggested a solution of the problem of its quadrature. As soon as + this pamphlet appeared its author was accused by Gilles Roberval + (1602-1675) of having appropriated a solution already offered by him. This + led to a long debate, during which Torricelli was seized with a fever, + from the effects of which he died, in Florence, October 25, 1647. There is + reason to believe, however, that while Roberval's discovery was made + before Torricelli's, the latter reached his conclusions independently. + </p> + <p> + <a name="link2H_4_0008" id="link2H_4_0008"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VI. TWO PSEUDO-SCIENCES—ALCHEMY AND ASTROLOGY + </h2> + <p> + In recent chapters we have seen science come forward with tremendous + strides. A new era is obviously at hand. But we shall misconceive the + spirit of the times if we fail to understand that in the midst of all this + progress there was still room for mediaeval superstition and for the + pursuit of fallacious ideals. Two forms of pseudo-science were peculiarly + prevalent—alchemy and astrology. Neither of these can with full + propriety be called a science, yet both were pursued by many of the + greatest scientific workers of the period. Moreover, the studies of the + alchemist may with some propriety be said to have laid the foundation for + the latter-day science of chemistry; while astrology was closely allied to + astronomy, though its relations to that science are not as intimate as has + sometimes been supposed. + </p> + <p> + Just when the study of alchemy began is undetermined. It was certainly of + very ancient origin, perhaps Egyptian, but its most flourishing time was + from about the eighth century A.D. to the eighteenth century. The stories + of the Old Testament formed a basis for some of the strange beliefs + regarding the properties of the magic "elixir," or "philosopher's stone." + Alchemists believed that most of the antediluvians, perhaps all of them, + possessed a knowledge of this stone. How, otherwise, could they have + prolonged their lives to nine and a half centuries? And Moses was surely a + first-rate alchemist, as is proved by the story of the Golden Calf.(1) + After Aaron had made the calf of gold, Moses performed the much more + difficult task of grinding it to powder and "strewing it upon the waters," + thus showing that he had transmuted it into some lighter substance. + </p> + <p> + But antediluvians and Biblical characters were not the only persons who + were thought to have discovered the coveted "elixir." Hundreds of aged + mediaeval chemists were credited with having made the discovery, and were + thought to be living on through the centuries by its means. Alaies de + Lisle, for example, who died in 1298, at the age of 110, was alleged to + have been at the point of death at the age of fifty, but just at this time + he made the fortunate discovery of the magic stone, and so continued to + live in health and affluence for sixty years more. And De Lisle was but + one case among hundreds. + </p> + <p> + An aged and wealthy alchemist could claim with seeming plausibility that + he was prolonging his life by his magic; whereas a younger man might + assert that, knowing the great secret, he was keeping himself young + through the centuries. In either case such a statement, or rumor, about a + learned and wealthy alchemist was likely to be believed, particularly + among strangers; and as such a man would, of course, be the object of much + attention, the claim was frequently made by persons seeking notoriety. One + of the most celebrated of these impostors was a certain Count de + Saint-Germain, who was connected with the court of Louis XV. His + statements carried the more weight because, having apparently no means of + maintenance, he continued to live in affluence year after year—for + two thousand years, as he himself admitted—by means of the magic + stone. If at any time his statements were doubted, he was in the habit of + referring to his valet for confirmation, this valet being also under the + influence of the elixir of life. + </p> + <p> + "Upon one occasion his master was telling a party of ladies and gentlemen, + at dinner, some conversation he had had in Palestine, with King Richard + I., of England, whom he described as a very particular friend of his. + Signs of astonishment and incredulity were visible on the faces of the + company, upon which Saint-Germain very coolly turned to his servant, who + stood behind his chair, and asked him if he had not spoken the truth. 'I + really cannot say,' replied the man, without moving a muscle; 'you forget, + sir, I have been only five hundred years in your service.' 'Ah, true,' + said his master, 'I remember now; it was a little before your time!'"(2) + </p> + <p> + In the time of Saint-Germain, only a little over a century ago, belief in + alchemy had almost disappeared, and his extraordinary tales were probably + regarded in the light of amusing stories. Still there was undoubtedly a + lingering suspicion in the minds of many that this man possessed some + peculiar secret. A few centuries earlier his tales would hardly have been + questioned, for at that time the belief in the existence of this magic + something was so strong that the search for it became almost a form of + mania; and once a man was seized with it, lie gambled away health, + position, and life itself in pursuing the coveted stake. An example of + this is seen in Albertus Magnus, one of the most learned men of his time, + who it is said resigned his position as bishop of Ratisbon in order that + he might pursue his researches in alchemy. + </p> + <p> + If self-sacrifice was not sufficient to secure the prize, crime would + naturally follow, for there could be no limit to the price of the stakes + in this game. The notorious Marechal de Reys, failing to find the coveted + stone by ordinary methods of laboratory research, was persuaded by an + impostor that if he would propitiate the friendship of the devil the + secret would be revealed. To this end De Reys began secretly capturing + young children as they passed his castle and murdering them. When he was + at last brought to justice it was proved that he had murdered something + like a hundred children within a period of three years. So, at least, runs + one version of the story of this perverted being. + </p> + <p> + Naturally monarchs, constantly in need of funds, were interested in these + alchemists. Even sober England did not escape, and Raymond Lully, one of + the most famous of the thirteenth and fourteenth century alchemists, is + said to have been secretly invited by King Edward I. (or II.) to leave + Milan and settle in England. According to some accounts, apartments were + assigned to his use in the Tower of London, where he is alleged to have + made some six million pounds sterling for the monarch, out of iron, + mercury, lead, and pewter. + </p> + <p> + Pope John XXII., a friend and pupil of the alchemist Arnold de Villeneuve, + is reported to have learned the secrets of alchemy from his master. Later + he issued two bulls against "pretenders" in the art, which, far from + showing his disbelief, were cited by alchemists as proving that he + recognized pretenders as distinct from true masters of magic. + </p> + <p> + To moderns the attitude of mind of the alchemist is difficult to + comprehend. It is, perhaps, possible to conceive of animals or plants + possessing souls, but the early alchemist attributed the same thing—or + something kin to it—to metals also. Furthermore, just as plants + germinated from seeds, so metals were supposed to germinate also, and + hence a constant growth of metals in the ground. To prove this the + alchemist cited cases where previously exhausted gold-mines were found, + after a lapse of time, to contain fresh quantities of gold. The "seed" of + the remaining particles of gold had multiplied and increased. But this + germinating process could only take place under favorable conditions, just + as the seed of a plant must have its proper surroundings before + germinating; and it was believed that the action of the philosopher's + stone was to hasten this process, as man may hasten the growth of plants + by artificial means. Gold was looked upon as the most perfect metal, and + all other metals imperfect, because not yet "purified." By some alchemists + they were regarded as lepers, who, when cured of their leprosy, would + become gold. And since nature intended that all things should be perfect, + it was the aim of the alchemist to assist her in this purifying process, + and incidentally to gain wealth and prolong his life. + </p> + <p> + By other alchemists the process of transition from baser metals into gold + was conceived to be like a process of ripening fruit. The ripened product + was gold, while the green fruit, in various stages of maturity, was + represented by the base metals. Silver, for example, was more nearly ripe + than lead; but the difference was only one of "digestion," and it was + thought that by further "digestion" lead might first become silver and + eventually gold. In other words, Nature had not completed her work, and + was wofully slow at it at best; but man, with his superior faculties, was + to hasten the process in his laboratories—if he could but hit upon + the right method of doing so. + </p> + <p> + It should not be inferred that the alchemist set about his task of + assisting nature in a haphazard way, and without training in the various + alchemic laboratory methods. On the contrary, he usually served a long + apprenticeship in the rudiments of his calling. He was obliged to learn, + in a general way, many of the same things that must be understood in + either chemical or alchemical laboratories. The general knowledge that + certain liquids vaporize at lower temperatures than others, and that the + melting-points of metals differ greatly, for example, was just as + necessary to alchemy as to chemistry. The knowledge of the gross + structure, or nature, of materials was much the same to the alchemist as + to the chemist, and, for that matter, many of the experiments in + calcining, distilling, etc., were practically identical. + </p> + <p> + To the alchemist there were three principles—salt, sulphur, and + mercury—and the sources of these principles were the four elements—earth, + water, fire, and air. These four elements were accountable for every + substance in nature. Some of the experiments to prove this were so + illusive, and yet apparently so simple, that one is not surprised that it + took centuries to disprove them. That water was composed of earth and air + seemed easily proven by the simple process of boiling it in a tea-kettle, + for the residue left was obviously an earthy substance, whereas the steam + driven off was supposed to be air. The fact that pure water leaves no + residue was not demonstrated until after alchemy had practically ceased to + exist. It was possible also to demonstrate that water could be turned into + fire by thrusting a red-hot poker under a bellglass containing a dish of + water. Not only did the quantity of water diminish, but, if a lighted + candle was thrust under the glass, the contents ignited and burned, + proving, apparently, that water had been converted into fire. These, and + scores of other similar experiments, seemed so easily explained, and to + accord so well with the "four elements" theory, that they were seldom + questioned until a later age of inductive science. + </p> + <p> + But there was one experiment to which the alchemist pinned his faith in + showing that metals could be "killed" and "revived," when proper means + were employed. It had been known for many centuries that if any metal, + other than gold or silver, were calcined in an open crucible, it turned, + after a time, into a peculiar kind of ash. This ash was thought by the + alchemist to represent the death of the metal. But if to this same ash a + few grains of wheat were added and heat again applied to the crucible, the + metal was seen to "rise from its ashes" and resume its original form—a + well-known phenomenon of reducing metals from oxides by the use of carbon, + in the form of wheat, or, for that matter, any other carbonaceous + substance. Wheat was, therefore, made the symbol of the resurrection of + the life eternal. Oats, corn, or a piece of charcoal would have "revived" + the metals from the ashes equally well, but the mediaeval alchemist seems + not to have known this. However, in this experiment the metal seemed + actually to be destroyed and revivified, and, as science had not as yet + explained this striking phenomenon, it is little wonder that it deceived + the alchemist. + </p> + <p> + Since the alchemists pursued their search of the magic stone in such a + methodical way, it would seem that they must have some idea of the + appearance of the substance they sought. Probably they did, each according + to his own mental bias; but, if so, they seldom committed themselves to + writing, confining their discourses largely to speculations as to the + properties of this illusive substance. Furthermore, the desire for secrecy + would prevent them from expressing so important a piece of information. + But on the subject of the properties, if not on the appearance of the + "essence," they were voluminous writers. It was supposed to be the only + perfect substance in existence, and to be confined in various substances, + in quantities proportionate to the state of perfection of the substance. + Thus, gold being most nearly perfect would contain more, silver less, lead + still less, and so on. The "essence" contained in the more nearly perfect + metals was thought to be more potent, a very small quantity of it being + capable of creating large quantities of gold and of prolonging life + indefinitely. + </p> + <p> + It would appear from many of the writings of the alchemists that their + conception of nature and the supernatural was so confused and entangled in + an inexplicable philosophy that they themselves did not really understand + the meaning of what they were attempting to convey. But it should not be + forgotten that alchemy was kept as much as possible from the ignorant + general public, and the alchemists themselves had knowledge of secret + words and expressions which conveyed a definite meaning to one of their + number, but which would appear a meaningless jumble to an outsider. Some + of these writers declared openly that their writings were intended to + convey an entirely erroneous impression, and were sent out only for that + purpose. + </p> + <p> + However, while it may have been true that the vagaries of their writings + were made purposely, the case is probably more correctly explained by + saying that the very nature of the art made definite statements + impossible. They were dealing with something that did not exist—could + not exist. Their attempted descriptions became, therefore, the language of + romance rather than the language of science. + </p> + <p> + But if the alchemists themselves were usually silent as to the appearance + of the actual substance of the philosopher's stone, there were numberless + other writers who were less reticent. By some it was supposed to be a + stone, by others a liquid or elixir, but more commonly it was described as + a black powder. It also possessed different degrees of efficiency + according to its degrees of purity, certain forms only possessing the + power of turning base metals into gold, while others gave eternal youth + and life or different degrees of health. Thus an alchemist, who had made a + partial discovery of this substance, could prolong life a certain number + of years only, or, possessing only a small and inadequate amount of the + magic powder, he was obliged to give up the ghost when the effect of this + small quantity had passed away. + </p> + <p> + This belief in the supernatural power of the philosopher's stone to + prolong life and heal diseases was probably a later phase of alchemy, + possibly developed by attempts to connect the power of the mysterious + essence with Biblical teachings. The early Roman alchemists, who claimed + to be able to transmute metals, seem not to have made other claims for + their magic stone. + </p> + <p> + By the fifteenth century the belief in the philosopher's stone had become + so fixed that governments began to be alarmed lest some lucky possessor of + the secret should flood the country with gold, thus rendering the existing + coin of little value. Some little consolation was found in the thought + that in case all the baser metals were converted into gold iron would then + become the "precious metal," and would remain so until some new + philosopher's stone was found to convert gold back into iron—a much + more difficult feat, it was thought. However, to be on the safe side, the + English Parliament, in 1404, saw fit to pass an act declaring the making + of gold and silver to be a felony. Nevertheless, in 1455, King Henry VI. + granted permission to several "knights, citizens of London, chemists, and + monks" to find the philosopher's stone, or elixir, that the crown might + thus be enabled to pay off its debts. The monks and ecclesiastics were + supposed to be most likely to discover the secret process, since "they + were such good artists in transubstantiating bread and wine." + </p> + <p> + In Germany the emperors Maximilian I., Rudolf II., and Frederick II. gave + considerable attention to the search, and the example they set was + followed by thousands of their subjects. It is said that some noblemen + developed the unpleasant custom of inviting to their courts men who were + reputed to have found the stone, and then imprisoning the poor alchemists + until they had made a certain quantity of gold, stimulating their activity + with tortures of the most atrocious kinds. Thus this danger of being + imprisoned and held for ransom until some fabulous amount of gold should + be made became the constant menace of the alchemist. It was useless for an + alchemist to plead poverty once it was noised about that he had learned + the secret. For how could such a man be poor when, with a piece of metal + and a few grains of magic powder, he was able to provide himself with + gold? It was, therefore, a reckless alchemist indeed who dared boast that + he had made the coveted discovery. + </p> + <p> + The fate of a certain indiscreet alchemist, supposed by many to have been + Seton, a Scotchman, was not an uncommon one. Word having been brought to + the elector of Saxony that this alchemist was in Dresden and boasting of + his powers, the elector caused him to be arrested and imprisoned. Forty + guards were stationed to see that he did not escape and that no one + visited him save the elector himself. For some time the elector tried by + argument and persuasion to penetrate his secret or to induce him to make a + certain quantity of gold; but as Seton steadily refused, the rack was + tried, and for several months he suffered torture, until finally, reduced + to a mere skeleton, he was rescued by a rival candidate of the elector, a + Pole named Michael Sendivogins, who drugged the guards. However, before + Seton could be "persuaded" by his new captor, he died of his injuries. + </p> + <p> + But Sendivogins was also ambitious in alchemy, and, since Seton was beyond + his reach, he took the next best step and married his widow. From her, as + the story goes, he received an ounce of black powder—the veritable + philosopher's stone. With this he manufactured great quantities of gold, + even inviting Emperor Rudolf II. to see him work the miracle. That monarch + was so impressed that he caused a tablet to be inserted in the wall of the + room in which he had seen the gold made. + </p> + <p> + Sendivogins had learned discretion from the misfortune of Seton, so that + he took the precaution of concealing most of the precious powder in a + secret chamber of his carriage when he travelled, having only a small + quantity carried by his steward in a gold box. In particularly dangerous + places, he is said to have exchanged clothes with his coachman, making the + servant take his place in the carriage while he mounted the box. + </p> + <p> + About the middle of the seventeenth century alchemy took such firm root in + the religious field that it became the basis of the sect known as the + Rosicrucians. The name was derived from the teaching of a German + philosopher, Rosenkreutz, who, having been healed of a dangerous illness + by an Arabian supposed to possess the philosopher's stone, returned home + and gathered about him a chosen band of friends, to whom he imparted the + secret. This sect came rapidly into prominence, and for a short time at + least created a sensation in Europe, and at the time were credited with + having "refined and spiritualized" alchemy. But by the end of the + seventeenth century their number had dwindled to a mere handful, and + henceforth they exerted little influence. + </p> + <p> + Another and earlier religious sect was the Aureacrucians, founded by Jacob + Bohme, a shoemaker, born in Prussia in 1575. According to his teachings + the philosopher's stone could be discovered by a diligent search of the + Old and the New Testaments, and more particularly the Apocalypse, which + contained all the secrets of alchemy. This sect found quite a number of + followers during the life of Bohme, but gradually died out after his + death; not, however, until many of its members had been tortured for + heresy, and one at least, Kuhlmann, of Moscow, burned as a sorcerer. + </p> + <p> + The names of the different substances that at various times were thought + to contain the large quantities of the "essence" during the many centuries + of searching for it, form a list of practically all substances that were + known, discovered, or invented during the period. Some believed that acids + contained the substance; others sought it in minerals or in animal or + vegetable products; while still others looked to find it among the + distilled "spirits"—the alcoholic liquors and distilled products. On + the introduction of alcohol by the Arabs that substance became of + all-absorbing interest, and for a long time allured the alchemist into + believing that through it they were soon to be rewarded. They rectified + and refined it until "sometimes it was so strong that it broke the vessels + containing it," but still it failed in its magic power. Later, brandy was + substituted for it, and this in turn discarded for more recent + discoveries. + </p> + <p> + There were always, of course, two classes of alchemists: serious + investigators whose honesty could not be questioned, and clever impostors + whose legerdemain was probably largely responsible for the extended belief + in the existence of the philosopher's stone. Sometimes an alchemist + practised both, using the profits of his sleight-of-hand to procure the + means of carrying on his serious alchemical researches. The impostures of + some of these jugglers deceived even the most intelligent and learned men + of the time, and so kept the flame of hope constantly burning. The age of + cold investigation had not arrived, and it is easy to understand how an + unscrupulous mediaeval Hermann or Kellar might completely deceive even the + most intelligent and thoughtful scholars. In scoffing at the credulity of + such an age, it should not be forgotten that the "Keely motor" was a late + nineteenth-century illusion. + </p> + <p> + But long before the belief in the philosopher's stone had died out, the + methods of the legerdemain alchemist had been investigated and reported + upon officially by bodies of men appointed to make such investigations, + although it took several generations completely to overthrow a + superstition that had been handed down through several thousand years. In + April of 1772 Monsieur Geoffroy made a report to the Royal Academy of + Sciences, at Paris, on the alchemic cheats principally of the sixteenth + and seventeenth centuries. In this report he explains many of the + seemingly marvellous feats of the unscrupulous alchemists. A very common + form of deception was the use of a double-bottomed crucible. A copper or + brass crucible was covered on the inside with a layer of wax, cleverly + painted so as to resemble the ordinary metal. Between this layer of wax + and the bottom of the crucible, however, was a layer of gold dust or + silver. When the alchemist wished to demonstrate his power, he had but to + place some mercury or whatever substance he chose in the crucible, heat + it, throw in a grain or two of some mysterious powder, pronounce a few + equally mysterious phrases to impress his audience, and, behold, a lump of + precious metal would be found in the bottom of his pot. This was the + favorite method of mediocre performers, but was, of course, easily + detected. + </p> + <p> + An equally successful but more difficult way was to insert surreptitiously + a lump of metal into the mixture, using an ordinary crucible. This + required great dexterity, but was facilitated by the use of many + mysterious ceremonies on the part of the operator while performing, just + as the modern vaudeville performer diverts the attention of the audience + to his right hand while his left is engaged in the trick. Such ceremonies + were not questioned, for it was the common belief that the whole process + "lay in the spirit as much as in the substance," many, as we have seen, + regarding the whole process as a divine manifestation. + </p> + <p> + Sometimes a hollow rod was used for stirring the mixture in the crucible, + this rod containing gold dust, and having the end plugged either with wax + or soft metal that was easily melted. Again, pieces of lead were used + which had been plugged with lumps of gold carefully covered over; and a + very simple and impressive demonstration was making use of a nugget of + gold that had been coated over with quicksilver and tarnished so as to + resemble lead or some base metal. When this was thrown into acid the + coating was removed by chemical action, leaving the shining metal in the + bottom of the vessel. In order to perform some of these tricks, it is + obvious that the alchemist must have been well supplied with gold, as some + of them, when performing before a royal audience, gave the products to + their visitors. But it was always a paying investment, for once his + reputation was established the gold-maker found an endless variety of ways + of turning his alleged knowledge to account, frequently amassing great + wealth. + </p> + <p> + Some of the cleverest of the charlatans often invited royal or other + distinguished guests to bring with them iron nails to be turned into gold + ones. They were transmuted in the alchemist's crucible before the eyes of + the visitors, the juggler adroitly extracting the iron nail and inserting + a gold one without detection. It mattered little if the converted gold + nail differed in size and shape from the original, for this change in + shape could be laid to the process of transmutation; and even the very + critical were hardly likely to find fault with the exchange thus made. + Furthermore, it was believed that gold possessed the property of changing + its bulk under certain conditions, some of the more conservative + alchemists maintaining that gold was only increased in bulk, not + necessarily created, by certain forms of the magic stone. Thus a very + proficient operator was thought to be able to increase a grain of gold + into a pound of pure metal, while one less expert could only double, or + possibly treble, its original weight. + </p> + <p> + The actual number of useful discoveries resulting from the efforts of the + alchemists is considerable, some of them of incalculable value. Roger + Bacon, who lived in the thirteenth century, while devoting much of his + time to alchemy, made such valuable discoveries as the theory, at least, + of the telescope, and probably gunpowder. Of this latter we cannot be sure + that the discovery was his own and that he had not learned of it through + the source of old manuscripts. But it is not impossible nor improbable + that he may have hit upon the mixture that makes the explosives while + searching for the philosopher's stone in his laboratory. "Von Helmont, in + the same pursuit, discovered the properties of gas," says Mackay; "Geber + made discoveries in chemistry, which were equally important; and + Paracelsus, amid his perpetual visions of the transmutation of metals, + found that mercury was a remedy for one of the most odious and + excruciating of all the diseases that afflict humanity."' As we shall see + a little farther on, alchemy finally evolved into modern chemistry, but + not until it had passed through several important transitional stages. + </p> + <p> + ASTROLOGY + </p> + <p> + In a general way modern astronomy may be considered as the outgrowth of + astrology, just as modern chemistry is the result of alchemy. It is quite + possible, however, that astronomy is the older of the two; but astrology + must have developed very shortly after. The primitive astronomer, having + acquired enough knowledge from his observations of the heavenly bodies to + make correct predictions, such as the time of the coming of the new moon, + would be led, naturally, to believe that certain predictions other than + purely astronomical ones could be made by studying the heavens. Even if + the astronomer himself did not believe this, some of his superstitious + admirers would; for to the unscientific mind predictions of earthly events + would surely seem no more miraculous than correct predictions as to the + future movements of the sun, moon, and stars. When astronomy had reached a + stage of development so that such things as eclipses could be predicted + with anything like accuracy, the occult knowledge of the astronomer would + be unquestioned. Turning this apparently occult knowledge to account in a + mercenary way would then be the inevitable result, although it cannot be + doubted that many of the astrologers, in all ages, were sincere in their + beliefs. + </p> + <p> + Later, as the business of astrology became a profitable one, sincere + astronomers would find it expedient to practise astrology as a means of + gaining a livelihood. Such a philosopher as Kepler freely admitted that he + practised astrology "to keep from starving," although he confessed no + faith in such predictions. "Ye otherwise philosophers," he said, "ye + censure this daughter of astronomy beyond her deserts; know ye not that + she must support her mother by her charms." + </p> + <p> + Once astrology had become an established practice, any considerable + knowledge of astronomy was unnecessary, for as it was at best but a system + of good guessing as to future events, clever impostors could thrive + equally well without troubling to study astronomy. The celebrated + astrologers, however, were usually astronomers as well, and undoubtedly + based many of their predictions on the position and movements of the + heavenly bodies. Thus, the casting of a horoscope that is, the methods by + which the astrologers ascertained the relative position of the heavenly + bodies at the time of a birth—was a simple but fairly exact + procedure. Its basis was the zodiac, or the path traced by the sun in his + yearly course through certain constellations. At the moment of the birth + of a child, the first care of the astrologer was to note the particular + part of the zodiac that appeared on the horizon. The zodiac was then + divided into "houses"—that is, into twelve spaces—on a chart. + In these houses were inserted the places of the planets, sun, and moon, + with reference to the zodiac. When this chart was completed it made a + fairly correct diagram of the heavens and the position of the heavenly + bodies as they would appear to a person standing at the place of birth at + a certain time. + </p> + <p> + Up to this point the process was a simple one of astronomy. But the next + step—the really important one—that of interpreting this chart, + was the one which called forth the skill and imagination of the + astrologer. In this interpretation, not in his mere observations, lay the + secret of his success. Nor did his task cease with simply foretelling + future events that were to happen in the life of the newly born infant. He + must not only point out the dangers, but show the means whereby they could + be averted, and his prophylactic measures, like his predictions, were + alleged to be based on his reading of the stars. + </p> + <p> + But casting a horoscope at the time of births was, of course, only a small + part of the astrologer's duty. His offices were sought by persons of all + ages for predictions as to their futures, the movements of an enemy, where + to find stolen goods, and a host of everyday occurrences. In such cases it + is more than probable that the astrologers did very little consulting of + the stars in making their predictions. They became expert physiognomists + and excellent judges of human nature, and were thus able to foretell + futures with the same shrewdness and by the same methods as the modern + "mediums," palmists, and fortune-tellers. To strengthen belief in their + powers, it became a common thing for some supposedly lost document of the + astrologer to be mysteriously discovered after an important event, this + document purporting to foretell this very event. It was also a common + practice with astrologers to retain, or have access to, their original + charts, cleverly altering them from time to time to fit conditions. + </p> + <p> + The dangers attendant upon astrology were of such a nature that the lot of + the astrologer was likely to prove anything but an enviable one. As in the + case of the alchemist, the greater the reputation of an astrologer the + greater dangers he was likely to fall into. If he became so famous that he + was employed by kings or noblemen, his too true or too false prophecies + were likely to bring him into disrepute—even to endanger his life. + </p> + <p> + Throughout the dark age the astrologers flourished, but the sixteenth and + seventeenth centuries were the golden age of these impostors. A skilful + astrologer was as much an essential to the government as the highest + official, and it would have been a bold monarch, indeed, who would + undertake any expedition of importance unless sanctioned by the governing + stars as interpreted by these officials. + </p> + <p> + It should not be understood, however, that belief in astrology died with + the advent of the Copernican doctrine. It did become separated from + astronomy very shortly after, to be sure, and undoubtedly among the + scientists it lost much of its prestige. But it cannot be considered as + entirely passed away, even to-day, and even if we leave out of + consideration street-corner "astrologers" and fortune-tellers, whose signs + may be seen in every large city, there still remains quite a large class + of relatively intelligent people who believe in what they call "the + science of astrology." Needless to say, such people are not found among + the scientific thinkers; but it is significant that scarcely a year passes + that some book or pamphlet is not published by some ardent believer in + astrology, attempting to prove by the illogical dogmas characteristic of + unscientific thinkers that astrology is a science. The arguments contained + in these pamphlets are very much the same as those of the astrologers + three hundred years ago, except that they lack the quaint form of wording + which is one of the features that lends interest to the older documents. + These pamphlets need not be taken seriously, but they are interesting as + exemplifying how difficult it is, even in an age of science, to entirely + stamp out firmly established superstitions. Here are some of the arguments + advanced in defence of astrology, taken from a little brochure entitled + "Astrology Vindicated," published in 1898: "It will be found that a person + born when the Sun is in twenty degrees Scorpio has the left ear as his + exceptional feature and the nose (Sagittarius) bent towards the left ear. + A person born when the Sun is in any of the latter degrees of Taurus, say + the twenty-fifth degree, will have a small, sharp, weak chin, curved up + towards Gemini, the two vertical lines on the upper lip."(4) The time was + when science went out of its way to prove that such statements were + untrue; but that time is past, and such writers are usually classed among + those energetic but misguided persons who are unable to distinguish + between logic and sophistry. + </p> + <p> + In England, from the time of Elizabeth to the reign of William and Mary, + judicial astrology was at its height. After the great London fire, in + 1666, a committee of the House of Commons publicly summoned the famous + astrologer, Lilly, to come before Parliament and report to them on his + alleged prediction of the calamity that had befallen the city. Lilly, for + some reason best known to himself, denied having made such a prediction, + being, as he explained, "more interested in determining affairs of much + more importance to the future welfare of the country." Some of the + explanations of his interpretations will suffice to show their + absurdities, which, however, were by no means regarded as absurdities at + that time, for Lilly was one of the greatest astrologers of his day. He + said that in 1588 a prophecy had been printed in Greek characters which + foretold exactly the troubles of England between the years 1641. and 1660. + "And after him shall come a dreadful dead man," ran the prophecy, "and + with him a royal G of the best blood in the world, and he shall have the + crown and shall set England on the right way and put out all heresies." + His interpretation of this was that, "Monkery being extinguished above + eighty or ninety years, and the Lord General's name being Monk, is the + dead man. The royal G or C (it is gamma in the Greek, intending C in the + Latin, being the third letter in the alphabet) is Charles II., who, for + his extraction, may be said to be of the best blood of the world."