468 OVERLYING ROCKS. 



however, like the preceding, relates only to indi- 

 vidual instances: because the existence of frag- 

 ments of these rocks in the lowest sandstone 

 conglomerate, proves that there have been forma- 

 tions of this nature, prior to the deposition of the 

 secondary strata ; and the intersection and shift- 

 ing of two or more veins, appear equally to prove, 

 that there has been more than one formation 

 among these. 



In granite, they only occur in veins ; sur- 

 mounting it when in masses. But among the 

 stratified rocks of both classes, they are found 

 intruding in masses, as well as in veins ; and 

 these sometimes put on a form so far parallel to 

 the stratification, as, when partially viewed, to 

 give them the semblance of beds. The veins, 

 which are also common, are sometimes, in the 

 same manner, partially parallel to the planes of 

 the including strata, so as to have led to similar 

 errors. In either case, the true nature of these 

 may be determined, with proper care, by finding 

 that the parallelism is not long maintained, but 

 that any one such supposed stratum, or vein, 

 quits its place to intersect the adjoining and in- 



