GLACIATION AND EROSION IN OHIO VALLEY. 119 



a point a few miles below Manchester, Ohio, down to the vicinity of 

 Louisville, Ky. But along the entire lengtli of the present valley assorted 

 material derived from glacial deposits has been distributed, and much may 

 be learned by determining the relation of this assorted material to the 

 valley excavation. 



The portion of the Ohio Valley which has experienced glaciation 

 covers nearly the interval from Louisville up to Maysville, Ky., 190 miles, 

 for the glaciation fell short but 5 to 10 miles of reaching the site of each 

 of these cities. The abandoned course of the Ohio near Cincinnati should 

 also be included, and as this is less direct than the present course it 

 increases the length of the glaciated portion of the valley to about 225 

 miles. Throughout this glaciated portion, including the abandoned course 

 of the stream, the drift deposits are found to extend down to a rock floor 

 lower than the bed of the present river, and as these include till or unmod- 

 ified glacial material it is evident that the excavation of the valley to its 

 lowest depth pieceded that stage of glaciation which produced these deposits. 

 This particular glaciation, as explained farther on, belonged to the Illinoian 

 stag'e. It is certain, therefore, that at that early stage this part of the Ohio 

 was excavated to its full depth. 



ON THE MIDDLE OHIO. 



The Middle Ohio or old Kanawha system is less favorably situated 

 than the Lower Ohio for determining the relation of the glacial deposits to 

 the erosion features, for the part of the Ohio Valley which falls in that sys- 

 tem was not reached by the ice sheet. It is also found that along the Old 

 northward outlet of that drainage system the Illinoian glaciation extended 

 but a few miles beyond the later or Wisconsin glaciation. There are, how- 

 ever, a few features outside the glacial boundary which tln-ow some liglit 

 upon this question. 



Above the level of the Wisconsin glacial terrace which leads down 

 the Scioto to the Ohio there are deposits of gravel and sand derived 

 apparently from Illinoian drift. Their height is 60 to 75 feet above the 

 Wisconsin terrace, and they have been found along the Scioto for about 

 30 miles soxith from the glacial boundary or nearly to the Ohio River. 

 They have been observed only on the remnants of the gradation j^lain of 

 the small stream, which, as above described, seems to have been a southern 

 or southwestern tributary of the old Kanawha, but the presence of glacial 



