MODIFIED DRIFI ON ASHUELOT RIVER. : 67 
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. 
AsnuEeLot 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 4o 
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 
