Scientific amusements . Whenthe little cpntrivance is turned round, the two designs areseen at the same time, and form but one image—that ofa bird in its cage. It is of course hardly necessary to addthat the designs may be varied. We have already referred to M. Plateaus rotating disc(the Phenakistoscope). Through the narrow slits weperceive in succession representations of different positionsof a certain action. The persistence of the luminousimpressions on the retina gives to the eye the sensationof a continuous image, which seems animated by the .samemovenients as those portrayed in the diff
Scientific amusements . Whenthe little cpntrivance is turned round, the two designs areseen at the same time, and form but one image—that ofa bird in its cage. It is of course hardly necessary to addthat the designs may be varied. We have already referred to M. Plateaus rotating disc(the Phenakistoscope). Through the narrow slits weperceive in succession representations of different positionsof a certain action. The persistence of the luminousimpressions on the retina gives to the eye the sensationof a continuous image, which seems animated by the .samemovenients as those portrayed in the different phases. THE ZOOTRQPE. 79 The Zootrope is a perfect specimen of this is composed of a cylinder of cardboard, turning on acentral axis. The cylinder is pierced with vertical slits atregular intervals, through which the spectator can seethe designs upon a band of paper adapted to the interiorof the apparatus in rotation. The designs are so executedthat they represent the different times of a movement. Appearance of the Tha,umatrope in rotation. between two extremes ; and in consequence of the impres-sions upon the retina the successive phases are mingled,so the spectator believes he sees, without transition, theentire movement. We give (page 82) a few specimensof the pictures for the Zootrope. We have here an apeleaping over a hedge, a dancing Punch, a gendarmepursuing a thief, a person holding the devil by the tail, arobber coming out of a box, and a sportsman firing at a 8o OPTICAL ILLUSIONS. bird. The extremes of the movement are right and left;the intermediary figures make the transitions, and theyare usually equal in number to the slits in the Zootrope,It is not difficult to construct such an instrument, andbetter drawings could be made than the specimens takenat random from a model. The earth might be representedturning in space, or a fire-engine pumping water could be
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