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, .5 square miles. 473 feet. 



Sanbornton bay, i.o " 490 " 



Great bay (Winnisquam lake), .... 5.0 " 490 " 



