The materials generally used as fuel are wood, charcoal, coal, kerosene oil, and gas.
Soft woods, such as pine or birch, kindle quickly, produce intense heat, and are best for a quick, blazing fire.
Hard woods, like oak, ash, and hickory, burn more slowly, but produce harder coals, which retain the heat longer, and are better where long-continued heat is required.
Charcoal, which is coal made by charring or burning wood with only a limited supply of air, burns easily and produces greater heat in proportion to its weight than any other fuel. It should never be burned in a close room.
Anthracite coal is a kind of mineral charcoal derived from ancient vegetation buried in the earth, and so thoroughly pressed that nothing is left but pure carbon, a little sulphur, and the incombustible ash. It kindles slowly, yields an intense, steady heat, and burns for a longer time without replenishing than the hardest wood.
Coke, often used in cities, is the residue of coal from which illuminating gas has been manufactured. The heat is intense, but transient.
Stoves for burning kerosene oil and gas have recently been introduced, and are now so nearly perfect that the care of a fire for cooking purposes is trifling. Gas can only be used in certain localities.
The cheapest fuel is the best kerosene oil. There need be no waste, no superfluous heat, no vitiated air, if the fire be extinguished immediately after the work is done, and if the stove be kept perfectly clean, so as to secure a free burning and perfect combustion. With two good stoves having all the latest and best improvements, a large amount of work can be easily and satisfactorily accomplished.