INFLUENCE OF LIMESTONE UPON THE ATMOSPHERE 611 
face of the earth is not, however, the atmosphere but the ocean. 
Reservoir in the ulterior sense is not meant, but in the immedi- 
ately available sense. I entertain the hypothesis that the 
interior of the earth is the chief terrestrial reservoir of carbon 
dioxide in the ulterior sense, and that it is a leading source of 
secular supply. If Tilden’s recent analyses of the carbon 
dioxide stored in the microscopic pores of rocks, or otherwise 
occluded within them, be representative of the whole interior of 
the earth, the total mass of carbon dioxide stored within 1s 
something prodigious.* To how great an extent this is given 
forth from age to age and becomes a source of atmospheric 
supply cannot be determined from present data, but Iam fully 
persuaded that the subject is one of the most vital which now 
invites investigation. The possible feeding of the atmosphere 
from cosmic sources also invites definite inquiry. But these are 
ulterior sources of supply of a secular nature and lie apart from 
the immediate question here discussed. This incidental men- 
tion may serve to definitely set them aside and to forestall mis- 
understanding. 
For the purposes of this paper it is assumed that the constit- 
uents of the atmosphere and of the ocean have been essentially 
the same as at present, and no ulterior source of supply or of 
loss is taken into account. The endeavor here is merely to 
trace the effects of a great epoch of limestone formation upon 
such an atmosphere as we now have, attended by an ocean 
similar to the present one, and with land relations such as 
accompany great limestone-forming epochs and their antitheses. 
A computation of the approximate amount of available 
carbon dioxide in the present ocean, based upon the observa- 
tions of the Challenger Expedition as elaborated by Dittmar, 
shows a content of about eighteen times that contained in the 
present atmosphere. This embraces only the carbon dioxide 
) ”) 
held in the two states familiarly known as ‘““free’’ and ‘loose; 
that is, (1) carbon dioxide which is simply held in solution, and 
«On the Gases enclosed in Crystalline Rocks and Minerals. By W. A. Tilden. 
Chemical News, April 9, 1897. 
