MODIFIED DRIFT ALONG MERRIMACK RIVER. 71 
this distance, which lies through Woodstock and Thornton, we have 
two principal terraces, the higher being that just described, and the 
lower being wholly or in part overflowed by spring floods; but small 
intervening terraces are also of frequent occurrence. 
All the modified drift of this valley, for the first seven miles to Wood- 
stock village, is made up of gravel of different degrees of coarseness. 
Southward, banks and terraces of sand begin to appear; but gravel still 
predominates for a long distance below. The stream here frequently 
occupies a broad, shallow channel, paved with pebbles of all sizes to two 
feet in diameter, with little admixture of fine gravel or sand, which can 
accumulate only in deep or sheltered places. 
Kames. In the south part of Thornton an interesting kame of coarse 
gravel is found on the west side of the river, between it and the highway. 
It extends north and south in a steep, sharp ridge about a fourth of a 
mile, and is less distinctly traceable for nearly a mile. Its top is go feet 
above the river, or 650 above the sea. Less than a mile farther south 
the road turns to the west around the steep face of a high plateau of 
kame-like gravel, which contains abundant pebbles up to a foot and a 
half in diameter. This deposit is of considerable extent, with its south- 
east portion nearly level, 660 feet above the sea, or about 100 above the 
river, but towards the north-west it has a broken surface, which in some 
places is 10 feet higher. It is from 30 to 40 feet higher than the normal 
upper terrace, which extends, with its regular slope of 15 feet in a mile, 
to this point, beyond which it also continues clearly traceable to the 
south. This higher plateau and the kame, which it resembles in mate- 
rial, date before the formation of the continuous high flood-plain. We 
must refer the latter to a time when the valley had become free from ice, 
while the former seem to belong to the period of its melting, owing their 
shape, in isolated plain and steep ridge, to the presence of ice-walls be- 
tween which they were deposited. 
In Campton the Pemigewasset receives two considerable tributaries 
from the east—Mad and Beebe rivers,—which drain basins on the north- 
west and south-east of the mountain range that culminates in Sandwich 
Dome. South from the latter stream the upper terrace, increased in 
height by alluvium from the tributary, forms a pine-covered plain a mile 
long and half a mile wide. These “pine plains,” appearing in a few 
