580 T. C. CHAMBERLIN 
amount of free carbon dioxide. It does not seem possible now 
to arrive at any closely approximate estimate of this ratio. 
Johnson’ expresses the belief that the growth of plants would 
exhaust the carbonic acid of the atmosphere in 100 years if there 
was no return. The average length of time during which plant 
products remain as living tissue is probably greater than one 
year, and much less than ten years, which would make the 
total amount of the carbonic acid so locked up a quite small per 
cent. of that in the air. The amount of carbon locked up in 
the tissue of marine life which probably was not embraced in 
Johnson’s estimate, would somewhat notably increase the figure, 
but if oceanic life is considered, the free carbonic acid of the 
ocean must be considered also which would greatly reduce the 
ratio. 
A study of the life of the geological periods seems to indi- 
cate that there were very notable fluctuations in the total mass 
of living matter. To be sure there was a reciprocal relation 
between the life of the land and that of the sea, so that when 
the latter was extended upon the continental platforms and 
greatly augmented, the former was contracted, but notwithstand- 
ing this it seems clear that the sum of life activity fluctuated 
notably during the ages. It is believed that on the whole it was 
greatest at the periods of sea extension and mild climates, and 
least at the times of disruption and climatic intensification. 
This factor then acted antithetically to the carbonic acid freeing 
previously noted, and, so far as it went, tended to offset its 
enmiectss 
THE FUNCTION OF THE OCEAN AS AN ABSORBENT OF CARBON 
DIOXIDE 
The atmosphere penetrates the ocean by simple diffusion 
according to the laws of gas diffusion, modified slightly by 
hydrostatic pressure, and this must be considered in close com- 
putations, but is too small a factor to seriously affect the larger 
issues. 
*How Plants Feed, p. 47. 
