thos disease), in pathology and therapeutics, the theory of curing diseases with very minute doses of medicine; the doctrine that diseases are cured by medicines which have the power to cause similar diseases in healthy persons.

Homog'amous (Gr.), in botany, having hermaphrodite florets.

Homogang'liate (Gr.), having the nervous ganglia arranged symmetrically. Homoge'nea (Gr. homos the same, and genea birth), an order of Infusoria, the bodies of which present neither viscera nor complication.

Homoge'neous (Gr. homogenes), of the same kind or nature; consisting of similar parts, or of elements of the like nature.

Homogen'esis (Gr.), in botany and zoology, the production of a similar kind or species.

Hom'ograph (Gr.), in military science, a system of telegraphic signals by means of a white handkerchief.

Homologous (Gr. homos, and logos ratio), in geometry, the sides of similar figures which are proportional to each other are said to be homologous.

Hom'ologue (Gr.), in anatomy, the same part or organ differing in form or functions.

Homology (Gr.), the doctrine of similar parts or proportions. Homomorphous (Gr. homos, and morphe 'change), in entomology, an epithet expressing similarity of form, applied to certain insects, of which the larva is like the perfect insect, but wingless.

Homophonous (Gr.), in music, having the same pitch.

Homop'oda (Gr. homos, and podes feet), a section of amphipodous Crustaceans with numerous feet, all terminating with a point or hook.

Homop'tera (Gr.), having the four wings alike.

Homotonous (Gr.), in pathology, a term applied to fevers, in which the symptoms exhibit the same intensity throughout their progress.

Hom'otype (Gr. homos, and typos a type), a part homologous with another in a series.

Hone (Swed. hen), a sort of fine whetstone for sharpening fine-edged instruments, as lancets, razors, &c. Honorarium (Lat.), a fee given to a professor of a university, or to a professional gentleman for his services. Hopeite (from Dr. Hope, professor of chemistry), white transparent mineral, crystallized in prisms: sp.gr. 2'76; H=2.5. Ho'rary (Lat. hora an hour), in astro

a

nomy, the horary motion of the sun or a planet is the arc which it describes in one hour.

Hordei'a (Lat. hordeum barley), a peculiar vegetable product found in barley; a yellowish powder insoluble in water.

Horizon (Gr.), the line that terminates the view when the eye is carried round in a level direction; this is called the sensible horizon. The rational horizon is an imaginary great circle, whose plane passes through the centre of the earth, and whose poles are the zenith and nadir. -Artificial horizon is an instrument used in connection with the quadrant or sextant for obtaining the altitude of a heavenly body, to procure which, a perfectly horizontal reflective surface is necessary. Horizontal projection is the projection made on a plane parallel to the horizon. This may be understood perspectively or orthographically, according as the projecting rays are directed to a given point.-Horizontal line, in perspective, is such an imaginary line in a picture as is parallel to the horizon, and at the height of the eye. It therefore passes through the centre of the picture.

Horn (Swed.), in zoology, a hard, semitransparent, pointed substance which grows on the heads of some quadrupeds. In music, a brass wind instrument of a spiral form. In architecture, a term sometimes applied to the Ionic volute, which has the appearance of a ram's horn.

Hornblende, a mineral of a darkish green colour, abounding in oxide of iron, and generally coarse and laminar. It consists of silica, magnesia, lime, alumina, protoxide of iron, and fluoric acid, and scratches glass: sp. gr. 3.15-3.38.-Hornblende schist is a metamorphic slate, in which hornblende is an ingredient.

Horn Ore, in mineralogy, a species of silver ore of a pearl-grey colour, consisting of silver, muriatic acid, sulphuric acid, oxide of iron, alumina, and lime sp. gr. 4.8.-Horn silver, the native chloride of silver. Hornstone, in mineralogy, a variety of quartz of a horn-like appearance.Hornstone porphyry, a variety of porphyry of a red or blackish colour, with a splintery or conchoidal fracture.

Horn-work, in fortification, an outwork having angular points or horns, usually situated in advance of the principal works of a place, and composed of two demibastions, joined by a curtain.

