But, for that matter, what is the nature of these intermolecular 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 intermolecular 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 relations 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 relations of the molecules of carbon compounds in particular, and other compounds are under investigation. 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 matter 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 demonstration that all the worlds known to us are composed of the same matter, subject to the same general laws, and probably passing through kindred stages of evolution and decay, would seem to carry with it the reasonable 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 variation, is conditioned within very narrow limits as to physical surroundings. Now it is easily to be conceived 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 influences 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 example, 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 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 bacteria 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" associations? Perhaps extreme pressure may be one of these conditions; and, for aught any man knows to the contrary, the "spontaneous generation" of living protoplasms may be taking place incessantly at the bottom of every ocean of the globe.

This of course is a mere bald statement of possibilities. It may be met by another statement of possibilities, 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 necessary 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 condition, like the other, being temporary and incidental. But, as I have said, the question of fact as to the exact 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 evolution 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 then and then only—by that assumption he removes the question of the origin of life utterly from the domain 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 as a "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 worker 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 terrestrial oceans.

To the timid reasoner that assumption of possibilities 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 timidity 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 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 generations among existing forms of life. Since the establishment of the doctrine of organic evolution, questions 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 elementary 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 Frommann and Arnold, that the reticulum is really a system of threads, which constitute the most important basis of the cell structure. It is even held that these 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 opposing views. Professor Wilson of Columbia has suggested 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 "intermediate units must exist, whether or not the microscope 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 suggestive manoeuvres in the process of cell multiplication. 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, discovered 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 complicated, but the accumulating researches are just at a point where much is obscure about many of the observed 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 incomprehensible, scientifically speaking, of observed phenomena, that a single microscopic egg cell should contain 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, focalizing 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, exactly 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 difference of opinion as to just which order of lower vertebrates 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 ancestry 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 inductive science. These are the problems of anthropology—a science of such wide scope, such far-reaching collateral implications, that as yet its specific field and functions are not as clearly defined or as generally recognized 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 religions. A mass of data is already at hand, and in process 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 government, of social evolution—are still this side the fixed 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 position 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

ANY one who has not had a rigid training in science may advantageously reflect at some length upon the meaning of true scientific induction. Various illustrations in our text are meant to convey the idea that logical thinking consists simply in drawing correct 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 always follow certain other phenomena, and these observations 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 consequent"—that is to say, they express an observed sequence which our experience has never contradicted.

Now the whole structure of science would be hopelessly undermined had not scientific men come to have the fullest confidence in the invariability of certain of these sequences of events. Let us, for example, take the familiar and fundamental observation that any unsupported object, having what we term weight, invariably falls directly towards the centre of the earth. We express this fact in terms of a so-called law of gravitation, 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 disregard 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 beyond 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 cannot 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 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 computation being, of course, myriads of years as we human pygmies compute time.

To us it would be a miracle if a heavy body, unsupported, 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 inferences. 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 "natural," 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 preconception as to what manner of phenomenon may, or may not, occur. All manner of things do occur constantly 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 learned 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 different 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 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 gravitation we, after all, know absolutely nothing as to its real nature; that we cannot even imagine how one portion 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 mysteries. 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 ultimate nature, altogether mysterious.

In a word, the student of nature is dealing everywhere 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 result, 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 together as obviously occurring under the domination of the same or similar causes, we speak of having determined a law of nature. For example, the fact that any body in motion tends to go on at the same rate of 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 revolve 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, dominating the world for many centuries, exerted a constantly hampering influence upon the progress of science. There were numerous other instances of the same retarding influence of deductive reasoning. Modern science tries to cast aside all such preconceptions. It does not always quite succeed, but it makes a strenuous 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 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 phenomena that seem to fall outside the range of such laws of nature as experience has seemed to demonstrate. 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 Aristotelian 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 perfect number, it would be futile to search for other planets. But even as he made this declaration another 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 demonstration, 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 advanced a jot beyond the Aristotelian stand-point. Untrained through actual experience in any field of inductive science, they remain easy victims of metaphysical 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 remains. 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 mistaken 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 future will see no radical distinction between the superstitions of the thirteenth century and the superstitions of the nineteenth century. But he will probably 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 primitive man was that he did not know the value of scientific evidence. He made wide leaps from observed phenomena to imagined causes, quite overlooking the proximal causes that were near to hand. The untrained 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-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 acceptance 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 systems. 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 seeming law of to-day may be proved false to-morrow, which is another way of saying that man's classification improves 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 principles 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 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 generalizations of primitive man which explain numberless phenomena of nature as due to an influence of unseen anthropomorphic beings remain to this day one of the most powerful influences that affect our race—an influence from which we shall never shake ourselves altogether 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 scientific 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 development of science. Scarcely anything is more illuminative than to observe critically the mistakes of our predecessors, noting how natural the mistakes were and how tenaciously they were held to, how strenuously 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 endeavor to extend the range of theoretical astronomy, and to gain a correct conception of the mechanism 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 generalizations and hasty inductions serve a temporary purpose. 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 vantage-ground thus gained, reach out after yet other truths. But, for the most part, the new laws thus accepted by the leaders remain unknown to the people at large for at least one or two generations. It required 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 understood that it is only the crude and more tangible bearings 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 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 dominant 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

