iv.] FARM-YARD MANURE. 29 



manure, whereas the manure obtained from pigs is 

 intermediate. One of the first things to be secured is 

 an even distribution of the different kinds of 

 manure, so that the bulk of manure may have a 

 similarity of character. This is most necessary, 

 if any measures are to be adopted for regulating the 

 fermentation; otherwise one portion is too hot, 

 and another portion is not hot enough, and that 

 treatment which is favourable for one part is injurious 

 for another. An even distribution is therefore 

 the first essential ; this being secured, the fer- 

 mentation of the heap can be readily controlled. 



52. For our present purposes, this fermentation may 

 be familiarly described as a decay or rotting, brought 

 on by the decomposing influence of the nitrogenous 

 matter present, whereby the non-nitrogenous matters 

 present also undergo decomposition. The chief pro- 

 ducts of this decomposition are ammonia, and 

 either carbonic acid, or some one or more of the 

 organic acids, such as the ulmic acid or humic 

 acid. The ammonia is formed from the nitrogenous 

 matters in the manure, and the non-nitrogenous 

 matters may yield either carbonic acid or the organic 

 acids we have named above, according to the manner 

 in which the decomposition of the manure takes place. 

 If the manure be allowed to get dry and hot, then 

 carbonic acid is formed ; but if the manure be kept 

 moist, one of the organic acids is produced. If car- 

 bonic acid be formed, it combines with ammonia, 

 and we have carbonate of ammonia formed. 

 This is a very volatile and pungent smelling salt, of 

 which you will have very little doubt after you have 

 once experienced its influence. But if instead of 

 carbonic acid being formed, we get one or more of 

 the organic acids produced, then you have, say, 

 ulmate of ammonia or humate of ammonia 

 formed, which has a very different character. You 

 have probably seen the black streams which 



