28G Agricultural Chemistry. 



To these determinations may be added the analysis of the 

 Russian black earth (tscherno-sem), in the government of Orel, 

 for which we are indebted to M. E. Schmid (' Petersburger 

 Academisches Bulletin,' vol, viii. p. 161). 



Schmid examined three samples of virgin soil, on which no 

 crop had ever been cultivated, and a sample of unmanured arable 

 land. (The density, or specific gravity of these soils, was found 

 to be from 2'1 to 2'2 ; but, on account of the porosity of soils, I 

 have not thought it necessary to estimate it higher than 1"5.) 

 From Schmid's results it appears that one acre, to the depth of 

 one foot, of these four samples contains the following quantities 

 of ammonia : — 



No. Russian Black Earth. Lbs. Ammonia. 



1. Upper Stratum 49,200 



2. Four wersckock deeper .. .. 22,140 



3. Subsoil 20,000 



4. Unmanured arable land .. .. 23,780 



In regard to the amount of ammonia, the following soils in 

 Munich, which I have analysed with a view to this subject, 

 approach very nearly to the Russian black earth : — 



No. Soils in Municb. Lbs. Ammonia. 



1. From the garden of my house 22,960 



2. From the neighbouring Botanic Garden .. 21,730 



3. From a wood in the vicinity 20,910 



Lastly, by the kindness of M, Schlossberger, in Havannah, I 

 have obtained six different samples of soils from the island of 

 Cuba, in which tobacco is grown (the crop which is richest in 

 nitrogen), and which have never been manured. These soils 

 contain, in one acre of soil, to the depth of 12 inches — 



No. Lbs. Ammonia. 



1 9,020 



2 12,300 



3 1,640 



4. .. • 9,344 



5 14,350 



6 10,250 



The source of all this nitrogen is easily pointed out. In my 

 work (pp. 57, 96, 115, &c.) I have shown that clay, alumina, and 

 peroxide of iron, all of which are present in the most fertile 

 soils, possess a most remarkable power of absorbing ammonia 

 from the air, and that all fertile soils contain a certain amount of 

 ammonia derived from the atmosphere. 



It is easy to form an idea of the quantity of ammonia which 

 the soil can take up from this source if we remember the ex- 

 periments of Thomas Way, who found (' Journal of the Royal 

 Agricultural Society,' vol. xiii. p. 126) that 100,000 parts, by 



