=105. Lighting a Kerosene Lamp.= When lighting a lamp, be sure it is in order and that any openings to the bowl are closed. Lift the chimney, turn the screw to raise the wick about one-eighth inch above the slit. Touch a lighted match to the wick, adjust the chimney, and, lastly, move the wick up or down until it burns clear and bright without smoking. After the burner becomes warm, the flame may grow higher and smoke. Do not leave a newly-lighted lamp unwatched. After the lamp is heated and adjusted, it should burn with a flame of even height. =106. To Extinguish a Lamp.= Turn the wick down until it is slightly below the top of the slit. Do not turn too far. It will then go out of itself, or a slight puff of air will extinguish it. This is safer and will smoke the chimney less than attempting to blow out the full flame. =107. Care of Lamps.= Keep the inside and outside of bowl and chimney clean. Wipe all soot from the burners. Trim the wick each day the lamp is used. Fill the bowl with oil to within one-half inch of the top. Get new wicks when the old ones become dirty. =108. Kerosene Mantle Lamps.= Kerosene mantle lamps (Fig. 52) give three to four times as much light per unit of oil as the ordinary kerosene lamp. Many mantle lamps on the market are unreliable. Care, therefore, should be taken to give the lamp a trial before investing so as to be sure to get a good one. The care and lighting of mantle lamps differ so much that the directions must be furnished by the manufacturer and should be followed with exactness. CHAPTER XV ALCOHOL AND GASOLINE LAMPS =109. Classification of Lamps.= Since the principle of operation is the same for most alcohol and gasoline lamps, they will be considered together. [Illustration: FIG. 53. Gasoline or alcohol lamp.] These lamps may be divided into two classes--gravity lamps and pneumatic, or pressure, lamps. =110. Gravity Lamps.= Gravity lamps have the tank elevated above the burner so that the force of gravity brings the fluid to the burner. It is usually a little to one side of the burner so that it cannot become heated by it. A pipe from the tank leads downward and either over the chimney or under the burner, where it will be heated by the flame of the lamp. When heated, it changes the gasoline or the alcohol to gas. The pipe carries the gas on to a point where it is mixed with air before it flows into the burner (Fig. 53). =111. Lighting the Gravity Lamp.= In order to light these lamps, the generator must first be heated so as to make the gas. After this has once been done, the heat of the lamp keeps the generator hot. As soon as the gas is formed, light the lamp. These lamps are furnished with mantles. The flame is blue and, consequently, gives out very little light, but much heat. The mantle covering the flame is heated to glowing white heat and gives off much light of a white color.