WATER, AND ITS USES 109 



2. In what respects is electric power preferable to water power? What rela- 

 tion has the existence of water power to cheap and abundant electric 

 power? Mention notable illustrations of this in the United States. 



3. What advantages are there in transportation by inland water ways over 

 transportation by railroads? What limitations are there for the former? 



4. What notable illustrations recorded in history of the rise of nations as they 

 have engaged in foreign commerce? 



5. Name ways in which water is changing the surface forms of earth (a) 

 under man's direction; (6) without any part taken by man. 



6. Tell of efforts by man to control the destructive effects of surface waters. 



7. Explain valley formation through the agency of water. 



8. Why is running water more likely to be pure than stagnant water? 



