WATER 



549 



As the water percolates tlirough the soil it becomes charg-ed with 

 carbon dioxide from the air interstices of the soil, after which it may 

 dissolve out lime, mineral salts and organic matter. The soil tends 

 to filter and remove this while the oxygen present in the soil may 

 oxidize it with the formation of nitrates. 



The water may be contaminated by : Cesspools, privies, manure 

 heaps, sullage water, stables, burial grounds, latrines, and as the 

 result of men and animals residing on the area. The contamination 



Well with hath and washhouse on one side. These are covered with old 

 galvanized iron, old rail, &c. Tubs where horses and cattle stand and drink. 

 The drainage runs back into the well. 



mav not be obvious until the rains have washed the filth into the 

 water or until the water has risen in level until it reaches the filth, 

 or carries water with the pollution over eminences of the impervious 

 layer contaminating the wells and springs beyond. 



In India and China infected natives often wash themselves neai 

 to a well or spring, so tliat the ablution water will drain back again 

 into the well or spring in a polluted condition. 



A native will bathe thrice daily, yet he will drink water unhesi- 

 tatingly which is obviously filthy. 



