A. By stirring the mud at the bottom of any stagnant pool, and collecting the gas (as it escapes upwards) in an inverted glass vessel.
Q. What is coal gas?
A. Carburetted hydrogen extracted from coals, by the heat of fire.
Q. Why is carburetted hydrogen gas called fire-damp, or inflammable air?
A. Because it very readily catches fire and explodes, when a light is introduced to it.
Q. Why is carburetted hydrogen gas frequently called marsh gas?
A. Because it is generated in meadows and marshes from putrefying vegetable substances. (See ignis fatuus, p. [285]).
Q. What gas is evolved by the wick of a burning candle?
A. Carburetted hydrogen gas: that is, the carbon and hydrogen of the tallow combine into a gas from the heat of the flame; and this gas is carburetted hydrogen, or inflammable air.