The magic lantern shown in figures 50 and 51 consists of a dark box, containing a lamp and a concave metallic mirror, constructed in such a way that the whole of the rays proceeding from the lamp are reflected through the aperture holding the optical portion of the apparatus. In front of the box is fixed a double tube C D, one-half of which (D) slides in the other. A large plano-convex lens _c_ is fixed at the inner extremity of the double tube, and a small one at its outer end. To the fixed tube C E is attached a groove _b b_, which serves to hold the painted glass. These glasses, or slides as they are generally called, are painted with strong transparent colours. The direct light of the lamp G, as well as that reflected by the mirror and passing through the lens _c_, is so concentrated as to project a brilliant beam of light through the painted slide, which being in the conjugate focus of the large plano-convex lens _d_, the pictures on the glass are refracted in a magnified form on the white cloth P Q. The magic lantern, therefore, consists of a box to hold the lamp, a concave mirror, and a convex lens to concentrate the light on the slide, and a second convex lens to throw the image on the screen. ------------------------------------------------------------------------ [Illustration: FIG. 51.—Magic Lantern. ] ------------------------------------------------------------------------ CHAPTER II. THE PHANTASMAGORIA. THE phantasmagoria may be described as a perfected magic lantern, and bears the same relation to its prototype that a shilling telescope bought in the Lowther Arcade does to one of Dollond’s or Ross’s field glasses. The position of the spectators, too, is different, being on the other side of the scene which receives the magnified pictures, already described when speaking of the magic lantern. [Illustration: FIG. 52.—The Phantasmagoria. ]