into a great
loss. For example, a 25-watt electric lamp may be operated ten hours a
day for a whole year at the expense of one eighth of a ton of coal.
Suppose this lamp to be over a stairway or at any vital point and that
by extinguishing it there occurs a single accident which involves the
loss of only one day's work on the part of the worker. If this one day's
time could have produced coal, there would have been enough coal mined
in the ten hours to operate the lamp for thirty-two years. The
insignificant cost of lighting is also shown by the distribution of the
consumption of fuel for heating, cooking, and lighting in the home. Of
the total amount of fuel consumed in the home for these purposes, 87 per
cent. is for heating, 11 per cent. for cooking and 2 per cent. for
lighting. The amount of coal used for lighting purposes in general is
about 2.5 per cent. of the total consumption of coal, so it is seen that
the curtailment of lighting at best cannot save much fuel; and it may
actually result in a great economic loss. By replacing inefficient lamps
and accessories with efficient lighting-equipment and by washing windows
and artificial lighting devices, a real saving can be realized.

Improper lighting may be as productive of accidents as inadequate
lighting, and throughout the industries and upon the streets the misuse
of light is in evidence. The blinding effect of a brilliant light-source
is easily proved by looking at the sun. After a few moments great
discomfort is experienced, and on looking away from this brilliant
source the eyes are temporarily blinded by the after-images. When this
happens in a factory as the result of gazing into an unshielded
light-source, the workman may be injured by moving machinery, by
stumbling over objects, and in many other ways. Unshaded light-sources
are too prevalent in the industries. Improper lighting is likely to
cause deep shadows wherein many dangers may be hidden. On the street the
glare from automobile head-lamps is very prevalent and nearly everybody
may testify from experience to the dangers of glare. Even the glaring
locomotive head-lamp has been responsible for many casualties.

Unfortunately, natural lighting outdoors has not been under the control
of man and he has accepted it as it is. The sky is a harmless source of
light when viewed outdoors and the sun is in such a position that it is
usually easy to avoid looking at it. It is so intensely glaring that man
unco