LANTERN, magic, an optic machine, whereby little painted images are repre sented so much magnified as to be ac counted the effect of magic by the ig norant. See OPTICS.
The contrivance is briefly this: A B C 13 (Plate rim Miscel. fig. 1.) is a tin lan tern, from whose side there proceeds a square tube bail e line, consisting of two parts ; the outermost of which, n k lm, slides over the other, so as that the whole tube may be lengthened or shortened by that means. In the end of the arm, 12 k Ian, is fixed a convex glass, k 1; about d e there is a contrivance for admitting and placing an object, d e, painted in dilute and trans parent colours, on a plane thin glass ; which object is there to be placed inverted. This is usually some ludicrous or fright fill representation, the more to divert the spectators ;b /lc is a deep convex lass, placed in the other end of the prominent tube, the only use of which is to cast the light of the flame, a, strongly on the -pic ture, d e, painted on the plane thin glass. Hence, if the object, d e, be placed fur ther from the glass, VI, than its focus, it is manifest that the distinct image of the object will be projected by the glass, k 1, on the opposite white wall, F H, at fg; and that in an erect posture : so that, in effect, this appearance of • the lantern is the same with that of the camera obscura, or darkened room; since here the chamber, E F G H, is supposed quite dark, excepting the light in the lan tern A 11 C D. And here we may obi
serve, that if the tube, bnklm c, be eon, tracted, and tliereby the glass, lel, brought nearer the object, d e, the representa tion, fg, will be projected so much the larger, and so much the more distant from the glass k l; so that the smallest picture at d e may be projected at fg in any greater proportion required, within due limits : whence it is, that this lantern 'got the name of lanterna megalographica. On the other hand, protracting the tube will diminish the object.
Instead of the convex glass to heighten the light, some prefer a concave specu him, its focus being nearer than that of a lens; and in this focus they place the candle.