120 AMERICAN MANURES. 



position of 25 bushels of wheat, only 107 Ibs. of 

 carbon could possibly be furnished in this way. 

 As there are 2377 Ibs. of carbon in 25 bushels 

 of wheat and the straw, not the one-twentieth 

 part required could be thus supplied. We will 

 ascertain what amount could be supplied by the 

 agency of rain water. The rain-fall from the 

 first of April to the first of October the time 

 during which plants are coming to maturity is 

 on an average about 1,000,000 Ibs. to an acre. 

 Now, experiments have demonstrated that 1,000,- 

 000 Ibs. will render soluble only 10 Ibs. of car- 

 bon ; so that only 10 Ibs. could be thus furnished, 

 even if every pound of the water is taken up by 

 the roots, which is far from being the case. The 

 trees of the forest and the grass of the meadow 

 rarely receive any carbon in the shape of ma- 

 nure ; and yet there is no lack of it, though car- 

 bon is taken away every year in the form of 

 wood and hay. From all this we conclude that 

 manures are not needed to furnish carbon, and 

 that the atmosphere is capable of furnishing all 

 that vegetation requires. 



Immense quantities of carbonic acid are con- 

 stantly supplied to the atmosphere by our fires 

 and furnaces, by fermentation and the decay of 

 animal and vegetable substances, as well as by 

 the respiration of men and animals. Is it not 

 wonderful that this carbonic acid, so fatal to ani- 



