66 NEW YORK STATE MUSEUM 



Fluvial period 



Niagara falls came into existence when the waters of Lake Iro- 

 quois, the predecessor of Lake Ontario, fell beneath the level of the 

 escarpment at Lewiston. At first it was only a small cataract, but 

 day by day, as the lake subsided, it gained in hight and consequently 

 in force of fall, as well as efficiency in cutting its channel. That the 

 entire gorge from Lewiston to the present falls is the product of 

 river erosion is scarcely questioned by any one today, but there are 

 excellent reasons which lead some to believe that this cutting was 

 not wholly the work of the Niagara. When the falls were at Lewis- 

 ton, the Niagara was a placid stream from Lake Erie to near the 

 falls, much as it is today from Buffalo to the northern end of Grand 

 island. Its banks consisted chiefly of glacial till, into which terraces 

 were cut by the stream, most of which are visible at the present day. 

 The lower ones are well marked in Prospect park, though there 

 they have been grassed over and modified to a considerable extent. 

 From Niagara falls to the railroad bridges at Suspension Bridge, on 

 the New York side of the river, the old bank runs parallel to the 

 edge of the gorge and at a short distance inland from this. From 

 Suspension Bridge to the whirlpool it makes a curve somewhat more 

 crescentic than that of the margin of the gorge, and a similar curve 

 from the whirlpool to Bloody run at the Devil's hole. On the Can- 

 adian side these old river banks can be traced from above the falls 

 almost to Brock's monument, and in some cases two or three suc- 

 cessive terraces are recognizable. In Queen Victoria park they 

 constitute the steep slope which bounds the park on the west, and 

 parts of which are still actively eroded. Less than a mile below 

 the carriage bridge, the old banks approach close to the modern 

 one and continue, almost coincident with it, to the railway bridges 

 at Clifton. From here to the whirlpool the old river margin has a 

 nearly straight course, while the modern one is curved, and a similar 

 relation holds below the whirlpool, though here, from the great 

 curvature of the modern channel, the old banks are in places nearly 

 a mile distant. 1 (Plate 6) 



1 These old river banks are indicated on the geologic map by dotted 

 lines; the localities where shells have been found are shown by crosses. 



