MALT-HOUSES, LIMEKILNS, BRICK-KILNS, ETC. 605 purpose, ^^^len a portion of the burnt lime is taken away either by Count Rumford's manner or Mr. Hcathorns, the empty space formed in the top of the kihi, by the sub- sidence which necessarily follows, is inunediately filled with fresh limestone ; and, when the opening at the bottom, through which the burnt lime is taken away, is closed, a very small aperture is left, to admit as much air as will create a draught through the hot limestone, now occupynig the place of that which was removed, in order to carry up its heat to the limestone in the upper part of the kiln, lliis aperture in both kilns is furnished with a register. We observe by the Dictionnaire Technologique, and the article Four a chaux, in the Cours Complet cT Agriculture, that the pei-petual kiln is reconmiended for France ; but there is no evidence of any of them having been actually erected in that country, llie form given as that now in general use in France is egg-shaped, with the ujiper orifice about two feet in diameter, and the lower one somewhat larger ; be- cause wood is burnt there on a hearth, and the calcination of the stone is effected by the flame passing through it, and not by the mixture of fuel with the limestone. In the turf and peat districts of France, these kinds of fuel are mixed with the stone to be burnt, in the same manner as it is commonly done in Britain. Design VII. — A Kiln for burning Bricks or Tiles, or other Earthenware used in the Construction of Buildings; and which may also be used as a Kiln for burning Lime or Clay for Manure, or coking Coal or Peat, or charring Wood, impregnating Timber with PyroUgnous Acid, kiln-drying Corn, or drying Corn in the Sheaf in wet Seasons, and for other agricultu/-al Purposes. 1290. The Art of Brickmaking was, probably, one of the first inventions of man after the art of agriculture ; because houses and utensils are only second, in point of necessity, to food and clothing. Bricks may be formed in three ways : by compressing loamy soil, in an intermediate state between wet and dry, into convenient shapes of a rectangular form ; by moulding moistened clay, and drying it in the sun ; and by vitrifying these moulded forms by the application of fire. As the art of preparing the clay for making tdther bricks or tiles must be of great importance to the settlers in new countries, we shall, previously to describing a farm or country brick-kiln, give a short account of the manner of preparing the clay, and moulding it into bricks. 1^91. The Soil most suitable for making Bricks is a clayey loam. The surface should be removed from it in the autumn, and the subsoil dug up, and niixed ■n'itli about one sixth part of coal-ashes, during the winter; the whole being, diuing this season, exposed to the weather. In spring, it is turned over once or twice, and, after all risk is past from frost, the clay is prepared or worked, either by chopping and beating it, as dough is worked and kneaded by a baker, or by passing it through a mill, called a pug-mill, which effects the same object mechanically. The mass being sufficiently mixed and kneaded, it is laid on a table sprinkled with dry sand, ii-om which it is taken in small portions, and pressed into moulds of the shape of the brick or tile which it is desired to form. These are first dried in the sun, or in the open air, under sheds, and afterwards burned in one or other of the modes which we are about to describe. 1292. Clamp-kilns for burning Bricks are nothing more than stacks or masses, com- posed of bricks, interspersed with layers of coal cinders. The first three or four layers or courses of bricks are placed on edge, diagonalwise, an inch or more asunder, and the superincumbent course breaking joint ; the second, third, aaid fourth courses on edge over them are also placed diagonalwise, and so as to leave considerable interstices for being filled up with the cinders. Thus, the lower part of the clamp, or kiln, is formed of about three fourths of the cubic contents of imperfectly burned bricks, and one fourth of coal cinders in the interstices between them. The superincumbent part of the clamp is formed of new-moulded bricks set close together on edge, every layer having a stratum of half an inch of small ashes placed under it. The size of the kiln is without limit as to length and breadth ; but it is found that the weight of more than fifteen or twenty coiu-ses of unburned bricks, laid one over the other, will crusli or deform those at the bottom. In placing the lower stratum of four courses of open brickwork and cinders, there is a kind of horizontal tunnel, or channel, continued through the work upon the ground, about a foot broad, and eighteen inches high, which is filled with wood and coal, to serve as the means of lighting the cinders among the bricks on each side. When the contents of this tunnel are once thoroughly lighted, its ends are closed up with brick or clay. The stack or clamp is carried up in sections, or vertical strata, of between tliree and four feet in thick- ness ; and when as many bricks are put together as it is desired to burn, the whole is surrounded by a double casing of refuse bricks or such as are impcrfectlv formed, for the purpose of keeping in the heat, as well as of, to a certain extent, reburning them. A elamp-kiln generally continues burning twenty days, and is used for biu-ning bricks only.
