Charcoal Air Furnace for Crucibles, Drawn by a Chimney

The chemist's furnace for melting in crucibles needs no bellows: a firebrick box closed on every side, air entering only under the grate, and a tall chimney to draw it through the burning charcoal. George Fownes (1856) describes it; a sliding damper in the flue sets the heat, from dull red upward. The picture: a 16th-century assay workshop woodcut with wind furnaces, one on a tripod, for melting silver in crucibles (Deutsche Fotothek).