FARMYAKD MANURE. 15 



of ammonia which passes into the atmosphere from fermenting 

 dung-heaps, and the loss which hereby is occasioned, is much 

 less considerable than it is generally assumed to be. In fer- 

 menting dung-heaps the carbonaceous constituents at first are 

 changed into humus substances, but these are rapidly oxidized 

 by atmospheric oxygen, and partly changed into carbonic acid, 

 a gaseous substance which, in conjunction with oxide of carbon 

 and carburetted hydrogen, is given off abundantly from all 

 putrefying organic matters. 



I have endeavoured to describe briefly the principal changes 

 which take place in the fermentation of farmyard manure. It 

 has been shown : 



1. That during the fermentation of dung the proportion of both 

 soluble organic and soluble mineral matters rapidly increases. 



2. That peculiar organic acids, not existing at least, not in 

 considerable quantities are generated, during the ripening of 

 dung from the litter and other non-nitrogenized organic consti- 

 tuents of manure. 



3. That these acids (humic, ulmic, and similar acids) form, 

 with potash, soda, and ammonia, dark-coloured, very soluble 

 compounds. Hence the dark colour of the drainings of dung- 

 heaps. 



4. That ammonia is produced from the nitrogenous consti- 

 tuents of dung, and that this ammonia is fixed, for the greater 

 part, by the humus substances produced at the same time. 



5. That a portion of the sulphur and phosphorus of the excre- 

 mentitious matters of dung is dissipated, in the form of sul- 

 phuretted and phosphoretted hydrogen. 



6. That volatile ammoniacal compounds, apparently in incon- 

 siderable quantities, escape into the air. 



7. That the proportion of organic substances in fresh dung 

 rapidly decreases during the fermentation of dung, whilst the 

 mineral substances increase in a corresponding degree. 



8. That this loss of organic substances is accounted for by the 

 formation of carbonic acid, oxide of carbon, and light-carburetted 

 hydrogen, or marsh- gas. 



9. That the proportion of nitrogen is larger in rotten than in 

 fresh dung. 



The practical result of these changes is, that fresh manure, in 

 ripening, becomes more concentrated, more easily available to 

 plants, and, consequently, more energetic and beneficial in its 

 action. Tt may be questioned, with much propriety, Is this 

 apparently desirable result attained without any appreciable loss ? 

 or is it realised at too great an expense ? In other words, Is the 

 fermentation of dung, or is it not, attended with considerable loss 

 of really valuable fertilizing substances ? 



