SECOND REPLY. 177 



constituents, which we are accustomed to despise and over- 

 look, are exactly those which have the most essential 

 importance to the vegetable world. All the nitrogenous 

 components of plants, which we use as food, consist, it is 

 true, of merely carbon, hydrogen, oxygen and nitrogen. 

 But the presence of these substances alone does not help 

 the plant in the least ; it cannot form from them a granule 

 of albumen or gluten, unless it contains, at the same time 

 and in the proper relative condition, salts of phosphoric 

 acid. The useful starch, the sweet sugar, the cooling citric 

 acid, the aromatic oil of oranges, are indeed composed 

 solely of carbon, hydrogen and oxygen ; but the plant 

 cannot prepare those gifts for us, out of ever so great an 

 abundance of these elements, if it does not possess also 

 alkaline salts. The slender stalk of the wheat could not 

 lift itself to ripen its grain in the sun's rays, unless the soil 

 furnished it with silex, through which it gives its cells that 

 solidity necessary to enable it to maintain an erect 

 position. 



Supported by these facts, Liebig has recently sought to 

 revolutionize our whole agricultural system, by the recom- 

 mendation of a mineral manure he has discovered ; for the 

 preparation of which he has taken out a patent in England, 

 and sold it to Messrs. Muspratt and Co. His aim is to 

 furnish to every kind of soil and plant, a proper com- 

 post of those mineral substances which the plant requires 

 and the soil is deficient in, and in such a peculiar state of 

 combination, that the substances shall be soluble enough 

 to be taken up by the plants, and yet not so readily 

 soluble, that the rain can wash away any considerable 

 quantity. Whether Leibig has attained to this end, can 

 only be determined after experience has given its evidence. 

 In theory, it must be affirmed, that the principle is correct 



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