Horog'raphy (Lat. from Gr. hora an hour, and graphe description), the art or science of constructing dials, or drawing hour-lines.

Horologe (Gr.), a machine or instrument for measuring time.

Horology (Gr.), an explanation of the method of measuring hours; the art of constructing time-pieces. Horom'etry (Gr.), the art of measuring hours.

Horoscope (Gr.), in astrology, a figure or scheme of the hours or twelve signs of the zodiac, from which observations are professed to be made of the aspect of the heavenly bodies.

Horse. (See Equus.)-Horse-shoe magnet, an artificial magnet in the shape of a horse-shoe.

Horse-whim, in mechanical science, a machine for raising ore from a mineshaft, usually worked by a horse. Horticulture (Lat.), the culture of kitchen-gardens, orchards, or flowerbeds. Horticulturist, one skilled in gardening and floriculture.

Hortus Siccus (Lat.), a collection of dried plants.

Hot-pressing, in mechanical science, the application of heat, in conjunction with mechanical pressure, for the purpose of giving a smooth and glossy surface to paper, linen, &c.

Hour (Gr. hora), in the measurement of time, the twenty-fourth part of a natural day; the space of sixty minutes. -In angular measure, it is the twenty-fourth part of a circle or complete revolution = 15°.-The time indicated by a chronometer or other time-piece.

Hour Circle, in cosmography, a term applied to any great circle that passes through the two poles; the hour of the day being known when that circle is ascertained upon which the sun is for the time being. Hourcircles are drawn on the globe at 15° distant from each other on the equator.

Howitzer (Germ.), in gunnery, a piece of ordnance intermediate between the gun and the mortar.

Humate (Lat. humus the ground), a compound of humic acid with a base. Humbold'tilite (from Humboldt, the great naturalist), a vitreous, transparent mineral, found in the lavas of Vesuvius, consisting of silica, lime, magnesia, alumina, and protoxide of iron: sp. gr. 3.104.-Humboldtine is a mineral found in the moor coal of Bohemia, which is composed of oxalic acid and protoxide of iron. Humectant (Lat.), in therapeutics, an epithet applying to remedies which are supposed to augment the fluidity

of the blood.-Humectantia are medicines for moistening and softening. -Humectation, in pharmacy, is the preparation of medicine by steeping it in water for a given time.

Hu'mero-cu'bital (Lat.), in anatomy, the brachial internal muscle which extends from the humerus to the cubitus.

Humerus (Lat.), in anatomy, the arm from the shoulder to the ulnus, or elbow; the arm-bone, which articulates with the scapula.-Humeral, belonging to the humerus.

Humine (Lat. humus), in chemistry, the black nutritive matter of vegetables, consisting of carbon united with oxygen. Humiria'cese, in botany, a nat. order of exogenous plants, consisting of trees flowing with balsam, of which the Humirium is the genus.

Humite (from Sir A. Hume), a mineral found in yellow-brown or colourless crystals.

Hu'moral (Lat.), in pathology, relating to the humours of the body. Humoral pathology, a system in medicine which attributes all the diseases to morbid changes in the humours, or fluid parts of the body. Humours (Lat. humeo to be wet), in physiology, cutaneous eruptions, or the moisture of the body. The humours of the eye are the aqueous, or watery; the crystalline, or icy; and the vitreous. The first two contain about 80 per cent. of albumen, muriate, acetate of soda, and animal matter; the last, besides the usual salts, 36 per cent. of a peculiar matter like albumen.

Hu'mulus (Lat. humus), a genus of climbing plants (the Hop), used in the making of beer. Humus (Lat. vegetable mould), a pulverulent brown substance formed by the action of air on solid animal or vegetable matter.

Hurdles, in fortification, twigs of willows or osiers interwoven, sustained by long stakes, and made in the figure of an oblong square.

Hu'realite, a crystallized mineral, with a vitreous lustre, whose constituents are phosphoric acid, protoxide of iron, protoxide of manganese, and water: sp. gr. 2.270. Hu'ronite, the name of a yellowishgreen mineral which occurs in boulder stones in the neighbourhood of Lake Huron; its constituents are silica, alumina, protoxide of iron, lime, magnesia, and water: sp. gr. 2'86; H=2*25.

