William Harvey

THE WORLD'S
GREATEST
BOOKS

JOINT EDITORS
ARTHUR MEE
Editor and Founder of the Book of Knowledge
J.A. HAMMERTON
Editor of Harmsworth's Universal Encyclopaedia

VOL. XV
SCIENCE

WM. H. WISE & Co.

Table of Contents

A Complete Index of The World's Greatest Books will be found at the end of Volume XX.

Acknowledgment

Acknowledgment and thanks for the use of the following selections are herewith tendered to the Open Court Publishing Company, La Salle, Ill., for "Senses of Insects," by Auguste Forel; to G.P. Putnam's Sons, New York, for "Prolongation of Human Life" and "Nature of Man," by Elie Metchnikoff; and to the De La More Press, London, for "Hypnotism, &c.," by Dr. Bramwell.

Science

JOHN MILNE BRAMWELL

Hypnotism: Its History, Practice and Theory

John Milne Bramwell was born in Perth, Scotland, May 11, 1852. The son of a physician, he studied medicine in Edinburgh, and after obtaining his degree of M.B., in 1873, he settled at Goole, Yorkshire. Fired by the unfinished work of Braid, Bernheim and Liébeault, he began, in 1889, a series of hypnotic researches, which, together with a number of successful experiments he had privately conducted, created considerable stir in the medical world. Abandoning his general practice and settling in London in 1892, Dr. Bramwell became one of the foremost authorities in the country on hypnotism as a curative agent. His Works include many valuable treatises, the most important being "Hypnotism: its History, Practice and Theory," published in 1903, and here summarised for the World's Greatest Books by Dr. Bramwell himself.

I.—Pioneers of Hypnotism

Just as chemistry arose from alchemy, astronomy from astrology, so hypnotism had its origin in mesmerism. Phenomena such as Mesmer described had undoubtedly been observed from early times, but to his work, which extended from 1756 to his death, in 1815, we owe the scientific interest which, after much error and self-deception, finally led to what we now term hypnotism.

John Elliotson (1791–1868), the foremost physician of his day, was the leader of the mesmeric movement in England. In 1837, after seeing Dupotet's work, he commenced to experiment at University College Hospital, and continued, with remarkable success, until ordered to desist by the council of the college. Elliotson felt the insult keenly, indignantly resigned his appointments, and never afterwards entered the hospital he had done so much to establish. Despite the persistent and virulent attacks of the medical press, he continued his mesmeric researches up to the time of his death, sacrificing friends, income and reputation to his beliefs.

The fame of mesmerism spread to India, where, in 1845, James Esdaile (1808–1859), a surgeon in the East India Company, determined to investigate the subject. He was in charge of the Native Hospital at Hooghly, and successfully mesmerised a convict before a painful operation. Encouraged by this, he persevered, and, at the end of a year, reported 120 painless operations to the government. Investigations were instituted, and Esdaile was placed in charge of a hospital at Calcutta, for the express purpose of mesmeric practice; he continued to occupy similar posts until he left India in 1851. He recorded 261 painless capital operations and many thousand minor ones, and reduced the mortality for the removal of the enormous tumours of elephantiasis from 50 to 5 per cent.

According to Elliotson and Esdaile, the phenomena of mesmerism were entirely physical in origin. They were supposed to be due to the action of a vital curative fluid, or peculiar physical force, which, under certain circumstances, could be transmitted from one human being to another. This was usually termed the "od," or "odylic," force; various inanimate objects, such as metals, crystals and magnets, were supposed to possess it, and to be capable of inducing and terminating the mesmeric state, or of exciting or arresting its phenomena.

The name of James Braid (1795–1860) is familiar to all students of hypnotism. Braid was a Scottish surgeon, practising in Manchester, where he had already gained a high reputation as a skilful surgeon, when, in 1841, he first began to investigate mesmerism. He successfully demonstrated that the phenomena were entirely subjective. He published "Neurypnology, or the Rationale of Nervous Sleep," in 1843, and invented the terminology we now use. This was followed by other more or less important works, of which I have been able to trace forty-one, but all have been long out of print.

During the eighteen years Braid devoted to the study of hypnotism, his views underwent many changes and modifications. In his first theory, he explained hypnosis from a physical standpoint; in the second, he considered it to be a condition of involuntary monoideism and concentration, while his third theory differed from both. He recognised that reason and volition were unimpaired, and that the attention could be simultaneously directed to more points than one. The condition, therefore, was not one of monoideism. He realised more and more that the state was a conscious one, and that the losses of memory which followed on waking could always be restored in subsequent hypnoses. Finally, he described as "double consciousness" the condition he had first termed "hypnotic," then "monoideistic."

Braid maintained an active interest in hypnotism up to his death, and, indeed, three days before it, sent his last MS. to Dr. Azam, of Bordeaux, "as a mark of esteem and regard." Sympathetic notices appeared in the press after his death, all of which bore warm testimony to his professional character. Although hypnotic work practically ceased in England at Braid's death, the torch he had lighted passed into France.

In 1860, Dr. A.A. Liébeault (1823–1900) began to study hypnotism seriously, and four years later gave up general practice, settled in Nancy, and practised hypnotism gratuitously among the poor. For twenty years his labours were unrecognised, then Bernheim (one of whose patients Liébeault had cured) came to see him, and soon became a zealous pupil. The fame of the Nancy school spread, Liébeault's name became known throughout the world, and doctors flocked to study the new therapeutic method.

While Liébeault's work may justly be regarded as a continuation of Braid's, there exists little difference between the theories of Charcot and the Salpêtrière school and those of the later mesmerists.

II.—Theory of Hypnotism

The following is a summary of Braid's latest theories: (1) Hypnosis could not be induced by physical means alone. (2) Hypnotic and so-called mesmeric phenomena were subjective in origin, and both were excited by direct or by indirect suggestion. (3) Hypnosis was characterised by physical as well as by psychical changes. (4) The simultaneous appearance of several phenomena was recognised, and much importance was attached to the intelligent action of a secondary consciousness. (5) Volition was unimpaired, moral sense increased, and suggested crime impossible. (6) Rapport was a purely artificial condition created by suggestion. (7) The importance of direct verbal suggestion was fully recognised, as also the mental influence of physical methods. Suggestion was regarded as the device used for exciting the phenomena, and not considered as sufficient to explain them. (8) Important differences existed between hypnosis and normal sleep. (9) Hypnotic phenomena might be induced without the subject having passed through any condition resembling sleep. (10) The mentally healthy were the easiest, the hysterical the most difficult, to influence.

In England, during Braid's lifetime, his earlier views were largely adopted by certain well-known men of science, particularly by Professors W.B. Carpenter and J. Hughes Bennett, but they appear to have known little or nothing of his latest theories. Bennett's description of the probable mental and physical conditions involved in the state Braid described as "monoideism" is specially worthy of note. Not only is it interesting in itself, but it serves also as a standard of comparison with which to measure the theories of later observers, who have attempted to explain hypnosis by cerebral inhibition, psychical automatism, or both these conditions combined.

(a) Physiological.—According to Bennett, hypnosis was characterised by alterations in the functional activity of the nerve tubes of the white matter of the cerebral lobes. He suggested that a certain proportion of these became paralysed through continued monotonous stimulation; while the action of others was consequently exalted. As these tubes connected the cerebral ganglion-cells, suspension of their functions was assumed to bring with it interruption of the connection between the ganglion-cells.

(b) Psychical.—From the psychical side, he explained the phenomena of hypnosis by the action of predominant and unchecked ideas. These were able to obtain prominence from the fact that other ideas, which, under ordinary circumstances, would have controlled their development, did not arise, because the portion of the brain with which the latter were associated had its action temporarily suspended—i.e., the connection between the ganglion-cells was broken, owing to the interrupted connection between the "fibres of association." Thus, he said, the remembrance of a sensation could always be called up by the brain; but, under ordinary circumstances, from the exercise of judgment, comparison, and other mental faculties, we knew it was only a remembrance. When these faculties were exhausted, the suggested idea predominated, and the individual believed in its reality. Thus, he attributed to the faculties of the mind a certain power of correcting the fallacies which each of them was likely to fall into; just as the illusions of one sense were capable of being detected by the healthy use of the other senses. There were mental and sensorial illusions, the former caused by predominant ideas and corrected by proper reasoning, the latter caused by perversion of one sense and corrected by the right application of the others.

In hypnosis, according to this theory, a suggested idea obtained prominence and caused mental and sensorial illusions, because the check action—the inhibitory power—of certain higher centres had been temporarily suspended. These theories were first published by Professor Bennett in 1851.

III.—Hypnotic Induction

The methods by which hypnosis is induced have been classed as follows: (1) physical; (2) psychical; (3) those of the magnetisers. The modern operator, whatever his theories may be, borrows his technique from Mesmer and Liébeault with equal impartiality, and thus renders classification impossible. The members of the Nancy school, while asserting that everything is due to suggestion, do not hesitate to use physical means, and, if these fail, Bernheim has recourse to narcotics.

The following is now my usual method: I rarely begin treatment the first time I see a patient, but confine myself to making his acquaintance, hearing his account of his case, and ascertaining his mental attitude with regard to suggestion. I usually find, from the failure of other methods of treatment, that he is more or less sceptical as to the chance of being benefited. I endeavour to remove all erroneous ideas, and refuse to begin treatment until the patient is satisfied of the safety and desirability of the experiment. I never say I am certain of being able to influence him, but explain how much depends on his mental attitude and power of carrying out my directions. I further explain to the patient that next time he comes to see me I shall ask him to close his eyes, to concentrate his attention on some drowsy mental picture, and try to turn it away from me. I then make suggestions of two kinds: the first refer to the condition I wish to induce while he is actually in the armchair, thus, "Each time you see me, you will find it easier to concentrate your attention on something restful. I do not wish you to go to sleep, but if you can get into the drowsy condition preceding natural sleep, my suggestions are more likely to be responded to." I explain that I do not expect this to happen at once, although it does occur in rare instances, but it is the repetition of the suggestions made in this particular way which brings about the result. Thus, from the very first treatment, the patient is subjected to two distinct processes, the object of one being to induce the drowsy, suggestible condition, that of the other to cure or relieve disease.

I wish particularly to mention that although I speak of hypnotism and hypnosis—and it is almost impossible to avoid doing so—I rarely attempt to induce so-called hypnosis, and find that patients respond to treatment as readily, and much more quickly, now that I start curative suggestions and treatment simultaneously, than they did in the days when I waited until hypnosis was induced before making curative suggestions.

I have obtained good results in treating all forms of hysteria, including grande hysterie, neurasthenia, certain forms of insanity, dipsomania and chronic alcoholism, morphinomania and other drug habits, vicious and degenerate children, obsessions, stammering, chorea, seasickness, and all other forms of functional nervous disturbances.

It is impossible to discuss the different theories in detail here, but I will briefly summarise the more important points, (1) Hypnotism, as a science, rests on the recognition of the subjective nature of its phenomena. (2) The theories of Charcot and the Salpêtrière school are practically a reproduction of mesmeric error. (3) Liébeault and his followers combated the views of the Salpêtrière school and successfully substituted their own, of which the following are the important points: (a) Hypnosis is a physiological condition, which can be induced in the healthy. (b) In everyone there is a tendency to respond to suggestion, but in hypnosis this condition is artificially increased. (c) Suggestion explains all. Despite the fact that the members of the Nancy school regard the condition as purely physiological and simply an exaggeration of the normal, they consider it, in its profound stages at all events, a form of automatism.

These and other views of the Nancy school have been questioned by several observers. As Myers justly pointed out, although suggestion is the artifice used to excite the phenomena, it does not create the condition on which they depend. The peculiar state which enables the phenomena to be evoked is the essential thing, not the signal which precedes their appearance.

Within recent times another theory has arisen, which, instead of explaining hypnotism by the arrested action of some of the brain centres which subserve normal life, attempts to do so by the arousing of certain powers over which we normally have little or no control. This theory appears under different names, "Double Consciousness," "Das Doppel-Ich," etc., and the principle on which it depends is largely admitted by science. William James, for example, says: "In certain persons, at least, the total possible consciousness may be split into parts which co-exist, but mutually ignore each other."

