Autunite, a yellowish-green mineral, found in granite.

Avalanche (Fr.), an immense accumulation of snow and ice, which, on being detached from the mountain's height, descends with terrible ponderosity, and often with devastating and fatal results.

Ave'na (Lat. oats), in botany, a genus of the Gramineæ, or Grass family; the oat-grass.-A. sativa, the common

oat.

Aves (Lat. birds), in zoology, the second class of the Vertebrata, comprehending the feathered animals which are oviparous.

Avicu'lidæ (Lat. little birds), in ichthyology, a family of bivalve Mollusca, belonging to the tribe Atrachia, of which the Avicula is the type. It has a shell with equal valves, and a rectilinear hinge, often extended into wings on each side (whence the name); the shells interiorly are of a pearly lustre; and one of the species is the well-known oyster, A. margaritifera, from which the most valuable pearls are obtained. Avoirdupois (Fr. to have weight), a pound weight, containing 16 ounces, 256 drachms, or 7,000 grains; 28 pounds making 1 qr., and 4 qrs. I cwt.

Awl Tree, in commerce, the name of the Indian mulberry (Morinda citrifolia), the roots of which are used for dyeing.

Awm, a Dutch measure, equal to 34.16 imperial gallons. Awn, in botany, the hairy-pointed beard of corn or other grasses. Axe'stone, a mineral found in New Zealand, and other islands of the Pacific, with which hatchets, &c., are made by the inhabitants.

Axil, or Axil'la (Lat. the arm-pit), in botany, the angle formed by the separation of a leaf from its stem. Ax'illary (Lat.), in botany, a term applied to flower-stalks, when proceeding from the axilla, or angle made by a leaf and stem, or branch and stem. -In anatomy, applied to the arteries, veins, glands, lymphatics, and plexus connected therewith.

Ax'inite, a mineral of a brown, grey, black, or blue colour, with axe-shaped crystals, and consisting of silica, alumina, lime, oxide of iron, and oxide of manganese.

Axis (Lat.), a straight line, either real or imaginary, passing through the centre of a body on which it may be supposed to revolve; a pivot on which anything turns. In the sciences and the mechanical arts, the term is of very general application. In astronomy, axis is an imaginary line supposed

to pass through the centre of the earth and the heavenly bodies, about which they perform their diurnal revolutions. In geometry, it is the straight line in a plane figure, about which it revolves to produce or generate a solid. In mechanics, the axis of a balance is the line about which it moves, or rather turns about; the axis of oscillation is a right line, parallel to the horizon, passing through the centre, about which a pendulum vibrates; the wheel and axis is one of the mechanical powers, consisting of a wheel concentric with the base of a cylinder, and movable together with it about its axis.-In architecture, spiral axis is the axis of a twisted column drawn spirally, in order to trace the circumvolutions without; -the axis of the Ionic capital is a line passing perpendicularly through the middle of the eye of the volute. In optics, an axis is that particular ray of light, coming from any object, which falls perpendicularly on the eye. In anatomy, the axis is the second vertebra of the neck; it has a process, or tooth, which goes into the first vertebra, and this by some is called the axis.In botany, the axis is a taper column, placed in the centre of some flowers or catkins, round which the other parts are disposed; or it signifies the stem round which the leaves, or modified leaves, are produced.-Axal is an epithet relating to the axis; thus axal section is a section through any body, whatever shape it may be.

Axminster Carpet (so called from having been first manufactured at Axminster), in the arts, a term applied to carpets manufactured in imitation of Turkey carpets, and noted for their thick and soft pile; they are woven in one piece.

Ay'mestry Limestone, in geology, one of the calcareous beds of the Upper Silurian series, which has been produced by coral and shell accumulations amidst the masses of argillaceous sediments. It occurs near Ludlow, Malvern, and some localities in Wales.

Azalea (Gr. dry), in botany, a beautiful shrubby plant, with richly-coloured bell-shaped flowers; order Rhododendreæ.

Az'imuth (Arab.), in astronomy, the arc of the horizon intercepted between the meridian and the vertical circle passing through a star or other celestial body. -The azimuth of the sun, or of a star, is an arch between the meridian of the place and any

earth-bags contain about a cubical foot of earth, and are used to raise a parapet in haste, or to repair one that is beaten down; sand-bags are filled with earth or sand, to repair breaches, and the embrasures of batteries, when damaged by the enemy's fire.

