MODIFIED DRIFT ON ASHUELOT RIVER. 6/ 



sixth of a mile wide and 30 feet high, gently sloping from the middle to 

 the shores. This is used as a picnic ground, and is covered by pitch and 

 white pines and white birches, the characteristic trees of our sandy plains. 

 The southern portion is most like our ordinary kames, being mainly nar- 

 row, and in some places scarcely a rod wide. This peculiar accumulation 

 of modified drift appears to be due to a depression formed here in the ice 

 at its melting, into which these materials were carried by the glacial 

 streams. Afterwards a hollow was left on each side at the disappearance 

 of the ice. 



AsiiuELOT River in Keene and Swanzey. 



The principal valley of Cheshire county has its widest development in 

 Keene and Swanzey, as shown on Plate V. When the ice melted here, 

 this basin contained for a short time a body of water somewhat larger and 

 probably deeper than Sunapee lake, which soon became filled by the allu- 

 vium of floods which the retreating ice-sheet sent down by every tributary 

 from north, east, and south. The city of Keene is built on the east por- 

 tion of these level deposits, which are here two and a half miles wide, 

 and extend with nearly the same width two miles to the north and the 

 same distance to the south. The Ashuelot river flows through this basin, 

 lying near its east side above Keene, but crosses to its west side in the 

 north part of Swanzey. Its west portion in Keene is drained by the last 

 four miles of Ash Swamp brook. Three miles south from Keene the 

 Ashuelot river finds an avenue westward, along which it is also bordered 

 by low modified drift for several miles. The straight valley, however, 

 continues to the south through Swanzey, being occupied by the South 

 branch and Great brook, with an alluvial area which decreases from one 

 mile to one third of a mile in width. We thus find here a valley ten 

 miles long from north to south, filled with nearly level deposits which are 

 but slightly higher than the streams, and bordered by steep and nearly 

 continuous ranges of hills, which rise from 400 to 600 feet upon each 

 side. This alluvium consists almost everywhere of sand or fine gravel, 

 perhaps extensively underlaid by clay, which is worked for brick-making 

 near the south edge of the city of Keene. Its height is from 10 to 40 

 feet above the river ; and the whole plain was originally of the same 

 height with the highest portions, which still occupy the greater part of 



