MAGIC LANTERN. An optical instrument by means of which magnified images of small transparent pictures can he thrown upon a white wall or screen in a darkened room. It consists of some powerful source of illumination such as an oxyhydrogen or electric light, though in a small hall or room and with an instrument of limited power it is possible to employ an Argand or incandescent gas burner, or an acetylene or oil lamp. which is contained in a box of wood or sheet metal. The rays from the illuminant fall upon a lens known as a condenser. which is either a thick convex lens, or, better, two plano-convex lenses with their curved surfaces in close prox imity. and whose function is to collect the rays, and transmitting them in either a parallel or slightly converging beam to illuminate the slide, as the transparent picture on glass is termed. The slide is usually a transparent photographic positive, or a drawing or painting on glass, and is inserted in an inverted position in a frame in front of the condenser. To produce an image of the picture, another lens or system of lenses known as the objective is used, which must he achromatic and free from distortion. so as to
form an image with a flat field. By varying the distance between the slide and the objective, the image on the screen is brought to a focus, and in modern instruments great magnification and sharpness are secured. Many improvements have been made in the magic lantern, and it now is considered a necessary adjunct to lectures and scientific demonstrations. as. in addition to the presentation of photographs and diagrams. nu merous experiments in physical science can he shown on such a scale as to be visible to a large audience. There are also arrangements known as anematographs. vitascopes. biographic. kineto scopes, etc. (see KINETOSCOPEL whereby mov ing pictures can be shown in the marric lan tern by using in place of a slide a rapidly mov ing film, on which have been photographed a series of pictures taken in quick succession. As the successive images follow each other on the screen more rapidly than the eye is able to re ceive the separate and distinct impressions, they accordingly blend into each other and the effect of moving pictures is produced.