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Return this book on or before the Latest Date stamped below. A charge is made on all overdue books. U. of I. Library JAN = "9 —~ Ve atk * ~ her ee AUG 1 3 i965 Ji MAYI939 | yur 13 i940 DEC TT WF 8057-S BEACON LIGHTS OF SCIENCE a ~~ ° Peetige: } SIDUAII Oo fwmapvo DUO14D "SUqUOLT Wn " Suk 2 . Pat NQ- Sy ta i 5s icy temiig tM UA ARS AS AVH pataitet He te SMW IA | & RSS. SEGEVIIHOW Z1LOUMY 2 I'd OddlH BEACON LIGHTS OF SCIENCE A SURVEY OF HUMAN ACHIEVEMENT FROM THE EARLIEST RECORDED TIMES BY THEO. F. VAN WAGENEN NEW YORK THOMAS Y. CROWELL CO. PUBLISHERS Copyright, 1924 By THOMAS Y. CROWELL CoO. Printed in the United States of America INTRODUCTION In the following pages the attempt has been made to sketch, in outline, the development of Science throughout the centuries, in the lives of those individuals who, in their time, have contributed notably to its progress. Naturally it has been impossible to include all who have taken some part in the great work. And also, many of the most promi- nent are still with us, their labors unfinished. To the young man preparing himself for a scientific career, or entering upon its duties and obligations, the efforts of those thinkers and discoverers who have passed on and left to him the rich heritage of knowledge so far ac- cumulated should be an inspiration and an incentive. Or, taking a lower view of the matter, he should at least know enough of their lives to be able to connect the discoveries with the discoverers and to have some conception of their personality. We cannot be too mindful of the difficulties with which they had to contend in their explorations in a field of mystery, where none before them had blazed a path. Doubtless there were true scientists before Euclid. But of them so little is certainly known, and with their dis- coveries so much of mysticism has been blended, that their stories come to us enveloped in a haze through which it is difficult to arrive at a fixed starting point. It is also hard to draw a line which shall clearly leave on one side the con- clusions of speculation, and on the other the logical deduc- tions from correctly observed phenomena. It seems clear, however, that the habit of collecting and classifying ob- served facts of nature (mainly astronomical) began with the Semitic people, and from them passed to the Aryans by way of that first intellectual flowering of its civilization, the Greeks. But the latter lived in an environment so beauti- ful, and possessed—probably as a result of it—a tempera- Vv OG0UG73 al Introduction ment so aesthetic, that cold-blooded study of nature was un- congenial, and to all but a very few impossible. If the con- tents of the lost Alexandrian library could be restored in- tact and made accessible to the modern student, it would no doubt prove of surpassing interest, but probably also of little value to science. As the glory of Greece faded under the stern shadow of Roman dominion, about all that the latter inherited from it, in the way of real knowledge, was the beginnings of the science of mathematics. Rome contributed practically noth- ing in its day to the explanation of natural phenomena, though it acquired a vast amount of empirical information through experience in dealing with its forces. And when, through the revival of mysticism, the Dark Ages came on, enveloping all Europe in their gloom, Science slumbered and dreamed for centuries, while Astrology and Alchemy wore its mask, and posed on the stage in the tinsel gar- ments of a dead and forgotten past. It is difficult for us today to believe that in Europe, for more than a thousand years, the children who were born into the world were taught by their elders that there was but one true source of knowledge—religion—and that it was not only useless but impious to seek for the explanation of natural phenomena elsewhere. When at last revolt against this monstrous misconception began, Science awoke from its long sleep; at first—as before—in the form of a revival of interest in the fundamental branch of mathe- matics, which was quickly followed by renewed activity in astronomy and mechanics, the two departments whose manifestations were most readily open to observation. Once recalled to life, other departments of knowledge be- came recognized in turn as they appeared as true children of science, and worthy descendants of those few masters among the ancients who, brushing aside as unworthy of their time the delights of speculation, devoted their energies to observation, and to the drawing of conclusions from the marshaling and classification of well demon- strated facts, rather than from the processes of ratiocina- tion. Yet the paths of these pioneers were beset with dif- Introduction Vil ficulties. Copernicus was proclaimed a heretic by both of the grand divisions of the Christian church, Galileo was compelled to recant on his knees, and Darwin of a much later time was called an atheist, though all were men of deep religious feeling whose lives were full of love and re- spect for their fellows. In arranging the order of these sketches, the life period has determined the sequence. With a few unimportant exceptions this brings to the reader in turn the different branches of knowledge as they were developed. Thus, with the exception of the early Greek studies in anatomy, mathe- matics, mechanics, and astronomy were the only sciences in existence up to the early years of the seventeenth century, when Mersenne, Harvey, and Gunter led the way with dis- coveries in acoustics, physiology, and magnetism. During the remainder of that period optics and physics were added. The eighteenth century witnessed the beginnings of the elec- trical, chemical, and geological sciences, and towards its close physiology and anatomy had become well founded on demonstrated facts. In the nineteenth century all these departments of re- search were greatly developed, and chemistry, the science of matter, easily took first place in importance, with physics a close second, and philology, embryology, meteorology, anthropology, ethnology, pathology, biology, and a host of minor ‘‘ologies’’ crowding upon the stage from the wings and demanding recognition. Towards its end, physies, the science of energy, displaced chemistry in importance, and at the present time is well in advance, while the thinkers of the world are reaching out into the new fields of psycho- physics and psychology in the hope—and the expectation —of being able to solve with their aid some of the mysteries behind those concepts of matter and energy whose laws and manifestations are now fairly well understood, but whose causes still remain unexplained. OOo August 1, 1924. Ue ae rey ie Pa ae N iy 2508) 1M ene buds WAl ag wis a ts BAL s ae , yy ts Pa Nie : ¥ Het ale I crit 6 A a jena ip 8% oe uf a » ¥ THALES ANAXIMANDER PYTHAGORAS EMPEDOCLES DEMOCRITUS HIPPOCRATES PLATO ARISTOTLE THEOPHRASTUS ERASISTRATUS EUCLID ARCHIMEDES ERATOSTHENES ARISTARCHUS APOLLONIUS HIPPARCHUS DIOSCORIDES PTOLEMY GALEN DIOPHANTUS ARYABHATTA BRAHMAGUPTA AL KHUWARISMI AL HaZEN BHASKARA Bacon PEUERBACH MULLER (Regio- montanus) Da VINCI CoPERNICUS FALLOPIUS CONTENTS I. ANCIENT TIMES PAGE Erimitive: ‘Theones:') 7veuoid wants, cle see area ae 3 Mathematics on oy. fecneui eae etre ee cceen + PEALE OUOTAY cc's sin a Sgro ae oe Maan ed Salk mle @atale 5 JEVOUIIETONY Witla ini alas aos ae ditt ake sravevesalten racers 8 INA TUTE POLODICO'! yf siayg lghuis! a bint ofale's\e ea eres 9 PI BAICINGE Sirs Vale | Sale MGT ae idee Via wi eS 11 Philosophy and Mathematics............... 12 PUTS EI CLONOR oy) is tsa) a Mia's die o are! ae! a, shaaad a8 ess 14 j SUN UEP ARN ie Ss SR A Be arb: Ge PR ee Dy, SA URUIIE VON Te eile iw viel sia, ax ey cathe 4 ater atevateelesd ais 18 DVS LEMON UEGEL 4 pa ‘gk Garth Rie Aris: ce a eidlial ma aN 19 IS COBO ica Puls gin 46 5 RAM thse a dle or erenee 21 AEROMPOUAW Cate 4 e's a'ehd eis Micaela ie «ss <\'sl tation 23 UU MERODEMING 1. 5'3 + iu th GRIMY IE ves ocd Wie Dahee ata 24 CITA LICE ahs. os Sie ar EA Woe are b orwigan gee Sede 26 PE POMC VV g'5. 5 iis aid MTS ne owas Ries goa de wee 27 AOA TE OUR Ghats areas vind cvaed Pia aA Mlle dicts, ei aka \o wielooml 29 Cosmology and Geographysceicis « siscsse ele 30 GAEGINV oi knw intee stereo aia Malate oe’ x Glin mete lhe ale 33 DIATOMS TICS «hwo. a.pincain A ofa ee Whee) male Bla laa die / ai 35 II, THE MIDDLE AGES PAGEPOMONEN is ake aceda 'sailarbebt aioe ane bale ocaie etecaes 41 I ENG ROS LICE L.'s «i use ey Me he oS! a ea vag araet atl 42 BEGG EI STIGH foc sits eiel on REM NO aig: sy roll eae dea 3 Pe POINT ICM sa) wets eigrar teint aiuaty ace Aisle stg DUN alone 45 MathcriataGanns 1's sinew, oe aera crete ogra aah we aleing 46 Speculative Philosophy and Natural Science.. 48 PEACH OOIAUI Crane Fone didls | nate Saterday pices algee Eee ovens 52 MGtNGmStGa! c. nianieiec dee muitei as dine ee cslewee ¢ 53 CODOTR I CIENOG .'s cccotehe anions selec slew Stemiele 56 PASELONGULV s calars-sd dbetaieta vbatanteiara/en asl eaaxveemtte 58 ARACOTOV 0 sae s Wise ea he © biteleite bse te Hoinamenme 62 Contents WI. THE SIXTEENTH CENTURY TARTAGLIA VESALIUS GESNER EUSTACIO FABRIZIO GILBERT BRAHE STEVIN NAPIER GALILEO KEPLER HARVEY MERSENNE DESARGUES DESCARTES IV. FERMAT GUERICKE TORRICELLI PASCAL BOYLE CASSINI MALPIGHI HUYGENS LEEUWENHOEK HOOKE NEWTON ROEMER LEIBNITZ HALLEY BRADLEY MACLAURIN DE JUSSIEU GRAY BERNOUILLI FRANKLIN BUFFON LINNAEUS Mathematics) io.'ss sc sis seis eeiaise be Sir eta pian ATACOMY hee telds cieies sais Bi viekeltiaws es tebi ee teleneiy etme Natural: History” ...'0), so s.se siecle ee uteens eine ADALODIY isis sib oi = 5's pypivies hiss) nee las ec ATISCOMIYy fa deems <5 bees tis Bee sn bles ea ee Natural (Science |.) ccs sac oes a se a ASEEOTIONIY. oy ie oss Lente etn Sate otk Bale sta eee Mathemticaies sisi ees stele «eee oa ee Cee Matheniaties ios istic ae oie a ie ee AStrODORIY: yrs oles ss GI Rs oe oe A SEPOT OILY) | os oj shini ssate'in ln ei ‘nd era elit ete ceate eee Physiology. ose inl, SESE Sade eles ore wee PUYBICS ie na ow bee ot cs EVIE oe aie a ee Mathoma ties). «ics bi a SES wo hew one tenn MGCDOMATICB 4 shel iatsidie’ vie" Ub) a ode ei ace THE SEVENTEENTH CENTURY Mathomatics) . 50's fe MUL ar ele ous ues, wie ane PHYSICS 6 i)s.0 le ano w'arsl ee UNDA Wnts eee ae an PR YSICR us o's bas p. sisiehn caete een oR Lee eee Mathematics v./.'4 4 24a eee ea = ev ee CHEM IBELY 9 6 o's oo o's clearer eae ot Sia bbe re ee AStronomy. \. 4+ sio0 pA. oneal e vies eae sie een AMAtOmUyyy 66: a cree ene 237 PRY SIGS. 5 8s vies Yow webct Ok et eae 239 ABtronomny (ssi ornithine sian eso eee 241 Chemistry's V0 vss 4.0 dy oe oR ee ee 242 Chemistry 35a aes shy cee Ea en eae 243 Astronomy ns. oy os ~ ee AON Mae sees Eee 245 PYROS yi a Rs e's i os ke ROG hee 247 BALGCETICI EY: inn oy 50's GPRD freee otasie e 248 Ved h a ite why eo Perera Ke ey} 250 PHOCOSTAPHY 10) o4v swe se ieee geht 251 FULOGETUCHGY i) bieih bist 0s SMALE SCAN taoe ingle a 253 ERA TYOLO MY): 5/0), sss! eileen ele We ae eta 255 Mathematles. ii \ii 5 ie cw shih aoe ee 258 BBV SOLO RY 5.0 sil! e 44 iyo alata tah arta 259 ERY BICB ie 6's p's\e'e 4. 