IOWA ACADEMY OF SCIENCES. 
25 
40 to 50 feet. One of the most interesting of these buried chan- 
nels has recently been described by Gordon,* and the figures 
given by him bring out in startling contrast the size and volume 
of this ancient river as compared with its present insignificant 
successor, the Mississippi. 
At Bloomfield and Belknap, in Davis county, traces of a sim- 
ilar channel have been encountered, and in Appanoose such 
channels are by no means uncommon. At Des Moines there 
lies between Capitol Hill and the sand ridge upon which the 
fair grounds are located a broad, level plain, having an eleva- 
tion of about 800 feet. It stands in marked contrast to the high 
hills both west and east of it. McGee and Call, f in discussing the 
loess and associated deposits of this region considered the current 
opinion that this represented an abandoned channel of the Des 
Moines river erroneous, and referred its origin to glacial agen- 
cies. Since their studies were carried on the work of the num- 
erous mines along its edge, including the Giant, Garver, Stan- 
dard and others, have conclusively shown that this is a filled 
channel, and that the bed rock here lies at least 90 feet below 
the present water level of the Des Moines river, or 120 feet 
below the surface of neighboring outcrops. Similar channels 
have been encountered in all portions of the state. 
A comparison of the facts show quite conclusively that in 
preglacial time the land surface of Iowa stood at an elevation 
considerably above that now obtaining. This is well in accord 
with results obtained from studies in the driftless area and on 
the Missouri and Mississippi rivers. In the recent borings for 
locating the piers of the Pacific Short Line bridge at Sioux 
City, it was found that the Missouri river channel had been at 
that point filled in some eighty feet with loose sand and gravel 
above the hard shale of the Cretaceous. The river is also 
known to have filled in its channel to an average depth of from 
70 to 100 feet between Sioux City and Kansas City. The Mis- 
sissippi River Commission reported in 1881 that river to have 
also filled in its channel 100 feet or more with sand and gravel, 
along the eastern boundary of Iowa, the water now only reach- 
ing the rock at two points; the LeClaire and the Keokuk 
rapids. Throughout the driftless area there is evidence that 
the region, after being reduced to a base level of erosion, has 
been elevated and is now being reduced to a second base level, 
*Iowa Geol. Sur., vol. Ill, 237-255, 1895. 
+Am. .Jour. Sci., (3), XXI V, 202-223, New Haven, 1882. 
