124 SURFACE GEOLOGY. 
At Tilton, and for a mile above, the river has no modified drift. In the 
upper part of this distance the very steep slopes of till between which it 
flows indicate that a channel 50 feet deep may have been excavated in 
this material by the river. We next come to the largest area of modified 
drift found on this river. This extends nearly two miles along its north- 
west side, bordering Little bay nearly to East Tilton. A large part of 
this deposit was brought by the tributary which comes from Sanbornton 
Square. An interesting kame, forming a ridge of very coarse water- 
worn gravel, 30 to 40 feet high and a quarter of a mile long, lies on the 
west side of this stream at the margin of the modified drift. From its 
east side a plain of coarse gravel, 30 to 50 feet above the river, extends 
a third of a mile eastward, beyond which to Little bay the height is less, 
being 10 to 20 feet above the bay, and the material is finer gravel or sand. 
The edge of the high plain of coarse gravel is cut by the railroad; and 
the section shows the upper fifteen feet to consist of levelly stratified 
gravel, with its largest pebbles one foot or more in diameter, underlaid 
by several feet of sand, which is partly horizontal and partly oblique in 
stratification. The gravel is interstratified with the upper portion of the 
sand. This fine alluvium was probably brought by the large stream 
which comes in from Belmont, joining the Winnipiseogee from its oppo- 
site side at a short distance farther east. This tributary is bordered on 
the north by a wide sand plain, about 30 feet in height, which extends 
nearly two miles above its mouth. This was deposited in the Champlain 
period, since which time the stream has excavated a considerable portion 
of its plain, forming a wide meadow along its last mile. Previous to any 
erosion, this plain appears to have been continuous across the present 
channel of Winnipiseogee river; and we thus find a portion of it under- 
lying the coarse gravel which came from the opposite direction, being 
supplied abundantly at a little later date as the melting of the ice-sheet 
advanced to the north-west. 
The successive expansions of the Winnipiseogee river are called bays. 
In ascending the river they are met in the following order: 
Height 
Approximate area. above sea. 
Little bay, ‘ F : é 4 ‘4 ‘ . -5 square miles. 473 feet. 
Sanbornton bay, . 7 ‘ Fi 7 ‘ 1.0 ee 4go ‘“* 
Great bay (Winnisquam lake), 3 ‘ 5 : 5.0 “ 490 ‘“ 
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