Bag'shot-sand, in geology, a term applied to one of the Middle Eocene formations, consisting of extensive beds of sand, in which shells and the bones of a sea-serpent above 20 feet long have been discovered. They occur at Highgate and Hampstead, and other localities in Surrey, &c. According to Dr. Mantell, the boulders and masses of sandstone, which are abundant in some of the chalk valleys, and on the flanks of the Downs, are called Sardenstone, or Druid Sandstone, from being the principal material employed in the construction of Stonehenge and other Druidical monuments.

Bai'kalite (from Lake Baikal, in Siberia, and lithos a stone), in mineralogy, a variety of augite.

Bailey's Beads, in astronomy, an appearance as of a string of beads round the sun in an eclipse.

Ba'la Limestone, in geology, a fossiliferous series of slaty calcareous strata, occurring in the Silurian system.

Bala Ruby (Sp.), a rose-coloured variety of spinel, not nearly so valuable as the oriental ruby or sapphire.

Balæ'na (Lat. a whale), in ichthyology, a genus of Cetaceans, which comprehends the Balena mysticetus, or common Greenland whale, and other species, which are inhabitants of the polar seas and the Atlantic Ocean. -Balana boöps is a species of whale which attains the length of about 54

feet.

Balance (Fr.), one of the powers in mechanics. In astronomy, one of the twelve signs of the zodiac, commonly called Libra (2).-The hydrostatic balance is a balance used for determining the specific gravity of bodies, whether fluid or solid, by weighing them in water. Assay balance is a balance used in assaying metals.Balance-wheel is one of the wheels of a watch or chronometer, which answers the purposes of a clock pendulum, and regulates its motion.In commerce, balance-sheet is the financial statement of a merchant or trader's affairs.

Bal'anite (Gr. acorn-shaped), in botany, a genus of ornamental plants, of the order Olacaceæ.-In zoology, the name of a barnacle which is fixed by its shell.

Bala'nius (Gr. balanos, an acorn), in entomology, a genus of small weevil possessed of a long snout, by means of which it bores a hole into the common hazel-nut or filbert, for the purpose of depositing its egg, which is soon hatched into a larva or maggot. Bal'anoid (Gr. like an acorn), in ich. thyology, a family of barnacles, with shells arranged conically, like acorns. Bala'nus (Gr. an acorn-shell), in ichthyology, a genus of Cirripeds, the shells of which consist of a testaceous tube, attached to rocks and other substances.

Baldwin's Phosphorus, the ignited anhydrous phosphate of lime. Balis'tide (Gr. speckled), in ichthyology, a family of cheliform fishes, with oval bodies, mailed with plates, or covered by a hard coriaceous skin. Ball-and-Socket, in anatomy and mechanics, a peculiar kind of joint, of which one part is shaped like a ball, and the other is a hollow socket, in which the other moves.

Ball-valve, a simple contrivance, by which a ball is placed in a circular cup with a hole in its bottom, the ball being surrounded by four arms. Being placed in a tube, it is made to act as a piston in pumping water. Ballast Engine, a steam engine for dredging up shingle in a river, or drawing gravel or earth on a railway.

Ballis'tics (Gr. ballo to throw), the science of projecting heavy missiles by an engine. -Ballistic pendulum is an instrument for measuring the force or velocity of cannon or musket balls. Bal'lium (Lat.), in military architecture, the open space or court-yard within a fortified castle.

Balloon (Fr. ballon a little ball), a large inflated bag, of a spherical shape, inflated with hydrogen gas, which, being lighter than the atmospheric air, causes it to ascend, and pass through the air. In chemistry, a round vessel with a short neck, or a glass receiver of a spherical form.In fireworks, a ball of pasteboard filled with combustible matter, which, when ignited, shoots into the atmosphere, and then bursts, scattering around brilliant sparks of fire, resembling stars. In architecture, a ball or globe placed on the top of pillar.

