Burners are constructed in vary ing sizes to burn 1, 2, 3, 4, or 5 cubic feet of gas per hour, accord ing to the size of the flame when turned on full. Under equal condi tions the larger burners are more economical than the smaller. That is, a burner which consumes 4 feet of gas gives twice as much light as two burners that consume each 2 feet. Hence there is great economy in the use of a few large burners over many small ones.
Pressure of Gas.—Gas is frequently supplied at a much higher pressure than is necessary to give the best re sults. Hence if the jet is turned on full some of the gas will escape, caus ing the well-known " blowing" noise.
To prevent this, always on lighting the jet turn the stopcock backward as much as possible without percep tibly decreasing the light. This prac tice alone, if adhered to, will make a very important difference in the con sumption of gas.
Or the gas may be partially turned off at the meter, or a check can be introduced into the burner. One of the best checks is to screw a burner intended to consume 5 or 6 feet of gas an hour over a • 3- or 4-foot burner. A low pressure with a burner which secures a supply of air just enough to prevent smoking gives a maximum amount of light.
A Welsbach burner having a cap or mantle constructed on the well-known principle of the miner's safety lamp consumes from 3 to 31 feet of gas an hour and gives about 60 candle power, as against the 16 candle power of the ordinary electric light bulb. In a well-regulated Welsbach burner there should be no smoke. The blackening of the mantle is caused by the im proper adjustment of the air shutter and consequent clogging of the wire gauze or air holes in the burner which produces an improper mixture of gas and air.
To prevent the heat of the Welsbach light from discoloring the ceiling, put a mica dome over it. This is made to fit into or clamp to the top of the lamp chimney. Or suspend a glass smoke bell from the ceiling. If Wels bach lights, after being used for a month or two, become dim, probably the wire gauze of the burner is rusted or dirty. It should be removed and cleaned before a new mantle is ad j usted.
To Change a Mantle on a Welsbach Lamp.—To change a cap mantle take it up gently and put it down on a steady base, say, on the mantelpiece, handling it by the base or cap. To change a loop mantle, disengage the supporting rod by setting back the set screw. Lift the mantle off care
fully by raising the supporting wire. Slip a stiff wire or knitting needle through the loop in the top of the mantle at right angles with it. Hang the mantle in a pitcher having the ends of the knitting needle rest on each side. Be careful not to jar or knock the mantle in raising or re placing it. The best of these mantles are exceedingly delicate and will fall to pieces at a touch.
Gas Troubles.—If the gas goes out, send for the gas fitter or notify the office of the company. But as this may occur at night when help cannot be obtained it is well to know how to meet the emergency. The cause may be a deficiency of water or an excess of water, freezing of the meter, freez ing of the service pipes, or the con densation of water in the house pipes. Close the cocks of all the burners except one. When approaching the meter with a candle or open-flame lamp, keep the light at a distance to prevent an explosion. Turn off the gas at the main cock between the street surface pipe and the meter. Unscrew the plug of the waste-water system to let out any excess of water.
If the meter is frozen, cover it with a flannel cloth and pour boiling water over it. Afterwards wrap it in dry flannel or protect it by felt, straw, tan bark, sawdust, or sand. If the surface pipe is frozen outside the house, it will be necessary to uncover it and apply heat.
If water has condensed in the pipes it will cause the gas to jump up and down for some days before it finally puts the gas out. Hence, when it jumps or flickers, the gas company should be notified.
Or, on emergency, remove a burner and blow violently into the pipe. This will sometimes force the water below the hollow. If the trouble persists, the location of the meter should be changed to a lower one, and the pipes inclined so that all condensed water will trickle back to the meter.
Gas Arc Lamps.—These lamps are intended to give a maximum light with a minimum consumption of gas. They are composed of four burners of the incandescent burner or Welsbach type, and give a wonderfully high illumina ting power, especially adapted for use in rooms of large area like stores, assembly halls, and churches having lofty ceilings. They are made for both outside and interior lighting, and are especially valuable for commercial purposes.