MODIFIED DRIFT ALONG CONNECTICUT RIVER. 3 1 



By estimate, French pond is about 770 feet above the sea, and the 

 water-shed on the road northward is from 40 to 50 feet higher. This 

 hollow, bounded on both sides by high hills, seems to have been for a 

 time the outlet of the melting ice at the north, before the way was opened 

 westward for the Lower Ammonoosuc river. The glacier which covered 

 the mountains at the south-east also contributed to these deposits of 

 modified drift, as is shown by the high moraine mentioned, and by others 

 three fourths of a mile south from the town-house, at the mouth of a gap 

 in the first high range of hills. The highest of these last has been modi- 

 fied by a current of water. It presents on the west side a steep escarp- 

 ment of clear sand, reaching from 980 to 1020 feet above the sea. At 

 the top this changes to gravel, which becomes coarse as we recede from 

 the edge of the steep slope; next are large glaciated boulders, heaped 

 together with no earth among them, which again present a steep face and 

 somewhat level top 1050 feet above the sea. These rest at the east 

 against the hillside. On the north-west nothing intervenes to the town- 

 house and North Haverhill, 300 and 550 feet below, where we find the 

 sand and clay which were brought down by these glacial streams. 



At Haverhill there are only scanty remains of modified drift above 

 the interval, which is nearly a mile wide. The highest terrace, best 

 shown on the Vermont side, is 80 feet above the river ; enough of it is 

 left on the east side to indicate that it was once continuous across the 

 valley. Hall's brook and Oliverian brook, which have their mouths here 

 opposite to each other, have brought down large amounts of modified 

 drift, which is deposited along the lower portion of their course. On the 

 former this slopes in one mile to 125 feet above the upper terrace of the 

 Connecticut. On the east side only slight vestiges of this terrace are 

 found, and we have a direct rise of 220 feet from the interval to the mod- 

 ified drift of Oliverian brook, which thus commences at a greater height 

 than is reached in the first mile on Hall's brook. In two miles this 

 slopes upward 100 feet, or to 340 feet above the river, being well shown 

 all the way, and at one place nearly a mile wide. These streams are both 

 of large size, but the deposits along their course cannot be attributed 

 to their ordinary action, any more than the modified drift east of North 

 Haverhill is due to the brooks there. All these deposits are plainly of 

 the same date and from one cause, — the melting of the ice-sheet. 



