WATER SUPPLY. 



761 



to guard against accident, it has been found necessary 

 to provide storage ; this is accomplished by means of 

 reservoirs. (See RESERVOIRS in ENCYCLOPAEDIA 

 BRITANNICA.) The capacity of these receptacles is 

 determined by the needs of the city, and it is found 

 best to provide a series of reservoirs, not only to meet 

 any emergency that may arise but also for the purpose 

 of permitting the water which has been pumped into 

 the initial receptacle to settle in the additional ones 

 before it is turned into the mains and pipes' for distri- 

 bution. Filtration is also employed to free the water 

 of impurities, and many .systems have been adonted 

 lor this purpose, one of the latest being a proposal by a 

 Isew York company of a plan by which the filter beds 

 arc erected over the reservoir and the water is pumped 

 into the beds, whence it percolates into the reservoir 

 below. Another is known as the "Hyatt pure water 

 filter," so arranged that the water is filtered after it 

 leaves the reservoir and before its distribution. While 

 the construction of reservoirs requires engineering skill, 

 the location with reference to the surroundings is one 

 that should engage the attention of the sanitarian. The 

 water may become contaminated while stored from the 

 proximity of the reservoir to the cultivated or inhabited 

 Luds which surround it, or from fungi or other for- 

 eign substances which may grow or be thrown or fall 

 into it. The _ sides should be well protected, and 

 if the ground rises .iboye it, that should be sodded and 

 kept free from everything contaminating and objection- 

 able, such as swine, cattle, or other stork, cte. The 

 niniall is an important factor in deciding the quantity 

 of water that may be obtained from whatever source ; 

 it is estimated that one-third of the rainfall disappears 

 by evaporation and the absorption of vegetation, one- 

 third descends into the earth to rrappoar as springs or 

 remains as subterranean reservoirs that may be tapped 

 by wells ; and one-third flows as rivers and streams or 

 forms lakes and pools. 



W hile the question of cost ought not to have control, 

 ling weight where health is concerned, it is well in 

 determining between different sources of supply to ox- 

 ominc into the relative cost of subsidence, precipita- 

 tion, filtration, etc., as applicable to the several sourves 

 under consideration, always bearing in mind that rivers 

 or streams receiving sewage or refuse of manufactories 

 within a limit of twelve miles are never a proper 

 source of water supply whether chemical analysis or 

 biological research develop the existence of impurities 

 or not. 



Referring to the question of a pure watrr fijrpfi/ and 

 the difficulty of determining whether organic matter is 

 present or not, Prof. J. W. Mallet, F. 11. S., in an 

 exhaustive pa|>er upon water analysis prepared by him 

 for the National Board of Health United States (see 

 N. B. II. Rrjtort, 1882, p. 207), in which betakes the 

 ground above indicated, sums up the result of different 

 processes of water analysis conducted by himself and 

 other experts in the following general conclusions : 



1. It is not possible to decide absolutely upon the whole- 

 someiiess or unwliolesorneness of drinking water by the 

 mere use of any of the processes examined lor the estimation 

 of organic matter or its constituents. 



2. I would even go further, and say that, in judging the 

 Military character of a water, not only nm-t such processes 

 be used in connection with the investigation of other evi- 

 dence of a more general sort, as to the source and history 

 of the water, hut should even be deemed of secondary im- 

 portance in welching the reasons for accepting or rejecting 

 a water not manifestly unfit for drinking on other grounds. 



3. There are no sound grounds on which to establish such 

 general "standards of purity " as have been proposed, look- 

 ing to exact amounts of organic carbon or nitrogen, "albu- 

 iiiinnid ammonia," oxygen f permanganate consumed, etc., 

 ns permissible or not. Distinctions drawn bv the applica- 

 tion nfsiiflh standard* are arbitrary and may be misleading. 



