97. Why, when we put fresh coals upon a fire, do we hear the gas escaping from the coals without taking fire?
Because, the fire being slow, the temperature is not high enough to ignite the gas.
"I will praise thee, O Lord, with my whole heart; I will show forth thy marvellous work."—Psalm ix.
98. What is the gas which escapes from the coals?
Carburetted hydrogen.
99. Why, if we light a piece of paper, and lay it where the gas is escaping from the coals, will it burst into flame?
Because the lighted paper gives a heat sufficient to ignite the gas; and because also hydrogen requires the contact of flame to ignite it.