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Balls, in military science, a general term applied to every kind of spherical or conical shot fired from a musket, rifle, or cannon; leaden balls being chiefly used for small arms, and iron ones for the artillery; their sizes and weights being distinguished by their calibres. Minie-ball is, comparatively, a new species of military fire-arm, in which the ball, instead of being round, is conical; the base being concave, and the conical or pointed end being drawn towards its object with much more force and velocity than the common ball. It received its name from Captain Minié, the inventor. In military science, there are various kinds of balls: as Light-balls, which are made of combustible materials, and are of great use in discovering the working parties of the besiegers by the strong light they throw on distant objects. Fire-balls are bags of canvas, filled with combustibles, thrown from mortars for the purpose of firing houses, magazines, &c.-Smoke-balls are intended to conceal the position of the troops, and annoy the enemy. Skyballs are those which ascend to a great height, and are useful in showing the situation of forts or lofty buildings, which are about to be attacked. Stink-balls are composed of combustible and suffocating materials. and are intended to stifle an enemy, or drive him out of his stronghold. - Ball-cartridge, the charge for a fire-arm, packed in paper, with a ball at the end.-National Cycl. Suppl.; Military Dict., &c. Ealm, the name of the labiate plant Melissa, the juice of which is of a highly aromatic and odoriferous character. Balm of Gilead is the fragrant balm extracted from the plant Baisamodendron Gileadense. Fal'neum (Lat. a bath), in chemical science, a vessel filled with sand or water, in which another vessel is placed, requiring a more gentle heat than the naked fire. - The varieties of Balnea are usually designated by Latin epithets: as, B. frigidum, the cold bath; B. pluviale, the shower bath; B. tepidum, the luke-warm bath; B. calidum, the hot bath, from 95° to 100o Fahr.; B. vaporis, the vapour bath, from 100 to 130° Fahr.; B. capitiluvium, the headbath; B. maniluvium, the handbath; B. pediluvium, the foot-bath; Demi-bain, the hip-bath; B. aquosum, the water-bath; B. arena, the sand-bath.

Balsam (Lat. balsamum), an unctuous, aromatic, healing substance, flowing spontaneously, or by incision, from certain plants; the natural mixture of resin with a volatile oil. The name is also given to certain drug preparations, as balsam of sulphur, an admixture of sulphur and olive oil.The true balsams are the brown bal

sam of Peru; the pale balsam of Tolu; balsam of Capivi, &c. Balsama'cese (Lat. flowing balsam), a nat. order of exogenous plants, consisting of lofty trees flowing with balsamic juices; it has only one genus, the Liquid-amber. Balsam'ina (Lat.), a genus of handsome flowering plants, natives of the East Indies. Balsamina hortensis is a well-known odoriferous garden flower, order Balsaminaceæ.

Balsamina'cesæ, or Balsamin'eæ (Lat.). a nat. order of exogenous plants, consisting of succulent annual herbs. Bal'uster, in architecture, a small column or pilaster, belonging to a balustrade, or row of balusters, for defence or ornament.

Bana'na (Sp.), a tall herbaceous plant, of the West Indies; also the fruit of the plant, used as food. It is known as the Musa paradisiaca; order Musaceæ. The fruit, when fully ripe, is exposed to the sun, and preserved as figs are, forming in this state an agreeable and wholesome food.

Ban'berry, the herb Christopher, the berries of which are very noxious. Ban'dages (Fr.), in architecture, the rings or chains of iron inserted in the corners of a stone wall, or round the circumference of a tower, at the springing of a dome, which act as a tie to keep the walls together. Ban'dala (Sp.), in the arts, a kind of fibre made from the strong outer layers of the Musa textilis, chiefly used in the manufacture of cordage. Ban'delet, in architecture, any little bend or flat mould that encompasses a column like a ring. Bandicoot, a genus of marsupial mammalians of Australia.

Banewort (Sax. bane destruction), in botany, the Atropa belladonna, or deadly nightshade, a poisonous herbaceous plant, found growing in waste grounds and hedges. Ban'gia, a kind of hempen cloth, made from the fibre of a gigantic stingingnettle in India.

Banian, or Banyan (Sans.), in botany, the Ficus Indica, or Indian fig tree, which spreads to such an extent that a single tree sometimes affords shelter to a cavalry regiment.

Bank'sia (after Sir J. Banks), a genus of umbellated bushy plants, found in the forest land or rocks over the whole known continent of Australia; order Proteaceæ.

Ba'phia (Gr. baphea dye), a genus of plants, the wood of which is im. ported into this country from Africa, as a dye stuff, by the name of camwood; erder Leguminosæ.

