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Plate II.—Various representations of the gallop. Fig. 1.—From Géricault's picture, "The Epsom Derby, 1821." Figs. 2 and 3.—From gold-work on the handle of a Mycenæan dagger, 1800 b.c. Fig. 4.—From iron-work found at Koban, east of the Black Sea, dating from 500 b.c. Fig. 5.—From Muybridge's instantaneous photograph of a fox-terrier, showing the probable origin of the pose of the "flying gallop" transferred from the dog to other animals by the Mycenæans. Fig. 6.—The stretched-leg prance from the Bayeux tapestry (eleventh century). Fig. 7.—The stretched-leg prance used to represent the gallop by Carle Vernet in 1760. Fig. 8.—The stretched-leg prance used by early Egyptian artists.

Plate III.—Representations of the gallop. Fig. 1.—A combination of the hinder half of Fig. 10, Pl. I, with the front half of Fig. 4, Pl. I. Fig. 2.—One of the many admirable Chinese representations of the galloping horse. This is very early, namely, 100 a.d. The pose is that of the "flying gallop" as in Figs. 2, 4 and 5 of Pl. II. Fig. 3.—From a Japanese drawing of the seventeenth century; the pose is a modification of the "flying gallop," and agrees closely with that of Fig. 1 in this plate. Fig. 4.—The flex-legged prance from a bas-relief in the frieze of the Parthenon, b.c. 300. Fig. 5.—A modern French drawing giving a pose very similar to that of Figs. 1 and 3. It is the most "effective" pose yet adopted by artists, and is an improvement on the full-stretched flying gallop, though failing to suggest the greatest effort and rapidity. Fig. 6.—Instantaneous photographs of four phases of a horse "jumping."

Two very interesting questions arise in connection with the discovery by instantaneous photography of the actual positions successively taken up by the legs of a galloping horse. The first is one of historical and psychological importance, viz. why and when did artists adopt the false but generally accepted attitude of the "flying gallop"? The second is psychological and also physiological, viz. if we admit that the true instantaneous phases of the horse's gallop (or of any other very rapid movement of anything) cannot be seen separately by the human eye, but can only be separated by instantaneous photography, ought an artist to introduce into a picture, which is not intended to serve merely as a scientific diagram, an appearance which has no actual existence so far as his or other human eyes are concerned, viz. that of the actual pose assumed instantaneously and simultaneously by the four legs of the galloping horse? And further, if he ought not to do this, what ought he to do, on the supposition that his purpose is to convey to others the same impression of rapid movement which exists—not, be it observed, in his eye, or on the retina of that eye—but in his mind, as the result of attention and judgment?

The first of these questions has been answered by the great French authority on archæology and the history of art, M. Salomon Reinach,[2] whose writings are as lucid and terse as they are accurate, and solidly based on research. M. Reinach shows (and produces drawings to support his statement) that in Assyrian, Egyptian, Greek, Roman, mediæval, and modern art up to the end of the eighteenth century "the flying gallop" does not appear at all! The first example (so far as those schools are concerned) is an engraving by G. T. Stubbs in 1794 of a horse called "Baronet." The essential points about "the flying gallop" are that the fore-limbs are fully stretched forward, the hind limbs fully stretched backward, and that the flat surfaces of the hinder hoofs are facing upwards. After this engraving of 1794 the attitude introduced by Stubbs became generally adopted in English art to represent a galloping horse, and the French painter, Géricault, introduced it into France in 1821 in his celebrated picture, the "Derby d'Epsom," (see Pl. II, fig. 1) which is now in the Louvre.

Previously to this there had been three other conventional poses for the running horse in art, of which only the third (to be mentioned below) has any resemblance to a real pose, and that not one of rapid movement. We find: (1) The elongated or stretched-leg "prance" (French, "cabré allongé"), in which, whilst the front legs are off the ground, and all four legs are stretched nearly as much as in the flying gallop, there is this essential difference, viz. that the hoofs of the hind legs are firmly planted on the ground (see Pl. II, fig. 7). This pose is seen in a picture by the same artist (Stubbs) of two years' earlier date than that in which he introduced "the flying gallop." The "stretched-leg prance" is found in Egyptian works (Pl. II, fig. 8) of 580 b.c., and is a favourite pose to indicate the gallop, in ancient Assyrian as well as mediæval art, for instance, in the Bayeux tapestry (Pl. II, fig. 6). We find, further, (2) that the second pose made use of for this purpose is the "flexed-leg prance," in which all the four legs are flexed, so that the hind legs rest on the ground beneath the horse's body, whilst the forelegs "paw" the air. This is seen both in Egyptian, Greek, and Renaissance art (Leonardo, Raphael, and Velasquez). It is by no means so graceful or true to Nature as the next pose, but gives an impression of greater energy and rapidity. The third pose represents a kind of "prancing," and is seen on the frieze of the Parthenon (Pl. III, fig. 4), and in many subsequent Greek, Roman, and other works copied from or inspired by, this Greek original. One only of the hind legs is on the ground, and the animal's body is thrown up as though its advance were checked by the rein. It is called "the canter" by M. Reinach, but that term can only be applied to it when the axis of the body is horizontal and parallel to the surface of the ground.

