CATARACT, in Hydrography, a precipice in the channel of a river, caused by rocks or other obstacles stopping the course of the stream, whence the water falls with great noise and impetuosity. The word is derived from καρα, down, and φρακω, deicio, I throw down. Strabo calls that a cataract which we call a cascade; and what we call a cataract the ancients usually called a catadupa. Herminius has an express dissertation, "De admirandis mundi Cataractis supra et subterraneis;" where he uses the word in a new sense, meaning by cataract any violent motion of the elements.