136 STUDIES, SCIENTIFIC AND SOCIAL chap, vi 



mind all the facts I have in regard to stream-channels in 

 unglaciated areas, and I cannot recall a single instance of 

 such a gorge. Those most nearly approaching it are 

 some of the mountain gorges in the diamond regions of 

 Brazil, but those belong to an entirely different type." 

 (Sketches are given showing deep valleys vertical on one 

 side and sloping on the other.) " There are no such gorges 

 as you describe in any part of Brazil that I have seen. 

 In the United States there are such in the glaciated area, 

 such as Watkin Glen in the State of New York. South 

 of the glaciated area I have no recollection of ever having 

 seen such gorges." 



By the kindness of Mr. Percy Kendall I am able to 

 give a photo-plate of one of the gorges referred to by 

 Professor Branner, that of the Gorner glacier at Zermatt. 

 It exhibits the plug of rotten ice filling the narrow gorge 

 and the sub-glacial torrent rushing out beneath it. It 

 thus shows us on a very small scale the actual mode of 

 formation of the Aarschlucht and other Alpine gorges of 

 the same character. 



I have endeavoured, by means of collateral evidence, to 

 support the generally accepted view that the gorge of the 

 Aar and others of like nature have been wholly formed 

 by sub-glacial torrents, because, if they have been so 

 formed, they afford a distinct class of evidence in favour 

 of the large amount of glacial erosion in general, and of 

 the theory of the glacial origin of the Swiss valley-lakes 

 in particular, but which has, so far as I know, been over- 

 looked by most writers on the subject. The nature and 

 bearing of this evidence I will now briefly discuss. 



The large-scale Swiss Government Map shows us that 

 the valley above the gorge of the Aar is less than 20 feet 

 above the level of the valley below the gorge. Both are 

 flat alluvial plains having every appearance of being 

 filled-up lake basins. The Kirchet hill, pierced by the 

 gorge, is about 450 feet high, the highest ice-ground 

 bosses being nearly 600 feet, while the lowest point over 

 which the road passes is a little more than 300 feet, but 

 this notch is apparently the continuation of the lateral 

 gorge already described. During the long time occupied 



