BY SALINE MANURES. 315 



Theory. Carbonate of lime acts like all saline compounds ; 

 the base is let loose, by the action of the living plant, and 

 acts in its caustic state upon insoluble vegetable matter, and 

 converts it into vegetable food. The carbonic acid acts upon 

 the silicates and obtains the potash and soda, which react up- 

 on the humus, and render larger portions of it soluble. The 

 action is slow, but the effects are sure. 



When lime is applied in a caustic state, it slowly absorbs 

 carbonic acid, and becomes a carbonate. If a large quanti- 

 tity is used it may form a super-salt with humic acid, and 

 become inert because insoluble. It is in this way that it 

 proves injurious. But this state cannot always last, for the 

 salt will, in time, be decomposed and rendered useful. 



When acids exist in the soil, both the caustic and carbon- 

 ate of lime tend to neutralize their effects ; hence it aj^ears 

 that the base of lime acts in a four-fold capacity, as a con- 

 verter, a ncutralizer, a decomposer, and a retainer. , > 



(1) Lime acts as a converter, when it convertajlpsgetable 

 fibre into vegetable food. This appears to be the most im- 

 portant use of lime, and the most difficult to explain. It has 

 been referred to its " catalytic" power or to the action of 

 presence, but whatever may be the nature of the force, it is 

 well established, that when lime is brought into contact with 

 vegetable matter, it hastens its decay. The humic or geic 

 acid thus formed combines with it, and becomes a soluble 

 salt, ready to enter the vegetable organs. 



(2) Lime acts as a neutralizer, whenever acids exist in 

 the soil in a free state. Some soils are called acid soils, and, 

 as the carbonic acid is displaced by most other acids, the 

 lime will combine with the acid and neutralize its effects. 

 Peat and smamp muck often contain acids, which may be 

 neutralized in this way ; hence lime should be applied to peat 

 earth, before it is used. 



(3) Lime acts as a decomposer, when it decomposes any 

 inert or injurious substance in the soil, as metallic salts. Veg- 



