% I wfi* Y* Digitized by the Internet Archive in 2010 with funding from Boston Library Consortium Member Libraries http://www.archive.org/details/historyofscience05will ENTRANCE TO THE ROYAL SOCIETY ROOMS, BURLINGTON HOUSE, LONDON A HISTORY OF SCIENCE BY HENRY SMITH WILLIAMS, M.D., LL.D. ASSISTED BY EDWARD H. WILLIAMS, M.D. IN FIVE VOLUMES VOLUME V. ASPECTS OF RECENT SCIENCE ILLUSTRATED NEW YORK AND LONDON HARPER & BROTHERS PUBLISHERS « MCMI V Copyright, 1904, by Harper & Brothers. All rights reserved. Published November, 1904. 67083 CONTENTS BOOK V CHAPTER I THE BRITISH MUSEUM The founding of the British Museum, p. 4 — Purchase of Sir Hans Sloane's collection of curios by the English government, p. 4 — Collection of curios and library located in Montague Mansion, p. 5 — Acquisition of the collection of Sir William Hamilton, p. 5 — Capture of Egyptian antiquities by the English, p. 5 — Construc- tion of the present museum building, p. 6 — The Mesopotamian department, p. 8 — The Museum of Natural History in South Ken- sington, p. 8 — Novel features in the structure of the building, p. 9 — Arrangement of specimens to illustrate evolution, protective coloring, etc., p. 10 — Exhibits of stuffed specimens amid their natural surroundings, p. 10 — Interest taken by visitors in the institution, p. 12. CHAPTER II THE ROYAL SOCIETY OF LONDON FOR IMPROVING NATURAL KNOWLEDGE The Royal Society, p. 14 — Weekly meetings of the society, p. 15 — The tea before the opening of the lecture, p. 15 — Announcement of the beginning of the lecture by bringing in the great mace, p. 16— The lecture -room itself, p. 17— Comparison of the Royal So- ciety and the Royal Academy of Sciences at Berlin, p. 18 — The library and reading-room, p. 19 — The busts of distinguished members, p. 20 — Newton's telescope and Boyle's air-pump, p. 21. iii CONTENTS CHAPTER III THE ROYAL INSTITUTION AND LOW-TEMPERATURE RESEARCHES The founding of the Royal Institution, p. 29 — Count Rumford, p. 30 — His plans for founding the Royal Institution, p. 32 — Change in the spirit of the enterprise after Rumford's death, p. 33 — Atti- tude of the earlier workers towards the question of heat as a form of motion, p. 34 — Experiments upon gases by Davy and Faraday, p. 35 — Faraday's experiments with low temperatures, p. 39 — Other experiments to produce lower temperature, p. 39 — Professor De- war begins low - temperature research, p. 39 — His liquefaction of hydrogen, p. 43 — Hampson's method of producing low tempera- tures, p. 44 — Dewar's invention of the vacuum vessel, p. 53 — Its use in retaining liquefied gases, p. 54 — Changes in physical properties of substances at excessively low temperatures, p. 56 — Magnetic phenomena at low temperatures, p. 56 — Changes in the color of substances at low temperatures, p. 57 — Substances made luminous by low temperatures, p. 58 — Effect of low temperatures upon the strength of materials, p. 59 — Decrease of chemical activ- ity at low temperatures, p. 60 — Olzewski's experiments with burn- ing substances in liquid oxygen, p. 61 — Approach to the absolute zero made by liquefying hydrogen, p. 69 — Probable form of all matter at the absolute zero, p. 70 — Uncertain factors that enter into this determination, p. 71. CHAPTER IV SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS Sir Norman Lockyer and Spectroscopic Studies of the Sun and Stars, p. 73 — Observations made at South Kensington by Sir Norman and his staff, p. 74 — His theories as to the influence of sun-spots and terrestrial weather, p. 75 — Spectroscopic studies of sun-spots, p. 76 — Studies of the so-called reverse lines of the spec- trum, p. 78 — Discovery of the new star in the constellation of Perseus, p. 80 — Spectroscopic studies of the new star, p. 81 — Professor Ramsay and the new gases, p. 82 — University College in London, p. 83 — Professor Ramsay's laboratory and its equip- ment, p. 84 — The discovery of argon, p. 86 — Professor Ramsay's work on krypton, neon, and zenon, p. 87 — Discoveries of new constituents of the atmosphere, p. 88 — Interesting questions raised by these discoveries, p. 89 — Professor J. J. Thomson and the nature of electricity, p. 92 — Study of gases in relation to the con- iv CONTENTS duction of electricity, p. 93 — Electricity regarded as a form of matter, p. 97 — Radio-activity, p. 97 — The nature of emanations from radio-active bodies, p. 102 — The source of energy of radio- activity, p. 106 — Radio-activity and the structure of the atom, p. 108 — Effect of radio-activity upon heat-giving life of the sun and the earth, p. in. CHAPTER V THE MARINE BIOLOGICAL LABORATORY The aquarium, p. 113 — The arrangement of the tanks and exhib- its, p. 114 — The submarine effect of this arrangement, p. 115 — Ap- pearance of the submarine dwellers in their natural surroundings, p. 116 — The eels and cuttle-fishes, p. 116 — The octopuses, p. 117 — The technical department of the laboratory, p. 119 — The work of Dr. Anton Dohrn, founder of the laboratory, p. 121 — The associ- ates of Dr. Dohrn, p. 122 — The collecting of surface specimens, p. 123 — Collecting specimens by dredging, p. 124 — Fauna of the Bay of Naples, p. 124 — Abundance of the material for biological study, p. 125 — Advantages offered by marine specimens for biological study, p. 126 — Method of preserving jelly-fish and similar fragile creatures, p. 127 — Uses made of the specimens in scientific study, p. 128 — Different nationalities represented among the workers at the laboratory, p. 130 — Methods of investigation, p. 131 — Dr. Diesch's studies of heredity at the laboratory, p. 131 — Other subjects under scientific investigation, p. 132 — The study of chromosomes, p. 133 — Professor Weismann's theory of heredity based on these studies, p. 133 — Experiments in the division of egg-cells, p. 134 — Experi- ments tending to refute Weismann's theory, p. 136 — Dr. Dohrn's theory of the type of the invertebrate ancestor, p. 137 — Publica- tions of the laboratory, p. 139 — Meetings of the investigators at Signor Bifulco's, p. 141 — Marine laboratories of other countries, p. 142. CHAPTER VI I ERNST HAECKEL AND THE NEW ZOOLOGY The "dream city" of Jena, p. 145 — The old market-place, p. 147 — The old lecture-halls of the university, p. 148 — Ernst Haeckel, p. 151 — His discoveries of numerous species of radiolarians, p. 153 — The part played in evolution by radiolarians, p. 156 — Haeckel's work on morphology, and its aid to Darwinian philosophy, p. 156 — Freedom of thought and expression in the University of Jena, p. 1 57 V CONTENTS — Haeckel's laboratory, p. 160 — His method of working, p. 161 — His methods of teaching, p. 164 — The import of the study of zool- ogy, p. 166 — Its bearing upon evolution, p. 168 — The present status of Haeckel's genealogical tree regarding the ancestry of man, p. 171 — Dubois's discovery of the skull of the ape-man of Java, p. 173 — Its close resemblance to the skull of the ape, p. 173 — Man's line of descent clearly traced by Haeckel, p. 175 — The "missing link" no longer missing, p. 176. CHAPTER VII SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS The Boulevard Pasteur, p. 179 — The Pasteur Institute, p. 180 — The tomb of Pasteur within the walls, p. 181 — Aims and objects of the Pasteur Institute, p. 182 — Antirabic treatment given, p. 183 — Methods of teaching in the institute, p. 185 — The director of the institute and his associates, p. 185 — The Virchow Institute of Pathology, p. 186 — Studies of the causes of diseases, p. 187 — Or- ganic action and studies of cellular activities, p. 188 — The discov- eries of Rudolph Virchow, p. 188 — His work in pathology, p. 189 — Character of the man, his ways of living and working, p. 189 — His methods of lecturing and teaching, p. 191 — The Berlin .Institute of Hygiene, p. 193 — Work of Professor Koch as carried on in the in- stitute, p. 194 — Work of his successors in the institute, p. 195 — Investigations in hygiene, p. 196 — Investigations of the functions of the human body in their relations to everyday environment, p. 197 — The Museum of Hygiene, p. 198 — Studies in methods of con- structing sewerage systems in large cities, p. 199 — Studies in prob- lems of ventilation, p. 200. CHAPTER VIII SOME UNSOLVED SCIENTIFIC PROBLEMS The ever-shifting ground of scientific progress, p. 203 — Solar and telluric problems, p. 205 — Mayer's explanation of the continued heat of the sun, p. 206 — Helmholtz's suggestion as to the explana- tion, p. 207 — The estimate of the heat-giving life of the sun by Lord Kelvin and Professor Tait, p. 208 — Lockyer's suggestion that the chemical combination of elements might account for the sun's heat, p. 209 — Computations as to the age of the earth's crust, p. 210 — Lord Kelvin's computation of the rigidity of the telluric structure, p. 2 11 — Estimates of the future life of the earth, p. 2 1 2 — vi CONTENTS Physical problems, p. 213 — Attempts to explain the power of gravi- tation, p. 214 — The theory of Le Sage, p. 214 — Speculations based upon the hypothesis of the vortex atom, p. 216 — Lord Kelvin's estimate of the vortex theory, p. 217 — Attempted explanation of the affinity of atoms, p. 217 — Solubility, as explained by Ostwald and Mendeleef, p. 218 — Professor Van 't Hoof's studies of the space relations of atoms, p. 219 — Life problems, p. 220 — Question as to living forms on other worlds besides our own, p. 211 — The question of the "spontaneous generation" of living proto- plasm, p. 222 — The question of the evolution from non-vital to vital matter, p. 223 — The possibility of producing organic matter from inorganic in the laboratory, p. 224 — Questions as to the structure of the cell, p. 225 — Van Beneden's discovery of the centrosome, p. 226 — Some problems of anthropology, p. 227. CHAPTER IX RETROSPECT AND PROSPECT The scientific attitude of mind, p. 2 30 — Natural versus supernatural , p. 233 — Inductive versus deductive reasoning, p. 235 — Logical in- duction versus hasty generalization, p. 239— The future of Darwin- ism, p. 241. APPENDIX 243 A LIST OF SOURCES 245 INDEX 271 ILLUSTRATIONS ENTRANCE TO THE ROYAL SOCIETY ROOMS, BURLINGTON HOUSE, LONDON Frontispiece ENTRANCE TO THE BRITISH MUSEUM, LONDON . . . Facing p. 6 ASSEMBLY-ROOM OF THE ROYAL SOCIETY " 16 LIBRARY OF THE ROYAL SOCIETY " 20 ENTRANCE TO THE ROYAL INSTITUTION, LONDON . . " 32 PROFESSOR DEWAR'S APPARATUS WITH WHICH HYDRO- GEN WAS FIRST LIQUEFIED " 42 HAMPSON'S APPARATUS FOR LIQUEFYING AIR .... " 44 SIR NORMAN LOCKYER " 74 SKETCH OF SIR WILLIAM RAMSAY " 84 PROFESSOR J. J. THOMSON " 94 PROFESSOR W. C. ROENTGEN DISCOVERER OF THE X-RAY " 96 PROFESSOR HENRI BECQUEREL " 98 DISCHARGING AN ELECTROSCOPE WITH RADIUM ... " 102 SIR WILLIAM CROOKES " 106 ERNEST RUTHERFORD, F.R.S . " HO THE AQUARIUM OF THE MARINE BIOLOGICAL LABORA- TORY " Il6 TANKS FOR HOLDING SPECIMENS, MARINE BIOLOGICAL LABORATORY AT NAPLES " 134 THE MARKET-PLACE, JENA " 148 PROFESSOR ERNEST HAECKEL IN HIS STUDY .... " 160 ix ILLUSTRATIONS HAECKEL TEACHING IN HIS LABORATORY Facing p. 164 haeckel's laboratory " 172 entrance to the tomb of pasteur " 180 elias metchnikoff " 184 professor rudolf virchow in his laboratory . . " iq2 A HISTORY OF SCIENCE BOOK V ASPECTS OF RECENT SCIENCE STUDENTS of the classics will recall that the old Roman historians were accustomed to detail the events of the remote past in what they were pleased to call annals, and to elaborate contemporary events into so-called histories. Actuated perhaps by the same motives, though with no conscious thought of imitation, I have been led to conclude this history of the development of natural science with a few chapters somewhat different in scope and in manner from the ones that have gone before. These chapters have to do largely with recent con- ditions. Now and again, to be sure, they hark back into the past, as when they tell of the origin of such in- stitutions as the British Museum, the Royal Society, and the Royal Institution; or when the visitor in modern Jena imagines himself transplanted into the Jena of the sixteenth century. But these reminiscent A HISTORY OF SCIENCE moods are exceptional. Our chief concern is with strictly contemporary events — with the deeds and per- sonalities of scientific investigators who are still in the full exercise of their varied powers. I had thought that such outlines of the methods of contemporary workers, such glimpses of the personalities of living celebrities, might form a fitting conclusion to this record of progress. There is a stimulus in contact with great men at first hand that is scarcely to be gain- ed in like degree in any other way. So I have thought that those who have not been privileged to visit the great teachers in person might like to meet some of them at second hand. I can only hope that something of the enthusiasm which I have gained from contact with these men may make itself felt in the succeeding pages. It will be observed that these studies of contem- porary workers are supplemented with a chapter in which a hurried review is taken of the field of cos- mical, of physical, and of biological science, with ref- erence to a few of the problems that are still unsolved. As we have noted the clearing up of mystery after mys- tery in the past, it may be worth our while in conclu- sion thus to consider the hordes of mysteries which the investigators of our own age are passing on to their suc- cessors. For the unsolved problems of to-day beckon to the alluring fields of to-morrow. THE BRITISH MUSEUM IN the year 1753 a remarkable lottery drawing took place in London. It was authorized, through Parliament, by "his gracious Majesty" King George the Second. Such notables as the archbishop of Can- terbury and the lord chancellor of the realm took official interest in its success. It was advertised far and wide — as advertising went in those days — in the Gazette, and it found a host of subscribers. Of the fifty thousand tickets — each costing three pounds — more than four thousand were to be of the class which the act of Parliament naively describes as "fortunate tickets." The prizes aggregated a hundred thousand pounds. To be sure, state lotteries were no unique feature in the England of that day. They formed as common a method of raising revenue in the island realm of King George II. as they still do in the alleged continental portion of his realm, France, and in the land of his nativity, Germany. Indeed, the particular lottery in question was to be officered by the standing committee on lotteries, whose official business was to "secure two and a half million pounds for his Majesty" by this means. But the great lottery of 1754 had interest far beyond the common run, for it aimed to meet a na- tional need of an anomalous kind — a purely intellectual 3 A HISTORY OF SCIENCE need. The money which it was expected to bring was to be used to purchase some collections of curi- osities and of books that had been offered the govern- ment, and to provide for their future care and disposal as a public trust for the benefit and use of the people. The lottery brought the desired money as a matter of course, for the "fool's tax" is the one form of revenue that is paid without stint and without grumbling. Al- most fifty thousand pounds remained in the hands of the archbishop of Canterbury and his fellow-trus- tees after the prizes were paid. And with this sum the institution was founded which has been increasingly famous ever since as the British Museum. The idea which had this splendid result had origi- nated with Sir Hans Sloane, baronet, a highly respect- ed practising physician of Chelsea, who had accumu- lated a great store of curios, and who desired to see the collection kept intact and made useful to the public after his death. Dying in 1753, this gentleman had directed in his will that the collection should be offered to the government for the sum of twenty thousand pounds; it had cost him fifty thousand pounds. The government promptly accepted the offer — as why should it not, since it had at hand so easy a means of raising the necessary money? It was determined to supplement the collection with a library of rare books, for which ten thousand pounds was to be paid to the " Right Honorable Henrietta Cavendish Holies, Coun- tess of Oxford and Countess Mortimer, Relict of Ed- ward, Earl of Oxford and Earl Mortimer, and the Most Noble Margaret Cavendish, Duchess of Portland, their only daughter." 4 THE BRITISH MUSEUM The purchases were made and joined with the Cot- tonian library, which was already in hand. A home was found for the joint collection, along with some minor ones, in Montague Mansion, on Great Russell Street, and the British Museum came into being. Viewed retrospectively, it seems a small affair; but it was a noble collection for its day; indeed, the Sloane collection of birds and mammals had been the finest private natural history collection in existence. But, oddly enough, the weak feature of the museum at first was exactly that feature which has been its strongest element in more recent years — namely, the depart- ment of antiquities. This department was augmented from time to time, notably by the acquisition of the treasures of Sir William Hamilton in 1773; but it was not till the beginning of the nineteenth century that the windfall came which laid the foundation for the future incomparable greatness of the museum as a repository of archaeological treasures. In that memorable year the British defeated the French at Alexandria, and received as a part of the conqueror's spoils a collection of Egyptian antiquities which the savants of Napoleon's expedition had gath- ered and carefully packed, and even shipped prepara- tory to sending them to the Louvre. The feelings of these savants may readily be imagined when, through this sad prank of war, their invaluable treasures were envoyed, not to their beloved France, but to the land of their dearest enemies, there to be turned over to the trustees of the British Museum. The museum authorities were not slow to appreciate the value of the treasures that had thus fallen into their 5 A HISTORY OF SCIENCE hands, yet for the moment it proved to them some- thing of a white elephant. Montague Mansion was al- ready crowded ; moreover, its floors had never been in- tended to hold such heavy objects, so it became im- peratively necessary to provide new quarters for the collection. This was done in 1807 by the erection of a new building on the old site. But the trustees of that day failed to gauge properly the new impulse to growth that had come to the museum with the Egyptian an- tiquities, for the new building was neither in itself sufficient for the needs of the immediate future nor yet so planned as to be susceptible of enlargement with reasonable architectural effect. The mistakes were soon apparent, but, despite various tentatives and "meditatings," fourteen years elapsed before the pres- ent magnificent building was planned. The construc- tion, wing by wing, began in 1823, but it was not until 1846 that the last vestige of the old museum buildings had vanished, and in their place, spreading clear across the spacious site, stood a structure really worthy of the splendid collection for which it was designed. But no one who sees this building to-day would sus- pect its relative youth. Half a century of London air can rival a cycle of Greece or Italy in weathering effect, and the fine building of the British Museum frowns out at the beholder to-day as grimy and ancient-seem- ing as if its massive columns dated in fact from the old Grecian days which they recall. Regardless of age, however, it is one of the finest and most massive speci- mens of Ionic architecture in existence. Forty - four massive columns, in double tiers, form its frontal col- onnade, jutting forward in a wing at either end. The 6 THE BRITISH MUSEUM flight of steps leading to the central entrance is in itself one hundred and twenty-five feet in extent; the front as a whole covers three hundred and seventy feet. Capping the portico is a sculptured tympanum by Sir Richard Westmacott, representing* the "Progress of Civilization" not unworthily. As a whole, the build- ing is one of the few in London that are worth visiting for an inspection of their exterior alone. It seems ad- mirably designed to be, as it is, the repository of one of the finest collections of Oriental and classical antiqui- ties in the world. There is an air of repose about the ensemble that is in itself suggestive of the Orient ; and the illusion is helped out by the pigeons that flock everywhere undisturbed about the approaches to the building, fluttering to be fed from the hand of some recognized friend, and scarcely evading the feet of the casual wayfarer. With this scene before him, if one will close his ears to the hum of the great city at his back he can readily imagine himself on classical soil, and, dreaming of Greece and Italy, he will enter the door quite prepared to find himself in the midst of antique marbles and the atmosphere of by-gone ages. I have already pointed out that the turning-point in the history of the British Museum came just at the beginning of the century, with the acquisition of the Egyptian antiquities. With this the institution threw off its swaddling-clothes. Hitherto it had been largely a museum of natural history; in future, without neg- lecting this department, it was to become equally important as a museum of archaeology. The Elgin marbles, including the wonderful Parthenon frieze, con- 7 A HISTORY OF SCIENCE firmed this character, and it was given the final touch by the reception, about the middle of the century, of the magnificent Assyrian collection just exhumed at the seat of old Nineveh by Mr. (afterwards Sir Henry) Layard. Since then these collections, with additions of similar character, have formed by far the most im- portant feature of the British Museum. But in the mean time archaeology has become a science. THE MUSEUM OF NATURAL HISTORY Within recent years the natural history collection has been removed in toto from the old building to a new site far out in South Kensington, and the casual visitor is likely to think of it as a separate institution. The building which it occupies is very modern in ap- pearance as in fact. It is a large and unquestionably striking structure, and one that gives opportunity for very radical difference of opinion as to its architectu- ral beauty. By some it is much admired ; by others it is almost equally scoffed at. Certain it is that it will hardly bear comparison with the parent build- ing in Great Russell Street. Interiorly, the building of the natural history museum is admirably adapted for its purpose. Its galleries are for the most part well lighted, and the main central hall is particularly well adapted for an exhibition of specimens, to which I shall refer more at length in a moment. For the rest there is no strik- ing departure from the conventional. Perhaps it is not desired that there should be, since long experience seems to have settled fairly well the problem of greatest economy of space, combined with best lighting fa- THE BRITISH MUSEUM cilities, which always confronts the architect in found- ing a natural history museum. There is, however, one striking novel feature in connection with the structure of the natural history museum at Kensington which must not be overlooked. This is the quite unprecedented use of terra-cotta orna- mentation. Without there is a striking display of half- decorative and half -realistic forms; while within the walls and pillars everywhere are covered with terra- cotta bas-reliefs representing the various forms of life appropriate to the particular department of the mu- seum which they ornament. This very excellent feat- ure might well be copied elsewhere, and doubtless will be from time to time. As to the exhibits proper within the museum, it may be stated in a word that they cover the entire range of the faunas and floras of the globe in a va- riety and abundance of specimens that are hardly excelled anywhere, and only duplicated by one or two other collections in Europe and two or three in America. It would be but a reiteration of what the catalogues of all large collections exhibit were one to enumerate the various forms here shown, but there are two or three exhibits in this museum which are more novel and which deserve special mention. One of these is to be found in a set of cases in the main central hall. Here are exhibited, in a delightfully popular form, some of the lessons that the evolutionist has taught us dur- ing the last half -century. Appropriately enough, a fine marble statue of Darwin, whose work is the foun- tain-head of all these lessons, is placed on the stairway 9 A HISTORY OF SCIENCE just beyond, as if to view with approval this beautiful exemplification of his work. One of these cases illustrates the variations of animals under domestication, the particular specimens selected being chiefly the familiar pigeon, in its various forms, and the jungle-fowl with its multiform domesticated descendants. Another case illustrates very strikingly the subject of protective coloration of animals. Two companion cases are shown, each occupied by specimens of the same species of birds and animals — in one case in their summer plumage and pelage and in the other clad in the garb of winter. The surroundings in the case have, of course, been carefully prepared to represent the true environments of the creatures at the appropriate sea- sons. The particular birds and animals exhibited are the willow-grouse, the weasel, and a large species of hare. All of these, in their summer garb, have a brown color, which harmonizes marvellously with their sur- roundings, while in winter they are pure white, to match the snow that for some months covers the ground in their habitat. The other cases of this interesting exhibit show a large variety of birds and animals under conditions of somewhat abnormal variation, in the one case of al- binism and the other of melanism. These cases are, for the casual visitor, perhaps the most striking of all, although, of course, they teach no such comprehensive lessons as the other exhibits just referred to. The second of the novel exhibits of the museum to which I wish to refer is to be found in a series of alcoves close beside the central cases in the main hallway. 10 THE BRITISH MUSEUM Each of these alcoves is devoted to a class of animals — one to mammals, one to birds, one to fishes, and so on. In each case very beautiful sets of specimens have been prepared, illustrating the anatomy and physiology of the group of animals in question. Here one may see, for example, in the alcove devoted to birds, specimens showing not only details of the skeleton and muscular system, but the more striking examples of variation of form of such members as the bill, legs, wings, and tails. Here are preparations also illustrating, very strikingly, the vocal apparatus of birds. Here, again, are finely prepared wings, in which the various sets of feathers have been outlined with different-colored pigments, so that the student can name them at a glance. In fact, every essential feature of the anatomy of the bird may be studied here as in no other collection that I know of. And the same is true of each of the other grand divisions of the animal kingdom. This exhibit alone gives an opportunity for the student of natural history that is invaluable. It is quite clear to any one who has seen it that every natural history museum must prepare a similar educational exhibit before it can claim to do full justice to its patrons. A third feature that cannot be overlooked is shown in the numerous cases of stuffed birds, in which the specimens are exhibited, not merely by themselves on conventional perches, but amid natural surroundings, usually associated with their nests and eggs or young. These exhibits have high artistic value in addition to their striking scientific worth. They teach ornithology as it should be taught, giving such clews to the recog- nition of birds in the fields as are not at all to be found ii A HISTORY OF SCIENCE in ordinary collections of stuffed specimens. This feature of the museum has, to be sure, been imitated in the American Museum of Natural History in New York, but the South Kensington Museum was the first in the field and is still the leader. PUBLIC INTEREST IN THE MUSEUM A few words should be added as to the use made by the public of the treasures offered for their free inspec- tion by the British Museum. I shall attempt nothing further than a few data regarding actual visits to the museum. In the year 1899 the total number of such visits aggregated 663,724; in 1900 the figures rise to 689,249 — well towards three-quarters of a million. The number of visits is smallest in the winter months, but mounts rapidly in April and May ; it recedes slight- ly for June and July, and then comes forward to full tide in August, during which month more than ninety- five thousand people visited the museum in 1901, the largest attendance in a single day being more than nine thousand. August, of course, is the month of tourists — particularly of tourists from America — but it is in- teresting and suggestive to note that it is not the tour- ist alone who visits the British Museum, for the flood- tide days of attendance are always the Bank holidays, including Christmas boxing-day and Easter Monday, when the working-people turn out en masse. On these days the number of visits sometimes mounts above ten thousand. All this, it will be understood, refers exclusively to the main building of the museum on Great Russell Street. But, meantime, out in Kensington, at the nat- 12 THE BRITISH MUSEUM ural history museum, more than half a million visits each year are also made. In the aggregate, then, about a million and a quarter of visits are paid to the British Museum yearly, and though the bulk of the visitors may be mere sight-seers, yet even these must carry away many ideas of value, and it hardly requires argument to show that, as a whole, the educational influence of the British Museum must be enormous. Of its more direct stimulus to scientific work through the trained experts connected with the institution I shall perhaps speak in another connection. II THE ROYAL SOCIETY OF LONDON FOR IMPROV- ING NATURAL KNOWLEDGE A SESSION OF THE SOCIETY THERE is one scientific institution in London more venerable and more famous even than the British Museum. This, of course, is the Royal Society, a world-famous body, whose charter dates from 1662, but whose actual sessions began at Gresham College some twenty years earlier. One can best gain a pres- ent-day idea of this famous institution by attending one of its weekly meetings in Burlington House, Pic- cadilly— a great, castle-like structure, which serves also as the abode of the Royal Chemical Society and the Royal Academy of Arts. The formality of an invita- tion from a fellow is required, but this is easily secured by any scientific visitor who may desire to attend the meeting. The programme of the meeting each week appears in that other great British institution, the Times, on Tuesdays. The weekly meeting itself is held on Thursday after- noon at half -past four. As one enters the door leading off the great court of Burlington House a liveried attend- ant motions one to the rack where great-coat and hat may be left, and without further ceremony one steps into the reception-room unannounced. It is a middle-sized, THE ROYAL SOCIETY OF LONDON almost square room, pillared and formal in itself, and almost without furniture, save for a long temporary table on one side, over which cups of tea are being handed out to the guests, who cluster there to receive it, and then scatter about the room to sip it at their leisure. We had come to hear a lecture and had ex- pected to be ushered into an auditorium ; but we had quite forgotten that this is the hour when all England takes its tea, the elite of the scientific world, seemingly, quite as much as the devotees of another kind of soci- ety. Indeed, had we come unawares into this room we should never have suspected that we had about us other than an ordinary group of cultured people gath- ered at a conventional "tea," except, indeed, that sus- picion might be aroused by the great preponderance of men — there being only three or four women present — and by the fact that here and there a guest appears in unconventional dress — a short coat or even a velvet working-jacket. For the rest there is the same gather- ing into clusters of three or four, the same inarticulate clatter of many voices that mark the most common- place of gatherings. But if one will withdraw to an inoffensive corner and take a critical view of the assembly, he will pres- ently discover that many of the faces are familiar to him, although he supposed himself to be quite among strangers. The tall figure, with the beautiful, kindly face set in white hair and beard, has surely sat for the familiar portrait of Alfred Russel Wallace. This short, thick-set, robust, business-like figure is that of Sir Norman Lockyer. Yonder frail-seeming scholar, with white beard , is surely Professor Crookes . And this other 15 A HISTORY OF SCIENCE scholar, with tall, rather angular frame and most kind- ly gleam of eye, is Sir Michael Foster ; and there beyond is the large - seeming though not tall figure, and the round, rosy, youthful-seeming, beautifully benevolent face of Lord Lister. " What ! a real lord there ?" said a little American girl to whom I enumerated the com- pany after my first visit to the Royal Society. " Then how did he act? Was he very proud and haughty, as if he could not speak to other people?" And I was happy to be able to reply that though Lord Lister, per- haps of all men living, would be most excusable did he carry in his manner the sense of his achievements and honors, yet in point of fact no man could conceivably be more free from any apparent self -consciousness. As one watches him now he is seen to pass from group to group with cordial hand-shake and pleasant word, clearly ^the most affable of men, lord though he be, and president of the Royal Society, and foremost scientist of his time. Presently an attendant passed through the tea- room bearing a tremendous silver mace, perhaps five feet long, surmounted by a massive crown and cross, and looking like nothing so much as a "gigantic war- club." This is the mace which, when deposited on the president's desk in the lecture-room beyond, will signify that the society is in session. "It is the veri- table mace," some one whispers at your elbow, "con- cerning which Cromwell gave his classical command to 'Remove that bauble.'" But since the mace was not made until 1663, some five years after Cromwell's death, this account may lack scientific accuracy. Be that as it may, this mace has held its own far more 16 THE ROYAL SOCIETY OF LONDON steadily than the fame of its alleged detractor, and its transportation through the tea-room is the only man- ner of announcement that the lecture is about to open in the hall beyond. Indeed, so inconspicuous is the proceeding, and so quietly do the members that choose to attend pass into the lecture-hall, leaving perhaps half the company engaged as before, that the "stran- ger ' ' — as the non-member is here officially designated — might very readily fail to understand that the seance proper had begun. In any event, he cannot enter until permission has been formally voted by the society. When he is allowed to enter he finds the meeting- room little different from the one he has left, except that it is provided with a sort of throne on a raised platform at one end and with cushioned benches for seats. On the throne, if one may so term it, sits Lord Lister, scarcely more than his head showing above what seems to be a great velvet cushion which sur- mounts his desk, at the base of which, in full view of the society, rests the mace, fixing the eye of the " stran- ger," as it is alleged to have fixed that of Cromwell aforetime, with a peculiar fascination. On a lower plane than the president, at his right and left, sit Sir Michael Foster and Professor Arthur William Rticker, the two permanent secretaries. At Sir Michael's right, and one stage nearer the audience, stands the lecturer, on the raised platform and behind the desk which ex- tends clear across the front of the room. As it chances, the lecturer this afternoon is Professor Ehrlich, of Ber- lin and Frankfort-on-the-Main, who has been invited to deliver the Croonian lecture. He is speaking in German, and hence most of the fellows are assisting VOL. V.— 2 I J A HISTORY OF SCIENCE their ears by following the lecture in a printed trans- lation, copies of which, in proof, were to be secured at the door. The subject of the lecture is "Artificial Immuniza- tion from Disease." It is clear that the reader is fol- lowed with interested attention, which now and again gives rise to a subdued shuffle of applause. The fact that the lecturer is speaking German serves perhaps to suggest even more vividly than might other- wise occur to one the contrast between this meeting and a meeting of the corresponding German society — the Royal Academy of Sciences at Berlin. Each is held in an old building of palatial cast and dimensions, of which Burlington House, here in Piccadilly, is much the older — dating from 1664 — although its steam- heating and electric-lighting apparatus, when con- trasted with the tile stoves and candles of the other, would not suggest this. For the rest, the rooms are not very dissimilar in general appearance, except for the platform and throne. But there the members of the society are shut off from the audience both by the physical barrier of the table and by the striking effect of their appearance in full dress, while here the fellows chiefly compose the audience, there being only a small company of "strangers" present, and these in no way to be distinguished by dress or location from the fellows themselves. It may be added that the custom of the French Academy of Sciences is intermediate between these two. There the visitors occupy seats apart, at the side of the beautiful hall, the main floor being reserved for members. But the members them- selves are not otherwise distinguishable, and they 18 THE ROYAL SOCIETY OF LONDON come and go and converse together even during the reading of a paper almost as if this were a mere social gathering. As it is thus the least formal, the French meeting is also by far the most democratic of great scientific gatherings. Its doors are open to whoever may choose to enter. The number who avail them- selves of this privilege is not large, but it includes, on occasions, men of varied social status and of diverse races and colors — none of whom, so far as I could ever discern, attracts the slightest attention. At the German meeting, again, absolute silence reigns. No one thinks of leaving during the session, and to make any sound above a sigh would seem al- most a sacrilege. But at the Royal Society an occa- sional auditor goes or comes, there are repeated audible signs of appreciation of the speaker's words, and at the close of the discourse there is vigorous and prolonged applause. There is also a debate, of the usual char- acter, announced by the president, in which "stran- gers" are invited to participate, and to which the lect- urer finally responds with a brief Nachwort, all of which is quite anomalous from the German or French stand-points. After that, however, the meeting is de- clared adjourned with as little formality in one case as in the others, and the fellows file leisurely out, while the attendant speedily removes the mace, in official token that the seance of the Royal Society is over. THE LIBRARY AND READING-ROOM But the "stranger" must not leave the building without mounting to the upper floor for an inspec- tion of the library and reading-room. The rooms 19 A HISTORY OF SCIENCE below were rather bare and inornate, contrasting un- favorably with the elegant meeting-room of the French institute. But this library makes full amends for any- thing that the other rooms may lack. It is one of the most charming — "enchanting" is the word that the Princess Christian is said to have used when she visited it recently — and perhaps quite the most inspiring room to be found in all London. It is not very large as library rooms go, but high, and with a balcony supported by Corinthian columns. The alcoves be- low are conventional enough, and the high tables down the centre, strewn with scientific periodicals in engag- ing disorder, are equally conventional. But the color- scheme of the decorations — sage - green and tawny — is harmonious and pleasing, and the effect of the whole is most reposeful and altogether delightful. Chief distinction is given the room, however, by a row of busts on either side and by certain pieces of apparatus on the centre tables. The busts, as will readily be surmised, are portraits of distinguished fellows of the Royal Society. There is, however, one exception to this, for one bust is that of a woman — Mary Somerville, translator of the Me- canique Celeste, and perhaps the most popular of the scientific writers of her time. It is almost superflu- ous to state that the row of busts begins with that of Newton. The place of honor opposite is held by that of Faraday. Encircling the room to join these two one sees, among others, the familiar visages of Dr. Gil- bert; of Sir Joseph Banks, the famous surgeon of the early nineteenth century, who had the honor of being the only man that ever held the presidential chair of 20 THE ROYAL SOCIETY OF LONDON the Royal Society longer than it was held by Newton ; of James Watts, of "steam-engine" fame; of Sabine, the astronomer, also a president of the society; and of Dr. Falconer and Sir Charles Lyell, the famous geolo- gists. There are numerous other busts in other rooms, some of them stowed away in nooks and crannies, and the list of those selected for the library does not, per- haps, suggest that this is the room of honor, unless, in- deed, the presence of Newton and Faraday gives it that stamp. But in the presence of the images of these two, and of Lyell, to go no farther, one feels a certain sacredness in the surroundings. If this is true of the mere marble images, what shall we say of the emblems on the centre table ? That little tubular affair, mounted on a globe, the whole cased in a glass frame perhaps two feet high, is the first reflecting telescope ever made, and it was shaped by the hand of Isaac Newton. The brass mechanism at the end of the next table is the perfected air-pump of Robert Boyle, Newton's contemporary, one of the founders of the Royal Society and one of the most acute scientific minds of any time. And here between these two mementos is a higher apparatus, with crank and wheel and a large glass bulb that make it conspicuous. This is the electrical machine of Joseph Priestley. There are other mementos of Newton — a stone graven with a sun-dial, which he carved as a boy, on the paternal manor-house; a chair, said to have been his, guarded here by a silk cord against profanation ; bits of the fa- mous apple-tree which, as tradition will have it, aided so tangibly in the greatest of 'discoveries ; and the man- 21 A HISTORY OF SCIENCE uscript of the Principia itself — done by the hand of an amanuensis, to be sure, but with interlinear corrections in the small, clear script of the master- hand itself. Here, too, is the famous death - mask, so much more interesting than any sculptured por- trait, and differing so strangely in its broad -based nose and full, firm mouth from the over - refined lineaments of the sculptured bust close at hand. In a room not far away, to reach which one passes a score or two of portraits and as many busts of celebrities — including, by-the-bye, both bust and portrait of Benjamin Franklin — one finds a cabinet containing other mementos similar to those on the library tables. Here is the first model of Davy's safety -lamp ; there a chronometer which aided Cook in his famous voy- age round the world. This is Wollaston's celebrated " Thimble Battery." It will slip readily into the pock- et, yet he jestingly showed it to a visitor as " his entire laboratory." That is a model of the double-decked boat made by Sir William Petty, and there beyond is a specimen of almost, if not quite, the first radiometer devised by Sir William Crookes. As one stands in the presence of all these priceless relics, so vividly do the traditions of more than two centuries of science come to mind that one seems al- most to have lived through them. One recalls, as if it were a personal recollection, the founding of the Royal Society itself in 1662, and the extraordinary scenes which the society witnessed during the years of its adolescence. As one views the mementos of Boyle and Newton, one seems to be living in the close of the seventeenth 22 THE ROYAL SOCIETY OF LONDON century. It is a troublous time in England. Revolu- tion has followed revolution. Commonwealth has sup- planted monarchy and monarchy commonwealth. At last the "glorious revolution" of 1688 has placed a secure monarch on the throne. But now one external war follows another, and the new king, William of Orange, is leading the "Grand Alliance" against the French despot Louis XIV. There is war everywhere in Europe, and the treaty of Ryswick, in 1697, is but the preparation for the war of the Spanish Alliance, which will usher in the new century. But amid all this political turmoil the march of scientific discovery has gone serenely on; or, if not serenely, then steadily, and perhaps as serenely as could be hoped. Boyle has discovered the law of the elasticity of gases and a host of minor things. Robert Hooke is on the track of many marvels. But all else pales before the fact that Newton has just given to the world his marvellous law of gravitation, which has been published, with authority of the Royal Society, through the financial aid of Halley. The brilliant but erratic Hooke has contested the priority of discovery and strenuously claimed a share in it. Halley eventually urges New- ton to consider Hooke's claim in some of the details, and Newton yields to the extent of admitting that the great fact of gravitational force varying inversely as the square of the distance had been independently dis- covered by Hooke; but he includes also Halley him- self and Sir Christopher Wren, along with Hooke, as equally independent discoverers of the same principle. To the twentieth-century consciousness it seems odd to hear Wren thus named as a scientific discoverer ; but 23 A HISTORY OF SCIENCE in truth the builder of St. Paul's began life as a pro- fessor of astronomy at Gresham College, and was the immediate predecessor of Newton himself in the presi- dential chair of the Royal Society. Now, at the very close of the seventeenth century, Boyle is recently dead, but Hooke, Wren, Halley, and Newton still survive: some of them are scarcely past their prime. It is a wonderful galaxy of stars of the first magnitude, and even should no other such names come in after-time, England's place among the scientific constellations is secure. But now as we turn to the souvenirs of Cooke and Wollaston and Davy the scene shifts by a hundred years. We are standing now in the closing epoch of the eighteenth century. These again are troublous times. The great new colony in the West has just broken off from the parent swarm. Now all Europe is in turmoil. The French war-cloud casts its omi- nous shadow everywhere. Even in England mutter- ings of the French Revolution are not without an echo. The spirit of war is in the air. And yet, as before, the spirit of science also is in the air. The strain of the political relations does not prevent a perpetual ex- change of courtesy between scientific men and scien- tific bodies of various nations. Davy's dictum that "science knows no country" is perpetually exempli- fied in practice. And at- the Royal Society, to match the great figures that were upon the scene a century before, there are such men as the eccentric Cavendish, the profound Wollaston, the marvellously versatile Priestley, and the equally versatile and even keener- visioned Rumford. Here, too, are Herschel, who is 24 THE ROYAL SOCIETY OF LONDON giving the world a marvellous insight into the consti- tution of the universe; and Hutton, who for the first time gains a clear view of the architecture of our earth's crust; and Jenner, who is rescuing his fellow- men from the clutches of the most deadly of plagues ; to say nothing of such titanic striplings as Young and Davy, who are just entering the scientific lists. With such a company about us we are surely justified in feeling that the glory of England as a scientific centre has not dimmed in these first hundred and thirty years of the Royal Society's existence. And now, as we view the radiometer, the scene shifts by yet another century, and we come out of cloud-land and into our own proper age. We are at the close of the nineteenth century — no, I forget, we are fairly entering upon the twentieth. Need I say that these again are troublous times ? Man still wages warfare on his fellow -man as he has done time out of mind; as he will do — who shall say how long? But meantime, as of yore, the men of science have kept steadily on their course. But recently here at the Royal Society were seen the familiar figures of Dar- win and Lyell and Huxley and Tyndall. Nor need we shun any comparison with the past while the present lists can show such names as Wallace, Kelvin, Lister, Crookes, Foster, Evans, Rayleigh, Ramsay, and Lock- yer. What revolutionary advances these names con- note! How little did those great men of the closing decades of the seventeenth and eighteenth centuries know of the momentous truths of organic evolution for which the names of Darwin and Wallace and Hux- ley stand! How little did they know a century ago, 2^ A HISTORY OF SCIENCE despite Hutton's clear prevision, of these marvellous slow revolutions through which, as Lyell taught us, the earth's crust had been built up! Not even Jen- ner could foresee a century ago the revolution in sur- gery which has been effected in our generation through the teachings of Lister. And what did Rumford and Davy know of energy in its various manifestations as compared with the knowl- edge of to-day, of Crookes and Rayleigh and Ramsay and Kelvin? What would Joseph Priestley, the dis- coverer of oxygen, and Cavendish, the discoverer of nitrogen, think could they step into the laboratory of Professor Ramsay and see test-tubes containing argon and helium and krypton and neon and zenon ? Could they more than vaguely understand the papers con- tributed in recent years to the Royal Society, in which Professor Ramsay explains how these new constituents of the atmosphere are obtained by experiments on liquid air. "Here," says Professor Ramsay, in effect, in a late paper to the society, "is the apparatus with which we liquefy hydrogen in order to separate neon from helium by liquefying the former while the helium still remains gaseous." Neon, helium, liquid air, liquid hydrogen — these would seem strange terms to the men who on discovering oxygen and nitrogen named them " dephlogisticated air" and "phlogisti- cated air" respectively. - Again, how elementary seems the teaching of Her- schel, wonderful though it was in its day, when com- pared with our present knowledge of the sidereal system as outlined in the theories of Sir Norman Lock- yer. Herschel studied the sun-spots, for example, with 26 THE ROYAL SOCIETY OF LONDON assiduity, and even suggested a possible connection be- tween sun-spots and terrestrial weather. So far, then, he would not be surprised on hearing the announce- ment of Professor Lockyer's recent paper before the Royal Society on the connection between sun-spots and the rainfall in India. But when the paper goes on to speak of the actual chemical nature of the sun-spots, as tested by a spectroscope; to tell of a "cool" stage when the vapor of iron furnishes chief spectrum lines, and of a "hot" stage when the iron has presumably been dissociated into unknown "proto-iron" constitu- ents— then indeed does it go far beyond the compre- hension of the keenest eighteenth-century intellect, though keeping within the range of understanding of the mere scientific tyro of to-day. Or yet again, consider a recent paper contributed by Professor Lockyer to the Royal Society, entitled "The New Star in Perseus: Preliminary Note" — referring to the new star that flashed suddenly on the vision of the terrestrial observers at more than first magnitude on February 22, 1901. This "star," the paper tells us, when studied by its spectrum, is seen to be due to the impact of two swarms of meteors out in space — swarms moving in different directions "with a differential ve- locity of something like seven hundred miles a second." Every astronomer of to-day understands how such a record is read from the displacement of lines on the spectrum, as recorded on the photographic negative. But imagine Sir William Herschel, roused from a cen- tury's slumber, listening to this paper, which involves a subject of which he was the first great master. " Neb- ulae," he might say; "yes, they were a specialty of 27 A HISTORY OF SCIENCE mine ; but swarms of meteors — I know nothing of these. And 'spectroscopes,' 'photographs' — what, pray, are these ? In my day there were no such words or things as spectroscope and photograph ; to my mind these words convey no meaning." But why go farther? These imaginings suffice to point a moral that he who runs may read. Of a truth the march of science still goes on as it has gone on with steady tread throughout the long generations of the Royal Society's existence. If the society had giants among its members in the days of its childhood and adolescence, no less are there giants still to keep up its fame in the time of its maturity. The place of Eng- land among the scientific constellations is secure through tradition, but not through tradition alone. Ill THE ROYAL INSTITUTION AND THE LOW- TEMPERATURE RESEARCHES FOUNDATION AND FOUNDER GEORGE THE THIRD, by the Grace of God King of Great Britain, France, and Ireland, Defender of the Faith, etc., to all to whom these presents shall come, greeting. Whereas several of our loving sub- jects are desirous of forming a Public Institution for diffusing the knowledge and facilitating the general in- troduction of Useful Mechanical Inventions and Im- provements ; and for teaching, by Courses of Philosoph- ical Lectures and Experiments, the Application of Science to the Common Purposes of Life, we do hereby give and grant" — multifarious things which need not here be quoted. Such are the opening words of the charter with which, a little more than a century ago, the Royal Institution of Great Britain came into exist- ence and received its legal christening. If one reads on he finds that the things thus graciously "given and granted," despite all the official verbiage, amount to nothing more than royal sanction and approval, but doubtless that meant more in the way of assuring popu- lar approval than might at first glimpse appear. So, too, of the list of earls, baronets, and the like, who ap- pear as officers and managers of the undertaking, and who are described in the charter as " our right trusty and 29 A HISTORY OF SCIENCE right well-beloved cousins," " our right trusty and well- beloved counsellors," and so on, in the skilfully grad- uated language of diplomacy. The institution that had the King for patron and such notables for officers seemed assured a bright career from the very beginning. In name and in personnel it had the flavor of aristoc- racy, a flavor that never palls on British palate. And right well the institution has fulfilled its promise, though in a far different way from what its originator and founder anticipated. Its originator and founder, I say, and say advisedly ; for, of course, here, as always, there is one man who is the true heart and soul of the movement, one name that stands, in truth, for the whole project, and to which all the other names are mere appendages. You would never suspect which name it is, in the present case, from a study of the charter, for it appears well down the file of graded titles, after "cousins" and "counsellors" have had their day, and is noted simply as "our trusty and well-beloved Benjamin, Count of Rumford, of the Holy Roman Empire." Little as there is to signalize it in the charter, this is the name of the sole projector of the enterprise in its incipiency, of the projector of every detail, of the writer of the char- ter itself even. The establishment thus launched with royal title might with full propriety have been called, as indeed it sometimes is called, the Rumford Institu- tion. The man who thus became the founder of this re- markable institution was in many ways a most ex- traordinary person. He was an American by birth, and if not the most remarkable of Americans, he surely 3° LOW-TEMPERATURE RESEARCHES was destined to a more picturesque career than ever fell to the lot of any of his countrymen of like eminence. Born on a Massachusetts farm, he was a typical " down- east Yankee," with genius added to the usual shrewd, inquiring mind and native resourcefulness. He was self-educated and self-made in the fullest sense in which those terms can be applied. At fourteen he was an unschooled grocer-lad — Benjamin Thompson by name — in a little New England village ; at forty he was a world-famous savant, as facile with French, Italian, Spanish, and German as with his native tongue ; he had become vice-president and medallist of the Royal Society, member of the Berlin National Acade- my of Science, of the French Institute, of the American Academy of Science, and I know not what other learn- ed bodies ; he had been knighted in Great Britain after serving there as under-secretary of state and as an officer; and he had risen in Bavaria to be more than half a king in power, with the titles, among others, of privy councillor of state, and head of the war de- partment, lieutenant-general of the Bavarian armies, holder of the Polish order of St. Stanislas and the Bavarian order of the White Eagle, ambassador to England and to France, and, finally, count of the Holy Roman Empire. Once, in a time of crisis, Rumford was actually left at the head of a council of regency, in full charge of Bavarian affairs, the elector having fled. The Yankee grocer-boy had become more than half a king. Never, perhaps, did a man of equal scientific attain- ments enjoy a corresponding political power. Never was political power wielded more justly by any man. 3i A HISTORY OF SCIENCE For in the midst of all his political and military tri- umphs, Rumford remained at heart to the very end the scientist and humanitarian. He wielded power for the good of mankind ; he was not merely a ruler but a public educator. He taught the people of Bavaria economy and Yankee thrift. He established kitchens for feeding the poor on a plan that was adopted all over Europe ; but, better yet, he created also workshops for their employment and pleasure - gardens for their recreation. He actually banished beggary from the principality. It was in the hope of doing in some measure for London what he had done for Munich that this large- brained and large-hearted man was led to the project of the Royal Institution. He first discussed his plans with a committee of the Society for Alleviating the Condition of the Poor, for it was the poor, the lower ranks of society, whom he wished chiefly to benefit. But he knew that to accomplish his object, he must work through the aristocratic channels; hence the name of the establishment and the charter with its list of notables. The word institution was selected by Rumford, after much deliberation, as, on the whole, the least objectionable title for the establishment, as having a general inclusiveness not possessed by such words as school or college. Yet in effect it was a school which Rumford intended to found— a school for the general diffusion of useful knowledge. There were to be classes for mechanics, and workshops, kitchens, and model -rooms, where the "application of science to the useful purposes of life" might be directly and practically taught; also a laboratory for more tech- ENTRANCE TO THE ROYAL INSTITUTION, LONDON LOW-TEMPERATURE RESEARCHES nical investigations, with a "professor" in charge, who should also deliver popular lectures on science. Finally, there was to be a scientific library. All these aims were put into effect almost from the beginning. The necessary funds were supplied solely by popular subscription and by the sale of lecture tickets (as all funds of the institution have been ever since), and before the close of the year 1800 Rumford's dream had become an actuality — as this practical man's dreams nearly always did. The new machine did not move altogether without friction, of course, but on the whole all went well for the first few years. The institution had found a local habitation in a large building in Albemarle Street, the same building which it still occupies, and for a time Rumford lived there and gave the enterprise his undivided attention. He appointed the brilliant young Humphry Davy to the professorship of chemistry, and the even more wonder- ful Thomas Young to that of natural philosophy. He saw the workshops and kitchens and model-rooms in running order — the entire enterprise fully launched. Then other affairs, particularly an attachment for a French lady, the widow of the famous chemist La- voisier (whom he subsequently married, to his sor- row), called him away from England never to return. And the first chapter in the history of the Royal Institution was finished. METHOD AND RESULT Rumford, the humanitarian, gone, a curious change came over the spirit of the enterprise he had founded. The aristocrats who at first were merely ballast for the vol. v —3 23 A HISTORY OF SCIENCE enterprise now made their influence felt. With true British reserve, they announced their belief that the education of the masses involved a dangerous political tendency. Hence the mechanics' school was suspended and the workshops and kitchens abolished; in a word, the chief ends for which the institution was founded were annulled. The library and the lectures remained, to be sure, but they were for the amusement of the rich, not for the betterment of the poor. It was the West End that made a fad of the institution and a society function of the lectures of Sydney Smith and of the charming youth Davy. Thus the institution came to justify its aristocratic title and its regal patronage; and the poor seemed quite forgotten. But indeed the institution itself was poor enough in these days, after the first flush of enthusiasm died away, and it is but fair to remember that without the support of its popular lectures its very existence would have been threatened. Nor in any event are regrets much in order over the possible might-have-beens of an institution whose laboratories were the seat of the physical investigations of Thomas Young, through which the wave theory of light first gained a footing, and of the brilliant chemical researches of Davy, which practically founded the science of electro-chemistry and gave the chemical world first knowledge of a galaxy of hitherto unknown elements. Through the labors of these men, and through the popular lecture- courses delivered at the institution by such other notables of science as Wollaston, Dalton, and Rum- ford, the enterprise had become world-famous before the close of the first decade of its existence. 