CHAP. i. FARM-YARD MANURE. 1005 



considered as a perfect and universal manure. It is a universal 

 manure, because it contains all the constituents which our cultivated 

 crops require to come to perfection, and is suited for almost every 

 description of agricultural produce. As far as the inorganic fertilising 

 substances are concerned, we find in farm-yard 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 farm-yard manure some which are 

 readily soluble in water, and contain a large proportion of nitrogen, 

 and others insoluble in water, and containing, 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 compounds. These organic acids constitute the mass 

 of the brown vegetable substances, or rather mixture of substances, 

 which, practically speaking, pass under the name of humus. 



" Farm-yard manure is a perfect manure, because experience, as 

 well as chemical analysis, shows that the fertilising constituents are 

 present in dung 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 in analysing farm-yard 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 farm- yard manure is capable of producing. This mechanical 

 effect, especially important 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 

 ammonia, soluble nitrogenised organic matter, and insoluble nitro- 

 genised organic substance, or no less than four different states in 

 which the one element, nitrogen, occurs in fresh manure. In well 

 rotted dung, the same element, nitrogen, probably is found in several 

 other forms. This complexity of composition difficult, if not im- 

 possible, to imitate by art is one of the reasons which render farm- 

 yard manure a perfect as well as a universal manure." 



By far the most valuable portions of farm-yard manure, or " dung," 

 are those constituents contributed by the urine of the animals which 

 make the manure. The absorbent nature of straw is such that it can 

 hold a large quantity of liquid without its draining away, but unless 

 the use of litter is extravagant, it generally happens that in the farm- 

 yard the litter becomes super- saturated, and a certain quantity of liquor 

 flows away. The loss of this liquor involves great waste, and the loss 

 of the dark brown liquor that flows from dung heaps that have entered 

 into the fermenting stage may involve even greater waste, since this 



