834 RED PRIMARY SANDSTONE. 



quently with those' of a coarse texture, whicli 

 contain either mica, or sand, or both, and which 

 are commonly known by the name of graywacke. 

 In most cases, the schist is far inferior in quan- 

 tity to the sandstone ; and, in many, it is entirely 

 absent for a very considerable space. Some few* 

 instances may however be observed, where it 

 considerably exceeds that rock, and where, if the 

 term subordinate were admissible, the sandstone 

 should be considered the subordinate substance: 

 Respecting these alternating schists, it may yet 

 be remarked, that some of them contain frag- 

 ments of older rocks, and that a few are highly 

 indurated, so as almost to lose their ordinary cha- 

 racters. If ever the sandstone appears to pass 

 into the schists, the transition is almost always 

 too imperfect to deserve notice as an instance of 

 that occurrence. In most cases, the two rocks 

 are separated in a very decided manner. 



The thickness of the strata is extremely vari- 

 able ; amounting sometimes to many yards ; and 

 in those cases where schist is present, they are 

 frequently of extreme tenuity. In some places, 

 the beds are even separated into their lamhiefe 



