In showery weather, the bricks on the hacks are to be carefully covered with wheat or ru e straw, to keep them dry ; unless sheds or roofs be erected over the hacks, as is done in some country ;daces; but in Lundon this is impracticable, from the'very great extent of the grounds.
In fine weather the bricks will be dry enough for in a few days ; in doing which they are reset more open than at first ; and in six or eight days inure they will be ready for burning.
The best bricks. that is, those made of the best materials, and well tempered. as they are harder and more ponderous, so they require half as much more earth, and longer time for drying and burning, than the common sort, which are light, spongy, and full of cracks. The well drying of bricks before they are burned, prevents their cracking and crumbling in the kiln or clamp.
In the vicinity of London, bricks are commonly burned in clamp: farther in the country it is the custom to burn them in kilns. In building the clamps, the bricks are laid after the manner of arches in the kilns, with a vacancy between every two bricks, for the tire to play through ; yet with this ditli2renee, that instead of arching, the vacuity for the fuel is spanned over, by making the layers project one over the other from each side, till they meet at top. The flue is about the width of a brick, carried up straight on both sides about three feet ; it is then nearly filled with dry bayins, or wood, on which is laid a covering of sea-eoal and cinders (or breeze, as they are called); the arch is then overspanued, and buyers of breeze are strewed over the clamp, as well as between the rows of bricks.
When the clamp is about the width of six feet, another flue is made, in every respect similar to the first ; this is repeated at every distance of six feet, throughout the whole clamp, which when completed, is surrounded with old bricks, if there be any on the grounds, if' not, with some of the driest unhaked ones, that have been reserved for the purpose. On the top of all, a thick layer of breeze is laid. The wood is then kindled, which gives lire to the coal ; and hen all is consumed, which will be in about twenty or thirty days if the weather be tolerable, the bricks are concluded to be sufficiently burned. Should there be no immediate hurry for the bricks, the dues may be placed nine feet asunder, and the noel left to burn If the tire in the clamp burns well, the mouths of the flues are stopped with old bricks, plastered over with clay. The
outside of the whole clamp is also plastered with clay, if the weather be precarious. or if the fire burn too furiously ; and against any side particularly exposed to the rain, &e., screens are laid, made of reeds worked into frames about six feet high, and sufficiently wide to be moved about with ease.
This is the ordinary method of manntiteturing common gray•stocks. But washed maims. or marls, are made with still greater attention. A circular recess is built, about four feet high, and from ten to twelve feet in diameter, paved at the bottom, with a horse-wheel placed in its centre, from which a beam extends to the outside, fur the horse to turn it by. The earth is then raised to a level with the top of the recess, on which a platform is laid, for the horse to walk upon. This mill is always placed as near a well or spring as possible, and a pump is set up, to supply it with water. A harrow, made to tit the interior of the recess, thick-set with long iron teeth, and well loaded, is chained to the beam of the wheel. to which motion, the soil, as prepared in the heap in the ordinary manner, is brought in barrows, and distributed regularly round time recess, with the addition of a sufficient quantity of water ; the horse then moves on, and drags the harrow, which forces its way into the soil, admits the water into it, and by tearing and separating its particles, not only mixes the ingre dients, but also affords an opportunity for stones and other heavy substances to fall to the bottom. Fresh soil and water continue to be Lidded till the recess is full.
On one side of the recess, and as near to it as possible, a hollow square is prepared, about IS inches or two feet deep. The soil being sufficiently harrowed and purified, and redneed to a kind of liquid paste, is ladled out of the recess, and by means of wooden troughs conveyed into this square pit ; care being taken to leave the sediment behind, whirl is afterwards to be cleared out and thrown on the sides of the recess. The fluid soil diffuses itself over the hollow square, or pit. where it settles of an equal thickness, and remains till wanted for use, the superfluous water being either drained away or evaporated, by exposure to the atmosphere. 1\ hen one of these square pits is full, another is made by its side. and so on progressively. till as much soil is prepared as is likely to be wanted for the season.