1 36 
FOURTEENTH REPORT. 
t<> ju.>t i t \ such a theory and moreover it is open to an objection similar 
to that brought against Croll's theory, namely, that in oscillations be- 
tween the equator and the two poles there would be two zones of 
minimum fluctuation. These might be looked for reasonably, in the 
neighborhood of the 45th parallels of latitude. -Vs it happens, this 
parallel, in the northern hemisphere, passes through the Bay of Biscay 
where less than two degrees to the south, we have one of the best-deter- 
mined and deepest instances (outside of the extremely high figures for 
the Antillean region) of a drowned river, 0,000 feet. Further to the 
north, in about 50 degrees of north latitude, Hull found one of 7,800 
feet. 
< Imnge ol the axis of the earth with respect to its contour has been 
discussed time and again and apart from all the mathematical reasons 
that have been urged against the suggestion it is open to the same sort 
ol objection, that it cannot account for the Postglacial submergences 
which extend over all latitudes and longitudes as far as we can deter- 
mine. 
shall have then to exclude, in searching for an adequate explana- 
tion, displacements, changes in the lithosphere, and fluctuations or 
oscillations either from pole-to pole or between the poles and the equator. 
We must therefore reject the idea that the volume of the ocean remained 
constant. 
CHANGE OF SEA-LEVEL INVOLVING CHANGE OF VOLUME. 
Relying upon simple reasoning, we must conclude that the volume of 
the oceanic water has varied, and varied widely enough to explain, for 
instance, the 6,000 feet of Congo drowning. 
The rise of the ocean to some such value or more would doubtless be 
an adequate explanation of the termination of the Glacial Epoch in the 
same way and to the same extent that the depression of the land to a 
similar degree has long been held to be sufficient. It would be merely 
a question of just what height was necessary for glaciation to begin. 
In the matter of climate the elevation that counts is not distance from 
fhe earth's center but distance above the prevailing surface, that is, 
altitude above sea level.* 
Such an increase of ocean volume would presumably produce a dif- 
ferential elevation in the land masses by water-weighting of the oceanic 
areas of the lithosphere, so that a tendency toward the recovery by 
the land of some of its lost altitude relative to the sea must be filed 
as an offset against any increase of oceanic volume. Such a eustatic 
negative tendency following a positive one would be comparable to the 
elevation of the Terrace Epoch following the depression of the Cham- 
plain. Where the land was laden with ice the relief upon melting 
would operate in the same direction, tending to give higher values to 
this late recession of the strand. This is in harmony with the post- 
glacial epeirogenic movements which are w r ell known to have occurred 
in northwestern Europe and in glaciated North America. 
*Mr. Frank Leveret f, in discussion, mentions that the evidence indicates that during the melting 
of the last stage of glaciation there was only a gentle slope from the ice-front, southward to the Gulf of 
Mexico. Earlier, as Hilgard pointed out, there are signs of a much higher gradient. This harmonizes 
with the trend of the present inquiry. Whatever causes may have operated to produce fluctuations 
in glaciation, the epeirogenic theory contemplates the final melting as being due to relative change of 
altitude. The gentle Mississippi gradient referred to by Mr. Leverett may represent the change to 
Champlain conditions. 
