MODIFIED DRIFT ALONG LOWER AMMONOOSUC RIVER. 63 
diminishing extent at a later date. At both these dates great amounts 
of alluvium were brought down by its streams, forming a wide interval 
between the Fabyan house and the Lower falls, which fills what must at 
first have been a deep lake basin, and spreading out at and below the 
Twin Mountain house in an extensive low plain. The height of the 
former is from 1,560 to 1,550, and of the latter from 1,375 to 1,350 feet 
above the sea. Considerable deposits of modified drift occur at other 
points along the upper portion of this valley. 
Below Littleton we find the alluvium continuous, and usually in large 
amount on one or both sides of the river to its mouth. This is a distance 
of nearly twenty miles, in which the river descends about 400 feet, having 
its mouth 407 feet above the sea. The highest terraces near Littleton 
are from 60 to 75 feet above the river, but scarcely any deposits occur for 
the first five miles above the low terrace, which is partly interval. Below 
North Lisbon both this and the high terrace, which sometimes widens 
into plains, are well shown. South-west from North Lisbon the high 
terrace is about 100 feet above the river; at Lisbon, about 125; at the 
east line of Bath, 150; at Bath village, 175; and one mile from its mouth, 
200 feet, or 220 on its south side and 225 on its north side above Con- 
necticut river. The slope of the ancient high flood-plain of the Lower 
Ammonoosuc was thus about 12 feet to a mile, descending but little more 
than half as much as the present river. The only kame observed in this 
lower part of its valley was a short ridge of gravel between the railroad 
and highway at the east line of Bath. 
Mopiriep DrirT AND WATER-worN Rocks AT ORANGE AND NEWEuURY 
SumnIts. 
The lowest point in New Hampshire, upon the water-shed which 
divides the Connecticut and Merrimack basins, is at the summit of the 
Northern Railroad in Orange. Two rock-cuts, each about 30 feet in 
depth and together a quarter of a mile in length, were here made for the 
passage of the railroad through ledges of gneiss. Both these excavations 
were at the lowest points over which water could flow between these val- 
leys. At the south excavation the top of the ledge on the east side 
shows in a distance of about fifty feet three water-worn cavities, 4, 6, and 
12 feet deep, in order from north to south, one half of each of which has 
