modation of a fraternity under ecclesiastical government. Abbey gate-house, a lodge for warders or porters at the entrance of an abbey edifice.

Abbot, the superior of a monastery of monks erected into an abbey or priory: there are various classes of abbots, as mitred, crosiered, cardinal, regular, and commendatory abbots.

Abbot's lodgings, in the early times of English ecclesiastical architecture, a complete house, with hall, chapel, and every convenience for the residence of a spiritual baron. Abbreviate, to contract a word in writing or printing.

Abbreviations, characters or marks

over letters to signify either a word or syllable.

Abel (John), an English architect of

considerable notoriety, died in 1674, aged 97: built, during the periods of James I. and Charles I., the market-houses of Brecon, Hereford, Weobly, with its schoolhouse, Kingston, and Leominster, and the timberwork of the church at Abbeydore; and being in Hereford when the Scots besieged it in 1645, he constructed mills to grind corn, which were of great use to the besieged, and for which Charles I. afterwards made him one of his carpenters. Abele-tree, a species of white poplar. Aber, or Abber, the fall or emptying a lesser water into a greater, as of a brook into a river: hence several towns situated on or near the mouth of rivers generally derive the first parts of their names. Aberration, in astronomy, an apparent motion of the celestial bodies occasioned by the progressive motion of light and the earth's annual motion in its orbit. Aberration, in optics, the deviation

or dispersion of the rays of light when reflected by a lens, by which they are prevented from meeting or uniting in the same point, called the geometrical focus; but spread

over a small span, they produce a confusion of images.

Ablactation, in gardening, the method of grafting.

Ablaqueation, the opening of the ground around the roots of trees, for the admission of the air. Aboard, a nautical term, the inside of a ship, or to go on board. Abobe, unbaked bricks in Spain, used for the erection of cottages in Castile and Leon.

About-ship, the situation of a ship after she has tacked. About-sledge, the largest hammer employed by smiths; it is slung round near the extremity of the handle, and generally used by under workmen, called hammer-men. Abrasion, the effect produced by attrition or rubbing.

Abraum, a red clay, used in England to give a red colour to new mahogany.

Abreast, as when two ships have their sides parallel.

Abreuvoir, a watering-place. Abreuvoir, in masonry, the interstice or joint between two stones to be filled up with mortar or cement. Abscissa, a geometrical term for a

segment cut off from the straight line by an ordinate to a curve. Absis, or Apsis, the bowed or arched roof of an oven, room, or house. Absis, or Apsis, the ring or compass of a wheel. Absorbents, in chemistry, those earthy substances capable of uniting, by capillary attraction, a large proportion of water: such are magnesia, lime, and clay, when dry and porous. Absorbing-well, a shaft or boring for removing either the excess of drainage-waters, or the foul waters produced by manufacturing purposes. Absorption is the successive and intimate penetration of a gas, or a liquid, into any substance; but familiarly, the taking up moisture, in any material, by capillary attraction.

Absthánes, a lower kind of nobility

formerly in Scotland, but now extinct.

Abstract (To), a term used by artificers and surveyors in arranging and apportioning their work, to explain and price it. Abstract mathematics, otherwise denominated pure mathematics, that branch of the science which treats of simple properties, magnitude, figure, or quantity, absolutely and generally considered.

Abstraction and absorption of heat is that process under which caloric, or heat, passes from any body to whatever surrounds it, or to any conducting substance with which it is in contact.

Absurd, a term used in demonstrating converse propositions.

Abundant number, a number whose aliquot parts, added together, make a sum which is greater than the number itself.

Abuses: "Architecture," says Palladio, "being an imitatrix of Nature, delights in that which is most consonant with her prototype." Ancient edifices were built with wood, trees forming the columns; and when architects began to build with stone, they made the columns to imitate the trunks of trees, tapering from their bases. Being thus originally of wood, and therefore liable to split when much loaded, they bound them with rings at top and bottom. Thus the bases and capitals in the different orders seem originally derived from these bandages, though they are now become essential ornaments. Thus also in entablatures, the triglyphs, modillions, and dentils represent the ends of those beams and timbers which are employed for the support of the floors and roofs. If therefore all these conditions be duly considered, those practices in building are highly to be reprobated which are in opposition to that analogy which should exist between the original and its imitation, or which depart from Na

ture and the simplicity observable in all her works.

Consoles or cartouches, which are of a scroll-like form, should never be employed for the apparent support of great weights, in place of columns or pilasters; nor should they ever project from, or spring out of cornices.

Pediments and frontispieces over doors and windows, or elsewhere, should on no account be broken or disconnected in the middle; for the intention of these is to shelter the parts below from the rain, and this result is completely obviated by such a practice.

