MODIFIED DRIFT ALONG CONNECTICUT RIVER. 53 
From South Charlestown to Cold river the precipitous face of Kilburn 
peak or Fall mountain forms the eastern boundary of the modified drift. 
Opposite Bellows Falls this leaves scarcely room for the railroad and the 
highway between it and the river. The height of this mountain is about 
1,200 feet above the sea. The water-shed on‘its north-east side in Lang- 
don, between the brook which flows into the Connecticut at South 
Charlestown and one of the branches of Cold river, is a swamp one sixth 
of a mile wide, 458 feet above the sea, or 175 feet above the river. Mod- 
ified drift, mainly coarse, extends south from this water-shed to Cold 
river. It was formérly supposed that the modified drift was deposited at 
a time when the valleys were made a series of lakes by the existence of 
barriers since swept away, and the narrowest space at Bellows Falls was 
regarded as the probable site of such an obstruction. No evidence point- 
ing to this was seen by us here or in any other portion of the valley, 
except so far as deltas, the ridge of the kame, or other unusually high 
deposits of modified drift may have acted in this way for a short time. 
It is obvious that with any high barrier here the river would have found 
passage over the low water-shed. north-east of the mountain. 
At Bellows Falls the river descends 49 feet (from 283 to 234 feet above 
the sea), through a narrow, water-worn channel of rock. Distinct glacial 
striz are seen upon these ledges at the head of the falls. The original 
highest plain seems to be shown by the upper terrace, 425 feet above the 
sea, which extends one mile north from the falls on the east side. This 
is about 30 feet higher than the remnant of the kame (p. 47), around 
which the high plain has been wholly:swept away and -the principal ter- 
race of the village formed, from 325 to 320 feet-above the sea. This 
area of fine alluvitim extends a third of a mile west from the falls, and 
it is almost certain that somewhere beneath it is a rocky channel lower 
than the head of the falls, in which the river flowed before the glacial 
period. In excavating the modified drift which was afterwards deposited, 
‘the river has formed its present channel close upon the east side of its 
valley, passing over ledges which are probably-much higher than its pre- 
‘glacial. bed. 
‘Cold and Saxton’s rivers have brought down large amounts of modified 
drift 75 feet above the normal high plain. The proper delta of the 
former has been eroded so far as it occupied the main valley, but the 