(5) + </p> + <p> + This may be taken as a fair sample of Lilly's interpretations of + astrological prophesies, but many of his own writings, while somewhat more + definite and direct, are still left sufficiently vague to allow his + skilful interpretations to set right an apparent mistake. One of his + famous documents was "The Starry Messenger," a little pamphlet purporting + to explain the phenomenon of a "strange apparition of three suns" that + were seen in London on November 19, 1644—-the anniversary of the + birth of Charles I., then the reigning monarch. This phenomenon caused a + great stir among the English astrologers, coming, as it did, at a time of + great political disturbance. Prophecies were numerous, and Lilly's + brochure is only one of many that appeared at that time, most of which, + however, have been lost. Lilly, in his preface, says: "If there be any of + so prevaricate a judgment as to think that the apparition of these three + Suns doth intimate no Novelle thing to happen in our own Climate, where + they were manifestly visible, I shall lament their indisposition, and + conceive their brains to be shallow, and voyde of understanding humanity, + or notice of common History." + </p> + <p> + Having thus forgiven his few doubting readers, who were by no means in the + majority in his day, he takes up in review the records of the various + appearances of three suns as they have occurred during the Christian era, + showing how such phenomena have governed certain human events in a very + definite manner. Some of these are worth recording. + </p> + <p> + "Anno 66. A comet was seen, and also three Suns: In which yeer, Florus + President of the Jews was by them slain. Paul writes to Timothy. The + Christians are warned by a divine Oracle, and depart out of Jerusalem. + Boadice a British Queen, killeth seventy thousand Romans. The Nazareni, a + scurvie Sect, begun, that boasted much of Revelations and Visions. About a + year after Nero was proclaimed enemy to the State of Rome." + </p> + <p> + Again, "Anno 1157, in September, there were seen three Suns together, in + as clear weather as could be: And a few days after, in the same month, + three Moons, and, in the Moon that stood in the middle, a white Crosse. + Sueno, King of Denmark, at a great Feast, killeth Canutus: Sueno is + himself slain, in pursuit of Waldemar. The Order of Eremites, according to + the rule of Saint Augustine, begun this year; and in the next, the Pope + submits to the Emperour: (was not this miraculous?) Lombardy was also + adjudged to the Emperour." + </p> + <p> + Continuing this list of peculiar phenomena he comes down to within a few + years of his own time. + </p> + <p> + "Anno 1622, three Suns appeared at Heidelberg. The woful Calamities that + have ever since fallen upon the Palatinate, we are all sensible of, and of + the loss of it, for any thing I see, for ever, from the right Heir. Osman + the great Turk is strangled that year; and Spinola besiegeth Bergen up + Zoom, etc." + </p> + <p> + Fortified by the enumeration of these past events, he then proceeds to + make his deductions. "Only this I must tell thee," he writes, "that the + interpretation I write is, I conceive, grounded upon probable foundations; + and who lives to see a few years over his head, will easily perceive I + have unfolded as much as was fit to discover, and that my judgment was not + a mile and a half from truth." + </p> + <p> + There is a great significance in this "as much as was fit to discover"—a + mysterious something that Lilly thinks it expedient not to divulge. But, + nevertheless, one would imagine that he was about to make some definite + prediction about Charles I., since these three suns appeared upon his + birthday and surely must portend something concerning him. But after + rambling on through many pages of dissertations upon planets and + prophecies, he finally makes his own indefinite prediction. + </p> + <p> + "O all you Emperors, Kings, Princes, Rulers and Magistrates of Europe, + this unaccustomed Apparition is like the Handwriting in Daniel to some of + you; it premonisheth you, above all other people, to make your peace with + God in time. You shall every one of you smart, and every one of you taste + (none excepted) the heavie hand of God, who will strengthen your subjects + with invincible courage to suppress your misgovernments and Oppressions in + Church or Common-wealth;... Those words are general: a word for my own + country of England.... Look to yourselves; here's some monstrous death + towards you. But to whom? wilt thou say. Herein we consider the Signe, + Lord thereof, and the House; The Sun signifies in that Royal Signe, great + ones; the House signifies captivity, poison, Treachery: From which is + derived thus much, That some very great man, what King, Prince, Duke, or + the like, I really affirm I perfectly know not, shall, I say, come to some + such untimely end."(6) + </p> + <p> + Here is shown a typical example of astrological prophecy, which seems to + tell something or nothing, according to the point of view of the reader. + According to a believer in astrology, after the execution of Charles I., + five years later, this could be made to seem a direct and exact prophecy. + For example, he says: "You Kings, Princes, etc.,... it premonisheth you... + to make your peace with God.... Look to yourselves; here's some monstrous + death towards you.... That some very great man, what King, Prince,. shall, + I say, come to such untimely end." + </p> + <p> + But by the doubter the complete prophecy could be shown to be absolutely + indefinite, and applicable as much to the king of France or Spain as to + Charles I., or to any king in the future, since no definite time is + stated. Furthermore, Lilly distinctly states, "What King, Prince, Duke, or + the like, I really affirm I perfectly know not"—which last, at + least, was a most truthful statement. The same ingenuity that made "Gen. + Monk" the "dreadful dead man," could easily make such a prediction apply + to the execution of Charles I. Such a definite statement that, on such and + such a day a certain number of years in the future, the monarch of England + would be beheaded—such an exact statement can scarcely be found in + any of the works on astrology. It should be borne in mind, also, that + Lilly was of the Cromwell party and opposed to the king. + </p> + <p> + After the death of Charles I., Lilly admitted that the monarch had given + him a thousand pounds to cast his horoscope. "I advised him," says Lilly, + "to proceed eastwards; he went west, and all the world knows the result." + It is an unfortunate thing for the cause of astrology that Lilly failed to + mention this until after the downfall of the monarch. In fact, the sudden + death, or decline in power, of any monarch, even to-day, brings out the + perennial post-mortem predictions of astrologers. + </p> + <p> + We see how Lilly, an opponent of the king, made his so-called prophecy of + the disaster of the king and his army. At the same time another celebrated + astrologer and rival of Lilly, George Wharton, also made some predictions + about the outcome of the eventful march from Oxford. Wharton, unlike + Lilly, was a follower of the king's party, but that, of course, should + have had no influence in his "scientific" reading of the stars. Wharton's + predictions are much less verbose than Lilly's, much more explicit, and, + incidentally, much more incorrect in this particular instance. "The Moon + Lady of the 12," he wrote, "and moving betwixt the 8 degree, 34 min., and + 21 degree, 26 min. of Aquarius, gives us to understand that His Majesty + shall receive much contentment by certain Messages brought him from + foreign parts; and that he shall receive some sudden and unexpected supply + of... by the means of some that assimilate the condition of his Enemies: + And withal this comfort; that His Majesty shall be exceeding successful in + Besieging Towns, Castles, or Forts, and in persuing the enemy. + </p> + <p> + "Mars his Sextile to the Sun, Lord of the Ascendant (which happeneth the + 18 day of May) will encourage our Soldiers to advance with much alacrity + and cheerfulness of spirit; to show themselves gallant in the most + dangerous attempt.... And now to sum up all: It is most apparent to every + impartial and ingenuous judgment; That although His Majesty cannot expect + to be secured from every trivial disaster that may befall his army, either + by the too much Presumption, Ignorance, or Negligence of some particular + Persons (which is frequently incident and unavoidable in the best of + Armies), yet the several positions of the Heavens duly considered and + compared among themselves, as well in the prefixed Scheme as at the + Quarterly Ingresses, do generally render His Majesty and his whole Army + unexpectedly victorious and successful in all his designs; Believe it + (London), thy Miseries approach, they are like to be many, great, and + grievous, and not to be diverted, unless thou seasonably crave Pardon of + God for being Nurse to this present Rebellion, and speedily submit to thy + Prince's Mercy; Which shall be the daily Prayer of Geo. Wharton."(7) + </p> + <p> + In the light of after events, it is probable that Wharton's stock as an + astrologer was not greatly enhanced by this document, at least among + members of the Royal family. Lilly's book, on the other hand, became a + favorite with the Parliamentary army. + </p> + <p> + After the downfall and death of Napoleon there were unearthed many alleged + authentic astrological documents foretelling his ruin. And on the death of + George IV., in 1830, there appeared a document (unknown, as usual, until + that time) purporting to foretell the death of the monarch to the day, and + this without the astrologer knowing that his horoscope was being cast for + a monarch. A full account of this prophecy is told, with full belief, by + Roback, a nineteenth-century astrologer. He says: + </p> + <p> + "In the year 1828, a stranger of noble mien, advanced in life, but + possessing the most bland manners, arrived at the abode of a celebrated + astrologer in London," asking that the learned man foretell his future. + "The astrologer complied with the request of the mysterious visitor, drew + forth his tables, consulted his ephemeris, and cast the horoscope or + celestial map for the hour and the moment of the inquiry, according to the + established rules of his art. + </p> + <p> + "The elements of his calculation were adverse, and a feeling of gloom cast + a shade of serious thought, if not dejection, over his countenance. + </p> + <p> + "'You are of high rank,' said the astrologer, as he calculated and looked + on the stranger, 'and of illustrious title.' The stranger made a graceful + inclination of the head in token of acknowledgment of the complimentary + remarks, and the astrologer proceeded with his mission. + </p> + <p> + "The celestial signs were ominous of calamity to the stranger, who, + probably observing a sudden change in the countenance of the astrologer, + eagerly inquired what evil or good fortune had been assigned him by the + celestial orbs. + </p> + <p> + "'To the first part of your inquiry,' said the astrologer, 'I can readily + reply. You have been a favorite of fortune; her smiles on you have been + abundant, her frowns but few; you have had, perhaps now possess, wealth + and power; the impossibility of their accomplishment is the only limit to + the fulfilment of your desires.'" + </p> + <p> + "'You have spoken truly of the past,' said the stranger. 'I have full + faith in your revelations of the future: what say you of my pilgrimage in + this life—is it short or long?' + </p> + <p> + "'I regret,' replied the astrologer, in answer to this inquiry, 'to be the + herald of ill, though TRUE, fortune; your sojourn on earth will be short.' + </p> + <p> + "'How short?' eagerly inquired the excited and anxious stranger. + </p> + <p> + "'Give me a momentary truce,' said the astrologer; 'I will consult the + horoscope, and may possibly find some mitigating circumstances.' + </p> + <p> + "Having cast his eyes over the celestial map, and paused for some moments, + he surveyed the countenance of the stranger with great sympathy, and said, + 'I am sorry that I can find no planetary influences that oppose your + destiny—your death will take place in two years.' + </p> + <p> + "The event justified the astrologic prediction: George IV. died on May 18, + 1830, exactly two years from the day on which he had visited the + astrologer."(8) + </p> + <p> + This makes a very pretty story, but it hardly seems like occult insight + that an astrologer should have been able to predict an early death of a + man nearly seventy years old, or to have guessed that his well-groomed + visitor "had, perhaps now possesses, wealth and power." Here again, + however, the point of view of each individual plays the governing part in + determining the importance of such a document. To the scientist it proves + nothing; to the believer in astrology, everything. The significant thing + is that it appeared shortly AFTER the death of the monarch. + </p> + <p> + On the Continent astrologers were even more in favor than in England. + Charlemagne, and some of his immediate successors, to be sure, attempted + to exterminate them, but such rulers as Louis XI. and Catherine de' Medici + patronized and encouraged them, and it was many years after the time of + Copernicus before their influence was entirely stamped out even in + official life. There can be no question that what gave the color of truth + to many of the predictions was the fact that so many of the prophecies of + sudden deaths and great conflagrations were known to have come true—in + many instances were made to come true by the astrologer himself. And so it + happened that when the prediction of a great conflagration at a certain + time culminated in such a conflagration, many times a second but + less-important burning took place, in which the ambitious astrologer, or + his followers, took a central part about a stake, being convicted of + incendiarism, which they had committed in order that their prophecies + might be fulfilled. + </p> + <p> + But, on the other hand, these predictions were sometimes turned to account + by interested friends to warn certain persons of approaching dangers. + </p> + <p> + For example, a certain astrologer foretold the death of Prince Alexander + de' Medici. He not only foretold the death, but described so minutely the + circumstances that would attend it, and gave such a correct description of + the assassin who should murder the prince, that he was at once suspected + of having a hand in the assassination. It developed later, however, that + such was probably not the case; but that some friend of Prince Alexander, + knowing of the plot to take his life, had induced the astrologer to + foretell the event in order that the prince might have timely warning and + so elude the conspirators. + </p> + <p> + The cause of the decline of astrology was the growing prevalence of the + new spirit of experimental science. Doubtless the most direct blow was + dealt by the Copernican theory. So soon as this was established, the + recognition of the earth's subordinate place in the universe must have + made it difficult for astronomers to be longer deceived by such + coincidences as had sufficed to convince the observers of a more credulous + generation. Tycho Brahe was, perhaps, the last astronomer of prominence + who was a conscientious practiser of the art of the astrologer. + </p> + <p> + <a name="link2H_4_0009" id="link2H_4_0009"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VII. FROM PARACELSUS TO HARVEY + </h2> + <h3> + PARACELSUS + </h3> + <p> + In the year 1526 there appeared a new lecturer on the platform at the + University at Basel—a small, beardless, effeminate-looking person—who + had already inflamed all Christendom with his peculiar philosophy, his + revolutionary methods of treating diseases, and his unparalleled success + in curing them. A man who was to be remembered in after-time by some as + the father of modern chemistry and the founder of modern medicine; by + others as madman, charlatan, impostor; and by still others as a + combination of all these. This soft-cheeked, effeminate, woman-hating man, + whose very sex has been questioned, was Theophrastus von Hohenheim, better + known as Paracelsus (1493-1541). + </p> + <p> + To appreciate his work, something must be known of the life of the man. He + was born near Maria-Einsiedeln, in Switzerland, the son of a poor + physician of the place. He began the study of medicine under the + instruction of his father, and later on came under the instruction of + several learned churchmen. At the age of sixteen he entered the University + of Basel, but, soon becoming disgusted with the philosophical teachings of + the time, he quitted the scholarly world of dogmas and theories and went + to live among the miners in the Tyrol, in order that he might study nature + and men at first hand. Ordinary methods of study were thrown aside, and he + devoted his time to personal observation—the only true means of + gaining useful knowledge, as he preached and practised ever after. Here he + became familiar with the art of mining, learned the physical properties of + minerals, ores, and metals, and acquired some knowledge of mineral waters. + More important still, he came in contact with such diseases, wounds, and + injuries as miners are subject to, and he tried his hand at the practical + treatment of these conditions, untrammelled by the traditions of a + profession in which his training had been so scant. + </p> + <p> + Having acquired some empirical skill in treating diseases, Paracelsus set + out wandering from place to place all over Europe, gathering practical + information as he went, and learning more and more of the medicinal + virtues of plants and minerals. His wanderings covered a period of about + ten years, at the end of which time he returned to Basel, where he was + soon invited to give a course of lectures in the university. + </p> + <p> + These lectures were revolutionary in two respects—they were given in + German instead of time-honored Latin, and they were based upon personal + experience rather than upon the works of such writers as Galen and + Avicenna. Indeed, the iconoclastic teacher spoke with open disparagement + of these revered masters, and openly upbraided his fellow-practitioners + for following their tenets. Naturally such teaching raised a storm of + opposition among the older physicians, but for a time the unparalleled + success of Paracelsus in curing diseases more than offset his + unpopularity. Gradually, however, his bitter tongue and his coarse + personality rendered him so unpopular, even among his patients, that, + finally, his liberty and life being jeopardized, he was obliged to flee + from Basel, and became a wanderer. He lived for brief periods in Colmar, + Nuremberg, Appenzell, Zurich, Pfeffers, Augsburg, and several other + cities, until finally at Salzburg his eventful life came to a close in + 1541. His enemies said that he had died in a tavern from the effects of a + protracted debauch; his supporters maintained that he had been murdered at + the instigation of rival physicians and apothecaries. + </p> + <p> + But the effects of his teachings had taken firm root, and continued to + spread after his death. He had shown the fallibility of many of the + teachings of the hitherto standard methods of treating diseases, and had + demonstrated the advantages of independent reasoning based on observation. + In his Magicum he gives his reasons for breaking with tradition. "I did," + he says, "embrace at the beginning these doctrines, as my adversaries + (followers of Galen) have done, but since I saw that from their procedures + nothing resulted but death, murder, stranglings, anchylosed limbs, + paralysis, and so forth, that they held most diseases incurable.... + therefore have I quitted this wretched art, and sought for truth in any + other direction. I asked myself if there were no such thing as a teacher + in medicine, where could I learn this art best? Nowhere better than the + open book of nature, written with God's own finger." We shall see, + however, that this "book of nature" taught Paracelsus some very strange + lessons. Modesty was not one of these. "Now at this time," he declares, + "I, Theophrastus Paracelsus, Bombast, Monarch of the Arcana, was endowed + by God with special gifts for this end, that every searcher after this + supreme philosopher's work may be forced to imitate and to follow me, be + he Italian, Pole, Gaul, German, or whatsoever or whosoever he be. Come + hither after me, all ye philosophers, astronomers, and spagirists.... I + will show and open to you... this corporeal regeneration."(1) + </p> + <p> + Paracelsus based his medical teachings on four "pillars"—philosophy, + astronomy, alchemy, and virtue of the physician—a strange-enough + equipment surely, and yet, properly interpreted, not quite so anomalous as + it seems at first blush. Philosophy was the "gate of medicine," whereby + the physician entered rightly upon the true course of learning; astronomy, + the study of the stars, was all-important because "they (the stars) caused + disease by their exhalations, as, for instance, the sun by excessive + heat"; alchemy, as he interpreted it, meant the improvement of natural + substances for man's benefit; while virtue in the physician was necessary + since "only the virtuous are permitted to penetrate into the innermost + nature of man and the universe." + </p> + <p> + All his writings aim to promote progress in medicine, and to hold before + the physician a grand ideal of his profession. In this his views are wide + and far-reaching, based on the relationship which man bears to nature as a + whole; but in his sweeping condemnations he not only rejected Galenic + therapeutics and Galenic anatomy, but condemned dissections of any kind. + He laid the cause of all diseases at the door of the three mystic elements—salt, + sulphur, and mercury. In health he supposed these to be mingled in the + body so as to be indistinguishable; a slight separation of them produced + disease; and death he supposed to be the result of their complete + separation. The spiritual agencies of diseases, he said, had nothing to do + with either angels or devils, but were the spirits of human beings. + </p> + <p> + He believed that all food contained poisons, and that the function of + digestion was to separate the poisonous from the nutritious. In the + stomach was an archaeus, or alchemist, whose duty was to make this + separation. In digestive disorders the archaeus failed to do this, and the + poisons thus gaining access to the system were "coagulated" and deposited + in the joints and various other parts of the body. Thus the deposits in + the kidneys and tartar on the teeth were formed; and the stony deposits of + gout were particularly familiar examples of this. All this is visionary + enough, yet it shows at least a groping after rational explanations of + vital phenomena. + </p> + <p> + Like most others of his time, Paracelsus believed firmly in the doctrine + of "signatures"—a belief that every organ and part of the body had a + corresponding form in nature, whose function was to heal diseases of the + organ it resembled. The vagaries of this peculiar doctrine are too + numerous and complicated for lengthy discussion, and varied greatly from + generation to generation. In general, however, the theory may be summed up + in the words of Paracelsus: "As a woman is known by her shape, so are the + medicines." Hence the physicians were constantly searching for some object + of corresponding shape to an organ of the body. The most natural + application of this doctrine would be the use of the organs of the lower + animals for the treatment of the corresponding diseased organs in man. + Thus diseases of the heart were to be treated with the hearts of animals, + liver disorders with livers, and so on. But this apparently simple form of + treatment had endless modifications and restrictions, for not all animals + were useful. For example, it was useless to give the stomach of an ox in + gastric diseases when the indication in such cases was really for the + stomach of a rat. Nor were the organs of animals the only "signatures" in + nature. Plants also played a very important role, and the herb-doctors + devoted endless labor to searching for such plants. Thus the blood-root, + with its red juice, was supposed to be useful in blood diseases, in + stopping hemorrhage, or in subduing the redness of an inflammation. + </p> + <p> + Paracelsus's system of signatures, however, was so complicated by his + theories of astronomy and alchemy that it is practically beyond + comprehension. It is possible that he himself may have understood it, but + it is improbable that any one else did—as shown by the endless + discussions that have taken place about it. But with all the vagaries of + his theories he was still rational in his applications, and he attacked to + good purpose the complicated "shot-gun" prescriptions of his + contemporaries, advocating more simple methods of treatment. + </p> + <p> + The ever-fascinating subject of electricity, or, more specifically, + "magnetism," found great favor with him, and with properly adjusted + magnets he claimed to be able to cure many diseases. In epilepsy and + lockjaw, for example, one had but to fasten magnets to the four + extremities of the body, and then, "when the proper medicines were given," + the cure would be effected. The easy loop-hole for excusing failure on the + ground of improper medicines is obvious, but Paracelsus declares that this + one prescription is of more value than "all the humoralists have ever + written or taught." + </p> + <p> + Since Paracelsus condemned the study of anatomy as useless, he quite + naturally regarded surgery in the same light. In this he would have done + far better to have studied some of his predecessors, such as Galen, Paul + of Aegina, and Avicenna. But instead of "cutting men to pieces," he taught + that surgeons would gain more by devoting their time to searching for the + universal panacea which would cure all diseases, surgical as well as + medical. In this we detect a taint of the popular belief in the + philosopher's stone and the magic elixir of life, his belief in which have + been stoutly denied by some of his followers. He did admit, however, that + one operation alone was perhaps permissible—lithotomy, or the + "cutting for stone." + </p> + <p> + His influence upon medicine rests undoubtedly upon his revolutionary + attitude, rather than on any great or new discoveries made by him. It is + claimed by many that he brought prominently into use opium and mercury, + and if this were indisputably proven his services to medicine could hardly + be overestimated. Unfortunately, however, there are good grounds for + doubting that he was particularly influential in reintroducing these + medicines. His chief influence may perhaps be summed up in a single phrase—he + overthrew old traditions. + </p> + <p> + To Paracelsus's endeavors, however, if not to the actual products of his + work, is due the credit of setting in motion the chain of thought that + developed finally into scientific chemistry. Nor can the ultimate aim of + the modern chemist seek a higher object than that of this + sixteenth-century alchemist, who taught that "true alchemy has but one aim + and object, to extract the quintessence of things, and to prepare arcana, + tinctures, and elixirs which may restore to man the health and soundness + he has lost." + </p> + <p> + THE GREAT ANATOMISTS + </p> + <p> + About the beginning of the sixteenth century, while Paracelsus was + scoffing at the study of anatomy as useless, and using his influence + against it, there had already come upon the scene the first of the great + anatomists whose work was to make the century conspicuous in that branch + of medicine. + </p> + <p> + The young anatomist Charles etienne (1503-1564) made one of the first + noteworthy discoveries, pointing out for the first time that the spinal + cord contains a canal, continuous throughout its length. He also made + other minor discoveries of some importance, but his researches were + completely overshadowed and obscured by the work of a young Fleming who + came upon the scene a few years later, and who shone with such brilliancy + in the medical world that he obscured completely the work of his + contemporary until many years later. This young physician, who was + destined to lead such an eventful career and meet such an untimely end as + a martyr to science, was Andrew Vesalius (1514-1564), who is called the + "greatest of anatomists." At the time he came into the field medicine was + struggling against the dominating Galenic teachings and the theories of + Paracelsus, but perhaps most of all against the superstitions of the time. + In France human dissections were attended with such dangers that the young + Vesalius transferred his field of labors to Italy, where such + investigations were covertly permitted, if not openly countenanced. + </p> + <p> + From the very start the young Fleming looked askance at the accepted + teachings of the day, and began a series of independent investigations + based upon his own observations. The results of these investigations he + gave in a treatise on the subject which is regarded as the first + comprehensive and systematic work on human anatomy. This remarkable work + was published in the author's twenty-eighth or twenty-ninth year. Soon + after this Vesalius was invited as imperial physician to the court of + Emperor Charles V. He continued to act in the same capacity at the court + of Philip II., after the abdication of his patron. But in spite of this + royal favor there was at work a factor more powerful than the influence of + the monarch himself—an instrument that did so much to retard + scientific progress, and by which so many lives were brought to a + premature close. + </p> + <p> + Vesalius had received permission from the kinsmen of a certain grandee to + perform an autopsy. While making his observations the heart of the + outraged body was seen to palpitate—so at least it was reported. + This was brought immediately to the attention of the Inquisition, and it + was only by the intervention of the king himself that the anatomist + escaped the usual fate of those accused by that tribunal. As it was, he + was obliged to perform a pilgrimage to the Holy Land. While returning from + this he was shipwrecked, and perished from hunger and exposure on the + island of Zante. + </p> + <p> + At the very time when the anatomical writings of Vesalius were startling + the medical world, there was living and working contemporaneously another + great anatomist, Eustachius (died 1574), whose records of his anatomical + investigations were ready for publication only nine years after the + publication of the work of Vesalius. Owing to the unfortunate + circumstances of the anatomist, however, they were never published during + his lifetime—not, in fact, until 1714. When at last they were given + to the world as Anatomical Engravings, they showed conclusively that + Eustachius was equal, if not superior to Vesalius in his knowledge of + anatomy. It has been said of this remarkable collection of engravings that + if they had been published when they were made in the sixteenth century, + anatomy would have been advanced by at least two centuries. But be this as + it may, they certainly show that their author was a most careful dissector + and observer. + </p> + <p> + Eustachius described accurately for the first time certain structures of + the middle ear, and rediscovered the tube leading from the ear to the + throat that bears his name. He also made careful studies of the teeth and + the phenomena of first and second dentition. He was not baffled by the + minuteness of structures and where he was unable to study them with the + naked eye he used glasses for the purpose, and resorted to macerations and + injections for the study of certain complicated structures. But while the + fruit of his pen and pencil were lost for more than a century after his + death, the effects of his teachings were not; and his two pupils, + Fallopius and Columbus, are almost as well known to-day as their + illustrious teacher. Columbus (1490-1559) did much in correcting the + mistakes made in the anatomy of the bones as described by Vesalius. He + also added much to the science by giving correct accounts of the shape and + cavities of the heart, and made many other discoveries of minor + importance. Fallopius (1523-1562) added considerably to the general + knowledge of anatomy, made several discoveries in the anatomy of the ear, + and also several organs in the abdominal cavity. + </p> + <p> + At this time a most vitally important controversy was in progress as to + whether or not the veins of the bodies were supplied with valves, many + anatomists being unable to find them. Etienne had first described these + structures, and Vesalius had confirmed his observations. It would seem as + if there could be no difficulty in settling the question as to the fact of + such valves being present in the vessels, for the demonstration is so + simple that it is now made daily by medical students in all physiological + laboratories and dissecting-rooms. But many of the great anatomists of the + sixteenth century were unable to make this demonstration, even when it had + been brought to their attention by such an authority as Vesalius. + Fallopius, writing to Vesalius on the subject in 1562, declared that he + was unable to find such valves. Others, however, such as Eustachius and + Fabricius (1537-1619), were more successful, and found and described these + structures. But the purpose served by these valves was entirely + misinterpreted. That they act in preventing the backward flow of the blood + in the veins on its way to the heart, just as the valves of the heart + itself prevent regurgitation, has been known since the time of Harvey; but + the best interpretation that could be given at that time, even by such a + man as Fabricius, was that they acted in retarding the flow of the blood + as it comes from the heart, and thus prevent its too rapid distribution + throughout the body. The fact that the blood might have been going towards + the heart, instead of coming from it, seems never to have been considered + seriously until demonstrated so conclusively by Harvey. + </p> + <p> + Of this important and remarkable controversy over the valves in veins, + Withington has this to say: "This is truly a marvellous story. A great + Galenic anatomist is first to give a full and correct description of the + valves and their function, but fails to see that any modification of the + old view as to the motion of the blood is required. Two able dissectors + carefully test their action by experiment, and come to a result, the exact + reverse of the truth. Urged by them, the two foremost anatomists of the + age make a special search for valves and fail to find them. Finally, + passing over lesser peculiarities, an aged and honorable professor, who + has lived through all this, calmly asserts that no anatomist, ancient or + modern, has ever mentioned valves in veins till he discovered them in + 1574!"