36 
Copper* 
flat, otherwise some parts of the hot copper not quite 
fixed, may be thrown off against the workman. 
The essay should be frequent : when finished, the cop- 
per throws out small globules and is red, and filamentous 
with few yellow spots. The scoriae from being black, 
Become brown and brownish red, and emit no smoke. 
When the refining is carried further than is necessary, 
the plates are thicker, the under side also is full of pointed 
drops, but the metal is not the worse. 
If the copper is not sufficiently refined, the plates are of 
unequal thickness, and have inequalities of a dark colour 
near the edges, or the metal has pale coloured spots in its 
fracture. 
The refining hearth may be near the foundery furnace : 
it may be of fire stone, fire brick, or brasque. 
The refining occupies from an hour and a half to two 
hours. 
If the basin must be emptied, it may be done by ladles 
well covered with clay inside and out. 
The scorise should always be so removed, that the blast 
may strike the surface. 
The hearth ought to be examined and mended after 
each operation. 
There should be an iron ring to retain the coals. 
I shall now proceed to give the processes used at the 
mines ofFahlun, in Sweden, andTresburgh near Bruns- 
wick, in Germany, from 3 Jars Voyages Mineralogiques. 
I select these, because the Swedish copper is very good, 
and because the works at Tresburgh were under the di- 
rection of M. Cramer, whose skill is well known. At 
Fahlun, they do not find it necessary to wash the ore : at 
Tresburgh it is washed, after being broken, and sorted, 
and sifted. 
At Tresburgh, owing to the quantity of fluor spar that 
accompanies the ore and assists the fusion* the ore is not 
