tory furnaces it is smelted by fuel in a
fireplace, separate from the ore, and in cupolas the fuel, generally
coke, is in direct contact with the ore. When Swansea was the centre of
the copper-smelting industry in Europe, many varieties of ores from
different mines were smelted in the same furnaces, and the Welsh
reverberatory furnaces were used. To-day more than eight-tenths of the
copper ores of the world are reduced to impure copper bars or to fine
copper at the mines; and where the character of the ore permits, the
cupola furnace is found more economical in both fuel and labour than the
reverberatory.

The Welsh method finds adherents only in Wales and Chile. In America the
usual method is to roast ores or concentrates so that the matte yielded
by either the reverberatory or cupola furnace will run from 45 to 50% in
copper, and then to transfer to the Bessemer converter, which blows it
up to 99%. In Butte, Montana, reverberatories have in the past been
preferred to cupola furnaces, as the charge has consisted mainly of fine
roasted concentrates; but the cupola is gaining ground there. At the
Boston and Great Falls (Montana) works tilting reverberatories, modelled
after open hearth steel furnaces, were first erected; but they were
found to possess objectionable features. Now both these and the
egg-shaped reverberatories are being abandoned for furnaces as long as
43 ft. 6 in. from bridge to bridge and of a width of 15 ft. 9 in. heated
by gas, with regenerative checker work at each end, and fed with ore or
concentrates, red-hot from the calciners, through a line of hoppers
suspended above the roof. Furnaces of this size smelt 200 tons of charge
a day. But even when the old type of reverberatory is preferred, as at
the Argo works, at Denver, where rich gold-and silver-bearing copper
matte is made, the growth of the furnace in size has been steady.
Richard Pearce's reverberatories in 1878 had an area of hearth of 15 ft.
by 9 ft. 8 in., and smelted 12 tons of cold charge daily, with a
consumption of 1 ton of coal to 2.4 tons of ore. In 1900 the furnaces
were 35 ft. by 16 ft., and smelt 50 tons daily of hot ore, with the
consumption of 1 ton of coal to 3.7 tons of ore.

The home of cupola smelting was Germany, where it has never ceased to
make steady progress. In Mansfeld brick cupola furnaces are without a
rival in size, equipment and performance. They are round stacks,
designed on the model of iron blast furnaces, 29 f