SOURCES OF SEGREGATED CARBON. 971 



of carbon dioxide. This fact has been noted again and again since the 

 days of Bischof. "Lecoq has calculated that of the mineral springs those 

 of Auvergne alone give off in the same time [one j r ear] 7,000,000,000 

 cubic meters of the gas, an amount rather less than one-tenth of the volume 

 produced by the annual combustion of the coal employed throughout the 

 whole of Europe." a It is to be remembered that Auvergne is but a single 

 region, and while the amount of carbon dioxide emitted is exceptional, it 

 is approximated in other regions where there are hot carbonated springs. 

 The total amount of carbon dioxide emitted in the few areas where it is 

 exceptionally abundant is probably small as compared with the quantity 

 carried by the vastly larger amount of water of the great mass of springs 

 of the world. 



If the argument given on pages 176-177, 677-679 be correct, the 

 carbon dioxide furnished by deep-seated springs is largely that liberated 

 by the process of silication of carbonates, although some part of it may be 

 derived from the carbon dioxide originally occluded in the earth. 



The segregation of carbon as carbonates in the sedimentary rocks is a 

 consequence of the reaction of carbonation, and chiefly of carbonation of the 

 silicates. These carbonates, as already seen, are mainly concentrated in the 

 carbonate formations, but to a considerable extent are found as accessory 

 minerals in the shales and in the sandstones. When the rocks of the zone of 

 katamorphism are buried so deeply as to pass into the zone of anamorphism 

 the silication of the carbonates occurs with the liberation of the carbon 

 dioxide. That this process has taken place almost completely in the pelites 

 thus buried is shown by the very small percentage of carbonates in the 

 schists, which are the metamorphosed equivalents of ancient muds. The 

 silication of the limestones which have passed into the zone of anamorphism 

 is in various stages, ranging from slight to complete. It is certain that 

 this process is going on at the present time on a very great scale. Indeed, 

 it is not impossible that the process of silication in the zone of anamorphism 

 is taking place with a close approximation to the speed of the process of 

 carbonation in the belt of weathering. 



In so far as the process of silication with decarbonation is taking place 

 in the deep-seated zone, and the liberated carbon dioxide is carried by the 

 ground water to the atmosphere or to the hydrosphere, the depletion of the 



« Letts and Blake, cit., p. 159. 



