From Dr. Brewer's "Guide to Science."
Originally published in The Leisure Hour (Religious Tract Society) vol.1 #15 (08 Apr 1852).
Why is rain water soft—Because it is not impregnated with earths and minerals.
Why is it more easy to wash with soft water than with hard?—Because soft water unites freely with soap, and dissolves it, instead of decomposing it, as hard water does.
Why do wood ashes make hard water soft?—1st, Because the carbonic acid of wood ashes combines with the sulphate of lime in the hard water, and converts it into chalk; and, 2ndly, Wood ashes convert some of the soluble salts of water into insoluble, and throw them down as a sediment; by which the water remains more pure.
Why has rain water such an unpleasant smell, when it is collected in a rain-water tub or tank?—Because it is impregnated with decomposed organic matters, washed from roofs, trees, or the casks in which it is collected.
Why does water melt salt?—Because very minute particles of water insinuate themselves into the pores of the salt by capillary attraction, and force the crystals apart from each other.
How does blowing hot foods make them cool?—It causes the air which has been heated by the food to change more rapidly, and give place to fresh cold air.
Why do ladies fan themselves in hot weather?—That fresh particles of air may be brought in contact with their face by the action of the fan; and as every fresh particle of air absorbs some heat from the skin, this constant change makes them cool.
Does a fan cool the air?—No; it makes the air hotter, by imparting to it the heat out of our face: but it cools our face, by transferring its heat to the air.
Why is there always a strong draught through the keyhole of a door?—Because the air in the room we occupy is warmer than the air in the hall; therefore, the air from the hall rushes through the keyhole into the room, and causes a draught.
Why is there always a strong draught under the door, and through the crevices on each side?—Because cold air rushes from the hall, to supply the void in the room caused by the escape of warm air up the chimney, etc.
Why is there always a draught through the window crevices?—Because the external air, being colder than the air of the room we occupy, rushes through the window crevices to supply the deficiency caused by the escape of warm air up the chimney, etc.
If you open the lower sash of a window, there is more draught than if you open the upper sash. Explain the reason of this—If the lower sash be open, cold external air will rush freely into the room, and cause a great draught inwards: but if the upper sash be open, the heated air of the room will rush out; and, of course, there will be less draught inwards.
By which means is a room better ventilated—by opening the upper or the lower sash?—A room is better ventilated by opening the upper sash; because the hot vitiated air, which always ascends towards the ceiling, can escape more easily.
By which means is a hot room more quickly cooled—by opening the upper or the lower sash?—A hot room is cooled more quickly by opening the lower sash; because the cold air can enter more freely at the lower part of the room than at the upper.
Why does wind dry damp linen?—Because dry wind, like a dry sponge, imbibes the particles of vapour from the surface of the linen, as fast as they are formed.
Which is the hottest place in a church or chapel?—The gallery.
Why is the gallery of all public places hotter than the lower parts of the building?—Because the heated air of the building ascends; and all the cold air which can enter through the doors and windows, keeps to the floor, till it has become heated.
Why do plants often grow out of walls and towers?—Either because the wind blew the seed there with the dust; or else because some bird, flying over, dropped seed there, which it had formerly eaten.
What is a barometer?—A weather glass, or instrument to measure the variations in the weight of the air; by means of which variations we may judge what weather may be expected.
How can a barometer, which measures the weight of air, be of service as a weather glass?—When air is moist or filled with vapour, it is lighter than usual; and the column of mercury stands low. When air is dry and free from vapour, it is heavier than usual; and the mercury stands high. Thus the barometer, by showing the variations in the weight of the air, indicates the changes of the weather also.
Why can you tell, by looking at a barometer, what kind of weather it will be?—Because the mercury in the tube rises and falls, as the air becomes heavier or lighter: and we can generally tell, by the weight of the air, what kind of weather to expect.
Does the weight of the air vary much?—Yes; the atmosphere in England varies as much as one-tenth part more or less.
Why is the barometer highest of all during a long frost?—Because a long frost condenses the air very greatly; and the more condensed air is, the greater is its pressure on the mercury of a barometer.
Why does the barometer generally rise with north-east winds?—Because north-east winds make the air both cold and dry: and being both condensed and without vapour, it is much heavier.
Why does the barometer fall lowest of all, at the breaking up of a long frost?—1st, Because the air, which had been much dried by the frost, absorbs the moisture of the fresh warm current of wind from the south or south-west; and 2ndly, The air, which had been much condensed by the frost, is suddenly expanded by the warm wind which is introduced.
Why does the barometer fall very low with south and west winds?—Because south and west winds come heavily laden with vapour; and vaporized air is lighter than dry air.