214 FREDERICK G. CLAPP 



CONCLUSIONS. 



The most important generalizations to be drawn from this study 

 are as follows: 



1. The decay of the ice in situ for many miles back from the ice- 

 front — the decaying glacier consisting of a mass of stagnant ice over- 

 lain and buried by sheets of water and by extensive deposits of sand 

 and gravel. 



2. The more rapid disappearance of the ice on the west than 

 farther east, causing a nearly open lake in parts of the Sudbury 

 valley, while as yet the ice in the lower portions of the Boston basin 

 had not decayed sufficiently to allow the formation of a single sand 

 plain. 



3. The interdependence of the water levels of the individual lake- 

 lets belonging to each stage, and their correspondence with some 

 common outlet toward the sea. 



Frederick G. Clapp. 



Washington, D. C. 



