drifi-stages of the dabent valley. 161 



Discussion. 



Mr. ToPLEY referred to the importance of this paper as completing 

 the history of the Darent Yalley, and also as discussing questions of 

 wider interest. He would not take up time by speaking upon the 

 numerous matters in which he fully agreed with the Author, but 

 would rather refer to a few points which still required consideration 

 or as to which he was inclined to dissent from the Author's con- 

 clusions. 



Many of the supposed implements from the Chalk plateau might 

 reasonably excite suspicion, but some no doubt were artificial. He 

 wished to know if there was any clear case of these occurring 

 undoubtedly in place in these gravels ; for the extremely high 

 antiquity of any gravels in such positions was beyond question : it 

 was clearly older than the excavation of the great Chalk valleys and 

 of the present features of the AVealden area. 



The high gravel at Limpsfield Common lies on the watershed, and 

 therefore could not have been formed by the Darent in its present 

 form. The Darent Yalley probably once stretched farther to the 

 west and south than now, having been robbed of its area by the 

 recession of the higher tributaries of the Medway; but he was 

 inclined to doubt if even this would explain the occurrence of so 

 great a deposit at so high a point, and was rather disposed to think 

 that the Limpsfield gravel itself had an origin independent of the 

 present valley-system of the Darent. He fully agreed with the 

 Author, however, in regarding the gravels lower down the Darent 

 as river-gravels, largely made up from the waste of the higher and 

 older bed. 



Whilst admitting the evidence furnished for some kind of ice- 

 action within the area, he could not follow the Author in attributing 

 the escarpment to glacial action. He failed to see how ice could 

 excavate the deep transverse valleys and cut back the escarpment at 

 the same time, there being no doubt that these two very different 

 kinds of denudation proceeded simultaneously. He showed that 

 glaciation tends to destroy escarpments. Existing escarpments 

 in glaciated areas are such as were too bold to be destroyed, 

 or, if small, are such as may have been developed since the 

 glaciation. Lastly, escarpments are universally distributed over 

 the world, whilst glaciation has influenced only parts of it. 



Prof. Le ^Jeve Foster wished to say a few words respecting the 

 denudation of the Weald, having studied that subject carefully with 

 his friend Mr. Topley some six or seveu-and-twenty years ago. He 

 did not find his old views shaken by the paper which he had just 

 heard, and was still of opinion that the formation of the Chalk 

 escarpment was due in the main to rain and rivers. Mr. Topley 

 had forestalled him in one remark, viz. that any theory accounting 

 for the Chalk escarpment should also account for escarpments else- 

 where. If, by glacial action. Prof. Prestwich meant that glaciers 

 liad helped to carve out the Chalk escarpment, ought there not to 

 be some evidence of the fact in the shape of scratched stones ? He 



