350 H. H. ROBINSON 



line and evidently vary in height on the shores of different lakes. 

 The configuration of the shore and its relation to the direction of 

 storms exercise a great influence on the height of such beaches, and 

 many interesting observations have been made on this point/ 

 Lawson states^ that on the north shore of Lake Superior he measured 

 crests of living beaches facing the open lake at all elevations between 

 9 and 14 feet above calm water, while in less exposed parts of the 

 shore they did not usually exceed 6 feet in height. Goldthwait,^ for 

 the western shore of Lake Michigan, sets the upper limit at 6 feet, and 

 in one instance possibly at 8 or 9 feet. A correction should be applied 

 to Lawson' s figures, at least, to allow for the drop in the lake level 

 from the high-water stage of 1886 to the 1891 stage on which his 

 observations were based. This correction may be taken at 2 feet, so 

 that the figures read 7, 12, and 4 feet, respectively. The error intro- 

 duced by the variable position of a beach may be placed at 4 feet, 

 allowance being made for the 3-foot correction above noted. 



3, Cyclic fluctuations in water-level of the ancient lakes, due to 

 short climatic variations, no doubt occurred as they do in the present 

 lakes. The Milwaukee (Wis.) record shows an average change of i . 5 

 feet in the level of Lake Michigan from summer to winter. Lane says : 

 "The water-level of the lakes at those (former) times undoubtedly 

 varied from year to year and from month to month as it does now, 

 probably in even more marked degree, as the cold of winter would 

 have even more effect in checking the flow of water from the ice sheet ;"4 

 while Upham states: "Fluctuations of the lake level (in Lake Agas- 

 siz) , which doubtless rose in summer a few feet higher than in winter 

 because of variations in the volume of water supplied, have given a 

 variability within the limits generally 5 feet and perhaps sometimes 

 8 or 10 feet apart to the heights of the lake and of its shore deposits 



1 Chas. Whittlesey, "Fluctuations in the Level of the North American Lakes." 

 Smithsonian Contributions to Knowledge. Vol. XII; A. J. Henry, " Wind Velocity 

 and Fluctuations of Water Level on Lake Erie," U. S. Weather Bureau, Bull. J., 1902. 



2 A. C. Lawson, "Coastal Topograph)' of the North Side of Lake Superior," 

 Geological and National History Survey oj Minnesota, Twentieth Annual Report, 

 p. 231. 



3 Personal communication. 



4 A. C. Lane, "Geological Report on Huron County, Michigan," Geological Survey 

 0} Michigan, Vol. VII, Pt. II, p. 65. 



