The Phosphates of America. 13 



Our grandfathers could not understand why lands once so fertile 

 and productive should show signs of approaching exhaustion. The 

 light only came to us after we had studied how out-door plants 

 live, whence they obtain their food, of what elements that food is 

 composed and how it is conveyed and absorbed into their organ- 

 isms. In point of fact, we have discovered that the manner of life in 

 plants is very similar to the manner of life in animals and man. 

 They require certain foods in stated proportions which pass through 

 the process of digestion, they must breathe a certain atmosphere, 

 and they are subject to the influences of heat and cold, light and 

 darkness. 



The tissues of their bodies, like ours, are composed of carbon, 

 hydrogen, oxygen, nitrogen and certain mineral acids and bases, 

 such as phosphoric and sulphuric acids, lime potash, magnesia and 

 iron. Since, therefore, it is admittedly necessary for man to con- 

 stantly absorb a sufliciency of these elements in the form of food, 

 it follows that similar food is required by plants for similar pur- 

 poses. 



Having determined the elementary composition of plants, inves- 

 tigators directed their attention to the analysis of soils, in order to 

 establish comparisons between virgin or uncultivated lands and 

 old varieties which had long been tributaries to every kind of 

 culture. 



It was found that in the former there is an abundance of most 

 of the dominating mineral ingredients discovered in plant organ- 

 isms, whereas in the latter they either exist only in minute propor- 

 tions or are lacking altogether. 



This marked a most important stage in our progress. Argument 

 is no longer necessary to prove that if agriculture is to continue to 

 be the basis of national wealth and prosperity, means must be found 

 of restoring to our soils the chief elements yearly taken away from 

 them by the crops. These chief elements have been shown to be 

 nitrogen, phosphoric acid, and potash, and that they play the most 

 important parts in the functions of vegetation, and are the most 

 liable to exhaustion, is proved by the following figures, borrowed 

 from an address delivered by Prof. H. W. Wiley at the Buf- 

 falo meeting of the American Association for the Advancement of 

 Science. 



According to this careful and painstaking chemist, the estimated 

 mean annual values of some of the agricultural' products of the 

 United States closely approach the following figures : 



