Chapter Viii. of the "life and Letters". (vol. I. Page 304. for Darwin's

religious views see also "Descent of Man", 1871, Vol. I. page 65; 2nd edition. Vol. I. page 142.) On board the "Beagle" he was simply orthodox and was laughed at by several of the officers for quoting the Bible as an unanswerable authority on some point of morality. By 1839 he had come to see that the Old Testament was no more to be trusted than the sacred books of the Hindoos. Next went the belief in miracles, and next Paley's "argument from design" broke down before the law of natural selection; the suffering so manifest in nature is seen to be compatible rather with Natural Selection than with the goodness and omnipotence of God. Darwin felt to the full all the ignorance that lay hidden under specious phrases like "the plan of creation" and "Unity of design." Finally, he tells us "the mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an Agnostic."

The word Agnostic is significant not only of the humility of the man himself but also of the attitude of his age. Religion, it is clear, is still conceived as something to be KNOWN, a matter of true or false OPINION. Orthodox religion was to Darwin a series of erroneous hypotheses to be bit by bit discarded when shown to be untenable. The ACTS of religion which may result from such convictions, i.e. devotion in all its forms, prayer, praise, sacraments, are left unmentioned. It is clear that they are not, as now to us, sociological survivals of great interest and importance, but rather matters too private, too personal, for discussion.

Huxley, writing in the "Contemporary Review" (1871.), says, "In a dozen years "The Origin of Species" has worked as complete a revolution in biological science as the "Principia" did in astronomy." It has done so because, in the words of Helmholtz, it contained "an essentially new creative thought," that of the continuity of life, the absence of breaks. In the two most conservative subjects, Religion and Classics, this creative ferment was slow indeed to work. Darwin himself felt strongly "that a man should not publish on a subject to which he has not given special and continuous thought," and hence wrote little on religion and with manifest reluctance, though, as already seen, in answer to pertinacious inquiry he gave an outline of his own views. But none the less he foresaw that his doctrine must have, for the history of man's mental evolution, issues wider than those with which he was prepared personally to deal. He writes, in "The Origin of Species" (6th edition, page 428.), "In the future I see open fields for far more important researches. Psychology will be securely based on the foundation already well laid by Mr Herbert Spencer, that of the necessary acquirement of each mental power and capacity by gradation."

Nowhere, it is true, does Darwin definitely say that he regarded religion as a set of phenomena, the development of which may be studied from the psychological standpoint. Rather we infer from his PIETY--in the beautiful Roman sense--towards tradition and association, that religion was to him in some way sacrosanct. But it is delightful to see how his heart went out towards the new method in religious study which he had himself, if half-unconsciously, inaugurated. Writing in 1871 to Dr Tylor, on the publication of his "Primitive Culture", he says ("Life and Letters", Vol. III. page 151.), "It is wonderful how you trace animism from the lower races up the religious belief of the highest races. It will make me for the future look at religion--a belief in the soul, etc.--from a new point of view."

Psychology was henceforth to be based on "the necessary acquirement of each mental capacity by gradation." With these memorable words the door closes on the old and opens on the new horizon. The mental focus henceforth is not on the maintaining or refuting of an orthodoxy but on the genesis and evolution of a capacity, not on perfection but on process. Continuous evolution leaves no gap for revelation sudden and complete. We have henceforth to ask, not when was religion revealed or what was the revelation, but how did religious phenomena arise and develop. For an answer to this we turn with new and reverent eyes to study "the heathen in his blindness" and the child "born in sin." We still indeed send out missionaries to convert the heathen, but here at least in Cambridge before they start they attend lectures on anthropology and comparative religion. The "decadence" theory is dead and should be buried.

The study of primitive religions then has been made possible and even inevitable by the theory of Evolution. We have now to ask what new facts and theories have resulted from that study. This brings us to our second point, the advanced outlook on religion to-day.

The view I am about to state is no mere personal opinion of my own. To my present standpoint I have been led by the investigations of such masters as Drs Wundt, Lehmann, Preuss, Bergson, Beck and in our own country Drs Tylor and Frazer. (I can only name here the books that have specially influenced my own views. They are W. Wundt, "Volkerpsychologie", Leipzig, 1900, P. Beck, "Die Nachahmung", Leipzig, 1904, and "Erkenntnisstheorie des primitiven Denkens" in "Zeitschrift f. Philos. und Philos. Kritik", 1903, page 172, and 1904, page 9. Henri Bergson, "L'Evolution Creatrice" and "Matiere et Memoire", 1908, K. Th. Preuss, various articles published in the "Globus" (see page 507, note 1), and in the "Archiv. f. Religionswissenschaft", and for the subject of magic, MM. Hubert et Mauss, "Theorie generale de la Magie", in "L'Annee Sociologique", VII.)

Religion always contains two factors. First, a theoretical factor, what a man THINKS about the unseen--his theology, or, if we prefer so to call it, his mythology. Second, what he DOES in relation to this unseen--his ritual. These factors rarely if ever occur in complete separation; they are blended in very varying proportions. Religion we have seen was in the last century regarded mainly in its theoretical aspect as a doctrine. Greek religion for example meant to most educated persons Greek mythology. Yet even a cursory examination shows that neither Greek nor Roman had any creed or dogma, any hard and fast formulation of belief. In the Greek Mysteries (See my "Prolegomena to the Study of Greek Religion", page 155, Cambridge, 1903.) only we find what we should call a Confiteor; and this is not a confession of faith, but an avowal of rites performed. When the religion of primitive peoples came to be examined it was speedily seen that though vague beliefs necessarily abound, definite creeds are practically non-existent. Ritual is dominant and imperative.

This predominance and priority of ritual over definite creed was first forced upon our notice by the study of savages, but it promptly and happily joined hands with modern psychology. Popular belief says, I think, therefore I act; modern scientific psychology says, I act (or rather, REact to outside stimulus), and so I come to think. Thus there is set going a recurrent series: act and thought become in their turn stimuli to fresh acts and thoughts. In examining religion as envisaged to-day it would therefore be more correct to begin with the practice of religion, i.e. ritual, and then pass to its theory, theology or mythology. But it will be more convenient to adopt the reverse method. The theoretical content of religion is to those of us who are Protestants far more familiar and we shall thus proceed from the known to the comparatively unknown.

I shall avoid all attempt at rigid definition. The problem before the modern investigator is, not to determine the essence and definition of religion but to inquire how religious phenomena, religious ideas and practices arose. Now the theoretical content of religion, the domain of theology or mythology, is broadly familiar to all. It is the world of the unseen, the supersensuous; it is the world of what we call the soul and the supposed objects of the soul's perception, sprites, demons, ghosts and gods. How did this world grow up?

We turn to our savages. Intelligent missionaries of bygone days used to ply savages with questions such as these: Had they any belief in God? Did they believe in the immortality of the soul? Taking their own clear-cut conceptions, discriminated by a developed terminology, these missionaries tried to translate them into languages that had neither the words nor the thoughts, only a vague, inchoate, tangled substratum, out of which these thoughts and words later differentiated themselves. Let us examine this substratum.

Nowadays we popularly distinguish between objective and subjective; and further, we regard the two worlds as in some sense opposed. To the objective world we commonly attribute some reality independent of consciousness, while we think of the subjective as dependent for its existence on the mind. The objective world consists of perceptible things, or of the ultimate constituents to which matter is reduced by physical speculation. The subjective world is the world of beliefs, hallucinations, dreams, abstract ideas, imaginations and the like. Psychology of course knows that the objective and subjective worlds are interdependent, inextricably intertwined, but for practical purposes the distinction is convenient.

But primitive man has not yet drawn the distinction between objective and subjective. Nay, more, it is foreign to almost the whole of ancient philosophy. Plato's Ideas (I owe this psychological analysis of the elements of the primitive supersensuous world mainly to Dr Beck, "Erkenntnisstheorie des primitiven Denkens", see page 498, note 1.), his Goodness, Truth, Beauty, his class-names, horse, table, are it is true dematerialised as far as possible, but they have outside existence, apart from the mind of the thinker, they have in some shadowy way spatial extension. Yet ancient philosophies and primitive man alike needed and possessed for practical purposes a distinction which served as well as our subjective and objective. To the primitive savage all his thoughts, every object of which he was conscious, whether by perception or conception, had reality, that is, it had existence outside himself, but it might have reality of various kinds or different degrees.

It is not hard to see how this would happen. A man's senses may mislead him. He sees the reflection of a bird in a pond. To his eyes it is a real bird. He touches it, HE PUTS IT TO THE TOUCH, and to his touch it is not a bird at all. It is real then, but surely not quite so real as a bird that you can touch. Again, he sees smoke. It is real to his eyes. He tries to grasp it, it vanishes. The wind touches him, but he cannot see it, which makes him feel uncanny. The most real thing is that which affects most senses and especially what affects the sense of touch. Apparently touch is the deepest down, most primitive, of senses. The rest are specialisations and complications. Primitive man has no formal rubric "optical delusion," but he learns practically to distinguish between things that affect only one sense and things that affect two or more--if he did not he would not survive. But both classes of things are real to him. Percipi est esse.

So far, primitive man has made a real observation; there are things that appeal to one sense only. But very soon creeps in confusion fraught with disaster. He passes naturally enough, being economical of any mental effort, from what he really sees but cannot feel to what he thinks he sees, and gives to it the same secondary reality. He has dreams, visions, hallucinations, nightmares. He dreams that an enemy is beating him, and he wakes rubbing his head. Then further he remembers things; that is, for him, he sees them. A great chief died the other day and they buried him, but he sees him still in his mind, sees him in his war-paint, splendid, victorious. So the image of the past goes together with his dreams and visions to the making of this other less real, but still real world, his other-world of the supersensuous, the supernatural, a world, the outside existence of which, independent of himself, he never questions.

And, naturally enough, the future joins the past in this supersensuous world. He can hope, he can imagine, he can prophesy. And again the images of his hope are real; he sees them with that mind's eye which as yet he has not distinguished from his bodily eye. And so the supersensuous world grows and grows big with the invisible present, and big also with the past and the future, crowded with the ghosts of the dead and shadowed with oracles and portents. It is this supersensuous, supernatural world which is the eternity, the other-world, of primitive religion, not an endlessness of time, but a state removed from full sensuous reality, a world in which anything and everything may happen, a world peopled by demonic ancestors and liable to a splendid vagueness, to a "once upon a time-ness" denied to the present. It not unfrequently happens that people who know that the world nowadays obeys fixed laws have no difficulty in believing that six thousand years ago man was made direct from a lump of clay, and woman was made from one of man's superfluous ribs.

The fashioning of the supersensuous world comes out very clearly in primitive man's views about the soul and life after death. Herbert Spencer noted long ago the influence of dreams in forming a belief in immortality, but being very rational himself, he extended to primitive man a quite alien quality of rationality. Herbert Spencer argued that when a savage has a dream he seeks to account for it, and in so doing invents a spirit world. The mistake here lies in the "seeks to account for it." (Primitive man, as Dr Beck observes, is not impelled by an Erkenntnisstrieb. Dr Beck says he has counted upwards of 30 of these mythological Triebe (tendencies) with which primitive man has been endowed.) Man is at first too busy LIVING to have any time for disinterested THINKING. He dreams a dream and it is real for him. He does not seek to account for it any more than for his hands and feet. He cannot distinguish between a CONception and a PERception, that is all. He remembers his ancestors or they appear to him in a dream; therefore they are alive still, but only as a rule to about the third generation. Then he remembers them no more and they cease to be.

Next as regards his own soul. He feels something within him, his life-power, his will to live, his power to act, his personality--whatever we like to call it. He cannot touch this thing that is himself, but it is real. His friend too is alive and one day he is dead; he cannot move, he cannot act. Well, something has gone that was his friend's self. He has stopped breathing. Was it his breath? or he is bleeding; is it his blood? This life-power IS something; does it live in his heart or his lungs or his midriff? He did not see it go; perhaps it is like wind, an anima, a Geist, a ghost. But again it comes back in a dream, only looking shadowy; it is not the man's life, it is a thin copy of the man; it is an "image" (eidolon). It is like that shifting distorted thing that dogs the living man's footsteps in the sunshine; it is a "shade" (skia). (The two conceptions of the soul, as a life-essence, inseparable from the body, and as a separable phantom seem to occur in most primitive systems. They are distinct conceptions but are inextricably blended in savage thought. The two notions Korperseele and Psyche have been very fully discussed in Wundt's "Volkerpsychologie" II. pages 1-142, Leipzig, 1900.)

Ghosts and sprites, ancestor worship, the soul, oracles, prophecy; all these elements of the primitive supersensuous world we willingly admit to be the proper material of religion; but other elements are more surprising; such are class-names, abstract ideas, numbers, geometrical figures. We do not nowadays think of these as of religious content, but to primitive men they were all part of the furniture of his supernatural world.

With respect to class-names, Dr Tylor ("Primitive Culture", Vol. II. page 245 (4th edition), 1903.) has shown how instructive are the first attempts of the savage to get at the idea of a class. Things in which similarity is observed, things indeed which can be related at all are to the savage KINDRED. A species is a family or a number of individuals with a common god to look after them. Such for example is the Finn doctrine of the haltia. Every object has its haltia, but the haltiat were not tied to the individual, they interested themselves in every member of the species. Each stone had its haltia, but that haltia was interested in other stones; the individuals disappeared, the haltia remained.

Nor was it only class-names that belonged to the supersensuous world. A man's own proper-name is a sort of spiritual essence of him, a kind of soul to be carefully concealed. By pronouncing a name you bring the thing itself into being. When Elohim would create Day "he called out to the Light 'Day,' and to the Darkness he called out 'Night'"; the great magician pronounced the magic Names and the Things came into being. "In the beginning was the Word" is literally true, and this reflects the fact that our CONCEPTUAL world comes into being by the mental process of naming. (For a full discussion of this point see Beck, "Nachahmung" page 41, "Die Sprache".) In old times people went further; they thought that by naming events they could bring them to be, and custom even to-day keeps up the inveterate magical habit of wishing people "Good Morning" and a "Happy Christmas."

Number, too, is part of the supersensuous world that is thoroughly religious. We can see and touch seven apples, but seven itself, that wonderful thing that shifts from object to object, giving it its SEVENness, that living thing, for it begets itself anew in multiplication--surely seven is a fit denizen of the upper-world. Originally all numbers dwelt there, and a certain supersensuous sanctity still clings to seven and three. We still say "Holy, Holy, Holy," and in some mystic way feel the holier.

The soul and the supersensuous world get thinner and thinner, rarer and more rarified, but they always trail behind them clouds of smoke and vapour from the world of sense and space whence they have come. It is difficult for us even nowadays to use the word "soul" without lapsing into a sensuous mythology. The Cartesians' sharp distinction between res extensa non cogitans and res cogitans non extansa is remote.

So far then man, through the processes of his thinking, has provided himself with a supersensuous world, the world of sense-delusion, of smoke and cloud, of dream and phantom, of imagination, of name and number and image. The natural course would now seem to be that this supersensuous world should develop into the religious world as we know it, that out of a vague animism with ghosts of ancestors, demons, and the like, there should develop in due order momentary gods (Augenblicks-Gotter), tribal gods, polytheism, and finally a pure monotheism.

This course of development is usually assumed, but it is not I think quite what really happens. The supersensuous world as we have got it so far is too theoretic to be complete material of religion. It is indeed only one factor, or rather it is as it were a lifeless body that waits for a living spirit to possess and inform it. Had the theoretic factor remained uninformed it would eventually have separated off into its constituent elements of error and truth, the error dying down as a belated metaphysic, the truth developing into a correct and scientific psychology of the subjective. But man has ritual as well as mythology; that is, he feels and acts as well as thinks; nay more he probably feels and acts long before he definitely thinks. This contradicts all our preconceived notions of theology. Man, we imagine, believes in a god or gods and then worships. The real order seems to be that, in a sense presently to be explained, he worships, he feels and acts, and out of his feeling and action, projected into his confused thinking, he develops a god. We pass therefore to our second factor in religion:--ritual.

The word "ritual" brings to our modern minds the notion of a church with a priesthood and organised services. Instinctively we think of a congregation meeting to confess sins, to receive absolution, to pray, to praise, to listen to sermons, and possibly to partake of sacraments. Were we to examine these fully developed phenomena we should hardly get further in the analysis of our religious conceptions than the notion of a highly anthropomorphic god approached by purely human methods of personal entreaty and adulation.

Further, when we first come to the study of primitive religions we expect a priori to find the same elements, though in a ruder form. We expect to see "The heathen in his blindness bow down to wood and stone," but the facts that actually confront us are startlingly dissimilar. Bowing down to wood and stone is an occupation that exists mainly in the minds of hymn-writers. The real savage is more actively engaged. Instead of asking a god to do what he wants done, he does it or tries to do it himself; instead of prayers he utters spells. In a word he is busy practising magic, and above all he is strenuously engaged in dancing magical dances. When the savage wants rain or wind or sunshine, he does not go to church; he summons his tribe and they dance a rain-dance or wind-dance or sun-dance. When a savage goes to war we must not picture his wife on her knees at home praying for the absent; instead we must picture her dancing the whole night long; not for mere joy of heart or to pass the weary hours; she is dancing his war-dance to bring him victory.

Magic is nowadays condemned alike by science and by religion; it is both useless and impious. It is obsolete, and only practised by malign sorcerers in obscure holes and corners. Undoubtedly magic is neither religion nor science, but in all probability it is the spiritual protoplasm from which religion and science ultimately differentiated. As such the doctrine of evolution bids us scan it closely. Magic may be malign and private; nowadays it is apt to be both. But in early days magic was as much for good as for evil; it was publicly practised for the common weal.

The gist of magic comes out most clearly in magical dances. We think of dancing as a light form of recreation, practised by the young from sheer joie de vivre and unsuitable for the mature. But among the Tarahumares (Carl Lumholtz, "Unknown Mexico", page 330, London, 1903.) in Mexico the word for dancing, nolavoa, means "to work." Old men will reproach young men saying "Why do you not go to work?" meaning why do you not dance instead of only looking on. The chief religious sin of which the Tarahumare is conscious is that he has not danced enough and not made enough tesvino, his cereal intoxicant.

Dancing then is to the savage WORKING, DOING, and the dance is in its origin an imitation or perhaps rather an intensification of processes of work. (Karl Bucher, "Arbeit und Rhythmus", Leipzig (3rd edition), 1902, passim.) Repetition, regular and frequent, constitutes rhythm and rhythm heightens the sense of will power in action. Rhythmical action may even, as seen in the dances of Dervishes, produce a condition of ecstasy. Ecstasy among primitive peoples is a condition much valued; it is often, though not always, enhanced by the use of intoxicants. Psychologically the savage starts from the sense of his own will power, he stimulates it by every means at his command. Feeling his will strongly and knowing nothing of natural law he recognises no limits to his own power; he feels himself a magician, a god; he does not pray, he WILLS. Moreover he wills collectively (The subject of collective hallucination as an element in magic has been fully worked out by MM. Hubert and Mauss. "Theorie generale de la Magie", In "L'Annee Sociologique", 1902--3, page 140.), reinforced by the will and action of his whole tribe. Truly of him it may be said "La vie deborde l'intelligence, l'intelligence c'est un retrecissement." (Henri Bergson, "L'Evolution Creatrice", page 50.)

The magical extension and heightening of personality come out very clearly in what are rather unfortunately known as MIMETIC dances. Animal dances occur very frequently among primitive peoples. The dancers dress up as birds, beasts, or fishes, and reproduce the characteristic movements and habits of the animals impersonated. (So characteristic is this impersonation in magical dancing that among the Mexicans the word for magic, navali, means "disguise." K. Th. Preuss, "Archiv f. Religionswissenschaft", 1906, page 97.) A very common animal dance is the frog-dance. When it rains the frogs croak. If you desire rain you dress up like a frog and croak and jump. We think of such a performance as a conscious imitation. The man, we think, is more or less LIKE a frog. That is not how primitive man thinks; indeed, he scarcely thinks at all; what HE wants done the frog can do by croaking and jumping, so he croaks and jumps and, for all he can, BECOMES a frog. "L'intelligence animale JOUE sans doute les representations plutot qu'elle ne les pense." (Bergson, "L'Evolution Creatrice", page 205.)

We shall best understand this primitive state of mind if we study the child "born in sin." If a child is "playing at lions" he does not IMITATE a lion, i.e. he does not consciously try to be a thing more or less like a lion, he BECOMES one. His reaction, his terror, is the same as if the real lion were there. It is this childlike power of utter impersonation, of BEING the thing we act or even see acted, this extension and intensification of our own personality that lives deep down in all of us and is the very seat and secret of our joy in the drama.

A child's mind is indeed throughout the best clue to the understanding of savage magic. A young and vital child knows no limit to his own will, and it is the only reality to him. It is not that he wants at the outset to fight other wills, but that they simply do not exist for him. Like the artist he goes forth to the work of creation, gloriously alone. His attitude towards other recalcitrant wills is "they simply must." Let even a grown man be intoxicated, be in love, or subject to an intense excitement, the limitations of personality again fall away. Like the omnipotent child he is again a god, and to him all things are possible. Only when he is old and weary does he cease to command fate.

The Iroquois (Hewitt, "American Anthropologist", IV. I. page 32, 1902, N.S.) of North America have a word, orenda, the meaning of which is easier to describe than to define, but it seems to express the very soul of magic. This orenda is your power to do things, your force, sometimes almost your personality. A man who hunts well has much and good orenda; the shy bird who escapes his snares has a fine orenda. The orenda of the rabbit controls the snow and fixes the depth to which it will fall. When a storm is brewing the magician is said to be making its orenda. When you yourself are in a rage, great is your orenda. The notes of birds are utterances of their orenda. When the maize is ripening, the Iroquois know it is the sun's heat that ripens it, but they know more; it is the cigala makes the sun to shine and he does it by chirping, by uttering his orenda. This orenda is sometimes very like the Greek thumos, your bodily life, your vigour, your passion, your power, the virtue that is in you to feel and do. This notion of orenda, a sort of pan-vitalism, is more fluid than animism, and probably precedes it. It is the projection of man's inner experience, vague and unanalysed, into the outer world.

The mana of the Melanesians (Codrington, "The Melanesians", pages 118, 119, 192, Oxford, 1891.) is somewhat more specialised--all men do not possess mana--but substantially it is the same idea. Mana is not only a force, it is also an action, a quality, a state, at once a substantive, an adjective, and a verb. It is very closely neighboured by the idea of sanctity. Things that have mana are tabu. Like orenda it manifests itself in noises, but specially mysterious ones, it is mana that is rustling in the trees. Mana is highly contagious, it can pass from a holy stone to a man or even to his shadow if it cross the stone. "All Melanesian religion," Dr Codrington says, "consists in getting mana for oneself or getting it used for one's benefit." (Codrington, "The Melanesians", page 120, Oxford, 1891.)

Specially instructive is a word in use among the Omaka (See Prof. Haddon, "Magic and Fetishism", page 60, London, 1906. Dr Vierkandt ("Globus", July, 1907, page 41) thinks that "Fernzauber" is a later development from Nahzauber.), wazhin-dhedhe, "directive energy, to send." This word means roughly what we should call telepathy, sending out your thought or will-power to influence another and affect his action. Here we seem to get light on what has always been a puzzle, the belief in magic exercised at a distance. For the savage will, distance is practically non-existent, his intense desire feels itself as non-spatial. (This notion of mana, orenda, wazhin-dhedhe and the like lives on among civilised peoples in such words as the Vedic brahman in the neuter, familiar to us in its masculine form Brahman. The neuter, brahman, means magic power of a rite, a rite itself, formula, charm, also first principle, essence of the universe. It is own cousin to the Greek dunamis and phusis. See MM. Hubert et Mauss, "Theorie generale de la Magie", page 117, in "L'Annee Sociologique", VII.)

Through the examination of primitive ritual we have at last got at one tangible, substantial factor in religion, a real live experience, the sense, that is, of will, desire, power actually experienced in person by the individual, and by him projected, extended into the rest of the world.

At this stage it may fairly be asked, though the question cannot with any certainty be answered, "at what point in the evolution of man does this religious experience come in?"

