204 



HOW TO KEEP WELL 



Some communities deodorize this sewage and make fertilizer 

 of it. Other communities send it from the tanks into beds 

 of gravel and sand through which it seeps (Fig. 71). Sewage 

 which has been filtered by seepage through sufficient soil is 

 harmless and can be discharged into streams and harbors 

 without contaminating them. But large numerous beds are 

 necessary. Many cities pay no attention to the proper disposal 

 of sewage and send it into the streams unfiltered, thus en- 

 dangering the health of the citizens. 



FIG. 71. Metnod of filtering sewage before discharging it into rivers. 



In small towns and villages there is no common sewage sys- 

 tem, and the individual house disposes of its own wastes. 

 This is usually done by sending the waste matter through an 

 underground pipe to a cesspool a short distance from the house. 

 In time the cesspool fills up and must be cleaned out. Such a 

 disposal of wastes is satisfactory unless the cesspool is near a 

 well or other source of water. If the wastes spread through 

 the ground and reach the well before they are purified by fil- 

 tration, they contaminate the water and make it the carrier of 

 disease. For absolute safety the cesspool of an ordinary house 

 should be 75 feet from a well, and the cesspool of a country 

 hotel should be much farther from the water supply (Fig. 72). 

 The more people there are in a building, the more abundant 



