AREAL DESCRIPTION 621 



altitude 400 feet, is the only conspicuous plain, which stands so much 

 above the marine level as to be wholly credited to glacial waters. 



The most extensive and interesting static-water deposits in the dis- 

 trict are the wide plains about Clinton village. Crosby writes: 



". . . the Clinton plains, which are unquestionably equal in interest to 

 all the rest of the modified drift of the Nashua Valley" . . . (58, page 

 323). 



The Clinton plains lie west, north, and east of the village. The 

 cemetery on the west edge of the village is contoured at 360 feet, while 

 the extensive plain farther west, traversed by the railroad and the 

 Sterling road, is 380 feet on the south of the roads and 360 feet on the 

 north. East of the village, toward Bolton Station, the railroad cuts 

 another plain with height about 360 feet. 



Apparently the whole width of the valley at Clinton was filled with 

 detritus from 340 to 380 feet. The theoretic marine level is about 375 

 feet by the map of isobases. Possibly the higher deposits may be 

 credited to Crosby^s Clinton stage of the glacial waters before the Soutli 

 Dike outflow had cleared the pass; and possibly the marine plane is 

 higher than indicated in the map. The inferior plains certainly repre- 

 sent sealevel waters, which entered the net of valleys from the south 

 and southeast. 



As the ice-front receded the oceanic waters took possession of the 

 broad valley northward, toward Ayer, and as the land rose out of the 

 water the smooth stretches of sand and silt were formed at inferior 

 levels, producing the plains down (northward) the Nashua Valley 

 toward Ayer and up the valley of the North Nashua toward Fitchburg. 

 The villages of Lancaster, South Lancaster, and Lancaster Commons 

 stand on wave-leveled tracts. The oceanic waters covered the region 

 before any measurable uplift had occurred, as indicated by the full- 

 height deltas at Fitchburg and northward in New Hampshire. The 

 horizontal deposits at all altitudes below the plains at Clinton indicate 

 long-lived and very slowly falling water (relative to the land) and could 

 not be produced in any glacial lake waters. 



BOSTON-WELLESLEY-yiSHLAND DISTRICT 



The steep hills of rock and the coarse drift about Boston were un- 

 favorable for registering conspicuous standing-water phenomena, and 

 it is not surprising that the fact of recent deep submergence has not 

 been generally recognized. The inconspicuous evidences exist and are 



