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.
Fig. 13. - Reading the gas meter.