39 
Copper • 
a mass of cinder at the surface. When formed take it 
out with a scraper and let the metal remain in a fluid 
state long enough to allow the remaining oxydable sub- 
stances to come to the surface, and then renew the opera- 
tion with sand should that second operation prove neces- 
sary ; and let the cinder be again scraped out. Then 
throw on the surface of the fluid copper, powdered char- 
coal to cany off the oxygen remaining. When this char- 
coal is burnt down, dip into and stir the copper well with 
a stick which whilst burning, occasions an ebullition 
which throws up to the surface those parts of the metal, 
that had not been in contact with the coal, and throw 
some more coal upon it and renew the operation until 
you ascertain, that the refining is complete which is easi- 
ly done by taking out a little of the melted copper with a 
small ladle ; cast, cool and break it, if the metal appears 
silky and of a good colour, the metal is pure and fit for 
any purpose* — when cast into large thin moulds, it requires 
to be very hot, and at the same time the moulds ought 
to be very dry, to prevent accidents, or the losing the in- 
tended casting piece. Mr. Da Costa believes that this 
process depends on the difference of affinity between cop- 
per and iron, which last is the principal impurity in the 
copper brought from the Spanish main. 
N. B. G. H. has examined several samples of copper 
brought from Spanish America and never found any iron 
in them— he generally found sulphur and antimony. 
Perhaps powdered magnesia (manganese) would have 
a good effect in separating the semi- metals, which are 
commonly found in a small proportion in copper in pigs, 
and thereby facilitate the malleability of it, by stirring it 
well with the melted copper. Nitre is too dear. 
Having now given some ideas of the mode of working 
copper ores, from writers who have treated on the subject, 
I will give the substance of my own notes, taken on a 
