GLACIAL SUCCESSION IN OHIO. I 35 



upon comparing the amount of leaching in the two districts. In 

 the earlier drift sheet it is rare to get a response with acid within 

 six to eight feet of the surface, whereas in the newer drift the 

 leaching has seldom been carried to so great a depth as six feet. 

 It seems clear from the position and relations of this old surface 

 that the leaching took place before its burial. 



Concerning the amount of valley erosion accomplished in 

 south-western Ohio during this interval no conclusion was reached. 

 Sufficient time was not given to the study of the region to suc- 

 cessfully eliminate the effects of post-glacial erosion and of 

 erosion accomplished between the deposition of the silt and the 

 invasion which produced the older moraine of the later drift. 

 In eastern Indiana, however, there are exceptionally favorable 

 conditions for determining the amount of erosion accomplished 

 between the deposition of the earlier and later drift sheets, and it 

 is believed that data of some importance can be furnished. Near 

 the head waters of the Whitewater river there is a district 

 covered by a thick deposit of drift. We may judge from wells 

 made on interfluvial tracts that the level of the rock surface in 

 that region is no higher than the valley bottoms of the several 

 headwater tributaries of West Whitewater, and these valleys are, 

 therefore, simply channels cut in the drift. The evidence all 

 opposes the view that the ridges and valleys are in any way 

 dependent upon preglacial erosion. The valleys along these 

 headwater tributaries of the West Whitewater (Noland's fork, 

 Green's fork, and West fork) are conspicuous for their size, 

 their width being one -fourth to one -half mile or more and their 

 depth sixty to one hundred feet. A similar broad valley is occu- 

 pied by the headwaters of East Whitewater, though this stream 

 has, since the later ice -invasion, cut a narrow gorge down into 

 the rock strata. 



This district of eroded drift was overridden by the western 

 edge of the Miami and the eastern edge of the East White River 

 lobe of the later incursion, but it so happens that the amount of 

 drift deposited does not greatly conceal the outlines of these old 

 valleys, the general thickness of the later drift sheet in this region 



