The Supply and Uses of Water 249 



ton water wheel is 85 per cent efficient and adapted to a high head and 

 small volume of water, as in Scandinavia and on the Pacific Coast. 



The water turbine is 95 per cent efficient and adapted to a low 

 head and a large volume of water, as at Niagara and Keokuk. 



Energy may be measured in the units which are used in measuring 

 work. 



The amount of energy represented by a quantity of falling water 

 is found by multiplying the unit of energy (one foot-pound) by the 

 number of units of weight (pounds) and the number of units of dis- 

 tance (feet). 



Power is the rate in time of doing work. 



The English unit of power is defined as the horse power. 



The horse power is doing work at the rate of 33,000 foot-pounds a 

 minute. 



Efficiency equals* the useful work delivered divided by the energy 

 supplied. 



A machine transmits or transforms energy already existing, but 

 does not create it. 



The use of water power is increasing because of improvements in 

 switches, transformers, and other appliances for the transmission of 

 electric energy. 



Examples of long-distance transmission lines are those between 

 Keokuk and St. Louis, Big Creek and Los Angeles, and in the region 

 of Niagara. 



Electrical energy has a wide and increasing use for domestic and 

 industrial purposes. 



REVIEW QUESTIONS 



1. Of what importance is power to man? 2. What is the relation 

 of water pressure to the use of water for power? 3. What are the 

 chief sources of energy for power purposes? 4. What proportion of 

 the total power used is derived from each source of energy ? 5. What 

 is the situation in regard to the known coal supply? How many 

 years is it estimated to last at the present rate of consumption? 

 6. How would the increased use of water power influence the coal 

 situation ? 



7. What are the estimated water power resources of our country? 

 8. What energy might be harnessed in the Niagara River? What 

 are the chief obstacles to this ? 9. Compare cost of water power with 

 that of heat from fuel. 10. What is the estimated saving of coal per 

 year in the California Big Creek power plant? How is this estimate 

 made? 



