632 EVERYDAY SCIENCE 



doubtful of the purity of the water you may find, take a canteen 

 of pure water with you. 



Chlorine is the substance most commonly used by city water 

 departments in the purification of contaminated water-supplies. 

 Chlorine tablets are sold for home use or for camping trips. Some 

 city health departments furnish them free or sell them at cost to 

 people who plan to spend their vacations camping. The tablets 

 may be used according to directions accompanying them to rid 

 water of all dangerous germ life. They are exceedingly con- 

 venient to have, especially when time or means is lacking for the 

 boiling of suspected water. All campers should be supplied with 

 them. 



Water from ponds, lakes, or running stream in truly wild regions 

 is generally safe. If water is uncontaminated by animal refuse, 

 it will not cause disease, no matter how much decaying vegetation 

 there may be in it. Sometimes the murky water of ponds or even 

 swamps is purer than the clear water of running streams, which 

 may be polluted by careless campers upstream. The murky 

 water of ponds or swamps may be clarified by the digging of an 

 Indian well. 



A few feet from the edge of the pond or swamp, dig a hole from 

 12 to 18 inches in diameter, with the bottom of the hole extending 

 6 inches below the water-level of the swamp or pond. Let the 

 water seep into it and then bail it out quickly. Repeat this process 

 at least three times. After the third or fourth bailing, the Indian 

 well will be filled with filtered water. 



If you are at all in doubt as to the purity of the water, either 

 boil it or use the chlorine tablets as directed. 



PROJECT LIV. How to Exterminate the Mosquito, pages 452- 

 454 (Community Project) 



This is a community project, except in rural districts where 

 houses are widely separated. But in the city or village it does no 

 good whatever to destroy the breeding places of mosquitoes on your 

 own premises if your neighbors provide favorable conditions for 



