On the Formation and Decomposition of Carbonic Acid. 207 



me through the kindness of Mr. Robert Hunt, of the Museum 

 of Practical Geology; and although they somewhat exceed two 

 tons per acre per annum, I have based my calculation on that 

 amount. 



The figures relating to imports are based upon the larger 

 articles of food (such as live animals, meat, sugar, potatoes) 

 and combustible substances (as tallow, petroleum, &c). 



With regard to the carbon given off by the consumption of 

 home produce, so far as relates to the 33 j million acres which 

 constitute the cultivated area, my estimates are formed upon 

 what I believe to be the average yield of the land ; upon the 

 remaining area, consisting of mountains, heath, and waste, 

 the only basis for calculation is to be derived from the rental 

 value of such land, and the amount of stock which it will 

 carry. 



Without going into the detail of the figures, I have given 

 in the following table a summary of the whole. 



Carbon given off as Carbonic Acid per acre per annum in 

 Great Britain. 



lbs. 



By coal 3942 



By imported products 300 



By home-grown products... 1275 



Total 5517 



We find, according to the more recent estimates, that the 

 amount of carbon, as carbonic acid, resting upon an acre of 

 ground is equal to about 14,000 lbs. Now the amount given 

 off by the sources which I have mentioned above would more 

 than double the carbonic acid in our atmosphere in three 

 years, provided that no compensation took place ! I propose 

 to examine into what is the probable extent of the compensa- 

 tion which may come in to limit this large increase. 



With regard to coal and imported products, there is very 

 little compensation possible; but with the products grown 

 upon our own soils, there is a continuous exchange going on 

 between the atmosphere and the plant ; and the question is on 

 which side the balance lies. 



I am disposed to think that, upon arable land (when kept in 

 a uniform state of fertility), the amount of carbonic acid, fixed 

 and exhaled, would be nearly the same, but that, wherever 

 the fertility of the soil was diminished, there the carbonic acid 

 given off would be in excess of that fixed. 



In the ordinary case of a farmer selling a certain amount 

 of the products of his land and consuming the residue, the 

 saleable products, consisting of corn and meat, are burnt into 



Q2 



