FIVPOTHESIS OF CAUSE: OF GLACIAL PERIODS. 675 
depletion and there began to be an increase of carbon dioxide in 
the air, the following influences would codperate to hasten and 
intensify the reactive movement. 
1. The dissociation of the second equivalent of carbonic 
acid associated with the carbonates of the ocean would be 
increased, and as the temperature rose from the diffusion of the 
freed carbon dioxide into the air this would be still further aug- 
mented by its own reactive effects. This is one of those inter- 
esting agencies whose effects at once become causes of further 
like effects. 
2. The increased warmth would call forth more lime- 
secreting life in the ocean, and thus also hasten the freeing 
of carbon dioxide, and this again would react favorably on 
itself. 
3. The increase of water from melting ice would some- 
what extend the shallow-water zone and favor lime-secreting 
life. If the land were depressed by the load of ice, as some sup- 
pose, this would increase the sea area and favor lime-secreting 
life. With this may be associated the falling of the water level 
in the high latitudes (to which it had been drawn by the gravi- 
tation of the accumulated ice mass) and a corresponding rise of 
the water level in lower latitudes. Since the lower-latitude life 
is more abundant than the high-latitude life, and more effective 
in extracting lime, the shift would involve a gain in lime-secret- 
ing potency. 
4. The increased decay of organic matter attendant on the 
warmer temperature would develop carbon dioxide; but over 
and against this must be set the increased carbon locked up in 
the augmented living matter: These, as before, are’set aside, as 
perhaps mutually offsetting each other. 
5. Lhe ianerease of temperature arising from the preceding 
causes would increase the water vapor in the air and thereby add 
to the thermal capacity of the atmosphere, and this would react 
favorably upon itself and upon the other agencies favored by 
high temperature. 
Thus the reaction once started would be self-augmenting, 
