66 SURFACE GEOLOGY. 



present water-shed. Along the half mile between this summit and the 

 lake, kame-like banks of gravel and sand are found; but in general the 

 shores of the lake are destitute of modified drift, being composed of till 

 or ledge. The heights of these points, in feet above the sea, are as fol- 

 lows: Sunapee lake, low to high water, 1,090 to 1,103; Newbury summit, 

 1,130; top of railroad cut, 1,181; pot-hole, about 1,175; lowest point over 

 which water could flow towards the Merrimack river, 400 feet south-west 

 from the rock-cut, 1,161. It seems probable that when this pot-hole was 

 formed, the lower avenue at the south-west was still filled with ice. 



Another pot-hole, 10 inches in diameter and 3 feet deep, the origin of 

 which we cannot explain, occurs about 20 rods north of Newbury station, 

 at the shore of Sunapee lake, halfway between high and low water. There 

 is no rivulet or depression leading to the lake at this point. 



In Warwick, Mass., two miles north-east from the village, the drainage 

 during part of the Champlain period was also over the present line of 

 water-shed, which separates Ashuelot and Miller's rivers.* The current 

 here was from north to south, as shown by an area 40 feet square of in- 

 disputably water-worn ledges, with numerous pot-holes, which are locally 

 known as "Indian kettles." This place is near the lowest point of the 

 water-shed, which is a swamp perhaps 25 feet below these water-worn 

 rocks. While the pot-holes were being formed here, the lowest place 

 over which water could have flowed was probably occupied by an un- 

 melted portion of the ice-sheet, as at Newbury summit. 



Little Sunapee Lake, New London. 



The peculiar form of this lake, as shown on the county map, led to an 

 examination of its surface geology. It is a mile and a half long from 

 east to west, and is divided into nearly equal parts by a kame-like tongue 

 of land, which extends fully a half mile from north to south, leaving at 

 the south shore only a shallow channel about 50 feet wide. It is princi- 

 pally surrounded by gently sloping hills of ledge or till, but a narrow 

 margin of alluvium, 10 feet in height, borders its north-east shore. The 

 materials of the dividing peninsula are sand or gravel, with boulders at its 

 south end. Its width is less than 100 feet and its height about six feet, 

 where it is joined to the north shore. The central portion is about a 



* Jackson's Final Report on Geology of New Hampshire, p. 282. 



