176 THE FARMER OF TO-MORROW 



century that Sir William Crookes arose before 

 the British Association for the Advancement 

 of Science, and, with the authority of one of 

 the greatest scientists of to-day, and the added 

 prestige of being president of the organiza- 

 tion he addressed, made the startling predic- 

 tion that the world must cease growing wheat 

 in another fifty years because of the exhaus- 

 tion of nitrate beds. 



The exhaustion of the world's supply of 

 commercial nitrates is being hastened not only 

 by the demands to feed men, but by the neces- 

 sity of perfecting devices to kill men. The 

 manufacture of gunpowder and other ex- 

 plosives used in war requires many times as 

 much nitrogen annually as the demands of 

 agriculture, and at the present rate of con- 

 sumption the end seemed imminent. 



So again the bogey of the Malthusian doc- 

 trine became a specter and the governments 

 of the world set about surveying and protect- 

 ing, for their own use, by laws, their supplies 

 of mineral "plant foods." By the beginning 

 of the new century, the new lands of the 

 United States, under cultivation in the main 

 for less than sixty years, were consuming up- 

 ward of $100,000,000 annually in chemical 