So long as an organism reacts immediately to outside stimulus, with a certainty and conformity that is almost chemical, there is, it would seem, no place, no possibility for magical experience. But when the germ appears of an intellect that can foresee an end not immediately realised, or rather when a desire arises that we feel and recognise as not satisfied, then comes in the sense of will and the impulse magically to intensify that will. The animal it would seem is preserved by instinct from drawing into his horizon things which do not immediately subserve the conservation of his species. But the moment man's life-power began to make on the outside world demands not immediately and inevitably realised in action (I owe this observation to Dr K. Th. Preuss. He writes ("Archiv f. Relig." 1906, page 98), "Die Betonung des Willens in den Zauberakten ist der richtige Kern. In der Tat muss der Mensch den Willen haben, sich selbst und seiner Umgebung besondere Fahigkeiten zuzuschreiben, und den Willen hat er, sobald sein Verstand ihn befahigt, EINE UBER DEN INSTINKT HINAUSGEHEN DER FURSORGE fur sich zu zeigen. SO LANGE IHN DER INSTINKT ALLEIN LEITET, KONNEN ZAUBERHANDLUNGEN NICHT ENSTEHEN." For more detailed analysis of the origin of magic, see Dr Preuss "Ursprung der Religion und Kunst", "Globus", LXXXVI. and LXXXVII.), then a door was opened to magic, and in the train of magic followed errors innumerable, but also religion, philosophy, science and art.

The world of mana, orenda, brahman is a world of feeling, desiring, willing, acting. What element of thinking there may be in it is not yet differentiated out. But we have already seen that a supersensuous world of thought grew up very early in answer to other needs, a world of sense-illusions, shadows, dreams, souls, ghosts, ancestors, names, numbers, images, a world only wanting as it were the impulse of mana to live as a religion. Which of the two worlds, the world of thinking or the world of doing, developed first it is probably idle to inquire. (If external stimuli leave on organisms a trace or record such as is known as an Engram, this physical basis of memory and hence of thought is almost coincident with reaction of the most elementary kind. See Mr Francis Darwin's Presidential Address to the British Association, Dublin, 1908, page 8, and again Bergson places memory at the very root of conscious existence, see "L'Evolution Creatrice", page 18, "le fond meme de notre existence consciente est memoire, c'est a dire prolongation du passee dans le present," and again "la duree mord dans le temps et y laisse l'enpreint de son dent," and again, "l'Evolution implique une continuation reelle du passee par le present.")

It is more important to ask, Why do these two worlds join? Because, it would seem, mana, the egomaniac or megalomaniac element, cannot get satisfied with real things, and therefore goes eagerly out to a false world, the supersensuous other-world whose growth we have sketched. This junction of the two is fact, not fancy. Among all primitive peoples dead men, ghosts, spirits of all kinds, become the chosen vehicle of mana. Even to this day it is sometimes urged that religion, i.e. belief in the immortality of the soul, is true "because it satisfies the deepest craving of human nature." The two worlds, of mana and magic on the one hand, of ghosts and other-world on the other, combine so easily because they have the same laws, or rather the same comparative absence of law. As in the world of dreams and ghosts, so in the world of mana, space and time offer no obstacles; with magic all things are possible. In the one world what you imagine is real; in the other what you desire is ipso facto accomplished. Both worlds are egocentric, megalomaniac, filled to the full with unbridled human will and desire.

We are all of us born in sin, in that sin which is to science "the seventh and deadliest," anthropomorphism, we are egocentric, ego-projective. Hence necessarily we make our gods in our own image. Anthropomorphism is often spoken of in books on religion and mythology as if it were a last climax, a splendid final achievement in religious thought. First, we are told, we have the lifeless object as god (fetichism), then the plant or animal (phytomorphism, theriomorphism), and last God is incarnate in the human form divine. This way of putting things is misleading. Anthropomorphism lies at the very beginning of our consciousness. Man's first achievement in thought is to realise that there is anything at all not himself, any object to his subject. When he has achieved however dimly this distinction, still for long, for very long he can only think of those other things in terms of himself; plants and animals are people with ways of their own, stronger or weaker than himself but to all intents and purposes human.

Again the child helps us to understand our own primitive selves. To children animals are always people. You promise to take a child for a drive. The child comes up beaming with a furry bear in her arms. You say the bear cannot go. The child bursts into tears. You think it is because the child cannot endure to be separated from a toy. It is no such thing. It is the intolerable hurt done to the bear's human heart--a hurt not to be healed by any proffer of buns. He wanted to go, but he was a shy, proud bear, and he would not say so.

The relation of magic to religion has been much disputed. According to one school religion develops out of magic, according to another, though they ultimately blend, they are at the outset diametrically opposed, magic being a sort of rudimentary and mistaken science (This view held by Dr Frazer is fully set forth in his "Golden Bough" (2nd edition), pages 73-79, London, 1900. It is criticised by Mr R.R. Marett in "From Spell to Prayer", "Folk-Lore" XI. 1900, page 132, also very fully by MM. Hubert and Mauss, "Theorie generale de la Magie", in "L'Annee Sociologique", VII. page 1, with Mr Marett's view and with that of MM. Hubert and Mauss I am in substantial agreement.), religion having to do from the outset with spirits.

But, setting controversy aside, at the present stage of our inquiry their relation becomes, I think, fairly clear. Magic is, if my view (This view as explained above is, I believe, my own most serious contribution to the subject. In thinking it out I was much helped by Prof. Gilbert Murray.) be correct, the active element which informs a supersensuous world fashioned to meet other needs. This blend of theory and practice it is convenient to call religion. In practice the transition from magic to religion, from Spell to Prayer, has always been found easy. So long as mana remains impersonal you order it about; when it is personified and bulks to the shape of an overgrown man, you drop the imperative and cringe before it. "My will be done" is magic, "Thy Will be done" is the last word in religion. The moral discipline involved in the second is momentous, the intellectual advance not striking.

I have spoken of magical ritual as though it were the informing life-spirit without which religion was left as an empty shell. Yet the word ritual does not, as normally used, convey to our minds this notion of intense vitalism. Rather we associate ritual with something cut and dried, a matter of prescribed form and monotonous repetition. The association is correct; ritual tends to become less and less informed by the life-impulse, more and more externalised. Dr Beck ("Die Nachahmung und ihre Bedeutung fur Psychologie und Volkerkunde", Leipzig, 1904.) in his brilliant monograph on "Imitation" has laid stress on the almost boundless influence of the imitation of one man by another in the evolution of civilisation. Imitation is one of the chief spurs to action. Imitation begets custom, custom begets sanctity. At first all custom is sacred. To the savage it is as much a religious duty to tattoo himself as to sacrifice to his gods. But certain customs naturally survive, because they are really useful; they actually have good effects, and so need no social sanction. Others are really useless; but man is too conservative and imitative to abandon them. These become ritual. Custom is cautious, but la vie est aleatoire. (Bergson, op. cit. page 143.)

Dr Beck's remarks on ritual are I think profoundly true and suggestive, but with this reservation--they are true of ritual only when uninformed by personal experience. The very elements in ritual on which Dr Beck lays such stress, imitation, repetition, uniformity and social collectivity, have been found by the experience of all time to have a twofold influence--they inhibit the intellect, they stimulate and suggest emotion, ecstasy, trance. The Church of Rome knows what she is about when she prescribes the telling of the rosary. Mystery-cults and sacraments, the lineal descendants of magic, all contain rites charged with suggestion, with symbols, with gestures, with half-understood formularies, with all the apparatus of appeal to emotion and will--the more unintelligible they are the better they serve their purpose of inhibiting thought. Thus ritual deadens the intellect and stimulates will, desire, emotion. "Les operations magiques... sont le resultat d'une science et d'une habitude qui exaltent la volonte humaine au-dessus de ses limites habituelles." (Eliphas Levi, "Dogme et Rituel de la haute Magie", II. page 32, Paris, 1861, and "A defence of Magic", by Evelyn Underhill, "Fortnightly Review", 1907.) It is this personal EXPERIENCE, this exaltation, this sense of immediate, non-intellectual revelation, of mystical oneness with all things, that again and again rehabilitates a ritual otherwise moribund.

To resume. The outcome of our examination of ORIGINES seems to be that religious phenomena result from two delusive processes--a delusion of the non-critical intellect, a delusion of the over-confident will. Is religion then entirely a delusion? I think not. (I am deeply conscious that what I say here is a merely personal opinion or sentiment, unsupported and perhaps unsupportable by reason, and very possibly quite worthless, but for fear of misunderstanding I prefer to state it.) Every dogma religion has hitherto produced is probably false, but for all that the religious or mystical spirit may be the only way of apprehending some things and these of enormous importance. It may also be that the contents of this mystical apprehension cannot be put into language without being falsified and misstated, that they have rather to be felt and lived than uttered and intellectually analysed, and thus do not properly fall under the category of true or false, in the sense in which these words are applied to propositions; yet they may be something for which "true" is our nearest existing word and are often, if not necessary at least highly advantageous to life. That is why man through a series of more or less grossly anthropomorphic mythologies and theologies with their concomitant rituals tries to restate them. Meantime we need not despair. Serious psychology is yet young and has only just joined hands with physiology. Religious students are still hampered by mediaevalisms such as Body and Soul, and by the perhaps scarcely less mythological segregations of Intellect, Emotion, Will. But new facts (See the "Proceedings" of the Society for Psychical Research, London, passim, and especially Vols. VII.-XV. For a valuable collection of the phenomena of mysticism, see William James, "Varieties of Religious Experience", Edinburgh, 1901-2.) are accumulating, facts about the formation and flux of personality, and the relations between the conscious and the sub-conscious. Any moment some great imagination may leap out into the dark, touch the secret places of life, lay bare the cardinal mystery of the marriage of the spatial with the non-spatial. It is, I venture to think, towards the apprehension of such mysteries, not by reason only, but by man's whole personality, that the religious spirit in the course of its evolution through ancient magic and modern mysticism is ever blindly yet persistently moving.

Be this as it may, it is by thinking of religion in the light of evolution, not as a revelation given, not as a realite faite but as a process, and it is so only, I think, that we attain to a spirit of real patience and tolerance. We have ourselves perhaps learnt laboriously something of the working of natural law, something of the limitations of our human will, and we have therefore renounced the practice of magic. Yet we are bidden by those in high places to pray "Sanctify this water to the mystical washing away of sin." Mystical in this connection spells magical, and we have no place for a god-magician: the prayer is to us unmeaning, irreverent. Or again, after much toil we have ceased, or hope we have ceased, to think anthropomorphically. Yet we are invited to offer formal thanks to God for a meal of flesh whose sanctity is the last survival of that sacrifice of bulls and goats he has renounced. Such a ritual confuses our intellect and fails to stir our emotion. But to others this ritual, magical or anthropomorphic as it is, is charged with emotional impulse, and others, a still larger number, think that they act by reason when really they are hypnotised by suggestion and tradition; their fathers did this or that and at all costs they must do it. It was good that primitive man in his youth should bear the yoke of conservative custom; from each man's neck that yoke will fall, when and because he has outgrown it. Science teaches us to await that moment with her own inward and abiding patience. Such a patience, such a gentleness we may well seek to practise in the spirit and in the memory of Darwin.

XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. By P. Giles, M.A., LL.D. (Aberdeen),

Reader in Comparative Philology in the University of Cambridge.

In no study has the historical method had a more salutary influence than in the Science of Language. Even the earliest records show that the meaning of the names of persons, places, and common objects was then, as it has always been since, a matter of interest to mankind. And in every age the common man has regarded himself as competent without special training to explain by inspection (if one may use a mathematical phrase) the meaning of any words that attracted his attention. Out of this amateur etymologising has sprung a great amount of false history, a kind of historical mythology invented to explain familiar names. A single example will illustrate the tendency. According to the local legend the ancestor of the Earl of Erroll--a husbandman who stayed the flight of his countrymen in the battle of Luncarty and won the victory over the Danes by the help of the yoke of his oxen--exhausted with the fray uttered the exclamation "Hoch heigh!" The grateful king about to ennoble the victorious ploughman at once replied:

"Hoch heigh! said ye And Hay shall ye be."

The Norman origin of the name Hay is well-known, and the battle of Luncarty long preceded the appearance of Normans in Scotland, but the legend nevertheless persists.

Though the earliest European treatise on philological questions which is now extant--the "Cratylus" of Plato,--as might be expected from its authorship, contains some acute thinking and some shrewd guesses, yet the work as a whole is infantine in its handling of language, and it has been doubted whether Plato was more than half serious in some of the suggestions which he puts forward. (For an account of the "Cratylus" with references to other literature see Sandys' "History of Classical Scholarship", I. page 92 ff., Cambridge, 1903.) In the hands of the Romans things were worse even than they had been in the hands of Plato and his Greek successors. The lack of success on the part of Varro and later Roman writers may have been partly due to the fact that, from the etymological point of view, Latin is a much more difficult language than Greek; it is by no means so closely connected with Greek as the ancients imagined, and they had no knowledge of the Celtic languages from which, on some sides at least, much greater light on the history of the Latin language might have been obtained. Roman civilisation was a late development compared with Greek, and its records dating earlier than 300 B.C.--a period when the best of Greek literature was already in existence--are very few and scanty. Varro it is true was much more of an antiquary than Plato, but his extant works seem to show that he was rather a "dungeon of learning" than an original thinker.

A scientific knowledge of language can be obtained only by comparison of different languages of the same family and the contrasting of their characteristics with those of another family or other families. It never occurred to the Greeks that any foreign language was worthy of serious study. Herodotus and other travellers and antiquaries indeed picked up individual words from various languages, either as being necessary in communication with the inhabitants of the countries where they sojourned, or because of some point which interested them personally. Plato and others noticed the similarity of some Phrygian words to Greek, but no systematic comparison seems ever to have been instituted.

In the Middle Ages the treatment of language was in a sense more historical. The Middle Ages started with the hypothesis, derived from the book of Genesis, that in the early world all men were of one language and of one speech. Though on the same authority they believed that the plain of Shinar has seen that confusion of tongues whence sprang all the languages upon earth, they seem to have considered that the words of each separate language were nevertheless derived from this original tongue. And as Hebrew was the language of the Chosen People, it was naturally assumed that this original tongue was Hebrew. Hence we find Dante declaring in his treatise on the Vulgar Tongue (Dante "de Vulgari Eloquio", I. 4.) that the first word man uttered in Paradise must have been "El," the Hebrew name of his Maker, while as a result of the fall of Adam, the first utterance of every child now born into this world of sin and misery is "heu," Alas! After the splendidly engraved bronze plates containing, as we now know, ritual regulations for certain cults, were discovered in 1444 at the town of Gubbio, in Umbria, they were declared, by some authorities, to be written in excellent Hebrew. The study of them has been the fascination and the despair of many a philologist. Thanks to the devoted labours of numerous scholars, mainly in the last sixty years, the general drift of these inscriptions is now known. They are the only important records of the ancient Umbrian language, which was related closely to that of the Samnites and, though not so closely, to that of the Romans on the other side of the Apennines. Yet less than twenty years ago a book was published in Germany, which boasts itself the home of Comparative Philology, wherein the German origin of the Umbrian language was no less solemnly demonstrated than had been its Celtic origin by Sir William Betham in 1842.

It is good that the study of language should be historical, but the first requisite is that the history should be sound. How little had been learnt of the true history of language a century ago may be seen from a little book by Stephen Weston first published in 1802 and several times reprinted, where accidental assonance is considered sufficient to establish connection. Is there not a word "bad" in English and a word "bad" in Persian which mean the same thing? Clearly therefore Persian and English must be connected. The conclusion is true, but it is drawn from erroneous premises. As stated, this identity has no more value than the similar assonance between the English "cover" and the Hebrew "kophar", where the history of "cover" as coming through French from a Latin "co-operire" was even in 1802 well-known to many. To this day, in spite of recent elaborate attempts (Most recently in H. Moller's "Semitisch und Indogermanisch", Erster Teil, Kopenhagen, 1907.) to establish connection between the Indo-Germanic and the Semitic families of languages, there is no satisfactory evidence of such relation between these families. This is not to deny the possibility of such a connection at a very early period; it is merely to say that through the lapse of long ages all trustworthy record of such relationship, if it ever existed, has been, so far as present knowledge extends, obliterated.

But while Stephen Weston was publishing, with much public approval, his collection of amusing similarities between languages--similarities which proved nothing--the key to the historical study of at least one family of languages had already been found by a learned Englishman in a distant land. In 1783 Sir William Jones had been sent out as a judge in the supreme court of judicature in Bengal. While still a young man at Oxford he was noted as a linguist; his reputation as a Persian scholar had preceded him to the East. In the intervals of his professional duties he made a careful study of the language which was held sacred by the natives of the country in which he was living. He was mainly instrumental in establishing a society for the investigation of language and related subjects. He was himself the first president of the society, and in the "third anniversary discourse" delivered on February 2, 1786, he made the following observations: "The Sanscrit language, whatever be its antiquity, is of a wonderful structure; more perfect than the GREEK, more copious than the LATIN, and more exquisitely refined than either, yet bearing to both of them a stronger affinity, both in the roots of verbs and in the forms of grammar, than could possibly have been produced by accident; so strong indeed, that no philologer could examine them all three, without believing them to have sprung from some common source, which, perhaps, no longer exists: there is a similar reason, though not quite so forcible, for supposing that both the Gothick and the Celtick, though blended with a very different idiom, had the same origin with the Sanscrit; and the old Persian might be added to the same family, if this was the place for discussing any question concerning the antiquities of Persia." ("Asiatic Researches", I. page 422, "Works of Sir W. Jones", I. page 26, London, 1799.)

No such epoch-making discovery was probably ever announced with less flourish of trumpets. Though Sir William Jones lived for eight years more and delivered other anniversary discourses, he added nothing of importance to this utterance. He had neither the time nor the health that was needed for the prosecution of so arduous an undertaking.

But the good seed did not fall upon stony ground. The news was speedily conveyed to Europe. By a happy chance, the sudden renewal of war between France and England in 1803 gave Friedrich Schlegel the opportunity of learning Sanscrit from Alexander Hamilton, an Englishman who, like many others, was confined in Paris during the long struggle with Napoleon. The influence of Schlegel was not altogether for good in the history of this research, but he was inspiring. Not upon him but upon Franz Bopp, a struggling German student who spent some time in Paris and London a dozen years later, fell the mantle of Sir William Jones. In Bopp's Comparative Grammar of the Indo-Germanic languages which appeared in 1833, three-quarters of a century ago, the foundations of Comparative Philology were laid. Since that day the literature of the subject has grown till it is almost, if not altogether, beyond the power of any single man to cope with it. But long as the discourse may be, it is but the elaboration of the text that Sir William Jones supplied.

With the publication of Bopp's Comparative Grammar the historical study of language was put upon a stable footing. Needless to say much remained to be done, much still remains to be done. More than once there has been danger of the study following erroneous paths. Its terminology and its point of view have in some degree changed. But nothing can shake the truth of the statement that the Indo-Germanic languages constitute in themselves a family sprung from the same source, marked by the same characteristics, and differentiated from all other languages by formation, by vocabulary, and by syntax. The historical method was applied to language long before it reached biology. Nearly a quarter of a century before Charles Darwin was born, Sir William Jones had made the first suggestion of a comparative study of languages. Bopp's Comparative Grammar began to be published nine years before the first draft of Darwin's treatise on the Origin of Species was put on paper in 1842.

It is not therefore on the history of Comparative Philology in general that the ideas of Darwin have had most influence. Unfortunately, as Jowett has said in the introduction to his translation of Plato's "Republic", most men live in a corner. The specialisation of knowledge has many advantages, but it has also disadvantages, none worse perhaps than that it tends to narrow the specialist's horizon and to make it more difficult for one worker to follow the advances that are being made by workers in other departments. No longer is it possible as in earlier days for an intellectual prophet to survey from a Pisgah height all the Promised Land. And the case of linguistic research has been specially hard. This study has, if the metaphor may be allowed, a very extended frontier. On one side it touches the domain of literature, on other sides it is conterminous with history, with ethnology and anthropology, with physiology in so far as language is the production of the brain and tissues of a living being, with physics in questions of pitch and stress accent, with mental science in so far as the principles of similarity, contrast, and contiguity affect the forms and the meanings of words through association of ideas. The territory of linguistic study is immense, and it has much to supply which might be useful to the neighbours who border on that territory. But they have not regarded her even with that interest which is called benevolent because it is not actively maleficent. As Horne Tooke remarked a century ago, Locke had found a whole philosophy in language. What have the philosophers done for language since? The disciples of Kant and of Wilhelm von Humboldt supplied her plentifully with the sour grapes of metaphysics; otherwise her neighbours have left her severely alone save for an occasional "Ausflug," on which it was clear they had sadly lost their bearings. Some articles in Psychological Journals, Wundt's great work on "Volkerpsychologie" (Erster Band: "Die Sprache", Leipzig, 1900. New edition, 1904. This work has been fertile in producing both opponents and supporters. Delbruck, "Grundfragen der Sprachforschung", Strassburg, 1901, with a rejoinder by Wundt, "Sprachgeschichte" and "Sprachpsychologie", Leipzig, 1901; L. Sutterlin, "Das Wesen der Sprachgebilde", Heidelberg, 1902; von Rozwadowski, "Wortbildung und Wortbedeutung", Heidelberg, 1904; O. Dittrich, "Grundzuge der Sprachpsychologie", Halle, 1904, Ch. A. Sechehaye, "Programme et methodes de la linguistique theorique", Paris, 1908.), and Mauthner's brilliantly written "Beitrage zu einer Kritik der Sprache" (In three parts: (i) "Sprache und Psychologie, (ii) "Zur Sprachwissenschaft", both Stuttgart 1901, (iii) "Zur Grammatic und Logik" (with index to all three volumes), Stuttgart and Berlin, 1902.) give some reason to hope that, on one side at least, the future may be better than the past.

Where Charles Darwin's special studies came in contact with the Science of Language was over the problem of the origin and development of language. It is curious to observe that, where so many fields of linguistic research have still to be reclaimed--many as yet can hardly be said to be mapped out,--the least accessible field of all--that of the Origin of Language--has never wanted assiduous tillers. Unfortunately it is a field beyond most others where it may be said that

"Wilding oats and luckless darnel grow."

If Comparative Philology is to work to purpose here, it must be on results derived from careful study of individual languages and groups of languages. But as yet the group which Sir William Jones first mapped out and which Bopp organised is the only one where much has been achieved. Investigation of the Semitic group, in some respects of no less moment in the history of civilisation and religion, where perhaps the labour of comparison is not so difficult, as the languages differ less among themselves, has for some reason strangely lagged behind. Some years ago in the "American Journal of Philology" Paul Haupt pointed out that if advance was to be made, it must be made according to the principles which had guided the investigation of the Indo-Germanic languages to success, and at last a Comparative Grammar of an elaborate kind is in progress also for the Semitic languages. (Brockelmann, "Vergleichende Grammatik der semitischen Sprachen", Berlin, 1907 ff. Brockelmann and Zimmern had earlier produced two small hand-books. The only large work was William Wright's "Lectures on the Comparative Grammar of the Semitic Languages", Cambridge, 1890.) For the great group which includes Finnish, Hungarian, Turkish and many languages of northern Asia, a beginning, but only a beginning has been made. It may be presumed from the great discoveries which are in progress in Turkestan that presently much more will be achieved in this field. But for a certain utterance to be given by Comparative Philology on the question of the origin of language it is necessary that not merely for these languages but also for those in other quarters of the globe, the facts should be collected, sifted and tabulated. England rules an empire which contains a greater variety of languages by far than were ever held under one sway before. The Government of India is engaged in producing, under the editorship of Dr Grierson, a linguistic survey of India, a remarkable undertaking and, so far as it has gone, a remarkable achievement. Is it too much to ask that, with the support of the self-governing colonies, a similar survey should be undertaken for the whole of the British Empire?

Notwithstanding the great number of books that have been written on the origin of language in the last three and twenty centuries, the results of the investigation which can be described as certain are very meagre. The question originally raised was whether language came into being thesei or phusei, by convention or by nature. The first alternative, in its baldest form at least, has passed from out the field of controversy. No one now claims that names were given to living things or objects or activities by formal agreement among the members of an early community, or that the first father of mankind passed in review every living thing and gave it its name. Even if the record of Adam's action were to be taken literally there would still remain the question, whence had he this power? Did he develop it himself or was it a miraculous gift with which he was endowed at his creation? If the latter, then as Wundt says ("Volkerpsychologie", I. 2, page 585.), "the miracle of language is subsumed in the miracle of creation." If Adam developed language of himself, we are carried over to the alternative origin of phusei. On this hypothesis we must assume that the natural growth which modern theories of development regard as the painful progress of multitudinous generations was contracted into the experience of a single individual.

But even if the origin of language is admitted to be NATURAL there may still be much variety of signification attached to the word: NATURE, like most words which are used by philosophers, has accumulated many meanings, and as research into the natural world proceeds, is accumulating more.

