A Guide to the Scientific Knowledge of Things Familiar. Ebenezer Cobham Brewer
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 it.
Q. What is smoke?
A. Small particles of carbon, separated by combustion from the fuel, but not consumed.
Q. Why do smoke and steam curl, as they ascend?
A. Because they are moved in a right line, and then pushed on all sides; and this forces them into a circular motion.
Q. What are blacks?
A. When the hot air of the chimney has been cooled by the external air, it can no longer buoy up the solid smoke; so it falls to the earth in condensed flakes, called “blacks.”
Q. Why are there no blacks in the smoke of a railway engine?
A. The smoke of a railway engine consists chiefly of watery vapour, which dissolves in air, as sugar does in water; but the smoke of a common chimney consists of small fragments of unburnt fuel.
Q. Why does a “COPPER HOLE” DRAW up more fiercely than an open stove?
A. As the air, which supplies the copper hole, must pass through the furnace, it becomes exceedingly heated, and rushes up the chimney with great violence.
Q. What produces the roaring noise made by a copper-hole fire?
A. Air rushing rapidly through the crevices of the iron door, and up the chimney flue.
Q. Why is the roar less, if the copper-hole door be thrown open?
A. Because fresh air gets access to the fire more easily; and as the air is not so intensely heated, its motion is not so violent.
Q. Why do some chimneys smoke?
A. If fresh air is not admitted into a room, as fast as it is consumed by the fire, a current of air will rush down the chimney to supply the deficiency, and bring the smoke along with it.
Q. What prevents air being supplied, as fast as it is consumed by the fire?
A. Leather and curtains round the doors; sand-bags at the threshhold and on the window-frames; and other contrivances to keep out the draught.
Q. Why is it needful for cold fresh air to be so constantly supplied?
A. If water be taken with a pail out of a river, other water will rush towards the hole, as soon as the pail is lifted out; and if air be taken from a room, (as it is, when some of it goes up the chimney) other air will rush towards the void to fill it up.
Q. Why will it come down the chimney?
A. Because if doors and windows are all made air-tight, it can get to the room in no other way.
Q. What is the best remedy in such a case?
A. The speediest remedy is to open the door or window: but by far the best remedy is to carry a small tube from the hearth into the external air.
Q. Why is that the best remedy?
A. Because the fire will be plentifully supplied with air by the tube; the doors and windows may all remain air-tight; and we may enjoy a warm fireside, without the inconvenience of draughts and cold feet.
Q. Why is a chimney raised so high above the roof?
A. If it were not so, it would smoke; as all funnels do which are too short.
Q. What is meant by the funnel, or flue of a chimney?
A.