218 NEOZOIC TIME. [CHAP. XI. 



and it is more likely that they were bordered by sand 

 dunes than by chalk cliffs. 



Passing now to the Reading Beds, we find evidence in 

 their wider extension of a further and more general sub- 

 sidence, which carried the sea over the whole of the London 

 basin, and southward over Hampshire into the southern 

 basin. In the shallow gulf thus formed were deposited the 

 marine basal beds of the Beading group, in which large 

 oysters are the most abundant shell, but there is no 

 evidence that these beds ever extended over the area of 

 the Weald, and very good reason to think that they did 

 not. 



That the rise of the Wealden dome began in early 

 Eocene times is by no means a new idea. It was suggested 

 as long ago as 1852, by Professor Prestwich, in his paper 

 on the Thanet Sands, 1 though some of the data from 

 which he inferred its existence would not now be accepted ; 

 in 1866 Mr. Whitaker 2 remarked upon the southerly over- 

 lap of the Woolwich and Blackheath Beds, and at a later 

 date 3 we find him inferring from this " that the planing 

 down of the chalk which once spread over the Wealden 

 area began in Lower Eocene times, and that the pebble 

 beds of Bromley, Blackheath, &c., are one of the direct re- 

 sults of that denudation." 



The very limitation of the Thanet Sands to the northern 

 side of the Wealden area seems to indicate the existence 

 of land, or at any rate of a large shoal, over that area 

 during their formation, and it is not at all improbable 

 that the depression of the Anglo-Belgian basin was con- 

 temporaneous with an uplift of the region which is now 

 the axis of the Weald and Artois. If this were so, and if 

 the force of the uplift was concentrated more especially on 



1 " Quart. Journ. Geol. Soc.," vol. viii. p. 256. 



2 Ibid., vol. xxii. p. 420. 



3 " Mem. Geol. Survey," 1872, vol. iv. p. 241. 