Forty years ago an animated controversy raged among the supporters of the theories which were named for short the bow-wow, the pooh-pooh and the ding-dong theories of the origin of language. The third, which was the least tenacious of life, was made known to the English-speaking world by the late Professor Max Muller who, however, when questioned, repudiated it as his own belief. ("Science of Thought", London, 1887, page 211.) It was taken by him from Heyse's lectures on language which were published posthumously by Steinthal. Put shortly the theory is that "everything which is struck, rings. Each substance has its peculiar ring. We can tell the more or less perfect structure of metals by their vibrations, by the answer which they give. Gold rings differently from tin, wood rings differently from stone; and different sounds are produced according to the nature of each percussion. It may be the same with man, the most highly organised of nature's work." (Max Muller as above, translating from Heyse.) Max Muller's repudiation of this theory was, however, not very whole-hearted for he proceeds later in the same argument: "Heyse's theory, which I neither adopted nor rejected, but which, as will be seen, is by no means incompatible with that which for many years has been gaining on me, and which of late has been so clearly formulated by Professor Noire, has been assailed with ridicule and torn to pieces, often by persons who did not even suspect how much truth was hidden behind its paradoxical appearance. We are still very far from being able to identify roots with nervous vibrations, but if it should appear hereafter that sensuous vibrations supply at least the raw material of roots, it is quite possible that the theory, proposed by Oken and Heyse, will retain its place in the history of the various attempts at solving the problem of the origin of language, when other theories, which in our own days were received with popular applause, will be completely forgotten." ("Science of Thought", page 212.)

Like a good deal else that has been written on the origin of language, this statement perhaps is not likely to be altogether clear to the plain man, who may feel that even the "raw material of roots" is some distance removed from nervous vibrations, though obviously without the existence of afferent and efferent nerves articulate speech would be impossible. But Heyse's theory undoubtedly was that every thought or idea which occurred to the mind of man for the first time had its own special phonetic expression, and that this responsive faculty, when its object was thus fulfilled, became extinct. Apart from the philosophical question whether the mind acts without external stimulus, into which it is not necessary to enter here, it is clear that this theory can neither be proved nor disproved, because it postulates that this faculty existed only when language first began, and later altogether disappeared. As we have already seen, it is impossible for us to know what happened at the first beginnings of language, because we have no information from any period even approximately so remote; nor are we likely to attain it. Even in their earliest stages the great families of language which possess a history extending over many centuries--the Indo-Germanic and the Semitic--have very little in common. With the exception of Chinese, the languages which are apparently of a simpler or more primitive formation have either a history which, compared with that of the families mentioned, is very short, or, as in the case of the vast majority, have no history beyond the time extending only over a few years or, at most, a few centuries when they have been observed by competent scholars of European origin. But, if we may judge by the history of geology and other studies, it is well to be cautious in assuming for the first stages of development forces which do not operate in the later, unless we have direct evidence of their existence.

It is unnecessary here to enter into a prolonged discussion of the other views christened by Max Muller, not without energetic protest from their supporters, the bow-wow and pooh-pooh theories of language. Suffice it to say that the former recognises as a source of language the imitation of the sounds made by animals, the fall of bodies into water or on to solid substances and the like, while the latter, also called the interjectional theory, looks to the natural ejaculations produced by particular forms of effort for the first beginnings of speech. It would be futile to deny that some words in most languages come from imitation, and that others, probably fewer in number, can be traced to ejaculations. But if either of these sources alone or both in combination gave rise to primitive speech, it clearly must have been a simple form of language and very limited in amount. There is no reason to think that it was otherwise. Presumably in its earliest stages language only indicated the most elementary ideas, demands for food or the gratification of other appetites, indications of danger, useful animals and plants. Some of these, such as animals or indications of danger, could often be easily represented by imitative sounds: the need for food and the like could be indicated by gesture and natural cries. Both sources are verae causae; to them Noire, supported by Max Muller, has added another which has sometimes been called the Yo-heave-ho theory. Noire contends that the real crux in the early stages of language is for primitive man to make other primitive men understand what he means. The vocal signs which commend themselves to one may not have occurred to another, and may therefore be unintelligible. It may be admitted that this difficulty exists, but it is not insuperable. The old story of the European in China who, sitting down to a meal and being doubtful what the meat in the dish might be, addressed an interrogative Quack-quack? to the waiter and was promptly answered by Bow-wow, illustrates a simple situation where mutual understanding was easy. But obviously many situations would be more complex than this, and to grapple with them Noire has introduced his theory of communal action. "It was common effort directed to a common object, it was the most primitive (uralteste) labour of our ancestors, from which sprang language and the life of reason." (Noire "Der Ursprung der Sprache", page 331, Mainz, 1877.) As illustrations of such common effort he cites battle cries, the rescue of a ship running on shore (a situation not likely to occur very early in the history of man), and others. Like Max Muller he holds that language is the utterance and the organ of thought for mankind, the one characteristic which separates man from the brute. "In common action the word was first produced; for long it was inseparably connected with action; through long-continued connection it gradually became the firm, intelligible symbol of action, and then in its development indicated also things of the external world in so far as the action affected them and finally the sound began to enter into a connexion with them also." (Op. cit. page 339.) In so far as this theory recognises language as a social institution it is undoubtedly correct. Darwin some years before Noire had pointed to the same social origin of language in the fourth chapter of his work on "The Expression of the Emotions in Man and Animals". "Naturalists have remarked, I believe with truth, that social animals, from habitually using their vocal organs as a means of intercommunication, use them on other occasions much more freely than other animals... The principle, also, of association, which is so widely extended in its power, has likewise played its part. Hence it allows that the voice, from having been employed as a serviceable aid under certain conditions, inducing pleasure, pain, rage, etc., is commonly used whenever the same sensations or emotions are excited, under quite different conditions, or in a lesser degree." ("The Expression of the Emotions", page 84 (Popular Edition, 1904).

Darwin's own views on language which are set forth most fully in "The Descent of Man" (page 131 ff. (Popular Edition, 1906).) are characterised by great modesty and caution. He did not profess to be a philologist and the facts are naturally taken from the best known works of the day (1871). In the notes added to the second edition he remarks on Max Muller's denial of thought without words, "what a strange definition must here be given to the word thought!" (Op. cit. page 135, footnote 63.) He naturally finds the origin of language in "the imitation and modification of various natural sounds, the voices of other animals, and man's own instinctive cries aided by signs and gestures (op. cit. page 132.)... As the voice was used more and more, the vocal organs would have been strengthened and perfected through the principle of the inherited effects of use; and this would have reacted on the power of speech." (Op. cit. page 133.) On man's own instinctive cries, he has more to say in "The Expression of the Emotions". (Page 93 (Popular Edition, 1904) and elsewhere.) These remarks have been utilised by Prof. Jespersen of Copenhagen in propounding an ingenious theory of his own to the effect that speech develops out of singing. ("Progress in Language", page 361, London, 1894.)

For many years and in many books Max Muller argued against Darwin's views on evolution on the one ground that thought is impossible without speech; consequently as speech is confined to the human race, there is a gulf which cannot be bridged between man and all other creatures. (Some interesting comments on the theory will be found in a lecture on "Thought and Language" in Samuel Butler's "Essays on Life, Art and Science", London, 1908.) On the title-page of his "Science of Thought" he put the two sentences "No Reason without Language: No Language without Reason." It may be readily admitted that the second dictum is true, that no language properly so-called can exist without reason. Various birds can learn to repeat words or sentences used by their masters or mistresses. In most cases probably the birds do not attach their proper meaning to the words they have learnt; they repeat them in season and out of season, sometimes apparently for their own amusement, generally in the expectation, raised by past experience, of being rewarded for their proficiency. But even here it is difficult to prove a universal negative, and most possessors of such pets would repudiate indignantly the statement that the bird did not understand what was said to it, and would also contend that in many cases the words which it used were employed in their ordinary meaning. The first dictum seems to be inconsistent with fact. The case of deaf mutes, such as Laura Bridgeman, who became well educated, or the still more extraordinary case of Helen Keller, deaf, dumb, and blind, who in spite of these disadvantages has learnt not only to reason but to reason better than the average of persons possessed of all their senses, goes to show that language and reason are not necessarily always in combination. Reason is but the conscious adaptation of means to ends, and so defined is a faculty which cannot be denied to many of the lower animals. In these days when so many books on Animal Intelligence are issued from the press, it seems unnecessary to labour the point. Yet none of these animals, except by parrot-imitation, makes use of speech, because man alone possesses in a sufficient degree of development the centres of nervous energy which are required for the working of articulation in speech. On this subject much investigation was carried on during the last years of Darwin's life and much more in the period since his death. As early as 1861 Broca, following up observations made by earlier French writers, located the centre of articulate speech in the third left frontal convolution of the brain. In 1876 he more definitely fixed the organ of speech in "the posterior two-fifths of the third frontal convolution" (Macnamara, "Human Speech", page 197, London, 1908.), both sides and not merely the left being concerned in speech production. Owing however to the greater use by most human beings of the right side of the body, the left side of the brain, which is the motor centre for the right side of the body, is more highly developed than its right side, which moves the left side of the body. The investigations of Professors Ferrier, Sherrington and Grunbaum have still more precisely defined the relations between brain areas and certain groups of muscles. One form of aphasia is the result of injury to or disease in the third frontal convolution because the motor centre is no longer equal to the task of setting the necessary muscles in motion. In the brain of idiots who are unable to speak, the centre for speech is not developed. (Op. cit. page 226.) In the anthropoid apes the brain is similarly defective, though it has been demonstrated by Professors Cunningham and Marchand "that there is a tendency, especially in the gorilla's brain, for the third frontal convolution to assume the human form... But if they possessed a centre for speech, those parts of the hemispheres of their brains which form the mechanism by which intelligence is elaborated are so ill-developed, as compared with the rest of their bodies, that we can not conceive, even with more perfect frontal convolutions, that these animals could formulate ideas expressible in intelligent speech." (Op. cit. page 223.)

While Max Muller's theory is Shelley's

"He gave man speech, and speech created thought, Which is the measure of the universe" ("Prometheus Unbound" II. 4.),

it seems more probable that the development was just the opposite--that the development of new activities originated new thoughts which required new symbols to express them, symbols which may at first have been, even to a greater extent than with some of the lower races at present, sign language as much as articulation. When once the faculty of articulation was developed, which, though we cannot trace the process, was probably a very gradual growth, there is no reason to suppose that words developed in any other way then they do at present. An erroneous notion of the development of language has become widely spread through the adoption of the metaphorical term "roots" for the irreducible elements of human speech. Men never talked in roots; they talked in words. Many words of kindred meaning have a part in common, and a root is nothing but that common part stripped of all additions. In some cases it is obvious that one word is derived from another by the addition of a fresh element; in other cases it is impossible to say which of two kindred words is the more primitive. A root is merely a convenient term for an abstraction. The simplest word may be called a root, but it is nevertheless a word. How are new words added to a language in the present day? Some communities, like the Germans, prefer to construct new words for new ideas out of the old material existing in the language; others, like the English, prefer to go to the ancient languages of Greece and Rome for terms to express new ideas. The same chemical element is described in the two languages as sour stuff (Sauerstoff) and as oxygen. Both terms mean the same thing etymologically as well as in fact. On behalf of the German method, it may be contended that the new idea is more closely attached to already existing ideas, by being expressed in elements of the language which are intelligible even to the meanest capacity. For the English practice it may be argued that, if we coin a new word which means one thing, and one thing only, the idea which it expresses is more clearly defined than if it were expressed in popularly intelligible elements like "sour stuff." If the etymological value of words were always present in the minds of their users, "oxygen" would undoubtedly have an advantage over "sour stuff" as a technical term. But the tendency in language is to put two words of this kind which express but one idea under a single accent, and when this has taken place, no one but the student of language any longer observes what the elements really mean. When the ordinary man talks of a "blackbird" it is certainly not present to his consciousness that he is talking of a black bird, unless for some reason conversation has been dwelling upon the colour rather than other characteristics of the species.

But, it may be said, words like "oxygen" are introduced by learned men, and do not represent the action of the man in the street, who, after all, is the author of most additions to the stock of human language. We may go back therefore some four centuries to a period, when scientific study was only in its infancy, and see what process was followed. With the discovery of America new products never seen before reached Europe, and these required names. Three of the most characteristic were tobacco, the potato, and the turkey. How did these come to be so named? The first people to import these products into Europe were naturally the Spanish discoverers. The first of these words--tobacco--appears in forms which differ only slightly in the languages of all civilised countries: Spanish tabaco, Italian tabacco, French tabac, Dutch and German tabak, Swedish tobak, etc. The word in the native dialect of Hayti is said to have been tabaco, but to have meant not the plant (According to William Barclay, "Nepenthes, or the Virtue of Tobacco", Edinburgh, 1614, "the countrey which God hath honoured and blessed with this happie and holy herbe doth call it in their native language 'Petum'.") but the pipe in which it was smoked. It thus illustrates a frequent feature of borrowing--that the word is not borrowed in its proper signification, but in some sense closely allied thereto, which a foreigner, understanding the language with difficulty, might readily mistake for the real meaning. Thus the Hindu practice of burning a wife upon the funeral pyre of her husband is called in English "suttee", this word being in fact but the phonetic spelling of the Sanskrit "sati", "a virtuous woman," and passing into its English meaning because formerly the practice of self-immolation by a wife was regarded as the highest virtue.

The name of the potato exhibits greater variety. The English name was borrowed from the Spanish "patata", which was itself borrowed from a native word for the "yam" in the dialect of Hayti. The potato appeared early in Italy, for the mariners of Genoa actively followed the footsteps of their countryman Columbus in exploring America. In Italian generally the form "patata" has survived. The tubers, however, also suggested a resemblance to truffles, so that the Italian word "tartufolo", a diminutive of the Italian modification of the Latin "terrae tuber" was applied to them. In the language of the Rhaetian Alps this word appears as "tartufel". From there it seems to have passed into Germany where potatoes were not cultivated extensively till the eighteenth century, and "tartufel" has in later times through some popular etymology been metamorphosed into "Kartoffel". In France the shape of the tubers suggested the name of earth-apple (pomme de terre), a name also adopted in Dutch (aard-appel), while dialectically in German a form "Grumbire" appears, which is a corruption of "Grund-birne", "ground pear". (Kluge "Etymologisches Worterbuch der deutschen Sprache" (Strassburg), s.v. "Kartoffel".) Here half the languages have adopted the original American word for an allied plant, while others have adopted a name originating in some more or less fanciful resemblance discovered in the tubers; the Germans alone in Western Europe, failing to see any meaning in their borrowed name, have modified it almost beyond recognition. To this English supplies an exact parallel in "parsnep" which, though representing the Latin "pastinaca" through the Old French "pastenaque", was first assimilated in the last syllable to the "nep" of "turnep" ("pasneppe" in Elizabethan English), and later had an "r" introduced into the first syllable, apparently on the analogy of "parsley".

The turkey on the other hand seems never to be found with its original American name. In England, as the name implies, the turkey cock was regarded as having come from the land of the Turks. The bird no doubt spread over Europe from the Italian seaports. The mistake, therefore, was not unnatural, seeing that these towns conducted a great trade with the Levant, while the fact that America when first discovered was identified with India helped to increase the confusion. Thus in French the "coq d'Inde" was abbreviated to "d'Inde" much as "turkey cock" was to "turkey"; the next stage was to identify "dinde" as a feminine word and create a new "dindon" on the analogy of "chapon" as the masculine. In Italian the name "gallo d'India" besides survives, while in German the name "Truthahn" seems to be derived onomatopoetically from the bird's cry, though a dialectic "Calecutischer Hahn" specifies erroneously an origin for the bird from the Indian Calicut. In the Spanish "pavo", on the other hand, there is a curious confusion with the peacock. Thus in these names for objects of common knowledge, the introduction of which into Europe can be dated with tolerable definiteness, we see evinced the methods by which in remoter ages objects were named. The words were borrowed from the community whence came the new object, or the real or fancied resemblance to some known object gave the name, or again popular etymology might convert the unknown term into something that at least approached in sound a well-known word.

"The Origin of Species" had not long been published when the parallelism of development in natural species and in languages struck investigators. At the time, one of the foremost German philologists was August Schleicher, Professor at Jena. He was himself keenly interested in the natural sciences, and amongst his colleagues was Ernst Haeckel, the protagonist in Germany of the Darwinian theory. How the new ideas struck Schleicher may be seen from the following sentences by his colleague Haeckel. "Speech is a physiological function of the human organism, and has been developed simultaneously with its organs, the larynx and tongue, and with the functions of the brain. Hence it will be quite natural to find in the evolution and classification of languages the same features as in the evolution and classification of organic species. The various groups of languages that are distinguished in philology as primitive, fundamental, parent, and daughter languages, dialects, etc., correspond entirely in their development to the different categories which we classify in zoology and botany as stems, classes, orders, families, genera, species and varieties. The relation of these groups, partly coordinate and partly subordinate, in the general scheme is just the same in both cases; and the evolution follows the same lines in both." (Haeckel, "The Evolution of Man", page 485, London, 1905. This represents Schleicher's own words: Was die Naturforscher als Gattung bezeichnen wurden, heisst bei den Glottikern Sprachstamm, auch Sprachsippe; naher verwandte Gattungen bezeichnen sie wohl auch als Sprachfamilien einer Sippe oder eines Sprachstammes... Die Arten einer Gattung nennen wir Sprachen eines Stammes; die Unterarten einer Art sind bei uns die Dialekte oder Mundarten einer Sprache; den Varietaten und Spielarten entsprechen die Untermundarten oder Nebenmundarten und endlich den einzelnen Individuen die Sprechweise der einzelnen die Sprachen redenden Menschen. "Die Darwinische Theorie und die Sprachwissenschaft", Weimar, 1863, page 12 f. Darwin makes a more cautious statement about the classification of languages in "The Origin of Species", page 578, (Popular Edition, 1900).) These views were set forth in an open letter addressed to Haeckel in 1863 by Schleicher entitled, "The Darwinian theory and the science of language". Unfortunately Schleicher's views went a good deal farther than is indicated in the extract given above. He appended to the pamphlet a genealogical tree of the Indo-Germanic languages which, though to a large extent confirmed by later research, by the dichotomy of each branch into two other branches, led the unwary reader to suppose their phylogeny (to use Professor Haeckel's term) was more regular than our evidence warrants.

Without qualification Schleicher declared languages to be "natural organisms which originated unconditioned by the human will, developed according to definite laws, grow old and die; they also are characterised by that series of phenomena which we designate by the term 'Life.' Consequently Glottic, the science of language, is a natural science; its method is in general the same as that of the other natural sciences." ("Die Darwinische Theorie", page 6 f.) In accordance with this view he declared (op. cit. page 23.) that the root in language might be compared with the simple cell in physiology, the linguistic simple cell or root being as yet not differentiated into special organs for the function of noun, verb, etc.

In this probably all recent philologists admit that Schleicher went too far. One of the most fertile theories in the modern science of language originated with him, and was further developed by his pupil, August Leskien ("Die Declination im Slavisch-litanischen und Germanischen", Leipzig, 1876; Osthoff and Brugmann, "Morphologische Untersuchungen", I. (Introduction), 1878. The general principles of this school were formulated (1880) in a fuller form in H. Paul's "Prinzipien der Sprachgeschichte", Halle (3rd edition, 1898). Paul and Wundt (in his "Volkerpsychologie") deal largely with the same matter, but begin their investigations from different points of view, Paul being a philologist with leanings to philosophy and Wundt a philosopher interested in language.), and by Leskien's colleagues and friends, Brugmann and Osthoff. This was the principle that phonetic laws have no exceptions. Under the influence of this generalisation much greater precision in etymology was insisted upon, and a new and remarkably active period in the study of language began. Stated broadly in the fashion given above the principle is not true. A more accurate statement would be that an original sound is represented in a given dialect at a given time and in a given environment only in one way; provided that the development of the original sound into its representation in the given dialect has not been influenced by the working of analogy.

It is this proviso that is most important for the characterisation of the science of language. As I have said elsewhere, it is at this point that this science parts company with the natural sciences. "If the chemist compounds two pure simple elements, there can be but one result, and no power of the chemist can prevent it. But the minds of men do act upon the sounds which they produce. The result is that, when this happens, the phonetic law which would have acted in the case is stopped, and this particular form enters on the same course of development as other forms to which it does not belong." (P. Giles, "Short Manual of Comparative Philology", 2nd edition, page 57, London, 1901.)

Schleicher was wrong in defining a language to be an organism in the sense in which a living being is an organism. Regarded physiologically, language is a function or potentiality of certain human organs; regarded from the point of view of the community it is of the nature of an institution. (This view of language is worked out at some length by Prof. W.D. Whitney in an article in the "Contemporary Review" for 1875, page 713 ff. This article forms part of a controversy with Max Muller, which is partly concerned with Darwin's views on language. He criticises Schleicher's views severely in his "Oriental and Linguistic Studies", page 298 ff., New York, 1873. In this volume will be found criticisms of various other views mentioned in this essay.) More than most influences it conduces to the binding together of the elements that form a state. That geographical or other causes may effectively counteract the influence of identity of language is obvious. One need only read the history of ancient Greece, or observe the existing political separation of Germany and Austria, of Great Britain and the United States of America. But however analogous to an organism, language is not an organism. In a less degree Schleicher, by defining languages as such, committed the same mistake which Bluntschli made regarding the State, and which led him to declare that the State is by nature masculine and the Church feminine. (Bluntschli, "Theory of the State", page 24, Second English Edition, Oxford, 1892.) The views of Schleicher were to some extent injurious to the proper methods of linguistic study. But this misfortune was much more than fully compensated by the inspiration which his ideas, collected and modified by his disciples, had upon the science. In spite of the difference which the psychological element represented by analogy makes between the science of language and the natural sciences, we are entitled to say of it as Schleicher said of Darwin's theory of the origin of species, "it depends upon observation, and is essentially an attempt at a history of development."

Other questions there are in connection with language and evolution which require investigation--the survival of one amongst several competing words (e.g. why German keeps only as a high poetic word "ross", which is identical in origin with the English work-a-day "horse", and replaces it by "pferd", whose congener the English "palfrey" is almost confined to poetry and romance), the persistence of evolution till it becomes revolution in languages like English or Persian which have practically ceased to be inflectional languages, and many other problems. Into these Darwin did not enter, and they require a fuller investigation than is possible within the limits of the present paper.

XXVII. DARWINISM AND HISTORY. By J.B. Bury, Litt.D., LL.D.

Regius Professor of Modern History in the University of Cambridge.

1. Evolution, and the principles associated with the Darwinian theory, could not fail to exert a considerable influence on the studies connected with the history of civilised man. The speculations which are known as "philosophy of history," as well as the sciences of anthropology, ethnography, and sociology (sciences which though they stand on their own feet are for the historian auxiliary), have been deeply affected by these principles. Historiographers, indeed, have with few exceptions made little attempt to apply them; but the growth of historical study in the nineteenth century has been determined and characterised by the same general principle which has underlain the simultaneous developments of the study of nature, namely the GENETIC idea. The "historical" conception of nature, which has produced the history of the solar system, the story of the earth, the genealogies of telluric organisms, and has revolutionised natural science, belongs to the same order of thought as the conception of human history as a continuous, genetic, causal process--a conception which has revolutionised historical research and made it scientific. Before proceeding to consider the application of evolutional principles, it will be pertinent to notice the rise of this new view.

2. With the Greeks and Romans history had been either a descriptive record or had been written in practical interests. The most eminent of the ancient historians were pragmatical; that is, they regarded history as an instructress in statesmanship, or in the art of war, or in morals. Their records reached back such a short way, their experience was so brief, that they never attained to the conception of continuous process, or realised the significance of time; and they never viewed the history of human societies as a phenomenon to be investigated for its own sake. In the middle ages there was still less chance of the emergence of the ideas of progress and development. Such notions were excluded by the fundamental doctrines of the dominant religion which bounded and bound men's minds. As the course of history was held to be determined from hour to hour by the arbitrary will of an extra-cosmic person, there could be no self-contained causal development, only a dispensation imposed from without. And as it was believed that the world was within no great distance from the end of this dispensation, there was no motive to take much interest in understanding the temporal, which was to be only temporary.

