The fuels most widely used in this country are coal, gas, and kerosene. Wood is still used for cooking by those who own wood lots, or who live in a district where wood is abundant, but in a sense it is the fuel of the past. Electricity is generated from coal except in the few communities where the electric current is derived through machinery from the energy of falling water but electricity is not in common household use, and is still the method of the future for the average family. Other substances are burned for fuel occasionally or in restricted localities. Corn cobs are used sometimes in the corn belt. Peat is an old-world fuel. It is a vegetable substance taken in blocks from marshes, in reality the first stage of coal formation. It is a slow-burning fuel which is cheap in its own locality.

Economy of fuel is a world problem, for it is evident that the coal supply will be exhausted in course of time, and this is true also of coal oil or petroleum. Scientists are experimenting to discover practical methods, not dependent upon the burning of coal, for generating electricity. Water power is the only practicable method so far, and to make it permanently available we must conserve the forests still remaining to us, and thus safeguard the sources of our rivers.

Another effort toward economy is seen in the use for fuel of waste products treated in some way to make them readily combustible. The briquet is used in Europe where the fuel supply is limited. It is made of sawdust or waste coal, with some petroleum, tar, resin, or other substance, heated together and molded. Good briquets yield a large amount of heat in proportion to bulk and weight. The problem here, as with all waste, is to find a manufacturing process that will make the product cheap enough to be practical for common use.

It is a natural impulse to use lavishly whatever is at hand in abundance, and it is only a highly civilized community that takes thought for the economy of the future. Considered only from a selfish point of view, however, with coal and petroleum at the high prices that are likely to prevail, the saving of fuel is one of our most important economies.

The common fuels.—Coal is of two kinds, anthracite and bituminous, or hard and soft. Hard coal of good quality has 90 per cent or more of carbon, and burns with little flame. Soft coal contains as much as 18 per cent of flame-making substances, and gives off a heavy smoke. Hard coal is therefore cleaner, but it is more costly than soft coal, because the supply is smaller. The most important anthracite mines are found in the eastern United States, and hard coal is used more in this section than elsewhere. Good hard coal may be recognized by its glossy black color and bright surfaces. It is sold under different names taken often from the locality where it is mined. There are two kinds, one leaving a reddish ash, and the other a white. The red ash coal burns more freely than the white ash and the ash is heavier and therefore cleaner. The price is higher per ton or bag.

Coal is sorted in different sizes, a medium size being best for the ordinary range. Poor coal has slaty pieces in it, that will not burn but break up and mingle with the ashes. You can learn to detect it by the slaty color. Clinkers are formed by unburnable minerals, mixed with the coal, that melt and stick together, and even adhere to the lining or the grate. They are not often troublesome in the cooking range.

Coal is measured by the ton of two thousand pounds avoirdupois. A common hod of coal holds about thirty pounds. Coal should be bought in large quantity, and stored away in summer, if possible. The retail dealer in the city often charges an exorbitant sum for coal by the bag, so that the buyer of small quantities pays a much higher price for a ton bought in this way. The wholesale price of coal has increased on an average about 13 per cent since 1900.

Coke is the solid substance remaining after gas has been made from certain kinds of coal, and is sometimes sold by gas companies, as a by-product. It is light, and therefore easy to handle and does not smoke, but it burns out quickly, and the fire of coke requires frequent replenishing. It is sold by the bag, or in large quantities by the ton, also sometimes by the chaldron, an old English measure for coal, containing from thirty-two to thirty-six bushels.

Gas was used for illuminating long before it came into common use for heating and cooking. Commercial gas manufactured for both lighting and cooking is really a mixture of various gases. One method produces it from bituminous coal heated in retorts. Another method gives “water gas,” by passing steam through heated coal. The value of gas will depend upon the components of the mixture, and the manufacturer has an opportunity to make an inferior gas unless the law stipulates what the quality shall be.

The small town or country dweller may use a gas machine on the premises, the gas to be stored or generated in some tank in the ground, and piped into the house. Acetylene, a compound of carbon and hydrogen, is used in this way. Acetylene has a low flashing point, and there is question as to its safety. One firm sends a mixed gas of good quality in metal bottles to the consumer, the bottles being placed in a metal closet above ground outside the house. The firm claims that an explosion has never occurred.

Gas is measured by the cubic foot, and its price estimated per 1000 cubic feet. The amount is recorded on a meter as the gas passes into the house. See Fig. 13. It is an easy matter to learn to read a meter, and every one should do so who uses gas. Always compare the gas bill with the amount recorded by the meter. If the gas bill becomes larger than usual, and you feel sure that the consumption has been normal, report the matter to the company. A meter may be out of order, and need repair.

To read the meter.—Figure 13 shows the three dials found on the face of a gas meter. The arrows show the direction. The dial at the right indicates 100 cubic feet between the numbers, the middle dial 1000 and the left-hand dial 10,000. The dials in this figure record 53,250 cubic feet. The price of gas varies from eighty cents to a dollar and a half per thousand cubic feet. “Eighty-cent gas” is the hope of many a consumer. At a dollar and a half it is not a cheap fuel.

