EXTENT OF THE WEALDEN BEDS. 



199 



to that of the Wealden formation. I think it evident, however, that 

 certain parts of the Wealden were once dry land, or shallow water. 

 The Cypris faba in the clay beds, probably lived and died where its 

 crustaceous remains are so abundant, and many of the plants must 

 have flourished on dry land. Indeed, we do not remove ihe neces- 

 sity of admitting a submergence, by supposing the Wealden to have 

 been deposited in a deep esiuary ; for to form a large river, and such 

 an estuary, filled with fresh water, extensive mountain ranges of great 

 elevation would be required, and these must have been submerged 

 or removed, before the deposition of tiie chalk formation, which it 

 cannot be doubted took place in a deep ocean,, as that formation is 

 more than one thousand feet in thickness. 



