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610 I, Cn CIELAMITBIBTRILION 
Taking the average constitution of the crystalline rocks as a 
basis, even a rude inspection shows that the consumption of 
carbon dioxide involved in their decomposition far surpasses 
the consumption of oxygen.* Or, reversing the mode, an esti- 
mate of the amounts of carbon dioxide and of oxygen respec- 
tively, which would be freed from the sedimentary deposits of 
the earth if they were again reduced to the condition of sili- 
cates analogous to their primitive state shows a like excess of 
carbon dioxide. From these considerations, which do not need 
to be given numerical expression, it will be apparent that carbon 
dioxide has suffered much more consumption in the progress of 
the geologic ages than has oxygen. That its consumption has 
surpassed that of nitrogen is too obvious to require argument. 
Whatever the original quantitative relations of the atmos- 
pheric constituents, the effect of geologic processes has been 
their reduction to a quantitative order which is inverse to their 
functional activity. There is hence a preponderance of the 
inert and relatively non-participant nitrogen, a medium amount 
of the more active oxygen, and a minimum amount of the most 
participant element, carbon dioxide. 
Now as the activities of the atmospheric constituents are in 
many respects connected with each other and mutually depend- 
ent, it is obvious that the factor which is at once minimum in 
quantity and maximum in participation must necessarily be the 
critical factor of the atmosphere. It is not too much to say 
that the whole order of vital procedure is hung preéminently 
upon the function of carbon dioxide as the decisive factor, and 
it is scarcely too much to say the same of many of the most 
important of inorganic processes. 
The chief reservoir of available carbon dioxide on the sur- 
<The amount of carbon dioxide which crystalline rocks hold in their microscopic 
cavities, recently shown by Tilden to be considerable, is only a small fraction of what 
is required for the carbonation of the rock containing it, on the average. We cannot 
look to this as a source of enrichment of the atmosphere so far as the superficial rocks 
which undergo chemical decomposition are concerned, though it may be an important 
source of enrichment when freed from the deeper rocks by the processes of vulcanism 
and by other means. 
