Wacke (Germ.), in mineralogy, a rock nearly allied to basalt, of which it is a soft and earthy variety, and chiefly composed of silica. Wagnerite, a rare mineral resembling the Brazilian topaz. It consists of phosphoric and fluoric acids, magnesia, the oxide of iron, and manganese. Wal'lerite, a variety of orthoclase, found in small compact masses, yellowish and translucent.

Wall-plate, in architecture, a piece of timber lying on a wall, on which girders, joists, &c., rest. -Wallspring, a spring issuing from stratified rocks.

War'wickite, a mineral containing titanium.

Watch (Swed.), in mechanical science,

a small portable time-piece, the machinery of which is moved by a spring. Those watches intended for astronomical or nautical observations are called chronometers, sometimes made with such precision as to vary but a few seconds in the course of a year. At Goldsmiths' Hall, from 14,000 to 15,000 gold watches, and from 80,000 to 90,000 silver ones, are annually assayed.-In watchmaking there are various trades or professions called into action, as the watch-dial silverer, the watchglass maker, the watch-tool maker, watch balance-wheel maker, watchbarrel maker, watch-cap maker, watch-case maker, &c.

Water (Sax.), a colourless, inodorous, transparent fluid, composed of oxygen and hydrogen, in the relative proportions, by weight, of 8 to 1. Water presents itself in three distinct forms: first, in a state of vapour or steam; secondly, in its liquid state; and, lastly, in its frozen or solidified state. When fluid, it is not in its most simple state, for its fluidity de. pends on a certain quantity of caloric, which enters into combination with it, and insinuating itself between the particles of the water, renders them capable of moving in all directions. -In the arts and mechanical science there are various combinations of this word as a prefix; as, Water-gauge, an instrument for measuring the depth and quantity of water;-Waterline, in nautical science, the line which distinguishes that part of a ship which is under water from that part which is above;-Water-ram, a machine by which water is raised much above its level by the momentum of a larger

a

stream than the one raised;-Waterspout, a remarkable meteorological phenomenon, which appears as a conical pillar descending from dense cloud;-Water-thermometer, an instrument for ascertaining the degree of cold at which water ceases to be condensed;-Water-wheel, a wheel of a mill moved by water; an engine for raising water out of a deep well;-Water-works, hydraulic en

gines or structures; artificial spouts of water.

Wa'vellite (in honour of Dr. Wavel, the discoverer), a mineral consisting of small slender crystals radiating from a centre, composed of phosphoric acid, alumina, water, fluoric acid, lime, oxides of iron and manganese: sp. gr. 333; H=3'5—4°0.

Weald, or Wealden (Dutch), in geology, a term signifying a peculiar formation or strata of rocks, so named from the wealds of Kent or Sussex. The great wealden formation is a series of fresh-water deposits, covering an area 200 miles in length from east to west, and 220 miles from north-west to south-east, the total thickness averaging about 2,000 feet. The organic remains consist of leaves, stems, and branches of plants of a tropical character; bones of enormous reptiles of extinct genera, of crocodiles, turtles, flying reptiles, birds, and fishes. The wealden is supposed to have formed the estuary of an immense river.-Wealden clay is the blue clay which forms part of the wealden group.

Weasand (Sax.), in anatomy, the windpipe or trachea, the canal through which air passes to and from the lungs.

Wedgwood Ware, in the arts, a supe rior kind of earthenware, so called from its inventor, Mr. Wedgwood.Wedgwood's pyrometer is an instrument used for ascertaining very high degrees of heat.

Wehrlite, in mineralogy, a mineral containing iron. Weighing Machine, in

mechanical science, a machine for weighing heavy bodies, and particularly wheelcarriages at turnpike gates. Weight (Sax.), in statics, the pressure which a body exerts vertically downwards, in consequence of the action of gravity; anything to be raised, sustained, or moved by a machine. -In natural philosophy, the weight of a body is synonymous with its

specific gravity multiplied by its bulk. Weissite (in honour of Professor Weiss,

of Berlin), a translucent mineral found at Falun in Sweden. Its constituents are potash, soda, silica, alumina, magnesia, protoxide of iron, protoxide of manganese, oxide of zinc, and water: sp. gr. 2'80. Weld (Germ. wellen to join), according to the laws of mechanical affinity, to unite two or more pieces, generally of iron, by hammering them together when softened by heat. Werne'rian The'ory, in geology, the doctrine propounded by Werner, the celebrated German mineralogist, which ascribed the origin of all rocks to aqueous deposition, as opposed to the Huttonian theory.

