406 LOWEST RED SANDSTONE. 



ti notion in the mineral character of the primary 

 sandstone, is most perceptible. 



The rocks which, by their fragments, con- 

 tribute to the formation of the coarser varieties, 

 may consist of any one, or of all, of the members 

 of the primary class. It is very rare, however, that 

 the whole of these are found together. Granite, 

 as among the most durable, is also among the 

 most frequent ; and the argillaceous schists, as 

 possessing a more feeble texture, are least com- 

 mon. Large fragments of common quartz, are 

 also of frequent occurrence among the fragments 

 of the compound rocks. It is an interesting point 

 in geology, to note the relation borne by the 

 fragments in any of these sandstones, to the pri- 

 mary rocks in the immediate vicinity ; but it 

 does not form part of the present examination. 



It is also an important geological fact to re- 

 mark, that fragments of the trap rocks, here con- 

 sidered as, in a general way, belonging to the 

 secondary class, are sometimes found in the con- 

 glomerates ; as it proves that some of these, at 

 least, are of an origin prior to the secondary 

 strata; unless indeed such fragments may be 



