i. A structure in which, with the aid of heat so produced, (1) the operations of roasting, reduction, fusion, steam-generation, desiccation, etc., are carried on, or, (2) as in some mines, the upcast air current is heated, to facilitate its ascent and thus aid ventilation.

Ref: Fay

ii. Structure in which materials are exposed to high temperatures. Fuels used to maintain this include alcohols, paraffins, gas, coal, hydrogen, electricity, wood, and sulfur. A furnace is called batch type if its contents are treated in successive charges, or continuous when a stream of material passes through, being changed during transit. The main types are (1) the arc, which uses the heat of an electric arc; (2) the blast furnace; (3) the crucible furnace, a laboratory appliance for heating small charges, or, if large, for melting metals held in bigger crucibles; (4) the induction furnace, heated by electrically induced currents; (5) the muffle, in which the material is placed in a sleeve not in direct contact with the heating atmosphere, so that close control of entering and departing gas is possible; (6) the reverberatory, in which head developed on the roof is reflected onto a horizontal bed below; (7) the revolving furnace, a horizontal cylinder; (8) the roasting furnace in which material is oxidized, kilned to drive off carbon dioxide, or heated to remove moisture.

See Also:cupola,continuous furnace,converter

Ref: Pryor, 3