12 Transactions of the Canadian Institute. [Vol. VII. 



of the original hard rock, the shale having been removed by the action 

 of the water, and its place filled by detritus, Mr. H. Dixon, assistant 

 engineer to Mr. C. H. Mitchell, went with the writer to Queenston, 

 where we, using transit and chain, found the thickness of the different 

 layers of rock and shale along the cliff We tried to correlate the hard 

 layers with those mentioned in the borings under the bridge, but found 

 no relation whatever existing between them. We then decided that 

 these masses of solid rock were simply very large boulders. In his 

 report on the soundings taken under the bridge, the engineer expresses 

 the same opinion. 



The Canadian fall at present furnishes very good evidence of the 

 correctness of the above hypothesis. On the margin of the Horseshoe 

 Fall, both next Goat Island and the Canadian shore, great boulders are 

 lying at the foot of the cliff There is no sign of any such in the centre. 

 Then one of two things must happen, — the rocks sink where they fall at 

 the base of the cliff, or the force of the water carries them down stream 

 to be finally deposited somewhere else. The soundings support the 

 latter hypothesis, for the water is deepest not right under the fall, but a 

 considerable distance down stream. The force of the water carries the 

 rocks forward while their gravity causes them to sink, so they wear out 

 the basin described above. 



The American fall has great masses of huge boulders at its base. 

 These, as in the Canadian fall, have dropped from the overhanging 

 Niagara and Clinton rocks, but the water coming over them is not 

 strong enough to displace them. Accordingly they pile up where they 

 fall, and instead of wearing a deeper hole, protect the underlying shale 

 from erosion and stop the wearing action of the fall. This explains the 

 fact that, so far, observations on the American fall can detect but little 

 retreat, as all differences found in measurement are not appreciably 

 greater than the allowance which may be made for errors of 

 observation. 



Evidences of a similar state of affairs are found at Niagara Glen. 

 The main stream on the American side was strong enough to move the 

 great rock masses, and the erosion went on continuously, leaving a clear 

 channel, while on the Canadian side a fall of water much smaller in 

 volume and corresponding to the present American fall, descended. 

 During the greater part of its course it was unable to remove the larger 

 rocks, though its central part was stronger than the sides, and in the 

 lower part, at least, left a tolerably clear channel. In the upper part, 