The reader will perhaps now suppose that we must attribute the "flying gallop" to the original, if inaccurate genius of an eighteenth century English horse-painter. That, however, is not the case. M. Reinach has shown that it has a much more extraordinary history. It is neither more nor less than the fact that in the pre-Homeric art of Greece—that which is called "Mycenæan" (of which so much was made known by the discoveries of that wonderful man Schliemann when he dug up the citadel of Agamemnon)—the figures of animals, horses, deer, bulls (see the beautiful gold cups of Vaphio), dogs, lions, and griffins, in the exact conventional pose of "the flying gallop," are quite abundant! (See Pl. II, figs. 2, 3 and 4.) There was an absolute break in the tradition of art between the early gold-workers of Mykené (1800 to 1000 b.c.) and the Greeks of Homer's time (800 b.c.). Europe never received it, nor did the Assyrians nor the Egyptians. Thirty centuries and more separate the reappearance in Europe of the flying gallop—through Stubbs—from the only other European examples of it—the Mycenæan. What, then, had become of it, and how did it come to England? M. Reinach shows, by actual specimens of art-work, that the Mycenæan art tradition, and with it the "flying gallop," passed slowly through Asia Minor north eastwards to the Trans-caucasus (Koban, 500 b.c.), to Northern Persia, and thence by Southern Siberia to the Chinese Empire (Pl. III, fig. 2) as early as 150 b.c., and that the "flying gallop," so to speak, "flourished" there for centuries, and was transmitted by the Chinese artists to the Japanese, in whose drawings it is frequent (Pl. III, fig. 3). It was at last finally brought back to Europe, and to the extreme west of it, namely, England, by the importation in the eighteenth century into England of large numbers of Japanese works of art. It was a Japanese drawing (M. Reinach infers) which suggested to Stubbs the upturned hinder hoofs and the detachment from the ground of "the flying gallop" which he gave in his portrait of "Baronet," and so established that pose for a century in modern European art. This is a delightful tracing out of the wanderings of an artistic "convention," and the curious thing is that its chief importance is not that it has to do with the movements of the horse, but that it tends (as do other discoveries) to establish the gradual passage of pre-classical Mycenæan art across Central Asia to China and Japan by trade routes and human migrations which had no touch with later Greece nor with Assyria nor India.

How did the Mycenæans come to invent, or at any rate adopt, the convention of "the flying gallop," seeing that it does not truly represent either the fact or the appearance of a galloping horse? Though 20,000 years ago the earliest of all known artists, the wonderful cave-men of the Reindeer period, drew bison, boars, and deer in rapid running movement with consummate skill, they were (be it said to their credit!) innocent of the conventional pose of the "flying gallop." I base this statement on my own knowledge of their work. M. Reinach thinks that the "flying gallop" was devised as an intentional expression of energy in movement. I venture to hold the opinion that it was observed by the Mycenæans in the dog, in which Muybridge's photographs (now before me) demonstrate that it occurs regularly as an attitude of that animal's quickest pace or gallop (see fig. 5, Pl. II). It is easy to see the "flying gallop" in the case of the dog, since the dog does not travel so fast as the galloping horse, and can be more readily brought under accurate vision on account of its smaller size. The late Professor Marey (a great investigator of animal movement) appears to have denied that the dog exhibits the full stretch of both limbs with the pads of the hind-feet upturned, and all the feet free from the ground. He was mistaken, as Muybridge's photograph giving side and back view of a galloping fox-terrier amply demonstrates. It is quite in accordance with probability that the early Mycenæan artists, having seen how the dog gallops, erroneously proceeded to put the galloping horse, and all other animals which they wished "to make gallop," into the same position.

