SPOLIATION OF THE FALLS OF NIAGARA 



297 



dividing currents on either side. Tims for perhaps half of the river 

 from the Goat Island side, I have estimated the mean depth of the 

 water over the rock rim as not exceeding two feet. Indeed, much of 

 it is not over a foot in depth. Nearer the Canadian side it increases 

 to nine feet (see figures 3 and 5). 



Fig. 3. Profile of Rim of First Cascade, with forebay of Ontario Power 

 Company in foreground. 



12. Portion of Falls in Immediate Peril. — As the river is so shallow 

 over the rock rim on the Goat Island side of the main channel, it forms 

 only a thin sheet of water on the eastern side of the Canadian or Horse- 

 shoe Falls, for a distance of 800 feet from the Goat Island end. In- 

 deed, from the changes already effected, this sheet of water has heen 

 reduced in depth by sixteen inches, thus in many places exposing the 

 shelf of rock over which the rapids are passing (figure 4). This por- 

 tion of the falls I had considered as being in most immediate peril, even 

 more so than the American Falls, but recent soundings, about the head 

 of Goat Island, show that a rocky floor extends almost across to the 

 main shore of N"ew York, which in the future must divert to a large 

 degree the supply of water from the American channel between the 

 island and the shore. Accordingly, the American Falls are in equal 

 danger with the eastern side of the Canadian cataract. 



I hope that in this study of the physics of the river, the importance 

 of this rim has been sufficiently emphasized ; for any lowering of the 

 water in the basin, will cause the draining of the higher parts of this 

 rocky barrier, which extends nearly two thirds of the breadth of the 



