THEORY OF SOIL FERTILITY 175 



how simple it was to mine them, pack them in 

 bags, and scatter them where they were needed 

 for growing crops. 



He conceived the soil, figuratively at least, 

 as a medium in which might be mixed, syntheti- 

 cally, all the nutrients required by plants. As 

 a matter of fact this idea is practiced in ex- 

 perimental laboratories at the present day, by 

 growing plants in distilled water, to which 

 have been added the requisite amounts of the 

 different "plant foods" in soluble form. 



The world took heart at the announcement 

 of this theory, which seemed to establish the 

 secret of soil fertility by actual field tests. 

 The weight of the name of the great chemist, 

 the greatest of his times, and the seemingly 

 striking verification following the practice of 

 his teachings, caused this theory, the "theory 

 of the mineral requirements of plants," to be 

 generally accepted. 



The possibility that the niter beds from 

 which the world derived its agricultural 

 nitrates, and the potash and phosphate mines 

 would prove as limited in extent as the supply 

 of coal or iron or gold began to worry the 

 thinkers in another generation. It was less 

 than ten years after the opening of the present 



