CARBONATE OF LIME. 101 



its solvent powers are much increased, and in 

 this way it is absorbed by the spongelets of the 

 roots, and assimilated by the plants; and its slow 

 solution by water is one reason why its eftects 

 are so lasting when applied to a soil. Chalk 

 has been and is extensively used as a manure, 

 and even in some cases on calcareous soils 

 themselves with advantage. 



It produces a mechanical as well as a che-* 

 mical action wherever it is applied. Mecha- 

 nically by dividing the soil, and rendering it 

 more light or friable as it is termed, and che- 

 mically by absorbing moisture from the atmo* 

 sphere and giving it out slowly as vegetation 

 subsequently requires it, as well as by its solu- 

 tion affording a necessary ingredient to the 

 development of all plants. 



All these carbonates of lime w^hen burnt lose 

 their carbonic acid gas, and pure lime is left. 

 The heat destroying the affinity, previously 

 existing between them. Lime in this state is 

 most extensively used for agricultural pur- 

 poses, and as it loses nearly 44 per cent, in 

 weight in burning, it may be well worth the 

 consideration of those agriculturists who live 

 at a distance from chalk to know whether in 

 this state it may not be equally beneficial, as 

 the saving in carriage on such a substance, is 

 a material item in the expense. 



The same remarks we have applied to chalk 

 will equally explain how lime acts on vegeta- 

 tion. 



It is soluble to a slight extent in water^ 

 more largely in cold than in hot water, and 

 10 



