METALLURGY. 135 
breast ; @ is the shaft, 4 the crucible for the metal and slag. The sole, d, 
consists of cement, and rises towards the tuyere opening at the back. 
Figs. 14 a and 14d are sections of a furnace in use at the Falun copper 
works. The shaft terminates in the sink in the clay at f; the fore-hearth 
in front of the breast-opening, 4, communicates by a canal with the cru- 
cible 0. The layer, ¢, is firmly rammed clay, d cinders, m iron plates in 
front of the hearth. 
There are also blast-furnaces from which the iron runs uninterruptedly 
through the tap hole, which is never closed. Pl. 28, jig. 2a, is a furnace 
of this description, constructed something like the German blue oven. ais 
the shaft, c the crucibles into which the metal flows, e the openings for the 
tuyere. 
3. REVERBERATORY Furnaces. Those furnaces in which the fuel does not 
come in contact with the metal, but operates upon it by its flame, are called 
reverberatory or puddling furnaces. In furnaces of this description the ore 
is placed upon a level or concave hearth, and the walls and arch are so 
constructed as to throw back the flame upon the metal to be melted. In 
pl. 28, jigs. 3 a, 36, 3c, and 3d, is represented a double roasting furnace 
on the reverberatory plan, in which there are two hearths one above the 
other, A and #’. This furnace may be used in two different ways: either 
each hearth may be used with its separate blast, or the blast may be applied 
to the lower hearth only, passing thence with the stream of hot gases to the 
upper one. In the former case the smoke passage, 7, is closed with an iron 
plate, and the smoke passes immediately to the chamber x, and the double 
roasting furnace performs the functions of two reverberatory furnaces, with 
this difference, however, that the upper one is easier to heat. Where it is 
used as a double roasting furnace, the passage f is opened and there is but 
one fire, viz. upon the grate r ; the upper hearth then serves for preparatory 
roasting and the latter for finishing the operation. The working openings, 
o and o’, are upon opposite sides of the furnace, that two laborers may be 
employed at the same time without interrupting each other. 
P1. 27, figs. 15 a, 155, 15, represent a puddling-furnace used for con- 
verting cast-iron into wrought-iron; @ is the ash-pit, r the grate, 6 the fire- 
bridge, A the hearth upon which the pig metal is placed. The bridges 6 
and d are hollow, having each in its centre a cast-iron pipe through which 
a stream of water is kept constantly running; 7 is an opening beneath the 
chimney, through which ashes which collect there may be withdrawn ; ¢are 
cast-iron columns which support the stack. Beneath the hearth is an open 
space, and the openings, x, are for the purpose of giving access to the same. 
4, Crucrpte-Furnaces. Those furnaces in which the substances to be 
acted upon are confined in a crucible which is exposed to the action of the 
fire, are called crucible-furnaces. Their construction is very various, accord- 
ing to the use to which they are to be applied. Of this class are mufile-fur- 
naces made use of for various metallurgic processes, in which the material 
is to be kept from immediate contact with the fire. PJ. 28, jigs. Ta, 76, 
represent a furnace for roasting or distilling arsenic with muftile-formed 
chamber. a isthe ash-pit, B the grate, p the hearth of a double layer of fire- 
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