gned
especially for this purpose. Apparently their use has been very
effective in curing many skin diseases. Certainly if radiant energy is
effective, it has a great advantage over drugs. An authority has stated
in regard to skin diseases that,

treatment with the ultra-violet rays, especially in conjunction
with the Roentgen rays, radium and mesothorium is that treatment
which in most instances holds rank as the first, and in many as
the only and often enough the most effective mode of handling
the disease.

Sterilization by means of the radiation from the quartz mercury-arc has
been practised successfully for several years. Compact apparatus is in
use for the sterilization of water for drinking, for surgical purposes,
and for swimming-pools, and the claims made by the manufacturers of the
apparatus apparently are substantiated. One type of apparatus withstands
a pressure of one hundred pounds per square inch and may be connected in
series with the water-main. The water supplied to the sterilizer should
be clear and free of suspended matter, in order that the radiant energy
may be effective. Such apparatus is capable of sterilizing any quantity
of water up to a thousand gallons an hour, and the lamp is kept burning
only when the water is flowing. It is especially useful in hotels,
stores, factories, on ships, and in many industries where sterile water
is needed.

Water is a vital necessity in every-day life, whether for drinking,
cooking, or industrial purposes. It is recognized as a carrier of
disease and the purification of water-supply in large cities is an
important problem. Chlorination processes are in use which render the
treated water disagreeable to the taste and filtration alone is looked
upon with suspicion. The use of chemicals requires constant analysis,
but it is contended that the bactericidal action of ultra-violet rays is
so certain and complete that there is never any doubt as to the
sterilization of the water if it is clear, or if it has been properly
filtered before treating. The system of sterilization by ultra-violet
rays is the natural way, for the sun's rays perform this function in
nature. Apparatus for sterilization of water by means of ultra-violet
rays is built for public plants in capacities up to ten million gallons
per day and these units may be multiplied to meet the needs of the
largest cities. Large mechanical filters are used in conjunction with
these ster