MODIFIED DRIFT IN PISCATAQUA BASIN. 151 
in width, enclosing Round pond. Except on this side, its shores are till 
or ledge. No examination has been made between this pond and Milton 
Mills. In the two miles from this village to Branch river, the modified 
drift rises in irregular slopes to a height of 20 or 30 feet. 
Along Branch river the modified drift is well shown, forming swampy 
areas and terraces of sand or gravel 20 to 40 feet in height. Kames 
were noted in Wakefield a quarter of a mile west from Wolfeborough 
Junction, and at several other points southward to Union village. At 
one half mile to two miles south from this station they are finely dis- 
played along the railroad, mostly on its west side. They are composed 
of coarse water-worn gravel, in ridges 25 to 40 feet high, with their trend 
generally north and south. These kames descend with the valley from 
about 575 to 475 feet above the sea. 
The valley of Salmon Falls river in Milton contains three natural 
ponds, through two of which the river flows. The two south-west ponds 
lie near the east foot of Teneriffe mountain. They are bordered by 
kames on their west and south sidés; and low, sandy plains extend be- 
tween them and the North-east pond. They are all flowed to the same 
height by the dam at Milton Three Ponds village, which has been re- 
cently raised a few feet, overflowing a large meadow above North-east 
pond, and holding the river level six miles, or to within a half mile of 
Milton Mills. Below this dam the river descends about 200 feet in the 
next three miles, its channel lying between ledges or steep slopes of till. 
The next modified drift is in the north part of Rochester (Plate VI, 
p. 146), where for a distance of two miles it occupies the entire area a 
mile and a half wide between Salmon Falls and Cochecho rivers, This 
tract is crossed by the Portsmouth, Great Falls & Conway Railroad. It 
consists of sandy plains, 25 to 40 feet above the river, or of extensive 
swamps and peat-bogs. The latter were scantily filled with modified 
drift, while it was more abundantly supplied on all sides, preventing 
drainage. Salmon Falls river here turns to the south-east. A straight 
course would carry it southward across this area, bringing it to a junc- 
tion with the Cochecho at Rochester. In the Champlain period the 
highest floods of these rivers were united here, and nearly all the modi- 
fied drift which they brought down was deposited in these plains. 
At East Rochester a narrow belt of alluvium, from 20 to 30 feet high, 
