Whirlpool and Rapids beloiv the Falls of Niagara 



29 



of the 



grounds. 



The ques- 



tion naturally arises, how is 

 it possible for this immense 

 volume of water to escape 



through 



so narrow a 



On 



referring 



to 1 



defile, 

 and then suddenly to become i 

 comparativel 

 whirlpool. 



Mr. Lyell's admirable work on 

 America which I had with me, 

 and examining the section of 

 the strata from Niagara to the 

 whirlpool, which Mr. L. had 

 taken from Mr. Hall's geologi- 

 cal Report on the Geology of 

 New York, it occurred to me 

 that a satisfactory explanation 

 might be given. The projec- 

 ting rock under the water is un- 

 questionably the hard quartz- 

 ose sandstone, and underneath 

 this lies a very thick bed of 

 soft red shale. A short dis- 

 tance before the waters enter 

 the whirlpool, this floor of 

 hard sandstone rock is broken 

 through, and the resistless tor- 

 rent has made itself a passage 

 underneath this rock, on each 

 side of the ravine, and it is by 

 this excavation that the waters 

 escape. This perhaps will be 

 made more apparent, when ex- 

 plaining in the sequel the sup- 

 posed origin of the whirlpool. 

 The section, fig. 12, is prin- 

 cipally from Lyell, in which 

 I have introduced the river, 

 whirlpool, and the ancient late- 

 ral valley, (H,) filled with drift. 

 In the following remarks, great 

 stress is laid on the relative 

 hardness of the rocks which 

 compose the Niagara group: 

 consisting as it does, of hard 

 limestone, calcareous shale, 

 soft shaly sandstone, and of 

 quartzose sandstone. Had all 

 the strata consisted of solid 

 limestone, as I remarked in 

 the communication before re- 



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