(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.

(p. 96). Ibid., pp. 88, 89. 3 (p- 97)- Ibid., p. 89.

(p. 97). Ibid., p. 87.

(p. 102). George F. Kunz, "Radium and its Wonders," in the Review of Reviews for November, 1903, p. 589.

(p. 105). E. Rutherford, Radio-Activity, p. 330, Cambridge, 1904.

(p. 106). Ibid., p. 330.

(p. 106). Compte Rendu, pp. 136, 673, Paris, 1903.

(p. 106). Revue Scientifique, April 13, 1901. 10 (p. 106). Compte Rendu, p. 136, Paris, 1903.

(p. 108). J. J. Thompson, Electricity and Matter, p. 162, New York, 1904.

(p. —). E. Rutherford, Radio-Activity, p. 340, Cambridge, 1904.

(p. 185). Dr. Duclaux, who was one of Pasteur's chief assistants, and who succeeded him in the directorship of the Institute, died in 1903. He held a professorship in the University of Paris during the later years of his life, and his special studies had to do largely with the chemical side of bacteriology.

(p. 217). Lord Kelvin's estimate as quoted was expressed to the writer verbally. I do not know whether he has anywhere given a similar written verdict.



A LIST OF SOURCES

I.—PERIOD COVERED BY VOLUME I.

An ax agoras. 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 Vastronomie 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 Phoenician, Chaldean, Egyptian, and Other Writers, London, 1826; second edition, 1832.

Democritus. See vol. i., p. 161.

Fragments only of the numerous works ascribed to Democritus have been preserved. Democriii Abdereo 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. English 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 published at Berlin, 1822, under the title Eratosthenica. 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. Kuhn, in 21 volumes.

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.t p. 103.

History. English trans, by Beloe, 1791 and 1806. Trans, by Canon Rawlinson, London, 1858-1860. 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.

Khamurabi, Codb op. 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 December, 1901.

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. Ptolbmy (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 Grocorum, 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.

Utpivlaroplas, On the History of Plants. Written in 10 books. This is one of the earliest works on botany which have come to us. It was largely used by Pliny. In complete works, Schneider, Leipzig, 1818-1821, 5 vols. On Plants, edited by Wimmer, Breslau, 247

1842-1862. On Plants, edited by Slackhouse, Oxford, 1814. atria, 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 bbn Jabir. See vol. ii., p. 15.

The original MS. of his principal work, Zidje Sabt, is in the Vatican. A Latin translation was first published by Plato Tiburtinus at Nuremberg, in 1537, under the title De scientia stellarunt. Various reprints of this have been made. Albertus Magnus. See vol. ii., p. 127.

Philosophic* Naturalis Isagoge, Vienna, 1514. 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, 1760-1770.

Bacon, Francis. See vol. ii., p. 192.

Novum Organum was published in London, 1620. The Letters and Life of Lard 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 collecting them. His great work is the Opus ma jus, "the Encyclopaedia and the Organum of the Thirteenth Century." A partial list of some of his other works is the following: Speculum alchemio, 1541 (trans, into English); De mirabili potestate artis et naturo, 1542 (trans, into English, 1659); Libellus de retardants se-nectutis accidentibus, 1590 (trans, as "The Cure of Old. Age," 1683); and Sanioris medicino Magistri d. Rogeri Baconis Anglici de arte chymio scripta, 1603. 248

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 revolutionism eruditiss. viri et mathemattci excellentiss. Rev. Doctoris Nicolai Copernici Torunnaei, Canonici Warmiensis, per quemdam juvenem mathematico studio sum, Narratio prima, Dantzic, 1540. This was the first published statement of the doctrine of Copernicus, and was a letter published by Rheticus. Three years afterwards Copernicus's De orbium colestium revolutionibus, Libri VI., was published at Nuremberg (1543).

