Il6 SURFACE GEOLOGY. 



The principal outlet from the part of this basin in Hillsborough county- 

 appears to have been through Greenfield south-easterly to Souhegan 

 river. South from this pass the east border of the Contoocook valley 

 is formed by Pack Monadnock, Temple, Kidder, and Barrett mountains, 

 which extend in a continuous range through the west portions of Temple 

 and New Ipswich. Northward this valley has a high eastern water-shed 

 two to four miles from the river, with no deep depression till we reach 

 the pass through which we have supposed a former outflow towards Pis- 

 cataquog river. The culminating points of this water-shed are at its 

 south and north ends, in Crotched mountain and Craney hill. 



When the melting of the ice-sheet had advanced so far as to open an 

 avenue from this valley through Greenfield, vv'c may suppose that large 

 streams descended from the glacier to this point, by which the kames on 

 the east side of the railroad south of the village, those between Hogback 

 and Pollard ponds and along the road northward between Greenfield and 

 Bennington, and those at Bennington station and for a mile north-west on 

 both sides of Contoocook river, were in succession deposited. The fine 

 alluvium of these streams was at first spread out in the level plain east of 

 Cragin pond, while ice still remained over the area now occupied by this 

 pond. A small lake was afterward formed by the melting of the ice on 

 the north-west side of the pass. This lake received the finer drift brought 

 down by the glacial rivers, producing the alluvial plain west and north- 

 west from Greenfield. 



A channel appears next to have been formed farther to the north-west, 

 skirting the hills upon the east side of the valley and walled on the west 

 by ice. This became filled by the nearly level-topped and terrace-like 

 gravel and sand seen on the east side of the Manchester & Keene Rail- 

 road south from Bennington station, which seem to belong to the same 

 date with the kames at this station and about Whittemore pond. The 

 kames were probably formed in ice-channels which were narrow and 

 somewhat higher than the former, with so rapid a descent that only 

 coarse gravel was deposited in them by the summer floods, the sand be- 

 ing carried onward to the quiet waters of the channel below, which was 

 an arm of the lake. With the full melting of the ice, however, such of the 

 kames as had been formed over the middle of the valley sank to its bot- 

 tom, and arc found at a lower level than the principal deposits of fine 



