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ROYAL HORTICULTURAL SOCIETY. 



hand, rotting dung, as Davy has shown, evolves, besides carbonic 

 acid, gaseous acetate and carbonate of ammonia, and is by no 

 means entirely decomposed into carbonic acid and ammoniacal 

 gas, but leaves behind a solid ammoniacal humus or mould — which 

 is contrary to the views of Ingenhousz, who supposed the whole of 

 the dung passed into a gaseous form by fermentation and putres- 

 cence, so that all the constituents which were nutritive to plants 

 were communicated to the air ; whereas, on the contrary, the nu- 

 tritive properties reside, for the most part, in the mould which 

 arises from the dung by means of decomposition. 



The ammoniacal matter in the atmosphere is therefore extremely 

 small, whereas that of the soil, and of many particular soils, is very 

 large. Clay is the richest of all in ammonia. According to 

 Baumhauer, the clay of the Zuidersee of Holland, contains in a 

 thousand parts *075- - 078 of ammonia, which is about 0*13 or 



per cent. The virgin forest-soil of Texas contains J per cent, 

 of ammonia ; 100 lbs. of it contain 6 ozs. of sal ammoniac, or 2 ozs. 

 of ammonia. According to Krocker's experiments, loam contains 

 J per cent., sand and marl J- Q ^ per cent, of ammonia. In four 

 acres of land having 1 foot depth of soil, containing -1 per cent, of 

 ammonia, there are above 16,000 lbs., or 4000 lbs. per acre. This 

 quantity is greater than what is given to land by manure. If 

 an acre of land contains 120 cwt. of manure, supposing it to 

 contain 2lro-th °f ammonia, there are only 66 lbs. of ammonia, 

 whereas in the soil just mentioned there are 4000 lbs. The 

 dung is by no means effectual merely by addition of ammonia, 

 but besides by the accumulation of humus as a ferment for other 

 constituents. 



The mode in which ammonia is formed in the soil is elucidated by 

 the experiments of Kuhlmann on the formation of saltpetre, and has 

 been further followed out by Mulder in his ' Physiological Chemis- 

 try.' Ammonia is formed in rotting, porous matters, which evolve 

 hydrogen, while the nitrogen of the air combines with the nascent 

 hydrogen, as in the rusting of metals by decomposition of water — 

 as, for instance, in damp iron-filings, in consequence of which iron- 

 rust also contains ammonia. So porous fermenting soil without 

 dung forms ammonia by the elimination of hydrogen, which at a 

 later period is oxidized into saltpetre. Thus humate of ammonia 

 is first formed in the ground, and then nitrogenous geic acid and 

 crenic acid, which are absorbed as vegetable nutriments. De- 

 cidedly, therefore, the ammonia is not contained in the soil as 

 carbonate of ammonia. The nitrogen, on the contrary, is com- 



