558 T. C. CHAMBERLIN 
-(Moissan) formed within the earth and extruded from it. Some 
carbonates probably have been formed by carbonic acid con- 
tained within the rocks or extruded from the interior. In cer- 
tain phases of the problem, deduction is to be made for such 
carbonaceous compounds and carbonates as are formed in the 
sea by marine plants and other agencies which derive their 
carbonic acid from the sea water; but in the general discussion 
of the question, the carbonic acid of the sea must be reckoned 
in with the carbonic acid of the air, for the two are in equi- 
librium and constitute essentially and potentially one body. 
The necessity for this assumption will be more obvious when we 
come to discuss the function of the ocean in influencing the con- 
stitution of the atmosphere. 
Sources of permanent gain.— Over against these sources of 
secular loss there are certain sources of gain. If the assump- 
tion that the constitution of the atmosphere has varied through 
only moderate limits within the known ages be adopted, it is 
necessary to postulate sources of supply of a competency approxi- 
mately equal to the sources of loss. The data for such postu- 
lation are exceedingly unsatisfactory and a function of the 
hypothesis should be to stimulate investigation in these lines 
which have been barely touched by serious inquiry. 
a. Gain from the interior— The crystalline rocks of the sur- 
face of the earth have been shown by the recent examinations 
of Tilden* to contain very notable quantities of gas, consisting of 
hydrogen in preponderance, carbon dioxide and carbon monoxide 
in large percentages, and nitrogen and marsh gas in small quan- 
tities, with water vapor, but with a practical absence of oxygen. 
Twenty-five analyses, including ancient and modern volcanic and 
even some metamorphic rocks, gave an average volume of gas 
equal to about four and a half times the volumes of the contain- 
ing rocks. A computation on this basis shows that an atmosphere 
equivalent in mass to the present one would be contained in a 
very superficial rind of the earth, and that if this volume of 
*On Gases Contained in Crystalline Rocks and Minerals: W. A. TILDEN, 
Chemical News, April 9, 1897. 
