To illustrate the manner in which the cost of gas consumed may be determined, assume that gas costs 90 cents per 1,000 cubic feet, that the previous reading of the gas meter, say on May 15, was 52,600 cubic feet, and that on June 15 the meter registered as shown in Fig. 1. As was just explained, the left dial of the meter reads 5, the center dial 5, and the right dial 200. Therefore, put these figures down so that they follow one another, as 5-5-200. This means then that the reading on June 15 is 55,200 cubic feet. With this amount ascertained, subtract from it the previous reading, or 52,600 cubic feet, which will give 2,600 cubic feet, or the quantity of gas burned from May 15 to June 15. Since gas costs 90 cents per 1,000 cubic feet, the cost of the amount burned, or 2,600 cubic feet, may be estimated by dividing 2,600 cubic feet by 1,000 and multiplying the result by 90; thus 2,600 ÷ 1,000 = 2.6, and 2.6 x .90 = 2.34
58. PREPAYMENT METERS.--In many places, gas concerns install what are called prepayment meters; that is, meters in which the money is deposited before the gas is burned. Such meters register the consumption of the gas in the same way as the meters just mentioned, but they contain a receptacle for money. A coin, generally a quarter, is dropped into a slot leading to this receptacle, and the amount of gas sold for this sum is then permitted to pass through as it is needed. When this amount of gas has been burned, another coin must be inserted in the meter before more gas will be liberated.
KEROSENE
59. In communities where gas is not available, kerosene, which is produced by the refinement of petroleum, is used extensively as a fuel for cooking, especially in hot weather when the use of a coal or a wood stove adds materially to the discomfort of the person who does the cooking. Kerosene is burned in stoves especially designed for its use, and while it is a cheap fuel it is not always the same in quality. It contains water at all times, but sometimes the proportion of water is greater than at others. The greater the amount of water, the less fuel will be contained in each gallon of kerosene. The quality of kerosene can be determined by checking up the length of time the stove will burn on a specified quantity of each new purchase of it.
Another product of the refinement of petroleum is gasoline. However, it is not used so extensively for fuel as kerosene, because it is more dangerous and more expensive.
ELECTRICITY
60. The use of electricity for supplying heat for cooking is very popular in some homes, especially those which are properly wired, because of its convenience and cleanliness and the fact that the heat it produces can be applied direct. The first electrical cooking apparatus was introduced at the time of the World's Fair in Chicago, in 1892, and since that time rapid advancement has been made in the production of suitable apparatus for cooking electrically. Electricity would undoubtedly be in more general use today if it were possible to store it in the same way as artificial gas, but as yet no such method has been devised and its cost is therefore greater. Electricity is generated in large power plants, and as it is consumed in the home for lighting and cooking it passes through a meter, which indicates the quantity used in much the same manner as a gas meter. It will be well, therefore, to understand the way in which an electric meter is read, so that the bills for electricity can be checked.
61. READING AN ELECTRIC METER.--An electric meter, which is similar in appearance to a gas meter, consists of three or four dials, which are
placed side by side or in the shape of an arc. In the usual type, which is shown in Fig. 2 and which consists of four dials placed side by side, each one of the dials contains ten spaces and a hand, or indicator, that passes over numbers ranging from to 9 to show the amount of electricity used. The numbers on the dials represent kilowatt-hours, a term meaning the energy resulting from the activity of 1 kilowatt for 1 hour, or 1 watt, which is the practical unit of electrical power, for 1,000 hours. Since 1,000 hours equal 1 kilowatt, 1,000 watt-hours equal 1 kilowatt-hour. It will be observed from the accompanying illustration that the dial on the extreme right has the figures reading in a clockwise direction, that is, from right to left, the second one in a counter-clockwise direction, or from left to right, the third one in a clockwise direction, and the fourth one in a counter-clockwise direction; also that above each dial is indicated in figures the number of kilowatt-hours that one complete revolution of the hand of that dial registers.