DRAINAGE SYSTEMS AND THE GLACIAL PERIOD. 228 



which have successfully resisted the attrition of the waves. 

 Ordinarily these ridges are steepest upon the side facing 

 the lake. According to Mr. Upham, who has driven over 

 them with me, the Lake Erie ridges correspond, both in 

 general appearance and in all other important respects, 



$k&Mid&Mii 



I! 



Fig. 57.— Section of the lake ridges near Sandusky, Ohio. 



to those which he has so carefully surveyed around the 

 shores of the ancient Lake Agassiz in Minnesota and 

 Manitoba, au account of which will be given a little far- 

 ther on in this chapter. 



