Science, Geology and Physics 



still preserve many base levels of erosion — the doctrine of which 1898 

 has not been applied to them, and consequently their history is as penccl 

 yet unwritten. The extreme views concerning glacial erosion, 

 held a decade ago, are now greatly modified and do not belong 

 to the present day. 



In 1882, fragments of great beaches, and others which were 

 delta deposits, were described as occurring about the western 

 end of Lake Ontario at various elevations from 500 feet above 

 the lake down to its present level. 1 Other fragments of beaches 

 had been known for many decades, the most notable of which 

 were the ridge roads of New York state, that Prof. James Hall, 

 as early as 1 842, found to be rising gently upon proceeding east- 

 ward; 2 and the same was found to be true at the eastern end of 

 Lake Ontario. About this time Prof. Gilbert was studying the 

 beaches of the western lakes, and Mr. Warren Upham those 

 of the Winnipeg basin. The beaches in both places were found 

 to record the evidences of gentle terrestrial movements. Follow- 

 ing up his investigations, Prof. Gilbert connected the various 

 fragments of a great beach upon the southern and eastern sides 

 of Lake Ontario, as far as Adams Centre, near Watertown, 

 N. Y., and found that the old waterline was deformed to the 

 extent of several hundred feet in proceeding northeastward. This 

 was an admirable piece of work, which was invaluable to the 

 writer, who extended the observations further 4 and made use of 

 them in measuring the amount of the long sought for terrestrial 

 deformation as the outlet of Lake Ontario, and found that these 

 post-glacial movements were sufficient to account for the rocky 

 barrier across the Laurentian valley, producing the basin which 

 retains the waters of Lake Ontario. The channels across this 

 rocky barrier, however, were closed with drift deposits reaching 



1 Surface geology about the region of the western end of Lake Ontario, 

 cited before. 



2 Geology of N. Y. Vol. IV, 1843, p. 351. 

 3 Rept. A. A. A. S., Science, Sept., 1885, p. 222. 



4 The Iroquois beach; Spencer. Trans. Roy. Can., 1889, pp. 121- 

 134. Reaa Phil. Soc, Wash., Mar., 1888. 



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