Niagara Falls 



1901 cliff, or may be due in part to the superior hardness of the rock 



Hitchcock a j- f ne k ase f t ne f a ll s> as suggested by Professor James Hall. 



Some authors, following Pohlman, believe this part of the 

 gorge was made by a smaller stream in pre-glacial times, perhaps 

 in connection with the St. David's Channel, and before the 

 modern Niagara came into being. This seems inadmissible, 

 because the St. David's Channel evidently required a river of 

 large volume for its excavation, greater than the Erie— Niagara, 

 and the whirlpool rapids' gorge had a later origin. These facts 

 also enforce the conclusion that it is not likely that in any case a 

 small gorge would have been enlarged to the full width by the 

 later greater volume of water. Were this true, this narrow section 

 should show evidences of increasing enlargement during the latest 

 episode of excavation. All agree that the river which excavated 

 this section was of comparatively small size, and, consequently, 

 that the duration of this episode must have been correspondingly 

 great. 



There is a shoal ledge between the whirlpool and Eddy basin 

 not unlike the one between the whirlpool and cove, which was 

 accounted for by supposing the presence of the water removed 

 a rim of rock rapidly, without the aid of the cataract. Mr. 

 Taylor suggests a species of weathering for its presence here. It 

 is presumed that the St. David's Niagara eroded the gorge back 

 to this ledge, when the work suddenly stopped. If the cliff were 

 exposed to the elements for a time, the falling of talus blocks 

 would ensue, with some weathering. Or the ice known to have 

 moved through the buried gorge may have impinged against this 

 ledge and fractured it. It must be remembered that, according 

 to our views, this ledge was exposed for a very long time — 

 while the whole of the gorge between the whirlpool and Lewiston 

 was being excavated; so that the cliff could hardly fail to have 

 been operated upon in some way. When the cataract com- 

 menced above the whirlpool, it would be occupied first with 

 removing debris, and not in channelling out the bottom. These 

 suggestions may show why that ledge remained shoal. 



636 



