2. =Heavy Carburetted Hydrogen.= (C_{2}H_{4}.) See OLEFIANT GAS.

_Obs._ COAL GAS, OIL GAS, and RESIN GAS, consist, for the most part, of

mixtures of these two gaseous hydrocarbons in uncertain proportions,

obtained respectively from coal, oil, and resin, by the action of heat,

and used for the purposes of illumination. See GAS.

=Hydrogen, Oxides of.= There are two well-defined compounds of hydrogen

and oxygen:--