198 GLACIAL HISTORY. 



which fell to the bottom of the sea, and in some portions of 

 their accumulations buried marine animals which had been living 

 there,, and which belonged to a northern race. At a later period 

 there occurred another elevation of the land, upheaving from 

 the depths of the ocean the glacial debris which are now met 

 with in some places at a height of 1400 feet above the sea. To 

 this extent, at least, the land must have been elevated ; and pro- 

 bably the upheaval was still more considerable. If the soil of 

 Great Britain were to be now elevated about 600 feet, it would 

 join the European continent, and become connected with Den- 

 mark, Holland, and France. And this result appears to have 

 taken place at that time. 



During the second continental ice-period the mountains of 

 Scotland and Wales were covered with glaciers, which have left 

 behind them traces of their action. But a gradual depression 

 of the land again occurred ; and this by degrees produced the 

 present configuration of land and sea. On the Norwegian coast 

 at the present time the land is observed to be gradually rising ; 

 its upheaval is estimated at the rate of 2| feet in a century. If 

 this standard be assumed as a basis for the calculation of move- 

 ments of the land, its depression to the extent of 1400 feet would 

 require 50,000 years, and its re-elevation to the same height 

 would occupy the same amount of time. Such numbers are 

 arbitrary, yet they suffice to demonstrate that the Glacial epoch 

 must have lasted very long, and that a continued succession of 

 ages allowed sufficient time for the slow dispersion of the erratic 

 blocks. 



Scandinavia, like England and Scotland, affords evidence of 

 two glacial epochs. Lofty stratified masses of debris (Osars) 

 lie, in Northern Europe, on the smoothed surfaces of rocks ; 

 these had very probably been produced under the sea ; and upon 

 them are found erratic blocks which, like the smoothed rocks, 

 indicate a time when glaciers spread over all the country. 



Local causes do not explain glacial phenomena, as the traces 

 of glaciers are seen in North America in the same way as in 

 Europe. After the close of the Tertiary epoch such a diminu- 

 tion of temperature must have occurred over the whole of the 

 Northern hemisphere that the glaciers of the Alps descended 



