In a paper read before the Royal Society, on the 23rd of January 1817, entitled, "Some new Experiments and Observations on the Combustion of Gaseous Mixtures, with an Account of a method of preserving a continued Light in mixtures of inflammable Gases and Air without Flame," Sir H. Davy announces the application of a principle which he had discovered in the progress of his researches for increasing the utility of the Safety-lamp, and which, a century ago, would have unquestionably exposed its author to the charge of witchcraft. Having ascertained that the temperature of flame is infinitely higher than that necessary for the ignition of solid bodies, it appeared to him probable that, in certain combinations of gaseous bodies, although the increase of temperature might not be sufficient to render the gaseous matters themselves luminous, they might nevertheless be adequate to ignite solid matters exposed to them. During his experiments on this subject, he was led to the discovery of the curious phenomenon of slow combustion without flame. He observes, that there cannot be a better mode of illustrating the fact, than by an experiment on the vapour of ether or of alcohol. Let a few coils of wire of platinum of the one-sixtieth or one-seventieth of an inch be heated by a hot poker or candle, and let it be brought into the glass; it will presently become glowing, almost white hot, and will continue so, as long as a sufficient quantity of vapour and of air remain in the glass.[36] [36] This principle has been applied for constructing what has been termed the _Aphlogistic Lamp_, which is formed by placing a small coil of platinum wire round the wick of a common spirit lamp. When the lamp, after being lighted for a few moments, is blown out, the platinum wire continues to glow for several hours, as long as there is a supply of spirit of wine, and to give light enough to read by; and sometimes the heat produced is sufficient to rekindle the lamp spontaneously. The same phenomena are produced by the vapour of camphor; and an aromatic fumigating lamp has lately been advertised for sale, which is no other than the contrivance above described; and it is evident that, if the spirit be impregnated with fragrant principles, an aromatic vinegar will be developed during its slow combustion, and diffused in fumes through the apartment. This experiment on the slow combustion of ether is accompanied with the formation of a peculiar acrid and volatile substance possessed of acid properties, which has been particularly examined by Mr. Daniell, who, having at first regarded it as a new acid, proposed for it the name of _Lampic_ acid, in allusion to the researches which led to its discovery; he has, however, since ascertained that its acidity is owing to the acetic acid, which is combined with some compound of carbon and hydrogen, different both from ether and alcohol.