FIRE-PROOF BUILDINGS (ante). Many attempts have been made to construct buildings in such a manner and of such material as to make them indestructible by fire, but they have been only partially successful. It is easy to employ incombustible mate rials in the construction of walls, floors, stairways, doors, etc. ; but it is not so easy to make them proof against disintegration from intense heat and the application of water. In the great Chicago and Boston conflagrations it was•found that walls of granite, brick, and marble, which no fire could consume, crumbled into ruin under the combined influence of fire and water, and so were no barrier to the progress of the flames. The fire could hardly have made its way more rapidly or surely if all the buildings in its path had been of wood, Hard-burned bricks no doubt make the safest walls and par titions, while ceilings and floors of the same material laid in cement are as nearly indestructible by fire as anything that the ingenuity of man has invented. It was thought at first that iron buildings would be proof against fire; but the iron girders, beams, and posts, though they cannot be consumed, are so expanded and bent under the influence of heat as to be rendered useless for supports in time of a fire. No doubt a building may be so constructed that a fire in one of its rooms may destroy what is combustible therein, without going any further and without endangering the building itself; but if it is contiguous to other buildings in conflagration, its walls must be very hard and thick to resist the power of the flames, while they can hardly protect anything within that is combustible, for the fire will make its way through doors or windows, unless extraordinary precautions have been observed. Many brick walls fail to resist fire on account of defective mortar, which crumbles from heat, causing them to deflect and fall. Wood, well pugged with cement, is strongly recommended by many archi tects as preferable to iron for girders and beams, but unless the cement is of the best quality, it will afford little protection. In London, safety is sometimes sought in arrangements for flooding buildings with water through pipes constantly connected with a reservoir; but in many cases this would afford but slight protection. The system of pugging wood with cement for light structures is in common use in Paris. Oak timber, on account of its hardness, is chiefly used for this purpose. The framework, made in the ordinary way, is battened with oak inside and outside, the battens being only a few inches apart. The space between the two series of vertical battens is filled with burnt clay, chips of stone, or broken brick, and then the surface on each side is coated with plaster of Paris, completely filling the interstices, covering the wood, and making a hard, smooth wall, impervious to fire to a certain extent, but liable to crack and fall away under the influence of great and protracted heat. The ceilings and floors are also battened and protected in the same way. It is difficult to isolate the different stories of a building from each other on account of the openings for hoistways and stairways; but this has been effected in some cases—notably in that of the book-warehouse of Harper & Brothers in New York—by putting the stairways outside the walls. Mansard roofs
have been made less dangerous by the use of iron instead of wood to support the slate. Floors now are sometimes made fire-proof by clay bedded upon a metal support. But none of these devices, nor any others thus far adopted, afford absolute protection, under all circumstances, against the invasions of fire.
Attempts have continually been made to render cotton, linen, and other textile fabrics, timber, etc., incombustible; but at present they have been but partially successful. There are many means by which fabrics may be prevented from flaming, their combustion being reduced to a slow smoldering; and the many cases of fatal results from the extravagant dimensions of ladies' dresses (crinoline) rendered the adoption of some such protection against fire very desirable. By moistening the fabric with a solution of any saline substance, which, upon drying, will leave minute crystals deposited in or between the fibers, its inflammability will be greatly diminished, but the salt imparts a degree of harshness to the fabric, and in many cases weakens the fibers. Alum, sulphate of zinc, and sulphate of soda have been used, and are effectual to prevent flaming, but they weaken the fiber. Common salt does the same. Phosphate and sulphate of ammonia are less objectionable on this account, but the former decomposes by contact with the hot iron in ironing. Tungstate of soda has been proposed, and is said to have no injurious effect on the fiber. Sulphate of ammonia, chloride of ammonium (sal ammoniac), and borax, are among the best fitted for domestic use, though they are not unobjectionable. For made-up cloth ing, borax is, perhaps, the best, and it is most effectual in its action, and is the least injurious to the appearance of the article, though it is stated to have some weakening effect on the fiber; this, however, is only perceptible in case of a tearing strain, and will not perceptibly damage such articles as ladies' underclothing, or anything else only subject to ordinary wear. Wood has been treated in a similar manner. Milk of lime, alum, sal ammoniac, sulphate of ammonia, chloride and sulphate of zinc, suiphuret of lime and baryta, etc., have been used, and its inflammability, but not its combusti bility, is destroyed. Like the fabrics, when similarly treated, wood smolders slowly. The most efficient protection to wood is silicate of soda. If planks of moderate thick ness be brushed three or four times over, on each side with a strong solution, they are rendered almost incombustible; they will only burn when very intensely heated. The silicate fuses and forms a glass which envelops the F tir him, and even the internal fibers of the wood, if it be sufficiently saturated, and thus seals it from the oxygen of the air.