THE WEALDEN GEOUP. 393 



belong to the lower greensaiid formation. At a very 

 early period of his researches, Dr. Mantell observed that 

 the fossils collected from these deposits were wholly of 

 a fluviatile character. Instead of the sea-weeds, sponges, 

 corals, shells, and the other marine exuviae found in the 

 chalk, he discovered the leaves, branches, and stems of 

 plants, with bones of reptiles, and fresh-water shells. The 

 stems were deprived of their branches, the branches 

 were denuded of their leaves, while the animal remains 

 bore similar proofs of maceration and transport, arising 

 from fluviatile action. Pursuing these inquiries, Dr. 

 Mantell determined the true character of the strata, and 

 established the fact, that instead of being of marine, they 

 were of fresh-water origin, and, from the evidence of 

 drift, arrived at the conclusion that this district formed 

 the delta of an ancient river where it poured its waters 

 into the sea. 



The evidence of so unexpected a fact as the intercalation 

 of a great fresh-water formation between the chalk and the 

 oolites was, at first, received with much doubt ; but subse- 

 quent investigations proved the correctness of the original 

 observations. The relative position of the beds in the Isle 

 of Wight especially is unequivocal. The lower greensand is 

 seen reposing conformably on the wealden. At their junc- 

 tion near Atherfield Point, we have removed a mass of rock 

 about a foot in thickness, the upper, half of which contained 

 in situ the marine shells of the lower greensand, whilst in 

 the lower half of the same we found the fluviatile shells of 

 the wealden. In the Vale of Wardour, the Purbeck beds 

 are seen reposing conformably on the upper stages of the 

 oolites. 



The following subdivisions, from Dr. Mantell' s Greology 

 of the S.E. of England, exhibit the wealden stages of Kent 

 and Sussex : 



1. WEALD CLAY, average thickness 140 to 200 feet. 

 Character. Fossils. Localities. 



Stiff Clav, of various'i ,, , ,. ^ . ~ f The Wealds of Sussex, 

 shades, of blue and PJudma Cypns Cyre- 



brown , with subordi- . * the Ie 



nate beds of limestone, , T. fm^i. tween the Downs and 



sand, and Stplaria. J and Bones f * lshe8 ' L the Forest Ridge. 