(2) + </p> + <p> + Among the anatomists who probably discovered these valves was Michael + Servetus (1511-1553); but if this is somewhat in doubt, it is certain that + he discovered and described the pulmonary circulation, and had a very + clear idea of the process of respiration as carried on in the lungs. The + description was contained in a famous document sent to Calvin in 1545—a + document which the reformer carefully kept for seven years in order that + he might make use of some of the heretical statements it contained to + accomplish his desire of bringing its writer to the stake. The awful fate + of Servetus, the interesting character of the man, and the fact that he + came so near to anticipating the discoveries of Harvey make him one of the + most interesting figures in medical history. + </p> + <p> + In this document which was sent to Calvin, Servetus rejected the doctrine + of natural, vital, and animal spirits, as contained in the veins, + arteries, and nerves respectively, and made the all-important statement + that the fluids contained in veins and arteries are the same. He showed + also that the blood is "purged from fume" and purified by respiration in + the lungs, and declared that there is a new vessel in the lungs, "formed + out of vein and artery." Even at the present day there is little to add to + or change in this description of Servetus's. + </p> + <p> + By keeping this document, pregnant with advanced scientific views, from + the world, and in the end only using it as a means of destroying its + author, the great reformer showed the same jealousy in retarding + scientific progress as had his arch-enemies of the Inquisition, at whose + dictates Vesalius became a martyr to science, and in whose dungeons + etienne perished. + </p> + <p> + THE COMING OF HARVEY + </p> + <p> + The time was ripe for the culminating discovery of the circulation of the + blood; but as yet no one had determined the all-important fact that there + are two currents of blood in the body, one going to the heart, one coming + from it. The valves in the veins would seem to show conclusively that the + venous current did not come from the heart, and surgeons must have + observed thousands of times the every-day phenomenon of congested veins at + the distal extremity of a limb around which a ligature or constriction of + any kind had been placed, and the simultaneous depletion of the vessels at + the proximal points above the ligature. But it should be remembered that + inductive science was in its infancy. This was the sixteenth, not the + nineteenth century, and few men had learned to put implicit confidence in + their observations and convictions when opposed to existing doctrines. The + time was at hand, however, when such a man was to make his appearance, + and, as in the case of so many revolutionary doctrines in science, this + man was an Englishman. It remained for William Harvey (1578-1657) to solve + the great mystery which had puzzled the medical world since the beginning + of history; not only to solve it, but to prove his case so conclusively + and so simply that for all time his little booklet must he handed down as + one of the great masterpieces of lucid and almost faultless demonstration. + </p> + <p> + Harvey, the son of a prosperous Kentish yeoman, was born at Folkestone. + His education was begun at the grammar-school of Canterbury, and later he + became a pensioner of Caius College, Cambridge. Soon after taking his + degree of B.A., at the age of nineteen, he decided upon the profession of + medicine, and went to Padua as a pupil of Fabricius and Casserius. + Returning to England at the age of twenty-four, he soon after (1609) + obtained the reversion of the post of physician to St. Bartholomew's + Hospital, his application being supported by James I. himself. Even at + this time he was a popular physician, counting among his patients such men + as Francis Bacon. In 1618 he was appointed physician extraordinary to the + king, and, a little later, physician in ordinary. He was in attendance + upon Charles I. at the battle of Edgehill, in 1642, where, with the young + Prince of Wales and the Duke of York, after seeking shelter under a hedge, + he drew a book out of his pocket and, forgetful of the battle, became + absorbed in study, until finally the cannon-balls from the enemy's + artillery made him seek a more sheltered position. + </p> + <p> + On the fall of Charles I. he retired from practice, and lived in + retirement with his brother. He was then well along in years, but still + pursued his scientific researches with the same vigor as before, directing + his attention chiefly to the study of embryology. On June 3, 1657, he was + attacked by paralysis and died, in his eightieth year. He had lived to see + his theory of the circulation accepted, several years before, by all the + eminent anatomists of the civilized world. + </p> + <p> + A keenness in the observation of facts, characteristic of the mind of the + man, had led Harvey to doubt the truth of existing doctrines as to the + phenomena of the circulation. Galen had taught that "the arteries are + filled, like bellows, because they are expanded," but Harvey thought that + the action of spurting blood from a severed vessel disproved this. For the + spurting was remittant, "now with greater, now with less impetus," and its + greater force always corresponded to the expansion (diastole), not the + contraction (systole) of the vessel. Furthermore, it was evident that + contraction of the heart and the arteries was not simultaneous, as was + commonly taught, because in that case there would be no marked propulsion + of the blood in any direction; and there was no gainsaying the fact that + the blood was forcibly propelled in a definite direction, and that + direction away from the heart. + </p> + <p> + Harvey's investigations led him to doubt also the accepted theory that + there was a porosity in the septum of tissue that divides the two + ventricles of the heart. It seemed unreasonable to suppose that a thick + fluid like the blood could find its way through pores so small that they + could not be demonstrated by any means devised by man. In evidence that + there could be no such openings he pointed out that, since the two + ventricles contract at the same time, this process would impede rather + than facilitate such an intra-ventricular passage of blood. But what + seemed the most conclusive proof of all was the fact that in the foetus + there existed a demonstrable opening between the two ventricles, and yet + this is closed in the fully developed heart. Why should Nature, if she + intended that blood should pass between the two cavities, choose to close + this opening and substitute microscopic openings in place of it? It would + surely seem more reasonable to have the small perforations in the thin, + easily permeable membrane of the foetus, and the opening in the adult + heart, rather than the reverse. From all this Harvey drew his correct + conclusions, declaring earnestly, "By Hercules, there ARE no such + porosities, and they cannot be demonstrated." + </p> + <p> + Having convinced himself that no intra-ventricular opening existed, he + proceeded to study the action of the heart itself, untrammelled by too + much faith in established theories, and, as yet, with no theory of his + own. He soon discovered that the commonly accepted theory of the heart + striking against the chest-wall during the period of relaxation was + entirely wrong, and that its action was exactly the reverse of this, the + heart striking the chest-wall during contraction. Having thus disproved + the accepted theory concerning the heart's action, he took up the subject + of the action of arteries, and soon was able to demonstrate by vivisection + that the contraction of the arteries was not simultaneous with + contractions of the heart. His experiments demonstrated that these vessels + were simply elastic tubes whose pulsations were "nothing else than the + impulse of the blood within them." The reason that the arterial pulsation + was not simultaneous with the heart-beat he found to be because of the + time required to carry the impulse along the tube. + </p> + <p> + By a series of further careful examinations and experiments, which are too + extended to be given here, he was soon able further to demonstrate the + action and course of the blood during the contractions of the heart. His + explanations were practically the same as those given to-day—first + the contraction of the auricle, sending blood into the ventricle; then + ventricular contraction, making the pulse, and sending the blood into the + arteries. He had thus demonstrated what had not been generally accepted + before, that the heart was an organ for the propulsion of blood. To make + such a statement to-day seems not unlike the sober announcement that the + earth is round or that the sun does not revolve about it. Before Harvey's + time, however, it was considered as an organ that was "in some mysterious + way the source of vitality and warmth, as an animated crucible for the + concoction of blood and the generation of vital spirits."(3) + </p> + <p> + In watching the rapid and ceaseless contractions of the heart, Harvey was + impressed with the fact that, even if a very small amount of blood was + sent out at each pulsation, an enormous quantity must pass through the + organ in a day, or even in an hour. Estimating the size of the cavities of + the heart, and noting that at least a drachm must be sent out with each + pulsation, it was evident that the two thousand beats given by a very slow + human heart in an hour must send out some forty pounds of blood—more + than twice the amount in the entire body. The question was, what became of + it all? For it should be remembered that the return of the blood by the + veins was unknown, and nothing like a "circulation" more than vaguely + conceived even by Harvey himself. Once it could be shown that the veins + were constantly returning blood to the heart, the discovery that the blood + in some way passes from the arteries to the veins was only a short step. + Harvey, by resorting to vivisections of lower animals and reptiles, soon + demonstrated beyond question the fact that the veins do carry the return + blood. "But this, in particular, can be shown clearer than daylight," says + Harvey. "The vena cava enters the heart at an inferior portion, while the + artery passes out above. Now if the vena cava be taken up with forceps or + the thumb and finger, and the course of the blood intercepted for some + distance below the heart, you will at once see it almost emptied between + the fingers and the heart, the blood being exhausted by the heart's + pulsation, the heart at the same time becoming much paler even in its + dilatation, smaller in size, owing to the deficiency of blood, and at + length languid in pulsation, as if about to die. On the other hand, when + you release the vein the heart immediately regains its color and + dimensions. After that, if you leave the vein free and tie and compress + the arteries at some distance from the heart, you will see, on the + contrary, their included portion grow excessively turgid, the heart + becoming so beyond measure, assuming a dark-red color, even to lividity, + and at length so overloaded with blood as to seem in danger of + suffocation; but when the obstruction is removed it returns to its normal + condition, in size, color, and movement."(4) + </p> + <p> + This conclusive demonstration that the veins return the blood to the heart + must have been most impressive to Harvey, who had been taught to believe + that the blood current in the veins pursued an opposite course, and must + have tended to shake his faith in all existing doctrines of the day. + </p> + <p> + His next step was the natural one of demonstrating that the blood passes + from the arteries to the veins. He demonstrated conclusively that this did + occur, but for once his rejection of the ancient writers and one modern + one was a mistake. For Galen had taught, and had attempted to demonstrate, + that there are sets of minute vessels connecting the arteries and the + veins; and Servetus had shown that there must be such vessels, at least in + the lungs. + </p> + <p> + However, the little flaw in the otherwise complete demonstration of Harvey + detracts nothing from the main issue at stake. It was for others who + followed to show just how these small vessels acted in effecting the + transfer of the blood from artery to vein, and the grand general statement + that such a transfer does take place was, after all, the all-important + one, and the exact method of how it takes place a detail. Harvey's + experiments to demonstrate that the blood passes from the arteries to the + veins are so simply and concisely stated that they may best be given in + his own words. + </p> + <p> + "I have here to cite certain experiments," he wrote, "from which it seems + obvious that the blood enters a limb by the arteries, and returns from it + by the veins; that the arteries are the vessels carrying the blood from + the heart, and the veins the returning channels of the blood to the heart; + that in the limbs and extreme parts of the body the blood passes either by + anastomosis from the arteries into the veins, or immediately by the pores + of the flesh, or in both ways, as has already been said in speaking of the + passage of the blood through the lungs; whence it appears manifest that in + the circuit the blood moves from thence hither, and hence thither; from + the centre to the extremities, to wit, and from the extreme parts back + again to the centre. Finally, upon grounds of circulation, with the same + elements as before, it will be obvious that the quantity can neither be + accounted for by the ingesta, nor yet be held necessary to nutrition. + </p> + <p> + "Now let any one make an experiment on the arm of a man, either using such + a fillet as is employed in blood-letting or grasping the limb tightly with + his hand, the best subject for it being one who is lean, and who has large + veins, and the best time after exercise, when the body is warm, the pulse + is full, and the blood carried in large quantities to the extremities, for + all then is more conspicuous; under such circumstances let a ligature be + thrown about the extremity and drawn as tightly as can be borne: it will + first be perceived that beyond the ligature neither in the wrist nor + anywhere else do the arteries pulsate, that at the same time immediately + above the ligature the artery begins to rise higher at each diastole, to + throb more violently, and to swell in its vicinity with a kind of tide, as + if it strove to break through and overcome the obstacle to its current; + the artery here, in short, appears as if it were permanently full. The + hand under such circumstances retains its natural color and appearances; + in the course of time it begins to fall somewhat in temperature, indeed, + but nothing is DRAWN into it. + </p> + <p> + "After the bandage has been kept on some short time in this way, let it be + slackened a little, brought to the state or term of middling tightness + which is used in bleeding, and it will be seen that the whole hand and arm + will instantly become deeply suffused and distended, injected, gorged with + blood, DRAWN, as it is said, by this middling ligature, without pain, or + heat, or any horror of a vacuum, or any other cause yet indicated. + </p> + <p> + "As we have noted, in connection with the tight ligature, that the artery + above the bandage was distended and pulsated, not below it, so, in the + case of the moderately tight bandage, on the contrary, do we find that the + veins below, never above, the fillet swell and become dilated, while the + arteries shrink; and such is the degree of distention of the veins here + that it is only very strong pressure that will force the blood beyond the + fillet and cause any of the veins in the upper part of the arm to rise. + </p> + <p> + "From these facts it is easy for any careful observer to learn that the + blood enters an extremity by the arteries; for when they are effectively + compressed nothing is DRAWN to the member; the hand preserves its color; + nothing flows into it, neither is it distended; but when the pressure is + diminished, as it is with the bleeding fillet, it is manifest that the + blood is instantly thrown in with force, for then the hand begins to + swell; which is as much as to say that when the arteries pulsate the blood + is flowing through them, as it is when the moderately tight ligature is + applied; but when they do not pulsate, or when a tight ligature is used, + they cease from transmitting anything; they are only distended above the + part where the ligature is applied. The veins again being compressed, + nothing can flow through them; the certain indication of which is that + below the ligature they are much more tumid than above it, and than they + usually appear when there is no bandage upon the arm. + </p> + <p> + "It therefore plainly appears that the ligature prevents the return of the + blood through the veins to the parts above it, and maintains those beneath + it in a state of permanent distention. But the arteries, in spite of the + pressure, and under the force and impulse of the heart, send on the blood + from the internal parts of the body to the parts beyond the bandage."(5) + </p> + <p> + This use of ligatures is very significant, because, as shown, a very tight + ligature stops circulation in both arteries and veins, while a loose one, + while checking the circulation in the veins, which lie nearer the surface + and are not so directly influenced by the force of the heart, does not + stop the passage of blood in the arteries, which are usually deeply + imbedded in the tissues, and not so easily influenced by pressure from + without. + </p> + <p> + The last step of Harvey's demonstration was to prove that the blood does + flow along the veins to the heart, aided by the valves that had been the + cause of so much discussion and dispute between the great + sixteenth-century anatomists. Harvey not only demonstrated the presence of + these valves, but showed conclusively, by simple experiments, what their + function was, thus completing his demonstration of the phenomena of the + circulation. + </p> + <p> + The final ocular demonstration of the passage of the blood from the + arteries to the veins was not to be made until four years after Harvey's + death. This process, which can be observed easily in the web of a frog's + foot by the aid of a low-power lens, was first demonstrated by Marcello + Malpighi (1628-1694) in 1661. By the aid of a lens he first saw the small + "capillary" vessels connecting the veins and arteries in a piece of dried + lung. Taking his cue from this, he examined the lung of a turtle, and was + able to see in it the passage of the corpuscles through these minute + vessels, making their way along these previously unknown channels from the + arteries into the veins on their journey back to the heart. Thus the work + of Harvey, all but complete, was made absolutely entire by the great + Italian. And all this in a single generation. + </p> + <p> + LEEUWENHOEK DISCOVERS BACTERIA + </p> + <p> + The seventeenth century was not to close, however, without another + discovery in science, which, when applied to the causation of disease + almost two centuries later, revolutionized therapeutics more completely + than any one discovery. This was the discovery of microbes, by Antonius + von Leeuwenhoek (1632-1723), in 1683. Von Leeuwenhoek discovered that "in + the white matter between his teeth" there were millions of microscopic + "animals"—more, in fact, than "there were human beings in the united + Netherlands," and all "moving in the most delightful manner." There can be + no question that he saw them, for we can recognize in his descriptions of + these various forms of little "animals" the four principal forms of + microbes—the long and short rods of bacilli and bacteria, the + spheres of micrococci, and the corkscrew spirillum. + </p> + <p> + The presence of these microbes in his mouth greatly annoyed Antonius, and + he tried various methods of getting rid of them, such as using vinegar and + hot coffee. In doing this he little suspected that he was anticipating + modern antiseptic surgery by a century and three-quarters, and to be + attempting what antiseptic surgery is now able to accomplish. For the + fundamental principle of antisepsis is the use of medicines for ridding + wounds of similar microscopic organisms. Von Leenwenhoek was only + temporarily successful in his attempts, however, and took occasion to + communicate his discovery to the Royal Society of England, hoping that + they would be "interested in this novelty." Probably they were, but not + sufficiently so for any member to pursue any protracted investigations or + reach any satisfactory conclusions, and the whole matter was practically + forgotten until the middle of the nineteenth century. + </p> + <p> + <a name="link2H_4_0010" id="link2H_4_0010"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES + </h2> + <p> + Of the half-dozen surgeons who were prominent in the sixteenth century, + Ambroise Pare (1517-1590), called the father of French surgery, is perhaps + the most widely known. He rose from the position of a common barber to + that of surgeon to three French monarchs, Henry II., Francis II., and + Charles IX. Some of his mottoes are still first principles of the medical + man. Among others are: "He who becomes a surgeon for the sake of money, + and not for the sake of knowledge, will accomplish nothing"; and "A tried + remedy is better than a newly invented." On his statue is his modest + estimate of his work in caring for the wounded, "Je le pansay, Dieu le + guarit"—I dressed him, God cured him. + </p> + <p> + It was in this dressing of wounds on the battlefield that he accidentally + discovered how useless and harmful was the terribly painful treatment of + applying boiling oil to gunshot wounds as advocated by John of Vigo. It + happened that after a certain battle, where there was an unusually large + number of casualties, Pare found, to his horror, that no more boiling oil + was available for the surgeons, and that he should be obliged to dress the + wounded by other simpler methods. To his amazement the results proved + entirely satisfactory, and from that day he discarded the hot-oil + treatment. + </p> + <p> + As Pare did not understand Latin he wrote his treatises in French, thus + inaugurating a custom in France that was begun by Paracelsus in Germany + half a century before. He reintroduced the use of the ligature in + controlling hemorrhage, introduced the "figure of eight" suture in the + operation for hare-lip, improved many of the medico-legal doctrines, and + advanced the practice of surgery generally. He is credited with having + successfully performed the operation for strangulated hernia, but he + probably borrowed it from Peter Franco (1505-1570), who published an + account of this operation in 1556. As this operation is considered by some + the most important operation in surgery, its discoverer is entitled to + more than passing notice, although he was despised and ignored by the + surgeons of his time. + </p> + <p> + Franco was an illiterate travelling lithotomist—a class of itinerant + physicians who were very generally frowned down by the regular + practitioners of medicine. But Franco possessed such skill as an operator, + and appears to have been so earnest in the pursuit of what he considered a + legitimate calling, that he finally overcame the popular prejudice and + became one of the salaried surgeons of the republic of Bern. He was the + first surgeon to perform the suprapubic lithotomy operation—the + removal of stone through the abdomen instead of through the perineum. His + works, while written in an illiterate style, give the clearest + descriptions of any of the early modern writers. + </p> + <p> + As the fame of Franco rests upon his operation for prolonging human life, + so the fame of his Italian contemporary, Gaspar Tagliacozzi (1545-1599), + rests upon his operation for increasing human comfort and happiness by + restoring amputated noses. At the time in which he lived amputation of the + nose was very common, partly from disease, but also because a certain pope + had fixed the amputation of that member as the penalty for larceny. + Tagliacozzi probably borrowed his operation from the East; but he was the + first Western surgeon to perform it and describe it. So great was the fame + of his operations that patients flocked to him from all over Europe, and + each "went away with as many noses as he liked." Naturally, the man who + directed his efforts to restoring structures that bad been removed by + order of the Church was regarded in the light of a heretic by many + theologians; and though he succeeded in cheating the stake or dungeon, and + died a natural death, his body was finally cast out of the church in which + it had been buried. + </p> + <p> + In the sixteenth century Germany produced a surgeon, Fabricius Hildanes + (1560-1639), whose work compares favorably with that of Pare, and whose + name would undoubtedly have been much better known had not the + circumstances of the time in which he lived tended to obscure his merits. + The blind followers of Paracelsus could see nothing outside the pale of + their master's teachings, and the disastrous Thirty Years' War tended to + obscure and retard all scientific advances in Germany. Unlike many of his + fellow-surgeons, Hildanes was well versed in Latin and Greek; and, + contrary to the teachings of Paracelsus, he laid particular stress upon + the necessity of the surgeon having a thorough knowledge of anatomy. He + had a helpmate in his wife, who was also something of a surgeon, and she + is credited with having first made use of the magnet in removing particles + of metal from the eye. Hildanes tells of a certain man who had been + injured by a small piece of steel in the cornea, which resisted all his + efforts to remove it. After observing Hildanes' fruitless efforts for a + time, it suddenly occurred to his wife to attempt to make the extraction + with a piece of loadstone. While the physician held open the two lids, his + wife attempted to withdraw the steel with the magnet held close to the + cornea, and after several efforts she was successful—which Hildanes + enumerates as one of the advantages of being a married man. + </p> + <p> + Hildanes was particularly happy in his inventions of surgical instruments, + many of which were designed for locating and removing the various missiles + recently introduced in warfare. + </p> + <p> + The seventeenth century, which was such a flourishing one for anatomy and + physiology, was not as productive of great surgeons or advances in surgery + as the sixteenth had been or the eighteenth was to be. There was a gradual + improvement all along the line, however, and much of the work begun by + such surgeons as Pare and Hildanes was perfected or improved. Perhaps the + most progressive surgeon of the century was an Englishman, Richard Wiseman + (1625-1686), who, like Harvey, enjoyed royal favor, being in the service + of all the Stuart kings. He was the first surgeon to advocate primary + amputation, in gunshot wounds, of the limbs, and also to introduce the + treatment of aneurisms by compression; but he is generally rated as a + conservative operator, who favored medication rather than radical + operations, where possible. + </p> + <p> + In Italy, Marcus Aurelius Severinus (1580-1656) and Peter Marchettis + (1589-1675) were the leading surgeons of their nation. Like many of his + predecessors in Europe, Severinus ran amuck with the Holy Inquisition and + fled from Naples. But the waning of the powerful arm of the Church is + shown by the fact that he was brought back by the unanimous voice of the + grateful citizens, and lived in safety despite the frowns of the + theologians. + </p> + <p> + The sixteenth century cannot be said to have added much of importance in + the field of practical medicine, and, as in the preceding and succeeding + centuries, was at best only struggling along in the wake of anatomy, + physiology, and surgery. In the seventeenth century, however, at least one + discovery in therapeutics was made that has been an inestimable boon to + humanity ever since. This was the introduction of cinchona bark (from + which quinine is obtained) in 1640. But this century was productive of + many medical SYSTEMS, and could boast of many great names among the + medical profession, and, on the whole, made considerably more progress + than the preceding century. + </p> + <p> + Of the founders of medical systems, one of the most widely known is Jan + Baptista van Helmont (1578-1644), an eccentric genius who constructed a + system of medicine of his own and for a time exerted considerable + influence. But in the end his system was destined to pass out of + existence, not very long after the death of its author. Van Helmont was + not only a physician, but was master of all the other branches of learning + of the time, taking up the study of medicine and chemistry as an + after-thought, but devoting himself to them with the greatest enthusiasm + once he had begun his investigations. His attitude towards existing + doctrines was as revolutionary as that of Paracelsus, and he rejected the + teachings of Galen and all the ancient writers, although retaining some of + the views of Paracelsus. He modified the archaeus of Paracelsus, and added + many complications to it. He believed the whole body to be controlled by + an archaeus influus, the soul by the archaei insiti, and these in turn + controlled by the central archeus. His system is too elaborate and + complicated for full explanation, but its chief service to medicine was in + introducing new chemical methods in the preparation of drugs. In this way + he was indirectly connected with the establishment of the Iatrochemical + school. It was he who first used the word "gas"—a word coined by + him, along with many others that soon fell into disuse. + </p> + <p> + The principles of the Iatrochemical school were the use of chemical + medicines, and a theory of pathology different from the prevailing + "humoral" pathology. The founder of this school was Sylvius (Franz de le + Boe, 1614-1672), professor of medicine at Leyden. He attempted to + establish a permanent system of medicine based on the newly discovered + theory of the circulation and the new chemistry, but his name is + remembered by medical men because of the fissure in the brain (fissure of + Sylvius) that bears it. He laid great stress on the cause of fevers and + other diseases as originating in the disturbances of the process of + fermentation in the stomach. The doctrines of Sylvius spread widely over + the continent, but were not generally accepted in England until modified + by Thomas Willis (1622-1675), whose name, like that of Sylvius, is + perpetuated by a structure in the brain named after him, the circle of + Willis. Willis's descriptions of certain nervous diseases, and an account + of diabetes, are the first recorded, and added materially to scientific + medicine. These schools of medicine lasted until the end of the + seventeenth century, when they were finally overthrown by Sydenham. + </p> + <p> + The Iatrophysical school (also called iatromathematical, iatromechanical, + or physiatric) was founded on theories of physiology, probably by Borelli, + of Naples (1608-1679), although Sanctorius; Sanctorius, a professor at + Padua, was a precursor, if not directly interested in establishing it. + Sanctorius discovered the fact that an "insensible perspiration" is being + given off by the body continually, and was amazed to find that loss of + weight in this way far exceeded the loss of weight by all other excretions + of the body combined. He made this discovery by means of a peculiar + weighing-machine to which a chair was attached, and in which he spent most + of his time. Very naturally he overestimated the importance of this + discovery, but it was, nevertheless, of great value in pointing out the + hygienic importance of the care of the skin. He also introduced a + thermometer which he advocated as valuable in cases of fever, but the + instrument was probably not his own invention, but borrowed from his + friend Galileo. + </p> + <p> + Harvey's discovery of the circulation of the blood laid the foundation of + the Iatrophysical school by showing that this vital process was comparable + to a hydraulic system. In his On the Motive of Animals, Borelli first + attempted to account for the phenomena of life and diseases on these + principles. The iatromechanics held that the great cause of disease is due + to different states of elasticity of the solids of the body interfering + with the movements of the fluids, which are themselves subject to changes + in density, one or both of these conditions continuing to cause stagnation + or congestion. The school thus founded by Borelli was the outcome of the + unbounded enthusiasm, with its accompanying exaggeration of certain + phenomena with the corresponding belittling of others that naturally + follows such a revolutionary discovery as that of Harvey. Having such a + founder as the brilliant Italian Borelli, it was given a sufficient + impetus by his writings to carry it some distance before it finally + collapsed. Some of the exaggerated mathematical calculations of Borelli + himself are worth noting. Each heart-beat, as he calculated it, overcomes + a resistance equal to one hundred and eighty thousand pounds;—the + modern physiologist estimates its force at from five to nine ounces! + </p> + <p> + THOMAS SYDENHAM + </p> + <p> + But while the Continent was struggling with these illusive "systems," and + dabbling in mystic theories that were to scarcely outlive the men who + conceived them, there appeared in England—the "land of + common-sense," as a German scientist has called it—"a cool, clear, + and unprejudiced spirit," who in the golden age of systems declined "to be + like the man who builds the chambers of the upper story of his house + before he had laid securely the foundation walls."(1) This man was Thomas + Sydenham (1624-1689), who, while the great Harvey was serving the king as + surgeon, was fighting as a captain in the parliamentary army. Sydenham + took for his guide the teachings of Hippocrates, modified to suit the + advances that had been made in scientific knowledge since the days of the + great Greek, and established, as a standard, observation and experience. + He cared little for theory unless confirmed by practice, but took the + Hippocratic view that nature cured diseases, assisted by the physician. He + gave due credit, however, to the importance of the part played by the + assistant. As he saw it, medicine could be advanced in three ways: (1) "By + accurate descriptions or natural histories of diseases; (2) by + establishing a fixed principle or method of treatment, founded upon + experience; (3) by searching for specific remedies, which he believes must + exist in considerable numbers, though he admits that the only one yet + discovered is Peruvian bark."(2) As it happened, another equally specific + remedy, mercury, when used in certain diseases, was already known to him, + but he evidently did not recognize it as such. + </p> + <p> + The influence on future medicine of Sydenham's teachings was most + pronounced, due mostly to his teaching of careful observation. To most + physicians, however, he is now remembered chiefly for his introduction of + the use of laudanum, still considered one of the most valuable remedies of + modern pharmacopoeias. The German gives the honor of introducing this + preparation to Paracelsus, but the English-speaking world will always + believe that the credit should be given to Sydenham. + </p> + <p> + <a name="link2H_4_0011" id="link2H_4_0011"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING + </h2> + <p> + We saw that in the old Greek days there was no sharp line of demarcation + between the field of the philosopher and that of the scientist. In the + Hellenistic epoch, however, knowledge became more specialized, and our + recent chapters have shown us scientific investigators whose efforts were + far enough removed from the intangibilities of the philosopher. It must + not be overlooked, however, that even in the present epoch there were men + whose intellectual efforts were primarily directed towards the subtleties + of philosophy, yet who had also a penchant for strictly scientific + imaginings, if not indeed for practical scientific experiments. At least + three of these men were of sufficient importance in the history of the + development of science to demand more than passing notice. These three are + the Englishman Francis Bacon (1561-1626), the Frenchman Rene Descartes + (1596-1650); and the German Gottfried Leibnitz (1646-1716). Bacon, as the + earliest path-breaker, showed the way, theoretically at least, in which + the sciences should be studied; Descartes, pursuing the methods pointed + out by Bacon, carried the same line of abstract reason into practice as + well; while Leibnitz, coming some years later, and having the advantage of + the wisdom of his two great predecessors, was naturally influenced by both + in his views of abstract scientific principles. + </p> + <p> + Bacon's career as a statesman and his faults and misfortunes as a man do + not concern us here. Our interest in him begins with his entrance into + Trinity College, Cambridge, where he took up the study of all the sciences + taught there at that time. During the three years he became more and more + convinced that science was not being studied in a profitable manner, until + at last, at the end of his college course, he made ready to renounce the + old Aristotelian methods of study and advance his theory of inductive + study. For although he was a great admirer of Aristotle's work, he became + convinced that his methods of approaching study were entirely wrong. + </p> + <p> + "The opinion of Aristotle," he says, in his De Argumentum Scientiarum, + "seemeth to me a negligent opinion, that of those things which exist by + nature nothing can be changed by custom; using for example, that if a + stone be thrown ten thousand times up it will not learn to ascend; and + that by often seeing or hearing we do not learn to see or hear better. For + though this principle be true in things wherein nature is peremptory (the + reason whereof we cannot now stand to discuss), yet it is otherwise in + things wherein nature admitteth a latitude. For he might see that a + straight glove will come more easily on with use; and that a wand will by + use bend otherwise than it grew; and that by use of the voice we speak + louder and stronger; and that by use of enduring heat or cold we endure it + the better, and the like; which latter sort have a nearer resemblance unto + that subject of manners he handleth than those instances which he + allegeth."(1) + </p> + <p> + These were his opinions, formed while a young man in college, repeated at + intervals through his maturer years, and reiterated and emphasized in his + old age. Masses of facts were to be obtained by observing nature at first + hand, and from such accumulations of facts deductions were to be made. In + short, reasoning was to be from the specific to the general, and not vice + versa. + </p> + <p> + It was by his teachings alone that Bacon thus contributed to the + foundation of modern science; and, while he was constantly thinking and + writing on scientific subjects, he contributed little in the way of actual + discoveries. "I only sound the clarion," he said, "but I enter not the + battle." + </p> + <p> + The case of Descartes, however, is different. He both sounded the clarion + and entered into the fight. He himself freely acknowledges his debt to + Bacon for his teachings of inductive methods of study, but modern + criticism places his work on the same plane as that of the great + Englishman. "If you lay hold of any characteristic product of modern ways + of thinking," says Huxley, "either in the region of philosophy or in that + of science, you find the spirit of that thought, if not its form, has been + present in the mind of the great Frenchman."(2) + </p> + <p> + Descartes, the son of a noble family of France, was educated by Jesuit + teachers. Like Bacon, he very early conceived the idea that the methods of + teaching and studying science were wrong, but be pondered the matter well + into middle life before putting into writing his ideas of philosophy and + science. Then, in his Discourse Touching the Method of Using One's Reason + Rightly and of Seeking Scientific Truth, he pointed out the way of seeking + after truth. His central idea in this was to emphasize the importance of + DOUBT, and avoidance of accepting as truth anything that does not admit of + absolute and unqualified proof. In reaching these conclusions he had + before him the striking examples of scientific deductions by Galileo, and + more recently the discovery of the circulation of the blood by Harvey. + This last came as a revelation to scientists, reducing this seemingly + occult process, as it did, to the field of mechanical phenomena. The same + mechanical laws that governed the heavenly bodies, as shown by Galileo, + governed the action of the human heart, and, for aught any one knew, every + part of the body, and even the mind itself. + </p> + <p> + Having once conceived this idea, Descartes began a series of dissections + and experiments upon the lower animals, to find, if possible, further + proof of this general law. To him the human body was simply a machine, a + complicated mechanism, whose functions were controlled just as any other + piece of machinery. He compared the human body to complicated machinery + run by water-falls and complicated pipes. "The nerves of the machine which + I am describing," he says, "may very well be compared to the pipes of + these waterworks; its muscles and its tendons to the other various engines + and springs which seem to move them; its animal spirits to the water which + impels them, of which the heart is the fountain; while the cavities of the + brain are the central office. Moreover, respiration and other such actions + as are natural and usual in the body, and which depend on the course of + the spirits, are like the movements of a clock, or a mill, which may be + kept up by the ordinary flow of water."