ORGANIC CONSTITUENTS Ot SOIL. 53 



are again subject to the laws of affinity, and during 

 the decay of vegetables, they return to the earth, 

 not only those substances which the plants had tak- 

 en from the soil, but also those which have been 

 elaborated by their living structure. The former 

 are silicates and salts, or the inorganic elements ; 

 the latter, are the organic parts of soil. 



89. It is thus seen, that soil, presents itself in a 

 new view. Soil consists of two grand divisions of 

 elements. Inorganic, and organic. The inorganic 

 are wholly mineral, they are the products of the 

 chemical action of the metallic, or unmetallic ele- 

 ments of rocks. They existed before plants or ani- 

 mals. Life has not called them into existence, nor 

 created them, out of simple elements. Organic ele- 

 ments are the product of substances once endowed 

 with life. This power influences the elements, re- 

 combines them in forms, so essentially connected 

 with life, that they are with few exceptions, produc- 

 ed only by a living process. They are the products 

 of living organs, hence termed, organic ; and when 

 formed, are subject to chemical laws. The number 

 of elements in the inorganic parts of soil, is twelve. 

 Oxygen, sulphur, phosphorus, carbon, silicon, and 

 the metals, potassium, sodium, calcium, aluminium, 

 magnesium, iron, and manganese. The number of el- 

 5* 



