TEMPORARY DISPLACEMENT OF THE MISSISSIPPI. 93 



or 60 feet at the south. It is occupied for about 4 miles by Little Cedar 

 Creek just south of the bend of Big- Cedar. The remainder of its course is 

 drained by Sugar Creek. The excavation along the channel from Colui nbus 

 Junction to Viele is estimated to be one-half a cubic mile. 



The precise elevation of the bottom of this old channel has been deter- 

 mined at only a few points in the portion south from Columbus Junction. 

 The elevation at the border of the Iowa River 12 miles north of Winfield 

 is apparently not more than 710 feet, At Winfield its elevation is about 10 

 feet below the railway station or 703 feet above tide. The altitude 

 appears to fall but little in the 15 miles between Winfield and Skunk River. 

 The aneroid determinations made at Coppock give the old channel an alti- 

 tude of about 700 feet above tide. In the oxbow near Rome the altitude is 

 about 675 feet. At the point where the Keokuk and Northern Railroad 

 crosses the channel, near the line of Henry and Lee counties, the elevation 

 is 657 feet. At St. Paul station on the Fort Madison and Des Moines Rail- 

 road 5 miles southeast; the elevation is 645 feet, and at the point where the 

 channel joins the Mississippi, 14 miles farther southeast, about 620 feet. 

 The distance from the point where this channel leaves the Iowa River to 

 its junction with the Mississippi is about 75 miles. The fall of 90 feet 

 which it makes in this distance would therefore give an average of slightly 

 more than 1 foot a mile. The fact if it be proved that the channel has no 

 fall in the portion leading west from Winfield may bring support to the 

 hypothesis suggested by studies farther north that the surface has been sub- 

 jected to a westward differential uplift in. the later part of the Pleistocene. 1 

 The measurements of altitude, however, are not sufficiently exact to justify 

 the presentation of these data in support of the hypothesis. 



The writer has been unable to discover any notable amount of sand or 

 gravel in the bed of this channel. It generally appears to be swept clean 

 of such deposits. The valley is coated with a sheet of loess similar to that 

 which occurs on the bordering uplands, but this deposit is apparently as 

 late in deposition as the Iowan stage of glaciation, in which case it can not 

 be considered as a deposit of the stream which formed this channel. In 

 northwestern Lee County sand to a depth of 10 to 20 feet is found along 

 the channel. Chamberlin has suggested that the ground in which this 

 channel was excavated may have been frozen at the time of the Illinoian 

 glaciation, its situation being on the immediate border of the ice sheet, and 



' See Chamberlin : Third Ann. Rept. U. S. Geol. Survey, p. 391. 



