CATARACT, in hydrography, a precipice in the channel of a river, caused by rocks, or other obstacles, stopping the course of the stream, from whence the water falls with a greater noise and impetuosity. The word comes from kataptes, "I tumble down with violence;" compounded of katas, "down," and ptesis, dijicio, "I throw down."—Such are the cataracts of the Nile, the Danube, Rhine, &c. In that of Niagara, the perpendicular fall of the water is 137 feet; and in that of Pifill Rhaindr, in North Wales, the fall of water is near 240 feet from the mountain to the lower pool.
Strabo calls that a cataract which we call a cascade; and what we call a cataract, the ancients usually called a cataracta. Herminius has an express dissertation, "De admirandis mundi Cataractis supra et subterraneis;" where he uses the word in a new sense; signifying, by cataract, any violent motion of the elements.