5o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



j^O. 10 SOLAR RADIATION AND WEATHER STUDIES — ABBOT 6] 



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UNITED STATES LAKE SURVEY 



MONTHLY MEAN WATER LEVELS OF THE GREAT LAKES 



From Official Records. 1910 to dale. 



Fig. 25.— Levels of Lake Ontario, 23-year cycles. Note 



general ■• ^e about the sixth year, also approximate repetition of features a, b, c, d. 



