54 REVIEWS—THE OLD GLACIERS OF SWITZERLAND, E'C. 
beyond its present termination ; and further, that its actual surface 
of to-day is a thousand feet and more beneath its ancient level.” 
With regard to the Aar valley, the glaciers of which are taken as 
type-forms in relation to this inquiry, our author observes in addition : 
‘‘ Below the lower glacier of the Aar, the stream winds through one 
of those gravelly flats, so frequent in old glacier valleys, and at its 
lower end, where this plain narrows towards the Grimsel, a boss of 
granitic gneiss, well moutonnée, nearly bars the valleys across which 
the path leads. It is partly covered by striations, well marked on 
the slope that tooks up the valley, telling the observer not only of the 
previous extension of the glacier thus far, but also that the ice which 
filled the plain pressed strongly on the higher side of the boss, and 
was forced upwards till it fairly slid over the rock, the lower part of 
the ice being quite uncnecked by the opposing bar. I mention this 
especially, because similar phenomena were often pointed out by 
Buckland in describing the old glaciers of North Wales. On either 
hand, all the way from the glacier to this point, the mountain sides 
show the same mammillated contours that mark the rock above the 
ice, and a little further down the valley, the signs of glacial action 
become even unusually obtrusive. A large hill rises from the valley 
on the right, up which the road winds to the Hospice of the Grim- 
sel. On the left is the narrow gorge of the Aar, and on the other 
side of the hill the sullen lake of the Grimsel half encircles it far 
above the level of the river. At its outflow the lake is partly dam- 
med up by a little moraine-like débris; but it requires no soundings 
to tell that the rounded rocks close by, passing under the rubbish, 
form the chief retaining barrier of the water. On both banks, ex- 
cept when weather-worn, the rocks are ice-worn, and the lake is 
nearly looped into two by roches moutonnées that project from either 
bank toward the centre, like Llyn Idwal above Nant Francon, and 
the lakes of Llanberis, if these were undivided by the alluvial strip 
below Dolbadarn Tower. At its farther end a long, narrow, high, 
rounded barrier of solid rock (over which the glacier formerly pour- 
ed) crosses the valley, damming up the lake in that direction; and 
here so great has been the pressure, that I found proof of the ice 
having been forced into a narrow transverse fissure, which it polished 
and striated quite out of the direction of its general flow. The lake 
is a complete rock basin similar to some of the tarns of North 
