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POPULAR SCIENCE MONTHLY. 



which commenced with the submergence of the lake district to 

 sea level. 



The Tilting of the Ancient Shore Lines. The shore lines 

 of ponds, lakes, or seas are alike water levels. In this respect the 



Fig. 10. Ancient Bowlder Pavement of Algonquin Beach, whose crest rises one hundred 

 and eighty-seven feet above Georgian Bay, upon the northeast side of Blue Mountains 

 of Collingwood, Ontario. 



elevated coast lines present a striking difference from those now 

 being formed, for the abandoned strands are everywhere tilted 

 toward the northeast (see Figs. 11, 12, 15). 



The tilted beach represents the deformation of the Algonquin 

 beach. At the head of Lake Erie the deformation of the old 

 water planes is not over a very few inches in a mile, while it 



Fig. 11. Section of the Lake District from the Highlands of New York to those of 

 the Laurentian Hills North of Lake Huron, along a Line passing through Buffalo 

 and La.ke Nfpissing. Length of section, four hundred miles ; heights given in feet; t is 

 a ridge of drift north of Lake Ontario. The tilted beach represents the Algonquin plain 

 deformed. 



increases toward the northeast, so that it amounts to four feet per 

 mile northeast of Lake Huron, and seven feet per mile near the 

 outlet of Lake Ontario and north of the Adirondack Mountains, 

 to which locality the writer himself has traced the deserted shores 