The clearest statement of this view was given by the late Frederic Myers; he suggested that the stream of consciousness in which we habitually lived was not our only one. Possibly our habitual consciousness might be a mere selection from a multitude of thoughts and sensations—some, at least, equally conscious with those we empirically knew. No primacy was granted by this theory to the ordinary waking self, except that among potential selves it appeared the fittest to meet the needs of common life. As a rule, the waking life was remembered in hypnosis, and the hypnotic life forgotten in the waking state; this destroyed any claim of the primary memory to be the sole memory. The self below the threshold of ordinary consciousness Myers termed the "subliminal consciousness," and the empirical self of common experience the "supraliminal." He held that to the subliminal consciousness and memory a far wider range, both of physiological and psychical activity, was open than to the supraliminal. The latter was inevitably limited by the need of concentration upon recollections useful in the struggle for existence; while the former included much that was too rudimentary to be retained in the supraliminal memory of an organism so advanced as that of man. The recollection of processes now performed automatically and needing no supervision, passed out of the supraliminal memory, but might be retained by the subliminal. The subliminal, or hypnotic, self could exercise over the vaso-motor and circulatory systems a degree of control unparalleled in waking life.

Thus, according to the Nancy school, the deeply hypnotised subject responds automatically to suggestion before his intellectual centres have had time to bring their inhibitory action into play; but, on the other hand, in the subliminal consciousness theory, volition and consciousness are recognised to be unimpaired in hypnosis.

IV.—Curative Value of Hypnotism

The intelligent action of the secondary self may be illustrated by the execution of certain post-hypnotic acts. Thus, one of my patients who, at a later period, consented to become the subject of experiment, developed an enormously increased power of time appreciation. If told, during hypnosis, for example, that she was to perform some specific act in the waking state at the expiration of a complicated number of minutes, as, for example, 40,825, she generally carried out the suggestion with absolute accuracy. In this and similar experiments, three points were noted. (1) The arithmetical problems were far beyond her normal powers; (2) she normally possessed no special faculty for appreciating time; (3) her waking consciousness retained no recollection of the experimental suggestions or of anything else that had occurred during hypnosis.

It is difficult to estimate the exact value of suggestion in connection with other forms of treatment. There are one or two broad facts which ought to be kept in mind.

1. Suggestion is a branch of medicine, which is sometimes combined by those who practise it with other forms of treatment. Thus it is often difficult to say what proportion of the curative results is due to hypnotism and what to other remedies.

2. On the other hand, many cases of functional nervous disorder have recovered under suggestive treatment after the continued failure of other methods. Further, the diseases which are frequently cured are often those in which drugs are of little or no avail. For example, what medicine would one prescribe for a man in good physical health who had suddenly become the prey of an obsession? Such patients are rarely insane; they recognise that the idea which torments them is morbid; but yet they are powerless to get rid of it.

3. In estimating the results of suggestive treatment, it must not be forgotten that the majority of cases are extremely unfavourable ones. As the value of suggestion and its freedom from danger become more fully recognised, it will doubtless be employed in earlier stages of disease.

4. It should be clearly understood that the object of all suggestive treatment ought to be the development of the patient's will power and control of his own organism. Much disease would be prevented if we could develop and control moral states.

BUFFON

Natural History

Georges Louis Leclerc, created in 1773 Comte de Buffon, was born at Montbard, in France, on September 7, 1707. Evincing a marked bent for science he became, in 1739, director of the Jardin du Roi and the King's Museum in Paris. He had long contemplated the preparation of a complete History of Nature, and now proceeded to carry out the work. The first three volumes of the "Histoire Naturelle, Générale et Particulière" appeared in 1749, and other volumes followed at frequent intervals until his death at Paris on April 16, 1788. Buffon's immense enterprise was greeted with abounding praise by most of his contemporaries. On July 1, 1752, he was elected to the French Academy in succession to Languet de Gergy, Archbishop of Sens, and, at his reception on August 25 in the following year, pronounced the oration in which occurred the memorable aphorism, "Le style est l'homme même" (The style is the very man). Buffon also anticipated Thomas Carlyle's definition of genius ("which means the transcendent capacity of taking trouble, first of all") by his famous axiom, "Le génie n'est autre chose qu'une grande aptitude à la patience."

Scope of the Work

Buffon planned his "Natural History" on an encyclopaedic scale. His point of view was unique. Natural history in its widest sense, he tells us, embraces every object in the visible universe. The obvious divisions of the subject, therefore, are, first, the earth, the air, and the water; then the animals—quadrupeds, birds, fishes, and so on—inhabiting each of these "elements," to use the phrase of his day. Now, Buffon argued, if man were required to give some account of the animals by which he was surrounded, of course he would begin with those with which he was most familiar, as the horse, the dog, the cow. From these he would proceed to the creatures with which he was less familiar, and finally deal—through the medium of travellers' tales and other sources of information—with the denizens of field, forest and flood in foreign lands. In similar fashion he would consider the plants, minerals, and other products of Nature, in addition to recounting the marvels revealed to him by astronomy.

Whatever its defects on the scientific side, Buffon's plan was simplicity itself, and was adopted largely, if not entirely, in consequence of his contempt—real or affected—for the systematic method of the illustrious Linnæus. Having charted his course, the rest was plain sailing. He starts with the physical globe, discussing the formation of the planets, the features of the earth—mountains, rivers, seas, lakes, tides, currents, winds, volcanoes, earthquakes, islands, and so forth—and the effects of the encroachment and retreat of the ocean.

Animate nature next concerns him. After comparing animals, plants and minerals, he proceeds to study man literally from the cradle to the grave, garnishing the narrative with those incursions into the domains of psychology, physiology and hygiene, which, his detractors insinuated, rendered his work specially attractive and popular.

I.—The Four-Footed Animals

Such questions occupied the first three volumes, and the ground was now cleared for the celebrated treatise on Quadrupeds, which filled no fewer than twelve volumes, published at various dates from 1753 (vol. iv.) to 1767 (vol. xv., containing the New World monkeys, indexes, and the like). Buffon's modus operandi saved him from capital blunders. Though inordinately vain—"I know but five great geniuses," he once said; "Newton, Bacon, Leibniz, Montesquieu, and myself"—he was quite conscious of his own limitations, and had the common-sense to entrust to Daubenton the description of the anatomy and other technical matters as to which his own knowledge was comparatively defective. He reserved to himself what may be called the "literary" aspect of his theme, recording the place of each animal in history, and relating its habits with such gusto as his ornate and grandiose style permitted.

After a preliminary dissertation on the nature of animals, Buffon plunges into an account of those that have been domesticated or tamed. Preference of place is given to the horse, and his method of treatment is curiously anticipatory of modern lines. Beginning with some notice of the horse in history, he goes on to describe its appearance and habits and the varieties of the genus, ending (by the hand of Daubenton) with an account of its structure and physiology. As evidence of the pains he took to collect authority for his statements, it is of interest to mention that he illustrates the running powers of the English horse by citing the instance of Thornhill, the postmaster of Stilton, who, in 1745, wagered he would ride the distance from Stilton to London thrice in fifteen consecutive hours. Setting out from Stilton, and using eight different horses, he accomplished his task in 3 hours 51 minutes. In the return journey he used six horses, and took 3 hours 52 minutes. For the third race he confined his choice of horses to those he had already ridden, and, selecting seven, achieved the distance in 3 hours 49 minutes. He performed the undertaking in 11 hours and 32 minutes. "I doubt," comments Buffon, "whether in the Olympic Games there was ever witnessed such rapid racing as that displayed by Mr. Thornhill."

Justice having been done to it, the horse gives place to the ass, ox, sheep, goat, pig, dog, and cat, with which he closes the account of the domesticated animals, to which three volumes are allotted. It is noteworthy that Buffon frequently, if not always, gives the synonyms of the animals' names in other languages, and usually supports his textual statements by footnote references to his authorities.

When he comes to the Carnivores—"les animaux nuisibles"—the defects of Buffon's higgledy-piggledy plan are almost ludicrously evident, for flesh-eaters, fruit-eaters, insect-eaters, and gnawers rub shoulders with colossal indifference. Doubtless, however, this is to us all the more conspicuous, because use and wont have made readers of the present day acquainted with the advantages of classification, which it is but fair to recognise has been elaborated and perfected since Buffon's time.

As his gigantic task progressed, Buffon's difficulties increased. At the beginning of vol. xii. (1764) he intimates that, with a view to break the monotony of a narrative in which uniformity is an unavoidable feature, he will in future, from time to time, interrupt the general description by discourses on Nature and its effects on a grand scale. This will, he naively adds, enable him to resume "with renewed courage" his account of details the investigation of which demands "the calmest patience, and affords no scope for genius."

II.—The Birds

Scarcely had he finished the twelve volumes of Quadrupeds when Buffon turned to the Birds. If this section were less exacting, yet it made enormous claims upon his attention, and nine volumes were occupied before the history of the class was concluded. Publication of "Des Oiseaux" was begun in 1770, and continued intermittently until 1783. But troubles dogged the great naturalist. The relations between him and Daubenton had grown acute, and the latter, unwilling any longer to put up with Buffon's love of vainglory, withdrew from the enterprise to which his co-operation had imparted so much value. Serious illness, also, and the death of Buffon's wife, caused a long suspension of his labours, which were, however, lightened by the assistance of Guéneau de Montbéliard.

One stroke of luck he had, which no one will begrudge the weary Titan. James Bruce, of Kinnaird, on his return from Abyssinia in 1773, spent some time with Buffon at his château in Montbard, and placed at his disposal several of the remarkable discoveries he had made during his travels. Buffon was not slow to appreciate this godsend. Not only did he, quite properly, make the most of Bruce's disinterested help, but he also expressed the confident hope that the British Government would command the publication of Bruce's "precious" work. He went on to pay a compliment to the English, and so commit them to this enterprise. "That respectable nation," he asserts, "which excels all others in discovery, can but add to its glory in promptly communicating to the world the results of the excellent travellers' researches."

Still unfettered by any scheme of classification, either scientific or logical, Buffon begins his account of the birds with the eagles and owls. To indicate his course throughout the vast class, it will suffice to name a few of the principal birds in the order in which he takes them after the birds of prey. These, then, are the ostrich, bustard, game birds, pigeons, crows, singing birds, humming birds, parrots, cuckoos, swallows, woodpeckers, toucans, kingfishers, storks, cranes, secretary bird, herons, ibis, curlews, plovers, rails, diving birds, pelicans, cormorants, geese, gulls, and penguins. With the volume dealing with the picarian birds (woodpeckers) Buffon announces the withdrawal of Guéneau de Montbéliard, and his obligations for advice and help to the Abbé Bexon (1748–1784), Canon of Sainte Chapelle in Paris.

III.—Supplement and Sequel

At the same time that the Birds volumes were passing through the press, Buffon also issued periodically seven volumes of a supplement (1774–1789), the last appearing posthumously under the editorship of Count Lacépède. This consisted of an olla podrida of all sorts of papers, such as would have won the heart of Charles Godfrey Leland. The nature of the hotchpotch will be understood from a recital of some of its contents, in their chronological order. It opened with an introduction to the history of minerals, partly theoretical (concerning light, heat, fire, air, water, earth, and the law of attraction), and partly experimental (body heat, heat in minerals, the nature of platinum, the ductility of iron). Then were discussed incandescence, fusion, ships' guns, the strength and resistance of wood, the preservation of forests and reafforestation, the cooling of the earth, the temperature of planets, additional observations on quadrupeds already described, accounts of animals not noticed before, such as the tapir, quagga, gnu, nylghau, many antelopes, the vicuña, Cape ant-eater, star-nosed mole, sea-lion, and others; the probabilities of life (a subject on which the author plumed himself), and his essay on the Epochs of Nature.

Nor did these concurrent series of books exhaust his boundless energy and ingenuity, for in the five years preceding his death (1783–1788), he produced his "Natural History of Minerals" in five volumes, the last of which was mainly occupied with electricity, magnetism, and the loadstone. It is true that the researches of modern chemists have wrought havoc with Buffon's work in this field; but this was his misfortune rather than his fault, and leaves untouched the quantity of his output.

Buffon invoked the aid of the artist almost from the first, and his "Natural History" is illustrated by hundreds of full-page copper-plate engravings, and embellished with numerous elegant headpiece designs. The figures of the animals are mostly admirable examples of portraiture, though the classical backgrounds lend a touch of the grotesque to many of the compositions. Illustrations of anatomy, physiology, and other features of a technical character are to be numbered by the score, and are, of course, indispensable in such a work. The editio princeps is cherished by collectors because of the 1,008 coloured plates ("Planches Enluminées") in folio, the text itself being in quarto, by the younger Daubenton, whose work was spiritedly engraved by Martinet. Apparently anxious to illustrate one section exhaustively rather than several sections in a fragmentary manner, the artist devoted himself chiefly to the birds, which monopolise probably nine-tenths of the plates, and to which he may also have been attracted by their gorgeous plumages.