(3) + </p> + <p> + In such passages as these Descartes anticipates the ideas of physiology of + the present time. He believed that the functions are performed by the + various organs of the bodies of animals and men as a mechanism, to which + in man was added the soul. This soul he located in the pineal gland, a + degenerate and presumably functionless little organ in the brain. For + years Descartes's idea of the function of this gland was held by many + physiologists, and it was only the introduction of modern high-power + microscopy that reduced this also to a mere mechanism, and showed that it + is apparently the remains of a Cyclopean eye once common to man's remote + ancestors. + </p> + <p> + Descartes was the originator of a theory of the movements of the universe + by a mechanical process—the Cartesian theory of vortices—which + for several decades after its promulgation reigned supreme in science. It + is the ingenuity of this theory, not the truth of its assertions, that + still excites admiration, for it has long since been supplanted. It was + certainly the best hitherto advanced—the best "that the observations + of the age admitted," according to D'Alembert. + </p> + <p> + According to this theory the infinite universe is full of matter, there + being no such thing as a vacuum. Matter, as Descartes believed, is uniform + in character throughout the entire universe, and since motion cannot take + place in any part of a space completely filled, without simultaneous + movement in all other parts, there are constant more or less circular + movements, vortices, or whirlpools of particles, varying, of course, in + size and velocity. As a result of this circular movement the particles of + matter tend to become globular from contact with one another. Two species + of matter are thus formed, one larger and globular, which continue their + circular motion with a constant tendency to fly from the centre of the + axis of rotation, the other composed of the clippings resulting from the + grinding process. These smaller "filings" from the main bodies, becoming + smaller and smaller, gradually lose their velocity and accumulate in the + centre of the vortex. This collection of the smaller matter in the centre + of the vortex constitutes the sun or star, while the spherical particles + propelled in straight lines from the centre towards the circumference of + the vortex produce the phenomenon of light radiating from the central + star. Thus this matter becomes the atmosphere revolving around the + accumulation at the centre. But the small particles being constantly worn + away from the revolving spherical particles in the vortex, become + entangled in their passage, and when they reach the edge of the inner + strata of solar dust they settle upon it and form what we call sun-spots. + These are constantly dissolved and reformed, until sometimes they form a + crust round the central nucleus. + </p> + <p> + As the expansive force of the star diminishes in the course of time, it is + encroached upon by neighboring vortices. If the part of the encroaching + star be of a less velocity than the star which it has swept up, it will + presently lose its hold, and the smaller star pass out of range, becoming + a comet. But if the velocity of the vortex into which the incrusted star + settles be equivalent to that of the surrounded vortex, it will hold it as + a captive, still revolving and "wrapt in its own firmament." Thus the + several planets of our solar system have been captured and held by the + sun-vortex, as have the moon and other satellites. + </p> + <p> + But although these new theories at first created great enthusiasm among + all classes of philosophers and scientists, they soon came under the ban + of the Church. While no actual harm came to Descartes himself, his + writings were condemned by the Catholic and Protestant churches alike. The + spirit of philosophical inquiry he had engendered, however, lived on, and + is largely responsible for modern philosophy. + </p> + <p> + In many ways the life and works of Leibnitz remind us of Bacon rather than + Descartes. His life was spent in filling high political positions, and his + philosophical and scientific writings were by-paths of his fertile mind. + He was a theoretical rather than a practical scientist, his contributions + to science being in the nature of philosophical reasonings rather than + practical demonstrations. Had he been able to withdraw from public life + and devote himself to science alone, as Descartes did, he would + undoubtedly have proved himself equally great as a practical worker. But + during the time of his greatest activity in philosophical fields, between + the years 1690 and 1716, he was all the time performing extraordinary + active duties in entirely foreign fields. His work may be regarded, + perhaps, as doing for Germany in particular what Bacon's did for England + and the rest of the world in general. + </p> + <p> + Only a comparatively small part of his philosophical writings concern us + here. According to his theory of the ultimate elements of the universe, + the entire universe is composed of individual centres, or monads. To these + monads he ascribed numberless qualities by which every phase of nature may + be accounted. They were supposed by him to be percipient, self-acting + beings, not under arbitrary control of the deity, and yet God himself was + the original monad from which all the rest are generated. With this + conception as a basis, Leibnitz deduced his doctrine of pre-established + harmony, whereby the numerous independent substances composing the world + are made to form one universe. He believed that by virtue of an inward + energy monads develop themselves spontaneously, each being independent of + every other. In short, each monad is a kind of deity in itself—a + microcosm representing all the great features of the macrocosm. + </p> + <p> + It would be impossible clearly to estimate the precise value of the + stimulative influence of these philosophers upon the scientific thought of + their time. There was one way, however, in which their influence was made + very tangible—namely, in the incentive they gave to the foundation + of scientific societies. + </p> + <p> + SCIENTIFIC SOCIETIES + </p> + <p> + At the present time, when the elements of time and distance are + practically eliminated in the propagation of news, and when cheap printing + has minimized the difficulties of publishing scientific discoveries, it is + difficult to understand the isolated position of the scientific + investigation of the ages that preceded steam and electricity. Shut off + from the world and completely out of touch with fellow-laborers perhaps + only a few miles away, the investigators were naturally seriously + handicapped; and inventions and discoveries were not made with the same + rapidity that they would undoubtedly have been had the same men been + receiving daily, weekly, or monthly communications from fellow-laborers + all over the world, as they do to-day. Neither did they have the advantage + of public or semi-public laboratories, where they were brought into + contact with other men, from whom to gather fresh trains of thought and + receive the stimulus of their successes or failures. In the natural course + of events, however, neighbors who were interested in somewhat similar + pursuits, not of the character of the rivalry of trade or commerce, would + meet more or less frequently and discuss their progress. The mutual + advantages of such intercourse would be at once appreciated; and it would + be but a short step from the casual meeting of two neighborly scientists + to the establishment of "societies," meeting at fixed times, and composed + of members living within reasonable travelling distance. There would, + perhaps, be the weekly or monthly meetings of men in a limited area; and + as the natural outgrowth of these little local societies, with frequent + meetings, would come the formation of larger societies, meeting less + often, where members travelled a considerable distance to attend. And, + finally, with increased facilities for communication and travel, the great + international societies of to-day would be produced—the natural + outcome of the neighborly meetings of the primitive mediaeval + investigators. + </p> + <p> + In Italy, at about the time of Galileo, several small societies were + formed. One of the most important of these was the Lyncean Society, + founded about the year 1611, Galileo himself being a member. This society + was succeeded by the Accademia del Cimento, at Florence, in 1657, which + for a time flourished, with such a famous scientist as Torricelli as one + of its members. + </p> + <p> + In England an impetus seems to have been given by Sir Francis Bacon's + writings in criticism and censure of the system of teaching in colleges. + It is supposed that his suggestions as to what should be the aims of a + scientific society led eventually to the establishment of the Royal + Society. He pointed out how little had really been accomplished by the + existing institutions of learning in advancing science, and asserted that + little good could ever come from them while their methods of teaching + remained unchanged. He contended that the system which made the lectures + and exercises of such a nature that no deviation from the established + routine could be thought of was pernicious. But he showed that if any + teacher had the temerity to turn from the traditional paths, the daring + pioneer was likely to find insurmountable obstacles placed in the way of + his advancement. The studies were "imprisoned" within the limits of a + certain set of authors, and originality in thought or teaching was to be + neither contemplated nor tolerated. + </p> + <p> + The words of Bacon, given in strong and unsparing terms of censure and + condemnation, but nevertheless with perfect justification, soon bore + fruit. As early as the year 1645 a small company of scientists had been in + the habit of meeting at some place in London to discuss philosophical and + scientific subjects for mental advancement. In 1648, owing to the + political disturbances of the time, some of the members of these meetings + removed to Oxford, among them Boyle, Wallis, and Wren, where the meetings + were continued, as were also the meetings of those left in London. In + 1662, however, when the political situation bad become more settled, these + two bodies of men were united under a charter from Charles II., and + Bacon's ideas were practically expressed in that learned body, the Royal + Society of London. And it matters little that in some respects Bacon's + views were not followed in the practical workings of the society, or that + the division of labor in the early stages was somewhat different than at + present. The aim of the society has always been one for the advancement of + learning; and if Bacon himself could look over its records, he would + surely have little fault to find with the aid it has given in carrying out + his ideas for the promulgation of useful knowledge. + </p> + <p> + Ten years after the charter was granted to the Royal Society of London, + Lord Bacon's words took practical effect in Germany, with the result that + the Academia Naturae Curiosorum was founded, under the leadership of + Professor J. C. Sturm. The early labors of this society were devoted to a + repetition of the most notable experiments of the time, and the work of + the embryo society was published in two volumes, in 1672 and 1685 + respectively, which were practically text-books of the physics of the + period. It was not until 1700 that Frederick I. founded the Royal Academy + of Sciences at Berlin, after the elaborate plan of Leibnitz, who was + himself the first president. + </p> + <p> + Perhaps the nearest realization of Bacon's ideal, however, is in the Royal + Academy of Sciences at Paris, which was founded in 1666 under the + administration of Colbert, during the reign of Louis XIV. This institution + not only recognized independent members, but had besides twenty + pensionnaires who received salaries from the government. In this way a + select body of scientists were enabled to pursue their investigations + without being obliged to "give thought to the morrow" for their + sustenance. In return they were to furnish the meetings with scientific + memoirs, and once a year give an account of the work they were engaged + upon. Thus a certain number of the brightest minds were encouraged to + devote their entire time to scientific research, "delivered alike from the + temptations of wealth or the embarrassments of poverty." That such a plan + works well is amply attested by the results emanating from the French + academy. Pensionnaires in various branches of science, however, either + paid by the state or by learned societies, are no longer confined to + France. + </p> + <p> + Among the other early scientific societies was the Imperial Academy of + Sciences at St. Petersburg, projected by Peter the Great, and established + by his widow, Catharine I., in 1725; and also the Royal Swedish Academy, + incorporated in 1781, and counting among its early members such men as the + celebrated Linnaeus. But after the first impulse had resulted in a few + learned societies, their manifest advantage was so evident that additional + numbers increased rapidly, until at present almost every branch of every + science is represented by more or less important bodies; and these are, + individually and collectively, adding to knowledge and stimulating + interest in the many fields of science, thus vindicating Lord Bacon's + asseverations that knowledge could be satisfactorily promulgated in this + manner. + </p> + <p> + <a name="link2H_4_0012" id="link2H_4_0012"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE + </h2> + <p> + We have now to witness the diversified efforts of a company of men who, + working for the most part independently, greatly added to the data of the + physical sciences—such men as Boyle, Huygens, Von Gericke, and + Hooke. It will be found that the studies of these men covered the whole + field of physical sciences as then understood—the field of so-called + natural philosophy. We shall best treat these successors of Galileo and + precursors of Newton somewhat biographically, pointing out the + correspondences and differences between their various accomplishments as + we proceed. It will be noted in due course that the work of some of them + was anticipatory of great achievements of a later century. + </p> + <p> + ROBERT BOYLE (1627-1691) + </p> + <p> + Some of Robert Boyle's views as to the possible structure of atmospheric + air will be considered a little farther on in this chapter, but for the + moment we will take up the consideration of some of his experiments upon + that as well as other gases. Boyle was always much interested in alchemy, + and carried on extensive experiments in attempting to accomplish the + transmutation of metals; but he did not confine himself to these + experiments, devoting himself to researches in all the fields of natural + philosophy. He was associated at Oxford with a company of scientists, + including Wallis and Wren, who held meetings and made experiments + together, these gatherings being the beginning, as mentioned a moment ago, + of what finally became the Royal Society. It was during this residence at + Oxford that many of his valuable researches upon air were made, and during + this time be invented his air-pump, now exhibited in the Royal Society + rooms at Burlington House.(1) + </p> + <p> + His experiments to prove the atmospheric pressure are most interesting and + conclusive. "Having three small, round glass bubbles, blown at the flame + of a lamp, about the size of hazel-nuts," he says, "each of them with a + short, slender stem, by means whereof they were so exactly poised in water + that a very small change of weight would make them either emerge or sink; + at a time when the atmosphere was of convenient weight, I put them into a + wide-mouthed glass of common water, and leaving them in a quiet place, + where they were frequently in my eye, I observed that sometimes they would + be at the top of the water, and remain there for several days, or perhaps + weeks, together, and sometimes fall to the bottom, and after having + continued there for some time rise again. And sometimes they would rise or + fall as the air was hot or cold."(2) + </p> + <p> + It was in the course of these experiments that the observations made by + Boyle led to the invention of his "statical barometer," the mercurial + barometer having been invented, as we have seen, by Torricelli, in 1643. + In describing this invention he says: "Making choice of a large, thin, and + light glass bubble, blown at the flame of a lamp, I counterpoised it with + a metallic weight, in a pair of scales that were suspended in a frame, + that would turn with the thirtieth part of a grain. Both the frame and the + balance were then placed near a good barometer, whence I might learn the + present weight of the atmosphere; when, though the scales were unable to + show all the variations that appeared in the mercurial barometer, yet they + gave notice of those that altered the height of the mercury half a quarter + of an inch."(3) A fairly sensitive barometer, after all. This statical + barometer suggested several useful applications to the fertile imagination + of its inventor, among others the measuring of mountain-peaks, as with the + mercurial barometer, the rarefication of the air at the top giving a + definite ratio to the more condensed air in the valley. + </p> + <p> + Another of his experiments was made to discover the atmospheric pressure + to the square inch. After considerable difficulty he determined that the + relative weight of a cubic inch of water and mercury was about one to + fourteen, and computing from other known weights he determined that "when + a column of quicksilver thirty inches high is sustained in the barometer, + as it frequently happens, a column of air that presses upon an inch square + near the surface of the earth must weigh about fifteen avoirdupois + pounds."(4) As the pressure of air at the sea-level is now estimated at + 14.7304 pounds to the square inch, it will be seen that Boyle's + calculation was not far wrong. + </p> + <p> + From his numerous experiments upon the air, Boyle was led to believe that + there were many "latent qualities" due to substances contained in it that + science had as yet been unable to fathom, believing that there is "not a + more heterogeneous body in the world." He believed that contagious + diseases were carried by the air, and suggested that eruptions of the + earth, such as those made by earthquakes, might send up "venomous + exhalations" that produced diseases. He suggested also that the air might + play an important part in some processes of calcination, which, as we + shall see, was proved to be true by Lavoisier late in the eighteenth + century. Boyle's notions of the exact chemical action in these phenomena + were of course vague and indefinite, but he had observed that some part + was played by the air, and he was right in supposing that the air "may + have a great share in varying the salts obtainable from calcined + vitriol."(5) + </p> + <p> + Although he was himself such a painstaking observer of facts, he had the + fault of his age of placing too much faith in hear-say evidence of + untrained observers. Thus, from the numerous stories he heard concerning + the growth of metals in previously exhausted mines, he believed that the + air was responsible for producing this growth—in which he + undoubtedly believed. The story of a tin-miner that, in his own time, + after a lapse of only twenty-five years, a heap, of earth previously + exhausted of its ore became again even more richly impregnated than before + by lying exposed to the air, seems to have been believed by the + philosopher. + </p> + <p> + As Boyle was an alchemist, and undoubtedly believed in the alchemic theory + that metals have "spirits" and various other qualities that do not exist, + it is not surprising that he was credulous in the matter of beliefs + concerning peculiar phenomena exhibited by them. Furthermore, he + undoubtedly fell into the error common to "specialists," or persons + working for long periods of time on one subject—the error of + over-enthusiasm in his subject. He had discovered so many remarkable + qualities in the air that it is not surprising to find that he attributed + to it many more that he could not demonstrate. + </p> + <p> + Boyle's work upon colors, although probably of less importance than his + experiments and deductions upon air, show that he was in the van as far as + the science of his day was concerned. As he points out, the schools of his + time generally taught that "color is a penetrating quality, reaching to + the innermost part of the substance," and, as an example of this, + sealing-wax was cited, which could be broken into minute bits, each + particle retaining the same color as its fellows or the original mass. To + refute this theory, and to show instances to the contrary, Boyle, among + other things, shows that various colors—blue, red, yellow—may + be produced upon tempered steel, and yet the metal within "a + hair's-breadth of its surface" have none of these colors. Therefore, he + was led to believe that color, in opaque bodies at least, is superficial. + </p> + <p> + "But before we descend to a more particular consideration of our subject," + he says, "'tis proper to observe that colors may be regarded either as a + quality residing in bodies to modify light after a particular manner, or + else as light itself so modified as to strike upon the organs of sight, + and cause the sensation we call color; and that this latter is the more + proper acceptation of the word color will appear hereafter. And indeed it + is the light itself, which after a certain manner, either mixed with + shades or other-wise, strikes our eyes and immediately produces that + motion in the organ which gives us the color of an object."(6) + </p> + <p> + In examining smooth and rough surfaces to determine the cause of their + color, he made use of the microscope, and pointed out the very obvious + example of the difference in color of a rough and a polished piece of the + same block of stone. He used some striking illustrations of the effect of + light and the position of the eye upon colors. "Thus the color of plush or + velvet will appear various if you stroke part of it one way and part + another, the posture of the particular threads in regard to the light, or + the eye, being thereby varied. And 'tis observable that in a field of ripe + corn, blown upon by the wind, there will appear waves of a color different + from that of the rest of the corn, because the wind, by depressing some of + the ears more than others, causes one to reflect more light from the + lateral and strawy parts than another."(7) His work upon color, however, + as upon light, was entirely overshadowed by the work of his great + fellow-countryman Newton. + </p> + <p> + Boyle's work on electricity was a continuation of Gilbert's, to which he + added several new facts. He added several substances to Gilbert's list of + "electrics," experimented on smooth and rough surfaces in exciting of + electricity, and made the important discovery that amber retained its + attractive virtue after the friction that excited it bad ceased. "For the + attrition having caused an intestine motion in its parts," he says, "the + heat thereby excited ought not to cease as soon as ever the rubbing is + over, but to continue capable of emitting effluvia for some time + afterwards, longer or shorter according to the goodness of the electric + and the degree of the commotion made; all which, joined together, may + sometimes make the effect considerable; and by this means, on a warm day, + I, with a certain body not bigger than a pea, but very vigorously + attractive, moved a steel needle, freely poised, about three minutes after + I had left off rubbing it."(8) + </p> + <p> + MARIOTTE AND VON GUERICKE + </p> + <p> + Working contemporaneously with Boyle, and a man whose name is usually + associated with his as the propounder of the law of density of gases, was + Edme Mariotte (died 1684), a native of Burgundy. Mariotte demonstrated + that but for the resistance of the atmosphere, all bodies, whether light + or heavy, dense or thin, would fall with equal rapidity, and he proved + this by the well-known "guinea-and-feather" experiment. Having exhausted + the air from a long glass tube in which a guinea piece and a feather had + been placed, he showed that in the vacuum thus formed they fell with equal + rapidity as often as the tube was reversed. From his various experiments + as to the pressure of the atmosphere he deduced the law that the density + and elasticity of the atmosphere are precisely proportional to the + compressing force (the law of Boyle and Mariotte). He also ascertained + that air existed in a state of mechanical mixture with liquids, "existing + between their particles in a state of condensation." He made many other + experiments, especially on the collision of bodies, but his most important + work was upon the atmosphere. + </p> + <p> + But meanwhile another contemporary of Boyle and Mariotte was interesting + himself in the study of the atmosphere, and had made a wonderful invention + and a most striking demonstration. This was Otto von Guericke (1602-1686), + Burgomaster of Magdeburg, and councillor to his "most serene and potent + Highness" the elector of that place. When not engrossed with the duties of + public office, he devoted his time to the study of the sciences, + particularly pneumatics and electricity, both then in their infancy. The + discoveries of Galileo, Pascal, and Torricelli incited him to solve the + problem of the creation of a vacuum—a desideratum since before the + days of Aristotle. His first experiments were with a wooden pump and a + barrel of water, but he soon found that with such porous material as wood + a vacuum could not be created or maintained. He therefore made use of a + globe of copper, with pump and stop-cock; and with this he was able to + pump out air almost as easily as water. Thus, in 1650, the air-pump was + invented. Continuing his experiments upon vacuums and atmospheric pressure + with his newly discovered pump, he made some startling discoveries as to + the enormous pressure exerted by the air. + </p> + <p> + It was not his intention, however, to demonstrate his newly acquired + knowledge by words or theories alone, nor by mere laboratory experiments; + but he chose instead an open field, to which were invited Emperor + Ferdinand III., and all the princes of the Diet at Ratisbon. When they + were assembled he produced two hollow brass hemispheres about two feet in + diameter, and placing their exactly fitting surfaces together, proceeded + to pump out the air from their hollow interior, thus causing them to stick + together firmly in a most remarkable way, apparently without anything + holding them. This of itself was strange enough; but now the worthy + burgomaster produced teams of horses, and harnessing them to either side + of the hemispheres, attempted to pull the adhering brasses apart. Five, + ten, fifteen teams—thirty horses, in all—were attached; but + pull and tug as they would they could not separate the firmly clasped + hemispheres. The enormous pressure of the atmosphere had been most + strikingly demonstrated. + </p> + <p> + But it is one thing to demonstrate, another to convince; and many of the + good people of Magdeburg shook their heads over this "devil's + contrivance," and predicted that Heaven would punish the Herr Burgomaster, + as indeed it had once by striking his house with lightning and injuring + some of his infernal contrivances. They predicted his future punishment, + but they did not molest him, for to his fellow-citizens, who talked and + laughed, drank and smoked with him, and knew him for the honest citizen + that he was, he did not seem bewitched at all. And so he lived and worked + and added other facts to science, and his brass hemispheres were not + destroyed by fanatical Inquisitors, but are still preserved in the royal + library at Berlin. + </p> + <p> + In his experiments with his air-pump he discovered many things regarding + the action of gases, among others, that animals cannot live in a vacuum. + He invented the anemoscope and the air-balance, and being thus enabled to + weight the air and note the changes that preceded storms and calms, he was + able still further to dumfound his wondering fellow-Magde-burgers by more + or less accurate predictions about the weather. + </p> + <p> + Von Guericke did not accept Gilbert's theory that the earth was a great + magnet, but in his experiments along lines similar to those pursued by + Gilbert, he not only invented the first electrical machine, but discovered + electrical attraction and repulsion. The electrical machine which he + invented consisted of a sphere of sulphur mounted on an iron axis to + imitate the rotation of the earth, and which, when rubbed, manifested + electrical reactions. When this globe was revolved and stroked with the + dry hand it was found that it attached to it "all sorts of little + fragments, like leaves of gold, silver, paper, etc." "Thus this globe," he + says, "when brought rather near drops of water causes them to swell and + puff up. It likewise attracts air, smoke, etc."(9) Before the time of + Guericke's demonstrations, Cabaeus had noted that chaff leaped back from + an "electric," but he did not interpret the phenomenon as electrical + repulsion. Von Guericke, however, recognized it as such, and refers to it + as what he calls "expulsive virtue." "Even expulsive virtue is seen in + this globe," he says, "for it not only attracts, but also REPELS again + from itself little bodies of this sort, nor does it receive them until + they have touched something else." It will be observed from this that he + was very close to discovering the discharge of the electrification of + attracted bodies by contact with some other object, after which they are + reattracted by the electric. + </p> + <p> + He performed a most interesting experiment with his sulphur globe and a + feather, and in doing so came near anticipating Benjamin Franklin in his + discovery of the effects of pointed conductors in drawing off the + discharge. Having revolved and stroked his globe until it repelled a bit + of down, he removed the globe from its rack and advancing it towards the + now repellent down, drove it before him about the room. In this chase he + observed that the down preferred to alight against "the points of any + object whatsoever." He noticed that should the down chance to be driven + within a few inches of a lighted candle, its attitude towards the globe + suddenly changed, and instead of running away from it, it now "flew to it + for protection"—the charge on the down having been dissipated by the + hot air. He also noted that if one face of a feather had been first + attracted and then repelled by the sulphur ball, that the surface so + affected was always turned towards the globe; so that if the positions of + the two were reversed, the sides of the feather reversed also. + </p> + <p> + Still another important discovery, that of electrical conduction, was made + by Von Guericke. Until his discovery no one had observed the transference + of electricity from one body to another, although Gilbert had some time + before noted that a rod rendered magnetic at one end became so at the + other. Von Guericke's experiments were made upon a linen thread with his + sulphur globe, which, he says, "having been previously excited by rubbing, + can exercise likewise its virtue through a linen thread an ell or more + long, and there attract something." But this discovery, and his equally + important one that the sulphur ball becomes luminous when rubbed, were + practically forgotten until again brought to notice by the discoveries of + Francis Hauksbee and Stephen Gray early in the eighteenth century. From + this we may gather that Von Guericke himself did not realize the import of + his discoveries, for otherwise he would certainly have carried his + investigations still further. But as it was he turned his attention to + other fields of research. + </p> + <p> + ROBERT HOOKE + </p> + <p> + A slender, crooked, shrivelled-limbed, cantankerous little man, with + dishevelled hair and haggard countenance, bad-tempered and irritable, + penurious and dishonest, at least in his claims for priority in + discoveries—this is the picture usually drawn, alike by friends and + enemies, of Robert Hooke (1635-1703), a man with an almost unparalleled + genius for scientific discoveries in almost all branches of science. + History gives few examples so striking of a man whose really great + achievements in science would alone have made his name immortal, and yet + who had the pusillanimous spirit of a charlatan—an almost insane + mania, as it seems—for claiming the credit of discoveries made by + others. This attitude of mind can hardly be explained except as a mania: + it is certainly more charitable so to regard it. For his own discoveries + and inventions were so numerous that a few more or less would hardly have + added to his fame, as his reputation as a philosopher was well + established. Admiration for his ability and his philosophical knowledge + must always be marred by the recollection of his arrogant claims to the + discoveries of other philosophers. + </p> + <p> + It seems pretty definitely determined that Hooke should be credited with + the invention of the balance-spring for regulating watches; but for a long + time a heated controversy was waged between Hooke and Huygens as to who + was the real inventor. It appears that Hooke conceived the idea of the + balance-spring, while to Huygens belongs the credit of having adapted the + COILED spring in a working model. He thus made practical Hooke's + conception, which is without value except as applied by the coiled spring; + but, nevertheless, the inventor, as well as the perfector, should receive + credit. In this controversy, unlike many others, the blame cannot be laid + at Hooke's door. + </p> + <p> + Hooke was the first curator of the Royal Society, and when anything was to + be investigated, usually invented the mechanical devices for doing so. + Astronomical apparatus, instruments for measuring specific weights, clocks + and chronometers, methods of measuring the velocity of falling bodies, + freezing and boiling points, strength of gunpowder, magnetic instruments—in + short, all kinds of ingenious mechanical devices in all branches of + science and mechanics. It was he who made the famous air-pump of Robert + Boyle, based on Boyle's plans. Incidentally, Hooke claimed to be the + inventor of the first air-pump himself, although this claim is now + entirely discredited. + </p> + <p> + Within a period of two years he devised no less than thirty different + methods of flying, all of which, of course, came to nothing, but go to + show the fertile imagination of the man, and his tireless energy. He + experimented with electricity and made some novel suggestions upon the + difference between the electric spark and the glow, although on the whole + his contributions in this field are unimportant. He also first pointed out + that the motions of the heavenly bodies must be looked upon as a + mechanical problem, and was almost within grasping distance of the exact + theory of gravitation, himself originating the idea of making use of the + pendulum in measuring gravity. Likewise, he first proposed the wave theory + of light; although it was Huygens who established it on its present + foundation. + </p> + <p> + Hooke published, among other things, a book of plates and descriptions of + his Microscopical Observations, which gives an idea of the advance that + had already been made in microscopy in his time. Two of these plates are + given here, which, even in this age of microscopy, are both interesting + and instructive. These plates are made from prints of Hooke's original + copper plates, and show that excellent lenses were made even at that time. + They illustrate, also, how much might have been accomplished in the field + of medicine if more attention had been given to microscopy by physicians. + Even a century later, had physicians made better use of their microscopes, + they could hardly have overlooked such an easily found parasite as the + itch mite, which is quite as easily detected as the cheese mite, pictured + in Hooke's book. + </p> + <p> + In justice to Hooke, and in extenuation of his otherwise inexcusable + peculiarities of mind, it should be remembered that for many years he + suffered from a painful and wasting disease. This may have affected his + mental equilibrium, without appreciably affecting his ingenuity. In his + own time this condition would hardly have been considered a disease; but + to-day, with our advanced ideas as to mental diseases, we should be more + inclined to ascribe his unfortunate attitude of mind to a pathological + condition, rather than to any manifestation of normal mentality. From this + point of view his mental deformity seems not unlike that of Cavendish's, + later, except that in the case of