34 LOW-TEMPERATURE RESEARCHES From that day till this the character of the Royal Institution has not greatly changed. The enterprise shifted around during its earliest years, while it was gaining its place in the scheme of things ; but once that was found, like a true British institution it held its course with an inertia that a mere century of time could not be expected to alter. Rumford was the sole founder of the enterprise, but it was Davy who gave it the final and definitive cast. He it was who estab- lished the tradition that the Royal Institution was to be essentially a laboratory for brilliant original inves- tigations, the investigator to deliver a yearly course of lectures, but to be otherwise untrammelled. It occu- pied, and has continued to occupy, the anomalous position of a school to which pupils are on no account admitted, and whose professors teach nothing except by a brief course of lectures to which whoever cares to pay the admission price may freely enter. But the marvellous results achieved at the Royal Institution have more than justified the existence of so anomalous an enterprise. Superlatives are always dangerous, but it may well be doubted whether there is another single institution in the world where so many novel original discoveries in physical science have been made as have been brought to light in the laboratories of the building on Albemarle Street dur- ing this first century of its occupancy ; for practically all that is to be credited to Thomas Young, Humphry Davy, Michael Faraday, and John Tyndall, not to men- tion living investigators, is to be credited also to the Royal Institution, whose professorial chairs these great men have successively occupied. Davy spent here the 35 A HISTORY OF SCIENCE best years of his youth and prime. Faraday, his direct successor, came to the institution in a subordinate ca- pacity as a mere boy, and was the life of the institu- tion for half a century. Tyndall gave it forty years of service. What wonder, then, that the Briton speaks of the institution as the "Pantheon of Science"? If you visit the Royal Institution to-day you will find it in most exterior respects not unlike what it pre- sumably was a century ago. Its long, stone front, dinged with age, with its somewhat Pantheon-like colonnade, has an appearance of dignity rather than of striking impressiveness. The main entrance, jutting full on the sidewalk, is at the street level, and the glass door gives hospitable glimpses of the interior. Enter- ing, one finds himself in a main central hall, at the foot of the main central staircase. The air of eminent re- spectability so characteristic of the British institu- tion is over all ; likewise the pervasive hush of British reserve. But you will not miss also the atmosphere of sincere if uneffusive British courtesy. At your right, as you mount the stairway, is a large statue of Faraday ; on the wall right ahead is a bronze medallion of Tyndall, placed beneath a large portrait of Davy. At the turn of the stairs is a marble bust of Wollaston. Farther on, in hall and library, you will find other busts of Faraday, other portraits of Davy; portraits _of Faraday everywhere, and various other busts of notables who have had connection with the institution. You will be shown the lecture-hall where Davy, Faraday, and Tyndall pronounced their mar- vellous discourses; the arrangement, the seats, the cushions even if appearances speak truly, and certain- 36 LOW-TEMPERATURE RESEARCHES ly the lecture-desk itself, unchanged within the cen- tury. You may see the crude balance, clumsy indeed to modern eyes, with which Davy performed his won- ders. The names and the memories of three great men — Davy, Faraday, and Tyndall — will be incessant- ly before you, and the least impressionable person could not well escape a certain sense of consecration of his surroundings. The hush that is over every- thing seems but fitting. All that is as it should be. But there are other memories connected with these surroundings which are not so tangibly presented to the senses. For where, amid all these busts and portraits, is the image of that other great man, the founder of the institution, the sole originator of the enterprise which has made possi- ble the aggregation of all these names and these memo- ries ? Where are the remembrances of that extraordi- nary man whom the original charter describes as "our well-beloved Benjamin, Count of Rumford?" Well, you will find a portrait of him, it is true, if you search far enough, hung high above a doorway in a room with other portraits. But one finds it hard to escape the feeling that there has been just a trifling miscarriage of justice in the disposal. Doubtless there was no such intention, but the truth seems to be that the glamour of the newer fame of Faraday has dazzled a little the eyes of the rulers of the institution of the present generation. But that, after all, is a small matter about which to quibble. There is glory enough for all in the Royal Institution, and the disposal of busts and portraits is unworthy to be mentioned in connection with the lasting fame of the great men 37 A HISTORY OF SCIENCE who are here in question. It would matter little if there were no portrait at all of Rumford here, for all the world knows that the Royal Institution itself is in effect his monument. His name will always be linked in scientific annals with the names of Young, Davy, Faraday, and Tyndall. And it is worthy such asso- ciation, for neither in native genius nor in realized accomplishments was Rumford inferior to these suc- cessors. FROM LIQUID CHLORINE TO LIQUID HYDROGEN Nor is it merely by mutual association with the his- tory of the Royal Institution that these great names are linked. There was a curious and even more last- ing bond between them in the character of their scientific discoveries. They were all pioneers in the study of those manifestations of molecular activity which we now, following Young himself, term energy. Thus Rumford, Davy, and Young stood almost alone among the prominent scientists of the world at the beginning of the century in upholding the idea that heat is not a material substance — a chemical element — but merely a manifestation of the activities of particles of matter. Rumford 's papers on this thesis, communi- cated to the Royal Society, were almost the first widely heralded claims for this then novel idea. Then Davy came forward in support of Rumford, with his famous experiment of melting ice by friction. It was perhaps this intellectual affinity that led Rumford to select Davy for the professorship at the Royal Institution, and thus in a sense to predetermine the character of the scientific work that should be accomplished there 38 LOW-TEMPERATURE RESEARCHES — the impulse which Davy himself received from Rum- ford being passed on to his pupil Faraday. There is, then, an intangible but none the less potent web of association between the scientific work of Rumford and some of the most important researches that were conducted at the Royal Institution long years after his death ; and one is led to feel that it was not merely a coincidence that some of Faraday's most important labors should have served to place on a firm footing the thesis for which Rumford battled; and that Tyndall should have been the first in his "beautiful book" called Heat, a Mode of Motion, to give wide popular announcement to the fact that at last the scientific world had accepted the proposition which Rumford had vainly demonstrated three-quarters of a century before. This same web of association extends just as clearly to the most important work which has been done at the Royal Institution in the present generation, and which is still being prosecuted there — the work, namely, of Professor James Dewar on the properties of matter at excessively low temperatures. Indeed, this work is in the clearest sense a direct continuation of researches which Davy and Faraday inaugurated in 1823 and which Faraday continued in 1844. In the former year Faraday, acting on a suggestion of Davy's, performed an experiment which resulted in the production of a "clear yellow oil" which was presently proved to be liquid chlorine. Now chlorine, in its pure state, had previously been known (except in a forgotten experi- ment of Northmore's) only as a gas. Its transmu- tation into liquid form was therefore regarded as a very 39 A HISTORY OF SCIENCE startling phenomenon. But the clew thus gained, other gases were subjected to similar conditions by- Davy, and particularly by Faraday, with the result that several of them, including sulphurous, carbonic, and hydrochloric acids were liquefied. The method employed, stated in familiar terms, was the applica- tion of cold and of pressure. The results went far towards justifying an extraordinary prediction made by that extraordinary man, John Dalton, as long ago as 1 80 1, to the effect that by sufficient cooling and compressing all gases might be transformed into liquids — a conclusion to which Dalton had vaulted, with the sureness of supreme genius, from his famous studies of the properties of aqueous vapor. Between Dalton's theoretical conclusion, however, and experimental demonstration there was a tremen- dous gap, which the means at the disposal of the scien- tific world in 1823 did not enable Davy and Faraday more than partially to bridge. A long list of gases, including the familiar oxygen, hydrogen, and nitrogen, resisted all their efforts utterly — notwithstanding the facility with which hydrogen and oxygen are liquefied when combined in the form of water-vapor, and the relative ease with which nitrogen and hydrogen, com- bined to form ammonia, could also be liquefied. Davy and Faraday were well satisfied of the truth of Dal- ton's proposition, but they saw the futility of further efforts to put it into effect until new means of produc- ing, on the one hand, greater pressures, and, on the other, more extreme degrees of cold, should be prac- tically available. So the experiments of 1823 were abandoned. 40 LOW-TEMPERATURE RESEARCHES But in 1844 Faraday returned to them, armed now with new weapons, in the way of better air-pumps and colder freezing mixtures, which the labors of other workers, chiefly Thilorier, Mitchell, and Natterer, had made available. With these new means, and without the application of any principle other than the use of cold and pressure as before, Faraday now succeeded in reducing to the liquid form all the gases then known with the exception of six ; while a large number of these substances were still further reduced, by the applica- tion of the extreme degrees of cold now attained, to the condition of solids. The six gases which still proved intractable, and which hence came to be spoken of as "permanent gases," were nitrous oxide, marsh gas, carbonic oxide, oxygen, nitrogen, and hydrogen. These six refractory gases now became a target for the experiments of a host of workers in all parts of the world. The resources of mechanical ingenuity of the time were exhausted in the effort to produce low tem- peratures on the one hand and high pressures on the other. Thus Andrews, in England, using the bath of solid carbonic acid and ether which Thilorier had dis- covered, and which produces a degree of cold of — 8o° Centigrade, applied a pressure of five hundred at- mospheres, or nearly four tons to the square inch, without producing any change of state. Natterer in- creased this pressure to two thousand seven hundred atmospheres, or twenty-one tons to the square inch, with the same negative results. The result of Andrews' experiments in particular was the final proof of what Cagniard de la Tour had early suspected and Faraday had firmly believed, that pressure alone, regardless of 41 A HISTORY OF SCIENCE temperature, is not sufficient to reduce a gas to the liquid state. In other words, the fact of a so-called "critical temperature," varying for different sub- stances, above which a given substance is always a gas, regardless of pressure, was definitively discovered. It became clear, then, that before the resistant gases would be liquefied means of reaching extremely low temperatures must be discovered. And for this, what was needed was not so much new principles as elab- orate and costly machinery for the application of a principle long familiar — the principle, namely, that an evaporating liquid reduces the temperature of its im- mediate surroundings, including its own substance. Ingenious means of applying this principle, in con- nection with the means previously employed, were developed independently by Pictet in Geneva and Cailletet in Paris, and a little later by the Cracow pro- fessors Wroblewski and Olzewski, also working inde- pendently. Pictet, working on a commercial scale, em- ployed a series of liquefied gases to gain lower and lower temperatures by successive stages. Evaporating sulphurous acid liquefied carbonic acid, and this in evaporating brought oxygen under pressure to near its liquefaction point; and, the pressure being suddenly released (a method employed in Faraday's earliest ex- periments), the rapid expansion of the compressed oxygen liquefies a portion of its substance. This re- sult was obtained in 1877 by Pictet and Cailletet al- most simultaneously. Cailletet had also liquefied the newly discovered acetylene gas. Five years later Wroblewski liquefied marsh gas, and the following year nitrogen ; while carbonic oxide and nitrous oxide yielded 42 '■':'f:V-V ."■:•?.. PROFESSOR DEWAR'S APPARATUS WITH WHICH HYDROGEN WAS FIRST LIQUEFIED LOW-TEMPERATURE RESEARCHES to Olzewski in 1884. Thus forty years of effort had been required to conquer five of Faraday's refractory gases, and the sixth, hydrogen, still remains resistant. Hydrogen had, indeed, been seen to assume the form of visible vapor, but it had not been reduced to the so- called static state — that is, the droplets had not been collected in an appreciable quantity, as water is col- lected in a cup. Until this should be done, the final problem of the liquefaction of hydrogen could not be regarded as satisfactorily solved. More than another decade was required to make this final step in the completion of Faraday's work. And, oddly enough, yet very fittingly, it was reserved for Faraday's successor in the chair at the Royal In- stitution to effect this culmination. Since 1884 Pro- fessor Dewar's work has made the Royal Institution again the centre of low - temperature research. By means of improved machinery and of ingenious de- vices for shielding the substance operated on from the accession of heat, to which reference will be made more in detail presently, Professor Dewar was able to liquefy the gas fluorine, recently isolated by Moussan, and the recently discovered gas helium in 1897. And in May, 1898, he was able to announce that hydrogen also had yielded, and for the first time in the history of science that elusive substance, hitherto "perma- nently" gaseous, was held as a tangible liquid in a cuplike receptacle; and this closing scene of the long struggle was enacted in the same laboratory in which Faraday performed the first liquefaction experiment with chlorine just three-quarters of a century before. It must be noted, however, that this final stage in 43 A HISTORY OF SCIENCE the liquefaction struggle was not effected through the use of the principle of evaporating liquids which has just been referred to, but by the application of a quite different principle and its elaboration into a perfectly novel method. This principle is the one established long ago by Joule and Thomson (Lord Kelvin), that compressed gases when allowed to expand freely are lowered in temperature. In this well-known principle the means was at hand greatly to simplify and im- prove tlje method of liquefaction of gases, only for a long time no one recognized the fact. Finally, how- ever, the idea had occurred to two men almost simul- taneously and quite independently. One of these was Professor Linde, the well-known German experimenter with refrigeration processes; the other, Dr. William Hampson, a young English physician. Each of these men conceived the idea — and ultimately elaborated it in practice — of accumulating the cooling effect of an expanding gas by allowing the expansion to take place through a small orifice into a chamber in which the coil containing the compressed gas was held. In Dr. Hampson's words : "The method consists in directing all the gas im- mediately after its expansion over the coils which con- tain the compressed gas that is on its way to the ex- pansion-point. The cold developed by expansion in the first expanded gas is thus communicated to the on- coming compressed gas, which consequently expands from, and therefore to, a lower temperature than the preceding portion. It communicates in the same way its own intensified cold to the succeeding portion of 44 KAMPSON S APPARATUS FOR LIQUEFYING AIR LOW-TEMPERATURE RESEARCHES compressed gas, which, in its turn, is made colder, both before and after expansion, than any that had gone before. This intensification of cooling goes on until the expansion-temperature is far lower than it was at starting; and if the apparatus be well arranged the effect is so powerful that even the smaller amount of cooling due to the free expansion of gas through a throttle-valve, though pronounced by Siemens and Coleman incapable of being utilized, may be made to liquefy air without using other refrigerants." So well is this principle carried out in Dr. Hamp- son's apparatus for liquefying air that compressed air passing into the coil at ordinary temperature without other means of refrigeration begins to liquefy in about six minutes — a result that seems almost miraculous when it is understood that the essential mechanism by which this is brought about is contained in a cylinder only eighteen inches long and seven inches in diameter. As has been said, it was by adopting this principle of self-intensive refrigeration that Professor Dewar was able to liquefy hydrogen. More recently the same result has been attained through use of the same prin- ciple by Professor Ramsay and Dr. Travers at Uni- versity College, London, who are to be credited also with first publishing a detailed account of the various stages of the process. It appears that the use of the self -intensification principle alone is not sufficient with hydrogen as it is with the less volatile gases, including air, for the reason that at all ordinary temperatures hydrogen does not cool in expanding, but actually becomes warmer. It is only after the compressed hy- 45 A HISTORY OF SCIENCE drogen has been cooled by immersion in refrigerating media of very low temperature that this gas becomes amenable to the law of cooling on expansion. In the apparatus used at University College the coil of com- pressed hydrogen is passed successively through (i) a jar containing alcohol and solid carbonic acid at a temperature of — 8o° Centigrade; (2) a chamber con- taining liquid air at atmospheric pressure, and (3) liquid air boiling in a vacuum bringing the tempera- ture to perhaps 2050 Centigrade before entering the Hampson coil, in which expansion and the self-inten- sive refrigeration lead to actual liquefaction. With this apparatus Dr. Travers succeeded in producing an abundant quantity of liquid hydrogen for use in the experiments on the new gases that were first dis- covered in the same laboratory through the experi- ments on liquid air — gases about which I shall have something more to say in another chapter. PRINCIPLES AND EXPERIMENTS At first blush it seems a very marvellous thing, this liquefaction of substances that under all ordinary con- ditions are gaseous. It is certainly a little startling to have a cup of clear, water-like liquid offered one, with the assurance that it is nothing but air ; still more so to have the same air presented in the form of a white " avalanche snow." In a certain sense it is marvellous, because the mechanical difficulties that have been overcome in reducing the air to these unusual condi- tions are great. Yet, in another and broader view, there is nothing more wonderful about liquid air than 46 LOW-TEMPERATURE RESEARCHES about liquid water, or liquid mercury, or liquid iron. Long before air was actually liquefied, it was perfectly understood by men of science that under certain con- ditions it could be liquefied just as surely as water, mer- cury, iron, and every other substance could be brought to a similar state. This being known, and the princi- ples involved understood, had there been nothing more involved than the bare effort to realize these con- ditions all the recent low - temperature work would have been mere scientific child's-play, and liquid air would be but a toy of science. But in point of fact there are many other things than this involved ; new principles were being searched for and found in the course of the application of the old ones ; new light was being thrown into many dark corners; new fields of research, some of them as yet barely entered, were be- ing thrown open to the investigator; new applications of energy, of vast importance not merely in pure science but in commercial life as well, were being made available. That is why the low-temperature work must be regarded as one of the most important scien- tific accomplishments of our century. At the very outset it was this work in large measure which gave the final answer to the long-mooted ques- tion as to the nature of heat, demonstrating the cor- rectness of Count Rumford's view that heat is only a condition not itself a substance. Since about the middle of the century this view, known as the mechan- ical theory of heat, has been the constant guide of the physicists in all their experiments, and any one who would understand the low-temperature phenomena must keep this conception of the nature of heat clearly 47 A HISTORY OF SCIENCE and constantly in mind. To understand the theory, one must think of all matter as composed of minute isolated particles or molecules, which are always in motion — vibrating, if you will. He must mentally magnify and visualize these particles till he sees them quivering before him, like tuning-forks held in the hand. Remember, then, that, like the tuning-fork, each molecule would, if left to itself, quiver less and less violently, until it ran down altogether, but that the motion thus lessening is not really lost. It is sent out in the form of ether waves, which can set up like mo- tion in any other particles which they reach, be they near or remote ; or it is transmitted as a direct push — a kick, if you will — to any other particle with which the molecule comes in physical contact. But note now, further, that our molecule, while in- cessantly giving out its energy of motion in ether waves and in direct pushes, is at the same time just as ceaslessly receiving motion from the ether waves made by other atoms, and by the return push of the molecules against which it pushes. In a word, then, every molecule of matter is at once a centre for the distribution of motion (sending out impulses which affect, sooner or later, every other atom of mat- ter in the universe), and, from the other point of view, also a centre for the reception of motion from every direction and from every other particle of matter in the universe. Whether any given molecule will on the whole gain motion or lose it depends clearly on the simple mechanical principles of give and take. From equally familiar mechanical principles, it is clear that our vibrating molecule, in virtue of its vi- 48 LOW-TEMPERATURE RESEARCHES brations, is elastic, tending to be thrown back from every other molecule with which it comes in contact, just as a vibrating tuning-fork kicks itself away from anything it touches. And of course the vigor of the recoil will depend upon the vigor of the vibration and the previous movements. But since these movements constitute temperature, this is another way of saying that the higher the temperature of a bod)'" the more its molecules will tend to spring asunder, such separation in the aggregate constituting expansion of the mass as a whole. Thus the familiar fact of expansion of a body under increased temperature is explained. But now, since all molecules are vibrating, and so tending to separate, it is clear that no unconfined mass of molecules would long remain in contiguity unless some counter influence tended to draw them together. Such a counter influence in fact exists, and is termed the "force" of cohesion. This force is a veritable gravitation influence, drawing every molecule towards every other molecule. Possibly it is identical with gravitation. It seems subject to some law of de- creasing in power with the square of the distance; or, at any rate, it clearly becomes less potent as the dis- tance through' which it operates increases. Now, between this force of cohesion which tends to draw the molecules together, and the heat vibrations which tend to throw the molecules farther asunder, there seems to be an incessant battle. If cohesion pre- vails, the molecules are held for the time into a relative- ly fixed system, which we term the solid state. If the two forces about balance each other, the molecules move among themselves more freely but maintain an VOL. V.— 4 49 A HISTORY OF SCIENCE average distance, and we term the condition the liquid state. But if the heat impulse preponderates, the molecules (unless restrained from without) fly farther and farther asunder, moving so actively that when they collide the recoil is too great to be checked by cohesion, and this condition we term the gaseous state. Now after this statement, it is clear that what the low-temperature worker does when he would liquefy a gas is to become the champion of the force of co- hesion. He cannot directly aid it, for so far as is known it is an unalterable quantity, like gravitation. But he can accomplish the same thing indirectly by weakening the power of the rival force. Thus, if he encloses a portion of gas in a cylinder and drives a pis- ton down against it, he is virtually aiding cohesion by forcing the molecules closer together, so that the hold of cohesion, acting through a less distance, is stronger. What he accomplishes here is not all gain, however, for the bounding molecules, thus jammed together, come in collision with one another more and more frequently, and thus their average activity of vibration is increased and not diminished; in other words, the temperature of the gas has risen in virtue of the com- pression. Compression alone, then, will not avail to enable cohesion to win the battle. But the physicist has another resource. He may place the cylinder of gas in a cold medium, so that the heat vibrations sent into it will be less vigorous than those it sends out. That is a blow the molecule cannot withstand. It is quite impotent to cease sending out the impulses however little comes in return ; hence the 5o LOW-TEMPERATURE RESEARCHES aggregate motion becomes less and less active, until finally the molecule is moving so sluggishly that when it collides with its fellow cohesion is able to hold it there. Cohesion, then, has won the battle, and the gas has become a liquid. Such, stated in terms of the mechanical theory of heat, is what is brought to pass when a gas is liquefied in the laboratory of the physicist. It remains only to note that different chemical substances show the widest diversity as to the exact point of temperature at which this balance of the expansive and cohesive tendencies is affected, but that the point, under uniform conditions of pressure, is always the same for the same substance. This diversity has to do pretty clearly with the size of the individual molecules involved; but its exact ex- planation is not yet forthcoming, and, except in a gen- eral way, the physicist would not be able to predict the "critical temperature" of any new gas presented to him. But once this has been determined by ex- periment, he always knows just what to expect of any given substance. He knows, for example, that in a mixture of gases hydrogen would still remain gaseous after all the others had assumed the liquid state, and most of them the solid state as well. These mechanical conceptions well in mind, it is clear that what the would-be liquefier of gases has all along sought to attain is merely the insulation of the portion of matter with which he worked against the access of heat-impulse from its environment. It is clear that were any texture known which would permit a heat- impulse to pass through it in one direction only, noth- ing more would be necessary than to place a portion of 5i A HISTORY OF SCIENCE gas in such a receptacle of this substance, so faced as to permit egress but not entrance of the heat, and the gas thus enclosed, were it hydrogen itself, would very- soon become liquid and solid, through spontaneous giving off of its energy, without any manipulation whatever. Contrariwise, were the faces of the recep- tacle reversed, a piece of iron placed within it would be made red-hot and melted though the receptacle were kept packed in salt and ice and no heat applied ex- cept such as came from this freezing mixture. One could cook a beefsteak with a cake of ice had he but such a material as this with which to make his stove. Not even Rumford or our modern Edward Atkinson ever dreamed of such economy of fuel as that. But, unfortunately, no such substance as this is known, nor, indeed, any substance that will fully pre- vent the passage of heat-impulses in either direction. Hence one of the greatest tasks of the experimenters has been to find a receptacle that would insulate a cooled substance even partially from the incessant bombardment of heat - impulses from without. It is obvious that unless such an insulating receptacle could be provided none of the more resistent gases, such as oxygen, could be long kept liquid, even when once brought to that condition, since an environment of requisite frigidity could not practicably be provided. But now another phase of the problem presents it- self to the experimenter. Oxygen has assumed the quiescent liquid state, to be sure, but in so doing it has fallen below the temperature of its cooling medium; hence it is now receiving from that medium more en- ergy of vibration than it gives, and unless this is pre- 52 LOW-TEMPERATURE RESEARCHES vented very soon its particles will again have power to kick themselves apart and resume the gaseous state. Something, then, must be done to insulate the liquefied gas, else it will retain the liquid state for too short a time to be much experimented with. How might such insulation be accomplished ? The most successful attack upon this important problem has been made by Professor Dewar. He in- vented a receptacle for holding liquefied gases which, while not fulfilling the ideal conditions referred to above, yet accomplishes a very remarkable degree of heat insulation. In consists of a glass vessel with double walls, the space between which is rendered a vacuum of the highest practicable degree. This vacu- um, containing practically no particles of matter, can- not, of course, convey heat-impulses to or from the matter in the receptacle with any degree of rapidity. Thus one of the two possible means of heat transfer is shut off and a degree of insulation afforded the lique- fied substance. But of course the other channel, ether radiation, remains. Even this may be blocked to a large extent, however, by leaving a trace of mercury vapor in the vacuum space, which will be deposited as a fine mirror on the inner surface of the chamber. This mirror serves as an admirable reflector of the heat-rays that traverse the vacuum, sending more than half of them back again. So, by the combined action of vacuum and mirror, the amount of heat that can penetrate to the interior of the receptacle is reduced to about one-thirtieth of what would enter an ordinary vessel. In other words, a quantity of liquefied gas which would evaporate in one minute from an ordinary 53 A HISTORY OF SCIENCE vessel will last half an hour in one of Professor Dewar's best vacuum vessels. Thus in one of these vessels a quantity of liquefied air, for example, can be kept for a considerable time in an atmosphere at ordinary tem- perature, and will only volatilize at the surface, like water under the same conditions, though of course more rapidly ; whereas the same liquid in an ordinary vessel would boil briskly away, like water over a fire. Only, be it remembered, the air in "boiling" is at a tem- perature of about one hundred and eighty degrees be- low zero, so that it would instantly freeze almost any substance placed into it. A portion of alcohol poured on its surface will be changed quickly into a globule of ice, which will rattle about the sides of the vessel like a marble. That is not what one ordinarily thinks of as a "boiling" temperature. If the vacuum vessel containing a liquefied gas be kept in a cold medium, and particularly if two vacuum tubes be placed together, so that no exposed surface of liquid remains, a portion of liquefied air, for example, may be kept almost indefinitely. Thus it becomes possible to utilize the liquefied gas for experimental investigation of the properties of matter at low tem- peratures that otherwise would be quite impracticable. Great numbers of such experiments have been per- formed in the past decade or so by all the workers with low temperatures already mentioned, and by various others, including, fittingly enough, the holder of the Rumford professorship of experimental physics at Harvard, Professor Trowbridge. The work of Pro- fessor Dewar has perhaps been the most comprehensive and varied, but the researches of Pictet, Wroblewski, 54 LOW-TEMPERATURE RESEARCHES and Olzewski have also been important, and it is not always possible to apportion credit for the various dis- coveries accurately, since the authorities themselves are in unfortunate disagreement in several questions of priority. But in any event, such questions of exact priority have no great interest for any one but the persons directly involved. We may quite disregard them here, confining attention to the results them- selves, which are full of interest. The questions investigated have to do with the phys- ical properties, such as electrical conductivity, magnet- ic condition, light-absorption, cohesion, and chemical affinities of matter at excessively low temperatures. It is found that in all these regards most substances are profoundly modified when excessively cooled. Thus if a piece of any pure metal is placed in an electric circuit and plunged into liquid air, its resistance to the passage of the electricity steadily decreases as the metal cools, until at the temperature of the liquid it is very trifling indeed. The conclusion seems to be justified that if the metal could be still further cooled until it reached the theoretical "absolute zero," or absolutely heatless condition, the electrical resistance would also be nil. So it appears that the heat vibra- tions of the molecules of a pure metal interfere with the electrical current. The thought suggests itself that this may be because the ether waves set up by the vi- brating molecules conflict with the ether strain which is regarded by some theorists as constituting the electrical "current." But this simple explanation falters before further experiments which show, paradoxically enough, that the electrical resistance of carbon exactly reverses 55 A HISTORY OF SCIENCE what has just been said of pure metals, becoming great- er and greater as the carbon is cooled. If an hypothesis were invented to cover this case there would still re- main a puzzle in the fact that alloys of metals do not act at all like the pure metals themselves, the electrical resistance of such alloys being, for the most part, un- affected by changed temperature. On the whole, then, the facts of electrical conduction at low tem- peratures are quite beyond the reach of present ex- planation. They must await a fuller knowledge of molecular conditions in general than is at present available— a knowledge to which the low-temperature work itself seems one of the surest channels. Even further beyond the reach of present explana- tion are the facts as to magnetic conditions at low tem- peratures. Even as to the facts themselves different experimenters have differed somewhat, but the final conclusion of Professor Dewar is that, after a period of fluctuation, the power of a magnet repeatedly sub- jected to a liquid - air bath becomes permanently in- creased. Various substances not markedly magnetic at ordinary temperatures become so when cooled. Among these, as Professor Dewar discovered, is liquid oxygen itself. Thus if a portion of liquid air be further cooled until it assumes a semi-solid condition, the oxy- gen may be drawn from the mass by a magnet, leaving a pure nitrogen jelly. These facts are curious enough, and full of suggestion, but like all other questions hav- ing to do with magnetism, they hold for the present generation the double fascination of insoluble mystery. To be sure, one may readily enough suggest that if magnetism be really a whirl in the ether, this whirl is 56 LOW-TEMPERATURE RESEARCHES apparently interfered with by the waves of radiant heat; or, again, that magnetism is presumably due to molecular motions which are apparently interfered with by another kind of molecular motions which we call heat vibrations ; but there is a vagueness about the terms of such guesses that leaves them clearly within the category of explanations that do not explain. When it comes to the phenomena of light, we can, as is fitting, see our way a little more clearly, since, thanks to Thomas Young and his successors, we know pretty definitely what light really is. So when we learn that many substances change their color utterly at low temperatures — red things becoming yellow and yellow things white, for example — we can step easily and surely to at least a partial explanation. We know that the color of any object depends simply upon the particular ether waves of the spectrum which that particular substance absorbs; and it does not seem anomalous that molecules packed close together at — 1800 of temperature should treat the ether waves differently than when relatively wide apart at an ordinary temperature. Yet, after all, that may not be the clew to the explanation. The packing of the mole- cules may have nothing to do with it. The real ex- planation may lie in the change of the ether waves sent out by the vibrating molecule; indeed, the fact that the waves of radiant heat and those of light differ only in amplitude lends color to this latter supposition. So the explanation of the changed color of the cooled substance is at best a dubious one. Another interesting light phenomenon is found in the observed fact that very many substances become 57 A HISTORY OF SCIENCE markedly phosphorescent at low temperatures. Thus, according to Professor Dewar, "gelatine, celluloid, par- affine, ivory, horn, and india-rubber become distinctly luminous, with a bluish or greenish phosphorescence, after cooling to — 1800 and being stimulated by the electric light." The same thing is true, in varying degrees, of alcohol, nitric acid, glycerine, and of paper, leather, linen, tortoise-shell, and sponge. Pure water is but slightly luminous, whereas impure water glows brightly. On the other hand, alcohol loses its phos- phorescence when a trace of iodine is added to it. In general, colored things are but little phosphorescent. Thus the white of egg is very brilliant but the yolk much less so. Milk is much brighter than water, and such objects as a white flower, a feather, and egg-shell glow brilliantly. The most remarkable substances of all, says Professor Dewar, whom I am all along quot- ing, are "the platinocyanides among inorganic com- pounds and the ketonic compounds among organic. Ammonium platinocyanide, cooled while stimulated by arc light, glows fully at - 1 8o° ; but on warming it glows like a lamp. It seems clear," Professor Dewar adds, " that the substance at this low temperature must have acquired increased power of absorption, and it may be that at the same time the factor of molecular friction or damping may have diminished." The cau- tious terms in which this partial explanation is couched suggest how far we still are from a full understanding of the interesting phenomena of phosphorescence. That a molecule should be able to vibrate in such a way as to produce the short waves of light, dissevered from the usual linking with the vibrations represented by 58 LOW-TEMPERATURE RESEARCHES high temperature, is one of the standing puzzles of physics. And the demonstrated increase of this ca- pacity at very low temperatures only adds to the mys- tery. There are at least two of the low-temperature phe- nomena, however, that seem a little less puzzling — the facts, namely, that cohesion and rigidity of structure are increased when a substance is cooled and that chemical activity is very greatly reduced, in fact al- most abolished. This is quite what one would expect a priori — though no wise man would dwell on his ex- pectation in advance of the experiments — since the whole question of liquids and solids versus gases ap- pears to be simply a contest between cohesive forces that are tending to draw the molecules together and the heat vibration which is tending to throw them apart. As a substance changes from gas to liquid, and from liquid to solid, contracting meantime, simply through the lessening of the heat vibrations of its molecules, we might naturally expect that the solid would become more and more tenacious in structure as its molecules came closer and closer together, and at the same time became less and less active, as hap- pens when the solid is further cooled. • And for once experiment justifies the expectation. Professor De- war found that the breaking stress of an iron wire is more than doubled when the wire is cooled to the tem- perature of liquid air, and all other metals are largely strengthened, though none other to quite the same degree. He found that a spiral spring of fusible metal, which at ordinary temperature was quickly drawn out into a straight wire by a weight of one ounce, would, 59 A HISTORY OF SCIENCE when cooled to — 1820, support a weight of two pounds, and would vibrate like a steel spring so long as it was cool. A bell of fusible metal has a distinct metallic ring at this low temperature; and balls of iron, tin, lead, or ivory cooled to — 1820 and dropped from a height, "in all cases have the rebound greatly increased. The flattened surface of the lead is only one-third what it would be at ordinary temperature. " "These conditions are due solely to the cooling, and persist only while the low temperature lasts." If this increased strength and hardness of a con- tracted metal are what one would expect on molecular principles, the decreased chemical activity at low tem- peratures is no less natural-seeming, when one reflects how generally chemical phenomena are facilitated by the application of heat. In point of fact, it has been found that at the temperature of liquid hydrogen practically all chemical activity is abolished, the un- ruly fluorine making the only exception. The ex- planation hinges on the fact that every atom, of any kind, has power to unite with only a limited number of other atoms. When the " affinities" of an atom are satisfied, no more atoms can enter into the union un- less some atoms already there be displaced. Such displacement takes place constantly, under ordinary conditions of temperature, because the vibrating atoms tend to throw themselves apart, and other atoms may spring in to take the places just vacated — such inter- change, in fact, constituting the essence of chemical activity. But when the temperature is reduced the heat-vibration becomes insufficient to throw the atoms apart, hence any unions they chance to have made are 60 LOW-TEMPERATURE RESEARCHES permanent, so long as the low temperature is main- tained. Thus it is that substances which attack one another eagerly at ordinary temperatures will lie side by side, utterly inert, at the temperature of liquid air. Under certain conditions, however, most interesting chemical experiments have been made in which the liquefied gases, particularly oxygen, are utilized. Thus Olzewski found that a bit of wood lighted and thrust into liquid oxygen burns as it would in gaseous oxy- gen, and a red-hot iron wire thrust into the liquid burns and spreads sparks of iron. But more novel still was Dewar's experiment of inserting a small jet of ignited hydrogen into the vessel of liquid oxygen; for the jet continued to burn, forming water, of course, which was carried away as snow. The idea of a gas- jet burning within a liquid, and having snow for smoke, is not the least anomalous of the many strange concep- tions that the low-temperature work has made familiar. PRACTICAL RESULTS AND ANTICIPATIONS Such are some of the strictly scientific results of the low - temperature work. But there are other re- sults of a more directly practical kind — neither more important nor more interesting on that account, to be sure, but more directly appealing to the generality of the non-scientific public. Of these applications, the most patent and the first to be made available was the one forecast by Davy from the very first — namely, the use of liquefied gases in the refrigeration of foods. Long before the more resistant gases had been liquefied, the more manageable ones, such as ammonia and sul- 61 A HISTORY OF SCIENCE phurous acid, had been utilized on a commercial scale for refrigerating purposes. To-day every brewery and every large cold-storage warehouse is supplied with such a refrigerator plant, the temperature being thus regulated as is not otherwise practicable. Many large halls are cooled in a similar manner, and thus made comfortable in the summer. Ships carrying perish- ables have the safety of their cargoes insured by a re- frigerator plant. In all large cities there are ice manu- factories using the same method, and of late even relatively small establishments, hotels, and apart- ment houses have their ice-machine. It seems prob- able that before long all such buildings and many private dwellings will be provided with a cooling ap- paratus as regularly as they are now equipped with a heating apparatus. The exact details of the various refrigerator machines of course vary, but all of them utilize the principles that the laboratory workers first established. Indeed, the entire refrigerator industry, now assuming significant proportions, may be said to be a direct outgrowth of that technical work which Davy and Faraday inaugu- rated and prosecuted at the Royal Institution — a re- sult which would have been most gratifying to the founder of the institution could he have forecast it. The usual means of distributing the cooling fluids in the commercial plants is by the familiar iron pipes, not dissimilar in appearance (when not in operation) to the familiar gas, water, and steam pipes. When operating, however, the pipes themselves are soon hidden from view by the thick coating of frost which forms over them. In a moist beer-cellar this coating 62 LOW-TEMPERATURE RESEARCHES is often several inches in thickness, giving a very char- acteristic and unmistakable appearance. Another commercial use to which refrigerator ma- chines are now put is in the manufacture of various drugs, where absolute purity is desirable. As different substances congeal at different temperatures, but the same substances at uniform pressure always at the same temperature, a means is afforded of freeing a drug from impurities by freezing, where sometimes the same result cannot be accomplished with like thorough- ness by any other practicable means. Indeed, by this means impurities have been detected where not previously suspected. And Professor Ramsay has de- tected some new elementary substances even, as con- stituents of the air, which had previously not been dissociated from the nitrogen with which they are usually mixed. Such applications of the refrigerator principles as these, however, though of vast commercial importance, are held by many enthusiasts to be but a bagatelle compared with other uses to which liquefied gases may some time be put. Their expectations are based upon the enormous potentialities that are demonstrably stored in even a tiny portion of, say, liquefied air. These are, indeed, truly appalling. Consider, for ex- ample, a portion of air at a temperature above its critical point, to which, as in Thilorier's experiments, a pressure of thirty-one tons to the square inch of the encompassing wall is being applied. Recall that ac- tion and reaction are equal, and it is apparent that the gas itself is pushing back — struggling against being compressed, if you will — with an equal power. Suppose 63 A HISTORY OF SCIENCE the bulk of the gas is such that at this pressure it occupies a cubical space six inches on a side — something like the bulk of a child's toy balloon, let us say. Then the total outward pressure which that tiny bulk of gas exerts, in its desperate molecular struggle, is little less than five thousand tons. It would support an enormous building without budging a hair's-breadth. If the building weighed less than five thousand tons it would be lifted by the gas ; if much less it would be thrown high into the air as the gas expanded. It gives one a new sense of the power of numbers to feel that infinitesimal atoms, merely by vibrating in unison, could accomplish such a result. But now suppose our portion of gas, instead of being placed under our hypothetical building, is plunged into a cold medium, which will permit its heat- vibrations to exhaust themselves without being correspondingly restored. Then, presently, the temperature is lowered below the critical point, and, presto! the mad struggle ceases, the atoms lie amicably together, and the gas has become a liquid. What a transformed thing it is now. Instead of pressing out with that enormous force, it has voluntarily contracted as the five thousand tons pressure could not make it do ; and it lies there now, limpid and harmless -seeming, in the receptacle, for all the world like so much water. And, indeed, the comparison with water is more than superficial, for in a cup of water also there are wonder- ful potentialities, as every steam-engine attests. But an enormous difference, not in principle but in prac- tical applications, exists in the fact that the potentiali- ties of the water cannot be utilized until relatively 64 LOW-TEMPERATURE RESEARCHES high temperatures are reached. Costly fuel must be burned and the heat applied to the water before it can avail to do its work. But suppose we were to place our portion of liquid air, limpid and water-like, in the cylinder of a locomotive, where the steam of water ordinarily enters. Then, though no fuel were burned — though the entire engine stood embedded in the snow of an arctic winter — it would be but a few moments before the liquid air would absorb even from this cold medium heat enough to bring it above its critical tem- perature ; and, its atoms now dancing apart once more and re-exerting that enormous pressure, the piston of the engine would be driven back and then the entire cylinder burst into fragments as the gas sought exit. In a word, then, a portion of liquid air has a store of potential energy which can be made kinetic merely by drawing upon the boundless and free supply of heat which is everywhere stored in the atmosphere we breathe and in every substance about us. The diffi- culty is, not to find fuel with which to vaporize it, as in case of water, but to keep the fuel from finding it whether or no. Were liquid air in sufficient quantities available, the fuel problem would cease to have any significance. But of course liquid air is not indefinitely available, and exactly here comes the difficulty with the calculations of many enthusiasts who hail liquefied gas as the motive power of the near future. For of course in liquefying the air power has been applied, for the moment wasted, and unless we can get out of the liquid more energy than we have applied to it, there is no economy of power in the transaction. Now the simplest study of the conditions, with the mechanical VOL. V. S 65 A HISTORY OF SCIENCE theory of matter in mind, makes it clear that this is precisely what one can never hope to accomplish. Action and reaction are equal and in opposite direc- tions at all stages of the manipulation, and hence, under the most ideal conditions, we must expect to waste as much work in condensing a gas (in actual practice more) as the condensed substance can do in expanding to the original volume. Those enthusiasts who have thought otherwise, and who have been on the point of perfecting an apparatus which will readily and cheaply produce liquid air after the first portion is produced, are really but following the old perpetual- motion-machine will-o'-the-wisp. It does not at all follow from this, however, that the energies of liquefied air may not be utilized with enor- mous advantage. It is not always the cheapest form of power-transformer that is the best for all purposes, as the use of the electrical storage battery shows. And so it is quite within the possibilities that a multitude of uses may be found for the employment of liquid air as a motive power, in which its condensed form, its transportability or other properties will give it prece- dence over steam or electricity. It has been suggested, for example, that liquefied gas would seem to afford the motive power par excellence for the flying-machine, once that elusive vehicle is well in harness, since one of the greatest problems here is to reduce the weight of the motor apparatus. In a less degree the same problem enters into the calculations of ships, particu- larly ships of war ; and with them also it may come to pass that a store of liquid air (or other gas) may come to take the place of a far heavier store of coal. It is 66 LOW-TEMPERATURE RESEARCHES even within the possibilities that the explosive powers of the same liquid may take the place of the great mag- azines of powder now carried on war-ships ; for, under certain conditions, the liquefied gas will expand with explosive suddenness and violence, an "explosion" being in any case only a very sudden expansion of a confined gas. The use of the compressed air in the dynamite guns, as demonstrated in the Cuban cam- paign, is a step in this direction. And, indeed, the use of compressed air in many commercial fields already competing with steam and electricity is a step towards the use of air still further compressed, and cooled, meantime, to a condition of liquidity. The enormous advantages of the air actually liquefied, and so for the moment quiescent, over the air merely compressed, and hence requiring a powerful retort to hold it, are patent at a glance. But, on the other hand, the diffi- culty of keeping it liquid is a disadvantage that is equally patent. How the balance will be struck be- tween these contending advantages and disadvantages it remains for the practical engineering inventors of the future — the near future, probably — to demonstrate. Meantime there is another line of application of the ideas which the low-temperature work has brought into prominence which has a peculiar interest in the pres- ent connection because of its singularly Rumfordian cast, so to speak. I mean the idea of the insulation of cooled or heated objects in the ordinary affairs of life, as, for example, in cooking. The subject was a veri- table hobby with the founder of the Royal Institution all his life. He studied the heat - transmitting and heat-reflecting properties of various substances, in- 67 A HISTORY OF SCIENCE eluding such directly practical applications as rough surfaces versus smooth surfaces for stoves, the best color for clothing in summer and in winter, and the like. He promulgated his ideas far and wide, and dem- onstrated all over Europe the extreme wastefulness of current methods of using fuel. To a certain extent his ideas were adopted everywhere, yet on the whole the public proved singularly apathetic; and, especially in America, an astounding wastefulness in the use of fuel is the general custom now as it was a century ago. A French cook will prepare an entire dinner with a splinter of wood, a handful of charcoal, and a half- shovelful of coke, while the same fuel would barely suffice to kindle the fire in an American cook - stove. Even more wonderful is the German stove, with its great bulk of brick and mortar and its glazed tile sur- face, in which, by keeping the heat in the room instead of sending it up the chimney, a few bits of compressed coal do the work of a hodful. It is one merit of the low-temperature work, I repeat, to have called attention to the possibilities of heat in- sulation in application to " the useful purposes of life." If Professor Dewar's vacuum vessel can reduce the heat- transmitting capacity of a vessel by almost ninety-seven percent., why should not the same principle, in modi- fied form, be applied to various household appliances — to ice-boxes, for example, and to cooking utensils, even to ovens and cook-stoves? Even in the construction of the walls of houses the principles of heat insulation might advantageously be given far more attention than is usual at present ; and no doubt will be so soon as the European sense of economy shall be brought home to 68 LOW-TEMPERATURE RESEARCHES the people of the land of progress and inventions. The principles to be applied are already clearly to hand, thanks largely to the technical workers with low temperatures. It remains now for the practical in- ventors to make the "application to the useful pur- poses of life." The technical scientists, ignoring the example which Rumford and a few others have set, have usually no concern with such uninteresting con- cerns. For the technical scientists themselves, however, the low-temperature field is still full of inviting possibilities of a strictly technical kind. The last gas has indeed been liquefied, but that by no means implies the last stage of discovery. With the successive conquest of this gas and of that, lower and lower levels of tempera- ture have been reached, but the final goal still lies well beyond. This is the north pole of the physicist's world, the absolute zero of temperature — the point at which the heat-vibrations of matter are supposed to be ab- solutely stilled. Theoretically this point lies 2 7 20 be- low the Centigrade zero. With the liquefaction of hydrogen, a temperature of about — 2530 or — 2540 Centigrade has been reached. So the gap seems not so very great. But like the gap that separated Nansen from the geographical pole, it is a very hard road to travel. How to compass it will be the study of all the low-temperature explorers in the immediate future. Who will first reach it, and when, and how, are ques- tions for the future to decide. And when the goal is reached, what will be revealed ? That is a question as full of fascination for the physicist as the north-pole mystery has ever been for the gen- 69 A HISTORY OF SCIENCE erality of mankind. In the one case as in the other, any attempt to answer it to-day must partake largely of the nature of a guess, yet certain forecasts may be made with reasonable probability. Thus it can hardly be doubted that at the absolute zero all matter will have the form which we term solid ; and, moreover, a degree of solidity, of tenacity and compactness greater than ever otherwise attained. All chemical activity will presumably have ceased, and any existing com- pound will retain unaltered its chemical composition so long as absolute zero pertains; though in many, if not in all cases, the tangible properties of the sub- stance— its color, for example, and perhaps its crys- talline texture — will be so altered as to be no longer recognizable by ordinary standards, any more than one would ordinarily recognize a mass of snowlike crystals as air. It has, indeed, been suggested that at absolute zero all matter may take the form of an impalpable powder, the forces of cohesion being destroyed with the vibra- tions of heat. But experiment seems to give no war- rant to this forecast, since cohesion seems to increase exactly in proportion to the decrease of the heat- vibrations. The solidity of the meteorites which come to the earth out of the depths of space, where some- thing approaching the zero temperature is supposed to prevail, also contradicts this assumption. Still less warrant is there for a visionary forecast at one time entertained that at absolute zero matter will utterly disappear. This idea was suggested by the observa- tion, which first gave a clew to the existence of the ab- solute zero, that a gas at ordinary temperatures and 70 LOW-TEMPERATURE RESEARCHES at uniform pressure contracts by 1-2 7 2d of its own bulk with each successive degree of lowered tempera- ture. If this law held true for all temperatures, the gas would apparently contract to nothingness when the last degree of temperature was reached, or at least to a bulk so insignificant that it would be inappreciable by standards of sense. But it was soon found by the low-temperature experimenters that the law does not hold exactly at extreme temperatures, nor does it ap- ply at all to the rate of contraction which the sub- stance shows after it assumes the liquid and solid con- ditions. So the conception of the disappearance of matter at zero falls quite to the ground. But one cannot answer with so much confidence the suggestion that at zero matter may take on properties hitherto quite unknown, and making it, perhaps, differ as much from the conventional solid as the solid differs from the liquid, or this from the gas. The form of vi- bration which produces the phenomena of temperature has, clearly, a determining share in the disposal of mo- lecular relations which records itself to our senses as a condition of gaseousness, liquidity, or solidity ; hence it would be rash to predict just what inter-molecular re- lations may not become possible when the heat- vibra- tion is altogether in abeyance. That certain other forms of activity may be able to assert themselves in unwonted measure seems clearly forecast in the phe- nomena of increased magnetism, and of phosphores- cence at low temperatures above outlined. Whether still more novel phenomena may put in an appearance at the absolute zero, and if so, what may be their nat- ure, are questions that must await the verdict of ex- 7i A HISTORY OF SCIENCE periment. But the possibility that this may occur, together with the utter novelty of the entire subject, gives the low-temperature work precedence over al- most every other subject now before the world for investigation (possible exceptions being radio-activity and bacteriology). The quest of the geographical pole is but a child's pursuit compared with the quest of the absolute zero. In vital interest the one falls as far short of the other as the cold of frozen water falls short of the cold of frozen air. Where, when, and by whom the absolute zero will be first reached are questions that may be answered from the most unexpected quarter. But it is interest- ing to know that great preparations are being made to- day in the laboratories of the Royal Institution for a further attack upon the problem. Already the re- search equipment there is the best in the world in this field, and recently this has been completely over- hauled and still further perfected. It would not be strange, then, in view of past triumphs, if the final goal of the low-temperature workers should be first reached in the same laboratory where the outer territories of the unknown land were first penetrated three-quarters of a century ago. There would seem to be a poetic fitness in the trend of events should it so transpire. But of course poetic fitness does not always rule in the land of science. IV SOME PHYSICAL LABORATORIES AND PHYS- ICAL PROBLEMS SIR NORMAN LOCKYER AND SOLAR CHEMISTRY SIR NORMAN LOCKYER is professor of astronom- ical physics and director of the solar observatory at the Royal College of Science in South Kensington. Here it is that his chief work has been done for some thirty years past. The foundation - stone of that work is spectroscopic study of the sun and stars. In this study Professor Lockyer was a pioneer, and he has for years been recognized as the leader. But he is no mere observer ; he is a generalizer as well ; and he long since evolved revolutionary ideas as to the origin of the sidereal and solar systems. For a man whose chief occupation is the study of the sun and stars, smoky, foggy, cloudy London may seem a strange location. I asked Professor Lockyer about this, and his reply was most characteristic. "The fact is," he said, "the weather here is too fine from one point of view: my working staff is so small, and the number of working nights so large, that most of the time there is no one about to do anything during the day. Then, another thing, here at South Ken- sington I am in touch with my colleagues in the other departments — physics, chemistry, and so forth — and 73 A HISTORY OF SCIENCE can at once draw upon their special knowledge for aid on any obscure point in their lines that may crop up. If we were out in the country this would not be so. You see, then, that it is a choice between weather and brains. I prefer the brains." Professor Lockyer went on to state, however, that he is by no means altogether dependent upon the ob- servations made at South Kensington. For certain purposes the Royal Observatory at Greenwich is in requisition, and there are three observatories at differ- ent places in India at which photographs of the sun- spots and solar spectra are taken regularly. From these combined sources photographs of the sun are forthcoming practically every day of the year; to be accurate, on three hundred and sixty days out of the three hundred and sixty-five. It was far otherwise when Professor Lockyer first began his studies of the sun, as observations were then made and recorded on only about one-third of the days in each year. Exteriorly the observatory at South Kensington is not at all such a place as one might expect to find. It is, in Professor Lockyer's own words, " little more than a collection of sheds," but within these alleged sheds may be found an excellent equipment of telescopes, both refracting and reflecting, and of all other things requisite to the peculiar study which forms the subject of special research here. I have had occasion again and again to call atten- tion to this relatively meagre equipment of the Euro- pean institutions, but in no case, perhaps, is the con- trast more striking between the exterior appearance of a famous scientific institution and the work that is 74 SIR NORMAN LOCKYER SOME PHYSICAL PROBLEMS being accomplished within it than is shown in the case of the South Kensington observatory. It should be added that this remark does not apply to the chief building of the Royal College of Science itself. The theories for which Professor Lockyer has so long been famous are well known to every one who takes much interest in the progress of scientific ideas. They are notably the theory that there is a direct causal association between the prevalence of sun-spots and terrestrial weather; the theory of the meteoritic origin of all members of the sidereal family; and the disso- ciation theory of the elements, according to which our so-called elements are really compounds, capable of being dissociated into simpler forms when subjected to extreme temperatures, such as pertain in many stars. As I have said, these theories are by no means new. Professor Lockyer has made them familiar by expounding them for a full quarter of a century or more. But if not new, these theories are much too im- portant to have been accepted at once without a pro- test from the scientific world. In point of fact, each of them has been met with most ardent opposition, and it would, perhaps, not be too much to say that not one of them is, as yet, fully established. It is of the high- est interest to note, however, that the multitudinous observations bearing upon each of these topics during the past decade have tended, in Professor Lockyer's opinion, strongly to corroborate each one of these opinions. Two or three years ago Sir Norman Lockyer, in asso- ciation with his son, communicated to the Royal So- ciety a paper in which the data recently obtained as 75 A HISTORY OF SCIENCE to the relation between sun-spots and the weather in India — the field of observations having been confined to that territory — are fully elaborated. A remarkable feature of the recent work in that connection has been the proof, or seeming proof, that the temperature of the sun fluctuates from year to year. At times when the sun-spots are numerous and vigorous in their ac- tion, the spectrum of the elements in these spots be- comes changed. During the times of minimum sun- spot activity the spectrum shows, for example, the presence of large quantities of iron in these spots — of course in a state of vapor. But in times of activity this iron disappears, and the lines which previously vouched for it are replaced by other lines spoken of as the enhanced lines of iron — that is to say, the lines which are believed to represent the unknown substance or substances into which the iron has been decomposed ; and what is true of iron is true of various other elements that are detected in the sun-spots. The explanation of this phenomena, if Professor Lockyer reads the signs aright, is that during times of minimum sun-spot ac- tivity the temperature of the sun-spots is relatively cool, and that in times of activity the temperature be- comes greatly increased. One must come, therefore, to speaking of hot spots and cool spots on the sun ; al- though the cool spots, it will be understood, would hardly be considered cool in the terrestrial sense, since their temperature is sufficient to vaporize iron. Now the point of the recent observations is that the fluctuations in the sun's heat, due to the periodic in- crease and subsidence of sun-spot disturbances — such fluctuations having been long recognized as having 76 SOME PHYSICAL PROBLEMS regular cyclic intervals of about eleven years — are instrumental in effecting changes in the terrestrial weather. According to the paper just mentioned, it would appear to be