Inter glacial Submergence in England. 7 



by the southerly retreat of the Pliocene fauna and the incom- 

 ing of subarctic and arctic species ; so that shells of diverse 

 nature became commingled all over the bottom of the Irish 

 and North Seas. Scandinavian glaciers advanced over the 

 shallow North Sea till they reached the shores of England at 

 Flainborough Head, where they were met by the glaciers that 

 had been slowly coming down from southeastern Scotland and 

 northeastern England. This latter movement of the ice was 

 compelled to hug the shore by the Scandinavian glacier, and 

 its boulders are found only as far south as Flamborough Head. 

 The Scandinavian movement reached pretty generally to the 

 line extending from Flamborough Head to London. 



Contemporaneous with this movement over the North Sea, 

 glaciers began to push out in all directions from the northern 

 part of Wales, having their center in the broad elevated area 

 of the Arenig mountains about twenty five miles southeast of 

 Snowdon. Towards the east this movement extended across 

 Shropshire and the southern part of Staffordshire to a line ex- 

 tending from Litchfield, through Birmingham, and Broms- 

 grove to the Severn Yalley. But meanwhile a more powerful 

 ice-movement was under way, originating in the snown'elds of 

 Eastern Ireland, Southwestern Scotland, and the Lake District 

 in England. The glaciers from these centers, meeting in the 

 Irish Sea, advanced to the north shore of Wales, and in divided 

 currents passed over Anglesey on the west, and on the east 

 through the broad Vale of Chester which separates the Welsh 

 Mountains from the Pennine Chain by a distance of 60 or TO 

 miles. Immense quantities of Scotch and Lake boulders were 

 thus transported into the valley of the Severn as far as Wolver- 

 hampton, about half way between Wellington and Birmingham. 

 This northern ice seems to have predominated over, and 

 pushed aside, the weaker movement from the Welsh Moun- 

 tains, which had deposited the band of boulders just mentioned, 

 extending from Litchfield to Bromsgrove. I shall be surprised 

 if future explorations do not reveal Welsh boulders under- 

 neath the Scotch drift, so extensively developed near Wolver- 

 hampton. It is in this northern drift that the shell-bed 

 discovered by Mr. Baldwin at Wellington occurs. 



The triple stratification spoken of as characterizing the 

 marginal deposits near Flamborough Head, and in Lancashire 

 and Shropshire, need not necessitate anything more than a 

 local recession of the front, followed by a subsequent corres- 

 ponding advance. Indeed, it is evident that the problems of 

 the glacial margin in England closely resemble those in the 

 United States, and Professor Lewis's observations require the 

 same corrections for the personal equation in England that we 

 have had to make for him in America, — corrections which he 



