DRUMLINS. 287 



in Dodge and Jefferson counties, these are mainly replaced by 

 long parallel ridges, sometimes several miles in length, with 

 corresponding linear marshes interspersed. These correspond 

 accurately to the direction of the ice-motion. " * According to 

 Mr. Upham, drumlins are not found in the abundant drift of 

 Minnesota. A few examples are mentioned for Pennsylvania, 

 near its western border, by Professor Lewis, f 



In endeavoring to account for this class of hills, two or 

 three facts are of special importance : 1. The material of 

 which they are composed is very heavy and compact — almost 

 as heavy and compact, indeed, as ice. Such masses could 

 not have been shoved along bodily beneath the ice. In fact, 



Fir,. <2.— Dnimliii- in GofEstown, N. H. (Hitchcock.) 



there would seem to be no reason why they might not resist 

 the erosion of the glacier almost as well as many of the softer 

 rocks did. especially when we remember that the pressure of 

 the ice on the bottom need not have been uniform, but 

 greater in some places than in others. 2. There are many 

 indications that these hills were formed by accretion under 

 the ice. there being, as Mr. Upham has shown, a tendency to 

 lamination or coarse glacial stratification in the structure of 



* "Geology of Wisconsin." vol. i. 1883, p - 



f "Second Geological Survey of Pennsylvania, Z," pp. 29, 188. 



