for extracting Gold and Silver from other Ores. 27 
put into copper boilers in the form of an inverted cone, rounded 
at the bottom and opén at the top, in which an instrument was 
made constantly to revolve; thus keeping the whole in agitation, 
while a very moderate heat was applied under the boilers; and 
this process having been continued for from ten to twenty hours 
according to the nature of the ore, the whole of the silver was 
found to be disengaged from the ore and taken up by the mer- 
cury. Baron Born made many attempts to conduct this part of 
the process without the assistance of fire; but it was Gellert 
who first perfectly succeeded, and of his success the very com- 
plete machinery of Freyberg was the result. From many com- 
parative calculations and experiments which have been made, it 
has appeared that the saving in the consumption of wood, and in 
the lead wasted by the common processes of smelting and re- 
fining, is so great, that ores of silver and gold which are of a na- 
ture fitted for this process can be worked at nearly half the ex- 
pense by amalgamation; and it is satisfactory to be assured that 
the mercury, so far from producing the deleterious effects upon 
the health of the workmen which were at first dreaded, is in fact 
by no means so hurtful as the heat and fumes which are to be 
encountered in the usual operations of the smelting furnace. 
The process now used at Harlsbriick is as follows: The ores, 
after having been sorted, stamped, and washed in a manner si- 
milar to that which has been described, are brought in separate 
lots to the mills, where each lot is sampled with much care. 
These samples are divided ;—the one part is assayed by the 
assay-master of the mine from which the ore was brought; the 
other by the officers of the works,—a very necessary check to 
prevent errors, and more particularly in this case, as the amal- 
gam works belong to Government, whilst many of the mines are 
worked by companies of individuals. 
The ores are then appropriated either for the operations of 
the furnace, or of amalgamation, according to their qualities ; 
those being chosen for the latter, which are the most free from 
an intermixture of lead and copper; and preference is likewise 
given to ores which yield froin three to four ounces of silver in 
the centner, it being found by experience that such are best 
fitted for this process, “fhe different pareels, the produce of which 
has been ascertained by assay, are therefore so fixed that the 
whole may average about this proportion. To this ore is added 
one-tenth of its weight of muriate of soda, finely sifted. This 
mixture is then parcelled out, in heaps of three or four hundred 
weight each, upon the floor of a. chamber over the reverberatory 
furnaces in which it is to be roasted. Here it is dried for some 
hours, and is then passed down a pipe which communicates with 
the 
