796 
ADDRESS OF THE PRESIDENT BEFORE THE 
SECTION OF GEOGRAPHY OF THE BRIT- 
ISH ASSOCIATION FOR THE AD- 
VANCEMENT OF SCIENCE. 
II. 
Evolution of the Continental and Oceanic 
Areas. 
I have now pointed out what appear to 
me to be some of the more general results 
arrived at in recent years regarding the 
present condition of the floor of the ocean. 
I may now be permitted to indicate the 
possible bearing of these results on opinions 
as to the origin of some fundamental geo- 
graphical phenomena ; for instance, on the 
evolution of the protruding continents and 
sunken ocean-basins. In dealing with such 
a problem much that is hypothetical must 
necessarily be introduced, but these specu- 
lations are based on ascertained scientific 
facts. 
The well-known American geologist, Dut- 
ton, says: ‘It has been much the habit of 
geologists to attempt to explain the pro- 
gressive elevation of plateaus and mountain 
platforms, and also the folding of strata, by 
one and the same process. I hold the two 
processes to be distinct, and having no nec- 
essary relation to each other. There are 
plicated regions which are little or not at all 
elevated, and there are elevated regions 
which are not plicated.”’ Speaking of great 
regional uplifts, he says further: ‘‘ What the 
real nature of the uplifting force may be is, 
to my mind, an entire mystery, but I think 
we may discern at least one of its attri- 
butes, and that is a gradual expansion or 
diminution of density of the subterranean 
magmas. * * * Weknow of no cause 
which could either add to the mass or 
diminish the density, yet one of the two 
must surely have happened. * * * Hence 
I infer that the cause which elevates the 
land involves an expansion of the underly- 
ing magmas, and the cause which depresses 
SCIENCE. 
[N. S. Von. X. No. 257. 
itis a shrinkage of the magmas ; the nature 
of the process is at present a complete mys- 
tery.’’ Ishall endeavor to show how the 
detailed study of marine deposits may help © 
to solve the mystery here referred to by 
Dutton. 
The surface of the globe has not always 
been as we now see it. When, in the past, 
the surface had a temperature of about 
400° F., what is now the water of the ocean 
must have existed as water vapor in the 
atmosphere, which would thereby—as well 
as because of the presence of other sub- 
stances—be increased in density and vol- 
ume. : 
Life, as we know it, could not then exist. 
Again, science forsees a time when low tem- 
peratures, like those produced by Professor 
Dewar at the Royal Institution, will prevail 
over the face of the earth. The hydro- 
sphere and atmosphere will then have dis- 
appeared within the rocky crust, or the 
waters of the ocean will have become solid 
rock, and over their surface will roll an 
ocean of liquid air about forty feet in depth. 
Life, as we know it, unless it undergoes 
suitable secular modifications, will be ex- 
tinct. Somewhere between these two in- 
definite points of time in the evolution of 
our planet it is our privilege to live, to — 
investigate, and to speculate concerning 
the antecedent and future conditions of 
things. 
When we regard our globe with the 
mind’s eye, it appears at the present time 
to be formed of concentric spheres, very like, 
and still very unlike, the successive coats 
of an onion. Within is situated the vast 
nucleus or centrosphere; surrounding this id 
what may be called the tektosphere,* a shell 
of materials in a state bordering on fusion, 
upon which rests and creeps the lithosphere. 
Then follow hydrosphere and atmosphere, with 
the included biosphere.t To the interaction 
*cnK76c, molten. 
t Bios. 
