94 



clayey soils, as it changes their character entirely. 

 It renders the soil porous, decomposes the clay 

 silicates, sets their alkalis free in short, it effects 

 in twelve months a change in the condition of 

 the soil that perhaps a hundred years of thorough 

 exposure to climatic influences could not have 

 produced. Organic matter decaying in the soil, 

 assists also in its disintegration by the carbonic 

 acid which it evolves, and which possesses the 

 remarkable property of dissolving the phosphates of 

 lime and magnesia. This property of acting as 

 a solvent of phosphates otherwise insoluble in 

 water, is shared likewise by other chemical sub- 

 stances, such as common salt, nitrate of potash, 

 sulphate of ammonia, &c. 



The increased yield, due to the use of these 

 materials as manures, must therefore be considered 

 as owing partly to their solvent actions on otherwise 

 insoluble food constituents, and partly to being 

 elements of plant-food themselves, and therefore 

 augmenting the existing supply in the soil. When 

 the cause of the nutritive powers of the soil is once 

 known, it becomes an easy matter to explain and 

 remedy sundry unaccountable occurrences and 

 defects which but too often have been misunderstood 

 and misinterpreted. 



Lieutenant- Colonel Corbett, in a small pamphlet 

 against irrigation, mentions several injurious effects 

 which he asserts water has on the soil. " Lands," 



