510 F. G. CLAPP — GLACIAL PERIOD IN NEW ENGLAND 



scribed by irphaiii, was best set forth by Crosby and Ballard in 1894.* 

 In 1896, in connection with a discussion of the "Glacial brick clays of 

 Ehode Island and southeastern Massachusetts," Woodworth described the 

 "Geology and geograpliy of the clays,"f in which he postulated three 

 glacial stages separated by interglacial stages. In the same report Mar- 

 but and Wood\vorth described "The clays about Boston" and published 

 many sections and other evidences of till overlying the clays. J 



An account of the geology of the Cape Cod district was given by Shaler 

 in 1898,§ in which he followed Woodworth in his general outline of Pleis- 

 tocene succession and described inany occurrences of folded sands and 

 clays, till overlying clays and sands, and other evidences of glacial com- 

 plexity. 



In 1899 Stone, in his "Glacial gravels of Maine and their associated 

 deposits," gave a number of evidences of probahle pre-Wisconsin deposits, 

 l)ut did not interpret the phenomena in this way.|| 



While several observers had described differences in the tills of New 

 England which in the light of our present knowledge would seem to indi- 

 cate differences in age, up to 1901 all geologists except Woodworth had 

 assumed them to simply represent stages of a single invasion, the Wiscon- 

 sin. In that year, however, Puller,^ in discussing the region in the 

 vicinity of Brockton and Stoughton, a short distance south of Boston, 

 pointed out the existence of two distinct tills characterized by marked 

 differences in composition and weathering, which he definitely stated 

 were the representatives not of a single glacial epoch, as had previously 

 been assumed, but of two widely separated epochs, the Wisconsin and the 

 Ivansan or pre-Ivansan. Examples of deep weathering and disintegra- 

 tion of rock ledges between the two epochs were also described. 



Continuing along the lines of investigation begun by Woodworth, 

 Brown, in 1902,** described a number of cases of till overlying sand and 

 clay in Everett, Chelsea, and Eevere, near Boston. 



In 1903 the term "interglacial" was questionably applied by Tarr to 

 some fossiliferous beds at cape Ann,f f not far from the locality described 

 by Shaler 40 years before. 



■ * W. O. Crosby and Hettie O. Ballard : Am. .Tour. Sci., third series, vol. xlviii, pp. 

 486-496. 



t Seventeenth Ann. Rept. TI. S. Geological Survey, part i, pp. 075-988. 



t Op. cit, pp. 989-1004. 



§ Eighteenth Ann. Rept. U. S. Geological Survey, part ii, 1898, pp. .50.3-.59.3. 



II Geo. H. Stone : Monograph .3-1, U. S. Geological Survey. 1899. 



11 M. L. Fuller : Probable representatives of pre-Wisconsin till in southeastern Massa- 

 chusetts. .Tournal of Geology, vol. 9, pp. :?ll-.329. 



**R. M. Brown: The clays of the Boston basin. Am. .Tour. Sci., fourth series, vol. 

 xiv, pp. 445-450. 



tt R. S. Tarr: Postglacial and interglacial (?) changes of level at Cape Ann, Massa- 

 chusetts. Bull. Harv. Coll. Mus. Comp. Zool., vol. xlii, pp. 181-191. 



