480 THE ILLINOIS GLACIAL LOBE. 



LOST CREEK. 



Lost Creek, a small western tributary of the Mississippi draining the 

 eastern portion of Lee County, Iowa, occupies a valley markedly larger 

 than other streams of its size which have cut channels in the Illinoian drift, 

 a feature which appears to be due to an occupancy of the valley by a 

 larger stream than the present one prior to the Illinoian ice invasion. The 

 present head of the stream is in the marginal ridge of Illinoian drift near 

 West Point. It seems not improbable that streams now draining south- 

 ward through Sugar Creek found their outlet through Lost Creek Valley 

 prior to the Illinoian invasion. The interpretation is rendered difficult 

 because of the interruption made by the large stream channel of the tem- 

 porary Mississippi, a channel which, as noted above, governs the present 

 drainage of the streams outside the Illinoian drift from Skunk River 

 southward. 



BEAR CREEK. 



Two small eastern tributaries of the Mississippi River remain to be 

 considered — Bear Creek and Bay Creek. The former drains the south- 

 western part of Hancock and the northern part of Adams counties, Illinois. 

 It has a widely branching drainage system, and the courses of the several 

 tributaries were probably determined by the slope of the drift plain. One 

 of the tributaries heading near Sutter leads northeastward for a few miles 

 along "Big Meadow Channel," an abandoned A-alley of a larger stream, but 

 turns away from that valley to form the north fork of Bear Creek. This 

 north fork traverses a region of very thick drift, yet it may have no 

 dependence on the course of preglacial drainage, but the lower course of 

 Bear Creek evidently follows a preglacial line. The abandoned valley 

 just mentioned is described below. 



BAY CREEK. 



This stream drains much of Pike County, Illinois. Its headwater por- 

 tion leads from the north border of the county southeastward toward the 

 Illinois, following a sag between two Illinoian drift ridges and nearly reach- 

 ing the Illinois River, opposite the village of Bedford. It then curves 

 around to the southwest, passes through a gap in the rocky ridge, which to 

 the north and south constitutes the divide between the Mississippi and the 



