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 greater noise and impetuosity. The word comes from *kataracta*, "I tumble down with violence;" compounded of *kata*, "down," and *rakto*, "dejecto," "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 Pistil Rhaiadr, 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 *catadupa*. 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.

in Medicine and Surgery, a disorder of the humours of the eye, by which the pupilla, that ought to appear transparent and black, looks opaque, blue, gray, brown, &c., by which vision is variously impeded, or totally destroyed. See SURGERY.

CATARA, a town of Dalmatia, and capital of the territory of the same name, with a strong castle, and a bishop's see. It is subject to Venice, and is seated on a gulf of the same name. E. Long. 19. 19. N. Lat. 42. 25.