of the Py sites. 347 



alfo in fome meafure arfenic, quartz and fpathe, 

 are very fluxile : much more itubborn are glimmer, 

 Mufcovy- glafs, talc, cat-filver, fhiver and horn- 

 ftone i moft of all lime-flone, gypfum, alabafter 

 and chalk. All which particulars I have learned 

 from the proofs. It remains to be enquired why^y- 

 rites, which is properly of the ftubborn ores, is a 

 flux, and in what circumftances. Pyrites is three-. 

 fold ; yellowiffi, yellow and white \ or iron, cop-r 

 per and arfenic pyrites. The white or axfemc pyrites 

 is quite unfit for the operation of cruder/meltings and 

 hence kept from it as much as may be ; in regard 

 its arfenic eats away and fcorifies the lead, which 

 is already amongft it either in eyes of glitter, or 

 lodged in the foft leady flags, or otherwife added 

 thereto, as is well known of both thefe bodies : or 

 again, when the arfenic has nothing to do with 

 lead, it feparates with difficulty, or not at all from, 

 its earth (as the crude -working is a ftrong fmelt- 

 ing lire, wherein it directly cakes therewith, and 

 rather requires a foft roafling fire for its feparation) 

 cor.fequently the earth cannot fcorify, as it fhould, 

 to anfwer the end of crude- /melting. Again, this 

 inconvenience happens, that the arfenic, lodging 

 in the iron of the pyrites earth, will not be fepa- 

 rated from it in the following lead and copper 

 workings, but is ftill to be feparated in that arfe- 

 nical, irony mafs, called /pe.i/e and leg. Further, 

 its earth is fo crude, as to become, if not unfer- 

 viceable for fcorification, the principal thing here 

 intended, yet not fo eafy- flowing ; efpecially as the 

 white pyrites is fo overdofed therewith : and again, 

 it gives none, or but an arfenical, impure crude- 

 /lone, or regulus. 



But the yellowifh and yellow ; or, as they are 



cal- 



