MINERALOGY. 5 



melting heat, if we only carefully obferve thofe 

 marks, which, befides, plainly (hew their having 

 once been foft, or diflblved. 



That mineral bodies are ilill prepared in that 

 large workfhop of Nature, the Earth, in the fame 

 manner as thofe which are already full grown 

 feem to indicate, is hardly to be pofitively afTeit- 

 ed, fmce we yet want fufncient obfervations and 

 experiments thereon. 



I will, for inftance, mention the whole Flinty 

 Clafs, of which we have not one obfervation, 

 how they are generated. For if any one pre- 

 tends to have hit upon the quartz cryftals * in 

 the very inftant of their mooting, it might be 

 afked, Whether he only depended upon the fi- 

 gure, or if he made fuch experiments thereon 

 as might convince us, that no calcareous earth, 

 either pure or dilguifed, was alio at the fame 

 time mixed therewith ? To enumerate the many 

 different ways of generation, which we have any 

 reafon to fufpect, does not properly belong to this 

 work ; befides, it would carry me too far from my 

 ftibjeot, and might alfo furpafs my capacity to 

 explain. I will, however, by mentioning the fol- 

 lowing opinions, try to fpirit up perfons of more 

 experience and leifure, willing to purfue thefe en- 

 quiries. 



Precipitation from or by water, is already menti- 

 oned, as well as a hint given about the formation 

 of flints. This laft does not fuppofe fuch a foft- 

 nefc as that of clay when mollified with water, 

 but a fliminefs, a gelatinous, or a mucilaginous 

 matter, and confequently a more radical foiution, 



* The author ufes the term Quirt z crifbls for the true 

 •ils; for all foremen authors call figured fpara alfo cr;f- 

 talf ; and diftinguifh them by the name of fpath or frar crif- 

 :. D L, 



E] if 



