NATURAL HISTORY, TORONTO REGION 



visit of Sir Charles Lyell in 1842, and many papers 

 have been written on the subject. The most impor- 

 tant contributions to the literature have been made 

 by Gilbert, Spencer and Taylor, who do not entirely 

 agree as to the succession of events. 



All agree that the falls began at the Niagara 

 escarpment near Queenston on the Canadian side and 

 Lewiston on the American when the ice of the 

 Ontario lobe had so far withdrawn as to set free a 

 large part of the basin. It is probable that the falls 

 began as three separate plunges over the three harder 

 rock layers of the escarpment, the Cataract sand- 

 stone, the Clinton limestone and the Niagara (Lock- 

 port) limestone. The upper limestone is the thick- 

 est and most resistant of the three beds, so that ulti- 

 mately the two lower falls worked their way back 

 to the upper fall, probably at Niagara Glen; since 

 then there has been only one fall. 



The Niagara gorge is 300 feet deep at Queenston 

 Heights, but diminishes to 158 feet at the Canadian 

 or Horseshoe Fall. Dr. Spencer has sounded below 

 the falls, finding a depth of water of 192 feet, maki 

 a total depth of 340 feet for the chasm. 



The width of the gorge varies to an important 

 degree, having two stretches which are narrower 

 than the rest, at Niagara Glen and just below the 

 railway bridges, both accompanied by powerful 

 rapids. These narrower portions may be accounted 

 for by supposing the greater part of the drainage of 

 the Tipper Lakes to be diverted to the Trent Valley 

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