It appears, then, that the poses used by artists at different times and in different parts of the world to represent the "galloping" of the horse have no correspondence to any of the poses actually assumed by a galloping horse as now demonstrated by instantaneous photography. The "prancing" attitude of the horses of the frieze of the Parthenon was probably not intended to represent rapid movement at all. The "stretched-leg" pose and the "flex-leg" pose are, as a matter of fact, phases of "the jump," and are definitely recorded in Muybridge's instantaneous photographs of the jumping horse, but have no existence in "galloping" nor in any rapid running of the horse. They were probably adopted by the artists of Egypt, Assyria, Greece, and their successors in Europe as an expedient without conviction, to represent rapid movement, the true poses of which defied satisfactory reproduction. And it is also the fact that the "flying gallop," which appeared in Mycenæan art thirty-seven centuries ago, and then travelled by a "Scythian" route through Tartary to China, and came back to Europe at the end of the eighteenth century, is also—so far as it has any real representative in the action of the horse—only approached by a brief phase of the "jump." The poses of the horse in jumping are shown in the small figures taken from instantaneous photographs and reproduced in Fig. 6 of Pl. III. The "flying gallop" ("ventre a terre"), with all four legs stretched, and the under surface of the hind feet upturned, is really seen by us all every day in the dog, and is recorded in instantaneous photographs of that animal going at full speed. In fact, the gallop of the dog (and of some other small animals) is a series of jumps; the animal "bounds along." But this is a totally different thing from the gallop of the horse. It is probable that the dog's gallop was transferred, so to speak, to the horse by artists, and a certain justification for it was found in one of the attitudes of a jumping horse, which, however, never exhibits both the front and the hind legs simultaneously in so completely horizontal a position as they are made to take in the Mycenæan gold-work and the modern "racing plates."

How, then, we may now ask, ought an artist to represent a galloping horse? Some critics say that he ought not to represent anything in such rapid action at all. But, putting that opinion aside, it is an interesting question as to what a painter should depict on his canvas in order to convey to others who look at it the state of mind, of impression, feeling, emotion, judgment, which a live, galloping horse produces in him. The scientific draughtsman would, of course, present to us a series of drawings exactly like the instantaneous photographs, his object being to show what "is," and not what the artist aims at, namely, what "appears," "seems," or (without pondering and analysis) "is thought to be." The painter, in his quality of artist, would be wrong to select any one of the dozen or more poses of the galloping horse published by Muybridge, each limited to the fortieth of a second, since no human eye can fix (as the photographic camera can) separate pictures following one another at the rate of twenty a second, each enduring one fortieth of a second, and each separated by an interval of a fortieth of a second from the next. All the phases which occur in any one-tenth of a second (only two, or possibly three of the Muybridge series shown in Pl. I) are, as it were, fused in our visual impression, because each picture lasts on the retina of the eye for one-tenth of a second, or (to put it more accurately) because the "impression" or condition of the retina produced by each picture persists or endures for the tenth of a second.

It may, perhaps, be suggested (and, indeed, has been), that it is the "blurred" or "fused" picture produced by the successive poses of the galloping horse's legs in one-tenth of a second that the painter ought to imitate on his canvas. In support of this notion we have the fact that the rapidly running wheels of a coach or of a gun-carriage (as in the pictures by Wouwerman) are represented by artists, not with the twelve or fourteen spokes which we know to be there—and would be photographed as separate things in an exposure of the fortieth of a second—but as a blurred haze of some fifty or more indistinct "spokes." In this case it undoubtedly results that the observer of the picture is satisfied and receives the mental impression or illusion of a rapid rotation of the wheel. I have tried the experiment with instantaneous photographs of the galloping horse, and I get three results: first, no combination of successive phases occupying one-tenth of a second gives anything resembling the "flying gallop" of the racing plates (the Mycenæan and Stubbsian pose), or any other conventional pose; second, no combination of successive instantaneous photographs limited to ten second gives any pose which satisfies the judgment and suggests a movement like the gallop; third, the combination which comes nearest to satisfying the judgment as being a natural appearance, but does not quite succeed in doing so, is one formed by the fusion of figs. 2 and 3 of Pl. I. This gives all four legs off the ground, drawn up or flexed beneath the horse's body, as in Morot's picture of the sabre-charge at Resonville.