demonstrated that the periods of decreased rainfall in India have a direct and relatively unvarying relationship to the prevalence of the sun- spots, and that, therefore, it has now become possible, within reasonable limits, to predict some years in ad- vance the times of famine in India. So important a conclusion as this is certainly not to be passed over lightly, and all the world, scientific and unscientific alike, will certainly watch with acute interest for the verification of this seemingly startling practical result of so occult a science as solar spectroscopy. The theory of the decomposition of the elements is closely bound up with the meteoritic theory. In a word, it may be said of each that Professor Lockyer is firmly convinced that all the evidence that has accu- mulated in recent years is so strongly in favor as to bring these theories almost to a demonstration. The essence of the meteoritic theory, it will be recalled, is that all stars have their origin in nebulas which consist essentially of clouds of relatively small meteorites. It will be recalled further that Professor Lockyer long ago pointed out that stars pass through a regular series of changes as to temperature, with correspond- ing changes of structure, becoming for a time hotter and hotter until a maximum is reached, and then pass- ing through gradual stages of cooling until their light dies out altogether. Very recently Professor Lockyer has been enabled, through utilization of the multiform records accumulated during years of study, to define 77 A HISTORY OF SCIENCE the various typical stages of the sidereal evolution; and not merely to define them but to illustrate them practically by citing stars which belong to each of these stages, and to give them yet clearer definition by naming the various elements which the spectro- scope reveals as present in each. His studies have shown that the elements do not al- ways give the same spectrum under all conditions; a result quite at variance with the earlier ideas on the subject. Even in the terrestrial laboratory it is possi- ble to subject various metals, including iron, to tem- peratures attained with the electric spark at which the spectrum becomes different from that, for example, which was attained with the lower temperature of the electric arc. Through these studies so-called series- spectra have been attained for various elements, and a comparison of these series-spectra with the spectra of various stars has led to the conclusion that many of the unknown lines previously traced in the spectra of such stars are due to the decomposition products of familiar elements ; all of which, of course, is directly in line of proof of the dissociation hypothesis. Another important result of Professor Lockyer's very recent studies has come about through observa- tion of the sun in eclipse. A very interesting point at issue all along has been the question as to what layers of the sun's atmosphere are efficient in produc- ing the so-called reverse lines of the spectrum. It is now shown that the effect is not produced, as formerly supposed, by the layers of the atmosphere lying just above the region which Professor Lockyer long ago named the chromosphere, but by the gases of higher 78 SOME PHYSICAL PROBLEMS regions. Reasoning from analogy, it may be supposed that a corresponding layer of the atmosphere of other stars is the one which gives us the reverse spectrum of those stars. The exact composition of this layer of the sidereal atmosphere must, of course, vary with the temperature of the different stars, but in no case can we expect to receive from the spectroscope a full record of all the substances that may be present in other layers of the atmosphere or in the body of the star it- self. Thus, for example, the ordinary Freuenhofer spectrum of the sun shows us no trace of the element helium, though through other observations at the time of eclipse Professor Lockyer had discovered that element there, as we have seen, some thirty years be- fore anything was known of it on the earth. In a recent eclipse photographs were taken of the spectra of the lower part of the sun's atmosphere by itself, and it was found that the spectrum of this re- stricted area taken by itself gave the lines which specialize the spectra of so different a star as Procyon. "I recognize in the result," says Professor Lockyer, "a veritable Rosetta Stone which will enable us to read the celestial hieroglyphics presented to us in stellar spectra, and help us to study the spectra and to get at results much more distinctly and certainly than ever before." But the most striking confirmation which the me- teoritic hypothesis has received has come to hand through study of the spectrum of the new star which appeared in the constellation Perseus in February, 1 90 1, and which was so widely heralded everywhere in the public press. This star was discovered on the 79 A HISTORY OF SCIENCE morning of February 220! by star-gazers in Scotland, and in America almost simultaneously. It had cer- tainly not been visible a few hours before, and it had blazed up suddenly to a greater brilliancy than that of a first -magnitude star. At first it was bluish -white in color, indicating an extremely high temperature, but it rapidly subsided in brilliancy and assum d a red color as it cooled, passing thus, in the course of a few days, through stages for which ordinary stars require periods of many millions of years. The most interesting feature of the spectrum of this new star was the fact that it showed both light and dark lines for the same substances, the two lying some- what apart. This means, being interpreted, that some portions of a given substance are giving out light, thus producing the bright lines of the spectrum, and that other portions of the same substance are stopping certain rays of transmitted light, thus pro- ducing the dark lines. The space between the bright and dark lines, being measured, indicated that there was a differential motion between the two portions of substance thus recorded of something like seven hun- dred miles a second. This means, according to theory — and it seems hardly possible to explain it otherwise — that two sidereal masses, one at least of which was moving at an enormous rate of speed, had collided, such collision, of course, being the cause of the incan- descence that made the mass suddenly visible from the earth as a new star. New stars are by no means e very-day affairs, there having been but thirty-two of them recorded in the world's history, and of these only two have exceeded 80 SOME PHYSICAL PROBLEMS the present one in brilliancy. As a mere spectacle, therefore, this new star was of great interest ; but a far greater importance attaches to it through the fact that it conforms so admirably to the course that meteoritic hypothesis would predict for it. "That is what con- founds my opponents," said Professor Lockyer, in talking to me about the new star. " Most of those who oppose my theory have not taken the trouble to make observations for themselves, but have contented them- selves with falling back apparently on the postulate that because a theory is new it must be wrong. Then, outside the scientific world, comparatively few people appreciate the extreme parsimony of nature. They expect, therefore, that when such a phenomenon as the appearance of a new star occurs, the new-comer will establish new rules for itself and bring chaos into the scientific world. But in point of fact nature never does things in two ways if she can possibly do them in one, and the most striking thing about the new stars is that all the phenomena they present conform so admirably to the laws built up through observation of the old familiar stars. As to our particular theories, we here at South Kensington" — it will be understood that this use of the editorial "we" is merely a modest subterfuge on the part of Professor Lockyer — "have no regard for them at all simply as ours. Like all scientists worthy the name, we seek only the truth, and should new facts come along that seem to antago- nize our theory we should welcome them as eagerly as we welcome all new facts of whatever bearing. But the truth is that no such new facts have appeared in all these years, but that, on the contrary, the me- VOL. V. — 6 8 I A HISTORY OF SCIENCE teoritic hypothesis has received ever -increasing sup- port from most unexpected sources, from none more brilliantly or more convincingly than from this new star in Perseus." And I suspect that as much as this at least — if not indeed a good deal more — will be freely admitted by every candid investigator of Sir Norman Lockyer's theory. SIR WILLIAM RAMSAY AND THE NEW GASES The seat of Sir William Ramsay's labors is the University College, London. The college building it- self, which is located on Gower Street, is, like the British Museum, reminiscent or rather frankly du- plicatory in its columned architecture of the classical. Interiorly it is like so many other European institutions in its relative simplicity of equipment. One finds, for example, Professor Ramsay and Dr. Travers generating the hydrogen for their wonderful experiments in an old beer-cask. Professor Ramsay himself is a tall, rather spare man, just entering the gray stage of life, with the earnest visage of the scholar, the keen, pierc- ing eye of the investigator — yet not without a twinkle that justifies the lineage of the "canny Scot." He is approachable, affable, genial, full of enthusiasm for his work, yet not taking it with such undue serious- ness as to rob him of human interest — in a word, the type of a man of science as one would picture him in imagination, and would hope, with confident expecta- tion, to find him in reality. I have said that the equipment of the college is somewhat primitive, but this must not be taken too comprehensively. Such instances as that of the beer- 82 SOME PHYSICAL PROBLEMS cask show, to be sure, an adaptation of means to ends on economical lines ; yet, on the other hand, it should not be forgotten that the beer-cask serves its purpose admirably; and, in a word, it may be said that Pro- fessor Ramsay's laboratory contains everything that is needed to equip it fully for the special work to which it has been dedicated for some years past. In general, it looks like any other laboratory — glass tubes, Bunsen burners, retorts and jars being in more or less mean- ingless tangles; but there are two or three bits of ap- paratus pretty sure to attract the eye of the casual visitor which deserve special mention. One of these is a long, wooden, troughlike box which extends across the room near the ceiling and is accessible by means of steps and a platform at one end. Through this box- like tube the chief expert in spectroscopy (Dr. Bay- ley) spies on the spectrum of the gas, and learns some of its innermost secrets. But an even more mystify- ing apparatus is an elaborate array of long glass tubes, some of them carried to the height of several feet, interspersed with cups of mercury and with ther- mometers of various sizes and shapes. The technical scientist would not make much of this description, but neither would an untechnical observer make much of the apparatus; yet to Dr. Travers, its inventor, it is capable of revealing such extraordinary things as the temperature of liquid hydrogen — a temperature far below that at which the contents of even an alcoholic thermometer are solidified ; at which, indeed, the prime constituents of the air suffer a like fate. The respon- sible substance which plays the part of the familiar mercury, or alcohol, in Dr. Travers's marvellous ther- 83 A HISTORY OF SCIENCE mometer is hydrogen gas. The principle by which it is utilized does not differ, in its rough essentials, from that of ordinary thermometers, but the details of its construction are much too intricate to be elaborated here. But if you would see the most wonderful things in this laboratory — or rather, to be quite accurate, I should say, if you would stand in the presence of the most wonderful things — you must go with Professor Ram- say to his own private laboratory, and be introduced to some little test-tubes that stand inverted in cups of mercury decorating a shelf at one end. You would never notice these tubes of your own accord were you to browse ever so long about the room. Even when your attention is called to them you still see nothing remarkable. These are ordinary test-tubes inverted over ordinary mercury. They contain something, since the mercury does not rise in them completely, but if that something be other than ordinary air there is nothing about its appearance, or rather lack of ap- pearance, to demonstrate it. But your interest will hardly fail to be arrested when Professor Ramsay, in- dicating one and another of these little tubes, says: " Here you see, or fail to see, all the krypton that has ever been in isolated existence in the world, and here all the neon, and here, again, all the zenon." You will understand, of course, that krypton, neon, and zenon are the new gases of the atmosphere whose existence no one suspected until Professor Ramsay ferreted them out a few years ago and isolated them. In one sense there should be nothing mysterious about substances that every air-breathing creature on the 84 SKETCH OF SIR WILLIAM RAMSAY SOME PHYSICAL PROBLEMS globe has been imbibing pretty constantly ever since lungs came into fashion. But in another view the universal presence of these gases in the air makes it seem all the more wonderful that they could so long have evaded detection, considering that chemistry has been a precise science for more than a century. Dur- ing that time thousands of chemists have made millions of experiments in the very midst of these atmospheric gases, yet not one of the experimenters, until recently, suspected their existence. This proves that these gases are no ordinary substances — common though they be. Personally I have examined many scientific exhibits in many lands, but nowhere have I seen any- thing that filled my imagination with so many scien- tific visions as these little harmless test-tubes at the back of Professor Ramsay's desk. Perhaps I shall at- tempt to visualize some of these imaginings before finishing this paper, but for the moment I wish to speak of the modus operandi of the discovery of these additions to the list of elements. The discovery of argon came about in a rather singu- lar way. Lord Rayleigh, of the Royal Institution, had noticed in experiments with nitrogen that when sam- ples of this element were obtained from chemicals, such samples were uniformly about one per cent, lighter in weight than similar quantities of nitrogen obtained from the atmosphere. This discrepancy led him to believe that the atmospheric nitrogen must contain some impurity. Curiously enough, the experiments of Cavendish, the discoverer of nitrogen — • experiments made more than a century ago — had seemed to show quite con- 85 A HISTORY OF SCIENCE clusively that some gaseous substance different from nitrogen was to be found mixed with the samples of this gas as he obtained it from the atmosphere. This conclusion of Cavendish, put forward indeed but ten- tatively, had been quite ignored by his successors. Now, however, it transpired, by experiments made jointly by Lord Rayleigh and Professor Ramsay, that the conclusion was quite justified, it being shown pres- ently that there actually exists in every portion of ni- trogen, as extracted from the atmosphere, a certain quantity of another gas, hitherto unknown, and which now received the name of argon. It will be recalled with what astonishment the scientific and the un- scientific world alike received the announcement made to the Royal Society in 1895 of the discovery of argon, and the proof that this hitherto unsuspected constitu- ent of the atmosphere really constitutes about one per cent, of the bulk of atmospheric nitrogen, as previously estimated. The discovery here on the earth of a substance which Professor Lockyer had detected as early as 1868 in the sun, and which he had provisionally named helium, excited almost equal interest ; but this element was found in certain minerals, and not as a constituent of the atmosphere. Having discovered so interesting a substance as argon, Professor Ramsay and his assistants naturally devoted much time and attention to elucidating the peculiarities of the new substance. In the course of these studies it became evident to them that the pres- ence of argon alone did not fully account for all the phenomena they observed in handling liquefied air, and 86 SOME PHYSICAL PROBLEMS in 1898 Professor Ramsay was again able to electrify his audience at the Royal Society by the announce- ment of the discovery, in pretty rapid succession, of three other elementary substances as constituents of the atmosphere, these three being the ones just re- ferred to — krypton, neon, and zenon. It is a really thrilling experience, standing in the presence of the only portions of these new substances that have been isolated, to hear Professor Ramsay and Dr. Travers, his chief assistant, tell the story of the discovery — how they worked more and more eagerly as they found themselves, so to say, on a "warmer scent," following out this clew and that until the right one at last brought the chase to a successful issue. " It was on a Sabbath morning in June, if I re- member rightly, when we finally ran zenon down," says Dr. Travers, with a half smile; and Professor Ramsay, his eyes twinkling at the recollection of this very unorthodox procedure, nods assent. "And have you got them all now?" I queried, after hearing the story. "Yes; we think so," replied Professor Ram- say. "And I am rather glad of it," he adds, with a half sigh, "for it was wearisome even though fascinat- ing work." Just how wearisome it must have been only a professional scientific investigator can fully comprehend ; but the fascination of it all may be com- prehended in some measure by every one who has ever attempted creative work of whatever grade or in what- ever field. I have just said that the little test-tubes contain the only bit of each of the substances named that has ever been isolated. This statement might lead the un- 87 A HISTORY OF SCIENCE technical reader to suppose that these substances, once isolated, have been carefully stored away and jealously guarded, each in its imprisoning test-tubes. Jealously guarded they have been, to be sure, but there has not been, by any means, the solitary confinement that the words might seem to imply. On the contrary, each little whiff of gas has been subjected to a variety of experiments — made to pass through torturing-tubes under varying conditions of temperature, and brought purposely in contact with various other substances, that its physical and chemical properties might be tested. But in each case the experiment ended with the return of the substance, as pure as before, to its proper tube. The precise results of all these experi- ments have been communicated to the Royal Society by Professor Ramsay. Most of these results are of a technical character, hardly appealing to the average reader. There is one very salient point, however, in regard to which all the new substances, including argon and helium, agree; and it is that each of them seems to be, so far as present experiments go, absolutely devoid of that fundamental chemical property, the power to combine with other elements. All of them are believed to be monatomic — that is to say, each of their molecules is composed of a single atom. This, however, is not an absolutely novel feature as com- pared with other terrestrial elements, for the same thing is true, for example, of such a familiar substance as mercury. But the incapacity to enter into chemical combinations seems very paradoxical; indeed it is al- most like saying that these are chemical elements which lack the most fundamental of chemical properties. 88 SOME PHYSICAL PROBLEMS It is this lack of combining power, of course, that explains the non-discovery of these elements during all these years, for the usual way of testing an element is to bring it in contact with other substances under con- ditions that permit its atoms to combine with other atoms to the formation of new substances. But in the case of new elements such experiments as this have not proved possible under any conditions as yet at- tained, and reliance must be had upon other physical tests — such as variation of the bulk of the gas under pressure, and under varying temperatures, and a study of the critical temperatures and pressures under which each gas becomes a liquid. The chief reliance, however, is the spectroscope — the instrument which revealed the presence of helium in the sun and the stars more than a quarter of a century before Professor Ramsay ferreted it out as a terrestrial element. Each whiff of colorless gas in its test-tube interferes with the light passing through it in such a way that when viewed through a prism it gives a spectrum of alto- gether unique lines, which stamp it as krypton, neon, or zenon as definitely as certain familiar and more tangible properties stamp the liquid which imprisons it as mercury. Queries Suggested by the New Gases Suppose that a few years ago you had asked some chemist, ' ' What are the constituents of the atmos- phere?" He would have responded, with entire confi- dence, " Oxygen and nitrogen chiefly, with a certain amount of water- vapor and of carbonic-acid gas and a trace of ammonia." If questioned as to the chief prop- 89 A HISTORY OF SCIENCE erties of these constituents, he would have replied, with equal facility, that these are among the most important elements ; that oxygen might almost be said to be the life - giving principle, inasmuch as no air - breathing creature could get along without it for many moments together; and that nitrogen is equally important to the organism, though in a different way, inasmuch as it is not taken up through the lungs. As to the water- vapor, that, of course, is a compound of oxygen and hydrogen, and no one need be told of its importance, as every one knows that water makes up the chief bulk of protoplasm; carbonic-acid gas is also a compound of oxygen, the other element this time being carbon, and it plays a quite different role in the economy of the living organism, inasmuch as it is produced by the breaking down of tissues, and must be constantly ex- haled from the lungs to prevent the poisoning of the organism by its accumulation ; while ammonia, which exists only in infinitesimal quantities in the air, is a compound of nitrogen and hydrogen, introducing, therefore, no new element. If one studies somewhat attentively the relation which these elements composing the atmosphere bear to the living organism he cannot fail to be struck with it; and it would seem a safe inductive reasoning from the stand -point of the evolutionist that the constitu- ents of the atmosphere have come to be all-essential to the living organism, precisely because all their com- ponents are universally present. But, on the other hand, if we consider the matter in the light of these researches regarding the new gases, it becomes clear that perhaps the last word has not been said on this 90 SOME PHYSICAL PROBLEMS subject ; for here are four or five other elementary sub- stances which, if far less abundant than oxygen and nitrogen, are no less widely distributed and universally present in the atmosphere, yet no one of which ap- parently takes any chemical share whatever in min- istering to the needs of the living organism. This surely is an enigma. Taking another point of view, let us try to imagine the real status of these new gases of the air. We think of argon as connected with nitrogen because in isolation experiments it remains after the oxygen has been exhausted, but in point of fact there is no such connection between argon and nitrogen in nature. The argon atom is just as closely in contact with the oxygen in the atmosphere as with the nitrogen; it simply repels each indiscriminately. But consider a little further; the argon atom not only repels all ad- vance on the part of oxygen and nitrogen, but it equally holds itself aloof from its own particular kin- dred atoms. The oxygen or nitrogen atom never rests until it has sought out a fellow, but the argon atom declines all fellowship. "When the chemist has played his tricks upon it, it finds itself crowded together with other atoms of the same kind ; but lift up the little test- tube and these scurry off from one another in every direction, each losing its fellows forever as quickly as possible. As one ponders this one is almost disposed to sug- gest that the atom of argon (or of krypton, helium, neon, or zenon, for the same thing applies to each and all of these) seems the most perfect thing known to us in the world, for it needs no companionship, it is self- 9i A HISTORY OF SCIENCE sufficing. There is something sublime about this mag- nificient isolation, this splendid self-reliance, this un- daunted and undauntable self-sufficiency — these are traits which the world is wont to ascribe to beings more than mortal. But let us pause lest we push too far into the old, discredited territory of metaphysics. PROFESSOR J. J. THOMPSON AND THE NATURE OF ELEC- TRICITY Many fascinating questions suggest themselves in connection with these strange, new elements — new, of course, only in the sense of human knowledge — which all these centuries have been about us, yet which have managed until now to keep themselves as invisible and as intangible as spirits. Have these celibate atoms remained thus always isolated, taking no part in world- building ? Are they destined throughout the sweep of time to keep up this celibate existence ? And why do these elements alone refuse all fellowship, while the atoms of all the other seventy-odd known elements seek out mates under proper conditions with unvary- ing avidity? It is perhaps not possible fully to answer these ques- tions as yet, but recent studies in somewhat divergent fields give us suggestive clews to some of them. I refer in particular to the studies in reference to the passage of electricity through liquids and gases and to the observations on radio-activity. The most con- spicuous worker in the field of electricity is Professor J. J. Thompson, who for many years has had charge of the Cavendish laboratory at Cambridge. In briefly reviewing certain phases of his work we shall find our- 92 SOME PHYSICAL PROBLEMS selves brought into contact with some of the same problems raised by workers in the other fields of phys- ics, and shall secure some very interesting bits of testi- mony as to the solution of questions already outlined. The line of observation which has led to the most striking results has to do, as already suggested, with the conduction of electricity through liquids and gases. It has long been known that many liquids conduct elec- tricity with relative facility. More recently it has been observed that a charge of electricity carried by any liquid bears a curious relation to the atomic com- position of that liquid. If the atom in question is one of the sort that can combine with only a single other atom (that is to say, a monovalent atom), each atom conveys a unit charge, which is spoken of as an ion of electricity. But if a divalent atom is in question the charge carried is double, and, similarly, a trivalent atom carries a triple charge. As there are no intermediate charges it is obvious that here a very close relation is suggested between electrical units and the atomic units of matter. This, however, is only a beginning. Far more in- teresting are the results obtained by the study of gases in their relation to the conduction of electricity. As is well known, gases under ordinary conditions are non- conductors. But there are various ways in which a gas may be changed so as to become a conductor; for example, by contact with incandescent metals or with flame, or by treating with ultra-violet light, with Rontgen rays, or with the rays of a radio-active sub- stance. Now the all-important question is as to just what change has taken place in the gas so treated to 93 A HISTORY OF SCIENCE make it a conductor of electricity. I cannot go into details here as to the studies that have been addressed to the answer of this question, but I will briefly epit- omize what, for our present purpose, are the important results. First and foremost of these is the fact that a gas thus rendered conductive contains particles that can be filtered out of it by passing the gas through wool or through water. These particles are the actual agents of conduction of electricity, since the gas when filtered ceases to be conductive. But there is another way in which the particles may be removed — namely, by action of electricity itself. If the gas be caused to pass between two metal plates, one of them insulated and attached to an electrometer, a charge of positive electricity at high potential sent through the other plate will drive part of the particles against the in- sulated plate. This proves that the particles in ques- tion are positively electrified. The amount of the charge which they carry may be measured by the electrometer. The aggregate amount of the electrical charge car- ried by these minute particles in the gas being known, it is obvious that could we know the number of particles involved the simplest calculation would determine the charge of each particle. Professor Thompson devised a singularly ingenious method of determining this num- ber. The method was based on the fact discovered by C. T. R. Wilson that charged particles acted as nuclei round which small drops of water condense much as dust particles serve the same purpose. " In dust-free air," says Professor Thompson, "as Aitken showed, it is very difficult to get a fog when damp air is cooled, 94 SOME PHYSICAL PROBLEMS since there are no nuclei for the drops to condense round. If there are charged particles in dust-free air, however, the fog will be deposited round these by super- saturation far less than that required to produce any appreciable fog when no charged particles are present. "Thus, in sufficiently supersaturated damp air a cloud is deposited on these charged particles and they are thus rendered visible. This is the first step tow- ards counting them. The drops are, however, far too small and too numerous to be counted directly. We can, however, get their number indirectly as follows: suppose we have a number of these particles in dust- free air in a closed vessel, the air being saturated with water-vapor; suppose now that we produce a sudden expansion of the air in the vessel ; this will cool the air, it will be supersaturated with vapor, and drops will be deposited round the charged particles. Now if we know the amount of expansion produced we can calcu- late the cooling of the gas, and, therefore, the amount of water deposited. Thus we know the volume of water in the form of drops, so that if we know the volume of one drop we can deduce the number of drops. To find the size of a drop, we make use of the investiga- tions made by Sir George Stokes on the rate at which small spheres fall through the air. In consequence of the viscosity of the air small bodies fall exceedingly slowly, and the smaller they are the slower they fall." * Professor Thompson gives us the formula by which Stokes made his calculation. It is a relatively simple algebraic one, but need not be repeated here. For us it suffices that with the aid of this formula, by merely measuring the actual descent of the top of a vapor 95 A HISTORY OF SCIENCE cloud, Professor Thompson was able to find the volume of the drops and thence the number of particles. The number of particles being known, the charge of elec- tricity carried by each could be determined, as already suggested. Experiments were made with air, hydro- gen, and carbonic acid, and it was found that the par- ticles had the same charge in all of these gases. "A strong argument," says Professor Thompson, "in favor of the atomic character of electricity." When we add that the charge in question was found to be the same as the unit charge of an ion in a liquid, it will be seen that the experiment has other points of interest and suggestiveness. Even more interesting in some regards were the re- sults of computation as to the actual masses of the charged particles in question. Professor Thompson found that the carrier of a negative charge could have only about one-thousandth part of the mass of a hydrogen atom, which latter had been regarded as the smallest mass able to have an independent existence. Professor Thompson gave the name corpuscle to these units of negative electricity; they are now more generally termed electrons. "These corpuscles," he says, "are the same however the electrification may have risen or wherever they may be found. Negative electricity in a gas at a low pressure has thus a struct- ure analogous to that of a gas, the corpuscles taking the place of the molecules. The 'negative electric fluid,' to use the old notation, resembles the gaseous fluid with a corpuscular instead of a molecular struct- ure."2 Professor Thompson does not hesitate to de-' clare that we now "know more about 'electric fluid' 96 PROFESSOR W. C. ROENTGEN (Discoverer of the X-Ray.) SOME PHYSICAL PROBLEMS than we know about such fluids as air or water."3 The results of his studies lead him, he declares, "to a view of electrification which has a striking resemblance to that of Franklin's One Fluid Theory of Electricity. Instead of taking, as Franklin did, the electric fluid to be positive electricity," he says, " we take it to be neg- ative. The ' electric fluid ' of Franklin corresponds to an assemblage of corpuscles, negative electrification being a collection of these corpuscles. The transference of electrification from one place to another is effected by the motion of corpuscles from the place where there is a gain of positive electrification to the place where there is a gain of negative. A positively electri- fied body is one that has lost some of its corpuscles."4 According to this view, then, electricity is not a form of energy but a form of matter ; or, to be more precise, the electrical corpuscle is the fundamental structure out of which the atom of matter is built. This is a quite different view from that scarcely less recent one which regards electricity as the manifestation of ether strain, but it must be admitted that the corpuscular theory is supported by a marvellous array of experi- mental evidence, though it can perhaps hardly be claimed that this brings the theory to the plane of demonstration. But all roads of physical science of late years have seemed to lead towards the electron, as will be made further manifest when we consider the phenomena of radio-activity, to which we now turn. RADIO-ACTIVITY In 1896, something like a year after the discovery of the X-ray, Niewenglowski reported to the French VOL. V.— 7 0"7 A HISTORY OF SCIENCE Academy of Sciences that the well-known chemical compound calcium sulphide, when exposed to sunlight, gave off rays that penetrated black paper. He had made his examinations of this substance, since, like several others, it was known to exhibit strong fluores- cent or phosphorescent effects when exposed to the cathode rays, which are known to be closely connected with the X-rays. This discovery was followed very shortly by confirmatory experiments made by Bec- querel, Troost, and Arnold, and these were followed in turn by the discovery of Le Bon, made almost simulta- neously, that certain bodies when acted upon by sun- light give out radiations which act upon a photographic plate. These manifestations, however, are not the effect of radio-activity, but are probably the effects of short ultra-violet light waves, and are not produced spontaneously by the substances. The radiations, or emanations, of the radio-active substances, on the other hand, are given out spontaneously, pass through substances opaque to ordinary light, such as metal plates, act upon photographic plates, and discharge electrified bodies. The substances uranium, thorium,- polonium, radium, and their compounds are radio- active, radium being by far the most active. The first definite discovery of such a radio-active substance was made by M. Henri Becquerel, in 1896, while making some experiments upon the peculiar ore pitch-blende. Pitch-blende is a heavy, black, pitchy- looking mineral, found principally at present in some parts of Saxony and Bohemia on the Continent, in Cornwall in Great Britain, and in Colorado in America. It is by no means a recently discovered mineral, having 98 PROFESSOR HENRI BECQUEREL SOME PHYSICAL PROBLEMS been for some years the source of uranium and its com- pounds, which, on account of their brilliant colors, have been used in dye-stuffs and some kinds of stained glass. It is a complex mineral, containing at least eight or ten elements, which can be separated from it only with great difficulty and by complicated chemical processes. Becquerel's discovery was brought about by a lucky accident, although, like so many other apparently ac- cidental scientific discoveries, it was the outcome of a long series of scientific experiments all trending in the same direction. He had found that uranium, when exposed to the sun's rays, appeared to possess the property of absorbing them and of then acting upon a photographic plate. Since pitch-blende contained uranium, or uranium salts, he surmised that a some- what similar result might be obtained with the ore itself. He therefore prepared a photographic plate wrapped in black paper, intending to attempt making an impression on the plate of some metal body inter- posed between it and the pitch-blende. For this pur- pose he had selected a key ; but as the day proved to be cloudy he put the plate, with the key and pitch-blende resting upon it, in a dark drawer in his desk, and did not return to the experiment for several days. Upon doing so, however, he developed the plate without further exposure, when to his astonishment he found that the developed negative showed a distinct im- pression of the key. Clearly this was the manifestation of a property heretofore unknown in any natural sub- stance, and was strikingly similar to the action of the Roentgen rays. Further investigations by Lord Kel- 99 A HISTORY OF SCIENCE vin, Beattie, Smolan, and Rutherford confirmed the fact that, like the Roentgen rays, the uranium rays not only acted upon the photographic plate but discharged electrified bodies. And what seemed the more won- derful was the fact that these " Becquerel rays," as they were now called, emanated spontaneously from the pitch-blende. But although this action is analogous to the Roentgen rays, at least as regards its action upon the photographic plate and its influence on the electric field, its action is extremely feeble in comparison, the Roentgen rays producing effects in minutes, or even sec- onds, which require days of exposure to uranium rays. The discovery of the radio - active properties of uranium was followed about two years later by the dis- covery that thorium, and the minerals containing thorium, possess properties similar to those of uranium. This discovery was made independently and at about the same time by Schmidt and Madame Skaldowska Curie. But the importance of this discovery was soon completely overshadowed by the discovery of radium by Madame Curie, working with her husband, Pro- fessor Pierre Curie, at the Ecole Polytechnique in Paris. Madame Curie, stimulated by her own discov- eries and those of the other scientists just referred to, began a series of examinations upon various substances by numerous complicated methods to try and find a possible new element, as certain peculiarities of the substances found in the pitch-blende seemed to indicate the presence of some hitherto unknown body. The search proved a most difficult one on account of the peculiar nature of the object in question, but the tire- less enthusiasm of Madame Curie knew nothing of in- ioo SOME PHYSICAL PROBLEMS surmountable obstacles, and soon drew her husband into the search with her. Her first discovery was that of the substance polonium — -so named by Madame Curie after her native country, Poland. This proved to be another of the radio-active substances, differing from any other yet discovered, but still not the sought- for element. In a short time, however, the two Curies made the great discovery of the element radium — a substance which, according to their estimate, is some one million eight hundred thousand times more radio- active than uranium. The name for this element, radium, was proposed by Madame Curie, who had also suggested the term "radio-activity." The bearing of the discovery of radium and radio- activity upon theories of the atom and matter will be considered in a moment ; first the more tangible qual- ities of this wonderful substance may be briefly referred to. The fact that radio-active emanations traverse all forms of matter to greater or less depth— that is, pass through wood and iron with something the same ease that light passes through a window-glass — makes the subject one of greatest interest; and particularly so as the demonstration of this fact is so tangible. While the rays given out by radium cannot, of course, be seen by the unaided eye, the effects of these rays upon certain substances, which they cause to phos- phoresce, are strikingly shown. One of such sub- stances is the diamond, and a most striking illustra- tion of the power of radium in penetrating opaque sub- stances has been made by Mr. George F. Kunz, of the American Museum of Natural History. Mr. Kunz de- scribes this experiment as follows: IOI A HISTORY OF SCIENCE "Radium bromide of three hundred thousand activ- ity was placed in a sealed glass tube inside a rubber thermometer-holder, which was tightly screwed to prevent any emanation of any kind from passing through the joints. This was placed under a heavy silver tureen fully one-sixteenth of an inch in thickness ; upon this were placed four copper plates, such as are used for engraving; upon these a heavy graduated measuring-glass 10 cm. in diameter; this was filled with water to a depth of six inches. A diamond was suspended in the water and immediately phosphor- esced. Whenever the tube of radium was drawn away more than two or three feet the phosphor- esce ce ceased; whenever it was placed under the tureen the diamond immediately phosphoresced again. This experiment proves that the active power of the radium penetrated the following sub- stances : " Glass in the form of a tube, sealed at both ends ; the rubber thermometer-holder ; silver tureen ; four copper plates; a glass vase or measuring-glass one-quarter of an inch in thickness ; three inches of water. There is no previously known substance or agent, whether it be even light or electricity, that possesses such wonder- fully penetrative powers."5 The Nature of Emanations from Radio-active Bodies What, then, is the nature of these radiations ? Are they actually material particles hurled through the ether? Or are they like light — and possibly the Roentgen rays — simply undulations in the ether ? As yet this question is an open one, although several of 102 SOME PHYSICAL PROBLEMS the leading investigators have postulated tentative hypotheses which at least serve as a working basis until they are either confirmed or supplanted. On one point, however, there seems to be unanimity of opinion — there seems to be little question that there are at least three different kinds of rays produced by radio-active substances. According to Sir William Crookes, the first of these are free electrons, or matter in an ultra- gaseous state, as shown in the cathode stream. These particles are extremely minute. They carry a negative charge of electricity, and are identified with the electric corpuscles of Thompson. Rays of the second kind are comparable in size to the hydrogen atom, and are pos- itively electrified. These are easily checked by ma- terial obstructions, although they render the air a con- ductor and affect photographic plates. The third are very penetrating rays, which are not deflected by elec- tricity and which are seemingly identical with Roentgen rays. Professor E. Rutherford has named these rays beta (/3), alpha (a), and gamma (7) rays respectively. Of these the beta rays are deviated strongly by the magnetic field, the alpha much less so — very slightly, in fact— while the gamma rays are not affected at all. The action of these three different sets of rays upon certain substances is not the same, the beta and gamma rays acting strongly upon barium platinocyanide, but feebly on Sidot's blende, while the alpha rays act ex- actly the reverse of this, acting strongly on Sidot's blende. If a surface is coated with Sidot's blende and held near a piece of radium nitrate, the coated surface be- gins to glow. If now it is examined with a lens, brill- 103 A HISTORY OF SCIENCE iant sparks or points can be seen. As the radium is brought closer and closer these sparks increase in number, until, as Sir William Crookes says, we seem to be witnessing a bombardment of flying atoms hurled from the radium against the surface of the blende. A little instrument called a spinthariscope, devised by Dr. Crookes and on sale at the instrument and optical- goods shops, may be had for a trifling sum. It is fitted with a lens focused upon a bit of Sidot's blende and radium nitrate, and in a dark room shows these beau- tiful scintillations " like a shower of stars." A still less expensive but similar device is now made in the form of a microscopic slide, to be used with the ordinary lens. As we said a moment ago, radium appears to be an elementary substance, as shown by its spark-spectrum being different from that of any other known substance — the determinative test as fixed by the International Chemical Congress. A particle of radium free from impurities should, therefore, according to the conven- tional conception of an element, remain unchanged and unchangeable. If any such change did actually take place it would mean that the conception of the Dal- tonian atom as the ultimate particle of matter is definitively challenged from a new direction. This is precisely what has taken place. In July of 1903 Sir William Ramsay and Mr. Soddy, in making some ex- periments with radium, saw produced, apparently from radium emanations, another quite different and dis- tinct substance, the element helium. The report of such a revolutionary phenomenon was naturally made with scientific caution. Though the observation seem- 104 SOME PHYSICAL PROBLEMS ed to prove the actual transformation of one element into another, Professor Ramsay himself was by no means ready to declare the absolute certainty of this. Yet the presumption in favor of this interpretation of the observed phenomena is very strong; and so cautious a reasoner as Professor Rutherford has de- clared recently that "there can be no doubt that helium is derived from the emanations of radium in consequence of changes of some kind occurring in it."6 " In order to explain the presence of helium in radi- um on ordinary chemical lines," says Professor Ruther- ford, "it has been suggested that radium is not a true element, but a molecular compound of helium with some substance known or unknown. The helium compound gradually breaks down, giving rise to the helium observed. It is at once obvious that this postu- lated helium compound is of an entirely different char- acter to any other compound previously observed in chemistry. Weight for weight, it emits during its change an amount of energy at least one million times greater than any molecular compound known. In ad- dition, it must be supposed that the rate of breaking up of the helium compound is independent of great ranges of temperature — a result never before observed in any molecular change. The helium compound in its breaking up must give rise to the peculiar radia- tions and also pass through the successive radio-active change observed in radium. . . . On the other hand, radium, as far as it has been examined, has fulfilled every test required of an element. It has a well- marked and characteristic spectrum, and there is no 105 A HISTORY OF SCIENCE reason to suppose that it is not an element in the ordinarily accepted sense of the term."7 The Source of Energy of Radio -Activity In 1903 Messrs. Curie and Laborde8 made the re- markable announcement that a crystal of radium is persistently warmer than its surrounding medium; in other words, that it is perpetually giving out heat without apparently becoming cooler. At first blush this seemed to contradict the great physical law of the conservation of energy, but physicists were soon agreed that a less revolutionary explanation of the phe- nomenon is perfectly tenable. The giving off of heat is indeed only an additional evidence of the dissipa- tion of energy to which the radio-active atom is sub- jected. And no one now believes that radio-activity can persist indefinitely without actually exhausting the substance of the atom. Even so, the evidence of so great a capacity to give out energy is startling, and has given rise to various theories (all as yet tentative) in explanation. Thus J. Perrin9 has suggested that atoms may consist of parts not unlike a miniature planetary system, and in the atoms of the radio- elements the parts more distant from the centre are continually escaping from the central attraction, thus giving rise to the radiations. Monsieur and Madame Curie have suggested that the energy may be borrowed from the surrounding air in some way, the energy lost by the atom being instantly regained. Filipo Re,10 in 1903, advanced the theory that the various parts of the atom might at first have been free particles constituting an extremely tenuous nebula. 106 w Ml , LA pk>. 1 % ; I'/f J ; ' IS SIR WILLIAM CROOKES SOME PHYSICAL PROBLEMS These parts gradually becoming collected around con- densed centres have formed what we know as the atoms of elements, the atom thus becoming like an extinct sun of the solar system. From this point of view the radio-active atoms represent an interme- diate stage between nebulas and chemical atoms, the process of contraction giving rise to the heat emissions. Lord Kelvin has called attention to the fact that when two pieces of paper, one white and the other black, are placed in exactly similar glass vessels of water and exposed to light, the temperature of the vessel containing the black paper is raised slightly higher than the other. This suggests the idea that in a similar manner radium may keep its temperature higher than the surrounding air by the absorption of other radiations as yet unknown. Professor J. J. Thompson believes that the source of energy is in the atom] itself and not external to it. " The reason," he says, " which induces me to think that the source of the energy is in the atom of radium itself and not external to it is that the radio-activity of sub- stances is in all cases in which we have been able to localize it a transient property. No substance goes on being radio-active very long. It may be asked, how can this statement be reconciled with the fact that thorium and radium keep up their activity without any appreciable falling off with time. The answer to this is that, as Rutherford and Soddy have shown in the case of thorium, it is only an exceedingly small frac- tion of the mass which is at any one time radio-active, and that this radio-active portion loses its activity in a 107 A HISTORY OF SCIENCE few hours, and has to be replaced by a fresh supply from the non-radio-active thorium." " If Professor Thompson's view be correct, the amount of potential energy inherent in the atom must be enormous. Radio -Activity and the Structure of the Atom But whatever the source of the energy displayed by the radio-active substances, it is pretty generally agreed that the radio-activity of the radio-elements results in the disruption of their atoms. Since all sub- stances appear to be radio-active in a greater or less degree, it would seem that, unless there be a very gen- eral distribution of radio-active atoms throughout all substances, all atoms must be undergoing disruption. Since the distribution of radio-active matter throughout the earth is so great, however, it is as yet impossible to determine whether this may not account for the radio-activity of all substances. As we have just seen, recent evidence seems to point to the cause of the disruption of radio-active atoms as lying in the atoms themselves. This view is quite in accord with modern ideas of the instability of certain atoms. It has been suggested that some atoms may undergo a slower disintegration without necessarily throwing off part of their systems with great velocity. It is even possible that all matter may be under- going transformation, this transformation tending to simplify and render more stable the constituents of the earth. The radio-active bodies, however, are the only ones that have afforded an opportunity for studying this transformation. In these the rapidity of the 1 08 SOME PHYSICAL PROBLEMS change would be directly proportionate to their radio- activity. Radium, according to the recent estimate of the Curies, would be disintegrating over a million times more rapidly than uranium. Since the amount of transformation occurring in radium in a year amounts to from 1-2000 to i -10,000 of the total amount, the time required for the complete transformation of an atom of uranium would be somewhere between two billion and ten billion years — figures quite beyond the range of human comprehension. Various hypotheses have been postulated to account for the instability of the atom. Perhaps the most thinkable of these to persons not specially trained in dealing with abstruse subjects is that of Professor Thompson. It has the additional merit, also, of coming from one of the best-known investigators in this particular field. According to this hypothesis the atom may be considered as a mass of positively and negatively charged particles, all in rapid motion, their mutual forces holding them in equilibrium. In case of a very complex structure of this kind it is possi- ble to conceive of certain particles acquiring sufficient kinetic energy to be projected from the system. Or the constraining forces may be neutralized momen- tarily, so that the particle is thrown off at the same velocity that it had acquired at the instant it is re- leased. The primary cause of this disintegration of the atom may be due to electro-magnetic radiation causing loss of energy of the atomic system. Sir Oliver Lodge suggests that this instability of the atom may be the result of the atom's radiation of energy. " Lodge considered the simple case of a nega- 109 A HISTORY OF SCIENCE tively charged electron revolving round an atom of mass relatively large but having an equal positive charge and held in equilibrium by electrical forces. This system will radiate energy, and since the radiation of energy is equivalent to motion in a resisting medium, the particle tends to move towards the centre and its speed consequently increases. The rate of radiation of energy will increase rapidly with the speed of the electron. When the speed of the electron becomes very nearly equal to the velocity of light, according to Lodge, the system is unstable. It has been shown that the apparent mass of an electron increases very rapidly as the speed of light is approached, and is theoretically infinite at the speed of light. There will be at this stage a sudden increase of the mass of the revolving atom, and, on the supposition that this stage can be reached, a consequent disturbance of the balance of forces hold- ing the system together. Lodge considers it probable that under these conditions the parts of the system will break asunder and escape from the sphere of one another's influence. "It is probable," adds Rutherford, "that the pri- mary cause of the disintegration of the atom must be looked for in the 1 ss of energy of the atomic system due to electro-magnetic radiation." 12 Several methods have been devised for testing the amount of heat given off by radium and its com- pounds, and for determining its actual rise in tempera- ture above that of the surrounding atmosphere. One of these methods is to place some substance, such as barium chloride, in a calorimeter, noting at what point the mercury remains stationary. Radium is then in- IIO ERNEST RUTHERFORD, F.R.S. SOME PHYSICAL PROBLEMS troduced, whereupon the mercury in the tube gradually rises, falling again when the radium is removed. By careful tests it has been determined that a gram of radium emits about twenty-four hundred gram-calories in twenty -four hours. On this basis a gram of radium in a year emits enough energy to dissociate about two hundred and twenty-five grams of water. What seems most remarkable about this constant emission of heat by the radium atom is that it does not apparently draw upon external sources for it, but maintains it by the internal energy of the atom itself. This latent energy must be enormous, but is only manifested when the atom is breaking up. In this process of disruption many of the particles are thrown off; but the greater part seem to be stopped in their flight in the radium itself, so that their energy of motion is manifested in the form of heat. Thus, if this explanation is correct, the temperature of the radium is maintained above that of surrounding sub- stances by the bombardment of its own particles. Since the earth and the atmosphere contain appreci- able quantities of radio-active matter, this must play a very important part in determining the temperature of the globe — so important a part, indeed, that all for- mer estimates as to the probable length of time during which the earth and sun will continue to radiate heat are invalidated. Such estimates, for example, as that of Lord Kelvin as to the probable heat-giving life of the sun must now be multiplied from fifty to five hundred times. In like manner the length of time that the earth has been sufficiently cool to support animal and vegetable in A HISTORY OF SCIENCE life must be re-estimated. Until the discovery of radium it seemed definitely determined that the earth was gradually cooling, and would continue to cool, un til, like the moon, it would become too cold to support any kind of vegetable or animal life whatever. But recent estimates of the amount of radio-active matter in the earth and atmosphere, and the amount of heat constantly given off from this source, seem to indicate that the loss of heat is (for the moment) about evenly balanced by the heat given out by radio-active matter. Thus at the beginning of the new century we see the phenomenon of a single discovery in science com- pletely overturning certain carefully worked out calcu- lations, although not changing the great principles in- volved. It is but the repetition of the revolutionary changes that occur at intervals in the history of science, a simple discovery setting at naught some of the most careful calculations of a generation. V THE MARINE BIOLOGICAL LABORATORY AT NAPLES THE AQUARIUM MANY tourists who have gone to Naples within l recent years will recall their visit to the aquari- um there among their most pleasant experiences. It is, indeed, a place worth seeing. Any Neapolitan will direct you to the beautiful white building which it oc- cupies in the public park close by the water's side. The park itself, statue-guarded and palm-studded, is one of the show-places of the city; and the aquarium building, standing isolated near its centre, is worthy of its surroundings. As seen from the bay, it gleams white amid the half -tropical foliage, with the circling rampart of hills, flanked by Vesuvius itself, for back- ground. And near at hand the picturesque cactus growth scrambling over the walls gives precisely the necessary finish to the otherwise rather severe type of the architecture. The ensemble prepares one to be pleased with whatever the structure may have to show within. It prepares one also, though in quite another way, for a surprise ; for when one has crossed the threshold and narrow vestibule, while the gleam of the outside brightness still glows before his eyes, he is plunged VOL. V.