194 Indications of Glacial Action in Xorth Wales. 



the accumulation against the latter of debris brought clown 

 by winter rains, for there is no stream running into the Cwm. 

 The rocks on the side of the Cwm are rounded, scratched, 

 and polished. 



At the head of the pass of Nant Francon, near Llyn Ogwen, 

 on rocks on the south side of the Ogwen, are curious glacial 

 markings crossing each other at right angles. The deepest 

 groovings, and those which appear to be the most ancient 

 (the polish and minor scratches having disappeared), indicate, 

 I think, the existence of a glacier ranging down the valley 

 from Llyn Ogwen. These groovings are crossed by smaller 

 scratches and polishing, which appear to be more recent, and 

 to have been caused by a glacier descending from Llyn Idwal ; 

 which, originating at a higher elevation, may possibly have 

 continued to exist for some years after the disappearance of 

 that in Llyn Ogwen, both having previously been united in 

 one glacier at this point. 



The marks of glacial action are very frequent about Cader 

 Idris. At the base of the north peak of the mountain is a 

 small lake nearly filled by torrent-borne debris, and in front 

 of it a considerable transverse moraine, and also lateral ones, 

 as there are also near Llyn-y-Gader, at the north-west base 

 of the principal height. These moraines are very extensive, 

 and visible at a considerable distance, as was well shewn in 

 Glover's Panorama of Cader Idris, and in the engraving of 

 it, where they are described as " immense beds of lava." 

 Great part of the moraines are quite bare, and form a very 

 striking scene of desolation ; they are formed in parts of 

 enormous angular fragments, as of the wreck of a mountain. 



In the neighbourhood of Barmouth I traced the marks of 

 glacial action and boulders to the height of about 1450 feet 

 above the sea. The marks indicate a glacier coming down 

 the valley from Cader Idris ; and from the great height at 

 which they appear, and the direction of the marks after they 

 have passed over the summit ridge, would also tend to shew 

 that at one period of the glacial era great part of the country 

 had been covered with ice, and that it was not merely limited 

 to the mountain valleys. 



There is hardly a valley in North Wales, as in most moun- 