As soon as the labourer's task was over, his scientific friends thought the best monument which they could raise to his memory was to complete his "Natural History." This duty was discharged by two men, who, both well qualified, worked, however, on independent lines. Count Lacépède, adhering to the format of the original, added two volumes on the Reptiles (1788–1789), five on the Fishes (1798–1803), and one on the Cetaceans (1804). Sonnini de Manoncourt (1751–1812), feeling that this edition, though extremely handsome, was cumbersome, undertook an entirely new edition in octavo. This was begun in 1797, and finished in 1808. It occupied 127 volumes, and, Lacépède's treatises not being available, Sonnini himself dealt with the Fishes (thirteen volumes) and Whales (one volume), P.A. Latreille with the Crustaceans and Insects (fourteen volumes), Denys-Montfort with the Molluscs (six volumes), F.M. Dandin with the Reptiles (eight volumes), and C.F. Brisseau-Mirbel and N. Jolyclerc with the Plants (eighteen volumes). Sonnini's edition constituted the cope-stone of Buffon's work, and remained the best edition, until the whole structure was thrown down by the views of later naturalists, who revolutionised zoology.

IV.—Place and Doctrine

Buffon may justly be acclaimed as the first populariser of natural history. He was, however, unscientific in his opposition to systems, which, in point of fact, essentially elucidated the important doctrine that a continuous succession of forms runs throughout the animal kingdom. His recognition of this principle was, indeed, one of his greatest services to the science.

Another of his wise generalisations was that Nature proceeds by unknown gradations, and consequently cannot adapt herself to formal analysis, since she passes from one species to another, and often from one genus to another, by shades of difference so delicate as to be wholly imperceptible.

In Buffon's eyes Nature is an infinitely diversified whole which it is impossible to break up and classify. "The animal combines all the powers of Nature; the forces animating it are peculiarly its own; it wishes, does, resolves, works, and communicates by its senses with the most distant objects. One's self is a centre where everything agrees, a point where all the universe is reflected, a world in miniature." In natural history, accordingly, each animal or plant ought to have its own biography and description.

Life, Buffon also held, abides in organic molecules. "Living beings are made up of these molecules, which exist in countless numbers, which may be separated but cannot be destroyed, which pierce into brute matter, and, working there, develop, it may be animals, it may be plants, according to the nature of the matter in which they are lodged. These indestructible molecules circulate throughout the universe, pass from one being to another, minister to the continuance of life, provide for nutrition and the growth of the individual, and determine the reproduction of the species."

Buffon further taught that the quantity and quality of life pass from lower to higher stages—in Tennysonian phrase, men "rise on stepping-stones of their dead selves to higher things"—and showed the unity and structure of all beings, of whom man is the most perfect type.

It has been claimed that Buffon in a measure anticipated Lamarck and Darwin. He had already foreseen the mutability of species, but had not succeeded in proving it for varieties and races. If he asserted that the species of dog, jackal, wolf and fox were derived from a single one of these species, that the horse came from the zebra, and so on, this was far from being tantamount to a demonstration of the doctrine. In fact, he put forward the mutability of species rather as probable theory than as established truth, deeming it the corollary of his views on the succession and connection of beings in a continuous series.

Some case may be made out for regarding Buffon as the founder of zoogeography; at all events he was the earliest to determine the natural habitat of each species. He believed that species changed with climate, but that no kind was found throughout all the globe. Man alone has the privilege of being everywhere and always the same, because the human race is one. The white man (European or Caucasian), the black man (Ethiopian), the yellow man (Mongol), and the red man (American) are only varieties of the human species. As the Scots express it with wonted pith, "We're a' Jock Tamson's bairns."

As to his geological works, Buffon expounded two theories of the formation of the globe. In his "Théorie de la Terre" he supported the Neptunists, who attributed the phenomena of the earth to the action of water. In his "Epoques de la Nature" he amplified the doctrines of Leibniz, and laid down the following propositions: (1) The earth is elevated at the equator and depressed at the poles in accordance with the laws of gravitation and centrifugal force; (2) it possesses an internal heat, apart from that received from the sun; (3) its own heat is insufficient to maintain life; (4) the substances of which the earth is composed are of the nature of glass, or can be converted into glass as the result of heat and fusion—that is, are verifiable; (5) everywhere on the surface, including mountains, exist enormous quantities of shells and other maritime remains.

To the theses just enumerated Buffon added what he called the "monuments," or what Hugh Miller, a century later, more aptly described as the Testimony of the Rocks. From a consideration of all these things, Buffon at length arrived at his succession of the Epochs, or Seven Ages of Nature, namely: (1) the Age of fluidity, or incandescence, when the earth and planets assumed their shape; (2) the Age of cooling, or consolidation, when the rocky interior of the earth and the great vitrescible masses at its surface were formed; (3) the Age when the waters covered the face of the earth; (4) the Age when the waters retreated and volcanoes became active; (5) the Age when the elephant, hippopotamus, rhinoceros, and other giants roamed through the northern hemisphere; (6) the Age of the division of the land into the vast areas now styled the Old and the New Worlds; and (7) the Age when Man appeared.

ROBERT CHAMBERS

Vestiges of Creation

Robert Chambers was born in Peebles, Scotland, July 10, 1802, and died at St. Andrews on March 17, 1871. He was partner with his brother in the publishing firm of W. & R. Chambers, was editor of "Chambers's Journal," and was author of several works when he published anonymously, in October 1844, the work by which his name will always be remembered, "Vestiges of the Natural History of Creation." His previous works, some thirty in number, did not deal with science, and his labour in preparing his masterpiece was commensurate with the courage which such an undertaking involved. When the book was published, such interest and curiosity as to its authorship were aroused that we have to go back to the publication of "Waverley" for a parallel. Little else was talked about in scientific circles. The work was violently attacked by many hostile critics, F.W. Newman, author of an early review, being a conspicuous exception. In the historical introduction to the "Origin of Species," Darwin speaks of the "brilliant and powerful style" of the "Vestiges," and says that "it did excellent service in this country in calling attention to the subject, in removing prejudice, and in thus preparing the ground for the reception of analogous views." Darwin's idea of selection as the key to the history of species does not occur in the "Vestiges," which belongs to the Lamarckian school of unexamined belief in the hereditary transmission of the effects of use and disuse.

I.—The Reign of Universal Law

The stars are suns, and we can trace amongst them the working of the laws which govern our sun and his family. In these universal laws we must perceive intelligence; something of which the laws are but as the expressions of the will and power. The laws of Nature cannot be regarded as primary or independent causes of the phenomena of the physical world. We come, in short, to a Being beyond Nature—its author, its God; infinite, inconceivable, it may be, and yet one whom these very laws present to us with attributes showing that our nature is in some way a faint and far-cast shadow of His, while all the gentlest and the most beautiful of our emotions lead us to believe that we are as children in His care and as vessels in His hand. Let it then be understood—and this for the reader's special attention—that when natural law is spoken of here, reference is made only to the mode in which the Divine Power is exercised. It is but another phrase for the action of the ever-present and sustaining God.

Viewing Nature in this light, the pursuit of science is but the seeking of a deeper acquaintance with the Infinite. The endeavour to explain any events in her history, however grand or mysterious these may be, is only to sit like a child at a mother's knee, and fondly ask of the things which passed before we were born; and in modesty and reverence we may even inquire if there be any trace of the origin of that marvellous arrangement of the universe which is presented to our notice. In this inquiry we first perceive the universe to consist of a boundless multitude of bodies with vast empty spaces between. We know of certain motions among these bodies; of other and grander translations we are beginning to get some knowledge. Besides this idea of locality and movement, we have the equally certain one of a former soft and more diffused state of the materials of these bodies; also a tolerably clear one as to gravitation having been the determining cause of both locality and movement. From these ideas the general one naturally suggested to us is—a former stage in the frame of material things, perhaps only a point in progress from some other, or a return from one like the present—universal space occupied with gasiform matter. This, however, was of irregular constitution, so that gravitation caused it to break up and gather into patches, producing at once the relative localities of astral and solar systems, and the movements which they have since observed, in themselves and with regard to each other—from the daily spinning of single bodies on their own axes, to the mazy dances of vast families of orbs, which come to periods only in millions of years.

How grand, yet how simple the whole of this process—for a God only to conceive and do, and yet for man, after all, to trace out and ponder upon. Truly must we be in some way immediate to the august Father, who can think all this, and so come into His presence and council, albeit only to fall prostrate and mutely adore.

Not only are the orbs of space inextricably connected in the manner which has been described, but the constitution of the whole is uniform, for all consist of the same chemical elements. And now, in our version of the romance of Nature, we descend from the consideration of orb-filled space and the character of the universal elements, to trace the history of our own globe. And we find that this falls significantly into connection with the primary order of things suggested by Laplace's theory of the origin of the solar system in a vast nebula or fire-mist, which for ages past has been condensing under the influence of gravitation and the radiation of its heat.

II.—History of the Earth's Crust

When we study the earth's crust we find that it consists of layers or strata, laid down in succession, the earlier under the influence of heat, the later under the influence of water. These strata in their order might be described as a record of the state of life upon our planet from an early to a comparatively recent period. It is truly such a record, but not one perfectly complete.

Nevertheless, we find a noteworthy and significant sequence. We learn that there was dry land long before the occurrence of the first fossils of land plants and animals. In different geographical formations we find various species, though sometimes the same species is found in different formations, having survived the great earth changes which the record of the rocks indicates. There is an unbroken succession of animal life from the beginning to the present epoch. Low down, where the records of life begin, we find an era of backboneless animals only, and the animal forms there found, though various, are all humble in their respective lines of gradation.

The early fishes were low, both with respect to their class as fishes, and the order to which they belong—that of the cartilaginous or gristly fishes. In all the orders of ancient animals there is an ascending gradation of character from first to last. Further, there is a succession from low to high types in fossil plants, from the earliest strata in which they are found to the highest. Several of the most important living species have left no record of themselves in any formation beyond what are, comparatively speaking, modern. Such are the sheep and the goat, and such, above all, is our own species. Compared with many humbler animals, man is a being, as it were, of yesterday.

Thus concludes the wondrous section of the earth's history which is told by geology. It takes up our globe at an early stage in the formation of its crust—conducts it through what we have every reason to believe were vast spaces of time, in the course of which many superficial changes took place, and vegetable and animal life was gradually evolved—and drops it just at the point when man was apparently about to enter on the scene. The compilation of such a history, from materials of so extraordinary a character, and the powerful nature of the evidence which these materials afford, are calculated to excite our admiration, and the result must be allowed to exalt the dignity of science as a product of man's industry and his reason.

It is now to be remarked that there is nothing in the whole series of operations displayed in inorganic geology which may not be accounted for by the agency of the ordinary forces of Nature. Those movements of subterranean force which thrust up mountain ranges and upheaved continents stand in inextricable connection, on the one hand, with the volcanoes which are yet belching forth lavas and shaking large tracts of ground, as, on the other, with the primitive incandescent state of the earth. Those forces which disintegrated the early rocks, of which detritus formed new beds at the bottom of the sea, are still seen at work to the same effect.

To bring these truths the more nearly before us, it is possible to make a substance resembling basalt in a furnace; limestone and sandstone have both been formed from suitable materials in appropriate receptacles; the phenomena of cleavage have, with the aid of electricity, been simulated on a small scale, and by the same agent crystals are formed. In short, the remark which was made regarding the indifference of the cosmical laws to the scale on which they operated is to be repeated regarding the geological.

A common furnace will sometimes exemplify the operation of forces which have produced the Giant's Causeway; and in a sloping ploughed field after rain we may often observe, at the lower end of a furrow, a handful of washed and neatly deposited mud or sand, capable of serving as an illustration of the way in which Nature has produced the deltas of the Nile and Ganges. In the ripple-marks on sandy beaches of the present day we see Nature's exact repetition of the operations by which she impressed similar features on the sandstones of the carboniferous era. Even such marks as wind-slanted rain would in our day produce on tide-deserted sands have been read upon tablets of the ancient strata.

