Safety-lamp
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.