Drainage Features of the Upper Ohio Basin 



vated gradation-plane, or to the upper part of the trench 

 within it. They seem to show that it is inapplicable to the 

 lower part. 



Other changes of drainage in the Ohio Basin. — Though 

 heyond the field of this paper, we call attention, by way of 

 suggestion, to possible changes of drainage in portions of the 

 Ohio basin further west. The present divide between the 

 Lake Erie and Ohio basins in eastern Ohio is apparently much 

 farther north than the preglacial divide, there being a series of 

 deeply filled valleys crossing the watershed and connecting 

 with the Mahoning and Cuyahoga valleys. A well near this 

 watershed, about six miles southwest of Akron, penetrated 400 

 feet of drift and struck rock not far from the level of the sur- 

 face of Lake Erie, though distant 35 miles from the present 

 shore of the lake. Several wells a few miles farther west, in 

 the vicinity of Sterling, penetrate about as great an amount of 

 drift and enter rock at the same low level. How much terri- 

 tory was thus drained to the Lake Erie basin has not been de- 

 termined. The size of the Cuyahoga valley and of the upper 

 part of the Mahoning warrants the presumption that it was a 

 large territory. The relation of these drainage systems to the 

 present watershed, and the lines of possible connection across 

 the watershed, are shown, in part, on map 2. 



We would also add that the small size of the lower Ohio 

 valley is suggestive of great enlargement of drainage area 

 within a recent period. 



The suggestion has been entertained by several geologists, 

 notably Professor J. F. James,* that the Ohio river formerly 

 departed from its present course just above Cincinnati and 

 followed Mill Creek valley to Hamilton, and thence the Great 

 Miami valley to its junction with the present Ohio, and that it 

 was forced from this course by the ice invasion, and caused to 

 cut the trench which it now occupies at and below Cincinnati. 

 This hypothesis is to be carefully distinguished from that of 

 the Cincinnati ice dam, with which it is in ill accord since the 

 Cincinnati trench could not have been dammed until it was 

 formed, and, by hypothesis, it was only formed after the ice 

 forced the river out of the Mill Creek channel. 



It has long been known that the present channel of the 

 Ohio, at Louisville, Kentucky, is recent. Its present location 

 seems to be the result of valley filling during the later glacial 

 stages. 



Summary. — Summing up the preceding, it appears that the 

 evidence is very strong that the two uppermost sections of the 

 Allegheny basin, including also Oil Creek basin, formerly dis- 



* Journal Cincinnati Soc. Nat. Hist., 1888, pp. 96-101. 



