EXAMPLES OF RIVER ACTION 



99 



2. In the northern parts of the United States the great ice- 

 sheet, which in late geological times covered the country, brought 

 down with it vast quantities of drift, that filled up the channels 



Fig. 32. — The Au Sable Chasm, N.Y. (Copyright by S. R. Stoddard, Glens Falls, N.Y.) 



