94 The Organic Matter of Soil. [August, 



the wants of vegetation in several ways, without its becoming the 

 food itself. It ministers to the vegetable by its presence, pro- 

 curing thereby an open state of the soil, by which air is more freely 

 conveyed to the roots. It ministers, also, to the wants of vegeta- 

 tion by its absorbent and retentive powers. Indeed, in this respect 

 it is ahnost indispensable to vegetation. These, then, though 

 not all the uses which mould exercises in vegetation, still are 

 sufficiently important to meiit the attention of the agriculturisl;. 

 In neither, do we find that the brown or black matter of soil becomes 

 the nutriment of vegetables, and yet its service is immense. To un- 

 derstand the nature of the changes which take place in the organic 

 matter of the soil, it is necessary to know what agents exist there. 

 A mixtureof carbonate of lime and magnesia, silex and aluraine, and 

 orgainic matter, would remain without change forever, were there 

 no other bodies of a more active kind, whose affinities become a pre- 

 sent and efficient cause for action. These powers or forces exist in 

 the atmosphere and in the water diffused through the soil, and it 

 is proper to make a distinction of the atmosphere within the soil, 

 from that above or without it. The atmosphere is composed of 

 two elements, oxygen and nitrogen, in the proportion of 79 nitro- 

 gen to 21 oxygen. The latter is free and uncon:ibined with the 

 nitrogen, or is merely dissolved in it, just as sugar or salt is dis- 

 solved in water. The consequences which follow from this con- 

 dition or state of the elements, is, that bo'h are free to unite with 

 other bodies, that is, so far as attraction for each other is concerned 

 there is no hindrance or force to be overcome to bring about a 

 separation. Hence, in the respiration of animals, the oxygen of 

 the atmosphere which is inhaled combines readily with the carbon 

 suspended in the return or venous blood. So in the soil, there 

 is the same independence^ the oxygen or nitrogen is not hin- 

 dered from uniting with other bodies by any affinity existing 

 between themselves. The final end or cause of this is, the ulti- 

 mate union of the oxygen with certain bodies in the soil, espe- 

 cially with the organic part. The other agent, water, undergoes 

 chemical changes of a different kind. In this the elements are 

 chemically combined, and hence they are not so readily separated 

 from each other, and hence, too, its action is constant, and that 

 which is proper to it in its state of integrity — it is the solvent 

 power so necessary to bring all particles to a state of fineness that 

 they may pass into the organism of vegetables; for solution is 

 merely that separation of particles to that degree of minuteness 

 that they are capable of being suspended in the medium. They are 

 merely farther apart, and they are brought thereby into a condition 

 to undergo farther and more thorough changes than they were 

 previous to their solution or suspension in the ujeilium itself But 

 certain bodies can and do decompose it, the final end or cause 



