NIAGARA. 201 



of the gorge are determined by those of the river chan- 

 nel above it. Were the Niagara centre above the fall 

 sinuous, the gorge would obediently follow its sinuosi- 

 ties. 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 tolerably uniform texture, had the river been ex- 

 amined 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 pre- 

 dict the course to be pursued by the erosion in the 

 future. 



But not only has the Niagara River 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 ceas- 

 ing on the abutting points of the boulders, thus with- 

 drawing 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 dif- 

 ference of depths between the Niagara River and Lake 

 Ontario, where the river enters it. The depth falls 

 from 72 feet to 20 feet, in consequence of the deposi- 

 tion of solid matter caused by the diminished motion 

 of the river.* 



* Near the mouth of the gorge at Qtieenston, the depth, ac- 

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

 gorge it is 182 feet 



