from the P Y ri T e s. 299 



boration and coclion ; confequently, the air may 

 wcrk on one fore fooner and eafier than on another. 



Now, tho' the proportion and manner of con- 

 nection of the particles of pyrites may caufe a dif- 

 ference, yet we cannot furHcientiy judge of it from 

 their apparent denfity and rarity ; as I meet with 

 pyrites, which, befides their fimilar nature, appear 

 entirely of an equal grain and cohefion, though 

 not equally fubjed: to vitriolifation. From the co- 

 lour it holds, the yellower the pyrites, the lefs, 

 though not the converfe ; and the paler, the more 

 ready it is to give or vitriolife, 



From the figures, both the external and internal, 

 as the angular, the round, the radiated, the tefta- 

 ceous, £s?r. there appeared fome faint glimmerings 

 of truth. Thus it holds, that the round pyrites 

 vitriolife with more eafe than the angular ; and the 

 radiated, than the teftaceous. The reafons I alfo 

 find in the copper and arfenic, of which, both the 

 round and radiated are ufually free. 



In a word, I at length difcovered the caufes 

 that now render eafy, then difficult, or quite im- 

 pede, the bufinefs of vitriolifation to be various ; 

 one caufe taking place in one inftance •, another, in 

 another, and often two together, often one only, 

 and often neither of the two : now, thefe are cop- 

 per, arfenic, and the texture, and what arifes 

 thence, the denfity •, not to mention the unmetallic 

 earth, concerning the difference of which we may 

 entertain fome fufpicion, nor the different mixtional 

 proportion. 



Copper, certainly, is the greateft obftacle of all 

 to thisvitriotic refolution, when even in the fmalleft 



quantity 5 



