82 THE SOIL OF THE FARM. 



tinue to breathe into the lime-water after it has become 

 milky, it will soon become perfectly clear as at the start. 

 The continued breathing supplies more carbonic acid 

 than is needed to convert the lime into an insoluble car- 

 bonate; the excess of carbonic acid in the water re- 

 dissolves the carbonate. Heating this solution drives off 

 the excess of carbonic acid, and the carbonate of lime 

 will be deposited again. Carbonic acid is always present 

 in the atmosphere, and when slaked lime is long ex- 

 posed, it takes up this acid and slowly becomes carbonate 

 of lime. 



Why wc use Quick-Lime upon the Land. — All culti- 

 vated plants contain lime in their ashes, and it is con- 

 sidered necessary to their proper growth. But soils 

 generally contain enough lime for the use of the jolants, 

 and we apply it for its action upon the otlier constituents 

 of the soil. Lime acts upon and greatly aids the decom- 

 position of organic matter in the soil. It is thought to 

 neutralize the organic acids contained in what are called 

 ** sour soils." In a complicated manner it aids in the 

 fixing of ammonia. It also acts upon the inorganic or 

 mineral constituents of the soil, and aids in converting 

 them into forms in which they can be taken up by the 

 plants, especially in liberating potash from its combina- 

 tions. The effect of lime upon the mechanical condition 

 of the soil is an important feature. Upon heavy clay 

 soils its effect is most marked; the particles lose their ad- 

 hesiveness, and allow air and water to enter. These are 

 the leading effects that follow the use of lime. In view 

 of the claims made for ground, unburned limestone, it 

 is an important question how far it can produce the 

 above effects. That the unburned limestone will su]i])ly 

 the demands of tlic ])hint for lime, tliat it may slowly 

 neutralize organic acids, and help tlie mechanical texture 

 of the soil seems very i)robable. But that it will perform 



