ON COTEMPORANEOUS VEINS. 



in those cases when the beds or strata are of 

 uncommon thickness. Their direction is not tor- 

 tuous, and they seldom give off many branches. 

 The mass of the vein is generally distinctly se- 

 parated from its walls : it is frequently disposed 

 in beds or layers, and these are parallel with the 

 walls of the vein. At the outgoing of bedded 

 veins, the beds are near the walls ; but farther 

 down, they approach the middle of the veins, and 

 consequently are so arranged, that the newer beds 

 are contained in the older. They often contain 

 fragments, which lie promiscuously, and are either 

 acute- angular, blunt-angular, or rounded. Last- 

 ly, the materials of true veins, are more or less 

 different from the rock which they traverse, and 

 the same vein sometimes contains several forma- 

 tions.- 



2. Cotemporaneoas Veins are from a few inches 

 to the smallest discernible breadth. Their length 

 is from a few inches to an hundred feet and up- 

 wards. Their course is tortuous, and they give 

 off numerous branches. The mass of the vein is 

 generally intimately mixed with and passes into 

 that of its walls, and differs but little in its con- 

 stituent parts from that of the rock which it tra- 

 verses. They contain but few drusy cavities ; 

 never more than one formation ; and when they 

 contain apparent fragments, the slaty structure 

 of these is ever conformable to that of the con- 

 tiguous rocks. Lastly, they traverse but single 



