Illuminating Gas

— Hydrocarbon gas supplied through piping from a central source or place of manufacture, and whose flame is used for lighting purposes. It is generally obtained by means of the destructive distillation of bituminous coal in closed retorts, yielding a number of very complex hydrocarbons. Water gas is made by the decomposition of steam blown through red hot fuel, yielding hydrogen and carbon monoxide. The two proce es are frequently used in conjunction, the coke or residue from coal gas manufacture furnishing the fuel for the water gas. Oil gas is made by spraying petroleum in heated retorts, converting the liquid into a fixed gas, burnt either by itself, or used to enrich coal or water gas. In certain places natural gas, principally methane, i ues from the earth and is used as an illuminant.