78 SURFACE GEOLOGY. 
has an equal elevation above the river, which is greater than in any other 
portion of this valley. In the next nine miles below Franklin the upper 
terrace falls to a height of 125 feet above the river, which continues for 
more than 20 miles to the north part of Manchester, the highest terrace 
seeming to descend most rapidly near the present falls of the river, so 
that a nearly uniform height above the river is maintained. 
Opposite the Webster place, two and a half miles below Franklin, this 
high terrace presents a quite remarkable form. Its base is washed by 
the river, which here sweeps eastward, leaving a fertile low terrace of 
large extent on its west side. Ascending from the river to the east we 
have first the steep escarpment, more than 150 feet high, the top of which 
has nearly the normal height of the upper terrace; but this, without any 
level space as usual, is succeeded by a sloping surface of sand, which ex- 
tends to the road, and rises about 120 feet in less than a fourth of a mile, 
appearing in all except its slope like an ordinary terrace. Very high 
sand-dunes occur on the hill south-east, and it seems probable that this 
unusual slope, rising more than 100 feet above the normal height of this 
terrace, was heaped above it by the north-west wind, soon after the time 
of its deposition. A similar sloping surface of the upper terrace, but 
much less in amount, is also seen for a mile or more north and south, 
and at many other points along the river. Between one and two miles 
farther south we find the greatest profusion of dunes observed in New 
Hampshire, the highest of which, however, do not exceed 250 feet above 
the river. 
In Canterbury the upper terrace spreads out into plains, which are at 
some places a mile wide. The Boston, Concord & Montreal Railroad 
through the town is upon these high plains, while the Northern Railroad, 
in Boscawen and Concord, lies on the lowest terrace, being embanked 
much of the way to raise it above the high floods of spring. The plains of 
the south part of Canterbury, extending one mile into Concord, show an 
unusually rapid continuous slope, amounting to 80 feet in four miles, or 
from 130 to only 50 feet above the river, which is here 250 feet above 
the sea. The north end of this slope appears to be at the normal height, 
representing the level of the river at the time of deposition of these 
plains, while the terrace of Boscawen village, on the opposite side of the 
river, is 40 feet lower. The south end of this slope is about 70 feet 