Cavendish it manifested itself as an + abnormal sensitiveness instead of an abnormal irritability. + </p> + <p> + CHRISTIAN HUYGENS + </p> + <p> + If for nothing else, the world is indebted to the man who invented the + pendulum clock, Christian Huygens (1629-1695), of the Hague, inventor, + mathematician, mechanician, astronomer, and physicist. Huygens was the + descendant of a noble and distinguished family, his father, Sir + Constantine Huygens, being a well-known poet and diplomatist. Early in + life young Huygens began his career in the legal profession, completing + his education in the juridical school at Breda; but his taste for + mathematics soon led him to neglect his legal studies, and his aptitude + for scientific researches was so marked that Descartes predicted great + things of him even while he was a mere tyro in the field of scientific + investigation. + </p> + <p> + One of his first endeavors in science was to attempt an improvement of the + telescope. Reflecting upon the process of making lenses then in vogue, + young Huygens and his brother Constantine attempted a new method of + grinding and polishing, whereby they overcame a great deal of the + spherical and chromatic aberration. With this new telescope a much clearer + field of vision was obtained, so much so that Huygens was able to detect, + among other things, a hitherto unknown satellite of Saturn. It was these + astronomical researches that led him to apply the pendulum to regulate the + movements of clocks. The need for some more exact method of measuring time + in his observations of the stars was keenly felt by the young astronomer, + and after several experiments along different lines, Huygens hit upon the + use of a swinging weight; and in 1656 made his invention of the pendulum + clock. The year following, his clock was presented to the states-general. + Accuracy as to time is absolutely essential in astronomy, but until the + invention of Huygens's clock there was no precise, nor even approximately + precise, means of measuring short intervals. + </p> + <p> + Huygens was one of the first to adapt the micrometer to the telescope—a + mechanical device on which all the nice determination of minute distances + depends. He also took up the controversy against Hooke as to the + superiority of telescopic over plain sights to quadrants, Hooke contending + in favor of the plain. In this controversy, the subject of which attracted + wide attention, Huygens was completely victorious; and Hooke, being unable + to refute Huygens's arguments, exhibited such irritability that he + increased his already general unpopularity. All of the arguments for and + against the telescope sight are too numerous to be given here. In + contending in its favor Huygens pointed out that the unaided eye is unable + to appreciate an angular space in the sky less than about thirty seconds. + Even in the best quadrant with a plain sight, therefore, the altitude must + be uncertain by that quantity. If in place of the plain sight a telescope + is substituted, even if it magnify only thirty times, it will enable the + observer to fix the position to one second, with progressively increased + accuracy as the magnifying power of the telescope is increased. This was + only one of the many telling arguments advanced by Huygens. + </p> + <p> + In the field of optics, also, Huygens has added considerably to science, + and his work, Dioptrics, is said to have been a favorite book with Newton. + During the later part of his life, however, Huygens again devoted himself + to inventing and constructing telescopes, grinding the lenses, and + devising, if not actually making, the frame for holding them. These + telescopes were of enormous lengths, three of his object-glasses, now in + possession of the Royal Society, being of 123, 180, and 210 feet focal + length respectively. Such instruments, if constructed in the ordinary form + of the long tube, were very unmanageable, and to obviate this Huygens + adopted the plan of dispensing with the tube altogether, mounting his + lenses on long poles manipulated by machinery. Even these were unwieldy + enough, but the difficulties of manipulation were fully compensated by the + results obtained. + </p> + <p> + It had been discovered, among other things, that in oblique refraction + light is separated into colors. Therefore, any small portion of the convex + lens of the telescope, being a prism, the rays proceed to the focus, + separated into prismatic colors, which make the image thus formed edged + with a fringe of color and indistinct. But, fortunately for the early + telescope makers, the degree of this aberration is independent of the + focal length of the lens; so that, by increasing this focal length and + using the appropriate eye-piece, the image can be greatly magnified, while + the fringe of colors remains about the same as when a less powerful lens + is used. Hence the advantage of Huygens's long telescope. He did not + confine his efforts to simply lengthening the focal length of his + telescopes, however, but also added to their efficiency by inventing an + almost perfect achromatic eye-piece. + </p> + <p> + In 1663 he was elected a fellow of the Royal Society of London, and in + 1669 he gave to that body a concise statement of the laws governing the + collision of elastic bodies. Although the same views had been given by + Wallis and Wren a few weeks earlier, there is no doubt that Huygens's + views were reached independently; and it is probable that he had arrived + at his conclusions several years before. In the Philosophical Transactions + for 1669 it is recorded that the society, being interested in the laws of + the principles of motion, a request was made that M. Huygens, Dr. Wallis, + and Sir Christopher Wren submit their views on the subject. Wallis + submitted his paper first, November 15, 1668. A month later, December + 17th, Wren imparted to the society his laws as to the nature of the + collision of bodies. And a few days later, January 5, 1669, Huygens sent + in his "Rules Concerning the Motion of Bodies after Mutual Impulse." + Although Huygens's report was received last, he was anticipated by such a + brief space of time, and his views are so clearly stated—on the + whole rather more so than those of the other two—that we give them + in part here: + </p> + <p> + "1. If a hard body should strike against a body equally hard at rest, + after contact the former will rest and the latter acquire a velocity equal + to that of the moving body. + </p> + <p> + "2. But if that other equal body be likewise in motion, and moving in the + same direction, after contact they will move with reciprocal velocities. + </p> + <p> + "3. A body, however great, is moved by a body however small impelled with + any velocity whatsoever. + </p> + <p> + "5. The quantity of motion of two bodies may be either increased or + diminished by their shock; but the same quantity towards the same part + remains, after subtracting the quantity of the contrary motion. + </p> + <p> + "6. The sum of the products arising from multiplying the mass of any hard + body into the squares of its velocity is the same both before and after + the stroke. + </p> + <p> + "7. A hard body at rest will receive a greater quantity of motion from + another hard body, either greater or less than itself, by the + interposition of any third body of a mean quantity, than if it was + immediately struck by the body itself; and if the interposing body be a + mean proportional between the other two, its action upon the quiescent + body will be the greatest of all."(10) + </p> + <p> + This was only one of several interesting and important communications sent + to the Royal Society during his lifetime. One of these was a report on + what he calls "Pneumatical Experiments." "Upon including in a vacuum an + insect resembling a beetle, but somewhat larger," he says, "when it seemed + to be dead, the air was readmitted, and soon after it revived; putting it + again in the vacuum, and leaving it for an hour, after which the air was + readmitted, it was observed that the insect required a longer time to + recover; including it the third time for two days, after which the air was + admitted, it was ten hours before it began to stir; but, putting it in a + fourth time, for eight days, it never afterwards recovered.... Several + birds, rats, mice, rabbits, and cats were killed in a vacuum, but if the + air was admitted before the engine was quite exhausted some of them would + recover; yet none revived that had been in a perfect vacuum.... Upon + putting the weight of eighteen grains of powder with a gauge into a + receiver that held several pounds of water, and firing the powder, it + raised the mercury an inch and a half; from which it appears that there is + one-fifth of air in gunpowder, upon the supposition that air is about one + thousand times lighter than water; for in this experiment the mercury rose + to the eighteenth part of the height at which the air commonly sustains + it, and consequently the weight of eighteen grains of powder yielded air + enough to fill the eighteenth part of a receiver that contained seven + pounds of water; now this eighteenth part contains forty-nine drachms of + water; wherefore the air, that takes up an equal space, being a thousand + times lighter, weighs one-thousandth part of forty-nine drachms, which is + more than three grains and a half; it follows, therefore, that the weight + of eighteen grains of powder contains more than three and a half of air, + which is about one-fifth of eighteen grains...." + </p> + <p> + From 1665 to 1681, accepting the tempting offer made him through Colbert, + by Louis XIV., Huygens pursued his studies at the Bibliotheque du Roi as a + resident of France. Here he published his Horologium Oscillatorium, + dedicated to the king, containing, among other things, his solution of the + problem of the "centre of oscillation." This in itself was an important + step in the history of mechanics. Assuming as true that the centre of + gravity of any number of interdependent bodies cannot rise higher than the + point from which it falls, he reached correct conclusions as to the + general principle of the conservation of vis viva, although he did not + actually prove his conclusions. This was the first attempt to deal with + the dynamics of a system. In this work, also, was the true determination + of the relation between the length of a pendulum and the time of its + oscillation. + </p> + <p> + In 1681 he returned to Holland, influenced, it is believed, by the + attitude that was being taken in France against his religion. Here he + continued his investigations, built his immense telescopes, and, among + other things, discovered "polarization," which is recorded in Traite de la + Lumiere, published at Leyden in 1690. Five years later he died, + bequeathing his manuscripts to the University of Leyden. It is interesting + to note that he never accepted Newton's theory of gravitation as a + universal property of matter. + </p> + <p> + <a name="link2H_4_0013" id="link2H_4_0013"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XI. NEWTON AND THE COMPOSITION OF LIGHT + </h2> + <p> + Galileo, that giant in physical science of the early seventeenth century, + died in 1642. On Christmas day of the same year there was born in England + another intellectual giant who was destined to carry forward the work of + Copernicus, Kepler, and Galileo to a marvellous consummation through the + discovery of the great unifying law in accordance with which the planetary + motions are performed. We refer, of course, to the greatest of English + physical scientists, Isaac Newton, the Shakespeare of the scientific + world. Born thus before the middle of the seventeenth century, Newton + lived beyond the first quarter of the eighteenth (1727). For the last + forty years of that period his was the dominating scientific personality + of the world. With full propriety that time has been spoken of as the "Age + of Newton." + </p> + <p> + Yet the man who was to achieve such distinction gave no early premonition + of future greatness. He was a sickly child from birth, and a boy of little + seeming promise. He was an indifferent student, yet, on the other hand, he + cared little for the common amusements of boyhood. He early exhibited, + however, a taste for mechanical contrivances, and spent much time in + devising windmills, water-clocks, sun-dials, and kites. While other boys + were interested only in having kites that would fly, Newton—at least + so the stories of a later time would have us understand—cared more + for the investigation of the seeming principles involved, or for testing + the best methods of attaching the strings, or the best materials to be + used in construction. + </p> + <p> + Meanwhile the future philosopher was acquiring a taste for reading and + study, delving into old volumes whenever he found an opportunity. These + habits convinced his relatives that it was useless to attempt to make a + farmer of the youth, as had been their intention. He was therefore sent + back to school, and in the summer of 1661 he matriculated at Trinity + College, Cambridge. Even at college Newton seems to have shown no unusual + mental capacity, and in 1664, when examined for a scholarship by Dr. + Barrow, that gentleman is said to have formed a poor opinion of the + applicant. It is said that the knowledge of the estimate placed upon his + abilities by his instructor piqued Newton, and led him to take up in + earnest the mathematical studies in which he afterwards attained such + distinction. The study of Euclid and Descartes's "Geometry" roused in him + a latent interest in mathematics, and from that time forward his + investigations were carried on with enthusiasm. In 1667 he was elected + Fellow of Trinity College, taking the degree of M.A. the following spring. + </p> + <p> + It will thus appear that Newton's boyhood and early manhood were passed + during that troublous time in British political annals which saw the + overthrow of Charles I., the autocracy of Cromwell, and the eventual + restoration of the Stuarts. His maturer years witnessed the overthrow of + the last Stuart and the reign of the Dutchman, William of Orange. In his + old age he saw the first of the Hanoverians mount the throne of England. + Within a decade of his death such scientific path-finders as Cavendish, + Black, and Priestley were born—men who lived on to the close of the + eighteenth century. In a full sense, then, the age of Newton bridges the + gap from that early time of scientific awakening under Kepler and Galileo + to the time which we of the twentieth century think of as essentially + modern. + </p> + <p> + THE COMPOSITION OF WHITE LIGHT + </p> + <p> + In December, 1672, Newton was elected a Fellow of the Royal Society, and + at this meeting a paper describing his invention of the refracting + telescope was read. A few days later he wrote to the secretary, making + some inquiries as to the weekly meetings of the society, and intimating + that he had an account of an interesting discovery that he wished to lay + before the society. When this communication was made public, it proved to + be an explanation of the discovery of the composition of white light. We + have seen that the question as to the nature of color had commanded the + attention of such investigators as Huygens, but that no very satisfactory + solution of the question had been attained. Newton proved by demonstrative + experiments that white light is composed of the blending of the rays of + diverse colors, and that the color that we ascribe to any object is merely + due to the fact that the object in question reflects rays of that color, + absorbing the rest. That white light is really made up of many colors + blended would seem incredible had not the experiments by which this + composition is demonstrated become familiar to every one. The experiments + were absolutely novel when Newton brought them forward, and his + demonstration of the composition of light was one of the most striking + expositions ever brought to the attention of the Royal Society. It is + hardly necessary to add that, notwithstanding the conclusive character of + Newton's work, his explanations did not for a long time meet with general + acceptance. + </p> + <p> + Newton was led to his discovery by some experiments made with an ordinary + glass prism applied to a hole in the shutter of a darkened room, the + refracted rays of the sunlight being received upon the opposite wall and + forming there the familiar spectrum. "It was a very pleasing diversion," + he wrote, "to view the vivid and intense colors produced thereby; and + after a time, applying myself to consider them very circumspectly, I + became surprised to see them in varying form, which, according to the + received laws of refraction, I expected should have been circular. They + were terminated at the sides with straight lines, but at the ends the + decay of light was so gradual that it was difficult to determine justly + what was their figure, yet they seemed semicircular. + </p> + <p> + "Comparing the length of this colored spectrum with its breadth, I found + it almost five times greater; a disproportion so extravagant that it + excited me to a more than ordinary curiosity of examining from whence it + might proceed. I could scarce think that the various thicknesses of the + glass, or the termination with shadow or darkness, could have any + influence on light to produce such an effect; yet I thought it not amiss, + first, to examine those circumstances, and so tried what would happen by + transmitting light through parts of the glass of divers thickness, or + through holes in the window of divers bigness, or by setting the prism + without so that the light might pass through it and be refracted before it + was transmitted through the hole; but I found none of those circumstances + material. The fashion of the colors was in all these cases the same. + </p> + <p> + "Then I suspected whether by any unevenness of the glass or other + contingent irregularity these colors might be thus dilated. And to try + this I took another prism like the former, and so placed it that the + light, passing through them both, might be refracted contrary ways, and so + by the latter returned into that course from which the former diverted it. + For, by this means, I thought, the regular effects of the first prism + would be destroyed by the second prism, but the irregular ones more + augmented by the multiplicity of refractions. The event was that the + light, which by the first prism was diffused into an oblong form, was by + the second reduced into an orbicular one with as much regularity as when + it did not all pass through them. So that, whatever was the cause of that + length, 'twas not any contingent irregularity. + </p> + <p> + "I then proceeded to examine more critically what might be effected by the + difference of the incidence of rays coming from divers parts of the sun; + and to that end measured the several lines and angles belonging to the + image. Its distance from the hole or prism was 22 feet; its utmost length + 13 1/4 inches; its breadth 2 5/8; the diameter of the hole 1/4 of an inch; + the angle which the rays, tending towards the middle of the image, made + with those lines, in which they would have proceeded without refraction, + was 44 degrees 56'; and the vertical angle of the prism, 63 degrees 12'. + Also the refractions on both sides of the prism—that is, of the + incident and emergent rays—were, as near as I could make them, + equal, and consequently about 54 degrees 4'; and the rays fell + perpendicularly upon the wall. Now, subducting the diameter of the hole + from the length and breadth of the image, there remains 13 inches the + length, and 2 3/8 the breadth, comprehended by those rays, which, passing + through the centre of the said hole, which that breadth subtended, was + about 31', answerable to the sun's diameter; but the angle which its + length subtended was more than five such diameters, namely 2 degrees 49'. + </p> + <p> + "Having made these observations, I first computed from them the refractive + power of the glass, and found it measured by the ratio of the sines 20 to + 31. And then, by that ratio, I computed the refractions of two rays + flowing from opposite parts of the sun's discus, so as to differ 31' in + their obliquity of incidence, and found that the emergent rays should have + comprehended an angle of 31', as they did, before they were incident. + </p> + <p> + "But because this computation was founded on the hypothesis of the + proportionality of the sines of incidence and refraction, which though by + my own experience I could not imagine to be so erroneous as to make that + angle but 31', which in reality was 2 degrees 49', yet my curiosity caused + me again to make my prism. And having placed it at my window, as before, I + observed that by turning it a little about its axis to and fro, so as to + vary its obliquity to the light more than an angle of 4 degrees or 5 + degrees, the colors were not thereby sensibly translated from their place + on the wall, and consequently by that variation of incidence the quantity + of refraction was not sensibly varied. By this experiment, therefore, as + well as by the former computation, it was evident that the difference of + the incidence of rays flowing from divers parts of the sun could not make + them after decussation diverge at a sensibly greater angle than that at + which they before converged; which being, at most, but about 31' or 32', + there still remained some other cause to be found out, from whence it + could be 2 degrees 49'." + </p> + <p> + All this caused Newton to suspect that the rays, after their trajection + through the prism, moved in curved rather than in straight lines, thus + tending to be cast upon the wall at different places according to the + amount of this curve. His suspicions were increased, also, by happening to + recall that a tennis-ball sometimes describes such a curve when "cut" by a + tennis-racket striking the ball obliquely. + </p> + <p> + "For a circular as well as a progressive motion being communicated to it + by the stroke," he says, "its parts on that side where the motions + conspire must press and beat the contiguous air more violently than on the + other, and there excite a reluctancy and reaction of the air + proportionately greater. And for the same reason, if the rays of light + should possibly be globular bodies, and by their oblique passage out of + one medium into another acquire a circulating motion, they ought to feel + the greater resistance from the ambient ether on that side where the + motions conspire, and thence be continually bowed to the other. But + notwithstanding this plausible ground of suspicion, when I came to examine + it I could observe no such curvity in them. And, besides (which was enough + for my purpose), I observed that the difference 'twixt the length of the + image and diameter of the hole through which the light was transmitted was + proportionable to their distance. + </p> + <p> + "The gradual removal of these suspicions at length led me to the + experimentum crucis, which was this: I took two boards, and, placing one + of them close behind the prism at the window, so that the light must pass + through a small hole, made in it for the purpose, and fall on the other + board, which I placed at about twelve feet distance, having first made a + small hole in it also, for some of the incident light to pass through. + Then I placed another prism behind this second board, so that the light + trajected through both the boards might pass through that also, and be + again refracted before it arrived at the wall. This done, I took the first + prism in my hands and turned it to and fro slowly about its axis, so much + as to make the several parts of the image, cast on the second board, + successively pass through the hole in it, that I might observe to what + places on the wall the second prism would refract them. And I saw by the + variation of these places that the light, tending to that end of the image + towards which the refraction of the first prism was made, did in the + second prism suffer a refraction considerably greater than the light + tending to the other end. And so the true cause of the length of that + image was detected to be no other than that LIGHT consists of RAYS + DIFFERENTLY REFRANGIBLE, which, without any respect to a difference in + their incidence, were, according to their degrees of refrangibility, + transmitted towards divers parts of the wall."(1) + </p> + <p> + THE NATURE OF COLOR + </p> + <p> + Having thus proved the composition of light, Newton took up an exhaustive + discussion as to colors, which cannot be entered into at length here. Some + of his remarks on the subject of compound colors, however, may be stated + in part. Newton's views are of particular interest in this connection, + since, as we have already pointed out, the question as to what constituted + color could not be agreed upon by the philosophers. Some held that color + was an integral part of the substance; others maintained that it was + simply a reflection from the surface; and no scientific explanation had + been generally accepted. Newton concludes his paper as follows: + </p> + <p> + "I might add more instances of this nature, but I shall conclude with the + general one that the colors of all natural bodies have no other origin + than this, that they are variously qualified to reflect one sort of light + in greater plenty than another. And this I have experimented in a dark + room by illuminating those bodies with uncompounded light of divers + colors. For by that means any body may be made to appear of any color. + They have there no appropriate color, but ever appear of the color of the + light cast upon them, but yet with this difference, that they are most + brisk and vivid in the light of their own daylight color. Minium appeareth + there of any color indifferently with which 'tis illustrated, but yet most + luminous in red; and so Bise appeareth indifferently of any color with + which 'tis illustrated, but yet most luminous in blue. And therefore + Minium reflecteth rays of any color, but most copiously those indued with + red; and consequently, when illustrated with daylight—that is, with + all sorts of rays promiscuously blended—those qualified with red + shall abound most in the reflected light, and by their prevalence cause it + to appear of that color. And for the same reason, Bise, reflecting blue + most copiously, shall appear blue by the excess of those rays in its + reflected light; and the like of other bodies. And that this is the entire + and adequate cause of their colors is manifest, because they have no power + to change or alter the colors of any sort of rays incident apart, but put + on all colors indifferently with which they are enlightened."(2) + </p> + <p> + This epoch-making paper aroused a storm of opposition. Some of Newton's + opponents criticised his methods, others even doubted the truth of his + experiments. There was one slight mistake in Newton's belief that all + prisms would give a spectrum of exactly the same length, and it was some + time before he corrected this error. Meanwhile he patiently met and + answered the arguments of his opponents until he began to feel that + patience was no longer a virtue. At one time he even went so far as to + declare that, once he was "free of this business," he would renounce + scientific research forever, at least in a public way. Fortunately for the + world, however, he did not adhere to this determination, but went on to + even greater discoveries—which, it may be added, involved still + greater controversies. + </p> + <p> + In commenting on Newton's discovery of the composition of light, Voltaire + said: "Sir Isaac Newton has demonstrated to the eye, by the bare + assistance of a prism, that light is a composition of colored rays, which, + being united, form white color. A single ray is by him divided into seven, + which all fall upon a piece of linen or a sheet of white paper, in their + order one above the other, and at equal distances. The first is red, the + second orange, the third yellow, the fourth green, the fifth blue, the + sixth indigo, the seventh a violet purple. Each of these rays transmitted + afterwards by a hundred other prisms will never change the color it bears; + in like manner as gold, when completely purged from its dross, will never + change afterwards in the crucible."(3) + </p> + <p> + <a name="link2H_4_0014" id="link2H_4_0014"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XII. NEWTON AND THE LAW OF GRAVITATION + </h2> + <p> + We come now to the story of what is by common consent the greatest of + scientific achievements. The law of universal gravitation is the most + far-reaching principle as yet discovered. It has application equally to + the minutest particle of matter and to the most distant suns in the + universe, yet it is amazing in its very simplicity. As usually phrased, + the law is this: That every particle of matter in the universe attracts + every other particle with a force that varies directly with the mass of + the particles and inversely as the squares of their mutual distance. + Newton did not vault at once to the full expression of this law, though he + had formulated it fully before he gave the results of his investigations + to the world. We have now to follow the steps by which he reached this + culminating achievement. + </p> + <p> + At the very beginning we must understand that the idea of universal + gravitation was not absolutely original with Newton. Away back in the old + Greek days, as we have seen, Anaxagoras conceived and clearly expressed + the idea that the force which holds the heavenly bodies in their orbits + may be the same that operates upon substances at the surface of the earth. + With Anaxagoras this was scarcely more than a guess. After his day the + idea seems not to have been expressed by any one until the seventeenth + century's awakening of science. Then the consideration of Kepler's Third + Law of planetary motion suggested to many minds perhaps independently the + probability that the force hitherto mentioned merely as centripetal, + through the operation of which the planets are held in their orbits is a + force varying inversely as the square of the distance from the sun. This + idea had come to Robert Hooke, to Wren, and perhaps to Halley, as well as + to Newton; but as yet no one had conceived a method by which the validity + of the suggestion might be tested. It was claimed later on by Hooke that + he had discovered a method demonstrating the truth of the theory of + inverse squares, and after the full announcement of Newton's discovery a + heated controversy was precipitated in which Hooke put forward his claims + with accustomed acrimony. Hooke, however, never produced his + demonstration, and it may well be doubted whether he had found a method + which did more than vaguely suggest the law which the observations of + Kepler had partially revealed. Newton's great merit lay not so much in + conceiving the law of inverse squares as in the demonstration of the law. + He was led to this demonstration through considering the orbital motion of + the moon. According to the familiar story, which has become one of the + classic myths of science, Newton was led to take up the problem through + observing the fall of an apple. Voltaire is responsible for the story, + which serves as well as another; its truth or falsity need not in the + least concern us. Suffice it that through pondering on the familiar fact + of terrestrial gravitation, Newton was led to question whether this force + which operates so tangibly here at the earth's surface may not extend its + influence out into the depths of space, so as to include, for example, the + moon. Obviously some force pulls the moon constantly towards the earth; + otherwise that body would fly off at a tangent and never return. May not + this so-called centripetal force be identical with terrestrial + gravitation? Such was Newton's query. Probably many another man since + Anaxagoras had asked the same question, but assuredly Newton was the first + man to find an answer. + </p> + <p> + The thought that suggested itself to Newton's mind was this: If we make a + diagram illustrating the orbital course of the moon for any given period, + say one minute, we shall find that the course of the moon departs from a + straight line during that period by a measurable distance—that: is + to say, the moon has been virtually pulled towards the earth by an amount + that is represented by the difference between its actual position at the + end of the minute under observation and the position it would occupy had + its course been tangential, as, according to the first law of motion, it + must have been had not some force deflected it towards the earth. + Measuring the deflection in question—which is equivalent to the + so-called versed sine of the arc traversed—we have a basis for + determining the strength of the deflecting force. Newton constructed such + a diagram, and, measuring the amount of the moon's departure from a + tangential rectilinear course in one minute, determined this to be, by his + calculation, thirteen feet. Obviously, then, the force acting upon the + moon is one that would cause that body to fall towards the earth to the + distance of thirteen feet in the first minute of its fall. Would such be + the force of gravitation acting at the distance of the moon if the power + of gravitation varies inversely as the square of the distance? That was + the tangible form in which the problem presented itself to Newton. The + mathematical solution of the problem was simple enough. It is based on a + comparison of the moon's distance with the length of the earth's radius. + On making this calculation, Newton found that the pull of gravitation—if + that were really the force that controls the moon—gives that body a + fall of slightly over fifteen feet in the first minute, instead of + thirteen feet. Here was surely a suggestive approximation, yet, on the + other band, the discrepancy seemed to be too great to warrant him in the + supposition that he had found the true solution. He therefore dismissed + the matter from his mind for the time being, nor did he return to it + definitely for some years. + </p> + <p> + {illustration caption = DIAGRAM TO ILLUSTRATE NEWTON'S LAW OF GRAVITATION + (E represents the earth and A the moon. Were the earth's pull on the moon + to cease, the moon's inertia would cause it to take the tangential course, + AB. On the other hand, were the moon's motion to be stopped for an + instant, the moon would fall directly towards the earth, along the line + AD. The moon's actual orbit, resulting from these component forces, is AC. + Let AC represent the actual flight of the moon in one minute. Then BC, + which is obviously equal to AD, represents the distance which the moon + virtually falls towards the earth in one minute. Actual computation, based + on measurements of the moon's orbit, showed this distance to be about + fifteen feet. Another computation showed that this is the distance that + the moon would fall towards the earth under the influence of gravity, on + the supposition that the force of gravity decreases inversely with the + square of the distance; the basis of comparison being furnished by falling + bodies at the surface of the earth. Theory and observations thus + coinciding, Newton was justified in declaring that the force that pulls + the moon towards the earth and keeps it in its orbit, is the familiar + force of gravity, and that this varies inversely as the square of the + distance.)