THE WORK OF SNOW AND ICE 



115 



covered and enclosed by the snow, and when it becomes ice and 

 begins to move, they are carried along with it. Glacier ice, there- 

 fore, has some load when it begins to move. 



2. Where the snow and ice bury projecting points of bed-rock, 

 the ice tends to break them off when it moves. If they are too 

 strong to be torn away bodily, their surfaces are worn and smoothed. 

 When the bed-rock over which a glacier advances is in blocks par- 

 tially separated from one another by joints (Fig. 2, PI. XIII, p. 52, 

 and Fig. 115), the moving ice may remove large blocks, especially 

 from cliffs over which it descends, and from jagged walls of rock 

 against which it crowds. Fig. 115 represents a cliff the Palisades, 

 west of the Hudson River. Glacier ice once passed over this ridge 



Fig. 117. Ice-worn rock, Bell's Island, Lake Huron. 



and carried masses of rock from the cliff over to the area where New 

 York City and Brooklyn now stand. 



3. As a glacier creeps out over surfaces covered with soil or 

 other mantle rock, the ice freezes to the soil; that is, the ice above 



