362 W. TJpho/m, — Marine Shells and Fragments 



development upon most of the country in the neighborhood of 

 Boston, rising with smooth, ovally rounded contour to heights 

 from 50 to 200 feet, and have been the subject of several papers 

 before this Society.* Approximate elevations of the drumlins 

 in which fossils have been found are as follows : Grover's cliff, 

 60 feet above the sea; Great Head, 100 feet; Eagle hill, East 

 Boston, 120 feet; north end of Long island, 75 feet; George's 

 island, 60 feet ; Moon island, 100 feet ; north end of Peddock's 

 island, 10 feet ; Nut island, 40 feet ; Quincy Great hill, 100 

 feet ; on the north shore of Hull, 80 feet ; Telegraph hill, 125 

 feet ; and Sagamore Head, 65 feet. The cliffs eroded by the 

 sea on most of these drumlins extend from 10 or 15 feet above 

 mean tide sea level upward very steeply or often in part ver- 

 tically to near their tops. 



Excepting Great Head, which contains modified drift near 

 its base, to be presently described, these sections consist wholly 

 of till or bowlder-clay, the direct deposit of the ice-sheet, un- 

 modified by the transporting and assorting action of water. 

 Weathering has changed the small ingredient of iron in this 

 deposit from the protoxide combinations which it still retains 

 in the lower part of the till to the hydrous sesquioxide in its 

 upper part for a depth of commonly fifteen or twenty feet 

 from the surface, thereby giving to the latter a yellowish color 

 in contrast with the darker gray or bluish color of the former. 

 Both portions are very compact and hard till, an intimate un- 

 stratified commingling of bowlders, gravel, sand, and clay, and 

 seem by these characters, and by their abundant striated bowl- 

 ders and smaller fragments of stone, to be distinctly the ground 

 moraine of the ice-sheet. The southeast and east-southeast trends 

 of the longer axes of the drumlins in this vicinity, coinciding at 

 least approximately with the direction of striation of the bed- 

 rock, further indicate that these oval hills of till were accumu- 

 lated beneath the ice-sheet, this form being that which would op- 

 pose the least resistance to the glacial current passing over them. 

 Though the till is destitute of stratification, its materials, coarse 

 and fine, from boulders often several feet and occasionally ten 

 feet or more in diameter to the finest rock-fiour, being indis- 

 criminately mixed in the same mass, it yet generally shows an 

 obscure lamination in parallelism with the surface, having thus 

 in the drumlins an inclination like that of their slopes. This 

 structure is best displayed after some exposure of the section to 

 the action of the weather. It seems to be an imperfect cleavage 



* By Prof. N. S. Shaler, Proceedings B. S. N. H., vol. xiii, pp. 198-203; by 

 Prof. C. H. Hitchcock, vol. xix. pp.63-67 ; and by the present writer, vol. xx, pp. 

 220-234. Also, see Geology of New Hampshire, vol. iii, pp. 285-309; "The 

 Distribution and Origin of Drumlins," by W. M. Davis, in this Journal, III, vol. 

 xxviii, pp. 407-416, Dec. 1884; and Illustrations of the Earth's Surface : Glaciers, 

 by Professors Shaler and Davis, Plate xxiv. 



