Scientific American. 82 [AuGusT 8, 1885. A CURIOUS OPTICAL ILLUSION. They all have thesame diameter, 1°5inches, and are all tremity being comnected with the pile. The most con- venient arrangement of the pile is this: The number of elements is equal to that of the wheels, or one of the multiples… … tance. Like other sirens, it gives at will one or AN OPTICAL ILLUSION, dynamic one, constructed by Mr. Hipp accord- several tones, and the interval between these may ing to an American model.—Condensed from La be fixed in advance. In its simplest form it consists es- Lumiere Hlectrique. corresponds…
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