Q2 SURFACE GEOLOGY. 
extending far from the melting edge of the ice-sheet. In this lower por- 
tion of the Merrimack valley, and elsewhere in eastern New Hampshire 
and Massachusetts, the retreat of the glacier seems to have been so rapid 
that extensions of these kames were often entirely deposited in a single 
year. The ice-walls by which they were enclosed melted back about as 
fast as the formation of the channels and kames advanced. Though 
separate portions of these kames were thus probably wholly deposited 
in a single year, their annual progress was small; and the formation of 
the entire series, extending 20 miles, occupied a long period. 
The substitution of coarse angular materials, instead of the common 
water-worn gravel, seems to have taken place at times of very rapid melt- 
ing, whenever such materials happened to be set free from the ice in large 
amount near the mouth of the glacial rivers. They were then swept by 
the violent current into the place of the ordinarily water-worn kames. 
At the most notable of these localities, which occurs in Hooksett (p. 88), 
a medial moraine, or a similar train of materials which had become en- 
closed within the ice, seems to have been thus undermined by the glacial 
river, and left to appear as a portion of this series. 
It remains to add a few statements in regard to kames found farther 
southward in this valley. A fourth of a mile west from Reed’s Ferry 
we noted irregular ridges of partly angular and partly water-worn mate- 
rials, which enclose small ponds in their hollows. These kames appear 
to be isolated, not forming a portion of any series. After discontinuance 
for fourteen miles next below the long series which extends from Loudon 
to Manchester, we again find lines of kames in the main valley, upon both 
sides of the river and a mile apart, in Hudson and Nashua. They begin 
in Hudson, a short distance south-west of Otternic pond, and extend 
southward two miles. This series may be seen at the north side of the 
road leading east from Nashua bridge, near where the river road. turns 
off to the south. It is traceable from this point a half mile north- 
ward, consisting of two or more crooked ridges 20 to 30 feet in height. 
This material is considerably water-worn, the largest pebbles seen being 
a foot and a half in diameter. Following the river road southward, we 
find but.a single ridge, similar in height and material, but nearly straight, 
which lies for the first third of a mile on the east side of the road, and 
beyond on the west side, diverging from it towards the river. This ridge 
