OF THE EARTH. 479 



cause of their general similarity of character, because 

 of the nature and extent of the strata which immedi- 

 ately follow them, because of their correspondence 

 in geological features, and because, to suppose other- 

 wise, is to render still more complicated the view of 

 the revolutions on which their present states must 

 have depended. I must at least reason on them as if 

 they were of one period ; that I may preserve the 

 needful simplicity of this enquiry : should they prove 

 of different aeras, the modifications that will be re- 

 quired are obvious, and the train of reasoning is 

 pointed out. 



The composition and nature of these strata, no less 

 than the presence of their peculiar organic fossils, 

 prove that they were formed, as far as they are earthy 

 substances, from the ruins of rocks then above the 

 surface of the water which received these. Those 

 must have consisted both of the primary and the 

 lower secondary strata, as both were then elevated 

 above the waters. But although the coal strata were 

 formed beneath water, they could not have been pro- 

 duced beneath the ocean. They include, throughout, 

 the remains of terrestrial plants which could not have 

 undergone transportation, as the very coal itself is 

 proved to be the result of an accumulation of vege- 

 tables. Their analogy to the recent depositions of 

 peat, and to its alternations with sand, marl, and 

 clay, as these occur in our present fresh water lakes 

 and bogs, equally tend to show that they were formed 

 on the land ; in marshes, or on the margins and bot- 

 toms of lakes and aestuaries, in a manner similar 

 to that in which strata are now formed in lakes or 

 beneath the ocean. Though there should be some 

 difficulty in accounting for the great depth and the 

 numerous alternations in some of these deposits, the 



