38 
Copper . 
The matt, or produce of the first smelting of the roast- 
ed ore, is again melted in a similar furnace of smaller di- 
mensions, where it produces large pigs of black copper. 
The details of all this are best given in 2 Schlutter, p. 
492, who also treats at large on the refining of copper. 
The refining furnace, is about 3 feet 8 inches by 3 feet 
2 1-4 inches deep. The tweer of copper has an inclina- 
tion of about 25 degrees, and the blast is directed toward 
the most distant part of the furnace. The basin of the 
furnace, is made of a composition of two parts well tem- 
pered clay, beaten up with one part charcoal dust and one 
part cinders. Of this composition or brasque there are 
three layers. When well made, it will last for three or 
four refinings. The loss amounts to ten per cent. The 
copper is taken out in rosettes as above described. 
At Tresburgh the furnace is 5 French feet high, 3 feet 
deep, 16 inches wide at one end, and 21 at the other 
where the tweer enters, which is not elevated above 4 or 
5 inches above the basin of the front hearth. 
The copper undergoes repeated fusions at the refining, 
till it becomes pure, which is tried as has been already 
mentioned in the case of the English furnaces. 
The following note I copy from some manuscripts 
lent me by my much respected friend Dr. Hunter of Phi- 
ladelphia. 
Copper Refined 1 
Memorandum of a process for refining copper at one 
smelting, given by Mr. Francis Da Costa. The kop- 
perpys (the ore) are put into an air furnace, which is first 
heated slowly to give an opportunity for the sulphur and 
other volatile metallic substances such as antimony and 
arsenic to evaporate— half an hour afterwards increase the 
heat to fusion. Then throw on the surface of the metal 
a layer of fine white clear sand which melts and dissolves 
