12 Among the Ancient Glaciers of North Wales, 
though less regular lines, by which we may very nearly map out the 
exact extent of the ancient moraine to which they belonged. The 
last deposited blocks are not a hundred feet higher than the out- 
cropping of conglomerate ; and we are now standing nearly upon 
the brink of the huge lake of ice which must have filled up the 
bason of the Glyder Fawr and the Glyder Fach, and poured out 
through the opening above the well-known little inn of Pen-y- 
gwryd into the valley of Gwryd, and terminated in the open space of 
the wide valley. Many of the rocks on the southern side of the 
opening, just above the lake which now occupies the bottom of the 
hollow between the two Glyders, present the general appearance of 
glacier- rounded rocks. But the material is so soft, and therefore so 
ill adapted for preserving the minuter and more indisputable marks 
of glacier action, that it would be unsafe to draw conclusions from 
their configuration, were they not supported by the independent 
testimony of the old moraine, which, with the exception perhaps of 
the moraine of the great glacier that filled up the whole basin of 
Snowdon, is the best defined that we may see in North Wales. The 
southern side of this hollow — forming the northern flank of the 
ridge along which lies the moraine of the Glyder— is also of a soft 
and easily disrupted stone, and much covered with turf and mould ; 
and accordingly we are unable to find any very distinct marks of 
striae. The places where the rock is least covered and has been 
least exposed to the obliterating action of trickling water, are the 
places where such indications could not be expected to exist — 
namely, near the top of the ridge, and on its southern flank, high 
above the Vale of Llanberris. 
It is not easy to say to what system the great block in the Vale 
of Llanberris belongs. An attentive examination will show that it 
lies higher than the well-defined line of deposits which extend 
along the same side of the valley. Indeed, it is considerably above 
the level of the actual crest or col of the pass ; and there is no pre- 
cipitous or disintegrated height in its immediate neighborhood from 
which it could very well have been detached. Indications appear 
to be not wanting that the great glacier of the Glyder, at some re- 
mote period, rose above the lowest part of the hollow in the ridge 
toward the Vale of Llanberris, and overlapped the southern flank 
of the ridge. If so, this block, instead of belonging to the Llan- 
berris glacier proper, is really a contribution from the stones of the 
Glyder glacier, and was brought down upon its surface from some 