It is the same Nature—that is to say, God through or in the manner of Nature—working everywhere and in all time, causing the wind to blow, and the rain to fall, and the tide to ebb and flow, inconceivable ages before the birth of our race, as now. So also we learn from the conifers of those old ages that there were winter and summer upon earth, before any of us lived to liken the one to all that is genial in our own nature, or to say that the other breathed no airs so unkind as man's ingratitude. Let no one suppose there is any necessary disrespect for the Creator in thus tracing His laws in their minute and familiar operations. There is really no true great and small, grand and familiar, in Nature. Such only appear when we thrust ourselves in as a point from which to start in judging. Let us pass, if possible, beyond immediate impressions, and see all in relation to Cause, and we shall chastenedly admit that the whole is alike worshipful.

The Creator, then, is seen to have formed our earth, and effected upon it a long and complicated series of changes, in the same manner in which we find that he conducts the affairs of Nature before our living eyes; that is, in the manner of natural law. This is no rash or unauthorised affirmation. It is what we deduce from the calculation of a Newton and a Laplace on the one hand, and from the industrious observation of facts by a Murchison and a Lyell on the other. It is a point of stupendous importance in human knowledge; here at once is the whole region of the inorganic taken out of the dominion of marvel, and placed under an idea of Divine regulation.

III.—The History of the Earth's Life

Mixed up, however, with the geological changes, and apparently as final object connected with the formation of the globe itself, there is another set of phenomena presented in the course of our history—the coming into existence, namely, of a long suite of living things, vegetable and animal, terminating in the families which we still see occupying the surface. The question arises: In what manner has this set of phenomena originated? Can we touch at and rest for a moment on the possibility of plants and animals having likewise been produced in a natural way, thus assigning immediate causes of but one character for everything revealed to our sensual observation; or are we at once to reject this idea, and remain content, either to suppose that creative power here acted in a different way, or to believe unexaminingly that the inquiry is one beyond our powers? Taking the last question first, I would reply that I am extremely loth to imagine that there is anything in Nature which we should, for any reason, refrain from examining. If we can infer aught from the past history of science, it is that the whole of Nature is a legitimate field for the exercise of our intellectual faculties; that there is a connection between this knowledge and our well-being; and that, if we may judge from things once despaired of by our inquiring reason, but now made clear and simple, there is none of Nature's mysteries which we may not hopefully attempt to penetrate. To remain idly content to presume a various class of immediate causes for organic Nature seems to me, on this ground, equally objectionable.

With respect to the other question the idea has several times arisen that some natural course was observed in the production of organic things, and this even before we were permitted to attain clear conclusions regarding inorganic nature. It was always set quickly aside as unworthy of serious consideration. The case is different now, when we have admitted law in the whole domain of the inorganic.

Otherwise, the absurdities into which we should be led must strike every reflecting mind. The Eternal Sovereign arranges a solar or an astral system, by dispositions imparted primordially to matter; he causes, by the same means, vast oceans to join and continents to rise, and all the grand meteoric agencies to proceed in ceaseless alternation, so as to fit the earth for a residence of organic beings. But when, in the course of these operations, fuci and corals are to be, for the first time, placed in these oceans, a change in his plan of administration is required. It is not easy to say what is presumed to be the mode of his operations. The ignorant believe the very hand of Deity to be at work. Amongst the learned, we hear of "creative fiats," "interferences," "interpositions of the creative energy," all of them very obscure phrases, apparently not susceptible of a scientific explanation, but all tending simply to this: that the work was done in a marvellous way, and not in the way of Nature.

But we need not assume two totally distinct modes of the exercise of the divine power—one in the course of inorganic nature and the other in intimately connected course of organic nature.

Indeed, when all the evidence is surveyed, it seems difficult to resist the impression that vestiges, at least, are seen of the manner and method of the Creator in this part of His work. It appears to be a case in which rigid proof is hardly to be looked for. But such evidences as exist are remarkably consistent and harmonious. The theory pointed to consorts with everything else which we have learned accurately regarding the history of the universe. Science has not one positive affirmation on the other side. Indeed, the view opposed to it is not one in which science is concerned; it appears as merely one of the prejudices formed in the non-age of our race.

For the history, then, of organic nature, I embrace, not as a proved fact, but as a rational interpretation of things as far as science has revealed them, the idea of progressive development. We contemplate the simplest and most primitive types of being as giving birth to a type superior to it; this again producing the next higher, and so on to the highest. We contemplate, in short, a universal gestation of Nature, like that of the individual being, and attended as little by circumstances of a miraculous kind as the silent advance of an ordinary mother from one week to another of her pregnancy.

Thus simple—after ages of marvelling—appears organic creation, while yet the whole phenomena are, in another point of view, wonders of the highest kind, being the undoubted results of ordinances arguing the highest attributes of foresight, skill and goodness on the part of their Divine Author.

If, finally, we study the mind of man, we find that its Almighty Author has destined it, like everything else, to be developed from inherent qualities.

Thus the whole appears complete on one principle. The masses of space are formed by law; law makes them in due time theatres of existence for plants and animals; sensation, disposition, intellect, are all in like manner sustained in action by law.

It is most interesting to observe into how small a field the whole of the mysteries of Nature thus ultimately resolve themselves. The inorganic has been thought to have one final comprehensive law—gravitation. The organic, the other great department of mundane things, rests in like manner on one law, and that is—development. Nor may even these be after all twain, but only branches of one still more comprehensive law, the expression of a unity flowing immediately from the One who is first and last.

IV.—The Future and its Meaning

The question whether the human race will ever advance far beyond its present position in intellect and morals is one which has engaged much attention. Judging from the past, we cannot reasonably doubt that great advances are yet to be made; but, if the principle of development be admitted, these are certain, whatever may be the space of time required for their realisation. A progression resembling development may be traced in human nature, both in the individual and in large groups of men. Not only so, but by the work of our thoughtful brains and busy hands we modify external nature in a way never known before. The physical improvements wrought by man upon the earth's surface I conceive as at once preparations for, and causes of, the possible development of higher types of humanity, beings less strong in the impulsive parts of our nature, more strong in the reasoning and moral, more fitted for the delights of social life, because society will then present less to dread and more to love.

The history and constitution of the world have now been hypothetically explained, according to the best lights which a humble individual has found within the reach of his perceptive and reasoning faculties.

We have seen a system in which all is regularity and order, and all flows from, and is obedient to, a divine code of laws of unbending operation. We are to understand from what has been laid before us that man, with his varied mental powers and impulses, is a natural problem of which the elements can be taken cognisance of by science, and that all the secular destinies of our race, from generation to generation, are but evolutions of a law statuted and sustained in action by an all-wise Deity.

There may be a faith derived from this view of Nature sufficient to sustain us under all sense of the imperfect happiness, the calamities, the woes and pains of this sphere of being. For let us but fully and truly consider what a system is here laid open to view and we cannot well doubt that we are in the hands of One who is both able and willing to do us the most entire justice. Surely, in such a faith we may well rest at ease, even though life should have been to us but a protracted malady. Thinking of all the contingencies of this world as to be in time melted into or lost in some greater system, to which the present is only subsidiary, let us wait the end with patience and be of good cheer.

GEORGES CUVIER

The Surface of the Globe

Georges Cuvier was born Aug. 24, 1769, at Montbéliard, France. He had a brilliant academic career at Stuttgart Academy, and in 1795, at the age of twenty-six, he was appointed assistant professor of comparative anatomy at the Museum d'Histoire Naturelle in Paris, and was elected a member of the National Institute. From this date onwards to his death in 1832, his scientific industry was remarkable. Both as zoologist and palæontologist he must be regarded as one of the greatest pioneers of science. He filled many important scientific posts, including the chair of Natural History in the Collège de France, and a professorship at the Jardin des Plantes. In 1808 he was made member of the Council of the Imperial University; and in 1814, President of the Council of Public Instruction. In 1826 he was made grand officer of the Legion of Honour, and five years later was made a peer of France. The "Discours sur les Révolutions de la Surface du Globe," published in 1825, is essentially a preliminary discourse to the author's celebrated work, "Recherches sur les Ossemens fossiles de Quadrupèdes." It is an endeavour to trace the relationship between the changes which have taken place on the surface of the globe and the changes which have taken place in its animal inhabitants, with especial reference to the evidence afforded by fossil remains of quadrupeds. "It is apparent," Cuvier writes, "that the bones of quadrupeds conduct us, by various reasonings, to more precise results than any other relics of organised bodies." The two books together may be considered the first really scientific palæontology.

I.—Effects of Geological Change

My first object will be to show how the fossil remains of the terrestrial animals are connected with the theory of the earth. I shall afterwards explain the principles by which fossil bones may be identified. I shall give a rapid sketch of new species discovered by the application of these principles. I shall then show how far these varieties may extend, owing to the influence of the climate and domestication. I shall then conceive myself justified in concluding that the more considerable differences which I have discovered are the results of very important catastrophes. Afterwards I shall explain the peculiar influence which my researches should exercise on the received opinions concerning the revolutions of the globe. Finally, I shall examine how far the civil and religious history of nations accords with the results of observation on the physical history of the earth.

When we traverse those fertile plains, where tranquil waters cherish, as they flow, an abundant vegetation, and where the soil, trod by a numerous people, adorned with flourishing villages, rich cities, and superb monuments, is never disturbed save by the ravages of war, or the oppression of power, we can hardly believe that Nature has also had her internal commotions. But our opinions change when we dig into this apparently peaceful soil, or ascend its neighboring hills. The lowest and most level soils are composed of horizontal strata, and all contain marine productions to an innumerable extent. The hills to a very considerable height are composed of similar strata and similar productions. The shells are sometimes so numerous as to form the entire mass of the soil, and all quarters of the globe exhibit the same phenomenon.

The time is past when ignorance could maintain that these remains of organised bodies resulted from the caprice of Nature, and were productions formed in the bosom of the earth by its generative powers; for a scrupulous comparison of the remains shows not the slightest difference between the fossil shells and those that are now found in the ocean. It is clear, then, that they inhabited the sea, and that they were deposited by the sea in the places where they are now found; and it follows, too, that the sea rested in these places long enough to form regular, dense, vast deposits of aquatic animals.

The bed of the sea, accordingly, must have undergone some change either in extent or situation.

Further, we find under the horizontal strata, inclined strata. Thus the sea, previously to the formation of the horizontal strata, must have formed others, which have been broken, inclined, and overturned by some unknown causes.

More than this, we find that the fossils vary with the depth of the strata, and that the fossils of the deeper and more ancient strata exhibit a formation proper to themselves; and we find in some of the strata, too, remains of terrestrial life.

The evidence is thus plain that the animal life in the sea has varied, and that parts of the earth's surface have been alternately dry land and ocean. The very soil, which terrestrial animals at present inhabit has a history of previous animal life, and then submersion under the sea.

The reiterated irruptions and retreats of the sea have not all been gradual, but, on the contrary, they have been produced by sudden catastrophes. The last catastrophe, which inundated and again left dry our present continents, left in the northern countries the carcasses of large quadrupeds, which were frozen, and which are preserved even to the present day, with their skin, hair and flesh. Had they not been frozen the moment they were killed, they must have putrefied; and, on the other hand, the intense frost could not have been the ordinary climatic condition, for they could not have existed at such low temperatures. In the same instant, then, in which these animals perished the climate which they inhabited must have undergone a complete revolution.

The ruptures, the inclinations, the overturnings of the more ancient strata, likewise point to sudden and violent changes.

Animal life, then, has been frequently disturbed on this earth by terrific catastrophes. Living beings innumerable have perished. The inhabitants of the dry land have been engulfed by deluges; and the tenants of the water, deserted by their element, have been left to perish from drought.

Even ancient rocks formed or deposited before the appearance of life on the earth show signs of terrific violence.

It has been maintained by some that the causes now at work altering the face of the world are sufficient to account for all the changes through which it has passed: but that is not so. None of the agents Nature now employs—rain, thaw, rivers, seas, volcanoes—would have been adequate to produce her ancient works.

To explain the external crust of the world, we require causes other than those present in operation, and a thousand extraordinary theories have been advanced. Thus, according to one philosopher, the earth has received in the beginning a uniform light crust which caused the abysses of the ocean, and was broken to produce the Deluge. Another supposed the Deluge to be caused by the momentary suspension of the cohesion of minerals.

Even accomplished scientists and philosophers have advanced impossible and contradictory theories.

