1888.] 
141 
[Cresson. 
would be expected for agreement with the views of Jamieson 1 and 
Shaler , 2 that the ice-sheet must depress the earth’s crust to a 
vertical extent approximately measured by a thickness of rock 
equal to the ice in weight. 
Besides the testimony of marine fossils, one further observation 
contributes greatly to our knowledge of the relation of land and 
sea on the south side of Massachusetts bay while this area was en- 
veloped by the continental glacier. On the shore of a peninsula 
in Cohasset Little Harbor, fifteen miles southeast of Boston, pot- 
holes similar to those of water-falls on rivers are found in two lo- 
calities, reaching from sea level to a height of fifteen feet. The 
contour of this vicinity precludes the possibility of referring their 
origin to any stream since the close of the glacial period ; and they 
must doubtless be attributed to the action of a water-fall plung- 
ing down hundreds of feet through a moulin of the ice-sheet . 3 To 
Mr. Bouve, long the president of this Society, belongs the honor 
of first observing these pot-holes and appreciating their signifi- 
cance. It was under his guidance that my visit to them was made ; 
and it is with his permission that I speak of them here, previous 
to the detailed description which he will later present before the 
Society. Such water- wearing of the bed-rock could not take place 
beneath the sea level, so that they prove that here during a part, 
probably the later part, of the time when this area was covered by 
the ice-sheet, the land stood at least as high as now, not being de- 
pressed under its vast weight. 
EARLY MAN IN THE DELAWARE VALLEY. 
BY HILBORNE T. CRESSON. 
Special assistant of the Peabody Museum. 
At Professor Putnam’s request, I have prepared this brief ac- 
count of work carried on for the past two years, under the direc- 
tion of the Peabody Museum, and included some previous researches, 
1 Quart. Journ. Geol. Soc., vol. xxi, 1865, p. 178. Geol. Mag., n, vol. ix, Sept, and Oct., 
1882; and ill, vol. iv, Aug., 1887. Also, see Fisher’s Physics of the Earth’s Crust, and 
Geol. Mag., II, ix, p. 526. 
2 Proceedings of this Society, vol. xii,1868, pp. 128-136; and xxiii, 1884, pp. 36-44. Me- 
moirs of this Society, vol. i, 1874, pp. 320-340. Am. Journ. Sc., ill, vol. xxxiii, 1887, pp. 
210-221. Lowell Lectures, Nov. and Dec., 1888. 
3 Compare Quart. Journ. Geol. Soc., vol. xxx, 1874, pp. 750-771. 