The intellectual movements of the fifteenth and sixteenth centuries prepared the way for a new conception, but it did not emerge immediately. The historians of the Renaissance period simply reverted to the ancient pragmatical view. For Machiavelli, exactly as for Thucydides and Polybius, the use of studying history was instruction in the art of politics. The Renaissance itself was the appearance of a new culture, different from anything that had gone before; but at the time men were not conscious of this; they saw clearly that the traditions of classical antiquity had been lost for a long period, and they were seeking to revive them, but otherwise they did not perceive that the world had moved, and that their own spirit, culture, and conditions were entirely unlike those of the thirteenth century. It was hardly till the seventeenth century that the presence of a new age, as different from the middle ages as from the ages of Greece and Rome, was fully realised. It was then that the triple division of ancient, medieval, and modern was first applied to the history of western civilisation. Whatever objections may be urged against this division, which has now become almost a category of thought, it marks a most significant advance in man's view of his own past. He has become conscious of the immense changes in civilisation which have come about slowly in the course of time, and history confronts him with a new aspect. He has to explain how those changes have been produced, how the transformations were effected. The appearance of this problem was almost simultaneous with the rise of rationalism, and the great historians and thinkers of the eighteenth century, such as Montesquieu, Voltaire, Gibbon, attempted to explain the movement of civilisation by purely natural causes. These brilliant writers prepared the way for the genetic history of the following century. But in the spirit of the Aufklarung, that eighteenth-century Enlightenment to which they belonged, they were concerned to judge all phenomena before the tribunal of reason; and the apotheosis of "reason" tended to foster a certain superior a priori attitude, which was not favourable to objective treatment and was incompatible with a "historical sense." Moreover the traditions of pragmatical historiography had by no means disappeared.

3. In the first quarter of the nineteenth century the meaning of genetic history was fully realised. "Genetic" perhaps is as good a word as can be found for the conception which in this century was applied to so many branches of knowledge in the spheres both of nature and of mind. It does not commit us to the doctrine proper of evolution, nor yet to any teleological hypothesis such as is implied in "progress." For history it meant that the present condition of the human race is simply and strictly the result of a causal series (or set of causal series)--a continuous succession of changes, where each state arises causally out of the preceding; and that the business of historians is to trace this genetic process, to explain each change, and ultimately to grasp the complete development of the life of humanity. Three influential writers, who appeared at this stage and helped to initiate a new period of research, may specially be mentioned. Ranke in 1824 definitely repudiated the pragmatical view which ascribes to history the duties of an instructress, and with no less decision renounced the function, assumed by the historians of the Aufklarung, to judge the past; it was his business, he said, merely to show how things really happened. Niebuhr was already working in the same spirit and did more than any other writer to establish the principle that historical transactions must be related to the ideas and conditions of their age. Savigny about the same time founded the "historical school" of law. He sought to show that law was not the creation of an enlightened will, but grew out of custom and was developed by a series of adaptations and rejections, thus applying the conception of evolution. He helped to diffuse the notion that all the institutions of a society or a notion are as closely interconnected as the parts of a living organism.

4. The conception of the history of man as a causal development meant the elevation of historical inquiry to the dignity of a science. Just as the study of bees cannot become scientific so long as the student's interest in them is only to procure honey or to derive moral lessons from the labours of "the little busy bee," so the history of human societies cannot become the object of pure scientific investigation so long as man estimates its value in pragmatical scales. Nor can it become a science until it is conceived as lying entirely within a sphere in which the law of cause and effect has unreserved and unrestricted dominion. On the other hand, once history is envisaged as a causal process, which contains within itself the explanation of the development of man from his primitive state to the point which he has reached, such a process necessarily becomes the object of scientific investigation and the interest in it is scientific curiosity.

At the same time, the instruments were sharpened and refined. Here Wolf, a philologist with historical instinct, was a pioneer. His "Prolegomena" to Homer (1795) announced new modes of attack. Historical investigation was soon transformed by the elaboration of new methods.

5. "Progress" involves a judgment of value, which is not involved in the conception of history as a genetic process. It is also an idea distinct from that of evolution. Nevertheless it is closely related to the ideas which revolutionised history at the beginning of the last century; it swam into men's ken simultaneously; and it helped effectively to establish the notion of history as a continuous process and to emphasise the significance of time. Passing over earlier anticipations, I may point to a "Discours" of Turgot (1750), where history is presented as a process in which "the total mass of the human race" "marches continually though sometimes slowly to an ever increasing perfection." That is a clear statement of the conception which Turgot's friend Condorcet elaborated in the famous work, published in 1795, "Esquisse d'un tableau historique des progres de l'esprit humain". This work first treated with explicit fulness the idea to which a leading role was to fall in the ideology of the nineteenth century. Condorcet's book reflects the triumphs of the Tiers etat, whose growing importance had also inspired Turgot; it was the political changes in the eighteenth century which led to the doctrine, emphatically formulated by Condorcet, that the masses are the most important element in the historical process. I dwell on this because, though Condorcet had no idea of evolution, the pre-dominant importance of the masses was the assumption which made it possible to apply evolutional principles to history. And it enabled Condorcet himself to maintain that the history of civilisation, a progress still far from being complete, was a development conditioned by general laws.

6. The assimilation of society to an organism, which was a governing notion in the school of Savigny, and the conception of progress, combined to produce the idea of an organic development, in which the historian has to determine the central principle or leading character. This is illustrated by the apotheosis of democracy in Tocqueville's "Democratie en Amerique", where the theory is maintained that "the gradual and progressive development of equality is at once the past and the future of the history of men." The same two principles are combined in the doctrine of Spencer (who held that society is an organism, though he also contemplated its being what he calls a "super-organic aggregate") (A society presents suggestive analogies with an organism, but it certainly is not an organism, and sociologists who draw inferences from the assumption of its organic nature must fall into error. A vital organism and a society are radically distinguished by the fact that the individual components of the former, namely the cells, are morphologically as well as functionally differentiated, whereas the individuals which compose a society are morphologically homogeneous and only functionally differentiated. The resemblances and the differences are worked out in E. de Majewski's striking book "La Science de la Civilisation", Paris, 1908.), that social evolution is a progressive change from militarism to industrialism.

7. the idea of development assumed another form in the speculations of German idealism. Hegel conceived the successive periods of history as corresponding to the ascending phases or ideas in the self-evolution of his Absolute Being. His "Lectures on the Philosophy of History" were published in 1837 after his death. His philosophy had a considerable effect, direct and indirect, on the treatment of history by historians, and although he was superficial and unscientific himself in dealing with historical phenomena, he contributed much towards making the idea of historical development familiar. Ranke was influenced, if not by Hegel himself, at least by the Idealistic philosophies of which Hegel's was the greatest. He was inclined to conceive the stages in the process of history as marked by incarnations, as it were, of ideas, and sometimes speaks as if the ideas were independent forces, with hands and feet. But while Hegel determined his ideas by a priori logic, Ranke obtained his by induction--by a strict investigation of the phenomena; so that he was scientific in his method and work, and was influenced by Hegelian prepossessions only in the kind of significance which he was disposed to ascribe to his results. It is to be noted that the theory of Hegel implied a judgment of value; the movement was a progress towards perfection.

8. In France, Comte approached the subject from a different side, and exercised, outside Germany, a far wider influence than Hegel. The 4th volume of his "Cours de philosophie positive", which appeared in 1839, created sociology and treated history as a part of this new science, namely as "social dynamics." Comte sought the key for unfolding historical development, in what he called the social-psychological point of view, and he worked out the two ideas which had been enunciated by Condorcet: that the historian's attention should be directed not, as hitherto, principally to eminent individuals, but to the collective behaviour of the masses, as being the most important element in the process; and that, as in nature, so in history, there are general laws, necessary and constant, which condition the development. The two points are intimately connected, for it is only when the masses are moved into the foreground that regularity, uniformity, and law can be conceived as applicable. To determine the social-psychological laws which have controlled the development is, according to Comte, the task of sociologists and historians.

9. The hypothesis of general laws operative in history was carried further in a book which appeared in England twenty years later and exercised an influence in Europe far beyond its intrinsic merit, Buckle's "History of Civilisation in England" (1857-61). Buckle owed much to Comte, and followed him, or rather outdid him, in regarding intellect as the most important factor conditioning the upward development of man, so that progress, according to him, consisted in the victory of the intellectual over the moral laws.

10. The tendency of Comte and Buckle to assimilate history to the sciences of nature by reducing it to general "laws," derived stimulus and plausibility from the vista offered by the study of statistics, in which the Belgian Quetelet, whose book "Sur l'homme" appeared in 1835, discerned endless possibilities. The astonishing uniformities which statistical inquiry disclosed led to the belief that it was only a question of collecting a sufficient amount of statistical material, to enable us to predict how a given social group will act in a particular case. Bourdeau, a disciple of this school, looks forward to the time when historical science will become entirely quantitative. The actions of prominent individuals, which are generally considered to have altered or determined the course of things, are obviously not amenable to statistical computation or explicable by general laws. Thinkers like Buckle sought to minimise their importance or explain them away.

11. These indications may suffice to show that the new efforts to interpret history which marked the first half of the nineteenth century were governed by conceptions closely related to those which were current in the field of natural science and which resulted in the doctrine of evolution. The genetic principle, progressive development, general laws, the significance of time, the conception of society as an organic aggregate, the metaphysical theory of history as the self-evolution of spirit,--all these ideas show that historical inquiry had been advancing independently on somewhat parallel lines to the sciences of nature. It was necessary to bring this out in order to appreciate the influence of Darwinism.

12. In the course of the dozen years which elapsed between the appearances of "The Origin of Species" (observe that the first volume of Buckle's work was published just two years before) and of "The Descent of Man" (1871), the hypothesis of Lamarck that man is the co-descendant with other species of some lower extinct form was admitted to have been raised to the rank of an established fact by most thinkers whose brains were not working under the constraint of theological authority.

One important effect of the discovery of this fact (I am not speaking now of the Darwinian explanation) was to assign to history a definite place in the coordinated whole of knowledge, and relate it more closely to other sciences. It had indeed a defined logical place in systems such as Hegel's and Comte's; but Darwinism certified its standing convincingly and without more ado. The prevailing doctrine that man was created ex abrupto had placed history in an isolated position, disconnected with the sciences of nature. Anthropology, which deals with the animal anthropos, now comes into line with zoology, and brings it into relation with history. (It is to be observed that history is not only different in scope but) not coextensive with anthropology IN TIME. For it deals only with the development of man in societies, whereas anthropology includes in its definition the proto-anthropic period when anthropos was still non-social, whether he lived in herds like the chimpanzee, or alone like the male ourang-outang. (It has been well shown by Majewski that congregations--herds, flocks, packs, etc.--of animals are not SOCIETIES; the characteristic of a society is differentiation of function. Bee hives, ant hills, may be called quasi-societies; but in their case the classes which perform distinct functions are morphologically different.) Man's condition at the present day is the result of a series of transformations, going back to the most primitive phase of society, which is the ideal (unattainable) beginning of history. But that beginning had emerged without any breach of continuity from a development which carries us back to a quadrimane ancestor, still further back (according to Darwin's conjecture) to a marine animal of the ascidian type, and then through remoter periods to the lowest form of organism. It is essential in this theory that though links have been lost there was no break in the gradual development; and this conception of a continuous progress in the evolution of life, resulting in the appearance of uncivilised Anthropos, helped to reinforce, and increase a belief in, the conception of the history of civilised Anthropos as itself also a continuous progressive development.

13. Thus the diffusion of the Darwinian theory of the origin of man, by emphasising the idea of continuity and breaking down the barriers between the human and animal kingdoms, has had an important effect in establishing the position of history among the sciences which deal with telluric development. The perspective of history is merged in a larger perspective of development. As one of the objects of biology is to find the exact steps in the genealogy of man from the lowest organic form, so the scope of history is to determine the stages in the unique causal series from the most rudimentary to the present state of human civilisation.

It is to be observed that the interest in historical research implied by this conception need not be that of Comte. In the Positive Philosophy history is part of sociology; the interest in it is to discover the sociological laws. In the view of which I have just spoken, history is permitted to be an end in itself; the reconstruction of the genetic process is an independent interest. For the purpose of the reconstruction, sociology, as well as physical geography, biology, psychology, is necessary; the sociologist and the historian play into each other's hands; but the object of the former is to establish generalisations; the aim of the latter is to trace in detail a singular causal sequence.

14. The success of the evolutional theory helped to discredit the assumption or at least the invocation of transcendent causes. Philosophically of course it is compatible with theism, but historians have for the most part desisted from invoking the naive conception of a "god in history" to explain historical movements. A historian may be a theist; but, so far as his work is concerned, this particular belief is otiose. Otherwise indeed (as was remarked above) history could not be a science; for with a deus ex machina who can be brought on the stage to solve difficulties scientific treatment is a farce. The transcendent element had appeared in a more subtle form through the influence of German philosophy. I noticed how Ranke is prone to refer to ideas as if they were transcendent existences manifesting themselves in the successive movements of history. It is intelligible to speak of certain ideas as controlling, in a given period,--for instance, the idea of nationality; but from the scientific point of view, such ideas have no existence outside the minds of individuals and are purely psychical forces; and a historical "idea," if it does not exist in this form, is merely a way of expressing a synthesis of the historian himself.

15. From the more general influence of Darwinism on the place of history in the system of human knowledge, we may turn to the influence of the principles and methods by which Darwin explained development. It had been recognised even by ancient writers (such as Aristotle and Polybius) that physical circumstances (geography, climate) were factors conditioning the character and history of a race or society. In the sixteenth century Bodin emphasised these factors, and many subsequent writers took them into account. The investigations of Darwin, which brought them into the foreground, naturally promoted attempts to discover in them the chief key to the growth of civilisation. Comte had expressly denounced the notion that the biological methods of Lamarck could be applied to social man. Buckle had taken account of natural influences, but had relegated them to a secondary plane, compared with psychological factors. But the Darwinian theory made it tempting to explain the development of civilisation in terms of "adaptation to environment," "struggle for existence," "natural selection," "survival of the fittest," etc. (Recently O. Seeck has applied these principles to the decline of Graeco-Roman civilisation in his "Untergang der antiken Welt", 2 volumes, Berlin, 1895, 1901.)

The operation of these principles cannot be denied. Man is still an animal, subject to zoological as well as mechanical laws. The dark influence of heredity continues to be effective; and psychical development had begun in lower organic forms,--perhaps with life itself. The organic and the social struggles for existence are manifestations of the same principle. Environment and climatic influence must be called in to explain not only the differentiation of the great racial sections of humanity, but also the varieties within these sub-species and, it may be, the assimilation of distinct varieties. Ritter's "Anthropogeography" has opened a useful line of research. But on the other hand, it is urged that, in explaining the course of history, these principles do not take us very far, and that it is chiefly for the primitive ultra-prehistoric period that they can account for human development. It may be said that, so far as concerns the actions and movements of men which are the subject of recorded history, physical environment has ceased to act mechanically, and in order to affect their actions must affect their wills first; and that this psychical character of the causal relations substantially alters the problem. The development of human societies, it may be argued, derives a completely new character from the dominance of the conscious psychical element, creating as it does new conditions (inventions, social institutions, etc.) which limit and counteract the operation of natural selection, and control and modify the influence of physical environment. Most thinkers agree now that the chief clews to the growth of civilisation must be sought in the psychological sphere. Imitation, for instance, is a principle which is probably more significant for the explanation of human development than natural selection. Darwin himself was conscious that his principles had only a very restricted application in this sphere, as is evident from his cautious and tentative remarks in the 5th chapter of his "Descent of Man". He applied natural selection to the growth of the intellectual faculties and of the fundamental social instincts, and also to the differentiation of the great races or "sub-species" (Caucasian, African, etc.) which differ in anthropological character. (Darwinian formulae may be suggestive by way of analogy. For instance, it is characteristic of social advance that a multitude of inventions, schemes and plans are framed which are never carried out, similar to, or designed for the same end as, an invention or plan which is actually adopted because it has chanced to suit better the particular conditions of the hour (just as the works accomplished by an individual statesman, artist or savant are usually only a residue of the numerous projects conceived by his brain). This process in which so much abortive production occurs is analogous to elimination by natural selection.)

16. But if it is admitted that the governing factors which concern the student of social development are of the psychical order, the preliminary success of natural science in explaining organic evolution by general principles encouraged sociologists to hope that social evolution could be explained on general principles also. The idea of Condorcet, Buckle, and others, that history could be assimilated to the natural sciences was powerfully reinforced, and the notion that the actual historical process, and every social movement involved in it, can be accounted for by sociological generalisations, so-called "laws," is still entertained by many, in one form or another. Dissentients from this view do not deny that the generalisations at which the sociologist arrives by the comparative method, by the analysis of social factors, and by psychological deduction may be an aid to the historian; but they deny that such uniformities are laws or contain an explanation of the phenomena. They can point to the element of chance coincidence. This element must have played a part in the events of organic evolution, but it has probably in a larger measure helped to determine events in social evolution. The collision of two unconnected sequences may be fraught with great results. The sudden death of a leader or a marriage without issue, to take simple cases, has again and again led to permanent political consequences. More emphasis is laid on the decisive actions of individuals, which cannot be reduced under generalisations and which deflect the course of events. If the significance of the individual will had been exaggerated to the neglect of the collective activity of the social aggregate before Condorcet, his doctrine tended to eliminate as unimportant the roles of prominent men, and by means of this elimination it was possible to found sociology. But it may be urged that it is patent on the face of history that its course has constantly been shaped and modified by the wills of individuals (We can ignore here the metaphysical question of freewill and determinism. For the character of the individual's brain depends in any case on ante-natal accidents and coincidences, and so it may be said that the role of individuals ultimately depends on chance,--the accidental coincidence of independent sequences.), which are by no means always the expression of the collective will; and that the appearance of such personalities at the given moments is not a necessary outcome of the conditions and cannot be deduced. Nor is there any proof that, if such and such an individual had not been born, some one else would have arisen to do what he did. In some cases there is no reason to think that what happened need ever have come to pass. In other cases, it seems evident that the actual change was inevitable, but in default of the man who initiated and guided it, it might have been postponed, and, postponed or not, might have borne a different cachet. I may illustrate by an instance which has just come under my notice. Modern painting was founded by Giotto, and the Italian expedition of Charles VIII, near the close of the sixteenth century, introduced into France the fashion of imitating Italian painters. But for Giotto and Charles VIII, French painting might have been very different. It may be said that "if Giotto had not appeared, some other great initiator would have played a role analogous to his, and that without Charles VIII there would have been the commerce with Italy, which in the long run would have sufficed to place France in relation with Italian artists. But the equivalent of Giotto might have been deferred for a century and probably would have been different; and commercial relations would have required ages to produce the rayonnement imitatif of Italian art in France, which the expedition of the royal adventurer provoked in a few years." (I have taken this example from G. Tarde's "La logique sociale" 2 (page 403), Paris, 1904, where it is used for quite a different purpose.) Instances furnished by political history are simply endless. Can we conjecture how events would have moved if the son of Philip of Macedon had been an incompetent? The aggressive action of Prussia which astonished Europe in 1740 determined the subsequent history of Germany; but that action was anything but inevitable; it depended entirely on the personality of Frederick the Great.

Hence it may be argued that the action of individual wills is a determining and disturbing factor, too significant and effective to allow history to be grasped by sociological formulae. The types and general forms of development which the sociologist attempts to disengage can only assist the historian in understanding the actual course of events. It is in the special domains of economic history and Culturgeschichte which have come to the front in modern times that generalisation is most fruitful, but even in these it may be contended that it furnishes only partial explanations.

17. The truth is that Darwinism itself offers the best illustration of the insufficiency of general laws to account for historical development. The part played by coincidence, and the part played by individuals--limited by, and related to, general social conditions--render it impossible to deduce the course of the past history of man or to predict the future. But it is just the same with organic development. Darwin (or any other zoologist) could not deduce the actual course of evolution from general principles. Given an organism and its environment, he could not show that it must evolve into a more complex organism of a definite pre-determined type; knowing what it has evolved into, he could attempt to discover and assign the determining causes. General principles do not account for a particular sequence; they embody necessary conditions; but there is a chapter of accidents too. It is the same in the case of history.

18. Among the evolutional attempts to subsume the course of history under general syntheses, perhaps the most important is that of Lamprecht, whose "kulturhistorische Methode," which he has deduced from and applied to German history, exhibits the (indirect) influence of the Comtist school. It is based upon psychology, which, in his view, holds among the sciences of mind (Geisteswissenschaften) the same place (that of a Grundwissenschaft) which mechanics holds among the sciences of nature. History, by the same comparison, corresponds to biology, and, according to him, it can only become scientific if it is reduced to general concepts (Begriffe). Historical movements and events are of a psychical character, and Lamprecht conceives a given phase of civilisation as "a collective psychical condition (seelischer Gesamtzustand)" controlling the period, "a diapason which penetrates all psychical phenomena and thereby all historical events of the time." ("Die kulturhistorische Methode", Berlin, 1900, page 26.) He has worked out a series of such phases, "ages of changing psychical diapason," in his "Deutsche Geschichte" with the aim of showing that all the feelings and actions of each age can be explained by the diapason; and has attempted to prove that these diapasons are exhibited in other social developments, and are consequently not singular but typical. He maintains further that these ages succeed each other in a definite order; the principle being that the collective psychical development begins with the homogeneity of all the individual members of a society and, through heightened psychical activity, advances in the form of a continually increasing differentiation of the individuals (this is akin to the Spencerian formula). This process, evolving psychical freedom from psychical constraint, exhibits a series of psychical phenomena which define successive periods of civilisation. The process depends on two simple principles, that no idea can disappear without leaving behind it an effect or influence, and that all psychical life, whether in a person or a society, means change, the acquisition of new mental contents. It follows that the new have to come to terms with the old, and this leads to a synthesis which determines the character of a new age. Hence the ages of civilisation are defined as the "highest concepts for subsuming without exception all psychical phenomena of the development of human societies, that is, of all historical events." (Ibid. pages 28, 29.) Lamprecht deduces the idea of a special historical science, which might be called "historical ethnology," dealing with the ages of civilisation, and bearing the same relation to (descriptive or narrative) history as ethnology to ethnography. Such a science obviously corresponds to Comte's social dynamics, and the comparative method, on which Comte laid so much emphasis, is the principal instrument of Lamprecht.

19. I have dwelt on the fundamental ideas of Lamprecht, because they are not yet widely known in England, and because his system is the ablest product of the sociological school of historians. It carries the more weight as its author himself is a historical specialist, and his historical syntheses deserve the most careful consideration. But there is much in the process of development which on such assumptions is not explained, especially the initiative of individuals. Historical development does not proceed in a right line, without the choice of diverging. Again and again, several roads are open to it, of which it chooses one--why? On Lamprecht's method, we may be able to assign the conditions which limit the psychical activity of men at a particular stage of evolution, but within those limits the individual has so many options, such a wide room for moving, that the definition of those conditions, the "psychical diapasons," is only part of the explanation of the particular development. The heel of Achilles in all historical speculations of this class has been the role of the individual.

The increasing prominence of economic history has tended to encourage the view that history can be explained in terms of general concepts or types. Marx and his school based their theory of human development on the conditions of production, by which, according to them, all social movements and historical changes are entirely controlled. The leading part which economic factors play in Lamprecht's system is significant, illustrating the fact that economic changes admit most readily this kind of treatment, because they have been less subject to direction or interference by individual pioneers.

Perhaps it may be thought that the conception of SOCIAL ENVIRONMENT (essentially psychical), on which Lamprecht's "psychical diapasons" depend, is the most valuable and fertile conception that the historian owes to the suggestion of the science of biology--the conception of all particular historical actions and movements as (1) related to and conditioned by the social environment, and (2) gradually bringing about a transformation of that environment. But no given transformation can be proved to be necessary (pre-determined). And types of development do not represent laws; their meaning and value lie in the help they may give to the historian, in investigating a certain period of civilisation, to enable him to discover the interrelations among the diverse features which it presents. They are, as some one has said, an instrument of heuretic method.

20. The men engaged in special historical researches--which have been pursued unremittingly for a century past, according to scientific methods of investigating evidence (initiated by Wolf, Niebuhr, Ranke)--have for the most part worked on the assumptions of genetic history or at least followed in the footsteps of those who fully grasped the genetic point of view. But their aim has been to collect and sift evidence, and determine particular facts; comparatively few have given serious thought to the lines of research and the speculations which have been considered in this paper. They have been reasonably shy of compromising their work by applying theories which are still much debated and immature. But historiography cannot permanently evade the questions raised by these theories. One may venture to say that no historical change or transformation will be fully understood until it is explained how social environment acted on the individual components of the society (both immediately and by heredity), and how the individuals reacted upon their environment. The problem is psychical, but it is analogous to the main problem of the biologist.

XXVIII. THE GENESIS OF DOUBLE STARS. By Sir George Darwin, K.C.B., F.R.S.

Plumian Professor of Astronomy and Experimental Philosophy in the University of Cambridge.

