ty increase.

5 From the viewpoint of the police: The horses will
get frightened and the thieves emboldened.

6 From the point of view of national economy: Great
sums of money will be exported to foreign countries.

7 From the point of view of the common people: The
constant illumination of streets by night will rob
festive illuminations of their charm.

The foregoing objections require no comment, for they speak volumes
pertaining to the thoughts and activities of men a century ago. It is
difficult to believe that civilization has traveled so far in a single
century, but from this early beginning of street-lighting social
progress received a great impetus. Artificial light-sources were feeble
at that time, but they made the streets safer and by means of them
social intercourse was extended. The people increased their hours of
activity and commerce, industry, and knowledge grew apace.

The open gas-jet and kerosene-flame lamps held forth on the streets
until within the memory of middle-aged persons of to-day. The
lamplighter with his ladder is still fresh in memory. Many of the towns
and villages have never been lighted by gas, for they stepped from the
oil-lamp to the electric lamp. The gas-mantle has made it possible for
gas-lighting to continue as a competitor of electric-lighting for the
streets.

In 1877 Mr. Brush illuminated the Public Square of Cleveland with a
number of arc-lamps, and these met with such success that within a short
time two hundred and fifty thousand open-arc lamps were installed in
this country, involving an investment of millions of dollars. Adding to
this investment a much greater one in central-station equipment, a very
large investment is seen to have resulted from this single development
in lighting.

This open-arc lamp was the first powerful light-source available and,
appearing several years before the gas-mantle, it threatened to
monopolize street-lighting. It consumed about 500 watts and had a
maximum luminous intensity of about 1200 candles at an angle of about 45
degrees. Its chief disadvantage was its distribution of light, mainly at
this angle of 45 degrees, which resulted in a spot of light near the
lamp and little light at a distance. A satisfactory street-lighting unit
must emit its light chiefly just below the horizontal in those cases
where the lamps must be spaced far apart for economical reasons. On
referring to the chapter on the electric arc