Hurtoir (Fr.), in fortification, a piece of timber placed at the head of the

platform next to the interior stone of the parapet, for the purpose of preventing the wheels of the gun-carriages from rolling upon the interior

stone.

Hyacinth (Gr.), a plant with a beautiful flower; a yellow, brown, or reddish mineral or gem.

Hyacin'thine, a brown or greenish mineral in eight-sided prisms. Hyades (Gr.), in astronomy, a small constellation of five stars in the face of Taurus.

Hyaline (Gr.), like glass; transparent. Hyalite, a grey variety of uncleavable quartz.

Hyali'tis (Gr.), inflammation of the hyaloid membrane of the eye. Hyaloid (Gr.), in anatomy, applied to a transparent membrane. Hyalosiderite (Gr.), a variety of chrysolite, with a vitreous lustre and metallic surfaces. Its constituents are silica, alumina, lime, magnesia, protoxide of iron, soda, and potash: sp. gr. 2.875; H =5.5.

Hyb'odonts (Gr. hybos a hump, and odontes teeth), in fossilology, a subfamily of extinct sharks. Their fossil remains commence with the coal formation, and terminate with the commencement of the chalk.

Hybrid (Gr.), the offspring of two plants or animals of different varieties or species.

Hydarthrus (Gr. hydor water, and arthron a joint), in surgery, a white swelling of the joints.

Hydatid (Gr. hydatis a watery vesicle), a small worm, a genus of Entozoa, which is formed like a bladder, and infests the entrails of the human body; an insect in the skull of sheep. -In pathology, a term applied to all encysted humours containing an aqueous fluid.

Hy'datoid (Gr.), in physiology, an epithet applied to the aqueous humour of the eye, and to the pellucid membrane by which the two chambers of that organ are invested. Hydra (Gr.), in zoology, a genus of gelatinous Polypi, the entire organization of which consists of a small gelatinous horn, the edges being provided with filaments that act as tentacula; order Gelatinosi.

Hydrac'id (Gr. hydor water), in chemistry, an acid containing hydrogen. Hydragogue (Gr. hydor, and ago to expel), a violent cathartic to expel watery secretions.

Hydral (Gr.), in botany, a term applied to an alliance of plants consisting of unisexual aquatic Endogens, with perfect or imperfect flowers. The Hydral alliance comprises the orders

Hydraulicon (Gr.), a musical instrument acted upon by water; a waterorgan.

Hydraulics (Gr.), that branch of hydrodynamics which treats of fluids in motion, and of conveying water through pipes; the science of the motion of fluids, and the construction of all kinds of machines relating thereto. -Hydraulic Press, in mechanical science, a machine in which powerful pressure is produced by water forced into a cylinder, and therein acting on a piston which raises a table on which the material to be pressed is placed.

Hy'driodate (Gr.), in chemistry, a salt formed by hydriodic acid with a base. Hydriod'ic (Gr.), noting an acid composed of hydrogen and iodine. Hydrobo'racite (Gr.), a mineral of a whitish colour, with red spots, consisting of lime, magnesia, boracic acid, and water: sp. gr. 19. Hydrobro'macite (Gr.), a mineral of a brightish colour.

Hydrobro'mic, in chemistry, composed of hydrogen and bromine. Hydrocanthar'idæ (Gr. hydor, and cantharis a scarab), in entomology, a

family of coleopterous insects. Hydrocarbon, Hydrocarburet, a compound of hydrogen and carbon. Hydrocarbonate, carburetted hydrogen

gas.

Hydrocarbon'ic, an epithet used to denote an inflammable gas. Hydrocardia (Gr. hydor, and kardia the heart), in pathology, dropsy of the pericardium.

Hy'drocele (Gr.), a collection of serous fluid in the scrotum or spermatic cord. Hydrocephalus (Gr. hydor, and kephale the head), dropsy of the brain, or water in the head.

Hydrocharida'ceæ, in botany, a nat. order of plants. Hydrochemistry, that department of chemistry which relates more especially to water and other fluids. Hydrochlo'rate, in chemistry, a sup

posed compound of hydrochloric acid with a base.

