18 Theory of Jigriculture. [Jan., 



as that of gypsum and carbonate of ammonia, the latter of which 

 in the laboratory forms with the former sulphate of ammonia; 

 but in well-tilled grounds, the carbonate of lime reacts upon the 

 sulphate of ammonia, and there result carbonate of ammonia and 

 sulphate of lime.* 



The mechanical condition of the soil is practically important ; 

 but the theory of agriculture need not complicate itself with facts 

 relating to this part of the subject. Whatever is done to amelio- 

 rate the mechanical state of the soil, must operate so as to favor 

 and support the general theory which we have maintained in this 

 article. Coldness and wetness hinder the formation of organic 

 acids, and their combinations; compactness, has the same effect, 

 by excluding air and its circulation. If too sandy and loose, due 

 moisture will be wanting, which is required in all cases to pro- 

 mote chemical action.f 



It may appear to some of our readers, that we have spent too 

 much time in attempting to prove that plants derive their carbon 

 from the soil, through the roots; this may be so, still we hope 

 the facts we have given may be useful. There is another object 

 at this time in presenting in a strong light the value of organic 

 matter in soils, it is to prevent the injurious effects which will 

 follow if farmers rely upon patent mineral manures for maintain- 

 ing the fertility of their soils. For, however important these 

 manures may be, still they do not and cannot do aw^ay with the 

 organic. The two must go together. This position is supported 

 by the fact, that the gypsumed lands fail, sooner or later, not- 

 withstanding the clover crop is interposed to sustain them. 



•Bousingault's Rural Economy, p. 334. 



t When vegetable matter is immersed in water, and in a certain tempera- 

 ture, the chemical changes are of a different kind than where the same 

 matter is disseminated through a warm soil. In the former case, it is pre- 

 served in the form of peat, in the latter it is slowly burned. 



