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