All attempts at explanation have been stultified by an ignorance of the facts to be explained, or by a partial survey of them, and especially by a neglect of the evidence afforded by fossils. How was it possible not to perceive that the theory of the earth owes its origin to fossils alone? They alone, in truth, inform us with any certainty that the earth has not always had the same covering, since they certainly must have lived upon its surface before they were buried in its depths. If there were only strata without fossils, one might maintain that the strata had all been formed together. Hitherto, in fact, philosophers have been at variance on every point save one, and that is that the sea has changed its bed; and how could this have been known except for fossils?

From this consideration I was led to study fossils; and since the field was immense I was obliged to specialise in one department of fossils, and selected for study the fossil bones of quadrupeds. I made this selection because only from a study of fossil quadrupeds can one hope to ascertain the number and periods and contents of irruptions of the sea; and because, since the number of quadrupeds is limited, and most quadrupeds known, we have better means of assuring ourselves if the fossil remains are remains of extinct or extant animals. Animals such as the griffin, the cartazonon, the unicorn, never lived, and there are probably very few quadrupeds now living which have not been found by man.

But though the study of fossil quadruped be enlightening, it has its own special difficulties. One great difficulty arises from the fact that it is very rare to find a fossil skeleton approaching to a complete state.

Fortunately, however, there is a principle in comparative anatomy which lessens this difficulty. Every organised being constitutes a complete and compact system with all its parts in mutual correspondence. None of its parts can be changed without changing other parts, and consequently each part, taken separately, indicates the others.

Thus, if the intestines of an animal are made to digest raw flesh, its jaws must be likewise constructed to devour prey, its claws to seize and tear it, its teeth to rend it, its limbs to overtake it, its organs of sense to discern it afar. Again, in order to enable the jaw to seize with facility, a certain form of condyle is necessary, and the zygomatic arch must be well developed to give attachment to the masseter muscle. Again, the muscles of the neck must be powerful, whence results a special form in the vertebræ and the occiput, where the muscles are attached. Yet again, in order that the claws may be effective, the toe-bones must have a certain form, and must have muscles and tendons distributed in a certain way. In a word, the form of the tooth necessitates the form of the condyle, of the shoulder-blade, and of the claws, of the femur, and of all the other bones, and all the other bones taken separately will give the tooth. In this manner anyone who is scientifically acquainted with the laws of organic economy may from a fragment reconstruct the whole animal. The mark of a cloven hoof is sufficient to tell the form of the teeth and jaws and vertebræ and leg-bones and thigh-bones and pelvis of the animal. The least fragment of bone, the smallest apophysis, has a determinative character in relation to the class, the order, the genus, and species to which it may belong. This is so true that, if we have only a single extremity of bone well preserved, we may, with application and a skilful use of analogy and exact comparison, determine all those points with as much certainty as if we were in possession of the entire animal. By the application of these principles we have identified and classified the fossil remains of more than one hundred and fifty mammalia.

II.—What the Fossils Teach

An examination of the fossils on the lines I have indicated shows that out of one hundred and fifty mammiferous and oviparous quadrupeds, ninety are unknown to present naturalists, and that in the older layers such oviparous quadrupeds as the ichthyosauri and plesiosauri abound. The fossil elephant, the rhinoceros, the hippopotamus, and the mastodons are not found in the more ancient layers. In fact, the species which appear the same as ours are found only in superficial deposits.

Now, it cannot be held that the present races of animals differ from the ancient races merely by modifications produced by local circumstances and change of climate—for if species gradually changed, we must find traces of these gradual modifications, and between the palæotheria and the present species we should have discovered some intermediate formation; but to the present time none of these have appeared.

Why have not the bowels of the earth preserved the monuments of so remarkable a genealogy unless it be that the species of former ages were as constant as our own, or at least because the catastrophe that destroyed them had not left them time to give evidence of the changes?

Further, an examination of animals shows that though their superficial characteristics, such as colour and size, are changeable, yet their more radical characteristics do not change. Even the artificial breeding of domestic animals can produce only a limited degree of variation. The maximum variation known at the present time in the animal kingdom is seen in dogs, but in all the varieties the relations of the bones remain the same and the shape of the teeth undergoes no palpable change.

I know that some naturalists rely much on the thousands of ages which they can accumulate with a stroke of the pen; but there is nothing which proves that time will effect any more than climate and a state of domestication. I have endeavoured to collect the most ancient documents of the forms of animals. I have examined the engravings of animals including birds on the numerous columns brought from Egypt to Rome. M. Saint Hilaire collected all the mummies of animals he could obtain in Egypt—cats, ibises, birds of prey, dogs, monkeys, crocodiles, etc.—and we cannot find any more difference between them and those of the present day than between human mummies of that date and skeletons of the present day.

There is nothing, then, in known facts which can support the opinion that the new genera discovered among fossils—the palæotheria, anoplotheria, megalonyces, mastodontes, pterodactyli, ichthyosauri, etc.—could have been the sources of any animals now existing, which would differ only by the influence of time or climate.

As yet no human bones have been discovered in the regular layers of the surface of the earth, so that man probably did not exist in the countries where fossil bones are found at the epoch of the revolutions which buried these bones, for there cannot be assigned any reason why mankind should have escaped such overwhelming catastrophes, or why human remains should not be discovered. Man may have inhabited some confined tract of country which escaped the catastrophe, but his establishment in the countries where the fossil remains of land animals are found—that is to say, in the greatest part of Europe, Asia, and America—is necessarily posterior not only to the revolutions which covered these bones, but even to those which have laid open the strata which envelop them; whence it is clear that we can draw neither from the bones themselves nor from the rocks which cover them any argument in favour of the antiquity of the human species in these different countries. On the contrary, in closely examining what has taken place on the surface of the globe, since it was left dry for the last time, we clearly see that the last revolution, and consequently the establishment of present society, cannot be very ancient. An examination of the amount of alluvial matter deposited by rivers, of the progress of downs, and of other changes on the surface of the earth, informs us clearly that the present state of things did not commence at a very remote period.

The history of nations confirms the testimony of the fossils and of the rocks. The chronology of none of the nations of the West can be traced unbroken farther back than 3,000 years. The Pentateuch, the most ancient document the world possesses, and all subsequent writings allude to a universal deluge, and the Pentateuch and Vedas and Chou-king date this catastrophe as not more than 5,400 years before our time. Is it possible that mere chance gave a result so striking as to make the traditional origin of the Assyrian, Indian, and Chinese monarchies agree in being as remote as 4,000 or 5,000 years back? Would the ideas of nations with so little inter-communication, whose language, religion, and laws have nothing in common, agree on this point if they were not founded on truth? Even the American Indians have their Noah or Deucalion, like the Indians, Babylonians, and Greeks.

It may be said that the long existence of ancient nations is attested by their progress in astronomy. But this progress has been much exaggerated. But what would this astronomy prove even if it were more perfect? Have we calculated the progress which a science would make in the bosom of nations which had no other? If among the multitude of persons solely occupied with astronomy, even then, all that these people knew might have been discovered in a few centuries, when only 300 years intervened between Copernicus and Laplace.

Again, it has been pretended that the zodiacal figures on ancient temples give proof of a remote antiquity; but the question is very complicated, and there are as many opinions as writers, and certainly no conclusions against the newness of continents and nations can be based on such evidence. The zodiac itself has been considered a proof of antiquity, but the arguments brought forward are undoubtedly unsound.

Even if these various astronomical proofs were as certain as they are unconvincing, what conclusion could we draw against the great catastrophe so indisputably demonstrated? We should only have the right to conclude that astronomy was among the sciences preserved by those persons whom the catastrophe spared.

In conclusion, if there be anything determined in geology, it is that the surface of our globe has been subjected to a revolution within 5,000 years, and that this revolution buried the countries formerly inhabited by man and modern animals, and left the bottom of the former sea dry as a habitation for the few individuals it spared. Consequently, our present human societies have arisen since this catastrophe.

But the countries now inhabited had been inhabited before, as fossils show, by animals, if not by mankind, and had been overwhelmed by a previous deluge; and, indeed, judging by the different orders of animal fossils we find, they had perhaps undergone two or three irruptions of the sea.

CHARLES DARWIN

The Origin of Species

Charles Robert Darwin was born at Shrewsbury, England, Feb. 12, 1809, of a family distinguished on both sides. Abandoning medicine for natural history, he joined H.M.S. Beagle in 1831 on the five years' voyage, which he described in "The Voyage of the Beagle," and to which he refers in the introduction to his masterpiece. The "Origin of Species" containing, in the idea of natural selection, the distinctive contribution of Darwin to the theory of organic evolution, was published in November, 1859. In only one brief sentence did he there allude to man, but twelve years later he published the "Descent of Man," in which the principles of the earlier volume found their logical outcome. In other works Darwin added vastly to our knowledge of coral reefs, organic variation, earthworms, and the comparative expression of the emotions in man and animals. Darwin died in ignorance of the work upon variation done by his great contemporary, Gregor Mendel, whose work was rediscovered in 1900. "Mendelism" necessitates much modification of Darwin's work, which, however, remains the maker of the greatest epoch in the study of life and the most important contribution to that study ever made. Its immortal author died on April 19, 1882, and was buried in Westminster Abbey.

I.—Creation or Evolution?

When on board H.M.S. Beagle as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geographical relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, in 1837, it occurred to me that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years' work, I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions which then seemed to me probable. From that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.

In considering the origin of species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified so as to acquire that perfection of structure and co-adaptation which justly excites our admiration.

Naturalists continually refer to external conditions, such as climate, food, etc., as the only possible cause of variation. In one limited sense, as we shall hereafter see, this may be true; but it is preposterous to attribute to mere external conditions the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees. In the case of the mistletoe, which draws its nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of the parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself.

It is, therefore, of the highest importance to gain a clear insight into the means of modification and co-adaptation. At the beginning of my observations it seemed to me probable that a careful study of domesticated animals and of cultivated plants would offer the best chance of making out this obscure problem. Nor have I been disappointed; in this and in all other perplexing cases I have invariably found that our knowledge, imperfect though it be, of variation under domestication, afforded the best and safest clue. I may venture to express my conviction of the high value of such studies, although they have been very commonly neglected by naturalists.

Although much remains obscure, and will long remain obscure, I can entertain no doubt, after the most deliberate study and dispassionate judgment of which I am capable, that the view which most naturalists until recently entertained, and which I formerly entertained—namely, that each species has been independently created—is erroneous. I am fully convinced that species are not immutable, but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am also convinced that Natural Selection has been the most important, but not the exclusive, means of modification.

II.—Variation and Selection

All living beings vary more or less from one another, and though variations which are not inherited are unimportant for us, the number and diversity of inheritable deviations of structure, both those of slight and those of considerable physiological importance, are endless.

No breeder doubts how strong is the tendency to inheritance; that like produces like is his fundamental belief. Doubts have been thrown on this principle only by theoretical writers. When any deviation of structure often appears, and we see it in the father and child, we cannot tell whether it may not be due to the same cause having acted on both; but when amongst individuals, apparently exposed to the same conditions, any very rare deviation, due to some extraordinary combination of circumstances, appears in the parent—say, once amongst several million individuals—and it re-appears in the child, the mere doctrine of chances almost compels us to attribute its reappearance to inheritance.

Everyone must have heard of cases of albinism, prickly skin, hairy bodies, etc., appearing in members of the same family. If strange and rare deviations of structure are really inherited, less strange and commoner deviations may be freely admitted to be inheritable. Perhaps the correct way of viewing the whole subject would be to look at the inheritance of every character whatever as the rule, and non-inheritance as the anomaly.

The laws governing inheritance are for the most part unknown. No one can say why the same peculiarity in different individuals of the same species, or in different species, is sometimes inherited and sometimes not so; why the child often reverts in certain characters to its grandfather or grandmother, or more remote ancestor; why a peculiarity is often transmitted from one sex to both sexes, or to one sex alone, more commonly but not exclusively to the like sex.

The fact of heredity being given, we have evidence derived from human practice as to the influence of selection. There are large numbers of domesticated races of animals and plants admirably suited in various ways to man's use or fancy—adapted to the environment of which his need and inclination are the most essential constituents. We cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them; indeed, in many cases, we know that this has not been their history. The key is man's power of accumulative selection. Nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to have made for himself useful breeds.

The great power of this principle of selection is not hypothetical. It is certain that several of our eminent breeders have, even within a single lifetime, modified to a large extent their breeds of cattle and sheep. What English breeders have actually effected is proved by the enormous prices given for animals with a good pedigree; and these have been exported to almost every quarter of the world. The same principles are followed by horticulturists, and we see an astonishing improvement in many florists' flowers, when the flowers of the present day are compared with drawings made only twenty or thirty years ago.

