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An instrument by which an object is perceived as if in motion and with an appearance of solidity or relief as in nature. It consists of a series of stereoscopic pictures, generally eight, of an object in the successive positions it assumes in completing any motion, affixed to an octagonal drum revolving under an ordinary lenticular stereoscope, and viewed through a solid cylinder pierced in its entire length by two apertures, which makes four revolutions for one of the picture-drum. The observer thus sees the object constantly in one place, but its parts apparently in motion and in solid and natural relief.

ster'[=e]-[=o]-tr[=o]p, n. an optical contrivance by which an object is brought into relief and made to appear as if in motion. [Gr. stereos, solid, trop[=e], a turning.]