The ordinary coal or illuminating gas may be used for welding. The arrangement is extremely simple and inexpensive, as the heavy steel cylinder containing any of the combustible gases is substituted for a rubber tube, by means of which the gas is conveyed from the place of supply (from an ordinary gas-pipe tap) to the blowpipe as fully described under "Brazing," page 82.

The great advantage possessed by the coal gas over any other combustible gas is to be found simply in the cheapness of the installation, making it thus the cheapest welding system.

The application of coal gas is, however, limited to brazing, and welding of lead, bronze, brass, etc. How far it is suitable for welding of iron and steel is a question to be considered.