Cast and wrought-iron have been frequently fused at fires in large buildings such as warehouses, sugar houses, &c., but according to Mr. Fairbairn's experiments on cast iron in a heated state, it is not necessary that the fusing point should be attained to cause it to give way.[A] He also states, that the loss of strength in cold-blast cast iron, in a variation of temperature from 26 deg. to 190 deg. = 164 deg. Fahr., is 10 per cent., and in hot-blast at a variation of from 21 deg. to 190 deg. = 169 deg. Fahr., is 15 per cent.; now if the loss of strength advances in anything like this ratio, the iron will be totally useless as a support, long before the fusing point is attained. Much confidence has been placed in wrought-iron tie or tension rods, to take the lateral strain of the arches, and also in trusses to support the beams; but it must be evident that the expansion of the iron from the heat, would render them useless, and under a high temperature, it would be so great as to unsettle the brickwork, and accelerate its fall, on any part of the iron-work giving way: again, the application of cold water to the heated iron, in an endeavour to extinguish the fire, is almost certain to cause one or more fractures. The brick-arching is also very liable to fall, especially if only four and a half inches thick, independently of the weight which may be placed upon it, for it is not uncommon after a fire in a large building, to find the mortar almost completely pulverized to the depth of three inches, or four inches, from the face of the wall. When a fire occurred under one of the arches of the Blackwall Railway, on the 15th July, 1843, a portion of the lower ring fell down, and also a few bricks from the next ring.