56 GEORGE C. WHIPPLE 



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

 a public water supply, which 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 



