GLACIERS IN GREAT BRITAIN AND IRELAND. 141 



berland^ descends from the heart of Helvellyn towards the 

 head of Ulleswater. The rocks of porphyry which form 

 the bottom and flanks of the valley, up to an elevation 

 of about 500 feet on either side, are remarkably ice- 

 moulded, affording numerous examples of perched blocks 

 and lateral moraines. Striations are not, however, of fre- 

 quent occurrence, owing to the nature of the rocks. On 

 descending toAvards the mouth of the valley, the terminal 

 moraine arrests the attention, and appears like a congeries 

 of large rounded hummocks, strewn with boulders, rising 

 up the sides of the valley to about i^o feet above the bed 

 of the river. After the melting of the glacier, this mo- 

 raine, in all probability, produced a lake. But the torrent 

 has hewn a channel and levelled the ground over a breadth 

 of about 100 yards. The position of this moraine is not 

 more than 600 feet above the sea level, or 220 feet above 

 Ulleswater; and it enables us to measure with exactness 

 the dimensions of the glacier which formed it. Taken 

 from the tarn at the head of the valley, this glacier was 

 3 miles in length, about 500 feet in depth at its centre, 

 and from 200 to 400 yards in width. On the eastern side 

 it was bounded by a continuous and nearly vertical escarp- 

 ment of bedded trap ; but the western side was very irre- 

 gular and indented. 



The phenomena of this region appear to show : first, a 

 period when glaciers protruded far down the main valleys ; 

 secondly, an interval when the land was submerged about 

 1200 feet or more, during which the boulder clay was 

 spread over the flanks of the hills and valleys ; thirdly, a 

 period when the land had been again elevated, and gla- 

 ciers extended some distance down the minor valleys and 

 ploughed out the Drift. It was a glacier of this third 

 period which has left the terminal moraine of Grisedale. 



Scottish Highlands. — The glacial vestiges of the 

 Highlands of Scotland are on a scale more grand than 



