200 Dr. Mac Culloch on Mineral Veins. 



the earths prevents us from deriving much information from our 

 own circumscribed and cramped experiments. For the sake 

 of brevity, I have thought it expedient to throw them into the 

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

 their aqueous origin rests, these may be here given in a pre- 

 liminary form. 



The formation of quartz, chalcedony, and calcareous spar, 

 may almost be witnessed ; and that of the latter in particular 

 is so rapid, that it can be seen in calcareous caverns nearly 

 as well as the crystallization of ordinary salts. This substance 

 is generated both by infiltration, and in solutions of carbonat 

 of lime. Chalcedony is produced in the former way, and 

 quartz in both. In the work to which I have already referred, 

 it was also shewn that those veins which consist of quartz or 

 carbonat of lime, are generated in this manner. 



In the remarks on the amygdaloidal structure, to be found in 

 the same place, I have proved that the theory of infiltration 

 explains the imbedded nodules of the rocks of this character, 

 and that these have been produced in this manner. Thus 

 there is established a considerable list of minerals formed by 

 means of aqueous solution. That v/hich takes place in this 

 case may equally happen in a mineral vein. 



Although we have not yet proved that all the other earthy 

 saline minerals, as they are sometimes called, such as gypsum, 

 barytes, S-c.., are produced from watery solution, chemistry and 

 analogy both render it very probable ; and these may there- 

 fore be added to the aqueous list with little hazard of error ; 

 certainly with much less than they could be referred to an 

 io-neous origin. Lastly, we may pretty safely also refer to the 

 same division, those which are found associated or imbedded 

 in quartz, as disthene is. 



The list, constructed from these various kinds of evidence, 

 will therefore contain the following minerals, and possibly 

 many more ; and, it is liere divided under these several heads 

 of more or less unexceptionable proof. I do not add those 

 which are imbedded in primary limestone, because it is pos- 

 sible, or more than possible, that some of these have undergona 