The practice of selection is far from being a modern discovery. The principle of selection I find distinctly given in an ancient Chinese encyclopædia. Explicit rules are laid down by some of the Roman classical writers. It is clear that the breeding of domestic animals was carefully attended to in ancient times, and is now attended to by the lowest savages. It would, indeed, have been a strange fact had attention not been paid to breeding, for the inheritance of good and bad qualities is so obvious.

Study of the origin of our domestic races of animals and plants leads to the following conclusions. Changed conditions of life are of the highest possible importance in causing variability, both by acting directly on the organisation, and indirectly by affecting the reproductive system. Spontaneous variation of unknown origin plays its part. Some, perhaps a great, effect may be attributed to the increased use or disuse of parts.

The final result is thus rendered infinitely complex. In some cases the intercrossing of aboriginally distinct species appears to have played an important part in the origin of our breeds. When several breeds have once been formed in any country, their occasional intercrossing, with the aid of selection, has, no doubt, largely aided in the formation of new sub-breeds; but the importance of crossing has been much exaggerated, both in regard to animals and to those plants which are propagated by seed. Over all these causes of change, the accumulative action of selection, whether applied methodically and quickly, or unconsciously and slowly, but more efficiently, seems to have been the predominant power.

III.—Variation Under Nature

Before applying these principles to organic beings in a state of nature, we must ascertain whether these latter are subject to any variation. We find variation everywhere. Individual differences, though of small interest to the systematist, are of the highest importance for us, for they are often inherited; and they thus afford materials for natural selection to act and accumulate, in the same manner as man accumulates in any given direction individual differences in his domesticated productions. Further, what we call varieties cannot really be distinguished from species in the long run, a fact which we can clearly understand if species once existed as varieties, and thus originated. But the facts are utterly inexplicable if species are independent creations.

How have all the exquisite adaptations of one part of the body to another part, and to the conditions of life, and of one organic being to another being, been perfected? For everywhere we find these beautiful adaptations.

The answer is to be found in the struggle for life. Owing to this struggle, variations, however slight, and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to man's power of selection. But the expression, often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate.

We have seen that man, by selection, can certainly produce great results, and can adapt organic beings to his own uses, through the accumulation of slight but useful variations given to him by the hand of Nature. Natural Selection is a power incessantly ready for action, and is as immeasurably superior to man's feeble efforts as the works of Nature are to those of Art.

All organic beings are exposed to severe competition. Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult—at least, I have found it so—than constantly to bear this conclusion in mind. Yet, unless it be thoroughly engrained in the mind, the whole economy of Nature, with every fact of distribution, rarity, abundance, extinction, and variation, will be dimly seen or quite misunderstood. We behold the face of Nature bright with gladness; we often see superabundance of food. We do not see, or we forget, that the birds which are idly singing round us mostly live on insects or seeds, and are thus constantly destroying life; or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds or beasts of prey. We do not always bear in mind that, though food may be superabundant, it is not so at all seasons of each recurring year.

A struggle for existence, the term being used in a large, general, and metaphorical sense, inevitably follows from the high rate at which all organic beings tend to increase.

Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year; otherwise, on the principle of geometrical increase, its numbers would quickly become so inordinately great that no country could support the product. Hence, as more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them.

There is no exception to the rule that every organic being naturally increases at so high a rate that, if not destroyed, the earth would soon be covered by the progeny of a single pair. Even slow-breeding man has doubled in twenty-five years, and at this rate, in less than a thousand years, there would literally not be standing-room for his progeny. Linnæus has calculated that if an annual plant produced only two seeds—and there is no plant so unproductive as this—and their seedlings next year produced two, and so on, then in twenty years there would be a million plants. The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase. It will be safest to assume that it begins breeding when thirty years old, and goes on breeding until ninety years old, bringing forth six young in the interval, and surviving till one hundred years old. If this be so, after a period of from 740 to 750 years there would be nearly nineteen million elephants alive, descended from the first pair.

The causes which check the natural tendency of each species to increase are most obscure. Eggs or very young animals seem generally to suffer most, but this is not invariably the case. With plants there is a vast destruction of seeds. The amount of food for each species of course gives the extreme limit to which each can increase; but very frequently it is not the obtaining food, but the serving as prey to other animals, which determines the average number of a species. Climate is important, and periodical seasons of extreme cold or drought seem to be the most effective of all checks.

The relations of all animals and plants to each other in the struggle for existence are most complex, and often unexpected. Battle within battle must be continually recurring with varying success; and yet in the long run the forces are so nicely balanced that the face of Nature remains for long periods of time uniform, though assuredly the merest trifle would give the victory to one organic being over another. Nevertheless, so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!

The struggle for life is most severe between individuals and varieties of the same species. The competition is most severe between allied forms which fill nearly the same place in the economy of Nature. But great is our ignorance on the mutual relations of all organic beings. All that we can do is to keep steadily in mind that each organic being is striving to increase in a geometrical ratio; that each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life and to suffer great destruction. When we reflect on this struggle, we may console ourselves with the full belief that the war of Nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.

IV.—The Survival of the Fittest

How will the struggle for existence act in regard to variation? Can the principle of selection, which we have seen is so potent in the hands of man, apply under Nature? I think we shall see that it can act most efficiently. Let the endless number of slight variations and individual differences occurring in our domestic productions, and, in a lesser degree, in those under Nature, be borne in mind, as well as the strength of the hereditary tendency. Under domestication, it may be truly said that the whole organisation becomes in some degree plastic.

But the variability, which we almost universally meet with in our domestic productions, is not directly produced by man; he can neither originate variations nor prevent their occurrence; he can only preserve and accumulate such as do occur. Unintentionally he exposes organic beings to new and changing conditions of life, and variability ensues; but similar changes of condition might and do occur under Nature.

Let it also be borne in mind how infinitely complex and close-fitting are the mutual relations of all organic beings to each other and to their physical conditions of life, and consequently what infinitely varied diversities of structure might be of use to each being under changing conditions of life. Can it, then, be thought improbable, seeing what variations useful to man have undoubtedly occurred, that other variations, useful in some way to each being in the great complex battle of life, should occur in the course of many successive generations? If such do occur, can we doubt, remembering that many more individuals are born than can possibly survive, that individuals having any advantage over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable individual differences and variations, and the destruction of those which are injurious, I have called Natural Selection, or the Survival of the Fittest.

The term is too frequently misapprehended. Variations neither useful nor injurious would not be affected by natural selection. It is not asserted that natural selection induces variability. It implies only the preservation of such varieties as arise and are beneficial to the being under its conditions of life. Again, it has been said that I speak of natural selection as an active Power or Deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planets? It is difficult to avoid personifying the word Nature; but I mean by Nature only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us.

As man can produce, and certainly has produced, a great result by his methodical and unconscious means of selection, what may not natural selection effect? Man can act only on external and visible characters; Nature, if I may be allowed to personify the natural preservation or survival of the fittest, cares nothing for appearances, except in so far as they are useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends. Every selected character is fully exercised by her, as is implied by the fact of their selection. Man keeps the natives of many climates in the same country; he seldom exercises each selected character in some peculiar and fitting manner; he feeds a long and a short-beaked pigeon on the same food; he does not exercise a long-backed or long-legged quadruped in any peculiar manner; he exposes sheep with long and short wool to the same climate.

Man does not allow the most vigorous males to struggle for the females. He does not rigidly destroy all inferior animals, but protects during each varying season, as far as lies in his power, all his productions. He often begins his selection by some half-monstrous form; or at least by some modification prominent enough to catch the eye or to be plainly useful to him.

But under Nature, the slightest differences of structure or constitution may well turn the nicely-balanced scale in the struggle for life, and so be preserved. How fleeting are the wishes and efforts of man! How short his time! And, consequently, how poor will be his results compared with those accumulated by Nature during whole geological periods! Can we wonder that Nature's productions should be far "truer" in character than man's productions; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship?

It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress until the hand of time has marked the lapse of ages, and then so imperfect is our view into long-past geological ages that we see only that the forms of life are now different from what they formerly were.

Although natural selection can act only through and for the good of each being, yet characters and structures, which we are apt to consider as of very trifling importance, may thus be acted on.

Natural selection will modify the structure of the young in relation to the parent, and of the parent in relation to the young. In social animals it will adapt the structure of each individual for the benefit of the whole community, if the community profits by the selected change. What natural selection cannot do is to modify the structure of one species, without giving it any advantage, for the good of another species; and though statements to this effect may be found in works of natural history, I cannot find one case which will bear investigation.

A structure used only once in an animal's life, if of high importance to it, might be modified to any extent by natural selection; for instance, the great jaws possessed by certain insects, used exclusively for opening the cocoon, or the hard tip to the beak of unhatched birds, used for breaking the egg. It has been asserted that of the best short-beaked tumbler pigeons a greater number perish in the egg than are able to get out of it; so that fanciers assist in the act of hatching. Now, if Nature had to make the beak of a full-grown pigeon very short for the bird's own advantage, the process of modification would be very slow, and there would be simultaneously the most rigorous selection of all the young birds within the egg, for all with weak beaks would inevitably perish; or more easily broken shells might be selected, the thickness of the shell being known to vary like every other structure.

With all beings there must be much fortuitous destruction, which can have little or no influence on the course of natural selection. For instance, a vast number of eggs or seeds are annually devoured, and these could be modified through natural selection only if they varied in some manner which protected them from their enemies. Yet many of these eggs or seeds would perhaps, if not destroyed, have yielded individuals better adapted to their conditions of life than any of those which happened to survive. So, again, a vast number of mature animals and plants, whether or not they be the best adapted to their conditions, must be annually destroyed by accidental causes, which would not be in the least degree mitigated by certain changes of structure or constitution which would in other ways be beneficial to the species.

But let the destruction of the adults be ever so heavy, if the number which can exist in any district be not wholly kept down by such causes—or, again, let the destruction of eggs or seeds be so great that only a hundredth or a thousandth part are developed—yet of those which do survive, the best adapted individuals, supposing there is any variability in a favourable direction, will tend to propagate their kind in larger numbers than the less well adapted.

On our theory the continued existence of lowly organisms offers no difficulty; for natural selection does not necessarily include progressive development; it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life.

The mere lapse of time by itself does nothing, either for or against natural selection. I state this because it has been erroneously asserted that the element of time has been assumed by me to play an all-important part in modifying species, as if all the forms of life were necessarily undergoing change through some innate law.

V.—Sexual Selection

This form of selection depends, not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex. The result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than natural selection. Generally, the most vigorous males, those which are best fitted for their places in Nature, will leave most progeny. But, in many cases, victory depends not so much on general vigour as on having special weapons, confined to the male sex. A hornless stag or spurless cock would have a poor chance of leaving numerous offspring. Sexual selection, by always allowing the victor to breed, might surely give indomitable courage, length to the spur, and strength to the wing to strike in the spurred leg, in nearly the same manner as does the brutal cock-fighter by the careful selection of his best cocks.

How low in the scale of Nature the law of battle descends I know not. Male alligators have been described as fighting, bellowing, and whirling round, like Indians in a war-dance, for the possession of the females; male salmons have been observed fighting all day long; male stag-beetles sometimes bear wounds from the mandibles of other males; the males of certain other insects have been frequently seen fighting for a particular female who sits by, an apparently unconcerned beholder of the struggle, and then retires with the conqueror. The war is, perhaps, severest between the males of the polygamous animals, and these seem oftenest provided with special weapons. The males of carnivorous animals are already well armed, though to them special means of defence may be given through means of sexual selection, as the mane of the lion and the hooked jaw of the salmon. The shield may be as important for victory as the sword or spear.

Amongst birds, the contest is often of a more peaceful character. All those who have attended to the subject believe that there is the severest rivalry between the males of many species to attract, by singing, the females. The rock-thrush of Guiana, birds of paradise, and some others, congregate; and successive males display with the most elaborate care, and show off in the best manner, their gorgeous plumage; they likewise perform strange antics before the females, which, standing by as spectators, at last choose the most attractive partner.

If man can in a short time give beauty and an elegant carriage to his bantams, according to his standard of beauty, I can see no good reason to doubt that female birds, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect.