In ordinary speech a system of any sort is said to be stable when it cannot be upset easily, but the meaning attached to the word is usually somewhat vague. It is hardly surprising that this should be the case, when it is only within the last thirty years, and principally through the investigations of M. Poincare, that the conception of stability has, even for physicists, assumed a definiteness and clearness in which it was previously lacking. The laws which govern stability hold good in regions of the greatest diversity; they apply to the motion of planets round the sun, to the internal arrangement of those minute corpuscles of which each chemical atom is constructed, and to the forms of celestial bodies. In the present essay I shall attempt to consider the laws of stability as relating to the last case, and shall discuss the succession of shapes which may be assumed by celestial bodies in the course of their evolution. I believe further that homologous conceptions are applicable in the consideration of the transmutations of the various forms of animal and of vegetable life and in other regions of thought. Even if some of my readers should think that what I shall say on this head is fanciful, yet at least the exposition will serve to illustrate the meaning to be attached to the laws of stability in the physical universe.

I propose, therefore, to begin this essay by a sketch of the principles of stability as they are now formulated by physicists.

If a slight impulse be imparted to a system in equilibrium one of two consequences must ensue; either small oscillations of the system will be started, or the disturbance will increase without limit and the arrangement of the system will be completely changed. Thus a stick may be in equilibrium either when it hangs from a peg or when it is balanced on its point. If in the first case the stick is touched it will swing to and fro, but in the second case it will topple over. The first position is a stable one, the second is unstable. But this case is too simple to illustrate all that is implied by stability, and we must consider cases of stable and of unstable motion. Imagine a satellite and its planet, and consider each of them to be of indefinitely small size, in fact particles; then the satellite revolves round its planet in an ellipse. A small disturbance imparted to the satellite will only change the ellipse to a small amount, and so the motion is said to be stable. If, on the other hand, the disturbance were to make the satellite depart from its initial elliptic orbit in ever widening circuits, the motion would be unstable. This case affords an example of stable motion, but I have adduced it principally with the object of illustrating another point not immediately connected with stability, but important to a proper comprehension of the theory of stability.

The motion of a satellite about its planet is one of revolution or rotation. When the satellite moves in an ellipse of any given degree of eccentricity, there is a certain amount of rotation in the system, technically called rotational momentum, and it is always the same at every part of the orbit. (Moment of momentum or rotational momentum is measured by the momentum of the satellite multiplied by the perpendicular from the planet on to the direction of the path of the satellite at any instant.)

Now if we consider all the possible elliptic orbits of a satellite about its planet which have the same amount of "rotational momentum," we find that the major axis of the ellipse described will be different according to the amount of flattening (or the eccentricity) of the ellipse described. A figure titled "A 'family' of elliptic orbits with constant rotational momentum" (Fig. 1) illustrates for a given planet and satellite all such orbits with constant rotational momentum, and with all the major axes in the same direction. It will be observed that there is a continuous transformation from one orbit to the next, and that the whole forms a consecutive group, called by mathematicians "a family" of orbits. In this case the rotational momentum is constant and the position of any orbit in the family is determined by the length of the major axis of the ellipse; the classification is according to the major axis, but it might have been made according to anything else which would cause the orbit to be exactly determinate.

I shall come later to the classification of all possible forms of ideal liquid stars, which have the same amount of rotational momentum, and the classification will then be made according to their densities, but the idea of orderly arrangement in a "family" is just the same.

We thus arrive at the conception of a definite type of motion, with a constant amount of rotational momentum, and a classification of all members of the family, formed by all possible motions of that type, according to the value of some measurable quantity (this will hereafter be density) which determines the motion exactly. In the particular case of the elliptic motion used for illustration the motion was stable, but other cases of motion might be adduced in which the motion would be unstable, and it would be found that classification in a family and specification by some measurable quantity would be equally applicable.

A complex mechanical system may be capable of motion in several distinct modes or types, and the motions corresponding to each such type may be arranged as before in families. For the sake of simplicity I will suppose that only two types are possible, so that there will only be two families; and the rotational momentum is to be constant. The two types of motion will have certain features in common which we denote in a sort of shorthand by the letter A. Similarly the two types may be described as A + a and A + b, so that a and b denote the specific differences which discriminate the families from one another. Now following in imagination the family of the type A + a, let us begin with the case where the specific difference a is well marked. As we cast our eyes along the series forming the family, we find the difference a becoming less conspicuous. It gradually dwindles until it disappears; beyond this point it either becomes reversed, or else the type has ceased to be a possible one. In our shorthand we have started with A + a, and have watched the characteristic a dwindling to zero. When it vanishes we have reached a type which may be specified as A; beyond this point the type would be A - a or would be impossible.

Following the A + b type in the same way, b is at first well marked, it dwindles to zero, and finally may become negative. Hence in shorthand this second family may be described as A + b,... A,... A - b.

In each family there is one single member which is indistinguishable from a member of the other family; it is called by Poincare a form of bifurcation. It is this conception of a form of bifurcation which forms the important consideration in problems dealing with the forms of liquid or gaseous bodies in rotation.

But to return to the general question,--thus far the stability of these families has not been considered, and it is the stability which renders this way of looking at the matter so valuable. It may be proved that if before the point of bifurcation the type A + a was stable, then A + b must have been unstable. Further as a and b each diminish A + a becomes less pronouncedly stable, and A + b less unstable. On reaching the point of bifurcation A + a has just ceased to be stable, or what amounts to the same thing is just becoming unstable, and the converse is true of the A + b family. After passing the point of bifurcation A + a has become definitely unstable and A + b has become stable. Hence the point of bifurcation is also a point of "exchange of stabilities between the two types." (In order not to complicate unnecessarily this explanation of a general principle I have not stated fully all the cases that may occur. Thus: firstly, after bifurcation A + a may be an impossible type and A + a will then stop at this point; or secondly, A + b may have been an impossible type before bifurcation, and will only begin to be a real one after it; or thirdly, both A + a and A + b may be impossible after the point of bifurcation, in which case they coalesce and disappear. This last case shows that types arise and disappear in pairs, and that on appearance or before disappearance one must be stable and the other unstable.)

In nature it is of course only the stable types of motion which can persist for more than a short time. Thus the task of the physical evolutionist is to determine the forms of bifurcation, at which he must, as it were, change carriages in the evolutionary journey so as always to follow the stable route. He must besides be able to indicate some natural process which shall correspond in effect to the ideal arrangement of the several types of motion in families with gradually changing specific differences. Although, as we shall see hereafter, it may frequently or even generally be impossible to specify with exactness the forms of bifurcation in the process of evolution, yet the conception is one of fundamental importance.

The ideas involved in this sketch are no doubt somewhat recondite, but I hope to render them clearer to the non-mathematical reader by homologous considerations in other fields of thought (I considered this subject in my Presidential address to the British Association in 1905, "Report of the 75th Meeting of the British Assoc." (S. Africa, 1905), London, 1906, page 3. Some reviewers treated my speculations as fanciful, but as I believe that this was due generally to misapprehension, and as I hold that homologous considerations as to stability and instability are really applicable to evolution of all sorts, I have thought it well to return to the subject in the present paper.), and I shall pass on thence to illustrations which will teach us something of the evolution of stellar systems.

States or governments are organised schemes of action amongst groups of men, and they belong to various types to which generic names, such as autocracy, aristocracy or democracy, are somewhat loosely applied. A definite type of government corresponds to one of our types of motion, and while retaining its type it undergoes a slow change as the civilisation and character of the people change, and as the relationship of the nation to other nations changes. In the language used before, the government belongs to a family, and as time advances we proceed through the successive members of the family. A government possesses a certain degree of stability--hardly measurable in numbers however--to resist disintegrating influences such as may arise from wars, famines, and internal dissensions. This stability gradually rises to a maximum and gradually declines. The degree of stability at any epoch will depend on the fitness of some leading feature of the government to suit the slowly altering circumstances, and that feature corresponds to the characteristic denoted by a in the physical problem. A time at length arrives when the stability vanishes, and the slightest shock will overturn the government. At this stage we have reached the crisis of a point of bifurcation, and there will then be some circumstance, apparently quite insignificant and almost unnoticed, which is such as to prevent the occurrence of anarchy. This circumstance or condition is what we typified as b. Insignificant although it may seem, it has started the government on a new career of stability by imparting to it a new type. It grows in importance, the form of government becomes obviously different, and its stability increases. Then in its turn this newly acquired stability declines, and we pass on to a new crisis or revolution. There is thus a series of "points of bifurcation" in history at which the continuity of political history is maintained by means of changes in the type of government. These ideas seem, to me at least, to give a true account of the history of states, and I contend that it is no mere fanciful analogy but a true homology, when in both realms of thought--the physical and the political--we perceive the existence of forms of bifurcation and of exchanges of stability.

Further than this, I would ask whether the same train of ideas does not also apply to the evolution of animals? A species is well adapted to its environment when the individual can withstand the shocks of famine or the attacks and competition of other animals; it then possesses a high degree of stability. Most of the casual variations of individuals are indifferent, for they do not tell much either for or against success in life; they are small oscillations which leave the type unchanged. As circumstances change, the stability of the species may gradually dwindle through the insufficiency of some definite quality, on which in earlier times no such insistent demands were made. The individual animals will then tend to fail in the struggle for life, the numbers will dwindle and extinction may ensue. But it may be that some new variation, at first of insignificant importance, may just serve to turn the scale. A new type may be formed in which the variation in question is preserved and augmented; its stability may increase and in time a new species may be produced.

At the risk of condemnation as a wanderer beyond my province into the region of biological evolution, I would say that this view accords with what I understand to be the views of some naturalists, who recognise the existence of critical periods in biological history at which extinction occurs or which form the starting-point for the formation of new species. Ought we not then to expect that long periods will elapse during which a type of animal will remain almost constant, followed by other periods, enormously long no doubt as measured in the life of man, of acute struggle for existence when the type will change more rapidly? This at least is the view suggested by the theory of stability in the physical universe. (I make no claim to extensive reading on this subject, but refer the reader for example to a paper by Professor A.A.W. Hubrecht on "De Vries's theory of Mutations", "Popular Science Monthly", July 1904, especially to page 213.)

And now I propose to apply these ideas of stability to the theory of stellar evolution, and finally to illustrate them by certain recent observations of a very remarkable character.

Stars and planets are formed of materials which yield to the enormous forces called into play by gravity and rotation. This is obviously true if they are gaseous or fluid, and even solid matter becomes plastic under sufficiently great stresses. Nothing approaching a complete study of the equilibrium of a heterogeneous star has yet been found possible, and we are driven to consider only bodies of simpler construction. I shall begin therefore by explaining what is known about the shapes which may be assumed by a mass of incompressible liquid of uniform density under the influences of gravity and of rotation. Such a liquid mass may be regarded as an ideal star, which resembles a real star in the fact that it is formed of gravitating and rotating matter, and because its shape results from the forces to which it is subject. It is unlike a star in that it possesses the attributes of incompressibility and of uniform density. The difference between the real and the ideal is doubtless great, yet the similarity is great enough to allow us to extend many of the conclusions as to ideal liquid stars to the conditions which must hold good in reality. Thus with the object of obtaining some insight into actuality, it is justifiable to discuss an avowedly ideal problem at some length.

The attraction of gravity alone tends to make a mass of liquid assume the shape of a sphere, and the effects of rotation, summarised under the name of centrifugal force, are such that the liquid seeks to spread itself outwards from the axis of rotation. It is a singular fact that it is unnecessary to take any account of the size of the mass of liquid under consideration, because the shape assumed is exactly the same whether the mass be small or large, and this renders the statement of results much easier than would otherwise be the case.

A mass of liquid at rest will obviously assume the shape of a sphere, under the influence of gravitation, and it is a stable form, because any oscillation of the liquid which might be started would gradually die away under the influence of friction, however small. If now we impart to the whole mass of liquid a small speed of rotation about some axis, which may be called the polar axis, in such a way that there are no internal currents and so that it spins in the same way as if it were solid, the shape will become slightly flattened like an orange. Although the earth and the other planets are not homogeneous they behave in the same way, and are flattened at the poles and protuberant at the equator. This shape may therefore conveniently be described as planetary.

If the planetary body be slightly deformed the forces of restitution are slightly less than they were for the sphere; the shape is stable but somewhat less so than the sphere. We have then a planetary spheroid, rotating slowly, slightly flattened at the poles, with a high degree of stability, and possessing a certain amount of rotational momentum. Let us suppose this ideal liquid star to be somewhere in stellar space far removed from all other bodies; then it is subject to no external forces, and any change which ensues must come from inside. Now the amount of rotational momentum existing in a system in motion can neither be created nor destroyed by any internal causes, and therefore, whatever happens, the amount of rotational momentum possessed by the star must remain absolutely constant.

A real star radiates heat, and as it cools it shrinks. Let us suppose then that our ideal star also radiates and shrinks, but let the process proceed so slowly that any internal currents generated in the liquid by the cooling are annulled so quickly by fluid friction as to be insignificant; further let the liquid always remain at any instant incompressible and homogeneous. All that we are concerned with is that, as time passes, the liquid star shrinks, rotates in one piece as if it were solid, and remains incompressible and homogeneous. The condition is of course artificial, but it represents the actual processes of nature as well as may be, consistently with the postulated incompressibility and homogeneity. (Mathematicians are accustomed to regard the density as constant and the rotational momentum as increasing. But the way of looking at the matter, which I have adopted, is easier of comprehension, and it comes to the same in the end.)

The shrinkage of a constant mass of matter involves an increase of its density, and we have therefore to trace the changes which supervene as the star shrinks, and as the liquid of which it is composed increases in density. The shrinkage will, in ordinary parlance, bring the weights nearer to the axis of rotation. Hence in order to keep up the rotational momentum, which as we have seen must remain constant, the mass must rotate quicker. The greater speed of rotation augments the importance of centrifugal force compared with that of gravity, and as the flattening of the planetary spheroid was due to centrifugal force, that flattening is increased; in other words the ellipticity of the planetary spheroid increases.

As the shrinkage and corresponding increase of density proceed, the planetary spheroid becomes more and more elliptic, and the succession of forms constitutes a family classified according to the density of the liquid. The specific mark of this family is the flattening or ellipticity.

Now consider the stability of the system, we have seen that the spheroid with a slow rotation, which forms our starting-point, was slightly less stable than the sphere, and as we proceed through the family of ever flatter ellipsoids the stability continues to diminish. At length when it has assumed the shape shown in a figure titled "Planetary spheroid just becoming unstable" (Fig. 2.) where the equatorial and polar axes are proportional to the numbers 1000 and 583, the stability has just disappeared. According to the general principle explained above this is a form of bifurcation, and corresponds to the form denoted A. The specific difference a of this family must be regarded as the excess of the ellipticity of this figure above that of all the earlier ones, beginning with the slightly flattened planetary spheroid. Accordingly the specific difference a of the family has gradually diminished from the beginning and vanishes at this stage.

According to Poincare's principle the vanishing of the stability serves us with notice that we have reached a figure of bifurcation, and it becomes necessary to inquire what is the nature of the specific difference of the new family of figures which must be coalescent with the old one at this stage. This difference is found to reside in the fact that the equator, which in the planetary family has hitherto been circular in section, tends to become elliptic. Hitherto the rotational momentum has been kept up to its constant value partly by greater speed of rotation and partly by a symmetrical bulging of the equator. But now while the speed of rotation still increases (The mathematician familiar with Jacobi's ellipsoid will find that this is correct, although in the usual mode of exposition, alluded to above in a footnote, the speed diminishes.), the equator tends to bulge outwards at two diametrically opposite points and to be flattened midway between these protuberances. The specific difference in the new family, denoted in the general sketch by b, is this ellipticity of the equator. If we had traced the planetary figures with circular equators beyond this stage A, we should have found them to have become unstable, and the stability has been shunted off along the A + b family of forms with elliptic equators.

This new series of figures, generally named after the great mathematician Jacobi, is at first only just stable, but as the density increases the stability increases, reaches a maximum and then declines. As this goes on the equator of these Jacobian figures becomes more and more elliptic, so that the shape is considerably elongated in a direction at right angles to the axis of rotation.

At length when the longest axis of the three has become about three times as long as the shortest (The three axes of the ellipsoid are then proportional to 1000, 432, 343.), the stability of this family of figures vanishes, and we have reached a new form of bifurcation and must look for a new type of figure along which the stable development will presumably extend. Two sections of this critical Jacobian figure, which is a figure of bifurcation, are shown by the dotted lines in a figure titled "The 'pear-shaped figure' and the Jocobian figure from which it is derived" (Fig. 3.) comprising two figures, one above the other: the upper figure is the equatorial section at right angles to the axis of rotation, the lower figure is a section through the axis.

Now Poincare has proved that the new type of figure is to be derived from the figure of bifurcation by causing one of the ends to be prolonged into a snout and by bluntening the other end. The snout forms a sort of stalk, and between the stalk and the axis of rotation the surface is somewhat flattened. These are the characteristics of a pear, and the figure has therefore been called the "pear-shaped figure of equilibrium." The firm line shows this new type of figure, whilst, as already explained, the dotted line shows the form of bifurcation from which it is derived. The specific mark of this new family is the protrusion of the stalk together with the other corresponding smaller differences. If we denote this difference by c, while A + b denotes the Jacobian figure of bifurcation from which it is derived, the new family may be called A + b + c, and c is zero initially. According to my calculations this series of figures is stable (M. Liapounoff contends that for constant density the new series of figures, which M. Poincare discovered, has less rotational momentum than that of the figure of bifurcation. If he is correct, the figure of bifurcation is a limit of stable figures, and none can exist with stability for greater rotational momentum. My own work seems to indicate that the opposite is true, and, notwithstanding M. Liapounoff's deservedly great authority, I venture to state the conclusions in accordance with my own work.), but I do not know at what stage of its development it becomes unstable.

Professor Jeans has solved a problem which is of interest as throwing light on the future development of the pear-shaped figure, although it is of a still more ideal character than the one which has been discussed. He imagines an INFINITELY long circular cylinder of liquid to be in rotation about its central axis. The existence is virtually postulated of a demon who is always occupied in keeping the axis of the cylinder straight, so that Jeans has only to concern himself with the stability of the form of the section of the cylinder, which as I have said is a circle with the axis of rotation at the centre. He then supposes the liquid forming the cylinder to shrink in diameter, just as we have done, and finds that the speed of rotation must increase so as to keep up the constancy of the rotational momentum. The circularity of section is at first stable, but as the shrinkage proceeds the stability diminishes and at length vanishes. This stage in the process is a form of bifurcation, and the stability passes over to a new series consisting of cylinders which are elliptic in section. The circular cylinders are exactly analogous with our planetary spheroids, and the elliptic ones with the Jacobian ellipsoids.

With further shrinkage the elliptic cylinders become unstable, a new form of bifurcation is reached, and the stability passes over to a series of cylinders whose section is pear-shaped. Thus far the analogy is complete between our problem and Jeans's, and in consequence of the greater simplicity of the conditions, he is able to carry his investigation further. He finds that the stalk end of the pear-like section continues to protrude more and more, and the flattening between it and the axis of rotation becomes a constriction. Finally the neck breaks and a satellite cylinder is born. Jeans's figure for an advanced stage of development is shown in a figure titled "Section of a rotating cylinder of liquid" (Fig. 4.), but his calculations do not enable him actually to draw the state of affairs after the rupture of the neck.

There are certain difficulties in admitting the exact parallelism between this problem and ours, and thus the final development of our pear-shaped figure and the end of its stability in a form of bifurcation remain hidden from our view, but the successive changes as far as they have been definitely traced are very suggestive in the study of stellar evolution.

Attempts have been made to attack this problem from the other end. If we begin with a liquid satellite revolving about a liquid planet and proceed backwards in time, we must make the two masses expand so that their density will be diminished. Various figures have been drawn exhibiting the shapes of two masses until their surfaces approach close to one another and even until they just coalesce, but the discussion of their stability is not easy. At present it would seem to be impossible to reach coalescence by any series of stable transformations, and if this is so Professor Jeans's investigation has ceased to be truly analogous to our problem at some undetermined stage. However this may be this line of research throws an instructive light on what we may expect to find in the evolution of real stellar systems.

In the second part of this paper I shall point out the bearing which this investigation of the evolution of an ideal liquid star may have on the genesis of double stars.

II.

There are in the heavens many stars which shine with a variable brilliancy. Amongst these there is a class which exhibits special peculiarities; the members of this class are generally known as Algol Variables, because the variability of the star Beta Persei or Algol was the first of such cases to attract the attention of astronomers, and because it is perhaps still the most remarkable of the whole class. But the circumstances which led to this discovery were so extraordinary that it seems worth while to pause a moment before entering on the subject.

John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir of Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782, he noted that the brilliancy of Algol waxed and waned (It is said that Georg Palitzch, a farmer of Prohlis near Dresden, had about 1758 already noted the variability of Algol with the naked eye. "Journ. Brit. Astron. Assoc." Vol. XV. (1904-5), page 203.), and devoted himself to observing it on every fine night from the 28th December 1782 to the 12th May 1783. He communicated his observations to the Royal Society, and suggested that the variation in brilliancy was due to periodic eclipses by a dark companion star, a theory now universally accepted as correct. The Royal Society recognised the importance of the discovery by awarding to Goodricke, then only 19 years of age, their highest honour, the Copley medal. His later observations of Beta Lyrae and of Delta Cephei were almost as remarkable as those of Algol, but unfortunately a career of such extraordinary promise was cut short by death, only a fortnight after his election to the Royal Society. ("Dict. of National Biography"; article Goodricke (John). The article is by Miss Agnes Clerke. It is strange that she did not then seem to be aware that he was a deaf-mute, but she notes the fact in her "Problems of Astrophysics", page 337, London, 1903.)

It was not until 1889 that Goodricke's theory was verified, when it was proved by Vogel that the star was moving in an orbit, and in such a manner that it was only possible to explain the rise and fall in the luminosity by the partial eclipse of a bright star by a dark companion.

The whole mass of the system of Algol is found to be half as great again as that of our sun, yet the two bodies complete their orbit in the short period of 2d 20h 48m 55s. The light remains constant during each period, except for 9h 20m when it exhibits a considerable fall in brightness (Clerke, "Problems of Astrophysics" page 302 and chapter XVIII.); the curve which represents the variation in the light is shown in a figure titled "The light-curve and system of Beta Lyrae" (Fig. 7.).

The spectroscope has enabled astronomers to prove that many stars, although apparently single, really consist of two stars circling around one another (If a source of light is approaching with a great velocity the waves of light are crowded together, and conversely they are spaced out when the source is receding. Thus motion in the line of sight virtually produces an infinitesimal change of colour. The position of certain dark lines in the spectrum affords an exceedingly accurate measurement of colour. Thus displacements of these spectral lines enables us to measure the velocity of the source of light towards or away from the observer.); they are known as spectroscopic binaries. Campbell of the Lick Observatory believes that about one star in six is a binary ("Astrophysical Journ." Vol. XIII. page 89, 1901. See also A. Roberts, "Nature", Sept. 12, 1901, page 468.); thus there must be many thousand such stars within the reach of our spectroscopes.

The orientation of the planes of the orbits of binary stars appears to be quite arbitrary, and in general the star does not vary in brightness. Amongst all such orbits there must be some whose planes pass nearly through the sun, and in these cases the eclipse of one of the stars by the other becomes inevitable, and in each circuit there will occur two eclipses of unequal intensities.

It is easy to see that in the majority of such cases the two components must move very close to one another.

The coincidence between the spectroscopic and the photometric evidence permits us to feel complete confidence in the theory of eclipses. When then we find a star with a light-curve of perfect regularity and with a characteristics of that of Algol, we are justified in extending the theory of eclipses to it, although it may be too faint to permit of adequate spectroscopic examination. This extension of the theory secures a considerable multiplication of the examples available for observation, and some 30 have already been discovered.

Dr Alexander Roberts, of Lovedale in Cape Colony, truly remarks that the study of Algol variables "brings us to the very threshold of the question of stellar evolution." ("Proc. Roy. Soc. Edinburgh", XXIV. Part II. (1902), page 73.) It is on this account that I propose to explain in some detail the conclusion to which he and some other observers have been led.

Although these variable stars are mere points of light, it has been proved by means of the spectroscope that the law of gravitation holds good in the remotest regions of stellar space, and further it seems now to have become possible even to examine the shapes of stars by indirect methods, and thus to begin the study of their evolution. The chain of reasoning which I shall explain must of necessity be open to criticism, yet the explanation of the facts by the theory is so perfect that it is not easy to resist the conviction that we are travelling along the path of truth.

The brightness of a star is specified by what is called its "magnitude." The average brightness of all the stars which can just be seen with the naked eye defines the sixth magnitude. A star which only gives two-fifths as much light is said to be of the seventh magnitude; while one which gives 2 1/2 times as much light is of the fifth magnitude, and successive multiplications or divisions by 2 1/2 define the lower or higher magnitudes. Negative magnitudes have clearly to be contemplated; thus Sirius is of magnitude minus 1.4, and the sun is of magnitude minus 26.

