president's address. 



a distinct V; above this the slopes become less rapid, changing, say, 

 from 45° to not more than 30°, and that rather suddenly. Still higher 

 comes a region of stone-strewn upland valleys and rugged crags, termi- 

 nating in ridges and peaks of splintered rock, projecting from a mantle 

 of ice and snow. The V-like part is often from 800 to 1,000 feet in 

 depth, and the above-named authors maintain that this, with perhaps 

 as much of the more open trough above, was excavated during the 

 Glacial Epoch. Thus the floor of any one of these valleys prior to 

 the Ice Age must often have been at least 1,800 feet above its present 

 level. 1 As a rough estimate we may fix the deepening of one of 

 the larger Pennine valleys, tributary to the Ehone, to have been, 

 during the Ice Age, at least 1,600 feet in their lower parts. Most of 

 them are now hanging valleys ; the stream issuing, on the level of 

 the main river, from a deep gorge. Their tributaries are rather variable 

 in form; the larger as a rule being more or less V-shaped; the 

 shorter, and especially the smaller, corresponding more with the 

 upper part of the larger valleys ; but their lips generally are less deeply 

 notched. Whatever may have been the cause, this rapid change in 

 slope must indicate a corresponding change of action in the erosive 

 agent. Here and there the apex of the V may be slightly flattened, but 

 any approach to a real U is extremely rare. The retention of the more 

 open form in many small elevated recesses, from which at the present 

 day but little water descends, suggests that where one of them soon 

 became buried under snow, 3 but was insignificant as a feeder of a 

 glacier, erosion has been for ages almost at a standstill. 



The V-like lower portion in the section of one of the principal 

 valleys, which is all that some other observers have claimed for the work 

 of a glacier, cannot be ascribed to subsequent modification by water, 

 because ice- worn rock can be seen in many places, not only high up 

 its sides, but also down to within a yard or two of the present torrent. 



Thus valley after valley in the Alps seems to leave no escape from 

 the following dilemma : Either a valley cut by a glacier does not differ in 

 shape from one made by running water, or one which has been excavated 

 by the latter, if subsequently occupied, is but superficially modified 

 by ice. This, as we can repeatedly see in the higher Alpine valleys, 

 has not succeeded in obliterating the physical features due to the ordi- 

 nary processes of erosion. Even where its effects are most striking, as 



1 The amount varies in different valleys ; for instance, it was fully 2,880 feet at 

 Amsteg on the Reuss, just over 2,000 feet at Brieg in the Rhone Valley, about 

 1,000 feet at Guttanen in the Aare Valley, about 1,550 feet above Zermatt, and 

 1,100 feet above Saas Grand 



2 My own studies of mountain districts have led me to infer that on slopes of 

 low grade the action of snow is preservative rather than destructive. That con- 

 clusion was confirmed by Professor Garwood in a communication to the Royal 

 Geographical Society on June 20 of the present year. 



