=18. Gas-Stove Lighter.= There are two kinds of gas-stove lighters. These differ from the pilot in that they do not burn constantly. One of these is so constructed that it is first necessary to apply a match to any one of the top burners. The other burners can then be lighted by opening the valve in the regular manner and pressing down on the lighter knob. As soon as pressure on the lighter knob is removed, the gas supply to the lighter is automatically cut off (Fig. 9). The other lighter is made of metal which gives sparks easily when subjected to friction. The lighter is held over the stove, the gas turned on and the friction produced by rubbing one part of the lighter across the other, making a spark which ignites the gas. =19. Amount of Gas Used.= It is claimed that 1,000 feet of illuminating gas produce as much heat as 50 or 60 pounds of anthracite coal or 4-1/2 gallons of kerosene oil. (See table on page 219.) The difference in gas bills, due to management of gas stoves, is considerable. It is very easy for one woman to use three times as much gas as another in doing the same amount of work. Some women do not realize when they are wasting gas. Water boils in an uncovered vessel at 212 degrees Fahrenheit, and no amount of heat applied to it will make it any hotter. When a pot of food has reached the boiling point, a smaller flame will keep it boiling. Turn the gas as low as it may be safely turned and still keep the pot boiling, and the food will cook as rapidly as when the gas is turned on full. [Illustration: FIG. 10. Single top burner and valve.] Gas is a safe fuel in most hands; it saves the housekeeper much labor because it makes so little dirt. When properly managed, it is the cheapest fuel to be had at the present time. =20. Cold-Process Gasoline Gas Stoves.= Cold-process gasoline stoves require a burner fitted with valves in which the gas orifice can be enlarged or diminished. The best of these for using cold-process gasoline gas can be adjusted by a turn of the finger. [Illustration: FIG. 10-_a_. Oven burner.] The adjustment of the valve is to compensate for the neglect upon the part of users of these plants. Very frequently they will allow the supply of gasoline in the carburetor to run nearly out before they replenish it, in which case the gas comes to the burners in a thinner quality, and in order to provide the same volume of heat, it is necessary to adjust the burner valves and throw a larger stream of gas into the burner. They are sometimes fitted with burners having side-sawed caps (Figs. 10 and 10-_a_). These seem to expose the burning gas to the air in a way to make it burn better than in other burners built for gas forced into them by greater pressure than is this gas. The opening for air must be adjusted from time to time so as to keep the proportion of gas and air such that it will produce a blue flame.