246 
GEOLOGY: R. A. DALY 
Proc. N. a. S. 
that, whereas anesthetics may induce surface changes assumed to be as- 
sociated with permeabihty, they are active on the inside of the cell as 
evidenced in shrinkage of chloroplasts. Anesthetics affect different cell 
activities differently. This may be due to effects on different cell struc- 
tures : plasma membrane, chloroplasts and cytoplasm. 
A GENERAL SINKING OF SEA-LEVEL IN RECENT TIME 
By Reginald A. Daly 
Department of Geology and Geography, Harvard University 
Communicated by J. M. Clarke, March 10, 1920 
Among the causes of world-wide or "eustatic" shifts of sea-level are: 
appropriate crustal movements whereby the volume of the ocean basin 
is changed; delta- building and volcanic extravasation on the sea-floor, 
the displacement of sea- water not being compensated by crustal subsidence; 
volcanic addition of new water to the ocean; subtraction of water which 
becomes chemically bound during the alteration of rocks; glaciation on 
land, loweriag sea-level by the abstraction of water from the ocean; de- 
glaciation on land, raising sea-level; changes in the earth's center of gravity 
and in her speed of rotation. Numerous as these possibilities are, eustatic 
shifts at definite times and in definite amounts have not often been postu- 
lated by geologists. The proof of such a shift, either positive or negative, 
is not easy. The present note records some field facts suggesting the 
probability of a sinking of general sea-level to the extent of nearly 20 feet, 
during the Human period. The suggestion is published, not to express 
a fixed conclusion but to invite criticism by those familiar with shore- 
lines in different parts of the world, for its testing is manifestly a world- 
wide problem. The matter is important because it affects judgment as 
to the reality of many so-called uplifts of land or sea-bottom, and because 
a close study of the latest shift of sea-level may help to systematize the 
criteria for earlier and larger eustatic shifts. 
Nearly twenty years ago the hypothesis of a recent, negative movement 
of sea-level first presented itself to the writer while engaged in the correla- 
tion of post-Glacial elevated strands in Labrador and Newfoundland with 
those of Quebec. The highest strand mapped between Newfoundland 
and Nachvak Bay, 500 miles to the northwest, was found to be strongly 
warped, like the highest strand from Nev^oundland to Massachusetts. 
On the other hand, the lowest emerged terrace along the shores of the 
Gulf of St. Lawrence was seen to be conspicuously level throughout a 
distance of 300 miles or more below Quebec City. This apparent uniformity 
of level prompted the question whether this particular strand had been 
abandoned by the waves because of a sinking of general sea-level. For 
lack of accurate leveling, correlation with the more closely studied, lowest 
