238 J. W. GOLDTHWAIT ALGONQUIN AND IROQUOIS BEACHES 



For the Lake Michigan district these measurements give an average 

 of 605 feet. Measurements with hand-level and aneroid barometer and 

 contours of a large-scale map of the Sanitary District of Chicago agree 

 in putting the height of the "Toleston," or "Algonquin/' beacli close to 

 600-605 feet around the south end of Lake Michigan. At the south 

 ends of Saginaw Bay and Lake Huron the measurements average 607 

 feet. The altitudes at all 19 localities range from 603 to 610 feet. All 

 of this variation of 7 feet can be accounted for by original differences in 

 height of construction of the beach by the lake. 



Even if we take the strong 596-foot (Nipissing) shoreline of the Lake 

 Michigan basin as the equivalent of the 607-foot beach of the Lake 

 Huron basin (although in the latter basin also is a strong shoreline at 

 596 feet, which seems surely to be the equivalent of the Nipissing beach 

 of the Michigan basin), the extreme variation in height is between 593 

 feet and 610 feet, and of 40 wye-level measurements already recorded 

 only one is below 595 feet. Thus for 350 miles from east to west and 

 for 200 miles from north to south there is a variation of scarcely 17 feet 

 in altitude, at most, of the Algonquin beach, and, if the distinction be- 

 tween the Algonquin and the Nipissing shorelines has been correctly 

 made, of not more than 7 feet. 



That the beaches around the head of Lake Michigan give little indica- 

 tion of differential uplift has long been recognized by those at work in 

 the district, as reference to papers by Leverett, Alden, and others given 

 above will show. The gathering of wye-level measurements has simply 

 put the conclusion on a more satisfactory basis than heretofore, and has 

 shown that the horizontal condition is more nearly absolute than might 

 previously have been supposed. 



The horizontality of the Algonquin plane is also wholly in harmony 

 with the conclusions reached by Leverett and Taylor several years ago in 

 the case of the beaches of lakes Maumee, T^Hhittlesey, and Warren, around 

 the south and west sides of Lake Erie. For Lake Maumee, Leverett 

 states that 



"west of the Ohio-Pennsylvania line the slight variations displayed by each of 

 its beaches are no greater than may be found along the present shore of Lake 

 Erie; but near the Ohio-Pennsylvania line a differential uplift has caused the 

 beaches to increase perceptibly in altitude in passing eastward."" 



In the same region, the beach of Lake Whittlesey for a stretch of 200 

 miles varies less than 15 feet in altitude. 



^ Leverett : Glacial formations and drainage features of the Brie and Ohio basins. 

 Monograph of the tJ, S, Geological Survey, vol. 41., 1902, p. 739. 



