56 George C. Whipple 



are not named, have to be taken into consideration in connection with 

 a public water supply, w^hich may be put to any of these uses. 



If it is a difficult matter to define a pure and wholesome water in 

 strict scientific terms, it is still more difficult to compare waters which 

 differ in purity on any reasonable basis; and yet this often has to be 

 done. Given two water sources equally available to a city for pur- 

 poses of supply, both safe to drink, but one high-colored and soft, the 

 other colorless and hard — which is the better selection ? A water- 

 works plant is to be appraised : structurally the system is a good one 

 but the quality of the water is unsatisfactory because of its excessive 

 color or turbidity — how much should be deducted from the value of 

 the works because of the bad quality of the water ? The water- works 

 owned by a private company are to be purchased by the city ; the city 

 has a high typhoid fever death-rate due unquestionably to the water 

 supply — how much less should the city pay because of that fact ? A 

 city in the West is using turbid river water — how much can it afford 

 to pay to filter it ? A city in New England is using a water so 

 heavily laden with Anabaena that it is nauseous to drink — how much 

 can the city afford to pay to procure a new supply ? These are all 

 practical, everyday questions which deserve answers based on scien- 

 tific data. 



In valuation cases, where the quality of the water supply has been 

 unsatisfactory, the cost of filtration, or other appropriate method of 

 purification, has been sometimes taken as a measure of the inferior 

 quality of the water, and this amount deducted from the value of the 

 works. In case filtration was impractical, or more expensive than 

 securing a supply from a new source, the additional cost of such new 

 supply has been sometimes taken as a measure of the inferior quality 

 of the works and the amount deducted from the value of the works. 

 Both of these methods are similar in that they contemplate the sub- 

 stitution of a satisfactory water for one not satisfactory. 



Another method of measuring the depreciation applicable to a 

 water-works plant because of an inferior quality of the supply 

 would be to ascertain what the use of the impure water has cost the 

 consumers, compared with what a pure and satisfactory water would 

 have cost them. This method has not been used in practice, but it 

 seems to be a reasonable one, and one which would be of more general 



