118 SOILS AND MANUEES 



little apparent difference to it. There is, however, good 

 reason to believe that moss is more indifferent to the 

 absence of lime than grasses and other cultivated plants. 

 A sour condition of the soil therefore favours the growth of 

 moss by discouraging that of the other plants. Under these 

 circumstances lime will have a beneficial effect. It neutral- 

 ises the acids in the soil and so renders the conditions 

 more favourable for the growth of grasses and clovers, in 

 this case also the improvement is due to the action of the 

 lime upon the soil rather than to any direct influence upon 

 the plants, and it cannot be expected to take place unless 

 the soil is deficient in lime. 



In order that lime may be thoroughly incorporated with 

 the soil it must be reduced to a very fine state of division. 

 For this reason it is generally applied to the land in the 

 form of dry slaked lime. The limestone is " burned," i.e., 

 it is heated to a very high temperature, and so decomposed 

 into calcium oxide, or quicklime, and carbon dioxide. The 

 latter substance is a gas, and is driven off, and the quick- 

 lime remains in lumps of the same size and shape as the 

 pieces of limestone before burning, but considerably 

 lighter. The change may be represented by the following 

 equation : 



CaC0 3 CaO + C0 2 



Carbonate of lime Calcium oxide Carbon dioxide, 

 (limestone). (quicklime). 



The quicklime is carried out to the land, deposited in 

 heaps, and allowed to slake, i.e., to become converted into 

 the hydrate by absorbing moisture from the air. This 

 causes it to fall into a fine dry powder which is easily spread 

 over the land and mixed with the soil. The chemical 

 change can be represented by an equation, thus 



CaO + H 2 = Ca(OH) 2 



Quicklime. Water. Slaked lime (calcium hydrate). 



