Some years ago Mr. Stanford, formerly Governor of California, believing that the various positions assumed by a horse in executing its dif ferent paces were but little known and could only be ascertained by means of photography sought the assistance of Muybridge who succeeded in making some remarkable photographs. The arrangement employed is shown in Fig. 112.
on the left is a white inclined screen reflecting the sun light and marked with divisions at equal distances for convenience in measurement. A series of cameras was arranged on the opposite side and fine electric wires were stretched across the path. These latter were connected with the shutters of the camera. As the horse passed it broke the wires which set off the shutters of each camera in succession and a series of photographs was thus ob tained showing the various attitudes assumed by the animal.
In a book entitled " Le Mouvement," M. Marey details his method of obtaining chronophotographs of animals and gives reproductions of photographs obtained, illustrating almost every kind of living creature. Some of these we reproduce here.
Fig. i 16 shows a Medusa, or jelly-fish. They are transparent. The motion of these animals is produced by the alternate dilation and contraction of the upper part of the body, which resembles in shape a toadstool. The move ments are slow and can almost be followed with the unaided eye. When expanded, water is drawn in, which is expelled by the contraction, and the animal is propelled in the opposite direction. The specific gravity of these animals being almost the same as that of the medium in which they live, they need to exert but little power to (11,1‘, f attl, ••.0 A F. s./ tJ, 11,11/0,1 V ax v.,. la 1 OS-A-A.111UL necessary in order to examine the motion of the animals, and in the twelve pictures can be clearly seen the phases from the dilated condition of the head to that where it is con tracted. The exposure was made with the illumination coming from above, and against a dark background.
Fig. ri8 shows a sea-horse (Hippocampus). The principal propelling agent is the back fin, and its motion is so rapid that it cannot be followed with the eye. Twenty exposures per sec ond show us that the motion is undulating and that the undu lations take place from beneath upward.
It is easy to follow the phases, the pictures being more numerous and on a somewhat larger scale.
Fig. 119 shows a Comatula, a species of star-fish. Ordinarily it remains at the bottom of the aquarium and exhibits hardly any motion with its long arms.
When touched with a stick, however, it begins, after an instant, to move in a very peculiar fashion. The ten arms are moved alternately, five of them are drawn up and the five others are stuck down. The feathery filaments on the arms which are drawn up are not visible, as they lie flat against them; those on the other arms, however, are spread out as if seeking a support. This is not shown in the figure owing to its small scale.
If we examine these pictures made by chronophotography we notice that they present a very diffferent appearance from the object in motion itself. By a method of synthesis we can bring these pictures again before the eye in rapid succession and see the object apparently assume life-like motion. The principle was discovered by Plateau early in the present century, and to his apparatus he gave the name of " Phenakistoscope." It is shown in Fig. 120. As each slit passes in front of the eye it reveals a different picture, and if the images are representations of the successive positions assumed by an object in motion the im pression is that of a continuous movement. Under the names zoe trope, wheel of life, praxinoscope, etc., various arrangements, em bodying the same principle, have been constructed. Previous to the advances made in chronophotog raphy the pictures were drawn by hand, hut photography has en abled us to secure far more accu rate and instructive results. Fig. 125 represents an instrument de vised by M. Demeny. The images are brought before the eye in rapid succession or they can be enlarged by projection on a screen. This arrangement was especially designed for giving the illusions of the motions of the lips, and so successful were the results that deaf mutes were able to read pho tographed phrases. Edison's kinet oscope is arranged on the same principle. A number of images are made upon a band of celluloid film. From the negatives thus ob tained positives are made upon another band of film, and these are made to travel in front of the eye, each image being lighted up separately by an electric spark. In Edison's apparatus, however, only one person can view the image thus shown.