of the subject which deals particularly with the
safety of the light-source or method of lighting. As each innovation
in lighting appeared during the past century there immediately arose the
question of safety. The fire-hazard of open flames received attention in
early days, and when gas-lighting appeared it was condemned as a poison
and an explosive. Mineral-oil lamps introduced the danger of explosions
of the vapors produced by evaporation. When electric lighting appeared
it was investigated thoroughly. The result of all this has been an
effort to make lamps and methods safe. Insurance companies have the
relative safety of these systems established to their satisfaction and
to-day little fire-hazard is attached to the present modes of general
lighting if proper precautions have been taken.

When electric lighting was first introduced the public looked upon
electricity as dangerous and naturally many questions pertaining to
hazards arose. The distribution of electricity has been so highly
perfected that little is heard of the hazards which were so magnified in
the early years. Data gathered between 1884 and 1889 showed that about
13,000 fires took place in a certain district. Of these, 42 were
attributed to electric wires; 22 times as many to breakage and explosion
of kerosene lamps; and ten times as many through carelessness with
matches. These figures cannot be taken at their face value because of
the absence of data showing the relative amount of electric and kerosene
lighting; nevertheless they are interesting because they represent the
early period.

There are industries where unusual care must be exercised in regard to
the lighting. In certain chemical industries no lamps are used excepting
the incandescent lamp and this is enclosed in an air-tight glass globe.
Even a public-service gas company cautions its employees and patrons
thus: "_Do not look for a gas-leak with a naked light! Use electric
light._" The coal-mine offers an interesting example of the precautions
necessary because the same type of problems are found in it as in
industries in general, with the additional difficulties attending the
presence or possible presence of explosive gas. The surroundings in a
coal-mine reflect a small percentage of the light, so that much light is
wasted unless the walls are whitewashed. This is a practical method for
increasing safety in coal-mines. However, the most dangerous feature is
the light-source itself. Accor