SUCCESSION AMONG ROCKS. 279 



mitting granite among the primary, an appearance of 

 greater irregularity is given to the former than to the 

 latter. In justice, all the unstratified rocks should be 

 put out of the question in this case. 



I need only remark further, on the subject of the 

 secondary strata, that it is not easy to see how such a 

 resemblance Or identity can, in these cases, be so 

 proved, as to warrant any inference respecting simi- 

 larity or order of succession among them in remoter 

 countries, or in distant parts of the world. The mi- 

 neral characters of the various beds of limestone are 

 rarely very strongly marked. The differences among 

 shales and sandstones can scarcely be perceived. It 

 will be hereafter proved (Chap, xx.), that, in distant 

 countries, the identity of two strata cannot be inferred 

 from their organic fossils. Nothing then remains 

 but the juxtaposition, in analogous order, of two or 

 more strata ; and this, it is easy to see, is proving 

 the fact in dispute by means of the very thing to be 

 proved. 



It was just remarked, that as far as the question of 

 order or disorder, under the limitations thus made, 

 is concerned, the latter appears to arise from omission 

 rather than inversion. In the case of individual 

 strata in a group, whether in the primary or the 

 secondary, or in the coal series, as well as in gneiss 

 and quartz rock, an inversion is as common as an 

 omission ; and to what degree that really does extend 

 among the primary, we cannot, for the reasons just 

 given, as yet decide. But in the secondary, it is not 

 yet known for example, that chalk does, and it is not 

 probable, that it will, occur beneath the red marl ; 

 though, from the deficiency of the latter and of all 

 the intermediate strata, it might be in contact with 

 the coal series, or even with granite. Still, however. 



