FUELS.--Artificial heat is commonly produced by combustion, caused by the chemical action of the oxygen of the air upon the hydrogen and carbon found in fuel. The different fuels in common use for cooking purposes are hard wood, soft wood, charcoal, anthracite coal, bituminous coal, coke, lignite, kerosene oil, gasoline, and gas. As to their respective values, much depends upon the purpose for which they are to be used. Wood charcoal produces a greater amount of heat than an equal weight of any other fuel. Soft wood burns quicker and gives a more intense heat than hard wood, and hence is best for a quick fire. Hard wood burns slowly, produces a larger mass of coals, and is best where long-continued heat is desired. Anthracite coal kindles slowly, and burns with little flame or smoke, but its vapor is sulphurous, and on that account it should never be burned in an open stove, nor in one with an imperfect draft. Its heat is steady and intense. Bituminous coal ignites readily, burns with considerable flame and smoke, and gives a much less intense heat than anthracite, Lignite, or brown coal, is much less valuable as fuel. Coke is useful when a short, quick fire is needed. Kerosene and gas are convenient and economical fuels. MAKING FIRES.--If coal is the fuel to be used, first clean out the stove by shaking the grate and removing all ashes and cinders. Remove the stove covers, and brush the soot and ashes out of all the flues and draft holes into the fire-box. Place a large handful of shavings or loosely twisted or crumpled papers upon the grate, over which lay some fine pieces of dry kindling-wood, arranged crosswise to permit a free draft, then a few sticks of hard wood, so placed as to allow plenty of air spaces. Be sure that the wood extends out to both ends of the fire-box. Replace the covers, and if the stove needs blacking, mix the polish, and apply it, rubbing with a dry brush until nearly dry, then light the fuel, as a little heat will facilitate the polishing. When the wood is burning briskly, place a shovelful or two of rather small pieces of coal upon the wood, and, as they ignite, gradually add more, until there is a clear, bright body of fire, remembering, however, never to fill the stove above the fire bricks; then partly close the direct draft. When wood or soft coal is used, the fuel may be added at the same time with the kindling.