vapor. For
each candle-power of light per hour about 0.24 cubic foot of carbon
dioxide and 0.18 cubic foot of water-vapor are formed by a modern
oil-lamp. That an open flame devours something from the air is easily
demonstrated by enclosing it in an air-tight space. The flame gradually
becomes feeble and smoky and finally goes out. It will be noted that a
burning lamp will vitiate the atmosphere of a closed room by consuming
the oxygen and returning in its place carbon dioxide. This is similar to
the vitiation of the atmosphere by breathing persons and tests indicate
that for each two candle-power emitted by a kerosene flame the vitiation
is equal to that produced by one adult person. Inasmuch as oil-lamps are
ordinarily of 10 to 20 candle-power, it is seen that one lamp will
consume as much oxygen as several persons.

In order that oil-lamps may produce a brilliant light free from smoke,
combustion must be complete. The correct quantity of oil must be fed to
the burner and it must be properly vaporized by heat. If insufficient
oil is fed, the intensity of the light is diminished and if too much is
available at the burner, smoke and other products of incomplete
combustion will be emitted. The wick is an important factor, for,
through capillarity, it feeds oil forcefully to the burner against the
action of gravity. This action of a wick is commonly looked upon with
indifference but in reality it is caused by an interesting and really
wonderful phenomenon. Wicks are usually made of high-grade cotton fiber
loosely spun into coarse threads and these are woven into a loose plait.
The wick must be dry before being inserted into the burner; and it is
desirable that it be considerably longer than is necessary merely to
reach the bottom of the reservoir. A flame burning in the open will
smoke because insufficient oxygen is brought in contact with it. The
injurious products of this incomplete combustion are carbon monoxide and
oil vapors, which are a menace to health.

To supply the necessary amount of oxygen (air) to the flame, a forced
draft is produced. Chimneys are simple means of accomplishing this, and
this is their function whether on oil-lamps or factories. Other means of
forced draft have been used, such as small fans or compressed air. In
the railway locomotive the short smoke-stack is insufficient for
supplying large quantities of air to the fire-box so the exhausted steam
is allowed to escape into the stack. With eac