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 



