12. Agricultural industries in the United States. (Bishop and Keller, Industry and Trade, part ii. Smith, Commerce and Industry, chapters i, in, iv, v, and vi.)
13. Animal industries in the United States. (Bishop and Keller, Industry and Trade, part iii. Smith, Commerce and Industry, chapter ii.)
14. Power. (Smith, Commerce and Industry, chapter ix.)
15. Mineral industries in the United States. (Bishop and Keller, Industry and Trade, part iv. Smith, Commerce and Industry, chapters viii, xiii, xiv, and xv.)
16. Manufacturing industries in the United States. (Bishop and Keller, Industry and Trade, part v.)
17. Trade routes of North America. (Smith, Commerce and Industry, chapter xvi.)
18. The foreign trade of the United States. (Dryer, Elementary Economic Geography, chapter xxxii. See also any other recently published text on this general field.)
CHAPTER VII
WHAT IS MEANT BY PRODUCTION
63. WHY MEN WORK.—Ultimately everyone depends upon work for his living. Young children commonly live upon the earnings of their parents; most normal adults, on the other hand, depend upon their own efforts for their living. Since every individual probably works because of a combination of motives, it is possible somewhat to analyze the reasons why men work. The most fundamental reason for working is in order to preserve one's life. This assured, the individual is in a position to work in order to preserve the lives of those who are near and dear to him. When the necessities of life have been provided, work is commonly continued for the sake of acquiring comforts or luxuries.