'348 The Uses 



called at Friberg, the fulphur or iron pyrites , and 

 the copper-ores are what deferve particular mention 

 here for the operation of crude imclting, and mod 

 peculiarly, the yellowim, as what fo completely 

 anfwer, as to compenfate their want of copper : 

 Though indeed it were better, were the common 

 pyrites not only coppery, as it generally is at Fri- 

 berg, but alfo were copper ore added ; as then we 

 might expect a yield of copper, to help to com- 

 penfate the charges in working ; and in fome cir- 

 cumftances, indeed, where the work fhall prove 

 hot and refractory, cannot be omitted without 

 lofs in filver-yield , but in itfelf, and for promot- 

 ing the principal end of this method of working ; 

 that is (1) For the fcorification of the rocky, ftony, 

 and earthy matters. (2) For making theftone or 

 regulus, and concentrating the filver, it cannot be 

 confidered as abfolutely neceffary •, as it promotes 

 not the firft ; and as to the fecond, lead is fuffi- 

 cient ; which is already in the ore in glitter-eyes, 

 as coarfe veins are never without them ; or leady 

 additions may fupply that want for noble veins ; 

 where not only glitter, but alfo pyrites is generally 

 wanting. 



What the pyrites contributes in the operation 

 of crude-fmeltingi is to flux and fcorify the ftony 

 and earthy matters, to feparate the ore from them, 

 and make it give forth itfelf in what is called the 

 ftone, or crude regulus. Now as pyrites confifts 

 of feveral parts, as fulphur, arfenic, iron and cop- 

 per, we muft enquire which of thefe it is, that 

 promotes the above effects. The arfenic is here to 

 be fecluded, as corroding lead, tainting filver, and 

 as encumbering, nay proving detrimental to the 

 fcorification. Copper is in this cafe to be con- 



fider- 