0spe & Olde elbtahe Oe hag a en 261 ROTOR Yi 6ie aim ibis A te sk ve ahi ME NO cee uae a 263 Electricity < skis ga. wills Seale cent ah ene 264 VI. THE NINETEENTH AND TWENTIETH CENTURIES DUMAS WOHLER MULLER ABEL WHEATSTONE DOPPLER LIEBIG MAURY AGASSIZ GUYOT DARWIN FORBES GRAY ANDREWS DRAPER LEVERRIER BUNSEN PACINI DANA BERNARD VON MAYER ANGSTROM HOOKER J OULE FOUCAULT Chemistry, ibs 5s s'Gigtwels oe elalneco a eee tara 269 GHemIStr yi’. 5.48.4) s cc G88 ohana ie eee one ee 271 PRyBiOlogy.. cs's ihe kins be aeieR ee e 273 Matheomaties ..$ acy. iin 8908 ache ol ok oie rei PY RICE isis UV» Sc hikc. DCL Alc ee 277 PHY Sies.) 5 divs is o's aia Ree ree te 2 ea 278 Qhomistry. i.» 04)so24 yx seesieeiess «ae ee 279 Geography \. ns sin aye Mae kh GG eee 281 GeOlo gy). ins sm vidi, DANA IOLA ols 5 5 eee 282 Geography i.i.o'«. Ue 2kbee eae Ge wees sas eae 284 Biglogy) 24 sss eh ee ees se 286 PhHYSICH) Vos WAN 4s HD on So bs bn ee 287 Botany. J68 .'s6d 62 cas Me RU als en ee 289 Chemistry sss. eielet. ks Ge N ehey oor Le eae 291 Chemistry).'ssssy.boshe ae er eAle Wen > ho eka an 293 Astronomy), a) Nae ene Wee ae OMA ee Tr Pee Ror AnbeRRAy gs ILLUSTRATIONS “THE FOUNDERS OF SCIENCE” The above is the caption of a series of bas-relief portraits in bronze decorating the new million-dollar building of the National Academy of Sciences and the National Research Council, in Washington, D. C. Thirty-seven world scientists were chosen, only two of whom were American. HIppocraATEs, ARISTOTLE, ARCHIMEDES, COPERNICUS, VESA- PRUIG EPREVIY ass gained aes de Sie wie aie gaa oseee frontispiece PAGE GALILEO, LEoNARDO, Hipparcuus, Evcuip, Democrirvs, BUMS see ssath shade ules MN sala cde: G9: cles ae OUI Rae ELAN ALY CaRNOT, BERNARD, JOULE, PAstruR, MenpEL, MAXwELL.... 140 Humeoupt, DAtton, LAMARCK, WATT, FRANKLIN, HuyGens. 210 Descartes, Newton, LINNAEUS, LAvorsizr, LAPLACE, CUVIER, GAUSS eoeemwepeeeeeeeeeeeeeeeeeeeeseeeeee eeeeeeeeseeee eeee @¢ 290 GauTon, GiBBs, HetMHoutz, Darwin, Lye, FarapAy..... 380 ‘a ; 4 ss ' 7 ny : ’ A ‘ ran © “ee Shel 4 di + oe i ua (ane | yb \ “dh Ay r i "Wik Ge - Yh? word ‘ i y r i 7 3 ira Shoe 8 ie § 3 aes v " <1 i Hh rt ta ine td) be rs ; : 5 he Ps 7 : An ‘ : j ¢ : bat . , } mety)! : ‘ , Lo vai ' ie \ Oki Saat Nt : if hy Wi ih ' ; \ ite yi i reshs) ; J hs y i 5 . te ’ hee i N ’ Wi a! vy { ; } : } ‘ L fF ; - ‘a 4 an é t j f Py oy tive SG Fo) fe Xa | Mer aee we ON aR Ree ean My d ae ‘ ‘ \ .f ; i ' ‘y ay ; ty ‘ : yf rn aa er, mee | 4 } : p im || oe. ach fi fit ; n ‘ eA Wh ry. a mh y cay, gees A : 5 is nl } iS Tat r ‘ ' A 4k AL OE ve r - a we ‘ < tw ec eas ee by s AP Phu CHER te 2 iy ‘ M 4} ny iy J ANCIENT TIMES For the purpose of this volume it will be convenient to define its first department (Ancient Times), as the epoch extending from the beginnings of recorded human history, up to the fall of the Roman Empire in the year 476 of the present era, a period covering certainly 6000 years; for inscriptions that are clearly alphabetical in their character appear on many of the Egyptian and Chaldean monuments, whose age has been determined as early in the 5th millennium B.c. And before them for an unknown time were the years of hieroglyphs. But we may safely deduct at once at least four millenniums from this reckoning, as a period during which the art of writing was confined wholly within the priestly class, and employed only to record the principal acts of rulers, or startling occurrences like famines, floods, eclipses, etc. And about as safely another thou- sand, for the slow development of a script convenient enough in execution, to permit of the recording of conclusions arrived at by observers of those natural phenomena that were daily presented to the senses and minds of the civilized people among the ancients. This brings us down to a date somewhere between 750 B.c. and 500 B.c., at which time appeared Thales of Miletus, the first of whose story enough is known to warrant his inclusion in a list of scientists—that is, of collectors and classifiers of observed phenomena, apparent or real. Certainly there were students and scholars before his day, for by then much true knowledge of various kinds had accumulated, but their names and their histories have been lost. During the eleven hundred years remaining of the period, namely, from 624 B.c. to 476 a.D., history has preserved less than a score of names worthy of enrollment as ‘‘Beacon Lights of Science.’’ It is a significant fact that, of the total number, sixteen belonged to the Greek race, the other two, Thales and Ptolemy, being re- spectively of Phenecian and Egyptian ancestry or birth. And, as showing the versatility of Hellenic culture, four of these attained eminence in mathematics, four in astronomy, two each in botany and the healing art, one each in general philosophy, mechanics and anatomy, while to Empedocles must be accorded the supreme honor of having formulated the first known conception of the theory of evolution. BEACON LIGHTS OF SCIENCE THALES (cirea 624-560 B.c.) PRIMITIVE THEORIES THALES is reputed to have been a native of Miletus, a very famous ancient Greek city located on the western eoast of Asia Minor at the mouth of the Maeander river. By race he was of Phoenecian ancestry. He seems to have been possessed of engineering capacity, for he was en- gaged to construct an embankment along a portion of the shores of the river Halys. He was also a merchant of importance, and traveled extensively, particularly in Egypt, where he became familiar with such astronomical and mathematical knowledge as by then had accumulated among the priesthood. In consequence, upon his return to Miletus, he was able to predict an eclipse of the sun, which actually occurred in the year 585 B.c., and acquired thereby a great reputation. Being a man of wealth and leisure he decided to devote the balance of his life to philosophy, and was regarded either then or later, as one of the six or seven wise men of ancient Greece. He taught that the fundamental element of which all things was composed was water. That the earth floated upon it; that it was the cause of earthquakes and volcanos; that it was the main component of all vegetation—which apparently could not exist without it; of all animal life that lived on vegetable food, and hence by necessity, of all flesh-eating animals, including man. According to some of his commentators he regarded earth (soil and rocks), air and fire as also of elementary character, though of 3 4 Beacon Lights of Science secondary importance. He is credited with having be- lieved that the earth was of the form of a sphere, and that the year consisted of exactly 365 days. He expressed his views in words only and committed nothing to writing. Thales, whether a real or a legendary character, repre- sents the beginnings of Greek intellectual life. Before his day much information about the ordinary phenomena of life had been gathered in Egypt, Chaldea, Phoenecia, and te a lesser extent in India and China. But life was hard and unlovely among all those people, for they occupied regions where climatic conditions were severe, and the struggle for existence a pitiful one, except for the favored few. To the Greeks, however, had been given a pleasanter homeland, a more genial climate, and an environment that encouraged thoughtfulness and a desire to understand the causes of things. As their civilization advanced, a very considerable percentage of the mass of the population lived in comfort and comparative luxury. Out of such condi- tions arise appreciation of the beauties of nature, and a desire to produce beautiful things, in other words, the fine arts. Also a tendency to speculate about the mysteries of life and the universe, but without any observational foundation. These were the impelling and prevailing ten- dencies in Grecian life until the time of Aristotle (about 350 B.c), who taught a more correct way of looking at things. ANAXIMANDER (610-546 B.c.) MATHEMATICS ANAXIMANDER was born at Miletus, one of the populous and famous ancient cities of the western coast of Asia Minor. Very little is known of his personal history be- yond the fact that he became, after the death of the philosopher Thales, the head of the Ionian school of Greek thought. Aside from the reputation which this position brought to him, he is generally credited with having been the first among the ancients to proclaim that the axis of Ancient Times 5 the earth must be inclined to the extent of about 23 degrees to the plane in which it stood (or moved) with respect to the sun. In other words, he taught as a fact the phenome- non we now call the obliquity of the ecliptic. Yet there is no clear evidence that he had any true conception of the shape of the earth, of its revolution on its own axis, or of its annual journey around the sun. Yet he is believed to have been the inventor of those old astronomical de- vices the gnomon and the polos. The views of the cosmos held in his day were full of strange contradictions. It is difficult to believe that a mind capable of reaching so close an approximation to the cause of:the annual change of seasons, and of producing an instrument capable of indicating divisions of time by the changing positions of the shadow it cast, could have been wholly unacquainted with the causes behind these results. But, as was the case with most, if not all of the Greek philosophers, Anaxi- mander seems to have held and taught, along with a few eorrect facts of Nature, many others that now seem ab- surd. For instance, his conception of the Universe appears to have been that of at least three concentric transparent and revolving cylinders, to the outer one of which the sun was firmly fixed, while the middle one carried the moon, and the innermost one the stars. Within these was the earth, also cylindrical in form, and either stationary or moving with the others. He was uncertain as to the posi- tion of the five planets then known. On the other hand, according to some of the ancient writings, he made some excellent approximations of their size and relative dis- tances from each other. PYTHAGORAS (ce. 580-500 B.c.) ASTRONOMY SucH accounts as have come down to us of the life and activities of this traditionally famous Greek, are not at all clear, and much is plainly pure myth. He appears to have been a native of Samos, an island off the west coast 6 Beacon Lights of Science of Asia Minor; but of his ancestry and of his youthful years we have no reliable information. In his early ma- turity he appeared in the city of Cretona, in the southern part of Italy, which at the time was the seat of a Grecian colony. Here he founded a society or brotherhood, of the nature of an intellectual autocracy, which later took on a political cast, and became deeply involved in the fierce struggles then in progress throughout the Grecian world between democracy and plutocracy. In the end the few Pythagoreans who survived were driven from the country. It is not known whether Pythagoras escaped before the culmination of this event, or perished in it. Whichever