NATURE OF RIVER DEPOSITS. 267 



leaves, and bones of animals, became enclosed in 

 the solid rock, and refusing assent to our interpre- 

 tation, attribute their presence to the effect 

 of a deluge which softened the crust of the 

 earth, and imbedded in the sediments of its 

 waters the remains of animated nature — our 

 reply would be that such a catastrophe must 

 inevitably have intermingled the relics of the 

 animals and plants of the land, the rivers, and the 

 ocean, and that the regular stratification of the 

 materials, and the exclusively fluviatile and ter- 

 restrial character of the fossil remains, are fatal to 

 such a hypothesis, and confirmatory of our ex- 

 planation of the phenomena. It was by such a 

 train of reasoning that the fluviatile origin of the 

 Wealden deposits was established. 



The strata composing the Wealden formation of 

 the south-east of England, admit of the subdivisions 

 given in the tabular arrangement, p. 63. Alter- 

 nating layers of clays, sands, and limestones 

 almost wholly composed of freshwater univalves, 

 and of small bivalves with minute crustaceans, 

 form the upper series. Sand and sandstones, with 

 bands of arenaceous limestones or calciferous grits, 

 wdth shells and lignite, prevail in the middle 

 group ; while in the lowermost, sands, clays and 

 argillaceous shelly limestones again appear; and 

 Q 



