160 Prof. O. P. Hubbard on Erosion in New Hampshire. 
“The summit of the (new) road (passing through the Notch 
to Portland, Maine,) is 835 feet above the plain of Colebrook. 
The direction of the pass is N.E. and 8.W., and it is walled on 
1600 feet above Colebrook ; and the Notch is parallel to the di- 
rection of the strata, which clearly have been removed on this 
line. Can we discover any disturbing agency or predisposing 
cause for this depression, from the summit of which the streams 
flow either way into the Androscoggin and the Connecticut? 
We learn that “dikes of basaltiform trap intersect the strata near 
the middle (summit ?) of the Notch, and large loose blocks of it 
are seen in abundance on its northwest side. It contains very 
large crystals of basaltic hornblende and glassy white feldspar.” 
The course of these dikes is not given. “On the north side of 
this road, forty or fifty rods back in the forest, is a ravine called 
‘the Flume.’ It was formed by the decay of a large trap dike.” 
“The chasm is twenty feet deep and from ten to twenty feet 
wide, and is the channel of a stream of water, from whence it 
received its name. The trap dike runs N. 30° E., and 8. 30° W., 
and is six feet wide. It is slightly porphyritic with feldspar crys- 
tals, and is of a dark brown color. It divides into large cubical 
blocks which form a, series of steps, so that when there is but 
little water a person may walk a considerable distance up the 
ume upon them. The principal ledge at this spot is granite, 
which protrudes through the mica slate.” 
Here we find a gorge through a mica slate range parallel with 
its direction N.B. and S.W., the slate dipping N.W. 80°, inter- 
sected by trap dikes—and near, another trap dike in a fissure, 
having the course N. 30° E., which is a variation of only 15° 
from the direction of the Notch, and all coincide in direction with 
the slate. But whether the different dikes are connected or not, 
erosion would seem to be indicated, down to the present level of 
the dikes, to the amount of 800 feet. 
(d.) Tocite one more case where the agent is still acting. The 
Waterqueechy river at Queechy village, (Hartford, Vt.,) makes a 
high fall of twenty feet over a dam of ten feet, and its rocky 
channel and sides are covered with pot-holes, and the gravel banks 
are here some eighty feet above with several terraces extending 
down a mile or more, where the narrow valley becomes a cul de sac 
from which the water could not have escaped before the present 
outlet existed, except at a much higher level.* At this point the 
* I am informed by the Rev. Mr. Dudley of the village, that between the gulf and 
the village there are two distinct eeartad channels parallel to the present one, but 
much higher, where in all probability, the river once ran. 