Wernerite (in honour of Professor Werner), in mineralogy, a silicate of alumina, lime, and oxide of iron. It is found massive and crystallized in octahedral prisms.

Whale (Sax. and Swed.), the general name for an order of Mammalia inhabiting the ocean, arranged under the name Cetacea.-The Greenland whale is the largest animal of this or former ages of the earth. Wheel (Dutch and Swed.), in mechani

cal science, a simple machine, consisting of a round piece of wood, metal, or other material, which revolves on an axis. It is one of the principal powers which science has applied to mechanism.-Wheel-axle is a machine consisting usually of a cylinder, to which a wheel is firmly united, so that the mathematical axes of both are coincident.

Wheel An'imals, in natural history,

the popular name of the Rotifera, a genus of Infusoria which have their tentacula arranged in a wheel-like form.

an

Whelk (Sax. weoloc, hwylca), in zoology, the common name given to the marine shell Buccinum undatum, or Trumpet-shell.-In pathology, unsuppurative tubercular tumour, generally occurring on the face. Whinstone (Scotch quhyn resounding), in mineralogy, a provincial term applied to greenstone, clinkstone, porphyretic, and other trap rocks. Whirling Machine, in mechanical science, an apparatus for determining the resistance of air.-Whirlingtable, a machine contrived to exhibit the principal laws of gravitation, or the phenomena in philosophy and nature relative to the power of the centrifugal force.

Whirlwind, in physics or pneumatics, a body of air moving in a circular or

spiral form, as if round an axis, and at the same time having a progressive motion.

White (Sax.), a negative colour, which is the most significant of light, and reflects all its rays, as pure snow.White is a prefix to numerous terms connected with mineralogical science and the arts.-White antimony is a mineral of a snow-white or grey colour, consisting of antimony and oxygen: sp. gr. 5 ̊5; H-3°5.-White copper, a term applied to Chinese copper, which is alloyed with zinc, and forms a very hard white metal, but little disposed to tarnish.-White enamel, or calcine, an enamel made by calcining about 30 parts of tin and 60 parts of lead.-White-lead, the white oxide of lead, used for numerous purposes of painting, &c.-Whitelead ore is the carbonate of lead, which occurs in tabular crystals in six-sided prisms, variously terminated, and consists of carbonic acid and protoxide of lead: sp. gr. 6'3; H=30.-White manganese is an ore of manganese; carbonated oxidized manganese.-White metal, a kind of queen's metal, made by fusing together IO ounces of lead, 6 ounces of bismuth, and 4 drachms of regulus of antimony.-White precipitate is a compound of ammonia and corrosive sublimate, or of metallic mercury, hydrogen, and oxygen. -Spanish-white, a substance used in painting, prepared from chalk by separating it from its siliceous impurities. White vitriol is the sulphate of zinc, a mineral found principally in the deserted galleries of old mines. Its constituents are oxide of zinc, sulphuric acid, oxide of manganese, oxide of iron, and water: sp. gr. 20; H-2.-In botany, white balsam is pubescent myrrh-seed, the South American tree, Myrospermum pubescens, from which the perfume of quinquina is obtained.-In pathology, white gum is the Strophulus albinus, a species of gum-rash, in which the pimples are minute, hard, and whitish, surrounded by a reddish halo. Whooping-cough, in pathology, a violent convulsive cough, returning by fits at longer or shorter intervals. Whorl, in conchology, a wreath, convolution, or turn of the spire of a univalve shell: the axis of revolution is termed the columella, and the turns of the spiral are denominated whorls.-In botany, a species of inflorescence, in which the flowers surround the stem in the form of a ring. Wide Gauge, in railway science, a term

Y

applied to the widest gauge used on railways, as distinguished from the narrow gauge; the rails of the former being seven feet apart.

