Greater New York is supplied with water drawn entirely from surface water sources, from watersheds at some very considerable distance. Prior to 1911, water of a sufficiently high standard was obtainable, but as the population on the watershed areas increased the water became polluted and some form of treatment was found necessary.
Liquid chlorine was applied with 000 gallons per day. I have been} informed on very good authority that the last named_ installation has not proved a_ success, the difficulty being that it has been found impossible to get the ozone in contact with every particle of water.
Since 1910, sterilization has been effected by means of ultra-violet rays, on the principle that the violet ray has the shortest wave length of the spectrum, and that it has been established that the short wave light rays destroy micro-organisms. A plant has been in use in Marseilles since the above date, and on a: small scale in a few places in America and Europe.
Text read from the printed page and cleaned; old type leaves the occasional error.