Great Lakes, and their Deformation. 209 



and accurately measured Ridgeway Beach been surveyed, and 

 the warping movements measured therefrom. From the present 

 information, it will at once be seen that the same sheet of water 

 had also access to the Mississippi drainage by the depression at 

 the head of Lake Michigan, which is twenty feet or more 

 below the highest beach in the vicinity, the probable equiva- 

 lent of the Maumee Beach, east of the lake, now about a 

 hundred feet above its surface, near Columbia. 



Elevations of Maumee Beach near : 



Feet above the sea. 



Columbia, Mich, (dunes rise to 699 feet). 683 



Allegan (dunes to 740, terrace) 713 



East of Pewamo (barometric) _ 841 



Imlay _ 849 



Berville . _ 817 



Tpsilanti (terrace) . __ 784 



Adrian _ _ 789 



Fort Wayne (Gilbert) 788 to 778 



Cleveland (Geol. Ohio) 786 



Amount of Warping in the preceding Beaches. — Across the 

 State of Michigan, the Maumee Beach records a differential 

 eastward or northeastward elevation of scarcely more than a 

 foot per mile, while that of the Ridgeway Beach in the same 

 direction is a little less than a foot per mile. 



West and south of Lake Erie the unequal movement is re- 

 duced to almost zero. But east of Lake Erie the uplift reaches 

 two feet per mile as recorded in the Forest Beach. 



East of Lake Huron, the Arkona Beach rises to the north- 

 eastward at l'Yl feet per mile, and the parallel and younger 

 Forest Beach at 1*5 feet. The still younger Algonquin Beach* 

 rises 1 *33 feet, east of Lake Huron. This warping increases 

 so that east of Georgian Bay it amounts to 4*1 feet per mile, in 

 direction N. 25° E. The explored beaches north of Lake 

 Erie have an accelerated rise, so that, northwest of Lake 

 Ontario, it amounts to 3 feet or more per mile, in the higher 

 water margins. If the higher shore-lines in the Adirondacks 

 could be and were surveyed we would expect a differential 

 elevation to the northeast of more than five or six feet per 

 mile, as that amount has been measured in the lower Iroquois 

 Beach. f But most of the differential crust movement has 

 been since the Iroquois and Algonquin episodes. 



Higher coast lines. — There were sheets of water pre- 

 ceding the Maumee episode, for across the higher lands of 

 Michigan, there are extensive belts of flat land or plains 



* "Deformation of the Algonquin Beach," etc., this Journ., vol. xli, 1891, p. 15. 

 f " Deformation of the Iroquois Beach," etc., this Journ., vol. xl, 1890, p. 447. 



