solely a direct-current device. Those familiar
with the generation and distribution of electricity will realize this
disadvantage. However, its luminous intensity just below the horizontal
was about 700 candles and its general distribution of light was fairly
satisfactory. Later the flame-arcs began to appear and they were
installed to some extent. The arc-lamp has served well in
street-lighting from the year 1877, when the open-arc was introduced,
until the present time, when the luminous-arc is the chief survivor of
all the arc-lamps.

The carbon incandescent filament lamp was used extensively until 1909,
when the tungsten filament lamp began to replace it very rapidly.
However, it was not until 1914, when the gas-filled tungsten lamp
appeared, that this type of light-source could compete with arc-lamps on
the basis of efficiency. The helical construction of the filament made
it possible to confine the filament of a high-intensity tungsten lamp in
a small space and for the first time a high degree of control of the
light of street lamps was possible. Prismatic "refractors" were
designed, somewhat on the principle of the lighthouse refractor, so
that the light would be emitted largely just below the horizontal. This
type of distribution builds up the illumination at distant points
between successive street lamps, which is very desirable in
street-lighting. The incandescent filament lamp possesses many
advantages over other systems. It is efficient; capable of subdivision;
operates on direct and alternating current; requires little attention;
and is capable of most successful use with light-controlling apparatus.

According to the reports of the Department of Commerce the number of
electric arc-lamps for street-lighting supplied by public electric-light
plants decreased from 348,643 in 1912 to 256,838 in 1917, while the
number of electric incandescent filament lamps increased from 681,957 in
1912 to 1,389,382 in 1917.

Street-lighting is not only a reinforcement for the police but it
decreases accidents and has come to be looked upon as an advertising
medium. In the downtown districts the high-intensity "white-way"
lighting is festive. The ornamental street lamps have possibilities in
making the streets attractive and in illuminating the buildings.
However, it is to be hoped that in the present age the streets of cities
and towns will be cleared of the ragged equipment of the telephone and
lighting companies. These