﻿of North America, Great Britain and Ireland. 437 



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 gla- 

 ciers and laden with the well known bowlders of " 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 

 Eavensworth toward "Whitby, keeping north of the Cleveland 

 Hills, and all eastern England south of Whitby seems to be 

 non-glaciated. On the other hand all England north of Stain- 

 more Forest and the river Tees, except the very highest point, 

 was under a sea of solid ice. 



There is abundant evidence to prove that the ice lobe filling 

 the Irish Sea was thicker toward its axis than at its edges, and 

 at the north than at its southern terminus, and that it was rein- 

 forced 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 

 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 pe- 

 riod. Toward its edges 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, observations in England and in Switzer- 

 land coinciding with those in America to confirm this conclu- 

 sion. Numerous facts on both sides of the Atlantic indicate 

 that the upper portion of the ice sheet may move in a different 

 direction from its lower portion. It was also shown that a gla- 

 cier 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 grad- 

 ual upward passage of sand and stones in the Grindelwald gla- 

 cier, and applied the same explanation to the broken shells and 

 flint raised from the bed of the Irish Sea to the top of Moel 

 Tryfan, to Macclesfield and the Dublin mountains. The occur- 

 rence of stratified deposits connected with undoubted moraines 

 was shown to be a common phenomenon, and instances of strati- 

 fied 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, notwithstanding a general opinion to the con- 

 trary, that there is no evidence in Great Britain of any marine 

 submergence greater than about 450 feet. It was to be expec- 

 ted that an ice sheet advancing across a sea should deposit shell 

 fragments in its terminal moraine. 



The broad principle was enunciated that wherever in Great 

 Britain marine shells occur in glacial deposits at high levels, it 



