Vol. 65.] GLACIAL EROSION IN NORTH WALES. 347 



•and pointed out that this was one of a row of glaciers still occupy- 

 ing valleys which faced north-east, whereas no corresponding 

 glaciers or hanging valleys were found on the other side of the 

 Inn Valley, and the same feature was noticeable, as he had pointed 

 out, in the Ticino Valley and in Sikhim. Two other features, namely, 

 the marked step which occurred near the head of many of the 

 main valleys and those which often occurred far back in the lateral 

 hanging valleys, seemed unaccountable on the hypothesis of simple 

 glacial erosion ; whereas, if glaciers are regarded as relatively pro- 

 tective agents as compared with rivers, these steps would represent 

 the surface which had been relatively protected as the glacier 

 retreated, while the valley below was being deepened by water- 

 erosion. Such relative difference of erosion could be actually seen 

 in the gorges cut by subglacial streams. With regard to the origin 

 of cirques, alluded to by several speakers, this, again, seemed a case 

 where relative protection by ice might have taken place by the 

 accumulation of avalanche-snow on the floor of the cirque while 

 the sides were being eaten back by frost and weathering, so that the 

 snow accumulated farther back each year. A certain amount of 

 erosion, however, took place, as explained by the bergschrund hypo- 

 thesis alluded to by a previous speaker ; but, on the whole, the 

 effects of a corrie-glacier appeared to be relatively protective. 



The President (Prof. Sollas) congratulated the Author on the 

 successful manner in which he had rejuvenated a mildly-matured 

 •subject. His essay was an extremely consistent piece of deductive 

 reasoning, and it was almost impossible to restrain a feeling of 

 resentment towards the difficulties which presented themselves when 

 parts of the argument were brought into relation with existing 

 facts of detail. It was to be hoped that in his reply to criticisms, 

 especially those of Prof. Garwood, the Author would be able to 

 maintain the symmetry of his system in all its parts. 



The Author said that, owing to the lateness of the hour, it 

 was not possible for him to comment fully on the questions and 

 suggestions made by the several Fellows who had remarked upon 

 hi& communication. 



Regarding the contrasted forms of valleys, as seen in cross-profile, 

 it was well to note that a mature valley of normal erosion might 

 sometimes imitate what was called the U-shaped valley of glacier- 

 erosion ; that the V-shaped valley of normal erosion was only a 

 young normal valley ; and that many maturely glaciated valleys 

 had not a U-shaped but a catenary cross-profile : the U-shaped 

 glacial valley or trough was a young glacial trough, in which deep- 

 ening had been more active than widening. 



The Author was very glad to leave the Lake District in Dr. Marr's 

 Tiands, and looked forward with pleasure to his further account 

 of it. He begged leave to point out that what characterized his 

 paper was not so much the views to which it led, as the attempt to 

 provide a thoroughly discussed basis for these views, and thus to 

 •make them fully worthy of acceptance. 



As to the influence of structure on relief (regarding which 



