In the Pyrites. 171 



reguline body, again, that it then difcovers fome- 

 thing very peculiar, and worth noticing, particu- 

 larly, its eafy receptivity of the action of the air, 

 and of the fmutting or blacknefs thence arifing, 

 which is obfervable of no other metallic body what- 

 ever. Moreover, from this fmutting by the air, 

 we may probably infer, if not the formal prefence, 

 yet the production of the fatty, inflammable mat- 

 ter ; fince this blacknefs is equally as fuliginous, 

 or footy, as that generally in the fublimation from 

 the white pyrites, preceding, and fometimes partly 

 accompanying this volatile arfenic regulus; yet 

 there to be confidered, not fo much a part of the 

 regulus, as of the pyrites. Now, whether this 

 fmut or blacknefs be an actual fulphur, and thus 

 not its inflammable part alone, is not fo eafy to 

 determine, as it cannot be feparated, and brought 

 to any tell •, yet the firft is the more probable opi- 

 nion. 



As ( 1.) the fuliginous form fhews, if not a total 

 refclution, yet a fuperficial corrofion, rather than 

 a new production \ and yet this laft mould here 

 feem to be the cafe, as neither in the fubject alone, 

 the arfenic, nor in the agent alone, the air, a ge- 

 nuine formal fulphur can be exhibited : and fur- 

 ther, as white arfenic itfelf may, by the addition 

 of only an inflammable, not a fulphureous matter, 

 become, after a new fublimation, fmutted again. 

 Now, in this form arfenic is denominated flyftone, 

 fly-poifon \ in regard flies, and the like infects, are 

 by its means deftroyed -, though the above black 

 powder be fitter for the purpofe, as, on the fcore 

 of its tendernefs and porofity, it is more commu- 

 nicable of its virtue to the water tempered there- 

 with : and the appellation, ftone, has been bor- 

 rowed from the foffil, or native fly-ftone, which is 



a real 



