\ 
1879.) 225 [Upham. 
similar lenticular form. These have their position almost invariably 
upon either the south or north side of the ledgy hills against which 
they rest, showing a eonsiderable deflection towards the south-east 
and north-west in the east part of the state. It cannot be doubted 
that the trend of the lenticular hills, and the direction taken by these 
slopes, have been determined by the glacial current, which produced 
the striae with which they are parallel. 
The material of these hills may be well seen at many excavations 
for streets and other grading purposes near the city, as at the north- 
east part of Dorchester Heights in South Boston, at Powder Horn 
Hill, at Prospect Hill in Somerville, and at the west end of Parker 
Hill, as also in the sea-eliffs of Nantasket, Winthrop, and the islands 
of the harbor. These sections for grading vary from ten to fifty feet 
in depth, while the sea-cliffs near Point Allerton, and on Great 
Brewster, Lovell’s, Gallop’s, Deer, Long, Moon, and Spectacle islands, 
and at Winthrop Head and Grover’s Cliff, rise fifty to one hundred 
feet in height. They are in all cases found to be composed of the 
deposit which we have described as lower till, sometimes showing the 
laminated structure, but nowhere, so far as I have observed, with any 
traces of stratification by currents of water. The covering of upper 
till on these hills is probably in most cases only a foot or two thick, 
and it is not so distinctly separated from the lower till as in most 
parts of New Hampshire and at Worcester in this state, where it is 
usually from one and a half to three feet thick, resting at.a definite 
line upon the very hard and obscurely laminated, clayey lower till. 
The latter, with its dark gray color, presents a distinc contrast with 
the yellowish, gravelly and sandy, loose upper till, which shows no 
lamination, but is sometimes imperfectly stratified. In many of these 
accumulations near Boston, the upper ten to twenty feet are yellow- 
ish, gradually changing below to a dull gray eolor; but the whole 
bank is of nearly equal compactness, and contains abundant glaciated 
boulders and pebbles. 
- The earliest notice of any of our lenticular hills is found in Wood’s 
«¢ New England’s Prospect,” printed in London four years after the 
settlement of Boston, of which he says: — 
.* This Necke of land is not above foure miles in compasse, in forme 
almost square, having on the South-side at one corner, a great broad 
hill, whereon is planted a Fort, which can command any ship as shee 
sayles into any Harbour within the still Bay. On the North-side is 
another Hill equall in bignesse, whereon stands a Winde-mill. To 
PROCEEDINGS B. 8S. N. H.— VOL. XX. 15 NOVEMBER, 1879. 
