THE GLACIAL PERIOD. 205 



dragged up the southern slopes of the trough, until eventually it 

 made its escape and flowed on with the general mer de glace 

 of the North Sea. I have indicated the probahle path of the 

 bottom ice by the diverging arrows. A portion would spread 

 away to north-west, while another part seems to have swept on 

 with the ice that flowed south-west towards the English coast. 

 It is by this circuitous route that I believe the Norwegian 

 boulders in the till of Cornelian Bay and Holderness have 

 come. 1 While such was the course followed by a portion of the 

 bottom -ice that flowed from the Christiania district, there 

 can be little doubt that this was only a local deflection due to 

 the configuration of the ground, and that the main mass of 

 the ice, from base to surface, flowed S.S.W. from Christiania- 

 fjord, and crossed Denmark into Germany, for we find erratics 

 of the same origin as those above referred to, in Jutland, in 

 the island of Laaland, in the island of Urk in the Zuider Zee, 

 and at Hamburg. 



To support an ice-sheet extending over twenty degrees of 

 latitude, and showing a width of little less than 3000 miles, great 

 humidity and extreme cold were required. It is quite impossible 

 that the vast sheet of ice which overwhelmed all Northern 

 Europe could have been fed by the snows that fell upon the 

 mountains of Scandinavia and the British Islands. The precipi- 

 tation must have been excessive over the whole area, and the 

 cold which enabled the snow to accumulate and become perennial 

 upon the low grounds of England and Northern Germany could 

 not have been other than severe in the extreme. Some geolo- 

 gists have supposed that the great mer de glace poured down 

 upon Europe from the polar regions. But this is disproved by 

 the direction of the striae in the north of Norway, in the Shetland 

 Islands, and the Outer Hebrides. The mer de glace must have 



1 For further remarks upon the deflections of the European mer de glace, see 

 Appendix, Note B. I need hardly remind the geological reader that in this chapter 

 I refer only to the ice-sheet at the period of its greatest extension. Of the smaller 

 ice-sheet of the latest glacial epoch I speak in a subsequent chapter. 



