Trof. H. Carvill Lewis — Comparative Studies in Glaciation. 31 



in the mountain region about the Nine Standards, where local glaciers 

 met, and. were overpowered by the greater ice-sheet coming down from 

 Cumberland. The ice-sheet itself was here divided, one portion going 

 southward, the other in company with local glaciers, and laden with 

 the well-known boulders of the "Shap granite," being forced eastward 

 across Stainmoor Forest into Durham and Yorkshire, finally reaching 

 the North Sea at the mouth of the Tees. The terminal moraine runs 

 eastward through Kirkby Raven sworth towards Whitby, keeping 

 north of the Cleveland Hills, and all eastern England south of Whitby, 

 except Holderness, appears to be non- glaciated. On the other hand, 

 all England north of Stainmoor Forest and the B,iver Tees, except the 

 very highest points, was smothered in a sea of ice. 



There is abundant evidence to prove that the ice lobe filling the 

 Irish Sea was thicker towards its axis than at its edges, and at 

 the north at its southern terminus, and that it was reinforced by 

 smaller tributary ice-streams from both England and Ireland. It 

 may be compared with the glacier of the Hudson River valley in 

 New York, each having a maximum thickness of something more 

 than 3000 feet. The erosive power of the ice-sheet was found 

 to be extremely slight at its edge, but more powerful farther 

 north, where its action was continued for a longer period. Towards 

 its edge its function was to fill up inequalities rather than to 

 level them down. It was held that most glacial lakes are due to an 

 irregular dumping of drift, rather than to any scooping action, observa- 

 tions in England and in Switzerland coinciding with those in America 

 to confirm this conclusion. Numerous facts on both sides of the 

 Atlantic indicate that the upper portion of the ice-sheet may move in 

 a diff'erent direction from its lower portion. It was also shown that 

 a glacier in its advance had the power of raising stones from the 

 bottom to the top of the ice, a fact due to the retardation by friction of 

 its lower layers. The author had observed the gradual upward passage 

 of sand and stones in the Grindelwald glacier, and applied the same 

 explanation to the broken shells and flints raised from the bed of the 

 Irish Sea to the top of Moel Tryfaen, to Macclesfield and to the Dublin 

 mountains. The occurrence of stratified deposits in connection with 

 undoubted moraines was shown to be a common phenomenon, and 

 instances of stratified moraines in Switzerland, Italy, America, and 

 Wales were given. The stratification is due to waters derived from 

 the melting ice, and is not proof of submergence. It was held that, 

 notwithstanding a general opinion to the contrary, there is no evidence 

 in Great Britain of any marine submergence greater than about 450 

 feet. It was natural that an ice-sheet advancing across a sea should 

 deposit shell fragments in its moraine. 



The broad principle was enunciated that wherever in Great Britain 

 marine shells occur in glacial deposits at hi^h levels,^ it can be proved 

 both by striae and the transport of erratics that the ice advanced on to 

 the land from out of the sea. The shells on Three Rock Mountain 

 near Dublin, and in North Wales and Macclesfield, all from the Irish 

 Sea ; the shells in Cumberland transported from Solway Firth ; those 

 on the coast of Northumberland brought out of the North Sea ; those 



1 i.e. hio'her than about 450 feet. 



