140 PROCEEDINGS OF WASHINGTON MEETING. 



townships near the coast it is more, attaining there an average of 30 or 40 feet. 

 The distribution of the englacial drift, so far as can be judged by the derivative 

 stratified beds, was somewhat uniform throughout this state, while the subglacial 

 accumulations are very unequal and are wanting on perhaps half of its area. 



Dr. Edward Hitchcock estimated the maximum thickness of the drift in Massa- 

 chusetts, excepting the heavily drift-covered southeastern counties of Plymouth 

 and Barnstable, to be 100 feet, and its average thickness 20 or 25 feet.* Some of 

 the drumlins of Boston harbor and of Scituate give evidence of rapid accumulation, 

 and show that the ice-sheet passing over them was plentifully charged with engla- 

 cial drift which lodged on their surfaces ; hut neither there nor elsewhere have I 

 been able to determine that extraordinary amounts of ice-held detritus were de- 

 posited as superglacial or upper till. The mean depth of this deposit is probably 

 about the same as in New Hampshire, and its averages in different districts may 

 range from one or two feet to live or perhaps ten feet. Besides, there is much 

 modified drift spread along the river valleys and on lowlands, becoming most con- 

 spicuous southeastward, near the terminal moraines, where great thicknesses of 

 gravel and sand, washed from the departing ice-sheet, form extensive tracts, in- 

 cluding the fore-arm of Cape Cod. 



Vermont, Connecticut, and Rhode Island agree nearly with the foregoing as to 

 the amount and characters of the drift. For the whole of New England its volume 

 is probably equal to a uniform sheet 30 or 40 feet thick, of which about a quarter 

 part was englacial at the time of final melting of the ice. 



\i "■ York. — No other state surpasses New York in contrasts of topography and 

 in diverse development and distribution of«rhe drift. From Syracuse westward 

 along a distance of 00 miles the traveler on the New York Central railroad sees a 

 profusion of drumlins 50 to 150 feet in height, trending from north to south in 

 parallelism with the glaciation of the region and with the neighboring "finger" 

 lakes, which occupy fjord-like valleys on the south. Through this part of the state 

 and generally across its southern half, the drift has a greater average thickness 

 than in New England. Northward, between Vermont and Lake Ontario, the 

 Adirondack mountains and some lowland areas have tracts of very scanty drift, 

 while other continuous tracts are abundantly drift-covered. That a large amount 

 of drift was here enclosed within the ice and set free by its departure is shown by 

 the portions supplied from it to form such extensive -ravel and sand plains as 

 stretch from Coeymans northward to Albany and Schenectady, again from near 

 Rome across many miles northwestward, and through Clay and Schroeppel, west of 

 Oneida lake, and from the great bend of Black river northeastward in Wilna. 



Minnesota. — A very great depth of drift, averaging loo to 150 feet, is spread over 

 all the western half or two-thirds of Minnesota ; but in the northeastern part of 

 this state a large area was swept bare by the eroding ice-sheet. During the first 

 year of my work on the geological survey of Minnesota, in examination of twenty- 

 two counties lying in its central and western portions, I obtained notes of the order, 

 thickness, and characters of the drift deposits passed through by about 600 wells. 

 Nearly half of these found beneath the englacial upper till a much harder lower 

 till, which was compacted by the pressure of the ice during its subglacial deposition. 

 The extremes in thickness of the englacial till were ."> to ."i feet and 40 feet. t Later 



♦Geology of Mass., 1841, p. 365. 



t Geological Survey of Minnesota, Eighth annual report, for L879, pp. 109-117. 



