Part 949

4. (Astron.) A southern constellation of great length lying southerly from Cancer, Leo, and Virgo.

Hy*drach"nid (?), n. [Hydr- + arachnid.] (Zoˆl.) An aquatic mite of the genus Hydrachna. The hydrachnids, while young, are parasitic on fresh-water mussels.

Hy*drac"id (?), n. [Hydr- + acid: cf. F. hydracide.] (Chem.) An acid containing hydrogen; -- sometimes applied to distinguish acids like hydrochloric, hydrofluoric, and the like, which contain no oxygen, from the oxygen acids or oxacids. See Acid.

Hy`dra*cryl"ic (?), a. [Hydr- + acrylic.] (Chem.) Pertaining to, or designating, an isomeric variety of lactic acid that breaks down into acrylic acid and water.

Hy`drac*tin"i*an (?), n. [See Hydra, and Actinia.] (Zoˆl.) Any species or marine hydroids, of the genus Hydractinia and allied genera. These hydroids form, by their rootstalks, a firm, chitinous coating on shells and stones, and esp. on spiral shells occupied by hermit crabs. See Illust. of Athecata.

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||Hy*drÊ"mi*a (h*dr"m*), n. [NL., fr. Gr. "y`dwr water + a"i^ma blood.] ||(Med.) An abnormally watery state of the blood; anÊmia.

Hy"dra*gogue (?), a. [L. hydragogus conveying off water, Gr. &?;; "y`dwr water + &?; to lead: cf. F. hydragogue.] (Med.) Causing a discharge of water; expelling serum effused into any part of the body, as in dropsy. -- n. A hydragogue medicine, usually a cathartic or diuretic.

Hy*dram"ide (?), n. [Hydr- + -amide.] (Chem.) One of a group of crystalline bodies produced by the action of ammonia on certain aldehydes.

Hy*dram"ine (?), n. [Hydroxyl + amine.] (Chem.) One of a series of artificial, organic bases, usually produced as thick viscous liquids by the action of ammonia on ethylene oxide. They have the properties both of alcohol and amines.

Hy*dran"ge*a (?), n. [NL., fr. Gr. "y`dwr water + &?; vessel, capsule: cf. F. hydrangÈe.] (Bot.) A genus of shrubby plants bearing opposite leaves and large heads of showy flowers, white, or of various colors. H. hortensis, the common garden species, is a native of China or Japan.

Hy"drant (?), n. [Gr. &?; to irrigate, fr. "y`dwr water. See Hydra.] A discharge pipe with a valve and spout at which water may be drawn from the mains of waterworks; a water plug.

Hy"dranth (?), n. [Hydra + Gr. &?; a flower.] (Zoˆl.) One of the nutritive zooids of a hydroid colony. Also applied to the proboscis or manubrium of a hydroid medusa. See Illust. of Hydroidea.

Hy*drar"go*chlo"ride (?), n. [Hydrargyrum + chloride.] (Chem.) A compound of the bichloride of mercury with another chloride. [Obs.]

Hy*drar"gy*rate (?), a. Of or pertaining to mercury; containing, or impregnated with, mercury. [R.]

Hy*drar"gy*rism (?), n. (Med.) A diseased condition produced by poisoning with hydrargyrum, or mercury; mercurialism.

Hy*drar"gy*rum (-rm), n. [NL., fr. L. hydrargyrus, Gr. "ydra`rgyros; "y`dwr water + 'a`rgyros silver.] (Chem.) Quicksilver; mercury.

||Hy`drar*thro"sis (?), n. [NL. See Hydro-, 1, and Arthrosis.] (Med.) ||An effusion of watery liquid into the cavity of a joint.

Hy*dras"tine (?), n. (Chem.) An alkaloid, found in the rootstock of the golden seal (Hydrastis Canadensis), and extracted as a bitter, white, crystalline substance. It is used as a tonic and febrifuge.

Hy"dra-taint`ed (?), a. Dipped in the gall of the fabulous hydra; poisonous; deadly. Cowper.

Hy"drate (?), n. [Gr. "y`dwr water: cf. F. hydrate.] (Chem.) (a) A compound formed by the union of water with some other substance, generally forming a neutral body, as certain crystallized salts. (b) A substance which does not contain water as such, but has its constituents (hydrogen, oxygen, hydroxyl) so arranged that water may be eliminated; hence, a derivative of, or compound with, hydroxyl; hydroxide; as, ethyl hydrate, or common alcohol; calcium hydrate, or slaked lime.

Hy"drate (?), v. t. [imp. & p. p. Hydrated (?); p. pr. & vb. n. Hydrating (?).] To form into a hydrate; to combine with water.

Hy"dra*ted (?), a. Formed into a hydrate; combined with water.

Hy*dra"tion (?), n. (Chem.) The act of becoming, or state of being, a hydrate.

Water of hydration (Chem.), water chemically combined with some substance to form a hydrate; -- distinguished from water of crystallization.

Hy*drau"lic (?), a. [F. hydraulique, L. hydraulicus, fr. Gr. &?;, &?;, a water organ; "y`dwr water + &?; flute, pipe. See Hydra.] Of or pertaining to hydraulics, or to fluids in motion; conveying, or acting by, water; as, an hydraulic clock, crane, or dock.

Hydraulic accumulator, an accumulator for hydraulic machinery of any kind. See Accumulator, 2. -- Hydraulic brake, a cataract. See Cataract, 3. -- Hydraulic cement, a cement or mortar made of hydraulic lime, which will harden under water. -- Hydraulic elevator, a lift operated by the weight or pressure of water. -- Hydraulic jack. See under Jack. -- Hydraulic lime, quicklime obtained from hydraulic limestone, and used for cementing under water, etc. -- Hydraulic limestone, a limestone which contains some clay, and which yields a quicklime that will set, or form a firm, strong mass, under water. -- Hydraulic main (Gas Works), a horizontal pipe containing water at the bottom into which the ends of the pipes from the retorts dip, for passing the gas through water in order to remove ammonia. -- Hydraulic mining, a system of mining in which the force of a jet of water is used to wash down a bank of gold-bearing gravel or earth. [Pacific Coast] -- Hydraulic press, a hydrostatic press. See under Hydrostatic. -- Hydraulic propeller, a device for propelling ships by means of a stream of water ejected under water rearward from the ship. -- Hydraulic ram, a machine for raising water by means of the energy of the moving water of which a portion is to be raised. When the rush of water through the main pipe d shuts the valve at a, the momentum of the current thus suddenly checked forces part of it into the air chamber b, and up the pipe c, its return being prevented by a valve at the entrance to the air chamber, while the dropping of the valve a by its own weight allows another rush through the main pipe, and so on alternately. -- Hydraulic valve. (Mach.) (a) A valve for regulating the distribution of water in the cylinders of hydraulic elevators, cranes, etc. (b) (Gas Works) An inverted cup with a partition dipping into water, for opening or closing communication between two gas mains, the open ends of which protrude about the water.

Hy*drau"lic*al (?), a. Hydraulic.