VI.—The Struggle for Existence

Under domestication we see much variability, caused, or at least excited, by changed conditions of life; but often in so obscure a manner that we are tempted to consider the variations as spontaneous. Variability is governed by many complex laws—by correlated growth, compensation, the increased use and disuse of parts, and the definite action of the surrounding conditions. There is much difficulty in ascertaining how largely our domestic productions have been modified; but we may safely infer that the amount has been large, and that modifications can be inherited for long periods. As long as the conditions of life remain the same, we have reason to believe that a modification, which has already been inherited for many generations, may continue to be inherited for an almost infinite number of generations. On the other hand, we have evidence that variability, when it has once come into play, does not cease under domestication for a very long period; nor do we know that it ever ceases, for new varieties are still occasionally produced by our oldest domesticated productions.

Variability is not actually caused by man; he only unintentionally exposes organic beings to new conditions of life, and then Nature acts on the organisation and causes it to vary. But man can and does select the variations given to him by Nature, and thus accumulates them in any desired manner. He thus adapts animals and plants for his own benefit or pleasure. He may do this methodically, or he may do it unconsciously by preserving the individuals most useful or pleasing to him without an intention of altering the breed.

It is certain that he can influence the character of a breed by selecting, in each successive generation, individual differences so slight as to be inappreciable except by an educated eye. This unconscious process of selection has been the agency in the formation of the most distinct and useful domestic breeds. That many breeds produced by man have to a large extent the character of natural species is shown by the inextricable doubts whether many of them are varieties or aboriginally distinct species.

There is no reason why the principles which have acted so efficiently under domestication should not have acted under Nature. In the survival of favoured individuals and races, during the constantly recurrent struggle for existence, we see a powerful and ever-acting form of selection. The struggle for existence inevitably follows from the high geometrical ratio of increase which is common to all organic beings. This high rate of increase is proved by calculation; by the rapid increase of many animals and plants during a succession of peculiar seasons and when naturalised in new countries. More individuals are born than can possibly survive. A grain in the balance may determine which individuals shall live and which shall die; which variety or species shall increase in number, and which shall decrease, or finally become extinct.

As the individuals of the same species come in all respects into the closest competition with each other, the struggle will generally be most severe between them; it will be almost equally severe between the varieties of the same species, and next in severity between the species of the same genus. On the other hand, the struggle will often be severe between beings remote in the scale of Nature. The slightest advantage in certain individuals, at any age or during any season, over those with which they come into competition, or better adaptation, in however slight a degree, to the surrounding physical conditions, will, in the long run, turn the balance.

With animals having separated sexes, there will be in most cases a struggle between the males for the possession of the females. The most vigorous males, or those which have most successfully struggled with their conditions of life, will generally leave most progeny. But success will often depend on the males having special weapons, or means of defence, or charms; and a slight advantage will lead to victory.

As geology plainly proclaims that each land has undergone great physical changes, we might have expected to find that organic beings have varied under Nature in the same way as they have varied under domestication. And if there has been any variability under Nature, it would be an unaccountable fact if natural selection had not come into play. It has often been asserted, but the assertion is incapable of proof, that the amount of variation under Nature is a strictly limited quantity. Man, though acting on external characters alone, and often capriciously, can produce within a short period a great result by adding up mere individual differences in his domestic productions; and everyone admits that species present individual differences. But, besides such differences, all naturalists admit that natural varieties exist, which are considered sufficiently distinct to be worthy of record in systematic works.

No one has drawn any clear distinction between individual differences and slight varieties, or between more plainly marked varieties and sub-species and species. On separate continents, and on different parts of the same continent when divided by barriers of any kind, what a multitude of forms exist which some experienced naturalists rank as varieties, others as geographical races or sub-species, and others as distinct, though closely allied species!

If, then, animals and plants do vary, let it be ever so slightly or slowly, why should not variations or individuals, differences which are in any way beneficial, be preserved and accumulated through natural selection, or the survival of the fittest? If man can, by patience, select variations useful to him, why, under changing and complex conditions of life, should not variations useful to Nature's living products often arise, and be preserved, or selected? What limit can be put to this power, acting during long ages and rigidly scrutinising the whole constitution, structure, and habits of each creature—favouring the good and rejecting the bad? I can see no limit to this power, in slowly and beautifully adapting each form to the most complex relations of life.

In the future I see open fields for far more important researches. Psychology will be based on the foundation already well laid by Mr. Herbert Spencer—that of the necessary acquirement of each mental power and capacity by gradation. Much light will be thrown on the origin of man and his history.

Authors of the highest eminence seem to be fully satisfied with the view that each species has been independently created. To my mind it accords better with what we know of the laws impressed on matter by the Creator that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual. When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled. Judging from the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity.

Of the species now living very few will transmit progeny of any kind to a far distant futurity; for the manner in which all organic beings are grouped shows that the greater number of species in each genus, and all the species in many genera, have left no descendants, but have become utterly extinct. We can so far take a prophetic glance into futurity as to foretell that it will be the common and widely-spread species, belonging to the larger and dominant groups within each class, which will ultimately prevail and procreate new and dominant species. As all the living forms of life are the lineal descendants of those which lived long before the Cambrian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. We may look with some confidence to a secure future of great length. As natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.

It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance, which is almost implied by reproduction; Variability from the indirect and direct action of the conditions of life, and from use and disuse; a ratio of increase so high as to lead to a struggle for life, and, as a consequence, to Natural Selection, entailing Divergence of Character and the Extinction of less improved forms. Thus, from the war of Nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms, or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

SIR HUMPHRY DAVY

Elements of Chemical Philosophy

Humphry Davy, the celebrated natural philosopher, was born Dec. 17, 1778, at Penzance, England. At the age of seventeen he became an apothecary's apprentice, and at the age of nineteen assistant at Dr. Beddoes's pneumatic institution at Bristol. During researches at the pneumatic institution he discovered the physiological effects of "laughing gas," and made so considerable a reputation as a chemist that at the age of twenty-two he was appointed lecturer, and a year later professor, at the Royal Institution. For ten years, from 1803, he was engaged in agricultural researches, and in 1813 published his "Elements of Agricultural Chemistry." During the same decade he conducted important investigations into the nature of chemical combination, and succeeded in isolating the elements potassium, sodium, strontium, magnesium, and chlorine. In 1812 he was knighted, and married Mrs. Apreece, née Jane Kerr. In 1815 he investigated the nature of fire-damp and invented the Davy safety lamp. In 1818 he received a baronetcy, and two years later was elected President of the Royal Society. On May 29, 1829, he died at Geneva. Davy's "Elements of Chemical Philosophy," of which a summary is given here, was published in one volume in 1812, being the substance of lectures delivered before the Board of Agriculture.

I.—Forms and Changes of Matter

The forms and appearances of the beings and substances of the external world are almost infinitely various, and they are in a state of continued alteration. In general, matter is found in four forms, as (1) solids, (2) fluids, (3) gases, (4) ethereal substances.

1. Solids. Solids retain whatever mechanical form is given to them; their parts are separated with difficulty, and cannot readily be made to unite after separation. They may be either elastic or non-elastic, and differ in hardness, in colour, in opacity, in density, in weight, and, if crystalline, in crystalline form.

2. Fluids. Fluids, when in small masses, assume the spherical form; their parts possess freedom of motion; they differ in density and tenacity, in colour, and in opacity. They are usually regarded as incompressible; at least, a very great mechanical force is required to compress them.

3. Gases. Gases exist free in the atmosphere, but may be confined. Their parts are highly movable; they are compressible and expansible, and their volumes are inversely as the weight compressing them. All known gases are transparent, and present only two or three varieties of colour; they differ materially in density.

4. Ethereal Substances. Ethereal substances are known to us only in their states of motion when acting upon our organs of sense, or upon other matter, and are not susceptible of being confined. It cannot be doubted that there is such matter in motion in space. Ethereal matter differs either in its nature, or in its affections by motion, for it produces different effects; for instance, radiant heat, and different kinds of light.

All these forms of matter are under the influence of active forces, such as gravitation, cohesion, heat, chemical and electrical attraction, and these we must now consider.

1. Gravitation. When a stone is thrown into the atmosphere, it rapidly descends towards the earth. This is owing to gravitation. All the great bodies in the universe are urged towards each other by a similar force. Bodies mutually gravitate towards each other, but the smaller body proportionately more than the larger one; hence the power of gravity is said to vary directly as the mass. Gravitation also varies with distance, and acts inversely as the square of the distance.

2. Cohesion. Cohesion is the force which preserves the forms of solids, and gives globularity to fluids. It is usually said to act only at the surface of bodies or by their immediate contact; but this does not seem to be the case. It certainly acts with much greater energy at small distances, but the spherical form of minute portions of fluid matter can be produced only by the attractions of all the parts of which they are composed, for each other; and most of these attractions must be exerted at sensible distances, so that gravitation and cohesion may be mere modifications of the same general power of attraction.

3. Heat. When a body which occasions the sensation of heat on our organs is brought into contact with another body which has no such effect, the hot body contracts and loses to a certain extent its power of communicating heat; and the other body expands. Different solids and fluids expand very differently when heated, and the expansive power of liquids, in general, is greater than that of solids.

It is evident that the density of bodies must be diminished by expansion; and in the case of fluids and gases, the parts of which are mobile, many important phenomena depend upon this circumstance. For instance, if heat be applied to fluids and gases, the heated parts change their places and rise, and the currents in the ocean and atmosphere are due principally to this movement. There are very few exceptions to the law of the expansion of bodies at the time they become capable of communicating the sensation of heat, and these exceptions seem to depend upon some chemical change in the constitution of bodies, or on their crystalline arrangements.

The power which bodies possess of communicating or receiving heat is known as temperature, and the temparature of a body is said to be high or low with respect to another in proportion as it occasions an expansion or contraction of its parts.

When equal volumes of different bodies of different temperatures are suffered to remain in contact till they acquire the same temperature, it is found that this temperature is not a mean one, as it would be in the case of equal volumes of the same body. Thus if a pint of quicksilver at 100° be mixed with a pint of water at 50°, the resulting temperature is not 75°, but 70°; the mercury has lost thirty degrees, whereas the water has only gained twenty degrees. This difference is said to depend on the different capacities of bodies for heat.

Not only do different bodies vary in their capacity for heat, but they likewise acquire heat with very different degrees of celerity. This last difference depends on the different power of bodies for conducting heat, and it will be found that as a rule the densest bodies, with the least capacity for heat, are the best conductors.

Heat, or the power of repulsion, may be considered as the antagonist power to the attraction of cohesion. Thus solids by a certain increase of temperature become fluids, and fluids gases; and, vice versâ, by a diminution of temperature, gases become fluids, and fluids solids.

Proofs of the conversion of solids, fluids, or gases into ethereal substances are not distinct. Heated bodies become luminous and give off radiant heat, which affects the bodies at a distance, and it may therefore be held that particles are thrown off from heated bodies with great velocity, which, by acting on our organs, produce the sensations of heat or light, and that their motion, communicated to the particles of other bodies, has the power of expanding them. It may, however, be said that the radiant matters emitted by bodies in ignition are specific substances, and that common matter is not susceptible of assuming this form; or it may be contended that the phenomena of radiation do in fact, depend upon motions communicated to subtile matter everywhere existing in space.

The temperatures at which bodies change their states from fluids to solids, though in general definite, are influenced by a few circumstances such as motion and pressure.

When solids are converted into fluids, or fluids into gases, there is always a loss of heat of temperature; and, vice versâ, when gases are converted into fluids, or fluids into solids, there is an increase of heat of temperature, and in this case it is said that latent heat is absorbed or given out.

The expansion due to heat has been accounted for by supposing a subtile fluid, or caloric, capable of combining with bodies and of separating their parts from each other, and the absorption and liberation of latent heat can be explained on this principle. But many other facts are incompatible with the theory. For instance, metal may be kept hot for any length of time by friction, so that if caloric be pressed out it must exist in an inexhaustible quantity. Delicate experiments have shown that bodies, when heated, do not increase in weight.

It seems possible to account for all the phenomena of heat, if it be supposed that in solids the particles are in a constant state of vibratory motion, the particles of the hottest bodies moving with the greatest velocity and through the greatest space; that in fluids and gases the particles have not only vibratory motion, but also a motion round their own axes with different velocities, and that in ethereal substances the particles move round their own axes and separate from each other, penetrating in right lines through space. Temperature may be conceived to depend upon the velocity of the vibrations, increase of capacity on the motion being performed in greater space; and the diminution of temperature during the conversion of solids into fluids or gases may be explained on the idea of the loss of vibratory motion in consequence of the revolution of particles round their axes at the moment when the body becomes fluid or aeriform, or from the loss of rapidity of vibration in consequence of the motion of particles through greater space.

