MINERALOGY. 
5 , 
melting heat, if we only carefully obfers^e thofc 
marks, which, befides, plainly ftiew their having 
once been foft, or diffolved. 
That mineral bodies are ftill prepared in that 
large worklhop of Nature, the Earthy in the fame 
manner as thofe which are already full grown 
feem to indicate, is hardly to be pofitively 
cd, fince we yet want fufficient 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 cry dials ^ in 
the very inftant of their fhooting, it might be 
alked. Whether he only depended upon the fi- 
gure, or if he made fuch experiments thereon 
as might convince us, that no calcareous earth, 
cither pure or difguifed, was alfo at the fame 
time mixed therewith? To enumerate the many 
different ways of generation, which we have any 
reafon to fuipe(fi:, does not properly belong to this 
work ; befides, k would carry me too f^r from my 
fubjed, 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. I 
Precipitation from or hy water ^ is already menti- 
oned, as well as a hint given about the formation 
of flints. This lad; does not fuppofe fuch a foft- 
nefs as that of clay when mollified with water, 
but a fliminefs, a gelatinous, or a mucilaginous 
matter, and confequently a more radical folution, 
• The author ufes the term Quartz criftals for the true 
criftals ; for all foreign authors call figured fpars alfo crif- 
tals ; and diftinguiih them hy the name of fpath or frar crif- 
tals. D. C. 
Bs 
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