i 



19 



of carbonates at high temperatures by the action of silicic acid 

 which, according to Bischof {op. cit. p. 42), is even capable of 

 decomposing carbonates at 100°. 



4. The combustion of meteorites is mentioned by Högbom 

 and Chamberlin as a possible source of carbonic acid. Nothing 

 whatever is known about it quantitatively. 



6. The combustion of coal by man is an ever-increasing 

 factor that has in recent years reached very considerable magni- 

 tude. This factor can, unlike the others, be expressed in fairly 

 accurate figures. The worlds production of coal amounted in 

 1902 to 700 million tons (according to statistics published in 

 the Times), giving by combustion 2.6 X 10^ tons of carbonic 

 acid or rather more than Viooo of the quantity present in the 

 atmosphere, [n the geologically insignificant period of 1000 

 years the percentage of carbonic acid could therefore be doubled 

 by this cause alone, if all other factors remained unchanged. 



While the action of the diminishing factors may be sup- 

 posed to be fairly constant, so long as the climatic conditions 

 and the percentage of CO^ in the air do not vary too much, 

 the same obviously need not be the case with regard to the 

 increasing ones. It is extremely probable that the exhalation 

 of carbonic acid from the ground varies greatly, corresponding 

 to the variable volcanic action, and we know that the quantity 

 of coal burned by man is by no means an unalterable quantity. 

 We have no reason , therefore, to think that the amount of 

 carbonic acid present in the atmosphere is even approximately 

 constant. 



There exists, however, a great factor capable of acting as 

 a regulator upon the variations by checking and retarding 

 every increase as well as every decrease in the percentage in 

 the atmosphere. 



27* 



