The carbon of a clear fire, being sufficiently hot to unite with the oxygen of the air, produces carbonic acid gas, which soon envelops the paper laid flat upon the cinders: but carbonic acid gas will not blaze.
Q. If you blow the paper, it will blaze immediately. Why so?
A. By blowing, or opening the door suddenly, the carbonic acid is dissipated, and the paper is instantly fanned into flame.
Q. Why does water extinguish a fire?
1st—Because the water forms a coating over the fuel, and keeps it from the air:
2ndly—The conversion of water into steam, draws off the heat of the burning fuel.
Q. Why does a little water make a fire fiercer, while a larger quantity of water puts it out?
A. Water is composed of oxygen and hydrogen; when, therefore, the fire can decompose the water into its simple elements, it serves for fuel to the flame.
Q. How can water serve for fuel to fire?
A. The hydrogen of the water will burn with a flame; and the oxygen of the water will increase the intensity of that flame.
Q. If a house be on fire, is too little water worse than no water at all?
A. Certainly. Unless the water be supplied so plentifully as to quench the fire, it will increase the intensity, like fuel.
Q. When will water extinguish fire?
A. When the supply is so rapid and abundant, that the fire cannot convert it into steam.
Q. Does not a very little water slacken the heat of fire?
A. Yes, till it is converted into steam; but then it increases the intensity of fire, and acts like fuel.
Q. Why does the wick of a candle (when the flame has been blown out) catch fire so readily?
A. As the wick is already very hot, a little extra heat will throw it into flame.
Q. Why does the extra heat revive the flame?
A. Because it again liberates the hydrogen of the tallow, and ignites it.
Q. Cannot wood be made to blaze without actual contact with fire?
A. Yes; if a piece of wood be held near the fire for a little time it will blaze, even though it does not touch the fire.
Q. Why will wood blaze, even if it does not touch the fire?
A. The heat of the fire drives out the hydrogen gas of the wood; which is inflamed by contact with the red-hot coals.
Q. Why will a neighbour’s house sometimes catch fire, though no flame of the burning house ever touches it?
A. The heat of the burning house sets at liberty the hydrogen gas of the neighbouring wood-work, which is ignited by the flames or red-hot bricks of the house on fire.
Q. What is coke?
A. Coal freed from its volatile gases, by the action of artificial heat.
Q. Why do arnott’s stoves sometimes smell so strong of sulphur?
A. The fire is made of coke, which contains sulphur; and, whenever the draught is not rapid enough to drive the sulphur up the flue, it is emitted into the room.
Q. What is meant by spontaneous combustion?
A. Ignition produced by the action of one uninflamed body on another.
Q. Give an example of spontaneous combustion.
A. Goods packed in a warehouse will often catch fire of themselves; especially such goods as cotton, flax, hemp, rags, &c.
Q. Why do such goods sometimes catch fire of themselves?
A. Because they are piled together in very great masses in a damp state or place.
Q. Why does this produce spontaneous combustion?
A. The damp produces decay or the decomposition of the goods, and the great heat of the piled-up mass makes the decaying goods ferment.
Q. How does this fermentation produce combustion?
A. During fermentation, carbonic acid gas is given off by the goods—a slow combustion ensues—till at length the whole pile bursts into flame.
Q. Why is the heat of a large mass of goods greater than that of a smaller quantity?
A. Because compression squeezes out heat, as water is squeezed from a sponge; and as the goods of a large pile are greatly compressed, much of their latent heat is squeezed out.
Q. Why do hay-stacks sometimes catch fire of themselves?
A. Either because the hay was got up damp, or because rain has penetrated the stack.
Q. Why will a hay-stack catch fire if the hay be damp?
A. Damp hay soon decays, and undergoes a state of fermentation; during which, carbonic acid gas is given off, and the stack catches fire.
Q. Why does roasted coffee sometimes catch fire spontaneously?
A. The heat of coffee is greatly increased by being roasted; and the carbon of the coffee uniting with the oxygen of the air, produces carbonic acid gas, and bursts into flame.
Q. Why do old rags, used for cleaning lamps and candles, sometimes set a house on FIRE?
A. Because they very readily ferment, and (during fermentation) throw off exceedingly inflammable gases.
(N.B. Lamp-black mixed with linseed oil is more liable to spontaneous combustion, than anything that servants handle.)
CHAPTER IV.
SMOKE.
Q. Why does smoke ascend the chimney?
A. As the air of the room passes over the fire, it becomes heated; and (being thus made lighter,) ascends the chimney, carrying the smoke with
