Niagara Falls 



1898 In concluding a notice of this early work, 1 the modern aspect 



pencer Q f ^ e Niagara Ydver was emphasized, and the valley of St. 



Davids was regarded as of inter-glacial origin — in deference 

 to the prevailing theories of the time — in place of being, as is 

 now known, the channel of an insignificant stream of greater 

 antiquity. The Finger lakes of New York were explained as 

 closed up valleys which had formerly drained the rivers of the 

 highlands of New York, as for example Seneca lake, which 

 has since been found to be the ancient course of Chemung and 

 its tributaries. About this time the writer, from the data col- 

 lected by the Geological Survey of Pennsylvania, pointed out 

 the probability that the Monongahela and upper Ohio had 

 formerly been reversed and drained into the Erie valley. 2 This 

 hypothesis was afterward amplified by Dr. P. Max Foshay, 3 

 disputed by Prof. I. C. White; modified and confirmed by Mr. 

 F. Leverett, 4 and finally, with some modifications, reconfirmed 

 by Prof. I. C. White. 5 In order to test the validity of his 

 objections to the hypothesis of glacial excavation, the writer 

 visited Switzerland and Norway for the purpose of personally 

 observing the mechanical effects of modern glaciers, with the 

 result that he saw in them only the agents of abrasion — the ice 

 moulding itself round obstructions, or smoothing off irregularities, 

 and not ploughing out channels. 6 Indeed, in a more recent visit 

 to Norway, it became apparent that the great glacial valleys 



1 A short study of the features of the Great Lakes. Spencer. Proc. 

 A. A. A. S., vol. XXX, 1881, pp. 131-146; Surface Geology of the 

 Region about the western end of Lake Ontario. Spencer; Can. Nat., vol. 

 X, 1882, pp. 213-236, 265-312. 



2 On the ancient upper course of the Ohio river emptying into Lake Erie. 

 Proc. Am. Phil. Soc, Phila., XIX, 1881. 



3 Preglacial drainage and recent geological history of western Penn- 

 sylvania. Am. Jour. Sci., vol. XL, 1890, pp. 397-403. 



4 Pleistocene fluvial plains of western Pennsylvania. Am. Jour. Sci., 

 XLII, 1891 , pp. 200-2 1 2 ; and Further studies of the Upper Ohio basin. 

 Am. Jour. Sci., XLVII, 1894, pp. 247-283. 



5 Am. Geol., vol. XVIII, 1896, pp. 368-379. 



"The erosive power of glaciers as seen in Norway. Geol. Mag., Lond., 

 Dec. iii, vol. IV, 1887, pp. 167-173. 



614 



