FIRE-PROOF BUILDINGS. The most obvious method of rendering houses and other buildings indestructible by fire is to construct them entirely of incombustible ma terials, such as stone, brick, and iron. Such a mode of construction, however, is of very limited application. The use of iron, and especially of cast iron, in buildings, has in deed increased very much, and many plans for the construction of dwelling-houses almost entirely of that material have been brought forward.
Brickwork forms in this country the chief material of the external walls of houses, and it is occasionally employed without any admix ture of timber for the partition walls also,--a plan which, in conjunction with other precau tions, tends greatly to limit the damage done by a fire to the apartment in which it may happen to break out. Cast-iron pillars and brest-summers are very extensively employed in modern London shops and warehouses, where the whole front on the ground floor is Ieft open for shop-windows and doors. Fire proof floors are now often adopted, not only in public buildings, but also in the larger and better sort of private houses ; the beams being either of cast or wrought iron, and the brick vaultings, which abut upon the ledges of the beams, being often only half a brick' thick. In Farrow's patent method of fire-proof building, the floors are supported upon joists of wrought iron, formed with a projecting flange on each side, upon which are laid, stretching from joist to joist, a series of flat stones the upper surfaces of which lie flush with the upper edges of the joists. These
produce a level stone floor, interlined with iron, which may either be used as such or be covered with planks. Mr. Frost has invented a mode of constructing floors and roofs of hollow square earthenware tubes, laid in strata crossing each other in direction, and united with cement in such a way that the whole floor becomes one solid flagstone. In one I mode of construction, hollow earthen pots are employed to form a sort of vaulted roof.
The great use of timber in building renders very important any method by which it may be rendered incombustible. Solutions of mnriate of ammonia, muriate of, soda, sal ammoniac, borax, alum, and several other salts and alkalies, with which wood may be impregnated, or which may be applied to its surface, possess this finality in a limited degree; and by Payne's wood-pteseiving pro cess timber is made, for all practical purposes, completely incombustible. The non-conduct 'inn' power of earth and sand, or of a layer of sand placed over timber, has been the basis of 'many plans for preventing fires.