GLACIAL FORMATIONS 375 



more feet with broad flat tops miles in length. They 

 were indeed huge floating islands of ice. 



169. Glacial Formations. In a region which has been 

 glaciated, peculiar deposits are found which occur nowhere 

 else. Sometimes the end of a glacier remains compara- 

 tively stationary over an area for a considerable time, 

 owing to the advance of the ice being just balanced by 



A DRUMLIN. 



These low, smooth; rounded hills, like that seen in the bRckground, 

 usually extend nearly north and south. 



the melting. In this case, the morainic material which 

 has collected on the top is deposited over the surface, 

 forming irregular heaps of bowlders, gravel and sand, with 

 inclosed hollows between. This material is unstratified 

 and without any uniformity in its arrangement. 



When the glacier has retreated, ponds and lakes are 

 formed in the depressions, and streams wander about in 

 the low places between the heaps and receive the overflow 

 of some of the lakes and ponds. Others of these lakes and 

 ponds are so fully inclosed and receive the drainage from 

 so small a surface that not enough water enters to over- 

 flow the rim. The arrangement of the streams is unsym- 



