ANCIENT GLACIERS IN EASTERN HEMISPHERE. 171 



approach to the edge of the ice, water could have a free 

 escape. 



" Two principal objections have been urged to the land- 

 ice explanation of the Moel Tryfaen deposits. An able 

 critic asks, ' Can, then, ice walk up-hill ? ' To this we 

 answer, Given a sufficient ' head ' behind it, and ice can 

 certainly achieve that feat, as every roche moutonnee 

 proves. If it be granted that ice on the small scale can 

 move up-hill, there is no logical halting-place between the 

 uplift of ten or twenty feet to surmount a roche mouton- 

 nee, and an equally gradual elevation to the height of Moel 

 Tryfaen. Furthermore, the inland ice of Greenland is 

 known to extrude its ground-moraine on the ' weather- 

 side ' of the nunataks, and the same action would account 

 for the material uplifted on Moel Tryfaen. 



" The second objection brought forward was couched in 

 somewhat these terms : ' If the Lake District had its ice- 

 sheet, surely Wales had one also. Could not Snowdonia 

 protect the heart of its own domain ? ' Of course, Wales 

 had its ice-sheet, and the question so pointedly raised by 

 the objector needs an answer ; and though it is merely a 

 question of how much force is requisite to overcome a cer- 

 tain resistance (both factors being unknown), still there 

 are features in the case which render it specially interest- 

 ing and at the same time comparatively easy of explana- 

 tion. It seems rather like stating a paradox, yet the fact 

 is, that it was the proximity of Snowdon which, in my 

 opinion, enabled the foreign ice to invade Wales at that 

 point. 



" A glance at the map will show that the ' radiant point ' 

 of the Welsh ice was situated on or near Arenig Mawr, and 

 that the great mass of Snowdon stands quite on the pe- 

 riphery of the mountainous regions of North Wales, so 

 that it would oppose its bulk to fend off the native ice- 

 sheet and prevent it from extending seaward in that di- 

 rection. 



