f ) 1 
This vitrified Copper is then nothing but Copper de- j 
prived, by means of hear, of the falphurous part, that ^ 
gave it the form of a Meta!. ' A proof that this metallick ^ 
form proceeds from nothing elfe but this Sulphur, is, that 
if one expofes this vitrified Copper to the Focus upon i 
Charcoal, it realTumes in a little time the Colour and | 
Confiftence of melted Copper* and as it grows cold, ^ 
fixes into a good red malleable Copper, as fine and hard j 
as it was before it was vitrified. 
It follows from thefe Experiments, that the Bafis of 
Copper is a red Earth fufceptible of Vitrification. 
That this Earth receives its metallick Form from a ful- 
phurous fubftance, in appearance no ways different from 
the Oil of Vegetables or Animals. 
That one may,deprive Copper of this Oil, by holding ’ j 
it long enough in the Focus, or by calcining it in the 
Flame of common Fire. 
That Charcoal reftores again this oily Part to Copper, 
and at the fame time its metallick Form. 
It appears further, that the Oil of the Coal has not 
fo confiderable an effed upon Copper, as it has upon 
Iron. 
Copper expofed a long time to the Focus upon a Stone 
or Coppel, fumes very much, and diminifhes in weight 
very confiderably. 1 don't think that this fume is on- 
ly the fulphurous part of the Metal, the Evaporation of 
which muft be infenfible^ but I believe that with this Oil 
there is mixed a great deal of the earthy, vitrifiable part 
of the Metal, which the heat of the Sun fublimes and 
raifes in Flowers. 
OfTw. 
Tin expofed upon Coal to the Focus of the Burning- 
glafs, melts, and emits a grofs, white, thick Fume, until 
it is all confumed in Vapours. 
If 
