WATER SUPPLY 279 



conducted well through the scales, and the heat of the fire will 

 cause the boilers or pipes to melt, resulting in an explosion when 

 the water suddenly comes in contact with the red hot metal. 



Hard water sometimes causes stomach and intestinal troubles. 

 A person accustomed to soft water may be made ill by drinking 

 hard water, and vice versa. 



Purification of Water. Water for many cities and towns is 

 purified by sand filtration. Very fine sand is placed at the top of 

 the filter and coarse sand at the bottom. Water is allowed to run 

 through the sand an action which removes the impurities and a 

 great many of the bacteria. These filters are washed by forcing 

 water through them in the opposite direction. 



Boiling is another method of purifying water. Boiling kills the 

 bacteria but does not remove the impurities. Water may be puri- 

 fied in the home by this process and placed in stone jars to cool. 

 When water is boiled the air is driven out of it. By allowing the 

 water to stand a day or so it will absorb fresh air and again be 

 palatable. 



Distilling, still another process for purifying water not only 

 kills the bacteria but removes all impurities, since the water is 

 changed into steam and condensed again to water. Rain water 

 is nature's distilled water. In some countries this water is caught 

 in cisterns and used for drinking*water. 



House Filter. House filters for faucets are practically useless. 

 They may be dangerous. The only filter that is worth while is the 

 Pasteur-Chamberlain, made of a baked clay tube surrounded by 

 a metal tube. The pressure filters water through the clay into a 

 receptacle used for storing it. The filter must be washed daily 

 and baked every week in order to remove all unhealthy matter 

 which may have collected. 



Drinking Fountains. There is hardly any excuse to-day for 

 having the common drinking cup in any school or public building. 

 Where drinking fountains are not possible, individual drinking 

 cups may be used. 



Many diseases may be carried through common drinking cups. 



Figs. 176 to 180 teach valuable lessons about drinking fountains. 



Why are common drinking cups and towels dangerous? 