The definition of magnitude is also extended to fractions; for example, the lights given by two candles which are placed at 100 feet and 100 feet 6 inches from the observer differ in brightness by one-hundredth of a magnitude.

A great deal of thought has been devoted to the measurement of the brightness of stars, but I will only describe one of the methods used, that of the great astronomer Argelander. In the neighbourhood of the star under observation some half dozen standard stars are selected of known invariable magnitudes, some being brighter and some fainter than the star to be measured; so that these stars afford a visible scale of brightness. Suppose we number them in order of increasing brightness from 1 to 6; then the observer estimates that on a given night his star falls between stars 2 and 3, on the next night, say between 3 and 4, and then again perhaps it may return to between 2 and 3, and so forth. With practice he learns to evaluate the brightness down to small fractions of a magnitude, even a hundredth part of a magnitude is not quite negligible.

For example, in observing the star RR Centauri five stars were in general used for comparison by Dr Roberts, and in course of three months he secured thereby 300 complete observations. When the period of the cycle had been ascertained exactly, these 300 values were reduced to mean values which appertained to certain mean places in the cycle, and a mean light-curve was obtained in this way. Figures titled "Light curve of RR Centauri" (Fig. 5) and "The light-curve and system of Beta Lyrae" (Fig. 7) show examples of light curves.

I shall now follow out the results of the observation of RR Centauri not only because it affords the easiest way of explaining these investigations, but also because it is one of the stars which furnishes the most striking results in connection with the object of this essay. (See "Monthly notices R.A.S." Vol. 63, 1903, page 527.) This star has a mean magnitude of about 7 1/2, and it is therefore invisible to the naked eye. Its period of variability is 14h 32m 10s.76, the last refinement of precision being of course only attained in the final stages of reduction. Twenty-nine mean values of the magnitude were determined, and they were nearly equally spaced over the whole cycle of changes. The black dots in Fig. 5 exhibit the mean values determined by Dr Roberts. The last three dots on the extreme right are merely the same as the first three on the extreme left, and are repeated to show how the next cycle would begin. The smooth dotted curve will be explained hereafter, but, by reference to the scale of magnitudes on the margins of the figure, it may be used to note that the dots might be brought into a perfectly smooth curve by shifting some few of the dots by about a hundredth of a magnitude.

This light-curve presents those characteristics which are due to successive eclipses, but the exact form of the curve must depend on the nature of the two mutually eclipsing stars. If we are to interpret the curve with all possible completeness, it is necessary to make certain assumptions as to the stars. It is assumed then that the stars are equally bright all over their disks, and secondly that they are not surrounded by an extensive absorptive atmosphere. This last appears to me to be the most dangerous assumption involved in the whole theory.

Making these assumptions, however, it is found that if each of the eclipsing stars were spherical it would not be possible to generate such a curve with the closest accuracy. The two stars are certainly close together, and it is obvious that in such a case the tidal forces exercised by each on the other must be such as to elongate the figure of each towards the other. Accordingly it is reasonable to adopt the hypothesis that the system consists of a pair of elongated ellipsoids, with their longest axes pointed towards one another. No supposition is adopted a priori as to the ratio of the two masses, or as to their relative size or brightness, and the orbit may have any degree of eccentricity. These last are all to be determined from the nature of the light-curve.

In the case of RR Centauri, however, Dr Roberts finds the conditions are best satisfied by supposing the orbit to be circular, and the sizes and masses of the components to be equal, while their luminosities are to one another in the ratio of 4 to 3. As to their shapes he finds them to be so much elongated that they overlap, as exhibited in his figure titled "The shape of the star RR Centauri" (Fig. 6.). The dotted curve shows a form of equilibrium of rotating liquid as computed by me some years before, and it was added for the sake of comparison.

On turning back to Fig. 5 the reader will see in the smooth dotted curve the light variation which would be exhibited by such a binary system as this. The curve is the result of computation and it is impossible not to be struck by the closeness of the coincidence with the series of black dots which denote the observations.

It is virtually certain that RR Centauri is a case of an eclipsing binary system, and that the two stars are close together. It is not of course proved that the figures of the stars are ellipsoids, but gravitation must deform them into a pair of elongated bodies, and, on the assumptions that they are not enveloped in an absorptive atmosphere and that they are ellipsoidal, their shapes must be as shown in the figure.

This light-curve gives an excellent illustration of what we have reason to believe to be a stage in the evolution of stars, when a single star is proceeding to separate into a binary one.

As the star is faint, there is as yet no direct spectroscopic evidence of orbital motion. Let us turn therefore to the case of another star, namely V Puppis, in which such evidence does already exist. I give an account of it, because it presents a peculiarly interesting confirmation of the correctness of the theory.

In 1895 Pickering announced in the "Harvard Circular" No. 14 that the spectroscopic observations at Arequipa proved V Puppis to be a double star with a period of 3d 2h 46m. Now when Roberts discussed its light-curve he found that the period was 1d 10h 54m 27s, and on account of this serious discrepancy he effected the reduction only on the simple assumption that the two stars were spherical, and thus obtained a fairly good representation of the light-curve. It appeared that the orbit was circular and that the two spheres were not quite in contact. Obviously if the stars had been assumed to be ellipsoids they would have been found to overlap, as was the case for RR Centauri. ("Astrophysical Journ." Vol. XIII. (1901), page 177.) The matter rested thus for some months until the spectroscopic evidence was re-examined by Miss Cannon on behalf of Professor Pickering, and we find in the notes on page 177 of Vol. XXVIII. of the "Annals of the Harvard Observatory" the following: "A.G.C. 10534. This star, which is the Algol variable V Puppis, has been found to be a spectroscopic binary. The period 1d.454 (i.e. 1d 10h 54m) satisfies the observations of the changes in light, and of the varying separation of the lines of the spectrum. The spectrum has been examined on 61 plates, on 23 of which the lines are double." Thus we have valuable evidence in confirmation of the correctness of the conclusions drawn from the light-curve. In the circumstances, however, I have not thought it worth while to reproduce Dr Roberts's provisional figure.

I now turn to the conclusions drawn a few years previously by another observer, where we shall find the component stars not quite in contact. This is the star Beta Lyrae which was observed by Goodricke, Argelander, Belopolsky, Schur, Markwick and by many others. The spectroscopic method has been successfully applied in this case, and the component stars are proved to move in an orbit about one another. In 1897, Mr. G.W. Myers applied the theory of eclipses to the light-curve, on the hypothesis that the stars are elongated ellipsoids, and he obtained the interesting results exhibited in Fig. 7. ("Astrophysical Journ." Vol. VII. (1898), page 1.)

The period of Beta Lyrae is relatively long, being 12d 21h 47m, the orbit is sensibly eccentric, and the two spheroids are not so much elongated as was the case with RR Centauri. The mass of the system is enormous, one of the two stars being 10 times and the other 21 times as heavy as our sun.

Further illustrations of this subject might be given, but enough has been said to explain the nature of the conclusions which have been drawn from this class of observation.

In my account of these remarkable systems the consideration of one very important conclusion has been purposely deferred. Since the light-curve is explicable by eclipses, it follows that the sizes of the two stars are determinable relatively to the distance between them. The period of their orbital motion is known, being identical with the complete period of the variability of their light, and an easy application of Kepler's law of periodic times enables us to compute the sum of the masses of the two stars divided by the cube of the distance between their centres. Now the sizes of the bodies being known, the mean density of the whole system may be calculated. In every case that density has been found to be much less than the sun's, and indeed the average of a number of mean densities which have been determined only amounts to one-eighth of that of the sun. In some cases the density is extremely small, and in no case is it quite so great as half the solar density.

It would be absurd to suppose that these stars can be uniform in density throughout, and from all that is known of celestial bodies it is probable that they are gaseous in their external parts with great condensation towards their centres. This conclusion is confirmed by arguments drawn from the theory of rotating masses of liquid. (See J.H. Jeans, "On the density of Algol variables", "Astrophysical Journ." Vol. XXII. (1905), page 97.)

Although, as already explained, a good deal is known about the shapes and the stability of figures consisting of homogeneous incompressible liquid in rotation, yet comparatively little has hitherto been discovered about the equilibrium of rotating gaseous stars. The figures calculated for homogeneous liquid can obviously only be taken to afford a general indication of the kind of figure which we might expect to find in the stellar universe. Thus the dotted curve in Fig. 5, which exhibits one of the figures which I calculated, has some interest when placed alongside the figures of the stars in RR Centauri, as computed from the observations, but it must not be accepted as the calculated form of such a system. I have moreover proved more recently that such a figure of homogeneous liquid is unstable. Notwithstanding this instability it does not necessarily follow that the analogous figure for compressible fluid is also unstable, as will be pointed out more fully hereafter.

Professor Jeans has discussed in a paper of great ability the difficult problems offered by the conditions of equilibrium and of stability of a spherical nebula. ("Phil. Trans. R.S." Vol. CXCIX. A (1902), page 1. See also A. Roberts, "S. African Assoc. Adv. Sci." Vol. I. (1903), page 6.) In a later paper ("Astrophysical Journ." Vol. XXII. (1905), page 97.), in contrasting the conditions which must govern the fission of a star into two parts when the star is gaseous and compressible with the corresponding conditions in the case of incompressible liquid, he points out that for a gaseous star (the agency which effects the separation will no longer be rotation alone; gravitation also will tend towards separation... From numerical results obtained in the various papers of my own,... I have been led to the conclusion that a gravitational instability of the kind described must be regarded as the primary agent at work in the actual evolution of the universe, Laplace's rotation playing only the secondary part of separating the primary and satellite after the birth of the satellite.)

It is desirable to add a word in explanation of the expression "gravitational instability" in this passage. It means that when the concentration of a gaseous nebula (without rotation) has proceeded to a certain stage, the arrangement in spherical layers of equal density becomes unstable, and a form of bifurcation has been reached. For further concentration concentric spherical layers become unstable, and the new stable form involves a concentration about two centres. The first sign of this change is that the spherical layers cease to be quite concentric and then the layers of equal density begin to assume a somewhat pear-shaped form analogous to that which we found to occur under rotation for an incompressible liquid. Accordingly it appears that while a sphere of liquid is stable a sphere of gas may become unstable. Thus the conditions of stability are different in these two simple cases, and it is likely that while certain forms of rotating liquid are unstable the analogous forms for gas may be stable. This furnishes a reason why it is worth while to consider the unstable forms of rotating liquid.

There can I think be little doubt but that Jeans is right in looking to gravitational instability as the primary cause of fission, but when we consider that a binary system, with a mass larger than the sun's, is found to rotate in a few hours, there seems reason to look to rotation as a contributory cause scarcely less important than the primary one.

With the present extent of our knowledge it is only possible to reconstruct the processes of the evolution of stars by means of inferences drawn from several sources. We have first to rely on the general principles of stability, according to which we are to look for a series of families of forms, each terminating in an unstable form, which itself becomes the starting-point of the next family of stable forms. Secondly we have as a guide the analogy of the successive changes in the evolution of ideal liquid stars; and thirdly we already possess some slender knowledge as to the equilibrium of gaseous stars.

From these data it is possible to build up in outline the probable history of binary stars. Originally the star must have been single, it must have been widely diffused, and must have been endowed with a slow rotation. In this condition the strata of equal density must have been of the planetary form. As it cooled and contracted the symmetry round the axis of rotation must have become unstable, through the effects of gravitation, assisted perhaps by the increasing speed of rotation. (I learn from Professor Jeans that he now (December 1908) believes that he can prove that some small amount of rotation is necessary to induce instability in the symmetrical arrangement.) The strata of equal density must then become somewhat pear-shaped, and afterwards like an hour-glass, with the constriction more pronounced in the internal than in the external strata. The constrictions of the successive strata then begin to rupture from the inside progressively outwards, and when at length all are ruptured we have the twin stars portrayed by Roberts and by others.

As we have seen, the study of the forms of equilibrium of rotating liquid is almost complete, and Jeans has made a good beginning in the investigation of the equilibrium of gaseous stars, but much more remains to be discovered. The field for the mathematician is a wide one, and in proportion as the very arduous exploration of that field is attained so will our knowledge of the processes of cosmical evolution increase.

From the point of view of observation, improved methods in the use of the spectroscope and increase of accuracy in photometry will certainly lead to a great increase in our knowledge within the next few years. Probably the observational advance will be more rapid than that of theory, for we know how extraordinary has been the success attained within the last few years, and the theory is one of extreme difficulty; but the two ought to proceed together hand in hand. Human life is too short to permit us to watch the leisurely procedure of cosmical evolution, but the celestial museum contains so many exhibits that it may become possible, by the aid of theory, to piece together bit by bit the processes through which stars pass in the course of their evolution.

In the sketch which I have endeavoured to give of this fascinating subject, I have led my reader to the very confines of our present knowledge. It is not much more than a quarter of a century since this class of observation has claimed the close attention of astronomers; something considerable has been discovered already and there seems scarcely a discernible limit to what will be known in this field a century from now. Some of the results which I have set forth may then be shown to be false, but it seems profoundly improbable that we are being led astray by a Will-of-the-Wisp.

XXIX. THE EVOLUTION OF MATTER. By W.C.D. Whetham, M.A., F.R.S.

Trinity College, Cambridge.

The idea of evolution in the organic world, made intelligible by the work of Charles Darwin, has little in common with the recent conception of change in certain types of matter. The discovery that a process of disintegration may take place in some at least of the chemical atoms, previously believed to be indestructible and unalterable, has modified our view of the physical universe, even as Darwin's scheme of the mode of evolution changed the trend of thought concerning the organic world. Both conceptions have in common the idea of change throughout extended realms of space and time, and, therefore, it is perhaps not unfitting that some account of the most recent physical discoveries should be included in the present volume.

The earliest conception of the evolution of matter is found in the speculation of the Greeks. Leucippus and Democritus imagined unchanging eternal atoms, Heracleitus held that all things were in a continual state of flux--Panta rei.

But no one in the Ancient World--no one till quite modern times--could appreciate the strength of the position which the theory of the evolution of matter must carry before it wins the day. Vague speculation, even by the acute minds of philosophers, is of little use in physical science before experimental facts are available. The true problems at issue cannot even be formulated, much less solved, till the humble task of the observer and experimenter has given us a knowledge of the phenomena to be explained.

It was only through the atomic theory, at first apparently diametrically opposed to it, that the conception of evolution in the physical world was to gain an established place. For a century the atomic theory, when put into a modern form by Dalton, led farther and farther away from the idea of change in matter. The chemical elements seemed quite unalterable, and the atoms, of which each element in modern view is composed, bore to Clerk Maxwell, writing about 1870, "the stamp of manufactured articles" exactly similar in kind, unchanging, eternal.

Nevertheless throughout these years, on the whole so unfavourable to its existence, there persisted the idea of a common origin of the distinct kinds of matter known to chemists. Indeed, this idea of unity in substance in nature seems to accord with some innate desire or intimate structure of the human mind. As Mr Arthur Balfour well puts it, "There is no a priori reason that I know of for expecting that the material world should be a modification of a single medium, rather than a composite structure built out of sixty or seventy elementary substances, eternal and eternally different. Why then should we feel content with the first hypothesis and not with the second? Yet so it is. Men of science have always been restive under the multiplication of entities. They have eagerly watched for any sign that the different chemical elements own a common origin, and are all compounded out of some primordial substance. Nor, for my part, do I think that such instincts should be ignored... that they exist is certain; that they modify the indifferent impartiality of pure empiricism can hardly be denied." ("Report of the 74th Meeting of the British Association" (Presidential Address, Cambridge 1904), page 9, London, 1905.)

When Dalton's atomic theory had been in existence some half century, it was noted that certain numerical relations held good between the atomic weights of elements chemically similar to one another. Thus the weight (88) of an atom of strontium compared with that of hydrogen as unity, is about the mean of those of calcium (40) and barium (137). Such relations, in this and other chemical groups, were illustrated by Beguyer de Chancourtois in 1862 by the construction of a spiral diagram in which the atomic weights are placed in order round a cylinder and elements chemically similar are found to fall on vertical lines.

Newlands seems to have been the first to see the significance of such a diagram. In his "law of octaves," formulated in 1864, he advanced the hypothesis that, if arranged in order of rising atomic weight, the elements fell into groups, so that each eighth element was chemically similar. Stated thus, the law was too definite; no room was left for newly-discovered elements, and some dissimilar elements were perforce grouped together.

But in 1869 Mendeleeff developed Newland's hypothesis in a form that attracted at once general attention. Placing the elements in order of rising atomic weight, but leaving a gap where necessary to bring similar elements into vertical columns, he obtained a periodic table with natural vacancies to be filled as new elements were discovered, and with a certain amount of flexibility at the ends of the horizontal lines. From the position of the vacancies, the general chemical and physical properties of undiscovered elements could be predicted, and the success of such predictions gave a striking proof of the usefulness of Mendeleeff's generalisation.

When the chemical and physical properties of the elements were known to be periodic functions of their atomic weights, the idea of a common origin and common substance became much more credible. Differences in atomic weight and differences in properties alike might reasonably be explained by the differences in the amount of the primordial substance present in the various atoms; an atom of oxygen being supposed to be composed of sixteen times as much stuff as the atom of hydrogen, but to be made of the same ultimate material. Speculations about the mode of origin of the elements now began to appear, and put on a certain air of reality. Of these speculations perhaps the most detailed was that of Crookes, who imagined an initial chaos of a primordial medium he named protyle, and a process of periodic change in which the chemical elements successively were precipitated.

From another side too, suggestions were put forward by Sir Norman Lockyer and others that the differences in spectra observed in different classes of stars, and produced by different conditions in the laboratory, were to be explained by changes in the structure of the vibrating atoms.

The next step in advance gave a theoretical basis for the idea of a common structure of matter, and was taken in an unexpected direction. Clerk Maxwell's electromagnetic theory of light, accepted in England, was driven home to continental minds by the confirmatory experiments of Hertz, who in 1888 detected and measured the electromagnetic waves that Maxwell had described twenty years earlier. But, if light be an electromagnetic phenomenon, the light waves radiated by hot bodies must take their origin in the vibrations of electric systems. Hence within the atoms must exist electric charges capable of vibration. On these lines Lorentz and Larmor have developed an electronic theory of matter, which is imagined in its essence to be a conglomerate of electric charges, with electro-magnetic inertia to explain mechanical inertia. (Larmor, "Aether and Matter", Cambridge, 1900.) The movement of electric charges would be affected by a magnetic field, and hence the discovery by Zeeman that the spectral lines of sodium were doubled by a strong magnetic force gave confirmatory evidence to the theory of electrons.

Then came J.J. Thomson's great discovery of minute particles, much smaller than any chemical atom, forming a common constituent of many different kinds of matter. (Thomson, "Conduction of Electricity through Gases" (2nd edition), Cambridge, 1906.) If an electric discharge be passed between metallic terminals through a glass vessel containing air at very low pressure, it is found that rectilinear rays, known as cathode rays, proceed from the surface of the cathode or negative terminal. Where these rays strike solid objects, they give rise to the Rontgen rays now so well known; but it is with the cathode rays themselves that we are concerned. When they strike an insulated conductor, they impart to it a negative charge, and Thomson found that they were deflected from their path both by magnetic and electric forces in the direction in which negatively electrified particles would be deflected. Cathode rays then were accepted as flights of negatively charged particles, moving with high velocities. The electric and magnetic deflections give two independent measurements which may be made on a cathode ray, and both the deflections involve theoretically three unknown quantities, the mass of the particles, their electric charge and their velocity. There is strong cumulative evidence that all such particles possess the same charge, which is identical with that associated with a univalent atom in electrolytic liquids. The number of unknown quantities was thus reduced to two--the mass and the velocity. The measurement of the magnetic and electric deflections gave two independent relations between the unknowns, which could therefore be determined. The velocities of the cathode ray particles were found to vary round a value about one-tenth that of light, but the mass was found always to be the same within the limits of error, whatever the nature of the terminals, of the residual gas in the vessel, and of the conditions of the experiment. The mass of a cathode ray particle, or corpuscle, as Thomson, adopting Newton's name, called it, is about the eight-hundredth part of the mass of a hydrogen atom.

These corpuscles, found in so many different kinds of substance, are inevitably regarded as a common constituent of matter. They are associated each with a unit of negative electricity. Now electricity in motion possesses electromagnetic energy, and produces effects like those of mechanical inertia. In other words, an electric charge possesses mass, and there is evidence to show that the effective mass of a corpuscle increases as its velocity approaches that of light in the way it would do if all its mass were electromagnetic. We are led therefore to regard the corpuscle from one aspect as a disembodied charge of electricity, and to identify it with the electron of Lorentz and Larmor.

Thus, on this theory, matter and electricity are identified; and a great simplification of our conception of the physical structure of Nature is reached. Moreover, from our present point of view, a common basis for matter suggests or implies a common origin, and a process of development possibly intelligible to our minds. The idea of the evolution of matter becomes much more probable.

The question of the nature and physical meaning of a corpuscle or electron remains for consideration. On the hypothesis of a universal luminiferous aether, Larmor has suggested a centre of aethereal strain "a place where the continuity of the medium has been broken and cemented together again (to use a crude but effective image) without accurately fitting the parts, so that there is a residual strain all round the place." (Larmor, loc. cit.) Thus he explains in quasi-mechanical terms the properties of an electron. But whether we remain content for the time with our identification of matter and electricity, or attempt to express both of them in terms of hypothetical aether, we have made a great step in advance on the view that matter is made up of chemical atoms fundamentally distinct and eternally isolated.

Such was the position when the phenomena of radio-activity threw a new light on the problem, and, for the first time in the history of science, gave definite experimental evidence of the transmutation of matter from one chemical element to another.

In 1896 H. Becquerel discovered that compounds of the metal uranium continually emitted rays capable of penetrating opaque screens and affecting photographic plates. Like cathode and Rontgen rays, the rays from uranium make the air through which they pass a conductor of electricity, and this property gives the most convenient method of detecting the rays and of measuring their intensity. An electroscope may be made of a strip of gold-leaf attached to an insulated brass plate and confined in a brass vessel with glass windows. When the gold-leaf is electrified, it is repelled from the similarly electrified brass plate, and the angle at which it stands out measures the electrification. Such a system, if well insulated, holds its charge for hours, the leakage of electricity through the air being very slow. But, if radio-active radiation reach the air within, the gold-leaf falls, and the rate of its fall, as watched through a microscope with a scale in the eye-piece, measures the intensity of the radiation. With some form of this simple instrument, or with the more complicated quadrant electrometer, most radio-active measurements have been made.

It was soon discovered that the activity of uranium compounds was proportional to the amount of uranium present in them. Thus radio-activity is an atomic property dependent on the amount of an element and independent of its state of chemical combination.

In a search for radio-activity in different minerals, M. and Mme Curie found a greater effect in pitch-blende than its contents of uranium warranted, and, led by the radio-active property alone, they succeeded, by a long series of chemical separations, in isolating compounds of a new and intensely radio-active substance which they named radium.

Radium resembles barium in its chemical properties, and is precipitated with barium in the ordinary course of chemical analysis. It is separated by a prolonged course of successive crystallisation, the chloride of radium being less soluble than that of barium, and therefore sooner separated from an evaporating solution. When isolated, radium chloride has a composition, which, on the assumption that one atom of metal combines with two of chlorine as in barium chloride, indicates that the relative weight of the atom of radium is about 225. As thus prepared, radium is a well-marked chemical element, forming a series of compounds analogous to those of barium and showing a characteristic line spectrum. But, unlike most other chemical elements, it is intensely radio-active, and produces effects some two million times greater than those of uranium.

In 1899 E. Rutherford, then of Montreal, discovered that the radiation from uranium, thorium and radium was complex. (Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905.) Three types of rays were soon distinguished. The first, named by Rutherford alpha-rays, are absorbed by thin metal foil or a few centimetres of air. When examined by measurements of the deflections caused by magnetic and electric fields, the alpha-rays are found to behave as would positively electrified particles of the magnitude of helium atoms possessing a double ionic charge and travelling with a velocity about one-tenth that of light. The second or beta type of radiation is much more penetrating. It will pass through a considerable thickness of metallic foil, or many centimetres of air, and still affect photographic plates or discharge electroscopes. Magnetic and electric forces deflect beta-rays much more than alpha-rays, indicating that, although the speed is greater, approaching in some cases within five per cent. that of light, the mass is very much less. The beta-rays must be streams of particles, identical with those of cathode rays, possessing the minute mass of J.J. Thomson's corpuscle, some eight-hundredth part of that of a hydrogen atom. A third or gamma type of radiation was also detected. More penetrating even than beta-rays, the gamma-rays have never been deflected by any magnetic or electric force yet applied. Like Rontgen rays, it is probable that gamma-rays are wave-pulses in the luminiferous aether, though the possibility of explaining them as flights of non-electrified particles is before the minds of some physicists.