was the case, Pythagorism represented subsequently some very strange conceptions of the Universe, which have come to us through contemporaneous and subsequent writers, but so alloyed with fable and nonsense that students of Grecian history and thought have found it very difficult to decide with any degree of certainty much more than the outline of his teachings. Not a word that could be safely ascribed to him personally has been preserved, and of the writings of his disciples we have only fragmentary re- mains. From these, and from later writers, two of the more startling of the tenets of the cult appear to have been as follows: : As to the substance of the world, they conceived it to be composed of material atoms, each one of which was so infinitesimally minute as to represent position only, without size. Two, side by side, expressed a line and conveyed the idea of direction, but again without magnitude. Three (one being at right angles to the other two) indicated surface, but without thickness, thus being merely the rep- resentation of area or extension; while four (the fourth at right angles to the other three) constituted a solid, or the conception of Form. Thus the three-dimensional prop- erty of Space was reached and explained. It was regarded as unlimited in extent, and filled with air, or, according to others, a void. As to the atom, if it were of earthy matter it was believed to possess the shape of a cube; if of fire, that of a tetrahedron or three-sided solid; if of Ancient Times i water, that of an icosahedron or twenty-sided figure, while those of all other substances were twelve-sided masses. Out of all this rubbish the only item of importance is the conception of the atom as the ultimate component of mat- ter. In regard to the external Universe, the Pythagoreans taught that at its center there was a source of light and heat in the shape of a perpetual and intense fire, and that all the heavenly bodies—including the earth—revolved around this in concentric circles at various distances apart. That the earth was the nearest to this source, and made its revolution in such a way that one of its hemispheres always faced this source (just as one face of the moon only is presented to the earth), and was necessarily uninhabit- able, on account of its intense heat. All the other celestial bodies shone by reflected light only, the earth obtaining its share by reflection from the largest of them, the sun. When the earth is on the same side of the central fire as the sun the phenomenon of daylight exists. When it is on the opposite side, that of night supervenes. These examples of Pythagorean philosophy are suffi- cient to show that its founder and his disciples were people ~ gifted with vigorous imaginations, but poorly equipped with demonstrated facts; just such a combination as might have been expected of the lively and speculative Greek mind at that age of the world; so different in its nature from that of the still older Egyptians and Babylonians, each of whom developed theories of the Universe of a very different kind. Whether Pythagoras ever existed as an individual, or whether the name simply stands for a system of philosophy having for its object to account for the innumerable mys- teries of existence, the cult very properly takes its place among the beginnings of science for, in spite of the mass of error it stood for, here and there appear conceptions and conclusions that have since been demonstrated as re- alities. 8 Beacon Lights of Science EMPEDOCLES (495-435 B.c.) EVOLUTION Tus Greek philosopher was born of a distinguished fam- ily whose home was in the city of Agrigentum in Sicily, when that island was a Grecian colony. In addition to having attained a high standing as a physician, he is re- garded as one of the notable philosophers of the ancients. He also appears to have been a strong advocate of certain political doctrines of a democratic tendency, which he en- deavored to put in practice in his native city. Very little reliable information of his life has been preserved, but many marvelous stories have come down to us relating to his beliefs and ideas, and to his powers as a physician. The most of these are simply exaggeration, though perhaps based on real facts of a less startling nature. Of the manner of his death several tales are told. The most com- mon was to the effect that he leaped into the crater of Mt. Aetna. Another states that he experienced translation, after the manner of the Jewish prophet Elijah. He is said to have performed several miracles, one of which was to bring back to life a young girl long dead; and another to avert from Sicily a pestilence raging in southern Italy, by compelling a change in the direction from which the wind was blowing. Amid all this legendary nonsense it seems to be a fact that he was one of those early thinkers who had grasped some germs of the idea of evolution, in his endeavor to account for the mysterious phenomena of the Universe. Aristotle was another. With Empedocles the theory took form in the saying that ‘‘Nature produces those things which, being continually moved by a certain principle contained in themselves, arrive at a certain end.’’ To connect the rather obscure meaning of this sentence with the modern doctrine of evolution requires some knowledge of the brand of philosophy he represented. He held that ‘‘Being,’’ by which he meant Matter, was eternal and im- perishable. He considered it to be of four kinds or ele- Ancient Times 9 ments mutually independent, namely, earth, air, fire and water. He maintained the existence of two fundamental and opposing forces, which he typified as Friendship and Strife; the first of which was the indwelling and normal principle, and the second the external and abnormal one. These two, in their perpetual conflict, the one to maintain the status quo and the other to change it, produced all the phenomena of nature. He held that these changes were constantly and imperceptibly occurring, and had been throughout unknown ages in the past, with the effect of steady progress upward in all phases of existence. Finally, that man was, at the present, the highest product of the process. In thus indicating that the principle he ealled Strife—by which perhaps he intended to convey the idea of competition for existence or supremacy—was always in the end victorious, he may have grasped the germ of the idea at the foundation of Darwinianism, the survival of the fittest. With Empedocles chance, or acci- dent was the cause of the successes of Strife over Friend- ship. Aristotle rejected this as of the nature of an impiety. DEMOCRITUS (cirea 470-400 B.c.) NATURAL SCIENCE THis notable Greek, whose birthplace was the ancient town of Abdara in Thrace, went by the name of ‘‘The Smiling Philosopher’’ among his intimates, because of the geniality of his disposition and his optimistic temperament. About all that is known of the details of his life is that he was a man of high moral character and strong religious tendencies, was well educated according to the standards of the time, was deeply interested in mathematics and astronomy, wrote extensively on these subjects and on philosophy, and had traveled through much of the civilized world of his day. Only fragments of his writings have been preserved. These were collected and published by Mullach in Berlin in 1843. From them, aided by references in, and commentaries by other writers—both Greek and Latin, it 10 Beacon Inghts of Science has been possible to deduce the general system of philoso- phy which he held, and probably taught. It was based on a theory of that aspect of matter which the mind receives from the five senses, the essential nature of which has been considered, until recently as unknowable; but which now seems to have been resolved into one of the manifestations of the equally unknowable entity we call Energy. In his system a material atom was postulated, infinite in multitude, not all of one size or kind, but each endowed with the power of motion, and the ability to unite into aggregates of all dimensions, forms and quantities, under certain pre-ordained laws; some of which eventuated in the phenomenon of life, and others in static con- ditions, which were apparent in those manifestations like rocks and metals, which plainly lacked the vital quality. For these reasons his philosophy was known among the Greeks as the Atomic System. To Democritus therefore belongs the credit of having first conceived the idea of the material atom. To what the theory led, and what speculative structure he reared upon its foundation, is not clear. He denied the existence of Design in the Cosmos, but asserted that of immutable law. Animals, vegetation, moving air and water, he regarded as combinations of atoms of average quality. Consciousness and thought the product of the coming to- gether of particles of a finer kind. And he postulated the existence of a third and superior class, of which the sub- stance of the High Gods was composed. Happiness he considered as the supreme object of existence. To attain it, the passions must be controlled, and temperance made the rule in all departments of life. As to a possible future stage of being, he seems to have had no theory. It is thought by some students of the Greek mind that Epicurus (circa 324-270 B.c.) was a believer in his philos- ophy, and taught it, with probably some amplifications of his own. According to him, fear of the Gods and fear of death were the two great destroyers of human happiness, and the main objects in life were to overcome these terrors, by rising superior to them, Believing that Personality Ancient Times 11 ended with death, he argued against looking to the future for any amelioration of present condition; insisted that hfe was wholly an affair of to-day, that it was beautiful, that it was the summit of wisdom to enjoy its gifts as they eame, but always temperately, and with consideration for others. He thought that the gods were imperishable, and could have nothing to do with us, inasmuch as they lived on a different plane. If these were also the ideas of Democritus, they were rather above the average of the time, but have little value for the present. HIPPOCRATES (circa 460-375 B.c.) MEDICINE HIpPPocraAtEs, the most celebrated Greek physician of his time, who is called the Father of the Medical Art, was claimed by his contemporaries to have been the seventeenth or nineteenth in direct descent through his father from the mythical Aesculapius, and through his mother from the equally mythical Hercules. He was a native of Cos, one of the Aegean isles, where he practiced his profession, and was at the head of the medical school there until old age compelled retirement. Much of his supposed history is undoubtedly fabulous and unreliable, but that he was an unusual man for his time, and held some very advanced views in anatomy, and on the treatment of diseases, can hardly be denied. The latter, broadly, took the form of a strong reliance on the forces of nature, and on the power of the body itself, to eliminate or overcome disorders even of a serious kind, if aided by proper regimen and improved environment. With this was coupled an equally strong disinclination to interfere with the normal functions of the organism by the administration of drugs. Thus, he often prescribed merely a change of climate, or an altered and limited diet, or the securement of conditions that would provide absolute quiet and long hours of sleep. Frequent bathing of the entire body, sometimes in cold, and at others in warm or hot water, was also a favorite method adopted. 