304 The Vi TRioL 



cined, are often, without falling to pieces, entirely 

 fhattered and burft as by a force, evidently acting 

 from within outwards ; and this may be judged to 

 be owing to the vitriolifation. 



The reafons certainly are, the air's neither fo 

 brifkly entering into, nor fo powerfully acting up- 

 on them -, in regard they lie, if not in a peculiar 

 and firm narrow cafe or enclofure, as a ftone, 

 which yet is not uncommon, yet covered under 

 the earth, and in fome meafure only, not entirely, 

 expofed to the accefs of the air : again, tho' their 

 fhells may crack, yet their parts feparate not to 

 any diftance, as being urged or preffcd upon by 

 the adjoining earth and ftone -, and though by the 

 act of vitriolifation, they may turn to an earth, 

 yet they muft hold together, become compact, 

 nay even petrify. 



Such periwinkles and mufcles fluffed with py- 

 rites , or pieces of pyrites ", of the form of peri- 

 winkles and mufcles, are found cracked, rutted, 

 and again hardened, at Boll, and the adjoining 

 territory, in great quantities, and in various forts ; 

 particularly, cham<z, peffiunculi, cornua ammonis, &c. 

 but never, fo far as my experience has reached, in 

 lapis lyncis \ the cavity of which is neverthelefs often 

 found filled with pyrites, a circumftance deferving 

 peculiar notice ; and I have difcovered at the 

 Schlofsberg at Toplitz a terebratula> entirely rufted 

 and remaining firm •, a thing I never obferved be- 

 fore, whatever pains I took in the fearch. 



Further, I befides remarked, that many fuch 

 fea-fhells, exhaufted of their pyrites, were only 

 externally rufted over •, but upon preparing them 

 both in their entire ftate and beat fmall, for vitrio- 



lifation^ 



