BIG MEADOW CHANNEL. 481 



Illinois, and enters the Mississippi Valley opposite the town of Louisiana, 

 Missouri. The deflection to the west is due to the ridge of Ulinoian drift 

 which follows the east border of the stream and prevents it from entering 

 the Illinois Valley- The gap through the rock divide was apparently 

 broken down below the level of the drift-filled districts to the east prior to 

 the ice invasion, and thus offered no obstruction to the westward deflection 

 of the drainage. 



There are several small creeks entering the Mississippi between Bear 

 Creek and Bay Creek, but which scarcely merit special mention, since they 

 usually take a somewhat direct course to the river, following the slope of 

 the drift surface. Those in Adams and northwestern Pike counties are in 

 some cases deflected slightly by the drift ridges formed on the west border 

 of the Ulinoian drift, and find passage to the river through gaps in these 

 ridges. In Pike and portions of Adams counties these creeks in part follow 

 preglacial lines. 



BIG MEADOW CHANNEL. 



Under this name is discussed a channel which has been excavated in 

 the Ulinoian drift by a stream which long since ceased to flow. The chan- 

 nel is distinctly traceable in a course about S. 65° W. from near the town of 

 Bushnell, Illinois, to the valley of the Mississippi in western Hancock 

 County, a distance of 50 miles (see PI. VI). Throughout its entire length 

 the valley has bluff-like borders, which range in height from 20 feet to about 

 50 feet. In width it ranges from one-fourth to fully one-half mile. Its bot- 

 tom is underlain by sandy and gravelly material, apparently alluvial, and 

 there seems little question that it has been occupied and formed by a stream 

 of considerable volume. 



From near Bushnell the valley is now followed westward across 

 McDonough County by East Crooked Creek. From the mouth of this 

 stream the channel continues along Middle Creek (reversed) to the present 

 divide between the Illinois and Mississippi drainage systems. In its passage 

 across this divide it has cut a valley fully 40 feet in depth and more than 

 half a mile in width. It is this portion which has long been known by 

 the residents as the "Big Meadow." At the west it continues down Big 

 Meadow Creek to another headwater tributary of Bear Creek, and thence 

 follows the course of that creek (reversed) to the divide between Bear Creek 



3ION xxxviii 31 



