CON

186

CON

Composition, in plastering. See Plastering.

COMPOUND ARCH, a term applied by Willis to thosearches made up of a series of receding concentric arches, thedimensions contracting with each successive arch; or inother words, to those arches which may he resolved intoa number of concentric archways, successively placed withinand behind each other.

Compound Masonry. See Masonry.

Compound Pier,. the same as Clustered Column.

Compound Proportional Compasses. See Compasses .

CONCAMERATE (from the Latin , concamero) to archover.

CONCATENATE (from the Latin , catena) to chain orlink together.

CONCAVE (from the Latin , concavus , hollow) an epithetapplied to the interior side of a figure, or to the interior sur-face of a body.

Concavity of a Curve Line, the side next to a straightline, extended between the two points of a curve.

Concavity of a Solid, the curved surface of a solid, suchthat if any two points be taken in that surface, the straightline between them will be entirely in a void space, or willcoincide with the surface in one direction only. This defini-tion applies to cylinders, cones, spheres, and all other solidsgenerated by the rotation of conic sections about an axis.

When the surface of a solid is such, that two straight linesmay be drawn from any point in that surface to two otherpoints, so that the one line may be entirely in the void, andthe other pass through the substance or solid, the surfacemay be distinguished by the epithet concavo-convex ; of whichdescription are the surfaces of solids formed like a trumpet-mouth.

CONCENTRIC (from theLatin, concentricus ) in geometry,a term applied to such objects as have a common centre. Itis principally used in speaking of round bodies, or figuresthat have a circular or elliptic circumference; and may alsobe applied to polygons that have the same centre, and theirsides parallel to each other, about the same diagonals, radi-ating from the centre.

CONCHA, the concave surface of a semicircular vault, moreespecially applied to that of a semi-dome, or hemisphere.

CONCHOID (resembling a shell.) This name was givenby the inventor, Nicomedes, to a curve, by which he proposedthe finding of two mean proportionals, and the duplication ofthe cube. It may be described as a curve line which alwaysapproaches to a straight line but never meets it, though thestraight line and the curve be ever so far produced. It isthus generated : If A p and b d be two right lines intersect-ing each other at right angles; and if from a fixed point, P,a number of other lines, pfde, p f d e, &c. be also drawn,and if de be taken equal to a b, the curve drawn through allthe points E, e, e, &c. will be the first conchoid, or that ofNicomedes. In like manner, if d f, d f, &c. be taken eachequal to b C, the curve passing through all the points, f, iscalled tlie second conchoid. The straight line, d d, &c. bywhich the description of these curves is regulated, is calledthe asymptote. The inventor, Nicomedes, contrived an instru-ment for describing his conchoid by a mechanical motion, ofwhich the description will be found under Column.

CONCLAVE (from the Latin) a room in the Vatican ,wherein the cardinals used to meet to choose a pope. Thisroom was, in fact, a range of small cells or apartments, stand-ing in a line along the galleries and hall of the Vatican .The word was also used by the ancient Romans, to denote,generally, a room under lock and key.

CONCORD, Temple of, in Roman antiquities, a temple,built by Camillus at the foot of the Capitol, and seen from

w>'

ith

the Forum: the remains consist of a hexastyle portico,two columns at the back, of the Ionic order; the entail ^is very nearly entire ; a large portion of the tympanunba small part of the pediment, remain at the spring of the ^ gjncornice. The weight of the tympanum is discharged jthe entablature with arches. The columns are of S raI1 j nC liesone piece each, being 40 feet high, and 4 feet 2 1diameter. The bases are without plinths, except those (angular columns. The capitals are of a singular constr _ j (1

and differ from allhaving the four faces alike,

ancient examples of the same o^^jlyThe volutes are insigi 11

diminutive, and the mouldings too large, compared wt ^ a j. eother parts of the column. The architrave and f’nez e etllI -n.only one course in height; and on the front, and at ° ne j oJ1 byof the portico, are entirely plain, without any separa^ t j[ 3 .mouldings. The cornice has both modillions and or( j e r,This is perhaps the only ancient example of the Ion > c t , v -o

in which modillions are used: they are in number tw

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th«

in the front of the portico. An interval is placed 0 j ul ui>saxis of each column, and not a modillion ; and the care very high, being above nine diameters and a hattemple is supposed to have been pseudo-peripteral. in tef '

on the right angle is less than the rest, and the middcolumniation greater than the others, by about one-tof a module. j 0 usiy

CONCRETE, the name given to a composition,made, but in general use among architects as anfoundation for buildings. _ ,, 0 ,n by

The convenience of obtaining a firm and solid b° wthe formation of a compact mass of concrete; and t‘ , {0 d 3with which this composition is made and used, have ^ u jgit ealmost universal adoption in all situations where tbe h e> ie3materials can be procured. The proportions, and tn j D tb®of material vary, of course, in different localities, . a ” re die°^’practice of different architects, but the principal *-eU ’

good lime, clean sharp river-sand, and pebbles we ^

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will not fail to make a good concrete. , g .

Semple recommends to take 80 parts of pe® . ver -sa n 'about 7 or 8 ounces in weight—40 parts of sharp r ‘ gr to ‘‘and 10 of good lime; the last to be mixed with flge d bythinnish consistence, and grouted in. The concre ^builders in the neighbourhood of London , is made o ,,d *ballast, as taken from the bed of the river; th' s l3 an dconsist nearly of 2 parts of pebbles to 1 of sar '-, ( pvii>one-seventh to one-eighth part of lime. Mr- P 1 ^

the best method of making concrete is to mix V 1 *®.viously ground, with the ballast in a dry state ’; x tur e ’ , 3water being thrown over it to effect a perfect ® ^ g liO'’ eshould then be turned over two or three times wi . if ^put into barrows, and wheeled away for instant _ ra t! 0advisable to employ two sets of men to perform tm

with three men in each set, one man fetching

the S | g

while the other two turn over the mixture to the 9 t0 , t

and they, repeating the process, turn over the con ^ g j |0 ula^barrow-men. After being put into the barrows, > ^ I

wheeled up planks, so raised as to give it a fall o pa J ’ tlC t j ) e 1and thrown into the foundation, by which mean 3 eD to ^are driven closer together, and greater solidity j s d

whole mass. Soon after being thrown in, tne e vo*

- Q d much heat » s -

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observed usually to be in commotion, and

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with a copious emission of vapour. . g first -

The concrete should be thrown on in layers, ^ hs 1 *,^allowed to set, before a second is thrown down. get> e j 0 fload spreading over the ground in its fall, will o■j yaf ^a stratum of from 7 to 9 inches thick, and a cu ^ -

concrete will take about 30 feet cube of ba.Ua® ’ 0 fcube of ground lime, with a sufficient quan t J