} + </p> + <p> + It was to appear in due time that Newton's hypothesis was perfectly valid + and that his method of attempted demonstration was equally so. The + difficulty was that the earth's proper dimensions were not at that time + known. A wrong estimate of the earth's size vitiated all the other + calculations involved, since the measurement of the moon's distance + depends upon the observation of the parallax, which cannot lead to a + correct computation unless the length of the earth's radius is accurately + known. Newton's first calculation was made as early as 1666, and it was + not until 1682 that his attention was called to a new and apparently + accurate measurement of a degree of the earth's meridian made by the + French astronomer Picard. The new measurement made a degree of the earth's + surface 69.10 miles, instead of sixty miles. + </p> + <p> + Learning of this materially altered calculation as to the earth's size, + Newton was led to take up again his problem of the falling moon. As he + proceeded with his computation, it became more and more certain that this + time the result was to harmonize with the observed facts. As the story + goes, he was so completely overwhelmed with emotion that he was forced to + ask a friend to complete the simple calculation. That story may well be + true, for, simple though the computation was, its result was perhaps the + most wonderful demonstration hitherto achieved in the entire field of + science. Now at last it was known that the force of gravitation operates + at the distance of the moon, and holds that body in its elliptical orbit, + and it required but a slight effort of the imagination to assume that the + force which operates through such a reach of space extends its influence + yet more widely. That such is really the case was demonstrated presently + through calculations as to the moons of Jupiter and by similar + computations regarding the orbital motions of the various planets. All + results harmonizing, Newton was justified in reaching the conclusion that + gravitation is a universal property of matter. It remained, as we shall + see, for nineteenth-century scientists to prove that the same force + actually operates upon the stars, though it should be added that this + demonstration merely fortified a belief that had already found full + acceptance. + </p> + <p> + Having thus epitomized Newton's discovery, we must now take up the steps + of his progress somewhat in detail, and state his theories and their + demonstration in his own words. Proposition IV., theorem 4, of his + Principia is as follows: + </p> + <p> + "That the moon gravitates towards the earth and by the force of gravity is + continually drawn off from a rectilinear motion and retained in its orbit. + </p> + <p> + "The mean distance of the moon from the earth, in the syzygies in + semi-diameters of the earth, is, according to Ptolemy and most + astronomers, 59; according to Vendelin and Huygens, 60; to Copernicus, 60 + 1/3; to Street, 60 2/3; and to Tycho, 56 1/2. But Tycho, and all that + follow his tables of refractions, making the refractions of the sun and + moon (altogether against the nature of light) to exceed the refractions of + the fixed stars, and that by four or five minutes NEAR THE HORIZON, did + thereby increase the moon's HORIZONTAL parallax by a like number of + minutes, that is, by a twelfth or fifteenth part of the whole parallax. + Correct this error and the distance will become about 60 1/2 + semi-diameters of the earth, near to what others have assigned. Let us + assume the mean distance of 60 diameters in the syzygies; and suppose one + revolution of the moon, in respect to the fixed stars, to be completed in + 27d. 7h. 43', as astronomers have determined; and the circumference of the + earth to amount to 123,249,600 Paris feet, as the French have found by + mensuration. And now, if we imagine the moon, deprived of all motion, to + be let go, so as to descend towards the earth with the impulse of all that + force by which (by Cor. Prop. iii.) it is retained in its orb, it will in + the space of one minute of time describe in its fall 15 1/12 Paris feet. + For the versed sine of that arc which the moon, in the space of one minute + of time, would by its mean motion describe at the distance of sixty + semi-diameters of the earth, is nearly 15 1/12 Paris feet, or more + accurately 15 feet, 1 inch, 1 line 4/9. Wherefore, since that force, in + approaching the earth, increases in the reciprocal-duplicate proportion of + the distance, and upon that account, at the surface of the earth, is 60 x + 60 times greater than at the moon, a body in our regions, falling with + that force, ought in the space of one minute of time to describe 60 x 60 x + 15 1/12 Paris feet; and in the space of one second of time, to describe 15 + 1/12 of those feet, or more accurately, 15 feet, 1 inch, 1 line 4/9. And + with this very force we actually find that bodies here upon earth do + really descend; for a pendulum oscillating seconds in the latitude of + Paris will be 3 Paris feet, and 8 lines 1/2 in length, as Mr. Huygens has + observed. And the space which a heavy body describes by falling in one + second of time is to half the length of the pendulum in the duplicate + ratio of the circumference of a circle to its diameter (as Mr. Huygens has + also shown), and is therefore 15 Paris feet, 1 inch, 1 line 4/9. And + therefore the force by which the moon is retained in its orbit is that + very same force which we commonly call gravity; for, were gravity another + force different from that, then bodies descending to the earth with the + joint impulse of both forces would fall with a double velocity, and in the + space of one second of time would describe 30 1/6 Paris feet; altogether + against experience."(1) + </p> + <p> + All this is beautifully clear, and its validity has never in recent + generations been called in question; yet it should be explained that the + argument does not amount to an actually indisputable demonstration. It is + at least possible that the coincidence between the observed and computed + motion of the moon may be a mere coincidence and nothing more. This + probability, however, is so remote that Newton is fully justified in + disregarding it, and, as has been said, all subsequent generations have + accepted the computation as demonstrative. + </p> + <p> + Let us produce now Newton's further computations as to the other planetary + bodies, passing on to his final conclusion that gravity is a universal + force. + </p> +<pre xml:space="preserve"> + "PROPOSITION V., THEOREM V. +</pre> + <p> + "That the circumjovial planets gravitate towards Jupiter; the + circumsaturnal towards Saturn; the circumsolar towards the sun; and by the + forces of their gravity are drawn off from rectilinear motions, and + retained in curvilinear orbits. + </p> + <p> + "For the revolutions of the circumjovial planets about Jupiter, of the + circumsaturnal about Saturn, and of Mercury and Venus and the other + circumsolar planets about the sun, are appearances of the same sort with + the revolution of the moon about the earth; and therefore, by Rule ii., + must be owing to the same sort of causes; especially since it has been + demonstrated that the forces upon which those revolutions depend tend to + the centres of Jupiter, of Saturn, and of the sun; and that those forces, + in receding from Jupiter, from Saturn, and from the sun, decrease in the + same proportion, and according to the same law, as the force of gravity + does in receding from the earth. + </p> + <p> + "COR. 1.—There is, therefore, a power of gravity tending to all the + planets; for doubtless Venus, Mercury, and the rest are bodies of the same + sort with Jupiter and Saturn. And since all attraction (by Law iii.) is + mutual, Jupiter will therefore gravitate towards all his own satellites, + Saturn towards his, the earth towards the moon, and the sun towards all + the primary planets. + </p> + <p> + "COR. 2.—The force of gravity which tends to any one planet is + reciprocally as the square of the distance of places from the planet's + centre. + </p> + <p> + "COR. 3.—All the planets do mutually gravitate towards one another, + by Cor. 1 and 2, and hence it is that Jupiter and Saturn, when near their + conjunction, by their mutual attractions sensibly disturb each other's + motions. So the sun disturbs the motions of the moon; and both sun and + moon disturb our sea, as we shall hereafter explain. + </p> +<pre xml:space="preserve"> + "SCHOLIUM +</pre> + <p> + "The force which retains the celestial bodies in their orbits has been + hitherto called centripetal force; but it being now made plain that it can + be no other than a gravitating force, we shall hereafter call it gravity. + For the cause of the centripetal force which retains the moon in its orbit + will extend itself to all the planets by Rules i., ii., and iii. + </p> +<pre xml:space="preserve"> + "PROPOSITION VI., THEOREM VI. +</pre> + <p> + "That all bodies gravitate towards every planet; and that the weights of + the bodies towards any the same planet, at equal distances from the centre + of the planet, are proportional to the quantities of matter which they + severally contain. + </p> + <p> + "It has been now a long time observed by others that all sorts of heavy + bodies (allowance being made for the inability of retardation which they + suffer from a small power of resistance in the air) descend to the earth + FROM EQUAL HEIGHTS in equal times; and that equality of times we may + distinguish to a great accuracy by help of pendulums. I tried the thing in + gold, silver, lead, glass, sand, common salt, wood, water, and wheat. I + provided two wooden boxes, round and equal: I filled the one with wood, + and suspended an equal weight of gold (as exactly as I could) in the + centre of oscillation of the other. The boxes hanging by eleven feet, made + a couple of pendulums exactly equal in weight and figure, and equally + receiving the resistance of the air. And, placing the one by the other, I + observed them to play together forward and backward, for a long time, with + equal vibrations. And therefore the quantity of matter in gold was to the + quantity of matter in the wood as the action of the motive force (or vis + motrix) upon all the gold to the action of the same upon all the wood—that + is, as the weight of the one to the weight of the other: and the like + happened in the other bodies. By these experiments, in bodies of the same + weight, I could manifestly have discovered a difference of matter less + than the thousandth part of the whole, had any such been. But, without all + doubt, the nature of gravity towards the planets is the same as towards + the earth. For, should we imagine our terrestrial bodies removed to the + orb of the moon, and there, together with the moon, deprived of all + motion, to be let go, so as to fall together towards the earth, it is + certain, from what we have demonstrated before, that, in equal times, they + would describe equal spaces with the moon, and of consequence are to the + moon, in quantity and matter, as their weights to its weight. + </p> + <p> + "Moreover, since the satellites of Jupiter perform their revolutions in + times which observe the sesquiplicate proportion of their distances from + Jupiter's centre, their accelerative gravities towards Jupiter will be + reciprocally as the square of their distances from Jupiter's centre—that + is, equal, at equal distances. And, therefore, these satellites, if + supposed to fall TOWARDS JUPITER from equal heights, would describe equal + spaces in equal times, in like manner as heavy bodies do on our earth. + And, by the same argument, if the circumsolar planets were supposed to be + let fall at equal distances from the sun, they would, in their descent + towards the sun, describe equal spaces in equal times. But forces which + equally accelerate unequal bodies must be as those bodies—that is to + say, the weights of the planets (TOWARDS THE SUN) must be as their + quantities of matter. Further, that the weights of Jupiter and his + satellites towards the sun are proportional to the several quantities of + their matter, appears from the exceedingly regular motions of the + satellites. For if some of these bodies were more strongly attracted to + the sun in proportion to their quantity of matter than others, the motions + of the satellites would be disturbed by that inequality of attraction. If + at equal distances from the sun any satellite, in proportion to the + quantity of its matter, did gravitate towards the sun with a force greater + than Jupiter in proportion to his, according to any given proportion, + suppose d to e; then the distance between the centres of the sun and of + the satellite's orbit would be always greater than the distance between + the centres of the sun and of Jupiter nearly in the subduplicate of that + proportion: as by some computations I have found. And if the satellite did + gravitate towards the sun with a force, lesser in the proportion of e to + d, the distance of the centre of the satellite's orb from the sun would be + less than the distance of the centre of Jupiter from the sun in the + subduplicate of the same proportion. Therefore, if at equal distances from + the sun, the accelerative gravity of any satellite towards the sun were + greater or less than the accelerative gravity of Jupiter towards the sun + by one-one-thousandth part of the whole gravity, the distance of the + centre of the satellite's orbit from the sun would be greater or less than + the distance of Jupiter from the sun by one one-two-thousandth part of the + whole distance—that is, by a fifth part of the distance of the + utmost satellite from the centre of Jupiter; an eccentricity of the orbit + which would be very sensible. But the orbits of the satellites are + concentric to Jupiter, and therefore the accelerative gravities of Jupiter + and of all its satellites towards the sun, at equal distances from the + sun, are as their several quantities of matter; and the weights of the + moon and of the earth towards the sun are either none, or accurately + proportional to the masses of matter which they contain. + </p> + <p> + "COR. 5.—The power of gravity is of a different nature from the + power of magnetism; for the magnetic attraction is not as the matter + attracted. Some bodies are attracted more by the magnet; others less; most + bodies not at all. The power of magnetism in one and the same body may be + increased and diminished; and is sometimes far stronger, for the quantity + of matter, than the power of gravity; and in receding from the magnet + decreases not in the duplicate, but almost in the triplicate proportion of + the distance, as nearly as I could judge from some rude observations. + </p> +<pre xml:space="preserve"> + "PROPOSITION VII., THEOREM VII. +</pre> + <p> + "That there is a power of gravity tending to all bodies, proportional to + the several quantities of matter which they contain. + </p> + <p> + "That all the planets mutually gravitate one towards another we have + proved before; as well as that the force of gravity towards every one of + them considered apart, is reciprocally as the square of the distance of + places from the centre of the planet. And thence it follows, that the + gravity tending towards all the planets is proportional to the matter + which they contain. + </p> + <p> + "Moreover, since all the parts of any planet A gravitates towards any + other planet B; and the gravity of every part is to the gravity of the + whole as the matter of the part is to the matter of the whole; and to + every action corresponds a reaction; therefore the planet B will, on the + other hand, gravitate towards all the parts of planet A, and its gravity + towards any one part will be to the gravity towards the whole as the + matter of the part to the matter of the whole. Q.E.D. + </p> + <p> + "HENCE IT WOULD APPEAR THAT the force of the whole must arise from the + force of the component parts." + </p> + <p> + Newton closes this remarkable Book iii. with the following words: + </p> + <p> + "Hitherto we have explained the phenomena of the heavens and of our sea by + the power of gravity, but have not yet assigned the cause of this power. + This is certain, that it must proceed from a cause that penetrates to the + very centre of the sun and planets, without suffering the least diminution + of its force; that operates not according to the quantity of the surfaces + of the particles upon which it acts (as mechanical causes used to do), but + according to the quantity of solid matter which they contain, and + propagates its virtue on all sides to immense distances, decreasing always + in the duplicate proportions of the distances. Gravitation towards the sun + is made up out of the gravitations towards the several particles of which + the body of the sun is composed; and in receding from the sun decreases + accurately in the duplicate proportion of the distances as far as the orb + of Saturn, as evidently appears from the quiescence of the aphelions of + the planets; nay, and even to the remotest aphelions of the comets, if + those aphelions are also quiescent. But hitherto I have not been able to + discover the cause of those properties of gravity from phenomena, and I + frame no hypothesis; for whatever is not deduced from the phenomena is to + be called an hypothesis; and hypotheses, whether metaphysical or physical, + whether of occult qualities or mechanical, have no place in experimental + philosophy.... And to us it is enough that gravity does really exist, and + act according to the laws which we have explained, and abundantly serves + to account for all the motions of the celestial bodies and of our sea."(2) + </p> + <p> + The very magnitude of the importance of the theory of universal + gravitation made its general acceptance a matter of considerable time + after the actual discovery. This opposition had of course been foreseen by + Newton, and, much as he dreaded controversy, he was prepared to face it + and combat it to the bitter end. He knew that his theory was right; it + remained for him to convince the world of its truth. He knew that some of + his contemporary philosophers would accept it at once; others would at + first doubt, question, and dispute, but finally accept; while still others + would doubt and dispute until the end of their days. This had been the + history of other great discoveries; and this will probably be the history + of most great discoveries for all time. But in this case the discoverer + lived to see his theory accepted by practically all the great minds of his + time. + </p> + <p> + Delambre is authority for the following estimate of Newton by Lagrange. + "The celebrated Lagrange," he says, "who frequently asserted that Newton + was the greatest genius that ever existed, used to add—'and the most + fortunate, for we cannot find MORE THAN ONCE a system of the world to + establish.'" With pardonable exaggeration the admiring followers of the + great generalizer pronounced this epitaph: + </p> +<pre xml:space="preserve"> + "Nature and Nature's laws lay hid in night; + God said 'Let Newton be!' and all was light." +</pre> + <p> + <a name="link2H_4_0015" id="link2H_4_0015"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XIII. INSTRUMENTS OF PRECISION IN THE AGE OF NEWTON + </h2> + <p> + During the Newtonian epoch there were numerous important inventions of + scientific instruments, as well as many improvements made upon the older + ones. Some of these discoveries have been referred to briefly in other + places, but their importance in promoting scientific investigation + warrants a fuller treatment of some of the more significant. + </p> + <p> + Many of the errors that had arisen in various scientific calculations + before the seventeenth century may be ascribed to the crudeness and + inaccuracy in the construction of most scientific instruments. Scientists + had not as yet learned that an approach to absolute accuracy was necessary + in every investigation in the field of science, and that such accuracy + must be extended to the construction of the instruments used in these + investigations and observations. In astronomy it is obvious that + instruments of delicate exactness are most essential; yet Tycho Brahe, who + lived in the sixteenth century, is credited with being the first + astronomer whose instruments show extreme care in construction. + </p> + <p> + It seems practically settled that the first telescope was invented in + Holland in 1608; but three men, Hans Lippershey, James Metius, and + Zacharias Jansen, have been given the credit of the invention at different + times. It would seem from certain papers, now in the library of the + University of Leyden, and included in Huygens's papers, that Lippershey + was probably the first to invent a telescope and to describe his + invention. The story is told that Lippershey, who was a spectacle-maker, + stumbled by accident upon the discovery that when two lenses are held at a + certain distance apart, objects at a distance appear nearer and larger. + Having made this discovery, he fitted two lenses with a tube so as to + maintain them at the proper distance, and thus constructed the first + telescope. + </p> + <p> + It was Galileo, however, as referred to in a preceding chapter, who first + constructed a telescope based on his knowledge of the laws of refraction. + In 1609, having heard that an instrument had been invented, consisting of + two lenses fixed in a tube, whereby objects were made to appear larger and + nearer, he set about constructing such an instrument that should follow + out the known effects of refraction. His first telescope, made of two + lenses fixed in a lead pipe, was soon followed by others of improved + types, Galileo devoting much time and labor to perfecting lenses and + correcting errors. In fact, his work in developing the instrument was so + important that the telescope came gradually to be known as the "Galilean + telescope." + </p> + <p> + In the construction of his telescope Galileo made use of a convex and a + concave lens; but shortly after this Kepler invented an instrument in + which both the lenses used were convex. This telescope gave a much larger + field of view than the Galilean telescope, but did not give as clear an + image, and in consequence did not come into general use until the middle + of the seventeenth century. The first powerful telescope of this type was + made by Huygens and his brother. It was of twelve feet focal length, and + enabled Huygens to discover a new satellite of Saturn, and to determine + also the true explanation of Saturn's ring. + </p> + <p> + It was Huygens, together with Malvasia and Auzout, who first applied the + micrometer to the telescope, although the inventor of the first micrometer + was William Gascoigne, of Yorkshire, about 1636. The micrometer as used in + telescopes enables the observer to measure accurately small angular + distances. Before the invention of the telescope such measurements were + limited to the angle that could be distinguished by the naked eye, and + were, of course, only approximately accurate. Even very careful observers, + such as Tycho Brahe, were able to obtain only fairly accurate results. But + by applying Gascoigne's invention to the telescope almost absolute + accuracy became at once possible. The principle of Gascoigne's micrometer + was that of two pointers lying parallel, and in this position pointing to + zero. These were arranged so that the turning of a single screw separated + or approximated them at will, and the angle thus formed could be + determined with absolute accuracy. + </p> + <p> + Huygens's micrometer was a slip of metal of variable breadth inserted at + the focus of the telescope. By observing at what point this exactly + covered an object under examination, and knowing the focal length of the + telescope and the width of the metal, he could then deduce the apparent + angular breadth of the object. Huygens discovered also that an object + placed in the common focus of the two lenses of a Kepler telescope appears + distinct and clearly defined. The micrometers of Malvasia, and later of + Auzout and Picard, are the development of this discovery. Malvasia's + micrometer, which he described in 1662, consisted of fine silver wires + placed at right-angles at the focus of his telescope. + </p> + <p> + As telescopes increased in power, however, it was found that even the + finest wire, or silk filaments, were much too thick for astronomical + observations, as they obliterated the image, and so, finally, the + spider-web came into use and is still used in micrometers and other + similar instruments. Before that time, however, the fine crossed wires had + revolutionized astronomical observations. "We may judge how great was the + improvement which these contrivances introduced into the art of + observing," says Whewell, "by finding that Hevelius refused to adopt them + because they would make all the old observations of no value. He had spent + a laborious and active life in the exercise of the old methods, and could + not bear to think that all the treasures which he had accumulated had lost + their worth by the discovery of a new mine of richer ones."(1) + </p> + <p> + Until the time of Newton, all the telescopes in use were either of the + Galilean or Keplerian type, that is, refractors. But about the year 1670 + Newton constructed his first reflecting telescope, which was greatly + superior to, although much smaller than, the telescopes then in use. He + was led to this invention by his experiments with light and colors. In + 1671 he presented to the Royal Society a second and somewhat larger + telescope, which he had made; and this type of instrument was little + improved upon until the introduction of the achromatic telescope, invented + by Chester Moor Hall in 1733. + </p> + <p> + As is generally known, the element of accurate measurements of time plays + an important part in the measurements of the movements of the heavenly + bodies. In fact, one was scarcely possible without the other, and as it + happened it was the same man, Huygens, who perfected Kepler's telescope + and invented the pendulum clock. The general idea had been suggested by + Galileo; or, better perhaps, the equal time occupied by the successive + oscillations of the pendulum had been noted by him. He had not been able, + however, to put this discovery to practical account. But in 1656 Huygens + invented the necessary machinery for maintaining the motion of the + pendulum and perfected several accurate clocks. These clocks were of + invaluable assistance to the astronomers, affording as they did a means of + keeping time "more accurate than the sun itself." When Picard had + corrected the variation caused by heat and cold acting upon the pendulum + rod by combining metals of different degrees of expansibility, a high + degree of accuracy was possible. + </p> + <p> + But while the pendulum clock was an unequalled stationary time-piece, it + was useless in such unstable situations as, for example, on shipboard. But + here again Huygens played a prominent part by first applying the coiled + balance-spring for regulating watches and marine clocks. The idea of + applying a spring to the balance-wheel was not original with Huygens, + however, as it had been first conceived by Robert Hooke; but Huygens's + application made practical Hooke's idea. In England the importance of + securing accurate watches or marine clocks was so fully appreciated that a + reward of L20,000 sterling was offered by Parliament as a stimulus to the + inventor of such a time-piece. The immediate incentive for this offer was + the obvious fact that with such an instrument the determination of the + longitude of places would be much simplified. Encouraged by these offers, + a certain carpenter named Harrison turned his attention to the subject of + watch-making, and, after many years of labor, in 1758 produced a spring + time-keeper which, during a sea-voyage occupying one hundred and sixty-one + days, varied only one minute and five seconds. This gained for Harrison a + reward Of L5000 sterling at once, and a little later L10,000 more, from + Parliament. + </p> + <p> + While inventors were busy with the problem of accurate chronometers, + however, another instrument for taking longitude at sea had been invented. + This was the reflecting quadrant, or sextant, as the improved instrument + is now called, invented by John Hadley in 1731, and independently by + Thomas Godfrey, a poor glazier of Philadelphia, in 1730. Godfrey's + invention, which was constructed on the same principle as that of the + Hadley instrument, was not generally recognized until two years after + Hadley's discovery, although the instrument was finished and actually in + use on a sea-voyage some months before Hadley reported his invention. The + principle of the sextant, however, seems to have been known to Newton, who + constructed an instrument not very unlike that of Hadley; but this + invention was lost sight of until several years after the philosopher's + death and some time after Hadley's invention. + </p> + <p> + The introduction of the sextant greatly simplified taking reckonings at + sea as well as facilitating taking the correct longitude of distant + places. Before that time the mariner was obliged to depend upon his + compass, a cross-staff, or an astrolabe, a table of the sun's declination + and a correction for the altitude of the polestar, and very inadequate and + incorrect charts. Such were the instruments used by Columbus and Vasco da + Gama and their immediate successors. + </p> + <p> + During the Newtonian period the microscopes generally in use were those + constructed of simple lenses, for although compound microscopes were + known, the difficulties of correcting aberration had not been surmounted, + and a much clearer field was given by the simple instrument. The results + obtained by the use of such instruments, however, were very satisfactory + in many ways. By referring to certain plates in this volume, which + reproduce illustrations from Robert Hooke's work on the microscope, it + will be seen that quite a high degree of effectiveness had been attained. + And it should be recalled that Antony von Leeuwenhoek, whose death took + place shortly before Newton's, had discovered such micro-organisms as + bacteria, had seen the blood corpuscles in circulation, and examined and + described other microscopic structures of the body. + </p> + <p> + <a name="link2H_4_0016" id="link2H_4_0016"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO FRANKLIN + </h2> + <p> + We have seen how Gilbert, by his experiments with magnets, gave an impetus + to the study of magnetism and electricity. Gilbert himself demonstrated + some facts and advanced some theories, but the system of general laws was + to come later. To this end the discovery of electrical repulsion, as well + as attraction, by Von Guericke, with his sulphur ball, was a step forward; + but something like a century passed after Gilbert's beginning before + anything of much importance was done in the field of electricity. + </p> + <p> + In 1705, however, Francis Hauksbee began a series of experiments that + resulted in some startling demonstrations. For many years it had been + observed that a peculiar light was seen sometimes in the mercurial + barometer, but Hauksbee and the other scientific investigators supposed + the radiance to be due to the mercury in a vacuum, brought about, perhaps, + by some agitation. That this light might have any connection with + electricity did not, at first, occur to Hauksbee any more than it had to + his predecessors. The problem that interested him was whether the vacuum + in the tube of the barometer was essential to the light; and in + experimenting to determine this, he invented his "mercurial fountain." + Having exhausted the air in a receiver containing some mercury, he found + that by allowing air to rush through the mercury the metal became a jet + thrown in all directions against the sides of the vessel, making a great, + flaming shower, "like flashes of lightning," as he said. But it seemed to + him that there was a difference between this light and the glow noted in + the barometer. This was a bright light, whereas the barometer light was + only a glow. Pondering over this, Hauksbee tried various experiments, + revolving pieces of amber, flint, steel, and other substances in his + exhausted air-pump receiver, with negative, or unsatisfactory, results. + Finally, it occurred to him to revolve an exhausted glass tube itself. + Mounting such a globe of glass on an axis so that it could be revolved + rapidly by a belt running on a large wheel, he found that by holding his + fingers against the whirling globe a purplish glow appeared, giving + sufficient light so that coarse print could be read, and the walls of a + dark room sensibly lightened several feet away. As air was admitted to the + globe the light gradually diminished, and it seemed to him that this + diminished glow was very similar in appearance to the pale light seen in + the mercurial barometer. Could it be that it was the glass, and not the + mercury, that caused it? Going to a barometer he proceeded to rub the + glass above the column of mercury over the vacuum, without disturbing the + mercury, when, to his astonishment, the same faint light, to all + appearances identical with the glow seen in the whirling globe, was + produced. + </p> + <p> + Turning these demonstrations over in his mind, he recalled the well-known + fact that rubbed glass attracted bits of paper, leaf-brass, and other + light substances, and that this phenomenon was supposed to be electrical. + This led him finally to determine the hitherto unsuspected fact, that the + glow in the barometer was electrical as was also the glow seen in his + whirling globe. Continuing his investigations, he soon discovered that + solid glass rods when rubbed produced the same effects as the tube. By + mere chance, happening to hold a rubbed tube to his cheek, he felt the + effect of electricity upon the skin like "a number of fine, limber hairs," + and this suggested to him that, since the mysterious manifestation was so + plain, it could be made to show its effects upon various substances. + Suspending some woollen threads over the whirling glass cylinder, he found + that as soon as he touched the glass with his hands the threads, which + were waved about by the wind of the revolution, suddenly straightened + themselves in a peculiar manner, and stood in a radical position, pointing + to the axis of the cylinder. + </p> + <p> + Encouraged by these successes, he continued his experiments with + breathless expectancy, and soon made another important discovery, that of + "induction," although the real significance of this discovery was not + appreciated by him or, for that matter, by any one else for several + generations following. This discovery was made by placing two revolving + cylinders within an inch of each other, one with the air exhausted and the + other unexhausted. Placing his hand on the unexhausted tube caused the + light to appear not only upon it, but on the other tube as well. A little + later he discovered that it is not necessary to whirl the exhausted tube + to produce this effect, but simply to place it in close proximity to the + other whirling cylinder. + </p> + <p> + These demonstrations of Hauksbee attracted wide attention and gave an + impetus to investigators in the field of electricity; but still no great + advance was made for something like a quarter of a century. Possibly the + energies of the scientists were exhausted for the moment in exploring the + new fields thrown open to investigation by the colossal work of Newton. + </p> + <p> + THE EXPERIMENTS OF STEPHEN GRAY + </p> + <p> + In 1729 Stephen Gray (died in 1736), an eccentric and irascible old + pensioner of the Charter House in London, undertook some investigations + along lines similar to those of Hauksbee. While experimenting with a glass + tube for producing electricity, as Hauksbee had done, he noticed that the + corks with which he had stopped the ends of the tube to exclude the dust, + seemed to attract bits of paper and leaf-brass as well as the glass + itself. He surmised at once that this mysterious electricity, or "virtue," + as it was called, might be transmitted through other substances as it + seemed to be through glass. + </p> + <p> + "Having by me an ivory ball of about one and three-tenths of an inch in + diameter," he writes, "with a hole through it, this I fixed upon a + fir-stick about four inches long, thrusting the other end into the cork, + and upon rubbing the tube found that the ball attracted and repelled the + feather with more vigor than the cork had done, repeating its attractions + and repulsions for many times together. I then fixed the ball on longer + sticks, first upon one of eight inches, and afterwards upon one of + twenty-four inches long, and found the effect the same. Then I made use of + iron, and then brass wire, to fix the ball on, inserting the other end of + the wire in the cork, as before, and found that the attraction was the + same as when the fir-sticks were made use of, and that when the feather + was held over against any part of the wire it was attracted by it; but + though it was then nearer the tube, yet its attraction was not so strong + as that of the ball. When the wire of two or three feet long was used, its + vibrations, caused by the rubbing of the tube, made it somewhat + troublesome to be managed. This put me to thinking whether, if the ball + was hung by a pack-thread and suspended by a loop on the tube, the + electricity would not be carried down the line to the ball; I found it to + succeed accordingly; for upon suspending the ball on the tube by a + pack-thread about three feet long, when the tube had been excited by + rubbing, the ivory ball attracted and repelled the leaf-brass over which + it was held as freely as it had done when it was suspended on sticks or + wire, as did also a ball of cork, and another of lead that weighed one + pound and a quarter." + </p> + <p> + Gray next attempted to determine what other bodies would attract the bits + of paper, and for this purpose he tried coins, pieces of metal, and even a + tea-kettle, "both empty and filled with hot or cold water"; but he found + that the attractive power appeared to be the same regardless of the + substance used. + </p> + <p> + "I next proceeded," he continues, "to try at what greater distances the + electric virtues might be carried, and having by me a hollow walking-cane, + which I suppose was part of a fishing-rod, two feet seven inches long, I + cut the great end of it to fit into the bore of the tube, into which it + went about five inches; then when the cane was put into the end of the + tube, and this excited, the cane drew the leaf-brass to the height of more + than two inches, as did also the ivory ball, when by a cork and stick it + had been fixed to the end of the cane.... With several pieces of Spanish + cane and fir-sticks I afterwards made a rod, which, together with the + tube, was somewhat more than eighteen feet long, which was the greatest + length I could conveniently use in my chamber, and found the attraction + very nearly, if not altogether, as strong as when the ball was placed on + the shorter rods." + </p> + <p> + This experiment exhausted the capacity of his small room, but on going to + the country a little later he was able to continue his experiments. "To a + pole of eighteen feet there was tied a line of thirty-four feet in length, + so that the pole and line together were fifty-two feet. With the pole and + tube I stood in the balcony, the assistant below in the court, where he + held the board with the leaf-brass on it. Then the tube being excited, as + usual, the electric virtue passed from the tube up the pole and down the + line to the ivory ball, which attracted the leaf-brass, and as the ball + passed over it in its vibrations the leaf-brass would follow it till it + was carried off the board." + </p> + <p> + Gray next attempted to send the electricity over a line suspended + horizontally. To do this he suspended the pack-thread by pieces of string + looped over nails driven into beams for that purpose. But when thus + suspended he found that the ivory ball no longer excited the leaf-brass, + and he guessed correctly that the explanation of this lay in the fact that + "when the electric virtue came to the loop that was suspended on the beam + it went up the same to the beam," none of it reaching the ball. As we + shall see from what follows, however, Gray had not as yet determined that + certain substances will conduct electricity while others will not. But by + a lucky accident he made the discovery that silk, for example, was a poor + conductor, and could be turned to account in insulating the + conducting-cord. + </p> + <p> + A certain Mr. Wheler had become much interested in the old pensioner and + his work, and, as a guest at the Wheler house, Gray had been repeating + some of his former experiments with the fishing-rod, line, and ivory ball. + He had finally exhausted the heights from which these experiments could be + made by climbing to the clock-tower and exciting bits of leaf-brass on the + ground below. + </p> + <p> + "As we had no greater heights here," he says, "Mr. Wheler was desirous to + try whether we could not carry the electric virtue horizontally. I then + told him of the attempt I had made with that design, but without success, + telling him the method and materials made use of, as mentioned above. He + then proposed a silk line to support the line by which the electric virtue + was to pass. I told him it might do better upon account of its smallness; + so that there would be less virtue carried from the line of communication. + </p> + <p> + "The first experiment was made in the matted gallery, July 2, 1729, about + ten in the morning. About four feet from the end of the gallery there was + a cross line that was fixed by its ends to each side of the gallery by two + nails; the middle part of the line was silk, the rest at each end + pack-thread; then the line to which the ivory ball was hung and by which + the electric virtue was to be conveyed to it from the tube, being eighty + and one-half feet in length, was laid on the cross silk line, so that the + ball hung about nine feet below it. Then the other end of the line was by + a loop suspended on the glass cane, and the leaf-brass held under the ball + on a piece of white paper; when, the tube being rubbed, the ball attracted + the leaf-brass, and kept it suspended on it for some time." + </p> + <p> + This experiment succeeded so well that the string was lengthened until it + was some two hundred and ninety-three feet long; and still the attractive + force continued, apparently as strong as ever. On lengthening the string + still more, however, the extra weight proved too much for the strength of + the silk suspending-thread. "Upon this," says Gray, "having brought with + me both brass and iron wire, instead of the silk we put up small iron + wire; but this was too weak to bear the weight of the line. We then took + brass wire of a somewhat larger size than that of iron. This supported our + line of communication; but though the tube was well rubbed, yet there was + not the least motion or attraction given by the ball, neither with the + great tube, which we made use of when we found the small solid cane to be + ineffectual; by which we were now convinced that the success we had before + depended upon the lines that supported the line of communication being + silk, and not upon their being small, as before trial I had imagined it + might be; the same effect happening here as it did when the line that is + to convey the electric virtue is supported by pack-thread." + </p> + <p> + Soon after this Gray and his host suspended a pack-thread six hundred and + sixty-six feet long on poles across a field, these poles being slightly + inclined so that the thread could be suspended from the top by small silk + cords, thus securing the necessary insulation. This pack-thread line, + suspended upon poles along which Gray was able to transmit the + electricity, is very suggestive of the modern telegraph, but the idea of + signalling or making use of it for communicating in any way seems not to + have occurred to any one at that time. Even the successors of Gray who + constructed lines some thousands of feet long made no attempt to use them + for anything but experimental purposes—simply to test the distances + that the current could be sent. Nevertheless, Gray should probably be + credited with the discovery of two of the most important properties of + electricity—that it can be conducted and insulated, although, as we + have seen, Gilbert and Von Guericke had an inkling of both these + properties. + </p> + <p> + EXPERIMENTS OF CISTERNAY DUFAY + </p> + <p> + So far England had produced the two foremost workers in electricity. It + was now France's turn to take a hand, and, through the efforts of Charles + Francois de Cisternay Dufay, to advance the science of electricity very + materially. Dufay was a highly educated savant, who had been soldier and + diplomat betimes, but whose versatility and ability as a scientist is + shown by the fact that he was the only man who had ever contributed to the + annals of the academy investigations in every one of the six subjects + admitted by that institution as worthy of recognition. Dufay upheld his + reputation in this new field of science, making many discoveries and + correcting many mistakes of former observers. In this work also he proved + himself a great diplomat by remaining on terms of intimate friendship with + Dr. Gray—a thing that few people were able to do. + </p> + <p> + Almost his first step was to overthrow the belief that certain bodies are + "electrics" and others "non-electrics"—that is, that some substances + when rubbed show certain peculiarities in attracting pieces of paper and + foil which others do not. Dufay proved that all bodies possess this + quality in a certain degree. + </p> + <p> + "I have found that all bodies (metallic, soft, or fluid ones excepted)," + he says, "may be made electric by first heating them more or less and then + rubbing them on any sort of cloth. So that all kinds of stones, as well + precious as common, all kinds of wood, and, in general, everything that I + have made trial of, became electric by beating and rubbing, except such + bodies as grow soft by beat, as the gums, which dissolve in water, glue, + and such like substances. 