The fact is that we have to take into consideration two other factors in the process, which we call "seeing," besides the duration of the retinal impression or excitation. These are, first, attention, and second, judgment. We are apt to think that "seeing" is a simple, straightforward sort of thing, whereas it is really a strangely complex and delusive process. "I did not see it, therefore it was not there," or "You must have seen it; it was right in front of you," are common assertions, and the belief that such assertions are justified leads to miscarriage of justice in courts of law. Yet everyone knows that he may stare out of the window of a railway carriage and have a long panorama pass before his eyes, or may walk along a crowded street and look his acquaintances in the face, and in neither case will he have "seen" or recognized anything, or be able to give an account of the scene that was pictured on the back of his eye. Attention, the direction of the mind to the sensation, is necessary; and it appears that it is very difficult (to some more than to others) to hold the attention alert, and to give it to the unexpected. In fact, to a very large extent we can only "see" (using the word to signify the ultimate mental condition) that which we are prepared to see or that which we expect to see. In the absence of such expectation, a very strongly illuminated or well-marked, outstanding object is far more readily "seen" than less marked objects. Accordingly, the outstretched legs of the galloping horse, now in front and now behind, are "seen," whilst the rest of the phases are not observed. Moreover, it is a fact that the swinging pendulum of a clock is "seen" at the extreme position of the swing on each side, and not in the intermediate space. This is because the image is formed very quickly, twice in the space where the bob of the pendulum is coming to the limit of its swing and is again returning on its course. For the same reason, the outstretched legs of the horse going up to their limit and at once returning give in very quick succession, near their extreme limit, an ascending and a descending phase which are not strictly but sensibly alike, and so doubly impress the retina, and obtain for the legs "attention" when in that extreme position. The choice of the attitude depicted by Morot is explained by the fact that, as is shown by its persistence through two successive pictures (figs. 2 and 3 of Pl. I), this pose must produce a more continuous impression on the retina than any other of the attitudes shown, since none of them endure through two successive pictures.

The mental process of attention results in a certain duration or memory of the mental condition which is a distinct thing from the primary retinal impression, and leads to the ignoring or mental obliteration of an instantaneous interval separating two phases of the position of moving legs which have strongly "arrested the attention." Hence, it seems that the most forward pose of the galloping horse's front legs and the most backward pose of its hind legs—though far from simultaneous, even in the slow changing retinal impressions—may be mentally combined by "the arrest of attention," and that the artist really ought to present his picture of the galloping horse with those two poses combined (although as a matter of scientific truth they do not occur simultaneously) in order that he may produce by his painted piece of canvas, as nearly as he can, the mental result which we call "seeing" a horse gallop. This combination of the front half of one figure with the hinder half of another so as to give in each case the extreme phase of extension of the legs I have made in Pl. I, fig. 12.

But there is, further, in all "seeing" before even a mental result of attention to the retinal picture is, as it were, "passed," admitted and registered as "a thing seen," the further operation of rapid criticism or judgment, brief though it be. We are always unconsciously forming lightning-like judgments by the use of our eyes, rejecting the improbable, and (as we consider) preposterous, and accepting and therefore "seeing" what our judgment approves even when it is not there! We accept as "a thing seen" a wheel buzzing round with something like fifty spokes—but we cannot accept a horse with eight or sixteen legs! The four-leggedness of a horse is too dominant a prejudice for us to accept a horse with several indistinct blurred legs as representing what we see when the horse gallops. The mind revolts at such a presentation, though it is true, and the whole scheme and composition of the artist is perverted or fails to gain attention and to exercise its charm—by the unwelcome presence in his picture of the revolting truth. It is the consideration of facts of this kind which enables us to understand the origin and importance of what are called "conventions" in pictorial or glyptic art. The artist is, in fact, operating by means of his painted canvas or moulded clay upon a queer, prejudiced, ill-seeing, dull, living creature—his brother-man. In order to give if possible to that brother, by means of a painted sheet, some or all of the delights, emotions, suggestions, perceptions of beauty, and so on, which he himself has experienced in contemplating a real scene, the artist has to present that scene, not as it really is, nor even as he thinks it really is, but in such a way that his canvas shall appeal to his brother's attention and judgment with the same emotional and intellectual result as the scene itself produced in him. Therefore he must not aim at accuracy of reproduction of natural fact nor even of visual fact, but at the transference to another mind of his own mental condition—his inner judgment as to "things seen"—by means of necessarily imperfect pictorial mimicry. He must therefore avoid startling or abnormal truthfulness of observation of the unessential and even more strictly must he refuse to make his picture a scientific diagram demonstrating what "is" rather than what is "seen" or is "thought to have been seen."

