[62 



SURFACE GEOLOGY. 



interstratified gravel and sand. In this class, also, are, a ridge noted at 

 the west line of Durham, half a mile south-west from Oyster river; the 

 deposit, shown in Fig. 47, 

 cut by the Nashua & Roch- 

 ester Railroad at the divide 

 between Oyster and Lam- 



Fig. 47- 



Section in sand near Wheelwright 

 Pond, Lee. 



prey rivers; the gravel plain Height, 30 feet. Base of section is about 150 feet 

 of Lee Hill village, 190 feet ^^^^'^ '^'^ ^'"• 



above the sea ; and the plain of nearly the same height, two miles west 

 from Newmarket, on the road to Wadley's Falls, composed of coarse 

 gravel at the west, but of clear sand to a depth of 30 feet in its eastern 

 portion. 



One of these deposits near Newmarket Junction, composed mainly of 

 sand with no rocks embedded in it, has its surface strewn with angular 



Fig. 48. — Section on Boston & Maine Railroad, i mile 



north of Newmarket Junction. 



Length, about 600 feet; height, 35 feet. Base of section is 



about 50 feet above the sea. 



boulders, the largest of which are 10 feet in their greatest diameter, weigh- 

 ing 30 or 40 tons. The sand was deposited in the channel of a glacial 

 river. When the ice on both sides and beneath it melted, this fell to the 

 bottom of the shallow sea, which probably stood 150 feet above its pres- 

 ent height. The boulders were then dropped on its surface by blocks or 

 rafts of floating ice. 



The academy in Greenland is built on a broadly rounded, kame-likc 

 ridge of gravel, which at a short distance to the south-west becomes a 

 nearly level plain 40 or 50 rods wide, but still farther to the south-west 

 is narrowed to a typical kame. The length of this deposit is a half mile. 

 Its height is nearly 100 feet above the sea. 



At a school-house half a mile south from the academy, we rise to a 

 plain about 125 feet above the sea, which extends a mile to the south and 

 south-east, descending with a gentle slope 25 to 40 feet in that distance. 

 This plain forms the highest land between Winnicut river and Berry's 



