THE TERTIARY ERA 59 



land covered with a tropical vegetation. The mountain 

 chains of England, Scotland, and Wales rose as now, but 

 higher. Long denudation has worn them down since. 

 In the south-east of England the coast line fluctuated ; 

 and sea shells, and the remains of the plant and animal 

 life of the neighbourhood of a great tropical river alternate 

 in the deposits. 



The London clay is succeeded by a great thickness of 

 sands and clays which form the Bagshot series. These 

 are divided in the London basin into Lower, Middle, and 

 Upper Bagshot. In the Hampshire basin the strata are 

 now classified as Bagshot Sands, Bracklesham Beds, 

 Barton Beds, the last comprising the Barton Clay and the 

 Barton Sand, formerly termed Headon Hill Sands. There 

 is some uncertainty as to the manner in which these cor- 

 respond to the beds of the Bagshot district, as the Tertiary 

 strata have been divided by denudation into two groups, 

 and differ in character in the two areas. It is possible 

 that the Barton Sand represents a later deposit than 

 any in the London area. 



Almost the only fossil remains in the Bagshot Sands 

 are those of plants, but these are of great interest. In 

 Whitecliff Bay the beds consist for the most part of 

 yellow sands, above which is a band of flint pebbles, which 

 has been taken as the base of the Bracklesham series, for 

 in the clay immediately above marine shells occur. The 

 Bagshot Sands, in Whitecliff Bay, are about 138 feet 

 thick, in Alum Bay, 76 feet, according to the latest 

 classification. In Alum Bay the strata consist of sands, 

 yellow, grey, white, and crimson, with clays, and bands 

 of pipe clay. This is remarkably white and pure, as 

 though derived from white felspar, like the China clay in 

 Cornwall. The pipe clay contains leaves of trees, some- 

 times beautifully preserved. Specimens are not very 

 easy to obtain, as only the edges of the leaves appear at 

 the surface of the cliff. They have been found chiefly 



