North Wales. 



425 



when the water is still and pure, from a boat one can 

 see boulders here and there lying on the bottom of the 

 shallower parts of the lakes. In fig. 88 the Pass of 

 Llanberis is represented as it may have been at some 

 period when from end to end it was comparatively full 

 of ice. In fig. 89 it is shown as it must have existed 



FIG. 89. 



An episode in the history of the Glacier of Llanberis. 



for a time when the glacier, by amelioration of climate, 

 had retired from all the lower part of the valley, and 

 debouched into an upper part of what is now Llyn Peris. 

 As it gradually receded, moraine stones, that fell from 

 its end, got scattered over the bottom of the lake ; for 

 in those days the alluvial flat had no existence which, 

 but for a short river, now divides into two an older 



