112 SURFACE GEOLOGY. 



Half a mile south-west from these ridges, on the south side of the 

 river, we find a remarkable kame, half a mile long, with a course a little 

 to the east of south, composed of sandy gravel, with pebbles frequently 

 six to eight inches, but not commonly exceeding one foot in diameter. 

 This forms a steep ridge about lOO feet above the hollow which separates 

 it from a high hill an eighth of a mile west, and 125 feet above the low 

 alluvium, which extends two thirds of a mile wide on the east. A small 

 pond lies in this alluvium at the foot of the kame. The next third of a 

 mile south shows no ridge, but it is succeeded by a very interesting mo- 

 raine, which forms a steep and narrow crescent-shaped ridge, fully half 

 a mile long, lying in a similar position with the kame between the hills 

 and the low alluvial area. Its course is to the south-east and east, with 

 height descending from about 75 to less than 50 feet above the alluvium, 

 and it is separated from the hills by a hollow nearly as deep. The crest 

 of this moraine consists almost entirely of angular boulders of all sizes 

 up to ten feet in diameter, which cover the surface and are piled as 

 thickly as possible, with scarcely any space for finer material. On the 

 sides, and along the top near the east end of the ridge, we find earth and 

 boulders intermixed in the ordinary proportions of the coarse upper till. 

 These blocks are principally of two kinds, derived from the Lake and 

 porphyritic gneiss, which occupy the whole country for more than ten 

 miles to the north. The New Hampshire Central Railroad, now discon- 

 tinued, was built in the hollow on the south-west side of both kame and 

 moraine. 



A noticeable feature of the Contoocook basin is, that its east and south- 

 east water-shed is formed by high, irregular hills near the river, which 

 has no large tributaries from this side. The lowest points of this 

 water-shed usually exceed 400 feet above the river ; but one or two 

 miles south-east from this moraine the railroad found a line of depres- 

 sion only 150 feet above the river, or 537 feet above the sea. On each 

 side high hills border this pass, which connects the Contoocook valley 

 with that of the north branch of the Piscataquog river. No extensive 

 or remarkable deposits of modified drift were seen in a hasty journey 

 along the latter valley. 



A third of a mile above West Hopkinton the Contoocook river flows 

 between slopes of till 75 feet in height, and so steep as to suggest that 



