Page:The wonders of optics (1869).djvu/187

Rh lamp, the optical apparatus, and the figures in a comparatively small space, was particularly appropriate to the wants of the Homes and Davenports of the day, who until then had never possessed anything so convenient and portable.

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, one-half of which 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 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, as well as that reflected by the mirror and passing through the lens c, is