for measuring the velocity of a cannon ball, i. e. the force of gunpowder. It consists, in its simplest form, of a beam, which can swing on a fixed axis at one end, while the ball strikes the other end; and the angle through which that end moves being known, the velocity of the cannon ball may be computed

Balloon, a spherical hollow body, floating in the air by means of its inflation with gas specifically lighter than the atmosphere

Balloon, a globe placed on the top of a pillar or pediment, as an acroter or crowning

Balls, in electricity, invented by Mr. Canton, are two pieces of cork or pith of elder-tree, nicely turned in a lathe to the size of a small pea, and suspended by delicate threads Ball valves, the valves in the force

pumps of a locomotive engine: the balls are turned and ground truly spherical, so as to fit water-tight into the valve-seats in every position Balneac, in Greek, signifies a bath or bathing vessel

Balteum, a band or girdle, according

to Vitruvius: this word is used to denote the moulding on the bolsters or sides of the Ionic capital Baltei, the bands in the flanks of Ionic pulvinated capitals. Balteum and balteus were generally used by the Romans to signify the belt by which the sword or quiver was suspended

Baluster, a small column or pillar, used in a balustrade Balusters, placed round the gallery in the stern, and likewise in the quarter gallery of large ships Balustrade, a series or row of balusters, joined by a rail, serving for a rest to the arms, or as a fence or inclosure to balconies, altars, staircases, &c.

Balustrades, when intended for use, as against windows, on flights of steps, terraces, and the like, should not be more than three feet six inches, nor less than three feet in

BAN

height. When used for ornament, as on the summit of a building, their height may be from twothirds to four-fifths of the entablature whereon they are employed: and this proportion is to be taken exclusive of their zoccolo or plinth, so that from the proper point of sight the whole balustrade may be exposed to view. There are various species of balusters; if singlebellied, the best way is to divide the total height of the space allotted for the balustrade into thirteen equal parts, the height of the baluster to be eight, of the base three, and of the cornice two of those parts; or divide the total height into fourteen parts, making the baluster eight, the base four, and the cornice two. If doublebellied, the height should be divided into fourteen parts, two of which are to be given to the cornice, three to the base, and the remainder to the baluster.

The distance between two balusters should not be more than half the diameter of the baluster in its thickest part, nor less than onethird of it; but on inclined planes the intervals should not be quite so wide.-Gwilt.

Band, in architecture, denotes any

flat low member, or moulding, that is broad and not very deep Banderole, in heraldry, a narrow flag or streamer affixed under the crook of a crosier, and folding over the staff

Bandlet, a small fillet, or flat moulding
Bandrol, a little flag or streamer
affixed to the top of masts
Bank, a long piece of timber
Bank. To double bank an oar, is to

have it pulled by two men Banker, in bricklaying, is a bench

from 6 to 12 feet in length; is used for preparing the bricks for gauged work

Banker, a cushion or covering for a seat

Banneret, in heraldry, a knight made in the field

Banquet, the raised footway adjoining to the parapet on the sides of a bridge

Baptaterium, a back mill or fulling mill

Baptistery, a place or edifice where baptism is performed. A basin, pool, or place for bathing Bar, a barrier, gatehouse: in law, a place where counsellors plead Bar, a bank or shoal at the entrance of a harbour

Bar of ground, in mining, any course of vein which runs across a lode, or different from those in its vicinity Barberry wood is of small size, resembling alder, and is straight and tenacious

Barbican, in the middle ages, the part of a fortress where watch and ward was kept

Barcella, a vessel containing incense Barcon, a luggage vessel used in the Mediterranean

Bardiglione, a blue variety of anhy

drite, cut and polished for ornamental purposes

Bare poles, the condition of a ship when she has no sail set Barge, a large double-banked boat used by the commander of a vessel

in the navy

Barge board, the front or facing of

the former, to conceal the barge couples, laths, tiles, thatch, &c. Barge boards, or, more properly, verge boards, pendants, pinnacles, and brackets, being the chief decorations of houses in early domestic architecture, should always be made of strong oak, and left to acquire by age a grey hue; and not of slight deal, painted, as is now the too frequent practice Barge couples, in architecture, a beam mortised into another, to strengthen the building

Barge course, a part of the tiling or thatching of a roof, projecting over the gable, and filled up with boards, mortar, &c.

Bar iron, long prismatic pieces of iron, being rectangular parallelopipeds, prepared from pig iron, so as

to be malleable for the use of blacksmiths for the method of joining bars

Barium, a metal that exists in the sulphate and carbonate of barytes; found in nature in great abund

ance

Barker's mill, an hydraulic machine in much use

Barkery, a tan-house; also a sheepcote Barmkyn, the rampart or outer fortification of a castle

Barn, a covered farm-building for laying up grain, hay, straw, &c. Barnacle, a shell fish often found on a vessel's bottom

Barometer and Sympiesometer. The barometer is a measure for the weight of the atmosphere, or its pressure on the surface of the globe. It is well known, that it is owing to the atmospheric pressure that water rises in a common pump, after the air has been drawn from the barrel; but that the height to which it can be raised by this means is limited, and not much exceeds 30 feet. A little more than 30 feet of water, therefore, balances the atmosphere. Mercury being about twelve times heavier than water, about 30 inches of mercury will also counterpoise the atmosphere. The principle of the barometer is simple. If a tube, about 3 feet long, closed at one end and open at the other, be filled with mercury, and, with the open end stopped by a finger, this tube be reversed, and placed upright in a cup partly filled with the same liquid, the mercury in the tube, in ordinary states of the weather, will descend to 30 inches, measured from the surface of the fluid in the cup, and not much lower. The mercury is sustained in the tube by the pressure of the atmosphere on the surface of the fluid in the cup. Such a tube and cup, so filled, would in fact be a barometer; and if a moveable index were added to it, this simple instrument would indicate the changes which take place in the

The atmosphere is supposed to extend to about the height of 50 miles; and its density to diminish from the surface of the globe upwards, in a geometrical ratio.

