292 THE ICE AGE IN NORTH AMERICA. 



In this country, Professor C. H. Hitchcock and Mr. War* 

 ren ITpham, while engaged oq the geological survey of New 

 Hampshire, were the first to discover the parallelism between 

 glacial motion and the axes of drumlins in 1875. They con- 

 cluded that " the accumulation of these hills and slopes seems 

 to have been by slow and long-continued addition of material 

 to their surface, the mass remaining nearly stationary from the 

 beginning of its deposition. Obviously this was the case with 

 the lenticular slopes gathered behind the shelter of higher 

 ledgy hills or upon their opposite sides."* A little later Up- 

 ham wrote, " Although we do not discover the cause of the 

 peculiar distribution of these hills, it seems quite certain that 

 they were accumulated and molded in their lenticular form 

 beneath the ice."f President Chamberlin's observations led 

 him to a similar conclusion : " The drift presents some pecul- 

 iar tendencies to aggregation. ... A special tendency is ob- 

 served over certain considerable areas lying not far from the 

 Kettle Moraine to accumulate in mammillary or elliptical or 

 elongated hills of smooth-flowing outline." J And again, after 

 repeating this opinion, it is suggested that "a deeply hidden 

 boss of rock is usually and perhaps universally the determin- 

 ing cause of these peculiar accumulations." # 



In reviewing these explanations and the observations on 

 which they are based, together with such evidence as my own 

 studies have discovered, the conclusion that drumlins should 

 be compared to sand-banks in rivers appears the most satisfac- 

 tory yet advanced. They seem to be masses of unstratified 

 drift slowly and locally accumulated under the irregularly 

 moving ice-sheet where more material was brought than could 

 be carried away. The evidence for the subglacial growth of 

 drumlins may be summarized as follows : The scratched stones 

 in the mass of bowlder-clay show a differential motion of its 

 several parts as they were scraped and rubbed along from a 

 generally northern source and gradually accumulated where 



* "Geology of New Hampshire," vol. iii, p. 808. 



f "Proceedings of the Boston Society of Natural History," vol. xx, p. 223. 

 % " Geology of Wisconsin," vol. i, 1883, p. 283. 



# "Third Annual Report of the United States Geological Survey," 1883 p. 

 30fi. 



