SEGREGATION OF CARBON. 965 



atmosphere of our eaith ." The data upon which this calculation is made 

 are not given, and it may be a great overestimate, but that any calculation 

 could have given such a result shows how trivial is the amount of carbon 

 dioxide at present in the atmosphere as compared with that which has been 

 abstracted by carbonation. 



In 78 shales the amount of carbon dioxide is 2.64 per cent, in 624 

 sandstones it is 3.03 per cent, and in 843 limestones it is 38.58 per cent. 



While segregation of the carbonates is therefore the -rule for all the 

 rocks produced by the processes of denudation, this segregation takes 

 place to the least extent in the shales, to a greater extent in the sandstones, 

 and to the greatest extent in the limestones. 



If carbon dioxide composes but 0.81 per cent of the original rocks, it 

 appears that as compared with the average of the original rocks about three 

 times as much carbon dioxide is concentrated in the shales where it is 

 lowest, and forty-seven times in the limestones. This shows how enor- 

 mously the carbon in the secondary rocks has been increased, as compared 

 with the original rocks, by the process of carbonation in the zone of kata- 

 morphism. 



Combining the above figures with the masses of the sediments given 

 on page 940, it follows that the amount of carbon dioxide in the shales is 

 11,583,000,000,000,000 metric tons, in the sandstones is 6,135,750,000,- 

 000,000 metric tons, and in the limestones is 13,020,750,000,000,000 

 metric tons; total, 30,739,500,000,000,000 metric tons. From the fore- 

 going figures it appears that the fixed CG 2 in the shales, sandstones, and 

 limestones is 12,900 times the amount now in the atmosphere, and is 1,970 

 times the amount of free C0 2 in both atmosphere and hydrosphere, upon 

 the basis of 0.001 per cent in the hydrosphere, and is 660 times the total 

 free carbon dioxide of the atmosphere and the hydrosphere together, upon 

 the basis of Dittmar's figures." 



It appears from the foregoing that in the great limestone deposits 

 a large quantity of carbon dioxide, 38.58 per cent, has been segregated 

 from the exceedingly small amount of carbon in the original igneous rocks 

 and from the atmosphere and hydrosphere. As already seen there is 47 

 times as much carbon in the limestone formations as in the original igneous 

 rocks. The importance of this process of segregation, considered from an 

 economic point of view, is not generally appreciated. In order to realize 



a Dittroar, Narrative of the cruise, etc., p. 955. 