Thus, when observations are made on land, above the level of the sea, a correction is required for altitude, since the weight of the atmosphere diminishes as we ascend. It is owing to this that we are enabled to determine the height of mountains by barometers; and that aeronauts compute the altitude to which they ascend in balloons.

If any fluid in a cup be put into rapid circular motion, we should have a representation of the form that portion of the atmosphere assumes which is within the limits of a storm; the most depressed part of the fluid would represent the centre of the gale where the atmospheric pressure is the least.

The principle of the barometer should be explained in all works on navigation, and in all schools where navigation is taught Baron, in heraldry, a degree of nobility next to a viscount Baronet, in heraldry, the lowest de

gree of honour that is hereditary Baroscope, an instrument for proving the weight of the atmosphere Barque, a three-masted vessel having her fore and main masts rigged like a ship's, and her mizen-mast like the main-mast of a schooner, with no sail upon it but a spanker Barra, in the middle ages, a tower or bar at one end of a bridge Barrack, a building for the lodgment of soldiers

Barraly, in heraldry, the field divided barwise, into several parts, side to side Barrel, in machinery, is a term applied generally to any thing hollow and cylindrical

Barrow, in mining, a heap of dead

attle, rubbish, &c.

Barrows, or tumuli, monuments of the greatest antiquity, raised as sepulchres for the interment of the great

Barrulet, in heraldry, the fourth part of the bar, or one-half the closet Barry, in heraldry, is when an escutcheon is divided barwise, or into any number of compartments Barry-bendy, in heraldry, is when the escutcheon is divided evenly barwise and bendwise

Barry-pily, in heraldry, is when a coat is divided by several lines drawn obliquely from side to side, where they form acute angles Bars, straight pieces of timber or metal that run across from one part of a machine to another Bartisan, in architecture, the small overhanging turrets which project from the angles on the top of a tower, or from the parapet or other parts of a building Bartisan, a wooden tower; a turret on the top of a house, castle, or church tower

Barton, a manor-house, or out-house Bar Wood, is an African wood, four to five feet long. It is used as red dip wood, used for violin bows, ramrods, and turning

Barytes, a heavy mineral substance,

found in copper mines, and formerly named 'ponderous spar' Basalt, a variety of trap rock, usually of a dark green or brownish black colour, composed of augite and felspar, with some iron and olivine Basaltes, a heavy, hard stone, chiefly black or greenish, consisting of prismatic crystals, the number of whose sides is uncertain Basanite, a variety of schistose hornstone, called also Lydian stone Base of a figure, in geometry, denotes the lowest part of its perimeter Base of a conic section, is a right line in the parabola and hyperbola formed by the common intersection of the cutting plane and the base of the cone

Base, in architecture, the lower part or member of a column, on which the shaft stands Base-court, the outer or lower yard of a castle, appropriated to stables, offices, &c.

Base-line, in perspective, the common section of a picture and the geometrical plane

Base-line, in surveying, a line, measured with the greatest possible exactness, on which a series of triangles are constructed, in order to determine the position of objects and places. The measurement of degrees of the meridian, for the purpose of ascertaining the size of the earth, have been undertaken in various countries, with extreme accuracy. The arc measured by the French extended from Dunkirk to the southernmost point of the Balearic Islands, including 120°, 22′, 14", having its centre halfway between the equator and the north pole. Another survey of this kind was performed on a part of the shore of Pennsylvania, which happens to be so straight and level as to admit of a line of more than 100 miles being measured directly without triangulation. Very long lines have also been measured (trigonometrically) by order of the English government, both at home and in India, the mean result of which makes the earth's axis 7898 miles, 5 furlongs, 16 yards, and the diameter of the equator 7924 miles 7 furlongs

Basement, the lower story or floor of a building; the story of a house below the level of the ground Basements. As an alternative for employing orders upon orders, the ground floor is made to assume the appearance of a basement, and the order that decorates the principal story placed thereupon: in such cases the basements should not be higher than the order it supports, nor lower than one-half the height of the order; but if a basement be introduced merely for the purpose of raising the principal or groundfloor, it may be three, four, five, or six feet high, at pleasure.

These basement stories are generally in rock-worked or plain rustics; and in no case should the

BAS

height of a rustic course be less than one module of the order resting on the basement, nor should it ever much exceed it: their joints, if square, ought not to be broader than one-eighth of the height of the rustic, nor narrower than onetenth, and their depth should equal their breadth; if chamfered, the whole joint may be one-quarter to one-third the height of the rustic, the joint being always right-angled.

When the basement is high, it is sometimes crowned with a cornice, but a platband is more commonly used.-Gwilt.

Basenet, a helmet

Base-plate, the foundation plate of an engine

Basil, that angle the edge of a tool is ground to

Basilica, in the time of the Romans, a public hall or court of judicature. After the conversion of the emperor Constantine to Christianity, these edifices were converted into Christian churches The Basilica of the Romans were the types from which the early Christian places of worship were taken; and the ruins of these buildings were the chief materials used. In several instances the columns that divide the centre part of the church from the aisles have been taken from other edifices, either on account of the want of artists capable of executing any thing equal to them, or the haste with which they were erected. The expedient that was adopted tends to show that proportion was not considered; some columns were reduced from their former height, and others mounted on pedestals to suit the purposes to which they were applied. Besides this total disregard to proportion in the shafts of the columns, capitals and bases were applied without any consideration to their fitness. The heathen basilicæ, generally situated in the forums, were of rectangular form, and divided into three or five parts by rows of columns parallel to the