630 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



stream with its delta is marked on the map (1 f ^) by a color different from 

 that devoted to the lake bottom. The progress of this delta was arrested 

 (as detailed under a preceding heading, p. 621) by the breaching of the high 

 terrace sands and the passage of the Fall River south to the Connecticut. 

 Clay (1 b c) appears at the surface of the lake bottom at one place, back of 

 the schoolhouse, near the residence of A. Graves. It is abundant and is 

 the only occurrence in this area. 



THE GREEN RIVER GLACIER. 



High ground borders Greenfield north and west. In the eastern half of 

 the town all depressions are filled with flood sands, which we have traced 

 into the area through the Bernardston and the P^'all River passes. The 

 western half is a deeply sunken area. The two bodies of sand noted above 

 expand westwardly, wrapping around French HilP on the north and south, 

 and end very strangely on the west in a high bluff which overlooks the 

 broad, low basin of Green River and Glen Brook. 



One goes down from the edge of this bluff by a steep scarp 60 feet to 

 the bottom of the basin, and neither the scarp nor this broad bottom seem 

 to me to be the work of Mill River, which now flows in it, bounded on 

 either side by its own alluvial bottom and terraces. 



This valley, which I believe to have been filled with ice while the lake 

 deposits were gathering, stretches along the whole west side of Greenfield. 

 Not only is the mass of sand which must have been removed, if this basin 

 had been filled up at the flood time, out of all proportion to the amount 

 of work done by the other streams in the terrace period, but the bottom of 

 the basin and its eastern scarp is an irregular, kamy, kettle-holed surface, 

 entirely unlike the surface of the erosion terraces of this and the other tribu- 

 taries of the Connecticut; and the true terraces which border the stream, cut 

 at and below the level of this broad, irregular bottom, coiTespond in number 

 and extent with those of the other streams. 



Again, on the west the rocky and till-covered liorder of this basin slopes 

 rapidly to its bottom, and opposite eacli A'alley notch a great delta heading at 

 a level but little below that of the high terrace, and with its semicu-cular front 

 untouched by erosion, is thrust far out into the basin, showing conclusively 



' Tlii> hill 500 feet high in the north part, just east of the railroad. 



