I06 SURFACE GEOLOGY, 



this we find the valley for the next six miles, extending nearly to An- 

 trim, well-nigh destitute of any alluvial or terraced deposits ; yet it has 

 along most of the way an ample width with gently sloping sides, which 

 are usually the conditions for the accumulation of extensive plains. In 

 this distance, and for several miles farther north, the descent of the river 

 is small, amounting to 123 feet in the sixteen miles between North Peter- 

 borough and Hillsborough Bridge. More than half of this occurs at Ben- 

 nington, where its fall is from 6']6 to 606 feet above the sea; for the rest, 

 the average slope is about three feet to a mile. 



The only important deposits of modified drift seen along this river for 

 six miles were kames, which appear on the east side near the north line 

 of Peterborough, and are very well shown upon both sides of the valley 

 at one mile south-east and south-west from Bennington. In the north 

 edge of Peterborough these consist of sand or fine gravel, which lie in 

 numerous mounds and ridges, in depths to 20 or 30 feet, upon a sloping 

 hillside of till 90 to 100 feet above the river. These deposits are irregu- 

 larly stratified, conformably in some places, and perhaps generally, to the 

 underlying surface. They contain here and there embedded boulders, 

 the largest of which observed was four feet in diameter. 



From a half mile to more than a mile south of Bennington, on both 

 sides, we have large accumulations of kames. On the west they rise to 

 about 140 feet above the river, and consist of sand in hillocks and north 

 and south ridges, which are 50 to 75 feet in height, lying on till. In the 

 sand, which is irregularly stratified as seen in many places, there also 

 occur occasional boulders up to four feet in size. On the east side these 

 ridges and banks are well shown along the road to Greenfield before 

 coming to Whittemore pond. They are composed in large part of the 

 coarse, water-worn gravel which is characteristic of the kames, inter- 

 stratified with sand, and containing embedded boulders. These deposits 

 reach a height fully 175 feet above the river, or 850 feet above the sea. 

 Thence to the south-west similar deposits border the north and west 

 sides of the hills to within a half mile of Pollard pond, being well shown 

 on the east side of the Manchester & Keene Railroad, now being built, 

 for one mile south from Bennington station. Here they form nearly 

 level terrace-like banks of fine gravel or sand, 170 to 175 feet above the 

 river, irregularly stratified and rarely containing boulders. 



