510 ME. E. W. HARMER ON THE [K"0V. I907, 



producing and carrying with, or driving before it, when descending 

 towards lower ground, great masses of marly drift. 1 



Prof. Gregory considers that the Berkshire portion of the 

 escarpment, the White Horse Hills, took up its present position at 

 an earlier period than that of the Chilterns, maintaining that 

 while the latter is jagged and irregular, and breached in numerous 

 places, the former is regular and unbroken. A study of the 

 contour-map (PL XXXIY), however, does not seem altogether to 

 support that view. It appears to me more probable that the forma- 

 tion of both portions of the escarpment took place at the same time, 

 the latter forming, as it does, a continuous line of hills, broken 

 only by the trumpet-mouthed entrance to the gorge at Goring. 

 There is one part of the Chiltern escarpment, moreover, north-east 

 of Goring, which presents a continuous front for about 10 miles,, 

 resembling that of the White Horse Hills on the south-west. In 

 both cases the unbroken character of the crest coincides with 

 its greatest elevation : any overflow from Lake Oxford, and the 

 consequent breaching of the escarpment, would have taken place 

 near the lowest points of the range. 



XI. General Considerations. 



An obvious, but not, I think, an insuperable objection to the 

 views here taken presents itself. Features nearly resembling those 

 of the regions discussed are to be found also in the Wealden area, 

 and it is not easy, prima facie, to understand that they could have 

 arisen under the same conditions. Although much has been 

 written on the Pleistocene history of the Weald and of the Thames 

 Valley, I question whether the last word has been said. It is not 

 possible to deal with this apparent difficulty on the present occasion, 

 but I hope to do so hereafter. ' 



When commencing this investigation, to which my attention was 

 called accidentally, I had no thought of coming into conflict with 

 the fascinating and universally accepted views of Prof. W. M. Davis 

 on the erosion of this part of Central England. It seems to me, 

 however, that the relation of the present valle ,-system of the 

 region in question to that of some former perkx , v when a pene- 

 plain may have extended over the Jurassic and Cretaceous forma- 

 tions alike, and consequent rivers ran out to sea in the direction 

 of the dip, is remote and. not easy to trace. 



With the single exception of the gorge at C ring, as to the 

 origin of which I offer an alternative explanati 1, no connexion 

 whatever exists between the drainage-systems ar the topography 

 of the Jurassic and Cretaceous ridges : nor does a vestige remain 

 of any peneplain, which, at some unknown height above the 

 present surface of the land, may have once united them. 



1 I have indicated on the map the distribution of the different kinds of 

 Boulder-Clav. 



