Safety Lamp
2 of the 7 encyclopedias on this shelf carry an entry for Safety Lamp. Both are reproduced below, so you can see where they agree and where they differ.
The Encyclopedia of Founding (1892)
This is simply an ordinary oil-lamp enclosed in a cage of wire-gauze, which permits the light to pass out, but prevents the exit of flame. This lamp is the invention of Sir Humphry Davy. The explosions of carburetted hydrogen gas in coal-mines, from the unprotected lamps of the miners, caused great destruction of life, and various arrangements had been fruitlessly made to prevent such fearful accidents. This great philosopher found that when a lamp is surrounded with a wire gauze, under 1/40 of an inch mesh, any explosions taking place from the passage of fire-damp (light carburetted hydrogen) into the lamp are not communicated to the gaseous mixture outside. The space within the gauze often becomes filled with flame, from the burning of the mixed gases which penetrate the network, but the isolation is so complete that the explosive mixture outside is not fired. The power of wire-gauze to prevent the passage of flame may be usefully applied in the foundry. Let a wire-gauze be placed over the outlet or vent from beneath a hollow core where, when the mould has been cast, just such gases generate; the smoke and unburned gases will pass uninterruptedly through the gauze into the atmosphere, and may be ignited with safety, as no flame can possibly reach the dangerous gases below (to cause explosion) as long as the intervening gauze is there to prevent it. See VENTING.
Aiton's Encyclopedia (1910)
a miner's lamp. As is well known, the passages in mines, especially coal mines, fill not infrequently with an explosive gas called fire damp . It is a compound of hydrogen and carbon, mixed with atmospheric air. In the earlier days of coal mining, fire-damp explosions were so frequent and so disastrous to human life that Sir Humphry Davy, an English chemist, gave the subject serious attention and invented his so-called safety lamp. The flame of the lamp is surrounded by a wire gauze having about 625 meshes to the square inch. This lamp may be lighted and carried into the dangerous fire damp without an explosion. The gases pass through the meshes of the gauze and burn with a feeble blue flame within, but not in such a way as to obstruct the light of the lamp. The flame of the lamp and of the burning gas within cannot pass out through the meshes of the gauze without being cooled to such an extent that there is no danger of igniting the gas in the mine. The safety lamp is constructed in such a way that it may be attached to the miner's hat band and worn on the forehead as he goes about his work. See Damps ; Davy ; Sir Humphry