MANUTJES. 91 



but a mass of earthy matter will remain, except a 

 small quantity of carbon which has not been resolved 

 into carbonic acid. 



The proportion of solid manure lost by evaporation 

 (made volatile by the assistance of decay) may be a 

 very large part of the whole. Manure cannot be kept 

 a single day in its natural state without losing some- 

 thing. It commences to give out an offensive odor 

 immediatel}', and this odor is often accompanied, as 

 was before stated, by the loss of some of its fertiliz- 

 ing parts. 



Animal manure contains, as wull be seen by refer- 

 ence to p. 86, all of the substances contained in 

 plants, though not always in the correct relative pro- 

 portions to each other. When decomposition com- 

 mences, the carbon unites with the oxygen of the 

 air, and passes off as carbonic acid ; the hydrogen 

 and. oxygen combine to form water (which evapo- 

 rates), and the nitrogen is mostly resolved into am- 

 monia^ which escapes into the atmosjyhere, unless ab- 

 sorbed by substances artiticially applied for the pur- 

 pose, or retained by the carbon, organic acids, or 

 other products of decomposition with which it may 

 become united. 



If manure is thrown into heaps, it often ferments 

 ijo rapidly as to produce sufficien theat to set fire to 

 some parts of the manure, and cause its gases to be 

 thrown off with greater rapidity. This may be observ- 

 ed in nearly all heaps of animal excrement. When 

 they have lain for some time in mild weather, gray 

 streaks of ashes are often to be seen in the centre of 



