158 



SURFACE GEOLOGY. 



On the south this plain descends 25 to 50 feet in an escarpment, below 

 which the edge of the gravel and sand is overlain by a peculiar clayey 

 stratum, which extends with an undulating or nearly level surface south- 

 easterly to Garrison hill, and is also well shown south-west from Dover, 

 between the city and Bellamy river. Its margin reaches 125 to 150 feet 

 above the sea, and is marked by numerous springs. This deposit resem- 

 bles the gray clay of the brick-yards in its color; its usually obscure 

 stratification, which is, however, sometimes distinctly shown ; its occa- 

 sional division into small fragments, stained with iron-rust ; and its con- 

 taining infrequent pebbles from two or three inches to a foot in diameter. 

 Except these isolated pebbles it is wholly a fine, clayey silt. On any 

 exposed bank it is marked by many little channels, which have been 

 formed by the rains, and are preserved through dry weather by the hard- 

 ening of the surface. 



The kame-like gravel of Willand pond extends three miles northward, 

 to Cole's pond and the alluvial area of Salmon Falls river, near the east 

 corner of Rochester. Southward it is narrowed to an ordinary kame, 

 which is cut through by Cochecho river a quarter of a mile above the city 

 of Dover. A very instructive section of it is shown by a railroad cut on 

 the north side of this river (Fig. 40). The kame consists of gravel and 



Fig. 40. — Section of Kame on Dover & Winnipiseogee Railroad, i mile north- 

 west FROM Dover Station. Length, 300 feet; height, 40 feet. 



The base of the section is about 40 feet above Cochecho river, or 75 feet above the 

 sea. 



a, a, gray clay ; b, fine sand ; c, c, coarse gravel containing pebbles from 6 inches 

 to ih feet in diameter; d, d, fine gravel. 



sand, and is overlain on both sides by the widely spread gray clay. Nu- 

 merous angular boulders, 2 to 5 feet in diameter, had been stranded on 

 the north-west side of the kame before the deposition of the clay. An 

 excavation between this section and the river exposed a boulder 8 feet in 

 its greatest diameter and weighing 16 tons, with another two thirds as 

 large, which were embedded in the kame. 