12 Beacon Lights of Science It was probably this very sensible system which, as is now well known, will cure a very large percentage of human bodily ills, that brought him the high reputation accorded by his contemporaries. The writings that bear his name are seventy-two in number, but many of them are now ascribed to his sons, Thesalus and Draco, and his son-in-law, Polybus, all three of whom were his assistants in‘ his practice. The fifteen to twenty that are considered actually his are marked with a sanity of view and an absence of mysticism unusual for his age, and point to the conclusion that his reputation was well earned, though probably not so astonishing as some biographers of his time and since would have us believe. PLATO (427-347 s.c.) PHILOSOPHY AND MATHEMATICS THE real name of this Greek philosopher was Aristocles. He was a native of Aegina, a small island just off the southeast coast of Greece, and a dependaney of Athens. His parents were large land owners of the upper class, and in consequence he was given the best education that the times afforded, the most of- which was absorbed at the Lyceum conducted by Socrates. Of the details of his life little is known, but according to tradition he distinguished himself as a youth in athletics, and was a composer of poetry. But none of his productions in this line has been preserved, for at the age of twenty he became so interested in the philosophy of his great teacher, that he is said to have burned them as unworthy. He was so affected and even embittered against the authorities of the time at the judicial murder of Socrates, that it is thought he left Athens shortly thereafter, and spent the following ten to twelve years in travel in northern Greece, southern Italy, Sicily, Libya and Egypt, in the seareh of a civilization where more liberal and friendly and honest conditions pre- vailed. Of the truth of this quest there is no clear evi- Ancient Times 13 dence, but in the year 387 B.c. he was again in Athens, at the head of an organization called the Academia, which held its meetings in a public garden or grove outside of the city, that formerly had been a semi-sacred place, dedi- cated to the memory of a mythical hero named Academus. There, for forty years, and until his death, Plato taught, and discussed with his pupils the questions of the day and, as was the custom of the time, instructing them during the periods of recreation in athletics, on the theory that the body and mind should be developed together. Among his more famous pupils were Aristotle, Demosthenes, Lycurgus the financier and Eudoxus the astronomer. It is believed that Plato exercised unusual care in admitting students to his lectures, and refused to take pay from them, on the theory that Truth should be imparted freely to all who were earnest seekers after it. His standing as a scientist rests primarily on the well- attested fact that, for his day, he was a mathematician of a high order, though not a discoverer of any new prin- ciples in numbers, or the developer of any new system of working with them. Nor did he teach it directly. In fact no one was allowed to attend his classes who had not already become fairly proficient in the science. Regard- ing it as the one department of knowledge in which certi- tude of result could be obtained where correct premises had been employed, he endeavored to lay the foundations of a system of philosophy which could be depended upon with equal confidence. In this he attained a certain degree of success, yet by no means a complete one. For, though we can today read much of his writings with advantage, and admit the possibility of some of his conclusions, the best thought of the world at present is to the effect that certain conceptions of which the human mind is capable are scientifically unknowable, in the sense that their parts cannot be assembled, classified, grouped and organized into a coherent body of demonstrated fact, that can be relied upon as long as it continues to be satisfactorily explana- tory of observed phenomena. In a day when polytheism was the accepted religion of 14 Beacon Lights of Science the educated, Plato taught what may be described as a pure theism, that is, belief in a Deity related closely to all living things, vegetable, animal and human, but at the same time he made no attempt, toydefine the nature of the relationship and, in fact, asserted that definition was im- possible. Beyond this in religion he did not go. But in ethics he felt justified in going to great lengths. Plato wrote very extensively. But much has been lost, and much that was originally credite@ete. him is regarded as spurious by present-day students. Rejecting the latter, the fundamentals of the philosophy he taught seems to have been about as follows: Truth is hard to find, and in many cases impossible; but it is wise to discuss it in all its aspects Hecause, by such a treatment, much of error can be avoided. As to conduct, which he ealled the ‘‘ Royal Art,’’ he re: garded it as a science, which must be learned through experience, just like a material art, as carpentering. Its basic principle, self-sacrifice when necessary, once grasped, must be obeyed relentlessly to the end. Plato was inherently a metaphysician, and metaphysics is regarded today as a diversion, which leads nowhere, and to nothing except temporary mental amusemertt. In other words, it is not common sense to the average human mind as at present constituted. As it may with reason be as- serted that individual mentality has evolved to a higher state than was existent among the Greeks, his philosophy ean be admired as among the most advanced of that time, his ethics can be commended whole-heartedly, but many of his conclusions should be recognized as adolescent in char- acter, and below the standard which should be held now. id ‘ARISTOTLE (384-322 B.c.) NATURAL SCIENCE THE distinguished thinker, Aristotle, was a native of the ancient Greek city of Stagira, which was situated on that curious three-pronged peninsula projecting into the Aegean Ancient Times 15 sea to the south of the present city of Saloniki. In olden times the region was a part of the kingdom of Macedonia. He belonged to an aristocratic and wealthy family in which learning had been hereditary for many generations, his father having been court physician to King Amyntas IT. He received the best education that the times could afford. At the age of seventeen he went to Athens and associated himself with the school of which Plato was the head, and studied under that great teacher for nearly twenty years, becoming towards the last one of his chief assistants. After Plato’s death Aristotle moved to Mysia on the north- western coasts of Asia Minor. Three years later, just be- fore the capture of that place by the Persians, he removed to Mitylene, the capital city of the island of Lesbos in the Aegean sea. In 342 B.c. he moved to Pella, then the capi- tal of Macedonia, and for the next three years supervised the education of Alexander, the presumptive heir to the throne, who later became Alexander the Great. When, by the death of his father, this youth became king, Aristotle remained seven years longer, attached to his court, and held in high esteem by his former pupil, to whom, in that period, he acted as an adviser. In 334 B.c., at the age of fifty, Aristotle returned to Athens, and opened a school of his own, which at once be- came famous, and where he taught for twelve years until the death of Alexander in 328 B.c., when he moved to the city of Chalecis in Greece, and gave up his school in the attempt to recover his failing health. There, however, he died in the following year, at the early age of sixty-three years. Aristotle was probably the most voluminous writer of ancient times. In his works he dealt with almost every subject of which the people of his day had knowledge, or thought they had. These included religion, law, logic, rhetoric, metaphysics, physics, astronomy, meteorology, natural history, botany, zoology, anatomy, medicine, me- chanics, ethics, politics, physiology, psychology, poetry and literature in general. In matters of science (except mathe- matics and geometry) his works have no value at the pres- 16 Beacon LInghts of Scvence ent time, yet all of them exhibit remarkable analytical power, and such as have come down to us either in part or complete, have exercised an enormous influence. In many cases he gave expression to thoughts and conclusions which contain germs of discoveries made since. Perhaps the most notable of these was his speculation on origins and growths, which come very close to the fundamentals that are at the basis of the theory of Evolution. Accord- ing to him, Being, or Existence, was the summation or visible expression of four universal elements or principles, which he named as Matter (in all its manifestations), Form (in all its variation of shape), Causes (active forces) and Results (evident effects). At the beginning of things he postulated a definite plan which, at the end of things, was to produce a definite and foreordained result. This, for man, was happiness; and for all the other expressions or manifestations of matter, such as plants, animals, and all phases of inorganic nature from rocks to planets and stars, was perfect adaptation to environment. Change was everywhere in progress; had been from the beginning, and would continue until the end planned had been attained. This process of slow alteration advanced step by step through potentiality to actuality, never ceasing its march. For chance, or free will, which Empedocles regarded as the cause of changes, Aristotle substituted a potentiality in two directions—for good and for evil—maintaining that the choice of either resulted in the habit of either, culmi- nating in the two extremest of self-indulgence and asceti- eism, both of which were abnormal, reprehensible and un- fortunate, while virtue was a middle course between the two, that is, temperance in all things. As for the funda- mental cause of the continual changes in progress every- where, in both the animate and inanimate worlds, he con- tended that it must be found in the perpetual contest be- tween the inherent, invisible and unknown potentialities for good and evil. The ancients had no collection of demonstrated facts upon which to base their reasonings, such as the scientists of the present time possess. It is therefore not difficult Ancient Times 17 to understand the very diverse conclusions reached by their philosophers in their search for Truth. These have no value at the