PRACTICAL INFERENCES. 279 



**We may also derive from these considerations, some 

 useful cautions, as to the treatment of this same material. 



*' Ammonia, in the free or uncombined condition in which 

 it is generated from the decomposition of animal substances, 

 is caustic and noxious to vegetation, and is likewise so 

 volatile that it will escape into the atmosphere so soon as 

 it is produced, unless some means are taken to detain it. 



*'This causticity is readily removed by promoting its 

 combination with the carbonic acid of the atmosphere, but 

 to prevent its escape during the time necessary for effect- 

 ing this union, various expedients have been resorted to. 



'* Where water in sufficient quantity is present, along 

 with the other materials of the dung-heap, this alone will 

 in some measure tend to prevent its volatilization, and the 

 same object is further secured, by admixture with peat, as 

 recommended by Lord Meadowbank, or with sawdust, 

 tanner's bark, turf, and other similar substances. These 

 too are beneficial, not only by moderating the putrefactive 

 process, but also by detaining the ammonia generated 

 within their pores, and thus preventing its loss. 



"The advantage of compost heaps, which are strongly 

 advocated by some farmers, depends mainly on these prin- 

 ciples. 



"The method recommended by a writer, in a late num- 

 ber of the English Agricultural Journal,* to whom a prize 

 of ten sovereigns was awarded for his Essay, consisted, in 

 first making a substratum of peat fths, and sawdust Jth ; 

 spreading over it the dung from the cattle-sheds, and the 

 urine preserved for the purpose in tanks contiguous ; and 

 then, after allowing the mixture to remain exposed for a 

 week, covering it with a fresh layer, nine inches or a foot 

 thick, of peat and sawdust, or of peat alone. 



"Several such alternations of peat and manure are to 

 be piled one above the other during the winter, great care 

 being always taken, that the peat should be as dry as pos- 

 sible, by exposing it previously for several months to the 

 weather. 



"Now it will be immediately perceived, that these 

 recommendations of a practical farmer completely fulfil 

 the conditions, which theory suggests, for making the best 

 use of our manure, by first neutralizing the ammonia, and 

 afterwards detaining it within the pores of a spongy sub- 

 stance, until it is spread over the land. 



"The most effectual plan, however, of preventing its 



«* Part II p. 135." 



