WESTLETON BEDS TO THOSE OF NORFOLK, ETC. 151 



have had no existence at that time, the base of the escarpment 

 must have been limited by the level of the line of 440 to 500 feet. 

 By analogy the further relative heightening of the escarpment was 

 concurrent with the deepening of the valley itself, which would 

 correspond with B in fig. 15. In any case the escarpment could not 



Fig. 15. — Diagram- section from the Gonje of the Thames at Goring 

 to the Oolitic hills (J) near Oxford. 



2. Glacial gravel with Triassic, Cretaceous, and other rock-debris, on. Position 

 of Tertiary strata and of Westleton Shingle (outside the section). 

 Cr. Cretaceous strata. J. Jurassic strata. (See also fig. 13, p. 149.) 



at that early Glacial period (A.) have had a face more than from 

 100 to 150 feet high, while at the Westleton period it is more 

 than probable that it formed, with the distant Oolitic hills, a con- 

 tinuous plain {x). 



Of the escarpment of the Oolites one can speak with less certainty, 

 though if we admit the Kingsdown Drift outlier to be of Westleton 

 age, it favours the conclusion that the escarpment of the Oolites 

 dates no further back than the commencement of the Quaternary 

 or Pleistocene period. The fact likewise that the two escarpments 

 run in parallel lines seems in favour of a common denuding cause 

 in the same direction. The time, geologically measured, is, however, 

 so limited, and the extent of denudation so vast, that it is not 

 easy to realize that these limits can suffice. Nevertheless, I do not 

 see how the conclusions we have arrived at on this subject can well 

 be avoided. 



Another point to which I would draw attention is the small 

 amount of erosion by river-action (C) in the area under review, 

 compared with that effected by glacial or other agencies. To the 

 latter are due the broad plains and passes and the isolated hills, 

 whereas the effects of the former are limited to the valleys of com- 

 paratively moderate depth and width, which have been subsequently 

 cut through the glaciated and deeply abraded land. 



EXPLANATION OF PLATE VII. (see also Map, PI. VIII.). 



Diagram-sections of the Hill-Drifts of Pre-Glacial date in the Valley of the 

 Thames within the Chalk-basin. Owing to the length of these sections and the 

 limits of space the vertical scale is unavoidably exaggerated. In Fig. 1 it is 

 not so important, as the gradients of the Westleton Shingle and Boulder-clay 

 bear a tolerably uniform relation one to another; but in the other figuref it 

 misrepresents the incidence of level between the several Tlill-Drit'ts, for which 

 allowance nuist be made. The relative hciglit of the hills and depth of the 

 valleys are, however, on a true scale, and this is the essential point connected 

 with the question. These are taken from the new 1-inch Ordnance Maps. 



Q. J. G. 8. No. 182. M 



