lxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [March I913, 



It will be seen from this map (PL A, facing p. lxxviii) that in 

 two regions the platform is known to attain a depth of more than 

 1500 feet below sea-level, namely in the south and towards the 

 north-east. Between the two it forms comparatively high ground, 

 with a general trend to the south-east, as shown both by the —500 

 and the — 1000 foot contour-lines. No connexion, however, between 

 its features and its geological structure appears, so far as our limited 

 knowledge of the latter enables us to judge. For example, Cambrian 

 and Silurian strata enter into the composition of the highest parts 

 of the platform at Calvert, and into the lowest part at Harwich and 

 Lowestoft ; while the Coal Measures in Kent form higher ground 

 than do the highly inclined older Palaeozoic rocks anywhere near 

 them. Nor does the form of the platform give any obvious clue to 

 the strike of the rocks that compose it. 



This character is not in accordance with what is observable in a 

 Palaeozoic area which has been exposed to subaerial denudation. 

 In such a case, however complete the original planation has been, 

 the effect of erosion has been to develop features dependent upon 

 the relative resistance offered by the rock-masses. As a rule, 

 though not invariably, the Coal Measures survive only in basins. 



In seeking an explanation of its form we remember in the first 

 place that the greater part of the platform has never been exposed 

 to subaerial waste since it was planed by marine agencies. It has 

 suffered denudation in various parts at various epochs. Much of it 

 was trenched in Triassic, or planed down in Jurassic times ; some of 

 it contributed debris to Lower Cretaceous formations, while not a 

 little was levelled in Upper Cretaceous times before it was overspread 

 by the Gault. But, in every case except the first-mentioned, it was 

 immediately overspread by marine sediments,- and has remained so 

 covered ever since. There has, consequently, been no opportunity 

 for the development of the characteristic sculpturing of subaerial 

 denudation. 



A still more important cause, however, is to be sought in the 

 warping which the platform has undergone since its last planation. 

 That the faults and folds which are observable in the Secondary 

 rocks would be recognizable in the platform is not probable ; they are, 

 on the contrary, essentially surface-phenomena, and may be regarded 

 as the efforts of a skin to adapt itself to changes in form of an 

 underlying body. But that there has been tilting and warping of 

 the platform is certain, and that it has been intermittent and 

 oscillatory is capable of proof as for example in the case of the 