The projecture of cornices, though for the purpose of sheltering buildings, should not be more than in due proportion to their height, whether or not accompanied by columns; for if too heavy, they seem to threaten with danger those who are under them; and if too small in projection, they do not properly perform their office.

Again, those columns which are feigned to be composed of several pieces, by being jointed together with rings, should be carefully avoided, because the more solid and strong the columns appear, the better they seem to answer the purpose for which they were erected, which is securely to receive the superincumbent loading.

There are many other abuses which the authority of great masters may sanction, but not justify; and such will readily occur to the student, and themselves point out that they ought to be avoided. Abutment, the solid part of a pier from which the arch springs. Abutments, the extremities of a bridge, by which it joins upon the banks or sides of a river, etc.; in carpentry and joinery, the junctions or meetings of two pieces of timber, of which the fibres of the one run perpendicular to the joint, and those of the other parallel to

it.

Abuttals, the buttings or boundaries

of land.

Acacio, a heavy, durable wood, of the red mahogany character, but darker and plainer: it is highly esteemed in ship-building.

Academia, in antiquity, a villa or pleasure-house in one of the suburbs of Athens, where Plato and other philosophers assembled. Academician, a member of a society

or academy instituted for the cultivation of the arts and sciences. Academy-figure is a drawing or design, done after a model, with crayon or pencil. Acanthus, the plant Branca ursina, in English bear's-breech, the leaves of which are imitated in decorating the Corinthian and Composite capitals of columns.

Accelerated motion, a force acting incessantly upon a body; called also a constant or uniformly accelerating force when the velocity increases equally in equal times: the force of gravity near the earth's surface is of this kind; it generates a velocity of 32 feet in each second of time; that is, a body, after falling one second, acquires a velocity of 32 feet; after falling two seconds, it will acquire a velocity of 2 × 324 feet; after three seconds, a velocity of 3 x 324 feet, and so on. Accelerating force, in physics, the force which accelerates the motion or velocity of bodies; it is equal to, or expressed by, the quotient arising from the motion or absolute force, divided by the mass or the weight of the body moved. Accelerative or retardative force, is commonly understood to be that which affects the velocity only, or that by which the velocity is accelerated or retarded; it is equal or proportional to the motive force directly, and to the mass or body moved inversely.

Accesses, approaches or passages of communication between the various apartments of a building, as corridors.

Accessible, in surveying, a place which admits of having a distance or length of ground measured from it; or such a height or depth as can be measured by the application of a proper instrument. Accessories, or accompaniments, in painting, secondary objects to the principal one in a picture, introduced as explanatory and illustrative of the scene: sometimes they are considered as solely contributing to the general effect and harmony of the piece. Accidental point, in perspective, the

point in which a right line drawn from the eye, parallel to another right line, cuts the picture or per spective plane.

Acclivity, the slope or steepness of a line or plane inclined to the horizon, taken upwards; in contradistinction to declivity, which is taken downwards. Accouplement, in carpentry, a tie or brace, or the entire work when framed.

Accretion, in physics, the growth or increase of an organized body. Accubitus, a room annexed to large churches, in which the clergy occasionally reposed.

Aceric acid, in chemistry, an acid formed from the juice of the maple

tree.

Acerra, in antiquity, an altar erected,

among the Romans, near the bed of a person deceased, on which his friends daily offered incense until his burial.

Aces (a sea term), hooks for the chains.

Acestides, the chimneys of furnaces where brass was made; they were contrived to be narrow at top, on purpose to receive and collect the fumes of the melting metal, in order that cadmia might be produced in greater quantities. Acetate of lead,-sugar of lead,—a compound of acetic acid and lead.

Acetate of potash, a compound of acetic acid and potash, produced

by dissolving carbonate of potash

in distilled vinegar. Achievement, the ensigns armorial of a family.

Achleitner (Simon) was master of the works at St. Stephen's, in Vienna, 1481.

Achromatic, a term expressing absence of colour; in optics, applied to telescopes invented to remedy aberrations and colours. Achromatic, without colour, is applied in decorations to total absence of colour: mere white and black, or white and gold, may be considered in this sense achromatic. Acids, in chemistry, are sour to the taste, and convert vegetable blues to a red colour; they combine with alkalies, earths, and metallic oxides, and form, with them, the wellknown compounds named salts. Acinose, a term applied to iron ore found in masses, and of several colours.

Acisculis, a small pick used by masons, having one end like that of a hammer and the other pointed. 4-cock-bill, in navigation, the situation of the yards when they are topped up at an angle with the deck; the situation of an anchor when it hangs to the cat-head by the ring only.

Acolyte, in the ancient church, a person who trimmed the lamps, prepared for the sacrament, etc. Acorn, the seed of oak: imitations

of it are much used in architecture, and it is sometimes introduced instead of the egg in the Roman ovolo.

