The Zootrope (fig. 126) is a perfected specimen of this apparatus. It is composed of a cylinder of cardboard, turning on a central axis. The cylinder is pierced with vertical slits at regular intervals, and through which the spectator can see the designs upon a band of paper adapted to the interior of the apparatus in rotation. The designs are so executed that they represent the different times of a movement between two extremes; and in consequence of the impressions upon the retina the successive phases are mingled, so the spectator believes he sees, without transition, the entire movement. We give a few specimens of the pictures for the Zootrope (fig. 127). We have here an ape leaping over a hedge, a dancing “Punch,” a gendarme pursuing a thief, a person holding the devil by the tail, a robber coming out of a box, and a sportsman firing at a bird. The extremes of the movement are right and left; the intermediary figures make the transitions, and they are usually equal in number to the slits in the Zootrope. It is not difficult to construct such an instrument, and better drawings could be made than the specimens taken at random from a model. The earth might be represented turning in space, or a fire-engine pumping water could be given, and thus the Zootrope might be quite a vehicle of instruction as well as of amusement. This instrument is certainly one of the most curious in the range of optics, and never fails to excite interest. The ingenious contrivances which have up to the present time reproduced it, all consist in the employment of narrow slits, which besides reducing the light to a great extent, and consequently the light and clearness of the object, require the instrument to be set in rapid rotation, which greatly exaggerates the rapidity of the movements represented, and without which the intermissions of the spectacle could not unite in a continuous sensation. [Illustration: Fig. 126.—The Zootrope.] [Illustration: Fig. 127.—Pictures used in the Zootrope.]