Drainage Features of the Upper Ohio Basin. 249 



mile or more to less than one-fourth of a mile. This constric- 

 tion appears clearly to be the point at which a former col was 

 located and across which the stream was forced when reversed. 

 (2) From this point the buried rock floor of the valley slopes 

 northward to the vicinity of Steamburg, New York, in direct 

 opposition to the present flow of the river. (3) Here it is met 

 by a buried rock floor sloping with the present stream, but 

 from this point there is a broad continuous valley deeply 

 filled with drift leading westward and northward along the 

 line of the upper Conewango (reversed), and the lower Catta- 

 raugus valleys to the Lake Erie basin. The evidence of this is 

 in part shown diagram matically in the accompanying section 



State line. . Warren 



S6 j, Russell burg 



Sheffield. 



a;. 



izso' iZ6o- 



Profile B. 



Dayton. 

 Gowinda 



776' 

 Versailles i 

 LakefrU *?"' '-M 



State. Line, 

 frewsburg ! 



lifo' nia' Russelibury 



i; «,»■»■' mo' 1 Warren. 



'■ ■ j ! ii56: 



/?ne/c Floor-. - 



prob&?'~. 



"level of Lake Erie [173' A. T.) 



Profile C. 



n Milm. 



o 5 io is- 



Vertical Scm.£ 50 Times Horiiontau 



Dayton. 



Randolph. ... , . 



Rutledoe. Steamburg dta - be Lm * 



Kinz.ua 



I2./5' 



PROFILE D. 



Figure 1. Profile A shows the erosion interval between the early glacial grav- 

 els and the late glacial or moraine-headed terrace in the Conewango valley and 

 their altitudes compared with the head of the early glacial gravel train on the 

 Tionesta at Clarendon. With the exception of the rook floor the fluvial planes on 

 the Conewango and upper Tionesta belong to different drainage basins ; the sec- 

 tion is accordingly broken between Clarendon and Warren. The upper of the 

 two broken lines connecting the rock floor at Clarendon with that near Warren 

 was certainly reached by pre-glacial streams, and possibly the lower one. Else- 



