Page:Report from the Select Committee on Steam Carriages.pdf/61



Mr. G. Gurney. 5 August, 1831. boiler; the bottom of the boiler, consequently, got hot; the compound I alluded to was formed, or the rupture of this film, and the sudden contact of water against the hot surface below, produced such an immense and sudden volume of steam that it burst the boiler. I would explain it by saying it was analagous to the bursting of a gun, in which case an ounce or two of shot is placed only against the charge; whenever there is a sudden formation of elastic matter, and there be ever so small a weight opposed, the shock will be very great, and a gun will frequently burst, though there is not an ounce of shot in it, and which charge may be considered in the light of a safety valve in this case.

What precautions have you taken in your boilers, that there may be no probability of their being without water?—This compound never forms without a certain raised temperature. Before this temperature, necessary for decomposition, takes place, it melts a fuseable compound alloy of metal, placed so as to allow of its escape; the matter formed escapes, and all danger is prevented.

Have you any precaution to prevent the water escaping out of your narrow tubes, by bubbles of steam?—Yes; that I would explain by reference to the first drawing, (No. 1.) which will show that the bubble of water, as it escapes from a tube in connection with a part of the boiler, is supplied simultaneously from the lower part of the tube, and a stream of water is thus made constantly to pass through.

Would not that stream of water act as a safety valve?—When there is water it is sufficient, but when water gets down in any boiler there is no safety valve that will protect it, and hence arise the inexplicable accidents that have occurred frequently in steam boats; the size of the boiler is the only protection without the safety alloy.

Have you any guage, or means of ascertaining when there is a deficiency of water in the boiler?—Yes; the melting of the safety plug, I would state, only takes place in cases of great negligence, or in cases of extremity. The gauge by which we ascertain the