THE CINCINNATI ICE DAM. 185 



horizontal position. Through these comparatively horizontal 

 strata the Ohio River has worn a gorge of remarkable uniformity, 

 and several hundred feet in depth. Even to the ordinary observer 

 it is clear that this trough is one of erosion ; for the strata of rock 

 upon one side of the river match those upon the other as precisely 

 as do the two ends of a board which has been sawed apart. The 

 seams of sandstone, coal, and lime rock upon one side correspond 

 to similar seams upon the other ; while the river does not pursue 

 a straight course, but follows, throughout, a very tortuous chan- 

 nel, such as is begun by the meandering of a stream over a nearly 

 level surface. 



The width of this rocky gorge is from a quarter of a mile, 

 where the rocks are peculiarly hard, to a mile or over, where they 

 are more easily disintegrated. For the most part, also, the tribu- 

 taries occupy corresponding gorges, with a width contracted to 

 the proportion of the individual drainage basins. At the junction 

 of the main stream with the tributaries there is usually an en- 

 largement of the gorge such as would naturally follow from the 

 combination of erosive forces which there occurs. These features 

 of the trough of the Ohio and its tributaries give character to the 

 scenery throughout its course. Nowhere from the decks of the 

 steamer does one get an extended view on either side. Every- 

 where the vision is circumscribed by the hills, more or less pre- 

 cipitous, which rise close at hand upon both the right and the 

 left ; while the windings of the channel are such that no very dis- 

 tant views are obtained either before or behind. The railroads 

 which connect the cities in the valley are compelled either to hug 

 the side of the gorge between the river and the precipitous ledges, 

 or to strike up some one of the tributaries, and then, after cross- 

 ing the country for a while, follow down another to the level of the 

 main stream. The land a little back from the trough of the river 

 is very broken and hilly, since all the affluents of any size have 

 eroded channels for themselves down to the depth of the princi- 

 pal gorge. 



Above Louisville, Ky.,the large cities upon the Ohio strikingly 

 reveal the limitations imposed upon them by the character of the 

 river valley. Having begun as a cluster of houses upon the 

 river's bank, they have gradually spread back upon it, until 

 reaching the base of the rocky precipices. With the rapid 

 growth both of population and of improvements in later years, 

 Cincinnati and Pittsburg have literally overflowed their banks 

 and risen to the summit of the hills on either side, the inhabitants 

 being transported from their places of business to their residences 

 by long inclines up which the street cars are drawn at a steep 

 angle to a height of from three to five hundred feet, from which 

 positions extended views are given in every direction over the 



VOL. XLV. 14 



