HEALTH AND WELL-BEING 



53 



garden, and as ice for refrigeration. Large quantities of 

 water are necessary in factories, gas works, dye houses, and 

 other industries. It is indispensable for the maintenance of 

 all plant and animal life, and for human existence. 



New York City gets a portion of the enormous supply 

 needed by its population and for its varied industries from 

 the watershed of the Catskill Mountains ninety miles away. 

 The expenditures of this one city alone for its supply and 

 distributing systems represents outlays of hundreds of 



FIG. 21. Contamination of well water. (U. S. Public Health Service.) 



millions of dollars. Transportation by water has in all ages 

 been one of the chief agencies in the promotion of manufac- 

 tures, of commerce, and of .civilization itself. 



After surface waters from rainfall and melting snows have 

 soaked down into the earth's crust any considerable number 

 of feet, these waters commonly may be considered pure by 

 reason of filtration and aeration. Slow oxidation will have 

 freed the water of organic matter, and the material in solu- 

 tion will be harmless minerals. Drainage from barnyards, 

 cesspools, privies, and house drains may, however, find its 



