59 



having only a little more than half the average width of 

 the section above. From the quiet pool above, the water 

 moves with increasing speed as it enters the narrows. For 

 ioo yards or so it retains its glassy smoothness, but by the 

 time it passes the second railway bridge it breaks into the 

 tremendous billows of Whirlpool rapids. The old drift 

 banks of the river are well displayed in this section. They 

 are io to 25 feet (3 to 8 m.) high and stand 300 to 500 

 feet (100 to 150 m.) back from the cliff line on either side. 

 The head of the narrow gorge marks the place where the 

 present large-volume cataract resumed gorge making after 

 the smaller cataract had made the narrower section. It 

 is, therefore, a point of correlation with the lake history, 

 for it was the uplift at North Bay, Ontario, which closed 

 the outlet there and sent the discharge of the upper three 

 lakes back to Lake Erie and Niagara. This point in the 

 gorge marks that event, when the volume of the river was 

 suddenly increased nearly sevenfold. 



The Eddy Basin. — Half a mile north of the bridges 

 the cliff line turns to the west and the gorge widens per- 

 ceptibly. This wider part is the Eddy basin. The eddy 

 with its large and gentle return current is in the foreground 

 at the foot of the cliff, while on the far side billows dash 

 across from the mouth of the narrow gorge above. The 

 view to the north looks across the Eddy basin, and the reef 

 and small rapids at its lower side toward the outlet of the 

 whirlpool and the sharp separation of the two deep basins 

 by the upper reef is clearly seen. 



At Sinclair point the Eddy basin and the whirlpool 

 may be seen. The contraction in the width of the gorge 

 is as sudden and pronounced here as is the expansion 

 above the railroad bridges. Lake Algonquin came to an 

 end because the retreating ice sheet opened the outlet at 

 North Bay, Ontario. Before this, Niagara had had the 

 full discharge of the four lakes. But the opening of the 

 new outlet took the discharge of the upper three away 

 and left the discharge of Lake Erie alone, equal to only 

 15 per cent, of the previous volume. The contraction at 

 the upper side of the Eddy basin marks this event in the 

 lake history. 



The Whirlpool from Sinclair Point. — Trees largely 

 obstruct the view of the upper reef from this point, but 