Gas does away with the handling of coal and ashes in the kitchen and is thus a clean and labor-saving fuel. It gives an intense heat the moment the flame is lighted and this heat is easily regulated in a well-made stove. The flame should burn with a clear blue or greenish color. With a properly constructed stove only a small percentage of the heat is lost. In all these points it has the advantage over coal. The comparative cost is studied in the problems on page 53.

Natural gas is used in those regions where it occurs, piped to the house from a central source. It is found in limited areas only, and in some places has already been exhausted.

Coal oil, or petroleum, sometimes found oozing from crevices in rocks, or even floating on water, is a natural inflammable oil stored in the earth. It was known in ancient Persia, Greece, and Rome, but did not become of great commercial importance until the middle of the nineteenth century. It is now obtained by boring wells, and is found in great quantities in certain regions of the country. The crude oil yields many products valuable in the arts, medicine, and manufacture. Kerosene is the substance useful as a fuel and for giving light. When of good quality it is nearly colorless, and the flashing point should be 149° F., or 65° C. This flashing point is the temperature at which the vapor from the kerosene explodes or flashes. If the vapor flashes at a point lower than this, it means that the oil has not been sufficiently refined; that is, in the process of manufacture the substances that flash at a low temperature have not been removed, and therefore the oil is less safe.

Kerosene is sold by the gallon or barrel. The price for a good quality is about seventy cents for a five-gallon can. By the barrel a saving is made of several cents a gallon. It is useful as a fuel to those housekeepers who cannot have gas, and who find it a convenient substitute for coal in the summer. With the new blue-flame stoves it gives an intense heat, easily regulated. There is no heavy labor involved in its use, but even the best stove requires constant care and watchfulness. It is not so clean and easy to use as gas. The kerosene supply should be kept in a cool place, and stoves and lamps should never be filled by candle or lamplight.

Gasolene is used as a fuel for cooking in some places, but in others the fire insurance companies have such strict rules in regard to it that its use is practically prohibited. It is more volatile than kerosene, and its flashing point is very low. Kerosene is much safer for household use.

Alcohol is used with the chafing dish. Denatured alcohol is so cheap in Germany that it is used in large and especially adapted stoves for cooking purposes. There are denatured alcohol stoves on the market here, but they are little used.

Charcoal, wood partially burnt out, is little used for domestic purposes now.

The relative value of the common fuels is stated in quantities as follows, but this is of course dependent on the quality of the coal and the gas. One thousand feet of gas about equals from fifty to sixty pounds of coal, or four and one half gallons of kerosene; and one half ton of coal approximates a cord of wood.

Those who may be interested will find a fuller discussion of fuels and fuel values in Snell’s “Elementary Household Chemistry.”

Electricity is not a fuel, but is classed here as a source of heat. It may be supplied for cooking purposes by any company that furnishes electric light, and should be available in the country wherever an electric trolley runs. The energy supplied is measured and paid for by the kilowatt; that is, one thousand watts. The terms used for electrical measurements cannot be really understood until one has studied electricity. It may be said, however, that the ampere[6] is the unit of current strength, the volt is the unit of electrical pressure or electromotive force, the watt is the unit of electrical power and the basis of payment for current supplied for heating or lighting.

Voltage, amperage, and watt or kilowatt are the terms in common use. If you read the circulars that advertise electric cooking apparatus, you will find the request to state the voltage of your electric current in ordering a piece of apparatus. Or again, the number of watts used per hour is given, with the catalogue number and the size of an electric stove.

The cost of electricity per kilowatt (usually from ten to fifteen cents) varies in different localities.

The great advantage of electricity is that little heat is lost in radiation, and that the degree of heat is well under control. There are also no products of combustion present, and this is the only source of heat for cooking of which this is true. Both gas and kerosene vitiate the air to some extent.

Cooking apparatus.—The wastefulness of cooking operations, past and present, is due largely to the defects of the apparatus used. The open fireplace for wood, and the open grate for coal, are two arrangements that permit most of the heat to pass up the chimney, and into the room. See Frontispiece and Fig. 14. In Fig. 14 there is illustrated at the right a brick oven with a flue opening into the chimney. This was one of the earliest inventions for saving fuel and heat. This oven was lined with brick or stone, and the fire of wood was built in it, and allowed to remain until it had burned out. The coals and ashes were removed, and when the brick had cooled somewhat cakes and pies were put in to bake. This oven retained its heat for twenty-four hours, and beans put in Saturday afternoon were taken out hot for the Sunday morning breakfast. The method was clumsy, but a good heat saver.

Figure 15 is an American stove, early nineteenth century, wood the fuel; and from this form, modified for using coal, has developed the modern American coal range (Fig. 18). Even the latest types are very wasteful of heat. Stoves like that shown in Fig. 19 have been devised for use with gas. Even with these only a small percentage of the heat generated is available for cooking.

The ideal system is that which gives the largest possible percentage of its heat for cooking, and puts the degree of heat under quick control with the greatest saving of fuel, and of labor in operating. This does not mean that the stove which gives the most intense heat is the best, although some stoves seem to be constructed with that as the aim.

