4 6 



FARM DEVELOPMENT 



the larger valley of the first named river; but this is 

 not the most interesting fact. (Figures 10 and n.) 



As long as the original larger bed of the Minnesota 

 river was well filled with water at Fort Snelling, where 

 the two rivers come together, the water from the Missis- 

 sippi did not 

 fall over a 

 precipice, but 

 flowed gently 

 into a body 

 of water nearly 

 as high as its 

 own river bed, 

 as shown in 

 Figure 

 When the 

 dam 



V"!/--A SANDSTONE 



Figure 8 shows in cross-section the Minnesota river above 

 where it and the Mississippi come together. This river is a 

 type of the common rivers made in the glacial period. From 

 A to B was the surface of the flood water in the glacial times 

 when the melting water from the glacier added to that from 

 the annual precipitation of rain required a large channel. 

 From C to D is the present surface of the water, ordina- 

 rily forming but a small river. In the seasons of high water, 

 as at the time of spring floods, the water rises so as to cover 

 the bottoms from E to F. 



n 



I I. 



ice 

 the 



vicinity of Lake Winnipeg was melted low enough for the 

 water from " Ancient Lake Agassiz " to flow over it, and 

 thus drain the water of that lake to the northward into 

 Hudson Bay, instead of to the southward into the Gulf 



of Mexico, the Minne- 

 sota river no longer re- 

 ceived water from the 



mm, 



J LIMESTONE 



\ DRI FT EZZ3 SANDSTONE 



watershed of the valley 

 of the Red River of the 

 North and from the 

 melting glacier, but 

 only that falling in its 

 own valley, extending 

 from Big Stone Lake 

 on the west border 

 of Minnesota to where St. Paul, Minnesota, now 

 stands. This caused the great reduction mentioned 

 in the volume of the water in the Minnesota river ; it no 

 longer had as large a watershed as the Mississippi, which 



Figure 9 shows a cross-section of the Missis- 

 sippi river above where the Minnesota enters it, 

 but below the Falls of St. Anthony. This river 

 at one time carried much more water than now; 

 but, as shown by the width between the bluffs, it 

 never contained as much water as the Minnesota 

 river did during the recession of the great gla- 

 cier, as shown in Figure 8. 



