A. 1st—Because flame will never pass through fine gauze wire: and
2ndly—Though the wire get red-hot, it will not ignite the gas; for carburetted hydrogen gas can be ignited only by flame.
(N. B. The interstices of the gauze wire must not exceed the 7th of an inch in diameter.)
Q. Why will not flame pass through very fine wire-gauze?
A. Because the metal wire is a very rapid conductor of heat; and when the flame of burning gas in the lamp reaches the wire gauze, the heat (which is needful to produce flame) is conducted away by the wire, and the flame is extinguished.
Q. Does the gas of the coal-pit get through the wire gauze into the lantern?
A. Yes; but the inflammable gas ignites and burns inside the lamp: as soon, however, as this is the case, the miner is in danger, and should withdraw.
Q. Why is the miner in danger, if the gas ignites and burns in the inside of the safety-lamp?
A. Because the heat of the burning gas will soon destroy the wire gauze, and then the flame (being free) will set fire to the mine.