MA^S'URES. 135 



natural condition. In this way, the mechanioul tex- 

 ture of the soil is improved. 



It has just been said that Z/m^ causes the pulveriza- 

 tion of the particles of the soil ; and thus, by making 

 it finer, it improves its mechanical condition. 



Some mineral manures, such as plaster and salt, 

 liave the power of absorbing moisture from the at- 

 mosphere ; and this is a mechanical improvement to 

 dry soils. 



4th. Those mineral manures which have the 

 power of absorbing ammonia. 



Plaster^ chloride of lime^ aluinhia {clay), etc., arc 

 large absorbents of ammonia, whether arising from 

 the fermentation of animal manures or washed down 

 from the atmosphere by rains. 



Having now explained the reasons M'hy mineral 

 manures are necessary, and the manner in which 

 they produce their effects, we will proceed to examine 

 the various deficiencies of soils and the character of 

 various kinds of this class of fertilizers. 



CHAPTER IX. 



DEFICIENCIES OF SOILS, MEANS OF RESTORATION, ETC. 



As will be seen by referring to the analyses of soils 

 on p. 63, they may be deficient in certain ingre- 

 dients, which it is the object of mineral manures to 

 Bupply. These we will take up in order, and eudea- 