On these grounds I find that the most satisfactory pictures of the galloping horse are those which combine a phase of the movement of the front legs with a phase of the movement of the hind legs, not simultaneous in actual occurrence, but following one another. It is for the artist to select the combination best suited to producing the mental result aimed at. Some of the Chinese and Japanese representations of the galloping horse and some of their European imitations (but not all—certainly not that of Stubbs, of the Epsom Derby of Géricault, and the racing plates) seem to me to be eminently satisfactory and successful in this respect. In the pictures to which I allude (Pl. III, figs. 3 and 5) all the legs are off the ground; the front legs are advanced, but one or both may be more or less flexed, whilst the hind legs, though directed backwards with upturned hoofs, are not nearly horizontal (as they actually are in the galloping dog), but show the moderate extension which really occurs in the horse, and is recorded by instantaneous photography. This pose, favoured by many European and Japanese artists, can be obtained by uniting the outstretched hind legs of fig. 9 of the Muybridge series (Pl. I), with the outstretched forelegs of fig. 6, as shown in Pl. I, fig. 12, or by uniting the hind legs of fig. 10 with the forelegs of fig. 4 as shown in Pl. III, fig. 1.

With regard to the representation of other "gaits" of the horse than that of the rapid gallop—such as canter, trot, amble, rack, and walk—I have no doubt that instantaneous photography can (and in practice does) furnish the painter with perfectly correct and at the same time useful and satisfactory poses of the horse's limbs. These, though of longer duration than the poses of the gallop, can only be correctly estimated by the eye with great difficulty, and only sketched by artists of exceptional skill and patience. The movement of the wings of birds in flight has been very successfully analysed by instantaneous photography. Some of the poses revealed must familiarise the public with what can be, and, in fact, has been, observed in the case of large sea-birds, by the unassisted eye, and has been represented in pictures by the more careful observers of nature among modern painters. A large sea-bird sailing along with apparently motionless wings has been photographed in the act of giving a single stroke so rapid as to escape observation by the eye.

An interesting question in regard to the movements of the horse is that as to how far any known "pace" is natural to that animal, and how far it has been acquired by training and is, in a sense, artificial. We know so little of the wild horse, and of the more abundant wild asses and zebras, that it is difficult to say anything precise on this question. There is only one region in which the true original wild horse of the northern part of Asia and Europe still exists. That is the Gobi Desert, in Central Asia. This horse is known as Prevalsky's wild horse, in honour of the Russian traveller who discovered it. Live specimens are now to be seen in the Zoological Gardens and elsewhere. It closely resembles the drawings of horses made by the palæolithic Cromagnard cave-men. A century ago a wild horse, probably of the same race as this, inhabited the Kirghiz Steppes, and was known as the Tarpan: it is now extinct. The more southern Arabian horse is not known in the wild state, whilst the wild horses of America are descendants of domesticated European horses which have "run wild." I do not know of any studies of the movements of the true wild horse, nor of those of wild asses and zebras, carried out by the aid of instantaneous photography. It would be interesting to know whether untaught wild "equines" would fall naturally into the gaits known as "the amble" and "the rack," or whether the walk, the trot, and the gallop are their only natural gaits.

The amble, in which the fore and hind leg on the same side are advanced simultaneously, is a natural gait of the elephant, the fastest Muybridge could get from that great beast. He made a menagerie elephant amble at the rate of a mile in seven minutes. The only other animal known to habitually exhibit "the amble" is the giraffe. It is often exhibited by the giraffes in the Zoological Gardens in London, but has not, I believe, been recorded by a series of instantaneous photographs. When going at full speed over the grass wilds of Central Africa the giraffe exhibits a gait more like the galloping of deer and antelopes, and carries the long neck horizontally. No complete study of the "gaits" of large animals other than the horse has been made, since menagerie specimens and menagerie conditions are not satisfactory for the purpose, and, unfortunately, it has not been possible as yet to take series of photographs of them in their wild conditions.

The electric spark furnishes a most important means of taking instantaneous photographs, but the operator must perform in the dark. An electric spark can be obtained which lasts only the one two-thousandth of a second, and by its use as the sole illuminating agent we can get a photograph of a phase of movement lasting only that excessively short space of time, or, if we please, a succession of such phases by using a succession of sparks. Thus, a rifle bullet is readily photographed while in flight with scarcely perceptible distortion. A wheel revolving many hundred times a second can thus be photographed, and appears to be stationary. Dr. Schillings has applied this method to the photography of wild animals by night in the forests of tropical Africa, and has published an interesting book giving his photographic results. In order to take these pictures the track followed by certain animals has to be detected, and then a thread is stretched "breast-high" across the track, so that the animal coming along it by night shall pull the thread. Immediately the thread is pulled it sets an electric contact in action. There is a brief flash of one two-thousandth of a second, and a picture is taken by a camera previously fixed, out of harm's way, so as to focus the area where the thread was stretched.

Dr. Schillings obtained some very remarkable photographs of "the night life of the forest" in this way—lions and leopards advancing on their prey were suddenly revealed, and the helpless antelope or other victim was shown crouching in the dark, or making a desperate effort to escape.

