Farmyard Manure. 211 



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 constituents 

 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- 

 raentitious 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 piactical 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. It 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 consider- 

 able loss of really valuable fertilizing substances ? 



In putting this question we have to l)ear in mind that the loss 

 in valualjle mineral matters, under proper management, practi- 

 cally speaking, can be avoided, since they are non-volatile, and, 

 therefore, must remain incorporated with the dung, if care be 

 taken to prevent their being washed away by heavy falls of rain. 

 We have likewise to bear in mind that, in an agricultural point 

 of view, the ^carbonaceous, non-nitrogenized manurc-constitiients 

 do not possess a very higli intrinsic value ; and that we therefore 

 need not trouble ourselves about their diminution, if it can be 

 shown that it is accompanied with other beneficial changes. The 



r2 