'Tis also to be remarked that the hardest stones + or marbles require more chafing or heating than others, and that the same + rule obtains with regard to the woods; so that box, lignum vitae, and such + others must be chafed almost to the degree of browning, whereas fir, + lime-tree, and cork require but a moderate heat. + </p> + <p> + "Having read in one of Mr. Gray's letters that water may be made + electrical by holding the excited glass tube near it (a dish of water + being fixed to a stand and that set on a plate of glass, or on the brim of + a drinking-glass, previously chafed, or otherwise warmed), I have found, + upon trial, that the same thing happened to all bodies without exception, + whether solid or fluid, and that for that purpose 'twas sufficient to set + them on a glass stand slightly warmed, or only dried, and then by bringing + the tube near them they immediately became electrical. I made this + experiment with ice, with a lighted wood-coal, and with everything that + came into my mind; and I constantly remarked that such bodies of + themselves as were least electrical had the greatest degree of electricity + communicated to them at the approval of the glass tube." + </p> + <p> + His next important discovery was that colors had nothing to do with the + conduction of electricity. "Mr. Gray says, towards the end of one of his + letters," he writes, "that bodies attract more or less according to their + colors. This led me to make several very singular experiments. I took nine + silk ribbons of equal size, one white, one black, and the other seven of + the seven primitive colors, and having hung them all in order in the same + line, and then bringing the tube near them, the black one was first + attracted, the white one next, and others in order successively to the red + one, which was attracted least, and the last of them all. I afterwards cut + out nine square pieces of gauze of the same colors with the ribbons, and + having put them one after another on a hoop of wood, with leaf-gold under + them, the leaf-gold was attracted through all the colored pieces of gauze, + but not through the white or black. This inclined me first to think that + colors contribute much to electricity, but three experiments convinced me + to the contrary. The first, that by warming the pieces of gauze neither + the black nor white pieces obstructed the action of the electrical tube + more than those of the other colors. In like manner, the ribbons being + warmed, the black and white are not more strongly attracted than the rest. + The second is, the gauzes and ribbons being wetted, the ribbons are all + attracted equally, and all the pieces of gauze equally intercept the + action of electric bodies. The third is, that the colors of a prism being + thrown on a white gauze, there appear no differences of attraction. Whence + it proceeds that this difference proceeds, not from the color, as a color, + but from the substances that are employed in the dyeing. For when I + colored ribbons by rubbing them with charcoal, carmine, and such other + substances, the differences no longer proved the same." + </p> + <p> + In connection with his experiments with his thread suspended on glass + poles, Dufay noted that a certain amount of the current is lost, being + given off to the surrounding air. He recommended, therefore, that the + cords experimented with be wrapped with some non-conductor—that it + should be "insulated" ("isolee"), as he said, first making use of this + term. + </p> + <p> + DUFAY DISCOVERS VITREOUS AND RESINOUS ELECTRICITY + </p> + <p> + It has been shown in an earlier chapter how Von Guericke discovered that + light substances like feathers, after being attracted to the sulphur-ball + electric-machine, were repelled by it until they touched some object. Von + Guericke noted this, but failed to explain it satisfactorily. Dufay, + repeating Von Guericke's experiments, found that if, while the excited + tube or sulphur ball is driving the repelled feather before it, the ball + be touched or rubbed anew, the feather comes to it again, and is repelled + alternately, as, the hand touches the ball, or is withdrawn. From this he + concluded that electrified bodies first attract bodies not electrified, + "charge" them with electricity, and then repel them, the body so charged + not being attracted again until it has discharged its electricity by + touching something. + </p> + <p> + "On making the experiment related by Otto von Guericke," he says, "which + consists in making a ball of sulphur rendered electrical to repel a down + feather, I perceived that the same effects were produced not only by the + tube, but by all electric bodies whatsoever, and I discovered that which + accounts for a great part of the irregularities and, if I may use the + term, of the caprices that seem to accompany most of the experiments on + electricity. This principle is that electric bodies attract all that are + not so, and repel them as soon as they are become electric by the vicinity + or contact of the electric body. Thus gold-leaf is first attracted by the + tube, and acquires an electricity by approaching it, and of consequence is + immediately repelled by it. Nor is it reattracted while it retains its + electric quality. But if while it is thus sustained in the air it chance + to light on some other body, it straightway loses its electricity, and in + consequence is reattracted by the tube, which, after having given it a new + electricity, repels it a second time, which continues as long as the tube + keeps its electricity. Upon applying this principle to the various + experiments of electricity, one will be surprised at the number of obscure + and puzzling facts that it clears up. For Mr. Hauksbee's famous experiment + of the glass globe, in which silk threads are put, is a necessary + consequence of it. When these threads are arranged in the form of rays by + the electricity of the sides of the globe, if the finger be put near the + outside of the globe the silk threads within fly from it, as is well + known, which happens only because the finger or any other body applied + near the glass globe is thereby rendered electrical, and consequently + repels the silk threads which are endowed with the same quality. With a + little reflection we may in the same manner account for most of the other + phenomena, and which seem inexplicable without attending to this + principle. + </p> + <p> + "Chance has thrown in my way another principle, more universal and + remarkable than the preceding one, and which throws a new light on the + subject of electricity. This principle is that there are two distinct + electricities, very different from each other, one of which I call + vitreous electricity and the other resinous electricity. The first is that + of glass, rock-crystal, precious stones, hair of animals, wool, and many + other bodies. The second is that of amber, copal, gumsack, silk thread, + paper, and a number of other substances. The characteristic of these two + electricities is that a body of the vitreous electricity, for example, + repels all such as are of the same electricity, and on the contrary + attracts all those of the resinous electricity; so that the tube, made + electrical, will repel glass, crystal, hair of animals, etc., when + rendered electric, and will attract silk thread, paper, etc., though + rendered electrical likewise. Amber, on the contrary, will attract + electric glass and other substances of the same class, and will repel + gum-sack, copal, silk thread, etc. Two silk ribbons rendered electrical + will repel each other; two woollen threads will do the like; but a woollen + thread and a silken thread will mutually attract each other. This + principle very naturally explains why the ends of threads of silk or wool + recede from each other, in the form of pencil or broom, when they have + acquired an electric quality. From this principle one may with the same + ease deduce the explanation of a great number of other phenomena; and it + is probable that this truth will lead us to the further discovery of many + other things. + </p> + <p> + "In order to know immediately to which of the two classes of electrics + belongs any body whatsoever, one need only render electric a silk thread, + which is known to be of the resinuous electricity, and see whether that + body, rendered electrical, attracts or repels it. If it attracts it, it is + certainly of the kind of electricity which I call VITREOUS; if, on the + contrary, it repels it, it is of the same kind of electricity with the + silk—that is, of the RESINOUS. I have likewise observed that + communicated electricity retains the same properties; for if a ball of + ivory or wood be set on a glass stand, and this ball be rendered electric + by the tube, it will repel such substances as the tube repels; but if it + be rendered electric by applying a cylinder of gum-sack near it, it will + produce quite contrary effects—namely, precisely the same as + gum-sack would produce. In order to succeed in these experiments, it is + requisite that the two bodies which are put near each other, to find out + the nature of their electricity, be rendered as electrical as possible, + for if one of them was not at all or but weakly electrical, it would be + attracted by the other, though it be of that sort that should naturally be + repelled by it. But the experiment will always succeed perfectly well if + both bodies are sufficiently electrical."(1) + </p> + <p> + As we now know, Dufay was wrong in supposing that there were two different + kinds of electricity, vitreous and resinous. A little later the matter was + explained by calling one "positive" electricity and the other "negative," + and it was believed that certain substances produced only the one kind + peculiar to that particular substance. We shall see presently, however, + that some twenty years later an English scientist dispelled this illusion + by producing both positive (or vitreous) and negative (or resinous) + electricity on the same tube of glass at the same time. + </p> + <p> + After the death of Dufay his work was continued by his fellow-countryman + Dr. Joseph Desaguliers, who was the first experimenter to electrify + running water, and who was probably the first to suggest that clouds might + be electrified bodies. But about, this time—that is, just before the + middle of the eighteenth century—the field of greatest experimental + activity was transferred to Germany, although both England and France were + still active. The two German philosophers who accomplished most at this + time were Christian August Hansen and George Matthias Bose, both + professors in Leipsic. Both seem to have conceived the idea, + simultaneously and independently, of generating electricity by revolving + globes run by belt and wheel in much the same manner as the apparatus of + Hauksbee. + </p> + <p> + With such machines it was possible to generate a much greater amount of + electricity than Dufay had been able to do with the rubbed tube, and so + equipped, the two German professors were able to generate electric sparks + and jets of fire in a most startling manner. Bose in particular had a love + for the spectacular, which he turned to account with his new electrical + machine upon many occasions. On one of these occasions he prepared an + elaborate dinner, to which a large number of distinguished guests were + invited. Before the arrival of the company, however, Bose insulated the + great banquet-table on cakes of pitch, and then connected it with a huge + electrical machine concealed in another room. All being ready, and the + guests in their places about to be seated, Bose gave a secret signal for + starting this machine, when, to the astonishment of the party, flames of + fire shot from flowers, dishes, and viands, giving a most startling but + beautiful display. + </p> + <p> + To add still further to the astonishment of his guests, Bose then + presented a beautiful young lady, to whom each of the young men of the + party was introduced. In some mysterious manner she was insulated and + connected with the concealed electrical machine, so that as each gallant + touched her fingertips he received an electric shock that "made him reel." + Not content with this, the host invited the young men to kiss the + beautiful maid. But those who were bold enough to attempt it received an + electric shock that nearly "knocked their teeth out," as the professor + tells it. + </p> + <p> + LUDOLFF'S EXPERIMENT WITH THE ELECTRIC SPARK + </p> + <p> + But Bose was only one of several German scientists who were making + elaborate experiments. While Bose was constructing and experimenting with + his huge machine, another German, Christian Friedrich Ludolff, + demonstrated that electric sparks are actual fire—a fact long + suspected but hitherto unproved. Ludolff's discovery, as it chanced, was + made in the lecture-hall of the reorganized Academy of Sciences at Berlin, + before an audience of scientists and great personages, at the opening + lecture in 1744. + </p> + <p> + In the course of this lecture on electricity, during which some of the + well-known manifestations of electricity were being shown, it occurred to + Ludolff to attempt to ignite some inflammable fluid by projecting an + electric spark upon its surface with a glass rod. This idea was suggested + to him while performing the familiar experiment of producing a spark on + the surface of a bowl of water by touching it with a charged glass rod. He + announced to his audience the experiment he was about to attempt, and + having warmed a spoonful of sulphuric ether, he touched its surface with + the glass rod, causing it to burst into flame. This experiment left no + room for doubt that the electric spark was actual fire. + </p> + <p> + As soon as this experiment of Ludolff's was made known to Bose, he + immediately claimed that he had previously made similar demonstrations on + various inflammable substances, both liquid and solid; and it seems highly + probable that he had done so, as he was constantly experimenting with the + sparks, and must almost certainly have set certain substances ablaze by + accident, if not by intent. At all events, he carried on a series of + experiments along this line to good purpose, finally succeeding in + exploding gun-powder, and so making the first forerunner of the electric + fuses now so universally used in blasting, firing cannon, and other + similar purposes. It was Bose also who, observing some of the peculiar + manifestations in electrified tubes, and noticing their resemblance to + "northern lights," was one of the first, if not the first, to suggest that + the aurora borealis is of electric origin. + </p> + <p> + These spectacular demonstrations had the effect of calling public + attention to the fact that electricity is a most wonderful and mysterious + thing, to say the least, and kept both scientists and laymen agog with + expectancy. Bose himself was aflame with excitement, and so determined in + his efforts to produce still stronger electric currents, that he + sacrificed the tube of his twenty-foot telescope for the construction of a + mammoth electrical machine. With this great machine a discharge of + electricity was generated powerful enough to wound the skin when it + happened to strike it. + </p> + <p> + Until this time electricity had been little more than a plaything of the + scientists—or, at least, no practical use had been made of it. As it + was a practising physician, Gilbert, who first laid the foundation for + experimenting with the new substance, so again it was a medical man who + first attempted to put it to practical use, and that in the field of his + profession. Gottlieb Kruger, a professor of medicine at Halle in 1743, + suggested that electricity might be of use in some branches of medicine; + and the year following Christian Gottlieb Kratzenstein made a first + experiment to determine the effects of electricity upon the body. He found + that "the action of the heart was accelerated, the circulation increased, + and that muscles were made to contract by the discharge": and he began at + once administering electricity in the treatment of certain diseases. He + found that it acted beneficially in rheumatic affections, and that it was + particularly useful in certain nervous diseases, such as palsies. This was + over a century ago, and to-day about the most important use made of the + particular kind of electricity with which he experimented (the static, or + frictional) is for the treatment of diseases affecting the nervous system. + </p> + <p> + By the middle of the century a perfect mania for making electrical + machines had spread over Europe, and the whirling, hand-rubbed globes were + gradually replaced by great cylinders rubbed by woollen cloths or pads, + and generating an "enormous power of electricity." These cylinders were + run by belts and foot-treadles, and gave a more powerful, constant, and + satisfactory current than known heretofore. While making experiments with + one of these machines, Johann Heinrichs Winkler attempted to measure the + speed at which electricity travels. To do this he extended a cord + suspended on silk threads, with the end attached to the machine and the + end which was to attract the bits of gold-leaf near enough together so + that the operator could watch and measure the interval of time that + elapsed between the starting of the current along the cord and its + attracting the gold-leaf. The length of the cord used in this experiment + was only a little over a hundred feet, and this was, of course, entirely + inadequate, the current travelling that space apparently instantaneously. + </p> + <p> + The improved method of generating electricity that had come into general + use made several of the scientists again turn their attention more + particularly to attempt putting it to some practical account. They were + stimulated to these efforts by the constant reproaches that were beginning + to be heard on all sides that electricity was merely a "philosopher's + plaything." One of the first to succeed in inventing something that + approached a practical mechanical contrivance was Andrew Gordon, a Scotch + Benedictine monk. He invented an electric bell which would ring + automatically, and a little "motor," if it may be so called. And while + neither of these inventions were of any practical importance in + themselves, they were attempts in the right direction, and were the first + ancestors of modern electric bells and motors, although the principle upon + which they worked was entirely different from modern electrical machines. + The motor was simply a wheel with several protruding metal points around + its rim. These points were arranged to receive an electrical discharge + from a frictional machine, the discharge causing the wheel to rotate. + There was very little force given to this rotation, however, not enough, + in fact, to make it possible to more than barely turn the wheel itself. + Two more great discoveries, galvanism and electro-magnetic induction, were + necessary before the practical motor became possible. + </p> + <p> + The sober Gordon had a taste for the spectacular almost equal to that of + Bose. It was he who ignited a bowl of alcohol by turning a stream of + electrified water upon it, thus presenting the seeming paradox of fire + produced by a stream of water. Gordon also demonstrated the power of the + electrical discharge by killing small birds and animals at a distance of + two hundred ells, the electricity being conveyed that distance through + small wires. + </p> + <p> + THE LEYDEN JAR DISCOVERED + </p> + <p> + As yet no one had discovered that electricity could be stored, or + generated in any way other than by some friction device. But very soon two + experimenters, Dean von Kleist, of Camin, Pomerania, and Pieter van + Musschenbroek, the famous teacher of Leyden, apparently independently, + made the discovery of what has been known ever since as the Leyden jar. + And although Musschenbroek is sometimes credited with being the + discoverer, there can be no doubt that Von Kleist's discovery antedated + his by a few months at least. + </p> + <p> + Von Kleist found that by a device made of a narrow-necked bottle + containing alcohol or mercury, into which an iron nail was inserted, he + was able to retain the charge of electricity, after electrifying this + apparatus with the frictional machine. He made also a similar device, more + closely resembling the modern Leyden jar, from a thermometer tube partly + filled with water and a wire tipped with a ball of lead. With these + devices he found that he could retain the charge of electricity for + several hours, and could produce the usual electrical manifestations, even + to igniting spirits, quite as well as with the frictional machine. These + experiments were first made in October, 1745, and after a month of further + experimenting, Von Kleist sent the following account of them to several of + the leading scientists, among others, Dr. Lieberkuhn, in Berlin, and Dr. + Kruger, of Halle. + </p> + <p> + "When a nail, or a piece of thick brass wire, is put into a small + apothecary's phial and electrified, remarkable effects follow; but the + phial must be very dry, or warm. I commonly rub it over beforehand with a + finger on which I put some pounded chalk. If a little mercury or a few + drops of spirit of wine be put into it, the experiment succeeds better. As + soon as this phial and nail are removed from the electrifying-glass, or + the prime conductor, to which it has been exposed, is taken away, it + throws out a pencil of flame so long that, with this burning machine in my + hand, I have taken above sixty steps in walking about my room. When it is + electrified strongly, I can take it into another room and there fire + spirits of wine with it. If while it is electrifying I put my finger, or a + piece of gold which I hold in my hand, to the nail, I receive a shock + which stuns my arms and shoulders. + </p> + <p> + "A tin tube, or a man, placed upon electrics, is electrified much stronger + by this means than in the common way. When I present this phial and nail + to a tin tube, which I have, fifteen feet long, nothing but experience can + make a person believe how strongly it is electrified. I am persuaded," he + adds, "that in this manner Mr. Bose would not have taken a second + electrical kiss. Two thin glasses have been broken by the shock of it. It + appears to me very extraordinary, that when this phial and nail are in + contact with either conducting or non-conducting matter, the strong shock + does not follow. I have cemented it to wood, metal, glass, sealing-wax, + etc., when I have electrified without any great effect. The human body, + therefore, must contribute something to it. This opinion is confirmed by + my observing that unless I hold the phial in my hand I cannot fire spirits + of wine with it."(2) + </p> + <p> + But it seems that none of the men who saw this account were able to repeat + the experiment and produce the effects claimed by Von Kleist, and probably + for this reason the discovery of the obscure Pomeranian was for a time + lost sight of. + </p> + <p> + Musschenbroek's discovery was made within a short time after Von Kleist's—in + fact, only a matter of about two months later. But the difference in the + reputations of the two discoverers insured a very different reception for + their discoveries. Musschenbroek was one of the foremost teachers of + Europe, and so widely known that the great universities vied with each + other, and kings were bidding, for his services. Naturally, any discovery + made by such a famous person would soon be heralded from one end of Europe + to the other. And so when this professor of Leyden made his discovery, the + apparatus came to be called the "Leyden jar," for want of a better name. + There can be little doubt that Musschenbroek made his discovery entirely + independently of any knowledge of Von Kleist's, or, for that matter, + without ever having heard of the Pomeranian, and his actions in the matter + are entirely honorable. + </p> + <p> + His discovery was the result of an accident. While experimenting to + determine the strength of electricity he suspended a gun-barrel, which he + charged with electricity from a revolving glass globe. From the end of the + gun-barrel opposite the globe was a brass wire, which extended into a + glass jar partly filled with water. Musschenbroek held in one hand this + jar, while with the other he attempted to draw sparks from the barrel. + Suddenly he received a shock in the hand holding the jar, that "shook him + like a stroke of lightning," and for a moment made him believe that "he + was done for." Continuing his experiments, nevertheless, he found that if + the jar were placed on a piece of metal on the table, a shock would be + received by touching this piece of metal with one hand and touching the + wire with the other—that is, a path was made for the electrical + discharge through the body. This was practically the same experiment as + made by Von Kleist with his bottle and nail, but carried one step farther, + as it showed that the "jar" need not necessarily be held in the hand, as + believed by Von Kleist. Further experiments, continued by many + philosophers at the time, revealed what Von Kleist had already pointed + out, that the electrified jar remained charged for some time. + </p> + <p> + Soon after this Daniel Gralath, wishing to obtain stronger discharges than + could be had from a single Leyden jar, conceived the idea of combining + several jars, thus for the first time grouping the generators in a + "battery" which produced a discharge strong enough to kill birds and small + animals. He also attempted to measure the strength of the discharges, but + soon gave it up in despair, and the solution of this problem was left for + late nineteenth-century scientists. + </p> + <p> + The advent of the Leyden jar, which made it possible to produce strong + electrical discharges from a small and comparatively simple device, was + followed by more spectacular demonstrations of various kinds all over + Europe. These exhibitions aroused the interest of the kings and noblemen, + so that electricity no longer remained a "plaything of the philosophers" + alone, but of kings as well. A favorite demonstration was that of sending + the electrical discharge through long lines of soldiers linked together by + pieces of wire, the discharge causing them to "spring into the air + simultaneously" in a most astonishing manner. A certain monk in Paris + prepared a most elaborate series of demonstrations for the amusement of + the king, among other things linking together an entire regiment of nine + hundred men, causing them to perform simultaneous springs and contortions + in a manner most amusing to the royal guests. But not all the experiments + being made were of a purely spectacular character, although most of them + accomplished little except in a negative way. The famous Abbe Nollet, for + example, combined useful experiments with spectacular demonstrations, thus + keeping up popular interest while aiding the cause of scientific + electricity. + </p> + <p> + WILLIAM WATSON + </p> + <p> + Naturally, the new discoveries made necessary a new nomenclature, new + words and electrical terms being constantly employed by the various + writers of that day. Among these writers was the English scientist William + Watson, who was not only a most prolific writer but a tireless + investigator. Many of the words coined by him are now obsolete, but one at + least, "circuit," still remains in use. + </p> + <p> + In 1746, a French scientist, Louis Guillaume le Monnier, bad made a + circuit including metal and water by laying a chain half-way around the + edge of a pond, a man at either end holding it. One of these men dipped + his free hand in the water, the other presenting a Leyden jar to a rod + suspended on a cork float on the water, both men receiving a shock + simultaneously. Watson, a year later, attempted the same experiment on a + larger scale. He laid a wire about twelve hundred feet long across + Westminster Bridge over the Thames, bringing the ends to the water's edge + on the opposite banks, a man at one end holding the wire and touching the + water. A second man on the opposite side held the wire and a Leyden jar; + and a third touched the jar with one hand, while with the other he grasped + a wire that extended into the river. In this way they not only received + the shock, but fired alcohol as readily across the stream as could be done + in the laboratory. In this experiment Watson discovered the superiority of + wire over chain as a conductor, rightly ascribing this superiority to the + continuity of the metal. + </p> + <p> + Watson continued making similar experiments over longer watercourses, some + of them as long as eight thousand feet, and while engaged in making one of + these he made the discovery so essential to later inventions, that the + earth could be used as part of the circuit in the same manner as bodies of + water. Lengthening his wires he continued his experiments until a circuit + of four miles was made, and still the electricity seemed to traverse the + course instantaneously, and with apparently undiminished force, if the + insulation was perfect. + </p> + <p> + BENJAMIN FRANKLIN + </p> + <p> + Watson's writings now carried the field of active discovery across the + Atlantic, and for the first time an American scientist appeared—a + scientist who not only rivalled, but excelled, his European + contemporaries. Benjamin Franklin, of Philadelphia, coming into possession + of some of Watson's books, became so interested in the experiments + described in them that he began at once experimenting with electricity. In + Watson's book were given directions for making various experiments, and + these assisted Franklin in repeating the old experiments, and eventually + adding new ones. Associated with Franklin, and equally interested and + enthusiastic, if not equally successful in making discoveries, were three + other men, Thomas Hopkinson, Philip Sing, and Ebenezer Kinnersley. These + men worked together constantly, although it appears to have been Franklin + who made independently the important discoveries, and formulated the + famous Franklinian theory. + </p> + <p> + Working steadily, and keeping constantly in touch with the progress of the + European investigators, Franklin soon made some experiments which he + thought demonstrated some hitherto unknown phases of electrical + manifestation. This was the effect of pointed bodies "in DRAWING OFF and + THROWING OFF the electrical fire." In his description of this phenomenon, + Franklin writes: + </p> + <p> + "Place an iron shot of three or four inches diameter on the mouth of a + clean, dry, glass bottle. By a fine silken thread from the ceiling right + over the mouth of the bottle, suspend a small cork ball, about the bigness + of a marble; the thread of such a length that the cork ball may rest + against the side of the shot. Electrify the shot, and the ball will be + repelled to the distance of four or five inches, more or less, according + to the quantity of electricity. When in this state, if you present to the + shot the point of a long, slender shaft-bodkin, at six or eight inches + distance, the repellency is instantly destroyed, and the cork flies to the + shot. A blunt body must be brought within an inch, and draw a spark, to + produce the same effect. + </p> + <p> + "To prove that the electrical fire is DRAWN OFF by the point, if you take + the blade of the bodkin out of the wooden handle and fix it in a stick of + sealing-wax, and then present it at the distance aforesaid, or if you + bring it very near, no such effect follows; but sliding one finger along + the wax till you touch the blade, and the ball flies to the shot + immediately. If you present the point in the dark you will see, sometimes + at a foot distance, and more, a light gather upon it like that of a + fire-fly or glow-worm; the less sharp the point, the nearer you must bring + it to observe the light; and at whatever distance you see the light, you + may draw off the electrical fire and destroy the repellency. If a cork + ball so suspended be repelled by the tube, and a point be presented quick + to it, though at a considerable distance, 'tis surprising to see how + suddenly it flies back to the tube. Points of wood will do as well as + those of iron, provided the wood is not dry; for perfectly dry wood will + no more conduct electricity than sealing-wax. + </p> + <p> + "To show that points will THROW OFF as well as DRAW OFF the electrical + fire, lay a long, sharp needle upon the shot, and you cannot electrify the + shot so as to make it repel the cork ball. Or fix a needle to the end of a + suspended gun-barrel or iron rod, so as to point beyond it like a little + bayonet, and while it remains there, the gun-barrel or rod cannot, by + applying the tube to the other end, be electrified so as to give a spark, + the fire continually running out silently at the point. In the dark you + may see it make the same appearance as it does in the case before + mentioned."