28 Account of the Process of Amalgamation 
the furnace below, over the bottom of which it is spread by 
means of an iron rabble or rake. The fire, which is of wood 
and a mixture of coal and clay, is contained in a division of the 
furnace separate from that which receives the ore, with which 
it is connected only by a large aperture, through which the flame 
and heat pass into the vaulted compartment containing the ore, 
and out at the chimney erected over the other end of the fur- 
nace. By this means a high degree of heat is given to the ore 
without any contact with the fuel, and the sulphur and other 
volatile matters which arise from it are speedily carried off. The 
workman attending the furnace keeps the ore in a constant agi- 
tation with his iron rake, to prevent its adhering together in 
hard lumps, especially when it becomes red hot, and, by changing 
the surface, more regularlyto expose the whole to the operation 
of the flame and heat. This is continued, and the red heat 
maintained, for three or four hours, until there are no longer any 
signs of sulphur remaining inthe ore. The whole is then with- 
drawn from the furnace. During this operation a decomposition 
of the muriate of soda has taken place, the acid forming new 
combinations with the earthy parts, and the oxides of the im- 
perfect metals, and the soda with the sulphur which had not 
been expelled by the heat; whereby the union of the silver is ren- 
dered much less intimate with the substances from which it is 
to be separated. 
The calcined ore, as it is taken from the furnace, is put when 
cooled into boxes, which are raised by a crane w orked by water 
into an upper story, where it is sifted, and all the pieces which 
have caked together are separated from the rest. The cakes 
are broken, and being again mixed with a small portion of salt, 
are once more roasted; but the finer parts which have passed the 
sieve are conveyed down by pipes into the mills, where they are 
ground to an almost impalpable powder. These mills, of which 
there are several, are all turned by water; the mill-stones are of 
granite. 
When thus prepared, the ore is carried in barrows to a cham- 
ber, where twenty chests present themselves arranged in rows of 
five each. These stand immediately over corresponding vessels 
or barrels, in which in the room below the amalgamation is to 
be effected, and which barrels are charged from “the chests by 
means of moveable pipes. 
It is now that the important part of the process takes place. 
The twenty barrels are arranged in four rows, each turning on 
its separate axis by a motion communicated by a water-wheel to 
two long shafts, each shaft passing between two rows of the 
barrels and furnished with cog-wheels, working in others fixed 
on 
