46 SCIENTIFIC AGRICULTURE. 



plained, and perhaps never will be. Chemistry, how- 

 ever, has taught us how to stimulate the process, and 

 has shown us that there is no change of one element 

 into another, but a simple use of that which is in reach 

 of the plant, whether it be in the air above or in the 

 soil beneath. 



98. If it be absurd to suppose, as everybody must 

 admit, that one element can change into another, the 

 practical conclusion follows that, to insure fertility, 

 the necessary elements which compose the particular 

 plant under cultivation must exist in the soil, or its 

 growth is impossible. As simple and self-evident as 

 this statement may appear, there has ever been a 

 vague notion in the minds of men that nature has 

 some power of changing elements, or of supplying 

 them as needed for the growth of vegetation. 



99. It has not been many years since writers on 

 agriculture affirmed that the inorganic constituents 

 of a good soil are inexhaustible. Such statements 

 are contrary to the teachings of science and of prac- 

 tical experience. It is true, the application of scien- 

 tific principles in farming will not in every case pro- 

 duce a good crop, because there are conditions that 

 human agency cannot control. The wind, and rain, 

 and sunshine are given or withheld by a power 

 which we cannot govern, and without whose favor- 

 ing influence all our labor is in vain. 



100. Science not only determines the kind and 

 quality of food which plants need, but points out the 

 localities where this food can be obtained, and fur 



