216

ARCHITECTURE

The figure of the cove is commonly either a quadrant of a circleor of an ellipsis, taking its rise a little above the cornice, and fi-nish ng at tne border round the great panncl in the centre. Histo-rical and other paintings are often introduced with good effect inthe centre and angular compartments of large cielmgs ; and oflate an invention of painted silk and sattin in various ornamentsfrom the antique, has been introduced, to adorn the profiles ofwalls of rooms. Tin- e are inclosed in pannels, pilasters, andtablets, according to their situation ; and, when they have suitablegilt mouldings, produce a very pleasing and splendid effect.

OF BUILDINGS IN GENERAL.

Of Foundations.

The best foundation is that which consists of gravel or stone :but in order to know whether the inferior strata are sufficient forthe support of the building, it will he adviseable to sink wells atsome little distance. By attending to wlu.t is thrown up indigging these, the architect will be acquainted with what lies un-der the stony or gravely bed which on the surface promises somuch security, mid will know what me isures to take. But thougha stony or gravely bottom is undoubtedly the most sure and firm,where all is sound beneath, there is no kind of ground which mayprove more fallacious, or occasion such terrible accidents. The-reason is, that such ground often contains absolute vacuities ; noris rock itself, though a foundation upon a rock is strong even to aproverb, free from danger of the same kind. Caverns are very-frequent in rocky places; anti should a heavy building be erect-ed over one of these, it might suddenly fall ((own altogether. Toguard against accidents of this kind, Palladio advises the throw-ing down of great weights forcibly on the ground, and observ-ing whether it sounds hollow, or Shakes, lie says, if a drumbe placed on the suspected ground near to a vessel Idled with w-a-ter, a gentle stroke will not resound nor ruille the surface of thewater, if the earth he solid ; but, if it be hollow, the effects pro-duced will very clearly shew it. Where the foundation is gravel,it will be proper to examine the thickness of the stratum, and thequalities of those that lie under it, as they have appeared in dig-ging. If the bed of gravel be thick, and the under strata of asound and firm kind, there needs no assistance; if otherwise wemust have recourse to various methods in order to supply the de-fect. In case of boggy earths, or unfirm sand, piling is one of themost common methods of securing a foundation; and, notwith-standing the natural disadvantages in such a case, piles, when pro-perly executed, make one of the firmest and most secure founda-tions. In foundations near the edge of waters, we should alwayssound to the very bottom, as many- fatal accidents have happenedfrom the ground being undermined by rivers. The same methodis to he followed when the ground on which we build has been dugor wrought before. It ought never to be trusted in the conditionin which it is left; but we must dig through it into the solid andunmoved ground, and some way even into that, according to theweight and size of the intended edifice. It will he proper, how-ever, before the architect begins to lay the foundation of thebuilding, to construct such drains as may be necessary for carry-ing olf the rain, or other water, that would otherwise be collectedand lodge about the house. In forming drains for carrying olfthis water, it will be necessary to make large allowances for thedifferent quantities that may be collected at different times. Itmust also be considered, that water of this kind is always loadedwith a vast quantity of sediment, which by continually fallingtothe bottom will be very apt to choak up the drain, especially atthose places where there happens to be angles or corners in itscourse. The only method of preventing this is by means of cer-tain cavities disposed at proper distances from one another. Intothese the sediment will be collected, and they are for that reasoncalled sess-pools. All drains ought to be arched over at top, andmay be most conveniently built of brick. According to theirdifferent sizes, the following proportions of height and thicknessmay be observed. If the drain be 18 inches wide, the height ofthe walls may he one foot, and their thickness nine inches ; thebottom may be paved with brick laid flatwise, and the arch turnedfour inches. If (he drahi be 2'J inches wide, the side walls are thento be one foot three inches in height, and the rest constructed asbefore. If it he 14 inches wide, the height of the walls mnv lienice inches, and the sweep of the arch four. A drain

of a yard wide should have the same height, and the archturned over it ought to be nine inches thick. Upon thesame principles and proportions may other drains of any size beconstructed, hi laying the foundation of the wails, great caremust be taken that tile lloor of the toundation be pericctly smoothand level; all must be laid with the utmost accuracy by rule andline. The thickness of foundation walls, in general, ought tohe double that of the walls which they are to support. The looserthe ground, the thicker the foundation wall ought to be ; and itwill require the same addition aho in proportion to what is to beraised upon it The plane of the ground must be perfectly level,that the weight may press equally every where : for when it in-clines more to one side than the other, the wall will split.—The foundations must diminish as they rise, but the perpendicu-lar is to be exactly kept in the upper and lower parts of the wall ;and this caution ought to be observed all the way up with thesame strictness. In some ground, the foundation may be arched ;which will save materials and labour, at the same time that thesuperstiuclure has an equal security. This practice is peculiarlyserviceable where tl e foundation is piled.

Of Walls, Chimniks, Roofs, and Floors .

As the foundation walls are to diminish in thickness, so arethose also which are built upon them, 'l itis is necessary tosave expence, but is not absolutely so to strengthen the wall; forit would he no less strong, though it were continued all the way tothe top of an equal thickness, provided the perpendicular wereexactly kept. In common houses built of brick, the general di-minution from the bottom to the top is one half the thickness atthe bottom ; the beginning is two bricks, then a brick and a half,and lastly one brick in thickness. In larger edifices the walls musthe made proportionablv thicker ; but the diminution is preservedmuch in the same manner. When stones are used, regard musthe had to their nature, and the propriety of their figures tor hold-ing one another ; and where the walls are to he composed of diffe-rent materials, as stone and brick, the heaviest ought always tobe placed undermost. One additional particular respecting thestrength of a plain wall must he observed, viz. to fortify its an-gles. This is best done with good stone on each side, which givesnot only a great deal of strength, but a great deal of beauty. Pi-lasters properly applied afford great strength to walls. Their bestdistance is about every iO feet, and they should rise five or sixinches from the naked part of the wall. The openings in a wall are alltveakeners, and as the corners require to be the strongest parts,there should never be a window very near a corner. Along withthe construction of walls, that of the chinmies must also be con-sidered ; for errors in the construction of these will render themost elegant building extremely disagreeable. The commoncauses of smoking are either that the wind is too much let in aboveat the mouth of the shaft, or the smoke is stilled below : andsometimes a higher building, or a great elevation of the groundbehind, is the source of the mischief; or lastly, the room inwhich the chimney is may be so small or close, that there is nota sufficient current of air to drive up the smoke. Almost all thatcan be done, while the walls are constructing, to prevent smoke,is, to make the chimney vent narrower at bottom than at top: yetthis must not he carried to an extreme; because the smoke willthen linger in the upper part, and all the force of the draught willnot he able to send it up. For curing smoky chimnies in housesalready built. See Chimnky. After the wall is finished, the roofis the next consideration ; its weight must be proportioned to thestrength of the walls. It must lie so contrived as to press equallyupon the building ; and the inner walls must hear their share of theload as well as the outer ones. A roof ought neither to he too massynor too light; as being necessary for keeping the walls together lim-its pressure, which it is incapable of doing while too light; andif too heavy, it is in danger of throwing them down. Of thesetwo extremes, however, the last is to he accounted the worst.—Floors are most commonly made of wood; in which case, it isnecessary that it he well seasoned by being kept a considerabletime before it is used. The floors of the same story should be allperfectly on a level; not even a threshold rising above the rest:and if in any part there lie a room or closet whose lloor is not per-fectly level, it ought not to he left so, hut raised to an equalitywith"the rest ; what is w anting of a true floor being supplied by afalse one. The floors of low houses may be made of clav, ox

blood