ON M1NKAL VEINS. 395 



Of the Minerals which are, respectively, produced 

 from Solution and from the Action of Fire. 



It remains to examine by chemical and minera- 

 logical experience, how far any of the substances 

 found in mineral veins are the produce of crystalliza- 

 tion from watery solutions, and in what cases they 

 are crystallized from a state of igneous fluidity, or 

 from sublimation. If our information is still incom- 

 plete, a general view will be sufficient for the present 

 purpose. The facts themselves, as they regard the 

 two theories which have been examined, are singu- 

 larly conflicting ; though as far as they offer argu- 

 ments for either, the balance is palpably in favour of 

 an aqueous one, under some form, but not that of 

 Freyberg. It is evident that these are the facts on 

 which any future hypothesis must chiefly rest ; what- 

 ever further considerations may be required for ex- 

 plaining the various other circumstances which attend 

 mineral veins. 



In inquiring, first, respecting the earthy minerals, 

 so as to determine those which may be produced from 

 watery solution, I must have recourse almost entirely 

 to the chemistry of nature ; as the limited solubility of 

 the earths prevents us from deriving much information 

 from our own circumscribed experiments. For the 

 sake of brevity, I have thrown them into the form of 

 a list ; and, to save repetitions of the proofs on which 

 their aqueous origin rests, these may be given in a 

 preliminary form. 



The formation of quartz, chalcedony, and calca- 

 reous spar, may almost be witnessed ; and that of tbe 

 latter, in particular, is so rapid, that the crystals can 

 often be seen in calcareous caverns, such as that oi" 

 Sky, forming like common salt, while it if? also gene- 



