SAFETY LAMP

A [amp invented by Sir H. Davy, which is so constructed as to burn without danger in an explosive atmosphere. Flame may be considered as vapour or aeriform matter In a state of intense ignition; the temperature, therefore, of flame is always very high. It is, however, independent of its luminosity; for some of the dimmest flames, those of pure hydrogen gas, and of alcohol,for instance, are those which are hottest; and that this is so may be shown by projecting into them finely powdered substances, such as magnesia or lamp-black, or by holding in them fine platinum wire, when the intensity of their temperature is rendered evident by those substances becoming white hot. And whenever flames emit much light they derive that property from the presence of finely divided matter diffused through them: thus, the intense brilliancy of the flame of phosphorus appears to depend upon the particles of incombustible phosphoric acid diffused through it; and the bright light emitted by a gas flame depends upon finely-divided charcoal, which is ignited by the gas and at the same time burned. The correctne of this theory of flame is shown by the circumstance of its being extinguished by cooling; and this is best effected by causing it to pa through a piece of fine wire gauze, which, when held horizontally in the midst of the flame, extinguishes its upper part: the inflammable vapour or gas, and the soot or carbon, pa through, but in pa ing are so far cooled as to be extinguished; they may, however, be rekindled by applying a 1081flame above the wire gauze. That the wire gauze merely acts by [s. 1095]