t 304 J 
4 ' ' - 
ts already iii a volatilifing ftatc, will by this artifice' 
be driven out in form of a fubtil fmoke ; and by thus 
continuing by turns, to melt the mafs, and then ta 
blow off the lead, as has been faid, until no fmoke 
is any longer perceived, the filver will at laft be 
obtained pure. The fame obfervation holds good 
here alfo, which was made about the gold, that^ 
as none but very little bits of the ores can be em- 
ployed in thefe experiments, it will be difficult to 
extm6t the filver out of a poor ore 5 for fome part 
of it will fly off with the lead, and, what might 
be left, is too little to be difcerned by the eye. 
The filver, which, by this means is obtained, is 
cafily diftinguilhed from lead by the following ex- 
ternal marks, viz. that it muft be red-hot, before 
it can be melted : it cooles fooner than lead : it 
has a filver colour*, that is to fay, brighter and 
whiter than lead : and is harder to beat with the 
hammer. (Sed:. xxxiv.) 
SECT. XL. 
The Miners cupri catciformes^ (at leaft fome of 
them) when not mixed with too much flone or 
earth, are eafily reduced to copper with any flux : 
if the copper is found not to have its natural 
bright colour, it muft be melted with a little borax, 
which purifies it. Some of thefe ores do not at all 
difcover their metal, if not immediately melted 
with borax *, the heterogenea, contained in them, 
hindering the fufion, before thefe are fcorified by 
the flux. 
SECT. XLI. 
The grey Copper ores, which only confift of 
copper and fulphur, are tried almoft in the fame 
manner, as above-mentioned, (Sed:. xl.) Being 
expofed 
