MODIFIED DRIFT ALONG CONTOOCOOK RIVER. 109 
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 
