70 GEORGE C. WHIPPLE 



O v = odors due to vegetable matter, expressed according to 



standard numerical scale; 

 Od = odors due to decomposition, expressed according to 



standard numerical scale; 

 O = odors due to microscopic organisms, expressed accord- 



ing to standard numerical scale; 

 H = hardness of water in parts per million; 

 d = average temperature of water during four warmest months. 



APPLICATION OF THE FORMULA. 



It now remains to apply the principles above set forth to actual 

 cases and see to what conclusions they lead. 



EFFECT OF CONTAMINATION. 



The average death-rate from typhoid fever in American cities 

 which have more than 30,000 inhabitants is about 35 per 100,000. 

 Applying formula (i), and assuming a value of 20 for N, then 



that is, the average depreciation value of the water supplies of our 

 American cities, taken as a whole, is $41 . 25 per million gallons because 

 of their unsanitary quality, or about $15,000 per annum for each mil- 

 lion gallons a day of supply. 



The above figure takes into account both good and bad supplies. 

 The average typhoid fever death-rate in those cities which have rea- 

 sonably good water supplies may be taken in round numbers as about 

 20, while in those cities which have supplies more or less contaminated 

 it varies from this up to 40 or 60. In some of the worst cases it is 

 more than 100 per 100,000. In Pittsburg, for example, the typhoid 

 death-rate for several years has averaged 120. Here, according to 

 formula (i), ^ = 2.75 (120 20) =$275 per million gallons. This is 

 figured, however, on a per capita water consumption of 100 gallons 

 a day. The actual consumption is about 250 gallons per capita per 

 day; hence D should be taken as $$ of $275, or $110 per million 

 gallons. Each million gallons of polluted Allegheny River water 

 pumped to Pittsburg has therefore reduced the vital assets of the com- 

 munity by $110. This, for a population of 350,000, amounts to 

 $3,850,000 per year a sum enormously greater than the cost of 

 making the water pure. 



