640 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



any river, the sands having been carried a great distance by the main 

 stream. Against the north end of Snnderland street it is represented by a 

 horizontal shelf cut in the sandstone. The terrace then widens in the 

 extensive plain of South Leverett which rests against the sandstone moun- 

 tain on the west and against the crystalline rocks on the east, and runs up 

 into the gorge on the east side of Mount Toby. At its head, near the rail- 

 road-crossing north of the station, it is a coarse gravel with pebbles 6 inches 

 in diameter, and it has a height here of 310 feet above sea. It slopes 

 gently to its front, where it has a height of 290 feet above sea, and is made 

 up of coarse sand. 



By recurring to the description of the old course of the Locks Pond 

 Brook down through the Mount Toby gorge to empty into the Hadley 

 Lake at this point (see p. 584) when the ice still filled the Montague basin 

 to the north, the reader will understand my conclusion that the main por- 

 tion of the great mass of gravel gathered here was swept into its place by 

 the Locks Pond Brook, deflected southward, and only smoothed down to 

 its present level by the waters of the Hadley Lake. 1 imagine that this 

 deflection of the brook by ice filling the [Montague basin may have taken 

 place when the ice had abandoned all the Hadley Lake except its northern 

 lobe in Greenfield. 



Southward, the high ten-ace is only indistinctly marked against the till 

 for a long distance, as no brooks brought in material here. 



THE DELTA OF CDSHMANS BROOK AT NORTH AMHERST AND THE ISOLATION OF THE EAST STREET 



BASIN IN AMHERST. 



On reaching North Amherst we find the high terrace (1 s h) developed in 

 great force and, because of the rising of the block of hills north of Amherst 

 Center as a great island in the lake, with considerable complexity. 



A great depression, closed on all sides, extends along the eastern line 

 of Amherst, ending on the south at Dwight's station, having the village of 

 East Street in its center and being bounded on the north by the delta of 

 CvTshmans Brook. 



It is plain that when Cushmans Brook began to flow into the lake 

 there was free communication between this depression and the main area 

 of the lake to the west, across the space now occupied by the delta, and 

 that for a time the sands brought in by the brook were swept southward 



