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alkalis and silicates from their powerful chemical 

 combinations. 



We will understand now its action upon the 

 arable soil, the clay of which represents the greater 

 portion of inorganic plant-food in chemical combi- 

 nation. The action of moisture and atmospheric 

 air, as we have seen, converts yearly a percentage 

 of this store into that state of physical combination 

 in which alone it is available to the plant, and all 

 the mechanical operations of agriculture have as 

 their principal object the facilitation of this natural 

 decomposition. 



But the addition of Lime to the soil will liberate 

 in a single year more inorganic plant-food from 

 their chemical combinations, than moisture, atmos- 

 pheric air, and the mechanical operations of 

 agriculture can in a century. Carbonate of 

 lime in its unburnt state possesses the same 

 property as quicklime, namely, it decomposes the 

 alkaline silicates ; but as it acts much slower than 

 quicklime, and must be finely powdered to have 

 full effect, it is generally much more economical 

 to burn kunkur and slake it into an impalpable 

 powder. 



Another important source of lime available to 

 the Indian farmer is the shell-sand which abounds 

 on the sea-coast. Some of the shell-sand near 

 Bombay, I have found, contains as much as 70 per 

 cent, of pure carbonate of lime in the shape of small 



