550 



F. G. CLAPP GLACIAL PERIOD IN NEW ENGLAND 



Those writers believed that the dnimlins rested on the brick clay — an 

 assumption which would make the clay pre-Montauk. Several clay pits 

 in Chelsea, Everett, and Medford have been excavated directly up to the 

 base of drumlins, and several feet of till overlie the clay there. A good 

 example occurs in an old pit at the north end of Winter hill, Medford, 

 where the overlying till contains boulders up to 3 feet in diameter. It 

 can be confidently stated that the upper portion of the till rests on the 

 clay. This till, being the latest deposit, is assvimed to be Wisconsin. 



Mr B. F. Smith, a prominent well-driller of Boston, repudiates the 

 assumption -that the drumlins are later than the cla}^ as some of his 

 wells, sunk on the clay plain near the bases of drumlins, reach the bottom 

 of the clay within a few feet and enter "hardpan" corresponding to the 

 "toe" of the dnmilin. He states, moreover, that not in his experience has 

 a well drilled on a drumlin entered clay below it. In several cases, as in 



Figure 9.- 



-Sketch shoiciiuj pyohahlc Bclalioits of Clay to Dndiilins near Boston, Massa- 

 chusetts. 



A-B, marine clay ; W-S, slope of drumlin surface ; W-T, upper surface of Montauk 

 till ; S, sewer excavation near base of drumlin, passing through till into clay, according 

 to Marbut and Woodworth ; C-C, well on clay not far from drumlin, passing through 

 clay into till, according to Smith ; W-S, Wisconsin till. 



wells drilled on drumlins at Hull and Winter hill, Massachusetts, the 

 drumlin till has been found to extend to bed-rock. If the theory of the 

 post-Montauk age of the clay be true, Woodworth's observations can be 

 explained as follows (figure 9) : 



In the sketch, A-B is the clay plain; C-C is a well sunk through the 

 clay into the underlying till; S (not observed on the same drumlin, how- 

 ever), is a sewer excavation which penetrates till into the underlying clay; 

 W-S is veneer of Wisconsin till which adds a few feet to the height of 

 the drumlin W-T and extends out a short distance on the underlying clay 

 plain. 



In view of the fact that the till found in the bottom of clay pits near 

 the base of drumlins, and which is reported in deep wells sunk in the clay, 



