ON STRUCTURAL FEATURES OF MINERAL VEINS. 41 



very decisive, and this line of investigation is hardly to be con- 

 sidered a promising one. The importance attached to it in former 

 years may be illustrated by these words of De la Beche, one of 

 the ablest of English writers, in 1839. Speaking of veins in general, 

 after discussing those of Cornwall in particular, he says : " Mineral 

 veins result from the filling of fissures in rocks by chemical deposits, 

 from substances in solution in the fissures, such deposits being 

 greatly due to electro-chemical agency." 



