534 THE ILLINOIS GLACIAL LOBE. 



The drift has sufficient thickness on the west side of White River to 

 render the tracing of preglacial drainage lines difficult if not impracticable. 

 A smooth drift plain extends west from the bend of Eel River in south- 

 western Clay County to the Wabash Valley in Vigo and Sullivan counties, 

 in which preglacial lines are almost entirely concealed. The preglacial 

 divide was probably far from coincident with the present divide. In more 

 elevated districts east of the bend the drift is in places filled to the level of 

 the high rock ridges, completely disguising some of the lines of connection. 

 For example, just north of the town of Spencer a pregdacial valley connects 

 with White River, which, within a mile to the north, becomes traceable 

 only by means of well records, there being no depression between rock 

 ridges to indicate its course. This is thought to lead through to Mill Creek, 

 connecting with its valley just above the falls at Cataract. But whether 

 formed by a sfream flowing northward or in the reverse direction is not 

 known. 



EMBARRAS RIVER. 



This western tributary of Wabash River drains an area of about 

 2,000 square miles in eastern Illinois. Its soui'ce is in the Champaign 

 moramic system, immediately south of the city of Champaign. For about 

 20 miles it flows between the outer and main ridge of the Champaign system, 

 but passes through the outer ridge in northern Douglas County. It then 

 bears southeast for about 10 miles to a small till ridge, correlated with the 

 Cerro Gordo moraine, which it crosses in southeastern Douglas County. 

 The course is then slightly west of south for 25 miles, at which point it 

 leaves the Shelbyville or earliest AVisconsin sheet of drift. It continues 

 southward 25 or 30 miles farther to the vicinity of Newton, where it 

 changes to a southeastward course and maintains this course to its mouth, 

 a distance of 50 miles. 



The portion lying within the limits of the Wisconsin drift drains a 

 narrow strip and has a very small channel. Upon emerging from that drift 

 it at once enters a much broader valley, which appears to have been exca- 

 vated nearly to its present dimensions prior to the Wisconsin stage of 

 glaciation, for the valley gravels connected with the Shelbyville moraine 

 lead down the river bottom in such manner as to indicate the existence of 

 the valley at the time of their deposition. Upon following the valley down, 

 its width increases from less than a mile at the border of the Shelbyville 



