from Dr. Brewer's "Guide to Science."
Originally published in The Leisure Hour (Religious Tract Society) vol.1 #9 (26 Feb 1852).
Why does smoke ascend the chimney?—Because the air of the room, when it passes over the fire, becomes lighter for being heated; and, being thus made lighter, ascends the chimney, carrying the smoke with it.
What is smoke?—Small particles of carbon, separated by combustion from the fuel, but not consumed.
Why do smoke and steam cur], as they ascend?—Because they are pushed round and round by the ascending and descending currents of air.
Why does a "copper-hole" draw up more fiercely than an open stove?—Because the air, which supplies the copper-hole, must pass through the furnace; and, as it becomes exceedingly heated, rushes up the chimney with great violence.
What produces the roaring noise made by a copper-hole fire?—Air rushing rapidly through the crevices of the iron door, and up the chimney flue.
Why is the roar less, if the copper-hole door be thrown open?—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.
Why do some chimneys smoke?—Because fresh air is not admitted into a room so fast as it is consumed by the fire; in consequence of which, a current of air rushes down the chimney to supply the deficiency, driving the smoke along with it.
Why are the ceilings of public offices generally black and filthy?—Because the heated air of the office buoys up the soot and fine dust; which, being unable to escape through the plaster, is deposited on the ceiling.
Why are some parts of the ceiling blacker and more filthy than others?—Because the air, being unable to penetrate the thick joints of the ceiling, passes by those parts, and deposits its soot and dust on others more penetrable.
What is charcoal?—Wood which has been exposed to a red heat, till it has been deprived of all its gases and volatile parts.
Why does charcoal remove the taint of meat?—Because it absorbs all putrescent effluvia, whether arising from animal or vegetable matter.
Why is water purified by being filtered through charcoal?—Because charcoal absorbs the impurities of he water, and removes all disagreeable tastes and smells, whether they arise from animal or vegetable matter.
Why are water and wine casks charred inside?—Because charring the inside of a cask reduces it to a kind of charcoal; and charcoal, by absorbing animal and vegetable impurities, keeps the liquor sweet and good.
Why does a piece of burnt bread make impure water fit to drink?—Because the surface of the bread, which has been reduced to charcoal by being burnt, absorbs the impurities of the water, and makes it palatable.
Why should toast and water, placed by the side of the sick, be made of burnt bread?—Because the charcoal surface of burnt bread prevents the water from being affected by the impurities of the sick room.
Why should sick persons eat dry toast, rather than bread and butter?—Because the charcoal surface of the dry toast helps to absorb the acids and impurities of a sick stomach.
Why are timbers, which are to be exposed to damp, charred?—Because charcoal undergoes no change by exposure to air and water; in consequence of which, timber will resist weather much longer, after it has been charred.
Why does water simmer before it boils—Because the particles of water near the bottom of the kettle, being formed into steam sooner than the rest, shoot upwards; but are condensed again, as they rise, by the cold water, and produce what is called "simmering."
What is meant by simmering?—A gentle tremor or undulation on the surface of the water. When water simmers, the bubbles collapse (i.e. burst) beneath the surface, and the steam is condensed to water again; but when water boils, the bubbles rise to the surface, and the steam is thrown off.
Why does a kettle sing, when the water simmers?—Because the air, entangled in the water, escapes by fits and starts through the spout of the kettle; which makes a noise like a wind instrument.
Why does not a kettle sing, when the water boils?—Because all the water is boiling hot; so the steam escapes in a continuous stream, and not by fits and starts.
When does a kettle sing most?—When it is set on the hob to boil.
Why does a kettle sing more, when it is set on the side of a fire, than when it is set in the midst of the fire?—Because the heat is applied so unequally, that one side is made hotter then the other; in consequence of which, the steam is more entangled.
Why does a kettle sing, when the boiling water begins to cool again?—Because the upper surface cools first; and the steam, which arises from the lower part of the kettle, is again entangled, and escapes by fits and starts.
Why does the water of a kettle run out of the spout, when it boils?—Because the lid fits so tightly, that the steam cannot lift it up and escape; being confined, therefore, in the kettle, it presses on the water with great power, and forces it out of the spout.
What causes the rattling noise, so often made by the lid of a saucepan or boiler?—The steam, seeking to escape, forces up the lid of the boiler, and the weight of the lid carries it back again: this being done frequently, produces a rattling noise.
If the steam could not lift up the lid of the boiler, how would it escape?—If the lid fitted so tightly that the steam could not raise it up, the boiler would burst into fragments, and the consequences might be fatal.
What becomes of the steam? for it soon vanishes.—After it has been condensed into mist, it is dissolved by the air, and dispersed abroad as invisible vapour.
And what becomes of the invisible vapour?—Being lighter than air, it ascends to the upper regions of the atmosphere, where, being again condensed, it contributes to form clouds.
Why does a metal spoon left in a saucepan retard the process of boiling?—Because the metal spoon, being an excellent conductor, carries off the heat from the water, and, as heat is carried off by the spoon, the water takes a longer time to boil.
Why will a pot filled with water never boil, when immersed in another vessel full of water also?—Because water can never be heated above the boiling point: all the heat absorbed by water after it boils, is employed in generating steam.
Why does water clean dirty linen?—Because it dissolves the stains, as it would dissolve salt.
Why does soap greatly increase the cleansing power of water?—Because many stains are of a greasy nature; and soap has the power of uniting with greasy matters, and rendering them soluble in water.