86 Outlines of Geology, 



elation of shells, echini, and so on, peculiar to it ; but if we 

 compare the relics in the mountain limestone with those of the 

 chalk, we shall find that they, in all cases, are perfectly distinct ; 

 that there is not, even in any single instance, a remote resem- 

 blance or analogy between them. Even between contiguous beds, 

 there are often, in this respect, very striking distinctions, and the 

 whole subject is of so singular and problematical a nature, as to 

 have attracted, in an especial manner, the attention of the geolo- 

 gical theorist. We have, for instance, as the lowest crust of the 

 globe, or as its nucleus, as some mechanical philosophers will 

 have it, a compound crystalline rock, generally very hard and 

 permanent, in which the most inquisitive eye has as yet traced no 

 organic remains of either kingdom of nature, no rounded pebbles, 

 or any relic or detritus of other rocks. Symptoms of disturbance, 

 perhaps of fusion, it does, indeed, exhibit, as our specimens will 

 hereafter teach us. On this granitic foundation is reared a slaty 

 structure ; and in the rocks between it and the coal formations, 

 animal remains, characteristically different from any which now 

 exist, begin to make their appearance, and become abundant in 

 the carboniferous limestone. Rounded pebbles, and other proofs 

 of the existence and destruction of former rocks, are also here 

 met with ; but, what is not a little remarkable, we find in the 

 coal strata themselves, which thus repose on the coral limestone, 

 scarcely a single shell or relic of the kind ; but on the other hand, 

 abundance of vegetable remains, all, I believe, of unknown spe- 

 cies, but of genera often allied to plants that now inhabit tropical 

 "climes. In the magnesian limestone, resting upon the coal mea- 

 sures, marine remains are again frequent ; but in the red marl, 

 which next follows, scarcely a shell or plant of any kind occurs. 

 In formations that interv^ene between the red marl and the su- 

 perficial strata, that is, in the varieties of lias and freestone, in the 

 ferruginous and chloritic sands, and in the chalk itself, we find pe- 

 culiar corals and echini, the remains of testaceous and crustaceous 

 animals, of marine oviparous quadrupeds, and of vertebral fishes, 

 all of extinct species, but quite distinct from those which we found 

 "below the red marl, and often remarkably distinguished among 



