Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/381

BRI factory, so that after having been suffered to remain for five days, the second may be prepared, and thus the manufacture carried on without interruption. 4. The next step is that of treading and tempering the clay, which requires double the labour to what is usually bestowed on it j as the quality of the bricks chiefly depends upon the first pre- paration. If, in tempering them, too much water be used, they be- come dry and brittle ; but, if duly tempered, they will be smooth, so- lid, and durable. Such a brick requires nearly as much earth as one and a half made in the com- mon way, when too great a pro- portion of water is added; in which casethebricks become spongy,light, and full of flaws, partly through ne- glect in working them properly, and partly by a mixture of ashes and light sandy earth (asis generally practised in the vicinity of London), with a view to dispatch and facilitate the work, as well as to save culm or coals in the burning. 5. Bricks made of proper earth, being more solid and ponderous, require a much longer time for drying than those made in the common way ; they ought not to be removed to the kiln, till they have ^ecome lighter by one half, and give a hol- low sound on collision ; because the proper drying of bricks will prevent them from cracking and crumbling in the kiln. 6. Of whatever materials the kiln be constructed, each burning of from 6 to 10,000 bricks requires that the fire be kept up for 24 hours, and double that lime for a number of from 12 to 50,000. The uniform increase of heat deserves great at- tention; the duration of it should be regulated according to the sea- tons; and, during the last 24 hours, B R 1 [- 349 the fire should be uninterruptedly supported by means of flues ; but afterwards the kiln must not be suddenly closed ; as there is always some danger of bursting the flues, or melting the bricks. It would be useless here to en- ter into particulars relative to the manner of burning bricks in the neighbourhood of London; we shall therefore only observe, that they are chiefly burnt in damps built of the bricks themselves, after the manner of arches, in kilns, with a vacancy between each brick to admit the passage of the fire, but with this difference, that in- stead of being arched, the bricks project one over another on both sides of the space, for laying in the wood and coals till they meet, and are bounded by the bricks at the top. The place for the fuel is car- ried up straight on both sides, till about three feet high, when it is almost rilled with wood, over which is laid a stratum of sea-coal, and then the arch is spanned over. Farther, sea-coal is also strewed over the clamp, between all the rows of bricks; and lastly, the wood is kindled which also commu- nicates with the coals ; and when the whole is consumed, the manu- facturer concludes that the bricks are sufficiently burnt. Among the multiplicity of pa- tents lately obtained for the making of bricks, it is somewhat singular", that the inventors confine their lu- crative views chiefly to the forma- tion of this useful article, without paying much regard to the materials of which it may be composed. Of this nature are the patents granted to the following individuals : 1. Mr. Edmund Cartwright, of Doncaster, for his invention of a new principle, on which bricks,