138 Farmyard Manure. 



have detected readily the presence of nitric acid. In the liquid 

 from fresh manure there were apparently mere traces of nitrates, 

 but in that from rotten dung the proportion of nitric acid was so 

 considerable that I hoped to be able to determine it quantita- 

 tively. But I found the large amount of soluble organic matter 

 to interfere sadly with the nitric acid determination ; and, unable 

 to supply for the present correct results, I merely mention the 

 fact that these liquids contained nitrates, and trust to be able to 

 supply this deficiency in these analyses at a future period. 



In the next place I would observe that the proportion of 

 organic and inorganic matters bear to each other a different rela- 

 tion in the first and in the third liquid. 



In the liquid from rotten dung the proportion of mineral 

 matter exceeds that of organic substances, and in the third liquid 

 the reverse is the case. We learn from this that soluble organic 

 matters are very liable to become decomposed ; and it is not 

 unlikely that all putrescent organic matters before assuming a 

 gaseous state are first changed into soluble matters. 



In the first stage of decomposition, i.e., during the active fer- 

 mentation of dung, the constituents of farmyard manure are ren- 

 dered more and more soluble ; hence, up to a certain point the 

 amount of soluble organic matters increases in manures. But 

 when active fermentation in manure heaps becomes gradually 

 less and less energetic, and finally ceases, the remaining fer- 

 mented manure is still liable to great and important changes, for 

 it is subject to that slow but steady oxidation, or slow combus- 

 tion, which has been termed, appropriately, by Liebig, Erema- 

 causis. To this process of slow oxidation all organic substances 

 are more or less subject. It is a gradual combustion, which ter- 

 minates with their final destruction. 



Hence the larger proportion of organic matter in the liquid 

 from the manure heap formed of fresh dung, in an active state 

 of fermentation, and the smaller proportion of organic matter in 

 the drainings of the first heap, in which the dung had passed the 

 first stage of decomposition, and been exposed for a considerable 

 period to the subsequent process of eremacausis, or slow com- 

 bustion. 



The formation of nitric acid from putrefying organic matters 

 has long been observed, but the exact conditions under which it 

 proceeds are by no means satisfactorily established, and much 

 room is left to further extended investigations. 



The mineral substances in the drainings from fresh dung are 

 the same as those from rotten. Like the ash of the latter, the 

 liquid from fresh dung-heaps contains soluble phosphates, soluble 

 silica, and is rich in alkaline salts, especially in carbonate ot potash, 

 of which there are nearly 300 grs. in a gallon of the liquid. 



