502 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
not cease on reaching the former level of equilibrium but continues 
proportionally to the amount of the original pressure. A reciprocal 
motion is thus set up in the earth’s crust, the oscillations of which 
gradually become smaller and smaller.* 
Among the many complications which would arise from a consid- 
erable change of level in the North Atlantic one of the most im- 
portant would undoubtedly be the interference with the poleward 
transmission of warm water, a phenomenon for which we retain the 
convenient name of the Gulf Stream. A deflection of this flow, 
which should materially diminish the amount of the warmer water 
passing into that part of the north Atlantic Ocean lying north and 
east of a line between Scotland and Iceland might unquestionably 
bring about changes in the atmospheric conditions which would be 
both considerable and far-reaching, producing ice-age conditions 
there and in the countries adjacent. 
Taking this for granted and starting from this as our funda- - 
mental axiom we may then imagine the following sequence of events 
in the region we have discussed. 
Biologists as well as geologists are now fairly well agreed that 
the latter part of the Tertiary was characterized by a general eleva- 
tion of the land considerably higher than now,” the result of a 
gradual rise. 
In our region the rise continued until reaching the 600 sea-meter* 
level, thus shutting off the Gulf Stream from the North Atlantic by a 
land bridge connecting Scotland with the Fzrdes and Iceland though 
probably not extending to Greenland. The combination of such a 
great elevation, the cold due to the deflection of the warm current, 
and the increased volume of the cold Greenland current produced 
atmospheric changes resulting in the glaciation which gave Norway 
*See N. O. Holst, Bidrag til Kannedomen om Ostersjéns och Bottniska 
Vikens Postglaciala Geologi, in Sveriges Geol. Unders., Ser. C, No. 180, 1899, 
pp. 113-128, especially p. 127. 
* Say, on an average, 200 meters. See H. F. Osborn’s map, Science (n. s.), 
x1, April 13, 1900, p. 564. 
* The abolition of the old units of fathom and foot for the meter often 
results in obscurity or awkwardness in discussions of this kind, in as much 
as it is nearly always necessary to state whether the figures signify depths 
below the present sea level or heights above it. To avoid much confusion 
I have, therefore, employed the terms sea-meter and land-meter for the relative 
depth and height in question. Thus wheri I say that the land was raised 100 
sea-meters, I mean that the sea-level was lowered 100 meters below its present 
stand, and when I say that the land was depressed 100 land-meters I mean 
that sea-level then was 100 meters higher than at present. 