Descartes, Rene. See vol. ii., p. 193.

Traite de Vhomme (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 Homostatics, 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. Hauksbeb, Francis. See vol. ii., p. 259.

Physico-Mechanical Experiments on Various Subjects, London, 1709. This contains descriptions of his various discoveries in electricity, many of which are given in the Phil. Trans.

Hooee, 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 Ouvres 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 Stella Mortis, Leipzig, 1609, contains Kepler's two first laws; and Harmonices mundi, 1619, contains the third law, Phomomenon singulare, seu Mercurius in sole, Leipzig, 1609. Joannis KepUri 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.

LiNNiEus, Carolus (1707-1778). See vol. ii., p. 299.

His Systema natures was published in 1735. Tro years later (1737) he published Genera plantarum, which is generally 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

His De la nature de l'air, 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.

Philosophies naturalis principia mathematica, completed 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 published in 1666. His last work, Processus integri, appeared in 1692. His complete works, in Latin, were published by the Sydenham Society, London, 1844, which published also an English translation by Pr. R. G. Latham in 1848. There are several other English translations.

Torricelli, Evanoelista. See vol. ii., p. 120.

Opera geometrica, Florence, 1644. Tycho Brahe. See vol. ii., p. 65.

De mundi aetherei recentioribus phonomenis, 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 work as a scientist as well as an artist. The older French work, Essai sur les ouvrages physico-mathematiques de Leonard de Vinci, by J. B. Venturi, Paris, 1797, is excellent. In German, H. Grothe's Leonardo da Vinci als Ingenieur und Philosophy 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. Hi., p. 67.

Ouvres (complete), if 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 philosophio naturalis redacta ad unicam legem virium in natura existentium, Vienna, 1758. Bradley, James. See vol. iii., p. 13.

Concerning an Apparent Motion Observed in Sotne 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, 1812. (The introduction to this work was translated and published as a volume bearing title of Theory of the Earth, New York, 1818.)

Delambre, Jean Baptiste Joseph. See vol. iii., p. 16.

Histoire d'astronomie, Paris, 1817-1821. This work contains not only the history of the discoveries in astronomy, but is also a complete text-book of astronomy as understood at this period.

Falconer, Hugh. See vol. iii., p. 99.

In Paloontological Memoirs, vol. ii., pp. 596-598. 252

Herschbl, 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 chaleur 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 (i724-1804). See vol. iii., p. 27.

Allgemeine Naturgeschichte 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 systeme du monde, Paris, 1796, is available in Ouvres completes, in 12 vols., Paris, 1825-1833^01. vi., p. 498. Lyell, Charles. See vol. iii., p. 88.

Principles of Geology, 4 vols., London, 1834.

Marsh, O. C. See vol. Hi., 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.

Wells, W. C. See vol. iii., p. 185. Essay on Dew, London, 1818.



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 Alkaltne 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 composition 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 contains 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 " (Bakerian Lecture), Proc. Roy. Soc, 1901.

Dufay, Cisternay. See vol. ii., p. 267.

Histoire de l'Academie Royale des Sciences, between 1733 and 1737, contains Dufay's principal papers.

Eulbr, Leonard (1707-1783). See vol. iii., p. 17.

Lettres a une Princesse d'Allemagne sur quelques sujets de physique et de philosophie, 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, 1714. 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 Association for the Advancement of Science, 1843, vol. xii" p. 33-

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 description 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. 33.

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. Mendeleepp, 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, 1816.

Priestley, Joseph. See vol. iv., pp. 20, 36.

Experiments and Observations on Different Kinds of Air, 3 vols., Birmingham, 1790. History of Electricity, 256 vol. ii., p. 280, London, 1775. The Doctrine of Phlogiston Established, 1800.

Ramsay and Ravlbigh. 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.

ScHBBLB, Karl William. See vol. iv., p. 23.

Om Brunsten, eller Magnesia, och dess Egenakaper, Stockholm,1774. This contains his discovery of chlorine. His book, Chemische Abhandlung von der Luft und dent 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. i, contains a synoptic scale of chemical equivalents. This paper was confirmatory 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

Avenbruggbr, Lbopold. See vol. iv., p. 200.

