AMMONIA EVOLVtD FROM VOLCANOES. 157 



washed from Ine air by the waters of the sea itself, or by the rains which 

 fall directly into the wide oceans ; and we know of no compensating 

 process by which this ammonia can be restored to the air, and again 

 made useful to vegetation. 



Besides, of that which still remains in the air much must undergo 

 decomposition by natural processes. In treating in a preceding section 

 of the evolution of light carburetted hydrogen during the slow decay of 

 vegetable matter (p. 153), I have shown how, in consequence of its ad- 

 mixture with the oxygen of the atmosphere, tl]is gas is finely decom- 

 posed, while carbonic acid and water are produced. Ammonia in like 

 manner will burn in oxygen gas, and when mixed with atmospheric air 

 may be decomposed by the electric spark — water at the same time being 

 formed and nitrogen set free. Thus, 



if with 1 of Ammonia = NH3 



we mix 3 of Oxygen = O3 



3 of water. 1 of nitrogen. 



we have the sum NH3 O3 = 3 HO + N 



or, when diffused through the air, 1 of ammonia, with the aid of 3 of 

 oxygen, will yield 3 of watery vapour, while the nitrogen may* mingle 

 with the air in an elementary form. Can we doubt that ammonia 

 is tlius decomposed in the air? Not to speak of other forms assumed 

 by the electricity of the atmosphere, can the thunder-storms of the tropi- 

 cal regions pass unheeded the ammoniacal vapours they must meet 

 with in their course ? 



I conclude, then, that of the ammonia which is formed from the nitro- 

 gen actually existing in animal and vegetable substances during theit 

 decay, only a comimratively small portion ever returns again to minister 

 to the wants of new races.f " 



But if j)laiits obtain all their nitrogen from ammonia, J how is this 

 waste repaired — whence are new supplies constantly derived ? 



We have seen that, in certain volcanic countries, carbonic acid is 

 evolved in vast quantities from rents and fissures in the earth. In some 

 of these districts — and this has been observed more especially in Italy 

 and Sicily, and it is said also to some extent in China — ammonia is 

 likewise given off, in combination generally with some acid, and most 

 frequently with the muriatic acid in the form of sal-ammoniac (muriate 

 of ammonia). " This ammonia,'''' Liebig is correct in saying, "-lias not 

 been jjroduced by the animal organism ;" but he assumes a very doubt- 

 ful position when he adds, "zi existed before the creation of human be- 

 ings ; it is a part, a primary constituent of the globe itself .^^ — [Organic 

 Chemistry applied to Agriculture, p. 112.] 



Where, we might ask, has this ammonia existed during all past time 

 — from what deep caverns of the earth does it now escape ? 



* 1 say may, because it may at the same time combine with oxygen and form nitric acid. 

 —See the followinjt section, p. 239. 



I I might add, that of the ammonia which does return, and is again absorbed, a portion is 

 subsequently decomposed in the interior of hving plants, as is shown by the evolution of 

 nitrogen from the common leaves of i<ome and the flower leaves of otliers. 



i " Wild plants obtain more nitrogen from the atmosphere, in the form of ammonia, than they 

 require for their growth, for the water which evaporates through their leaves and blossoms 

 emits, after a time, a putrid smell— a peculiarity possessed only by such bodies as contain 

 nitrogen."— :[Liebig, Organic Chemistry applimi to Agj-iculture, p. 85.] Does the fact here 

 staled, justify the conclusion which appears to be drawn from it 7 



