306 SURFACE GEOLOGY. 



tion of lenticular slopes of glacial drift resting against ledgy hills is 

 increased. Carroll county is especially remarkable for the frequent oc- 

 currence of these slopes on the north-west side of hihs, directly facing 

 the powerful current of the ice. 



Nearly the whole of New Hampshire presents a very uneven surface, 

 consisting of broken and irregularly grouped hills and mountains. The 

 distribution of the lenticular hills does not seem, however, to depend 

 upon these features. They are very finely developed on the lowland near 

 the coast, but not less so in Dublin, Jaffrey, and Rindge, upon the height 

 of land between Merrimack and Connecticut rivers. Beside the coast 

 they are spread over an area which would otherwise be nearly level ; at 

 many places inland they are equally abundant among high, irregular hills. 

 They seem as likely to be found upon one side as another of any moun- 

 tain or prominent hill-range. The altitude at which they occur varies 

 from the level of the sea to 1,500 feet above it. By reference to a map 

 in the atlas, the relation of the lenticular hills to contour lines and striae 

 will be readily seen. 



The most noticeable feature of these remarkable deposits is their 

 smoothed oval form with a definite trend or longer axis, which lies 

 almost invariably in the same direction with the striae. Thus their 

 position is the one which opposed the least resistance to the glacial 

 current, and is that which would be assumed by accumulations formed 

 beneath the moving ice-sheet. Deflection in the trend of these hills 

 at any locality from their prevailing course over adjacent areas is usually 

 accompanied by deflected striae. An instance of this occurs in Dublin 

 on the north side of Monadnock mountain, where both lenticular hills 

 and striae point thirty or forty degrees more than usual to the east of 

 south. A similar deviation of the striae has been noted at Andover and 

 Potter Place, on the north side of Mt. Kcarsarge, but no lenticular hills 

 occur there. It would appear that any isolated mountain like these, 

 while enveloped in the ice-sheet, might cause only slight variation in its 

 current, which must overcome as great resistance in turning aside as in 

 passing upward without changing its course ; but near the end of the 

 glacial period, when such barriers were reached by the retreating termi- 

 nal front of the ice, its current from the north would no longer be 

 pushed upward by the continuous glacial sheet, so as to pass over the 