Inventum novum ex percussione thoracis humant interni pectoris morbos detegendi, Vienna, 1761. vot. V.-17 257

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 1811, etc.

Bernard, Claude. See vol. iv., p. 137.

BOERHAAVB, HERMANN. See Vol. IV., p. 182.

Institutions medicos, Leyden, 1708; and De chemie expurgante suos errores, Lugduni Batavorum, 1718. Brown, Robert. See vol. iv., p. 115.

On the Organs and Mode of Fecundation of Orchideo and Asclepiadeo, in Miscellaneous Botanical Works, London, 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.

Lecons sur Us maladies du systeme nerveux, Paris, beginning in 1873. Cuvier, George, Baron de. See vol. iv., p. 159.

Histoire naturelle des animaux sans vertebres, Paris, 1815. 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.

Pechner, 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 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.t p. 262.

Most of his original papers appeared in the PhU. 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 (1876), another Radiolaria, enumerating several thousand new species, accompanied by one hundred and forty plates (1887), and Die Weltrathsel, 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 Variolo Vaccino, 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 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."

Libbig, Justin. See vol. iv., p. 131.

Animal Chemistry, London, 1843.

Libbig and Wohler. See vol. iv., p. 56.

The important work of Liebig and Wohler appeared until 183a 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 Saftbewegung im Innern d. Zelle, Bot. Zei-tung, 1846. Morgagni, Giovanni Battista. See vol. iv., p. 76.

De sedibus et causis ntorborum, 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 Rendu of the Academy of Science, Paris, 1881 (vol. xcii.).

Saint-Hilaire, Etienne Geoffroy. See vol. iv., p. 160.

Philosophie anatomique, vol. i., Paris, 1818. Schwann, Theodor. See vol. iv., p. 119.

Mikroskopische Untersuchungen uber 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

Treviranus, Gottfried Reinhold. See vol. iv.t 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 Handwarter-buch der Physiologie, 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.

Grundzuge der physiologischen Psychologie, 1874. Many articles by Wundt have appeared in the Philosophische Studien, published at Leipzig.



V.—ASTRONOMY

Astronomische G es disc haft.

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 Vastronomie modern: Copernic, Tycho Brake, 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 Sphcren, Berlin, 1862.

Jensen, P.

Die Kosmologie der Babylonier, Strasburg, 1890. 261

Lockyer, Joseph Norman.

The Dawn of Astronomy; a Study of the Temple Worship and Mythology of the Ancient Egyptians, London, 1894. Loom is.

History of Astronomy, New York, 1855.

Rothmann.

History of Astronomy (in the Library of Useful Knowledge), 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.)

A tit della Associazione Elethotecnica 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 Atome, by Dr. Johannes Stark, 1903. Price 150 m. "A comprehensive view of the application of the electron theory to certain phenomena."—Nature, May, 1904.

Die Kathodenstrahlen, by G. C. Schmidt, Brunswick, 1904.

"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 knowledge."—Nature, July, 1904.

Hardin.

Rise and Development of the Liquefaction of Gases, New York, 1899.

La theorie de Maxwell et les oscillations hertziennes, la Telegraphie sans flt 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 properties of radium, marred, however, by an attempt to put in accord science and religion—a propos du radium! —Revue Scientifique, July, 1904.

Lehrbuch der Physik, by Von O. D. Chwolson, St. Petersburg, 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 is. "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 University by the Macmillan Company. 263

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, president 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.

Berthblot, P. E. M.

Introduction a l'etude de la chimie des anciens et du moyen age, Paris, 1889.

Les origines de l'alchimie, Paris, 1885.

Bulletin de la Societe Chimique de Paris. A monthly technical journal, treating all phases of the science of chemistry.

Food Inspection and Analysis, by Albert E. Leach, S. B. (John Wiley & Sons, N. Y., $7.50). Note. —This book is designed for the use of public analysts, health officers, food economists, etc.

Hoefer, J. C. F.

Histoire de la chimie, Paris, 1866-1869. This gives biographical sketches of many of the great chemists as well as the history of the development of chemistry.

Jahresbericht uber die Fortschritte der Chemie. A journal of the progress in chemistry, published irregularly in Brunswick.

Kopp, H.

Geschichte der Chemie (4 vols.), Brunswick, 1843-1847. This is an exhaustive history of the development of chemistry.

