THE COMPOST HEAP. 189 



termed oxidation ; being changed from an alkali 

 to an acid, forming nitrates of potash, soda, and 

 lime, if these bases are present. Some chemists 

 hold the opinion that the nitrogen contained in 

 these compounds, is far more valuable than as it 

 is presented in ammonia ; but this is a difficult 

 matter to decide, and more extended experiments 

 are required, to enable us to give a positive 

 opinion on the subject. As far as our present 

 knowledge of the matter goes, they are equally 

 valuable, although it is proved that the ammo- 

 nia is more permanent in the soil than nitric acid. 



A valuable addition to the compost heap, is 

 ground bones. This substance furnishes both 

 phosphoric acid and nitrogen ; and if the bones 

 are mixed with an equal weight of finely ground 

 gypsum, and fully incorporated with the heap, 

 the farmer will produce his own soluble phos- 

 phoric acid, at less than half the cost he would 

 have to pay for it, if purchased from the manu- 

 facturers. Again, when the pile is turned over 

 an operation that must be attended to in order 

 to produce good results should the farmer de- 

 tect the smell of escaping ammonia, another 

 light sprinkle of plaster must be applied. 



The time required to produce fermentation, 

 varies with the season ; in summer, the heap 

 may commence heating in from six to ten days ; 

 but in winter, it will require as many weeks. 