— 8 112 A HISTORY OF SCIENCE suddenly into what seems at first glimpse a cavern of Egyptian darkness, and the contrast is nothing less than startling. To add to the effect, one sees all about him, near the walls of the cavern, weird forms of mov- ing creatures, which seem to be floating about lazily in the air, in grottos which glow with a dim light or sparkle with varied colors. One is really looking through glass walls into tanks of water filled with marine life ; but both glass and water are so transparent that it is difficult at first glimpse to realize their pres- ence, unless a stream of water, with its attendant bub- bles, is playing into the tanks. And even then the effect is most elusive; for the surface of the water, which you are looking up to from below, mirrors the contents of the tanks so perfectly that it is difficult to tell where the reality ends and the image begins, were it not that the duplicated creatures move about with their backs downward in a scene all topsy-turvy. The effect is most fantastic. More than that, it is most beautiful as well. You are, in effect, at the bottom of the ocean — or rather, at the bottom of many oceans in one. No light comes to you except through the grottos about you — grottos haunted by weird forms of the deep, from graceful to grotesque, from almost colorless to gaudy-hued. To your dilated pupils the light itself has the weird glow of unreality. It is all like the wonders of the Arabian Nights made tangible or like a strange spectacular dream. If one were in a great diving-bell at the bottom of the veritable ocean he could hardly feel more detached from the ordinary aerial world of fact. 114 BIOLOGICAL LABORATORY AT NAPLES As one recovers his senses and begins to take definite note of things about him he sees that each one of the many grottos has a different set of occupants, and that not all of the creatures there are as unfamiliar as at first they seemed. Many of the fishes, for example, and the lobsters, crabs, and the like, are familiar enough under other conditions, but even these old ac- quaintances look strange under these changed cir- cumstances. But for the rest there are multitudes of forms that one had never seen or imagined, for the sea hides a myriad of wonders which we who sail over its surface, and at most glance dimly a few feet into its depths, hardly dream of. Even though one has seen these strange creatures "preserved" in museums, he does not know them, for the alleged preservation there has retained little enough of essential facies of the real creature, which the dead shell can no more than vaguely suggest. Here, however, we see the real thing. Each creat- ure lives and moves in a habitat as nearly as may be like that which it haunted when at liberty, save that tribes that live at enmity with one another are here sep- arated, so that the active struggle for existence, which plays so large a part in the wild life of sea as well as land, is not represented. For the rest the creatures of the deep are at home in these artificial grottos, and disport themselves as if they desired no other resi- dence. For the most part they pay no heed whatever to the human inspectors without their homelike prisons, so one may watch their activities under the most favor- able conditions. It is odd to notice how curiously sinuous are all the ii5 A HISTORY OF SCIENCE movements, not alone of the fish, but of a large propor- tion of the other forms of moving life of the waters. The curve, the line of beauty, is the symbol of their every act; there are no angles in their world. They glide hither and yon, seemingly without an effort, and always with wavy, oscillating gracefulness. The acme of this sinuosity of movement is reached with those long-drawn-out fishes the eels. Of these there are two gigantic species represented here — the conger, a dark- skinned, rather ill-favored fellow, and the beautiful Italian eel, with a velvety, leopard - spotted skin. These creatures are gracefulness itself. They are rib- bon-like in tenuousness, and to casual glance they give the impression of long, narrow pennants softly waving in a gentle breeze. The great conger — five or six feet in length — has, indeed, a certain propensity to extend himself rigidly in a fishlike line and lie im- movable, but the other species is always true to his colors, so to say — his form is always outlined in curves. The eels attract their full share of attention from the visitors, but there is one family of creatures which easily holds the palm over all the others in this regard. These are the various representatives of the great cult of squids and cuttle-fishes. The cuttle-fish proper — who, of course, is no fish at all — is shaped strangely like a diminutive elephant, with a filmy, waving membrane along its sides in lieu of legs. Like the other members of his clan, he can change his color variously. Some- times he is of a dull brown, again prettily mottled ; then, with almost kaleidoscopic suddenness, he will assume a garb beautifully striped in black and white, rivalled 116 THE AQUARIUM OF THE MARINE BIOLOGICAL LABORATORY BIOLOGICAL LABORATORY AT NAPLES by nothing but the coat of the zebra. The cuttle-fish is a sluggish creature, seeking out the darker corners of his grotto, and often lying motionless for long peri- ods together. But not so the little squid. He does not thrive in captivity, and incessantly wings his way back and forth, with slow, wavy flappings of his filmy appendages, until he wears himself out and dies un- reconciled. In marked contrast with both cuttle-fish and squid is their cousin the octopus — a creepy, crawly creature, like eight serpents in one — at once the oddest and the most fascinating creature in the entire aquarium. You will find a crowd almost always before his grotto watching his curious antics. Usually slow and delib- erate in movement, he yet has capacity for a certain agility. Now and again he dives off suddenly, head first, through the water, with the directness if not quite with the speed of an arrow. A moment later, tired of his flight, he sprawls his eight webbed legs out in every direction, breaking them seemingly into a thousand joints, and settles back like an animated parachute awreck. Then perchance he perches on a rock knowingly, with the appearance of owl-like wis- dom, albeit his head looks surprisingly like a frog's. Anon he holds his head erect and stretches out his long arms in what is most palpably a yawn. Then, for pure diversion, he may hold himself half erect on his umbrella frame of legs and sidle along a sort of quadrille — a veritable " eight hands in round." But all the while he conveys distinctly the impression of a creature to the last degree blase. Even when a 117 A HISTORY OF SCIENCE crab is let down into his grotto by an attendant for the edification of the visitors the octopus seems to regard it with only lukewarm interest. If he deigns to go in pursuit, it is with the air of one who says, "Anything to oblige," rather than of eagerness for a morsel of food. Yet withal, even though unhurried, he usually falls upon the victim with surprising sureness of aim, en- compassing it in his multiform net. Or perhaps, think- ing the game hardly worth so much effort, he merely reaches out suddenly with one of his eight arms — each of which is a long-drawn-out hand as well — and grasps the victim and conveys it to his distensible maw with- out so much as changing his attitude. All this of the giant octopus — brown and warty and wrinkled and blase. But the diminutive cousin in the grotto with the jelly fishes is a bird of quite another feather. Physically he is constructed on the same model as the other, but his mentality is utterly opposed. No grand roles for him ; his part is comedy. He finds life full of interest. He is satisfied with himself and with the world. He assumes an aspect of positive rakishness, and intelligence, so to say, beams from his every limb. All day long he must be up and doing. For want of better business he will pursue a shrimp for hours at a time with the zest of a true sportsman. Now he darts after his intended prey like a fox-hound. Again he resorts to finesse, and sidles off, with eyes fixed in another direction, like a master of stratagem. To be sure, he never catches the shrimp — but what of that ? The true sportsman is far removed from the necessity for mere material profit. I half suspect that little oc- topus would release the shrimp if once he caught him, 118 BIOLOGICAL LABORATORY AT NAPLES as the true fisherman throws back the excess of his catch. It is sport, not game, that he covets. THE LABORATORY AND ITS FOUNDER When one has made the circuit of the aquarium he will have seen and marvelled at some hundreds of cu- rious creatures utterly unlike anything to be found above water. Brightly colored starfishes, beautiful sea-urchins, strange stationary ascidians, and flower- like sea-anemones, quaint sea-horses, and filmy, fragile jellyfishes and their multiform kin — all seem novel and wonderful as one sees them in their native element. Things that appear to be parts of the rocky or sandy bed of the grottos startle one by moving about, and thus discovering themselves as living creatures, simu- lating their environment for purposes of protection. Or perhaps what seems to be a giant snail suddenly unfurls wings from its seeming shell, and goes waving through the water, to the utter bewilderment of the beholder. Such freaks as this are quite the rule among the strange tribes of the deep, for the crowding of pop- ulation there makes the struggle for existence keen, and necessitates all manner of subterfuges for the preserva- tion of species. Each and every one of the thirty-odd grottos will repay long observation, even on the part of the most casual visitor, and when one has seen them all, he will know more at first hand of the method of life of the creatures of the sea than all the books could teach him. He will depart fully satisfied, and probably, if he be the usual sight-seer, he will never suspect that what he has seen is really but an incidental part of the institution 119 A HISTORY OF SCIENCE whose building he has entered. Even though he note casually the inscription "Stazione Zoologica" above the entrance, he may never suspect that the aquarium he has just visited is only an adjunct — the popular ex- hibit, so to speak — of the famous institution of tech- nical science known to the English-speaking world as the Marine Biological Laboratory at Naples. Yet such is the fact. The aquarium seems worthy enough to exist by and for itself. It is a great popular educator as well as amuser, yet its importance is utterly insig- nificant compared with the technical features of the institution of which it is an adjunct. This technical department, the biological laboratory proper, has its local habitation in the parts of the build- ing not occupied by the aquarium — parts of which the general public, as a rule, sees nothing. There is, in- deed, little to see that would greatly interest the casual inspector, for in its outward aspects one laboratory is much like another, a seeming hodgepodge of water- tanks, glass jars of specimens, and tables for micro- scopes. The real status of a laboratory is not de- termined by the equipment. And yet it will not do to press this assertion too far, for in one sense it is the equipment of the Naples lab- oratory that has made it what it is. Not, however, the equipment in the sense of microscopes and other working paraphernalia. These, of course, are the best of their kind, but machinery alone does not make a great institution, any more than clothes make the man. The all-essential and distinctive equipment of the laboratory reveals itself in its personnel. In the present case, as always in a truly great institution of 120 BIOLOGICAL LABORATORY AT NAPLES any kind, there is one dominating personality, one moving spirit. This is Dr. Anton Dohrn, founder of the laboratory, and still its controller and director, in name and in fact. More than twenty -five years ago Dr. Dohrn, then a young man fresh from the universities of his native Germany, discovered what he felt to be a real need in the biological world. He was struck with the fact that nowhere in the world could be found an establish- ment affording good opportunities for the study of marine life. Water covers three-fifths of the earth's surface, as everybody knows, and everywhere this water teems with life, so that a vast preponderance of the living things of the globe find their habitat there. Yet the student who might desire to make special studies of this life would find himself balked at the threshold for want of opportunity. It was no great thing to discover this paucity, which, indeed, fairly beckoned the discoverer. The great thing was to supply the deficiency, and this was what Dr. Dohrn determined to do. He selected Naples as the best location for the laboratory he proposed to found, because of its climate and its location beside the teeming waters of the Mediterranean. He organ- ized a laboratory ; he called about him a corps of able assistants; he made the Marine Biological Laboratory at Naples famous, the Mecca of all biological eyes throughout the world. It was not all done in a day. It was far enough from being done without opposition and discouragement; but these are matters of history which Dr. Dohrn now prefers not to dwell upon. Suf- fice it that the result aimed at was finally achieved, 121 A HISTORY OF SCIENCE and in far greater measure than could at first be hoped for. And from that day till this Naples has been the centre of that branch of biological inquiry which has for its object the investigation of problems best studied with material gathered from the sea. And this, let me hast- en to add, includes far more than a mere study of the life histories of marine animals and plants as such. It includes problems of cell activity, problems of hered- ity, life problems of many kinds, having far wider horizons than the mere question as to how a certain fish or crustacean lives and moves and has its being. Dr. Dohrn's chief technical associates are all Ger- mans, like their leader, but, like him also, all gifted with a polyglot mastery of tongues that has stood them in good stead in their intercourse with the biologists of many nationalities who came to work at the laboratory. I must not pause to dwell upon the personnel of the staff in general, but there is one other member who cannot be overlooked even in the most casual survey of the work of the institution. One might almost as well forget Dr. Dohrn himself as to overlook Signor Lo BianCo, chief of the collecting department. Signor Bianco it is who, having expert knowledge of the haunts and habits of every manner of marine creature, can direct his fishermen where to find and how to se- cure whatever rare specimen any worker at the labora- tory may desire. He it is, too, who, by studying old methods and inventing new ones, has learned how to preserve the delicate forms for subsequent study in life- like ensemble that no one else can quite equal. Signor Bianco it is, in short, who is the indispensable right- 122 BIOLOGICAL LABORATORY AT NAPLES hand man of the institution in all that pertains to its practical working outside the range of the microscope. Each night Signor Lo Bianco directs his band of fishermen as to what particular specimens are most to be sought after next day to meet the needs of the work- ers in the laboratory. Before sunrise each day, weather permitting, the little scattered fleet of boats is far out on the Bay of Naples; for the surface collecting, which furnishes a large share of the best material, can be done only at dawn, as the greater part of the creatures thus secured sink into the retirement of the depths dur- ing the day, coming to the surface to feed only at night. You are not likely to see the collecting party start out, therefore, but if you choose you may see them return about nine or ten o'clock by going to the dock not far from the laboratory. The boats come in singly at about this hour, their occupants standing up to row, and pushing forward with the oars, after the awkward Neapolitan fashion. Many of the fishermen are quaint enough in appearance; some of them have grown old in the service of the laboratory. The morning's catch is contained in glass jars placed in baskets especially constructed for the purpose. The baskets have han- dles, but these are quite superfluous except to lift them from the boats, for in the transit to the laboratory the baskets are carried, as almost everything else is carried in Naples, on the head. To the novitiate it seems a striking risk to pile baskets of fragile glass and even more fragile specimens one above another, and attempt to balance the whole on the head, but nothing could be easier, or seemingly more secure, for these experts. Arrived at the laboratory, the jars are turned over to 123 A HISTORY OF SCIENCE Signor Lo Bianco and his assistants, who sort the ma- terial, and send to each investigator in the work- rooms whatever he may have asked for. Of course surface-skimming is not the only method of securing material for the laboratory. The institution owns a steam-launch named the Johannes Midler, in honor of the great physiologist, which operates a pow- erful dredge for securing all manner of specimens from the sea-bottom. Then ordinary lines and nets are more or less in requisition for capturing fish. And in addition to the regular corps of collectors, every fisher- man of the neighborhood has long since learned to bring to the laboratory all rare specimens of any kind that he may chance to capture. So in one way and another the institution makes sure of having in tribute all that the richly peopled waters of the Mediterranean can offer. And this well-regulated system of collecting, combined with the richness of the fauna and flora of the Bay of Naples, has no small share in the success of the marine laboratory. But these, of course, were fac- tors that Dr. Dohrn took into account from the be- ginning. Indeed, it was precisely with an eye to these im- portant factors that Naples was selected as the site of the future laboratory in the days when the project was forming. The Bay of Naples is most happily located for the needs of the zoologist. It is not too far south to ex- clude the fauna of the temperate zone, yet far enough south to furnish a habitat for many forms of life al- most tropical in character. It has, in short, a most varied and abundant fauna. And, on the other hand, 124 BIOLOGICAL LABORATORY AT NAPLES the large colony of Neapolitan fishermen made it cer- tain that skilled collectors would always be at hand to make available the wealth of material. It requires no technical education to appreciate the value of this to the original investigator, particularly to the student of life problems. A skilful worker may do much with a single specimen, as, for example, Johannes Miiller did half a century ago with the one available specimen of amphioxus, the lowest of vertebrates, then recently discovered. What Miiller learned from that one speci- men seems almost miraculous. But what if he had had a bucketful of the little boneless creatures at his dis- posal, as the worker at Naples now may have any day for the asking? When it comes to problems of development, of hered- ity, a profusion of material is almost a necessity. But here the creatures of the sea respond to the call with amazing proficiency. Most of them are, of course, oviparous, and it is quite the rule for them to deposit their eggs by hundreds of thousands, by millions even. Everybody knows, since Darwin taught us, that the average number of offspring of any given species of animal or plant bears an inverse proportion to the liability of that species to juvenile fatalities. When, therefore, we find a fish or a lobster or other pelagic creature depositing innumerable eggs, we may feel per- fectly sure that the vast majority of the eggs them- selves, or the callow creatures that come out of them, will furnish food for their neighbors at an early day. It is an unkind world into which the resident of the deep is born. But his adversity is his human contem- porary's gain, and the biologist will hardly be blamed, 125 A HISTORY OF SCIENCE even by the most tender-hearted anti-vivisectionist, for availing himself freely of material which otherwise would probably serve no better purpose than to ap- pease the appetite of some rapacious fish. Their abundance is not the only merit, however, of the eggs of pelagic creatures, in the eyes of the biologist. By equal good-fortune it chances that colorless things are at a premium in the sea, since to escape the eye of your enemy is a prime consideration. So the eggs in question are usually transparent, and thus, shielded from the vision of marine enemies, are beautifully adapted for the observation of the biologist. As a final merit, they are mostly of convenient size for manip- ulation under the microscope. For many reasons, then, the marine egg offers incomparable advantages to the student of cell life, an egg being the typical cell. And since nowadays the cell is the very focus of attention in the biological world, the importance of marine laboratories has been enhanced proportionately. But of course not all the work can be done with eggs or with living specimens of any kind. It is equally important on occasion to examine the tissues of adult specimens, and for this, as a rule, the tissues must first be subjected to some preserving and hardening proc- ess preliminary to the cutting of sections for micro- scopical examination. This is done simply enough in the case of some organisms, but there is a large class of filmy, tenuous, fragile creatures in the sea population of which the jellyfish may be mentioned as familiar examples. Such creatures, when treated in an ordinary way, by dropping them into alcohol, shrivel up, coming to resemble nothing in particular, and ceasing to have 126 BIOLOGICAL LABORATORY AT NAPLES any value for the study of normal structures. How to overcome this difficulty was one of the problems at- tacked from the beginning at the Naples laboratory. The chief part of the practical work of these experi- ments fell to the share of Signor Lo Bianco. The suc- cess that attended his efforts is remarkable. To-day you may see at the laboratory all manner of filmy, di- aphanous creatures preserved in alcohol, retaining every jot of their natural contour, and thus offering unexam- pled opportunities for study en masse, or for being sec- tioned for the microscope. The methods by which this surprising result has been accomplished are nat- urally different for different creatures; Signor Lo Bianco has written a book telling how it all has been done. Perhaps the most important principle involved with a majority of the more tenuous forms is to stupefy the animal by gradually adding small quantities of a drug, such as chloral, to the water in which the creature is detained. When by this means the animal has been rendered so insensible that it responds very sluggishly to stimuli, it is plunged into a toxic solution, usually formaline, which kills it so suddenly that its muscles in their benumbed state have not time to contract. Any one who has ever tried to preserve a jellyfish, for example, by ordinary methods will recall the sorry result, and be prepared to appreciate Signor Lo Bi- anco's wonderfully beautiful specimens. Naturalists have come from all over the world to Naples to learn "just how" the miracle is accomplished, for it must be understood that the mere citation of the modus ope- randi by no means enables the novitiate to apply it successfully at once. In the case of some of the long- 127 A HISTORY OF SCIENCE drawn-out forms of clustered ascidians and the like, the delicacy of manipulation required to make suc- cessful preservations raises the method as practised at Naples almost to the level of a fine art. It is a boon to naturalists everywhere that the institution here is able sometimes to supply other laboratories less favor- ably situated with duplicates from its wealth of beau- tifully preserved specimens. METHODS AND RESULTS These, then, are some of the material conditions that have contributed to make the results of the scientific investigations at the Naples laboratory notable. But of course, even with a superabundance of material, dis- coveries do not make themselves. "Who uses this material?" is, after all, the vital question. And in this regard the laboratory at Naples presents, for any one who gets at its heart, so to speak, an ensemble that is distinctive enough ; for the men who work in the light and airy rooms of the laboratory proper have come for the purpose from all corners of the civilized globe, and not a few of them are men of the highest distinction in their various lines of biological science. A large pro- portion are professors in colleges and universities of their various countries ; and for the rest there is scarcely one who is not in some sense master of the biological craft. For it must be understood that this laboratory at Naples is not intended as a training-school for the apprentice. It offers in the widest sense a university course in biology, and that alone. There is no in- structor here who shows the new-comer how to use the microscope, how to utilize the material, how to go 128 BIOLOGICAL LABORATORY AT NAPLES about the business of discovery. The worker who comes to Naples is supposed to have learned all these things long before. He is merely asked, then, what class of material he desires, and, this being furnished him, he is permitted to go his own way unmolested. He may work much or little, or not at all ; he may make epochal discoveries or no discoveries of any sort, and it will be all one to the management. No one will ask him, in any event, what he has done or why he has not done otherwise. In a word, the worker in the labora- tory here, while being supplied with opportunities for study such as he could hardly find elsewhere, retains all the freedom of his own private laboratory. Little wonder, then, that it is regarded as a rare privilege to be allowed to work in this laboratory. Fortunately, however, it is a privilege that may be ob- tained by almost any earnest worker who, having learned the technique of the craft elsewhere, desires now to prosecute special original studies in biology. Most of the tables here are leased in perpetuity, for a fixed sum per annum, by various public or private in- stitutions of different countries. Thus, for example, America has the right of use of several tables, the Smithsonian Institution leasing one, Columbia Uni- versity another, a woman's league a third, and so on. Any American desiring to work at Naples should make application to one of these various sources, stating the exact time when he would like to go, and if there be a vacancy for that time the properly accredited ap- plicant is almost sure to receive the privilege he asks for. Failing in this, however, there is still a court of last appeal in Dr. Dohrn himself, who may have a few VOL. V.— 9 129 A HISTORY OF SCIENCE unoccupied tables at his disposal, and who will surely extend the courtesy of their occupancy, for a reasonable period, to any proper applicant, come he whence he may. Thus it chances that one finds men of all nations working in the Naples laboratory — biologists from all over Europe, including Russia, from America, from Australia, from Japan. One finds women also, but these, I believe, are usually from America. Biologists who at home are at the head of fully equipped labora- tories come here to profit by the wealth of material, as well as to keep an eye upon the newest methods of their craft, and to gain the inspiration of contact with other workers in allied fields. Many of the German university teachers, for example, make regular pil- grimages to Naples during their vacations, and more than one of them have made the original investigations here that have given them an international reputation. As to the exact methods of study employed by the individual workers here, little need be said. In this regard, as in regard to instrumental equipment, one biological laboratory is necessarily much like another, and the general conditions of original scientific experi- ment are pretty much the same everywhere. What is needed is, first, an appreciation of the logical bearings of the problem to be solved ; and, secondly, the skill and patience to carry out long lines of experiments, many of which necessarily lead to no tangible result. The selection of material for the experiments planned, the watching and cultivating of the living forms in the laboratory tanks, the cutting of numberless filmy sec- tions for microscopical examination — these things, 130 BIOLOGICAL LABORATORY AT NAPLES variously modified for each case, make up the work of the laboratory student of general biology. And just in proportion as the experiments are logically planned and carefully executed will the results be valuable, even though they be but negative. Just in proportion as the worker, by inclusion and exclusion, attains au- thentic results — results that will bear the test of repe- tition— does his reputation as a dependable working biologist become established. The subjects attacked in the marine laboratory first and last are practically coextensive with the range of general biology, bacteriology excepted. Naturally enough, the life histories of marine forms of animals and plants have come in for a full share of attention. But, as I have already intimated, this zoological work forms only a small part of the investigations under- taken here, for in the main the workers prefer to at- tack those general biological problems which in their broader outlines apply to all forms of living beings, from highest to lowest. For example, Dr. Driesch, the well-known Leipzig biologist, spends several months of each year at the laboratory, and has made here most of those studies of cell activities with which his name is associated. The past season he has studied an in- teresting and important problem of heredity, endeavor- ing to ascertain the respective shares of the male .and female parents in the development of the offspring. The subjects of his experiments have been various species of sea-urchins, but the principles discovered will doubtless be found to apply to most, or perhaps all, forms of vertebrate life as well. While these studies were under way another devel- J3i A HISTORY OF SCIENCE opmental problem was being attacked in a neighboring room of the laboratory by Professor Kitasato, of the University of Tokio, Japan. The subjects this time were the embryos of certain fishes, and the investiga- tion had to do with the development of instructive monstrosities through carefully designed series of in- juries inflicted upon the embryo at various stages of its development. Meantime another stage of the develop- mental history of organic things — this time a micro- scopical detail regarding the cell divisions of certain plants — has been studied by Professor Mottier, of Indiana; while another American botanist, Professor Swingle, of the Smithsonian Institution, has been go- ing so far afield from marine subjects as to investigate the very practical subject of the fertilization of figs as practised by the agriculturists about Naples. Even from these few citations it will appear how varied are the lines of attack of a single biological prob- lem ; for here we see, at the hands of a few workers, a great variety of forms of life — radiates, insects, ver- tebrates, low marine plants and high terrestrial ones — made to contribute to the elucidation of various phases of one general topic, the all-important subject of hered- ity. All these studies are conducted in absolute inde- pendence, and to casual inspection they might seem to have little affinity with one another ; yet in reality they all trench upon the same territory, and each in its own way tends to throw light upon a topic which, in some of its phases, is of the utmost practical importance to the human family. It is a long vault from the em- bryo of an obscure sea-weed to the well-being of man, yet it may well happen — so wide in their application 132 BIOLOGICAL LABORATORY AT NAPLES are the general life principles — that study of the one may point a practical moral for the other. Indeed, it constantly happens that the student of biology, while gazing through his microscope, hits upon discoveries that have the most far-removed im- plications. Thus a few years ago it was discovered that when a cell is about to bisect itself and become two cells, its nucleus undergoes a curious transforma- tion. Within the nuclear substance little bodies are developed, usually threadlike in form, which take on a deep stain, and which the biologist calls chro- mosomes. These chromosomes vary in number in the cells of different animals, but the number is al- ways the same for any given species of animal. If one were to group animate beings in classes according to this very fundamental quality of the cells he would have some very curious relations established. Thus, under the heading " creatures whose cells have twenty- four chromosomes," one would find beings so different as "the mouse, the salamander, the trout, and the lily," while the sixteen-chromosome group would in- troduce the very startling association of the ox, the guinea-pig, the onion, and man himself. But what- ever their number, the chromosomes are always ex- actly bisected before the cell divides, one-half being apportioned to each of the two cells resulting from the division. Now the application is this: It was the study of these odd nuclear structures and their peculiar ma- nceuvrings that, in large measure, led Professor Weis- mann to his well-known theory of heredity, according to which the acquired traits of any being are not trans- i33 A HISTORY OF SCIENCE missible to the offspring. Professor Weismann came to believe that the apportionment of the nuclear sub- stance, though quantitatively impartial, is sometimes radically uneven in quality; in particular, that the first bisection of the egg - cell, which marks the be- ginning of embryonic development, produces two cells utterly different in potentiality, the one containing the "body plasm," which is to develop the main animal structures, the other encompassing the "germ plasm," by which the racial integrity is [to be preserved. Throughout the life of the individual, he believed, this isolation continued; hence the assumed lack of influ- ence of acquired bodily traits upon the germ plasm and its engendered offspring. Hence, also, the application of the microscopical discovery to the deepest ques- tions of human social evolution. Every one will recall that this theory, born of the laboratory, made a tremendous commotion in the out- side world. Its application to the welfare and progress of humanity gave it supreme interest, and polemics unnumbered were launched in its favor and in its con- demnation. Eager search was made throughout the fields of botany and zoology for new evidence pro or con. But the definitive answer came finally from the same field of exploration in which the theory had been originated — the world of the cell — and the Marine Biological Laboratory was the seat of the new series of experiments which demonstrated the untenability of the Weismannian position. Most curious experi- ments they were, for in effect they consisted of the making of two or more living creatures out of one, in the case of beings so highly organized as the sea-urchins, i34 BIOLOGICAL LABORATORY AT NAPLES the little fishlike vertebrate, amphioxus, and even the lower orders of true fishes. Of course the division of one being to form two is perfectly familiar in the case of those lowly, single-celled creatures such as the protozoa and the bacteria, but it seems quite another matter when one thinks of cutting a fish in two and having two complete living fish remaining. Yet this is virtually what the biologists did. Let me hasten to add that the miraculous feat was not accomplished with an adult fish. On the contrary, it is found necessary to take the subject quite at the beginning of its career, when it consists of an egg-cell in the earliest stages of proliferation. Yet the prin- ciple is quite the same, for the adult organism is, after all, nothing more than an aggregation of cells resulting from repeated divisions (growth accompanying) and redi visions of that original egg-cell. Considering its potentialities, the egg-cell, seemingly, is as much en- titled to be considered an individual as is the devel- oped organism. Yet it transpires that the biologist has been able so to manipulate a developing egg-cell, after its bisection, that the two halves fall apart, and that each half (now become an independent cell) de- velops into a complete individual, instead of the half- individual for which it seemed destined. A strange trick, that, to play with an individual Ego, is it not? The traditional hydra with its reanimating heads was nothing to this scientific hydra, which, when bisected bodily, rises up calmly as two whole bodies. But even this is not the full measure of the achieve- ment, for it has been found that in some cases the ex- periment may be delayed until the developing egg 135 A HISTORY OF SCIENCE has made a second bisection, thus reaching the four- cell stage, when four completely formed individuals emerge from the dismembered egg. And in the case of certain medusas, success has attended experiments made at the eight-cell and even at the sixteen-cell stage of development, the creature which had got thus far on its career in single blessedness becoming eight or six- teen individuals at the wave of the enchanted wand — that is to say, the dissecting-needle — of the biologist. All of which savors of con jury, but is really only matter - of - fact biological experiment — experiment, however, of which the implications by no means con- fine themselves to matters of fact biological. For clearly the fact that the separated egg-cells grow into complete individuals shows that Weismann's theory, according to which one of the cells contained only body plasm, the other only germ plasm, is quite untenable. Thus the theory of the non-transmissibility of acquired characters is deprived of its supposed anatomical sup- port and left quite in the air, to the imminent peril of a school of sociologists who had built thereon new theo- ries of human progress. Also the question of the mul- tiplied personalities clearly extends far beyond the field of the biologist, and must be turned over to the consideration of the psychologist — if, indeed, it does not fall rather within the scope of the moralist. But though it thus often chances that the biologist, while gazing stoically through his microscope, may dis- cover things in his microcosm that bear very closely upon the practical interests of the most unscientific members of the human family, it would be a mistake to suppose that it is this class of facts that the worker 136 BIOLOGICAL LABORATORY AT NAPLES is particularly seeking. The truth is that, as a rule, the pure biologist is engaged in work for the love of it, and nothing is further from his thoughts than the "practical" bearings or remote implications of what he may discover. Indeed, many of his most hotly pursued problems seem utterly divorced from what an outsider would call practical bearings, though, to be sure, one can never tell just what any new path may lead to. Such, for example, is the problem which, next to questions of cell activities, comes in for per- haps as large a share of attention nowadays as any other one biological topic — namely, the question as to just which of the various orders of invertebrate creat- ures is the type from which vertebrates were evolved in the past ages — in other words, what invertebrate creature was the direct ancestor of the vertebrates, in- cluding man. Clearly it can be of very little practical importance to man of to-day as to just who was his ancestor of several million years ago. But just as clearly the question has interest, and even the layman can understand something of the enthusiasm with which the specialist attacks it. As yet, it must be admitted, the question is not de- cisively answered, several rival theories contending for supremacy in the case. One of the most important of these theories had its origin at the Naples labora- tory ; indeed, Dr. Dohrn himself is its author. This is the view that the type of the invertebrate ancestor is the annelid — a form whose most familiar representa- tive is the earth-worm. The many arguments for and against accepting the credentials of this unaristocratic ancestor cannot be dwelt upon here. But it may be 137 A HISTORY OF SCIENCE consolatory, in view of the very' plebeian character of the earth-worm, to know that various of the annelids of the sea have a much more aristocratic bearing. Thus the filmy and delicately beautiful structures that decorate the pleasant home of the quaint little sea- horse in the aquarium — structures having more the appearance of miniature palm-trees than of animals — are really annelids. One can view Dr. Dohrn's theory with a certain added measure of equanimity after he learns this, for the marine annelids are seen, some of them, to be very beautiful creatures, quite fitted to grace their distinguished offspring should they make good their ancestral claims. These glimpses will suffice, perhaps, to give at least a general idea of the manner of thing which the worker at the marine laboratory is seeking to discover when he interrogates the material that the sea has given him. In regard to the publication of the results of work done at the Naples laboratory, the same liberal spirit prevails that actuates the conduct of the institu- tion from first to last. What the investigator dis- covers is regarded as his own intellectual property, and he is absolutely free, so far as the management of this institution is concerned, to choose his own medium in giving it to the world. He may, and often does, prefer to make his announcements in periodicals or books issued in his own country and having no connec- tion whatever with the Naples laboratory. But, on the other hand, his work being sufficiently important, he may, if he so desire, find a publisher in the institution itself, which issues three different series of important publications under the editorship of Professor Mayer. 138 BIOLOGICAL LABORATORY AT NAPLES One of these, entitled Mittheilungen aus der Zoolog- ische Station zu Neapel, permits the author to take his choice among four languages — German, English, French, or Italian. It is issued intermittently, as oc- casion requires. The second set of publications con- sists of ponderous monographs upon the fauna and flora of the Gulf of Naples. These are beautifully illustrated in color, and sometimes a single volume costs as much as seventeen thousand dollars to issue. Of course only a fraction of that sum is ever recovered through sale of the book. The third publication, called Zoologischen Jahresbericht, is a valuable resume of biological literature of all languages, keeping the worker at the laboratory in touch with the discoveries of investigators elsewhere. The latter end is attained further by the library of the institution, which is supplied with all the periodi- cals of interest to the biologist and with a fine assort- ment of technical books. The library - room, aside from its printed contents, is of interest because of its appropriate mural decorations, and because of the bronze portrait busts of the two patron saints of the institution, Von Baer and Darwin, which look down in- spiringly upon the reader. All in all, then, it would be hard to find a deficiency in the Stazione Zoologica as an instrument of biological discovery. A long list might be cited of the revela- tions first brought to light within its walls. And yet, as it seems to me, the greatest value of this institution as an educational factor in science — as a biological lever of progress — does not depend so much upon the tangible revelations of fact that have come out of its 139 A HISTORY OF SCIENCE laboratories as upon other of its influences. Scientific ideas, like all other forms of human thought, move more or less in shoals. Very rarely does a great dis- covery emanate from an isolated observer. The man who cannot come in contact with other workers in kindred lines becomes more or less insular, narrow, and unfitted for progress. Nowadays, of course, the free communication between different quarters of the globe takes away somewhat from the insularity of any quarter, and each scientist everywhere knows some- thing of what the others are doing, through wide-spread publications. But this can never altogether take the place of personal contact and the inspirational com- munication from man to man. Hence it is that a rendezvous, where all the men of a craft go from time to time and meet their fellows from all over the world, has an influence for the advancement of the guild which is enormous and unequivocal, even though diffi- cult of direct demonstration. This feature, then, it seems to me, gives Dr. Dohrn's laboratory its greatest value as an educational factor, as a moving force in the biological world. It is true that the new-comer there is likely to be struck at first with a sense of isolation, and to wonder at the seeming exclusiveness of the workers, the self - absorption of each and every one. Outside the management, whom he meets necessarily, no one pays the slightest atten- tion to him at first, or seems to be aware of his exist- ence. He is simply assigned to a room or table, told to ask for what he wants, and left to his own devices. As he walks along the hallways he sees tacked on the doors the cards of biologists from all over the world, 140 BIOLOGICAL LABORATORY AT NAPLES exposing names with which he has long been familiar. He understands that the bearers of the names are at work within the designated rooms, but no one offers to introduce him to them, and for some time, perhaps, he does not so much as see them, nor would he recog- nize them if he did. He feels strange and isolated in the midst of this stronghold of his profession. But soon this feeling leaves him. He begins to meet his fellow-workers casually here and there — in the hallways, at the distributing-tanks, in the library. There are no formal gatherings, and there are some workers who never seem to affiliate at all with the others ; but in the long-run, here as elsewhere, kindred spirits find one another out; and even the unsocial ones take their share, whether or no, in the indefinable but very sensible influence of massed numbers. Pres- ently some one suggests to the new-comer that he join some of the others of a Wednesday or Saturday evening, at a rendezvous where a number of them meet regu- larly. He goes, under escort of his sponsor, and is guided through one of those narrow, dark, hill-side streets of Naples where he would hardly feel secure to go alone, to a little wine-shop in what seems a veritable dungeon — a place which, if a stranger in Naples, he would never even remotely think of entering. But there he finds his confreres of the laboratory gathered about a long table, with the most conglomerate groups of Neapolitans of a seemingly doubtful class at their elbows. Each biologist has a caraffa of light wine on the table before him, and all are smoking. And, staid •men of science that they are, they are chattering away on trivial topics with the animation of a company of 141 A HISTORY OF SCIENCE school-boys. The stock language is probably Ger- man, for this bohemian gathering is essentially a Ger- man institution; but the Germans are polyglots, and you will hardly find yourself lost in their company, whatever your native tongue. Your companions will tell you that for years the laboratory fraternity have met twice a week at this homely but hospitable establishment. The host, hon- est Dominico Vincenzo Bifulco, will gladly corroborate the statement by bringing out for inspection a great blank-book in which successive companies of his guests from the laboratory have scrawled their names, written epigrams, or made clever sketches. That book will some day be treasured in the library of a bibliophile, but that will not be until Bifulco is dead, for while he lives he will never part with it. One comes to look upon this bohemian wine-shop as an adjunct of the laboratory, and to feel that the free- and-easy meetings there are in their way as important for the progress of science as the private seances of the individual workers in the laboratory itself. Not be- cause scientific topics are discussed here, though doubt- less that sometimes happens, but because of that vi- talizing influence of the contact of kindred spirits of which I am speaking, and because this is the one place where a considerable number of the workers at the laboratory meet together with regularity. The men who enter into such associations go out from them revitalized, full of the spirit of propaganda. Returned to their own homes, they agitate the ques- tion of organizing marine laboratories there; and it is largely through the efforts of the graduates, so to say, 142 BIOLOGICAL LABORATORY AT NAPLES of the Naples laboratory that similar institutions have been established all over the world. Thanks largely to the original efforts of Dr. Dohrn, nearly all civilized countries with a coast-line now have their marine laboratories. France has half a dozen, two of them under government control. Rus- sia has two on the Black Sea and one on the French Mediterranean coast. Great Britain has important stations at St. Andrews, at Liverpool, and at Plym- outh. The Scandinavian peninsula has also three im- portant stations. Germany shows a paucity by com- parison, which, however, is easily understood when one reflects that the mother-laboratory at Naples is essentially a German institution despite its location. The American stations are located at Woods' Holl and at Cold Spring Harbor, on opposite coasts of Long Island Sound. The Japanese station is an adjunct of Tokio University. For the rest, the minor offspring of the Naples laboratory are too numerous to be cited here. Nor can I enter into any details regarding even the more important ones. Each in its way enters into the same general line of work, varying the details according to the bent of mind of individual directors and the limitations of individual resources. But in the broader outlines the aim of all is the same, and what we have seen at Naples is typical of what is best in all the others. VI ERNST HAECKEL AND THE NEW ZOOLOGY THE DREAM CITY THE train crept on its tortuous way down the pict- uresque valley of the little Saale. At last we saw, high above us, on a jutting crag, three quaint old cas- tles, in one of which, as we knew from our Baedeker, Goethe at one time lived. We were entering the re- gion of traditions. Soon we knew we should be pass- ing that famous battle-field on which Napoleon, in 1806, sealed the fate of Germany for a generation. But this spot, as seen from the car window, bore no emblem to distinguish it, and before we were quite sure that we had reached it we had in point of fact passed on, and the train was coming to a stop. "Jena!" called the guard, and the scramble for "lug- gage" began, leaving us for the moment no place for other thoughts than to make sure that all our various parcels were properly dragged out along with ourselves. For a wonder no Dienstman appeared to give us aid — showing how unexpected is the arrival of any way- farer at this untoward season — and for a moment one seemed in danger of being reduced to the unheard-of expedient of carrying one's own satchel. But, fortu- nately, one is rescued from this most un-German pre- dicament by the porter of a waiting hotel omnibus, 144 HAECKEL AND THE NEW ZOOLOGY and so at last we have time to look about us, and to awaken to a realizing sense that we have reached the land of traditions ; that we have come to Mecca ; that we are in the quondam home of Guericke, Fichte, Goethe, Schiller, Oken, and Gagenbaur ; in the present home of Haeckel. The first glimpse of a mountain beaming down at us from across the way was in admirable conformity with our expectations, but for the rest, the vicinage of the depot presented a most distressing air of modernity. A cluster of new buildings — some of them yet unfin- ished— stared back at us and the mountain with the most barefaced aspect of cosmopolitanism. Was this, then, Jena, the home of traditions ? Or were we enter- ing some Iowa village, where the first settlers still live who but yesterday banished the prairie-dog and the buffalo? But this disappointment and its ironical prompt- ings were but fleeting. Five minutes' drive and we were in the true Jena with the real flavor of medieval- ism about us. Here is the hostelry where Luther met the Swiss students in 1522. There is nothing in that date to suggest our Iowa village, nor in the aspect of the hostelry itself, thank fortune. And there rises the spire of the city church, up the hill yonder, which was aging, as were most of the buildings that still flank it, when Luther made that memorable visit. America was not discovered, let alone Iowa, when these struct- ures were erected. Now, sure enough, we are in the dream city. A dream city it truly seems, when one comes to wander through its narrow, tortuous streets, between VOL. V.— IO I 4CJ A HISTORY OF SCIENCE time-stained walls, amid its rustic population. Com- ing from Berlin, from Dresden, from Leipzig — not to mention America — one feels as if he had stepped sud- denly back two or three centuries into the past. There are some evidences of modernity that mar the illusion, to be sure ; but the preponderance of the old-time em- blems is sufficient to leave the mind in a delightful glow of reminiscences. As a whole, the aspect of the central portion of the village — of the true Jena — can- not greatly have changed since the days when Luther stopped here on his way to Wittenberg; surely not since 1662, when the mighty young Leibnitz, the Aris- totle of Germany, came to Jena to study under Weigel, the most famous of German mathematicians of that century. Here and there an old house has been de- molished, to be sure ; even now you may see the work of destruction going on, as a new street is being cut through a time-honored block close to the old church. But in the main the old thoroughfares run hither and thither, seemingly at random, as of old, disclosing everywhere at their limits a sky-line of picturesque gables, and shut in by walls that often are almost cafi on-like in narrowness; while the heavy, buttressed doors and the small, high-placed windows speak of a time when every house partook of the nature of the fortress. The footway of the thoroughfares has no doubt vast- ly changed, for it is for the most part paved now — badly enough, to be sure, yet, after all, paved as no city was in the good old days when garbage filled the streets and cleanliness was an unknown virtue. The Jena streets of to-day are very modern in their cleanli- 146 HAECKEL AND THE NEW ZOOLOGY ness ; yet a touch of mediasvalism is retained in that the main work of cleaning is done by women. But, for that matter, it seems to the casual observer as if the bulk of all the work here were performed by the sup- posedly weaker sex. Certainly woman is here the chief beast of burden. In every direction she may be seen, in rustic garb, struggling cheerily along under the burden of a gigantic basket strapped at her back. You may see the like anywhere else in Germany, to be sure, but not often elsewhere in such preponderant numbers. And scarcely elsewhere does the sight jar so little on one's New-World sensibilities as in the midst of this mediaeval setting. One is even able to watch the old women sawing and splitting wood in the streets here, with no thought of anything but the picturesque- ness of the incident. If one follows a band of basket-laden women, he will find that their goal is that focal-point of every old- time city, the market-place. There arrived, he will witness a scene common enough in Europe but hardly to be duplicated anywhere in America. Hundreds of venders of meat, fish, vegetables, cloths, and house- hold utensils have their open-air booths scattered all across the wide space, and other hundreds of purchasers are there as well. Quaint garbs and quainter faces are everywhere, and the whole seems quite in keep- ing with the background of fifteenth-century houses that hedges it in on every side. Could John the Mag- nanimous, who rises up in bronze in the midst of the assembly, come to life, he would never guess that three and a half centuries have passed since he fell into his last sleep. 147 A HISTORY OF SCIENCE This same John the Magnanimous it was who found- ed the institution which gives Jena its fame and dis- tinguishes it from all the other quaint hypnotic clus- ters of houses that nestle similarly here and there in other picturesque valleys of the Fatherland — I mean, of course, its world-renowned university. It is but a few minutes' walk from the market-place, past the home where Schiller once lived and through the "street" scarcely more than arms'-breadth wide be- yond, to the site of the older buildings of the university. Inornate, prosaic buildings they are, unrelieved even by the dominant note of picturesqueness ; rescued, however, from all suggestion of the commonplace by the rugged ruins of the famed " powder- tower " jutting out from the crest of the hill just above, by the spire of the old church which seems to rise from the oldest university building itself, and by the mountain peaks that jut up into view far beyond. If you would enter one of the old buildings there is naught to hinder. Go into one of the lecture-halls which chances at the moment to be unoccupied, and you will see an array of crude old benches for seats that look as if they might have been placed there at the very inaugural of the institution. The boards that serve for desks, if you scan them closer, you will find scarred all over with the marks of knives, showing how some hundreds of successive classes of listeners have whiled away the weary lecture-hours. Not a square inch can you find of the entire desk surface that is un- scarred. If one would woo a new sensation, he has but to seat himself on one of these puritanical old benches and conjure up in imagination the long series 148 HAECKEL AND THE NEW ZOOLOGY of professors that may have occupied the raised plat- form in front, recalling the manner of thought and dogma that each laid down as verity. He of the first series appears in the garb of the sixteenth century, with mind just eagerly striving to peer a little way out of the penumbra of the Renaissance. The students who carve the first gashes in the new desks will learn, if perchance they listen in intervals of whittling, that this world on which they live is perhaps not flat, but actually round, like a ball. It is debatable doctrine, to be sure, but we must not forget that Signor Colum- bus, recently dead, found land off to the west which is probably a part of the Asiatic continent. If the earth be indeed a ball, then the sun and stars whirl clear around it in twenty-four hours, travelling thus at an astonishing speed, for the sphere in which they are fastened is situated hundreds of miles away. The sun must be a really great ball of fire — perhaps a mile even in diameter. The moon, as is plain to see, is nearly as large. The stars, of course, are only sparks, though of great brilliancy. They are fixed in a dif- ferent sphere from that of the sun. In still other spheres are the moon, and a small set of large stars called planets, of which latter there are four, in order that, with the sun, the moon, and the other stars, there may be made seven orders of heavenly bodies — seven being, of course, the magic number in accordance with which the universe is planned. This is, in substance, the whole subject of astronomy, as that first professor must have taught it, even were he the wisest man of his time. Of the other sciences, except an elementary mathematics, there was hardly 149 A HISTORY OF SCIENCE so much as an inkling taught that first class of students. You will find it appalling, as you muse, to reflect upon the amazing mixture of utter ignorance and false knowledge which the learned professor of that day brought to the class-room, and which the "educated" student carried away along with his degree. The one and the other knew Greek, Latin, and Bible history and doctrine. Beyond that their minds were as the minds of babes. Yet no doubt the student who went out from the University of Jena in the year 1550 thought himself upon the pinnacles of learning. So he was in his day and age, but could he come to life to-day, in the full flush of his scholarship, yonder wood- vender, plying her saw out here in front of the university build- ing, would laugh in derision at his simplicity and ig- norance. So it seems that, after all, the subjects of John the Magnanimous have changed more than a little during the three hundred and odd years that John himself, done in bronze, has been standing out there in the market-place. THE CAREER OF A ZOOLOGIST Had one time for it, there would be real interest in noting the steps by which the mental change in ques- tion has been brought about ; in particular to note the share which the successive generations of Jena pro- fessors have taken in the great upward struggle. But we must not pause for that here. Our real concern, despite the haunting reminiscences, is not with the Jena of the past, but with the Jena of to-day ; not with ghosts, but with the living personality who has made the Jena of our generation one of the greatest centres 150 HAECKEL AND THE NEW ZOOLOGY of progress in human thought in all the world. Jena is Jena to-day not so much because Guericke and Fichte and Hegel and Schiller and Oken taught here in the past, as because it has for thirty-eight years been the seat of the labors of Germany's greatest naturalist, one of the most philosophical zoologists of any country or any age, Professor Ernst Haeckel. It is of Professor Haeckel and his work that I chiefly mean to write, and if I have dwelt somewhat upon Jena itself, it is be- cause this quaint, retired village has been the theatre of Haeckel' s activities all the mature years of his life, and because the work he has here accomplished could hardly have been done so well elsewhere; some of it, for reasons I shall presently mention, could hardly have been done elsewhere at all — at least in another university. It was in 1861 that young Dr. Haeckel came first to Jena as a teacher. He had made a tentative effort at the practice of medicine in Berlin, then very gladly had turned from a distasteful pursuit to the field of pure science. His first love, before he took up the study of medicine, had been botany, though pictorial art, then as later, competed with science for his favorable atten- tion. But the influence of his great teacher, Johannes Muller, together with his medical studies, had turned his attention more directly to the animal rather than vegetable life, and when he left medicine it was to turn explicitly to zoology as a life study. Here he believed he should find a wider field than in art, which he loved almost as well, and which, it may be added, he has followed all his life as a dilettante of much more than amateurish skill. Had he so elected, Haeckel might 151 A HISTORY OF SCIENCE have made his mark in art quite as definitely as he has made it in science. Indeed, even as the case stands, his draughtsman's skill has been more than a mere recreation to him, for without his beautiful drawings, often made and reproduced in color, his classical mono- graphs on various orders of living creatures would have lacked much of their present value. Moreover, quite aside from these merely technical drawings, Professor Haeckel has made hundreds of paintings purely for recreation and the love of it, illus- trating— and that too often with true artistic feeling for both form and color — the various lands to which his zoological quests have carried him, such as Sicily, the Canaries, Egypt, and India. From India alone, after a four-months' visit, Professor Haeckel brought back two hundred fair-sized water-colors, a feat which speaks at once for his love of art and his amazing in- dustry. I dwell upon this phase of Professor Haeckel's char- acter and temperament from the very outset because I wish it constantly to be borne in mind, in connection with some of the doctrines to be mentioned presently, that here we have to do with no dry-as-dust scientist, cold and soulless, but with a broad, versatile, imagina- tive mind, one that links the scientific and the artistic temperaments in rarest measure. Charles Darwin, with whose name the name of Haeckel will always be linked, told with regret that in his later years he had become so steeped in scientific facts that he had lost all love for or appreciation of art or music. There has been no such mental warping and atrophy in the mind of Ernst Haeckel. Yet there is probably no man liv- 152 HAECKEL AND THE NEW ZOOLOGY ing to-day whose mind contains a larger store of tech- nical scientific facts than his, nor a man who has en- riched zoology with a larger number of new data, the result of direct personal observation in field or labora- tory. How large Haeckel's contribution in this last regard has been can be but vaguely appreciated by running over the long list of his important publications, though the list includes more than one hundred titles, unless it is understood that some single titles stand for mono- graphs of gigantic proportions, which have involved years of labor in the production. Thus the text alone of the monograph on the radiolarians, a form of micro- scopic sea-animalcule (to say nothing of the volume of plates), is a work of three gigantic volumes, weighing, as Professor Haeckel laughingly remarks, some thirty pounds, and representing twelve years of hard labor. This particular monograph, by-the-bye, is written in English (of which, as of several other languages, Pro- fessor Haeckel is perfect master), and has a history of more than ordinary interest. It appears that the radiolarians were discovered about a half -century ago by Johannes Miiller, who made an especial study of them, which was uncompleted at the time of his death in 1858. His monograph, describing the fifty species then known, was published posthumously. Haeckel, on whom the mantle of the great teacher was to fall, and who had been Muller's last pupil, took up the work his revered master had left unfinished as his own first great original Arbeit. He went to Messina and was de- lighted to find the sea there replete with radiolarians, of which he was able to discover one or two new species 153 A HISTORY OF SCIENCE almost every day, until he had added one hundred and fifty all told to Muller's list, or more than triple the whole number previously known. The description of these one hundred and fifty new radiolarians consti- tuted Haeckel's first great contribution to zoology, and won him his place as teacher at Jena in 1861. Henceforth Haeckel was, of course, known as the greatest authority on this particular order of creatures. For this reason it was that Professor Murray, the nat- uralist of the famous expedition which the British government sent around the world in the ship Chal- lenger, asked Haeckel to work up the radiolarian ma- terial that had been gathered during that voyage. Murray showed Haeckel a little bottle containing water, with a deposit of seeming clay or mud in the bottom. "That mud," he said, "was dredged up from the bot- tom of the ocean, and every particle of it is the shell of a radiolarian . " " Impossible , ' ' said Haeckel . ' ' Yet true," replied Murray, "as the microscope will soon prove to you." So it did, and Professor Haeckel spent twelve years examining that mud under the microscope, with the result that, before he had done, he had discovered no fewer than four thousand new species of radiolarians, all of which, of course, had to be figured, described, and christened. Think of baptizing four thousand creat- ures, finding a new, distinct, and appropriate Latin name for each and every one, and that, too, when the creatures themselves are of microscopic size, and the difference between them often so slight that only the expert eye could detect it. Think, too, of the deadly tedium of labor in detecting these differences, in sketch- 154 HAECKEL AND THE NEW ZOOLOGY ing them, and in writing out, to the length of three monster volumes, technical dissertations upon them. To the untechnical reader that must seem a deadly, a veritably mind-sapping task. And such, indeed, it would prove to the average zoologist. But with the mind of a Haeckel it is far otherwise. To him a radio- larian, or any other creature, is of interest, not so much on its own account as for its associations. He sees it not as an individual but as a link in the scale of organic things, as the bearer of a certain message of world- history. Thus the radiolarians, insignificant creatures though they seem, have really taken an extraordinary share in building up the crust of the earth. The ooze at the bottom of the sea, which finally becomes meta- morphosed into chalk or stone, is but the aggregation of the shells of dead radiolarians. In the light of such a r61e the animalcule takes on a new interest. But even greater is the interest that attaches to every creature in regard to the question of its place in the organic scale of evolution. What are the homol- ogies of this form and that? What its probable an- cestry ? What gaps does it bridge ? What can it tell us of the story of animal creation? These and such like are the questions that have been ceaselessly before Haeckel' s mind in all his studies of zoology. Hence the rich fountain of philosophical knowledge that has welled up from what otherwise might have been the most barren of laboratory borings. Thus from a care- ful investigation of the sponge Haeckel was led to his famous gastrula theory, according to which the pouch- like sponge-animalcule — virtually a stomach without members — is the type of organism on which all high i55 A HISTORY OF SCIENCE organisms are built, so to speak — that is, out of which all have evolved. This gastrula theory, now generally accepted, is one of Haeckel's two great fundamental contributions to the evolution philosophy with the history of which his life work is so intimately linked. The other contribu- tion is the theory, even more famous and now equally undisputed, that every individual organism, in its em- bryological development, rehearses in slurred but un- mistakable epitome the steps of evolution by which the ancestors of that individual came into racial being. That is to say, every mammal, for example, originating in an egg stage, when it is comparable to a protozoon, passes through successive stages when it is virtually in succession a gastrula, a fish, and an amphibian before it attains the mammalian status, because its direct an- cestors were in succession, through the long geological ages, protozoons, gastrulae, fishes, amphibians before the true mammal was evolved. This theory cast a flood of light into many dark places of the Darwinian philosophy. It was propounded in 1866 in Professor Haeckel's great work on morphology, and it has ever since been a guiding principle in his important philo- sophical studies. It was through this same work on morphology that Haeckel first came to be universally recognized as the great continental champion of Darwinism — the Huxley of Germany. Like Huxley, Haeckel had at once made the logical application of the Darwinian theory to man himself, and he sought now to trace the exact lineage of the human family as no one had hither- to attempted to fathom it. Utilizing his wide range 156 HAECKEL AND THE NEW ZOOLOGY of zoological and anatomical knowledge, he constructed a hypothetical tree of descent — or, if you prefer, ascent — from the root in a protozoon to the topmost twig or most recent offshoot, man. From that day till this Haeckel's persistent labors have been directed towards the perfection of that genealogical tree. This work on morphology was much too technical to reach the general public, but in 1868 Haeckel pre- pared, at the instigation of his friend and confrere Gagenbaur, what was practically a popular abridg- ment of the technical work, which was published under the title of The Natural History of Creation. This work created a furor at once. It has been translated into a dozen languages, and has passed through nine edi- tions in the original German. Through it the name of Haeckel became almost a household word the world over, and subject for mingled applause and opprobri- um— applause from the unprejudiced for its great merit ; opprobrium from the bigoted because of the unprecedented candor with which it followed the Dar- winian hypothesis to its logical goal. The same complete candor of expression has marked every stage of the unfolding of Professor Haeckel's philosophical pronouncements. This fact is the more remarkable because Professor Haeckel is, so far as I am aware, the only scientist of our generation who has felt at liberty to announce, absolutely without reserve, the full conclusions to which his philosophy has car- ried him, when these conclusions ran counter to the prevalent prejudices of his time. Some one has said that the German universities are oases of freedom. The remark is absolutely true of Jena. It is not true, i57 A HISTORY OF SCIENCE I believe, in anything like the same degree of any other German university, or of any other university in the world. One thing before others that has endeared Jena to Haeckel, and kept him there in the face of re- peated flattering calls to other universities, is that full liberty of spirit has been accorded him there, as he knew it would not be accorded elsewhere. "When a man comes into the atmosphere of Jena," says Pro- fessor Haeckel, " he perforce begins to think — there is no escape from it. And he is free to let his thoughts carry him whithersoever they honestly may. My be- liefs," he added, "are substantially the beliefs of my colleagues in science everywhere, as I know from pri- vate conversations; but they, unlike myself, are not free to speak the full truth as they see it. I myself would not be tolerated elsewhere, as I am well aware. Had I desired to remain in Berlin, for example, I must have kept silent. But here in Jena one is free." And he smiles benignly as he says it. The contro- versies through which he has passed and the calum- nies of which he has been the target have left no scars upon this broad, calm spirit. HAECKEL AS MAN AND TEACHER It is indeed a delightful experience to meet Professor Haeckel in the midst of his charming oasis of freedom, his beloved Jena. To reach his laboratory you walk down a narrow lane, past Schiller's house, and the gar- den where Schiller and Goethe used to sit and where now the new observatory stands. Haeckel's laboratory itself is a simple oblong building of yellowish brick, standing on a jutting point of land high above the 158 HAECKEL AND THE NEW ZOOLOGY street-level. Entering it, your eye is first caught by a set of simple panels in the wall opposite the door bear- ing six illustrious names: Aristotle, Linne, Lamarck, Cuvier, Muller, Darwin — a Greek, a Swede, two Frenchmen, a German, and an Englishman. Such a list is significant; it tells of the cosmopolitan spirit that here holds sway. The ground-floor of the building is occupied by a lecture-room and by the zoological collection. The latter is a good working-collection, and purports to be nothing else. Of course it does not for a moment com- pare with the collections of the museums in any large city of Europe or America, nor indeed is it numerically comparable with many private collections, or collec- tions of lesser colleges in America. Similarly, when one mounts the stairs and enters the laboratory proper, he finds a room of no great dimensions and nowise startling in its appointments. It is admirably lighted, to be sure, and in all respects suitably equipped for its purpose, but it is by no means so large or so luxurious as the average college laboratory of America. In- deed, it is not to be mentioned in the same breath with the laboratories of a score or two of our larger colleges. Yet, with Haeckel here, it is unquestionably the finest laboratory in which to study zoology that exists in the world to-day, or has existed for the last third of a century. Haeckel himself is domiciled, when not instructing his classes, in a comfortable but plain room across the hall — a room whose windows look out across the valley of the Saale on an exquisite mountain landscape, with the clear-cut mountain that Schiller's lines made fa- i59 A HISTORY OF SCIENCE mous at its focus. As you enter the room a big, ro- bust man steps quickly forward to grasp your hand. Six feet or more in height, compactly built, without corpulence; erect, vigorous, even athletic; with florid complexion and clear, laughing, light-blue eyes that belie the white hair and whitening beard ; the ensemble personifying at once kindliness and virility, simplicity and depth, above all, frank, fearless honesty, without a trace of pose or affectation — such is Ernst Haeckel. There is something about his simple, frank, earnest, sympathetic, yet robust, masculine personality that reminds one instinctively, as does his facial contour also, of Walt Whitman. A glance about the room shows you at once that it is a place for study, and also that it is the room of the most methodical of students. There are books and papers everywhere, yet not the slightest trace of dis- order. Clearly every book and every parcel of papers has a place, and is kept in that place. The owner can at any moment lay his hand upon anything he de- sires among all these documents. This habit of order- liness has had no small share, I take it, in contributing to Professor Haeckel's success in carrying forward many lines of research at the same time, and carrying all to successful terminations. Then there goes with it, as a natural accompaniment, a methodical habit of working, without which no single man could have put behind him the multifarious accomplishments that stand to Professor Haeckel's credit. Orderliness is not a more pronounced innate gift with Professor Haeckel than is the gift of initial energy to undertake and carry on work which leads to accom- 160 HAECKEL AND THE NEW ZOOLOGY plishment — a trait regarding which men, even active men, so widely differ. But Professor Haeckel holds that whatever his normal bent in this direction, it was enormously strengthened in boyhood by the precepts of his mother— from whom, by-the-bye, he chiefly in- herits his talents. "My mother," he says, "would never permit me to be idle for a moment. If I stood at a window day-dreaming, she would always urge me to be up and doing. 