The effect produced by light on the eyes depends upon the following points: First, _Steadiness_. Nothing is more injurious to the eyes than a flickering, unsteady flame. Hence, all flames used for light-giving purposes ought to be surrounded with glass chimneys or small shades. 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. One of the very best forms of lamp is that known as the “student’s reading-lamp,” which is, in the burner, an Argand. Provide small lamps with handles for carrying about, and broad-bottomed lamps for the kitchen, as these are not easily upset. Hand and kitchen lamps are best made of metal, unless they are to be used by very careful persons.