312 The Vitriol 



is therefore ufual, within the year and day, to bor 

 out the vitriol^ according to the plenty of heap- 

 work, and in proportion to the demand for the 

 commodity. And mould any one, in order to pro- 

 mote the bufinefs of vitriolifation, take it in his 

 head, that ore, the more it is (lamped fmall and 

 powdered, the more it would lie expofed to the 

 action of its menftruum, from the axiom, that the 

 more fides a body thus expofes, the fooner it will 

 be refolved, he would find himfelf greatly miftaken •, 

 as thus, the ore would lie more clofe together, fo 

 as to exclude the action of the air. Yet it depends 

 on practice and experience, to determine whether 

 the often turning what was infide outward, may be 

 of any advantage or no. 



It remains to fay fomething of the white vitriol, 

 a matter greatly unknown, both in its origination 

 and mixtion : it is white, and not barely fo to the 

 eye, as vitriol in general ufuaily appears, when in 

 a capillary or woolly ftate, and confequently fine 

 and tender, or when minutely rubbed, or dried and 

 crumbled by air and heat •, but eifentially, and in 

 its mixtion, white, as plainly appears from its cry- 

 stals, be they ever fo large and thick. It is true, 

 we have alfo a bluim fort, but this external blue caft 

 may, by a proper cryftallifation, be difcharged. 

 Though its origination be utterly unknown to us, 

 yet I cannot omit mentioning what I myfelf have 

 obferved, viz. that the pyrites of Pretzfchendorff, 

 which is a yellow cubical fort, intermixed with 

 fomewhat of a mock-Jeady matter, and lodged in 

 a black-grey fhivery rock, has, after defulphura- 

 tion, and a long expofure to the air, yielded an 

 actual white vitriol, differing in nothing from the 

 Rammelfberg fort, fo far as I hitherto find (after 

 purging fuch from its adhering copper-blue) cither 



in 



