MALT-HOUSES, LIMEKILNS, BRICK-KILNS, ETC. 1161 603 ©0 may be covered with a plate of cast-iron, regulated so as to give the exact degree of draught requh-ed. This contrivance will be found cheaper than the conical kilns of Booker ; and, where there is a kiln-shed, it will answer equally well. When there is not a kiln- shed, Booker's covers are un- doubtedly preferable ; as they not only keep in the heat, but throw off the rain. The shed over the mouth of the kiln is of the greatest use in keeping dry the stones and fuel before they are thrown into the kiln ; and not only keeping them dry, but heating them, and thus evapor- atmg part of their moisture. These materials, therefore, ought always to be kept as near as possible to the feeding mouths; and when the heat of the kiln is to be continued for some time by closing both the bottom and ' I top openings, the coal and un- burnt limestone should be heaped up over the latter, in order that they may absorb as much as possible of the escaping heat. The double iron doors to the fuel chamber should be nine inches or a foot apart, to prevent the escape of heat ; but single doors will suffice for the ash-pit below. The two side openings, for the admission of additional supplies of air at pleasure, may, when not wanted, •be blocked up with stone, to save the expense of doors. The bars of the grating of the fuel- chamber may be two feet and a half long, two inches wide, and three inches deep, cast hollow ; and the two cross bars
