OF THE SECONDARY CLASS. 387 



sion of different classes of organized beings, 

 which have occupied the former surfaces of the 

 e^rth. 



That the secondary rocks are much more 

 limited than the primary, in their extent as well 

 as in their depth, is so obvious, as scarcely to need 

 a remark. Were they not indeed often deficient, 

 the primary would not be visible on the surface. 

 While, in fact, the primary rocks constitute, as far 

 as we can discern, the mass of the earth, the se- 

 condary are distributed in a very partial and un- 

 equal manner. The primary rocks may also be 

 considered universal, since they are found with 

 similar characters over the whole globe ; and if 

 access could be obtained to them, they would 

 doubtless also be found to recur in a continued 

 and similar general succession every where. But 

 the secondary strata can only be. considered as 

 universal in a more limited sense, or inasmuch as 

 similar rocks occur, as far as their leading distinc- 

 tions, or species, are concerned, in every part of 

 the world. In other respects they are partial, 

 since they are not continuous. There is also 

 reason to suspect that they are partial in a still 

 c c 2 