present day beyond their literary merit, and the evidence they give of the gropings of the human mind in the darkness that then surrounded it. But for nearly two thousand years those of Aristotle were controlling in- fluences in the drama of humanity. THEOPHRASTUS (370-286 B.c.) BOTANY THEOPHRASTUS was born at Eresus, on the island of Les- bos, in the Aegean sea, and was of Greek parentage. He studied at Athens, at first under Plato, and then in the Aristotlean school, which was called—perhaps in a spirit of levity—the Peripatetics, because, during its lectures, it was the habit of its master to walk around the court, and in the gardens adjoining it, his pupils surrounding and folowing him. At the death of Aristotle, Theophrastus was elected its chief. In purely philosophical matters he followed the teachings of the departed leader; but, having himself decided inclinations to natural history in its bo- tanical aspect, he emphasized that science in his lectures until the school slowly came to be regarded as a collecting center, to which specimens from the world of vegetation were brought for investigation, classification and deter- mination of character. Unlike the herbalist Dioscorides, whose interest in plants was confined to the uses to which they could be put in the practice of medicine, Theophrastus sought to discover their relationship to each other, and was but slightly interested in their virtues. His first step was to separate them into the three broad categories of trees, shrubs and herbs, a classification which continued supreme from his day until near the close of the 17th century, when the better system of Linnaeus superseded it. Theophrastus is thus very properly regarded as the founder of the science of botany, for before him no one had attempted an organization of the members of the vegetable world. 18 Beacon Lights of Science Lacking the enormous aid which even the crude micro- scope of the day of Linnaeus afforded in the study of plants, the discoveries made and recorded by Theophrastus are remarkable. They appear in his writings mainly as isolated statement, which must have been obtained in dissection and analysis by unaided vision. And while his system was crude, being based only on the external feature of comparative size, and was only carried a few steps further by the subdivision of these three major orders, it was a beginning in the process of organization which at once differentiated his work from that of the herbalists. Two of his literary products have come down to us in complete condition. One, entitled ‘‘ History of Plants,’’ is in nine books. The other, called ‘‘Theoretical Botany’’ is in six books. Besides these, he wrote essays on Min- erals, on The Physical Senses, on Fire, on Metaphysics and on several other subjects of minor importance. But of them only fragmentary remains are extant. A volume of his sketches has been preserved almost intact. In 1592 a complete edition of all his known writings was published | in Leyden, and in 1818 and 1866 in Leipsic and Paris. The first is most famous and useful, because accompanied by commentaries. It is a remarkable fact that in its pages are to be found many accurate descriptions of details in plant anatomy, which were rediscovered by modern botan- ists only with the aid of the microscope. ERASISTRATUS (335-265 B.c.) ANATOMY THE Greek physician and anatomist, Erasistratus, was born on the island of Cos in the Aegean archipelago. The actual dates of his birth and death are unknown. But in 294 B.c., when presumably in his prime, he was employed as personal physician to Selucis Nikator, King of Syria. Subsequently he abondoned the active practice of his pro- fession, and devoted himself exclusively to the study of anatomy, where he made a number of important discov- Ancient Times 19 eries. He seems to have been the first to comprehend and define the difference between the sensory and motor nerves of the body, and to trace both to their source in the brain, though there is nothing in what remains of his writings to indicate that he conceived the latter to be the seat of the mind. He also made a close approach to a correct un- derstanding of the functions of the heart, and the duties of the veins and arteries which lead from it to all parts of the body, but did not appear to have comprehended the work of the blood which circulated in them. He was a voluminous writer, but only a few fragments of his trea- tises have been preserved. Perhaps, if more had come down to us it might appear that he preceded Galen nearly five hundred, and Harvey nearly two thousand years in the discoveries for which they have the credit. So great was his reputation while living that, after his death, a School or Society of physicians and surgeons was organized who called themselves Erasistrateans, and who professed to practice and teach the physiological and ana- tomical principles for which he stood. But it did not last long, and there are indications that many of its members were practitioners of an inferior order, if not what we would now class as quacks, who merely joined to obtain the advantage in reputation which would be thought to attach to real pupils of a great master. EUCLID (circa 300 B.c.) MATHEMATICS LitTLE is known of the ancient and famous mathema- tician, Euclid, beyond the fact that he was a Greek by birth, was living and teaching in Alexandria during the reign of the first Ptolemy (323-285 B.c) and was the most renowned writer of his day on his subjects. His extant works that are considered his own beyond question are: ‘‘The Elements,’’ ‘‘The Data,’’ ‘‘The Phenomena,’’ ‘‘The Opties,’’ ‘‘The Reflections,’’ ‘‘The Divisions of the Seale,’’ and ‘‘De Divisionibus.’’ It is thought that he 20 Beacon Lights of Science wrote several—perhaps many—others, which have been lost. Of this list the first mentioned is the one that has im- mortalized him. It was in thirteen parts. Its reputation was so great that it was translated into Arabie under Haroun al Rashid (Aaron the Just), the renowned caliph of Bagdad (A.p. 786-809), and again under his son, Al Mamun. The latter version was rendered into Latin about A.D. 1120, and printed in Venice in 1482. It is now more than twenty-two centuries since Euclid worked out his famous propositions in plane and solid geometry and trigonometry, yet today they are taught in our schools with but slight modifications. In the develop- ment of the sciences, mathematics is the first step. With- out it, the second, mechanics, cannot be taught, nor can the third, astronomy, advance beyond the stage of observation. A Euclid was necessary before man could do much more than take notes and speculate on the phenomena of nature. It is true that there were mathematicians of sorts before his day, but he is rightly considered the father of that science. All of his propositions but two remain undis- puted, and these two (which will be found under the chap- ter devoted to Lobatchevski) are still correct for plane surfaces, but not for curved ones. The city of Alexandria where he taught, was founded by Alexander the Great in the year 332 B.c., and was there- fore in its first youth in his time. It was laid out by the architect Dinocrates of Rhodes on mathematical lines, in the shape of a parallelogram, its streets crossing each other at right angles. Egyptians, Greeks and Jews were the principal elements of its population, the proportion of each being in the order given, the Greeks constituting the in- tellectual, the Jews the commercial, and the Egyptians the laboring classes. Under the dynasty of the Ptolemies it flourished amazingly, and rapidly became the foremost city of the ancient world both in commerce and culture. To it the scholars and students of all the civilized nations of the time flocked, the former to teach and the latter to learn. Euclid, as one of the first class, established his Ancient Times 91 school in an inconspicuous locality, where it at once became so famous that the king (Ptolemy I, surnamed Soter, The Preserver), provided a special auditorium for his use, and conferred on him every privilege and honor that could be desired. His classes were taught in Greek. The desire to attend them was so great that language schools were imme- diately established in the city, where the Egyptians, Arabs, Hindus, Persians, and other non-Hellenic people could ac- quire the classic tongue of the time. ARCHIMEDES (287-212 3.c.) MECHANICS ARCHIMEDES, who bears one of the most distinguished names among the ancients, was born at Syracuse in Sicily, at a time when that part of the island was still a colony of Greece, and under the rule of King Hiero II. As for several centuries it had been alternately in the possession of Greece and Phoenecia, it is possible that his ancestry was more or less of a mixture of the two races. His education was obtained at Alexandria, in Egypt, which was then a Greek colony under Ptolemy III, and ranked as the most famous center of learning in the world. His achievements indicate the possession of a gifted mathematical mind, coupled with the imagination of the natural inventor. He was a brilliant geometer, ranking in his time next to Euclid. He explained the principle of the lever, which indeed, as a mechanical contrivance, had been employed since remote antiquity; but so far as the records go, had not previously been mathematically investi- gated. Concerning its powers he is supposed to have said: ‘Give me a place where I can stand, and a fulerum, and I will move the earth.’’ He also was the discoverer—or at least the first known employer—of the principle that ‘‘the weights of bodies are proportional to their masses,’’ in which the word mass means ‘‘quantity of matter’’ and not volume. According to the story, the king had ordered a new crown, and had furnished the artificer with a definite weight of pure gold for its manufacture. When the article 29 Beacon Lights of Science was delivered there was a suspicion that silver or even a base metal had been substituted to some extent for the precious one, and the matter was referred to Archimedes for investigation. As the geometer was stepping into his bath one day while the problem was under study in his mind, he was struck by the amount of water displaced by his body and spilled over the edge of the tub. At once he saw the solution of the problem. In his excitement he ran through the streets to his home entirely naked, and shouting ‘‘Kureka!’’ (I have found it). To Archimedes was due the development of that depart- ment of geometry called ‘‘Conic Sections,’’ treating of the circle, ellipse, parabola and hyperbola, all of which had of course been recognized before his time, but whose prop- erties had not been mathematically studied. He was a voluminous writer for his day. Of his works that are extant, three are devoted to plane geometry, three to solid geometry, one to arithmetic and three to mechanics. Like all the earlier mathematicians he tried to square the circle, and as the result of his calculations announced that the value of «+ was somewhere between the figures 3.1408169 and 3.1428571, thus admitting in the end the insolubility of the problem, but indicating closely the ratio between diameter and circumference now employed. On the other hand, he succeeded in demonstrating that the area of a segment of a parabola is two-thirds that of the enclosing parallelogram, which was the first instance on record of the quadrature of a curvilinear surface. In his ‘‘Method of Exhaustion’’ he made an approach to the modern study of the Calculus. He was killed during the sack of Syracuse by the Romans under Marcellus. When that famous commander learned of his death he expressed great regret, and ordered a monu- ment to be erected to his memory. On it was engraved in stone a sphere inscribed in a cylinder. The great Roman statesman, Cicero, who was appointed governor of Sicily in 76 B.c., made a visit to this tomb, and gives a descrip- tion of it in his ‘‘Tuscan Disputations.’’ Its location at the present time is unknown. Ancient Times 93 ERATOSTHENES (276-196 B.c.) ASTRONOMY ERATOSTHENES was born at Cyrene on the north coast of Africa, in the ancient Greek province or colony called Cyrenica, the region now known as Barea. He was of pure Grecian ancestry, and was given an excellent educa- tion under the noted instructor Callimachus, who later became the chief at the Alexandrian library. Upon attain- ing manhood Eratosthenes went to Athens, and later to Alexandria, where he served under his old master; and finally in 240 B.c., succeeded him at his death. There he remained during the balance of his long life until, at the age of eighty or thereabouts, having become totally blind, he died of voluntary starvation. While in his prime he was a writer of note. Of his essays many fragments are extant, which indicate that his culture was an unusually broad one. He disliked to be called a philosopher, prefer- ring the title of philologist (a lover of learning). He wrote on poetry, geography, mythology, anatomy, philoso- phy and literature in general. In science he is remembered as the first to make an esti- mate of the size of the world, on the assumption that its shape was that of a perfect sphere; and also among the first to calculate the angle which its equator makes with the ecliptic, the plane of its orbit in its annual journey around the sun, a measurement which is technically called at the present day the ‘‘obliquity of the Ecliptie.’’ In regard to the first of these: having ascertained that at midsummer in the city of Syene on the upper Nile— now the modern city of Assuan—which is located at about latitude 24° North, the sun shone at the bottom of a deep well there, he properly concluded that at the moment its * position must be vertically overhead, or in the zenith. On the same day he measured the altitude of the sun at the eity of Alexandria, whose latitude is approximately 31° North. He found the altitude to be a little over seven de- grees from verticality. Between Syene and Alexandria 24 Beacon Laghts of Science (which are nearly on the same meridian) the distance was regarded as about 5000 stadia. The are of a circle sub- tended by an angle of seven degrees being approximately one-fiftieth of a circle, he concluded that the circumference would be fifty times five thousand, or 250,000 stadia. Un- fortunately, the exact length of the Greek stadium is un- known. It was the length of the national straight-away race course, and was always the equivalent of 600 Greek feet, which, if of the same length as the Latin foot, would be 0.2957 meter, or say 1114 inches, making the stadium 177.42 meters or 586.3 feet. But the Greek foot was itself a variable measure. However, calling the stadium 600 modern feet, or about one-ninth of a standard mile, the result reached by Eratosthenes would be 27,700 miles, which is so close an approximation to the true figure of the polar circumference (24,806 miles) as to make the per- formance a most ereditable one for the time, if we consider the crude instruments then available for measuring celes- tial altitudes, and the fact that the distance between the two cities was probably ascertained by pacing, and there- fore certain to be quite inaccurate. In the matter of the obliquity of the ecliptic he came much closer in his result, for his figure of 23° 51’ 19.5” differed but little from accuracy. At the present time the angle is 23° 45’. As this angle, in consequence of the pre- cession of the equinoxes, has been diminishing at the rate of about 50” per century since Eratosthenes made his esti- mate, the true figure for the angle at his time would have been 23° 62’ 20”. ARISTARCHUS (cirea 265 B.c.) ASTRONOMY THE native place of Aristarchus was at Samos, on the island of Cephalonia off the western coast of Greece. He is distinguished as having made the first recorded attempt to ascertain the comparative distances of the sun and the moon from the earth, by geometrical means. Nothing else Ancient Times 26 is known of his history, and all his writings have been lost except a short essay describing his solution of this problem. In his day the earth was regarded as fixed and immovable in space, while the sun, moon, planets and stars moved around it. But to him it seemed more reasonable that the earth was a satellite of the sun, and the phenomena of eclipses—which he seemed to have thoroughly under- stood—confirmed him in this belief, for at their oceur- rences it was evident that the shadows cast by the earth on the moon, and by the moon on the sun, indicated clearly the relative distance of each. He therefore reverted to the older theory, according to which the earth was not stationary but revolved daily on its axis, insisting that the central fire postulated by Pythagoras was a myth, and that the sun did not shine by reflected light, but was itself luminous and, in fact, the source of all light coming to the earth, not only directly, but by reflection from the moon, the planets and the stars. Acting on this theory he reasoned that when the moon’s phase was in its first or third quarter, at which times it showed itself as a half sphere, the position which the three bodies occupied with respect to each other must be those at the vertices of a right-angled triangle, the moon being at the right angle of 90°, the sun at the most acute of the other two, and the earth at the least acute. He then at- tempted to measure with such instrumental assistance as was available in his day, the amount of the angle between the sun and the moon at the earth, at the half-moon stage of the satellite, and after repeated observations concluded that it was in the close vicinity of 83°. As the sum of the angles of a plane triangle are invariably 180°, and as the angle at the position of the moon was, by assumption, 90°, that at the sun must be the difference between 83° and 90°, or 7°. Having then the three angles of the triangle, it was a simple geometrical problem to calculate the rela- tive length of the line extending from the earth to the moon as compared with that extending from the earth to the sun, namely as one to twenty. In theory Aristarchus was absolutely correct. But in his 26 Beacon Lights of Scrence day no instrument for measuring angles accurately between bodies at great distances from each other was in existence. Moreover, and for the same reason, it was not possible then to determine exactly the half-moon stage. His data there- fore were in error, and hence his conclusion. It is now known that the angle at the earth between the moon and the sun, at the half phase of the former, is only a fraction of a minute less than 90°, instead of 83°. In consequence, the comparative length of the two distances from the earth to the moon, and from the earth to the sun, is as one to four hundred in place of one to twenty. His essay on this subject was published in Latin at Venice in 1498, and at Oxford in 1688 in the original Greek text. APGLLONIUS (cirea (225 B.c.) MATHEMATICS APOLLONIUS was a native of the city of Pergamos, in Asia Minor. The date of his birth is unknown, and prac- tically nothing of his personal history has come down to us except that he was the author of a treatise on the conic sections, which was so highly regarded in his time and for many centuries afterwards, that nearly the entire work of eight books was translated into Arabic, and later the fifth and seventh into Latin. The conie sections are those curves produced at the in- tersection of a plane with an upright cone. If the latter is cut horizontally and at any point of its height, the curve resulting is a circle. If the intersection occurs at any angle below horizontal and above parallelism to the slope of the sides of the cone, the curve is an ellipse. These two are closed curves, as they return to themselves. If now the plane intersects the cone at an angle parallel to the slope of its sides, a parabola is produced; and finally, if the intersection is parallel to the vertical axis of the cone the resulting curve is the hyperbola. These two are open curves, not returning to themselves. All four were first Anctent Times Q7 described by a Greek geometer by the name of Menaechmus who lived at some time during the fourth century B.c. and about whom nothing is known beyond this fact. They greatly interested the mathematicians of the day and many of their properties became known. Especially in the case of the ellipse, which Apollonius aptly described as the curve with two centers. When Kepler showed that the planets revolved around the sun in ellipses, and Halley that the periodic or returning comets did also, that curve became of greater interest than ever to astronomers. To the layman the properties of the parabola are perhaps most attractive. It might be called a curve of one center, though better described as a curve of one focus. If, for ihdeatioe, a mirror is so constructed that all its axial sections are parabolas, and a beam of light is cast into it, all the rays will be reflected to the one point which is its focus. Or, conversely, if a source of light is set at the focus, all of it will be reflected outward in a beam whose rays are parallel to each other. This property is employed in the construc- tion of searchlights and lighthouse reflectors, producing a beam that penetrates a long distance before suffering dis- persion. Also, in a smaller way in locomotive and auto- mobile headlights. HIPPARCHUS (cirea 161-126 B.c.) ASTRONOMY THe Greek astronomer and mathematician, Hipparchus, was born at Nicaea in Bithynia, a political division of Asia Minor lying along the shores of the sea of Marmora and the Black sea. All his astronomical work, however, was done on the island of Rhodes. Of his personal history nothing is known. His writings also have been lost, but portions of them have come down to us through the works of Theon of Alexandria (circa A.D. 870), and of Ptolemy Philadelphus (A.p. 100-175). It is known that he wrote nine separate books, but of these only the ‘‘Commentary on Aratus’’ was reproduced com- plete by any subsequent writer. 