systems, and
traffic signals. Light has the advantages of being silent and
controllable as to position and direction, and of being a visible signal
at night. Thus, in another field artificial light has responded to the
demands of civilization.

XVI

THE COST OF LIGHT

Artificial light is so superior to natural light in many respects that
mankind has acquired the habit of retiring many hours after darkness has
fallen, a result of which has brought forth the issue known as "daylight
saving." Doubtless, daylight should be used whenever possible, but there
are two sides to the question. In the first place, it costs something to
bring daylight indoors. The architectural construction of windows and
skylights increases the cost of daylight. Light-courts, by sacrificing
valuable floor-area, add to the expense. The maintenance of windows and
sky lights is an appreciable item. Considering these and other factors,
it can be seen that daylight indoors is expensive; and as it is also
undependable, a supplementary system of artificial lighting is generally
necessary. In fact, it is easy to show in some cases that artificial
lighting is cheaper than natural lighting.

The average middle-class home is now lighted artificially for about
$15.00 to $25.00 per year, with convenient light-sources which are
available at all times. There is no item in the household budget which
returns as much satisfaction, comfort, and happiness in proportion to
its cost as artificial light. It is an artistic medium of great
potentiality, and light in a narrow utilitarian sense is always a
by-product of artistic lighting. The insignificant cost of modern
lighting may be emphasized in many ways. The interest on the investment
in a picture or a vase which cost $25.00 will usually cover the cost of
operating any decorative lamp in the home. A great proportion of the
investment in personal property in a home is chargeable to an attempt to
beautify the surroundings. The interest on only a small portion of this
investment will pay for artistic and utilitarian artificial lighting in
the home. The cost of washing the windows of the average house may be as
great as the cost of artificial lighting and is usually at least a large
fraction of the latter. It would become monotonous to cite the various
examples of the insignificant cost of artificial light and its high
return to the user. The example of the home has been chosen because the
reader may easily c