Niagara Falls 



1903 Niagara gorge occupied by the whirlpool rapids, having a middle 



Up m vertical fall over the Clinton limestone and terminating at an 



upper vertical fall over the Niagara limestone, above which, in 



its approach from the south, the stream was only a little lower 



than the adjoining country. 



Some of the latest contributions to the geologic literature of 

 Niagara, by Taylor, Hitchcock, and Gilbert, assign to the St. 

 David's channel an interglacial age, and regard it as the course 

 of a great river, an interglacial Niagara, which was allowed the 

 time requisite for the erosion of a gorge about three and a half 

 miles long, from the escarpment near St. David's to the south 

 side of the whirlpool, but was then interrupted by the accumula- 

 tion of ice again deeply enveloping all this region. This explana- 

 tion, however, seems to me inadmissible, because the St. David's 

 channel expands northward to the width of more than a mile 

 before it intersects the escarpment. If it had been cut by a 

 great interglacial cataract, its width would be nearly uniform, 

 like the present river gorge. A comparatively small stream, on 

 the contrary, working slowly through many million years, would 

 have the older part of the valley thus widened by the very long 

 subaerial decay and retreat of its rock cliffs on each side. So 

 great lateral erosion cannot be ascribed to glaciation, which was 

 light upon this area of confluent ice currents from the northeast 

 and northwest, with consequent deep drift deposition. 



Immediately after the melting of this southern part of the ice- 

 sheet and the withdrawal of the ice-dammed Lake Warren, the 

 Niagara river began to erode its gorge, and it has continued in 

 this work, under varying conditions, to the present time. It found 

 a lower passage along the course of the gorge to Lewiston than 

 in the course of the preglacial channel, deeply drift-covered, 

 between the whirlpool and St. David's. From my renewed 

 examination of these areas a year ago, with the aid of the con- 

 toured map distributed by the United States Geological Survey 

 at the Pan-American Exposition, of the latest studies by Gilbert, 

 published on the reverse side of the map, and the valuable 



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