28 Beacon Lnghts of Science He is regarded as the founder of the science of trigo- nometry. He computed a table of chords, and is credited with a knowledge of the quadratic equation. He was the discover of the phenomenon known as the precession of the equinoxes, and is supposed to have been the inventor of the astrolabe, that instrument of the ancients with which they took the altitude of the heavenly bodies, and which was employed for that purpose in navigation until super- seded by the quadrant about 1730 and later the sextant. Hipparchus drew up a catologue of more than one thou- sand of the fixed stars. The ecliptic is the name given to the great circle round which the sun seems to travel from west to east in the course of the year. It was so called because the ancient astronomers quickly observed that eclipses happen only when the sun and moon are in or close to that circle. As is now well known, it is really the plane along which the earth actually moves in its annual journey around the sun. The plane of the earth’s equator, which divides it into the northern and southern hemispheres, if it be imagined as extended out into space, would not coimecide with that of the ecliptic. Instead, the angle between the two at the present time is about 2314 degrees, and is diminishing at the rate of about 50 seconds (or one-seventieth of a degree) per century; or say a degree in seventy centuries. If it kept on diminishing at that rate, in 1645 centuries the two planes would coincide. Fortunately this angle— which is ealled the obliquity of the ecliptic—has limits, which it does not and cannot pass. Astronomers calculate that it will reach its lowest possible amount of about 2214 degrees in approximately 150 centuries from the present date, after which the motion will begin to reverse, and the angle between the two planes to increase until a maximum of nearly 25 degrees will be attained at the end of another 330 centuries, or 480 centuries from the present time, when again a reverse movement will be inaugurated. Early in the history of astronomy it was observed that twice each year, namely, about the 21st of March and the Ancient Times 29 23rd of September, the sun is vertically overhead at noon on the equator. These are called the equinoctial dates, and mark those places on the plane of the ecliptic where the plane of the equator, if extended sufficiently outward, would intersect it. These two points are not in- variable positions. Each year they move forward to the extent of about one-seventy-secondth part of a degree. As there are 360 degrees in a circle, it is plain that in about 25,920 years they will have made a complete circle of the plane of the ecliptic. This phenomenon is called the pre- cession of the equinoxes. It is very remarkable that it was detected by this Greek astronomer over 2000 years ago, whose only observational instruments were the astrolabe, the gnomon and the polos. He was unable to explain its cause, which remained more or less of a mystery until Newton announced the laws that control the movements of the planets in space. DIOSCORIDES (cirea a.p. 64) BOTANY PEDANIOS D10ScoRIDES was a native of the Greek city of Anazarbus in Asia Minor. His profession was that of a physician. In his day that occupation did not include the practice of surgery, nor require a knowledge of anat- omy, though, in ease of light injury, or in emergencies, he was allowed to do what he could to relieve suffering. Of his early history, or of the degree of his educational equipment, nothing is known. He is first heard of as at- tached to the Roman army in his professional capacity, which took him to many parts of the known world of the day. Apparently he was a lover of nature, and used the opportunities his occupation provided to study vegetable life, and to make a remarkable collection of all the plants encountered which yielded, or were supposed to yield, medicinal virtues. These he listed and described in his monumental work entitled ‘‘De Materia Medica,’’ after physical disabilties and advancing years compelled him to abandon army life. 30 Beacon Lights of Science So complete was this treatise that for fifteen centuries after his death it remained the standard work on the sub- ject. It was written in the Greek language, but while the author was still living a Latin translation was made; and later, from this, was rendered into most of the tongues of western Europe, as well as into Arabic, which was then the classical language of the East, as Latin was of the West. It was not until 1829, however, that it appeared in print, by which time naturally it possessed value mainly as one of the curiosities of ancient literature. Dioscorides was an observant man, and must have been as well educated for the duties of his occupation as could be expected for his time. But the knowledge of vegetable life that he gathered during his extensive journeyings was purely of the empirical kind, and in no sense scientific. While he discovered many plants of great value for their medicinal properties, and accurately described all that he collected, he made no attempts at classification, and was of course totally unaware of the chemical nature of the extracts and infusions he made from them, or why they produced the effects he observed. Nevertheless, his extra- ordinary industry in collecting, and his faithfulness in describing, as well as the methods he adopted for admin- istering his medicines, were of enormous service to man- kind during the Dark Ages, when science was non-existent, and superstition rampant. Even at the present time a few of his recipes are used in civilized countries, while most of them are rated as authoritative among the middle and lower class Turks and Arabs, and the people of North Africa. PTOLEMY (cirea a.p. 100-170) COSMOLOGY AND GEOGRAPHY CLAUDIUS PToLEMAEUS was a native of Upper Egypt, having been born in the vicinity of ancient Thebes. There are no records extant of his parentage or early life, but in the year a.p. 139 he was a personage of note in intellec- Ancient Times 31 tual circles of Alexandria, and evidence that he was still living there in 161 is believed to exist. As a geographer, he appears to have been merely an editor or commentator on a work (which has been lost) on the subject by a Phoenecian navigator known as Marinus of Tyre, which must have been a production of consider- able importance. Ptolemy’s reproduction of it consisted of eight books. Five of these contain nothing but lists of place names which had evidently been visited by the orig- inal writer. In each case the latitude and longitude were given, together with a brief description of the locality and surroundings, of the people found there, of the productions of the vicinity, and such other items of information as might be gathered by the ordinary observant traveler. The other three—which perhaps were original with Ptolemy—were devoted to a description of the way to de- termine latitudes and longitudes; estimates of the size of the earth on the theory of its spherical shape, and a de- scription of his (Ptolemy’s) method of projecting points on a hemispherical surface upon a flat one, which he claimed was superior to those employed by either Eratos- thenes, Hipparchus or Marinus. From these notes of the actual navigator he constructed twenty-six maps of the known world of the day. These, for many centuries, were regarded as standard geographical authorities. In astronomy he originated the theory of the Cosmos which bears his name, and which was accepted as correct throughout Europe until the time of Copernicus and Kepler. This represented the Earth as immovably fixed in space, and as the center of the Universe, around which the sun, the moon, the five known planets and the stars, moved at uniform speed, carried by concentric transpar- ent spheres or shells, to each of which they were attached more or less immoyably. The first or innermost of these erystalline shells carried the moon. Beyond it in order came those bearing Mercury, Venus, the Sun, Mars, Jupi- ter and Saturn. In the eighth shell were all the fixed stars. To account for the alternate progression and recession of the planets, he originated his famous theory of epicycles. 32 Beacon Lights of Science In this he claimed that the planets were not immovably — fixed in their respective shells, but that each one of them revolved in a circle of greater or less diameter, the center of which was immovably fixed on its particular shell. As to the Earth, he regarded it as the lowest and most stable of the elements of which matter in general was composed. Water, as exhibited in the ocean, and in lakes, rivers and rain, was the second element, and rested upon the first. Air was the third, being above these two, and fire the fourth. Beyond the last, and extending to the shell carry- ing the moon, was the blue sky, the vault of the heavens, to which he gave the name of the Ether. He appears to have made no efforts to explain the constitution or material of this last, nor to include it among his list of elements. Astronomers living shortly after Ptolemy’s day added in turn a ninth and tenth shell to the system. The first of these was to account for the phenomenon of the pre- cession of the equinoxes; and the second to explain more clearly the alternation of day and night. This was accom- plished by giving to it a daily circular motion from east — to west during which, by virtue of some mechanism all the others were carried with it. Still later, as the science of astronomy progressed, and new discoveries were made that could not be accounted for by the theory as originally out- lined, these were explained by its proponents by adding epicycle after epicycle to the scheme, until it became so complicated and so littered with these little circles as to draw from King Alphonso X of Castile—to whom it was being explained—the remark that ‘‘if he had been allowed to be present by the Deity when the Universe was being fashioned, he believed he could show him a better plan,”’ or words to that effect. By the time of Copernicus the whole theory was ready to fall to pieces by its own weight, though still adhered to by conservative minds, and even by such a brilliant observational astronomer as Tycho Brahe. To Ptolemy belongs the honor of having been the first to discover and describe that phenomenon called the moon’s ‘‘eviction,’’ but its cause was unknown to him, and to all Ancient Times 33 astronomers, until the day of La Place who, in 1786, com- pletely explained it. This is a perturbation or irregular- ity in the movement of the satellite due to the alternate increase and decrease in the eccentricity of the earth’s orbit. When this is at a maximum, it is capable of dis- placing the moon from its normal or average position in space sufficiently to alter the time of occurrences of lunar and solar eclipses as much as six hours. As eclipses are systematically recurrent phenomena, occurring in cycles of approximately eighteen years; and as this fact was well known (for the moon but not for the sun) to the ancients, whose astronomers were tireless observers of celestial hap- penings, and who prided themselves on their ability to predict