(3) + </p> + <p> + Von Guericke, Hauksbee, and Gray had noticed that pointed bodies attracted + electricity in a peculiar manner, but this demonstration of the "drawing + off" of "electrical fire" was original with Franklin. Original also was + the theory that he now suggested, which had at least the merit of being + thinkable even by non-philosophical minds. It assumes that electricity is + like a fluid, that will flow along conductors and accumulate in proper + receptacles, very much as ordinary fluids do. This conception is probably + entirely incorrect, but nevertheless it is likely to remain a popular one, + at least outside of scientific circles, or until something equally + tangible is substituted. + </p> + <p> + FRANKLIN'S THEORY OF ELECTRICITY + </p> + <p> + According to Franklin's theory, electricity exists in all bodies as a + "common stock," and tends to seek and remain in a state of equilibrium, + just as fluids naturally tend to seek a level. But it may, nevertheless, + be raised or lowered, and this equilibrium be thus disturbed. If a body + has more electricity than its normal amount it is said to be POSITIVELY + electrified; but if it has less, it is NEGATIVELY electrified. An + over-electrified or "plus" body tends to give its surplus stock to a body + containing the normal amount; while the "minus" or under-electrified body + will draw electricity from one containing the normal amount. + </p> + <p> + Working along lines suggested by this theory, Franklin attempted to show + that electricity is not created by friction, but simply collected from its + diversified state, the rubbed glass globe attracting a certain quantity of + "electrical fire," but ever ready to give it up to any body that has less. + He explained the charged Leyden jar by showing that the inner coating of + tin-foil received more than the ordinary quantity of electricity, and in + consequence is POSITIVELY electrified, while the outer coating, having the + ordinary quantity of electricity diminished, is electrified NEGATIVELY. + </p> + <p> + These studies of the Leyden jar, and the studies of pieces of glass coated + with sheet metal, led Franklin to invent his battery, constructed of + eleven large glass plates coated with sheets of lead. With this machine, + after overcoming some defects, he was able to produce electrical + manifestations of great force—a force that "knew no bounds," as he + declared ("except in the matter of expense and of labor"), and which could + be made to exceed "the greatest know effects of common lightning." + </p> + <p> + This reference to lightning would seem to show Franklin's belief, even at + that time, that lightning is electricity. Many eminent observers, such as + Hauksbee, Wall, Gray, and Nollet, had noticed the resemblance between + electric sparks and lightning, but none of these had more than surmised + that the two might be identical. In 1746, the surgeon, John Freke, also + asserted his belief in this identity. Winkler, shortly after this time, + expressed the same belief, and, assuming that they were the same, declared + that "there is no proof that they are of different natures"; and still he + did not prove that they were the same nature. + </p> + <p> + FRANKLIN INVENTS THE LIGHTNING-ROD + </p> + <p> + Even before Franklin proved conclusively the nature of lightning, his + experiments in drawing off the electric charge with points led to some + practical suggestions which resulted in the invention of the + lightning-rod. In the letter of July, 1750, which he wrote on the subject, + he gave careful instructions as to the way in which these rods might be + constructed. In part Franklin wrote: "May not the knowledge of this power + of points be of use to mankind in preserving houses, churches, ships, + etc., from the stroke of lightning by directing us to fix on the highest + parts of the edifices upright rods of iron made sharp as a needle, and + gilt to prevent rusting, and from the foot of these rods a wire down the + outside of the building into the grounds, or down round one of the shrouds + of a ship and down her side till it reaches the water? Would not these + pointed rods probably draw the electrical fire silently out of a cloud + before it came nigh enough to strike, and thereby secure us from that most + sudden and terrible mischief? + </p> + <p> + "To determine this question, whether the clouds that contain the lightning + are electrified or not, I propose an experiment to be tried where it may + be done conveniently. On the top of some high tower or steeple, place a + kind of sentry-box, big enough to contain a man and an electrical stand. + From the middle of the stand let an iron rod rise and pass, bending out of + the door, and then upright twenty or thirty feet, pointed very sharp at + the end. If the electrical stand be kept clean and dry, a man standing on + it when such clouds are passing low might be electrified and afford + sparks, the rod drawing fire to him from a cloud. If any danger to the man + be apprehended (though I think there would be none), let him stand on the + floor of his box and now and then bring near to the rod the loop of a wire + that has one end fastened to the leads, he holding it by a wax handle; so + the sparks, if the rod is electrified, will strike from the rod to the + wire and not effect him."(4) + </p> + <p> + Not satisfied with all the evidence that he had collected pointing to the + identity of lightning and electricity, he adds one more striking and very + suggestive piece of evidence. Lightning was known sometimes to strike + persons blind without killing them. In experimenting on pigeons and + pullets with his electrical machine, Franklin found that a fowl, when not + killed outright, was sometimes rendered blind. The report of these + experiments were incorporated in this famous letter of the Philadelphia + philosopher. + </p> + <p> + The attitude of the Royal Society towards this clearly stated letter, with + its useful suggestions, must always remain as a blot on the record of this + usually very receptive and liberal-minded body. Far from publishing it or + receiving it at all, they derided the whole matter as too visionary for + discussion by the society. How was it possible that any great scientific + discovery could be made by a self-educated colonial newspaper editor, who + knew nothing of European science except by hearsay, when all the great + scientific minds of Europe had failed to make the discovery? How indeed! + And yet it would seem that if any of the influential members of the + learned society had taken the trouble to read over Franklin's clearly + stated letter, they could hardly have failed to see that his suggestions + were worthy of consideration. But at all events, whether they did or did + not matters little. The fact remains that they refused to consider the + paper seriously at the time; and later on, when its true value became + known, were obliged to acknowledge their error by a tardy report on the + already well-known document. + </p> + <p> + But if English scientists were cold in their reception of Franklin's + theory and suggestions, the French scientists were not. Buffon, perceiving + at once the importance of some of Franklin's experiments, took steps to + have the famous letter translated into French, and soon not only the + savants, but members of the court and the king himself were intensely + interested. Two scientists, De Lor and D'Alibard, undertook to test the + truth of Franklin's suggestions as to pointed rods "drawing off + lightning." In a garden near Paris, the latter erected a pointed iron rod + fifty feet high and an inch in diameter. As no thunder-clouds appeared for + several days, a guard was stationed, armed with an insulated brass wire, + who was directed to test the iron rods with it in case a storm came on + during D'Alibard's absence. The storm did come on, and the guard, not + waiting for his employer's arrival, seized the wire and touched the rod. + Instantly there was a report. Sparks flew and the guard received such a + shock that he thought his time had come. Believing from his outcry that he + was mortally hurt, his friends rushed for a spiritual adviser, who came + running through rain and hail to administer the last rites; but when he + found the guard still alive and uninjured, he turned his visit to account + by testing the rod himself several times, and later writing a report of + his experiments to M. d'Alibard. This scientist at once reported the + affair to the French Academy, remarking that "Franklin's idea was no + longer a conjecture, but a reality." + </p> + <p> + FRANKLIN PROVES THAT LIGHTNING IS ELECTRICITY + </p> + <p> + Europe, hitherto somewhat sceptical of Franklin's views, was by this time + convinced of the identity of lightning and electricity. It was now + Franklin's turn to be sceptical. To him the fact that a rod, one hundred + feet high, became electrified during a storm did not necessarily prove + that the storm-clouds were electrified. A rod of that length was not + really projected into the cloud, for even a very low thunder-cloud was + more than a hundred feet above the ground. Irrefutable proof could only be + had, as he saw it, by "extracting" the lightning with something actually + sent up into the storm-cloud; and to accomplish this Franklin made his + silk kite, with which he finally demonstrated to his own and the world's + satisfaction that his theory was correct. + </p> + <p> + Taking his kite out into an open common on the approach of a + thunder-storm, he flew it well up into the threatening clouds, and then, + touching, the suspended key with his knuckle, received the electric spark; + and a little later he charged a Leyden jar from the electricity drawn from + the clouds with his kite. + </p> + <p> + In a brief but direct letter, he sent an account of his kite and his + experiment to England: + </p> + <p> + "Make a small cross of two light strips of cedar," he wrote, "the arms so + long as to reach to the four corners of a large, thin, silk handkerchief + when extended; tie the corners of the handkerchief to the extremities of + the cross so you have the body of a kite; which being properly + accommodated with a tail, loop, and string, will rise in the air like + those made of paper; but this being of silk is fitter to bear the wind and + wet of a thunder-gust without tearing. To the top of the upright stick of + the cross is to be fixed a very sharp-pointed wire, rising a foot or more + above the wood. To the end of the twine, next the hand, is to be tied a + silk ribbon; where the silk and twine join a key may be fastened. This + kite is to be raised when a thunder-gust appears to be coming on, and the + person who holds the string must stand within a door or window or under + some cover, so that the silk ribbon may not be wet; and care must be taken + that the twine does not touch the frame of the door or window. As soon as + any of the thunder-clouds come over the kite, the pointed wire will draw + the electric fire from them, and the kite, with all the twine, will be + electrified and the loose filaments will stand out everywhere and be + attracted by the approaching finger, and when the rain has wet the kite + and twine so that it can conduct the electric fire freely, you will find + it stream out plentifully from the key on the approach of your knuckle, + and with this key the phial may be charged; and from electric fire thus + obtained spirits may be kindled and all other electric experiments + performed which are usually done by the help of a rubbed glass globe or + tube, and thereby the sameness of the electric matter with that of + lightning completely demonstrated."(5) + </p> + <p> + In experimenting with lightning and Franklin's pointed rods in Europe, + several scientists received severe shocks, in one case with a fatal + result. Professor Richman, of St. Petersburg, while experimenting during a + thunder-storm, with an iron rod which he had erected on his house, + received a shock that killed him instantly. + </p> + <p> + About 1733, as we have seen, Dufay had demonstrated that there were two + apparently different kinds of electricity; one called VITREOUS because + produced by rubbing glass, and the other RESINOUS because produced by + rubbed resinous bodies. Dufay supposed that these two apparently different + electricities could only be produced by their respective substances; but + twenty years later, John Canton (1715-1772), an Englishman, demonstrated + that under certain conditions both might be produced by rubbing the same + substance. Canton's experiment, made upon a glass tube with a roughened + surface, proved that if the surface of the tube were rubbed with oiled + silk, vitreous or positive electricity was produced, but if rubbed with + flannel, resinous electricity was produced. He discovered still further + that both kinds could be excited on the same tube simultaneously with a + single rubber. To demonstrate this he used a tube, one-half of which had a + roughened the other a glazed surface. With a single stroke of the rubber + he was able to excite both kinds of electricity on this tube. He found + also that certain substances, such as glass and amber, were electrified + positively when taken out of mercury, and this led to his important + discovery that an amalgam of mercury and tin, when used on the surface of + the rubber, was very effective in exciting glass. + </p> + <p> + <a name="link2H_4_0017" id="link2H_4_0017"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XV. NATURAL HISTORY TO THE TIME OF LINNAEUS + </h2> + <p> + Modern systematic botany and zoology are usually held to have their + beginnings with Linnaeus. But there were certain precursors of the famous + Swedish naturalist, some of them antedating him by more than a century, + whose work must not be altogether ignored—such men as Konrad Gesner + (1516-1565), Andreas Caesalpinus (1579-1603), Francisco Redi (1618-1676), + Giovanni Alfonso Borelli (1608-1679), John Ray (1628-1705), Robert Hooke + (1635-1703), John Swammerdam (1637-1680), Marcello Malpighi (1628-1694), + Nehemiah Grew (1628-1711), Joseph Tournefort (1656-1708), Rudolf Jacob + Camerarius (1665-1721), and Stephen Hales (1677-1761). The last named of + these was, to be sure, a contemporary of Linnaeus himself, but Gesner and + Caesalpinus belong, it will be observed, to so remote an epoch as that of + Copernicus. + </p> + <p> + Reference has been made in an earlier chapter to the microscopic + investigations of Marcello Malpighi, who, as there related, was the first + observer who actually saw blood corpuscles pass through the capillaries. + Another feat of this earliest of great microscopists was to dissect + muscular tissue, and thus become the father of microscopic anatomy. But + Malpighi did not confine his observations to animal tissues. He dissected + plants as well, and he is almost as fully entitled to be called the father + of vegetable anatomy, though here his honors are shared by the Englishman + Grew. In 1681, while Malpighi's work, Anatomia plantarum, was on its way + to the Royal Society for publication, Grew's Anatomy of Vegetables was in + the hands of the publishers, making its appearance a few months earlier + than the work of the great Italian. Grew's book was epoch-marking in + pointing out the sex-differences in plants. + </p> + <p> + Robert Hooke developed the microscope, and took the first steps towards + studying vegetable anatomy, publishing in 1667, among other results, the + discovery of the cellular structure of cork. Hooke applied the name "cell" + for the first time in this connection. These discoveries of Hooke, + Malpighi, and Grew, and the discovery of the circulation of the blood by + William Harvey shortly before, had called attention to the similarity of + animal and vegetable structures. Hales made a series of investigations + upon animals to determine the force of the blood pressure; and similarly + he made numerous statical experiments to determine the pressure of the + flow of sap in vegetables. His Vegetable Statics, published in 1727, was + the first important work on the subject of vegetable physiology, and for + this reason Hales has been called the father of this branch of science. + </p> + <p> + In botany, as well as in zoology, the classifications of Linnaeus of + course supplanted all preceding classifications, for the obvious reason + that they were much more satisfactory; but his work was a culmination of + many similar and more or less satisfactory attempts of his predecessors. + About the year 1670 Dr. Robert Morison (1620-1683), of Aberdeen, published + a classification of plants, his system taking into account the woody or + herbaceous structure, as well as the flowers and fruit. This + classification was supplanted twelve years later by the classification of + Ray, who arranged all known vegetables into thirty-three classes, the + basis of this classification being the fruit. A few years later Rivinus, a + professor of botany in the University of Leipzig, made still another + classification, determining the distinguishing character chiefly from the + flower, and Camerarius and Tournefort also made elaborate classifications. + On the Continent Tournefort's classification was the most popular until + the time of Linnaeus, his systematic arrangement including about eight + thousand species of plants, arranged chiefly according to the form of the + corolla. + </p> + <p> + Most of these early workers gave attention to both vegetable and animal + kingdoms. They were called naturalists, and the field of their + investigations was spoken of as "natural history." The specialization of + knowledge had not reached that later stage in which botanist, zoologist, + and physiologist felt their labors to be sharply divided. Such a division + was becoming more and more necessary as the field of knowledge extended; + but it did not become imperative until long after the time of Linnaeus. + That naturalist himself, as we shall see, was equally distinguished as + botanist and as zoologist. His great task of organizing knowledge was + applied to the entire range of living things. + </p> + <p> + Carolus Linnaeus was born in the town of Rashult, in Sweden, on May 13, + 1707. As a child he showed great aptitude in learning botanical names, and + remembering facts about various plants as told him by his father. His + eagerness for knowledge did not extend to the ordinary primary studies, + however, and, aside from the single exception of the study of physiology, + he proved himself an indifferent pupil. His backwardness was a sore trial + to his father, who was desirous that his son should enter the ministry; + but as the young Linnaeus showed no liking for that calling, and as he had + acquitted himself well in his study of physiology, his father at last + decided to allow him to take up the study of medicine. Here at last was a + field more to the liking of the boy, who soon vied with the best of his + fellow-students for first honors. Meanwhile he kept steadily at work in + his study of natural history, acquiring considerable knowledge of + ornithology, entomology, and botany, and adding continually to his + collection of botanical specimens. In 1729 his botanical knowledge was + brought to the attention of Olaf Rudbeck, professor of botany in the + University of Upsala, by a short paper on the sexes of plants which + Linnaeus had prepared. Rudbeck was so impressed by some of the ideas + expressed in this paper that he appointed the author as his assistant the + following year. + </p> + <p> + This was the beginning of Linnaes's career as a botanist. The academic + gardens were thus thrown open to him, and he found time at his disposal + for pursuing his studies between lecture hours and in the evenings. It was + at this time that he began the preparation of his work the Systema + naturae, the first of his great works, containing a comprehensive sketch + of the whole field of natural history. When this work was published, the + clearness of the views expressed and the systematic arrangement of the + various classifications excited great astonishment and admiration, and + placed Linaeus at once in the foremost rank of naturalists. This work was + followed shortly by other publications, mostly on botanical subjects, in + which, among other things, he worked out in detail his famous "system." + </p> + <p> + This system is founded on the sexes of plants, and is usually referred to + as an "artificial method" of classification because it takes into account + only a few marked characters of plants, without uniting them by more + general natural affinities. At the present time it is considered only as a + stepping-stone to the "natural" system; but at the time of its + promulgation it was epoch-marking in its directness and simplicity, and + therefore superiority, over any existing systems. + </p> + <p> + One of the great reforms effected by Linnaeus was in the matter of + scientific terminology. Technical terms are absolutely necessary to + scientific progress, and particularly so in botany, where obscurity, + ambiguity, or prolixity in descriptions are fatally misleading. Linnaeus's + work contains something like a thousand terms, whose meanings and uses are + carefully explained. Such an array seems at first glance arbitrary and + unnecessary, but the fact that it has remained in use for something like + two centuries is indisputable evidence of its practicality. The + descriptive language of botany, as employed by Linnaeus, still stands as a + model for all other subjects. + </p> + <p> + Closely allied to botanical terminology is the subject of botanical + nomenclature. The old method of using a number of Latin words to describe + each different plant is obviously too cumbersome, and several attempts had + been made prior to the time of Linnaeus to substitute simpler methods. + Linnaeus himself made several unsatisfactory attempts before he finally + hit upon his system of "trivial names," which was developed in his Species + plantarum, and which, with some, minor alterations, remains in use to this + day. The essence of the system is the introduction of binomial + nomenclature—that is to say, the use of two names and no more to + designate any single species of animal or plant. The principle is quite + the same as that according to which in modern society a man has two names, + let us say, John Doe, the one designating his family, the other being + individual. Similarly each species of animal or plant, according to the + Linnaeean system, received a specific or "trivial" name; while various + species, associated according to their seeming natural affinities into + groups called genera, were given the same generic name. Thus the generic + name given all members of the cat tribe being Felis, the name Felis leo + designates the lion; Felis pardus, the leopard; Felis domestica, the house + cat, and so on. This seems perfectly simple and natural now, but to + understand how great a reform the binomial nomenclature introduced we have + but to consult the work of Linnaeus's predecessors. A single illustration + will suffice. There is, for example, a kind of grass, in referring to + which the naturalist anterior to Linnaeus, if he would be absolutely + unambiguous, was obliged to use the following descriptive formula: Gramen + Xerampelino, Miliacea, praetenuis ramosaque sparsa panicula, sive + Xerampelino congener, arvense, aestivum; gramen minutissimo semine. + Linnaeus gave to this plant the name Poa bulbosa—a name that + sufficed, according to the new system, to distinguish this from every + other species of vegetable. It does not require any special knowledge to + appreciate the advantage of such a simplification. + </p> + <p> + While visiting Paris in 1738 Linnaeus met and botanized with the two + botanists whose "natural method" of classification was later to supplant + his own "artificial system." These were Bernard and Antoine Laurent de + Jussieu. The efforts of these two scientists were directed towards + obtaining a system which should aim at clearness, simplicity, and + precision, and at the same time be governed by the natural affinities of + plants. The natural system, as finally propounded by them, is based on the + number of cotyledons, the structure of the seed, and the insertion of the + stamens. Succeeding writers on botany have made various modifications of + this system, but nevertheless it stands as the foundation-stone of modern + botanical classification. + </p> + <p> + <a name="link2H_APPE" id="link2H_APPE"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + APPENDIX + </h2> + <h3> + REFERENCE LIST + </h3> + <p> + <a name="link2HCH0001" id="link2HCH0001"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER I + </h2> + <h3> + SCIENCE IN THE DARK AGE + </h3> + <p> + (1) (p. 4). James Harvey Robinson, An Introduction to the History of + Western Europe, New York, 1898, p. 330. + </p> + <p> + (2) (p. 6). Henry Smith Williams, A Prefatory Characterization of The + History of Italy, in vol. IX. of The Historians' History of the World, 25 + vols., London and New York, 1904. + </p> + <p> + <a name="link2HCH0002" id="link2HCH0002"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER III + </h2> + <h3> + MEDIAEVAL SCIENCE IN THE WEST + </h3> + <p> + (1) (p. 47). Etigene Muntz, Leonardo do Vinci, Artist, Thinker, and Man of + Science, 2 vols., New York, 1892. Vol. II., p. 73. + </p> + <p> + <a name="link2HCH0003" id="link2HCH0003"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER IV + </h2> + <h3> + THE NEW COSMOLOGY—COPERNICUS TO KEPLER AND GALILEO + </h3> + <p> + (1) (p. 62). Copernicus, uber die Kreisbewegungen der Welfkorper, trans. + from Dannemann's Geschichle du Naturwissenschaften, 2 vols., Leipzig, + 1896. + </p> + <p> + (2) (p. 90). Galileo, Dialogo dei due Massimi Systemi del Mondo, trans. + from Dannemann, op. cit. + </p> + <p> + <a name="link2HCH0004" id="link2HCH0004"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER V + </h2> + <p> + GALILEO AND THE NEW PHYSICS (1) (p. 101). Rothmann, History of Astronomy + (in the Library of Useful Knowledge), London, 1834. + </p> + <p> + (2) (p. 102). William Whewell, History of the Inductive Sciences, 3 Vols, + London, 1847-Vol. II., p. 48. + </p> + <p> + (3) (p. 111). The Lives of Eminent Persons, by Biot, Jardine, Bethune, + etc., London, 1833. + </p> + <p> + (4) (p. 113). William Gilbert, De Magnete, translated by P. Fleury + Motteley, London, 1893. In the biographical memoir, p. xvi. + </p> + <p> + (5) (p. 114). Gilbert, op. cit., p. x1vii. + </p> + <p> + (6) (p. 114). Gilbert, op. cit., p. 24. + </p> + <p> + <a name="link2HCH0005" id="link2HCH0005"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER VI + </h2> + <h3> + TWO PSEUDO-SCIENCES—ALCHEMY AND ASTROLOGY + </h3> + <p> + (1) (p. 125). Exodus xxxii, 20. + </p> + <p> + (2) (p. 126). Charles Mackay, Popular Delusions, 3 vols., London, 1850. + Vol. II., p. 280. + </p> + <p> + (3) (p. 140). Mackay, op. cit., Vol. 11., p. 289. + </p> + <p> + (4) (P. 145). John B. Schmalz, Astrology Vindicated, New York, 1898. + </p> + <p> + (5) (p. 146). William Lilly, The Starry Messenger, London, 1645, p. 63. + </p> + <p> + (6) (p. 149). Lilly, op. cit., p. 70. + </p> + <p> + (7) (p. 152). George Wharton, An Astrological judgement upon His Majesty's + Present March begun from Oxford, May 7, 1645, pp. 7-10. + </p> + <p> + (8) (p. 154). C. W. Roback, The Mysteries of Astrology, Boston, 1854, p. + 29. + </p> + <p> + <a name="link2HCH0006" id="link2HCH0006"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER VII + </h2> + <h3> + FROM PARACELSUS TO HARVEY + </h3> + <p> + (1) (p. 159). A. E. Waite, The Hermetic and Alchemical Writings of + Paracelsus, 2 vols., London, 1894. Vol. I., p. 21. + </p> + <p> + (2) (p. 167). E. T. Withington, Medical History from the Earliest Times, + London, 1894, p. 278. + </p> + <p> + (3) (p. 173). John Dalton, Doctrines of the Circulation, Philadelphia, + 1884, p. 179. + </p> + <p> + (4) (p. 174). William Harvey, De Motu Cordis et Sanguinis, London, 1803, + chap. X. + </p> + <p> + (5) (p. 178). The Works of William Harvey, translated by Robert Willis, + London, 1847, p. 56. + </p> + <p> + <a name="link2HCH0007" id="link2HCH0007"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER VIII + </h2> + <h3> + MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES + </h3> + <p> + (1) (p. 189). Hermann Baas, History of Medicine, translated by H. E. + Henderson, New York, 1894, p. 504. + </p> + <p> + (2) (p. 189). E. T. Withington, Medical History from the Earliest Times, + London, 1894, p. 320. + </p> + <p> + <a name="link2HCH0008" id="link2HCH0008"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER IX + </h2> + <h3> + PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING + </h3> + <p> + (1) (p. 193). George L. Craik, Bacon and His Writings and Philosophy, 2 + vols., London, 1846. Vol. II., p. 121. + </p> + <p> + (2) (p. 193). From Huxley's address On Descartes's Discourse Touching the + Method of Using One's Reason Rightly and of Seeking Scientific Truth. + </p> + <p> + (3) (p. 195). Rene Descartes, Traite de l'Homme (Cousins's edition. in ii + vols.), Paris, 1824. Vol, VI., p. 347. + </p> + <p> + <a name="link2HCH0009" id="link2HCH0009"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER X + </h2> + <h3> + THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE + </h3> + <p> + (1) (p. 205). See The Phlogiston Theory, Vol, IV. + </p> + <p> + (2) (p. 205). Robert Boyle, Philosophical Works, 3 vols., London, 1738. + Vol. III., p. 41. + </p> + <p> + (3) (p. 206). Ibid., Vol. III., p. 47. + </p> + <p> + (4) (p. 206). Ibid., Vol. II., p. 92. + </p> + <p> + (5) (p. 207). Ibid., Vol. II., p. 2. + </p> + <p> + (6) (p. 209). Ibid., Vol. I., p. 8. + </p> + <p> + (7) (p. 209). Ibid., vol. III., p. 508. + </p> + <p> + (8) (p. 210). Ibid., Vol. III., p. 361. + </p> + <p> + (9) (p. 213). Otto von Guericke, in the Philosophical Transactions of the + Royal Society of London, No. 88, for 1672, p. 5103. + </p> + <p> + (10) (p. 222). Von Guericke, Phil. Trans. for 1669, Vol I., pp. 173, 174. + </p> + <p> + <a name="link2HCH0010" id="link2HCH0010"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER XI + </h2> + <h3> + NEWTON AND THE COMPOSITION OF LIGHT + </h3> + <p> + (1) (p. 233). Phil. Trans. of Royal Soc. of London, No. 80, 1672, pp. + 3076-3079. (2) (p 234). Ibid., pp. 3084, 3085. + </p> + <p> + (3) (p. 235). Voltaire, Letters Concerning the English Nation, London, + 1811. + </p> + <p> + <a name="link2HCH0011" id="link2HCH0011"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER XII + </h2> + <h3> + NEWTON AND THE LAW OF GRAVITATION + </h3> + <p> + (1) (p. 242). Sir Isaac Newton, Principia, translated by Andrew Motte, New + York, 1848, pp. 391, 392. + </p> + <p> + (2) (p. 250). Newton op. cit., pp. 506, 507. + </p> + <p> + <a name="link2HCH0012" id="link2HCH0012"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + CHAPTER XIV + </h2> + <h3> + PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO FRANKLIN + </h3> + <p> + (1) (p. 274). A letter from M. Dufay, F.R.S. and of the Royal Academy of + Sciences at Paris, etc., in the Phil. Trans. of the Royal Soc., vol. + XXXVIII., pp. 258-265. + </p> + <p> + (2) (p. 282). Dean von Kleist, in the Danzick Memoirs, Vol. I., p. 407. + From Joseph Priestley's History of Electricity, London, 1775, pp. 83, 84. + </p> + <p> + (3) (p. 288). Benjamin Franklin, New Experiments and Observations on + Electricity, London, 1760, pp. 107, 108. + </p> + <p> + (4) (p. 291). Franklin, op. cit., pp. 62, 63. + </p> + <p> + (5) (p. 295). Franklin, op. cit., pp. 107, 108. + </p> + <p> + (For notes and bibliography to vol. II. see vol. V.) + </p> + <p> + <br /> <br /> + </p> + <hr /> + <hr /> + <p> + <br /> <br /> + </p> + <h1> + TABLE OF CONTENTS <br /><br /> FOR THE FIVE VOLUMES + </h1> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0002"> <b>BOOK + I</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0003"> + I. PREHISTORIC SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0004"> + II. EGYPTIAN SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0005"> + III. SCIENCE OF BABYLONIA AND ASSYRIA </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0006"> + IV. THE DEVELOPMENT OF THE ALPHABET </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0007"> + V. THE BEGINNINGS OF GREEK SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0008"> + VI. THE EARLY GREEK PHILOSOPHERS IN ITALY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0009"> + VII. GREEK SCIENCE IN THE EARLY ATTIC PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0010"> + VIII. POST-SOCRATIC SCIENCE AT ATHENS—PLATO, ARISTOTLE, AND + THEOPHRASTUS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0011"> + IX. GREEK SCIENCE OF THE ALEXANDRIAN OR HELLENISTIC PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0012"> + X. SCIENCE OF THE ROMAN PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0013"> + XI. A RETROSPECTIVE GLANCE AT CLASSICAL SCIENCE </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0002"> <b>BOOK + II. THE BEGINNINGS OF MODERN SCIENCE</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0003"> + I. SCIENCE IN THE DARK AGE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0004"> + II. MEDIAEVAL SCIENCE AMONG THE ARABIANS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0005"> + III. MEDIAEVAL SCIENCE IN THE WEST </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0006"> + IV. THE NEW COSMOLOGY—COPERNICUS TO KEPLER AND GALILEO </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0007"> + V. GALILEO AND THE NEW PHYSICS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0008"> + VI. TWO PSEUDO-SCIENCES—ALCHEMY AND ASTROLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0009"> + VII. FROM PARACELSUS TO HARVEY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0010"> + VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0011"> + IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0012"> + X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0013"> + XI. NEWTON AND THE COMPOSITION OF LIGHT </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0014"> + XII. NEWTON AND THE LAW OF GRAVITATION </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0015"> + XIII. INSTRUMENTS OF PRECISION IN THE AGE OF NEWTON </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0016"> + XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO + FRANKLIN </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0017"> + XV. NATURAL HISTORY TO THE TIME OF LINNAEUS </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0001"> <b>BOOK + III. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0002"> + I. THE SUCCESSORS OF NEWTON IN ASTRONOMY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0003"> + II. THE PROGRESS OF MODERN ASTRONOMY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0004"> + III. THE NEW SCIENCE OF PALEONTOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0005"> + IV. THE ORIGIN AND DEVELOPMENT OF MODERN GEOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0006"> + V. THE NEW SCIENCE OF METEOROLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0007"> + VI. MODERN THEORIES OF HEAT AND LIGHT </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0008"> + VII. THE MODERN DEVELOPMENT OF ELECTRICITY AND MAGNETISM </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0009"> + VIII. THE CONSERVATION OF ENERGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0010"> + IX. THE ETHER AND PONDERABLE MATTER </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0001"> <b>BOOK + IV. MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0002"> + I. THE PHLOGISTON THEORY IN CHEMISTRY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0003"> + II. THE BEGINNINGS OF MODERN CHEMISTRY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0004"> + III. CHEMISTRY SINCE THE TIME OF DALTON </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0005"> + IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0006"> + V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0007"> + VI. THEORIES OF ORGANIC EVOLUTION </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0008"> + VII. EIGHTEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0009"> + VIII. NINETEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0010"> + IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0011"> + X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0001"> + <b>BOOK V. ASPECTS OF RECENT SCIENCE</b> </a><br /> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0003"> + I. THE BRITISH MUSEUM </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0004"> + II. THE ROYAL SOCIETY OF LONDON FOR IMPROVING NATURAL KNOWLEDGE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0005"> + III. THE ROYAL INSTITUTION AND THE LOW-TEMPERATURE RESEARCHES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0006"> + IV. SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0007"> + V. THE MARINE BIOLOGICAL LABORATORY AT NAPLES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0008"> + VI. ERNST HAECKEL AND THE NEW ZOOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0009"> + VII. SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0010"> + VII. SOME UNSOLVED SCIENTIFIC PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0011"> + IX. RETROSPECT AND PROSPECT </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> +<pre xml:space="preserve"> + + + + + +End of the Project Gutenberg EBook of A History of Science, Volume 2(of 5), by +Henry Smith Williams + +*** END OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V2 *** + +***** This file should be named 1706-h.htm or 1706-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/7/0/1706/ + +Produced by Charles Keller, 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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