The Collaborative International Dictionary of English v.0.48:

Furnace \Fur"nace\, n. [OE. fornais, forneis, OF. fornaise, F.
   fournaise, from L. fornax; akin to furnus oven, and prob. to
   E. forceps.]
   1. An inclosed place in which heat is produced by the
      combustion of fuel, as for reducing ores or melting
      metals, for warming a house, for baking pottery, etc.; as,
      an iron furnace; a hot-air furnace; a glass furnace; a
      boiler furnace, etc.
      [1913 Webster]

   Note: Furnaces are classified as wind or air. furnaces when
         the fire is urged only by the natural draught; as blast
         furnaces, when the fire is urged by the injection
         artificially of a forcible current of air; and as
         reverberatory furnaces, when the flame, in passing to
         the chimney, is thrown down by a low arched roof upon
         the materials operated upon.
         [1913 Webster]

   2. A place or time of punishment, affiction, or great trial;
      severe experience or discipline. --Deut. iv. 20.
      [1913 Webster]

   Bustamente furnace, a shaft furnace for roasting
      quicksilver ores.

   Furnace bridge, Same as Bridge wall. See Bridge, n., 5.


   Furnace cadmiam or Furnace cadmia, the oxide of zinc
      which accumulates in the chimneys of furnaces smelting
      zinciferous ores. --Raymond.

   Furnace hoist (Iron Manuf.), a lift for raising ore, coal,
      etc., to the mouth of a blast furnace.
      [1913 Webster]