4. Two entirely legitimate directions seem to he open for 

 the useful examination by chemical menus of the organic 

 roniiiiiiciiH of drinking water, namely: first, the detection 

 of very gross pollution, such as the contamination of the 

 water of a well by accidental Imrsting or crushing of soil- 



V..L. IV.- 2X 



pipes, extensive leakage of drains, etc. ; and secondly, the 

 jieriodical examination of a water supply, as of a great city, 

 in order that, the normal or usual character of the water 

 having been previously ascertained, any suspicious clumps 

 which from time to time may occur shall be promptly de- 

 tected, and their causes iuvestigated. 



5. In connection with this latter application of wnter 

 analysis, there seems to be no objection to the establishment 

 of local "standards of purity " for drinking-water, based 

 on sufficiently thorough examination of the water supply 

 iu its usual condition. 



6. With the facts of this investigation before me, I nm 

 inclined to attach special and very great importance to a 

 careful detenu i nation of the nitrites and nitrates iu water 

 to be used for drinking. 



7. If I had intrusted to me the charge of watching a 

 large city's water supply I should use all three of the 

 principal processes for the examination of the organic mat- 

 ter present; each gives a certain amount of intbrmation 

 which the others do not afford. 



Under circumstances admitting only of the use of simpler 

 means of investigation, the nlbumtnoid-animonia and per- 

 manganate processes might be employed together, but in no 

 case should one only of these methods be resorted to, such a 

 course entailing practically the neglect of carbon on the 

 one hand or nitrogen 011 the other. 



The Vienna Water Commissioners give the follow- 

 ing rules for determining healthy water : 



1. Water must be clear, sparkling, colorless. 



2. It must contain but a small quantity of solid materials 

 ami be entirely free of organi/.ed matter (infusoria). 



3. Of ilie alkaline earths (CaO, MirO) it must not contain 

 more than 18 parts by weight iu 100,000 parts by weight of 

 water. 



4. It must contain hut a small fractional part by weight 

 of soluble salts, particularly the sulphates and nitrates. 



5. The solids held in solution and the temperature of the 

 water must vary u ithin very narrow limit- during the year. 



0. It must be protected from contamination. 



7. The alnive requirements are fulfilled in many cases by 

 soft spring water, which alone is suitable for drinking pur- 

 |M>ses. 



8. The industries require water having nearly the same 

 properties. 



9. Filtered river water, if at all times free of turbidity, 

 will answer for technical purposes, but on account of not 

 fulfilling requirements 5 and 6, is not fit for drinking. 



10. To sprinkle or clean streets any water is suitable pro- 

 vided it is odorless and does not contain a great amount of 

 offensive material. 



A survey of the water supply of the cities of the 

 United States and the manner of securing it, etc., is 

 too comprehensive to be given in detail here; for 

 complete statistics upon this subject, embracing all 

 necessary information and covering 1088 cities and 

 towns, the reader is referred to the Manual of Ameri- 

 can Walrr- 1) 'or/us just published (1889) by the Enr/i- 

 nceriiirf Knc, New York, to whose editors the writer 

 is indebted for the table showing the supply, etc., of 

 several of the principal cities. (See p. 702.) 



The number of towns having a water-supply for 

 domestic use in the United States and Canada up to 

 Jan. 1, 1889, and their geographical distribution ia 

 here given : 



New England Maine, New Hampshire/Vermont, Mas- 

 sachusetts, Rhode Island, and Connecticut 



Middle New York, New Jersey, Delaware, Pennsyl- 

 vania, Maryland, District of Columbia 



South Atlantic Virginia, West Virginia, North Caro- 

 lina, South Carolina, Georgia, and Florida 



South Central Alabama, Mississippi, Louisiana, Ten- 

 nessee, Kentucky 



North Central Ohio, Indiana, Michigan, Illinois, Wis- 



North Western Iowa, Minnesota, Kansas, Nebraska, 

 Dakota, Montana, Wyoming 



South Western Missouri, Arkansas, Texas, Colorado, 

 New Mexico 



Pacific Washington, Oregon, California, Arizona, Ne- 

 vada, Utah, Idaho 



United States, Total 



Canada 



290 

 456 

 73 

 5? 

 330 

 222 

 ISO 



130 



1688 

 78 



