ON MINERAL VEINS. 405 



it is evident that this fact proves no more in this case 

 than in that of granite or trap ; since, in all of these 

 rocks alike, aqueous infiltration takes place, as well 

 into the veins as into the volcanic and trap amyg- 

 daloids. 



But it is here worthy of remark, that of the earthy 

 minerals actually found in mineral veins, there are 

 more of an aqueous than of an igneous origin; al- 

 though there are many more igneous than aqueous mi- 

 nerals in nature. With respect to the metallic ones, the 

 difference is still more in favour of the aqueous mi- 

 nerals. That many of hoth kinds have a double 

 origin, is only one out of the numerous difficulties 

 that beset this subject. These are, in fact, such, and 

 so apparently un surmountable at present, that a pru- 

 dent geologist will suspend his judgment on the sub- 

 ject; provided he does not also suspend his inves- 

 tigations. Both the theories are before him, and he 

 ought to try the facts by both, not by one only, 

 to the exclusion of the other. In this pursuit he 

 ought to take into his views the formation of minerals 

 by sublimation, and their production from infiltration ; 

 two processes which have been neglected by former 

 Theorists. Not however that these will, on either 

 side, form, in themselves, a theory; because, even 

 were there not many more circumstances at present 

 unintelligible in veins, we are still unable to explain 

 whence, on either hypothesis, the minerals have ar- 

 rived at their present places. This last objection ap- 

 plies also to a proposal which has been made towards, 

 explaining the formation of mineral veins, by means 

 of galvanic actions occurring between the vein itself 

 and its walls; though it is not impossible that such 

 causes may have aided in producing their disposition-, 

 or modifying the minerals themselves. 



