THE DRIFT BORDER. 35 



a southeastward course and comes to the Illinois River in the southeast part 

 of the county; thence it follows the Illinois Valley southward to the mouth 

 of the river, perhaps touching- the west bluff in southern Calhoun County. 

 The border then either follows the Mississippi bluff eastward past Alton, or 

 continues southward across the projecting point of Missouri which borders 

 the mouth of the Missouri River just above St. Louis. It is somewhat 

 uncertain whether the drift found on the Missouri side of the Mississippi is 

 of direct glacial deposition or a deposit made by streams; the greater part 

 of it is assorted material. The presence of drift on the Missouri side of the 

 Mississippi has been noted only in the district north from the citv of St. 

 Louis. Below that city the drift border apparently follows the line of the 

 valley of the Mississippi closely as far down as southern Jackson County. 

 The Mississippi River there turns southward, but the drift border passes 

 eastward, following the north slope of the elevated ridge which crosses south- 

 ern Illinois and entering Indiana in the extreme southwest corner of that 

 State. 



The drift border, as indicated on PL VIII, crosses the southwestern 

 county of Indiana (Posey) in a northeastward course lying near the valley 

 of the north fork of Big Creek. It cuts across the northwest corner of 

 Vanderburg County and enters Gibson County in sec. 10, T. 4 S., R. 11 W. 

 Thence it passes northeastward, touching the village of Haubstadt and 

 coming to Pigeon Creek in sec, 22, T. 3 S., R. 10 W., at the junction of Sand 

 Fork and Muddy Fork. From this creek the course for a few miles is 

 northward to the divide between Pigeon Creek and Patoka River, which it 

 crosses about 4 miles east of Princeton. It there swings eastward and 

 comes to Patoka River near the line of sees. 32 and 33, T. 1 S., R. 9 W. 

 It enters Pike County about 1 mile south of Oatsville, in sec. 27, T. 1 S., 

 R. 9 W. In that county it lies but a short distance north of Patoka River, 

 and apparently follows nearly the divide between the small northern tributa- 

 ries and Flat Creek, a large northern tributary, to the mouth of Flat Creek 

 in western Dubois County. From this point eastward to the vicinity of 

 Jasper, and thence northward to East White River, there is a sand-covered 

 plain in which the boundary is difficult to locate. Possibly this plain was 

 covered by the ice sheet, since glacial pebbles several inches in diameter 

 are found beneath the sand on its east border. The sand seems to have 

 been deposited in a small glacial lake, Lake Patoka, which occupied this 



