M 
Copper \ 
possible from the adhering earthy impurities ; after which 
it is piled in large kilns* and heat being applied at the bot- 
tom, the whole mass becomes gradually heated, and a 
large portion of the sulphur sublimes out, and may be ei- 
ther collected by proper flues, or allowed to escape ; this 
first process occupies about six months, at the expiration 
of which time, the evaporation of the sulphur ceases, and 
when the ore has cooled sufficiently, it is in a fit state to 
be smelted* 
If, however, the ore is largely combined with arsenic, 
it is not capable of keeping up a long combustion of it- 
self, nor is the heat thus generated adequate to the expul- 
sion of the arsenic ; a somewhat different method, there- 
fore, of roasting must be had recourse to* For this pur- 
pose the ore is still more carefully dressed than in the for- 
mer case, and is reduced to pieces not larger than a hazle- 
nut* It is then spread on the floor of a large reverbera- 
tory furnace, and exposed to a dull red heat, with frequent 
stirring, in order to offer fresh surfaces to the action of the 
flame. The arsenic and sulphur by this treatment are ra- 
pidly driven off*, and in about twelve hours the roasting is 
completed. 
The ore is now transferred into the fusing furnace, 
which is a reverberatory of the common construction ; a 
little bruised lime-stone is generally added by way of flux, 
and in the course of four or five hours the fusion is usually 
complete ; the slag, now of the consistence of soft dough, 
is raked off, and the copper is discharged through a plug- 
hole into water, by which it is reduced into small drops 
or grains. 
The copper, however, though in the metallic state, is 
still very impure, being largely mixed with sulphur and 
arsenic, which give it a grey colour, and render it perfect- 
ly brittle. In order to separate these impurities, it is re- 
melted and granulated twice more, or oftener, a considera- 
ble quantity of slag being separted at each fusion ; but as 
