ICE-RETREAT IN GLACIAL LAKE NEPONSET 195 



Lakelets of the earlier stages. — The position of the ice-front at the 

 beginning of the flow through the outlet was very near the crest of 

 the pass, as indicated by the distribution of the plains. Later, how- 

 ever, the ice drew back slightly, while farther north it receded at 

 the same time from the valley walls sufficiently to bring into existence 

 the East Sharon lakelet on the west side of the valley and the Stoughton 

 lakelet on the east. Ice-masses still occupied the Massapoag and 

 Ames Pond valleys, and the two southward-leading valleys southeast 

 of Stoughton, leaving the Rattlesnake Hill notch as the only available 

 passage to the south. The outlets of both lakelets were through 

 this pass, to reach which the drainage of both, as has been explained, 

 passed over the ice itself for a short distance. 



Opening of the Ames Pond outlet.- — The earlier or high-level stages 

 of the Stoughton Bay lakelets were brought to a close when, by the 

 shrinking away of the ice from the retaining hillsides, lower outlets 

 were opened through the valley of Ames Pond. This valley is marked 

 on both sides by terraces exhibiting ice-contact faces on the sides 

 nearest the pond, constituting, in fact, true kame or morainal ter- 

 races — a feature not often recognized in eastern Massachusetts. 

 From these it is evident that an ice-tongue still remained in the mid- 

 dle of the valley. This was at first possibly connected with the 

 larger remnant of the ice farther north in the valley, but the melting 

 of the ice, which had previously proceeded slowly by ordinary surface 

 ablation, now probably went on with much greater rapidity, owing to 

 the action of running water on both sides of the valley mass. This 

 rapidly cut away the ice, already greatly reduced by the stream cros- 

 sing from the Stoughton to the East Sharon lakelet, with the result 

 that the Ames Pond mass was early separated into an independent 

 block. 



Lakelets of the later stages. — The Elm Street lakelet was the first 

 of the lower-level bodies to be formed, and the waters found outlet 

 along both sides of the Ames Pond block, forming the kame terrace 

 deposits mentioned. The waters in part passed out from the valley 

 by a bowlder-strewn gorge through granite ledges at the head of 

 the bay just southeast of the highway across the pond, in part by 

 the wider, sand-filled valley between rock hills just above the lower 

 end of the pond, and in part directly southward along the main 

 valley. 



