ACTION OF SALTS. Ill 



the acid of salts acts upon silicates. Apply this principle to 

 all mineral 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 effect produced by such wonderfully 

 minute quantities is no longer astonishing. 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 decom- 

 posed 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 action 

 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 is the presence 

 of organic matter, or geine in the soil. It is the want of a- 

 principle like that which has been stated, which has led to a 

 waste of time and money, in applying mineral manures to 

 worn-out and barren soil. Whereas, the principle (145) 

 leads to the application of both salts and geine. The salts 

 alone would be useless. Their first effect in either case, 

 would be the same on silicates ; but with geine, this action, 

 like fermentation, goes on, begetting new salts ; without it, 

 this action ceases after the first chemical changes have occur- 

 red. In the first case, it goes on. In the second, it stops. 



155. Salts without geine, act only on silicates of ihe soil. 

 If, now, these silicates contain any portion of aqueous rock 

 (11), they usually contain also distinct traces of organic 

 matter. This matter is due, for the most part, to the geine, 

 held in solution in the water, from which the rocks were 

 deposited. It is certainly within the bounds, not only of a 



