614 HG (CLEA NASEIE /RILIONS 
beyond reason and beyond geological evidence to suppose that 
these are habitually in perfect or even in approximate balance, 
for at certain stages the exposure of the land has been large and 
its elevation high and the process of rock disintegration and 
carbonation has been notably favored. Coincident with this the 
ocean has at such times been extensively withdrawn from the 
continental platforms and the previous expanse of lime-deposit- 
ing areas thereby greatly circumscribed. In addition to this, 
the rejuvenation of the streams has at such times brought into 
the ocean exceptional amounts of detritus and rendered the 
coasts uncongenial to many of the limestone-forming organisms. 
It is probable also that even the pelagic calcareous organisms 
have been at such times adversely affected directly or indirectly 
by these conditions. On the other hand there have been times 
when the sea crept out over great areas of the continental plat- 
forms and afforded vast expanses of shallow water congenial to 
the maintenance of lime-depositing life. There is direct pale- 
ontological and physical evidence that such extensive epiconti- 
nental seas were spread upon the eastern and western continents 
at the same time, as for example, in the Ordovician, the Silu- 
rian, the Carboniferous, and the Cretaceous periods. Geological 
evidence compels us likewise to recognize recurrent fluctuations 
in the prevalence of such limestone deposition, intermittent with 
the antithetical process of land degradation. 
Returning now to our selected case based on the present 
status of atmosphere, ocean, land, and water, we may safely 
assume that one or the other of the two alternatives, the fixation 
of carbon dioxide, or the freeing of carbon dioxide, is at present 
preponderant. Either the carbonic consumption upon the land 
is in excess of the carbonic freeing in the ocean, or the reverse 
is the case; if not so momentarily, at least so habitually. 
Let us assume, in accordance with the probable fact, that the 
disintegration of the silicates is now exhausting the carbonic 
acid of the atmosphere faster than the deposition of limestone 
eliminates it, and that, therefore, the calcium bicarbonate in the 
ocean is increasing. The result of this process if prolonged 
