ANCIENT GLACIERS. 



73 



Portions of New England present the best illustra- 

 tions anywhere afforded in America of what are called 

 "drumlins." These are "lenticular-shaped" hills, com- 

 posed of till, and containing, interspersed through their 

 mass, numerous scratched stones of all sizes. They vary 

 in length from a few hundred feet to a mile, and are usu- 

 ally from half to two-thirds as wide as they are long. In 

 height they vary from twenty-five to two hundred feet. 



But, according to the description of Mr. Upham, what- 

 ever may be their size and height, they are singularly 

 alike in outline and form, usually having steep sides, with 

 gently sloping, rounded tops, and presenting a very 

 smooth and regular contour. From this resemblance in 

 shape to an elliptical convex lens, Professor Hitchcock 

 has called them lenticular hills to distinguish these de- 

 posits of till from the broadly flattened or undulating 

 sheets which are common throughout New England. 



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Fig. 27.— Drumlins in Goffstown, N. H. (Hitchcock). 



The trend, or direction of the longer axis, of these 

 lenticular hills is nearly the same for all of them com- 

 prised within any limited area, and is approximately like 

 the course of the striae or glacial furrows marked upon 

 the neighbouring ledges. In eastern Massachusetts and 



