in the Pyrites. ijtf 



greatly intermixed with all manner of earthy fo- 

 reign matters, confequently, is of a very ioofe, 

 fpongey texture, and hence as light, if not lighter, 

 than arfenic itfelf; and that matter, wherein it 

 principally fixes, not yet feparated from the faid 

 metals. 



But in the methods of lead-working and black- 

 copper-making, it plainly appears in our fmeltings, 

 where arfenical ores come into the additions, and 

 where arfenic-fyrites happen in the crude-workings 

 and the crude-ftone being, at length, duly prepared, 

 comes into the lead-working, and where the cop- - 

 per-ftone being fet y or drawn off, comes into the 

 copper-working-, nay, is there the whole, or prin- 

 cipal part, when the lead-working happens to em- 

 ploy no pure glitter^ or lead-ore, but is inter- 

 mixed with all manner of rich, chiefly arfenical > 

 ores, alfo with actual unfeparable cobaldifh ores : 

 in a word, where many forts come together, and 

 one working fucceeds another, 'tis no wonder, if, 

 in many places, little or no mention be found made 

 of fpeife, leg *, &e. 



What thus retains the arfenic to itfelf, and, in 

 fome meafure at. lead, fixes it, fo as to make it 

 flow like a metal, and bear the being caft, is, prin- 

 cipally, an iron-earth. I fay principally, and this 

 not only at our lead, but at our black-copper- 

 workings ; though particularly in thefe laft, fome 

 admixture of copper mud be allowed, and this, 

 fometimes, is called fpeife^tfytch.Wy, when produced 

 from the lead-working •, fometimes leg, alfo kupf- 

 fer-kg, when from the copper-working -, it floating 



N 2 and 



* Thefe are the fevera! appellation! of the abovsrr.emioned 

 g arfenaal re^ulu; 



