182 MAN AXD THE GLACIAL PERIOD. 



The depth of this northern ice-sheet is proved to have 

 been upwards of 1,400 feet where it met the Hartz Moun- 

 tains, for it has deposited northern debris upon them to 

 that height ; while, as already shown, it must have been 

 over 2,000 feet in the main valley of Switzerland. In 

 Norway it is estimated that the ice was between 6,000 

 and 7,000 feet thick. 



The amount of work done by the continental glaciers 

 of Europe in the erosion, transportation, and deposition of 

 rock and earthy material is immense. According to Hell- 

 and, the average depth of the glacial deposits over North 

 Germany and northwestern Eussia is 150 German feet, 

 i. e., about 135 English feet. As the deposition towards 

 the margin of a glacier must be commensurate with its 

 erosion near the centre of movement, this vast amount 

 implies a still greater proportionate waste in the moun- 

 tains of Scandinavia, where the area diminishes with every 

 contraction of the circle. Two hundred and fifty feet is 

 therefore not an extravagant calculation for the amount 

 of glacial erosion in the Scandinavian Peninsula. 



It is not difficult to see how the Scandinavian moun- 

 tains were able to contribute so much soil to the plains of 

 northern Germany and northwestern Eussia. Previous to 

 the Glacial period, a warm climate extended so far north as 

 to permit the growth of semi-tropical vegetation in Spits- 

 bergen, Greenland, and the northern shores of British 

 America. Such a climate, with its abundant moisture 

 and vegetation, afforded most favourable conditions for the 

 superficial disintegration of the rocks. When, therefore, 

 the cold of the Glacial period came on*, the moving cur- 

 rents of ice would have a comparatively easy task in strip- 

 ping the mantle of soil from the hills of Norway and 

 Sweden, and transporting it towards the periphery of its 

 movement. Of course, erosion in Scandinavia meant 

 subglacial deposition beyond the Baltic. Doubtless, there- 

 fore, the plains of northern Germany, with their great 



