NUTRITIVE MANURES. S3 



and the juices contained in them ; but the fibres, the fat- 

 ness, the oils, remain inactive in the earth ; and their 

 final decomposition is slow and imperfect. If, on the con- 

 trary, the collections of the farm-yard be heaped up in a 

 corner of it, the mass will speedily become heated, car- 

 bonic acid gas will be evolved, and afterwards carburetted 

 hydrogen, ammonia, azote, &c. A brown liquid, of which 

 the color deepens gradually almost to black, moistens the 

 heap, and flows upon the ground around it ; all is by de- 

 grees disorganized ; and when the fermentation is com- 

 pleted, there remains only a residue composed of earthy 

 and saline substances, mixed with a portion of blackened 

 fibre, and some carbon in powder. 



In those places where they do not allow fermentation 

 to arrive to this degree of decomposition, they still lose, by 

 mismanagement, a considerable part of their manure. 



The most common method is, to deposit in a corner of 

 the farm-yard the dung and litter, as it is drawn from the 

 stables, adding to the mass every time these are cleared, 

 and allowing it to ferment till the period of sowing arrives, 

 whether it be in spring or autumn, when it is carried 

 upon the fields requiring it. 



This method presents many imperfections. In the first 

 place, several successive layers being formed, no two of 

 them can have undergone the same degree of fermenta- 

 tion ; in some it will have gone on for six months, and in 

 others but for fifteen days. In the second place, the heap, 

 being exposed to rains, will, by frequent washings, have 

 parted with nearly all its salts and soluble juices. In the 

 third place, the extractive portions of the lower and cen- 

 tral parts of the mass, the mucilage, the albumen, and 

 the gelatine, will be entirely decomposed ; and, lastly, 

 those gases which nourish plants, if developed at their 

 roots, will have escaped into the air; and Davy has ob- 

 served, that, by directing these emanations beneath the 

 roots of the turf in a garden, the vegetation was rendered 

 very superior to that in the vicinity. 



How long should dunghills be allowed to ferment ; and 

 what methods ought to be pursued in forming them? 

 This question leads us to cast a glance upon the nature of 

 dunghills ; and it is not till after having ascertained the 

 difference amongst them, that it can be answered. 



The principal parts of vegetables which are employed 

 5* 



