Page:Popular Science Monthly Volume 41.djvu/27

Rh vivantoscope; but it is still not clear whether their purpose was carried out.

Dr. William Weber lived to see himself and his brother fully sustained, after nearly half a century, by instantaneous photography. Mr. Eadweard Muybridge, of San Francisco, applied it in 1872, at the suggestion of Mr. Stanford, to fix the attitudes of horses in the successive positions of different paces. The same phenomena were revealed in the photographs as in the Webers' schematic drawings. Pictures came out the like of which nobody believed had ever really been seen. Directed upon street scenes, processions, etc., the camera took many views of men in quite as astonishing positions as those which the brothers Weber had attributed to them on theoretical grounds. It was not different with the wonderful series of pictures of a flying bird and its wingstrokes which M. Marey has obtained with his photographic gun.

The explanation of these facts is evidently that, when an object moves with periodically varying velocities, we get a stronger and more durable impression of the situations in which it halts, and a weaker and more fugitive one of those in which it moves swiftly. Even without knowing this law, no painter will represent the Black Forest clock in a peasant's room with a vertical pendulum, for, if he did, every observer would ask why the clock was stopped. For the pendulum, when it has swung to one side and is about to return, necessarily stops for an instant, and this situation of pausing at one side impresses us more strongly than the one in which the pendulum is passing through its point of equilibrium with the greatest velocity. It is the same with the alternately swinging legs of the walking man: he pauses longer in the position in which both of his legs are at rest, and for the shortest time in that in which the moving leg swings in front of the resting leg. The last position and those near it, therefore, make substantially no impression upon us. We figure to ourselves the walking man, and the painter represents him accordingly in the position in which between two steps he touches the ground with both feet.

Something very curious is observed in the running of the horse. No matter how frequent the intervals at which the picture is taken, we never get the usual figure of a racing or hunting horse as it comes to us from England, and as we see it in the pictures that are hung up in the show-windows of the shops at the time of races and hunts, and as it in fact strikes our eyes on