MODIFIED DRIFT ALONG CONTOOCOOK RIVER, IO9 



The first of these ponds has its name from gravel ridges or kames. 

 These are well shown between this and Pollard pond, extending in north- 

 west to south-east ridges, not higher than the plain, but shown as ridges 

 because of intervening hollows. These kames, with most of the plain 

 northward, consist of coarse, rounded gravel, with the largest pebbles 

 from a foot to a foot and a half in diameter. Southward, sand predomi- 

 nates, but much kame-like gravel is also found. These materials are 

 spread out comparatively level, but the excavation for the railroad shows 

 that they have usually an oblique stratification, dipping mostly to the 

 south-east. Greenfield village lies at the east edge of this alluvial area, 

 which extends with its full width a half mile farther south. In this dis- 

 tance we find, on the east side of the railroad, kames containing pebbles 

 up to a foot and a half in diameter, and lying in north and south ridges 

 20 to 30 feet higher than the plain. These continue along the railroad 

 fully a mile to Cragin pond, forming a narrow belt, which is bordered by 

 hills of ledge or till. Their southern portion is mainly of sand or fine 

 gravel, and they terminate in a sand plain, which lies on the east side of 

 this pond, 25 feet above it. 



A water-shed scarcely higher than this plain and lower than the kames, 

 being 863 feet above the sea, separates Cragin pond from the head-stream 

 of Stony brook, which the railroad follows to Wilton, descending more 

 than 500 feet in nine miles. The modified drift of this valley consists 

 of occasional terraces and kames, but presents no remarkable features, 

 and is scanty in amount. 



No streams now exist, or can have existed with the present system of 

 drainage, capable of forming the large alluvial plain of Greenfield. Ex- 

 cepting north of Pollard pond, the hills which lie between it and the Con- 

 toocook do not exceed the plain in height. Its extent along the outlet of 

 Pollard pond is to the north-east corner of Peterborough, below which for 

 two miles this stream is destitute of alluvium, as are also the low hills and 

 even the valley of the Contoocook on the west. 



At Bennington the valley is closely bordered by hills, beyond which 

 we again find the modified drift continuous to Hillsborough Bridge, a 

 distance of nine miles. The Hillsborough & Peterborough Railroad, 

 now being built, is here on the east side of the river, and from South 

 Antrim northward lies on a low and partly swampy plain 15 to 20 feet 