Wil'lemite, a mineral of resinous lustre and yellowish colour. Wind (Sax.), in meteorology, a current in the atmosphere, conveying the air, with greater or less velocity, from one part to another -In pathology, wind-dropsy is a tumour filled with air. Wind-gauge is an instrument for ascertaining the velocity and force of wind.-Wind-gall, in farriery, a soft flatulent tumour which grows on each side of the fetlock joints, and makes a horse halt when on hard ground.—Wind-sail, a wide tube or funnel of canvas used to convey a stream of air into the lower apartments of a ship. Windage, in gunnery, the difference

between the diameter of the bore of a gun or other piece, and that of the ball or shell.

Windlass, in mechanical science, a machine for raising weights, in which a rope or chain is wound about a cylindrical body moved by levers. Winter Solstice, in cosmography, the entrance of the sun into the sign Capricorn, on the 21st of December. With amite, a siliceous crystallized mineral, found encrusting the surface of trap rock by Mr. Witham. Its constituents are silica, alumina, peroxide of iron, lime, and water: sp. gr. 2'85; H=6'0.

Woad (Sax.), the common name of plants of the genus Isatis: also the name of the plant Reseda luteola, known otherwise as Dyer's-woad.

X begins no word truly English, but is chiefly used in words of Greek origin, and hence it is frequently applied to terms of a scientific character. In arithmetical science, as a numeral, it stands for 10; when laid horizontally, X, for 1,000; and, on account of its corresponding with the Greek digraph Ch, it is used as a contraction for Christ. Xan'thian, an epithet pertaining to Xanthus, the ancient capital of Lydia, as the Xanthian marbles in the British Museum.

Xanthic (Gr. yellow), in chemistry, an epithet denoting an acid composed of sulphur, carbon, and oxy

Woad-blue is of a deep hue, and is the base of many other shades of colour.

Wolfe's Appara'tus, in chemistry, a term applied to a bottle with two or more openings, used for generating gases.

Wolfram, in mineralogy, a native tungstate of iron and manganese. Wollastonite, in mineralogy, a species of prismatic augite; a silicate of lime.

Works, in military science, a term generally applied to the fortifications about the body of a place. The word is also used to signify the approaches of the besiegers, and the several lines, trenches, &c., made for security. Worm (Sax.), in natural history, the class Vermes of Linnæus, including Intestinal Worms; the Mollusca, or Snails; the Testacea, or Shell-fish; and Zoophytes, or compound animals, including Corals, Polypes, and Sponges. In distillation and chemistry, worm is a spiral leaden pipe placed in a tub of water, in which it is cooled and condensed. Wor'mian Bones, in anatomy, the small triangular pieces of bone sometimes found lying between the other bones of the skull.-Dr. Henry.

Wort (Sax.), in brewing and distillation, the fermentable infusion of malt grain, consisting of saccharine matter, starch, gluten, and tannin. Worthite, a white and translucent mineral discovered by Von Worth, of St. Petersburg, consisting of silica, alumina, magnesia, and water. Wyvern, in heraldry, an imaginary bird with a serpent's tail.

ganic bodies found in chalk and flint, supposed to be fossil Infusoria. Xanthine (Gr.), in chemistry, the yellow dyeing matter contained in madder.

Xanthite (Gr.), a mineral of a light grey or yellow colour. Its constituents are silica, alumina, lime, peroxide of iron, peroxide of manganese, and water: sp. gr. 3°20. Xan'thogen (Gr. xanthos yellow, and gennao to generate), in chemistry, the base of an acid, procured by the action and reaction of carburet of sulphur and potash.-Xanthide is a compound of xanthogen and a metal. Xan'thophylle (Gr. xanthos, and phyllon a leaf), the yellow colouring matter or sappy exudation in plants. Xanthopic'rine (Gr. xanthos, and pik

ros bitter), a bitter principle obtained from the bark of the Xanthoxylum. Xanthoram'nine (Gr.), in chemistry, an organic compound existing in the ripe berries of certain species of Rhamnus. Xan'thortite (Gr.), in mineralogy, a yellowish variety of allanite.-Dana. Xanthous (Gr.), in ethnology, a term applied to varieties of mankind with yellow, red, or brown hair. Xanthoxyla'ce (Gr. xanthos, and xylon wood), in botany, a nat. order of exogenous plants, consisting of trees cr shrubs, of which Xanthoxylum, or Prickly Ash, is the type and genus. Xen'otime (Gr.), an opaque crystal mineral; a phosphate of yttria. Xera'sia (Gr. dryness), in pathology, a disease of the hair.

