MICHIGAN ACADEMY OF SCIENCE. 
117 
and a half and three miles. If we could restore to Ihe earth and dis- 
tribute over its surface, the crustal materials similar to those of our 
continents, which are claimed to have been taken away, the oceanic 
water would lie about two miles deep, on the average, the world over. 
Our ocean basins, so-called, which are in reality the major portion 
of the globular area, being ihe direct result of the removal from the 
earth of some of its surface materials, how can we suppose that any 
such basins existed prior to that separation even upon the large un- 
known area which is claimed to have been denuded of its crust? 
One of the results of the systematic investigation of continental 
structure has been to teach that while in Mesozoic time large areas 
that are now land were covered by water containing marine forms of 
life, these Mesozoic marine waters were not of such profound depth nor 
great expanse as would be necessary to account for any considerable 
portion of the oceans as they stand today. The Mesozoic record tells 
of very considerable areas of land interspersed with epicontinental seas 
of shallow or moderate and often of fluctuating depth. Certainly the 
facts give no hint of a world-wide ocean two miles deep. 
And if, in devotion to the theory, one attempts to dispose of the 
present excess of oceanic water by postulating great and deep depres- 
sions upon the unknown denuded portion of the earth’s area, he is 
confronted with an important and growing body of evidence in support 
of the belief that the earth’s crustal materials are in a state of approxi- 
mate isostatic equilibrium with respect to the underlying matter. There 
are also certain biological objections which he encounters but their men- 
tion must be reserved for another place. 
The first two propositions taken together, then, stand confronted 
with the present volume of oceanic water. If the volume was the same 
in Mesozoic time that it is now there must presumably be something- 
wrong with the data or the chain of reasoning by which the propositions 
have been reached. But was it the same? Geology is silent. 
Regarding the combined ocean beds as a container of water we have 
to contemplate the possibility of changes taking place in the capacity 
and in the form of the vessel as well as in the volume of the contents. 
Questions of level separate themselves from questions of amount. 
Up to the time of Sir Charles Lyell it was commonly thought that 
the general level of the ocean had fluctuated, but he was able to sway 
geological opinion and to establish the dictum that throughout the 
geological changes it has been the land which rose and fell, to be in 
turn, more free from or more submerged in the waters of the sea. The 
masterly way in which he connected observed present processes and 
observed past effects need not be praised today; but is that all? Did 
Lyell establish constancy of ocean volume? No. Nor has any one else. 
Nor yet, in any considerable degree, has inconstancy been proved. The 
question has not been widely discussed* and is an attractive one for 
further investigation. 
Under the epeirogenic theory of the glacial period as built up by 
Dana, LeConte, Jamieson, Wright, Uplmin, Spencer and others, three 
altitudes are recognized for continental lands in Pleistocene time. 
They are : 
*Mainly by Suess, Gregory, Geikie, Belt and Tylor. 
