ence will admit of it, the larger it is the better

Air-pump bucket, an open piston, with valves on the upper surface, opening upwards, so as to admit the air and water in the downstroke, and lift it with the upstroke of the pump Air-pump rod, the rod for connecting the bucket to the beam Air-tint, in painting, the tint by which the distant parts of a landscape are rendered more distinct, or sometimes giving a misty appearance to the whole: it is generally compounded of a blue-grey, occasionally approaching to purple Air-trap, a trap immersed in water, to prevent foul air arising from sewers or drains

Air-valve, applied to steam boilers for the purpose of preventing the formation of a vacuum when the steam is condensing in the boiler Air-vessel, the closed cylinder con

nected to the discharge-pipe of a force-pump, and by the action of which the water ejected by the piston or plunger of the pump enters the cylinder and compresses the air within; it acts as a spring during the return stroke, and thus renders the stream constant: also a chamber containing air, attached to pumps and other water engines, for the purpose of making the discharge constant when the supply is intermittent

Aisle, the side passage or division of

a church, partially separated from the nave and choir by columns or piers

Aitre, a hearth or chimney Alabaster, a species of gypsum, a mineral substance, chemically termed sulphate of lime: also a box or vase for holding perfumes and ointments; so called because originally made of alabaster, and for which the variety called onyx-alabaster was usually employed Alba, a beacon or light-house Albarium, white-wash; according to Pliny and Vitruvius, a white stucco

or plaster, made of a pure kind of lime burned from marble, and used to spread over the roofs of houses Albarium opus, according to Vitruvius, a species of stucco-work Alcahest, in ancient chemistry, a universal dissolvent

Alcha, a cellar, pantry, or an apartment for the reception of drinking vessels

Alchemist, one skilled in the art of alchemy or chemistry

Alchemy, that branch of chemistry which presumes the transmutation of metals: Lord Bacon calls it the art of distilling or drawing quintessences out of metals by fire Alcohol, in chemistry, a pure spirit Alcoholometer, an instrument for ascertaining the strength of spirits Alcorans, in oriental architecture, high slender towers attached to mosques, in which the Koran is read

Alcove, a recess in a chamber, or a

recess separated from other parts of the room by columns, antæ, and balusters

Alder, a wood formerly much used.

The common alder seldom exceeds 40 feet in height, is very durable under water, and was used for the piles of the Rialto at Venice, the buildings at Ravenna, &c.: it was formerly much used for pipes pumps, and sluices

Aleaceria, a palace, castle, or other large edifice

Aleatorium, an apartment in a Roman house appropriated to the use of persons playing with dice A-lee, a term used to denote the posi

tion of the helm when it is put in the opposite direction from that in which the wind blows Alembic, in chemistry, a vessel used in distillation

Aleois, loopholes in the walls of a castle or fortification, through which arrows may be discharged Algaroth, in chemistry, a white powder obtained from muriate of antimony Algebra, literal arithmetic, or the

Alkali, in chemistry: potash and soda

were usually termed fixed, and ammonia volatile, alkalies: alkalies combine with and neutralize acids, thereby producing salts; they also change vegetable blues to green Alkalimeter, an instrument for measuring and determining the quantity and strength of alkalies Allette, used to express a small wing of a building; also applied to a pilaster or buttress

Alley, a passage from one part of a building to another; a passage or court with houses

Alligation, one of the rules of arithmetic, by which are resolved questions which relate to the compounding or mixing together of divers simples or ingredients

Allorium, a piazza, corridor, or covered way in the flank of a building Alloy, baser metal, commonly mixed with the precious metals Alluvium, the débris occasioned by causes still in operation, as deposits left by the action of rivers, floods, and torrents

Henry I.

Do.

