VEINSTONES. 589 



lastly, by a laminar or venous disposition of the 

 mineral substances which they contain. 



Besides these venous rocks, of which the 

 origin can commonly be traced, it is not uncom- 

 mon to find, among masses of bedded or unstra- 

 tified rocks, other mechanical mixtures of similar 

 character, which cannot decidedly be traced to 

 their original situations. These may generally 

 be recognized to be derived from corresponding 

 sources, by peculiarities of an analogous, though 

 of a less decided nature. They are sometimes the 

 produce of veins also, of a less conspicuous cha- 

 racter, and less distinguished by the variety of 

 their ingredients. In many cases, they result 

 from the fracture, and consequent sliding or sepa- 

 ration, of a mass of rock. In such instances, a 

 species of imperfect vein is formed, containing 

 fragments of the separated masses, reunited by 

 minute fragments of the same and by clay, or by 

 the subsequent infiltration of the only two mine- 

 rals which appear still to exist in a state of occa- 

 sional solution, namely, quartz, and carbonat of 

 lime. 

 In some rare instances, of which two have been 



