ACTION OF SALTS. 117 



ing it soluble, is it not analogous to the action of air on oils 1 

 Both evolve, in this case, vast volumes of carbonic acid, the 

 oil becomes gelatinous and soluble in alkali ; does not a sim- 

 ilar change occur in geine ? It is possible that during the 

 action of lime on geine, a soluble substance may be pro- 

 duced, bearing the same relation to this process that gly- 

 cerine does to saponification. These views need to be 

 followed out experimentally, and may be possibly hereafter 

 considered. 



163. In the acid soil, lime acts to eliminate carbonic acid, 

 which then acts on silicates and geine, as has been explained. 

 All fat acids, or fats and oils, act in the same way upon sili- 

 cates, partly by their own acid properties, and partly by the 

 evolution of carbonic acid gas, which is evolved during their 

 conversion into the acid state. The quantity of carbonate 

 of lime which may be applied is unlimited, and the quantity 

 of alkali depends on the presence of insoluble geine. The 

 more abundant is the last, the more freely may alkalies be 

 applied. The carbonates include ashes of all kinds, and 

 agriculturally viewed, all kinds of lime, for the quick soon 

 becomes mild. The value of ashes in agriculture, depends 

 upon its being a combination of salts derived from plants, 

 all of which have a powerful and decidedly beneficial effect. 

 The question is often asked, What is the relative value of 

 spent or leeched and unleeched ashes 1 It may be answered 

 by reference to the analysis of ashes. 



Burning reduces organic substance to two classes, asTies 

 and volatile salts. The last are found in soot. The ashes 

 are formed of salts and silicates. These vary in quantity 

 and quality, not only in different plants, but, as is well known, 

 in different parts of the same plant. Let us take oak, beech, 

 basswood, birch, as the types of the composition of hard 



