WALTON COMirON EXPOSING LONDON CLAY ETC. 171 



has relations with a long mass of yellow sand, the exact nature of 

 which is somewhat donbtful. 



(3) That the London Claj in situ appears very suddenly west of 

 this mass of sand, and extends several hundred yards further to the 

 westward than is shown on the Survey map (iS'o. 8). In fact, as 

 regards the line itself, the London Clay on this map is represented 

 as terminating just where it should begin, i. e. about 320 yards west 

 of Walton Station. 



(4) That the Bagshot Beds near Sir Hichard's Bridge succeed the 

 London Clay unconformably, and that there is an argillaceous 

 member of the basement series, which may be the same as the 

 Ramsdell Clay of Mr. AYhitaker. 



(5) That the Plateau -gravel is abnormally thick towards the west 

 end of the section, where the underlying Bagshots present irregular 

 and deeply eroded surfaces ; and that, in this region of its greatest 

 development, something like three varieties may be distinguished, of 

 which the middle one is the most sandy. The general composition 

 of the Plateau-gravel of Walton Common and Oatlands Park bears 

 out in the main the observations of previous authors. 



(G) A comparison with other exposures in the neighbourhood 

 serves to show the great variety of deposit which at present is 

 classified under the head of '• Plateau-gravel." 



Discussion. 



Prof. Prestwich, speaking from memory of the original section, 

 which he had examined when the railway line was being constructed, 

 was inclined to argue more strongly than the author of the paper 

 against the idea of there being an unconformity between the London 

 Clay and the Lower Bagshot ; nor could he find any distinct 

 evidence of such unconformity in any other section in the district. 

 He thought all the appearances described in the paper might be 

 explained by a slight false-bedding, caused by the shoaling of the 

 sea after the deposition of the London Clay, and the shifting and 

 somewhat eroding currents of the shallower sea of the Lower 

 Bagshot. He was, indeed, inclined, from recent observations which 

 he had made, to regard the Lower Bagshot as the upper member 

 of the London Clay. Although northern-drift rocks were not found 

 in the Plateau-gravels of the district described by the author, yet 

 such rocks were found at other points lower down the Thames in 

 the same beds. 



Prof. T. Rupert Jones agreed with the author of the paper that 

 the slight discordance in the dip looked like unconformity, but 

 admitted, with Prof. Prestwich, that the appearance might be decep- 

 tive. He pointed out the extreme variability of the beds. 



The Rev. A. Irving agreed with the Author as to the distinctness 

 of the bedding in the Loudon Clay ; but he differed from him as to 

 the identity of the argillaceous bed at Walton-cutting with the 

 Ramsdell beds of the Geological Survey. He thought the Ramsdell 

 Clay belonged to the Middle and not to the Lower Bagshots. He 



