C 304 J 



Is already in a volatilifing ftate, 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 to 

 blow off the lead, as has been laid, 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 

 extract the filver out of apoor ore -, 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 

 eafily diftihguifhed from lead by the following ex- 

 ternal marks, viz. thatitmuft be red-hot, before 

 it can be melted: it eooles 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 Miner* cupri calciformes, (at lead fome of 

 them) when not mixed with too much ftone 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 5 the heterogenea, contained in them., 

 hindering the fufion, before thefe are fcorified by 

 the flux. 



SECT. XLI. 



The grey Copper ores, which only con fid of 

 copper and fulphur, are tried almoft in the fame 

 manner, as above-mentioned. (Seel, xl.) Being 



expoled 



