79 SURFACE GEOLOGY. 
and east. Nearer to the river here we have a lower terrace only from 5 
to 10 feet above it. In the excavation of the gravel deposits, the river 
has sometimes left numerous and well marked terraces, though small in 
extent, and differing but little in height. This is well shown near Tut- 
tle’s, in Lincoln, where four distinct terraces are seen between the road 
and the river, with from 3 to 5 feet escarpments, the highest being about 
20 feet above the river. 
The height of terraces in this valley was determined by levelling only 
as far north as to the mouths of East Branch and Moosilauke brook, 
which enter the Pemigewasset, from opposite sides, at nearly the same 
point. The river here is 710 feet above the sea, or only 242 feet higher 
than at Plymouth, eighteen miles farther south. Profile lake, its source, 
nine miles to the north, is about 1,950 feet above the sea, by barometric 
measurement, showing a descent to this point of more than 1,200 feet.* 
The plains above the East Branch, not determined by the level, appear 
to be somewhat lower than the highest modified drift just south of this 
stream. This terrace has a height of 70 feet above the sea, and is ten 
feet higher on the west side. Thence for ten miles southward, or nearly 
to the south line of Thornton, the highest terrace of the river, commonly 
well shown on both sides, has a uniform continuous slope of 15 feet to 
the mile. This is nearly the same as the descent of the river, which 
has cut its way from 70 to 100 feet deep through its former wide, sloping 
flood-plain. These remnants, lying at corresponding heights on opposite 
sides of the river, and sloping with it in the regular lines of the upper 
terrace, are here very interesting, as seen extending for miles up and 
down the valley. Nowhere else in New Hampshire is the erosion of 
a the modified drift, by which it 
ed has been shaped in terraces, so 
710, 
765. 
w ° 
wn fad 
nw nw 
Pes r. clearly and convincingly display- 
o9€%---© above sea. 
Fig. 17.—SECTION IN WOODSTOCK, 14 MILES 
BELOW THE MOUTH oF East Brancu. that an original flood-plain, ten 
Length, 3 mile. 
ed. Here no doubt can remain 
miles long, has been terraced as 
we see it by the excavation of the river. For most of the way along 
*The errors which occur in Vol. I, pp. 288, 308, and 322, in stating the height of Pemigewasset river at the 
mouth of East Branch, and of other points in this vicinity, arose by computing barometic observations from 
Thornton, which, through some mistake, is given 600 feet too high by Prof. Guyot, among the usually very cor- 
rect altitudes published in his memoir on the ‘‘Appalachian Mountain System.’ 
