162 ELEMENTS OF GENERAL SCIENCE 



The construction of the sanitary canal cost more than 

 456,000,000. Did it pay ? Let us look at some of the facts. 

 The City Health Department reports that during the ten 

 years before the opening of the canal in 1900, the average 

 annual death rate from typhoid was 66.8 per 100,000, but in 

 the ten years following, the rate was only 22.3. It is calcu- 

 lated that this represents a saving of 8814 lives. Each life 

 has a money value, dependent upon earning capacity. The 

 Health Department has calculated that the actual money value 

 of these lives to the community was nearly $53,000,000. In 

 other words, the canal almost paid for itself in the first ten 

 years. It will always pay any city to secure pure water at 

 any necessary cost. 



180. Sewage treatment and disposal. The common method 

 of disposing of sewage and other wastes by discharging them 

 into streams, lakes, or ocean is obviously highly objectionable, 

 and the nuisance tends to increase with the growth of popu- 

 lation. At many places it has become necessary to treat the 

 sewage in a manner that will remove its objectionable quali- 

 ties before allowing it to enter the watercourses. This is 

 usually accomplished by bacterial action and filtration, or by 

 using the sewage to irrigate land. Chemical treatment may 

 be used, also, to destroy bacteria. 



181. Rural water supplies. The water supply of farms and 

 villages has not usually received as much attention as that of 

 cities. Most of the inhabitants of a city secure their water 

 from the same source, the public waterworks, and any 

 fault in the system affects the whole city, thereby attracting 

 attention. In rural districts, on the contrary, each home has 

 its own independent source of water, commonly a well, and 

 contamination of any one well does not usually affect so many 

 people. It is quite possible, however, that many wells may 

 be in a polluted condition at the same time, and the average 

 character of the water hi a rural community may be very bad. 

 Indeed, at the present time typhoid and other water-borne 



