With the invention of the kerosene lamp came more efficient lighting of home and street, and with the advent of gas and electricity came a light so effective that the hours of business, manufacture, and pleasure could be extended far beyond the setting of the sun.

The production of light by candle, oil, and gas will be considered in the following paragraphs, while illumination by electricity will be reserved for a later Chapter.

142.  The Candle.  Candles were originally made by dipping a wick into melting tallow, withdrawing it, allowing the adhered tallow to harden, and repeating the dipping until a satisfactory thickness was obtained.  The more modern method consists in pouring a fatty preparation into a mold, at the center of which a wick has been placed.

The wick, when lighted, burns for a brief interval with a faint, uncertain light; almost immediately, however, the intensity of the light increases and the illumination remains good as long as the candle lasts.  The heat of the burning tallow melts more of the tallow near it, and this liquid fat is quickly sucked up into the burning wick.  The heat of the flame is sufficient to change most of this liquid into a gas, that is, to vaporize the liquid, and furthermore to set fire to the gas thus formed.  These heated gases burn with a bright yellow flame.

143.  The Oil Lamp.  The simple candle of our ancestors was now replaced by the oil lamp, which gave a brighter, steadier, and more permanent illumination.  The principle of the lamp is similar to that of the candle, except that the wick is saturated with kerosene or oil rather than with fat.  The heat from the burning wick is sufficient to change the oil into a gas and then to set fire to the gas.  By placing a chimney over the burning wick, a constant and uniform draught of air is maintained around the blazing gases, and hence a steady, unflickering light is obtained.  Gases and carbon particles are set free by the burning wick.  In order that the gases may burn and the solid particle glow, a plentiful supply of oxygen is necessary.  If the quantity of air is insufficient, the carbon particles remain unburned and form soot.  A lamp “smokes” when the air which reaches the wick is insufficient to burn the rapidly formed carbon particles; this explains the danger of turning a lamp wick too high and producing more carbon particles than can be oxidized by the air admitted through the lamp chimney.

One great disadvantage of oil lamps and oil stoves is that they cannot be carried safely from place to place.  It is almost impossible to carry a lamp without spilling the oil.  The flame soon spreads from the wick to the overflowing oil and in consequence the lamp blazes and an explosion may result.  Candles, on the other hand, are safe from explosion; the dripping grease is unpleasant but not dangerous.

The illumination from a shaded oil lamp is soft and agreeable, but the trimming of the wicks, the refilling of bowls, and the cleaning of chimneys require time and labor.  For this reason, the introduction of gas met with widespread success.  The illumination from an ordinary gas jet is stronger than that from an ordinary lamp, and the stronger illumination added to the greater convenience has made gas a very popular source of light.