’ 
166 Prof. O. P. Hubbard on Erosion in New Hampshire. 
to eighteen feet high above the track. On the north side it is, 
filled with the accumulations of gravel, and on the south side the 
basin in this gravel is filled with a deposit of peat, containing 
abundance of prostrate trees apparently of successive generations. 
The configuration of the excavated gravel shows the last result 
of moving water; the accumulation of the swamp muck and the 
growth of trees in this cavity are of course of subsequent date. 
The violence of the current which has here acted, may be infer- 
red from the wearing effects exhibited on the rocks of the valley, 
S. and E., where they are smoothed and rounded at elevations 
far above the stream now flowing there; also from the great 
depth of Tewksbury Pond, and from the extensive beds of peb- 
bles washed clean of all fine materials, sand and soil, in Danbury, 
about ten miles southeast. 
Again—we see no evidence at present that these excavations 
and irregularities were produced by water falling from a very 
eight ; they are rather the effect of a uniform though vio- 
lent current; the same marks are seen in the slate and hard trap 
of the bed of the Queechy, where pot-holes and channels and 
capacious excavations long and deep are abundant as the effects 
of a rapid stream. 
If we may safely conclude that where numerous dikes, and 
these it may be in groups of six or eight, are found crossing 
in a valley a river channel, as at Campton Falls, N. H., and re- 
duced to a level with its bed, with occasionally one harder than 
the rest forming a barrier of slight elevation, we have before 
us a present agency which in time past, may have been sufli- 
cient for the production of the degradation indicated by the ex- 
tent of the valley. So when there are large, elevated areas yet far 
below the peaks and ridges of the country intersected in many 
directions by trap dikes and the whole surface worn smooth, we 
hesitate not to admit that a general denuding or erosive force has 
acted with energy and during a long period. When we find a 
mountain ridge cut at right angles by one or more trap dikes, and 
these reduced to an even surface with the crest and sides of the 
mountain, and continuous across the valleys, it is not easy 
or the mind to forbear concluding that the valleys are valleys 
of erosion, although they may be narrow and some thousands of 
feet deep. This is illustrated by the following cases. 
* In connection with these effects of larger currents, and in proof of their forme 
existence in the channel of our present streams, I mention that a eut was made in 
West Hartford, Vt., on the Central Railroad, across the angle of a slate spur, about 
sixty feet above the White River, that opened a pot-hole to its bottom, seventeen 
feet deep and between three and four feet diameter. this were found two beau- 
in the track, and the other, almost a perfect sphere, two feet four inches in diameter, 
weighing over nine hundred pounds, is preserved for science at the University 
ur. n. ¢ » 
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