HAMILTON SCIENTIFIC ASSOCIATION. 33 



form settling basins, and all mud and sediment are deposited in 

 them. 



It is unique in other respects. Steamships of the largest ton- 

 nage can go up it 1,000 miles, to Montreal in fact. Another 

 unique feature is Niagara fall. I do not need to describe the Falls 

 to people in Hamilton. I was rather annoyed to see the many 

 ugly buildings they are putting up to disfigure the Falls. But I 

 suppose we must make use of the great power going to waste there. 



A vertical fall of 160 feet is not found in any other large river 

 in either America or Europe. How is this one to be accounted 

 for? A river always cuts its way farther and farther back, wear- 

 ing off first the upper edge of the cliff and becoming a cataract, 

 then a rapid, then in time a smooth stream. Why has the Niagara 

 not done this ? ' There are two things we can say about that. 

 Niagara is a young river. It did not build the canal in which it 

 flows. There was a time when the Upper I^akes flowed out across 

 from Lake Huron to I^ake Ontario at Scarboro Heights and To- 

 ronto. However, the last Ice Age that came along built up a great 

 morain of hills, 700 feet high, across the bed of the stream. The 

 outlet of that river was turned. When the ice departed the river 

 went a new way, and found a place at Queenston where it could 

 fall over a cliff. The Falls were at Queenston then. They have 

 since cut back to their present location, and are still cutting back. 



That the Falls are vertical is due to the geological structure. 

 The cliffs are composed of hard limestone on top. Under that 

 there are soft rocks. When the fall comes tumbling over it makes 

 a great eddy. The soft shale is undercut, so that the last part to 

 wear away is the top. If things go on long enough without inter- 

 ference it will in time wear its way back to I^ake Erie, 



