Hydra

hi'dra, n.; E. pi. -dras, -draz, L. pi. -DRyE, -dre. {Myth.) A water serpent having many heads, one of which, being cut oft, was succeeded by another, unle the wound was cauterized. A multifarious evil, or one not to be repre ed by a single effort. {ZooJ.) A minute kind of fresh water polyp. — Hy'drous, -drus, a. Containing water, watery. — Hydrangea, -je-a, n. {Bot.) A shrubby Hyacinth. genus of plants bearing opposite leaves and large heads of showy flowers. — Hy'drant, n. A pipe or spout at which water may be drawn from the mains of an aqueduct: a water-plug; street fountain.— Hy'drate, -drat, n. {Chem.) A compound formed by the union of a definite proportion of water with some other substance, generally forming a neutral salt. — Hy'dride, -drid, n. {Chem.) A compound of the binary type, in which hydrogen, as a negative, is united with some other element. — Hydrau'lic, -draw'lik, -lical, a. Pert, to hydraulics, or to fluids in motion. — Hydrau'lics, n. sing. That branch of science or of engineering which treats of fluids, esp. water, in motion. — Hydraulic cement. Cement which will harden under water. — H. pre . A pre in which great power is obtained from a forcing pump which forces water into a large cylinder. — H. ram. A machine for raising water by means of the momentum of the water of which a portion is to be Hydraulic Ram. raised.— Hy'drocele, -sel, n. {Med.) Dropsy of the scrotum or of the coverings of the testicles or spermatic cord. — Hydrocephalus, -sef'a-lus, n. {Med.) Dropsy of the brain. — Hy'drodynam'ic, «. Pert, to, or derived from, the force or pre ure of water. — Hy'drodynam'ics, n. Principles of dynamics, as applied to water and other fluids. — Hy'drofluor'ic, -floo-3r/'ik, a. {Chem.) Pert, to, or derived from, fluorine and hydrogen. — H. acid. An acid obtained by distilling fluor-spar with sulphuric linger or ink, then, boNboN, chair, get. acid. — Hy'drogen, -jen, n. (Chem.) An inflammable, colorle , ino'lorbus gas of extreme lightne , one of the elements of water.— Hydrog'rapher, n. One who draws maps of the sea, etc., with jacent shores. — Hydrog'raphy, -f I, n. Art of uring and describing the sea, lakes, rivers, etc., forming charts of the same. — Hydro-Fogy, n. ence of water, its properties, phenomena, and its distribution in likes, rivers, etc, over the surface.— Hydrometer, n. An instrument for mining the specinc gravities and thence the strength of liquids; also, one for measuring the velocity discharge of water, as in rivers, from reservoirs, — Hydrom'etry, -tri, n. The determining the ciric gravity and strength of liquids; art or operation of measuring the velocity or discharge of running water. — Hydrop'athy, -a-thi, n. The water-cure, mode of treating diseases by the use of pure — Hydropath'ic, -ical, a. Pert, to, etc. — Hydrop'athist. 198