90 THE ILLINOIS GLACIAL LOBE. 



But turning from the question of a permanent displacement to that of a 

 temporary one, the influence of the Illinoian invasion becomes more appar- 

 ent. Several years ago the writer found a large abandoned valley in Lee 

 County, Iowa, shown in fig. 4 (p. 468), which leads southeastward across the 

 county from Big Cedar Creek, a tributary of Skunk River, to the Mississippi 

 River, which it joins about 6 miles below Fort Madison. This large valley 

 is now occupied for a few miles by East Sugar Creek, a small tributary of 

 the Mississippi. This abandoned valley was at first supposed to have been 

 the former course of Big Cedar Creek, which now makes a singular deflec- 

 tion to the north, near its mouth, and this interpretation was published in 

 1885. 1 A few years later (in 1894) the writer began systematic investiga- 

 tions in southeastern Iowa and found evidence that the valley has a con- 

 tinuation northward from Lee County along the north-flowing portion of 

 Cedar Creek past Skunk River, the present valley of "that stream being 

 along it for a few miles above the village of Rome, in Henry County. The 

 study that season did not develop evidence of the further continuation of 

 the valley. But in 1896 the district between the Skunk and Iowa rivers 

 was examined, to determine whether the upper Mississippi with its western 

 tributaries did not utilize this abandoned valley during the Illinoian invasion. 

 This study resulted in the discovery of an abandoned channel which leaves 

 the Iowa Rh*er just north of Columbus Junction and passes southward iinme- 

 diatelv outside the limits of the Illinoian drift to the valley of Crooked Creek 

 near Winfield, and thence westward to Skunk River along a double channel, 

 the northern one being now occupied by Crooked Creek, while the southern 

 is only partially occupied by a stream. It thus appears that the waters of 

 the Iowa, with its main tributary, Cedar River, as well as of Skunk River 

 and Big Cedar Creek, have followed this abandoned channel southward 

 around the western edge of the Illinoian drift. To complete the connection 

 at the north and show that the Mississippi follows this channel it was only 

 necessary to utilize results already obtained by W J McCee and J. A. Udden. 

 Professor Udden three or four years previously conceived the idea that the 

 Mississippi, either in preglacial or in interglacial time, had taken a south- 

 westward course from the Wapsipmnicon to Cedar River, through a broad 

 sag now drained in opposite directions by streams each of which is called 



'The deflection of Big Cedar Creek, by Frank Leverett: The Aurora, Iowa Agr'l College 

 Monthly, November, 1885. 



