MANURES. 161 



may be applied in the form of salt (chloride of so- 

 dium), or chloride of lime. The former may be dis- 

 solved in the water used to slake lime, and the latter 

 may, with much advantage, be sprinkled around 

 stables and other places where fertilizing gases are 

 escaping, and, after being saturated with ammonia, 

 applied to the soil, thus serving a double purpose. 

 On a stock farm, a very good way to return to the 

 soil the chlorine contained in the produce sold, is to 

 give it freely to the animals. 



OXIDE OF IRON. 



Probably all soils contain sufficient quantities of 

 oxide of iron, or iron rust, so that this substance can 

 hardly be required as a manure. 



Some soils, however, contain the protoxide of iron 

 in such quantities as to be injurious to plants, see 

 page 74-. When this is the case, it is necessary to 

 plow the soil thoroughly, and use such other me- 

 chanical means as shall open it to the admission of 

 air. The protoxide of iron will then take up more 

 oxygen, and become the peroxide which is not only 

 inoffensive, but is conducive to fertility. 



OXIDE OF MANGANESE. 



This can hardly be called an essential constituent 

 of plants, and is never taken into consideration in 

 manuring lands. 



