Upham.] 
140 
[Dec. 19, 
After this the ocean within recent times has held even a somewhat 
lower level than at present, and seems to be now very slowly ris- 
ing upon this shore and indeed along the entire coast from New 
Jersey to the Gulf of Saint Lawrence, as is shown by submerged 
stumps of trees in many localities, rooted in the ground where they 
grew, and by tracts of marsh and peat-swamp covered by the sea. 1 
During part of the time of lower level of the sea, its temperature 
was apparently warmer, as indicated by the range of Venus merce- 
naria with other southern species northward to the Gulf of Saint 
Lawrence, though now it is wanting along the shore of Maine, the 
bay of Fundy, and Nova Scotia. 
Proceeding from Boston toward the north and northwest, the 
elevation of fossiliferous marine beds lying on the glacial drift in- 
creases to about 225 feet in Maine, about 520 feet in the Saint 
Lawrence valley at Montreal, and 440 feet at a distance of 130 
miles west-southwest of Montreal ; but eastward along the Saint 
Lawrence it decreases to 375 feet opposite the Saguenay, and does 
not exceed 200 feet in the basin of the Bay of Chaleurs, while these 
marine deposits are wanting in Nova Scotia and Cape Breton isl- 
and. 2 The changed condition in the relative heights of land and 
sea at the time of the recession of the ice-sheet thus caused the 
land to be submerged in increasing amount northwestward from a 
line drawn through Nova Scotia, Boston, and New York. This 
condition, due probably in part to depression of the land and in part 
to uplifting of the sea level by gravitation, seems to have been 
caused by the ice-sheet, which had its greatest thickness, estimated 
by Dana to be not less than two miles, on the highlands between 
the Saint Lawrence and Hudson bay, where its influence to pro- 
duce such changes of level would be greatest. The submergence 
seems to have been more than can be wholly attributed to gravi- 
tation of the sea toward the ice-sheet; 3 but it is much less than 
1 Outlines of the Min. and Geol. of Boston, p. 95; Memoirs of this Society, vol. i, p. 
324; Quart. Journ. Geol. Soc., vol. xvii, 1861, pp. 381-8; Geol. of N. H., vol. iii, p. 173; 
J. W. Dawson’s Acadian Geology, third ed., pp. 28-32, and Supplement of do., pp. 13-17. 
2 A. S. Packard, jr., in Memoirs of this Society, vol. i, pp. 231-262. J. W. Dawson in 
Notes on the Post-pliocene Geology of Canada; and Am. Journ. Sci., in, vol. xxv, 1883, 
pp. 200-202. C. H. Hitchcock in Proc. Am. Assoc, for Adv. of Sci., Portland, 1873, vol. 
xxii, pp. 169-175; Geol. of N. H., vol. iii, pp. 279-282; and Geol. Mag., II, vol. vi, 1879, pp. 
248-250. R. Chalmers in Transactions of the Royal Society of Canada, sec. iv, 1886, pp. 
139-145. 
3 Sixth Annual Report, U. S. Geol. Survey, 1885, pp. 291-300. 