Hydrochloric, noting an acid commonly called muriatic acid.

Hydrocor'isæ (Gr. hydor, and koris a bug), in entomology, a tribe of hemipterous insects, including the Water Scorpions, Nepida, and the Boatmen, Notonectida.

Hydrocotyl'eæ (Gr.), in botany, a tribe of umbelliferous plants, of the suborder Orthospermæa, of which the Hydrocotyle, or Pennywort, is the type. Hydrocyanate, a supposed compound of hydrocyanic acid with a base. Hydrocyan'ic, a term applied to an acid whose base is hydrogen, and its acidifying principle cyanogen.

Hydrodynamics (Gr.), the science which applies the principles of dynamics to determine the conditions of motion or rest in fluid bodies. It comprises hydrostatics and hydraulics.

Hydroflu'ate, in chemistry, a supposed compound of hydrofluoric acid and a base.

Hydrogen (Gr.), a colourless, tasteless gas, which, combined with oxygen, produces water; it is the lightest body in nature, and hence the best material for filling balloons. Its equivalent is r; symb. H. With oxygen it constitutes water--hence the name.

Hydrog'raphy (Gr.), the science or description of the watery part of the terraqueous globe.

Hydrog'uret, a compound of hydrogen with a metal.

Hydrolite (Gr. water-stone), a white crystallized mineral, consisting of silica, alumina, peroxide of iron, potash, and water: sp. gr. 2.054; Η = 4.00. Hydrology (Gr. hydor, and logos a discourse), the knowledge of the nature and properties of water.

Hydrometridæ (Gr. hydor, and metron a measure), in entomology, a family of Geocorisæ, or Land-bugs, of aquatic habits, frequenting the surface of water.

Hydrometrograph (Gr.), an instrument for measuring and recording the quantity of water discharged in a given time.

Hydrom'etry (Gr.), the art of determining the specific gravity of liquids, and thence the strength of spirituous liquors. Hydrometer, an instrument for measuring the specific gravity, &c., of fluids.

Hydrom'phalus (Gr. hydor, and omphalos the navel), a tumour formed by accumulation of serum in the sac of umbilical hernia; or simply distention of the navel by the fluid of ascites. Hydrono'sis (Gr. water-disease), in pathology, a kind of sweating sick

insects.

Hydrophobia (Gr.), in pathology, a preternatural dread of water, a symptom of canine madness. Hydrophthalmy (Gr.), in pathology, a disease in the eye, which causes it almost to start out of the socket. Hydrophylla'ceæ, a nat. order of exogenous plants. Hydrophyte (Gr. hydor, and phyton a plant), a variety of serpentine. Hydrophytology (Gr.), a treatise on water-plants. Hydropneumatic (Gr.), an epithet given to a vessel of water, used for the collection of gases in chemical experi

ments.

Hydrops (Gr. hydor, and opsis appearance), a generic term in nosology, comprehending every morbid accumulation of serum in cysts and cavities of adventitious formation. Hydropsy (Gr.), in pathology, a disease of extravasated water; the dropsy. Hy'dropult (Gr. hydor, and Lat. pello to force), a machine for throwing water by hand-power, used as a garden-engine or fire-annihilator, and applicable to all the purposes for which a hydrant or force-pump is required.

Hydror'achis (Gr. hydor, and rachis the spine), a collection of serum in the membranes of the spinal cord. Hydrosalts, salts, the acid or base of which is a compound containing hydrogen as one of its elements. Hydrosar cocele (Gr. hydor, sarx flesh, and kele a hernial tumour), a swelling formed by dropsy of the tunica vaginalis.

Hydrose'lenates, in chemistry, a family of salts formed by a combination of hydroselenic acid with salifiable bases.

Hydrostat (Gr.), an apparatus for preventing the explosion of steamengines.

