286 



When tlie ice-sheet had retreated from the northwest corner 

 of llingliam, but yet lingered in Weymouth Back River, the 

 prominent line of ledges extending from Huit's Cove across 

 Lincoln and Beal Streets to Beal's Cove, with the drumlins 

 back of it, formed a barrier northwest of which was spread a 

 very perfect sandplain having a normal elevation of from 25 to 

 30 feet and designated in the preceding pages as the Coastal 

 Plain. Traces of it may be observed all through the northern 

 part of Hingham, and corresponding to it are more or less 

 distinct erosion terraces on the southwestern side of Pleasant 

 Hill find the northeastern side of Squirrel Hill. 



So far as known, there are no deposits of stratified clay in 

 Hingham, above sea-level. This finest part of the modified 

 drift was probably carried far beyond the limits of the town by 

 the overflow waters from the glacial lakes. We may reasonably 

 suppose, however, that beneath the argillaceous silt now 

 depositing in Hingham Harbor and exposed to view at low-tide, 

 there is a considerable thickness of true glacial clay. 



POSTGLACIAL DEPOSITS AND CHANGES. 



The evidences of postglacial changes of level observed in 

 Nantasket are not repeated with equal distinctness, if at all, in 

 the Plingham area ; but above the present level of the sea there 

 are, so far as observed, no traces of marine erosion or marine 

 deposits, or any proofs of a postglacial elevation of the land. 

 The lowest or coastal sandplain, like the higher plains, is, as 

 already stated, best explained as the product of glacial lakes 

 and streams during the departure of the ice-sheet. Beneatli 

 some of the lower bogs and marshes there are, possibly, layers 

 of marine silt and shells, but nothing of the kind appears to 

 liave been observed. On the other hand, it is in the highest 

 degree probable that sections of the salt marshes would present, 

 in the form of buried peat beds, if not otherwise, evidence of a 

 moderate postglacial subsidence of the land. But even if such 