'Work or play,' she would urge, 'but do not stand idle.' Through this reiterated ad- monition, physical activity became a life-long habit with me, and work almost a necessity of my being, If I have been able to accomplish my full share of la- bors, this is the reason. I am never idle, and I scarcely know the meaning of ennui." This must not be interpreted as meaning, however, that Professor Haeckel takes up a task and works at it all day long unceasingly. That is not the Ger- man method of working, and in this regard Professor Haeckel is a thorough German. " When I was a young man," he says, "I at one time, thanks to the persua- sions of some English friends, became a convert to the English method of working, and even attempted to introduce it into Germany. But I soon relinquished it, and lapsed back into our German method, which I am convinced will produce better results for the average worker. The essential of this method is the long mid- day rest, which enables one late in the afternoon to begin what is virtually a new day's-work, and carry it out with vigor and without undue fatigue. Thus I, who am an early riser, begin work at five in summer and six in winter, after the customary light breakfast VOL. V. — II l6l A HISTORY OF SCIENCE of coffee and rolls. I do not take a second breakfast at ten or eleven, as many Germans do, but work con- tinuously until one o'clock, when I have dinner. This, with me, as with all Germans, is the hearty meal of the day. After dinner I perhaps take a half-hour's nap; then read the newspaper, or chat with my family for an hour, and perhaps go for a long walk. At about four, like all Germans, I take my cup of coffee, but without cake or other food. Then, at four, having had three full hours of brain-rest and diversion, I am ready to go to work again, and can accomplish four hours more of work without undue fatigue. At eight I have my rather light supper, and after that I at- tempt no further work, giving the evening to read- ing, conversation, or other recreation. I do not retire till rather late, as I require only five or six hours' sleep." Such is the method of labor division that enables not Professor Haeckel only, but a host of other German brain-workers to accomplish enormous labors, yet to thrive on the accomplishment and to carry the rug- gedness and health of youth far into the decades that are too often with our own workers given over to de- crepitude. Haeckel at sixty-five looks as if he were good for at least a score of years of further effort. And should he fulfil the promise of his present rugged- ness, he will do no more than numbers of his col- leagues in German universities have done and are doing. When one runs over the list of octogenarians, and considers at the same time the amount of the in- dividual output of the best German workers, he is led to feel that Professor Haeckel was probably right in 162 HAECKEL AND THE NEW ZOOLOGY giving up the continuous-day method of labor and re- verting to the German method. In addition to the original researches that Professor Haeckel has carried out, to which I have already made some reference, there has, of course, been all along an- other large item of time-consumption to be charged up to his duties as a teacher. These, to be sure, are somewhat less exacting in the case of a German uni- versity professor than they are in corresponding posi- tions in England or America. Thus, outside the hours of teaching, Professor Haeckel has all along been able to find about eight hours a day for personal, original research. When he told Professor Huxley so in the days of their early friendship, Huxley exclaimed: " Then you ought to be the happiest man alive. Why, I can find at most but two hours a day to use for myself. ' ' So much for the difference between German methods of teaching, where the university professor usually confines his contact with the pupils to an hour's lecture each day, and the English system, according to which the lecturer is a teacher in other ways as well. Yet it must be added that in this regard Professor Haeckel is not an orthodox German, for his contact with his students is by no means confined to the lecture-hour. Indeed, if one would see him at his best, he must go, not to the lecture-hall, but to the laboratory proper during the hours when Professor Haeckel personally presides there, and brings knowledge and inspiration to the eager band of young dissectors who gather there. It will perhaps seem strange to the reader to be told that the hours on which this occurs are from nine 163 A HISTORY OF SCIENCE till one o'clock of a day which is perhaps not devoted to class-room exercises in any other school of Christen- dom whatever — namely, the Sabbath. It is interest- ing to reflect what would be the comment on such a procedure in London, for example, where the under- ground railway trains even must stop running during the hours of morning service. But Jena is not Lon- don, and, as Professor Haeckel says, "In Jena one is free. It pleases us to have our Sabbath service in our tabernacle of science." All questions of time aside, it is a favored body of young men who occupy the benches in the laboratory during Professor Haeckel's unique Sunday - morning service. Each student has before him a microscope and a specimen of the particular animal that is the subject of the morning's lesson. Let us say that the subject this morning is the crawfish. Then in addition to the specimens with which the students are provided, and which each will dissect for himself under the pro- fessor's guidance, there are scattered about the room, on the various tables, all manner of specimens of allied creatures, such as crabs, lobsters, and the like. There are dissected specimens also of the crawfish, each prep- aration showing a different set of organs, exhibited in preserving fluids. Then there are charts hung all about the room illustrating on a magnified scale, by diagram and picture, all phases of the anatomy of the subjects under discussion. The entire atmosphere of the place this morning smacks of the crawfish and his allies. The session begins with a brief off-hand discussion of the general characteristics and affinities of the group 164 HAECKEL AND THE NEW ZOOLOGY of arthropoda, of which the crawfish is a member. Then, perhaps, the professor calls the students about him and gives a demonstration of the curious phe- nomena of hypnotism as applied to the crawfish, through which a living specimen, when held for a few moments in a constrained attitude, will pass into a rigid "trance," and remain standing on its head or in any other grotesque position for an indefinite period, until aroused by a blow on the table or other shock. Such are some of the little asides, so to speak, with which the virile teacher enlivens his subject and gives it broad, human interest. Now each student turns to his microscope and his individual dissection, and the professor passes from one investigator to another with comment, suggestion, and criticism; answering ques- tions, propounding anatomical enigmas for solution — enlivening, vivifying, inspiring the entire situation. As the work proceeds, Professor Haeckel now and again calls the attention of the entire class to some par- ticular phase of the subject just passing under their individual observation, and in the most informal of talks, illustrated on blackboard and chart, clears up any lurking mysteries of the anatomy, or enlivens the subject with an incursion into physiology, embryology, or comparative morphology of the parts under obser- vation. Thus by the close of the session the student has something far more than a mere first-hand knowl- edge of the anatomy of the crawfish — though that in itself were much. He has an insight also into a half- dozen allied subjects. He has learned to look on the crawfish as a link in a living chain — a creature with physiological, psychological, ontological affinities that 16s A HISTORY OF SCIENCE give it a human interest not hitherto suspected by the novitiate. And when the entire series of Sunday- morning " services" has been carried through, one order after another of the animal kingdom being similarly made tribute, the favored student has gone far tow- ards the goal of a truly philosophical zoology, as differ- ent from the old-time dry-bones anatomy as the living crawfish is different from the dead shell which it casts off in its annual moulting time. THE NEW ZOOLOGY What, then, is the essence of this "philosophical zool- ogy," of which Haeckel is the greatest living exponent and teacher and of which his pupils are among the most active promoters? In other words, what is the real status, and the import and meaning, the raison d'etre, if you will, of the science of zoology to-day? To clear the ground for an answer to that question, one must glance backward, say half a century, and note the status of the zoology of that day, that one may see how utterly the point of view has changed since then ; what a different thing zoology has become in our gen- eration from what it was, for example, when young Haeckel was a student at Jena back in the fifties. At that time the science of zoology was a conglomeration of facts and observations about living things, grouped about a set of specious and sadly mistaken principles. It was held, following Cuvier, that the beings of the animal kingdom had been created in accordance with five preconceived types: the vertebrate, with a spinal column ; the articulate, with jointed body and members, as represented by the familiar crustaceans and insects ; 166 HAECKEL AND THE NEW ZOOLOGY the mollusk, of which the oyster and the snail are familiar examples; the radiate, with its axially dis- posed members, as seen in the starfish; and the low, almost formless protozoon, most of whose representa- tives are of microscopic size. Each of these so-called classes was supposed to stand utterly isolated from the others, as the embodiment of a distinct and tangible idea. So, too, of the lesser groups or orders within each class, and of the still more subordinate groups, named technically families, genera; and, finally, the individual species. That the grouping of species into these groups was more or less arbitrary was of course to some extent understood, yet it was not questioned by the general run of zoologists that a genus, for ex- ample, represented a truly natural group of species that had been created as variations upon one idea or plan, much as an architect might make a variety of houses, no one exactly like any other, yet all conform- ing to a particular type or genus of architecture — for example, the Gothic or the Romanesque. That each of the groups defined by the classifiers had such status as this was the stock doctrine of zoology, as also that the individual species making up the groups, and hence the groups themselves, maintained their individual identity absolutely unaltered from the moment of their creation, throughout all successive generations, to the end of their racial existence. Such being the fundamental conception of zoology, it remained only for the investigator to study each in- dividual species with an eye to its affinities with other species, that each might be assigned by a scientific classification to the particular place in the original 167 A HISTORY OF SCIENCE scheme of creation which it was destined to occupy. Once such affinities had been correctly determined and interpreted for all species, the zoological classification would be complete for all time. A survey of the com- pleted schedule of classification would then show at a glance the details of the preconceived system in ac- cordance with which the members of the animal king- dom were created, and zoology would be a "finished" science. In the application of this relatively simple scheme, to be sure, no end of difficulties were encountered. Each higher animal is composed of so many members and organs, of such diverse variations, that naturalists could never agree among themselves as to just where a balance of affinities between resemblances and differ- ences should be struck; whether, for example, a given species varied so much from the type species of a genus — say the genus Gothic house — as to belong properly to an independent genus — say Romanesque house; or whether, on the other hand, its divergencies were still so outweighed by its resemblances as to permit of its retention as an aberrant member of genus number one. Perpetual quibbling over these matters was quite the order of the day, no two authorities ever agreeing as to details of classification. The sole point of agreement was that preconceived types were in question — if only the zoologists could ever determine just what these types were. Meantime, the student who supposed classifications to be matters of moment, and who laboriously learned to label the animals and birds of his acquaintance with an authoritative Latin name, was perpetually obliged to unlearn what he had 168 HAECKEL AND THE NEW ZOOLOGY acquired, as a new classifier brought new resources of hair-splitting pursuit of a supposed type or ideal to bear on the subject. Where, for example, our great ornithologists of the early part of the century, such as Wilson and Audubon, had classed all our numerous hawks in a genus falco, later students split the group up into numerous genera— just how many it is impossi- ble to say, as no two authorities agreed on that point. Wilson, could he have come back a generation after his death, would have found himself quite at a loss to converse with his successors about the birds he knew and loved so well, using their technical names — though the birds themselves had not changed. Notwithstanding all the differences of opinion about matters of detail, however, there was, nevertheless, substantial agreement about the broader outlines of classifications, and it might fairly enough have been hoped that some day, when longer study had led to finer discrimination, the mysteries of all the types of creation would be fathomed. But then, while this hope still seemed far enough from realization, Charles Darwin came forward with his revolutionizing doctrine — and the whole time-honored myth of "types" of creation vanished in thin air. It became clear that the zoologists had been attempting a task utterly Sisyphean. They had sought to establish "natural groups" where groups do not exist in nature. They were eagerly peering after an ideal that had no existence outside their imagination. Their barriers of words could not be made to conform to barriers of nature, because in nature there are no barriers. What, then, was to be done? Should the whole 169 A HISTORY OF SCIENCE fabric of classification be abandoned? Clearly not, since there can be no science without classification of facts about labelled groupings, however arbitrary. Classifications then must be retained, perfected; only in future it must be remembered that any classification must be more or less arbitrary, and in a sense false; that it is at best only a verbal convenience, not the embodiment of a final ideal. If, for example, we con- sider the very "natural" group of birds commonly called hawks, we are quite justified in dividing this group into several genera or minor groups, each com- posed of several species more like one another than like the members of other groups of species — that is, of other genera. But in so doing we must remember that if we could trace the ancestry of our various species of hawks we should find that in the remote past the differences that now separate the groups had been less and less marked, and originally quite non-existent, all the various species having sprung from a common ancestor. The genera of to-day are cousin-groups, let us say ; but the parents of the existing species were of one brood, brothers and sisters. And what applies to the minor groups called genera applies also, going farther into the past, to all larger groups as well, so that in the last analysis, all existing creatures being really the evolved and modified descendants of one primordial type, it may be said that all animate crea- tion is but a single kind. In this broadened view the details of classification ceased to have the importance once ascribed to them, and the quibblings of the classi- fiers seem amusing rather than serious. Yet the changed point of view left the subject by no 170 HAECKEL AND THE NEW ZOOLOGY means barren of interest. For if the multitudinous creatures of the living world are but diversified twig- lets of a great tree of ascent, spread by branching from a common root, at least it is worth knowing what larger branches each group of twiglets — representing a genus, let us say — has sprung from. In particular, since the topmost twig of the tree is represented by man himself and his nearest relatives, is it of human interest to inquire just what branches and main stems will be come upon in tracing back the lineage of this particular offshoot. This attempt had, perhaps, no vast, vital importance in the utilitarian sense in which these terms are oftenest used, but at least it had human in- terest. Important or otherwise, it was the task that lay open to zoology, and apparently its only task, so soon as the Darwinian hypothesis had made good its status. The man who first took this task in hand, and who has most persistently and wisely followed it, and hence the man who became the recognized leader in the field of the new zoology, was, as I have already intimated, Professor Haeckel. His hypothetical tree of man's lineage, tracing the ancestry of the human family back to the earliest geological times and the lowest orders of beings, has been familiar now for just a third of a century. It was at first confessedly only a tentative genealogy, with many weak limbs and untraced branches. It was perfected from time to time, as new data came to hand, through studies of paleontology, of embryology, and of comparative anatomy. It will be of interest, then, to inquire just what is its status to- day and to examine briefly Professor Haeckel's own most recent pronouncement regarding it. 171 A HISTORY OF SCIENCE Perhaps it is not worth our while here to go too far down towards the root of the genealogical tree to begin our inquiry. So long as it is admitted that the remote ancestry is grounded in the lowest forms of organisms, it perhaps does not greatly matter to the average reader that there are dark places in the lineage during the period when our ancestor had not yet developed a spinal column — when, in other words, he had not attained the dignity of the lowest fish. Neither, perhaps, need we mourn greatly that the exact branch by which our reptilian or amphibian non-mammalian ancestor be- came the first and most primitive of mammals is still hidden in unexplored recesses of early strata. The most patrician monarch of to-day would not be great- ly disturbed as to just who were his ancestors of the days of the cave-dweller. It is when we come a little nearer home that the question begins to take on its seemingly personal significance. Questions of grand- parents and great-grandparents concern the patrician very closely. And so all along, the question that has interested the average casual investigator of the Dar- winian theory has been the question as to man's im- mediate ancestor— the parents and grandparents of our race, so to speak. Hence the linking of the word "monkey" with the phrase "Darwinian theory" in the popular mind ; and hence, also, the interpretation of the phrase "missing link" in relation to man's ancestry, as applying only to our ancestor and not to any other of the gaps in the genealogical chain. What, then, is the present status of Haeckel's genea- logical tree regarding man's most direct ancestor? From what non - human parent did the human race 172 HAECKEL AND THE NEW ZOOLOGY directly spring? That is a question that has proved itself of lasting, vital human interest. It is a question that long was answered only with an hypothesis, but which Professor Haeckel to-day professes to be able to answer with a decisive and affirmative citation not of theories but of facts. In a word, it is claimed that man's immediate ancestor is now actually upon record, that the much- heralded " missing link" is missing no longer. The principal single document, so to speak, on which this claim is based consists of the now famous skull and thigh-bone which the Dutch surgeon, Dr. Eugene Dubois, discovered in the year 1891 in the tertiary strata of the island of Java. Tertiary strata, it should be explained, had never hitherto yielded any fossils bordering on the human type, but this now famous skeleton was unmistakably akin to the human. The thigh in particular, taken by itself, would have been pronounced by any competent anatomist to be of hu- man origin. Unquestionably the individual who bore it had been accustomed to take an erect attitude in walking. And yet the skull was far inferior in size and shape to that of any existing tribe of man — was, in- deed, rather of a simian type, though, on the other hand, of about twice the capacity of any existing ape. In a word, it seemed clear that the creature whose part skeleton had been found by Dr. Dubois was of a type intermediate between the lowest existing man and the highest existing man-apes. It was, in short, the actual prototype of that hypothetical creature which Haeckel, in his genealogical tree, had christened pithecanthropus, the ape-man. As such it was christened Pithecan- thropus erectus, the erect ape-man. 173 A HISTORY OF SCIENCE Now the discovery of this remarkable form did not make Professor Haeckel any more certain that some such form had existed than he was thirty years before when he christened a hypothetical subject with the title now taken by a tangible claimant. But, after all, there is something very taking about a prophecy ful- filled, and so the appearance of Pithecanthropus erectus created no small sensation in the zoological world. He was hailed by Haeckel and his followers as the veritable "missing link," and as such gained immediate notori- ety. But, on the other hand, a reactionary party at once attacked him with the most bitter animadver- sions, denouncing him as no true ancestor of man with a bitterness that is hard to understand, considering that the origin of man from some lower form has long ceased to be matter of controversy. " Pithecanthropus is at least half an ape," they cried, with the clear im- plication of "anything but an ape for an ancestor!" I confess I have always found it hard to understand just why this peculiar aversion should always be held against the unoffending ape tribe. Why it would not be quite as satisfactory to find one's ancestor in an ape as in the alternative lines of, for example, the cow, or the hippopotamus, or the whale, or the dog has always been a mystery. Yet the fact of this prejudice holds. Probably we dislike the ape because of the very patency of his human affinities. The poor relation is objection- able not so much because he is poor as because he is a relation. So, perhaps, it is not the apeness, so to speak, of the ape that is objectionable, but rather the human- ness. In any event, the aversion has been matter of common notoriety ever since the Darwinian theory 174 HAECKEL AND THE NEW ZOOLOGY became fully accepted; it showed itself now with re- newed force against poor pithecanthropus . A half- score of objections were launched against him. It is needless to rehearse them now, since they were all met valiantly, and the final verdict saw the new-comer tri- umphantly ensconced in man's ancestral halls as the oldest sojourner there who has any title to be spoken of as " human." He is only half human, to be sure — a veritable ape-man, as his name implies — but exactly therein lies his altogether unique distinction. He is the embodiment of that "missing link" whose non- appearance had hitherto given so much comfort to the sceptical. Perhaps some crumbs of comfort may be found by the reactionists in the fact that it is not held by Pro- fessor Haeckel, or by any other competent authority, that the link which pithecanthropus supplies welds man directly with any existing man-ape — with gorilla, chimpanzee, or orang. It is held that these highest existing apes are side branches, so to say, of the an- cestral tree, who developed, in their several ways, contemporaneously with our direct ancestors, but are not themselves directly of the royal line. The existing ape that has clung closest to the direct ancestral type of our own race, it appears, is the gibbon — a creature far less objectionable in that role because of the very paucity of his human characteristics, as revealed to the casual observer. Gibbon-like fossil apes are known, in strata representing a time some millions of years ante- cedent to the epoch of pithecanthropus even, which are held to be directly of the royal line through which pithecanthropus , and the hypothetical Homo stupidus, 175 A HISTORY OF SCIENCE and the known Homo neanderthalensis, and, lastly, proud Homo sapiens himself have descended. Thus Professor Haeckel is able to make the affirmation, as he did recently before the International Zoological Congress in Cambridge, that man's line of descent is now clearly traced, from a stage back in the Eocene time when our ancestor was not yet more than half arrived to the ape's estate, down to the time of true human development. "There no longer exists," he says, "a 'missing link.' The phyletic continuity of the primate stem, from the oldest lemurs down to man himself, is an historical fact." It should, perhaps, be added that the force of this rather startling conclusion rests by no means exclu- sively upon the rinding of pithecanthropus and the other fossils, nor indeed upon any paleontological evidence whatever. These, of course, furnish data of a very tangible and convincing kind; but the evidence in its totality includes also a host of data from the realms of embryology and comparative anatomy — data which, as already suggested, enabled Professor Haeckel to predicate the existence of pithecanthropus long in ad- vance of his actual discovery. Whether the more re- mote gaps in the chain of man's ancestry will be bridged in a manner similarly in accord with Professor Haeckel's predications, it remains for future discoveries of zoolo- gist and paleontologist to determine. In any event, the recent findings have added an increment of glory to that philosophical zoology of which Professor Haeckel is the greatest living exponent. This tracing of genealogies is doubtless the most spectacular feature of the new zoology, yet it must be 176 HAECKEL AND THE NEW ZOOLOGY clear that the establishment of lines of evolution is at best merely a preparation for the all-important ques- tion, Why have these creatures, man included, evolved at all? That question goes to the heart of the new- zoological philosophy. A partial answer was, of course, given by Darwin in his great doctrine of natural selec- tion. But this doctrine, while explaining the preser- vation of favorable variations, made no attempt to account for the variations themselves. Professor Haeckel's contribution to the subject consisted in the revival of the doctrine of Lamarck, that individual variations, in response to environmental influences, are transmitted to the offspring, and thus furnish the ma- terial upon which, applying Darwin's principle, evolu- tion may proceed. This Lamarck-Haeckel doctrine was under a cloud for a recent decade, during the brief passing of the Weismannian myth, but it has now emerged, and stands as the one recognized factor in the origin of those variations whose cumulative preserva- tion through natural selection has resulted in the evo- lution of organic forms. But may there not be other factors, as yet unrecog- nized, that supplement the Lamarckian and Darwinian principles in bringing about this marvellous evolu- tion of beings ? That, it would seem, is the most vital question that the philosophical zoology of our genera- tion must hand on to the twentieth century. For to- day not even Professor Haeckel himself can give it answer. VOL. V.— 12 VII SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS THE PASTEUR INSTITUTE THE national egotism that characterizes the French mind is not without its compensations. It leads, for example, to the tangible recognition of the merits of the great men of the nation and to the promulgation of their names in many public ways. Thus it would be hard to mention a truly distinguished Frenchman of the older generations whose name has not been given to a street in Paris. Of the men of science thus honored, one recalls off-hand the names of Buff on, Cuvier, GeofTroy Saint-Hilaire, Pinel, Esquirol, La- marck, Laplace, Lavoisier, Arago, Claude Bernard, Broca — indeed, one could readily extend the list to tiresome dimensions. Moreover, it is a list that is periodically increased by the addition of new names, as occasion offers, for the Parisian authorities never hesitate to rechristen a street or a portion of a street, regardless of former associations. One of the most recent additions to this roll of fame is the name of Pasteur. The boulevard that bears that famous name is situated in a somewhat out-of-the-way corner of the city, though to reach it one has but to traverse the relatively short course of the Avenue de 178 LABORATORIES AND PROBLEMS Breteuil from so central a position as the tomb of Napoleon. The Boulevard Pasteur itself is a not long but very spacious thoroughfare, which will some day- be very beautiful, when the character of its environing buildings has somewhat changed and its quadruple rows of trees have had time for development. At present its chief distinction, in the eyes of most ob- servers, would probably be found in the fact that it is the location of the famous fete forain at one of the an- nually recurring stages of the endless itinerary of that noted function. During the period of this distinc- tion, which falls in the month of May, the boulevard becomes transformed into a veritable Coney Island of merry-go-rounds, shooting-galleries, ginger-bread booths, and clap-trap side-shows, to the endless de- light of throngs of pleasure-seekers. There is no sight in all Paris worthier inspection for the foreigner than the Boulevard Pasteur offers at this season, for one gains a deep insight into the psychology of a people through observation of the infantile delight with which the adult population here throws itself into the spirit of amusements which with other nations are for the most part reserved for school-children. Only a race either in childhood or senescence, it would seem, could thus give itself over with undisguised delight to the enchantments of wooden horses, cattle, cats, and pigs ; to the catching of wooden fish with hooks ; to the shooting at targets that one could almost touch with the gun-muzzle, and to the grave observation of side- show performances that would excite the risibilities of the most unsophisticated audience that could be found in the Mississippi Valley. 179 A HISTORY OF SCIENCE As we move among this light-hearted and light- headed throng we shall scarcely escape a feeling of good-humored contempt for what seems an inferior race. It will be wholesome, therefore, for us to turn aside from the boulevard into the Rue Dotot, which leads from it near its centre, and walk a few hundred yards away from the pleasure-seekers, where an evi- dence of a quite different and a no less characteristic phase of the national psychology will be before us. For here, within easy sound of the jangling discords of the or- gans that keep time for the march of the cheveaux de bois, rises up a building that is in a sense the monument of a man who was brother in blood and in sentiment to the revellers we have just left in the boulevard, yet whose career stamped him as one of the greatest men of genius of any race or any time. That man was Louis Pasteur. The building before us is the famous institute that bears his name. In itself this building is a simple and unimposing structure, yet of pleasing contour. It is as well placed as the surroundings permit, on a grassed terrace, a little back from the street, where a high iron fence guards it and gives it a degree of seclusion. There are other buildings visible in the rear, which, as one learns on entering, are laboratories and the like, where the rabbits and guinea-pigs and dogs that are so essential to the work of the laboratory are kept. On the terrace in front is a bronze statue of a boy struggling with a rabid dog — a reminder of the particular labor of the master-worker which led directly to the foundation of the institution. It will be remembered that it was primarily to give Pasteur a wider opportunity to apply 180 LABORATORIES AND PROBLEMS his newly discovered treatment for the prevention of rabies that the subscription was undertaken which led finally to the erection of the buildings before us and brought the Pasteur Institute in its present form into being. Of the other aims and objects of the institution I shall speak more at length in a moment. I have just said that the building before us is in effect the monument of the great savant. This is true in a somewhat more literal sense than might be sup- posed, for the body of Pasteur rests in a crypt at its base. The personal labors of the great discoverer were practically ended at the time when the institute was opened in 1888, on which occasion, as will be remem- bered, the scientific representatives of all nations gath- ered in Paris to do honor to the greatest Frenchman of his generation. He was spared to the world, however, for seven years more, during which time he fully or- ganized the work of the institution along the lines it has since followed, and was, of course, the animating spirit of all the labors undertaken there by his devoted students and assistants. He is the animating spirit of the institution still, and it is fitting that his body should rest in the worthy mausoleum within the walls of that building whose erection was the tangible cul- mination of his life labors. The sarcophagus is a shrine within this temple of science which will serve to stimulate generations of workers here to walk worthily in the footsteps of the great founder of the institution. For he must be an unimaginative per- son indeed who, passing beneath that arch bearing the simple inscription " Ici Repose Pasteur," could descend into the simple but impressive mausoleum and stand 181 A HISTORY OF SCIENCE beside the massive granite sarcophagus without feeling the same kind of mental uplift which comes from con- tact with a great and noble personality. The preten- tious tomb of Galileo in the nave of Santa Croce at Florence, and the crowded resting-place of Newton and Darwin in Westminster Abbey, have no such impres- siveness as this solitary vault where rests the body of Pasteur, isolated in death as the mightier spirits must always be in life. Aims and Objects of the Pasteur Institute If one chances to come to the institute in the later hours of the morning he will perhaps be surprised to find a motley company of men, women, and children, apparently of many nationalities and from varied walks of life, gathered about one of the entrances or sauntering near by. These are the most direct bene- ficiaries of the institution, the unfortunate victims of the bites of rabid dogs, who have come here to take the treatment which alone can give them immunity from the terrible consequences of that mishap. Rabies, or hydrophobia as it is more commonly termed with us, is well known to be an absolutely fatal malady, there being no case on record of recovery from the disease once fully established. Even the treatment which Pasteur developed and which is here carried out can- not avail to save the victim in whom the active symp- toms of the malady are actually present. But, fortu- nately, the disease is peculiarly slow in its onset, some- times not manifesting itself for weeks or months after the inoculation; and this delay, which formerly was to the patient a period of fearful doubt and anxiety, 182 LABORATORIES AND PROBLEMS now suffices, happily, for the application of the pro- tective inoculations which enable the person otherwise doomed to resist the poison and go unscathed. Thus it is that the persons who gather here each day to the number of fifty, or even one hundred, have the appear- ance of and the feelings of average health, though a large proportion of them bear in their systems, on arrival, the germs of a disease that would bring them speedily to a terrible end were it not that the genius of Pasteur had found a way to give them immunity. The number of persons who have been given the anti-rabic treatment here is more than twenty-five thousand. To have given safety to such an army of unfortunates is, indeed, enough merit for any single in- stitution ; but it must not be supposed that this record is by any manner of means the full measure of the benefits which the Institut Pasteur has conferred upon humanity. In point of fact, the preparation and use of the anti-rabic serum is only one of many aims of the institution, whose full scope is as wide as the entire domain of contagious diseases. Pasteur's per- sonal discoveries had demonstrated the relation of certain lower organisms, notably the bacteria, to the contagious diseases, and had shown the possibility of giving immunity from certain of these diseases through the use of cultures of the noxious bacteria themselves. He believed that these methods could be extended and developed until all the contagious diseases, which hitherto have accounted for so startling a proportion of all deaths, were brought within the control of med- ical science. His deepest thought in founding the institute was to supply a tangible seat of operations 183 A HISTORY OF SCIENCE for this attempted conquest, where the brilliant assist- ants he had gathered about him, and their successors in turn, might take a share in this great struggle, un- hampered by the material drawbacks which so often confront the would-be worker in science. He desired also that the institution should be a cen- tre of education along the lines of its work, adding thus an indirect influence to the score of its direct achieve- ments. In both these regards the institution has been and continues to be worthy of its founder. The Pasteur Institute is in effect a school of bacteriology, where each of the professors is at once a teacher and a brilliant investigator. The chief courses of instruction consist of two series each year of lectures and labora- tory demonstrations on topics within the field of bac- teriology. These courses, at which all the regular staff of the institution assist more or less, are open to phy- sicians and other competent students regardless of na- tionality, and they suffice to inculcate the principles of bacteriology to a large band of seekers each year. But more important, perhaps, than this form of edu- cational influence is the impetus given by the institute to the researches of a small, select band of investigators who have taken up bacteriology for a life work, and who come here to perfect themselves in the final nice- ties of the technique of a most difficult profession. Thus such men as Calmette, the discoverer of the serum treatment of serpent-poisoning, and Yersin, famous for his researches in the prevention and cure of cholera by inoculation, are "graduates" of the Pasteur In- stitute. Indeed, almost all the chief laborers in this field in the world to-day, including the directors of 184 ELIAS METCHNIKOFF LABORATORIES AND PROBLEMS practically all the daughter institutes bearing the same name that are now scattered all over the world, have had at least a share of their training in the mother in- stitute here in Paris. Of the work of the men who form the regular staff of the Pasteur Institute only a few words need be said here. Doctors Roux, Grancher, Metchnikoff, and Chamberland all had the privilege of sharing Pas- teur's labors during the later years of the master's life, and each of them is a worthy follower of the be- loved leader and at the same time a brilliant original investigator.1 Roux is known everywhere in connec- tion with the serum treatment of diphtheria, which he was so largely instrumental in developing. Grancher directs the anti-rabic department and allied fields. Metchnikoff, a Russian by birth and Parisian by adop- tion, is famous as the author of the theory that the white blood-corpuscles of the blood are the efficient agents in combating bacteria. Chamberland directs the field of practical bacteriology in its applications to hygiene, including the department in which protective serums are developed for the prevention of various diseases of domesticated animals, notably swine fever and anthrax. About one million sheep and half as many cattle are annually given immunity from an- thrax by the serum here produced. Of the patient and unremitting toil demanded of the investigator in this realm of the infinitely little ; of the skill in manipulation, the fertility of resource, the scrupulous exactness of experiment that are absolutely prerequisite to success; of the dangers that attend in- vestigations which deal with noxious germs, every one 185 A HISTORY OF SCIENCE who knows anything of the subject has some concep- tion, but those alone can have full comprehension who have themselves attempted to follow the devious and delicate pathways of bacteriology. But the goals to which these pathways lead have a tangibility that give them a vital interest for all the world. The hopes and expectations of bacteriology halt at nothing short of the ultimate extirpation of contagious diseases. The way to that goal is long and hard, yet in time it will be made passable. And in our generation there is no company of men who are doing more towards that end than the staff of that most famous of bacteriological laboratories the Pasteur Institute. THE VIRCHOW INSTITUTE OP PATHOLOGY Even were the contagious diseases well in hand, there would still remain a sufficient coterie of maladies whose origin is not due to the influence of living germs. There are, for example, many diseases of the digestive, nutritive, and excretory systems, of the heart and arteries, of the brain and nerves, and various less clearly localized abnormal conditions, that owe their origin to inherent defects of the organism, or to various indiscretions of food or drink, to unhygienic surround- ings, to material injuries, or to other forms of environ- mental stress quite dissociated from the action of bac- teria. It is true that one would need to use extreme care nowadays in denning more exactly the diseases that thus lie without the field of the bacteriologist, as that prying individual seems prone to claim almost everything within sight, and to justify his claim with the microscope ; but after that instrument has done its 1 86 LABORATORIES AND PROBLEMS best or worst, there will still remain a fair contingent of maladies that cannot fairly be brought within the domain of the ever-present "germ." On the other hand, all germ diseases have of course their particular effects upon the system, bringing their results within the scope of the pathologist. Thus while the bac- teriologist has no concern directly with any disease that is not of bacterial origin, the pathologist has a direct interest in every form of disease whatever; in other words, bacteriology, properly considered, is only a special department of pathology, just as pathology itself is only a special department of general medicine. Whichever way one turns in science, subjects are always found thus dovetailing into one another and refusing to be sharply outlined. Nevertheless, here as elsewhere, there are theoretical bounds that suffice for purposes of definition, if not very rigidly lived up to in practice; and we are justified in thinking of the pathologist (perhaps I should say the pathological anatomist) as the investigator of disease who is di- rectly concerned with effects rather than with causes, who aims directly at the diseased tissue itself and reasons only secondarily to the causes. His prob- lem is : given a certain disease (if I may be permitted this personified form of expression), to find what tis- sues of the body are changed by it from the normal and in what manner changed. It requires but a moment's reflection to make it clear that a certain crude insight into the solution of this problem, as regards all common diseases, must have been the common knowledge of medical men since the earliest times. Thus not even medical knowledge 187 A HISTORY OF SCIENCE was needed to demonstrate that the tissues of an in- flamed part become red and swollen; and numerous other changes of diseased tissues are almost equally patent. But this species of knowledge, based on microscopic inspection, was very vague and untrust- worthy, and it was only after the advent of the per- fected microscope, some three-quarters of a century ago, that pathological anatomy began to have any proper claim to scientific rank. Indeed, it was not until about the year 1865 that the real clew was dis- covered which gave the same impetus to pathology that the demonstration of the germ theory of disease gave at about the same time to etiology, or the study of causes of disease. This clew consisted of the final demonstration that all organic action is in the last re- sort a question of cellular activities, and, specifically, that all abnormal changes in any tissues of the body, due to whatever disease, can consist of nothing more than the destruction, or the proliferation, or the al- teration of the cells that compose that tissue. That seems a simple enough proposition nowadays, but it was at once revolutionary and inspiring in the day of its original enunciation some forty years ago. The man who had made the discovery was a young German physician, professor in the University of Frei- burg, by name Rudolph Virchow. The discovery made him famous, and from that day to this the name of Virchow has held somewhat the same position in the world of pathology that the name of Pasteur occupied in the realm of bacteriology. Virchow was called presently to a professorship in the University of Berlin. In connection with this chair he established his fa- 188 LABORATORIES AND PROBLEMS mous Institute of Pathology, which has been the Mecca of all students of pathology ever since. He did a host of other notable things as well, among others, entering the field of politics, and becoming a recognized leader there no less than in science. Indeed, it seemed dur- ing the later decades of his life as if one encountered Virchow in whatever direction one turned in Berlin, and one feels that it was not without reason that his compatriots spoke of him as "the man who knows everything." To the end he retained all the alertness of intellect and the energy of body that had made him what he was. One found him at an early hour in the morning attending to the routine of his hospital duties, his lectures, and clinical demonstrations. These fin- ished, he rushed off, perhaps to his parliamentary duties ; thence to a meeting of the Academy of Sciences, or to preside at the Academy of Medicine or at some other scientific gathering. And in intervals of these diversified pursuits he was besieged ever by a host of private callers, who sought his opinion, his advice, his influence in some matter of practical politics, of state- craft, or of science, or who, perhaps, had merely come the length of the continent that they might grasp the hand of the " father of pathology." In whatever capacity one sought him out, provided the seeking were not too presumptuous, one was sure to find the great savant approachable, courteous, even cordial. A man of multifarious affairs, he impressed one as having abundance of time for them all, and to spare. There is a leisureliness about the seeming habit of existence on the Continent that does not per- tain in America, and one felt the flavor of it quite as 189 A HISTORY OF SCIENCE much in the presence of this great worker as among those people who from our stand -point seem never really to work at all. This is to a certain extent ex- plained if one visited Virchow in his home, and found to his astonishment that the world - renowned physi- cian, statesman, pathologist, anthropologist was dom- iciled in a little apartment of the most modest equip- ment, up two flights, in a house of most unpretentious character. Everything was entirely respectable, alto- gether comfortable, to be sure; but it was a grade of living which a man of corresponding position in Amer- ica could not hold to without finding himself quite out of step with his confreres and the subject of endless comment. But in this city of universal apartment- house occupancy and relatively low average of display in living it is quite otherwise. Virchow lived on the same plane, generally speaking, with the other scien- tists of Europe; it is only from the American stand- point that there is any seeming disparity between his fame and his material station in life; nor do I claim this as a merit of the American stand-point. Be that as it may, however, our present concern lies not with these matters, but with Virchow the pathologist and teacher. To see the great scientist at his best in this role, it was necessary to visit the Institute of Pathology on a Thursday morning at the hour of nine. On the morning of our visit we found the students already assembled and gathered in clus- ters all about the room, examining specimens of morbid anatomy, under guidance of various laboratory assist- ants. This was to give them a general familiarity with the appearances of the disease-products that would be 190 LABORATORIES AND PROBLEMS described to them in the ensuing lecture. But what is most striking about the room was the very unique method of arrangement of the desk or table on which the specimens rested. It was virtually a long-drawn- out series of desks winding back and forth throughout the entire room, but all united into one, so that a speci- men passed along the table from end to end will make a zigzag tour of the room, passing finally before each person in the entire audience. To facilitate such tran- sit, there was a little iron railway all along the centre of the table, with miniature turn-tables at the corners, along which microscopes, with adjusted specimens for examination, might be conveyed without danger of maladjustment or injury. This may seem a small de- tail, but it is really an important auxiliary in the teach- ing by demonstration with specimens for which this room was peculiarly intended. The ordinary lectures of Professor Virchow were held in a neighboring am- phitheatre of conventional type. Of a sudden there was a hush in the hum of voices, as a little, thin, frail-seeming man entered and stepped briskly to the front of the room and upon the low plat- form before the blackboard in the corner. A mo- ment's pause for the students to take their places, and the lecturer, who of course was Virchow himself, began, in a clear, conversational voice, to discourse on the topic of the day, which chanced to be the formation of clots in blood-vessels. There was no particular at- tempt at oratory; rather the lecturer proceeded as if talking man to man, with no thought but to make his meaning perfectly clear. He began at once putting specimens in circulation, as supplied on his demand by 191 A HISTORY OF SCIENCE his assistants from a rather grewsome-looking collection before him. Now he paused to chaff the assistant who was making the labels, poking good-humored jokes at his awkwardness, but with no trace of sting. Again he became animated, his voice raised a little, his speech more vehement, as he advanced his own views on some contested theory or refuted the objections that some opponent had urged against him, always, however, with a smile lurking about his eyes or openly showing on his lips. Constantly the lecturer turned to the blackboard to illustrate with colored, crayons such points of his dis- course as the actual specimens in circulation might leave obscure. Everything must be made plain to every hearer or he would not be satisfied. One can but contrast such teaching as this with the lectures of the average German professor, who seems not to con- cern himself in the least as to whether anything is understood by any one. But Virchow had the spirit of the true teacher. He had the air of loving his task, old story as it was to him. Most of his auditors were mere students, yet he appealed to them as earnestly as if they were associates and equals. He seemed to try to put himself on their level — to make his thought near to them. Physically he was near to them as he talked, the platform on which he stood being but a few inches in height, and such physical nearness con- duces to a familiarity of discourse that is best fitted for placing lecturer and hearers en rapport. All in all, appealing as it does almost equally to ear and eye, it is a type of what a lecturer should be. Not a student there but went away with an added fund of information, 192 PROFESSOR RUDOLF VIRCHOW IN HIS LABORATORY LABORATORIES AND PROBLEMS which is far more than can be said of most of the lect- ures in a German university. Needless to say, there are other departments to the Institute of Pathology. There are collections of beau- tifully preserved specimens for examination ; rooms for practical experimentation in all phases of the subject, the chemical side included; but these are not very different from the similar departments of similar in- stitutions everywhere. What was unique and charac- teristic about this institution was the personality of the director. Now he is gone, but his influence will not soon be forgotten. The pupils of a great teacher are sure to carry forward the work somewhat in the spirit of the master for at least a generation. THE BERLIN INSTITUTE OF HYGIENE I purposely refrain from entering into any details as to the character of the technical work done at the Virchow Institute, because the subject of pathology, despite its directly practical bearings, is in itself neces- sarily somewhat removed from the knowledge of the general reader. One cannot well understand the de- tails of changes in tissues under abnormal conditions unless one first understands the normal conditions of the tissues themselves, and such knowledge is reserved for the special students of anatomy. For the non- professional observer the interest of the Virchow In- stitute must lie in its general scope rather than in the details of the subjects there brought under investiga- tion, which latter have, indeed, of necessity, a some- what grewsome character despite the beneficent re- sults that spring from them. It is quite otherwise, VOL. V.