18

LIGHTING

Artificial light has been an important influence in the growth
of civilization, and its development is an interesting study. The
greatest single improvement in lighting was effected by electricity,
since it reduced simultaneously the labor, dirt, heat, and the danger
of fire that- were connected with other means of illumination.
New forms of lighting Include the fluorescent tube and the mer-
cury-vapor lamp. The fluorescent tube, which gives two and a
half times as much, light as the incandescent bulb or tube of equal
wattage, is more like daylight and produces very little heat.
Germicidal light to destroy air-borne bacteria is a desirable de-
velopment. The very newest lighting methods should be installed
in a new house because even these will be outmoded before the
house is old. The future possibilities of lighting are enormous.

The lighting industry has specialists who will help a home owner
solve his lighting problems correctly. Light meters are used to
show the amount of light needed, and how it should-be distributed.
It is now recommended that outlets for electricity be located at
the floor line every 5 feet or less for convenience.

Several methods of measuring light are practiced. In one sys-
tem the standard unit Is a foot-candle, which is the illumination on
a surface one foot away from, and perpendicular to, the rays of a
standard-size candle. Ten thousand foot-candles of light occur in
sunshine; about one thousand in the shade of a tree on a sunny day.
About 5 foot-candles of light fall on a book directly underneath a
40-watt lamp. From 10 to 20 foot-candles is considered suitable
for occupations like kitchen work or card playing, 25 to 50 foot-
candles for close work like studying, newspaper reading, or sew-
ing, and 50 to 100 foot-candles for close work over a long period
of time. However, these figures may be increased, for recent tests
show that insufficient light has been customary heretofore.

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