44 FARM DEVELOPMENT 



ground fine by glacial action, the broken particles of 

 sand have sharp, harsh edges. Where this sand has 

 been much worn, as in running water, or in sand dunes 

 often shifted by the winds, the particles become rounded. 

 In case of soils formed in situ, resulting from very long 

 continued action of the elements, the particles are not so 

 angular and firm. Like ripened cheese, they have lost 

 their toughness as well as their rough edges. 



Some interesting glacial geology: History of the 

 Falls of St. Anthony. A very interesting chapter in the 

 history of the glacial period, illustrating the magnitude 

 of the changes wrought by geologic forces, is recorded 

 in Minnesota. It includes the Falls of St. Anthony, the 

 Mississippi and the Minnesota rivers and their water- 

 shed in Minnesota; also the valley of the Red River of 

 the North, or the bed of the " Ancient Lake Agassiz," 

 all of which tell part of the story. 



The valley, from bluff to bluff, of the Minnesota river, 

 is considerably larger than the valley of the Mississippi 

 at their confluence, as illustrated in Figures 8 and 9. 

 This is evidence that when the glacier was rapidly melt- 

 ing, while its southern boundary was passing from north- 

 ern Minnesota, the Minnesota river was much larger 

 than the Mississippi, and that a much larger volume of 

 water was passing through these rivers than later, when 

 only the present watersheds furnished the surplus rain- 

 fall to be drained off. 



The Ancient Lake Agassiz. While the southern line 

 of the glacier was receding northward toward the region 

 of Hudson Bay, there was a lake in the valley of the 

 present Red River of the North, as shown in Figure 7. 

 This lake has recently been named " Ancient Lake 

 Agassiz." The land slopes to the north in that valley, 

 but the ice sheet as it receded northward served as a 

 dam to the waters, and this so-called " Ancient Lake 

 Agassiz " had its outlet to the southward where the Red 



