17 



at two different times in the past the first three of these 

 lakes discharged their whole overflow by another route, 

 not passing through Niagara. Taking the lake stages in 

 the order of their occurrence as named above, and noting 

 the lake area and the approximate frontage of the ice 

 sheet involved in each, with the location of the outlet, the 

 causes and times and approximate amounts of variation 

 of the volume of Niagara river are clearly and fully revealed. 



1. Early Lake Algonquin. — This lake occupied the 

 south half of the Lake Huron basin and received a large 

 affluent from smaller lakes in the south part of Georgian 

 Bay basin and the Lake Simcoe basin. The ice barrier 

 spanned Lake Huron from side to side and nothing was 

 received during this stage from the Lake Michigan or 

 Lake Superior basins. The volume of discharge was 

 relatively large however, for the lake and its affluents 

 all received large tributaries directly from the ice sheet 

 all along their northern sides. The outlet of early Lake 

 Algonquin was southward through St. Clair and Detroit 

 rivers to Lake Erie and the discharge through Niagara 

 river was correspondingly greater than that from Lake 

 Erie alone. The whole volume of Niagara river at that 

 time was probably nearly if not quite as large as it is now. 



2. Lake Algonquin, Kirkfield stage. — This lake occu- 

 pied the basins of Lakes Superior, Michigan and Huron 

 and some of the low-lying lands bordering upon them. 

 It did not attain its full extent in this stage, however, 

 because the ice barrier still occupied large areas along 

 its northern side. Thus, besides carrying the full dis- 

 charge of the upper three lakes, Lake Algonquin at this 

 stage received a large inflow of water directly from the 

 ice sheet, and its total discharge was therefore in all 

 probability slightly greater than the volume of the present 

 St. Clair river. The outlet was at Kirkfield, Ontario, 

 down the valley of Trent river to glacial Lake Iroquois, 

 which was in part a contemporary of Lake Algonquin. 

 The features of this outlet channel, caused by the scouring 

 action of the great river, are strongly developed throughout 

 its course and show unmistakably the great size of the 

 stream. 



3. Lake Algonquin, Port Huron stage. — At this 

 stage Lake Algonquin covered nearly the same ground 

 as before. The uplift of northern lands which changed the 

 outlet from Kirkfield to Port Huron raised considerable 



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