An optical machine employed to throw a magnified image of paintings upon glass or any transparent substance on a white screen in a darkened chamber. It has generally been devoted to the amusement of children, paintings of a ludicrous description being its usual accompaniments; but it may be employed with propriety to illustrate the principles of the sciences, by a selection of suitable diagrams. The apartment in which the exhibition is made should be completely darkened, and no light allowed to escape from the lantern except what passes through the glasses. To increase the light, a concave reflector is frequently used, of such a curvature, that the candle is in its focus, so that the rays proceeding from it, fall parallel upon the glass next the candle. The glass sliders upon which the pictures are made, are generally of sufficient length to contain several sets of figures; the sliders being introduced by an opening, cut in each side of the tube containing the lenses. A section of this machine is shown below.