115 



appears ; or tKey are alternately extenuated and 

 expanded, so as to present a sort of undulating- 

 appearance. 



The positions of veins with respect to the ho- 

 rizon, vary through every possible angle. The 

 direction and' the dip are estimated in the same 

 manner as they are in strata. 



When veins traverse stratified rocks, their po- 

 sitions with respect to the general plane of strati- 

 fication is equally various. They frequently in- 

 tersect it at some angle, so as to pass through 

 many successive strata. Occasionally, they are 

 parallel, for a greater or less space, to the plane of 

 stratification, and thus lie between any two strata 

 in a parallel manner. Sometimes the same vein 

 possesses both characters ; intersecting in one place 

 those strata to which it is parallel in another. ^ 



In such cases, it becomes sometimes difficult 

 to distinguish between a vein and a stratum ; and, 

 as the distinction is important, it is necessary to 

 state the circumstances by which it may be made. 

 They resemble those by which pseudo-strata are 

 distinguished from real strata. 



Veins, although in any one place parallel to 

 i2 