Xero'des (Gr. dryness), in pathology, something of a drying nature; a dry

tumour.

Xiph'ias (Gr. xiphos a sword), in ichthyology, the Sword-fish.-In astronomy, a comet like a sword. Xiphoid (Gr. sword-like), in anatomy, denoting a ligament or cartilage connected with the sternum, resembling a sword.

Xiphosu'ra (Gr. xiphos, and oura a tail), in malacology, a family of Crustaceans with sword-shaped tails. Xy'lidine (Gr.), in chemistry, an artifi-/ cial organic base or alkaloid, consisting of hydrogen, nitrogen, and carbon.

Xylo- (Gr. xylon wood), a prefix to numerous words connected with mechanical science and the arts, of which wood is the chief material.

Yapon, in botany, the name of a South Sea Tea, the Cassine, the produce of the Ilex cassine, which is applied medicinally, and used as a tea. It is the produce of the southern states of South America.

Yarrawa'ra, in botany, a tree of New South Wales, one of the largest of the Eucalipti, which produces excellent timber.

Year (Sax.), in chronology and natural philosophy, an important division of time, embracing the four seasons, and determined by the revolution of the earth in its orbit.-The civil year is the year of the calendar, i.e. 12 months, or 365 days in

common

years, and 366 in leap years, beginning with the 1st of January.-The sidereal year is the space of time the sun takes in passing from any fixed star till his return to it again; the

Xylobal'samum (Gr. xylon, and Lat. balsamum), the wood of the Balsam tree; a balsam obtained by decoction of the leaves of the Amyris Gileadensis.

Xylog'raphy (Gr. xylon, and graphe

writing), the art of engraving on wood; wood-engraving. Xy'lochlore (Gr. xylon, and chloros green), an olive-green crystalline mineral, closely resembling apophyllite.-Dana.

Xylo'idine, in chemical science, a term applied to paper after it has been immersed in strong nitric acid, and washed in distilled water; the paper then assumes the toughness of parchment, and is so combustible as to serve for tinder.

Xylole, in chemistry, a hydrocarbon found among the oils separated from crude wood-spirit by the addition of water.-Miller.

Xylotile, in mineralogy, an opaque green mineral, consisting of silver, iron, and magnesia. Xylor'etine, in chemistry, a crystallizable compound found on the femains of pine trees.

Xylopyrogʻraphy (Gr. xylon, pyroo to burn, and graphe engraving), the art or practice of engraving on charred wood.

Xyphirrhyn'chus (Gr. xiphos a sword, and rhynchos a beak), a family of fishes, of which the Sword-fish is the

type.

Xyster (Gr. xystron a scraper), in surgery, an instrument for scraping and shaving bones.

length of this is 365 d. 6 h. 9′ 11′′.—A lunar year is the space of twelve lunar months.-The Julian_year consists of 365 days. Julius Cæsar ordered that the civil year should consist of 365 days for three succes sive years, and the fourth of 366 days. Yeast (Sax.), a substance generated during the vinous fermentation of vegetable juices and decoctions, rising to the surface in the form of froth.

Yellow (Sax.), the lightest and warmest of the prismatic colours, situated in the solar spectrum between red and blue.

Yel'lowing, in the arts, a term for cleaning pins by boiling them in sour beer or solution of tartar.