eclipses, Ptolemy’s discovery was of much impor- tance, as it enabled them to increase the accuracy of their prophesies. GALEN (a.p. 130-201) ANATOMY CLADIUS GALENUS, as he was known in his time, ap- pears to have been a native of Mysia, an ancient province in the northwestern corner of Asia Minor, bordering on the Aegean and the Marmora seas, and was of Hellenic ancestry. During his youthful years he studied medicine, and such surgery as was known at the time, in Smyrna, Corinth, Alexandria and other large centers, and at the age of thirty received the appointment of physician to the school of gladiators at Pergamos. A few years later he moved to Rome, remaining there four years, during which time his reputation increased so greatly that he was offered the position of physician to the Emperor. Having re- turned to Mysia in his thirty-eighth year, he had hardly settled down to the practice of his profession, before he was summoned peremptorily by the emperors Aurelius and Lucius Verus, to attend them during a military expedition they were about to make, and obeyed at once. But on arrival at the camp of the army he found that a pestilence 34 Beacon Laghts of Science had broken out there, and that the emperors had started on the return journey to Rome, whither he followed them. Little else is known of his movements, but it is generally believed that his death occurred in his 70th or 71st year, and that at the time he was in Sicily. Galen was a student and a voluminous writer. There are still in existence 83 documents of his that are known to be genuine, besides more than 400 others, the authen- ticity of which is questionable, but which are preserved for what they may be wortk in the collection of his writ- ings. Very few of them have any value beyond that of ancient curiosities, for in his time, and for centuries after it, the medical art was in no sense a science. But Galen was also an anatomist of unusual ability and brillianey for his day, and made one memorable discovery for which he has won immortal credit. This was, that the brain was the organ of thought. Up to his time various opinions had been held as to the organ in the human body which was the seat of the mind. For instance, the word brain, or any word that might be thought to refer to that organ, is not to be found in the Bible or in any ancient literature. Among the Babylon- ians the liver was regarded as the thought center. With the Hellenes the heart was considered the home of the soul, and the kidneys that of the mind, while sentiment and the emotions were supposed to reside in the bowels. ‘‘Bowels of compassion.’’ In Plato’s time the brain, though well known as a separate bodily organ, was regarded as an ex- tension, in the shape of a gland, of the marrow of the bones. And while he—for no reason that can be deduced from his writings—called it the seat of the soul, he exhib- ited no conception of it as the seat of thought. Aristotle later ridiculed the Platonic view (which certainly was nonsense), and said that the brain was simply a gland set at the top of the body, for the purpose of keeping the blood from acquiring too high a temperature, in other words, simply a cooling gland. It is true that one Ale- maeon, a Greek of Italian birth, who lived in the 6th century B.c., and who was recognized locally as a physician Ancient Times 35 of ability for his time, had definitely taught that the brain was the seat of thought. But his opinion carried no weight with the philosophers, and was quickly forgotten. It re- quired a man of the experimental habits and international renown of Galen, to overthrow the childish speculation of his day on the subject. Accordingly, when, in about the year A.D. 160, he announced his discovery in a monograph entitled ‘‘De Anatomicis Administrationibus,’’ and elab- orated it inasecond one under the title of ‘‘De Usa Partium Corporis Humani,’’ his conclusions were at once accepted, and have never since been questioned. But many centur- ies elapsed before any further discovery of equal note oc- curred regarding the human body. In fact, not until Harvey, in 1628, published his work on the circulation of the blood, did man begin to know much about the temple in which his mind and personality made their dwelling place. DIOPHANTUS (cirea a.p, 250-350) MATHEMATICS DIOPHANTUS was a distinguished Greek mathematician, about whose personal history almost nothing is known, ex- cept that he lived and taught in Alexandria, Egypt. He is called the ‘‘Father of Algebra,’’ though that science is well known to have been developed to a considerable de- cree in India and Arabia centuries before his time. Of his three known works (‘‘On Arithmetie,’’ ‘‘On Polygonal Numbers’’ and ‘‘On Porisms’’) only six parts of the first mentioned are extant. These, however, display a remark- able grasp of algebra for the time, and fully warrant ac- cording to him the honor of having introduced the science to the European students of his day, and of having broad- ened its scope and capacity greatly. Algebra, the second department of the science of mathe- matics, derives its name from the title of a work by the Arabian philosopher Al-Khuwarasmi, who lived in the ninth century of the present era and was regarded as a 36 Beacon Lights of Science noted mathematician. His professional life was spent mainly at Bagdad, where he worked in the astronomical observatory there, and wrote several treatises on that science. Among them was one entitled ‘‘Al-jabr wa’l mugabalah (Re-integration and Comparison) signifying an investigation which had to do with the methods by which equations may be reduced to integral forms. To exactly define the domain of algebra is not easy, for in one direction it shades into the higher departments of arithmetic, and in the other into the primary regions of the Caleulus. Comte’s definition is to the effect that while arithmetic is the calculus of values, algebra is the calculus of functions; the word calculus in both eases being in- tended to convey the idea of numbering or calculating, while function is used in the sense of a generalized quan- tity whose value at any given time depends upon the value of another quantity, also of a general kind. Thus, when it is said that the circumference or the area of a circle varies—in accordance with a fixed mathematical law—with the length of its diameter, both the circumfer- ence and the area are functions of the diameter. These functional relations when expressed in symbols are called equations. The oldest known written equation appears in a manu- script attributed to an Egyptian scribe by the name of Ahmes, who lived about 1700 B.c. He claimed to have copied it from another manuscript dating back some seven to eight centuries. It reads: ‘‘The whole its seventh part, its whole, it makes 19.’’ Which, put in modern symbols would be o +a =19 this being the form of the simple equation, and the prob- lem being to find the value of x, which is 16.625. In Kuclid’s day a knowledge of certain quadratic equations existed, but not until Diophantus does it appear that the science was taught in any organized way. In the century following his time the Hindu mathematician, Aryabhatta, Ancient Times 37 made some important contributions to its growth, and from then until the writings of Al-Khuwarizmi appeared, no further progress seems to have been made. After him there was again a period of nearly seven hundred years until the Italian mathematicians, Tartaglia, Ferreo and others re- vived interest in it. Since then it has steadily advanced in capacity as a tool of science in all its departments. II THE MIDDLE AGES Historically, this period begins with the fall of the Roman Empire in the year A.D.. 476 and terminates at various dates between 1301 (which is regarded as the beginning of the Renaissance) and 1517, when Luther inaugurated the era of the Reformation. But as this work deals only with the subject of science, it is considered best to end with the life of Copernicus, the outstanding figure of the 15th century. The notable historical events of this thousand years may be briefly summarized as follows. During the remainder of the 5th and most of the 6th centuries the Germanic or Teutonic people of central and northern Europe overran all of the European parts of the Roman empire, and towards the close of the 6th century the rise of the Arabian nationality began, which was destined during the following years to absorb all its Asiatic and African possessions. Through the 7th and 8th centuries, a process of fusion between conquerers and conquered was in progress, from which the latter emerged physically improved, and the former mentally, On the whole, the advantage remained with the conquered, and during the 9th and 10th centuries this was shown in the rise to supreme temporal power of the Roman church in Europe, and of Mohammedanism elsewhere. Towards the close of the 11th century, the two forces came into conflict with each other, in the episodes of the Crusades (1096-1272). These were inconclusive, but during their progress so much of new fact and new thought reached Europe, that its Dark Ages came to an end. With the opening of the 14th century, the learning of ancient Greece began to filter slowly back to Europe, and with that the modern era of Science may be said to have begun. In the Middle Ages, Italy was the commercial and intellectual center of the civilized world. Its schools and universities became so noted, that students flocked to them from the surrounding coun- tries. Yet the Italian race contributed only four men of marked scientific attainment to the period, while Arabia and Hindustan contributed five. However, the latter were merely bearers of ancient Greek knowledge, and since then these countries have added nothing to the accumulations of knowledge. ARYABHATTA (476-550) ASTRONOMY A Hrinpvu astronomer, who was born at Pataliputra in the upper valley of the Ganges river, Aryabhatta appears to have held in his writings—which were in the Sanscrit language and were translated into Arabic—that the earth had the form of a sphere, and revolved upon its axis. He also seems to have been the first to correctly account for the phenomena of solar and lunar eclipses, and conse- quently must have known and taught that the moon re- volved around the earth, and the latter around the sun. His advanced ideas of the cosmos, though totally unknown in Europe in his day and for many centuries afterwards, were accepted without question among the educated classes in India and Arabia, and probably in China, largely be- cause there was nothing to the contrary in the so-called sacred literature of these people, or for the reason that the literature of that kind among Oriental races was not regarded as inerrant in secular matters. A thousand years later, when the same beliefs were expressed by Copernicus, they were received with horror, because they were con- sidered to be in opposition to the teachings of the Chris- tian Scriptures. His only worlk that has come down to us is known as the Aryabhattiya. 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