Acoumeter, an instrument invented

by Itard for estimating the extent of the sense of hearing. Acoustics, the doctrine or theory of sounds, consisting of diacoustics, or direct sounds, and catacoustics, or reflecting sounds.

Acre, a measure of land, containing,

by the ordinance for measuring land in the time of Edward I., 160 perches or square poles of land; and as the statute length of a pole

is 5 yards, or 164 feet, the acre contains 4840 square yards, or 43,560 square feet. The chain with which land is now commonly measured, invented by Gunter, is 4 poles, or 22 yards, in length; and the acre is therefore just 10 square chains; and as a mile contains 1760 yards, or 80 chains, in length, the square mile is equal to 640 acres. The acre, in surveying, is divided into 4 roods, and the rood into 4 perches.

Acrolithes, in sculpture, statues, the extremities of which are formed of stone.

Acropolis, a building strictly applicable to a Greek city, and usually erected upon a hill, rock, or some natural elevation, and devoted to a magnificent temple; also a tower, castle, or citadel. Acrostolion, in ancient naval archi

tecture, an ornament of the prow or forecastle of a ship, chiefly of war, most frequently circular or spiral.

Acroteria, small pedestals at the angles and vertex of a pediment: the gate of the Agora at Athens is the only instance in which they appear in Grecian buildings. Actinometer: Sir John Herschel, at the third meeting of the British Association, submitted an instrument for measuring at any instant the direct heating power of the solar ray it affords a dynamical measure of the solar radiation, by receiving a quantity of heat per second, or any short space of time, on a surface exposed to the sun. In making observations with this instrument, it should be freely exposed in the shade for one minute, and the variation read; afterwards expose it for the same time to the solar action, and again note it; and lastly, repeat the experiment in the shade: the mean of the two variations in the shade being subducted from the variation in the sun, the excess gives the dilatation per minute due to the sun's rays the

quantity subducted being the effect of the other causes at the time. Action, in painting or sculpture, the posture, attitude, expressive of the passion the painter or carver would convey to the mind of a spectator. Actus, a Roman measure of length, equal to 120 Roman feet. Acute angle, in geometry, less than a right angle, and measured by less than 90° or a quadrant of a circle. Acute-angled cone, that in which the opposite sides make an acute at the vertex, or whose axis, in a right cone, makes less than half a right angle with the side. Acute-angled section of a cone, an ellipsis made by a plane cutting both sides of an acute-angled cone. Acute-angled triangle, that in which the three angles are all acute. Adam (Wm.), an architect of Scotland, died about 1760, designed and built several edifices. Adam (John), of Edinburgh, son of the above, executed several designs in Scotland. Adam (Robert), second son of William he and his brother James executed very many very splendid buildings in England and Scotland, more particularly in London, the Adelphi, Portland-place, Lansdowne-house, and other noblemen's houses.

Mr. Weale purchased several unpublished (and posthumous) plates at the sale of the effects in Albemarle-street in 1822, which he published as a third or supplementary volume to the two volumes sometime previously published.

Adam (James), architect, also a son of William Adam, died in Albemarle-street in 1794, was with his brother Robert the intimate friend of Clerisseau, Zucchi, and patrons of other celebrated French and Italian artists.

Adam (William), architect, another

son of the same William, built several houses in Whitehall, died in 1822, aged 84.

Adamant, a very hard stone, used by the ancients for cutting and polishing other hard stones and glass. Adeling, a title of honour given to the children of princes among the Anglo-Saxons.

Adhesion, the force with which different bodies remain attached to each other when brought into contact. Adit, the passage or approach to a house; applied also to the horizontal shaft of a mine, driven for the purposes of ventilating, watering, or draining. Adit-level, in mining, a horizontal excavation through which the water is drawn by the engine. Adjacent angle, in geometry, an angle immediately contiguous to another, so that one side is common to both. Adjutage (Ajutage), or jet-d'eau, a tube fitted to the aperture of a vessel through which water is to be played. Admeasurement, the measuring or finding the dimensions and quantity of a thing by the application of a standard or rule. Admeasurement, a process in the art of mensuration for measuring and determining dimensions of work. Adonia, a festival celebrated in ho

nour of Aphrodite and Adonis in most of the Grecian cities. Adrift, the condition of a vessel broken from her moorings. Adytum, the most sacred place in the

heathen temples; the Holy of Holies; in Christian architecture, the chancel or altar-end of a church. Adze, an edged tool used to chip surfaces in a horizontal direction; the are being employed to chop materials in vertical positions. Ebrechts (H.) was with Louis Ger

brandt and Klas Huygens, in 1499, to build the town-hall at Gonda, in Holland. Ecclesiolo, in Domesday Book, a chapel subordinate to the mother church.

Edes, an inferior kind of temple; in Christian architecture, a chapel ; also sometimes applied to a house.