56 



MAN AND THE GLACIAL PERIOD. 



sive deposits of loose material devoid of stratification, and 

 composed of soil and rock gathered in considerable part 

 from other localities, and mixed in an indiscriminate 

 mass with material which has originated in the disinte- 

 gration of the underlying local strata. 



Fig. 22.— Ideal section, showing how the till overlies the stratified rocks. 



3. Transported boulders. 



Where there is a current of water deep enough to float 

 large masses of ice, there is scarcely any limit to the size 

 of boulders which may be transported upon them, or to 



Fig. 23.— Vessel Rock, a glacial boulder in Gilsum. N. H. (C. H. Hitchcock.) 



the distance to which the boulders may be carried and 

 dropped upon the bottom. The icebergs which break off 

 from the glaciers of Greenland may bear their burdens of 

 rock far down into the Atlantic, depositing them finally 

 amidst the calcareous ooze and the fine sediment from the 



