LOWER RAPIDS OF THE MISSISSIPPI 



5 



Date of the deflection across the loiver rapids. — In previous 

 years attention has been called, both by Mr. Fultz and myself, 



Fig. 2. Sketch map of region discussed, showing course of old channels. 



Note of Explanation. — The abandoned portion of the preglacial valley of the 



Mississippi is shaded. Hachures are used to indicate valley borders both above and 

 below the level of the high terraces, and along the temporary Mississippi channel, 

 opened at the Ulinoian stage of glaciation. The extent of the high terrace south of 

 the Des Moines Valley is not determined. 



to evidence that the region around the lower rapids presents a 

 complicated glacial history. 1 It has been shown that one 

 ice-field extended southward from Kewatin, in the Dominion of 

 Canada, across Manitoba, Minnesota, and Iowa, into Missouri, 

 1 F. M. Fultz, Proc. Iowa Acad. Sci. for 1895, v °l- H> PP- 209-212 ; ibid., 1896, 



