The use of fuels of different kinds is highly essential in the various industries for the producing and shaping of metals. Heat is indispensable (1) to bring about chemical action which breaks up the ore compounds in the smelting of metals, (2) for many chemical and mechanical operations as the refining of metals and the making of wrought iron and steel, and (3) for softening or melting metals to assist in their shaping for definite uses.