FARMYARD MANURE. 9 



we find in farmyard manure : potash, soda, lime, magnesia, oxide 

 of iron, silica, phosphoric acid, sulphuric acid, hydrochloric and 

 carbonic acid in short, all the minerals, not one excepted, that 

 are found in the ashes of agricultural crops. 



Of organic fertilising substances we find in farmyard manure 

 some which are readily soluble in water and contain a large 

 proportion of nitrogen, and others insoluble in water and con- 

 taining, comparatively speaking, a small proportion of nitrogen. 

 The former readily yield ammonia, the latter principally give 

 rise to the formation of humic acids and similar organic com- 

 pounds. These organic acids constitute the mass of the brown 

 vegetable substance, or rather mixture of substances, which, prac- 

 tically speaking, pass under the name of humus. 



Farmyard manure is a perfect manure, because experience as 

 well as chemical analysis shows that the fertilising constituents 

 are present in clung in states of combination, which appear to 

 be especially favourable to the luxuriant growth of our crops. 

 Since the number of the various chemical compounds in farm- 

 yard manure is exceedingly great, and many no doubt exist in 

 a different state of combination from that in which they are 

 obtained on analysing farmyard manure, in our present state of 

 knowledge it is impossible artificially to produce a concentrated, 

 universal, and perfect manure, which might entirely supersede 

 home-made dung. 



I do not refer to the mechanical effect which farmyard manure 

 is capable of producing. This mechanical effect, especially im- 

 portant in reference to heavy clay soils, ought to be duly regarded 

 in estimating the value of common dung, but for the present it 

 may suffice to draw attention to the fact, that even fresh dung 

 contains a great variety of both organic and inorganic compounds 

 of various degrees of solubility. Thus, for instance, we find in 

 fresh manure volatile and ammoniacal compounds, salts of am- 

 rnonia, soluble nitrogenized organic matters, and insoluble 

 nitrogenized organic substances, or no less than four different 

 states in which the one element, nitrogen, occurs in fresh 

 manure. In well-rotten dung the same element, nitrogen, pro- 

 bably is found in several other forms. This complexity of com- 

 position difficult, if not impossible, to imitate by art is one 

 of the reasons which render farmyard manure a perfect as well as 

 a universal manure. 



On the Changes which Fresh Farmyard Manure undergoes in 

 Ripening. The peculiar character of these changes becomes 

 apparent if the composition of fresh dung is compared with that 

 of well rotten dung. I would therefore in the next place direct 

 attention to the subjoined Table, representing the detailed com- 

 position of rotten dung : 



