Page:Popular Science Monthly Volume 52.djvu/194

180 viz., the display in rapid sequence of a long series of photographs, which hence convey to the eye and brain the impression of a continuous and animated scene. In the kinetoscope the small pictures are viewed through an enlarging lens by reflected light, whereas in the cinematograph, phantascope, vitascope, etc., they are projected upon a screen—a plan that is obviously best suited to the requirements of a public exhibition.

A machine of the last-mentioned type may be shortly described as a stereopticon, combined with such mechanism as is requisite for the precise manipulation of the celluloid picture film. When the



apparatus is set in motion the long band of celluloid passes quickly, though not continuously, behind the projecting lens, between spools or bobbins which revolve at a uniform rate. While thus passing from its original spool to the winding reel the film encounters certain pulleys and toothed rollers that serve to accurately direct its movements. Along its edges are numerous small perforations, into which the teeth of the rollers fit with precision; and by this means the small transparencies are made to occupy exactly similar positions when their images are projected upon the canvas. As each picture in its turn attains this critical position, it is momentarily brought to