OF THE SECONDARY CLASS. 385 



the primary strata, may be that on which the red 

 sandstone reposes. 



But in some instances, as was also shewn in 

 that table, even the red sandstone may be absent ; 

 arid thus, some other and superior member of the 

 secondary class, may be in contact with the pri- 

 mary rocks. Such deficiencies need excite no 

 surprise, and they can seldom be attended with 

 much practical inconvenience ; as the other cha- 

 racters of the strata which are superior to it, are 

 generally so well marked as to leave no ground 

 for doubt respecting their place in the arrange- 

 ment. 



In concluding these remarks on the boundary 

 between the primary and secondary strata, it is 

 necessary to say, that from finding that the first 

 member of the latter is composed of the frag- 

 ments of the former, geologists have concluded 

 that a marked interval of time had elapsed before 

 the secondary strata were consolidated and depo- 

 sited on the primary ; a consequence necessarily 

 arising from their composition. The highly in- 

 teresting conclusions with regard to the whole 

 class, which flow from the presence of coal, and 



c c 



