NIAGARA FALLS AND VICINITY 73 



rapidly. " When the Canadian fall reached the head of the island, 

 the American had just passed it, and part of the sheet of water on 

 Wintergreen flat was drained eastward into the gorge opened by the 

 American fall. The Canadian fall, through the loss of this water, 

 became less active, and soon fell out of the race." 1 By the final re- 

 treat of the American fall beyond the southern end of Wintergreen 

 flat, the latter was left as a dry platform with precipitous sides, over 

 which once poured a portion of Niagara's torrent. 



While the occurrence of an island in the position pointed out by 

 Gilbert was undoubtedly the immediate cause of the division of the 

 falls, the more fundamental cause, and the one to which the island 

 itself owed its existence, is to be sought elsewhere. From an in- 

 spection of the map the suggestion presents itself that there may 

 be a vital connection between the abandoned falls at Fosters flats 

 and the great bend of the river at the whirlpool. When a great 

 river runs for a mile or more in a straight line, as the Niagara does 

 above the whirlpool, and then abruptly turns to the right, the cur- 

 rent is deflected by this sudden change in direction to the right bank 

 of the river below the bend, which it continues to hug till again de- 

 flected. It is thus that the greatest amount of water will be carried 

 along the right bank of the river, causing a deeper channeling there. 

 When Niagara falls had receded to the present northern end of 

 Foster's flats, the greatest amount of water was carried over its 

 right side. The resulting deepening of the channel on the right, 

 and the consequent drawing off of the water toward that side, was 

 the cause of the appearance of the island (if such existed, as seems 

 probable from the remaining foundation) above the water and the 

 consequent division of the falls. A precisely analogous feature oc- 

 curs in the lower falls of the Genesee river below Portage. Here, 

 however, no island was formed, though in other respects the two 

 cases are nearly alike. In the Genesee the change has occurred 

 in comparatively recent times, and records of earlier conditions have 

 been preserved. An abrupt bend of the river to the right, deflected 

 the current to the right bank below the bend, and thus caused the 

 deepening of the river bed on that side, as well as the more rapid 



Gilbert. Nat. geog. monographs. Niagara falls and their history. 



