. Bulletin of the Geological Society of America. Geology. 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
. Bulletin of the Geological Society of America. Geology. 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 -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
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