Vol. 65.] GLACIAL EROSION IN NORTH WALES. 335 



prevented the formation of side-gulleys and ravines by cascading 

 streams. It is only since the ice has melted away that the 

 cascading streams have been at work, and in this post-Glacial 

 epoch there seems not to have been time for the accomplishment 

 of much ravining, even though the streams are rapid and vigorous 

 torrents. 



It is interesting to quote in this connexion a phrase of 

 Mr. Whymper's, in his ' Scrambles amongst the Alps ' : — 



'Given eternity, glaciers might even grind out valleys of a peculiar kind. 

 Such valleys would bear remarkably little resemblance to the valleys of the 

 Alps. They might be interesting, but they would be miserably unpicturesque ' 

 (2nd ed. 1871, p. 331). 



This probably means that the valleys ground out in an eternity of 

 time by large glaciers would be smooth-sided troughs, ' miserably 

 unpicturesque ' because of the simplicity and uniformity of their 

 sides. The idea is a good one, and ought to have been followed up. 

 The Norwegian fiords are, as I understand them, valleys (that is, 

 channels or troughs) of the peculiar kind that long-lasting glaciers 

 might grind out : they have little of the graceful variety of form 

 that is produced by normal erosion, yet they fail of having been so 

 perfectly smoothed as to have become ' miserably unpicturesque ' ; 

 and in size alone they are magnificently imposing. So in most 

 glaciated valleys, it would seem that glacial action did not continue 

 long enough to produce ideally smooth sides or smooth floors ; yet 

 the parts of the Welsh valleys instanced above really do present 

 just such trough-like forms as would appear to be appropriate to 

 maturely eroded glacial channels. The best example of this kind 

 that I have seen is by Llyn Cwellyn, where the northern side 

 especially is smoothed in a great concave slope, practically uncut by 

 ravines, although several streams run down it. It is by no means 

 miserably unpicturesque, but charmingly graceful, and full of 

 significant meaning. In the other fine example, the Gwynant Valley 

 on either side of the lake of the same name, the view south-west- 

 wards into this trough-valley from the pass at its head is certainly 

 as charming a sight as one may wish to see ; and the graceful concave 

 slope of the valley-sides, which are singularly free from entrench- 

 ment by side-ravines, is not its least pleasing element. I do not 

 believe that it is possible to explain either the concave curve or 

 the absence of ravines, if these valleys are taken to be the work 

 of normal erosion. But, if the valleys are regarded as the work of 

 glacial erosion, which deepened and widened pre- Glacial valleys, 

 their form is perfectly expectable ; glaciers would naturally wear 

 out just such channels if they had time enough. Probably the 

 troughs were better finished by Llyn Gwynant and Llyn Cwellyn 

 than elsewhere, because the rocks there were more yielding. 



Ragged or craggy slopes are seen at many points ; for example, 

 on the southern sides of the broad masses (Yr Aran and Craig 

 Wen) into which the southern spur of Snowdon expands near 

 Beddgelert ; and in the eastern side of the upper (south-eastern) end 



