WABASH RIVER DRAINAGE BASIN. 537 



of the valley. The headwaters are in the midst of the Bloomington 

 morainic system at the reentrant angle in Ford and Livingston counties, 

 Illinois, and only a few miles from the headwaters of a stream of the same 

 name flowing to the Illinois. To distinguish it from that stream the name 

 Wabash- Vermilion has come into use. 



The middle' or main fork has a southward course for a few miles from 

 its source, between two ridges of the Bloomington system in Ford County, 

 locally known as the Roberts and Melvin ridges. It then passes through 

 Melvin Ridge and receives a tributary draining a sag or narrow plain lying 

 between that ridge and the outer moraine of the Bloomington system. It 

 takes a southeastward course through this narrow plain across southeastern 

 Ford, northeastern Champaign, and western Vermilion counties, to the 

 village of Potomac, There it turns abruptly southward and passes through 

 the outer ridge of the Bloomington system. Upon emerging from this 

 moraine it receives West or Salt Fork, which drains a plain in eastern 

 Champaign and western Vermilion counties lying between the Bloomington 

 and Champaign morainic systems. The united stream flows east about 6 

 miles to the city of Danville, where North Fork leads in from the north. 

 That fork drains only a small area among the ridges of the Bloomington 

 system in eastern Vermilion County, Illinois, and adjacent parts of Indiana. 

 From the city of Danville the stream leads southeastward through a till 

 plain to the Wabash Valley. In this portion it trenches considerably into 

 the rock, but above the immediate vicinity of Danville, so far as known to 

 the writer, no rock is encountered' by any of the streams. 



The entire drainage system is independent of preglacial lines, for the 

 drift has built up the surface above the level of the rock divides. A boring 

 at Danville Junction, Illinois, and one near Eugene, Indiana, each strike 

 into a preglacial valle}- in which rock is first encountered at a level 100 

 feet, or more lower than rock ledges in that vicinity which have been cut 

 into by the present stream in deepening its valley. There is no surface 

 indication of the course of the preglacial drainage, but it may be inferred 

 that it passed from the points named into the preglacial valley occupied by 

 the Wabash. The Vermillion also crosses a preglacial valley a few miles 

 below Danville. Its bottom there spreads out to a width of more than a 

 mile, or to more than twice its usual width. This feature is well shown on 

 the Danville topographic sheet. 



