No naked flame can ever be steady. Second, _Color_.
This depends greatly upon the temperature of the flame. A hot flame
gives a bright, white light; a flame which has not a high temperature
gives a dull, yellow light, which is very injurious to the eyes. In
the naked gas-jet a large portion of the flame burns at a low
temperature, and the same is the case with the flame of the kerosene
lamp when the height of the chimney is not properly proportioned to
the amount of oil consumed; a high wick needs a high chimney. In the
case of a well-trimmed Argand oil-lamp, or an Argand burner for gas,
the flame is in general most intensely hot, and the light is of a clear
white character.
The third point which demands attention is the _amount of heat_
transmitted from the flame to the eyes. It often happens that people,
in order to economize light, bring the lamp quite close to the face.
This is a very bad habit. The heat is more injurious than the light.
Better burn a larger flame, and keep it at a greater distance. It is
also well that various sized lamps should be provided to serve the
varying necessities of the household in regard to quantity of light.
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