116 THE METAMOKPHOSES OF MATTER. 



We will not pause to calculate the figure to which this 

 carbon-evolution is raised by the breathing of animals ; the 

 reader curious in such matters may think out the case for 

 himself. 



From breathing and decay, and other sources, the air is 

 ever supplied with carbonic acid, and as continually yields 

 the carbon of it up to plants, wherein it becomes fixed. So 

 far as present operations and analogy can lead us to perceive, 

 all the carbon present in organic life must have come origin- 

 ally from the atmosphere, and, by a parity of reasoning, all 

 the carbon ever excavated in the form of pit-coal, or remain- 

 ing to be excavated. This seems astounding ; but accepting 

 Liebig's estimate, that the atmosphere holds no less than 

 1,332,142,857 tons of carbon dissolved under an invisible 

 form, present as carbonic acid gas, much of the astonish- 

 ment vanishes. 



In regard to the amount of pit-coal already excavated, 

 consumed, resolved into the atmosphere, a Prussian engineer, 

 M. de Carrnal, has made some curious calculations. The 

 quantity of coal actually dug up to the end of 1857 amounted, 

 according to him, to 125 millions of tons, a quantity repre- 

 sented by a compact cubical mass of ten miles across on 

 every face. Nineteen- twentieths of this at least are carbon ; 

 being equal to about one-eleventh the carbon-complement of 

 the whole world's atmosphere ; and nearly five times greater 

 than the carbon-estimate of the amount of animated creation 

 existing at the present time. Farther, if the world's 1200 

 millions of human inhabitants could live, breathing as they 

 do now, until their breath-carbon had yielded an amount 

 equal to the amount of coal already dug up and consumed, 

 they would have to live and breathe away for about 5432 

 days and a half. 



