﻿434 II C. Lewis — Comparative Studies upon Glaoiation 



terminal moraines and the direction of striation and glacial 

 movement. It was shown that, apart from the great ice sheet 

 of Northeastern America, an immense lobe of ice descended from 

 Alaska to Vancouver's Island on the western side of the Rocky 

 Mountains and that from various separate centers in the Cas- 

 cade, Sierra Nevada, and Rocky Mountains there radiated 

 smaller local glaciers. 



The mountains encircling the depression of Hudson Bay 

 seemed to be the principal source of the glaciers which became 

 confluent to form the great ice sheet. In its advance this ice 

 sheet probably met and amalgamated with a number of already 

 existing local glacial systems, and it was suggested that there 

 was no necessity for assuming either an extraordinary thickness 

 of ice at the Pole, or great and unequal elevations and depres- 

 sions of land. 



Detailed studies made by the author in Ireland, in 1885, had 

 shown remarkably similar glacial phenomena. The large ice 

 sheet which covered the greater part of Ireland was composed 

 of confluent glaciers, while distinct and local glacial systems oc- 

 curred in the non-glaciated area. The principal ice sheet resem- 

 bled that of America in having for its center a great inland de- 

 pression surrounded by a rim of mountains. These appear to- 

 have given rise to the first glaciers, which after uniting, poured 

 outward in all directions. Great lobes of this ice sheet flowed 

 westward out of the Shannon, and out of Galway, Clew, Sligo, 

 and Donegal Bays, northward out of Loughs Swilly and Foyle, 

 and southeasward out of Dundalk and Dublin Bays; while to 

 the south the ice sheet abutted against the Mullaghareirk, Galty r 

 and Wicklow mountains, or died out in the plains. Whether 

 it stopped among the mountains or in the lowlands, its edge 

 was approximately outlined by usual accumulations of drift 

 and bowlders, representing the terminal moraines. As in 

 America, this outer moraine was least distinct in the lowlands, 

 and was often bordered by an outer " fringe " of drift several 

 miles in width. 



South of an east and west line extending from Tralee to Dun- 

 garven is a non-glaciated zone free from drift. Several local 

 systems of glaciers occur in the south of Ireland, of which by 

 far the most important is that radiating from the Killarney 

 mountains, covering an area of over 2000 square miles, and en- 

 titled to be called a local ice sheet. Great glaciers from this 

 Killarney ice sheet flowed out of the fiord-like parallel bays 

 which indent the southwestern coast of Ireland. At the same 

 time the Dingle mountains, the Knockmeal Down and Comer- 

 agh mountains, and those of Wexford and Wicklow furnished 

 small separate glaciers, each sharply defined by its own mo- 

 raine. 



