THE SPRINGFIELD LAKE. (357 



chaiiuel between the two exteiisive bodies of water and a larger influx into 

 the western l)asin, and thus a current through into the eastern. There was 

 an eroding ciu'rent which cut a narrow channel back westward from the 

 gap and transported little material into the eastern basin, as the sands of 

 the western basin were delivered into it on the other (western) side. 



In the Springfield basin the broad Agawam plain, 220 to 230 feet high, 

 is composed of fine sand and extends right up into this narrow gorge, which 

 passes tlu'ough the gap and bends north and ends abruptly. This channel 

 is not occupied by a brook, and after passing- through the gap in the trap 

 range it extends into the Westfield plain, being there worn in till and high 

 teiTace gravels. 



Mounting to its rim, we find the coarse gravels of the Westfield i)lain 

 at 280 feet stretching westward, sinking- slightly, and growing finer, and 

 forming the broad sand plain that extends across to Congamuck ponds. A 

 brook which flows north to the Westfield River has cut its way back nearly 

 to this dry gorge; but the latter remains still intact, though a high, narrow 

 ridge is all that now separates them. This dry g'orge was the erosion chan- 

 nel caused by the escape of part of the surplus waters from the western into 

 the eastern basin. The waters stood at practically the same level, but the 

 coarse sands that drifted south in the western basin stood at 280 feet, and 

 the fine sands di-ifting south in the eastern basin stood at 220 feet. 



An examination of the diagram, PI. XIV, will show the relations of the 

 two basins. There remains a distinct possibility that part of this difference, 

 say about 20 feet, may prove to be due to a post-Glacial elevation of the 

 western portion of the area under consideration. The evidence of this is 

 that tlie broad, flat delta plains in front of the Chicopee River outlet 

 at Collins Mills, on the east of the basin, and of the Scantic Brook, at 

 Scantic, in Longmeadow, are 260 to 265 feet above sea, wliile the corre- 

 sponding levels at the head of the delta of the Westfield are 285 to 290 

 feet above sea. The eastern streams cut through glacial lake beds in tlieir 

 upper waters, and, it would seem, should have built out their deltas in the 

 lake up to flood level. 



THE SPRINGFIELD LAKE. 



The Holyoke range, lying in the midst of the Connecticut Valley like 

 an inverted L, or like a blowpipe, its tip appi-oaching the crystalline border 

 of the valley at the Belchertown ponds, broken at its bend and in tlie 



MON XXIX 42 



