204 THE WORK OF RUNNING WATER 



a population is greatly reduced by sickness. Cities that 

 receive their water supplies from uncontaminated up- 

 lands have a tremendous advantage. 



Cities along the Great Lakes have run pipes out for miles 

 to intakes, or cribs, in order to avoid shore contamination. 



ONE OF THE CHICAGO INTAKE CRIBS 



In time of heavy storms, the sewage from a city sometimes 

 contaminates the water even at these distant intakes; but 

 on the whole the supply of water to Great Lakes cities is 

 good. Those cities which receive water from rivers that are 

 constantly being polluted by the sewage of communities 

 farther upstream have a most serious problem, even though 

 running water tends somewhat to purify itself. In many 

 cases this problem has been admirably solved. 



