EIELDWORK AND ACKNOWLEDGMENTS 511 



Crosby, in his Eeport to the committee on the Charles Eiver dam,* 

 notes a number of cases of sands and clays locally interstratified with till. 

 Several sections in which till overlies fossiliferous and other clays in 

 northeastern Massachnsetts were given by Searsf in the "Geology of 

 Essex county, Massachusetts." The latest contribution is by Fuller,! 

 who in 1906 not only again correlates the earliest tills of the Brockton 

 region with the pre-Kansan, but refers the drumlins about Boston, with 

 few, if any, exceptions, to the Illinoisan, assigning only the thin, loose, 

 and relatively unoxidi zed surface tills to the Wisconsin. 



Although the number of references to phenomena indicative of more 

 than one glacial stage in northeastern New England is large, there has 

 been no attempt, except by Woodworth and Fuller, to correlate the de- 

 posits, or even to formulate conclusions, most writers adhering steadfastly 

 to the belief that the phenomena were caused simply by local retreats and 

 advances of the Wisconsin ice-sheet. 



FlELDWORK AND ACKNOWLEDGMENTS 



In 1905 the present writer had the privilege of being associated with 

 Mr M. L. Fuller in Pleistocene investigations in New England south of 

 Boston, and obtained many data in that region which throw light on the 

 problem in hand. In 1906 he was assigned to work in Maine and in 

 northeastern Massachusetts and southeastern New Hampshire for the 

 Water Eesourees branch of the U. S. Geological Survey, and in that con- 

 nection had opportunity to observe many Pleistocene phenomena north of 

 Boston. For a part of the data here presented he is indebted to Mr 

 George C. Matson, who assisted him in the underground water investi- 

 gations. He also wishes to express his thanks to Mr Fuller for many 

 useful suggestions and criticism of the manuscript, and to Dr W. H. Dall 

 for supplying the most modern names of the fossils found in the marine 

 clays. 



Eesults 



The writer is of the opinion that many of the phenomena observed can 

 be explained in Imt one way — by the invasion of New England by at least 

 three ice-sheets, separated by time intervals of long duration. On account 

 of the greater thickness of the drift and because of fewer exposures, due 



• A study of the geology of the Charles River estuary and the formation of Boston 

 harbor, in "Report of the committee on the Charles River dam." Boston, 1903, pp. 

 345-369. 



t J. H. Sears : Salem, Massachusetts, 1905, pp. 357 et seq. 



X M. L. Fuller : Science, new series, vol. 24, pp. 467-469. 



