968 A TREATISE ON METAMORPHISM. 



in the bicarbonates of the ocean beyond that required to balance the bases 

 as normal carbonates is about ten times the amount in the atmosphere. 

 It thus appears that the potentially free carbon dioxide of the ocean is in 

 much greater amount than the actual free carbon dioxide in the atmos- 

 phere. According to Schloesiug" there is a very delicate adjustment 

 between the amount of carbon dioxide in the atmosphere and the hydro- 

 sphere. Great additions to the amount in the atmosphere would result in 

 absorption by the hydrosphere. Depletion in the amount in the atmos- 

 phere is compensated by additions from the hydrosphere. This idea of the 

 balance between the amount of carbon dioxide in the atmosphere and that 

 contained as bicarbonate in the ocean has been elaborated by Chamberlin 

 and Tolman.'' They note that under the laws of physical chemistry, when 

 the amounts of free carbon dioxide in the atmosphere and in the ocean are 

 in equilibrium and this equilibrium is disturbed by a decrease of the carbon 

 dioxide of the amosphere, this compound will pass from the ocean to the 

 atmosphere until the equilibrium is restored. Chamberlin has also empha- 

 sized the fact that when the calcium bicarbonate of the ocean is precipitated 

 by organisms, one-half of the carbon dioxide is thereby liberated. Conse- 

 quently at periods of limestone building* the amount of free carbon dioxide 

 in the ocean, and therefore the amount in the atmosphere, would be greatly 

 increased. These considerations lead to the conclusion that at various times 

 in the history of the world the atmosphere has been replenished in carbon 

 dioxide at the expense of the ocean. 



Petrographic work of recent years shows that graphite and diamond 

 are original constituents of some of the igneous rocks, especially the 

 basalts. Further, Tilden/ by chemical analyses, has shown that the 

 plutonic igneous rocks granite and gabbro, and also the volcanic igneous 

 rock basalt, at certain localities contain considerable quantities of carbon 

 monoxide and methane. 



o Letts, E. A., and Blake, R. F., The carbonic anhydride of the atmosphere: Sci. Proc. Royal 

 Dublin Society, vol. 9, new series, pt. 2, 1900, pp. 160-161. 



6 Chamberlin, T. C, A group of hypotheses bearing on climatic changes: Jour. Geo]., vol. 5, 1897, 

 pp. 653-683. Chamberlin, T. C, The influence of great epochs of limestone formation upon the con- 

 stitution of the atmosphere: Jour t Geol., vol. 6, 1898, pp. 609-621. Chamberlin, T. C, An attempt to 

 frame a working hypothesis of the cause of glacial periods on an atmospheric basis: Jour. Geol., vol. 7, 

 1899, pp. 545-584. Tolman, C. F., The carbon dioxide of the ocean and its relations to the carbon 

 dioxide of the atmosphere: Jour. Geol., vol. 7, 1899, pp. 585-618. 



c Tilden, W. A., On the gases inclosed in crystalline rocks and minerals: The Chemical News, 

 vol. 75, 1897, pp. 169-170. 