Yenite, an opaque mineral of a black colour, with a shade of brown or green, consisting of silica, lime, prot

oxide of iron, protoxide of manganese, alumina, and water: sp. gr. 3'99. Y-level, in surveying, an instrument for measuring altitude and distance. Yttrium, a peculiar metal, discovered in the state of an oxide in Sweden; when heated to redness in the air, it takes fire, burns with splendour, and is converted into yttria. Yttroce'rite, a mineral which occurs

Zaffre, in chemistry, the residuum or impure oxide of cobalt, after sulphur, arsenic, and other volatile matters have been expelled by calcination. Zamite, in geology, a fossil Zamia, which is a kind of Palm. Zamtite (Sp.), a hydrous carbonate of nickel of an emerald-green colour. Zaph'ara, in the arts, a mineral used by potters to make a sky colour. Zar athan, in pathology, a hard tumour of the breast, resembling a cancer. Zarnich, a genus of fossils that burns with a whitish flame.

Zea (Gr. zoo to live), a genus of important Grasses, Indian Corn or Maize, extensively cultivated in warm countries as an article of food.

Zebra Wood, a beautiful cabinet wood obtained from Demerara. Zechstein (Germ.), in mineralogy, a magnesian limestone lying under the red sandstone.

Zenith (Ital. zenit), in natural philosophy and ouranology, that point in the visible celestial hemisphere which is vertical to the spectator; the point directly overhead, and opposite to the nadir.-Zenith distance is the distance of a star or planet from the zenith, measured on the vertical circle passing through the zenith.Zenith sector is an astronomical instrument for measuring, with great accuracy, the distances from the zenith of stars which pass near that point.

Ze'olite (Gr. zeo to foam, and lithos a stone), in mineralogy, a family of minerals, consisting of silica, alumina, lime, and water; natrolite. Zero (Ital.), in meteorology, the point at which the graduation of the thermometer commences.-The zero of Réaumur's and of the Centigrade thermometers is the freezing-point of water; that of Fahrenheit's thermometer, 32° below the freezing-point. Zetetios (Gr. zeteo to inquire), a part of algebra which consists in the direct search after unknown quantities.

Zeuxite (Gr.), a greenish-brown mineral,

crystallized and massive, and whose constituents are fluoric acid, yttria, oxide of cerium, and lime: sp. gr. 3°44. Yttrocolum'bite, the name of a mineral, of which there are three speciesthe yellow, brown, and black. Yttrotan'talite, a mineral containing yttria and oxide of columbium. Yu, in mineralogy, nephrite or jade.

consisting of silica, alumina, protoxide of iron, lime, and water: sp. gr. 3'0; H-4°25.

Zigzag (Fr.), an ornament in Gothic architecture; another name for the chevron.

Zigzags, in fortification, trenches or paths with several indented windings, so cut that the besieger cannot be enfiladed in his approaches. Zi'mome (Gr. zyme ferment), in che

mistry, that part of the gluten of wheat which is insoluble in alcohol. Zinc (Germ.), a metal of a bluish-white colour, brittle when cold, but malleable when heated; much used in the manufacture of brass and other alloys. It is found in solid masses, sometimes in six-sided prisms, having the ends terminated in pentagons.Sulphate of zinc is found efflorescent in the form of stalactites, or in rhombs.-Sulphuret of zinc is the most abundant of the zinc ores.-Flowers of zinc, the oxide of zinc which flies up on the exposure of the metal to a temperature in the air very little above the melting-point, in the form of white flowers.-Zinc

amyl, a colourless transparent liquid, composed of amyl and zinc. Zinc-bloom, an opaque mineral of a greyish dull lustre, composed of carbonic acid, oxide of zinc, and water. Zinc-ethyl, a colourless, transparent, and poisonous liquid, consisting of ethyl and zinc.-Zincomethyl, a volatile liquid of a very fetid smell, and consisting of carbon, hydrogen, and zinc. Zinc-white, the oxide of zinc, used as a pigment for the same purposes as white-lead. Zincog'raphy (Germ. zink, and Gr. grapho to write), the art of drawing upon, and printing from, plates of zinc. Zingibera'cem, a nat. order of aromatic endogenous plants, of which Zingiber is the type. Zin'kenite, a crystallized mineral containing antimony, sulphur, lead, and copper: sp. gr. 5*30; H=3-3'5. Zircon, a mineral composed chiefly of zirconia and silica, found in Ceylon.