271 



shells. It should be stated, however, tlmt the lower part of 

 this section is, unfortunately, concealed by the roadway and 

 the retaining wall, and the greatest accessible depth below the 

 original surface is probably not over 25 feet. Pleasant Hill 

 presents on the same shore a long low section which, although not 

 so satisfactory as the other, might, perhaps, be expected to 

 disclose the shells if they were at all abundant in the hill. But 

 this can not be said of the very low and imperfect sections 

 afforded by the shores of the World's End, Planter's Hill, and 

 Pine Hill. Turkey Hill, Otis Hill, and perhaps one or two 

 other drumlins, present shallow roadside sections ; but on none 

 of the inland drumlins are there clear sections, natural or 

 artificial, extending below the superficial and highly oxidized 

 till. The insufficiency of this purely negative evidence is 

 obvious, especially in view of the fact that shells have been 

 foiuid in well-sections in the inland drumlins of Cohasset 

 (p. 143) and Braintree ; and it may be safely predicted that 

 fossil shells would be found in some of the drumlins of 

 Hingham if the blue or unoxidized till were exposed to our 

 observation. 



The extremely local origin of the main part of the till 

 becomes very obvious immediately on passing southward from 

 the sedimentar}^ rocks of Hingham to the broad area of 

 granite. For tlie first mile or two fragments of conglomerate, 

 slate, and melaphyr are fairly abundant ; but beyond a distance 

 of three or four miles from the boundary they are rather rarely 

 met with. I have elsewhere^ pointed out that the ice-sheet 

 prol)ably slid over the subglacial till or ground moraine, the 

 latter moving very much less rapidly than the ice itself; just as 

 the stones in the bed of a river move less rapidly than the 

 water flowing over them. The englacial fragments only, like 

 floating objects in a river, are far-travelled or measure the 

 actual movement of the ice ; and these form but a very small 

 fraction of the till. 



'Pioc. B. S.N. H., V. -25,134. 



