22 OF THE ASSIMILATION OF CARBON. 



every square Hessian foot of the surface of the earth ; 

 the diameter of the earth and its superficies are like- 

 wise known, so that the weight of the atmosphere 

 can be calculated with the greatest exactness. The 

 thousandth part of this is carbonic acid, which 

 contains upwards of 27 per cent, carbon. By this 

 calculation it can be shown, that the atmosphere 

 contains 3000 billion Hessian Ibs. of carbon; a 

 quantity which amounts to more than the weight 

 of all the plants, and of all the- strata of mineral 

 and brown coal, which exist upon the earth. This 

 carbon is, therefore, more than adequate to all the 

 purposes for which it is required. The quantity 

 of carbon contained in sea- water, is proportionally 

 still greater. 



If, for the sake of argument, we suppose the super- 

 ficies of the leaves and other green parts of plants, 

 by which the absorption of carbonic acid is effected, 

 to be double that of the soil upon which they grow, 

 a supposition which is much under the truth in the 

 case of woods, meadows, and corn fields ; and if we 

 further suppose that carbonic acid equal to 0.00067 

 of the volume of the air, or 1-1 000th of its weight 

 is abstracted from it during every second of time, 

 for eight hours daily, by a field of 80,000 Hessian 

 square feet; then those leaves would receive 1000 

 Hessian Ibs. of carbon in 200 days.* 



* The quantity of carbonic acid which can be extracted from the air 

 in a given time, is shown by the following calculation. During the 

 whitewashing of a small chamber, the superficies of the walls and roof 



