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President's Address. 5 
present places since the beginning of geological time. As a 
corollary to this, it is held that the existing deep seas—z.e., 
areas now covered by water of more than 1000 fathoms in 
depth—have been permanent features in the physical con- 
figuration of the earth’s surface, and that the abysses of the 
ocean-floor have not been up-raised to form dry land since 
the oldest fossiliferous rocks were laid down. 
This doctrine is based upon a vast number of very com- 
plex data, and carries with it conclusions of the most vital 
import to both geologists and biologists, while it may safely 
be said that the time for its final solution has not yet arrived. 
From a merely theoretical point of view, it seems very un- 
likely that while the dry lands have been subjected to 
repeated movements which must in many instances have 
involved displacements of many thousands of feet, measured 
vertically, the ocean-floors should at the same time have 
been exempted from displacements of a contrary character. 
Thus, to take one example only, a large portion of the North 
American continent, including what are now the Rocky 
Mountains and Appalachians, must have been depressed 
during Paleozoic time to a depth of 30,000 to 40,000 feet, 
since it is now covered by a more or less absolutely con- 
tinuous series of Paleozoic marine sediments of the above 
thickness (Walcott, Amer. Geologist, vol. xii, p. 343). 
But, if the old Algonkian and pre-Cambrian floor had thus 
sunk some five or six miles, we can hardly suppose that the 
foundations of the Atlantic and Pacific had during the same 
time been free from some corresponding movement. In fact, 
if we are dealing with a curved surface, such as that of a 
slowly cooling globe, which is gradually shrinking in such a 
manner as to produce tangential thrust, it is hardly conceiv- 
able that elevation and depression should not be to some 
extent correlative. If one area sinks, another will tend to 
be pushed up; though it does not follow that the two move- 
ments will be precisely similar in kind or equal in amount. 
It may be freely admitted that the weight of the oceanic 
waters would tend in general to increase the stability of the 
ocean-floors in comparison with the dry lands; but this con- 
sideration would not warrant the view that the floor of the 
