Because the paper is more easily ignited than wood, and wood than coals; therefore the paper assists the ignition of the wood, and the wood assists the ignition of the coals.
"It is a good thing to give thanks unto the Lord, and to sing praises unto thy name, O Most High."—Psalm xcii.
299. Why will not wood ignite by the flame of a match?
It will do so, unless there is a great disproportion between the size of the wood and the flame of a match. A thin piece of wood will ignite, but a square block will not, because the heat of the flame is insufficient to raise the temperature of a large surface to the point that will drive out its gases.
300. Why do we place the paper under the wood, and the wood under the coals?
Because heat and flame, when surrounded by air, have a strong tendency to spread themselves upwards.
301. Would it be possible to light the coals by putting the paper and the wood upon the top?