46 



the ice moves. Resting on the I'ock are boulders and pebbles 

 (Fig. 22), sometimes on the bare rock, sometimes imbedded in 



a clay as they are 

 with us. As we 

 found when study- 

 ing the soil in our 

 own region, so here 

 the j3ebbles are often 

 scratched, and many 

 of them are quite 

 different from the 

 rock on which they 

 rest. 



Going nearer to 



24. — A 2Mrt of the edge of the Greenland glacier, clean ^"^ ^^^ ^^'^ ^^^^ ^^^^ 

 white ice above, and dark discolored bands heloic where lower part loaded 

 laden with rock fragments. In the Joreground is a ^yith pebbles bo'ul- 



houlder'StretD7i moraine. , i i ., r ^ 



ders and bits oi clay 



quite like those on the rocks near by. Fig. 23 shows one of these 

 scratclied and grooved, which I once dug from the ice of this 

 very glacier. The bot- 

 tom of the ice is like a 

 huge sandpaper, being- 

 dragged over the bed 

 rock with tremendous 

 force. It carries a load 

 of rock fragments, and 

 as it moves obtains more 

 b}' grinding or prying 

 them from the rocks be- 

 neath. These all travel 

 on toward the edge of 

 the ice, being constantly 



ground liner and liner as wheat is ground when it goes through the 

 mill. Indeed the resemblance is so close that the clay coming from 

 this grinding action is often called rock flour. 



438 



25. 



Hunmwcky surface of the boidder-sdcirn 

 7noraine of Greenland. 



