in the Pyrites. 131 



comparifon of the remaining fixed earth. (3.) This 

 unmartial refidue is by no methods reducible to 

 any other metal *, and tho' in the intended metal- 

 liiation many actual iron particles may be fcorified, 

 or vitrified, as may eafily happen in iron, nay, in 

 copper proofs, with an undue degree of fire, or 

 dole of additions, yet this cannot always be the 

 cafe •, and certainly we have reafon to believe, that 

 the glafs, or fcoria, to which the fixed white py- 

 rites earth runs, is moftly a crude, unmet attic earth. 

 As to the yellowifh, or fulphur pyrites, there is, 

 by the magnet, and the ufual fmetting-proof, more 

 iron in it than in the white pyrites : lb that ibme of 

 them amount to 50 or 60 lb. of iron in the cent- 

 ner, cr quintal •, w hi I ft others, or rather the moft, 

 in particular the fphericaJ, and thofe the purefl: 

 iron-pyrites, feldom yield more than between 10 

 and 12 pounds. And again we fee, that, befides 

 the fulphur part, which is generally about I, and 

 the meta!, which is not I of the f parts of the 

 fixed earth, including alio the fcorified iron-earth, 

 the half or above the half, which is neither ful- 

 phur, nor metal, mull be a crude earth. Laftly, 

 of the copper, or yellow pyrites, we may affirm the 

 fame as of the yellowifh, as being nearly allied to 

 each other. 



(4.) What the proper nature of this unmetallic 

 t r.h may be, cannot fo eafily be determined; we 

 mult therefore reft contented with the bare know- 

 ledge, that there is, in reality, fuch an earth, tho* 

 incapable of exhibiting it pure and in its unverified 

 ftate. I call it a crude earth, becaufe from it, as 

 from an unformed matter, a metal may be pro- 

 duced, if either the matrix prove not barren or un- 

 toward, or there be no want of impregnating juices, 

 or of a proper length of time for compleating the 

 maturation and codtion. 



K 2 CHAP, 