The electric-spark method was applied by a friend of mine to demonstrate the movements by which a kitten falling backwards from a table succeeds in turning itself so as to alight on its feet. During a fall of less than 3 feet he obtained five successive spark-pictures of the kitten, which, I beg it may be clearly understood, was a pet kitten, and was neither frightened nor hurt by the proceedings.

Instantaneous photographs, whether obtained by the use of an electric spark as a means of illumination, or by the less rapid method of a spring shutter working in combination with a sensitive film, which is jerked along so as to be exposed when the shutter is open and travel when it is shut, has been applied to the analysis of other movements than those I have mentioned, and has yet to be applied to many more, such as the crawling of insects and millipedes, and the beautiful rippling movement of the legs and body by which many marine worms swim. It has been extensively used in the study of human locomotion, and of the successive poses of the arms and legs in various athletic exercises, and in such games as baseball and golf.

A first-rate fencer of my acquaintance had a five-minutes' film of himself taken when fencing, giving 10,000 consecutive poses. He wished to see exactly what movements he made, and to ascertain by this minute examination any error or want of grace in his action, in order to avoid it. An unexpected picture is obtained when a man or woman is thus "biographed" whilst walking rapidly, and suddenly turns to the right or left. A fraction of a second occurs when the toes of the two feet are directed towards one another (that is to say, are "turned in"), as one of the legs swings round in the break-off to right or left. This instantaneous phase is very awkward and ugly in appearance. It is never pictured by artists, although regularly occurring, and seems to have been as little known before instantaneous photography was introduced as were most of the phases of the horse's gallop. The positions assumed when in the air by a high-jump athlete are almost incredible as revealed by the camera. He appears to be sitting in a most uncomfortable way on the rope over which he is projecting himself.

A very fine attitude is fixed for the artist in one of Muybridge's instantaneous series of the "bowler"—the cricket "bowler." The up-lifted right arm, the curve outwards of the whole figure on the right side, and the free hang of the right leg make a most effective pose for a sculptor to reproduce. Among the most remarkable results obtained in Muybridge's series are the stages of the growth or development of strong "expression" in the face. The anxiety in the face of the baseball batsman as he awaits the ball is painful; as he hits at the ball his expression is one of savage ferocity, and in a fraction of a second this gives place to a dawning smile, which as we pass along two or three later "instantanèes" develops into a broad grin of satisfaction. Another genuine study of expression both of face and gesture and movement is given in the series where a pailful of cold water is unexpectedly poured over the back of a bather seated in a sitz bath—astonishment, dismay, anger, eagerness to escape, and the reaction to shock are all clearly shown. Darwin's studies on "the expression of the emotions" would have been greatly assisted by such analysis, and the subject might even now be developed by the use of serial instantaneous records obtained by photography. It may be useful to those interested in this subject to know that copies of Muybridge's large series of instantaneous photographs[3] of animal and human subjects in movement are preserved both in the library of the Royal Academy of Arts in London and in the Radcliffe Library at Oxford. I may also mention the extremely valuable series of instantaneous photographs of living bacteria, blood-parasites and infusoria produced by MM. Pathé, and the series of fishes and various invertebrates (including the curious caterpillar-like Peripatus) taken by Mr. Martin Duncan.

The representation of the moon in pictures of the ordinary size (some three feet long by two in height) is a case in which the artist habitually—one may almost say invariably—departs greatly from scientific truth, and it is a question as to whether he is justified in what he does. Take first the case of the low-lying moon near the horizon as contrasted with the high moon. Everyone knows that the moon (and the sun[4] also) appears to be much bigger when it is low than when it is high. Everyone who has not looked into the matter closely is prepared to maintain that the luminous disc in the sky—whether of moon or of sun—not merely seems to, but actually does, occupy a bigger space when it is low down near the horizon than when it is high up, more nearly overhead. Of course, no one nowadays imagines that the moon or the sun swells as it sinks or diminishes in volume as it rises. Those who think about it at all, say that the greater length of atmosphere through which one sees the low sun or moon, as compared with the high, magnifies the disc as a lens might do. This, however, is not the case. If we take a photograph of the moon when low and another with the same instrument and the same focus when it is high, we find that the celestial disc produces on the plate (as it does on our eyes) a picture-disc of practically the same size in both positions. In fact, the high moon or sun produces a picture-disc of a little larger size than the low moon or sun. I have here reproduced (Pl. IV) a photograph, published by M. Flammarion, in which the moon has been allowed to print itself on a photographic plate exposed during the time the moon was rising, and it is seen that the track of the moon has not diminished in width as it rose higher and higher. No one will readily believe this, yet it is a demonstrable fact. Astronomers have made accurate measurements which show that there is no diminution of the disc under these circumstances, but a slight increase—since the moon is a very little nearer to us when overhead than when we see it across the horizon.

