The magic lantern shown in the annexed figure consists of a dark lantern, AB, containing a lamp G, and a concave metallic mirror, MN, and it is so constructed that when the lamp is lighted not a ray of light is able to escape from it. Into the side of the lantern is fitted a double tube, CD, the outer half of which D is capable of moving within the other half. A large plano-convex lens C, is fixed at the inner end of the double tube, and a small convex lens D, at the outer end; and to the fixed tube CE, there is joined a groove EF, in which the sliders containing the painted objects are placed, and through which they can be moved. Each slider contains a series of figures or pictures painted on glass with highly transparent colours. The direct light of the lamp G, and the light reflected from the mirror MN, falling upon the illuminating lens C, is concentrated by it so as to throw a brilliant light upon the painting on the slider, and as this painting is in the conjugate focus of the convex lens D, a magnified image of it will be formed on a white wall or white cloth placed at PQ. If the lens D is brought nearer to EF, or to the picture, the distinct image will be more magnified, and will be formed at a greater distance from D, so that if there is any particular distance of the image which is more convenient than another, or any particular size of the object which we wish, it can be obtained by varying the distance of the lens D from EF. [Illustration: _Fig. 5._] When the image is received on an opaque ground, as is commonly the case, the spectators are placed in the same room with the lantern; but, for the purposes of deception, it would be necessary to place the lantern in another apartment like the mirror in Fig. 4, and to throw the magnified pictures on a large plate of ground glass, or a transparent gauze screen, stretched across an opening EF, Fig. 4, made in the partition which separates the spectators from the exhibitor. The images might, like those of the concave mirror, be received upon wreaths of smoke. These images are of course always inverted in reference to the position of the painted objects; but in order to render them really erect, we have only to invert the sliders. The representations of the magic lantern never fail to excite a high degree of interest, even when exhibited with the ordinary apparatus; but by using double sliders, and varying their movements, very striking effects may be produced. A smith, for example, is made to hammer upon his anvil,--a figure is thrown into the attitude of terror by the introduction of a spectral apparition, and a tempest at sea is imitated, by having the sea on one slider, and the ships on other sliders, to which an undulatory motion is communicated.