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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



means computed from the original data for four lakes. It is unneces- 

 sary to include Lake Michigan, for its level practically duplicates that 

 of Lake Huron. Some features, as the low levels of the intervals from 



Fig. 26A. — Levels of Great Lakes, 23-year cycles. 



about the fourth to the tenth year, are so conspicuous as to be striking. 

 This shows distinctly in all of the Lakes, but least so in Lake Superior. 

 It may be remembered in this connection that much of the drainage 

 into Lake Superior comes from far to the north and west in Canada, 



