NIAGARA. 253 



flexures of the gorge are determined by those of the river 

 channel above it. Were the Niagara centre above the fall 

 sinuous, the gorge would obediently follow its sinuosities. 

 Once suggested, no doubt geographers will be able to 

 point out many examples of this action. The Zambesi 

 is thought to present a great difficulty to the erosion 

 theory, because of the sinuosity of the chasm below the 

 Victoria Falls. But, assuming the basalt to be of toler- 

 ably uniform texture, had the river been examined 

 before the formation of this sinuous channel, the present 

 zigzag course of the gorge below the fall could, I am 

 persuaded, have been predicted, while the sounding of 

 the present river would enable us to predict the course 

 to be pursued by the erosion in the future. 



But not only has the Niagara Eiver cut the gorge ; 

 it has carried away the chips of its own workshop. The 

 shale, being probably crumbled, is easily carried away. 

 But at the base of the fall we find the huge boulders 

 already described, and by some means or other these are 

 removed down the river. The ice which fills the gorge 

 in winter, and which grapples with the boulders, has 

 been regarded as the transporting agent. Probably it 

 is so to some extent. But erosion acts without ceasing 

 on the abutting points of the boulders, thus withdrawing 

 their support and urging them gradually down the 

 river. Solution also does its portion of the work. 

 That solid matter is carried down is proved by the differ- 

 ence of depth between the Niagara Kiver and Lake 

 Ontario, where the river enters it. The depth falls from 

 72 feet to 20 feet, in consequence of the deposition of 

 solid matter caused by the diminished motion of the 

 river. 1 



1 Near the mouth of the gorge at Queenston, the depth, ac- 

 cording to the Admiralty Chart, is 180 feet; well within the gorge 

 it is 132 feet. 



