Drainage Features of the Upper Ohio Basin. 257 



the hard subcarboniferous conglomerate appears, that is, from 

 Cobham near the Thompson col to the Brady bend below the 

 mouth of the Clarion, a distance of about 100 miles, the rock 

 floor descends 2"7 feet per mile, fluctuating between 6'85 for a 



few miles below Cobham, near where the stream is supposed to 

 have taken its rise, to "95 in the 18 miles immediately above 



