BY MIXED MANURES. 291 



to be decomposed in the process. This also escapes into 

 the air. 



(4) Sulphur and phosphorus are always constituents of 

 manures, and combine with the hydrogen and form sulphuret- 

 ed and phosphoreted hydrogen ; two gaseous bodies of very 

 offensive odors, which escape in part into the air. 



(5) The substances which contain nitrogen yield that ele- 

 ment to hydrogen, and form ammonia. A part of this sub- 

 stance is absorbed by water and the vegetable matter, and a 

 part is thrown off into the atmosphere ; the remainder, which 

 constitutes probably the largest portion, combines with car- 

 bonic acid, forming carbonate of ammonia, and with other 

 acids, as the muriatic and nitric, which are formed during 

 the process. 



The above, with the exception of water, are the gaseous 

 bodies given off in the process, and as the most valuable part 

 of the manure is liable to be dissipated in this way, v/e have 

 the best reason for covering the fermenting heap with a thick 

 coating of earth or peaty matter. 



(6) Nitric acid is usually formed in this process. Some 

 have supposed that it results from the transformation of am- 

 monia ; others suppose that it may obtain its nitrogen direct- 

 ly from the plant, or from the atmosphere. The acid being 

 formed, combines with the potash and forms nitre or salt- 

 petre ; and with other bases which may be present, such as 

 soda, lime and ammonia. 



(7) Sulphuric and hydrochloric acids are also formed ; the 

 latter acid deriving its chlorine from the salt which exists in 

 animal excrements. It is probable that other acids are formed. 

 All of them, however, are combined with bases in the form 

 of salts. It is rare that any acid, excepting the carbonic, ex- 

 ists in a free state. 



(8) The solid matters which remain, are found to consist 

 in part of humic acid, humin, extract of humus, crenic and 

 apocrenic acids. The acids are combined in some cases 



