14 GEOLOGY OF OHIO. 



the trough has not been reached. The falls of the Ohio, formed by a 

 rocky barrier across the stream, though at first sight seeming to disprove 

 the theory of a deep continuous channel, really affords no argument 

 against it ; for here, as in many other instances, the present river does 

 not follow accurately the line of the old channel, but runs along one 

 side of it. At the Louisville falls, the Ohio flows over a rocky point 

 which projects from the north side into the old valley, while the deep 

 channel passes on the south side, under the lowlands on which the city 

 of Louisville is built. 



The tributaries of the Ohio exhibit the same phenomena. At New 

 Philadelphia, Tuscarawas county, the borings for salt wells show that 

 the Tuscarawas is running 175 feet above its ancient bed. The Beaver, 

 at the junction of the Mahoning and Chenango, 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 some- 

 times vertical and even overhanging walls. 



An old channel of Mad river, now completely filled up, has been brought 

 to light by the railroad cutting at Springfield. It is described by Prof. 

 Orton in his report on Clarke county, and I here reproduce his notes upon 

 it, and the figure which illustrates them : 



" An old valley of Mad river is disclosed in the heavy cut of the Atlantic and Great 

 Western Railway, from the river bridge westward to Col. Peter Sinz's crossing. A 

 sketch of the course of the river, and also of the railroads that cross it, is appended, 

 by which the facts can be more readily understood. The tongue of land that occupies 

 this bend of the river has an elevation of 100 feet to 125 feet above the level of the 

 stream, and gives no hint in its contour of any break in the rocky floor underlying it. 

 The Sandusky railroad (O. S. & C), which was first in order of construction, cuts 

 across this tongue, as will be observed in the figure. A considerable portion of this 

 cut is wrought in solid cliff rock, the maximum depth of the stone cutting being 18 

 feet. With these facts before them, and guided also by the contour of the land, the 

 Atlantic and Great Western Company, whose line crosses the river half a mile higher 

 and on a grade of ten feet below the first road, expected also to find rock, and made 

 arrangements for tunneling the hill. The route that they selected, however, chanced 

 to be a buried channel of the river, which allowed an open cut of 65 feet through clay 

 and san4, instead of a rock tunnel. Soundings that have since been made from the 

 track to the level of the river show Drift materials through this whole extent. The 

 dotted lines in the figure indicate the buried channel, whose general limits can be as- 

 signed with a good degree of accuracy from the cliffs that remain and the soundings 

 that have been made. 



"It will be observed that the old channel was much Bhorter and more direct than 

 that which the river has since wrought out for itself, accomplishing in three-fourths 

 of a mile the same advance that is now gained by two and one-half miles." 



