THE MISSISSIPPI VALLEY. 467 



Mississippi River at Clinton, and perhaps sufficiently low to have carried 

 the drainage of the preglacial stream whose valley has been traced south- 

 ward to Clinton. The data are scarcely sufficient to fully establish the 

 connection of this channel across the Wapsipinnicon Basin, for there are 

 very few deep wells in the basin. Another feature which throws some 

 doubt upon this connection is the narrowness of the deep portion of the 

 channel along the Mud Creek sag. The well data indicate that its width 

 can not exceed 2 or 3 miles, and this seems rather narrow for the continua- 

 tion of so broad a valley as that above Clinton, a valley 4 or 5 miles in 

 width. 



Turning to the southeastward course, one finds a broad depression or 

 lowland tract leading from Clinton through to the Illinois River. This low- 

 land, except at the outer moraine of the Wisconsin drift in Bureau County, 

 stands only a few feet above the level of the Mississippi, and yet apparently 

 carries a heavy accumulation of drift. The drift is largely sand, and there 

 has been no necessity for sinking wells entirely through it. They have, 

 however, penetrated 40 to 50 feet without striking rock. The bed rock 

 gradually descends from each side toward the middle of the lowland, and 

 some of the creeks coming into the lowland occupy large and deep chan- 

 nels which have been only partially filled with drift, This rather throws 

 the balance of evidence in favor of the view that the preglacial stream 

 flowed southeastward into the Illinois. 



It should be observed that in case the southwestward route proves to 

 have been the course of the Mississippi, the present line of the stream 

 departs from it only a few miles and enters the same old valley below Musca- 

 tine, which it occupies above Clinton. But in case the southeastward route 

 proves to have been the preglacial course from Clinton, the preglacial valley 

 above Clinton finds its continuation down the Illinois instead of down the 

 Mississippi, and the present Mississippi passes from one drainage system to 

 another in its course between Clinton and Muscatine. 



REESTABLISHED STREAM BETWEEN THE UPPER AND LOWER RAPIDS. 



From the city of Muscatine southward to the head of the lower rapids, 

 12 miles above Keokuk, Iowa, the Mississippi River is flowing through a 

 broad preglacial valley. It has removed the drift throughout only a por- 

 tion of the width of the old valley in the district between Muscatine and 