4. Chemical Attraction. Oil and water will not combine; they are said to have no chemical attraction or affinity for each other. But if oil and solution of potassa in water be mixed, the oil and the solution blend and form a soap; and they are said to attract each other chemically or to have a chemical affinity for each other. It is a general character of chemical combination that it changes the qualities of the bodies. Thus, corrosive and pungent substances may become mild and tasteless; solids may become fluids, and solids and fluids gases.

No body will act chemically upon another body at any sensible distance; apparent contact is necessary for chemical action. A freedom of motion in the parts of the bodies or a want of cohesion greatly assists action, and it was formerly believed that bodies cannot act chemically upon each other unless one of them be fluid or gaseous.

Different bodies unite with different degrees of force, and hence one body is capable of separating others from certain of their combinations, and in consequence mutual decompositions of different compounds take place. This has been called double affinity, or complex chemical affinity.

As in all well-known compounds the proportions of the elements are in certain definite ratios to each other, it is evident that these ratios may be expressed by numbers; and if one number be employed to denote the smallest quantity in which a body combines, all other quantities of the same body will be multiples of this number, and the smallest proportions into which the undecomposed bodies enter into union being known, the constitution of the compounds they form may be learnt, and the element which unites chemically in the smallest quantity being expressed by unity, all the other elements may be represented by the relations of their quantities to unity.

5. Electrical Attraction. A piece of dry silk briskly rubbed against a warm plate of polished flint glass acquires the property of adhering to the glass, and both the silk and the glass, if apart from each other, attract light substances. The bodies are said to be electrically excited. Probably, all bodies which differ from each other become electrically excited when rubbed and pressed together. The electrical excitement seems of two kinds. A pith-ball touched by glass excited by silk repels a pith-ball touched by silk excited by metals. Electrical excitement of the same nature as that in glass excited by silk is known as vitreous or positive, and electrical excitement of the opposite nature is known as resinous or negative.

A rod of glass touched by an electrified body is electrified only round the point of contact. A rod of metal, on the contrary, suspended on a rod of glass and brought into contact with an electrical surface, instantly becomes electrical throughout. The glass is said to be a non-conductor, or insulating substance; the metal a conductor.

When a non-conductor or imperfect conductor, provided it be a thin plate of matter placed upon a conductor, is brought in contact with an excited electrical body, the surface opposite to that of contact gains the opposite electricity from that of the excited body, and if the plate be removed it is found to possess two surfaces in opposite states. If a conductor be brought into the neighbourhood of an excited body—the air, which is a non-conductor, being between them—that extremity of the conductor which is opposite to the excited body gains the opposite electricity; and the other extremity, if opposite to a body connected with the ground, gains the same electricity, and the middle point is not electrical at all. This is known as induced electricity.

The common exhibition of electrical effects is in attractions and repulsions; but electricity also produces chemical phenomena. If a piece of zinc and copper in contact with each other at one point be placed in contact at other points with the same portion of water, the zinc will corrode, and attract oxygen from the water much more rapidly than if it had not been in contact with the copper; and if sulphuric acid be added, globules of inflammable air are given off from the copper, though it is not dissolved or acted upon.

Chemical phenomena in connection with electrical effects can be shown even better by combinations in which the electrical effects are increased by alterations of different metals and fluids—the so-called voltaic batteries. Such are the decomposing powers of such batteries that not even insoluble compounds are capable of resisting their energy, for even glass, sulphate of baryta, fluorspar, etc., are slowly acted upon, and the alkaline, earthy, or acid matter carried to the poles in the common order.

The most powerful voltaic combinations are formed by substances that act chemically with most energy upon each other, and such substances as undergo no chemical changes in the combination exhibit no electrical powers. Hence it was supposed that the electrical powers of metals were entirely due to chemical changes; but this is not the case, for contact produces electricity even when no chemical change can be observed.

II.—Radiant or Ethereal Matter

When similar thermometers are placed in different parts of the solar beam, it is found that different effects are produced in the differently coloured rays. The greatest heat is exhibited in the red rays, the least in the violet rays; and in a space beyond the red rays, where there is no visible light, the increase of temperature is greatest of all.

From these facts it is evident that matter set in motion by the sun has the power of producing heat without light, and that its rays are less refrangible than the visible rays. The invisible rays that produce heat are capable of reflection as well as refraction in the same manner as the visible rays.

Rays capable of producing heat with and without light proceed not only from the sun, but also from bodies at the surface of the globe under peculiar agencies or changes. If, for instance, a thermometer be held near an ignited body, it receives an impression connected with an elevation of temperature; this is partly produced by the conducting powers of the air, and partly by an impulse which is instantaneously communicated, even to a considerable distance. This effect is called the radiation of terrestrial heat.

The manner in which the temperatures of bodies are affected by rays producing heat is different for different substances, and is very much connected with their colours. The bodies that absorb most light, and reflect least, are most heated when exposed either to solar or terrestrial rays. Black bodies are, in general, more heated than red; red more than green; green more than yellow; and yellow more than white. Metals are less heated than earthy or stony bodies, or than animal or vegetable matters. Polished surfaces are less heated than rough surfaces.

The bodies that have their temperatures most easily raised by heat rays are likewise those that are most easily cooled by their own radiation, or that at the same temperature emit most heat-making rays. Metals radiate less heat than glass, glass less than vegetable substances, and charcoal has the highest radiating powers of any body as yet made the subject of experiment.

Radiant matter has the power of producing chemical changes partly through its heating power, and partly through some other specific and peculiar influence. Thus chlorine and hydrogen detonate when a mixture of them is exposed to the solar beams, even though the heat is inadequate to produce detonation.

If moistened silver be exposed to the different rays of the solar spectrum, it will be found that no effect is produced upon it by the least refrangible rays which occasion heat without light; that a slight discoloration only will be produced by the red rays; that the effect of blackening will be greater towards the violet end of the spectrum; and that in a space beyond the violet, where there is no sensible heat or light, the chemical effect will be very distinct. There seem to be rays, therefore, more refrangible than the rays producing light and heat.

The general facts of the refraction and effects of the solar beam offer an analogy to the agencies of electricity.

In general, in Nature the effects of the solar rays are very compounded. Healthy vegetation depends upon the presence of the solar beams or of light, and while the heat gives fluidity and mobility to the vegetable juices, chemical effects are likewise occasioned, oxygen is separated from them, and inflammable compounds are formed. Plants deprived of light become white and contain an excess of saccharine and aqueous particles; and flowers owe the variety of their hues to the influence of the solar beams. Even animals require the presence of the rays of the sun, and their colours seem to depend upon the chemical influence of these rays.

Two hypotheses have been invented to account for the principal operations of radiant matter. In the first it is supposed that the universe contains a highly rare elastic substance, which, when put into a state of undulation, produces those effects on our organs of sight which constitute the sensations of vision and other phenomena caused by solar and terrestrial rays. In the second it is conceived that particles are emitted from luminous or heat-making bodies with great velocity, and that they produce their effects by communicating their motions to substances, or by entering into them and changing their composition.

Newton has attempted to explain the different refrangibility of the rays of light by supposing them composed of particles differing in size. The same great man has put the query whether light and common matter are not convertible into each other; and, adopting the idea that the phenomena of sensible heat depend upon vibrations of the particles of bodies, supposes that a certain intensity of vibrations may send off particles into free space, and that particles in rapid motion in right lines, in losing their own motion, may communicate a vibratory motion to the particles of terrestrial bodies.

MICHAEL FARADAY

Experimental Researches in Electricity

Michael Faraday was the son of a Yorkshire blacksmith, and was born in London on September 22, 1791. At the age of twenty he became assistant to Sir Humphry Davy, whose lectures he had attended at the Royal Institution. Here he worked for the rest of his laborious life, which closed on August 25, 1867. The fame of Faraday, among those whose studies qualify them for a verdict, has risen steadily since his death, great though it then was. His researches were of truly epoch-making character, and he was the undisputed founder of the modern science of electricity, which is rapidly coming to dominate chemistry itself. Faraday excelled as a lecturer, and could stand even the supreme test of lecturing to children. Faraday's "Experimental Researches in Electricity" is a record of some of the most brilliant experiments in the history of science. In the course of his investigations he made discoveries which have had momentous consequences. His discovery of the mutual relation of magnets and of wires conducting electric currents was the beginning of the modern dynamo and all that it involves; while his discoveries of electric induction and of electrolysis were of equal significance. Most of the researches are too technical for epitomisation; but those given are representative of his manner and methods.

I.—Atmospheric Magnetism

It is to me an impossible thing to perceive that two-ninths of the atmosphere by weight is a highly magnetic body, subject to great changes in its magnetic character, by variations in its temperature and condensation or rarefaction, without being persuaded that it has much to do with the variable disposition of the magnetic forces upon the surface of the earth.

The earth is a spheroidal body consisting of paramagnetic and diamagnetic substances irregularly disposed and intermingled; but for the present the whole may be considered a mighty compound magnet. The magnetic force of this great magnet is known to us only on the surface of the earth and water of our planet, and the variations in the magnetic lines of force which pass in or across this surface can be measured by their action on small standard magnets; but these variations are limited in their information, and do not tell us whether the cause is in the air above or the earth beneath.

The lines of force issue from the earth in the northern and southern parts and coalesce with each other over the equatorial, as would be the case in a globe having one or two short magnets adjusted in relation to its axis, and it is probable that the lines of force in their circuitous course may extend through space to tens of thousands of miles. The lines proceed through space with a certain degree of facility, but there may be variations in space, e.g., variations in its temperature which affect its power of transmitting the magnetic influence.

Between the earth and space, however, is interposed the atmosphere, and at the bottom of the atmosphere we live. The atmosphere consists of four volumes of nitrogen and one of oxygen uniformly mixed and acting magnetically as a single medium. The nitrogen of the air is, as regards the magnetic force, neither paramagnetic nor diamagnetic, whether dense or rare, or at high or low temperatures.

The oxygen of the air, on the other hand, is highly paramagnetic, being, bulk for bulk, equivalent to a solution of protosulphate of iron, containing of the crystallised salt seventeen times the weight of the oxygen. It becomes less paramagnetic, volume for volume, as it is rarefied, and apparently in the simple proportion of its rarefaction, the temperature remaining the same. When its temperature is raised—the expansion consequent thereon being permitted—it loses very greatly its paramagnetic force, and there is sufficient reason to conclude that when its temperature is lowered its paramagnetic condition is exalted. These characters oxygen preserves even when mingled with the nitrogen in the air.

Hence the atmosphere is a highly magnetic medium, and this medium is changed in its magnetic relations by every change in its density and temperature, and must affect both the intensity and direction of the magnetic force emanating from the earth, and may account for the variations which we find in terrestrial magnetic power.

We may expect as the sun leaves us on the west some magnetic effect correspondent to that of the approach of a body of cold air from the east. Again, the innumerable circumstances that break up more or less any average arrangement of the air temperatures may be expected to give not merely differences in the regularity, direction, and degree of magnetic variation, but, because of vicinity, differences so large as to be many times greater than the mean difference for a given short period, and they may also cause irregularities in the times of their occurrence. Yet again, the atmosphere diminishes in density upwards, and this diminution will affect the transmission of the electric force.

The result of the annual variation that may be expected from the magnetic constitution and condition of the atmosphere seems to me to be of the following kind.

Since the axis of the earth's rotation is inclined 23° 28' to the plane of the ecliptic, the two hemispheres will become alternately warmer and cooler than each other. The air of the cooled hemisphere will conduct magnetic influence more freely than if in the mean state, and the lines of force passing through it will increase in amount, whilst in the other hemisphere the warmed air will conduct with less readiness than before, and the intensity will diminish. In addition to this effect of temperature, there ought to be another due to the increase of the ponderable portion of the air in the cooled hemisphere, consequent on its contraction and the coincident expansion of the air in the warmer half, both of which circumstances tend to increase the variation in power of the two hemispheres from the normal state. Then, as the earth rolls on its annual journey, that which was at one time the cooler becomes the warmer hemisphere, and in its turn sinks as far below the average magnetic intensity as it before had stood above it, while the other hemisphere changes its magnetic condition from less to more intense.