36 



GENERAL INTRODUCTION 



Another great need for the immediate development of addi- 

 tional water power is the imperative necessity of increasing our 

 nitrate supply and making it independent of foreign deposits. 

 Fixed nitrogen is the most important constituent of plant food and 

 absolutely indispensable in the manufacture of explosives. Europe 



FIG. 9. Rjukan II Power and Furnace House for Nitrogen Fixation in Nor- 

 way. Capacity 120,000 horse-power. 



uses per acre of cultivated land 200 pounds of fertilizer; the 

 United States 28 pounds. Germany, in twenty years, by the use 

 of fertilizers, has increased the average yield of all crops grown 

 three and one-half times as much per acre as America, the yield 

 per acre in bushels for various crops being as follows: 