Baptis'ia (Gr. bapto to dye), a genus of herbaceous leguminous plants of N. America, the tincture of which is used as a dye-stuff.

Barba (Lat. a beard), a term of frequent application in different branches of natural history. In botany, it applies to any collection of long loose hairs into a tuft or crest. In zoology, it is the beard or long tuft of hair dependent from the chin or under jaw of a mammiferous animal.In ichthyology, it is a small kind of spine projecting from the mouth, with the teeth pointing backwards.In ornithology, it consists of feathers which hang from the skin covering the gullet or crop of certain birds.

Barbacan (Fr.), in mediæval architecture, a watch-tower or fort placed on the wall of a town; or a small round tower situated before the outward gate of a castle-yard or ballium. Barba'does Tar, a sort of bituminous oil, used in medicine and surgery. Barba'rea (herb of St. Barbara), a genus of cruciferous plants (winter cress), of which there are two British species, B. vulgaris and B. præcox. Barbel (Lat. barba a beard), in ichthyology, a genus of malacopterygious fishes, allied to the carp, which inhabits the rivers of England and Southern Europe.

Barbels (Lat. barba a beard), in ornithology, a family of scansorial or climbing birds, with bearded tufts and long conical bills.

Barbette (Fr.), in fortification, an earthen terrace, raised without a parapet; of sufficient height to enable the gunners to fire with a free range. Bar'botine (Fr.), a vegetable production of the East Indies, the constituents of which are wax, gum, and bitter extract. Crabbe.

Barilla (Sp.), a plant cultivated for its ashes, and the alkali procured from them; an impure carbonate of soda imported from Spain and other places, and chiefly used in the manufacture of glass and soap.

Baritone (Gr. heavy-toned), in music, a low pitch of voice, or a tone ranging between the bass and tenor. Ba'rium (Gr. barys heavy), in mineralogy, the metallic base of the mineral barytes, of the colour and lustre of silver; discovered by Sir H. Davy in 1807. When heated, it burns with a deep red light. It has a variety of chemical compounds, the principal of which are: -Bromide of barium, I atom of barium + 1 of bromine = 78.4; atomic weight, 147.1.-Chloride of bromium, I atom of barium + 1 of chlorine 35°42; atomic weight,

104 12.-Fluoride of barium, I atom of barium + 1 of fluorine = 18.68; atomic weight, 87 38.-Iodide of barium, I atom of barium + 1 of iodine 126°3; atomic weight, 1950. -Peroxide of barium I atom of barium + 2 of oxygen 16; atomic weight, 84.7.-Protoxide of barium, I atom of barium 687 + 1 of oxygen = 8; atomic weight, 76.7.Sulphuret of barium, I atom of barium + 1 of sulphur = 161; atomic weight, 84.8.

Bark (Germ.), in vegetable physiology, the external coating of the trunk and branches of trees, sometimes applied to medical or chemical purposes. Thus Peruvian bark is a very valuable medicine, the produce of the Cinchona, from many parts of South America, but chiefly from Peru; the medicinal property is termed quinine. Independently of its chemical properties, bark is of some importance for its organic products, which science and art have applied to many of the purposes of life. The liber, or bark of the lime tree, of the bread-fruit tree, and of the paper mulberry, is torn into slips, and manufactured into useful mats. Hence several kinds of bark, being used for processes in the arts or for medicines, enter extensively into commerce. Among these may be noticed the oak bark, cork bark, mimosa or wattle bark, the quercitron bark, cinnamon, cassia, &c. The oak bark it extensively used in tanning, for which it is valuable on account of the large proportion it contains of that peculiar astringent called tannin.-Barkery is the place where the tanners keep the bark used in the process of tanning. In horticulture, a bark-bed is a bed formed of the spent bark used by tanners, which is placed inside of a brick pit in a glazed house, constructed for forcing artificial warmth by the fermentation of the materials of which it consists. Barley (Sax. bere), the Hordeum of botanists, extensively used in malting, from which ale and porter are produced.

Barnacle (Fr.), in conchology, a family of sedentary crustaceans, protected by hard shell-like valves; the common name for the Pentalasmis anatifera is the duck barnacle, a Cirriped, with a shell attached to a fleshy stalk, found adhering to ships or floating timbers. In ornithology, Barnacle or Bernacle goose is a species of goose which is found in high northern latitudes, and visits Britain in the autumn. In farriery an in