Niagara Falls 



1895 recognize a single ice-dammed lake. Mr. Upham, on the other 

 Taylor hand, ascribes nearly all submergence to ice-dammed lakes, and 



admits none as marine except that which is proved by fossils. As 

 often happens in such cases, the probability is that the truth lies 

 between these wide extremes. Ice dams have played an 

 important part, but not to the exclusion of marine submergence 

 even at high levels. On the other hand, marine invasion is not 

 available as an explanation for some of the most important areas 

 of submergence. 



The St. Lawrence river and the Great Lakes with their 

 connecting channels are really all one stream. The lakes are 

 great reservoirs which feed the rivers below them, and because 

 they derive nearly all their supply from the lakes the rivers them- 

 selves have almost no independent existence. If anything hap- 

 pens to the lakes to turn their discharge in some other direction 

 the rivers go nearly or entirely dry. Niagara is one of these 

 rivers, and its history is inseparable from that of the lakes above 

 it. Prof. Spencer has described the salient features of the 

 Niagara gorge, and has also given many important facts bearing 

 on the lake history. But certain facts which he does not take into 

 account indicate a somewhat different lake history, and in con- 

 sequence a different Niagara history also. The lake history is 

 recorded in the larger characters, and it seems best therefore to 

 study it first. Reference will be made in the following pages to 

 six papers in which the writer's observations on the abandoned 

 shore lines of the upper lakes are recorded. Another paper dis- 

 cussing the latest chapter in the history of the Great Lakes also 

 belongs to this series. It is entitled, " The Second Lake Algon- 

 quin." It precedes this paper in order, and relates to the lake 

 stages following next after those discussed here. These two 

 papers together cover, in a preliminary way, the whole period 

 from the final disappearance of the great Laurentide glacier down 

 to the present time. But they do not include, except by incidental 

 reference, the period of the glacial recession with its lakes. 

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