662 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



oil the noi'tli ag-ainst the shoulder of the mountain, runs south nearly a mile. 

 Going up 35 feet to the top of this hill, one is surprised to see that on the 

 west it slopes suddenly down 190 feet to the river which is wearing at its 

 foot. The escarpment on the east which borders the channel is plainly a 

 scarp of deposition, and the whole terrace was possibly built by the rapid 

 current tlu'ough the Holyoke notch, meeting the current we have traced 

 from the Belchertown notch and allowing the sands to gather ix.. a bar in the 

 slack water between the two. Perhaps it should be assigned to a slightly 

 earlier period, when the ice, still abutting on the Holyoke range to the north, 

 projected through the notch and allowed the sands to gather against its 

 eastern flank and on melting let them cave to form the passage for the river. 

 The presence of the ice on the north spanning the Holyoke notch is essen- 

 tial to the formation of this great terrace of coarse material, because since 

 the ice disappeared nothing but fine clay has been brought by the waters 

 into the gorge from the north, while the section which treats of the glacial 

 gravels carried through the notches in this range (p. 586) furnishes a clear 

 explanation for this abnormal deposit. 



HIGH TEEEACE OR BENCH OF THE WEST SIDE OF THE LAKE FEOM THE HOLYOKE 

 NOTCH SOUTHWARD. 



From the notch to the north line of the town of Holyoke the ground 

 rises rapidly from the narrow, low ten-ace up a rocky slope to the crest of 

 the eastern trap ridge, and there is scarcely trace of any high terrace upon 

 its flank, because there was deep water in the Hadley Lake opposite the 

 mouth of the notch and little sand was brought through here. What was 

 brought stretched south in a great bar which is almost intact on the other 

 side of the river, in Dry Hill, in the north part of South Hadley, just 

 described, as can be beautifully seen from the inner trap ridge mentioned 

 above. All that passed through the notch on its west side was swept in 

 between the two trap ridges and filled a bay north of the burnt stone mill 

 above Smiths Ferry. All along the riverward flank of the east trap ridge 

 high sands were not laid down because, for this portion of the basin, the 

 supply came from the far-off" east side, mainly from the Chicopee River, and 

 as the deposit expanded westward its level lowered, so that no high terrace 

 sands were brought against the till-covered trap slope, and the small inden- 

 tation made by the waters at this level has left no trace of its presence. 