— 13 193 A HISTORY OF SCIENCE however, with the work of the allied institution of which I now come to speak. The Institute of Hygiene deals with topics not very remote from those studied in the Virchow Institute, part of its work, indeed, falling clearly within the scope of pathology ; but it differs in being clearly comprehensible to the general public and of immediate and tangible interest from the most strict- ly utilitarian stand-point, hygiene being, in effect, the tangible link between the more abstract medical sciences and the affairs of every-day life. The Institute of Hygiene has also the interest that always attaches to association with a famous name, for it was here that Professor Koch made the greater part of those investigations which made his name the best known, next to that of Pasteur, of any in the field of bacteriology. In particular, the researches on the cholera germ, and those even more widely heralded researches that led to the discovery of the bacillus of tuberculosis, and the development of the remedy tuber- culin, of which so much was at first expected, were made by Professor Koch in the laboratories of the antiquated building which was then and is still the seat of the Institute of Hygiene. More recently Pro- fessor Koch has severed his connection with the in- stitution after presiding over it for many years, having now a semi-private laboratory just across from the Virchow Institute, in connection with the Charite Hospital; but one still thinks of the Institute of Hy- giene as peculiarly the "Koch Institute" without in- justice, so fully does its work follow the lines laid out for it by the great leader. But however much the stamp of any individual per- 194 LABORATORIES AND PROBLEMS sonality may rest upon the institute, it is officially a de- partment of the university, just as is the Virchow In- stitute. Like the latter, also, its local habitation is an antiquated building, strangely at variance, according to American ideas, with its reputation, though by no means noteworthy in this regard in the case of a German institution. It is situated in a part of the city distant from any other department of the university, and there is nothing about it exteriorly to distinguish it from other houses of the solid block in which it stands. Interiorly, it reminds one rather of a con- verted dwelling than a laboratory proper. Its rooms are well enough adapted to their purpose, but they give one the impression of a makeshift. The smallest American college would be ill - satisfied with such an equipment for any department of its work. Yet in these dingy quarters has been accomplished some of the best work in the new science of bacteriology that our century will have to boast. The actual equipment of the bacteriological labora- tory here is not, indeed, quite as meagre as it seems at first, there being numerous rooms, scattered here and there, which in the aggregate give opportunity for work to a large number of investigators, though no single room makes an impressive appearance. There is one room, however, large enough to give audience to a considerable class, and here lectures were given by Professor Koch and continue to be given by his successors to the special students of bacteriology who come from all over the world, as well as to the uni- versity students who take the course as a part of their regular medical curriculum. In regard to this feature J95 A HISTORY OF SCIENCE of its work, the Institute of Hygiene differs in no es- sential respect from the Pasteur Institute and other laboratories of bacteriology. The same general rou- tine of work pertains: the patient cultivation of the minute organisms in various mediums, their careful staining by special processes, and their investigation under the microscope mark the work of the bacteriol- ogist everywhere. Many details of the special methods of culture or treatment originated here with Professor Koch, but such matters are never kept secret in science, so one may see them practised quite as generally and as efficiently in other laboratories as in this one. In- deed, it may frankly be admitted that, aside from its historical associations with the pioneer work in bacteri- ology, which will always make it memorable, there is nothing about the bacteriological laboratory here to give it distinction over hundreds of similar ones else- where; while in point of technical equipment, as al- ready noted, it is remarkable rather for what it lacks than for what it presents. The department of bacteriology, however, is only one of several important features of the institute. One has but to ascend another flight of stairs to pass out of the sphere of the microbe and enter a department where attention is directed to quite another field. We have now come to what may be considered the laboratory of hygiene proper, since here the investigations have to do directly with the functionings of the human body in their relations to the every-day environment. Here again one is struck with the meagre equipment with which important results may be attained by pa- tient and skilled investigators. In only one room does 196 LABORATORIES AND PROBLEMS one find a really elaborate piece of apparatus. This exceptional mechanism consists essentially of a cab- inet large enough to give comfortable lodgment to a human subject — a cabinet with walls of peculiar struct- ure, partly of glass, and connected by various pipes with sundry mysterious-seeming retorts. This single apparatus, however, is susceptible of being employed for the investigation of an almost endless variety of questions pertaining to the functionings of the human body considered as a working mechanism. Thus, for example, a human subject to be experi- mented upon may remain for an indefinite period within this cabinet, occupied in various ways, taking physical exercise, reading, engaged in creative mental labor, or sleeping. Meantime, air is supplied for respiration in measured quantities, and of a precisely determined composition, as regards chemical impurities, moisture, and temperature. The air after passing through the chamber being again analyzed, the exact constituents added to it as waste products of the human machine in action under varying conditions are determined. It will readily be seen that by indefinitely varying the conditions of such experiments a great variety of data may be secured as to the exact physiological accom- paniments of various bodily and mental activities. Such data are of manifest importance to the physiolo- gist and pathologist on the one hand, while at the same time having a direct bearing on such eminently prac- tical topics as the construction of shops, auditoriums, and dwellings in reference to light, heat, and ventila- tion. It remains only for practical architecture to take advantage of the unequivocal data thus placed at 197 A HISTORY OF SCIENCE its disposal — an opportunity of which practical archi- tecture, in Germany as elsewhere on the Continent, has hitherto been very slow to avail itself. The Museum of Hygiene The practical lessons thus given in the laboratory are supplemented in an even more tangible manner, because in a way more accessible to the public, in an- other department of the institution which occupies a contiguous building, and is known as the Museum of Hygiene. This, unlike the other departments of the institute, is open to the general public on certain days of each week, and it offers a variety of exhibits of dis- tinctly novel character and of high educational value. The general character of the exhibits may be inferred from the name, but perhaps the scope is even wider than might be expected. In a word, it may be said that scarcely anything having to do with practical hygiene has been overlooked. Thus one finds here numberless models of dwelling-houses, showing details of lighting, heating, and ventilation ; models not merely of individual dwellings, but also of school - buildings, hospitals, asylums, and even prisons. Sometimes the models represent merely ideal buildings, but more gen- erally they reproduce in miniature actual habitations. In the case of the public buildings, the model usually includes not merely the structures themselves but the surroundings — lawns, drives, trees, out-buildings — so that one can get a very good idea of the more important hospitals, asylums, and prisons of Germany by making a tour of the Museum of Hygiene. Regarding the de- tails of structure, one can actually gain a fuller knowl- 198 LABORATORIES AND PROBLEMS edge in many cases than he could obtain by actual visits to the original institutions themselves. The same thing is true of various other features of the subjects represented. Thus there is a very elaborate model here exhibited of the famous Berlin system of sewage-disposal. As is well known, the essential features of this system consist of the drainage of sewage into local reservoirs, from which it is forced by pumps, natural drainage not sufficing, to distant fields, where it is distributed through tile pipes laid in a net- work about a yard beneath the surface of the soil. The fields themselves, thus rendered fertile by the waste products of the city, are cultivated, and yield a rich harvest of vegetables and grains of every variety suit- able to the climate. The visitor to this field sees only rich farms and market-gardens under ordinary proc- ess of cultivation. The system of pipes by which the land is fertilized is as fully hidden from his view as are, for example, the tributary sewage-pipes beneath the city pavements. The average visitor to Berlin knows nothing, of course, about one or the other, and goes away, as he came, ignorant of the important fact that Berlin has reached a better solution of the great sewage problem than has been attained by any other large city. Such, at least, is likely to be the case unless the sight-seer chance to pay a visit to the Museum of Hygiene, in which case a few minutes' inspection of the model there will make the matter entirely clear to him. It is to be regretted that the authorities of other large cities do not make special visits to Berlin for this purpose; though it should be added that some of them have done so, and that the Berlin system of "canalization" 199 A HISTORY OF SCIENCE has been adopted in various places in America. But many others might wisely follow their example, nota- bly the Parisians, whose sewerage system, despite the boasted exhibition canal-sewer, is, like so many other things Parisian, of the most primitive character and a reproach to present-day civilization. It may be added that there are plenty of things ex- hibited in this museum which the Germans themselves might study to advantage, for it must be understood that the other hygienic conditions pertaining to Berlin are by no means all on a par with the high modern standard of the sewerage system. In the matter of ven- tilation, for example, one may find admirable models in the museum, showing just how the dwelling and shop and school-room should make provision for a proper supply of pure air for their occupants. But if one goes out from the museum and searches in the actual dwelling or shop or school-room for the counter- parts of these models, one will be sorely puzzled where to find them. The general impression which a casual inspection will leave in his mind is that the word ven- tilation must be as meaningless to the German mind as it is, for example, to the mind of a Frenchman or an Italian. This probably is not quite just, since the German has at least reached the stage of having mu- seum models of ventilated houses, thus proving that the idea does exist, even though latent, in his men- tal equipment, whereas the other continental nation- alities seem not to have reached even this incipient stage of progress. All over Europe the people fear a current of air as if veritable miasm must lurk in it. They seem quite oblivious to any systematic necessity 200 LABORATORIES AND PROBLEMS for replenishing the oxygen supply among large assem- blies, as any one can testify who has, for example, vis- ited their theatres or schools. And as to the private dwellings, after making them as nearly air-tight as practicable, they endeavor to preserve the status quo as regards air supply seemingly from season to season. They even seem to have passed beyond a mere nega- tive regard for the subject of fresh air, inasmuch as they will bravely assure you that to sleep in a room with an open window will surely subject you to the penalty of inflamed eyes. In a country like France, where the open fireplace is the usual means employed to modify the tempera- ture (I will not say warm the room), the dwellings do of necessity get a certain amount of ventilation, particu- larly since the windows are not usually of the best con- struction. But the German, with his nearly air-tight double windows and his even more nearly sealed tile stove, spends the winter in an atmosphere suggestive of the descriptions that arctic travellers give us of the air in the hut of an Eskimo. It is clear, then, that the models in the Museum of Hygiene have thus far failed of the proselyting purpose for which they were presumably intended. How it has chanced that the inhabitants of the country maintain so high an average of robust health after this open defiance is a subject which the physiological department of the Institute of Hygiene might well investigate. Even though the implied precepts of the Museum of Hygiene are so largely disregarded, however, it must be admitted that the existence of the museum is a hope- ful sign. It is a valuable educational institution, and 201 A HISTORY OF SCIENCE if its salutary lessons are but slowly accepted by the people, they cannot be altogether without effect. At least the museum proves that there are leaders in science here who have got beyond the range of eigh- teenth-century thought in matters of practical living, and the sign is hopeful for the future, though its prom- ise will perhaps not be fulfilled in our generation. VII SOME UNSOLVED SCIENTIFIC PROBLEMS IN recent chapters we have witnessed a marvellous development in many branches of pure science. In viewing so wonderfully diversified a field, it has of course been impossible to dwell upon details, or even to glance at every minor discovery. At best one could but summarize the broad sweep of progress somewhat as a battle might be described by a distant eye-witness, telling of the general direction of action, of the move- ments of large masses, the names of leaders of brigades and divisions, but necessarily ignoring the lesser fluct- uations of advance or recession and the individual gallantry of the rank and file. In particular, interest has centred upon the storming of the various special strongholds of ignorant or prejudiced opposition, which at last have been triumphantly occupied by the band of progress. In each case where such a stronghold has fallen, the victory has been achieved solely through the destructive agency of newly discovered or newly marshalled facts — the only weapons which the warrior of science seeks or cares for. Facts must be mar- shalled, of course, about the guidon of a hypothesis, but that guidon can lead on to victory only when the facts themselves support it. Once planted victoriously on the conquered ramparts the hypothesis becomes a theory — a generalization of science — marking a fresh 203 A HISTORY OF SCIENCE coign of vantage, which can never be successfully as- sailed unless by a new host of antagonistic facts. Such generalizations, with the events leading directly up to them, have chiefly occupied our attention. But a moment's reflection makes it clear that the battle of science, thus considered, is ever shifting ground and never ended. Thus at any given period there are many unsettled skirmishes under way ; many hypotheses are yet only struggling towards the strong- hold of theory, perhaps never to attain it; in many directions the hosts of antagonistic facts seem so evenly matched that the hazard of war appears uncertain ; or, again, so few facts are available that as yet no attack worthy the name is possible. Such unsettled contro- versies as these have, for the most part, been ignored in our survey of the field. But it would not be fair to conclude our story without adverting to them, at least in brief; for some of them have to do with the most comprehensive and important questions with which science deals, and the aggregate number of facts in- volved in these unfinished battles is often great, even though as yet the marshalling has not led to final vic- tory for any faction. In some cases, doubtless, the right hypothesis is actually in the field, but its suprem- acy not yet conclusively proved — perhaps not to be proved for many years or decades to come. Some of the chief scientific results of the nineteenth century have been but the gaining of supremacy for hypotheses that were mere forlorn hopes, looked on with general contempt, if at all heeded, when the eighteenth century came to a close — witness the doctrines of the great age of the earth, c\f the immateriality of heat, of the un- 204 SOME UNSOLVED SCIENTIFIC PROBLEMS dulatory character of light, of chemical atomicity, of organic evolution. Contrariwise, the opposite ideas to all of these had seemingly a safe supremacy until the new facts drove them from the field. Who shall say, then, what forlorn hope of to-day's science may not be the conquering host of to-morrow? All that one dare attempt is to cite the pretensions of a few hy- potheses that are struggling over the still contested ground. SOLAR AND TELLURIC PROBLEMS Our sun being only a minor atom of the stellar peb- ble, solar problems in general are of course stellar problems also. But there are certain special ques- tions regarding which we are able to interrogate the sun because of his proximity, and which have, further- more, a peculiar interest for the residents of our little globe because of our dependence upon this particular star. One of the most far-reaching of these is as to where the sun gets the heat that he gives off in such liberal quantities. We have already seen that Dr. Mayer, of conservation-of-energy fame, was the first to ask this question. As soon as the doctrine of the per- sistence and convertibility of energy was grasped, about the middle of the century, it became clear that this was one of the most puzzling of questions. It did not at all suffice to answer that the sun is a ball of fire, for computation showed that, at the present rate of heat-giving, if the sun were a solid mass of coal, he would be totally consumed in about five thousand years. As no such decrease in size as this implies had taken place within historic times, it was clear that some other explanation must be sought. 205 A HISTORY OF SCIENCE Dr. Mayer himself hit upon what seemed a tenable solution at the very outset. Starting from the ob- served fact that myriads of tiny meteorites are hurled into the earth's atmosphere daily, he argued that the sun must receive these visitants in really enormous quantities — sufficient, probably, to maintain his tem- perature at the observed limits. There was nothing at all unreasonable about this assumption, for the amount of energy in a swiftly moving body capable of being transformed into heat if the body be arrested is relatively enormous. Thus it is calculated that a pound of coal dropped into the sun from the mathe- matician's favorite starting-point, infinity, would pro- duce some six thousand times the heat it could en- gender if merely burned at the sun's surface. In other words, if a little over two pounds of material from in- finity were to fall into each square yard of the sun's surface each hour, his observed heat would be account- ed for; whereas almost seven tons per square yard of stationary fuel would be required each hour to produce the same effect. In view of the pelting which our little earth receives, it seemed not an excessive requisition upon the meteoric supply to suppose that the requisite amount of matter may fall into the sun, and for a time this explanation of his incandescence was pretty generally accepted. But soon astronomers began to make calculations as to the amount of matter which this assumption added to our solar system, particularly as it aggregated near the sun in the converging radii, and then it was clear that no such mass of matter could be there without interfering demonstrably with the observed course of the interior 206 SOME UNSOLVED SCIENTIFIC PROBLEMS planets. So another source of the sun's energy had to be sought. It was found forthwith by that other great German, Helmholtz, who pointed out that the falling matter through which heat may be generated might just as well be within the substance of the sun as with- out— in other words, that contraction of the sun's heated body is quite sufficient to account for a long-sustained heat-supply which the mere burning of any known substance could not approach. Moreover the amount of matter thus falling towards the sun's centre being enormous — namely, the total substance of the sun — a relatively small amount of contraction would be theo- retically sufficient to keep the sun's furnace at par, so to speak. At first sight this explanation seemed a little puzzling to many laymen and some experts, for it seemed to im- ply, as Lord Kelvin pointed out, that the sun contracts because it is getting cooler, and gains heat because it contracts. But this feat is not really as paradoxical as it seems, for it is not implied that there is any real gain of heat in the sun's mass as a whole, but quite the re- verse. All that is sought is an explanation of a main- tenance of heat-giving capacity relatively unchanged for a long, but not an interminable, period. Indeed, ex- actly here comes in the novel and startling feature of Helmholtz' s calculation. According to Mayer's me- teoric hypothesis, there were no data at hand for any estimate whatever as to the sun's permanency, since no one could surmise what might be the limits of the meteoric supply. But Helmholtz's estimate implied an incandescent body cooling — keeping up a some- what equable temperature through contraction for a 207 A HISTORY OF SCIENCE time, but for a limited time only; destined ultimately to become liquid, solid ; to cool below the temperature of incandescence — to die. Not only so, but it became possible to calculate the limits of time within which this culmination would probably occur. It was only necessary to calculate the total amount of heat which could be generated by the total mass of our solar sys- tem in falling together to the sun's centre from " infin- ity" to find the total heat-supply to be drawn upon. Assuming, then, that the present observed rate of heat- giving has been the average maintained in the past, a simple division gives the number of years for which the original supply is adequate. The supply will be ex- hausted, it will be observed, when the mass comes into stable equilibrium as a solid body, no longer subject to contraction, about the sun's centre — such a body, in short, as our earth is at present. This calculation was made by Lord Kelvin, Professor Tait, and others, and the result was one of the most truly dynamitic surprises of the century. For it transpired that, according to mathematics, the entire limit of the sun's heat-giving life could not exceed something like twenty -five millions of years. The publication of that estimate, with the appearance of authority, brought a veritable storm about the heads of the physicists. The entire geological and biological worlds were up in arms in a trice. Two or three gen- erations before, they hurled brickbats at any one who even hinted that the solar system might be more than six thousand years old ; now they jeered in derision at the attempt to limit the life-bearing period of our globe to a paltry fifteen or twenty millions. 208 SOME UNSOLVED SCIENTIFIC PROBLEMS The controversy as to solar time thus raised proved one of the most curious and interesting scientific dispu- tations of the century. The scene soon shifted from the sun to the earth ; for a little reflection made it clear that the data regarding the sun alone were not suffi- ciently definite. Thus Dr. Croll contended that if the parent bodies of the sun had chanced to be "flying stars" before collision, a vastly greater supply of heat would have been engendered than if the matter merely fell together. Again, it could not be overlooked that a host of meteors are falling into the sun, and that this source of energy, though not in itself sufficient to ac- count for all the heat in question, might be sufficient to vitiate utterly any exact calculations. Yet again, Pro- fessor Lockyer called attention to another source of variation, in the fact that the chemical combination of elements hitherto existing separately must produce large quantities of heat, it being even suggested that this source alone might possibly account for all the present output. On the whole, then, it became clear that the contraction theory of the sun's heat must it- self await the demonstration of observed shrinkage of the solar disk, as viewed by future generations of ob- servers, before taking rank as an incontestable theory, and that computations as to time based solely on this hypothesis must in the mean time be viewed askance. But the time controversy having taken root, new methods were naturally found for testing it. The ge- ologists sought to estimate the period of time that must have been required for the deposit of the sedimentary rocks now observed to make up the outer crust of the earth. The amount of sediment carried through the VOL. IV.— 14 209 A HISTORY OF SCIENCE mouth of a great river furnishes a clew to the rate of denudation of the area drained by that river. Thus the studies of Messrs. Humphreys and Abbot, made for a different purpose, show that the average level of the territory drained by the Mississippi is being reduced by about one foot in six thousand years. The sediment is, of course, being piled up out in the Gulf at a proportion- ate rate. If, then, this be assumed to be an average rate of denudation and deposit in the past, and if the total thickness of sedimentary deposits of past ages were known, a simple calculation would show the age of the earth's crust since the first continents were form- ed. But unfortunately these "ifs" stand mountain- high here, all the essential factors being indeterminate. Nevertheless, the geologists contended that they could easily make out a case proving that the constructive and destructive work still in evidence, to say nothing of anterior revolutions, could not have been accom- plished in less than from twenty-five to fifty millions of years. This computation would have carried little weight with the physicists had it not chanced that another computation of their own was soon made which had even more startling results. This computation, made by Lord Kelvin, was based on the rate of loss of heat by the earth. It thus resembled the previous solar estimate in method. But the result was very dif- ferent, for the new estimate seemed to prove that a period of from one hundred to two hundred millions of years has elapsed since the final crust of the earth formed. With this all controversy ceased, for the most grasp - 210 SOME UNSOLVED SCIENTIFIC PROBLEMS ing geologist or biologist would content himself with a fraction of that time. But the case for the geologist was to receive yet another prop from the studies of radio-activity, which seem to prove that the atom of matter has in store a tremendous supply of potential energy which may be drawn on in a way to vitiate utterly all the computations to which I have just re- ferred. Thus a particle of radium is giving out heat incessantly in sufficient quantity to raise its own weight of water to the boiling-point in an hour. The demon- strated wide distribution of radio-active matter — making it at least an open question whether all matter does not possess this property in some degree — has led to the suggestion that the total heat of the sun may be due to radio-active matter in its substance. Ob- viously, then, all estimates of the sun's age based on the heat-supply must for the present be held quite in abeyance. What is more to the point, however, is the fact, which these varying estimates have made patent, that computations of the age of the earth based on any data at hand are little better than rough guesses. Long before the definite estimates were undertaken, geologists had proved that the earth is very, very old, and it can hardly be said that the attempted computa- tions have added much of definiteness to that propo- sition. They have, indeed, proved that the period of time to be drawn upon is not infinite ; but the nebular hypothesis, to say nothing of common-sense, carried us as far as that long ago. If the computations in question have failed of their direct purpose, however, they have been by no means lacking in important collateral results. To mention 211 A HISTORY OF SCIENCE but one of these, Lord Kelvin was led by this controver- sy over the earth's age to make his famous computa- tion in which he proved that the telluric structure, as a whole, must have at least the rigidity of steel in order to resist the moon's tidal pull as it does. Hopkins had, indeed, made a somewhat similar estimate as early as 1839, proving that the earth's crust must be at least eight hundred or a thousand miles in thickness; but geologists had utterly ignored this computation, and the idea of a thin crust on a fluid interior had continued to be the orthodox geological doctrine. Since Lord Kelvin's estimate was made, his claim that the final crust of the earth could not have formed until the mass was solid throughout, or at least until a honeycomb of solid matter had been bridged up from centre to cir- cumference, has gained pretty general acceptance. It still remains an open question, however, as to what proportion the lacunae of molten matter bear at the present day to the solidified portions, and therefore to what extent the earth will be subject to further shrink- age and attendant surface contortions. That some such lacunae do exist is demonstrated daily by the phenomena of volcanoes. So, after all, the crust theory has been supplanted by a compromise theory rather than completely overthrown, and our knowledge of the condition of the telluric depths is still far from definite. If so much uncertainty attends these fundamental questions as to the earth's past and present, it is not strange that open problems as to her future are still more numerous. We have seen how, according to Professor Darwin's computations, the moon threatens to come back to earth with destructive force some 212 SOME UNSOLVED SCIENTIFIC PROBLEMS day. Yet Professor Darwin himself urges that there are elements of fallibility in the data involved that rob the computation of all certainty. Much the same thing is true of perhaps all the estimates that have been made as to the earth's ultimate fate. Thus it has been sug- gested that, even should the sun's heat not forsake us, our day will become month-long, and then year-long; that all the water of the globe must ultimately filter into its depths, and all the air fly off into space, leaving our earth as dry and as devoid of atmosphere as the moon ; and, finally, that ether-friction, if it exist, or, in default of that, meteoric friction, must ultimately bring the earth back to the sun. But in all these prog- nostications there are possible compensating factors that vitiate the estimates and leave the exact results in doubt. The last word of the cosmic science of our generation is a prophecy of evil — if annihilation be an evil. But it is left for the science of another genera- tion to point out more clearly the exact terms in which the prophecy is most likely to be fulfilled. PHYSICAL PROBLEMS In regard to all these cosmic and telluric problems, it will be seen, there is always the same appeal to one central rule of action — the law of gravitation. When we turn from macrocosm to microcosm it would appear as if new forces of interaction were introduced in the powers of cohesion and of chemical action of molecules and atoms. But Lord Kelvin has argued that it is pos- sible to form such a conception of the forms and space relations of the ultimate particles of matter that their mutual attractions may be explained by invoking that 213 A HISTORY OF SCIENCE same law of gravitation which holds the stars and plan- ets in their course. What, then, is this all-compassing power of gravitation which occupies so central a posi- tion in the scheme of mechanical things ? The simple answer is that no man knows. The wisest physicist of to-day will assure you that he knows absolutely nothing of the why of gravitation — that he can no more explain why a stone tossed into the air falls back to earth than can the boy who tosses the stone. But while this statement puts in a nutshell the scientific status of explanations of gravitation, yet it is not in human nature that speculative scientists should refrain from the effort to explain it. Such efforts have been made; yet, on the whole, they are surprisingly few in number; indeed, there are but two that need claim our attention here, and one of these has hardly more than historical interest. One of these is the so-called ultramundane-corpuscle hypothesis of Le Sage; the other is based on the vortex theory of matter. The theory of Le Sage assumes that the entire uni- verse is filled with infinitely minute particles flying in right lines in every direction with inconceivable rapid- ity. Every mass of tangible matter in the universe is incessantly bombarded by these particles, but any two non-contiguous masses (whether separated by an in- finitesimal space or by the limits of the universe) are mutually shielded by one another from a certain num- ber of the particles, and thus impelled towards one another by the excess of bombardment on their oppo- site sides. What applies to two masses applies also, of course, to any number of masses — in short, to all the 214 SOME UNSOLVED SCIENTIFIC PROBLEMS matter in the universe. To make the hypothesis work- able, so to say, it is necessary to assume that the " ultra- mundane " particles are possessed of absolute elasticity, so that they rebound from one another on collision without loss of speed. It is also necessary to assume that all tangible matter has to an almost unthinkable degree a sievelike texture, so that the vast proportion of the coercive particles pass entirely through the body of any mass they encounter — a star or world, for ex- ample— without really touching any part of its actual substance. This assumption is necessary because grav- itation takes no account of mere corporeal bulk, but only of mass or ultimate solidarity. Thus a very bulky object may be so closely meshed that it retards relatively few of the corpuscles, and hence gravitates with relative feebleness — or, to adopt a more familiar mode of expression, is light in weight. This is certainly heaping hypotheses together in a reckless way, and it is perhaps not surprising that Le Sage's conception did not at first arouse any very great amount of interest. It was put forward about a cen- tury ago, but for two or three generations remained practically unnoticed. The philosophers of the first half of our century seem to have despaired of explaining gravitation, though Faraday long experimented in the hope of establishing a relation between gravitation and electricity or magnetism. But not long after the middle of the century, when a new science of dynamics was claiming paramount importance, and physicists were striving to express all tangible phenomena in terms of matter in motion, the theory of Le Sage was revived and given a large measure of attention. It 215 A HISTORY OF SCIENCE seemed to have at least the merit of explaining the facts without conflicting with any known mechanical law, which was more than could be said of any other guess at the question that had ever been made. More recently, however, another explanation has been found which also meets this condition. It is a conception based, like most other physical speculations of the last generation, upon the hypothesis of the vor- tex atom, and was suggested, no doubt, by those spec- ulations which consider electricity and magnetism to be conditions of strain or twist in the substance of the universal ether. In a word, it supposes that gravita- tion also is a form of strain in this ether — a strain that may be likened to a suction which the vortex atom is supposed to exert on the ether in which it lies. Ac- cording to this view, gravitation is not a push from without, but a pull from within; not due to exterior influences, but an inherent and indissoluble property of matter itself. The conception has the further merit of correlating gravitation with electricity, magnetism, and light, as a condition of that strange ethereal ocean of which modern physics takes so much account. But here, again, clearly, we are but heaping hypothesis upon hypothesis, as before. Still, an hypothesis that violates no known law and has the warrant of philo- sophical probability is always worthy of a hearing. But we must not forget that it is hypothesis only, not conclusive theory. The same caution applies, manifestly, to all the other speculations which have the vortex atom, so to say, for their foundation-stone. Thus Professors Stewart and Tait's inferences as to the destructibility of matter, 216 SOME UNSOLVED SCIENTIFIC PROBLEMS based on the supposition that the ether is not quite f rictionless ; Professor Dolbear's suggestions as to the creation of matter through the development of new ether ripples, and the same thinker's speculations as to an upper limit of temperature, based on the mechan- ical conception of a limit to the possible vibrations of a vortex ring, not to mention other more or less fascinat- ing speculations based on the vortex hypothesis, must be regarded, whatever their intrinsic interest, as in- securely grounded, until such time as new experimental methods shall give them another footing. Lord Kel- vin himself holds all such speculations utterly in abey- ance. " The vortex theory," he says, " is only a dream. Itself unproven, it can prove nothing, and any specu- lations founded upon it are mere dreams about a dream." 1 That certainly must be considered an unduly modest pronouncement regarding the only workable hypothe- sis of the constitution of matter that has ever been imagined ; yet the fact certainly holds that the vortex theory, the great contribution of the nineteenth century towards the solution of a world-old problem, has not been carried beyond the stage of hypothesis, and must be passed on, with its burden of interesting corollaries, to another generation for the experimental evidence that will lead to its acceptance or its refutation. Our cen- tury has given experimental proof of the existence of the atom, but has not been able to fathom in the same way the exact form or nature of this ultimate particle of matter. Equally in the dark are we as to the explanation of that strange affinity for its neighbors which every atom 217 A HISTORY OF SCIENCE manifests in some degree. If we assume that the pow- er which holds one atom to another is the same which in the case of larger bodies we term gravitation, that answer carries us but a little way, since, as we have seen, gravi- tation itself is the greatest of mysteries. But again, how chances it that different atoms attract one another in such varying degrees, so that, for example, fluorine unites with everything it touches, argon with nothing ? And how is it that different kinds of atoms can hold to themselves such varying numbers of fellow-atoms — oxygen one, hydrogen two, and so on? These are questions for the future. The wisest chemist does not know why the simplest chemical experiment results as it does. Take, for example, a water-like solution of nitrate of silver, and let fall into it a few drops of an- other water-like solution of hydrochloric acid ; a white insoluble precipitate of chloride of silver is formed. Any tyro in chemistry could have predicted the result with absolute certainty. But the prediction would have been based purely upon previous empirical knowl- edge— solely upon the fact that the thing had been done before over and over, always with the same result. Why the silver forsook the nitrogen atom and grappled the atom of oxygen no one knows. Nor can any one as yet explain just why it is that the new compound is an insoluble, colored, opaque substance, whereas the antecedent ones were soluble, colorless, and transpar- ent. More than that, no one can explain with certainty just what is meant by the familiar word soluble itself. That is to say, no one knows just what happens when one drops a lump of salt or sugar into a bowl of water. We may believe with Professor Ostwald and his fol- 218 SOME UNSOLVED SCIENTIFIC PROBLEMS lowers that the molecules of sugar merely glide every- where between the molecules of water, without chem- ical action; or, on the other hand, dismissing this me- chanical explanation, we may say with Mendeleef that the process of solution is the most active of chemical phenomena, involving that incessant interplay of atoms known as dissociation. But these two explanations are mutually exclusive, and nobody can say positively which one, if either, is right. Nor is either theory at best more than a half explanation, for the why of the strange mechanical or chemical activities postulated is quite ignored. How is it, for example, that the molecules of water are able to loosen the intermolecular bonds of the sugar particles, enabling them to scamper apart ? But, for that matter, what is the nature of these in- termolecular bonds in any case? And why, at the same temperature, are some substances held together with such enormous rigidity, others so loosely ? Why does not a lump of iron dissolve as readily as the lump of sugar in our bowl of water ? Guesses may be made to-day at these riddles, to be sure, but anything like tenable solutions will only be possible when we know much more than at present of the nature of intermo- lecular forces and of the mechanism of molecular structures. As to this last, studies are under way that are full of promise. For the past ten or fifteen years Professor Van 't Hoof of Amsterdam (now of Berlin), with a company of followers, has made the space rela- tions of atoms a special study, with the result that so- called stereo-chemistry has attained a firm position. A truly amazing insight has been gained into the space 219 A HISTORY OF SCIENCE relations of the molecules of carbon compounds in particular, and other compounds are under investiga- tion. But these results, wonderful though they seem when the intricacy of the subject is considered, are, after all, only tentative. It is demonstrated that some molecules have their atoms arranged in perfectly definite and unalterable schemes, but just how these systems are to be mechanically pictured — whether as miniature planetary systems or what not — remains for the investigators of the future to determine. It appears, then, that whichever way one turns in the realm of the atom and molecule, one finds it a land of mysteries. In no field of science have more startling discoveries been made in the past century than here; yet nowhere else do there seem to lie wider realms yet unfathomed. LIFE PROBLEMS In the life history of at least one of the myriad star systems there has come a time when, on the surface of one of the minor members of the group, atoms of mat- ter have been aggregated into such associations as to constitute what is called living matter. A question that at once suggests itself to any one who conceives even vaguely the relative uniformity of conditions in the different star groups is as to whether other worlds than ours have also their complement of living forms. The question has interested speculative science more perhaps in our generation than ever before, but it can hardly be said that much progress has been made towards a definite answer. At first blush the demon- stration that all the worlds known to us are composed 220 SOME UNSOLVED SCIENTIFIC PROBLEMS of the same matter, subject to the same general laws, and probably passing through kindred stages of evolu- tion and decay, would seem to carry with it the rea- sonable presumption that to all primary planets, such as ours, a similar life-bearing stage must come. But a moment's reflection shows that scientific probabilities do not carry one safely so far as this. Living matter, as we know it, notwithstanding its capacity for varia- tion, is conditioned within very narrow limits as to physical surroundings. Now it is easily to be con- ceived that these peculiar conditions have never been duplicated on any other of all the myriad worlds. If not, then those more complex aggregations of atoms which we must suppose to have been built up in some degree on all cooling globes must be of a character so different from what we term living matter that we should not recognize them as such. Some of them may be infinitely more complex, more diversified in their capacities, more widely responsive to the influ- ences about them, than any living thing on earth, and yet not respond at all to the conditions which we apply as tests of the existence of life. This is but another way of saying that the peculiar limitations of specialized aggregations of matter which characterize what we term living matter may be mere incidental details of the evolution of our particular star group, our particular planet even — having some such relative magnitude in the cosmic order, as, for ex- ample, the exact detail of outline of some particular leaf of a tree bears to the entire subject of vegetable life. But, on the other hand, it is also conceivable that the conditions on all planets comparable in position to 221 A HISTORY OF SCIENCE ours, though never absolutely identical, yet pass at some stage through so similar an epoch that on each and every one of them there is developed something measurably comparable, in human terms, to what we here know as living matter; differing widely, perhaps, from any particular form of living being here, yet still conforming broadly to a definition of living things. In that case the life-bearing stage of a planet must be considered as having far more general significance; perhaps even as constituting the time of fruitage of the cosmic organism, though nothing but human egotism gives warrant to this particular presumption. Between these two opposing views every one is free to choose according to his preconceptions, for as yet science is unable to give a deciding vote. Equally open to discussion is that other question, as to whether the evolution of universal atoms into a " vital" association mass from which all the diversified forms evolved, or whether such shifting from the so-called non-vital to the vital was many times repeated — perhaps still goes on incessantly. It is quite true that the testimony of our century, so far as it goes, is all against the idea of "spontaneous generation" under existing conditions. It has been clearly enough demonstrated that the bac- teria and other low forms of familiar life which formerly were supposed to originate "spontaneously" had a quite different origin. But the solution of this special case leaves the general problem still far from solved. Who knows what are the conditions necessary to the evolution of the ever-present atoms into " vital" asso- ciations? Perhaps extreme pressure may be one of these conditions; and, for aught any man knows to the 222 SOME UNSOLVED SCIENTIFIC PROBLEMS contrary, the "spontaneous generation" of living pro- toplasms may be taking place incessantly at the bottom of every ocean of the globe. This of course is a mere bald statement of possibili- ties. It may be met by another statement of possibili- ties, to the effect that perhaps the conditions necessary to the evolution of living matter here may have been fulfilled but once, since which time the entire current of life on our globe has been a diversified stream from that one source. Observe, please, that this assumption does not fall within that category which I mention above as contraband of science in speaking of the origin of worlds. The existence of life on our globe is only an incident limited to a relatively insignificant period of time, and whether the exact conditions neces- sary to its evolution pertained but one second or a hundred million years does not in the least matter in a philosophical analysis. It is merely a question of fact, just as the particular temperature of the earth's surface at any given epoch is a question of fact, the one con- dition, like the other, being temporary and incidental. But, as I have said, the question of fact as to the ex- act time of origin of life on our globe is a question that science as yet cannot answer. But, in any event, what is vastly more important than this question as to the duration of time in which living matter was evolved is a comprehension of the philosophical status of this evolution from the "non- vital" to the " vital." If one assumes that this evolu- tion was brought about by an interruption of the play of forces hitherto working in the universe — that the correlation of forces involved was unique, acting 223 A HISTORY OF SCIENCE then and then only — by that assumption he removes the question of the origin of life utterly from the do- main of science — exactly as the assumption of an initial push would remove the question of the origin of worlds from the domain of science. But the science of to-day most emphatically demurs to any such assumption. Every scientist with a wide grasp of facts, who can think clearly and without prejudice over the field of what is known of cosmic evolution, must be driven to believe that the alleged wide gap between vital and non-vital matter is largely a figment of prejudiced human understanding. In the broader view there seem no gaps in the scheme of cosmic evolution — no break in the incessant reciprocity of atomic actions, whether those atoms be floating asa" fire mist" out in one part of space, or aggregated into the brain of a man in another part. And it seems well within the range of scientific expectation that the laboratory work- er of the future will learn how so to duplicate telluric conditions that the universal forces will build living matter out of the inorganic in the laboratory, as they have done, and perhaps still are doing, in the terres- trial oceans. To the timid reasoner that assumption of possibil- ities may seem startling. But assuredly it is no more so than seemed, a century ago, the assumption that man has evolved, through the agency of "natural laws" only, from the lowest organism. Yet the tim- idity of that elder day has been obliged by the progress of the past century to adapt its conceptions to that assured sequence of events. And some day, in all probability, the timidity of to-day will be obliged to 224 SOME UNSOLVED SCIENTIFIC PROBLEMS take that final logical step which to-day's knowledge foreshadows as a future if not a present necessity. The Mechanism of the Cell Whatever future science may be able to accomplish in this direction, however, it must be admitted that present science finds its hands quite full, without going farther afield than to observe the succession of gen- erations among existing forms of life. Since the es- tablishment of the doctrine of organic evolution, ques- tions of heredity, always sufficiently interesting, have been at the very focus of attention of the biological world. These questions, under modern treatment, have resolved themselves, since the mechanism of such transmission has been proximately understood, into problems of cellular activity. And much as has been learned about the cell of late, that interesting microcosm still offers a multitude of intricacies for solution. Thus, at the very threshold, some of the most ele- mentary principles of mechanical construction of the cell are still matters of controversy. On the one hand, it is held by Professor O. Butschli and his followers that the substance of the typical cell is essentially alveolar, or foamlike, comparable to an emulsion, and that the observed reticular structure of the cell is due to the intersections of the walls of the minute ultimate globules. But another equally authoritative school of workers holds to the view, first expressed by From- mann and Arnold, that the reticulum is really a sys- tem of threads, which constitute the most important basis of the cell structure. It is even held that these v — is 225 A HISTORY OF SCIENCE fibres penetrate the cell walls and connect adjoining cells, so that the entire body is a reticulum. For the moment there is no final decision between these op- posing views. Professor Wilson of Columbia has sug- gested that both may contain a measure of truth. Again, it is a question whether the finer granules seen within the cell are or are not typical structures, "capable of assimilation, growth, and division, and hence to be regarded as elementary units of structure standing between the cell and the ultimate molecules of living matter." The more philosophical thinkers, like Spencer, Darwin, Haeckel, Michael Foster, August Weismann, and many others, believe that such "in- termediate units must exist, whether or not the mi- croscope reveals them to view. Weismann, who has most fully elaborated a hypothetical scheme of the relations of the intracellular units, identifies the larger of these units not with the ordinary granules of the cell, but with a remarkable structure called chromatin, which becomes aggregated within the cell nucleus at the time of cellular division — a structure which divides into definite parts and goes through some most sug- gestive manoeuvres in the process of cell multiplica- tion. All these are puzzling structures; and there is another minute body within the cell, called the centro- some, that is quite as much so. This structure, dis- covered by Van Beneden, has been regarded as essential to cell division, yet some recent botanical studies seem to show that sometimes it is altogether wanting in a dividing cell. In a word, the architecture of the cell has been shown by modern researches to be wonderfully com- 226 SOME UNSOLVED SCIENTIFIC PROBLEMS plicated, but the accumulating researches are just at a point where much is obscure about many of the ob- served phenomena. The immediate future seems full of promise of advances upon present understanding of cell processes. But for the moment it remains for us, as for preceding generations, about the most incom- prehensible, scientifically speaking, of observed phe- nomena, that a single microscopic egg cell should con- tain within its substance all the potentialities of a highly differentiated adult being. The fact that it does contain such potentialities is the most familiar of every-day biological observations, but not even a proximal explanation of the fact is as yet attainable. The Ancestry of the Mammals Turning from the cell as an individual to the mature organism which the cell composes when aggregated with its fellows, one finds the usual complement of open questions, of greater or less significance, focaliz- ing the attention of working biologists. Thus the evolutionist, secure as is his general position, is yet in doubt when it comes to tracing the exact lineage of various forms. He does not know, for example, ex- actly which order of invertebrates contains the type from which vertebrates sprang, though several hotly contested opinions, each exclusive of the rest, are in the field. Again, there is like uncertainty and differ- ence of opinion as to just which order of lower verte- brates formed the direct ancestry of the mammals. Among the mammals themselves there are several orders, such as the whales, the elephants, and even man himself, whose exact lines of more immediate an- 227 A HISTORY OF SCIENCE cestry are not as fully revealed by present paleontology as is to be desired. The New Science of Anthropology All these, however, are details that hardly take rank with the general problems that we are noticing. There are other questions, however, concerning the history and present evolution of man himself that are of wider scope, or at least seemingly greater importance from a human stand-point, which within recent decades have come for the first time within the scope of truly induc- tive science. These are the problems of anthropology — a science of such wide scope, such far-reaching col- lateral implications, that as yet its specific field and functions are not as clearly defined or as generally rec- ognized as they are probably destined to be in the near future. The province of this new science is to correlate the discoveries of a wide range of collateral sciences — paleontology, biology, medicine, and so on — from the point of view of human history and human welfare. To this end all observable races of men are studied as to their physical characteristics, their mental and moral traits, their manners, customs, languages, and relig- ions. A mass of data is already at hand, and in proc- ess of sorting and correlating. Out of this effort will probably come all manner of useful generalizations, perhaps in time bringing sociology, or the study of human social relations, to the rank of a veritable science. But great as is the promise of anthropology, it can hardly be denied that the broader questions with which it has to deal — questions of race, of gov- ernment, of social evolution — are still this side the fixed 228 SOME UNSOLVED SCIENTIFIC PROBLEMS plane of assured generalization. No small part of its interest and importance depends upon the fact that the great problems that engage it are as yet unsolved problems. In a word, anthropology is perhaps the most important science in the entire hierarchy to-day, precisely because it is an immature science. Its posi- tion to-day is perhaps not unlike that of paleontology at the close of the eighteenth century. May its promise find as full fruition ! IX RETROSPECT AND PROSPECT THE SCIENTIFIC ATTITUDE OF MIND A NY one who has not had a rigid training in science A may advantageously reflect at some length upon the meaning of true scientific induction. Various il- lustrations in our text are meant to convey the idea that logical thinking consists simply in drawing cor- rect conclusions as to the probable sequence of events in nature. It will soon be evident to any one who carefully considers the subject that we know very little indeed about cause and effect in a rigid acceptance of these words. We observe that certain phenomena al- ways follow certain other phenomena, and these ob- servations fix the idea in our mind that such phenomena bear to one another the relation of effect and cause. The conclusion is a perfectly valid one so long as we remember that in the last analysis the words "cause" and "effect" have scarcely greater force than the terms "invariable antecedent" and "invariable con- sequent"— that is to say, they express an observed sequence which our experience has never contra- dicted. Now the whole structure of science would be hope- lessly undermined had not scientific men come to have the fullest confidence in the invariability of certain of 230 RETROSPECT AND PROSPECT these sequences of events. Let us, for example, take the familiar and fundamental observation that any- unsupported object, having what we term weight, in- variably falls directly towards the centre of the earth. We express this fact in terms of a so-called law of grav- itation, and every one, consciously or unconsciously, gives full deference to this law. So firmly convinced are we that the gravitation pull is a cause that works with absolute, unvarying uniformity that we should regard it as a miracle were any heavy body to disre- gard the law of gravitation and rise into the air when not impelled by some other force of which we have knowledge. Thanks to Newton, we know that this force of gravitation is not at all confined to the earth, but affects the whole universe, so that every two bits of matter, regardless of location, pull at each other with a force proportionate to their mass and inversely as the square of their distance. Were this so-called law of gravitation to cease to operate, the entire plan of our universe would be sadly disarranged. The earth, for example, and the other planets would leave their elliptical orbits and hurtle away on a tangential course. We should soon be be- yond the reach of the sun's beneficent influence; an arctic chill would pervade polar and tropical regions alike, and the term of man's existence would come suddenly to a close. Here, then, is a force at once the most comprehensible and most important from a human stand-point that can be conceived ; yet it can- not be too often repeated, we know nothing whatever as to the nature of this force. We do not know that there may not be other starlike clusters beyond our 231 A HISTORY OF SCIENCE universe where this force does not prevail. We do not know that there may not come a period when this force will cease to operate in our universe, and when, for example, it will be superseded by the universal domination of a force of mutual repulsion. For aught we know to the contrary, our universe may be a pulsing organism, or portion of an organism, all the particles of which are at one moment pulled together and the next moment hurled apart — the moments of this com- putation being, of course, myriads of years as we hu- man pygmies compute time. To us it would be a miracle if a heavy body, unsup- ported, should fly off into space instead of dropping towards the centre of the earth; yet the time may come when all such heavy objects will thus fly off into space, and when the observer, could there be such, must marvel at the miracle of seeing a heavy object fall towards the earth. Such thoughts as these should command the attention of every student of science who would really understand the meaning of what are termed natural laws. But, on the other hand, such suggestions must be held carefully in check by the observation that scientific imagining as to what may come to pass at some remote future time must in no wise influence our practical faith in the universality of certain natural laws in the present epoch. We may imagine a time when terrestrial gravitation no longer exerts its power, but we- dare not challenge that power in the present. There could be no science did we not accept certain constantly observed phenomena as the effect of certain causes. The whole body of science is made up solely of such observations and in- 232 RETROSPECT AND PROSPECT ferences. Natural science is so called because it has to do with observed phenomena of nature. NATURAL VERSUS SUPERNATURAL A further word must be said as to this word "nat- ural," and its complementary word "supernatural." I have said in an early chapter that prehistoric man came, through a use of false inductions, to the belief in supernatural powers. Let us examine this statement in some detail, for it will throw much light on our later studies. The thing to get clearly in mind is the idea that when we say "natural" phenomena we mean merely phenomena that have been observed to occur. From a truly scientific stand-point there is no pre- conception as to what manner of phenomenon may, or may not, occur. All manner of things do occur con- stantly that would seem improbable were they not matters of familiar knowledge. The simplest facts in regard to gravitation involve difficulties that were stumbling-blocks to many generations of thinkers, and which continue stumbling-blocks to the minds of each generation of present-day children. Thus most of us can recall a time when we first learn- ed with astonishment that the earth is "round like a ball ' ' ; that there are people walking about on the other side of the world with their feet towards ours, and that the world itself is rushing through space and spinning rapidly about as it goes. Then we learn, further, that numberless familiar phenomena would be quite differ- ent could we be transported to other globes. That, for example, a man who can spring two or three feet into the air here would be able, with the same muscular 233 A HISTORY OF SCIENCE exertion, to vault almost to the house-tops if he lived on a small planet like the moon ; but, on the other hand, would be held prone by his own weight if transported to a great planet like Jupiter. When, further, we reflect that with all our capacity to measure and estimate this strange force of gravita- tion we, after all, know absolutely nothing as to its real nature ; that we cannot even imagine how one por- tion of matter can act on another across an infinite abysm (or, for that matter, across the smallest space), we see at once that our most elementary scientific studies bring us into the presence of inscrutable mys- teries. In whatever direction we turn this view is but emphasized. Electricity, magnetism, the hypothetical ether, the inscrutable forces manifested everywhere in the biological field — all these are, as regard their ulti- mate nature, altogether mysterious. In a word, the student of nature is dealing every- where with the wonderful, the incomprehensible. Yet all the manifestations that he observes are found to repeat themselves in certain unvarying sequences. Certain applications of energy will produce certain movements of matter. We may not know the nature of the so-called cause, but we learn to measure the re- sult, and in other allied cases we learn to reason back or infer the cause from observation of results. The latter indeed is the essence of scientific inquiry. When certain series of phenomena have been classified to- gether as obviously occurring under the domination of the same or similar causes, we speak of having de- termined a law of nature. For example, the fact that any body in motion tends to go on at the same rate of 234 RETROSPECT AND PROSPECT speed in a direct line forever, expresses such a law. The fact that the gravitation pull is directly as the mass and inversely as the square of the distance of the bodies it involves, expresses another such law. The fact that the planetary bodies of the solar system re- volve in elliptical orbits under the joint influence of the two laws just named, expresses yet another law. In a word, then, these so-called "laws" are nothing more than convenient formulae to express the classification of observed facts. INDUCTIVE VERSUS DEDUCTIVE REASONING The ancient thinkers indulged constantly in what we now speak of as deductive reasoning. They gave heed to what we term metaphysical preconceptions as to laws governing natural phenomena. The Greeks, for example, conceived that the circle is the perfect body, and that the universe is perfect; therefore, sun and moon must be perfect spheres or disks, and all the orbits of the heavenly bodies must be exactly circular. We have seen that this metaphysical conception, dom- inating the world for many centuries, exerted a con- stantly hampering influence upon the progress of science. There were numerous other instances of the same retarding influence of deductive reasoning. Mod- ern science tries to cast aside all such preconceptions. It does not always quite succeed, but it makes a strenu- ous effort to draw conclusions logically from observed phenomena instead of trying to force observations into harmony with a preconeived idea. Herein lies the essential difference between the primitive method and the perfected modern method. Neither the one nor 235 A HISTORY OF SCIENCE the other is intended to transcend the bounds of the natural. That is to say, both are concerned with the sequence of actual events, with the observation of actual phenomena; but the modern observer has the almost infinite advantage of being able to draw upon an immense store of careful and accurate observations. A knowledge of the mistakes of his predecessors has taught him the value of caution in interpreting phe- nomena that seem to fall outside the range of such laws of nature as experience has seemed to demon- strate. Again and again the old metaphysical laws have been forced aside by observation ; as, for example, when Kepler showed that the planetary orbits are not circular, and Galileo's telescope proved that the spot- bearing sun cannot be a perfect body in the old Aristo- telian sense. New means of observation have from time to time opened up new fields, yet with all the extensions of our knowledge we come, paradoxically enough, to realize but the more fully the limitations of that knowledge. We seem scarcely nearer to-day to a true understanding of the real nature of the "forces *' whose operation we see manifested about us than were our most primitive ancestors. But in one great essential we have surely progressed. We have learned that the one true school is the school of experience; that metaphysical causes are of absolutely no consequence unless they can gain support through tangible observations. Even so late as the beginning of the nineteenth century, the great thinker, Hegel, retaining essentially the Greek cast of thought, could make the metaphysical declaration that, since seven planets were known, and since seven is the 236 RETROSPECT AND PROSPECT perfect number, it would be futile to search for other planets. But even as he made this declaration an- other planet was found. It would be safe to say that no thinker of the present day would challenge defeat in quite the Aristotelian or Hegelian manner ; but, on the other hand, it is equally little open to doubt that, in matters slightly less susceptible of tangible demonstra- tion, metaphysical conceptions still hold sway; and as regards the average minds of our time, it is perhaps not an unfair estimate to say they surely have not ad- vanced a jot beyond the Aristotelian stand-point. Untrained through actual experience in any field of inductive science, they remain easy victims of meta- physical reasoning. Indeed, since the conditions of civilization throw a protecting influence about us, and make the civilized man less amenable to results of illogical action than was the barbarian, it may almost be questioned whether the average person of to-day is the equal, as a scientific reasoner, of the average man of the Stone Age. A few of the more tangible superstitions of primitive man have been banished from even the popular mind by the clear demonstration of science, but a host re- mains. I venture to question whether, if the test could be made in the case of ten thousand average persons throughout Christendom, it would not be found that a majority of these persons entertain more utterly mis- taken metaphysical ideas regarding natural phenomena than they do truly scientific conceptions. We pride ourselves on the enlightenment of our age, but our pride is largely based on an illusion. Mankind at large is still in the dark age. The historian of the remote 237 A HISTORY OF SCIENCE future will see no radical distinction between the superstitions of the thirteenth century and the super- stitions of the nineteenth century. But he will prob- ably admit that a greater change took place in the world of thought between the year 1859 and the close of the nineteenth century than had occurred in the lapse of two thousand years before If this estimate be correct, it is indeed a privilege to be living in this generation, for we are on the eve of great things, and beyond question the revolution that is going on about us denotes the triumph of science and its inductive method. Just in proportion as we get away from the old metaphysical preconceptions, substituting for them the new inductive method, just in that proportion do we progress. The essence of the new method is to have no preconceptions as to the bounds of nature ; to regard no phenomenon, no sequence of phenomena, as impossible ; but, on the other hand, to accept no alleged law, no theory, no hypothesis, that has not the warrant of observed phenomena in its favor. The great error of the untrained mind of the primi- tive man was that he did not know the value of scien- tific evidence. He made wide leaps from observed phenomena to imagined causes, quite overlooking the proximal causes that were near to hand. The un- trained observer of to-day makes the same mistake; hence the continued prevalence of those superstitious misconceptions which primitive man foisted upon our race. But each new generation of to-day is coming upon the field better trained in at least the rudiments of scientific method than the preceding generation, and this is perhaps the most hopeful feature of present- 238 RETROSPECT AND PROSPECT day education. Some day every one will understand that there is no valid distinction between the natural and the supernatural ; in fact, that no such thing as a supernatural phenomenon, in the present-day accept- ance of the word, can conceivably exist. All conceivable manifestations of nature are natural, nor can we doubt that all are reducible to law — that is to say, that they can be classified and reduced to sys- tems. But the scientific imagination, as already pointed out, must admit that any and every scientific law of our present epoch may be negatived in some future epoch. It is always possible, also, that a seem- ing law of to-day may be proved false to-morrow, which is another way of saying that man's classification im- proves from generation to generation. For a " natural law," let it be repeated, is not nature's method, but man's interpretation of that method. LOGICAL INDUCTION VERSUS HASTY GENERALIZATION A great difficulty is found in the fact that men are forever making generalizations — that is, formulating laws too hastily. A few phenomena are observed and at once the hypothesis-constructing mind makes a guess as to the proximal causes of these phenomena. The guess, once formulated and accepted, has a certain influence in prejudicing the minds of future observers ; indeed, where the phenomena involve obscure princi- ples the true explanation of which is long deferred, a false generalization may impress itself upon mankind with such force as to remain a stumbling-block for an indefinite period. Thus the Ptolemaic conception of the universe dominated the thought of Europe for a 239 A HISTORY OF SCIENCE thousand years, and could not be substituted by the true theory without a fierce struggle; and, to cite an even more striking illustration, the early generaliza- tions of primitive man which explain numberless phe- nomena of nature as due to an influence of unseen an- thropomorphic beings remain to this day one of the most powerful influences that affect our race — an in- fluence from which we shall never shake ourselves alto- gether free until the average man — and particularly the average woman — learns to be a good observer and a logical reasoner. Something towards this end is being accomplished by the introduction of experimental research and scien- tific study in general in our schools and colleges. It is hoped that something towards the same end may be accomplished through study of the history of the de- velopment of science. Scarcely anything is more il- luminative than to observe critically the mistakes of our predecessors, noting how natural the mistakes were and how tenaciously they were held to, how strenu- ously defended. Most of all it would be of value to note that the false inductions which have everywhere hampered the progress of science have been, from the stand-point of the generation in which they originated, for the most part logical inductions. We have seen that the Ptolemaic scheme of the universe, false though it was in its very essentials, yet explained in what may be termed a thoroughly scientific fashion the observed phenomena. It is one way of expressing a fact to say that the sun moves across the heavens from the eastern to the western horizon ; and for most practical purposes this assumption answers perfectly. It is only when we 240 RETROSPECT AND PROSPECT endeavor to extend the range of theoretical astron- omy, and to gain a correct conception of the mechan- ism of the universe as a whole, that the essentially faulty character of the geocentric conception becomes apparent. And so it is in many another field ; the false general- izations and hasty inductions serve a temporaiy pur- pose. Our only quarrel with them is that they tend through a sort of inertia to go forever unchanged. It requires a powerful thrust to divert the aggregate mind of our race from a given course, nor is the effect of a new impulse immediately appreciable ; that is why the masses of the people always lag a generation or two behind the advanced thinkers. A few receptive minds, cognizant of new observations that refute an old generalization, accept new laws, and, from the van- tage-ground thus gained, reach out after yet other truths. But, for the most part, the new laws thus ac- cepted by the leaders remain unknown to the people at large for at least one or two generations. It re- quired about a century for the heliocentric doctrine of Copernicus to begin to make its way. In this age of steam and electricity, progress is more rapid, and the greatest scientific conception of the nineteenth century, the Darwinian theory, may be said to have made something that approaches an absolute conquest within less than half a century. This seems a marvellously sudden conquest, but it must be under- stood that it is only the crude and more tangible bear- ings of the theory that have thus made their way. The remoter consequences of the theory are not even suspected by the great majority of those who call VOL. V. — 16 241 A HISTORY OF SCIENCE themselves Darwinians to - day. It will require at least another century for these ideas to produce their full effect. Then, in all probability, it will appear that the nineteenth century was the most revolutionary epoch by far that the history of thought has known. And it owes this proud position to the fact that it was the epoch in all history most fully subject to the domi- nant influence of inductive science. Thanks to this influence, we of the new generation are able to start out on a course widely divergent from the path of our ancestors. Our leaders of thought have struggled free from the bogs of superstition, and are pressing forward calmly yet with exultation towards the heights. APPENDIX REFERENCE-LIST CHAPTER IV SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS 1 (P- 95)- J- J- Thompson, D.Sc, LL.D., Ph.D., F.R.S.,etc, Electricity and Matter, p. 75 ff., New York, 1904. The Silli- man Lectures, delivered at Yale University, May, 1903. 