Q. What are the sparks of fire, which burst from the wood?
A. Very small pieces of wood red hot, separated from the log by the force of the air, as it bursts from its confinement.
Q. Why does deal make more snapping than any other wood?
A. The pores of deal are very large, and contain much more air than wood of a closer grain.
Q. Why does dry wood make more snapping than green wood?
A. In green wood the pores are filled with sap, and therefore contain very little air; but in dry wood the sap is dried up, and the pores are filled with air instead.
Q. Why does dry wood burn more easily than green or wet wood?
A. Because the pores of dry wood are filled with air, which supports combustion; but the pores of green or wet wood are filled with vapour, which extinguishes flame.
Q. Why does vapour extinguish flame?