240 R. Chambers, Esq., on Glacial Phenomena 



ous glaciers of whose course we have described the memo- 

 rials. And as such basins are necessary for the formation of 

 glaciers, we can readily understand why no traces of glacia- 

 tion are to be found in the higher parts of the valleys meet- 

 ing at Dunmail Raise, as also why a mass of peculiar detri- 

 tus is left there. That place had been out of the scope of the 

 glaciers here spoken of, and its mass of detritus may be re- 

 garded as probably the result of some earlier operations. 



From the descriptions which have been given us of the 

 Snowdonian regions in North Wales by Dr Buckland, Mr 

 Darwin, Professor Ramsay, and others, and from what I 

 have seen of it myself, I entertain no doubt that it is another 

 example of a limited mountain district once occupied by local 

 glaciers. Seven valleys radiating from a centre of elevation 

 present, along their sides and bottoms, rock faces which have 

 been ground, smoothed, and striated by ice, the strise being 

 in each case parallel to the line of the valley. There are also 

 in and about these valleys certain detrital masses which have 

 been set down by several observers as the moraines connected 

 with their ancient glaciers ; but my own observations lead 

 me to consider some of these as deficient in the characteristic 

 form of moraines, and, as a general rule, the Snowdonian 

 valleys may be said to be remarkably bare of detrital matter. 

 While this is the case, the outer flanks of this group of moun- 

 tains, and many high table-lands interspersed amongst them, 

 are covered deeply with the " Northern Drift.' 1 That this, 

 however, is the product of a different condition of things, and 

 of an earlier epoch than that of the valley glaciers, appears 

 to me proved by two facts, namely, that the connection of the 

 sea with the origin of the drift is indicated by the shell de- 

 posits found in it, and that, as we learn from a late paper of 

 Professor Ramsay, " small patches of it alone remain nestled 

 amid the smaller bottoms of the hills." It hence appears that 

 the glaciers have removed or swept out this drift from the 

 valleys, while failing to disturb it on the high grounds and 

 the outskirts of the mountain district. Mr Ramsay, with his 

 usual acumen, has drawn this distinction, the importance of 

 which will appear in a stronger light before we have done 

 with the subject. 



