140 STATES OF THE RIVEK PLATE. 



a prior existence ; and the particles of these, disintegrated 

 by the washing of waters and the action of the atmo- 

 sphere, form fresh deposits in the seas, the ocean, and on 

 the low lands of the earth. Waters recede, or the land is 

 raised, and the conglomeration of the various atoms in 

 these deposits constitute soil. Soil is various in its class, 

 according to the nature of the rocks from which it has 

 been disintegrated. 



AU soU, however, contains certain elements, although 

 in different proportions ; these elements are identical with 

 those existing in and forming everything that grows or 

 lives ; accordingly, the proportion of those elements which 

 are essential for the growth of vegetation, contained in a 

 soil, constitutes a soil fertile or sterile. Some of these 

 elements are only found in small proportions, even in the 

 most fertile soils, and, among those of the smallest pro- 

 portions, are counted, in an agricultural sense, the most 

 important. 



IV. 



The action of the component parts of all soils, in rela- 

 tion to the growth of plants, may be classified in two 

 main divisions ; one mainly mechanical, the other che- 

 mical. To the former division by far the larger mass of 

 matter constituting soil belongs, leaving, indeed, but a 

 comparatively small percentage for the latter. 



The mechanical action or condition with which the 

 mass is invested consists in holding, distributed through 



science, and although interesting to the agriculturist, are only in ultimate 

 connexion with his science ; and to attempt to explain them would be to 

 go beyond the sphere of this paper, and would render it unnecessarily 

 complex. 



