61 



remains, or fragments of more antient rocks, is 

 discovered in a position geologically deeper than 

 that last assigned for the limits of the transition 

 strata. 



Lastly, it is admitted that the transition rocks 

 are frequently absent ; the primary and second- 

 ary coining into immediate contact. Although, 

 from their nature, the secondary rocks may fre- 

 quently be wanting, either from the effects of 

 waste, or from their never having been deposited 

 in some particular spot, it almost implies a con- 

 tradiction in terms to suppose that absent which 

 is esteemed to be a transition between two classes, 

 when these are both present. 



This class cannot therefore be considered a 

 natural division, if it does not necessarily exist, 

 if it does not form a transition between the pri- 

 mary and secondary classes, if it has no aggregate 

 of characters by which it can effectually be recog- 

 nized and distinguished from those, and if it has 

 no assignable boundary. 



If the transition class were productive of any 

 convenience in a practical view, it might never- 



