THE SOIL AND ITS CONSTITUENTS. 103 



to contain more or less potash, soda, lime, magnesia, 

 silica, alumina, oxide of iron, oxide of manganese, sul- 

 phuric acid, phosphoric acid, and chlorine. There 

 are three other substances, iodine, bromine, and fluo- 

 rine, that enter into the composition of most plants, 

 but in proportions so minute as to be of no practical 

 importance. The first-named substances, eleven in 

 number, constitute the inorganic parts of a plant, or 

 that portion which it derives entirely and exclusively 

 from the soil. Hence these elements, in one propor- 

 tion or another, will be found contained in every well- 

 conditioned soil. 



There is evidently, therefore, in corn-culture, but 

 one proper course for the farmer to pursue. It de- 

 volves upon him to ascertain, as nearly as possible, 

 what proportion of the constituents of maize his soil 

 already contains, and in what condition these con- 

 stituents exist. The latter point is especially import- 

 ant ; for whatever be the quantity of them, unless they 

 are in such a state that the plant can appropriate 

 them, they might nearly as well be entirely absent. 



On this subject the science of chemistry will enlight- 

 en the farmer up to a certain point ; beyond that he 

 must rely upon other sources of information. Chem- 

 ical investigation will determine, with sufficient accu- 

 racy, the elements of the soil on the one hand, and the 

 elements of maize on the other ; and a comparison of 

 these would seem to indicate precisely what ingre- 

 dients are yet wanting for the intended crop. But 

 this indication is, after all, not entirely reliable. As 

 the constituents of plants exist in the soil in various 



