"Oh yes," said Norah. "The coal gives of this gas in great quantities.""Teacher says that this gas is really the same as the coal-gas we are speaking about,and when it mixes with the
air in the mine it becomes terribly explosive.""I daresay you remember the Davy Lamp which theminers use," said Fred. "Teacher has got one, and he showed us what it is that makes it safe for burning in the mine.
"He held a piece of wire gauze two or three inches above the gas-burner, and turned on the tap.
Of course the gas passed up through the gauze. When he put a light near, the gas took fire above the gauze, but it did not burn at all below it.
"In the Davy Lamp, you know, the flame is shut in with this wire gauze. The explosive gas, if there is any in the mine, passes through into the lamp and burns round the flame, but the flame itself cannot pass out through the gauze, and so the air in the mine is safe from explosion."SUMMARY