2 (p. 96). Ibid., pp. 88, 89. 3 (p. 97). Ibid., p. 89. 4 (p. 97). Ibid., p. 87. 5 (p. 102). George F. Kunz, "Radium and its Wonders," in the Review of Reviews for November, 1903, p. 589. 9 (p. 105). E. Rutherford, Radio- Activity, p. 330, Cam- bridge, 1904. 7 (p. 106). Ibid., p. 330. 8 (p. 106). Compte Rendu, pp. 136, 673, Paris, 1903. 9 (p. 106). Revue Scientifique, April 13, 1901. 10 (p. 106). Compte Rendu, p. 136, Paris, 1903. 11 (p. 108). J. J. Thompson, Electricity and Matter, p. 162, New York, 1904. 12 (p. no). E. Rutherford, Radio- Activity, p. 340, Cam- bridge, 1904. CHAPTER VII SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS 1 (p. 185). Dr. Duclaux, who was one of Pasteur's chief as- sistants, and who succeeded him in the directorship of the In- 243 A HISTORY OF SCIENCE stitute, died in 1903. He held a professorship in the Univer- sity of Paris during the later years of his life, and his special studies had to do largely with the chemical side of bacteriology. CHAPTER VIII SOME UNSOLVED SCIENTIFIC PROBLEMS 1 (p. 217). Lord Kelvin's estimate as quoted was expressed to the writer verbally. I do not know whether he has any- where given a similar written verdict. A LIST OF SOURCES I— PERIOD COVERED BY VOLUME I. Anaxagoras. See vol. i., p. 240. Archimedes. See vol. i., p. 196. Many of the works of Archimedes are lost, but the following have come down to us : ( 1 ) On the Sphere and Cylinder; (2) The Measure of the Circle; (3) Conoids and Spheroids; (4) On Spirals; (5) Equiponderants and Centres of Gravity; (6) The Quadrature of the Parabola; (7) On Bodies Floating in Liquids; (8) The Psammites; (9) A Collection of Lemmas. Aristarchus. See vol. i., p. 212. Magnitudes and Distances of the Sun and Moon is the only surviving work. In the Armarius of Archimedes another work of Aristarchus is quoted — the one in which he anticipates the discovery of Copernicus. Delambre, in his Histoire de V astronomic ancienne, treats fully the discoveries of Aristarchus. Aristotle. See vol. i., p. 82. An edition of Aristotle was published by Aldus, Venice, 1495-1498, 5 vols. During the following eighty years seven editions of the Greek text of the entire works were published, and many Latin translations. Berosus. See vol. i., p. 58. The fragments of Berosus have been trans, by I. P. Cory, and included in his Ancient Fragments of Phoeni- cian, Chaldean, Egyptian, and Other Writers, London, 1826; second edition, 1832. 245 A HISTORY OF SCIENCE Democritus. See vol. i., p. 161. Fragments only of the numerous works ascribed to Democritus have been preserved. Democriti Abderitce operum fragmenta, Berlin, 1843, edited by F. G. A. Mullach. Diodorus Siculus. See vol. i., p. 77. The Historical Library. Perhaps the best available editions of Diodorus are Wesseling's, 2 vols.; Amstel, 1745; and Dindorf's, 5 vols., Leipzig, 1828-1831. Eng- lish trans, by Booth, London, 1700. Diogenes Laertius. See vol. i., p. 121. The Lives and Opinions of Eminent Philosophers (trans, by C. D. Yonge), London, 1853. Eratosthenes. See vol. i., p. 225. The fragments of his philosophical works were pub- lished at Berlin, 1822, under the title Erato sthenic a. His poetical works were published at Leipzig, 1872. Euclid. See vol. i., p. 193. His Elements of Geometry is still available as an English school text-book. Galen (Claudius Galenus). See vol. i., p. 272. Galen's preserved works are exceedingly bulky. The best-known edition is that of C. G. Kiihn, in 21 vol- umes. Hero. See vol. i., p. 242. The Pneumatics of Hero of Alexandria, from the original Greek. Trans, by B. Woodcroft, London, 1851. Herodotus. See vol. i., p. 103. History. English trans, by Beloe, 1791 and 1806. Trans, by Canon Rawlinson, London, 1 858-1 860. Hipparchus. See vol. i., p. 233. The only work of Hipparchus which has survived was published first by Vittorius at Florence, 1567. Hippocrates. See vol. i., p. 170. Numerous editions have been published of the Hippo- cratic writings, including many works not written by the master himself. One of the best editions is that of Littre, Paris, 1839, etc. 246 A LIST OF SOURCES Khamurabi, Code of. See vol. i., p. 76. This famous inscription is on a block of black diorite nearly eight feet in height. It was discovered at Susa by the French expedition under M. de Morgan in Decem- ber, 1 90 1. Leucippus. See vol. i., p. 161. Pliny (Caius Plinius Secundus). See vol. i., p. 265. His Natural History is available in several English editions and reprints. Perhaps the best edition of the original text is the one published by Julius Sillig, 5 vols., Leipzig, 1854-1859. Plutarch. See vol. i., p. 198. Life of Marcellus, in Parallel Lives. In this the mechanical inventions of Archimedes are described. Polybius. See vol. i., p. 201. In his Histories Polybius describes the mechanical contrivances and war - engines of Archimedes, and also gives an account of his death. Ptolemy (Claudius Ptolemaeus). See vol. i., p. 269. Geographia (or Almagest of the Arabs). The edition published by Nobbe, in 3 vols., Leipzig, 1842, was one of the best complete editions of the Greek text. The edition published in Didot's Bibliotheca Classicorum Grcecorum, Paris, 1883, is excellent. Earlier editions contain many errors. Strabo. See vol. i., p. 255. The Geography of Strabo. Trans, by H. C. Hamilton and W. Falconer, 3 vols., London, 1857. There are several other editions of Strabo 's work available in English. Tertullian. See vol. i., p. 195. Apologeticus. Theophrastus. See vol. i., p. 188. Iltpi (fyvTcbv la-Topias, On the History of Plants. Written in 10 books. This is one of the earliest works on bot- any which have come to us. It was largely used by Pliny. In complete works, Schneider, Leipzig, 1818- 182 1, 5 vols. On Plants, edited by Wimmer, Breslau, 247 A HISTORY OF SCIENCE 1 842-1 862. On Plants, edited by Slackhouse, Oxford, 1 814. flcpl 4>vtcov alnmv, On the Causes of Plants. This was originally in 8 books, of which 6 are now existant. Bibliog. vid. History of Plants. II.— PERIOD COVERED BY VOLUME II. Albategnius, Mohammed ben Jabir. See vol. ii., p. 15. The original MS. of his principal work, Zidje Sabi, is in the Vatican. A Latin translation was first published by Plato Tiburtinus at Nuremberg, in 1537, under the title Be scientia stellarum. Various reprints of this have been made. Albertus Magnus. See vol. ii., p. 127. Philosophies Naturalis Isagoge, Vienna, 15 14. Alhazen (full name, Abu Ali al-Hasan Ibn Alhasan). See vol. ii., p. 18. Only two of his works have been printed, his Treatise on Twilight and his Thesaurus opticae, these being available in Michael Casiri's Bibliotheca Arabico-Hispana Escuri- alensis, 2 vols., Madrid, 1 760-1 770. Bacon, Francis. See vol. ii., p. 192. Novum Organum was published in London, 1620. The Letters and Life of Lord Bacon, in 7 vols., by James Spedding, appeared in 1862 -1874. Bacon, Roger. See vol. ii., p. 44. Only an approximate estimate of the number of Bacon's works can be given even now, although an infinite amount of time and labor has been spent in col- lecting them. His great work is the Opus majus, "the Encyclopaedia and the Organum of the Thirteenth Century." A partial list of some of his other works is the following: Speculum alchemioe, 1541 (trans, into English); De mtrabili potestale artis et natures, 1542 (trans, into English, 1659); Libellus de retardanis se- nectutis accidentibus , 1590 (trans, as "The Cure of Old Age," 1683); and Sanioris medicines Magistri d. Rogeri Bacoms Anglici de arte chymioe scripta, 1603. 248 A LIST OF SOURCES Boyle, Robert. See vol. ii., p. 205. Philosophical Works, 3 vols., London, 1738. Copernicus, Nicolaus. See vol. ii., p. 54. Ad clar. v. d. Schonerum de libris revolutionum eruditiss. viri et mathemahci excellentiss. Rev. Doctoris Nicolai Copernici Torunnaei, Canonici Warmiensis, per quemdam juvenem mathematicce studiosum, Narratio prima, Dantzic, 1540. This was the first published state- ment of the doctrine of Copernicus, and was a letter pub- lished by Rheticus. Three years afterwards Copernicus's De orbium ccelestium revolutionibus , Libri VI., was pub- lished at Nuremberg (1543). Descartes, Rene. See vol. ii., p. 193. Traite de I'homme (Cousins's edition, in 11 vols., Paris, 1824). Galilei, Galileo. See vol. ii., p. 91. Dialogo dei due massimi sistemi del mondo, Florence, 1632. Discorsi e dimostrazioni matematiche intorno a due nuove scienze, Leyden, 1638. Gilbert, William (1540-1603). See vol. ii., p. 113. De magnete, magneticisque corporibus, et de magno magnete tellure, London, 1600. De magnete was trans, by P. Fleury Motteley, London, 1893. Guericke, Otto von (1620-1686). See vol. ii., p. 213. Experimenta nova, ut vocant, Magdeburgica de vacuo spatio, Amsterdam, 1672. In the Phil. Trans, of the Royal Society of London, No. 88, for 1672. Hales, Stephen (1677-1761). See vol. ii., p. 298. Statical Essays, comprising Vegetable Staticks, London, 1727, and Haemostatics, London, 1733. Harvey, William. See vol. ii., p. 169. Exercitatio anatomica de motu cordis et sanguinis, Frankfort-on-Main, 1628. The Works of, trans, by Robert Willis, London, 1847. Hauksbee, Francis. See vol. ii., p. 259. Physico- Mechanical Experiments on Various Subjects, London, 1709. This contains descriptions of his various 249 A HISTORY OF SCIENCE discoveries in electricity, many of which are given in the Phil. Trans. Hooke, Robert. See vol. ii., p. 215. Micrographia, or Some Philosophical Descriptions of Some Minute Bodies, London, 1665. An Attempt to Prove the Motion of the Earth, London, 1674. Microscopical Observations, London, 1780. Most of Hooke's important discoveries were contributed as papers to the Royal Society and are available in the Phil. Trans. Huygens, Christian (1629-1695). See vol. ii., p. 218. Traite de la lumiere, Leyden, 1690. Complete works were published at The Hague in 1888, under thetit le CEuvres completes, by the Societe Hollandaise des Sciences. These books have not been translated into English. Huygens 's famous paper on the laws governing the collision of elastic bodies appeared in the Phil. Trans, of the Royal Society for 1669. Kepler, Johann. See vol. ii., p. 70. Astronomia nova de motibus stellce Martis, Leipzig, 1609, contains Kepler's two first laws; and Harmonices mundi, 1 61 9, contains the third law, Phcenomenon singulare, sen Mercurius in sole, Leipzig, 1609. Joannis Kepleri opera omnia, in 8 vols., Frankfort, 1858-1871. Leeuwenhoek, Anthony van. See vol. ii., p. 179. His discoveries are mostly recorded in the Phil. Trans. of the Royal Society, between the years 1673 and 1723 — one hundred and twelve papers in all. His discovery of bacteria is recorded in Phil. Trans, for 1683; and that of the discovery of the capillary circulation of the blood in Phil. Trans, for 1790. Linn/eus, Carolus (1707-1778). See vol. ii., p. 299. His Sy sterna naturce was published in 1735. Two years later (1737) he published Genera plantarum, which is gen- erally considered as the starting-point of modern botany. His published works amount to more than one hundred and eighty. Mariotte, Edme (died 1684). See vol. ii., p. 210. Essais de physique (four essays), Paris, 1676- 1679. 250 A LIST OF SOURCES His De la nature de Vair, containing his statement of the law connecting the volume and pressure of a gas, is contained in the second essay. Newton, Sir Isaac. See vol. ii., p. 241. Philosophic naturalis principia mathematica, com- pleted in July of 1687. The first edition was exhausted in a few months. There are several translations, among others one by Andrew Motte, New York, 1848. Paracelsus. See vol. ii., p. 159. The Hermetic and Alchemical Writings of Paracelsus, trans, by A. E. Waite, 2 vols., London, 1894. Pascal, Blaise. See vol. ii., p. 122. Recit de la grande experience de Vequilibre de liqueurs, Paris, 1648. Sawtree, John. See vol. ii., p. 124 ff. Of the Philosopher's Stone, London, 1652. Swammerdam, John. See vol. ii., p. 297. Bibel der Natur, trans, into German, Leipzig, 1752. Sydenham, Thomas. See vol. ii., p. 189. His first work, Methodus curandi febres, was pub- lished in 1666. His last work, Processus integri, ap- peared in 1692. His complete works, in Latin, were published by the Sydenham Society, London, 1844, which published also an English translation by Dr. R. G. Latham in 1848. There are several other English trans- lations. Torricelli, Evangelista. See vol. ii., p. 120. Opera geometrica, Florence, 1644. Tycho Brahe. See vol. ii., p. 65. De mundi aether ei recentioribus phcenomenis, Prague, 1603. This has been trans, into German by M. Bruns, Karlsruhe, 1894. Vinci, Leonardo da. See vol. ii., p. 47. Leonardo da Vinci, Artist, Thinker, and Man of Science, by Eugene Muntz, 2 vols., New York, 1892, is perhaps the most complete treatment of all phases of Leonardo's 251 A HISTORY OF SCIENCE work as a scientist as well as an artist. The older French work, Essai sur les ouvrages physico - mathema- tiques de Leonard de Vinci, by J. B. Venturi, Paris, 1797, is excellent. In German, H. Grothe's Leonardo da Vinci als Ingenieur und Philosoph, Berlin, 1874, is good. III.— MODERN COSMICAL AND TELLURIC SCIENCES Agassiz, L. See vol. iii., p. 147. Etudes sur les glaciers, Neuchatel, 1840. Arago, Francois J. D. See vol. iii., p. 67. CEuvres (complete), 17 vols., Paris, 1854-1862. Arago' s Meteorological Essays, trans, into English, London, 1855. This has an introduction by Humboldt. Boscovich, Roger Joseph. See vol. iii., p. 293. Theoria philosophize naturalis redacta ad unicam legem virium in natura existentium, Vienna, 1758. Bradley, James. See vol. iii., p. 13. Concerning an Apparent Motion Observed in Some of the Fixed Stars, London, 1748, Phil. Trans., vol. xlv., pp. 8,9- Cuvier, Baron de. See vol. iv., p. 103. Recherches sur les ossements fossiles de quadrupedes, 4 vols., Paris, 181 2. (The introduction to this work was translated and published as a volume bearing title of Theory of the Earth, New York, 18 18.) Delambre, Jean Baptiste Joseph. See vol. iii., p. 16. Histoire d' astronomic, Paris, 181 7-182 1. This work contains not only the history of the discoveries in as- tronomy, but is also a complete text-book of astronomy as understood at this period. Falconer," Hugh. See vol. iii., p. 99. In Pal&ontological Memoirs, vol. ii., pp.. 596-598. 252 A LIST OF SOURCES Herschel, William. See vol. iii., p. 20 ff. On the Proper Motion of the Solar System, Phil. Trans., vol. 73, for 1783. (This paper was read in March, 1783.) The Constitution of the Heavens, Phil. Trans, for 1785, vol. 75, p. 213. Howard, Luke. See vol. iii., p. 182. Philosophical Magazine, 1803. Humboldt, Alexander von. See vol. iii., p. 192. Des lignes isothermes et de la distribution de la cha- leur sur le globe, published in vol. iii., of Memoires de physique et de chimie de la Societe d'Arcueil, Paris, 1819. Hutton, James. See vol. iii., p. 178. Theory of Rain, in Transactions of the Royal Society of Edinburgh, 1788, vol. i., pp. 53-56. See vol. iii., p. 121. From Transactions of the Royal Society of Edinburgh, 1788, vol. i., pp. 214-304. A paper on the "Theory of the Earth," read before the society in 1781. Kant, Immanuel (1724-1804). See vol. iii., p. 27. Allgemeine N aturgeschichte und Theorie des Himmels, 1755. Cosmogony, ed. and trans, by W. Hartie, D.D., Glasgow, 1900. Laplace, M. le Marquis de. See vol. iii., p. 32. Exposition du sysieme du monde, Paris, 1 7 96, is available in CEuvres completes, in 12 vols., Paris, 1825-1833, vol. vi., p. 498. Lyell, Charles. See vol. iii., p. 88. Principles of Geology, 4 vols., London, 1834. Marsh, O. C. See vol. iii., p. 107. Fossil Horses in America (reprinted from American Naturalist, vol. viii., May, 1874), pp. 288, 289. Playpair, John. See vol. iii., pp. 131, 165. Illustrations of the Huttonian Theory, 1802. Scrope, G. Poulett. See vol. iii., p. 132. Consideration of Volcanoes,. London, 1823, pp. 228- 234- 253 A HISTORY OF SCIENCE Wells, W. C. See vol. iii., p. 185. Essay on Dew, London, 181 8. IV— MODERN PHYSICAL AND CHEMICAL SCIENCES Black, Joseph. See vol. iv., p. 12. De acido e cibis orlo, et de magnesia, reprinted at Edinburgh, 1854. In this he sketched his discovery of carbonic acid. Later this paper was incorporated in his Experiments on Magnesia, Quicklime, and Other Alkaline Substances. Bunsen, William. See vol. iv., p. 69. Cavendish, Henry. See vol. iv., p. 15. "Experiments on Air," in Phil. Trans., 1784, p. 119. This paper contains Cavendish's discovery of the com- position of water and of nitric acid. Daguerre, Louis J. M. See vol. iv., p. 70. Historique et description des procedes du daguerreotype et du diorama, Paris, 1839. (This was translated into English.) Dalton, John. See vol. iv., p. 40. "On the Absorption of Gases by Water," read before the Literary and Philosophical Society of Manchester, October 21, 1803. This was published in 1805, and con- tains the atomic weight of twenty-one substances, some of which were probably added, or corrected, between the date of the first reading and the publication. Davy, Sir Humphry. See vol. iv., pp. 48, 209. "Some Chemical Agencies of Electricity," in Phil. Trans, for 1806, vol. viii. Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide or De- phlogisticated Nitrous Air and its Respiration, London, 1800. Dewar, James. See vol. v., p. 39. "Solid Hydrogen," in Proc. Roy. Inst, for 1900. "The Nadir of Temperature and Allied Problems " CBakerian Lecture), Proc. Roy. Soc, 1901. 254 A LIST OF SOURCES Dufay, Cisternay. See vol. ii., p. 267. Histoire de V Academic Roy ale des Sciences, between 1733 and 1737, contains Dufay 's principal papers. Euler, Leonard (1707-1783). See vol. iii., p. 17. Lettres a une Princesse d'Allemagne sur quelques sujets de physique et de philosophic, St. Petersburg, 1768. Faraday, Michael. See vol. iii., p. 241. On the Induction of Electric Currents, in Phil. Trans. of Royal Society for 1832, pp. 126-128. Explication of Arago's Magnetic Phenomena, by Michael Faraday, F.R.S., Phil. Trans, of Royal Society for 1832, pp. 146- 149. Franklin, Benjamin. See vol. ii., p. 286. New Experiments and Observations on Electricity, London, 1760. Galvani, Luigi (1737-1798). See vol. iii., p. 229. De viribus electricitatis in motu musculari commentatio, Bologna, 1791. This discovery of Galvani was first brought to notice by Volta's famous paper to the Royal Society, entitled "An Account of some Discoveries made by Mr. Galvani, of Bologna," published in the Phil. Trans, for 1793, pp. 10-44. Gay-Lussac, Joseph Louis. See vol. iv., p. 41. Memoire sur la combinaison des substances gazeuses, Mem. Soc. d'Arcueil, 1809. Halley, Edmund. See vol. iii., p. 7. An Account of Several Extraordinary Meteors or Lights in the Sky, in Phil. Trans., vol. xxix., pp. 159 - 162, London, 17 14. Helmholtz, H. L. F. See vol. iii., p. 280. Handbuch der physiologische Optik, Leipzig, 1867. Joule, J. P. See vol. iii., p. 269. On the Calorific Effects of Magneto -Electricity and the Mechanical Value of Heat, in Report of the British Asso- ciation for the Advancement of Science, 1843, v°l- xu-> P- 33- 255 A HISTORY OF SCIENCE Kirwan, R. See vol. iv., p. 3 ff. An Essay on Phlogiston and the Constitution of Acids, London, 1789. This is interesting, written as it was just before Lavoisier's Elements treated the same subject from the stand-point of the anti -phlogistic chemists. Kleist, Dean von. See vol. ii., p. 280. In the Danzick Memoirs, vol. i. contains the de- scription given by Von Kleist of his discovery of the Leyden jar. A translation is given also in Priestley's History of Electricity. Lavoisier, Antoine Laurent. See vol. iv., p. t>Z- Traite elementaire de chimie, Paris, 1774, trans, as Elements of Chemistry, by Robert Kerr, London and Edinburgh, 1790. Lister, Joseph Jackson. See vol. iv., p. 113. On Some Properties in Achromatic Object Glasses Applicable to the Improvement of the Microscope, in Phil. Trans, for 1830. Maxwell, James Clerk-. See vol. iii., p. 45. " On the Motions and Collisions of Perfectly Elastic Spheres " in Philosophical Magazine for January and July, i860. The Scientific Papers of J. Clerk-Maxwell, edited by W. D. Nevin (2 vols.), vol. i., pp. 372-374, Cambridge, 1896. This is a reprint of Maxwell's prize paper of 1859. Mayer, Dr. Julius Robert. See vol. iii., p. 259. The Forces of Inorganic Nature, 1842. This is Mayer's statement of the conservation of energy. Mendeleeff, Dmitri Ivanovitch. See vol. iv., p. 68. Principles of Chemistry, 2 vols., London, 1868-1870. (There have been several subsequent editions.) Oersted, Hans Christian. See vol. iii., p. 236. Experiments with the Effects of the Electric Current on the Magnetic Needle, published at Berlin, 181 6. Priestley, Joseph. See vol. iv., pp. 20, 36. Experiments and Observations on Different Kinds of Air, 3 vols., Birmingham, 1790. History of Electricity, 256 A LIST OF SOURCES vol. ii., p. 280, London, 1775. The Doctrine of Phlogiston Established, 1800. Ramsay and Rayleigh. See vol. v., p. 86. "On an Anomaly Encountered in Determining the Density of Nitrogen Gas," in Proc. Roy. Soc, April, 1894. A statement of the properties of argon was made by the discoverers to the Royal Society, given in Phil. Trans., clxxxvi., p. 187, January, 1895. Scheele, Karl William. See vol. iv., p. 23. Om Brunsten, eller Magnesia, och dess Egenakaper, Stockholm, 1 774. This contains his discovery of chlorine. His book, Chemische Abhandlung von der Luft und dem Feuer, was published in 1777. Thompson, Benjamin (Count Rumford). See vol. iii., p. 208. Essays Political, Economical, and Philosophical (2 vols.), vol. ii., pp. 470 - 493, London, T. Cadell, Jr., and W. Davies, 1797. Thomson, William (Lord Kelvin). See vol. iii., p. 276. On a Universal Tendency in Nature to the Dissipation of Mechanical Energy, in Transactions of the Royal Society of Edinburgh, 1852. Wollaston, William Hyde. See vol. iv., p. 41. Phil. Trans, for 1814, vol. civ., p. 1, contains a synoptic scale of chemical equivalents. This paper was confirma- tory of Dalton's theory. Young, Thomas. See vol. iii., p. 218. On the Colors of Thin Plates, I.e. in Phil. Trans, for 1802, pp. 35-37. V.— MODERN BIOLOGICAL SCIENCES AVENBRUGGER, LEOPOLD. See Vol. iv., p. 200. Inventum novum ex percussione thoracis humani interni pectoris morbos detegendi, Vienna, 1761. vol. v.— 17 257 A HISTORY OF SCIENCE Bell, Sir Charles See vol. iv., p. 249. An Exposition of the Natural System of Nerves of the Human Body, being a Republication of the Papers delivered to the Royal Society on the Subject of the Nerves in 18 11, etc. Bernard, Claude. See vol. iv., p. 137. Boerhaave, Hermann. See vol. iv., p. 182. Institutiones medics, Leyden, 1708; and De chemie expurgante suos errores, Lugduni Batavorum, 17 18. Brown, Robert. See vol. iv., p. 115. On the Organs and Mode of Fecundation of Orchidea and Asclepiade&, in Miscellaneous Botanical Works, Lon- don, 1866. Chambers, Robert. See vol. iv., p. 161. Vestiges of the Natural History of Creation, London, 1844 (published anonymously). His Sequel to Vestiges was published a year later. Charcot, Jean Martin. See vol. iv., p. 269. Legons sur les maladies du systeme nerveux, Paris, beginning in 1873. Cuvier, George, Baron de. See vol. iv., p. 159. Histoire naturelle des animaux sans vertebres, Paris, 181 5. Systeme des connaissances positives de Vhomme, Paris, 1820. Darwin, Erasmus. See vol. iv., pp. 94, 147. The Botanic Garden, London, 1799. The Temple of Nature, or The Origin of Society, edition published in London, 1807. Darwin, Charles. See vol. iii., p. 95, and vol. iv., p. 173. The Origin of Species, London, 1859. Fechner, Gustav. See vol. iv., p. 263. Elemente du Psychophysik, i860. Flourens, Marie Jean Pierre. See vol. iv., p. 270. Experiences sur le systeme nerveux, Paris, 1825. Cours sur la generation, Vovologie, et Vembryologie, Paris, 1836, etc. Gall, Franz Joseph. See vol. iv., p. 248. Recherches sur le systeme nerveux en general, et sur 258 A LIST OF SOURCES celui du cerveau en particulier, Paris, 1809. (This paper was laid before the Institute of France in March, 1808.) Goethe, Johann Wolfgang. See vol. iv., p. 140. Die Metamorphose der Pflanzen, 1790. Gray, Stephen. See vol. ii., p. 262. Most of his original papers appeared in the Phil. Trans, between 1720 and 1737. Haeckel, Ernst Heinrich. See vol. v., p. 144. Naturlich Schopfungsgeschichte, 1866, rewritten in a more popular style two years later as Natural History of Creation. Some of his more important monographs are: Radiolaria (1862), Siphonophora (1869), Monera (1870), Calcarious Sponges (1872), Arabian Corals C1876), an- other Radiolaria, enumerating several thousand new species, accompanied by one hundred and forty plates (1887), and Die Weltrdthsel, trans, in 1900 as The Riddle of the Universe. Hahnemann, Wilhelm von. See vol. iv., p. 189. Organon der rationellen Heilkunde, Dresden, 1810. Hall, Marshall, M.D., F.R.S.L. See vol. iv., p. 251. On the Reflex Functions of the Medulla Oblongata and the Medulla Spinalis, in Phil. Trans, of Royal Society, vol. xxxiii., 1833. Hunter, John. See vol. iv., p. 92. On the Digestion of the Stomach after Death, first edition, pp. 183-188. Jenner, Edward. See vol. iv., p. 190. An Inquiry into the Causes and Effects of the Variola? Vaccina?, London, 1799. Laennec, Rene Theophile Hyacinthe. See vol. iv., p. 201. Traite d' auscultation mediate, Paris, 1819. Lamarck, Jean Baptiste de. See vol. iv., p. 152. Philosophie zoologique, 8 vols., Paris, 1801. His famous statement of the supposed origin of species occurs on p. 235 of vol. i., as follows: "Everything which nature has caused individuals to acquire or lose by the influence of the circumstance to which their race is long exposed, and consequently by the influence of 259 A HISTORY OF SCIENCE the predominant employment of such organ, or its constant disuse, she preserves by generation to the new- individuals proceeding from them, provided that the changes are common to the two sexes, or to those which have produced these new individuals." Liebig, Justin. See vol. iv., p. 131. Animal Chemistry, London, 1843. Liebig and Wohler. See vol. iv., p. 56. The important work of Liebig and Wohler appeared until 1832 mostly in Poggendorff's Armalen, but after 1832 most of Liebig's work appeared in his own Annalen. About the earliest as well as one of his most important separate works is Anleitung zur Analyse organischen, Korper, 1837. Lotze, Hermann. See vol. iv., p. 263. Medizinische Psychologie, oder Physiologie der Seele, Leipzig, 1852. Mohl, Hugo von. See vol. iv., p. 125. Uber der Sajtbewegung im Innern d. Zelle, Bot. Zei- tung, 1846. Morgagni, Giovanni Battista. See vol. iv., p. 76. De sedibus et causis morborum, 2 vols., Venice, 1761. Oken, Lorenz. See vol. iv., p. 160. Philosophie der Natur, Zurich, 1802. Pasteur, Louis. See vol. iv., pp. 217, 233. Studies on Fermentation, London, 1879. His famous paper on attenuation and inoculation was published in the Compte Rendti of the Academy of Science, Paris, 1 88 1 (vol. xcii.). Saint-Hilaire, Etienne Geoffroy. See vol. iv., p. 160. Philosophie anatomique, vol. i., Paris, 181 8. Schwann, Theodor. See vol. iv., p. 119. Mikroskopische Untersuchungen itber die Ubereinstim- mung in der Structur und dem Wachsthum der Thiere und Pflanzen, Berlin, 1839. Trans, by Sydenham Soc, 1847. Spencer, Herbert. See vol. iv., p. 268. Principles of Psychology, London, 1855. 260 A LIST OF SOURCES Treviranus, Gottfried Reinhold. See vol. iv., p. 159. Biologie, oder Philosophie der lebenden Natur, 1802. Weber, E. H. See vol. iv., p. 263. The statement of "Weber's Law" was first made in articles by Weber contributed to Wagner's Handworter- buch der Physiologic, but is again stated and elaborated in Fechner's Psychophysik. (See Fechner.) Weismann, August. See vol. iv., p. 179. Studies in the Theories of Descent. Trans, by Professor R. Meldola, London, 1882. The introduction to this work was written by Darwin. Wohler, Friedrich. (See Liebig and Wohler.) Wundt, Wilhelm Max. See vol. iv., p. 268. Gnindziige der physiologischen Psychologie, 1874. Many articles by Wundt have appeared in the Philosophische Studien, published at Leipzig. V.— ASTRONOMY A strono mische Gesellschaft. A quarterly journal of astronomy published in Leipzig. Berry, Arthur. A Short History of Astronomy, New York, 1899. Bertrand, J. L. F. Les fondateurs de I'astronomie modem: Copernic, Tycho Brahe, Kepler, Galileo, et Newton, Paris, 1865. This gives an interesting account of the lives and works of these philosophers. Flammarion, C. Vie de Copernic, et histoire de la decouverte du systeme du monde, Paris, 1872. Forster, W. Johann Kepler und die Harmonie der Spharen, Berlin, 1862. Jensen, P. Die Kosmologie der Babylonier, Strasburg, 1890. 261 A HISTORY OF SCIENCE Lockyer, Joseph Norman. The Dawn of Astronomy; a Study of the Temple Worship and Mythology of the Ancient Egyptians, London, 1894. Loomis. History of Astronomy, New York, 1855. ROTHMANN. History of Astronomy (in the Library of Useful Knowl- edge), London, 1834. SOCIETE ASTRONOMIQUE DE FRANCE. Monthly bulletin, Paris. Thompson, R. Campbell. Reports of the Magicians and Astrologers of Nineveh and Babylon, p. 19, London, 1900. Wolf, R. Geschichte der Astronomie, Munich, 1877. VI.— PHYSICS (ELECTRICITY) Annalen der Physik, Leipzig. Edited by Dr. Paul Drude. (Note — Heavy, scientific, up-to-date. Is apparently under the patronage of all the big physicists, such as Roentgen, etc.) Atti della Associazione Elethoiecnica Italiana (at Rome). A large bi-monthly magazine, strictly technical, devoted largely to theoretical problems of electricity and allied subjects. Bulletin International de VElectricite et Journal de VElectricite (reunis). A semi-monthly four-page paper dealing with the technical application of electricity in its various fields. Die Dissozuerung und Umwandlung chemischer A.tome, by Dr. Johannes Stark, 1903. Price 150 m. "A compre- hensive view of the application of the electron theory to certain phenomena." — Nature, May, 1904. Die Kathodenstrahlen, by G. C. Schmidt, Brunswick, 1904. 262 A LIST OF SOURCES "A concise and complete account of the properties of the cathode rays." — Nature, June, 1904. Electrical Engineer. Electrical Magazine. Electricity. A weekly journal, published by the Electricity Newspaper Co., New York. Devoted largely to questions of the practical application of electricity, but dealing also with the theoretical side. Elements of Electro-magnetic Theory, by S. J. Barnett, Le- land Stanford, Junior, University. Macmillan & Co., 1904. ($3-) Handbuch der Physik, by Dr. A. Winkelmann, Leipzig, 1904. "An indispensable storehouse of expert knowl- edge."— Nature, July, 1904. Hardin. Rise and Development of the Liquefaction of Gases, New York, 1899. La theorie de Maxwell et les oscillations hertziennes, la Tele- graphie sans fil, by H. Poincare, Paris, 1904 (price 2 fr.). Interesting studies of light, etc. An interesting brochure. — Revue Scientifique, July, 1904. Le radium et la radioactivite, by Paul Besson, Paris, 1904 (price 2 fr. 75). A good exposition of the known prop- erties of radium, marred, however, by an attempt to put in accord science and religion — a propos du radium ! — Revile Scientifique, July, 1904. Lehrbuch der Physik, by Von O. D. Chwolson, St. Peters- burg, 1904. 2 vols. out. First vol. covers general physics and mechanics. Second vol. sound and radiant energy. "Excellent and quite comprehensive." — Science, review. Park, Benjamin. The Intellectual Rise in Electricity, New York, 1895. This is a popular account of the progress in the field of electricity from Gilbert to Franklin. Radium and all About It, by S. Bottone, London, 1904. Published by Whittaker & Co. Price 15. "An accurate account of the most important phenomena." — Nature, June, 1904. The Physical Review. A monthly journal of experimental and theoretical physics. Published for Cornell Uni- versity by the Macmillan Company. 263 A HISTORY OF SCIENCE Theory of Heat, by Thomas Preston, F.R.S. Second edition just out. Macmillan & Co., 185. VII.— CHEMISTRY American Chemical Journal. Edited by Ira Remsen, presi- dent of Johns Hopkins University. Published monthly at Baltimore, Maryland. Price $5 per annum. A strictly technical journal. Bacon, Roger. Mirror of Alchemy, and Admirable Power of Art and Nature, London, 1597. Berthelot, P. E. M. Introduction a Vetude de la chimie des anciens et du moyen age, Paris, 1889. Les origines de Valchimie, Paris, 1885. Bidletin de la Societe Chimique de Paris. A monthly tech- nical journal, treating all phases of the science of chem- istry. Food Inspection and Analysis, by Albert E. Leach, S. B. (John Wiley & Sons, N. Y., $7.50). Note. —This book is de- signed for the use of public analysts, health officers, food economists, etc. Hoefer, J. C. F. Histoire de la chimie, Paris, 1866-186 9. This gives biographical sketches of many of the great chemists as well as the history of the development of chemistry. Jahresbericht uber die Forts chritte der Chemie. A journal of the progress in chemistry, published irregularly in Bruns- wick. Kopp, H. Geschichte der Chemie (4 vols.), Brunswick, 1843-1847. This is an exhaustive history of the development of chemistry. Lehrbuch der Ster eo chemie , by A. Werner, Jena, 1904, price 10 m. "Should be in the hands of every organic chem- ist."— Nature for August, 1904. Lemoine, Y. F. La vitalism et Vaminisme de Stahl, Paris, 1864. This 264 A LIST OF SOURCES discusses fully Stahl's famous theories of matter and life. Meyer, E. von. A History of Chemistry from the Earliest Times to the Present Day, London, 1898. This treats fully the sub- ject of the phlogiston theory and its influence in the development of chemistry. Muir, M. P. Story of Alchemy and the Beginnings of Chemistry, London and New York, 1899. A popular account of the development of the phlogiston theory from alchemy, giving explanations of the curious beliefs and methods of working of the alchemists. Rodwell, G. F. The Birth of Chemistry, London, 1874. Thompson, C. J. S. The Mystery and Romance of Alchemy and Pharmacy , in the Scientific Press, London, 1897. This is very interesting and readable. Thompson, T. The History of Chemistry, London, 1830, 183 1. Waite, Arthur Edward. Lives of Alchemistical Philosophers, London, 1888. A biographical account of the most noted alchemists. This is very complete. Waite has also collected a list of the principal works of the alchemists, this list filling about thirty pages of fine print. VIII— GEOLOGY, BIOLOGY, PALEONTOLOGY American Geologist. American Museum of Natural History Bulletins, New York. American Naturalist. Annales de VInstitut Pasteur (18 fr. per annum). A monthly bulletin of the Pasteur Institute, containing mostly tech- nical articles, but also articles of interest to persons in- terested in problems of immunization and immune sera. 265 A HISTORY OF SCIENCE Annates des sciences naturelles : zoologie et paleontologie, Paris. Annals and Magazine of Natural History, including zoology, botany, and geology. Monthly. London. A technical magazine. Of little interest to the general reader. Archiv fur Naturgeschichte. A journal of natural history published bi-monthly at Berlin. Archiv fur Rassen-und — Geselischaft — Biologie einschliefslich Rassen — und Gesell.-Hygiene. Archives de biologie (quarterly), Liege. Archives des sciences biologiques. St. Petersburg. Five num- bers a year. Archives Italiennes de biologie. Turin. Bi-monthly. Biological Bulletin of the Marine Biological Laboratory, Wood's Holl, Massachusetts. Published monthly by the labor- atory. Managing editor, Frank R. Lillie. Scientific and technical — very good. Biologie generate des bacteries, by E. Bodin, professor of bac- teriology, University of Rennes, Paris, 1904. Price 2 fr. 50. Studies of bacteria in general treated in a semi-popular manner. Some new ideas prepared to explain bacterial action in normal life — very good. — Revue Scientifique, review, August, 1904. Biometrika. A journal for the statistical study of biological problems (quarterly), 305. per annum. Edited, in con- sultation with Francis Galton, by W. F. R. Weldon, Karl Pearson, and C. B. Davenport. A bulky journal, beau- tifully illustrated with plates and line cuts. Largely technical, but containing many articles of interest to general readers on laws of inheritance, hereditary in- fluences, etc. Bulletin of the Geological Society of America. Published irregularly at Rochester. Geologische und Palceontologische Abhandlungen, Jena. Johns Hopkins University, Memoirs from the Biological Laboratory. UEchange Revue Linnienne, fondee par le Docteur Jacquet. Directeur, M. Pic. A monthly journal of natural his- tory, devoted largely to entomology — small and technical. Of interest to entomologists only. Les lois naturelles, par Felix le Danteg, charge du cours 266 A LIST OF SOURCES d'embryologie generate a, la Sorbonne, Paris, 1904. Price 6 fr. A study in biology. "The name cor- responds exactly with the contents of this admirable work." — Revue Scientifique, review, September, 1904. Marine Biological Association of the United Kingdom, Plym- outh. Societe Dauphinoise d'Ethnologie et d' Anthropologic Quar- terly bulletin. Grenoble. Societe Zoologique de France. Monthly bulletin. Text-book of Geology, by Sir Archibald Geikie, 2 vols. Fourth edition. $10. Macmillan & Co., 1904. Text-book of Paleontology (Macmillan, 1904, $3), by Carl A. von Zittel, University of Michigan. The Geological Magazine, or Monthly Journal of Geology, edited by Henry Woodward, LL.D., F.R.S., etc. Lon- don, 15. 6d. per copy. A high-class technical magazine. The American Journal of Psychology, edited by G. Stanley Hall, E. C. Sanford, and E. B. Titchnener. Published at Worcester, Massachusetts, monthly. A technical jour- nal devoted to psychological researches. The Naturalist, London. A monthly journal for the north of England. Edited by J. Sheppard, F.G.S., and T. W. Woodhead, F.L.S. Annual subscription, 6s. 6d. A local journal, but containing general articles of interest. Semi-popular. The Quarterly Journal of Microscopical Science, edited by E. Ray Lankester, M.A., LL.D., F.R.S. IX— MEDICINE American Journal of Insanity. American Journal of the Medical Sciences, Philadelphia. Annates medico-psychologiques, Paris. Arbeiten aus dem leaiserlichen Gesundheitsamte. A journal of hygiene published irregularly at Berlin. Archiv fur Anatomie und Physiologic A semi - monthly journal of the progress in anatomy and physiology, pub- lished at Leipzig. 267 A HISTORY OF SCIENCE Archiv fur die gcsammte Physiologie, Bonn. British Medical Journal, London. Immune Sera, by Professor A. Wassermann, M.D., trans, by Charles Bolduan, M.D., New York and London, 1904. ' ' We confidently commend this little book to all persons desirous of acquainting themselves with the essential facts on the subject of immune sera." — N attire, July, 1904. Lancet, London. Leclerc, Lucien. Histoire de la medecine arabe, 2 vols., Paris, 1876. This work is very complete and well written. Medical Record, New York. Medical Times, New' York. Pagel, Julius. Einfuhrung in die Geschichte der Medicin, Berlin, 1898. This is not as exhaustive as Baas's book, but is written in a much more readable style. Park, Roswell. Epitome of the History of Medicine, Philadelphia, 1899. Paul of ^Egina. The Works of, published by the Sydenham Society, London, 1841, are well worth reading, as giving a clear understanding of the status of medicine in the seventh century. Sprengal, K. P. J. Histoire de la medecine depuis son origine jusqu'au dix-neuvieme Steele, 8 vols., Paris, 1815-1820. This is a French translation of the German work, and is more available than the original volumes. It is, per- haps, the most exhaustive history of medicine ever at- tempted. The Journal of Hygiene, edited by George H. F. Nuttall, M.D., Ph.D. A quarterly journal of hygiene (215. per annum), containing many interesting articles on subjects connected with hygiene and of interest to general readers. The Journal of Physiology, edited by Sir Michael Foster, K.C.B., M.D., F.R.S., and J. N. Langley, Sc.D., F.R.S. Issued quarterly. Price 85. C. J. Clay & Sons, Lon- don. 268 A LIST OF SOURCES X.— ANTHROPOLOGY AND ARCHEOLOGY American Anthropologist. F. W. Hodge, editor, Washington, D. C. Published quarterly for the American Anthropo- logical Association ($4.50 per annum). Technical (or semi -technical). "A medium of communication be- tween students of all branches of anthropology." Much space devoted to Indian language, etc. — a very good journal. American Jotirnal of Archceology. American Journal of Sociology. Archivo per V antropologia c V etnologia, Florence. Three numbers a year. A journal devoted to anthropology and ethnology. Avebury, Lord (Sir John Lubbock). The Origin of Civilization and the Primitive Condition of Man. Mental and social condition of modern savages. New York, 1870. Brinton, Daniel Garrison, M.D. The Basis of Social Relation, a Study in Ethnic Psychol- ogy, edited by L. Farrand, New York, 1902. Clodd, Edward. Myths and Dreams, London, 1885. Story of Primitive Man, 3d edition, London, 1897. The Childhood of the World. A simple account of man in early times. Lon- don, 1893. Dawkins, W. Boyd. Early Man in Britain, London, 1880. Cave Hunting. Researches on the evidence of caves respecting the early inhabitants of Europe. London, 1874. Dellenbaugh, Frederick S. The North Americans of Yesterday, New York, 1901. Deniker, Joseph. Races of Man. An outline of anthropology and ethnol- ogy. London, 1900. Grierson, P. J. H. Hamilton. The Silent Trade. A contribution to the early history of human intercourse. London, 1903. Haeckel, Dr. Ernst Heinrich. Anthropogenic; oder Entivickelungsgeschichte des Men- schen, 4th edition, 2 vols., Leipzig, 1891. 269 A HISTORY OF SCIENCE MtJLLER, FRIEDRICH. Ethnographie ; auf Grund des von K. von Scherzer gesammetten Materiales. Vienna, 1868. Murtillet, Gabriel de. Le prehistorique antiquite de I'homme. Paris, 1883. Powell, John Wesley. "Relation of Primitive Peoples to Environment." In Smithsonian Institution Report. Washington, 1896. Reports of American Ethnology, in the annual reports of the U. S. Bureau of Ethnology since 1877. Quatrefages (A. de Q. de Brun). Histoire generate des races humaines. Paris, 1889. Ratzel, Friedrich. The History of Mankind, 3 vols., trans, by A. J. Bubler, London, 1 896-1 898. Revue de I'Ecole d' Anthropologic de Paris. Monthly. Pub- lished by the professors. Treats all phases and branches of anthropology. Science de I'homme et methode anthropologique, by Alphonse Cels, Paris and Brussels, 1904. 7 francs. "As a highly abstract and suggestive exposition of the nature and scope of anthropology, this book deserves a place in the library of the anthropologist." — Nature, September 24, 1904. Societe Academique d'Archeologie, Paris. INDEX Abd-el-Letip, Arabian physi- cian, ii. 21. Absolute zero, approach to the, made by liquefying hydrogen, v. 69; probable form of all matter at, v. 70; quest of, v. 72. Academia Natura? Curiosorum, founded in Germany, ii. 201. Accademia del Cimento, ii. 200. Adams, John Couch, discoverer of the planet Neptune, iii. 42; discovers an error in Laplace's calculation about the moon, iii. 48. Aetius, Byzantine physician, ii. Agassiz, Louis, his idea of the glacial theory, iii. 147; his famous Etudes sur les Glaciers, iii. 154. Air, experiments with, iv. 6, 7. Air liquefied, v. 45, 46. Air-pump invented by Von Guericke, ii. 211. Albategnius, astronomer, ii. 15. Albucasis, Arabian writer on surgery, ii. 25. Alchemy, ii. 124; the four elements, ii. 129; "killing" and "reviving" metals, ii. 130; Rosicrucians, ii. 136; Aureacrucians, ii. 136; tricks of alchemists, ii. 138; useful discoveries of alchemists, ii. 140. Alcmaeon, the first Greek anat- omist, i. 171; his explanation of the sense of hearing, i. 172. Alemaean, his theories concern- ing the heart and brain, i. 126. Alexandrian library not burn- ed by Arabs, ii. 11. Alexandrian science adds a day to every fourth year, i. 36. Alfonso X., Alfonsine tables, ii. l7- . . Alhazen, Arabian scientist, 11. 18; calculates height of at- mosphere, ii. 19. Almagest translated into Arabic, "• 9- Alphabet, the, development of, 1. 86; introduction of letters, i. 87; Egyptian and Assyrian characters, ibid.; first steps in picture-writing, i. 89; Egyptian writing, i. 90; Baby- lonian writing, i. 93; achieve- ment of, i. 98; extension and perfection of, i. 101. Alyattus, king of the Lydians, i. 103. Amadeo, Avogadro, and law of combinations, iv. 43. Amelineau, a student of the phonetic value of Egyptian symbols, i. 28. Amici, Giovanni, constructs a reflecting microscope, iv. 112; introduced the improved micro- scope, iv. 113. Ampere, Andre Marie, discovered the principles of the science of electro-dynamics, iii. 239; and the law of combinations of volumes, iv. 43; paved the 271 A HISTORY OF SCIENCE way for the study of organic substances, iv. 55. Anaesthetic power of chloroform and ether, iv. 217. Anaesthetics, use of in the dark age, ii. 35. Anatomists in the sixteenth cen- tury, ii. 163. Anatomy and physiology in the nineteenth century, iv. 102- x39- Anaxagoras, banished from Greece, i. 141; his theories about the sun and the planets, i. 143 ; alleged prediction of the fall of the famous meteor at .^Egespotomi, i. 144; his ex- planation of the origin of the heavenly bodies, i. 145 ; a clear conception of the idea of universal gravitation, i. 146; the first to explain the phases of the moon, i. 147; his theory of the Milky Way, i. 150; "the father of meteorology," i. 151; his speculations concern- ing thunder and lightning, i. 152 ; his idea that fishes respire air through their gills, " at- tracting" it through water, i. 153 ; his speculations as to nat- ural objects, i. 154; he claimed that every unit or atom in nat- ure was unchangeable and in- destructible, i. 155; the dis- tinction between molecular processes and atomic processes, i. 158; nous, the omnipotent artificer of the material uni- verse, i. 159; the most far- seeing scientific imagination of pre-Socratic antiquity, i. 161 ; the founder of the atomic theory, i. 169; he took account of the hypothetical counter- earth in his explanation of the eclipses, i. 216; conceived the idea of universal gravitation before Newton, ii. 236. Anaximander, inventor of the sun-dial, i. 109; his conception of the form of the earth, i. no; the first teacher of or- ganic evolution, i. in. Anaximenes, assisted in perfect- ing the sun-dial, i. 109. Animal kingdom, new classifica- tion of, by Cuvier, iv. 102. Animists' system, theory of, iv. 185. Anthropology, problems in, v. 228; its position to-day, v. 229. Anthrax, cause of, iv. 227, 228; sheep and cattle given im- munity from, at the Pasteur Institute, v. 185. Antirabic treatment given at the Pasteur Institute, v. 183. Antisepsis, Lister's discovery of, iv. 229. Arabian hospitals, ii. 26. Arabian learning, its subjects, ii. 13; mathematics, ii. 14; astronomy, ii. 14-17; optics, ii. 18; chemistry, ii. 20; medi- cine, ii. 21. Arabian method of earth-meas- urement, ii. 14. Arabian numerals, period of their invention, ii. 13. Arabic translations, ii. 9. Arago, a convert to Fresnel's wave theory, iii. 226; demon- strated that electricity not only influenced a magnet, but actually produced magnetism, iii. 239. Archimedes, invented many me- chanical contrivances, i. 197; the Archimedean screw, ibid.; his devices for the defence of Syracuse, i. 198; his com- bination of multiple pulleys, i. 200; his invention of the catapult, i. 201; his con- trivance for wrecking galleys, i. 202; the mythical legend of the burning-glass, i. 205; his studies of the properties of the lever, i. 206; his ex- periment with King Hiero's crown, i. 207; his demon- strations* of the buoyancy of water, i. 208; the problem of 272 INDEX the triangle and a circle, i. 209; his crude conception of the idea of logarithms, i. 210; his assumption about the size of the sun and earth, ibid.; his computation about the number of grains of sand that would be required to cover the sphere of the sun's orbit, i. 211. Argon, discovery of, v. 85, 86. Aristarchus, of antiquity, i. 218, 220, 221. Aristotle, his name a synonym for Greek science a thousand years after his death, i. 182; his acceptance of the doctrine of the spherical figure of the earth, i. 183; a pathfinder in the science of zoology, i. 185; his divisions of the vertebrates and invertebrates are accepted by every one to-day, i. 186; his classification of blood-bear- ing animals and fishes not far afield from modern divi- sions, i. 187. Arnald of Villanova, physician, ii. 34. Arzachel, "trepidation of the fixed stars," ii. 16. Assyrian month, i. 64; sabbatical days, i. 65. Assyrian scripture, restoration of, iv. 293. Assyrio-Babylonian records, of greater historical accuracy than the Egyptian, i. 59; the discrepancy between the Baby- lonian and Egyptian years, i. 65; tablets dealing with magic make up a large pro- portion of, i. 70. Astrologers, in Babylon they were men of high rank and their office was hereditary, i. 67; gave their chief attention to the moon, i. 68. Astrology, ii. 141; present-day survival, ii. 144; predictions of Lilly, ii. 145 ; George Wharton, ii. 150; other alleged pre- dictions, ii. 152, 155; cause of the decline of astrology, ii. 155. Astronomer priests, their duty was to predict the rising of the Nile, i. 39. Asurbanipal, king of Assyria, his contribution of tablets, i. 67 ; the great library of, in the British Museum, iv. 295. Atmosphere, constituents of, v. 89- , . . Atom, the vortex, speculation m, v. 216; proof of the existence of, v. 217. Atomic weights, iv. 64-67; cu- rious relations between, of various elements, iv. 66; their relations with other charac- teristics, iv. 67. Atoms, affinity of, v. 218; space relations of, v. 219. Attempts to explain power of gravitation, v. 214. Aurora borealis, the, Franklin's explanation of, iii. 173; Eras- mus Darwin's theory of, ibid.; Biot's theory of, iii. 174; sun spots linked with, iii. 175. Avenzoar, Arabian physician, ii. 26. Averrhoes, commentator of Aris- totle, ii. 10, 26. Avicenna, Arabian "Prince of Physicians," ii. 24. Avogadro, Amadeo, iv. 43; law, iv. 57- Babylon, its fame at its height in the time of Herodotus, i. 57; in Babylonian science we have the Eastern mind at its best, i. 61. Babylonian astronomy, i. 61, 62; adjustment of the calen- dar, i. 63-66. Babylonian medicine, the prac- titioner of, occupied a position of authority, i. 75; his emolu- ments and penalties, i. 76. Babylonian science, estimates of, i. 77; Canon Rawlinson on i. 82; spelled superstition, i. 85. VOL. V. 18 273 A HISTORY OF SCIENCE Bacon, Francis, influence on sci- ence, ii. 1 92; indirectly a found- er of the Royal Society, ii. 201. Bacon, Roger, ii. 4; his use of lenses, ii. 45; supposed in- vention of gunpowder, ii. 46; estimate of his work, ii. 46. Bacteria, discovery of, ii. 179. Baglivi, Giorgio, distinguished in medicine, iv. 182. Barometer, mercurial, invented by Torricelli, ii. 122; statical, invented by Boyle, ii. 205. Bastian, Professor, revived the claims of Pouchet, iv. 180. Bay of Naples, the, fauna of, v. 124; abundance of material for biological study found in, v. 125 ; uses made of specimens found in, in scientific study, v. 128. Bayley, Dr., expert in spectro- scopy, v. 83. Becquerel, M. Henri, discovery of a radio-active substance, v. 98, 99; "rays," v. 100. Beginnings of modern chemistry, iv. 11-37. Behring's discovery of tetanus and diphtheria antitoxine, iv. 242. Bell, Dr. (Sir Charles), discovery of motor and sensory nerves, iv. 249. Berlin Institute of Hygiene, the, v. 193-202; work of Pro- fessor Koch in, v. 194; work of his successors in, v. 195; department of bacteriology in, v. 196; investigations of the functions of the human body in, v. 197; models in the Museum of Hygiene, v. 198, 200; studies in problems of ventilation, v. 200. Berlin Institute of Pathology, the, v. 186-193; study of diseases in, v. 187; studies of organic action and cellular activities in, v. 188; Virchow's methods of teaching in, v. 191, 192. Berlin system of sewage-disposal, the, v. 199. Bernard, Claude, studies of the ductless glands, iv. 137; dis- covers that the blood under- goes a change in passing through the liver, iv. 138; discovers that the sympathetic nerves regulate the blood supply, iv. 259; his discovery of inhibitory nerves, iv. 261. Berosus, a Babylonian historian, i. 58. Berthez, Paul Joseph, champion of the Vitalists' system, iv. 185. Berthelot's refusal to accept the atomic theory, iv. 41. Berzelius, Johan Jakob, accepts Dalton's theory, iv. 41-44; his binary theory, iv. 53; his dualistic theory, iv. 55; coined the word "isomerism," iv. 62. Bessel, predicted the existence of the planet Neptune, iii. 42 ; measured the parallax of a star in 1838, iii. 60. Bianco, Signer Lo, chief of the collecting department of the Marine Biological Laboratory, v. 122. Bichat, Marie Francois, studies of the animal and organic systems of vertebrates, iv. 107 ; his division of anatomical structures into sets of tissues, iv. 108. "Biology," word coined inde- pendently by Treviranus and Lamarck, iv. 160. Biot, Jean Baptiste, investigated the meteor of 1803, iii. 168; accounted for it on scientific grounds, iii. 169. Birch, a student of Egyptian writing, i. 27. Black, Dr. Joseph, his latent heat observations on the sub- ject of precipitation of vapor, iii. 182; disproved by Dr. Wells, iii. 183; continues Hale's 274 INDEX study of the elasticity of air, iv. 1 1 ; discovery of the prop- erties of carbonic - acid gas, iv. 12; studies continued by Cavendish, ibid. Blood corpuscles, functions of, iv. 135; important role played by, iv. 136. Boerhaave, Hermann, fame of, iv. 182; his classification of the different branches of medi- cine, iv. 183; his doctrines arranged into a "system" by Hoffmann, iv. 184. Bond, W. C, discoverer of the inner or crape ring of Saturn, iii. 44. Books, preservation of ancient, ii. 6. Borelli, "On the Motive of Animals," ii. 188. Boscovich, Roger Joseph, the ultimate constitution of mat- ter as conceived by, iii. 293. Bose, George Matthias, inventor of an electric machine, ii. 274; explanation of aurora borealis, ii. 277. Boulevard Pasteur, the, v. 179. Boyle, Robert, ii. 204; ex- periments on air, ii. 205; calculation of atmospheric pressure, ii. 206; views on color, ii. 208; work in electric- ity, ii. 209; his theories as to the composition of the at- mosphere, iv. 4-6; detected the existence of glands in the mucous membrane, iv. 129. Bradley, Dr. James, discovers the libratory motion of the earth's axis, iii. 12. Brahe, Tycho, a celebrated astronomer who declined to accept the heliocentric idea concerning the earth, i. 217. Braid, Dr. James, investigation of the phenomena of hypno- tism, iv. 269. Brain, studies of the, iv. 245- 249, 270-286; localization of, centres, iv. 272-274; minute structures of the, iv. 276- 286. Brewster, Dr. David, sugges- tions to improve the micro- scope, iv. no. Bridge, Dr., an Egyptologist, i. 28. British museum, the, founding of, v. 3; Sloan's collection purchased for, v. 4; acquisi- tion of Hamilton's treasures for, v. 5 ; Egyptian antiquities for, ibid.; erection of present building, v. 6; statue of Dar- win in, v. 9; arrangement of specimens in, v. 10, n; public interest in, v. 12. Broca, Dr. Paul, and localiza- tion of speech, iv. 272. Brown, Robert, discovery of the nuclei of plant cells, iv. 115. Brugsch, an Egyptologist, i. 28. "Brunonian" system, iv. 187. Buffon and the transmutation of species, iv. 149. Bunsen,with Kirchhoff, perfected the spectroscope, iv. 69. Burnham, S. W., discovers one thousand new clusters of stars, iii. 59. Cajal, Dr. S. Ramon y, demon- stration of independent nerve filaments, iv. 283; importance of discovery, iv. 285. Calmette, discoverer of the serum treatment for serpent- poisoning, v. 184. Calvin withholds the document of Servetus, ii. 168. Canton, John, produces both positive and negative elec- tricity on the same substance, ii. 295. Carbonic gas liquefied, v. 40. Carnot, Sadi, demonstrated that a definite quantity of work could be transformed into a definite quantity of heat, iii. 255- Carpenter, "William B., studies in embryology, iv. 132. 275 A HISTORY OF SCIENCE Cassini, Dominic, a celebrated French astronomer, iii. 13. Cathode rays, Sir William Crookes experiments with, iii. 249; Professor Roentgen's dis- covery of the remarkable effects of, iii. 250-252. Cavendish, Henry, continued Black's studies, iv. 13; dis- covery that water is formed by the combination of hydro- gen and oxygen, iv. 14; con- troversy with Watt, ibid.; ex- periments with air, iv. 16; discovery of nitrous acid, iv. I7- "Cedar of Lebanon," the, iv. 292. Cell contents, studies in, by Von Mohl, iv. 123; observed by Corti in 1774, iv. 124; rediscovered by Treviranus in 1807, ibid.; filled with fluid called "sarcode," iv. 124. Cell theory, Schwann and Schlei- den and the, iv. 1 18-122; fore- shadowed by Wolff and Trev- iranus, iv. 122; elaborated, iv. 122-128. Cell walls of vegetables, Payen and, iv. 124. Cells, essential structure of living organism, iv. 129; principles of mechanical construction of, v. 225. Celsus, Cornelius, his manu- script found in the fifteenth century, ii. 40. Centrosome, discovered by Van Beneden, v. 226. Chabas, a student of Egyptology, i. 28. Chaldean, a name once synony- mous with magician, i. 66. Chaldean magic, tablets relating to, i. 70; symbolism of the black and white cloth, i. 71; song of the seven spirits, i. 72; exorcisms to ward off disease, i. 73; birth portents, ibid.; omens furnished by dogs, i. 74. Chambers, Robert, his Vestiges , of the Natural History of Crea- tion, iv. 161; quotation from, iv. 162—164. Champollion, Jean Francois, a famous student of the science of Egyptology, i. 27; decipher- ment of the Rosetta Stone, iv. 290. Charcot, Dr., on the phenomena of hypnotism, iv. 269. Charms and incantations, i. 46- 51; effect of a lock of hair or nail parings incorporated in a waxen figure, i. 46; the magical spell of enemies the source of all human ailments, i. 47; efficacy of a beetle as a medicinal agent, i. 48. Chemical affinity, iv. 57-64; theory of digestion, iv. 88. Chemistry, the phlogiston theory in, iv. 3-10; at the beginning of the eighteenth century, iv. 1 1 ; Lavoisier and the founda- tion of modern, iv. 28; since the time of Dalton, iv. 38-72; organic, iv. 53-56; foremost workers in, iv. 55. Chicken cholera, Pasteur's ex- periments with, iv. 232. Chloroform, pain dispelling power of, discovered by Simp- son, iv. 217. Cholera, researches in the pre- vention and cure of, v. 184. Christian medical science, ii. 29. Christy, Henry, his discovery in the caves of Dordogne, iii. 1 04 ; presumptive evidence that man and the mammoth had been contemporaries, iii. 105. Chromosomes, the study of, v. 133; Professor Weismann's the- ory of heredity based on, v. x34- "Circuit," electrical term coined by Watson, ii. 285. Clark, Alvan, discovered the dark companion of Sirius, iii. 66. Clerk-Maxwell, J., he charac- terized the rings of Saturn as a 276 INDEX "shower of brickbats," iii. 44; thought they must consist of disconnected particles, iii. 45; advanced the idea that light waves were really electro- magnetic waves, iii. 247; be- lieved that electricity and magnetism were various condi- tions of stress and motion in the ethereal medium, iii. 280; all interstellar space filled with ether, iii. 283; his study of the kinetic theory of gases, iii. 295; his investigation of the subject of molecular dynamics, iii. 297; his calculations of the distance traversed by mole- cules between collisions in ordinary air, iii. 298. Clock, pendulum, invented by Huygens, ii. 219; marine, in- vented by Harrison, ii. 257. Cohesion, "force" of, v. 49. Colding, a Danish scientist, and the transformation of heat, iii. 257- Columbus, Christopher, effect of his discovery, ii. 50. Columbus, sixteenth - century anatomist, ii. 166. Comets, strangers to our plane- tary system, iii. 38; their movements not controlled by the general law, iii. 39; eccen- tric orbits, iii. 51; their spec- tacular tails, iii. 52, 53; Encke and Biela's discovery of, iii. 54; twenty are controlled by Jupiter and Saturn, ibid.; Biela's broken into fragments, iii. 55; Professor Newcombe's estimates of, iii. 56; minor nebulas drawn into our sys- tem, iii. 70. Communism as advocated by Pythagoras, i. 127. Computations, as to the age of the earth's crust, v. 2 10 ; of the earth's ultimate fate, v. 212. Conservation of energy, the, iii. 253-282. Constantinople, effect of its capture by the Turks upon contemporary learning, ii. 42. Cope, Professor, traced the an- cestry of the camel, iii. 113. Copernicus, Nicholas, famous astronomer, ii. 54; his system, ii. 56; introduction to his book, ii. 57; "On the Order of the Spheres," ii. 60; argument from parallax urged against him, ii. 63; advocates of his theory, ibid. Corti, Bonaventure, observed motion of the cell contents, iv. 124. Corvisart, Jean Nicolas de, phy- sician to the First Consul, iv. 199; lays the foundation of physical diagnosis, iv. 200. Cow-pox, iv. 194, 195; persons afflicted with, secure from small-pox, iv. 196. Crookes, Sir William, experi- ments with the cathode rays, iii. 249; and radio-active sub- stances, v. 103; his spinthari- scope, v. 104. Croll, Dr., computes that the Gulf Stream conveys to the North Atlantic one-fourth the heat which it receives from the sun, iii. 197 ; it is produced by the actual trade -winds, iii. 198; the effect on the climate of Europe should its course be deflected, ibid. Crotonian School of Philosophy, founded by Pythagoras, i. 112. Ctesibius, his studies of the problems of matter, i. 243. Curie, Madame Skaldowska, dis- covery of radium, v. 100; the theories of radio-activity of, v. 106. Curie, Professor Pierre, discovery of radium, v. 100; the theories of radio-activity of, v. 106. Cuvier, George, his investigations concerning extinct species, iii. 78; his inquiries respecting the fabulous animals of the an- cients, iii. 81; agrees with 277 A HISTORY OF SCIENCE Smith's views, iii. 83; on catastrophism, iii. 85; skulls the fossils discovered by Dr. Schmerling, iii. 103; his classification of the animal kingdom, iv. 102; his law of co-ordination, iv. 107; his opposition to the transmuta- tion doctrines, iv. 153, 158. Cyclones, iii. 199-205; a system of whirls, iii. 202; primary cause of, iii. 203; anti-, iii. 204. Daguerre, Louis J. M., brought photography to perfection, iv. 70. Daguerreotype perfected by Louis Daguerre in 1839, i v. 70. D'Alembert, Jean le Rond, determined the ratio of the attractive forces of the sun and moon, and the mutation of the axis of the earth, iii. Dalton, John, and the atomic theory, iv. 38-46; first con- ception of the chemical atom, iv. 39; his theory disputed, iv. 41 ; his theory adopted, iv. 44; predicted the liquefaction of gases, v. 42. Daniell, John Frederick, pro- duced the cell which bears his name, iii. 236. Darwin, Charles Robert, his Origin of Species, iii. 95; his work a revelation to the geological world, iii. 96; his work on doctrine of evolu- tion, iv. 167; his most avail- able field, iv. 168; years spent in gathering facts, i v. 171; joint paper of, and Wallace, presented to the Linnasan Society of London, iv. 173; makes converts of Hooker, Lyell, and Huxley, iv. 174; en- tombed in Westminster Abbey, iv. 178; statue of, in Museum of Natural History, v. 11; computations as to the earth's ultimate fate, v. 212. Darwin, Dr. Erasmus, his theory concerning the aurora bore- alis, iii. 173; concerning the vapor of water, iii. 177; and vegetable respiration, iv. 94- 99 ; his Botanic Garden, iv. 147 ; his Zoonomia and Temple of Nature, iv. 148; his suspicions, ibid.; at his death his idea of transmutation of species still an unsubstantiated dream, iv. 149. Darwinian theory, greatest scien- tific conception of the nine- teenth century, v. 241. Da Vinci, Leonardo, his theories concerning the creation similar to those expressed by Xenoph- anes two thousand years be- fore, i. 129. Davy, Sir Humphry, produced the first electric lamp, iii. 234; showed that labor may be transformed into heat, iii. 255; his experiment of melting ice by friction, iii. 277; heat a manifestation of motion among particles of matter, iii. 294; and electro-chemistry, iv. 46- 53; brilliant researches with his voltaic battery, iv. 47; his famous Bakerian lecture, iv. 48; his theory of binary composition of chemical com- pounds, iv. 53; experiments in the mysteries of respiration, iv. 93; experiments with sul- phuric ether, iv. 209-212; pro- fessor of chemistry in Royal Institute, v. 34; his science of electro-chemistry, v. 36; ex- periments with low tempera- tures, v. 40; his suggestion re- sults in production of liquid chlorine, v. 41; experiments upon gases, v. 42. Dawes, Rev. W. R., one of the discoverers of the inner or crape ring of Saturn, iii. 44. Day of Bel, the, a series of tablets written in the time of Sargon I. 3800 B.C., i. 67. 