APPENDIX. 



161 



We find tliem iu ashes. Burning decomposes and recoinposes them 

 anew. We are by no means to conclude, because we find various salts 

 in plants, that they existed as such in the soil. Of the soluble alkalijie 

 salts, probably none exist in the soil. They are products of vegetation 

 educed from the composition of silicates and salts. 



The composition of the insulublc part of ashes gives us nearly the 

 constituents of leeched ashes. If the soapboilers' process was as per- 

 fect as that which the chemist employs — still his leeched ashes would 

 show more lime, than the above tables, because he always employs a 

 portion of lime to make his lye caustic. This is a variable portion ; 

 whatever it is, it adds so much to the value of the leeched ashes. 

 Besides the soap-maker always leaves a portion of alkali, which is 

 combined with the silex. Exposure to air decomposes this, and then 

 the alkali can be extracted by water. This is one great source of the 

 active power of leeched ashes. The course of this wonderful power, 

 not only in fresh and in leeched ashes, but in some degree in all salts, 

 is to be found, in the action of the bases on geine and on silicates. 



There is one great, simple principle running through all the classes 

 of soils. It is this, ilmt in all salts and silicates the action of the base 

 is ever the same in vegetation. The base of the silicates and salts acts 

 always in one uniform mode. Peculiarities of action depend on the 

 acid constituent of the salt. Lime, for instance, acts ever the same, 

 whether it is used as carbonate, sulphate, or phosphate, marl, plaster, 

 or bone-dust. The salt is decomposed by the living plant. The various 

 acids combine with the alkalies, as they are eliminated, from the decom- 

 position of the silicates, and the lime, liberated, acts ever os lime. It 

 acts in its caustic state, as a converter of insoluble into soluble 

 geine. If this does not exist in the soil, all the lime in the world would 

 not cause plants to grow. The base of the lime-salts acts primarily on 

 geine, either solving the soluble or converting the insoluble. The 

 same is true of alumine, iron and the bases of all salts. The same gen- 

 eral rule applies to all alkaline, earthy or metallic salts and to silicates. 



The order in which the farmer may apply salts is the following. 

 Carbonate, phosphate, and sulphate of lime, carbonates, nitrates, mu- 

 riates, and sulphates of alkalies. No salts, excepting carbonates, can 

 be used in large quantities. The reason is at once explained by the 

 principle of unity of action of the bases. The acid of the salts, elimi- 

 nated, decomposes the geates, rendering the soluble insoluble, the 

 acid combines with any free base, produced from the decomposition 

 of the silicates, and thus prevents that forming soluble geine. Having 

 saturated the bases, any excess acts then as free acid, poisoning the 

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