206 



PHYSICAL GEOLOGY 



large enough to yield many different kinds of rock, and was 

 capable of carrying large bowlders as well as fine clay, some- 

 times for great distances. It was capable, furthermore, of 

 giving a part of the stones it carried the characteristics noted 

 above, but was incapable of arranging its irregular deposits 



FIG. 217. Map showing the areas in and about the borders of North 

 America covered by ice at the maximum stage of glaciation. The un- 

 shaded parts were covered by ice ; the dotted portions were land areas 

 free from ice. (Modified after Willis.) 





