MANURES LVALUE OF AMMONIACAL SALTS. 255 



rtie most active manures are precisely those which contain the largest 

 proportion of azotized principles. It is obvious indeed from every- 

 thing which precedes, that all the substances which contribute to 

 form farm dung, contain azote ; and that into many of them, such as 

 uric acid, hippuric acid, and urea, this element enters very largely. 



When we consider the immediate changes which all highly azo- 

 tized substances undergo in the process of putrefaction, we can fore- 

 see that in their transformation into manure, they must give origin 

 to ammoniacal salts ; and well-established facts prove beyond d.oubt 

 that salts, having ammonia for their base, must be ranked among 

 the most powerful of all the agents in promoting vegetation. It is 

 sufficient, for instance, to bear in mind that in the productive hus- 

 bandry of Flanders, putrid urine is the manure that is employed with 

 the greatest success ; but we have seen that by putrefaction, the 

 urea of the urine is entirely changed into carbonate of ammonia. 

 The fields of Flanders are consequently fertilized with a solution 

 of carbonate of ammonia in water. 



Along a great extent of the coast of Peru, the soil, which con- 

 sists of a quartzy sand mixed with clay, and is perfectly barren of 

 itself, is rendered fertile, is made to yield abundant crops, by the 

 application of guano; and this manure, which effects a change so 

 prompt and so remarkable, consists almost exclusively of ammoniacal 

 salts. It was with this fact before me that in 1832, when I was on 

 the coasts of the Southern Ocean, I adopted the opinion which I 

 now proclaim in regard to the utility of the salts having a basis of 

 ammonia in the phenomena of vegetation. I have stated my views 

 on this subject in a memoir published in 1837.* Previous to this 

 publication, however, M. Schattenmann, one of the most ingenious 

 manufacturers of Alsace, had already directed the attention of hus- 

 bandmen to this important matter, by reminding them that it is the 

 custom in Switzerland to add sulphate of iron or green vitriol to the 

 urine-vats, for the purpose of changing the carbonate of ammonia 

 into the sulphate, and thus obtaining a fixed instead of a highly vola- 

 tile salt, liable to escape and to be lost. In a communication made 

 in 1835 to the agricultural association of Bauchsweiler, M. Schat- 

 tenmann announced positively that the drainings from dunghills 

 thus prepared, applied upon meadow lands, produced very grea 

 effects. 



Such, to the best of my knowledge, are the practical facts whicK 

 establish the useful influence of ammonia on the growth of plants 

 far better than the experiments of the laboratory could have done. 

 Nevertheless, it must be acknowledged that long before the dates 

 above quoted, Davy had shown that water containing s^oih of car- 

 bonate of ammonia is singularly favorable to the growth of wheat, 

 far more so, under circumstances exactly similar, than the hydro- 

 chlorate and the nitrate of the same base ; and this influence, it is 

 important to observe, Davy ascribed to the fact that carbonate of 

 aimnonia contains carbon, hydrogen, oxygen, and azote ; in a wcrd, 



* Annates de Chimie, t. Ixv. 2e sirie, p. 301. 



