312 



PLEISTOCENE OF INDIANA AND MICHIGAN. 



surface of the drumlin until lodged in a position that offered least resistance to the ice movement. 

 Most of them show on both then* upper and under surfaces striation whose direction generally 

 coincides somewhat closely with the trend of the axis of the drumlin. The position of the 

 rock slabs, the indistinct bedding of the deposit, and the thorough admixture of pebbles seem 

 to bear evidence to the growth of the drumlins by slow accretion. 



In certain situations, however, evidences are not wanting of sculpturing of the till into 

 drumlin form. Shale lulls, which have been shaped into drumlinoid form as a result of the ice 

 movement over them, are found south of East Jordan in northern Echo Township, Antrim 



Figuke 3.— Drumlins in T. 33 N., E. 7 W-, Charlevoix County, Mich. 



County. A till drunilin near these shale hills is partly encircled at its northwest end by a 

 crescentic groove several feet in depth which appears to have been formed by the ice as it met 

 the obstruction presented by the drumlin, just as similar grooves are formed on a striated surface 

 on the stoss side of slight prominences on a rock surface. When the ice struck the drumlin it 

 appears to have intensified its action on the plain at the base of the drumlin and thus produced 

 the deep furrow. The flu tings which some drumlins display seems likely also to be due to sculp- 

 turing effect of the ice. The drumlins which show fluting and sculpturing are restricted chiefly 

 to places where the ice was making a rapid ascent. In places where the general slopes are down- 



