420 



and below. The valley is wide in Morgan County because of the easily 

 eroded Knobstone sandstones and shales, through which the valley has 

 been cut. It is wide in Greene County again on account of the same funda- 

 mental reason. Here the valley is in the soft sandstones and shales of the 

 Chester Group and the Coal Measures. In this county, however, the 

 Illinois glacier undoubtedly was an important factor in widening the 

 valley. In Owen County the strata in which the "Narrows" occur, are 

 hard, resisting limestones, which are little disintegrated by weathering 

 and suffer even less by abrasions. The widening of the valley in this 

 region must be carried on mainly by solution, which is a much slower proc- 

 ess than those involved in the region above and below. This narrowing 

 of the valley is identical with the appearance of the limestone bluffs in the 

 vicinity of Gosport. The same condition is to be seen on the East Fork of 

 the White River, where the valley is exceedingly wide in the Knobstone 

 region, and becomes almost gorge-like in the limestone region. 



Furthermore, if the valley in the limestone region were post-glacial 

 there would be very little alluvium below the present channel. This is not 

 the case. Wells at Spencer prove that the alluvium is at least 100 feet 

 deep, just as it is in the wide regions of the valley. 



White River Valley, then, in its passage across the limestone region of 

 Owen County is not a new opening. It is the same valley that is seen in 

 the wide portions of both Morgan and Greene counties. It is the same 

 valley that has carried the waters of the basin above since the time that 

 the present fundamental topographic features were initiated. In fact this 

 part of the valley and channel is more nearly where it has always been 

 than any part either above or below, for the simple reason that at this 

 point the Illinois glacier but little more than crossed the valley, while 

 both above and below, it crossed for many miles farther, and deranged the 

 drainage accordingly. 



We are now ready for the final chapter of the history of the Flatwoods 

 region, the chapter which really gives the explanation of the Flatwoods 

 phenomena. 



THE GLACIAL HISTORY OF FLATWOODS. 



It is not the writer's purpose to give here a treatise on glaciers and 

 glaciation, nor to give an intricate and detailed history of the period of 

 glaciation known to have been present in the Flatwoods region. The pur- 

 pose here rather is to show the relations of the edge of the Illinois ice- 