Let us consider some of the methods of saving heat, and study different kinds of apparatus with this knowledge in mind.

We recall the fact, first, that some substances are good conductors of heat, and others poor.[7] If you hold a metal poker in your hand, and place the other end in red hot coals, you will realize that metal is a rapid conductor of heat. If the poker has a wooden handle, the heat of the coals does not readily reach your hand, for the wood is a poor conductor. Moreover, this good conductor is a poor holder of heat, the heat radiating rapidly from it into the surrounding air, but the poor conductor, once thoroughly heated, cools off slowly.

It is not difficult to see how these facts apply in our cooking apparatus. From an oven with metal sides heat is lost by radiation. In a double oven, with an air space between the inner and outer part, some heat is saved. If the outer cover is of some non-conducting material, even less radiation takes place. This is the principle of the oven devised by Mr. Edward Atkinson. Here the inner oven is of sheet iron, and the outer covering of a non-conducting material, some composition with wood pulp or paper as the basis. If in this way heat can be trapped, as it were, in an oven, it will follow that less heat will have to be supplied, and we can use a smaller amount of fuel. This is the case in the Atkinson oven (Fig. 16), where the source of heat is either a kerosene lamp, or a small Bunsen burner of the rose type, which uses only a small amount of gas.

Another illustration of the conserving of heat by the prevention of radiation is in the fireless cooker. This is a method used in Sweden in simple form, and adapted and improved to suit modern needs. Heat is supplied in the first place by gas or kerosene, and the water in the vessel containing the food is raised to the boiling point, and held there in some cases for a few minutes. The vessel is then placed in the “cooker,” which is a box with thick walls of some non-conducting material, and the heat already present is sufficient to finish the cooking process, since the radiation is very slow. In some cookers a heated stone is introduced to raise the temperature slightly. Both of these devices are excellent for the long, slow cooking that seems to mellow the food material and develop the flavors that do not result from rapid cooking.

At the same time, we need rapid processes, such as broiling and toasting, which give characteristic flavors. To meet this double need, a new type of gas stove has been made. See Fig. 17.

This is a gas stove, where the oven has thick walls of a non-conducting material. The oven is heated, for a short time only, the gas flame being cut off when the oven has reached the desired temperature. At the left is an attachment where rapid cooking may be accomplished when desired, and there is a device at (1) with the same principle as the fireless cooker, or the tea “cosey.” This cover is dropped over the kettle when the boiling point is reached, the flame is turned out, and the heat in the water finishes the process. There is no good reason why stoves embodying this same principle should not be used with kerosene, and with the electric current. Improved stoves of this type will be constructed, and certainly will tend toward great economy of fuel.

One method of saving fuel is by the use of a steam cooker, which consists of a series of compartments, one above another, containing several kinds of food, all to be cooked over the same burner, either gas or kerosene, or on one section of the top of the coal range when space is being used for the wash boiler or irons.

It requires intelligence to use such devices, and those who lack it cling obstinately to hot fires and violent cooking.

The coal range.—Progress is slow, and the coal range will not be abolished at present. Figure 18 is an example of a good range as easy to manage as possible. The coal box at (1) has a lining that prevents the iron from burning out. The air enters at (2) and passes out at (3), when the fire is first made. When it is necessary to heat the oven, a damper is closed at (4), and the heated air then passes around the oven in the direction of the arrows. The coal is put in at (5) and the ashes shaken down at (6). Larger ranges, resting upon the floor, have a “dump” for the ashes directly into the ash box in the cellar, and some makes have a device for operating this with the foot. The coal stove involves the labor of bringing in coal and taking out ashes, and space must be given to the coal bin and ash pit. A range of this size would serve for a family of five or six. It requires from 2 to 3 hods per day. A hood should be placed above a large range, whether coal or gas.

To make a coal fire.—See that the grate is clean and that the ashes have been removed. You know that a current of air containing oxygen is needed to make the fire burn. How will you arrange the damper at (2) and (3) when you are starting the fire?

Coal does not begin to burn easily. Therefore we kindle it by materials that have a low kindling temperature, light wood, paper, and matches.

In the bottom of the grate, lay twisted pieces of paper, or very finely split pieces of wood, or shavings, next in order larger pieces of wood laid “crisscross,” yet close enough not to let the coal fall through, and on the top a shovelful or two of coal. Why do you not put in flat newspapers, and lay the kindling lengthwise and solid? Put on the stove lids, arrange the dampers properly, and touch the match. Why do you use the match? Why does the match light? Perhaps your nature study lessons will help you to explain this whole kindling process.

What should be the next step in the fire making? How should you finally arrange the dampers?

A coal fire will keep well for a considerable length of time, if the coal is put on and the ash removed regularly, provided the stove is well constructed, and the coal of good quality. Add fresh coal before the fire becomes a dull red, and shows ashes. If it gets too low, wood kindling will be needed, and this is poor management. Be careful not to put in so much coal that you cannot put the lid on firmly. It ruins the top of a stove if the hot coals touch it.

Soot must be removed once in a while from the top and bottom of the oven, and from the stove pipe.