6 ON THE FRESH-WATER GLACIAL DRIFT 



northwest do not differ materially from those of Wisconsin. Those at the head 

 of the Oconto river, and those between Sheboygan and Fond dn Lac, are more regular 

 in their outline than they are further north, on the Mesabi Range, in Minnesota. 

 Here on the dividing ridge, between the St. Louis and the Vermilion rivers, the 

 boulders are large, with less gravel and earth filling the interstices. To the west- 

 ward of the Apostle Islands, in Lake Superior, near Bayfield, Wisconsin, there are 

 huge terraces of boulders, with very little earth, rising from 400 to 600 feet above 

 lake level. 



Fig. 3. 



Outline views of Moraine Hillocks and Cavities. Randolph, Portage County, Ohio. 



Ease line about 500 feet above Lake Erie. 



View looking west. Height of summits above base 100 to 120 feet. 



Looking southwest. Elevation 70 to 80 feet above base. 



In other places, both north and south of Lake Superior, there are patches of 

 boulders nearly level, from among which the finer materials have been washed 

 away. A few miles to the northeast of the Twin Falls of the Menominee river, 

 in Michigan, there is, on the northern slope of a mountain, a field of boulders, 

 nearly a mile across. Every step in that distance might be taken Avithout touching 

 the soil. The boulders are smoothed and polished by attrition, and are forced 



