THE CINCINNATI ICE DAM. 187 



broken surface whose summits represent the once comparatively 

 level area. At Parker City, Pa., an elevator was once used to lift 

 foot travelers from the lower terrace to the upper terrace, two 

 hundred feet above. 



Although flowing in so deep a trough, the present Ohio River 

 is considerably elevated above the ancient bottom. This is owing 

 to the fact that during the Glacial period such an excessive 

 amount of gravel was brought down from the Alleghany River 

 and other northern tributaries that the old channel was silted up 

 to a considerable depth. At Cincinnati there is more than one 

 hundred feet of gravel between the present river bottom and the 

 rock bottom. Below the mouths of the most important northern 

 tributaries the accumulations were much greater than this. At 

 Cincinnati the channel was choked with gravel from the Little 

 Miami to a height of one hundred and twenty feet above the 

 present river. Subsequently this was partly eroded away, leaving 

 the one-hundred-and-twenty-foot gravel terrace which is now oc- 

 cupied by Fourth Street. 



It is fortunate for civilization that there are left along the 

 trough of the Ohio numerous remnants of this high-level glacial 

 terrace ; otherwise the cities would be even more subject to damage 

 from floods than they are now ; for the Ohio River is subject to 

 greater fluctuations of level than almost any other stream in the 

 world. During the flood of 1884 the water rose at Cincinnati 

 seventy-one feet, submerging the railroad stations and much 

 of the lower part of the city, but leaving that portion which 

 was upon the glacial terrace fifty feet above water. The cities 

 which were not favored with so marked a gravel terrace, or had 

 not taken advantage of their opportunities, were for many days 

 turned into miniature Venices, the lower stories of the houses 

 being generally submerged by the muddy torrent, and boats 

 being able to pass freely through all the streets. 



The cause of these enormous floods along the Ohio is readily 

 perceived ; for, as already remarked, the slope of the streams rising 

 along the summit of the Alleghany Mountains and flowing into the 

 Ohio is so rapid that the water from the rains and melting snows 

 finds its way into the main trough of the river in an incredibly 

 short time, while the trough is so narrow in places, especially just 

 below Cincinnati, as greatly to impede the progress of the current. 

 Two or three inches of rainfall over two hundred thousand square 

 miles provides an enormous quantity of water, which, upon being 

 suddenly transferred to the river channel, turns a stream which 

 can sometimes be forded in dry weather into a steadily advancing 

 column of water one thousand miles long and from fifty to 

 seventy-five feet deep. It is interesting to watch from the 

 weather bulletins the progress of the waves that move down the 



