_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.”