THE GLACIAL LAKE CHICAGO. 449 



Its course in Lake County, Indiana, is eastward through Hessvilie 

 and Tolleston and Miller. Farther east it becomes lost beneath the dunes 

 that border Lake Michigan. From the vicinity of Michigan City, Indiana, 

 northward through Berrien, Van Buren, and Allegan counties, .Michigan, it 

 has been extensively removed by Lake Michigan, for the lake bluff usually 

 rises above its level and presents deposits as old as the Second beach. 



The first appearance of a low beach of any notable extent in Michigan 

 is that found in the vicinity of the line of Allegan and Ottawa counties, 

 south of the lake-like expansion of Black River. This beach leads from 

 the shore of Lake Michigan eastward to Holland, Michigan, and there 

 takes a northward course, crossing Black River at the head of its lake-like 

 expansion. It stands about 25 feet above Lake Michigan, except where 

 sand dunes have given it greater height. Along Black River Valley above 

 this beach there is a gravel filling, apparently a later delta than that 

 described above, built up to about 25 feet above Lake Michigan, at the 

 point where the beach crosses, but rising to fully 30 feet near^Zeeland, 3 

 miles east. At the head of this delta there is a marshy valley with a width 

 of a half mile or more, which connects at the northeast with the valley of 

 Grand River, as indicated above. The bottom of this marshy valley at 

 the present divide, near Hudsonville, as shown by the Chicago and West 

 Michigan Railway survey, stands about 45 feet above Lake Michigan, thus 

 allowing only 15 feet fall from Hudsonville to Zeeland, a distance of 'fully 

 12 miles. Below the point where this beach crosses Black River there is, 

 as above stated, a channel which extends 30 feet or more below Lake 

 Michigan. It is a half mile to 1 mile in width, being as broad as the 

 gravel-filled valley above. From the gravel filling to the bottom of this 

 channel there is a descent of 50 or 60 feet in less than 2 miles. It is 

 probable, therefore, that, at the point where the beach crosses, the filling- 

 reaches at least 50 feet. The cause for the abrupt termination of the deep 

 part of the lower course of Black River appears, therefore, to be due to 

 the covering of this part by lake water while the beach and delta were 

 forming at the edge of the lake. It seems probable that the abrupt termi- 

 nation of the deep part of tributaries of Lake Michigan north from this 

 one is due to a similar relation to a beach, but this is merely an inference, 

 as that region has not been visited by the writer. Much remains to be 



MON XXXVIII 29 



