DRAINAGE SYSTEMS AND THE GLACIAL PERIOD. 205 



at Hamilton, twenty-five miles north of Cincinnati, where 

 the valley of the Great Miami is reached, the bedded rock 

 of the valley lies as much as ninety feet below present 

 low-water mark in the Ohio. 



Other indications of the greater depth of the pregla- 

 cial gorge of the Ohio are abundant. " At. the junction 

 of the Anderson with the Ohio, in Indiana, a well was 

 sunk ninety-four feet below the level of the Ohio before 

 rock was found." At Louisville, Ky., the occurrence of 

 falls in the Ohio seemed at first to discredit the theory in 

 question, but Professor Newberry was able to show that 

 the falls at Louisville are produced by the water's being 

 now compelled to flow over a rocky point projecting from 

 the north side into the old valley, while to the south there 

 is ample opportunity for an old channel to have passed 

 around this point underneath the city on the south side. 

 The lowlands upon which the city stands are made lands, 

 where glacial debris has filled up the old channel of the 

 Ohio. 



Above Cincinnati the tributaries of the Ohio exhibit 

 the same phenomena. At New Philadelphia, Tuscarawas 

 County, the borings for salt- wells show that the Tuscara- 

 was is running 175 feet above its ancient bed. The 

 Beaver, at the junction of the Mahoning and Shenango, 

 is flowing 150 feet above the bottom of its old trough, as 

 is demonstrated by a large number of oil-wells bored in 

 the vicinity. Oil Creek is shown by the same proofs to 

 run from 75 to 100 feet above its old channel, and that 

 channel had sometimes vertical and even overhanging 

 walls.* 



The course of preglacial drainage in the upper basin 

 of the Alleghany River is worthy of more particular men- 

 tion. Mr. Carll, of the Pennsylvania Geological Survey, 

 has adduced plausible reasons for believing that previous 



* Geological Survey of Ohio, vol. ii, pp. 13, 14. 