Almacantar, lines parallel to the horizon, and conceived to pass through every degree of the meridian Almehrab, a niche in the mosques of the Arabs, for praying Almond-tree, a hard, heavy, oily or resinous kind of wood, somewhat pliable

Almonry, a room or place where alms were formerly distributed to the poor

Almshouse, a house for the reception and support of the poor

Aloof, in navigation, to keep the ship near the wind when sailing upon a quarter wind

Alquifore, lead ore found in Cornwall, and used by potters to green varnish their wares

Alruna, small images carved out of

roots of trees, and anciently held in much veneration by the northern nations

Altar, an elevated table of either stone, marble, or wood, dedicated to the ceremonies of religious worship. "And Noah builded an altar unto the Lord; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar."-Gen. viii. 20. Altar-piece, the ornamental sculpture or painting behind the altar in a Christian church

Altar-screen, the back of an altar, or the partition by which the choir is separated from the presbytery and lady-chapel

Altars, among the Greeks, according to Wilkins's Vitruvius,' faced the east, and were placed lower than the statues arranged about the cella,

in order that those who offered up prayers and sacrifices might know, from their different heights, to what particular deities the several altars were consecrated Altare chori, a reading desk in a church

Altare farum, the lustre, chandelier,

or cresset, suspended over an altar Altimetry, the art of taking or mea

suring altitudes or heights Altitude, of a figure, the length of a line drawn perpendicularly from the vertex to the base Alto-rilievo, highly relieved sculpture representing figures either entirely or nearly detached from the background

Alum, a salt extracted from various minerals called alum ores; of great use to chemists, dyers, and artists; acid and sharp to the taste Aluminum, in chemistry, the metallic base of the earth alumina, which is found in nature along with some oxides, and acting as an acid: these combinations are termed aluminates, and are insoluble in acids Alveus, in hydrography, the channel or belly of a river

Amalgam, a mixture of mercury with any other metal, tin, lead, &c. Ambitus, an enclosure, more particu

larly applied to the space around a building, as a church-yard or a castle-yard

Ambo, Ambone, a rostrum or raised platform

Ambulatio, walks, or places of exercise, according to Vitruvius, adjacent to theatres

Ambulatory, a cloister, gallery, or alley Ammonia, in chemistry, a compound

of hydrogen and azote, which can only be exhibited pure in a state of gas; with carbonic acid, it forms volatile alkali or hartshorn. Ammonia is found in the urine of animals, in the earth, and also in the atmosphere: it was formerly obtained by distilling horn, from which it acquired the name of hartshorn. It is generally prepared from chloride of ammonium or sal

ammoniac, from which it receives its name

Ammoniac, a gum used for metallic vessels

Amphiprostyle, a term applied to a temple with a portico in front and also behind

Amphitheatre, an edifice formed by the junction of two theatres at the proscenium, so as to admit of seats all round the periphery Amphitheatre, in Roman antiquity, a large edifice of an elliptic form, with a series of rising seats or benches disposed around a spacious area, called the arena, in which the combats of gladiators and wild beasts, and other sports, were exhibited. It consisted exteriorly of a wall pierced in its circumference by two or more ranges of arcades, and interiorly of vaulted passages radiating from the exterior arcades towards the arena, and several transverse vaulted corridors which opened a free communication to the stairs at the ends of the passage and to every other part of the building; the corridors and ranges of seats forming elliptical figures parallel to the boundary wall Amphithura, in the Greek Church, the veil or curtain opening to the folding doors, and dividing the chancel from the rest of the church Amphora (pl. amphora), an earthen vase or jar, with a handle on each side of the neck; among the ancients, the usual receptacles of olives, grapes, oil, and wine. Hence, in decoration, amphoral means, shaped like an amphora or vase Amulet, in decoration, a figure or character to which miraculous powers were supposed to be attached, and which particularly distinguished the buildings of Egypt Amussium, anciently a carpenter's and mason's instrument, the use of which was to obtain a true plane surface; but the statements of the ancient writers render its construction extremely difficult Amylum, in chemistry, starch