70 ORGANIC ELEMENTS OF SOIL. 



necessary than is life to the vegetable ; but though one ele- 

 ment may be substituted for another, yet no one element 

 may supply the place of all others. This is a problem yet 

 to be solved. Nor may any possible mixture of mere sili- 

 cates and salts give fertility to a barren soil. Fertility 

 depends on the presence in soil, of matter, which has already 

 formed a part of a living structure, or the organic elements 

 of soil. This matter must be undergoing chemical change. 

 Change implies motion, motion induces motion in the sur 

 rounding elements. Without this chemically induced 

 motion, there is no fertility. 



99. The inorganic elements are simple combinations; the 

 organic are simple in number, but wonderfully complex in 

 their combinations. It is an established fact that all com- 

 plex compounds are unstable. They are prone to form new 

 combinations. The more complex, the easier decomposed 

 is any compound. The more complex, the more liable to 

 decomposition. Hence, the moment life departs, the plant 

 or animal speedily undergoes new changes ; its elements, 

 which life had organized, obey now, not the law of life, but 

 the laws of chemistry. The solids and fluids of a living 

 body, when life ceases, escaping in part as air or gas, leave 

 in a solid form, a substance, differing equally from any living 

 organic product, and from inorganic elements. The product 

 of the spontaneous decomposition of organic substances still 

 may exhibit the character which distinguishes this division, 

 viz. : complexity, great susceptibility and ease of decompo- 

 sition. This is a great practical agricultural fact. When 

 decomposition ceases in organic matter, the result is barren- 

 ness. 



100. In the products of the decomposition of organic 

 bodies, a variety is formed, differing according to the circum- 

 stances, and the time and progress of decay. However 