278 INDEX Days, lucky and unlucky, i. 44, 45. 46. De Bary, Heinrich, studies of protoplasm, iv. 125. De Jussieu, Antoine and Bernard founders of the "natural sys- tem in botany," ii. 303. De Lacaille, Nicolas Louis, his measurement of the French arc of the meridian, iii. 13 ; the question of the shape of the earth, iii. 14. De Lamarck, jean Baptiste, the work of, iv. 151; his idea of transmutation of species, iv. 152; coined the word "biol- ogy," iv. 160. Delambre, Jean Baptiste Joseph, determined the orbit of the planet Uranus, iii. 16. Delitzsch, Professor, his Assyrian grammar, i. 96. De Maillet, and transmutation of species, iv. 149. Democedes, the first physician of whom we have any trust- worthy history, i. 172. Democritus, a dreamer and a thinker, i. 162; his theory of atoms curiously foreshadowed nineteenth-century knowledge, i. 163; atoms differ from each other only in size and shape, i. 164; the quibble over the word quality, i. 166; a forecast of the chemistry of the future, i. 167, 169; a believer in omens, i. 170. De Morgan, a worker in the field of Egyptian exploration, i. 28. De Ronge, a follower of Dr. Young, i. 27; his theories con- cerning the symbols of the Phoenician alphabet, i. 87. Desaguliers, Dr. Joseph, electri- fies running water, ii. 274. Descartes, statement of the first law of motion, ii. 99; formu- lates law of refraction, ii. 119; estimate of his work, ii. 193; his physiological views, ii. 194; theory of vortices, ii. 195. Desmoulins, Louis Antoine, his studies of the brain, iv. 249. Devaine, discovery that anthrax is caused by bacteria, iv. 227. Development of the alphabet, i. 86-102. Deville, Ste. - Claire, dissolution and reformation of molecules fully appreciated by, iv. 61. Dewar, Professor James, ex- periments with low tempera- tures, v. 39; liquefied "hydro- gen," v. 43; his vacuum vessel for holding liquefied gases, v. 53. 54, 68. Digestion, chemical theory of, iv. 88-9 1 ; function of the glands that act in the process of, iv. 129, 130. Diodorus, the Sicilian, i. 56; left us a striking summary, i. 77. Diogenes Laertius, his story of the athletic prowess of Pythag- oras, i. 112. Diphtheria, discovery of toxine for, iv. 242. Disputed question of "spon- taneous" variations, iv. 178; Haeckel and Spencer and the, ibid. "Dissociation," the dissolution and reformation of molecules in a substance, iv. 61. Doctrine of irritability, Haller's greatest contribution to medi- cal science, iv. 74. Dohrn, Dr. Anton, founder of the Marine Biological Laboratory at Naples, v. 121; theory of the type of invertebrate an- cestor, v. 137. Dove, Heinrich W., his studies in climatology, iii. 199, 200. Draper, Dr. Henry, made the first successful photograph of a nebula, iii. 67. Draper, Dr. John W., application of photography to spectro- scope, iv. 70. Driesch, Dr., studies of heredity of, v. 131. Dubois, Dr. Eugene, the dis- 279 A HISTORY OF SCIENCE coverer of the ape-man fossil on the island of Java, iii. 113; discovers the skull and thigh- bone of the ape-man of Java, v. 173; the "missing link," v. 174; man's line of descent clearly traced by discoveries of, v. 176. Ductless glands, their functions discovered by Claude Bernard, iv. 137. Dufay, Cisternay, electrical ex- periments, ii. 267; discovers "vitreous" and "resinous" electricity, ii. 270. Dujardin, contents of cells named "sarcode" by, iv. 124. Dumas, Jean Baptiste, his school of physiological chemistry, iv. 128. Earth's, the, ultimate fate, v. 212; future life of, v. 213. Earth's crust, the, computation as to the age of, v. 210; es- „ timated thickness of, v. 212. Ecole Poly technique, Paris, dis- covery of "radium" at, v. 100. Economic condition of Europe, its influence on science in the dark age, ii. 6. Egg-cell, contents of, v. 227. Egypt, the first dynasty, i. 31; the building of the pyramids, i. 32; three seasons of, i. 36. Egyptian antiquities captured by the English, v. 5. Egyptian science, the summer solstice corresponded with the rising of the Nile, i. 34; the year divided into twelve months of thirty days each, i. 35; the three seasons, i. 36; the fixing of New Year's day, i. 37; the difficulties concerning the unreckoned quarter of a day, i. 38; efforts to reform the calendar, i. 40; arbitrary signs of the zodiac, i. 41; conceptions concerning the earth, sky, etc., i. 42; the recognition of the pulse, i. 51; practical mathematics, i. 52; science as science was un- known, i. 55. Egyptian seasons, three in num- ber, i. 36. Egyptian temples, oriented with reference to the point at which the sun rises on the day of the summer solstice, i. 34. Eighteenth - century medicine, iv. 182—244. Eleatic School, founded by Xe- nophanes, i. 114. Electric light, Sir Humphry Davy's experiments with, iii. 234-. Electricity, the first current passed through a wire by Oersted, iii. 236; its relation to magnetism, iii. 238; the dis- covery of the principles of electro - dynamics, iii. 239; the first electro-magnet, ibid.; experiments of Michael Fara- day, iii. 243; the first storage battery, iii. 246; Seebecle's battery, iii 247; the "Hertz- ian Waves," now used in wireless telegraphy, iii. 247; Professor Thompson and the nature of, v. 93; relation of gases to the conduction of, ibid.; atomic character of, v. 96; regarded as a form of matter, v. 97. Elixir of life, ii. 124, 131, 136. Embalming the dead, a purely religious observance, i. 50; to prevent the spirit's return to torment one, i. 54. Embryological development, the- ory of, v. 156. Embryology, studies in, by Von Baer, Muller, and Carpenter, iv. 122. Empedocles, one of the great Italic leaders of thought, i. 114; a practising physician, i. 133; his work as a sanitary engineer, i. 134; his idea of the impersonality of God, i. 135; his knowledge of em- 280 INDEX balming, i. 136; his conception of evolution , i . 137; he had a secure place among the anticipators of the modern evolutionist, i. 138; his studies of the force of air pressure, i. 247. Epagomenal days, the legend of Osiris explaining, i. 36. Epicycles, the doctrine of wheels, i. 237. Erasistratus, one of the first to discover that the nerve-trunks have their origin in the brain and spinal cord, i. 194; his disagreement with Herophilus as to the functions of the organs, i. 195. Eratosthenes, called the "sur- veyor of the world," i. 226; his important modification of the gnomon, i. 227; his method of determining the size of the earth, i. 230; his conclusions have ever been regarded with admiration, i. 231. Ermann, Professor, an Egyptol- ogist, i. 28. Ether, James Clerk - Maxwell's conception of, iii. 283; its dis- covery one of the most im- portant feats of the nineteenth century, iii. 284 ; discovered by Thomas Young, iii. 285; the speculations concerning it, iii. „ 286, 290. Etienne, Charles, discovers canal in spinal cord, ii. 163. Euclid, the father of systematic geometry, i. 193. Eudoxus, made special studies of the heavenly spheres, i. 216; remarked the obliquity of the eclipse, i. 228. Euler, Leonard, professor of physics and mathematics at St. Petersburg, iii. 17; his demonstration concerning the aphelia of Saturn and Jupiter, iii. 18; solved the problem of the procession of the equinoxes, iii. 19. Eustachius, sixteenth - century anatomist, ii. 165 ; tube, ibid. Evolution, Professor Marsh on, iii. 114. Experimental psychology, iv. 245-286. Experiments with air, iv. 6, 7. Falconer, Dr., his description of the fossil remains in the museum of M. de Perthes, iii. 100. Fallopius, sixteenth-century an- atomist, ii. 166. Faraday, Sir Michael, begins the study of electro-magnetic in- duction, iii. 240; his paper before the Royal Society, iii. 241; his rotating disk, iii. 245; just missed the discovery of the conservation of energy, iii. 253; claimed the existence of an invisible plenum every- where in space, iii. 287; pro- duces liquid chlorine, v. 39 ; experiments with gases, v. 40; hoped to establish a rela- tion between gravitation and electricity or magnetism, v. 2I5- Favus, cause of, iv. 208. Fechner, Gustav, his Psycho- physik , iv. 263 ; verifies Weber's fundamental law of psycho- physics, iv. 266. Ferrel, Professor William, form- ulated a general mathematical law concerning wind currents, iii. 200. Ferrier, Dr. David, and brain localization, iv. 273. Fifteenth - century medicine, ii. 39- Floods, those of the Nile, the Tigris, and Euphrates a most tangible index of the seasons, i. 66. Flourens, Marie Jean Pierre, ex- periments in nerve physiol- ogy, iv. 270; discovers the "vital knot," ibid. 2Sl A HISTORY OF SCIENCE Forbes, the discoverer of the polarization of heat, iii. 278. "Force" of cohesion, v. 49. Fossil beds of America, the, finest known, iii. 106. Fossil horse described by Pro- fessor Marsh, iii. 108. Fossil man, the collection of M. Boucher de Perthes, iii. 100. Foster, Sir Michael, permanent secretary Royal Society of London, v. 17. Franco, Peter, itinerant surgeon, ii. 182. Franklin, Benjamin, electrical experiments, ii. 286; his theory of electricity, ii. 288; his battery, ii. 289; invents the lightning-rod, ii. 290; proves that lightning is electricity, ii. 293; his theory concerning the aurora borealis, iii. 173; concerning the vapor of water, iii . 177. Fraunhofer, Joseph, the per- fector of the refracting tele- scope and the "heliometer," iii. 60. Fresnel, Augustin Jean, cham- pions Dr. Young's wave theory of light, iii. 226; elected a member of the French Academy, ibid. Fuhlrott, Dr., his discoveries in a cave at Neanderthal, iii. 102. Gale repercutee, iv. 204, 205. Galen, the last great scientist of the Alexandrian school, i. 272; a tireless worker, i. 277; his erroneous conceptions re- garding the heart, i. 278; his treatment of the ulner nerve, i. 279; his treatment of Emperor Marcus Aurelius, i. 280; his system of teatment, i. 281 ; his erroneous theories about res- piration and the pulse-beat, i. 282; his observations of the skin and heart, i. 283. Galileo, Galilei, life and work, ii. 76; construction of telescope, ii. 78, 253; telescopic ob- servations, ii. 78, 79, 80; dis- covery of sun-spots, ii. 80 trial for heresy, ii. 81 ; pub- lication of his work, ii. 83 extract from his work, ii 84; experiment at Pisa, ii 94; theory in regard to pro- jectiles, ii. 95; mechanical dis- coveries, ii. 98; experiments with inclined planes, ii. 100; with pendulum, ii. 100; ex- periments with fluids, ii. 105; account of his experiments with floating bodies, in his own words, ii. 106; invents the thermometer, ii. 119. Gall, Dr. Franz Joseph, studies in phrenology, iv. 247. Gallium discovered, iv. 68. Galvani, Luigi, the discoverer of the new agent galvanism, iii. 229; his experiments with frogs' legs, iii. 230. Ganglion cells, studies of, iv. 279. Gas, term coined by Van Hel- mont, ii. 186. Gases, liquefied, v. 40-42; meth- ods used, v. 45, 46; Dewar's vacuum vessel for holding, v. 53; new, discovered by Dr. Ramsey, v. 84; questions raised by discovery, v. 89-91; their relation to the con- duction of electricity, v. 93. Gastric juice, Reaumur's ex- periments with, iv. 89 ; Spallan- zani's and Hunter's theories oi,ibid.; action of, after death, iv. 90; hydrochloric acid dis- covered in, iv. 129; pepsin, active principle in, ibid. Gay-Lussac, Joseph Louis, ex- periments with gases, iv. 42. Geber, Arabian chemist, ii. 20. Genealogical tree, Haeckel's, re- garding the ancestry of man, v. 172; the "missing link," n v. 173. General science affected by the revival of learning, ii. 46. 282 INDEX Geocentric theory, i. 217. Geometry, according to Herodo- tus, was invented in Egypt, i. 107. Gerlach, the histological scheme of, iv. 281. Germanium discovered, iv. 68. Gilbert, William, study of mag- netism, ii. hi; the earth a magnet, ii. 113; "dipping" of the needle, ii. 114; other dis- coveries, ii. 116. Gill, Dr. David, at the Cape observatory made the first photograph of a comet, iii. 67. Glaciers, the phenomena of, iii. 147; the moraines, iii. 148; the perched bowlders, ibid.; the polished and striated rocks, the lapiaz, iii. 149 ; the ancient moraines, iii. 150; perched bowlders in the Alpine valley, iii. 152; Agassiz's Etudes sur les Glaciers, iii. 154; treated with contempt by most scien- tists, ibid.; a mile deep over New England, iii. 163; the results following the rending of the ice sheet, iii. 164. Gladstone, Professor J. H., iv. 68. Glands, discovery of, in the mucous membrane, iv. 129. Glycerine discovered by Karl Wilhelm Scheele, iv. 27. Goethe, Johann Wolfgang, studies of the metamorphosis of plants, iv. 140-145; ex- tends the doctrine to the animal kingdom, iv. 146. Golgi, Dr. Camille, process of staining nerve cells, iv. 282. Gordon, Andrew, his electric motor and bell, ii. 279. Gralath, Daniel, groups Leyden jars in a "battery," ii. 283. Gravitation, law of, discovered by Isaac Newton, ii. 236; New- tonian laws apply to every particle of matter in the universe, iii. 58; power of, v. 214; hope of establishing a relation between, and elec- tricity or magnetism, v. 215; so-called law of, v. 231. Gray, Asa, became an ardent propagandist, iv. 175. Gray, Stephen, experiments with electric conduction and in- sulation, ii. 262. Guerin, Alphonse, endeavors to protect wounds from germs, iv. 230. Gulf Stream, the, theories of Humboldt and Maury con- cerning it, iii. 196; it carries an enormous quantity of heat, iii. 197; its effect on the climate of the seaboard of the United States and Europe, iii. 198. Gun-shot wounds, effect on sur- gery, ii. 41. Guy of Chauliac, surgeon, ii. 38. Haeckel, Ernst Heinrich, and the Darwinian theory, iv. 175; and the disputed ques- tion of "spontaneous varia- tions," iv. 1 78; and the new zoology, v. 144-177; his many paintings, v. 152; discoveries of numerous species of radio- larians, v. 154; gastrula theory of, v. 155; his theory of embryological development, v. 156; great champion of Darwinism, ibid.; his work on morphology, v. 157; liberty of spirit accorded at Jena, v. 158; his laboratory at Jena, v. 159; his method of work, v. 161; his methods of teaching, v. 163; recognized leader in the new zoology, v. 171; his genealogical tree regarding the ancestry of man, v. 772; man's line of descent clearly traced by, v. 176. Hahnemann, Christian Samuel Friedrich, the system of, iv. 188. Hales, Stephen, father of vege- 283 A HISTORY OF SCIENCE table physiology, ii. 298; study of the elasticity of air, iv. 11. Hall, Marshall, and physical diagnosis, iv. 203; observa- tions on reflex action, iv. 251-258. Haller, Albrecht von, iv. 73- 75; doctrine of irritability, iv. 74; discoveries in embryology, iv. 75; first to use the watch in counting the pulse, iv. 76. Halley, his observations on the change in the variations of the compass, iii. 4; his observations on the transit of Mercury, iii. 5 ; his discovery of a method of determining the parallax of the planets, ibid.; calculated the orbit of a comet, iii. 6; specu- lations concerning meteors, iii. 7 ; showed that fixed stars have an actual or "proper" motion in space, iii. 57. Haly, Abbas, author of The Royal Book, ii. 24. Hamilton's, Sir William, col- lection acquired for British Museum, v. 5. Hampson, Dr. William, improved method of liquefaction of gases, v. 44; his apparatus for liquefying air, v. 45. Hansen, Christian August, in- ventor of an electrical ma- chine, ii. 274. Harets ben Kaladah, physician of Mohammed, ii. 23. Hartley, Dr., his famous vibra- tion theory, iv. 268. Harvey, William, life of, ii. 169; his discovery of the circula- tion of the blood, ii. 1 71-178. Hauksbee, Francis, his mer- curial fountain, ii. 259; dis- covery of "induction," ii. 259-262. Heat, Count Rumford's experi- ments with, iii. 209. Heidenham, Dr. Rudolf, on the phenomena of hypnotism, iv. 269. Heliocentric theory, i. 217. Helmholtz, Hermann von, his theory of solar energy, iii. 65; renounced all claim to the discovery of the conservation of energy in favor of Mayer, iii. 269; found that a vortex whirl once established in a frictionless medium must go on forever, iii. 290 ; his measure- ment of speed of nervous im- pulses, iv. 262; explanation of the continued heat of the sun, v. 207. Henderson, Thomas, his work at the Cape of Good Hope in detecting and measuring the parallax of a star, iii. 61. Henry, Joseph, his experi- ments with electric magnets, iii. 239. Heraclides first to point out the value of opium in certain diseases, i. 196. Hero, a pupil of Ctesibius, i. 243; an explicit champion of the molecular theory of matter, i. 245 ; his experiments with water and gases, i. 246; his experi- ments with heated air to produce motor power, i. 247; his experiments with air under pressure, i. 248; his steam- engine, i. 250; the inventor of the penny-in-the-slot machine, i. 251. Herodotus, his visit to Babylon, i- 57- io3- Herophilus, his records are the first we have of the dissection of the human body, i. 194; handed condemned criminals over to the medical profession to be operated on, i. 195. Herschel, John, in collaboration with James South he dis- covered many double stars, iii. 58; his improvement of the microscope, iv. in. Herschel, William, his positive genius for sidereal discovery, iii. 19; discovered the planet Uranus, iii. 20; conceived the 284 INDEX universe to be a vast galaxy of suns held to one centre, iii. 22; thinks that all the suns are "well supplied with inhabitants," iii. 23; theory of the Milky Way, iii. 24; thought all the suns of a system would be drawn together and de- stroyed by impact, iii. 26; suggests that the planets Ceres and Pallas be called asteroids, iii. 41 ; discovered that certain fixed stars have changed their relative positions, iii. 57. Hertz, Dr. Heinrich, discovered the method now used in wireless telegraphy, iii. 247 ; his electro-magnetic theory of light, iii. 280. Hevelius, Johannes, advanced astronomy by his accurate description of the face and the spots of the moon, iii. 3. Hildanes, Fabricius, German surgeon, ii. 183. Hinrichs, Professor Gustav, draws attention to "law of octaves," iv. 67. Hipparchus, demonstrated the eccentricity of the sun's seem- ing orbit, i. 234; his theory absolutely consistent with all the facts, i. 235; exemplified by a lantern on a cart-wheel, i. 237; the dominant scientific personality of his century, i. 238; demonstrated the pre- cession of the equinoxes, i. 242. Hippocrates, the "father of medicine," i. 174; his specula- tions about the heart, i. 175; his acceptance of the humoral theory of disease, i. 176. Histological scheme, the, of Ger- lach, iv. 281. Histology, the use of, iv. 113. Hoffmann, Friedrich, arranged Boerhaave's doctrines in a "system," iv. 184. Holland, Philemon, his transla- tion of the summary of Baby- 285 Ionian science by Diodorus, i. 77-. Honain ben Isaac, Arabian physician, ii. 24. Hooke, Robert, ii. 215; his flying machines, ii. 216; microscop- ical observations, ii. 217, 298; controversy with Newton, ii. 237- Hooker, Sir Joseph, half-convert to Darwin's views, iv. 171; accepts Darwin's theories, iv. 174. Hopkins's estimate of the thick- ness of the earth's crust, v. 212. Howard, Luke, his paper on clouds, iii. 182; his views con- cerning the formation of dew, iii. 183. Hughlings- Jackson, Dr., studies of epilepsy, iv. 272. Humboldt, Alexander, his me- moir on isothermal lines and the distribution of heat, iii. 192; made practicable a truly scientific study of compara- tive climatology, iii. 194; called our atmosphere an ' ' aerial ocean," iii. 195; his theories about the Gulf Stream, iii. 196. Hunter, John, physiologist and surgeon, iv. 78; his discovery of lymphatics, iv. 80; his dis- covery of the "collateral cir- culation" of the blood, iv. 82 ; his operation for aneurism, iv. 84; surgeon-extraordinary to the king, iv. 86 ; his theories of the action of gastric juices, iv. 89; proved the action of digestive fluid after death, iv. 90, 91. Hunter, William, physician and anatomist, iv. 77; his love of controversy, iv. 78. Hutton, Dr. James, claims that the face of nature is under- going metamorphic changes, iii . 118; the bases of the present continents were laid in ancient sea beds, iii. 119; the agency A HISTORY OF SCIENCE which solidified the ocean beds is subterranean heat, iii. 120; the destruction of our land inevitable, iii. 122; marks of marine animals in solid parts of the earth, iii. 124; the elevation of the land above the water was caused by the expansion of heated matter, iii. 128; finds no vestige of a beginning — no prospect of an end, iii. 129; his theories hostile to sacred history, iii. 130; his theories accepted, iii. 140; his theory concerning the vapor of water, iii. 178. Huxley, Thomas Henry, reviews the work of Professor Marsh, iii. 112; accepts Darwin's theory, iv. 174; his estimate of Darwin's accomplishments, iv. 178. Huygens, Christian, 11. 218; im- provement of the telescope, ii. 218, 219; his laws of motion, ii. 222; " pneumatical experi- ments," ii. 222; a resident of France, ii. 224; his micrometer, ii. 254; application of coiled balance-spring to watches, ii. 256; originator of the gen- eral doctrine of undulation as the explanation of light, iii. 224; gave the first hint of the existence of ether, iii. 284. Hydrochloric acid liquefied, v. 40. Hydrogen, liquefied by Professor Dewar, v. 43 ; approach to the absolute zero made by, v. 69. Hydrophobia, Pasteur's inocula- tions to prevent, iv. 240; slow in manifesting itself, v. 182. Hygiene, investigations in, at the Berlin Institute, v. 196. Hypnotism, phenomena of, iv. 269. Iatrochemical school of medi- cine, ii. 186. Iatrophysical school of medicine, ii. 187. Imhotep, the demi-god, consider- ed to be the creator of medical knowledge, i. 49. Imperial Academy of Sciences at St. Petersburg, ii. 202. Induction, electric, discovered by Hauksbee, ii. 259-262. Inductive versus deductive rea- soning, v. 235-238. _ Inorganic matter, possibilities of, v. 224. Insane, reforms in caring for, iv. 245- "Isomerism," word coined by Berzelius, iv. 62. Italic leaders of thought, Xe- nophanes, Parmenides, and Empedocles, i. 114. Jackson, Dr. Charles T., claim- ed the discovery of ether , i v. 215. Jansen, Zacharias, inventor of the microscope, ii. 77. Jena, the "dream city," v. 145; the streets of , v. 146; the market-place of, v. 147; its world-renowned university, v. 148. Jenner, his discovery of inocula- tion for preventing small-pox, iv. 190; his famous paper on vaccination, iv. 194; his first inoculation, iv. 196; recep- tion of the discovery in Europe, iv. 197. Jet-stone, supposed to possess a magical property that would cure epilepsy, hysteria, and gout, i. 277. Joule, James Prescott, the work of, iii. 256; his theory of the conservation of energy, iii. 257; his paper of 1843, iii. 269; his theories on the calorific effect of magneto-electricity and the mechanical value of heat, iii. 270. Julian calendar, it follows the Alexandrian theory, giving us the familiar leap year, i. 36. Jupiter, its moons discovered by Galileo, ii. 79. 86 INDEX Kadmus, a Phoenician, who, ac- cording to a Greek legend, brought the knowledge of letters to Europe, i. 86. Kant, Immanuel, his conception of the formation of the world, iii. 26; his theories of the solar system, iii. 27; defects in his conception, iii. 30; and trans- mutation of species, iv. 149. Kelvin, Lord, his theory of the developmental changes of the earth, iii. 165; he endorses Joule's theories on the conser- vation of energy, iii. 272; his doctrine of the dissipation of energy, iii. 276; learned noth- ing new concerning the nature of energy in fifty years, iii. 279 ; his speculation about ether, iii. 288; his doctrine of the vortex theories of atoms, iii. 290; his estimate of the size of the molecules floating in the air, iii. 298; theories of radio- activity, v. 106; explanation of the continued heat of the sun, v. 207; estimate of the heat-giving life of the sun, v. 208; computations as to the age of the earth's crust, v. 210; computations of the rigid- ity of the telluric structure, v. 212. Kepler, Johann, life and work, ii. 70; theory of planetary distances, ii. 73; assistant of Tycho Brahe, ii. 74; Kepler's Laws, ii. 75; studies of re- fraction of light, ii. 118; Keplerian telescope, ii. 253. Khamurabi, Babylonian king, his famous code concerning phy- sicians, i. 76. Kirchhoff, with Bunsen, perfect- ed the spectroscope, iv. 69. Kitasato, Professor, his studies in the embryos of fishes, v. 132. Koch, Dr. Robert, corroboration of Devaine's discovery, iv. 228. Koch, Professor, work of, in the Berlin Institute of Hygiene, v. 194. Kratzenstein, Christian Gottlieb, uses electricity in medical practice, ii. 278. Kriiger, Gottlieb, suggests the medicinal use of electricity, ii. 278. Krypton, discovery of, v. 87. Kunz, George F., his striking illustration of the power of radium, v. 101. Laborde, M., his theories of radio-activity, v. 106. Laennec, Rene Theophile Hya- cinth, his invention of the stethoscope, iv. 201; his Traite d' Auscultation Mediate, iv. 202. Lamarck, Jean Baptiste, a student of fossil shells about Paris while Cuvier was study- ing the vertebrates, iii. 93. Laplace, removed the last doubts as to the solidarity of New- tonian hypothesis of uni- versal gravitation, iii. 31; his explanation of the planet- ary system, iii. 32; his con- ception as to the formation of suns and stars, iii. 35; his reasoning about the ring of Saturn, iii. 38; he thinks comets are strangers to our planetary system, ibid.; ex- plains why the movements of comets escape this general law, iii. 39; thought that the rings of Saturn were solid, iii. 44- Lartet, Edouard, his discovery of fossils in the caves of Dordogne, iii. 104. La Tour, Cagniard, discovered pepsin in the gastric juice, iv. 129; studies of micro- organism, iv. 218. Laudanum, its introduction, ii. 190. Lavoisier, Antoine Laurent, the founder of modern chemistry, iv. 28-36; first blow to the 87 A HISTORY OF SCIENCE phlogiston theory, iv. 31; ex- periments in respiration, iv. 93- Law of valency, iv. 63. Leeuwenhoek discovers bacteria, ii. 179. Leibnitz, estimate of his work, ii. 197; theory of monads, ii. 198; president of the Royal Academy of Sciences at Berlin, ii. 202. Leidy, Joseph, found the cysts of trichina in pork, iv. 207. Leonardo da Vinci, ii. 47; denial of the sun's motion, ii. 48; his steam-engine, ibid.; his camera obscura, ibid.; his geo- logical observations, ii. 50. Lepsius, extended the study of the famous trilingual inscrip- tions of the Rosetta Stone, i. 2 7 ; determines that the ancient stadium was one hundred and eighty meters, i. 231. Le Sage, his theory of gravitation, v. 214. Lewes, George Henry, his transla- tion of Ritter's rendering of part of the poem of Parmenides concerning the origin of man, *■ I3I- . Leyden jar, invention of, by Von Kleist, ii. 280. Liebig, isomerism proved by, iv. 62; school of physiological chemistry, under guidance of, iv. 128; his studies of animal heat, iv. 131-135; his doctrine of fermentation, iv. 219. Light, heat, and atmospheric pressure, ii. 117. Light, the wave theory of, Thomas Young and, iii, 215- 225; endorsed by Fresnel and Arago, iii. 226; opposition to, ibid.; accepted by French Academy, iii. 227. Linde, Professor, improved meth- od of liquefaction of gases, v. 44. Linnasus, Carolus, member of Royal Swedish Society, ii. 203; life and work, ii. 299- Lippershey, Johannes, inventor of the telescope, ii. 78, 252. Liquefaction of gases, v. 40-46; improved methods of, v. 44; principles and experiments, v. 46-60; results and antic- ipations of the, v. 61-72; use of, in the refrigeration of foods, v. 61. Liquefied air, v. 45, 46, 63-67. Liquid chlorine, Faraday pro- duces, v. 39. Lister, Dr. Joseph (Lord Lister) , discovery of antisepsis, iv. 229; and surgery, iv. 231; president of the Royal Society of London, v. 19. Lister, Joseph Jackson, experi- ments with the microscope, iv. 112; studies of lenses, iv. 113; shape of the red corpuscles settled by, iv. 114. Liver, the, important share of, in preparing food for ab- sorption, iv. 130; not a duct- less organ, iv. 137; blood undergoes a change in passing through, iv. 138; cells, ibid. Living forms, question as to, on other worlds, v. 220. Lockyer, Sir Norman, his "me- teoric hypothesis," iii. 70; does not meet with unanimous acceptance, iii. 71; his deduc- tions from observations of the sun and stars through the spectroscope, iv. 71; spectro- scopic study of sun and stars, v. 73; his theories, v. 75; study of sun-spots, v. 76; studies of the reverse lines of spectrum, v. 78; Perseus dis- covered by, v. 79, 80. Lodge, Sir Oliver, and the in- stability of the atom, v. 109. Logical induction versus hasty generalization, v. 239-242. Long, Dr. Crawford W., claim to the discovery of ether, iv. 215. Lotze, Dr. Hermann, his Medi- 288 INDEX zinische Psychologie, oderPhys- tologie der Seek, iv. 263. Louis, the "statistical method " introduced by, iv. 203. Low temperature, experiments with, v. 39-41; electrical and magnetic conditions at, v. 56; changes in color of sub- stances at, v. 57; substances made luminous by, v. 58; effect of, upon the strength of materials, v. 59; decrease of chemical activity at, v. 60; approach to the absolute zero, v. 69. Lubbock, Sir John, a recruit to the Darwinian theory, iv. 175. Ludolff, Christian Friedrich, ex- periment with the electric spark, ii. 276. Lyell, Sir Charles, repudiated all thought of catastrophism, iii. 88; he adopted and extended the Huttonian doctrine, iii. 92; his theories are changed by Darwin's Origin of Species, iii. 97; claimed that past changes of the earth's surface have been like present changes, iii. 141 ; accepts Darwin's the- ory, iv. 174. Lyncean Society, ii. 200. Magendie, Francois, and phys- ical diagnosis, iv. 203. Malpighi, Marcello, demonstrates passage of blood from arteries to veins through capillaries, ii. 178; dissections of animal tissues and plants, ii. 297, 298. Mammalian types, the living fauna of Australia to-day existed in Europe and died out in the tertiary age, iii. 160. Marchettis, Peter, Italian sur- geon, ii. 185. Mariette, a worker in the field of practical exploration, i. 28. Marine Biological Laboratory at Naples, the, v. 1 13-143; the aquarium in, v. 11 3-1 19; ar- rangement of tanks and ex- hibits in, v. 114; eels and cuttle-fish in, v. 116; the octo- pus in, v. 117; the technical department of, v. 120; Dr. Anton Dohrn, founder of, v. 121; his associates, v. 122; collecting specimens for, v. 123, 124; methods of pre- serving jellyfish in, v. 127; many nationalities represented among the workers in, v. 130; Dr. Driesch's studies of hered- ity at, v. 131; the study of chromosomes at, v. 133; ex- periments in the division of egg-cells at, v. 134; publica- tions of, v. 139; marine labora- tories of other countries, v. 143- Mariotte, Edme, ii. 210. Marsh, Professor, his discovery of the remains of many verte- brates in the Rocky Mountain region, iii. 106; his description of the fossil horses, iii. 108. Maspero, a student of Egyptian history, i. 28; held that the epagomenal days were in use before the first Thinite dynas- ty, i. 36. Maupertuis and the idea of the transmutation of species, iv. 149. Maury, M. F., his theory as to the causes of the Gulf Stream, iii. 196. Mayer, Dr. Julius Robert, his paper on "The Forces of Inorganic Nature," iii. 259; asserts that a force once in ex- istence cannot be annihilated, iii. 263; gave for the first time a tenable explanation of the light and heat of the sun and stars, iii. 268; his explanation of the continued heat of the sun, v. 206. Mayow, John, experiments with air, iv. 6. Medical laboratories, some, v. 178-202. 289 A HISTORY OF SCIENCE Medicine, mixture of religion, necromancy, and mysticism, i. 170; the sick were carried to temples of the god of medicine, ^Esculapius, and took remedies revealed to them in dreams of the god, i. 171; many of the wealthy physicians had dis- pensaries, i. 173. Mena, king of Egypt, i. 28. Menant on the development of a rudimentary science of nat- ural history among the Baby- lonians, i. 75. Mendeleeff, Dmitri, attention drawn to the ' ' law of octaves," iv. 68. Mesopotamia, named _ by the Greeks, i. 56; its civilization fully on a par with that _ of Egypt, i. 59; its earliest in- habitants were an alien race, i. 60. Metamorphosis of parts, iv. 140; Goethe's studies of, in plants, iv. 140, 145; extended to the animal kingdom, iv. 146. Meteorites, the "fire ball"_ of 1803, iii. 168; Jean Baptiste Biot's investigation of, iii. 169; scientists differed as to its origin, ibid.; Chladni thought that they were one in kind and origin as the "shooting- stars," iii. 170; the great shower of 1833, iii. 171; the "miracle" of the falling stone, iii. 172. Meyer, Lothar, attention drawn to the "law of octaves," iv. 68. Micrometer, the, Huygens's in- vention of, ii. 254. Microscope, invented by Jensen, ii. 77; in the Newtonian period, ii. 258 ; attempts to im- prove the, iv. 109, 110,111; Dr. Amici's reflecting, iv. 112; Amici's improved compound, iv. 113; shape of red cor- puscles settled by use of the, iv. 114. Milky "Way explained by Galileo, ii. 79. _ "Missing link," the, no longer missing, v. 173. Mitchell, his theory about the Pleiades, iii. 35. Mohammed, his liberal view of medicine, ii. 23. Mohr, Karl Priedrich, held the doctrine that heat, light, elec- tricity, and magnetism cannot be created but only made manifest, iii. 257. Molecules, Lord Kelvin's estimate of the size of those floating in the air, iii. 298 ; under ordinary circumstances they are in a state of intense but variable vibration, iii. 300; they may be in the form of gas, liquid, or solid, iii, 301; experiments with Crookes's radiometer, ibid.; conditions under which they assume a liquid form, iii. 302. Mondino of Bologna, "the re- storer of anatomy," ii. 37. Montague Mansion, first home of British Museum, v. 5; erection of present building, v. 6. Moon, studies of the, iii. 48; speculations concerning, iii. 49; the possible lengthening of the day, iii. 50. "Moon's variation," determined by Arabian astronomer, ii. 17; rediscovered by Tycho Brahe, ii. 69. Moppert, translation of tablets concerning birth-portents, i. 73- Morgagni, Giovanni Battista, in- vestigations in anatomy, iv. 76. Morrison, his translation of Ritter's rendering of part of the poem of Parmenides on the origin of man, i. 131. Morton, Dr. W. T. G., experi- ments with sulphuric ether, iv. 214. Muller, Johannes, studies in em- bryology, iv. 122. 290 INDEX Munck, localization of motor centres, iv. 274. Muscles, iv. 137. Musschenbroek, Pieter van, in- ventor of the Leyden jar, ii. 280, 282. Naples, Marine Biological Labo- ratory at, v. 1 1 3-1 43. Natural versus supernatural, v. 233. 234- Neanderthal skull regarded by modern zoologists as a distinct species of man, iii. 102. Neolithic civilization supplanted by the invasion of cultivated people from the East, i. 31. Neon, discovery of, v. 87. Neptune, the planet, its exist- ence predicted by the Ger- man astronomer Bessel, iii. 42 ; discovered five years later by John Couch Adams, of England, ibid. Neptunists, a name given to the followers of Werner, who denied the theory of the metamorphosis of rocks, iii. Nerve cells, process of staining, iv. 282; each an isolated entity, iv. 283; importance of the discovery of, iv. 285. Nerves, function of, iv. 249- 261. Newlands, John A. R., studies of atomic weights, iv. 67. Newton, Isaac, ii. 225-251; dis- covery of the composition of white light, ii. 227; the nature of color, ii. 233; the law of gravitation, ii. 236; further computations in the Principia, ii. 243-250; invention of re- flecting telescope, ii. 255. Nicetas, taught that the world is in motion, i. 216. Nicholson and Carlisle, their experiments with the gal- vanic current in decomposing water, iii. 232; they produced a gas that on being mixed with common air exploded by the contact with a lighted taper, iii. 233. Nile floods, without which civ- ilization would be impossible in Egypt, i. 35. Nippur, expedition to, i. 59. Nitrogen, discovered by Caven- dish, v. 87. "Non- vital" to "vital," evolu- tion from, v. 223. Nuclei of plant cells, discovered by Robert Brown, iv. 115; Dr. Schleiden brings to popular attention, iv. 118. Oersted, Jean Christian, the first to pass an electric current through a wire, iii. 236; it showed the close relationship between magnetism and elec- tricity, iii. 238; effects of his important discovery, iii. 239. Oken, Lorenz, extends the doctrine of metamorphosis to the animal kingdom, iv. 146; his theory of spontaneous generation and evolution of species, iv. 160. Olbers, Dr., discoverer of the planet Pallas, iii. 40; his explosion theory, iii. 41; his opinion of the great comet of 1680, iii. 52. Olzewski's experiments in liquid oxygen, v. 61. Organic matter, possibilities of producing, out of inorganic, v. 224. Organi cists' system, iv. 185; theory of, iv. 187. Organism, comprehensive view of, iv. 137 ; economy of the, iv. 138. Oriental archaeology, new science of, iv. 287-302. Oriental ecclesiasticism as a cause of indifference to science in the dark age, ii. 4. Owen, Richard, discovers the Trichina spiralis, iv. 207. Oxygen, liquefied by Pictet and 291 A HISTORY OF SCIENCE Cailletet, v. 42; Olzewski's experiments in, v. 61 „ Paget, James, and the Trichina spiralis, iv. 207. Painless dentistry, iv. 213. Paleontology, new science of, iii. „ 74-iiS- , Pancreas, the, shares in digestion, iv. 129; all important in the digestion of starchy and fatty foods, iv. 130. Pappenheim discovered that the pancreas shares in digestion, iv. 129. Paracelsus, life, ii. 156; "four pillars" of his medical teach- ings, ii. 159; doctrine of "signatures," ii. 160; use of magnets, ii. 161; condemna- tion of surgery, ii. 162; his influence, ii. 162. Parasitic diseases, iv. 204. Pare, Ambroise, "the father of French surgery," ii. 181. Parisian system of sewage dis- posal, the, v. 200. Parmenides, a distinguished or- nament of the Eleatic School, i. 114; his theories concerning the earth, i. 130; his cos- mogonic speculations, i. 131. Pascal, barometrical experi- ment, ii. 122. Pasteur Institute, the, v. 178- 186; the tomb of Pasteur within the walls, v. 181; aims and objects of, v. 182; anti- rabic treatment given at, v. 183; a school of bacteriology, v. 184; the regular staff of, v. 185; sheep and cattle treated at, ibid. Pasteur, Louis, architectural de- sign of a molecule illustrated by, iv. 63; refutation of the doctrine of spontaneous gen- eration, iv. 180; corroborated by Tyndall, ibid; and the germ theory of disease, iv. 217; studies in fermentation, iv. 218; cause of the decay of organic tissues, iv. 220; ex- periments with grape sugar, iv. 221; settles question of bacilli as cause of anthrax, iv. 228; experiments with chicken cholera, iv. 232; and the microbe of anthrax, iv. 233; demonstrates the pro- tection afforded animals by inoculation, iv. 238, 239; his inoculations to prevent hydro- phobia, iv. 240; his tomb, v. 181. Paul of ^Egina, Byzantine sur- geon, ii. 32. Payen and cell walls of vege- tables, iv. 124. Pepsin, an active principle in gastric juice, iv. 129; de- tected by Spratt and Boyd, ibid. Percussion, Piorry's method of mediate, iv. 203. Perraudin, first accounted for the presence of "erratics" on the mountain-tops, iii. 145; his idea was laughed at by all except Charpentier, iii. 146. Perrin, J., his theories of radio- activity, v. 106. Peter of Abano, physician, ii. 36. Petrie, Professor, an Egyptolo- gist, i. 28. Phenomena of nature, a deer knows that the odor of a wolf means danger, i. 4; its instincts are no less logical, no less scientific than a man's, ibid. Philosopher's stone, ii. 124, 131. Phlogiston theory, the, in chemistry, iv. 3-10; influence of Boyle's teaching of, iv. 5 ; Stahl's theory of, iv. 6; pecu- liarities of, iv. 7; many com- plications and final overthrow of, iv. 9. Photography, discovery of, ren- dered the vitality of the spectroscope complete, iv. 70. Phrenology, studies in, iv. 247, 248. 292 INDEX Physical diagnosis, Corvisart lays the foundation of, iv. 199; overthrows depletive methods of, iv. 203. Physicians, in the early Roman days, i. 273; special laws enacted to protect, i. 275; exempted from taxes and military service, i. 276. Physiology in the nineteenth century, iv. 102-139. Piazzi, an Italian astronomer who discovered the planet Ceres, iii. 40. Pinel, Dr. Philippe, leader in reforms for the care of insane, iv. 245; liberation of the inmates at the Bicetre and the Salpetriere, iv. 246. Piorry's method of mediate per- cussion, iv. 203. Pitch-blende, a radio-active sub- stance, v. 98. Pithecanthropus erectus, the fos- sil of the ape-man found by Dr. Dubois in the island of Java, iii. 113. Plagues, their influence on me- diaeval medical science, ii. ^^, 41. Planche, Gaston, his invention of the electric storage battery, iii. 246. Plato, his visit to Egypt to study the mysteries of its fabled learning, i. 56, 84; the greatest thinker and writer of his time, i. 180; a mystical dreamer and sociologist, i. 182. Pleiades, an actual federation of associated stars, iii. 59. Plinius Secundus, the most fa- mous Latin writer of antiquity, i. 265; soldier and investiga- tor, i. 266. Pliny, his unbounded respect for Oriental learning, i. 56. Plutonists, a name given to the followers of Hutton, iii. 131. Polonium, discovery of the radio- active properties of, v. 101. Pouchet, M. F. A., belief in spontaneous generation, iv. 180. Predynastic period, the, i. 28-30. Prehistoric man, the, i. 29. Prehistoric science, not a con- tradiction of terms, i. 3; the distinctive prehistoric and his- toric epochs, i. 26, 27. Prestwich, his conclusions in regard to the flint instruments in the collection of M. de Perthes, iii. 101. Prevention and cure of cholera by inoculation, v. 184. Priestley, Joseph, important dis- coveries of, iv. 18; flight from French mob, iv. 19 ; oxygen his greatest discovery, iv. 20; re- fusal to reject the phlogiston theory, iv. 36; experiments in the mysteries of respiration, iv. 93. Primitive man, our knowledge of, i. 6; he observed that the sun gives heat and light and the moon and stars light only, i. 7 ; noted the changing phases of the seasons, ibid.; noted that the sun, moon, and stars move across the heavens, i. 8; had some idea of the law of uni- versal terrestrial gravitation, i . 9 ; knew the facts concerning the rigidity of solids and the mobility of liquids, i. 10; knew that friction produced heat and fire, i. n; practised in- stinctive therapeutics, i. 13; idea of death, i. 15; had vague conceptions of an end- less life, i. 18; ideas of psychol- ogy, mathematics, and politi- cal economy, i. 19; knew what was essential to communal harmony, i. 21; his basal principles are the foundations of modern science, i. 22; had "innate" ideas of a future life, i. 23; owes a debt of gratitude to his barbaric predecessor, i. 24. 293 A HISTORY OF SCIENCE Printing-press, its part in the development of medical learn- ing, ii. 39. Problems, in ventilation, v. 201; some unsolved scientific, v. 203-229; solar and telluric, v. 205-213; physical, v. 213-220; life, v. 220-229; of anthropol- ogy, v. 228. Protoplasm, studies in, by De Bary and Schultze, iv. 125. Proust, Louis Joseph, disputes Dal ton's atomic theory, iv. 41. Prout, Dr. William, studies of atomic weights, iv. 66; his alleged law revived by Du- mas, iv. 67; detected hydro- chloric acid in gastric juice, iv. 129. Ptolemy, erected a museum and collected a library which made Alexandria the culture-centre of the world, i. 190; the last great astronomer of antiquity, i. 267; discovered the moon's evection, i. 268; his writings became the sole astronomical text-book of the Middle Ages, i. 269; his theory of epicycles, i. 270; the errors in the colored maps attributed to him led to the discovery of America, i. 271. Purkinje discovers that the pan- creas shares in digestion, iv. 129. Pyramids, the building of, i. 32; oriented in strict accordance with some astronomical prin- ciple, i. 33. Pythagoras, a youthful athlete, i. 112; one of the fathers of Grecian thought, i. 114; the founder of an independent school of philosophy, i. 116; advocates the theory of the sphericity of the earth, i. 118, 119; the discoverer of the identity of Hesperus and Luci- fer, i. 120; carried the science of geometry to perfection, ibid.; no written line of his has come to us, i. 121; a summary of his doctrines as quoted by Diogenes, i. 122; an agnostic as regards the current Greek religion, i. 127. Question as to living forms on other worlds, v. 220. Quinine, its introduction, ii. 185. Rabies, or hydrophobia, slow in development, v. 182. Radio-active bodies, nature of emanations from, v. 102; dif- ferent kinds of rays produced by, v. 103 ; source of energy of, v. 106. "Radio-activity," v. 97-102; so termed by Madame Curie, v. 10 1 ; source of energy of, v. 106; and the structure of the atom, v. 107. Radiolarians, the discovery of numerous species by Ernst Haeckel, v. 154; part played in evolution, v. 155. Radium, discovered by Pierre Curie and his wife, v. 100; power of, in penetrating sub- stances, v. 101, 102; an ele- mentary substance, v. 104; Ramsay's experiments with, ibid.; presence of helium in, v. 105; methods devised for testing heat given off by, v. no; its heat-giving qualities, v. 211. Ramsay, Sir William, and new gases, v. 82-92; laboratory and equipment of, v. 83. Rawlinson, Canon, his estimate of Babylonian influence, i. 82; contrasted with that of Dio- dorus, i. 83. Rawlinson, Sir Henry, "father of Assyriology," iv. 229; v. 9. Rayleigh, Lord, of the Royal Institution, experiments with gases, v. 85, 86. Re, Filipo, his theories of radio- activity, v. 106. Reaumur, Rene, the stomach as 294 INDEX a grinding or triturating organ, settled by, iv. 88; his ex- periments with gastric juice, iv. 89. Red corpuscles of the human blood, shape of, settled by Lis- ter,iv. 114; functions of, iv. 135. Refrigerator machines, use of liquefied gases in, v. 61-63. Renucci, F., and the itch mite, iv. 206. Respiration, the function of, iv. 92; experiments in the mys- teries of, iv. 93, 94; Erasmus Darwin and vegetable, iv. 94. Restoration of Assyrian sculpt- ure, iv. 293. Retrospect and prospect, v. 230- 242 ; scientific attitude of mind, v. 230-232; natural versus supernatural, v. 233, 234; in- ductive versus deductive rea- soning, v. 235-238; logical induction versus hasty gen- eralization, v. 239-242. Retrospective glance, the span from Thales to Galen com- passed about eight hundred years, i. 286; the true hypoth- esis concerning the sun and the planetary system, i. 287; the beginnings of great things in the sciences, i. 288; the homes of the great scientists were scattered over a wide territory, i. 289; Plato the only great scientist who was born in Greece, ibid.; racial mingling, i. 290; early development of thought and Oriental science, i. 291; the entire school of Alexandrians free from super- stition, i. 292; the attitude of the Roman mind towards science, ibid.; beliefs based upon pseudo-scientific induc- tions, i. 294; miracle workers, i. 295; "The Thundering Legion," i. 296; Xiphilinus's account of the battle between the Romans and the hostile Quadi, i. 297. Rey, Jean, experiments with air, iv. 6. Rhazes, Arabian physician, ii. 24. "Riddle of the Sphinx," how read, iv. 287. Robinet and the idea of the transmutation of species, iv. 149- Rocks, the origin of stratified, iii. 143; the "transition" and "secondary" systems, iii. 156; the Silurian and Devonian systems, iii. 157; the Lauren- tian system, ibid.; the forma- tion of the Adirondack and Storm King range are patri- archs of the kind, iii. 158; dif- ferent in character, iii. 159; the backbone of the future continent, iii. 161; the strata of the Paleozoic period, iii. 162 ; the Rocky range, iii. 163. Roentgen, Professor Wilhelm Conrad, the discoverer of the "X-ray," iii. 248; its ex- traordinary results on the photographic film, ibid.; the apparatus for producing the rays, iii. 251; the composition of the rays not fully deter- mined, iii. 252. Rolando's method of cutting pieces of brain tissue for microscopical examination, iv. 277. Rosellini extended the knowl- edge of the phonetic value of inscriptions on the Rosetta Stone, i. 27. Rosetta Stone, its hieroglyphics deciphered by Dr. Thomas Young, i. 27; the, iv. 287; biography of, iv. 288; de- cipherment of, iv. 289, 290; in British Museum, v. 8. Rosicrucians, ii. 136. Roux, Dr., his paper on anti- toxine, iv. 242. Royal Academy of Sciences, at Paris, ii. 202; at Berlin, ibid. 295 A HISTORY OF SCIENCE Royal Institute, founded 1801, iv. 46; Humphry Davy as- sumed chair of chemical phil- osophy of, iv. 46. Royal Institution of Great Brit- ain, foundation and founder, v. 29, 30; methods and results at, v. 33-38. Royal Society of London, the, its origin, ii. 201; v. 14-28; visitors to, v. 15; the lecture- room of, v. 1 7 ; comparison be- tween and the Royal Acad- emy of Science of Berlin, v. 18; library and reading-rooms of, v. 19; busts of distinguish- ed members of, v. 20; price- less relics in, v. 21, 22. Royal Swedish Academy, ii. 202. Rucker, Arthur William, per- manent secretary, Royal So- ciety of London, v. 17. Rumford, Count, and the vibra- tory theory of heat, iii. 208; his experiments to determine the nature of heat, iii. 209; determines that heat is a form of motion, iii. 215; showed that labor may be transformed into heat, iii. 255 ; founder of the Royal In- stitution of Great Britain, v. 3°- Rush, Dr. Benjamin, leader in reforms for care of insane, iv. 245- Rutherford, Professor, explains the presence of helium in radium, v. 105; and the in- stability of the atom, v. no. Sabbatical days, the four days in the month set apart for rest from work by the Assyr- ians, i. 65; the foundation of the Hebrew Sabbath, ibid. Saint - Hilaire, Etienne Goef- froy, the doctrine of trans- mutation championed by, iv. 161. Salerno, medical school at, ii. 29. Saliva, share in preparing food for absorption, iv. 130. Sanctorius discovers "insensible perspiration," ii. 187. "Sarcode," the fluid contents of cells, iv. 124. Saturn, the discovery of the inner rings of, by Bond and Dawes, iii. 44; Maxwell's paper "On the Stability of Saturn's Rings," iii. 45-48. Savary, an astronomer of Paris, iii. 58. Sayce, Professor, on Chaldean superstitions, i. 70. Scandium discovered, iv. 68. Scheele, Karl Wilhelm, oxygen and chlorine discovered by, iv. 23; his discovery of chlo- rine, iv. 25; believed in the phlogiston theory, iv. 27; his many discoveries, iv. 27, 28; experiments in the mysteries of respiration, iv. 93. Schiaparelli discovered that meteor swarms move in the orbit of a previously observed comet, iii. 55. Schleiden, Dr. M. J., and the cell theory, iv. 118. Schmerling, Dr., fossil remains found by him in a cave in Westphalia rejected by Cuvier, iii. 103. Schmidt discovers the radio- active properties of thorium, v. 100. Schoenlein, J. L., discovery of the cause of favus, iv. 208. Schools of physiological chemis- try under guidance of Liebig and Wohler in Germany and Dumas in France, iv. 128. Schultze, Max, studies in proto- plasm, iv. 125. Schwann, Dr. Theodore, re- searches in animal cells, iv. 118; famous cell theory, iv. 119- 122; discovered pepsin in gas- tric juice, iv. 129; studies in micro-organism, iv. 218; stud- ies of the nerve tracts, iv. 258. 296 INDEX Scientific attitude of mind, v. 230-232. Scientific problems, some un- solved, v. 203—229. Scrope, G. Poulett, claimed that the highest mountains were masses of volcanic matter, iii. 132; his theories of rock formations, iii. 134. Serum-therapy, iv. 240; the es- tablishment of, iv. 244. Serum treatment for serpent- poisoning, v. 184. Servetus, discoverer of pulmo- nary circulation, ii. 168. Seven Wise Men of Greece, i. 104. Severinus, Marcus Aurelius, Ital- ian surgeon, ii. 185. Sewage - disposal, the famous system of Berlin, v. 199; the system of the Parisians, v. 200. Sextant, invention of the, ii. 257. Shooting- stars, iii. 55; the great shower of 1833, iii. 171; the same in kind and origin as meteors, iii. 172. Sibu, whose contorted attitudes caused the irregularities of the earth's surface, i. 43. Signatures, doctrine of, ii. 160. Simpson, Sir J. Y., discovers the anaesthetic power of chloro- form, iv. 217. Sloane's, Sir Hans, collection, purchased by British govern- ment, v. 4; finest in existence, v- 5- Small-pox, Jenner's discovery of inoculation for preventing, iv. 190-196. Smith, William, and fossil shells, iii. 74; his discovery that fossil rocks are arranged in regular systems, iii. 75. Snell, Willebrord, discovers the law of refraction, ii. 119. Societies, scientific, ii. 198. Solar and telluric problems, v. 205-213. Solubility, as explained by Ost- wald and Mendeleef, v. 218- 219. Sothic cycle measured by the heliacal rising of Sothis, i. 40. Sothis, the Egyptian name of the dog-star Sirius, the rising of which in the morning sky marked the beginning of the new year, i. 38. South, James, the discoverer of scores of hitherto unrecog- nized fixed stars, iii. 58. Spallanzani, Lazzaro, rival of Hunter, iv. 86; studies of spontaneous generation, iv. 87; his chemical theory of digestion, iv. 88; elaborates upon experiments of Reaumur, iv. 89; theory of gastric juices, ibid.; experiments in mysteries of respiration, iv. 93. Spectroscope, the, perfected by Kirchhoff and Bunsen, iii. 62; iv. 69; wonderful revelations of, iii. 63; the results of the studies of Rutherfurd and Secchi, iii. 64; what it reveals of the nature and condition of the stars, iii. 65; it discovered the existence of "dark stars"; its power to record the actual motion of stars, iii. 66; the speed of an invisible planetary body may be determined by it, iii. 67; it determined the character and composition of the nebulas, iii. 69; confirms the theory that meteorites and shooting-stars are one in kind and origin, iii. 172; and photography, iv. 68-72 ; utility of, rendered complete, iv. 70; observation of the sun and stars by, iv. 71. Spencer, Herbert, his definition of science, i. 3; lent his in- fluence to the Darwin cause, iv. 175; belief in transmuta- tion of species, iv. 176; and the disputed question of " spon- taneous" variations, iv. 178; his Principles of Psychology, iv. 268. 297 A HISTORY OF SCIENCE Spinthariscope, invented by Dr. Crookes, v. 104. Sponge, investigations of, by Ernst Haeckel, v. 155. "Spontaneous generation" of living protoplasm, v. 223. "Spontaneous" variations, dis- puted question of, iv. 178. Sprott, detected the existence of glands in the mucous mem- brane, iv. 129. Spurzheim, Dr. Kaspar, propa- gandist of phrenology, iv. 248. Stahl, George Ernst, experiments with air, iv. 6; his phlogiston theory, iv. 7, 10; exponent of Animists' system, iv. 185. Stars, the fixed, iii. 57; distance of the, iii. 61; observation of the, by the spectroscope, iv. 71; study of the, by Lockyer, v. 73; discovery of new, v. 79, 80. Stereo-chemistry, v. 219. Stethoscope, invented by Laen- nec, iv. 201. Stevinus and the law of equilib- rium, ii. 102; his horseless carriage, ii. 103; explanation of "hydrostatic paradox," ii. 104. Stone Age, man knew certain rudimentary principles of science, i. 5; the Egyptians of this age overthrown by an invading host, i. 29. Storm centre, merely an area of low barometric pressure, iii. 202; expansion of air through excess of temperature, iii. 203. Strabo, the most famous of ancient geographers, i. 255; an investigator of details, not an orHnal thinker, i. 257; be- lieved that a vessel could sail around the globe from Spam to India, i. 260; his idea of the arrangement of the zones, i. 262; his three fundamental principles, i. 264. Struve, F. G. W., discovered many double stars, iii. 58; discovered that many seem- ing single stars are really clusters, iii. 59. Studies in the division of egg- cells, v. 134, 135. Study of diseases in the Berlin Institute of Pathology, v. 186- i93- Sulphuric ether, vapor of, pain- dispelling power of, iv. 209; Morton's use of, in dentistry, iv. 214; claims of Jackson and Long as to priority of dis- covery, iv. 215. Sulphurous gas liquefied, v. 40. Sumerian, an alien civilized race, settled in Mesopotamia, over- thrown later by Semitic in- vaders, i. 60. Sun, the, observations of, by the spectroscope, iv. 71; study of, by Lockyer, v. 73; explana- tion of the continued heat of, v. 206, 207, 209; estimate of the heat-giving life of, v. 208; host of meteors falling into, v. 209. Sun-dial invented and perfected by Anaximander and Anax- imenes, i. 109. Sun-spots discovered by Galileo, ii. 79. Sydenham, Thomas, n. 188. Sylvius, founder of a medical system, ii. 186. Systems, medical, in the seven- teenth century, ii. 185. Tagliacozzi, Gaspar, restores amputated noses, ii. 183. Tait, Professor P. G., his ap- paratus for creating vortex rings in air, iii. 291; molecules measurable in inches, iii. 301; estimate of the heat -giving life of the sun, v. 208. Talbot, Fox, on Chaldean exorcisms, i. 71, 72. Telescope, invented by Lipper- shey, ii. 78, 252; constructed by Galileo, ii. 78, 253 ; Kepleri- an telescope, ii. 253; Newton's 298 INDEX reflecting telescope, ii. 255; achromatic, invented, ii. 256. Telluric structure, the rigidity of, v. 212. Temperature, iii. 302, 303, 305, 306; means employed to mod- ify, v. 201. Tennant's discovery of chloride of lime, iv. 26. Tetanus, discovery of toxine for, iv. 242. Thales, the Milesian, foretold the eclipse which stopped a battle between the Lydians and the Medes, i. 103; one of the Seven Wise Men of Greece, i. 104; a link connecting the learning of the old Orient with the scholarship of the new Occident, i. 105; predicted the great eclipse, 585 B.C., i. 106; the father of Greek astronomy, i. 106; a primitive geometer, i. 107; is credited with five geometrical truths, i. 108; in- ventor of science of triangula- tion, i. 108; thought the eclipse of the sun a purely natural phenomenon, i. 109; a pioneer philosopher of the West, i. 115. Theophrastus, did for the vege- table kingdom what Aristotle did for the animal, i. 188; his work on the mineral kingdom is the most notable that was produced in antiquity, ibid. Thermometer invented by Gal- ileo, ii. 119. Thinite dynasty, the first, i. Thirteenth-century medicine, ii. 33- Thompson, Benjamin (Count Rumford), an American, founder of the Royal In- stitution of Great Britain, v. 3°. 31. Thompson, J. J., and the nature of electricity, v. 92-97; and the source of energy of radio- activity, v. 107 ; his hypotheses of the instability of the atom, v. 109. Thompson, R. Campbell, his studies of the astronomical tablets of the Assyrians, i. 64; thought the Chaldean astrono- mers had a kind of machine for reckoning time, i. 67. Thomson, Thomas, adopted the atomic view of Dalton, iv. 44. Thorium, discovery of the radio- active properties of, v. 100. Thundering Legion, the, i. 296. Torricelli, disciple of Galileo, ii. 120; discovers that "suction" is air pressure, ii. 120; his barometer, ii. 122; discovery in hydraulics, ii. 123. Toxine, the discovery of, for tetanus and diphtheria, iv. 242. Transmutation of species, iv. 149, *5°> J52> !53. !59. l6l> l67. 170, 174, 176. Treviranus, Gottfried Reinhold, motion of cell contents, redis- covered in 1807 by, iv. 124; coined the word "biology," iv. 160. Trichina spiralis, Owen's dis- covery of, iv. 207. Trichinosis, the subject of, iv. 207. "Tropical centres," Waller and the study of, iv. 280. Trotula, woman physician, ii. 29. Tuke, Dr. William, leader in re- forms for care of insane, iv. Turpin, studies of micro-organ- ism, iv. 219. Tycho Brahe, great Danish as- tronomer, ii. 65; observation of comets, ii. 67; method of finding latitude, ii. 68; re- discovery of "moon's varia- tion," ii. 69; explanation of the new star in Cassiopeia, ii. 69. Tyndall, John, a recr 'it to the Darwinian theory, iv. 175; cor- roborates the results of Pas- teur, iv. 180. 299 A HISTORY OF SCIENCE Universities in the thirteenth century, ii. 43. - University College, London, Dr. Ramsay's labors in, v. 82. University of Jena, v. 148-150; freedom of thought and ex- pression at, v. 158. Uranium, discovery of the radio- active properties of, v. 100. Valves of the veins, con- troversy about them in the sixteenth century, ii. 166. Van Beneden, discovery of the centrosome, v. 226. Van Helmont, Jan Baptista, founder of medical system, ii. 185. Van 't Hoof's studies of the space relations of atoms, v. 219. Vegetables, leaves of, respiratory organs, iv. 94; cell walls of, iv. 124. Ventilation, problems in, v. 200, 201. Venus, phases of the planet discovered by Galileo, ii. 79. Vesalius, Andrew, "the greatest of anatomists," ii. 164. Virchow, Rudolf, demonstrates the correctness of Von Mohl's cell formation, iv. 127; the discoveries of, v. 188; his work in pathology, v. 189; his ways of living and working, v. 190; his method of teaching, v. 191, 192. Vitalists' system, iv. 185; theory of, iv. 186. Vitrous oxide in painless dentis- try, iv. 213. Volta, Alessandro, inventor of the "voltaic pile," now known as the galvanic current, iii. 230, 232. Von Baer, Karl Ernst, studies in embryology, iv. 122. Von Guericke, Otto, inventor of air-pump, ii. 211; demon- stration of atmospheric press- ure, ii. 212; electrical dis- coveries, 11. 213. Von Kleist, Dean, discovers principle of the Leyden jar, ii. 280. Von Mohl, Dr. Hugo, studies of the vegetable cell, iv. 123; dis- covery of the formation of cells, iv. 126; correctness of cell theory demonstrated by Virchow, iv. 127. Vortex atom, speculations based upon the hypothesis of, v. 216. Vortex theory, Lord Kelvin's estimate of , v. 217. Wallace, Alfred Russel, the work of, iv. 172; joint paper of, and Darwin presented to the Linnasan Society of London, iv. 173. Waller and the study of 'trop- ical centres," iv. 280. "Warren mastodon," iii. 113. Wars, their stimulating effect upon surgery in the thirteenth century, ii. 39. ' ' Water controversy ' ' between Cavendish and Watt, iv. 14, Watson, William, electrical ex- periments, ii. 284. Watt, James, controversy with Cavendish, iv. 14; Arago de- cides in favor of, iv. 15; his process of practical bleaching, iv. 26. Weber, E. H., experiments on nerve stimuli, iv. 264. Wedgwood, Josiah, gauged the highest temperature with the clay pyrometer, iii. 206. Weismann, August, objections to the Lamarckian conception, iv. 178; theory of heredity, v. 134; scheme of the relations of the intracellular units, v. 226. Wells, Dr. W. C, solved the problem of dew formation, iii. 183; his essay on dew, iii. 185. Wells, Dr. Horace, experiments in painless dentistry, iv. 213. Werner, a scientist of Saxony, 300 INDEX iii. 131; made the only con- spicuous attempt to classify the strata, iii. 155. Wilkinson, assisted in clearing up the mysteries of the in- scriptions on the Rosetta Stone, i. 27. Willis, Thomas, English phy- sician, ii. 187. Winds, controlled by a general mathematical law, iii. 200; their direction in a storm centre, iii, 201, 202; long time forecasts possible only in India, iii. 205. Winkler, Johann Heinrichs, tries to measure speed of electric current, ii. 278. Wiseman, Richard, English sur- geon, ii. 184. Wohler, Friedrich, synthesized the organic product urea, iv. 54; isomerism proved by, iv. 62; school of physiological chemistry under guidance of, iv. 128. Wollaston, Dr. William Hyde, his suggestions to improve the microscope, iv. no. Wortman, Dr. J. L., his evidence in connection with the fossil lineage of the edentates, iii. 114. Wundt, Dr. Wilhelm, studies of sensations, apperception, and volition, iv. 267. Xenophanes, founder of the famous Eleatic School, i. 114, 127; his theories concerning the creation, i. 128; the earliest paleontologist, i. 129. Xiphilinus, his account of the battle between the Romans and the hostile Quadi, i. 297. X-ray, discovered in 1895, v. 97. Yersin, famous for his re- searches in the prevention and cure of cholera, v. 184. Young, Dr. Thomas, and the wave theory of light, iii. 215- 225; his extraordinary pre- cocity, iii. 216; his "theory of light and colors," iii. 217; his experiments with microm- eters, iii. 222; his doctrine of the interference of un- dulations, iii. 223; his wave theory endorsed by Fresnel and Arago,iii. 226; determined op- position to his wave theory by French scientists, ibid.; final acceptance of his wave theory by the French academy, iii. 227; his theories about ether, iii. 285; decipherment of the Rosetta Stone, iv. 290; pro- fessor of natural history in Royal Institution , v. 35; wave theory of light, v. 36. Zenon, discovery of, v. 87. Zero, absolute, approach to the, v. 69; probable form of all matter at, v. 70. Zoological classifications, v. 168. Zoology at the close of the eighteenth century, iv. 99- 101. Zoology, the new, Ernst Haeckel and, v. 144; import of the study of, v. 166; fundamental conception of, v. 167; Haeckel the recognized leader in, v. 171. END OF VOL. 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