Hydrostatics (Gr. hydor, and statikos standing), the science which explains the equilibrium and pressure of water and other fluids; the art of weighing fluids. Hydrostatic paradox is a term often used to designate that principle in hydrostatics by which a very small quantity of water may be made to overcome a very great weight. -Hydrostatic balance is a machine for weighing substances in water, for the purpose of ascertaining their specific gravities. Hydrostatic press (commonly called Bramah's press) is a machine by which an enormous amount of pressure may be obtained through the medium of water. Hydrosulphurets, in chemistry, a genus of salts, resulting from the combination of hydrosulphuric acid with salifiable bases.

Hydrotel'lurates, a genus of salts, resulting from the combination of an acid composed of hydrogen and tellurium with salifiable base.

Hydrotho'rax (Gr.), dropsy in the chest. Hydrot'ic (Gr.), medicine to expel water or phlegm.

Hydroti'tis (Gr. hydor, and ous, otis the ear), in pathology, dropsy of the ear. Hydroxan'thate, a compound of hydroxanthic acid with a base. Hydroxan'thic, an acid formed by the action of alkalies on the deutosulphuret of carbon. Hydrox'ide, a metallic hydrate. Hydruret (Gr.), a combination of hydrogen destitute of acidity.

Hydrus (Gr.), a genus of ophidian reptiles, the Water-snake. In astronomy, a constellation in the southern hemisphere.

Hyetom'eter (Gr.), a rain gauge. Hyge'ia, the name of one of the newlydiscovered planets, first observed by De Gasparin in 1853. Its mean distance from the sun is 300,340,000 miles, and the time of its periodical revolution 5 years and 215 days. Hygeine, Hygiene (Gr.), that branch of medicine which relates to the means of preserving health.

Hygro- (Gr.), a prefix to compound words implying moisture. Hygroblepharic (Gr.), in anatomy, an epithet applied to the excretory ducts, and their orifices, of the lachrymal gland.

Hygrology (Gr. hygros, and logos a discourse), in pathology, the doctrine of the humours or fluids of the body.

Hygrometry (Gr.), the art of measuring the moisture of the atmosphere.Hygrometer, an instrument to measure the degrees of moisture or dryness of the atmosphere.

Hygroscope (Gr. hygros, and skopeo to view), an instrument to show the moisture and dryness of the air. Hygrostatics (Gr.), the measuring of degrees of moisture. Hyleosaurus (Gr. hyle a wood, and saurus a lizard), an extinct gigantic genus of reptiles, the fossil remains of which exist in the Wealden strata of Sussex.

Hylobates (Gr. hyle, and baino to walk), in zoology, a genus of Quadrumana, the Gibbons, or Long-armed Apes. Hymenology (Gr. hymen a membrane, and logos a discourse), in anatomy, a treatise on, and dissection of, the membranes of the animal system. Hymenomyce'tes (Gr. hymen, and mykes a mushroom), an order or tribe of Fungi.

Hymenop'tera (Gr. hymen, and pteron a wing), in entomology, a term applied to insects like the Bee.

Hymenop'teran (Gr.), a mandibulate insect, having four membranous wings. Hyoglossus (Gr.), in anatomy, a term applied to a muscle which extends from the hyoid bone to the tongue. Hyoid, resembling the Greek letter v ; and, in anatomy, applied to the bone which supports the tongue, from its shape.

Hyoscya'mia (Gr.), in chemistry, a vegetable alkali. Hyoscyamus, Henbane. -Hyoscyamine, the active principle of henbane.

Hypapophysis (Gr.), an apophysis of a vertebra growing downward. Hypargyrite, an ore of silver. Hyper, a Greek prefix, implying over, beyond, excess. In the compound terms of chemistry it corresponds with super.

Hyperæsthe'sia (Gr. hyper and aisthanomai to feel), in pathology, excessive sensibility.

Hyperbola (Gr.), in geometry, a curve formed by cutting a cone in a direction parallel to its axis.-Hyperbolic conoid or hyperboloid, a solid formed by the revolution of an hyperbola

about its axis.

Hypercatharsis (Gr. hyper, and kathairo to cleanse), excessive purgation.

Hypercrisis (Gr.), the crisis of a disease; a violent critical effort of evacuation. Hyperica'ceæ, an order of herbaceous exogenous plants. Hypericin'eæ (Gr.), in botany, a nat. order of exogenous plants, usually herbaceous, of which the Hypericum,