74 George C. Whipple 



Increase in sanitary value = $140— $io = $130 per million gallons, or $450,000 



per year, or $4 . 75 per capita per year. 

 Binghamton, N. Y. — 



Water supply, Susquehanna River, filtered by a mechanical filter. 



Population, 42,000 (approximately). 



Water consumption, 160 gallons per capita daily. 



Typhoid fever death-rate before filtration, 49; after filtration, 11 per 100,000. 



Before filtration D = 2.-js (49- n) Xifg =$65. 



After filtration Z) = 2. 75(11 — 11) Xj-n = o. 



Increase in sanitary value = $65.00 per million gallons, or $160,000 per year, 



or $3.80 per capita per year. 

 Watertown, N. Y. — 



Water supply. Black River filtered by mechanical filter. 



Population, 25,500 (approximately). 



Water consumption, 160 gallons per capita daily. 



Typhoid fever death-rate before filtration, 68 per 100,000; after filtration, 19.5. 



Before filtration D = 2.75 (68-20) XTgu = $82. 50. 



After filtration ^ = 2.75 (20— 20) X VV =o- 



Increase in sanitary value = $82. 50 per million gallons, or $120,000 per year, 



or $4.75 per capita per year. 



Illustrations like the above might be multiplied, but the four cases 

 selected are sufficient to illustrate the general fact. It is easily seen 

 from them that the filtration of a polluted public water supply increases 

 to a very great extent the vital assets of a community, and the increase 

 in most cases is many times greater than the cost of constructing and 

 operating the works. Money paid to the doctor, the apothecary, and 

 the undertaker is not, in one sense, a loss to a community, as it is 

 merely a transference of money from one man's pocket to another's, 

 but in the broader sense any loss of productive capacity or any 

 unnecessary expenditure is a loss. Deaths from typhoid fever and 

 from other diseases, however, represent a very material loss of the 

 productive capacity of a community, and consequently a decrease in 

 what may be termed the "vital assets." In the case of the city of 

 Albany, for instance, the increased worth of the water to the city, 

 because of its efficient filtration, amounts to $475,000 per year, of 

 which at least $350,000 may be considered as a real increase in 

 the vital assets of the city. 



If in the formula D=$2.js (T-N) we let T-N = i, then D = 

 $2.75; that is, a decrease in the typhoid fever death-rate of i per 

 100,000 causes an increase in the vital assets of the city of $2.75 for 

 each million gallons of the public water supply (assuming this to be 



