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been sometimes made a ground of distinction 

 for the primary class. In a practical view, this 

 character would be of no use in discriminating 

 individual rocks, were it even constant in that 

 class ; as, among the secondary strata, such re- 

 mains are but of partial occurrence. But it en- 

 tirely ceases to be a distinction, unless that ex- 

 pedient of a transition class, which has here been 

 rejected, is adopted . As the reasons for rejecting 

 this class have been given elsewhere, no further 

 remarks on this character, as distinguishing the 

 primary from the secondary rocks, are required. 

 It must therefore be concluded, that there is 

 no single character by which the primary class 

 can in all cases be distinguished. The proofs of 

 that essential circumstance, inferiority, on which 

 it is founded, being* sometimes inaccessible, re- 

 course must then be had to one or more of the 

 remaining characters ; and, although there are 

 cases where the distinction may call for all the 

 industry and acuteness of a geologist, his endea- 

 vours will rarely be disappointed. It is only by 

 such exertions that he can hope to improve an 



