“... 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.
On January 11th, 1816, he read a second paper to the Royal Society, entitled, “An account of an invention for giving light in explosive mixtures of fire-damp in coal mines by consuming the fire-damp,” in which he shows that the tubes or canals as well as the sides of the lanterns may be replaced by cages or cylinders of wire gauze. The inflammable mixture will readily pass through the meshes of the gauze and will burn within it, filling the cylinder with a bright flame, but no explosion will pass outwards, even although the wire becomes heated to redness.
A fortnight later he read a third paper to the Society, “On the Combustion of Explosive Mixtures confined by Wire Gauze, with some Observations on Flame,” in which he gives the results of further inquiries respecting the limits of the size of the apertures, and of the wire in the metallic gauze required to shield the flame of an oil-lamp, and describes a number of illustrations of the action of the gauze in lowering the temperature of the explosive mixture below the point of ignition. Some of these illustrations are now among the stock experiments of the lecture theatre. He offers some observations concerning the essential nature of flame, and concludes by informing the Society that his “cylinder lamps [_i.e._ lamps of which the flames are enclosed within a cylinder of gauze: see Fig. 11, p. 199] have been tried in two of the most dangerous mines near Newcastle with perfect success.”