After an account of the chemical characters of the fire-damp sent to him by Mr. Hodgson, he describes the results of experiments on its combustibility and explosive nature, and on the degree of heat required to explode it when mixed with air. In respect of its combustibility fire-damp was found to differ most materially from the other common inflammable gases in that it required a far higher temperature to effect its inflammation or explosion. Moreover, it was found that the flame formed by the union of air and fire-damp would not pass through tubes of a certain minimum diameter; “and in comparing the power of tubes of metal and those of glass, it appeared that the flame passed more readily through glass tubes of the same diameter; and that explosions were stopped by metallic tubes of one-fifth of an inch when they were an inch and a half long; and this phenomenon probably depends upon the heat lost during the explosion in contact with so great a cooling surface, which brings the temperature of the first portions exploded below that required for the firing of the other portions. Metal is a better conductor of heat than glass; and it has been already shown that fire-damp requires a very strong heat for its inflammation.” The observation that mixtures of air and coal-gas would not explode in very narrow tubes had been previously made, unknown to Davy, by Wollaston and Tennant. Davy likewise found that explosions would not pass through very fine wire sieves or wire gauze. He also noted that an admixture of carbonic acid and nitrogen, even in small proportions, with explosive mixtures of fire-damp greatly diminished the velocity of the inflammation. “... It is evident then, that to prevent explosions in coal mines it is only necessary to use air-tight lanterns, supplied with air from tubes or canals of small diameter, or from apertures covered with wire-gauze placed below the flame, through which explosions cannot be communicated and having a chimney at the upper part, as a similar system for carrying off the foul air; and common lanterns may be easily adapted to the purpose by being made air-tight in the door and sides, by being furnished with the chimney and the system of safety apertures below and above. The principle being known, it is easy to adapt and multiply practical applications of it.” [Illustration: DAVY’S EXPERIMENTAL SAFETY LAMPS.] He then devised a number of lamps on this principle, and subjected them to trial with explosive mixtures in various ways. The plate on page 199, copied from the original paper in the _Philosophical Transactions_, shows the successive forms through which the lamps passed. [Illustration]