ig6 M. L. FULLER 



Following the Elm Street, the West Stoughton lakelet was formed. 

 By this time the Ames Pond block had become much contracted, or 

 had entirely disappeared, affording an outlet, from lo to 20 feet lower 

 than the earlier, through the valley now occupied by the pond. These 

 later waters carried little sand, and are represented, therefore, not by 

 deposits, but by their erosive action. The faces of the terraces of the 

 valleys were shaped in places by these waters, but in the main they 

 are of the nature of ice-contact slopes. 



CONCLUSIONS. 



The results of the study of the Stoughton Bay area, in so far 

 as they apply to retreatal conditions, prove: (i) that in this area 

 the ice had become stagnant before the inception of the lakelets, 

 and remained so throughout their history; (2) that the ice, previous 

 to the emergence of the hills through its surface, was reduced almost 

 entirely by superficial ablation; (3) that the subsequent melting was 

 most rapid along the margins of the projecting land masses, because of 

 the radiation of heat from them and the concentration of drainage 

 along their borders; and (4) that the shrinkage continued to be out- 

 ward in all directions from the exposed land masses, until the ice 

 was reduced to narrow lines along the deeper valleys, and finally dis- 

 appeared essentially simultaneously from all portions of the area. 



APPLICATIONS. 



Extent of glacial lakes. — Hitherto, in the discussion of glacial 

 lakes in eastern Massachusetts, as was pointed out in the introduc- 

 tion, it has been assumed that the ice retreated with a rather definite 

 and regular margin, in front of which extensive bodies of water 

 accumulated in the northward-sloping valleys. While the observa- 

 tions of the writer have not been sufficiently extended to discuss in 

 detail the conditions in other lakes, it has appeared almost certain 

 from reconnaissance studies that the size of the open water bodies 

 in the various lakes at any given time were much smaller than has 

 usually been supposed, and that the marginal lakelets were very 

 numerous, and definite and regular margins relatively rare, the ice 

 having disappeared, in many instances, in the same manner as in the 

 Stoughton area. Which type of retreat prevailed can be determined 