Still another kind of radiation has been discovered more recently by Thomson, who has found that in high vacua, rays become apparent which are absorbed at once by air at any ordinary pressure.

The emission of all these different types of radiation involves a continual drain of energy from the radio-active body. When M. and Mme Curie had prepared as much as a gramme of radium chloride, the energy of the radiation became apparent as an evolution of heat. The radium salt itself, and the case containing it, absorbed the major part of the radiation, and were thus maintained at a temperature measurably higher than that of the surroundings. The rate of thermal evolution was such that it appeared that one gramme of pure radium must emit about 100 gramme-calories of heat in an hour. This observation, naturally as it follows from the phenomena previously discovered, first called attention to the question of the source of the energy which maintains indefinitely and without apparent diminution the wonderful stream of radiation proceeding from a radio-active substance. In the solution of this problem lies the point of the present essay.

In order to appreciate the evidence which bears on the question we must now describe two other series of phenomena.

It is a remarkable fact that the intensity of the radiation from a radio-active body is independent of the external conditions of temperature, pressure, etc. which modify so profoundly almost all other physical and chemical processes. Exposure to the extreme cold of liquid air, or to the great heat of a furnace, leaves the radio-activity of a substance unchanged, apparent exceptions to this statement having been traced to secondary causes.

Then, it is found that radio-activity is always accompanied by some chemical change; a new substance always appears as the parent substance emits these radiations. Thus by chemical reactions it is possible to separate from uranium and thorium minute quantities of radio-active materials to which the names of uranium-X and thorium-X have been given. These bodies behave differently from their parents uranium and thorium, and show all the signs of distinct chemical individuality. They are strongly radio-active, while, after the separation, the parents uranium and thorium are found to have lost some of their radio-activity. If the X-substances be kept, their radio-activity decays, while that of the uranium or thorium from which they were obtained gradually rises to the initial value it had before the separation. At any moment, the sum of the radio-activity is constant, the activity lost by the product being equal to that gained by the parent substance. These phenomena are explained if we suppose that the X-product is slowly produced in the substance of the parent, and decays at a constant rate. Uranium, as usually seen, contains a certain amount of uranium-X, and its radio-activity consists of two parts--that of the uranium itself, and that of the X product. When the latter is separated by means of its chemical reactions, its radio-activity is separated also, and the rates of decay and recovery may be examined.

Radium and thorium, but not uranium, give rise to radio-active gases which have been called emanations. Rutherford has shown that their radio-activity, like that of the X products, suffers decay, while the walls of the vessel in which the emanation is confined, become themselves radio-active. If washed with certain acids, however, the walls lose their activity, which is transferred to the acid, and can be deposited by evaporation from it on to a solid surface. Here again it is clear that the emanation gives rise to a radio-active substance which clings to the walls of the vessel, and is soluble in certain liquids, but not in others.

We shall return to this point, and trace farther the history of the radio-active matter. At present we wish to emphasise the fact that, as in other cases, the radio-activity of the emanation is accompanied by the appearance of a new kind of substance with distinct chemical properties.

We are now in a position to consider as a whole the evidence on the question of the source of radio-active energy.

(1) Radio-activity is accompanied by the appearance of new chemical substances. The energy liberated is therefore probably due to the associated chemical change. (2) The activity of a series of compounds is found to accompany the presence of a radio-active element, the activity of each compound depends only on the contents of the element, and is independent of the nature of its combination. Thus radio-activity is a property of the element, and is not affected by its state of isolation or chemical combination. (3) The radio-activity of a simple transient product decays in a geometrical progression, the loss per second being proportional to the mass of substance still left at the moment, and independent of its state of concentration or dilution. This type of reaction is well known in chemistry to mark a mono-molecular change, where each molecule is dissociated or altered in structure independently. If two or more molecules were concerned simultaneously, the rate of reaction would depend on the nearness of the molecules to each other, that is, to the concentration of the material. (4) The amount of energy liberated by the change of a given mass of material far transcends the amount set free by any known ordinary chemical action. The activity of radium decays so slowly that it would not sink to half its initial value in less than some two thousand years, and yet one gramme of radium emits about 100 calories of heat during each hour of its existence.

The energy of radio-activity is due to chemical change, but clearly to no chemical change hitherto familiar to science. It is an atomic property, characteristic of a given element, and the atoms undergo the change individually, not by means of interaction among each other. The conclusion is irresistible that we are dealing with a fundamental change in the structure of the individual atoms, which, one by one, are dissociating into simpler parts. We are watching the disintegration of the "atoms" of the chemist, hitherto believed indestructible and eternal, and measuring the liberation of some of the long-suspected store of internal atomic energy. We have stumbled on the transmutation dreamed by the alchemist, and discovered the process of a veritable evolution of matter.

The transmutation theory of radio-activity was formulated by Rutherford (Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.) and Soddy in 1903. By its light, all recent work on the subject has been guided; it has stood the supreme test of a hypothesis, and shown power to suggest new investigations and to co-ordinate and explain them, when carried out. We have summarised the evidence which led to the conception of the theory; we have now to consider the progress which has been made in tracing the successive disintegration of radio-active atoms.

Soon after the statement of the transmutation theory, a striking verification of one of its consequences appeared. The measurement of the magnetic and electric deflection of the alpha-rays suggested to Rutherford the idea that the stream of projectiles of which they consisted was a flight of helium atoms. Ramsay and Soddy, confining a minute bubble of radium emanation in a fine glass tube, were able to watch the development of the helium spectrum as, day by day, the emanation decayed. By isolating a very narrow pencil of alpha-rays, and watching through a microscope their impact on a fluorescent screen, Rutherford has lately counted the individual alpha-projectiles, and confirmed his original conclusion that their mass corresponded to that of helium atoms and their charge to double that on a univalent atom. ("Proc. Roy. Soc." A, page 141, 1908.) Still more recently, he has collected the alpha-particles shot through an extremely thin wall of glass, and demonstrated by direct spectroscopic evidence the presence of helium. ("Phil. Mag." February 1909.)

But the most thorough investigation of a radio-active pedigree is found in Rutherford's classical researches on the successive disintegration products of radium, in order to follow the evidence on which his results are founded, we must describe more fully the process of decay of the activity of a simple radio-active substance. The decay of activity of the body known as uranium-X is shown in a falling curve (Fig. 1.). It will be seen that, in each successive 22 days, the activity falls to half the value it possessed at the beginning.

This change in a geometrical progression is characteristic of simple radio-active processes, and can be expressed mathematically by a simple exponential formula.

As we have said above, solid bodies exposed to the emanations of radium or thorium become coated with a radio-active deposit. The rate of decay of this activity depends on the time of exposure to the emanation, and does not always show the usual simple type of curve. Thus the activity of a rod exposed to radium emanation for 1 minute decays in accordance with a curve (Fig. 2) which represents the activity as measured by the alpha-rays. If the electroscope be screened from the alpha-rays, it is found that the activity of the rod in beta- an gamma-rays increases for some 35 minutes and then diminishes (Fig. 3.).

These complicated relations have been explained satisfactorily and completely by Rutherford on the hypothesis of successive changes of the radio-active matter into one new body after another. (Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 379.) The experimental curve represents the resultant activity of all the matter present at a given moment, and the process of disentangling the component effects consists in finding a number of curves, which express the rise and fall of activity of each kind of matter as it is produced and decays, and, fitted together, give the curve of the experiments.

Other methods of investigation also are open. They have enabled Rutherford to complete the life-history of radium and its products, and to clear up doubtful points left by the analysis of the curves. By the removal of the emanation, the activity of radium itself has been shown to consist solely of alpha-rays. This removal can be effected by passing air through the solution of a radium salt. The emanation comes away, and the activity of the deposit which it leaves behind decays rapidly to a small fraction of its initial value. Again, some of the active deposits of the emanation are more volatile than others, and can be separated from them by the agency of heat.

From such evidence Rutherford has traced a long series of disintegration products of radium, all but the first of which exist in much too minute quantities to be detected otherwise than by their radio-activities. Moreover, two of these products are not themselves appreciably radio-active, though they are born from radio-active parents, and give rise to a series of radio-active descendants. Their presence is inferred from such evidence as the rise of beta and gamma radio-activity in the solid newly deposited by the emanation; this rise measuring the growth of the first radio-active offspring of one of the non-active bodies. Some of the radium products give out alpha-rays only, one beta- and gamma-rays, while one yields all three types of radiation. The pedigree of the radium family may be expressed in the following table, the time noted in the second column being the time required for a given quantity to be half transformed into its next derivative.

Time of half Radio- Properties decay activity

Radium About 2600 years alpha rays Element chemically analogous to barium.

Emanation 3.8 days alpha rays Chemically inert gas; condenses at -150 deg C.

Radium-A 3 minutes alpha rays Behaves as a solid deposited on surfaces; concentrated on a negative electrode.

Radium-B 21 minutes no rays Soluble in strong acids; volatile at a white heat; more volatile than A or C.

Radium-C 28 minutes alpha, beta, Soluble in strong acids; less gamma rays volatile than B.

Radium-D about 40 years no rays Soluble in strong acids; volatile below 1000 deg C.

Radium-E 6 days beta, gamma Non-volatile at 1000 deg C. rays

Radium-F 143 days alpha rays Volatile at 1000 deg C. Deposited from solution on a bismuth plate.

Of these products, A, B, and C constitute that part of the active deposit of the emanation which suffers rapid decay and nearly disappears in a few hours. Radium-D, continually producing its short-lived descendants E and F, remains for years on surfaces once exposed to the emanation, and makes delicate radio-active researches impossible in laboratories which have been contaminated by an escape of radium emanation.

A somewhat similar pedigree has been made out in the case of thorium. Here thorium-X is interposed between thorium and its short-lived emanation, which decays to half its initial quantity in 54 seconds. Two active deposits, thorium A and B, arise successively from the emanation. In uranium, we have the one obvious derivative uranium-X, and the question remains whether this one descent can be connected with any other individual or family. Uranium is long-lived, and emits only alpha-rays. Uranium-X decays to half value in 22 days, giving out beta- and gamma-rays. Since our evidence goes to show that radio-activity is generally accompanied by the production of new elements, it is natural to search for the substance of uranium-X in other forms, and perhaps under other names, rather than to surrender immediately our belief in the conservation of matter.

With this idea in mind we see at once the significance of the constitution of uranium minerals. Formed in the remote antiquity of past geological ages, these minerals must become store-houses of all the products of uranium except those which may have escaped as gases or possibly liquids. Even gases may be expected to some extent to be retained by occlusion. Among the contents of uranium minerals, then, we may look for the descendants of the parent uranium. If the descendants are permanent or more long-lived than uranium, they will accumulate continually. If they are short-lived, they will accumulate at a steady rate till enough is formed for the quantity disintegrating to be equal to the quantity developed. A state of mobile equilibrium will then be reached, and the amount of the product will remain constant. This constant amount of substance will depend only on the amount of uranium which is its source, and, for different minerals, if all the product is retained, the quantity of the product will be proportional to the quantity of uranium. In a series of analyses of uranium minerals, therefore, we ought to be able to pick out its more short-lived descendants by seeking for instances of such proportionality.

Now radium itself is a constituent of uranium minerals, and two series of experiments by R.J. Strutt and B.B. Boltwood have shown that the content of radium, as measured by the radio-activity of the emanation, is directly proportional to the content of uranium. (Strutt, "Proc. Roy. Soc." A, February 1905; Boltwood, "Phil. Mag." April, 1905.) In Boltwood's investigation, some twenty minerals, with amounts of uranium varying from that in a specimen of uraninite with 74.65 per cent., to that in a monazite with 0.30 per cent., gave a ratio of uranium to radium, constant within about one part in ten.

The conclusion is irresistible that radium is a descendant of uranium, though whether uranium is its parent or a more remote ancestor requires further investigation by the radio-active genealogist. On the hypothesis of direct parentage, it is easy to calculate that the amount of radium produced in a month by a kilogramme of a uranium salt would be enough to be detected easily by the radio-activity of its emanation. The investigation has been attempted by several observers, and the results, especially those of a careful experiment of Boltwood, show that from purified uranium salts the growth of radium, if appreciable at all, is much less than would be found if the radium was the first product of change of the uranium. It is necessary, therefore, to look for one or more intermediate substances.

While working in 1899 with the uranium residues used by M. and Mme Curie for the preparation of radium, Debierne discovered and partially separated another radio-active element which he called actinium. It gives rise to an intermediate product actinium-X, which yields an emanation with the short half-life of 3.9 seconds. The emanation deposits two successive disintegration products actinium-A and actinium-B.

Evidence gradually accumulated that the amounts of actinium in radio-active minerals were, roughly at any rate, proportional to the amounts of uranium. This result pointed to a lineal connection between them, and led Boltwood to undertake a direct attack on the problem. Separating a quantity of actinium from a kilogramme of ore, Boltwood observed a growth of 8.5 x (10 to the power -9) gramme of radium in 193 days, agreeing with that indicated by theory within the limits of experimental error. ("American Journal of Science", December, 1906.) We may therefore insert provisionally actinium and its series of derivatives between uranium and radium in the radio-active pedigree.

Turning to the other end of the radium series we are led to ask what becomes of radium-F when in turn it disintegrates? What is the final non-active product of the series of changes we have traced from uranium through actinium and radium?

One such product has been indicated above. The alpha-ray particles appear to possess the mass of helium atoms, and the growth of helium has been detected by its spectrum in a tube of radium emanation. Moreover, helium is found occluded in most if not all radio-active minerals in amount which approaches, but never exceeds, the quantity suggested by theory. We may safely regard such helium as formed by the accumulation of alpha-ray particles given out by successive radio-active changes.

In considering the nature of the residue left after the expulsion of the five alpha-particles, and the consequent passage of radium to radium-F we are faced by the fact that lead is a general constituent of uranium minerals. Five alpha-particles, each of atomic weight 4, taken from the atomic weight (about 225) of radium gives 205--a number agreeing fairly well with the 207 of lead. Since lead is more permanent than uranium, it must steadily accumulate, no radio-active equilibrium will be reached, and the amount of lead will depend on the age of the mineral as well as on the quantity of uranium present in it. In primary minerals from the same locality, Boltwood has shown that the contents of lead are proportional to the amounts of uranium, while, accepting this theory, the age of minerals with a given content of uranium may be calculated from the amount of lead they contain. The results vary from 400 to 2000 million years. ("American Journal of Science", October, 1905, and February, 1907.)

We can now exhibit in tabular form the amazing pedigree of radio-active change shown by this one family of elements. An immediate descent is indicated by >, while one which may either be immediate or involve an intermediate step is shown by.... No place is found in this pedigree for thorium and its derivatives. They seem to form a separate and independent radio-active family.

Atomic Weight Time of half Radio-Activity decay

Uranium 238.5 alpha

Uranium-X ? 22 days beta, gamma ... Actinium ? ? no rays

Actinium-X ? 10.2 days alpha (beta, gamma)

Actinium Emanation ? 3.9 seconds alpha

Actinium-A ? 35.7 minutes no rays

Actinium-B ? 2.15 minutes alpha, beta, gamma ... Radium 225 about 2600 years alpha

Radium Emanation ? 3.8 days alpha

Radium-A ? 3 minutes alpha

Radium-B ? 21 minutes no rays

Radium-C ? 28 minutes alpha, beta, gamma

Radium-D ? about 40 years no rays

Radium-E ? 6 days beta (gamma)

Radium-F ? 143 days alpha ... Lead 207 ? no rays

As soon as the transmutation theory of radio-activity was accepted, it became natural to speculate about the intimate structure of the radio-active atoms, and the mode in which they broke up with the liberation of some of their store of internal energy. How could we imagine an atomic structure which would persist unchanged for long periods of time, and yet eventually spontaneously explode, as here an atom and there an atom reached a condition of instability?

The atomic theory of corpuscles or electrons fortunately was ready to be applied to this new problem. Of the resulting speculations the most detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March, 1904.) Thomson regards the atom as composed of a number of mutually repelling negative corpuscles or electrons held together by some central attractive force which he represents by supposing them immersed in a uniform sphere of positive electricity. Under the action of the two forces, the electrons space themselves in symmetrical patterns, which depend on the number of electrons. Three place themselves at the corner of an equilateral triangle, four at those of a square, and five form a pentagon. With six, however, the single ring becomes unstable, one corpuscle moves to the middle and five lie round it. But if we imagine the system rapidly to rotate, the centrifugal force would enable the six corpuscles to remain in a single ring. Thus internal kinetic energy would maintain a configuration which would become unstable as the energy drained away. Now in a system of electrons, electromagnetic radiation would result in a loss of energy, and at one point of instability we might well have a sudden spontaneous redistribution of the constituents, taking place with an explosive violence, and accompanied by the ejection of a corpuscle as a beta-ray, or of a large fragment of the atom as an alpha-ray.

The discovery of the new property of radio-activity in a small number of chemical elements led physicists to ask whether the property might not be found in other elements, though in a much less striking form. Are ordinary materials slightly radio-active? Does the feeble electric conductivity always observed in the air contained within the walls of an electroscope depend on ionizing radiations from the material of the walls themselves? The question is very difficult, owing to the wide distribution of slight traces of radium. Contact with radium emanation results in a deposit of the fatal radium-D, which in 40 years is but half removed. Is the "natural" leak of a brass electroscope due to an intrinsic radio-activity of brass, or to traces of a radio-active impurity on its surface? Long and laborious researches have succeeded in establishing the existence of slight intrinsic radio-activity in a few metals such as potassium, and have left the wider problem still unsolved.

It should be noted, however, that, even if ordinary elements are not radio-active, they may still be undergoing spontaneous disintegration. The detection of ray-less changes by Rutherford, when those changes are interposed between two radio-active transformations which can be followed, show that spontaneous transmutation is possible without measureable radio-activity. And, indeed, any theory of disintegration, such as Thomson's corpuscular hypothesis, would suggest that atomic rearrangements are of much more general occurrence than would be apparent to one who could observe them only by the effect of the projectiles, which, in special cases, owing to some peculiarity of atomic configuration, happened to be shot out with the enormous velocity needed to ionize the surrounding gas. No evidence for such ray-less changes in ordinary elements is yet known, perhaps none may ever be obtained; but the possibility should not be forgotten.

In the strict sense of the word, the process of atomic disintegration revealed to us by the new science of radio-activity can hardly be called evolution. In each case radio-active change involves the breaking up of a heavier, more complex atom into lighter and simpler fragments. Are we to regard this process as characteristic of the tendencies in accord with which the universe has reached its present state, and is passing to its unknown future? Or have we chanced upon an eddy in a backwater, opposed to the main stream of advance? In the chaos from which the present universe developed, was matter composed of large highly complex atoms, which have formed the simpler elements by radio-active or ray-less disintegration? Or did the primaeval substance consist of isolated electrons, which have slowly come together to form the elements, and yet have left here and there an anomaly such as that illustrated by the unstable family of uranium and radium, or by some such course are returning to their state of primaeval simplicity?

INDEX.

Abraxas grossulariata.

Acquired characters, transmission of.

Acraea johnstoni.

Adaptation.

Adloff.

Adlumia cirrhosa.

Agassiz, A.

Agassiz, L.

Alexander.

Allen, C.A.

Alternation of generations.

Ameghino.

Ammon, O., Works of.

Ammonites, Descent of.

Amphidesmus analis.

Anaea divina.

Andrews, C.W.

Angiosperms, evolution of.

Anglicus, Bartholomaeus.

Ankyroderma.

Anomma.

Antedon rosacea.

Antennularia antennina.

Anthropops.

Ants, modifications of.

Arber, E.A.N.,--and J. Parkin, on the origin of Angiosperms.

Archaeopteryx.

Arctic regions, velocity of development of life in.

Ardigo.

Argelander.

Argyll, Huxley and the Duke of.

Aristotle.

Arrhenius.

Asterias, Loeb on hybridisation of.

Autogamy.

Avena fatua.

Avenarius.

Bacon, on mutability of species.

Baehr, von, on Cytology.

Baer, law of von.

Bain.

Baldwin, J.M.

Balfour, A.J.

Ball, J.

Barber, Mrs M.E., on Papilio nireus.

Barclay, W.

Barratt.

Bary, de.

Bates, H.W., on Mimicry.--Letters from Darwin to.--elsewhere.

Bateson, A.

BATESON, W., on "Heredity and Variation in Modern lights".--on discontinuous evolution.--on hybridisation.

Bateson, W. and R.P. Gregory.

Bathmism.

Beche, de la.

Beck, P.

Becquerel, H.

Beebe, C.W., on the plumage of birds.--on sexual selection.

Beguyer de Chancourtois.

Bell's (Sir Charles) "Anatomy of Expression".

Belopolsky.

Belt, T., on Mimicry.

Beneden, E. van.

Benson, M.

Bentham, G., on Darwin's species-theory.--on geographical distribution.

Bentham, Jeremy.

Bergson, H.

Berkeley.

Berthelot.

Betham, Sir W.

Bickford, E., experiments on degeneration by.

Bignonia capreolata.

Biophores.

Birds, geological history of.

Blanford, W.T.

Blaringhem, on wounding.

Blumenbach.

Bodin.

Boltwood, B.B.

Bonald, on war.

Bonnet.

Bonney, T.G.

Bonnier, G.

Bopp, F., on language.

BOUGLE C., on "Darwinism and Sociology".

Bourdeau.

Bourget, P.

Boutroux.

Boveri, T.

Brachiopods, history of.

Brassica, hybrids of.

Brassica Napus.

Broca.

Brock, on Kant.

Brown, Robert.

Brugmann and Osthoff.

Brugmann.

Brunetiere.

Bruno, on Evolution.

Buch, von.

Bucher, K.

Buckland.

Buckle.

Buffon.

Burchell, W.J.

Burck, W.

Burdon-Sanderson, J., letter from.

BURY, J.B., on "Darwinism and History".

Butler, A.G.

Butler, Samuel.

Butschli, O.

Butterflies, mimicry in.--sexual characters in.

Cabanis.

Campbell.

Camels, geological history of.

Camerarius, R.J.

Candolle, A. de.

Cannon and Davenport, experiments on Daphniae by.

Capsella bursapastoris.

Carneri.

Castnia linus.

Catasetum barbatum.

Catasetum tridentatum.

Caterpillars, variation in.

Celosia, variability of.

Cereals, variability in.

Cesnola, experiments on Mantis by.

Chaerocampa, colouring of.

Chambers, R., "The Vestiges of Creation" by.

Chromosomes and Chromomeres.

Chun.

Cieslar, experiments by.

Circumnutation, Darwin on.

Claus.

Cleistogamy.

Clerke, Miss A.

Clodd, E.

Cluer.

Clytus arietis.

Coadaptation.

Codrington.

Cohen and Peter.

Collingwood.

Colobopsis truncata.

Colour, E.B. Poulton on The Value in the Struggle for life of.--influence and temperature on changes in.--in relation to Sexual Selection.

Colours, incidental.--warning.

Comte, A.

Condorcet.

Cope.

Coral reefs, Darwin's work on.

Correlation of organisms, Darwin's idea of the.

Correlation of parts.

Corydalis claviculata.

Cournot.

Couteur, Col. Le.

Crooks, Sir William.

Cruger, on Orchids.

Cunningham and Marchand, on the brain.

Curie, M. and Mme.

Cuvier.

Cycadeoidea dacotensis.

Cycads, geological history of.

Cystidea, an ancient group.

Cytology and heredity.

Cytolysis and fertilisation.

Czapek.

Dalton's atomic theory.

Dana, J.D., on marine faunas.

Danaida chrysippus.

Danaida genutia.

Danaida plexippus.

Dante.

Dantec, Le,

Darwin, Charles, as an Anthropologist.--on ants.--and the "Beagle" Voyage.--on the Biology of Flowers.--as a Botanist.--his influence on Botany.--and S. Butler.--at Cambridge.--on Cirripedia.--on climbing plants.--on colour.--on coral reefs.--on the Descent of Man.--his work on Drosera.--at Edinburgh.--his influence on Animal Embryology.--on Geographical Distribution.--his work on Earthworms.--evolutionist authors referred to in the "Origin" by.--and E. Forbes.--on the geological record.--and Geology.--his early love for geology.--his connection with the Geological Society of London.--and Haeckel.--and Henslow.--and History.--and Hooker.--and Huxley.--on ice-action.--on igneous rocks.--on Lamarck.--on Language.--his Scientific Library.--and the Linnean Society.--and Lyell.--and Malthus.--on Patrick Matthew.--on mental evolution.--on Mimicry.--a "Monistic Philosopher."--on the movements of plants.--on Natural Selection.--a "Naturalist for Naturalists."--on Paley.

