624 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



and is made up of coarse gravel, eontaiuiug- cobbles up to 6 inches in length. 

 Its front edge has a height of 360 feet where it sinks down by a steep scarp 

 to the level of the Northfield village plain (1 b t). At its foot a brook runs 

 northwest into the Connecticut, which has cut a notcli in it, but has made no 

 delta projecting out onto the teiTace below, showing that when it was effect- 

 ively eroding the main stream was also strongly eroding, and carried on all 

 its contriljutions. This is the case, also, with all the tributaries down to 

 Millers Falls. 



South of this brook the high terrace (1 s h) is continuous, but narrows 

 rapidh', and by the side of the road going up to F. Johnson's, just north 

 of the single drumlin marked on the map, a section occurs in coarse gravel 

 much contorted. From this point the great sand masses of the next lower 

 level — the old lake bottom (1 b t) — which are here nearl}- a mile wide and 

 extend southward for over 2 miles in the great "Beers Plain," have been 

 thrown up in a wilderness of sand dunes, thus obliterating almost all trace 

 of the scarp which once connected the two levels. 



The plain of Northfield village, at the third level — 305 feet (t*) — is 

 thinly covered with sand. Immediately below is till or ledge, but south- 

 ward the rock lies much lower, while the level of 300 feet is maintained by 

 a great volume of sands. Southward these sands rest upon finer material. 

 Just over the railroad, on the road west from the station, 20 feet of coarse 

 sand, dipping S. 20°, rests upon very fine, horizontally bedded sands with 

 a single layer of fat clay 18 inches thick. The former stratum was laid 

 down while the stream was forming the terrace (t*); the lower is the 

 uueroded portion of the lake-bottom beds. Their present eroded sui-face 

 is 2.50 feet above sea, and they are exposed with a thickness of 42 feet, and 

 no bottom is seen; nor do the sands vary. 



Just south of the village street, where two brooks come together and 

 run under the railroad, the same sands rest, at a height of 270 feet above sea, 

 upon blue banded clays, the fat layers being one-third to two-thirds of an 

 inch thick, and the intervening layers of sandy clay 6 inches thick. Four 

 miles farther south, at the ferry at Gill station, the clay layers are one-half 

 of an inch wide and are separated by layers of fine sand 2 feet thick. 

 Farther south, below Northfield Farms, the Fom--mile Brook has cut 

 through heavy clay beds rising about 260 feet above sea. 



The above figures show that the basin was filled up with fine bedded 



