54 



falls have cut back half a mile farther the American fall 

 will run dry. These would appear to be natural tendencies 

 of development, but the interference of man may modify 

 them. 



The Dufferin Islands. — This group of small, low 

 islands forms part of the abandoned floor of a relatively 

 small embayment cut sharply into the deep drift sheet 

 which forms the southern bank of the river at this point. 

 The islands and the embayment in which they lie are of 

 relatively recent origin. The islands were four in number 

 and were divided by channels 50 to 100 feet (15 to 30 m.) 

 wide through which streams one to four or five feet 

 (1 to 1 -5 m.) deep rushed with rapid currents, but recently, 

 dams have been constructed with gates controlling the 

 volume of the two streams and another dam at the outlet 

 produces a large pond in the bend of the main stream south 

 and west of the islands. 



The embayment appears to be related to the rock 

 ledges which formed the First and Second cascades at the 

 head of the rapids. The bed rock dips gently toward the 

 south, so that its surface is lower at Dufferin islands 

 than at Sister islands on the north side. On this account 

 the line of deepest water and the strongest current has 

 had a tendency to hug the Canadian shore. In conse- 

 quence the river has been and is still cutting its bank 

 on the Canadian side. The Dufferin channel starts in 

 just above the First cascade and re-enters the river 

 below the Second cascade. This gives it a rapid descent 

 and high cutting power. The high, steep bluff which 

 borders the embayment shows how effective that cutting 

 was. The surface of the islands is composed mainly of 

 gravel, showing that they formed the floor of the embay- 

 ment as the cutting progressed. 



Chippawa Creek and the River above the Rapids.- 

 It is worth while to make the short trip on the car from 

 the head of the rapids to the village of Chippawa, in 

 order to get a view of the wide, placid river above the 

 rapids. Here the river is seen flowing quietly in a wide 

 shallow bed between banks of drift. At Chippawa the 

 river is a mile wide and its greatest measured depth is 

 22 feet (6-7 m.), about 1,000 feet (300 m.) from the south 

 shore. For several miles above the rapids the river 

 bank on the Canadian side is a freshly cut bluff of till, 

 while on the New York side the bank is an old, low bluff 