Lehrbuch der Stereochemie, by A. Werner, Jena, 1904, price 10 m. "Should be in the hands of every organic chemist."—Nature for August, 1904.

Lemoine, Y. F.

La vitalism et l'aminisme de Stahl, Paris, 1864. This 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 subject 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, 1831. Waite, Arthur Edward.

Lives of Alchemisttcal 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.

A merican Naturalist.

Annales de l'Institut Pasteur (18 fr. per annum). A monthly bulletin of the Pasteur Institute, containing mostly technical articles, but also articles of interest to persons interested in problems of immunization and immune sera.

Annales 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—Gesellschaft—Biologie einschliefslich Rassen—und Gesell.-Hygiene.

Archives de biologie (quarterly), Liege.

Archives des sciences biologiques. St. Petersburg. Five numbers a year.

Archives Italiennes de biologie. Turin. Bi-monthly.

Biological Bulletin of the Marine Biological Laboratory, Wood's Holl, Massachusetts. Published monthly by the laboratory. Managing editor, Prank R. Lillie. Scientific and technical—very good.

Biologie generale des bacteries, by E. Bodin, professor of bacteriology, University of Rennes, Paris, 1904. Price 2 It. 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 consultation with Francis Galton, by W. F. R. Weldon, Karl Pearson, and C. B. Davenport. A bulky journal, beautifully illustrated with plates and line cuts. Largely technical, but containing many articles of interest to general readers on laws of inheritance, hereditary influences, etc.

Bulletin of the Geological Society of America. Published irregularly at Rochester.

Gcologische und Paloontologische Abhandlungen, Jena.

Johns Hopkins University, Memoirs from the Biological ^ Laboratory.

L'Echange Revue Linnienne, fondee par le Docteur Jacquet. Directeur, M. Pic. A monthly journal of natural history, devoted largely to entomology—small and technical. Of interest to entomologists only.

Les lois naturelles, par Felix le Danteg, charge du cours d'embryologie generale a la Sorbonne, Paris, 1904. Price 6 fr. A study in biology. "The name corresponds exactly with the contents of this admirable work."—Revue Scientifique, review, September, 1904.

Marine Biological Association of the United Kingdom, Plymouth.

Societe Dauphinoise d'Ethnologie et d'Anthropologie. Quarterly bulletin. Grenoble.

Societe Zoologique de France. Monthly bulletin.

Text-book of Geology, by Sir Archibald Geikie, a 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. London, 15. ed. 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 journal devoted to psychological researches.

The Naturalist, London. A monthly journal for the north of England. Edited by J. Sheppard, P.G.S., and T. W. Woodhead, F.L.S. Annual subscription, 65. 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.

Annales 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, published at Leipzig.

Archiv fur die gesammte 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."—Nature, 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 thf History of Medicine, Philadelphia, 1899.

Paul of AEgina.

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 siecle, 8 vols., Paris, 1815-1820. This is a French translation of the German work, and is more available than the original volumes. It is, perhaps, the most exhaustive history of medicine ever attempted.

The Journal of Hygiene, edited by George H. F. Nuttall, M.D., Ph.D. A quarterly journal of hygiene (2 is. 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 Ss. C. J. Clay & Sons, London.



X.—ANTHROPOLOGY AND ARCHAEOLOGY

American Anthropologist. F. W. Hodge, editor, Washington, D. C. Published quarterly for the American Anthropological Association ($4.50 per annum). Technical (or semi-technical). "A medium of communication between students of all branches of anthropology." Much space devoted to Indian language, etc.—;a very good journal. American Journal of Archoology. American Journal of Sociology.

Archivo per V antropologia e 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 Psycliol-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 tlte World. A simple account of man in early times. London, 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 ethnology. 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 Entwickelungsgeschichtc des Men-schen, 4th edition, 2 vols., Leipzig, 1891. 269

Mueller, Friedrich.

Ethnographie; auf Grund des von K. von Scherzer gesammetten Materials. Vienna, 1868.

Murtillbt, Gabriel de.

Le prehistorique antiquite de Vhomme. 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.

Quatrepages (A. de Q. de Brun).

Histoire generale des races humaines. Paris, 1889.

Ratzel, Friedrich.

The History of Mankind, 3 vols., trans, by A. J. Bubler, London, 1896-1898.

Revue de l'Ecole d'Anthropologie de Paris. Monthly. Published by the professors. Treats all phases and branches of anthropology.

Science de l'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.

THE END