272 Prof. S. Arrhenius on the Influence of Carbonic Acid 



acid in the course of time have heen fixed in carbonates, if 

 we consider more closely the processes by means of which 

 carbonic acid has in all times been supplied to the atmosphere. 

 From these we may well conclude that enormous variations 

 have occurred, but not that the variation has always proceeded 

 in the same direction. 



ie Carbonic acid is supplied to the atmosphere by the follow- 

 ing processes : — (1) volcanic exhalations and geological phe- 

 nomena connected therewith ; (2) combustion of carbonaceous 

 meteorites in the higher regions of the atmosphere ; (3) com- 

 bustion and decay of organic bodies ; (4) decomposition of 

 carbonates ; (5) liberation of carbonic acid mechanically 

 inclosed in minerals on their fracture or decomposition. 

 The carbonic acid of the air is consumed chiefly by the 

 following processes : — (6) formation of carbonates from 

 silicates on weathering ; and (7) the consumption of carbonic 

 acid by vegetative processes. The ocean, too, plays an 

 important role as a regulator of the quantity of carbonic acid 

 in the air by means of the absorptive power of its water, 

 which gives off carbonic acid as its temperature rises and 

 absorbs it as it cools. The processes named under (4) and 

 (5) are of little significance, so that they may be omitted. 

 So too the processes (3) and (7), for the circulation of matter 

 in the organic world goes on so rapidly that their variations 

 cannot have any sensible influence. From this we must 

 except periods in which great quantities of organisms were 

 stored up in sedimentary formations and thus subtracted 

 from the circulation, or in which such stored-up products 

 were, as now, introduced anew into the circulation. The 

 source of carbonic acid named in (2) is wholly incalculable. 



"Thus the processes (1), (2), and (6) chiefly remain as 

 balancing each other. As the enormous quantities of car- 

 bonic acid (representing a pressure of many atmospheres) 

 that are now fixed in the limestone of the earth's crust 

 cannot be conceived to have existed in the air but as an insig- 

 nificant fraction of the whole at any one time since organic 

 life appeared on the globe, and since therefore the consump- 

 tion through weathering and formation of carbonates must 

 have been compensated by means of continuous supply, we 

 must regard volcanic exhalations as the chief source of car- 

 bonic acid for the atmosphere. 



" But this source has not flowed regularly and uniformly. 

 Just as single volcanoes have their periods of variation with 

 alternating relative rest and intense activity, in the same 

 manner the globe as a whole seems in certain geological 

 epochs to have exhibited a more violent and general volcanic 



