MODIFIED DRIFT ALONG MERRIMACK RIVER. 7 1 



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 niade 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 

 acctimulate only in deep or sheltered places. 



Kanics. 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 90 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 



