The mixture, however, of the nitrogen and carbon of the manure brings at once into existence a remarkably rapid action, which,_ as Professor Tanner says, "rends ;asunder the indivi dual elements of the various matters in'the dung, and affords them the opportunity of forming new associa tions or combinations." What they ore, a brief sentence or two will explain. Air and moisture being present in the duDg— as, practically, it is yre sent in all heaps of ifc — the fermentation caused by the union of the nitrogen with the carbon compounds goes rapidly on, and brings about the deposition of the various elements contained, in the manure, or ' forms new combinations : one of these is the union of the nitrogen with the hydrogen, which forms (I) ammonia ; next, the union of the oxygen with the carbon, which forms (2) carbonic acid ; and the union of the oxygen with the hydrogen and the car bonic acid, which, gives (3) humic acid. But these, whenever they are present together, do not j remain separate, but combine to form fresh airange. ments ; thus, the carbonic acid unites with the ! ammonia, and, carbonate of ammonia (one of the most volatile of compounds) is formed. With the combi nations of humic acid and ammonia wa have the humate of ammonia, a compound which is not volatile; but although not volatile— that is, not easily passing off from the manure to the air— it is very readily dis- , solved in water; and the black, rich-looking liquid which we see running from manure heaps is evidence, then, of this dissolving process going on, _ Hence. may be derived the practical value of having the sides and bottom of^ our manure pits impervious, so that all this drainage shall be kept. Hence also that other recommendation .which some authorities insist upon, of having the manure pit covered, so that large quantities of rain shall not be mixed with the manure. It is obvious enough that thi« solution of humate of ammonia will be better' carried on in the soil near the plants which it is to fertilise, than in the manure pit. 