314 English Formations. 



water and marine shells that I mentioned as occur- 

 ring in the Weald en and Pur beck strata ; but with this 

 difference, that though the shells belong mostly to the 

 same genera, they are of different species the old fresh- 

 water life is replaced by new. 



Upon the London Clay, which is a marine forma- 

 tion, varying from 200 to 500 feet thick, the Brackles- 

 ham and Bagshot beds were deposited. These consist 

 of marine unconsolidated sands and clays, occurring as 

 outliers isolated patches left by denudation around 

 Bagshot, and elsewhere on the London Clay, and over- 

 lying the same formation in the Isle of Wight, where 

 they are well seen in Alum Bay. In both these places 

 they are only sparingly fossiliferous, but at Brackles- 

 ham and Barton, on the Hampshire coast, they contain 

 a rich marine molluscan fauna of a tropical or sub- 

 tropical character. Upon these were formed various 

 newer fresh-water strata, occasionally interbedded with 

 thin marine bands, the whole evidently accumulated 

 at the mouth of a river. For the names of these 

 minor formations, I refer the reader to the column, 

 p. 30. 



I have in this chapter given a brief recapitulation 

 of the geological and stratigraphical positions of the 

 series of the larger and more solid geological formations 

 that are concerned in producing the physical structure 

 of England (see Map), and I will in the following 

 chapters endeavour to show by the help of fig. 57, and 

 other diagrams, the part that these formations play 

 in producing the scenery of the country. 



