146 SURFACE GEOLOGY. 



the level of Ossipee lake, which is 408 feet above the sea. In their west- 

 ern portion they are from 40 to 50 feet above Bear Camp river, which 

 along its last six miles flows through fertile intervals. These cover areas 

 from which the river has excavated the higher plain. The upper part of 

 this river is also frequently bordered by intervals and terraces. 



The shores of Ossipee lake are mostly low ; and it appears that this 

 area remains unfilled because sufficient material has not been supplied by 

 inflowing streams. We cannot thus explain the unfilled hollows of Six- 

 mile pond, and of Elliot and White ponds in Tamworth ; for the level 

 plain adjoining them is from 25 to 40 feet in height, and descends steeply 

 to their shores. Probably masses of ice filled these depressions while 

 the bordering plains were being deposited. 



Till extends in a gentle slope to the margin of Ossipee lake along a 

 distance of about a half mile on its north-east side. Barren pine-plains 

 reach thence for three miles to the east. These are divided by the irreg- 

 ular chain of Danforth ponds, which have the same height with the lake. 

 At Danforth bridge these plains are nearly level, and have a height of 

 35 feet above the ponds, to which they descend in steep escarpments. 

 Their material is mainly sand or fine gravel ; but coarse gravel, con- 

 taining pebbles from six inches to one foot in diameter, is occasionally 

 found, and appears to belong to kames which have been nearly buried 

 beneath the fine alluvium. 



Ossipee river, the outlet of this lake, flows over till at Effingham falls, 

 and along its last mile before entering Maine. In the intervening three 

 miles it is bordered by low modified drift, which extends to Swasey pond 

 in Freedom, and forms an extensive tamarack swamp in the north-east 

 corner of Effingham. 



On the west and south sides of Ossipee lake the modified drift is one 

 half mile to a mile and a half wide. Its highest portion is a delta-plain on 

 the north side of Lovell's river, 40 feet above the lake. Elsewhere it is 

 low, being swampy in many places, and rises only 15 to 25 feet above the 

 lake, towards which it slopes. 



These nearly level areas are bounded by hills and mountains, which 

 rise steeply from the edge of the plains. The supply of modified drift 

 was very abundant here, and fills three fourths of the natural lake-basin 

 which is thus enclosed. 



