74 SURFACE GEOLOGY. 
place is equal, by estimate, to a mass 1,000 feet long, 50 wide, and 2 feet 
deep, thus containing 100,000 cubic feet, or 5,000 tons, which have been 
raised by the wind an average height of 150 feet. 
Another very good illustration of this transporting: power of the wind 
is found in Sanbornton, a mile south-east from Hill, on a hillside which 
reaches a height 400 feet above the river, or 700 above the sea. Here 
the ancient dunes, as in New Hampton, have been swept forward anew 
since the land was cleared. The sand from a hollow 150 feet long, 40 
wide, and 2 to 5 feet deep has been carried in long north-west to south- 
east drifts 200 to 400 feet farther, and 25 to 30 feet higher up the hill. 
The depth of recent excavation is shown by a large stump which has 
been thus undermined. The highest of these dunes have now reached 
the crest of the hill, covering the originally naked ledges; but they 
will not stop here, and at length may be found far beyond in the hollow 
on the east side of this first hill range. 
Through Franklin and Northfield these dunes are numerous, occurring 
from 100 to 300 feet above the upper terrace of the valley, having their 
greatest altitude, 700 feet above the sea, a mile and a half north of North- 
field depot. They are generally found, however, within 100 feet of the 
highest terrace: at such height they are well shown within a mile north 
and south from Franklin Falls, near Northfield depot, and in great abun- 
dance, extending more than a mile on the north and west sides of Hart 
hill, In the next five miles no dunes were observed, but they appear 
again at a similar elevation for a mile in the south part of Canterbury. 
The instances of dunes found southward along the Merrimack are soon 
enumerated. They have a height of 70 feet, by estimate, above the high- 
est terrace in Pembroke, on the west side of the village street, where they 
are covered with grass; they reach about the same height in London- 
derry, two miles south-east from Goff’s Falls, where they appear in large 
amount, forming irregular mounds and ridges; and at a few points in 
Litchfield and Hudson we find on the high plain, and scarcely raised 
above it, similar areas of barren, wind-blown sand. 
From New Hampton to Bristol the river flows westerly, almost at right 
angles with its general direction, descending by a nearly continuous slope 
86 feet in the four miles, which are the most rapid portion of its course 
