Bricks in this country are generally baked either in a clamp or in a kiln. The latter is the more preferable method, as less waste arises, less fuel is consumed, and the bricks are sooner burnt. The kiln is usually 13 feet long, by feet wide, and about 12 feet in height. The walls are one foot two inches thick, carried up a little out of the perpendicular, inclining towards each other at the top. The bricks are placed on flat arches, having holes left in them resembling latticework; the kiln is then covered with pieces of tiles and bricks, and some wood put in, to dry them with a gentle fire. This continues two or three days before they are ready for burning, which is known by the smoke turning from a darkish colour to transparent. The mouth or mouths of the kiln are now damned up with a shinlog, which is pieces of brick piled one upon another, and closed with wet brick earth, leaving above it just room sufficient to receive a faggot. The faggots are made of furze, heath, brake, fern, &c. and the kiln is supplied with these un til its arches look white, and the fire appears at the top; which the fire is slackened for an hour, and the kiln allowed gradually to cool. This and cooling is repeated until the bricks be thoroughly burnt, which is generally done in 48 hours. One of these kilns will hold about 20,000 bricks.
Clamps are also in common use. They are made of the bricks themselves, and generally of an oblong form. The foundation is laid with place bricks or the driest of those just made, and then the bricks to be burnt are built up, tier upon tier, as high as the clamp is meant to be, with two or three inches of breeze or cinders strewed between each layer of bricks, and the whole covered with a thick strata of breeze. The fire-place is perpendicu lar about three feet high, and generally placed at the west cud ; and the flues are formed by gathering or arch ing the bricks over, so as to leave a space between each of nearly a brick wide. The flues run straight through the clamp, and are filled with wood, coals, and breeze, pressed closely together. If the bricks are to be burnt off quickly, which may be done in 20 or 30 days, accord ing as the weather may suit, the flues should be only at about six feet distance ; but if there be no immediate hurry, they may be placed nine feet asunder, and the clamp left to burn off slowly. Coke has been recom mended as a more suitable fuel than either coal or wood for this manufacture, both with regard to the expence, and the proper burning of the bricks; for if this sub stance be applied, the flues or empty places of the pile, as well as the strata of the fuel, may be considerably smaller ; which, since the interference of the legisla ture with regard to the measurement of clamps, is no small consideration; and as the heat produced by coke is more uniform and more intense than what is produced by the other materials, the charge of bricks has a better chance of being burnt perfectly throughout, so that the whole saving may be calculated at least at 32 per cent.
Mr Goldham observes, that bricks will have double the strength if, after one burning, they be steeped in water and burned afresh. " The excellency of bricks," says Mr Malcolm, in his Comfiendiunz of Modern Hus bandry," consists chiefly in the first and last operations —in the tempering of the clay, and in the burning of the bricks ; and as every man who has occasion to use bricks, whether on his 0 \In estate, or on that of his land lord, cannot but be sensible of the great value of a per fectly dry house ; and, as it is impossible a house can be dry if bricks are used which are insufficiently burnt, he will do well to consider whether it will be more advan tageous to him in the end, to make rise of the very best hard sound bricks, be the colour of them what they and be the cost of them what they will. Such bricks
are easily known by their sound, and by their striking fire with steel," For a more minute account of the va rious processes of brick-making, we must refer our rea ders to that author, from whom much of the preceding information has been extracted.
Bricks are made in various forms ; but those which are made fol. sale, and arc in common use for building, are required, by act of parliament, to he not less than 8+ inches long, 2- thick, and 4 inches wide. There are also square bricks, for pavement or facing walls ; and cutting bricks, which are used for arches over doors and windows, being rubbed to a centre, and gauged to a height. Various improvements, however, have of late been made in the moulding of bricks ; and as the use of this article is daily becoming more prevalent, they are now formed so as to suit almost every purpose in build ing. Among these the patent bricks oi Mr Cartwright deserve particular attention. These bricks are formed with a groove down the middle, a lit tle more than half the width of the side of the brick, leaving two shoulders, each of which will be nearly equal to one half of the groove. When these bricks arc laid in courses, the shoulders of the first course fit into the grooves of the second, and the shoulders of the se cond fall into the grooves of the first, thus forming an indented line of nearly equal divisions. The grooves, however, ought to he somewhat wider than the two ad joining shoulders, to allow for mortar, Scc. The con struction of these bricks is perfectly simple ; but the principle will be preserved, in whatever form of inden ture they may be made to lock into, or cramp each other. Brick walls, constructed upon this principle, require no bond timber; one universal bond connecting the whole building, which can neither crack nor bulge out without breaking through the bricks themselves. This inven tion is also particularly useful in the construction of arches; and when employed for this purpose, the shoul of the bricks and the sides of the grooves should be radii of the circle, of which the intended arch is a seg ment. It is, however, recommended, that if the arch be particularly flat, or applied in situations which do not admit of end walls, to have the shoulders dove-tailed, to prevent the arch cracking across, or giving way edge wise. In forming an arch, the bricks must be coursed across the centre, and a grooved side of the bricks must face the workmen. The bricks may be either laid in mortar, or dry, and the interstices after wards filled up by pouring in lime-putty, Paris plaster, or any other con venient material. The obvious advantages of arches constructed upon this principle, are, that the same cen tre, which, whatever be the breadth of the arch, may be in no case many feet wide, may be regularly shifted as the work proceeds; and as they have no lateral pressure, they require no abutments to prevent their expanding at the foot, nor any weight up...m the crown to prevent their springing up. They may be laid upon a common perpendicular wall, and if used in the construction of common buildings, they will not only preclude the neces sity, and save the expellee of timber, but will also afford an absolute security against the possibility of fire.