Science, Geology and Physics 



green flat, is a rock terrace, 750 feet long, and 600 feet broad, 1901 

 which is believed to have been fashioned by the western part 

 of the early Niagara; and at its northern end is a precipice over 

 which the water fell into Foster's glen. The sloping area between 

 the flat and the river, 2,500 feet long, and 750 feet wide, is 

 covered by immense blocks of Niagara limestone. 



History of the Great Lakes 

 From the statements now made of the history of the great 

 lakes, there seems to have been two former possible outlets for 

 the waters above St. Clair — by the Trent river and Lake 

 Nipissing; and it has been suggested by Dr. Gilbert that, when 

 the discharge was by the former route, the Niagara river cut its 

 way through the shoals at Wintergreen flat; and that when the 

 water flowed through the Nipissing channel, the gorge of the 

 whirlpool rapids was excavated. . . . It is not easy to show 

 just what part of the lower gorge was excavated when the upper 

 lakes discharged through the Trent outlet. At the present 

 writing, it may be best to say that, because of the limited time 

 during which this discharge was effective, no marked effect was 

 produced. 



It is different with the Nipissing outlet. Mr. Taylor has shown 

 that this discharge must have operated for a very long period. 

 The Nipissing beach is recognized upon all the upper lakes, 

 being the best defined of any of the ancient strands. . . . 

 Fully eight-ninths of the water passed to the Ottawa River, 

 leaving only one-ninth of the present volume for the Niagara. 

 Consequently the gorge made by the Erie— Niagara must have 

 been comparatively small. Its width at the top is 750 feet, and 

 the depth of the river estimated at 35 feet. The descent is 

 45 feet, and the length three-fourths of a mile. 



There is quite a contrast between these and the rapids above 

 the cataract, which descend the same amount and have a similar 

 length. The action is deliberate in the one, and impetuous in the 

 other. The shallowness may result because of the want of 

 erosive power in the smaller volume of water falling over the 



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