ilizers, and thus mankind copies nature's way, for natural
supplies of pure water have been filtered through sand and have been
exposed to the rays of the sun which free it from germ life.

Some sterilizers of this character are used at the place where a supply
of pure water is desired or at a point where water is bottled for use in
various parts of a factory, hospital, store, or office building. These
were used in some American hospitals during the recent war, where they
supplied sterilized water for drinking and for the antiseptic bathing of
wounds. In warfare the water supply is exceedingly important. For
example, the Japanese in their campaign in Manchuria boiled the water to
be used for drinking purposes. The mortality of armies in many previous
wars was often much greater from preventable diseases than from bullets,
but the Japanese in their war with Russia reversed the mortality
statistics. Of a total mortality of 81,000 more than 60,000 died of
casualties in battle.

The sterilization of water for swimming-pools is coming into vogue.
Heretofore it was the common practice to circulate the water through a
filter, in order to remove the impurities imparted to it by the bathers
and to return it to the pool. It is insisted by the adherents of
sterilization that filtration of this sort is likely to leave harmful
bacteria in the water. Sterilizers in which ultra-violet rays are the
active rays are now in use for this purpose, being connected beyond the
outflow from the filter. The effectiveness of the apparatus has been
established by the usual method of counting the bacteria. Near the
outlet of the ordinary filter a count revealed many thousand bacteria
per cubic inch of water and among these there were bacteria of
intestinal origin. Then a sterilizer was installed in which the
effective elements were two quartz mercury-lamps which consumed 2.2
amperes each at 220 volts. A count of bacteria in the water leaving the
sterilizer showed that these organisms had been reduced to 5 per cent.
and finally to a smaller percentage of their original value, and that
all those of intestinal origin had been destroyed. In fact, the water
which was returned to the pool was better than that which most persons
drink. Radiant energy possesses advantages which are unequaled by other
bactericidal agents, in that it does not contaminate or change the
properties of the water in any way. It does its work of destroying
bacteria and leaves the