Darwin, Charles, his Pangenesis hypothesis.--on the permanence of continents.--his personality.--his influence on Philosophy.--predecessors of.--his views on religion, etc.--his influence on religious thought.--his influence on the study of religions.--his methods of research.--and Sedgwick.--on Sexual Selection.--the first germ of his species theory.--on H. Spencer.--causes of his success.--on Variation.--on the "Vestiges of Creation".--on volcanic islands.--and Wallace.--letter to Wallace from.--letter to E.B. Wilson from.

Darwin, E., on the colour of animals.--Charles Darwin's reference to.--on evolution.

DARWIN, F., on "Darwin's work on the Movements of Plants".--on Darwin as a botanist.--observations on Earthworms by.--on Lamarckism.--on Memory.--on Prichard's "Anticipations".--various.

DARWIN, SIR G., on "The Genesis of Double Stars".--on the earth's mass.

Darwin, H.

Darwin, W.

Darwinism, Sociology, Evolution and.

Davenport and Cannon, experiments on Daphniae by.

David, T.E., his work on Funafuti.

Death, cause of natural.

Debey, on Cretaceous plants.

Debierne.

Degeneration.

Delage, experiments on parthenogenesis by.

Delbruck.

Democritus.

Deniker.

Descartes.

Descent, history of doctrine of.

"Descent of Man", G. Schwalbe on "The".--Darwin on Sexual Selection in "The".--rejection in Germany of "The".

Desmatippus.

Desmoulins, A., on Geographical Distribution.

Detto.

Development, effect of environment on.

Dianthus caryophyllus.

Diderot.

Digitalis purpurea.

Dimorphism, seasonal.

Dismorphia astynome.

Dismorphia orise.

Distribution, H. Gadow on Geographical.--Sir W. Thiselton-Dyer on.

Dittrick, O.

Dixey, F.A., on the scent of Butterflies.

Dolichonyx oryzivorus.

Dorfmeister.

Down, Darwin at.

Draba verna.

Dragomirov.

Driesch, experiments by.--elsewhere.

Drosera, Darwin's work on.

Dryopithecus.

Dubois, E., on Pithecanthropus.

Duhring.

Duhamel.

Duncan, J.S.

Duncan, P.B.

Duns Scotus.

Duret, C.

Durkheim, on division of labour.

Dutrochet.

Echinoderms, ancestry of.

Ecology.

Eimer.

Ekstam.

Elephants, geological history of.

Elymnias phegea.

E. undularis.

Embleton, A.L.

Embryology, A. Sedgwick on the influence of Darwin on.

Embryology, as a clue to Phylogeny.--the Origin of Species and.

Empedocles.

Engles.

Environment, action of.--Klebs on the influence on plants of.--Loeb on experimental study in relation to.

Eohippus.

Epicurus, a poet of Evolution.

Eristalis.

Ernst.

Ernst, A., on the Flora of Krakatau.

Eschscholzia californica.

Espinas.

Eudendrium racemosum.

Evolution, in relation to Astronomy.--and creation.--conception of.--discontinuous.--experimental.--factors of.--fossil plants as evidence of.--and language.--of matter, W.C.D. Whetham on.--mental.--Lloyd Morgan on mental factors in.--Darwinism and Social.--Saltatory.--Herbert Spencer on.--Uniformitarian.--Philosophers and modern methods of studying.

Expression of the Emotions.

Fabricius, J.C., on geographical distribution.

Farmer, J.B.

Farrer, Lord.

Fearnsides, W.G.

Felton, S., on protective resemblance.

Ferri.

Ferrier, his work on the brain.

Fertilisation, experimental work on animal-.

Fertilisation of Flowers.

Fichte.

Field, Admiral A.M.

Fischer, experiments on Butterflies by.

Fitting.

Flemming, W.

Flourens.

Flowering plants, ancestry of.

Flowers, K. Goebel on the Biology of.

Flowers and Insects.

Flowers, relation of external influences to the production of.

Fol, H.

Forbes, E.--and C. Darwin.

Ford, S.O. and A.C. Seward, on the Araucarieae.

Fossil Animals, W.B. Scott on their bearing on evolution.

Fossil Plants, D.H. Scott on their bearing on evolution.

Fouillee.

Fraipont, on skulls from Spy.

FRAZER, J.G., on "Some Primitive Theories of the Origin of Man".--various.

Fruwirth.

Fumaria officinalis.

Funafuti, coral atoll of.

Fundulus.

F. heteroclitus.

GADOW, H., on "Geographical Distribution of Animals".--elsewhere.

Gartner, K.F.

Gallus bankiva.

Galton, F.

Gamble, F.W. and F.W. Keeble.

Gasca, La.

Geddes, P.

Geddes, P. and A.W. Thomson.

Gegenbauer.

Geikie, Sir A.

Geitonogamy.

Genetics.

Geographical Distribution of Animals.--of Plants.--influence of "The Origin of Species" on.--Wallace's contribution to.

Geography of former periods, reconstruction of.

Geology, Darwin and.

Geranium spinosum.

Germ-plasm, continuity of.--Weismann on.

Germinal Selection.

Gibbon.

Gilbert.

GILES, P., on "Evolution and the Science of Language".

Giuffrida-Ruggeri.

Giotto.

Gizycki.

Glossopteris Flora.

Gmelin.

Godlewski, on hybridisation.

GOEBEL, K., on "The Biology of Flowers".--his work on Morphology.

Goethe and Evolution.--on the relation between Man and Mammals.--elsewhere.

Goldfarb.

Gondwana Land.

Goodricke, J.

Gore, Dr.

Gorjanovic-Kramberger.

Gosse, P.H.

Grabau, A.W., on Fusus.

Grand'Eury, F.C., on fossil plants.

Grapta C. album.

Gravitation, effect on life-phenomena of.

Gray, Asa.

Gregoire, V.

Groom, T.T., on heliotropism.

Groos.

Grunbaum, on the brain.

Guignard, L.

Gulick.

Guppy, on plant-distribution.

Guyau.

Gwynne-Vaughan, D.T., on Osmundaceae.

Gymnadenia conopsea.

Haberlandt, G.

Haddon, A.C.

HAECKEL, E., on "Charles Darwin as an Anthropologist".--on Colour.--and Darwin.--on the Descent of Man.--contributions to Evolution by.

Haeckel, E., on Lamarck.--on Language.--a leader in the Darwinian controversy.--on Lyell's influence on Darwin.--various.

Hacker.

Hagedoorn, on hybridisation.

Hales, S.

Hansen.

Harker, A.

HARRISON, J.E., on "The Influence of Darwinism on the Study of Religions".

Hartmann, von.

Harvey.

Haupt, P., on Language.

Haycraft.

Hays, W.M.

Hegel.

Heliconius narcaea.

Heliotropism in animals.

Henslow, Rev. J.S. and Darwin.

Hensen, Van.

Herbst, his experiments on sea urchins.

Heracleitus.

Herder.

Heredity and Cytology.--Haeckel on.--and Variation.--various.

Hering, E., on Memory.

Herschel, J.

Hertwig, R.

Hertwig, O.

Hertz.

Heteromorphosis.

Heterostylism.

Heuser, E.

Hewitt.

Heyse's theory of language.

Hinde, G.J., his work on Funafuti.

Hipparion.

Hippolyte cranchii.

Hirase.

History, Darwin and.

Hobbes, T.

Hobhouse.

HOFFDING, H., on "The Influence of the Conception of Evolution on Modern Philosophy".

Hofmeister, W.

Holmes, S.J., on Arthropods.

Holothurians, calcareous bodies in skin of.

Homo heidelbergensis.

Homo neandertalensis.

Homo pampaeus.

Homo primigenius.

Homunculus.

Hooker, Sir J.D., and Darwin.--on Distribution of Plants.--on Ferns.--Letter to the Editor from.

Horner, L.

Horse, Geological history of the.

Huber.

Hubert and Mauss.

Hubrecht, A.R.W.

Hugel, F. von.

Humboldt, A. von.

Humboldt, W. von.

Hume.

Hutcheson.

Hutton.

Huxley, T.H., and Darwin.--and the Duke of Argyll.--on Embryology.--on Geographical Distribution.--on Lamarck.--Letter to J.W. Judd from.--on Lyell.--on Man.--on "The Origin of Species".--on Selection.--on Teleology.--on transmission of acquired characters.--various.

Hybridisation.

Hybrids, Sterility of.

Hyracodon.

Iberis umbellata.

Ikeno.

Imperfection of the Geological Record.

Ingenhousz, on plant physiology.

Inheritance of acquired characters.

Insects and Flowers.

Instinct.

Instincts, experimental control of animal.

Ipomaea purpurea.

Irish Elk, an example of co-adaptation.

Jacobian figures.

Jacoby, "Studies in Selection" by.

James, W.

Janczewski.

Jeans, J.H.

Jennings, H.S., on Paramoecium.

Jentsch.

Jespersen, Prof., Theory of.

Johannsen, on Species.

Jones, Sir William, on Language.

Jordan.

JUDD, J.W., on "Darwin and Geology".

Kallima, protective colouring of.

Kallima inachis.

Kammerer's experiments on Salamanders.

Kant, I.

Keane, on the Primates.

Keeble, F.W. and F.W. Gamble, on Colour-change.

Keith, on Anthropoid Apes.

Kellogg, V., on heliotropism.

Kepler.

Kerguelen Island.

Kidd.

Kidston, R., on fossil plants.

Killmann, on origin of human races.

King, Sir George.

Klaatsch, on Ancestry of Man.

Klaatsch and Hauser.

KLEBS, G., on "The influence of Environment on the forms of plants".

Kniep.

Knies.

Knight, A., experiments on plants by.--on Geotropism.

Knight-Darwin law.

Knuth.

Kolliker, his views on Evolution.

Kolreuter, J.G.

Kohl.

Korschinsky.

Kowalevsky, on fossil horses.

Krakatau, Ernst on the Flora of.

Krause, E.

Kreft, Dr.

Kropotkin.

Kupelwieser, on hybridisation.

Lagopus hyperboreus.

Lamarck, his division of the Animal Kingdom.--Darwin's opinion of.--on Evolution.--on Man.--various.

Lamarckian principle.

Lamb, C.

Lamettrie.

Lamprecht.

Lanessan, J.L. de.

Lang.

Lange.

Language, Darwin on.--Evolution and the Science of.--various.

Lankester, Sir E. Ray, on degeneration.--on educability.--on the germ-plasm theory.--elsewhere.

Lapouge, Vacher de.

Larmor, J.

Lartet, M.E.

Lassalle.

Lathyrus odoratus.

Lavelaye, de.

Lawrence, W.

Lehmann.

Lehmann-Nitsche.

Leibnitz.

Lepidium Draba.

Lepidoptera, variation in.

Leskien, A., on language.

Lessing.

Leucippus.

Levi, E.

Lewes, G.H.

Lewin, Capt.

Liapounoff.

Liddon, H.P.

Light, effect on organisms of.

Limenitis archippus.--arthemis.

Linnaeus.

Livingstone, on plant-forms.

Llamas, geological history of.

Lockyer, Sir N.

Locy, W.A.

LOEB, J., on "The Experimental Study of the influence of environment on Animals.

Loew, E.

Longstaff, G.B., on the Scents of Butterflies.

Lorentz.

Lotsy, J.P.

Love, A.E.W.

Lovejoy.

Lubbock.

Lucas, K.

Lucretius, a poet of Evolution.

Lumholtz, C.

Luteva macrophthalma.

Lycorea halia.

Lyell, Sir Charles, and Darwin.--the influence of.--on geographical distribution.--on "The Origin of Species".--on the permanence of Ocean-basins.--publication of the "Principles" by.--the uniformitarian teaching of.

Lythrum salicaria.

Macacus, ear of.

MacDougal, on wounding.

Mach, E.

Macromytis flexuosa, colour-change in.

Magic and religion.

Mahoudeau.

Maillet, de.

Majewski.

Malthus, his influence on Darwin.--various.

Mammalia, history of.

Man, Descent of.--J.G. Frazer on some primitive theories of the origin of.--mental and moral qualities of animals and.--pre-Darwinian views on the Descent of.--religious views of primitive.--Tertiary flints worked by.

"Man", G. Schwalbe on Darwin's "Descent of".

Manouvrier.

Mantis religiosa, colour experiments on.

Marett, R.R.

Markwick.

Marshall, G.A.K.

Marx.

Massart.

Masters, M.

Matonia pectinata.

Matthew, P., and Natural Selection.

Maupertuis.

Maurandia semperflorens.

Mauss and Herbert.

Mauthner.

Maxwell.

Maxwell, Clerk.

Mayer, R.

Mechanitis lysimnia.

Meehan, T.

Meldola, R., Letters from Darwin to.

Melinaea ethra.

Mendel.

Mendeleeff.

Merrifield.

Merz, J.T.

Mesembryanthemum truncatum.

Mesohippus.

Mesopithecus.

Metschnikoff.

Mill, J.S.

Mimicry.--H.W. Bates on.--F. Muller on.

Mimulus luteus.

Miquel, F.W.A.

Mobius.

Mohl, H. von.

Moltke, on war.

Monachanthus viridis.

Monkeys, fossil.

Montesquieu.

Montgomery, T.H.

Monstrosoties.

Monticelli.

Moore, J.E.S.

MORGAN, C. LLOYD, on "Mental Factors in Evolution".--on Organic Selection.

Morgan, T.H.

Morse, E.S., on colour.

Morselli.

Mortillet.

Moseley.

Mottier, M.

Muller, Fritz, "Fur Darwin" by.--on Mimicry.

Muller, Fritz.

Muller, J.

Muller, Max, on language.

Murray, A., on geographical distribution.

Murray, G.

Mutability.

Mutation.

Myanthus barbatus.

Myers, G.W., on Eclipses.

Nageli.

Nathorst, A.G.

Nathusius.

Natural Selection, and adaptation.--Darwin's views on.--Darwin and Wallace on.--and design.--and educability.--Fossil plants in relation to.--and human development.--and Mimicry.--and Mutability.--various.

Naudin.

Neandertal skulls.

Nemec.

Neoclytus curvatus.

Neodarwinism.

Neumayr, M.

Newton, A.

Newton, I.

Niebuhr.

Nietzsche.

Nilsson, on cereals.

Nitsche.

Noire.

Noll.

Novicow.

Nuclear division.

Nussbaum, M.

Nuttall, G.H.F.

Occam.

Odin.

Oecology, see Ecology.

Oenothera biennis.

Oenothera gigas.

Oenothera Lamarckiana.

Oenothera muricata.

Oenothera nanella.

Oestergren, on Holothurians.

Oken, L.

Oliver, F.W., on Palaeozoic Seeds.

Ononis minutissima.

Ophyrs apifera.

Orchids, Darwin's work on the fertilisation of.

Organic Selection.

"Origin of Species", first draft of the.--geological chapter in the.

Orthogenesis.

Ortmann, A.E.

Osborn, H.F.--"From the Greeks to Darwin" by.

Osthoff and Brugmann.

Ostwald, W.

Ovibos moschatus.

Owen, Sir Richard.

Oxford, Ashmolean Museum at.

Packard, A.S.

Palaeontological Record, D.H. Scott on the.--W.B. Scott on the.

Palaeopithecus.

Paley.

Palitzch, G.

Palm.

Pangenesis.

Panmixia, Weismann's principle of.

Papilio dardanus.

Papilio meriones.

Papilio merope.

Papilio nireus.

Paramoecium, Jennings on.

Parker, G.H., on Butterflies.

Parkin, J. and E.A.N. Arber, on the origin of Angiosperms.

Parthenogenesis, artificial.

Paul, H. and Wundt.

Pearson, K.

Peckham, Dr and Mrs, on the Attidae.

Penck.

Penzig.

Peripatus, distribution of.

Peridineae.

Permanence of continents.

Perrier, E.

Perrhybris pyrrha.

Perthes, B. de.

Peter, on sea urchin's eggs.

Petunia violacea.

Pfeffer, W.

Pfitzner, W.

Pflueger.

Phillips.

Philosophy, influence of the conception of evolution on modern.

Phryniscus nigricans.

Phylogeny, embryology as a clue to.--Palaeontological evidence on.

Physiology of plants, development of.

Piccard, on Geotropism.

Pickering, spectroscopic observations by.

Piranga erythromelas.

Pisum sativum.

Pithecanthropus.

Pitheculites.

Planema epaea.

Plants, Darwin's work on the movements of.--geographical distribution of.--Palaeontological record of fossil.

Platanthera bifolia.

Plate.

Plato.

Playfair.

Pliopithecus.

Pocock, R.I.

Poincare.

Polarity, Vochting on.

Polymorphic species.--variability in cereals.

Polypodium incanum.

Porthesia chrysorrhoea.

Potonie, R.

Pouchet, G.

POULTON, E.B., on "The Value of Colour in the Struggle for Life".--experiments on Butterflies by.--on J.C. Prichard.--on Mimicry.--various.

Pratt.

Pratz, du.

Premutation.

Preuss, K. Th.

Prichard, J.C.

Primula, heterostylism in.

Primula acaulis.

Primula elatior.

Primula officinalis.

Promeces viridis.

Pronuba yuccasella.

Protective resemblance.

Protocetus.

Protohippus.

Psychology.

Pteridophytes, history of.

Pteridospermeae.

Pucheran.

Pusey.

Quatrefages, A. de.

Quetelet, statistical investigations by.

Rabl, C.

Radio-activity.

Radiolarians.

Raimannia odorata.

Ramsay, Sir W. and Soddy.

Ranke.

Rau, A.

Ray, J.

Reade, Mellard.

Recapitulation, the theory of.

Reduction.

Regeneration.

Reid, C.

Reinke.

Religion, Darwin's attitude towards.--Darwin's influence on the study of.--and Magic.

Religious thought, Darwin's influence on.

Renard, on Darwin's work on volcanic islands.

Reproduction, effect of environment on.

Reptiles, history of.

Reversion.

Rhinoceros, the history of the.

Ridley, H.N.

Riley, C.V.

Ritchie.

Ritual.

Roberts, A.

Robertson, T.B.

Robinet.

Rolfe, R.A.

Rolph.

Romanes, G.J.

Rothert.

Roux.

Rozwadowski, von.

Ruskin.

Rutherford, E.

Rutot.

Sachs, J.

St Hilaire, E.G. de.

Salamandra atra.

Salamandra maculosa.

Saltatory Evolution, (see also Mutations).

Sanders, experiments on Vanessa by.

Saporta, on the Evolution of Angiosperms.

Sargant, Ethel, on the Evolution of Angiosperms.

Savigny.

Scardafella inca.

Scent, in relation to Sexual Selection.

Scharff, R.F.

Schelling.

Schlegel.

Schleicher, A., on language.

Schleiden and Schwann, Cell-theory of.

Schmarda, L.K., on geographical distribution.

Schoetensack, on Homo heidelbergensis.

Schreiner, K.E.

Schubler, on cereals.

Schultze, O., experiments on Frogs.

Schur.

Schutt.

SCHWALBE, G., on "The Descent of Man".

Sclater, P.L., on geographical distribution.

SCOTT, D.H., on "The Palaeontological Record (Plants)".--elsewhere.

SCOTT, W.B., on "The Palaeontological Record (Animals)".

Scrope.

Scyllaea.

Sechehaye, C.A.

SEDGWICK, A., on "The Influence of Darwin on Animal Embryology".

Sedgwick, A., Darwin's Geological Expedition with.

Seeck, O.

Seed-plants, origin of.

Segregation.

Selection, artificial.--germinal.

Selection, natural (see Natural Selection).--organic.--sexual.--social and natural.--various.

Selenka.

Semnopithecus.

Semon, R.

Semper.

Senebier.

Senecio vulgaris.

Sergi.

Seward, A.C.--and S.O. Ford.--and J. Gowan.

Sex, recent investigations on.

Sharpe, D.

Sherrington, C.S.

Shirreff, P.

Shrewsbury, Darwin's recollections of.

Sibbern.

Sinapis alba.

Smerinthus ocellata.

Smerinthus populi.

Smerinthus tiliae.

Smith, A.

Smith, W.

Snyder.

Sociology, Darwinism and.--History and.

Soddy.

Sollas, W.J.

Sorley, W.R.

Species, Darwin's early work on transmutation of.--geographical distribution and origin of.--immutability of.--influence on environment on.--Lamarck on.--multiple origin of.--the nature of a.--polymorphic.--production by physico-chemical means of.--and varieties.--de Vries's work on.

Spencer, H., on evolution.--on Lyell's "Principles".--on the nature of the living cell.--on primitive man.--on the theory of Selection.--on Sociology.

Spencer, H., on the transmission of acquired characters.--on Weismann.--various.

Sphingidae, variation in.

Spinoza.

Sports.

Sprengel, C.K.

Stability, principle of.

Stahl.

Standfuss.

Stars, evolution of double.

Stellaria media.

Stephen, L.

Sterility in hybrids.

Sterne, C.

Stockard, his experiments on fish embryos.

STRASBURBER, E., on "The Minute Structure of Cells in relation to Heredity".

Strongylocentrotus franciscanus.

Strongylocentrotus purpuratus.

Struggle for existence.

Strutt, R.J.

Stuart, A.

Sturdee, F.C.D.

Sutterlin, L.

Sully.

Sutton, A.W.

Sutton, W.S.

Svalof, agricultural station of.

Swainson, W.

Synapta, calcareous bodies in skin of.

S. lappa.

Syrphus.

Tarde, G.

Teleology and adaptation.

Tennant, F.R.

Teratology.

Tetraprothomo.

THISELTON-DYER, SIR WILLIAM, on "Geographical distribution of Plants".--on Burchell.--on protective resemblance.--elsewhere.

THOMSON, J.A., on "Darwin's Predecessors.--elsewhere.--and P. Geddes.

Thomson, Sir J.J.

Theology, Darwin and.

Tiedemann, F.

Tooke, Horne.

Totemism.

Treschow.

Treviranus.

Trifolium pratense quinquefolium.

Trigonias.

Trilobites, phylogeny of.

Tschermack.

Turgot.

Turner, Sir W.

Twins, artificial production of.

Tylor.

Tyndall, W.

Tyrrell, G.

Uhlenhuth, on blood reactions.

Underhill, E.

Use and disuse.

Vanessa.

Vanessa antiope.

Vanessa levana.

Vanessa polychloros.

Vanessa urticae.

Van 't Hoff.

Varanus Salvator.

Variability, Darwin's attention directed to.--W. Bateson on.--and cultivation.--causes of.--polymorphic.

Variation, continuous and discontinuous.--Darwin's views as an evolutionist, and as a systematist, on.--definite and indefinite.--environment and.--and heredity.--as seen in the life-history of an organism.--minute.--mutability and.--in relation to species.--H. de Vries on.

Varigny, H. de.

Varro, on language.

Veronica chamaedrys.

Verworn.

"Vestiges of Creation", Darwin on "The".

Vierkandt.

Vilmorin, L. de.

Virchow, his opposition to Darwin.

Virchow, on the transmission of acquired characters.

Vochting.

Vogt, C.

Voltaire.

Volvox.

VRIES, H. de, on "Variation"--the Mutation theory of.

WAGGETT, REV. P.N., on "The Influence of Darwin upon religious thought".

Wagner.

Waldeyer, W.

Wallace, A.R., on Malayan Butterflies.--on Colour.--and Darwin.--on the Descent of Man.--on distribution.--on Malthus.--on Natural Selection.--on the permanence of continents.--on social reforms.--on Sexual Selection.

Waller, A.D.

Walton.

Watson, H.C.

Watson, S.

Watt, J., and Natural Selection.

Watts, W.W.

Wedgwood, L.

Weir, J.J.

WEISMANN, A., on "The Selection Theory".--on Amphimixis.

Weismann, A., his germ-plasm theory.--on ontogeny.--and Prichard.--and Spencer.--on the transmission of acquired characters.--various.

Wells, W.C., and Natural Selection.

Weston, S., on language.

WHETHAM, W.C.D., on "The Evolution of Matter".

Whewell.

White, G.

Wichmann.

Wieland, G.R., on fossil Cycads.

Wiesner, on Darwin's work on plant movements.

Williams, C.M.

Williamson, W.C.

Wilson, E.B., on cytology.--letter from Darwin to.

Wolf.

Wollaston's, T.V. "Variation of Species".

Woltmann.

Woolner.

Wundt, on language.

Xylina vetusta.

Yucca, fertilisation of.

Zeiller, R., on Fossil Plants.

Zeller, E.

Zimmermann, E.A.W.

Zittel, on palaeontological research.

"Zoonomia", Erasmus Darwin's.