100 ACTION OF SALTS. 



for its own use, the acid of the salt which was in- 

 troduced. 



152. Fertility depends wholly on salts and geine. 

 Without the last there is no fruit formed ; without 

 the salts the geine is locked up, is insoluble. Con- 

 sider now the application of this principle, that the 

 base of the salts acts always in one uniform way, its 

 action is wholly upon geine ; that the acid of salts, 

 acts upon silicates. Apply this principle to all min- 

 eral manures, as they are called. They are all con-' 

 nected by one common mode of action of their base. 

 There is no speculation, there is no mystery, as to 

 the mode how they act. The effects produced by 

 such wonderfully minute quantities is no longer aston- 

 ishing. It is no more wonderful than that leaven 

 should make dough rise ; it is even less mysterious. 



153. Apply this principle to acids, which have 

 sometimes been used. Sprinkle a small portion of 

 oil of vitriol on the soil, supposing no free base 

 present, the silicates are decomposed by the oil of 

 vitriol, and sulphates of alkalies, and alkaline earths 

 are formed. These new formed salts are, in their 

 turn, decomposed by the living plants ; and the ac- 

 tion on geine commences, as has been explained. 



154. Consider how salts and geine are linked. It 

 is at once seen how essential to the action of salts 



