CHAPTER V 



HYGIENE AND SANITATION 

 WATER 



■Rain is the original source of all water. The water from 

 wells, deep and shallow, springs, and rivers all come from the 

 clouds. 



When rain descends it drains from the watersheds to brooks, 

 which make rivers, or percolates through the ground, or evapo- 

 rates. 



The amount of \yater that will percolate through soil de- 

 pends on the porosity of that soil, and upon the slope of the 

 ground as well as the time of year. 



The amount of water that evaporates from the surface of the 

 soil depends on the time of year and the temperature of the 

 atmosphere. A dry, warm air absorbs water from moist sur- 

 faces rather rapidly. 



Percolation occurs more rapidly in sand and gravel, where 

 the percentage may run as high as 90 per cent, of the rainfall 

 upon it. 



Red sandstone may absorb or percolate 25 per cent., while 

 magnesium limestone may percolate as much as 20 per cent. 



Water which percolates through the soil again returns to 

 the surface by wells and springs. 



As the water percolates through the soil and follows the 

 cracks and fissures of the rock it absorbs carbon dioxid gas 

 from the air, which aids in its erosive and soluble action in 

 dissolving mineral matter. 



The original water as it reaches the earth is free of any 

 mineral matter, and is termed "soft water." After reaching 

 the earth the absorption of considerable lime-salts causes the 

 so-called "hard water." 



Springs are surface outlets of underground water. The 

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