reasonable to expect that after many centuries of cultivation of the
appreciation of light-symphonies, these will take a place among the
arts. The elaborate and complicated music of the present time is
appreciated by civilized nations only after many centuries of slow
cultivation of taste and understanding.

Light-therapy is to-day a distinct science and art. The germicidal
action of light-rays and of some of the invisible rays which ordinarily
accompany the luminous rays is well proved. Wounds are treated
effectively and water is sterilized by the ultraviolet radiant energy in
modern artificial illuminants.

Thousands of lighthouses, light-ships, and light-buoys are scattered
along sea-coasts, rivers, and channels. They guide the wheelman and warn
the lookout of shoals and reefs. Some of these send forth flashes of
light whose intensities are measured in millions of candle-power. Many
are unattended for days and even months. These powerful lights dominated
by automatic mechanisms have replaced the wood-fires which were
maintained a few centuries ago upon certain prominent points.

Signal-lights now guide the railroad train through the night. A burning
flare dropped from the rear of a train keeps the following train at a
safe distance. Huge search-lights penetrate the night air for many
miles. When these are equipped with shutters, a code may be flashed from
one ship to another or between the vessel and land. A code from a
powerful search-light has been read a hundred miles away because the
flashes were projected upon a layer of high clouds and were thus visible
far beyond the horizon.

Artificial light played its part in the recent war. Huge search-light