122 Of the Copper 



wc might by degrees arrive to certain axioms, that 

 might be depended on, with refped to the metal- 

 lie mixtion of ores. 



Some of the above-mentioned ores, namely, anti- 

 mony and lead-glitter ^ agree more than a little, both 

 in their meafure of fulphur and metal-mix t ion ; alfo 

 in the kind of their volatile, namely, fulphur por- 

 tion ; nay, almoft in the volatility of their metallic 

 or femi-metallic portion ; and befides, in the fe- 

 parability of their metal from their fulphur. In 

 particular, that thefe, before all or mod other ores, 

 are in their mixtion found of a like proportion of 

 metal and fulphur, as that their metal, at leaft, ever 

 outweighs the remaining ore-portion, but the con- 

 trary never happens. Farther, that accordingly, 

 tin-ftone, cinnabar, glajfy y and red-goldijh ores may 

 be clafled amongft the firft, of whole metallic yield 

 the moft folid and conftant obfervations may be 

 made. 



Now to return to our pyrites-copper-ore ; I have 

 not only affayed various forts thereof, but employed 

 all the care and attention needful on fuch occafions ; 

 as feparating, picking, and cleaning; and found 

 their yield feldom amounting to half, nay, gene- 

 rally falling fhort by 3, 2, down to 1 pound ; 

 confequently a yield fo various, as is not eafily to 

 be met with in any other genuine ore ; a circum- 

 ftance that deferves a greater degree of attention 

 than has hitherto been thought proper to beftow 

 upon it 5 not to repeat what was faid of lead, 

 quickfilver, and regulus of antimony, whofe proper, 

 pure ores in metallic yield never fall fo low, nay 

 constantly hold to one and the fame degree of 

 weight, without any material difference, allowing 

 for what is loft, from their aptnefs to volatilife, to 



be 



