The Supply and Uses of Water 223 



favor and make use of in sewage purification ? 15. (a) What kind of 

 bacteria promotes decay in the presence of air or oxygen ? (6) What are 

 pathogenic bacteria? 16. What is a typhoid carrier? 17. Of what 

 practical importance is it to every one to know that certain diseases 

 may be distributed by food and water contaminated by human waste 

 or sewage? 18. Why should each individual consider the health of 

 others in disposing of waste products, refuse, etc.? 



19. What are the advantages and the disadvantages in the still 

 storage of water? 20. What especially dangerous elements are re- 

 moved from water by still storage? 21. What happens to water 

 when stored in casks for a long period of time? Explain. 22. In 

 what ways is a sand filter useful and effective? To what is its effec- 

 tiveness due? 23. Why is it sometimes necessary to purify water in 

 the home? 24. What are the usual methods employed? Describe 

 each. 25. Give reasons why the ordinary filter in the home is not a 

 protection from disease germs. 26. How may such a filter endanger 

 health? 



SUGGESTIVE QUESTIONS 



1. Give reasons why a community should be held responsible for 

 typhoid fever cases due to a contaminated water supply. 2. Why 

 should a community seek to discover the source of the disease and 

 bring it under control, as well as the agency in its distribution? 

 3. How may a community effectively protect its citizens from the 

 diseases mentioned in the text? 4. Typhoid fever is preventable by 

 vaccination. Why is it to the interest of the community to vaccinate 

 at public expense all its citizens, especially if they intend to travel 

 abroad. 5. Explain why city water may generally be safer than a 

 rural supply. 6. If an epidemic should occur and be suspected as 

 due to contaminated water, what can be done in the household to 

 insure safety in the use of the water? 



VIII. LOCAL WATER SUPPLY 



Exercise : The local water supply. A. Is the local water supply 

 under private or public control? To what extent is control exer- 

 cised over its use for different purposes? 



B. Study of the water provided. Is it soft, hard, or medium? 

 How can you test this property? Examine the inside of a teakettle. 

 Is there a white, hard substance on bottom and sides? What does 

 this indicate as to the character of the water? How does the water 



