THE ICE AGE. — CLIMATE AND TIME. 
239 
lie by the melting of the diminishing glacier.” Again to quote, — 
the following description by the same eminent geologist is very 
conclusive : — 
“ Above the bridge on the Snowdon side of the valley a 
great dark wall of rock rises abruptly from the broken lower 
slopes about a quarter of a mile from the road. From the 
bottom of the pass it looks almost inaccessible, but half-way up 
there is a rough terrace, at the foot of a Greenstone dyke that 
forms, in part, the face of the cliff. The slope of the precipice 
is about 68° towards the pass, and in one place especially the 
wall of rock is polished and striated in at least six principal 
grooves, which slope down the valley (not down the hill) at an 
angle of 12°. Some of them are deeply graven from two to 
two and a half feet wide , and twelve or eighteen inches deep , 
and they run so evenly along an almost vertical wall of rock 
that the idea is at once suggested that they were formed by the 
long-continued pressure of a glacier so large that it filled the 
valley to a far greater elevation than the grooves, and by reason 
of the huge overlying mass of ice, a middle stratum, as it were, 
of the glacier was jammed against its bounding walls, so power- 
fully, that by the help of the grinding of imprisoned stones, in 
time it graved the strong furrows still so perfect. To the very 
top of the pass, the same kind of evidence, both of moraine 
debris and striation, continue unabated, especially on the higher 
slopes on the north-eastern side of the valley, where above the 
modern shingle and broken cliffs that overlook the brook, 
numerous roches moutonnees remain still hardly unweathered, 
and here and there are dotted blocs perches .” From numerous 
evidences similar to these, so well described, it appears certain 
that the ice in this valley must have been in the glacial period 
at least 500 feet thick, and probably much thicker. 
Immediately below the peak of Snowdon scratched frag- 
ments are found, and moranic mounds, which in general cha- 
racter are undistinguishable from those which occur in Switzer- 
land. From a most careful study of the whole of this district, 
Professor Eamsay arrives at the conclusion, that Snowdon formed 
the centre of six glaciers which flowed from the direction of the 
peak down the surrounding valleys. 
Similar examples to those which have been so succinctly 
described, are found in abundance amongst the mountains and 
valleys of Scotland, and spread over England, are indications of 
the existence of similar influences. On the Cotteswold Hills 
Dr. Buckland found pebbles of hard red chalk, which must 
have come from the wolds of Yorkshire and Lincolnshire, and 
slaty and porphyritic pebbles derived, in all probability, from 
Charnwood Forest, near Leicester. Nearly all the drift found 
around Cheltenham has been carried thither from the debris of 
