Ch. XXL] 



DENUDATION OF WEALD VALLEY, 



293 



of the waves; its outcrop, therefore, is marked by a valley, the 

 breadth of which is often increased by the loose incoherent 

 nature of the uppermost beds of the lower green-sand, which 

 lie next to it, and which have often been removed with equal 

 facility. 



The formation last mentioned has been sometimes entirely 

 smoothed off like the gault ; but in those districts where chert, 

 limestone, and other solid materials enter largely into its com- 

 position, it forms a range of hills parallel to the chalk, which 

 sometimes rival the escarpment of the chalk itself in height, or 

 even surpass it, as in Leith Hill. This ridge often presents a 

 steep escarpment towards the Weald clay which crops out from 

 under it. (See the strong lines in diagram No. 63, p. 288.) 



The clay last mentioned forms, for the most part, a broad 

 valley, separating the lower green-sand from the Hastings 

 sands, or Forest ridge ; but where subordinate beds of sand- 

 stone of a firmer texture occur, the uniformity of the plain is 

 broken by waving irregularities and hillocks *. 



In the central region, or Forest ridge, the strata have been 

 considerably disturbed and are greatly fractured and shifted. 

 One fault is known where the vertical shift of a bed of 

 calcareous grit is no less than 60 fathoms [. It must not be 

 supposed that the anticlinal axis, which we have described as 

 running through the centre of the weald, is by any means 

 so simple as is usually represented in geological sections. 

 There are, on the contrary, a series of anticlinal and synclinal J 



* Martin, Geol. of Western Sussex. Fitton, Geol, of Hastings, p. 31. 

 f- Fitton, ibid., p. 55. 



I We adopt this term, first used, we believe, by Professor Sedgwick ; its signi- 

 fication will best be understood by reference to the accompanying diagram. 



No, 68. 



a, Anticlinal Hues. 



Synclinal lines. 