Plate IV.—The track of the rising moon registered by continuous exposure of a photographic plate. It is given here in order to show that the diameter of the visible disc of the moon does not diminish as it rises. The slight increase in the breadth of the track registered by the moon's disc is probably due to a little distortion caused by the side portion of the lens. After M. Flammarion. The actual width of the moon's disc as printed here is a little over one eighth of an inch, which, if we regard it as "a picture" and not merely as a mechanical record, implies that the observer's eye is only about 14–½ inches distant from the picture plane instead of the more usual 18 inches, which corresponds to a diameter of the pictured moon's disc of between ⅙th and 1/7th of an inch (.156 inch).

If we put a piece of glass coated with a thin layer of water-colour paint into a frame, and then make a peep-hole in a board which we fix upright between us and the upright piece of framed glass, we can keep the framed glass steady (let us suppose it to be part of the window of a room), and then we can move the peep-hole board back from it into the room to measured distances. At a distance of one and a half feet from the framed glass, which is that at which an artist usually has his eye from his canvas or paper, we can trace on the smeared or tinted piece of glass the outlines of things seen through it exactly as they fill up the area of the glass—men, houses, trees, the moon. The moon's disc (and the same is true of the sun) is found always to occupy a space on the glass which is 1/115th of the distance of the eye from the framed glass plate. When the eye-to-frame distance is eighteen inches, the diameter of the disc of the moon on the smeared glass will occupy exactly 1/115th of eighteen inches, which is between one-sixth and one-seventh of an inch. Similarly if the peep-hole is at nine and a half feet or 114 inches from the framed glass (which stands for us as the equivalent of an artist's picture) the moon will occupy almost exactly one inch in diameter—the size of a halfpenny. With such a simple apparatus of peep-hole and smeared glass in an upright frame, it is easy to mark off the size covered by the moon (or sun), whether low or high, on the smeared glass, and it is found never to vary whether high or low—so long as the same "eye-to-frame" or "peep-hole" distance is preserved. That seems to be an important fact for painters of sun-sets and moon-rises. But what do they do? They never give the right size (namely one-sixth of an inch) which corresponds to an eye-to-frame distance of eighteen inches. They give to a high moon, if they are very careful, a quarter of an inch for diameter. This means that the observer is about two and a half feet, or thirty inches from the picture—nearly twice what the artist's eye really is as he paints. And then—if painting a moon-rise or sunset—they suddenly pretend to go to a distance of nine and a half feet from the picture and make the moon an inch across because it is low down, or even give the moon two inches in diameter, which would mean that they (and those who look at the picture when hung up for view) are observing at nineteen feet distance from the front plane or frame of the picture. They do not alter the other features in the picture to suit this change of distance of the eye from the frame and there is no warning given. Certainly there is no obvious and necessary reason for treating a picture containing a high moon as though you were three feet from the front plane of the scene presented, and a low moon as though you were twenty feet from that plane! The confusion which may result in the representation of other objects when these changes of eye-to-frame distance are made is shown by the following simple facts. According to the simple laws of perspective, if the eye is at thirty inches from the picture-plane or frame (as declared by a moon drawn of a little more than a quarter of an inch broad), a post or a man six feet high drawn on the canvas as three inches high absolutely and definitely means that that man or post is sixty feet away from the observer inside the picture. The height of the represented object is the same fraction of the real object as the eye-to-frame distance is of the distance of the observer to the real object. If by a two-inch moon the artist has thrown you back from the front plane of the scene to a distance of nineteen feet, then the six-foot post or man drawn as three inches high definitely asserts that it or he is 456 feet distant within the picture. So, too, if the church tower which cuts the moon is really sixty feet high and is drawn of two inches vertical measure in the picture, it is an assertion—when the moon is represented one quarter of an inch broad—that the church tower is 290 yards, or a sixth of a mile distant. If, on the other hand, other things remaining the same, the moon is drawn two inches in diameter, the church tower is now asserted to be eight times as far off, or about a mile and a third. Very generally these facts are not considered by painters. They represent the low moon (or sun) big because the erroneous mental impression is common to all of us that it is big—that is, bigger, much bigger, than the high moon or sun, and they do not follow out the consequences in perspective of the pictorial increase of the moon's apparent diameter.

