﻿Yol. 66.] THE WESTERN END OF THE WEALD. 645 



plain) ; but elsewhere (fig. 59, p. 291) he gives a diagram of the 

 River Med way on a much larger scale than Ramsay's, and in it he 

 depicts the plain as absolutely horizontal over a distance of more 

 than 40 miles. Again, in his table of heights (26, p. 241), although 

 the rise from sides to centre is always evident, yet in most cases it 

 is very small, and only in one instance does it exceed 50 feet ; but 

 in that one exception the whole of the rise, amounting to over 

 130 feet, takes place within 4 miles of the escarpment. It is 

 pertinent, therefore, to ask how such a gradient is to be reconciled 

 with Topley's other data and with his diagram of the Med way ? 

 The fact is that his figures are rather carefully selected, and point to 

 conditions which are by no means universal ; indeed he admits this 

 when, in one of his series, he takes 812 feet as the height of the 

 North Downs, whereas only 3 miles farther west they rise to 876 

 feet. 1 No safe inferences, therefore, are to be drawn from this 

 part of Topley's tables, and if a plain is to be established at all, we 

 must admit the existence of greater warnings, local if not general, 

 than either Topley or Ramsay recognized ; but a full discussion of 

 this point must be deferred to a later stage of my paper. 



Reviewing the general results of this line of enquiry, we see that 

 the longitudinal coincidences of level in the lower beds (Hastings 

 Beds and Lower Greensand) are few and unconvincing, but that 

 those in the Chalk are very striking (figs. 1-3, p. 642) so long as 

 we do not insist on Topley's belief in a fall from west to east. Yet 

 even here we must be cautious in drawing conclusions. There can 

 be no doubt that the Chalk in this region exhibited on the whole a 

 very level surface before the Eocene beds were deposited on it, 

 and that both have since been tilted up together ; if then, rejecting 

 the hypothesis of more recent (post-Eocene) marine planation, we 

 imagine these strata to have been removed by subaerial forces alone, 

 we can easily understand how the steady outward spread, like a 

 centrifugal wave, of the crest of the Chalk escarpment would be 

 accompanied by a good deal of correspondence in levels along the 

 lines of the North and South Downs, although this correspondence 

 would be due in the main not to post-Eocene, but to pre-Eocene 

 causes. Transverse coincidences, however, between the summit-lines 

 of different strata could not easily arise in this way, and we sec 

 therefore that it is by the degree of perfection which these exhibit 

 that this line of argument must really be judged. Unfortunately, 

 as already shown, the evidence on this point is hardly as strong as 

 Topley's table (26, table iii, p. 241) might lead us to suppose ; 

 and it is not, therefore, surprising that although his figures have 

 been before us for more than a generation, his inference from them 

 has failed to meet with universal approval. 



(ii) Even bevelling of the crest of the escarpment. — 

 This is a line of argument not directly alluded to by the older 



1 These are Topley's figures ; but the most recent maps exhibit the same fact, 

 namely, that the sides are often higher than the centre. 