If we could ascertain why it is that the low moon produces a false impression of being bigger—as a mere disc in the scene—than does the high moon, we might be able to discover how an artist could produce, as Nature does, an impression or belief in its greater size whilst keeping it all the time to its proper size. The explanation of the illusion as to the increased size of the sun's or moon's disc when low, given by M. Flammarion and other astronomers, is that the low sun or moon is unconsciously judged by us as an object at a greater distance than the high moon or sun. This is due to the long vista of arching clouds above and of stretching landscape or sea below when the sun or moon is looked at as it appears on or near the horizon. The illusion is aided by the dulness of the low moon and the brightness (supposed nearness) of the high moon. Being judged of (unconsciously) as further off than the high moon, the low moon is estimated as of larger size although of the same size. This is, I believe, the correct explanation of the illusion. When one gazes upwards to the sky, a small insect slowly flying across the line of sight sometimes is "judged of" as a huge bird—an eagle or a vulture—since we refer it to a distance at which birds fly and not to the shorter distance to which insects approach us. It seems that it would be possible for the painter, by carefully studying actual natural facts and introducing their presentation into his picture, to produce the impression of greater distance, and therefore of size, into a quarter-inch moon placed near the horizon. He is not compelled for want of other means to "cut the difficulty" and paint a falsely inflated moon which shall brutally and by measurement call up the illusion of increased size. I reproduce here (Pl. V) an interesting drawing which shows how such illusions of size can be produced. It is none the worse for my purpose because it is an advertisement by the well-known firm who have kindly lent it to me. The three figures represented in black are all of the same height, yet the furthest one appears to be much taller and bigger altogether than the middle one, and the middle one than the nearest. This result is obtained by suggesting distance as separating the right-hand figure from us, whilst giving it exactly the same height as the others. This seems to me to be a simple case of an illusion of increased size produced by a suggestion of increased distance when all the time there is equality in size—as in the case of the moon on the horizon compared with the moon overhead. It would be interesting to see an attempt on the part of a competent painter to produce in this way (which is, I believe, Nature's way) the illusion of increased size in a low-lying moon without really increasing the visual size of his painted moon as compared with one in another picture (to be painted by him) representing the moon bright, clear and small, overhead.

Plate V.—Drawing of three figures—Lord Lansdowne, Mr. Lloyd George, and Mr. Asquith—showing how an illusion of size may be produced in a picture. The figure of Mr. Asquith is of the same actual vertical measurement as that of Lord Lansdowne, viz. two inches and one eighth. Yet owing to the position in which the three figures are placed and the converging lines—suggesting perspective—the drawing of Mr. Asquith does not merely represent a much taller man than does that of Lord Lansdowne, but actually gives the impression, at first sight, that the little black figure representing Mr. Asquith is longer and bigger altogether than that representing Lord Lansdowne. Yet the figures are of the same dimensions. It is owing to illusion of the same nature that the disc of the low moon appears larger than that of the high moon.

The theatrical scene-painter has another kind of difficulty with the low moon and the setting sun. He can never be right for more than one row of seats—one distance—in the theatre. Here there is no peep-hole, no frame or picture-plane. The observer is in the picture. If the moon is represented by an illuminated disc of one foot in diameter, it will, when looked at at a distance of 115 feet, have the same visual size as the moon itself, but if your seat is nearer the scene it will look too large, if further off it will look too small. There is no getting over this difficulty, as the standard of actual Nature is set up on the stage by the men and women appearing on it at a known distance. It used to be asked in classical times by ingenious puzzle-makers—"What is the size of the moon?" A true answer to that question would be "that of a plate a foot in diameter seen at a distance of a hundred and fifteen feet."

To a large extent the painter, like other artists, has to produce things which do not shock common opinion and experience, and must even consciously concede to that necessity, and make the sacrifice of objective truth, in order to secure attention for his higher appeal to the sense of beauty, to emotion, and sentiment. Approved departures by the artist from scientific truth are those which are deliberately made in order to give emphasis—as, for instance, in the huge, but tender hand of the man in the emotional masterpiece, "Le Baiser," by the great sculptor Rodin. Another departure from objective truth which is justified, is seen in Troyon's picture in the Louvre, where the false drawing and exaggerated size of the leg of a calf advancing towards the observer suggest, and almost give the illusion of, movement.

But it can hardly be maintained that any and all the liberties which a painter or a whole school of painters choose to take with fact in their presentation of Nature—are beyond criticism. It is possible for a landscape painter to improve in his treatment of the moon by better observation and increased knowledge—just as other painters have learnt not to introduce into their pictures the sort of wooden rocking-horse to stand for a beautiful living animal, which satisfied Velasquez, Carl Vernet and the ancient Egyptians.