A Guide to the Scientific Knowledge of Things Familiar. Ebenezer Cobham Brewer
flash of lightning.
Q. Why is the thunder often several moments after the flash?[1]
A. The flash travels nearly a million times faster than the thunder; if, therefore, the thunder has far to come, it will not reach the earth till a considerable time after the flash.
[1] The speed of lightning is so great, that it would go 480 times round the earth in one minute: whereas, thunder would go scarcely 13 miles in the same space of time.
Q. Can we not tell the distance of a thunder-cloud, by observing the interval which elapses between the flash and the peal?
A. Yes; the flash is instantaneous, but the thunder will take a whole second of time to travel 380 yards: hence, if the flash is 5 seconds before the thunder, the cloud is 1900 yards off.
(i.e. 380 × 5 = 1900 yards.)
Q. What places are most dangerous to be in, during a storm?
A. It is very dangerous to be near a tree, or lofty building; it is dangerous also, to be near a river, or any running water.
Q. Why is it dangerous to be near a tree, or lofty building, during a thunder-storm?
A. Because a tall pointed object, (like a tree or spire,) will frequently discharge a lightning-cloud; and then the electric fluid will pass down it, in its way to the earth.
Q. How can a tree or spire discharge a lightning-cloud?
A. A lightning-cloud (floating over a plain) may be too far off to be discharged by it; but as a tree, or spire, would shorten the distance between the cloud and its conductor, it might no longer be too far off a conductor to be discharged.
Q. Is not air a conductor of lightning?
A. No; dry air is not a conductor of lightning; and therefore, the flash rends it in twain, to get to some conductor.
Q. Why would it be dangerous to stand near a tree or spire, while lightning is passing down it?
A. Because the electric fluid (called lightning) always rushes down the outside of the tree or spire; and if any one were standing near, might pass through him, and kill or maim him.
Q. Does lightning go through the inside or outside of a tree?
A. It rolls down the outside of a tree; but passes through the inside of a man.
Q. Why does lightning pass down the outside of a tree?
A. Lightning always makes choice of the best conductors; and the outside of a tree is a better conductor than the inside.
Q. Why does lightning pass through the inside of a man?
A. As the fluids of the human body make a better conductor than the skin, therefore lightning passes through a man, and not down the skin.
Q. Why is it dangerous to be near a deep river, or any other running water, during a thunder-storm?
A. Because running water is a good conductor; and lightning always takes in its course the best conductors.
Q. Why is it dangerous for a man to be near water, in a thunder-storm?
A. Because the height of a man may be sufficient to discharge a cloud: and (if there were no taller object nigh) the lightning might make the man its conductor to the water.
Q. Why is it dangerous to ring church-bells during a thunder-storm?
A. For two reasons: 1st—Because the steeple may discharge the lightning-cloud, in consequence of its mere height.
2ndly—The swinging of the bells causes a current of air, which collects electric fluid.
Q. Why is it unsafe to run or drive fast during a thunder-storm?
A. The rapid motion of running causes a current of air, which collects electric fluid, and is often fatal.
Q. What parts of a dwelling are most dangerous during a thunder-storm?
A. The fire-place, (especially if the fire be lighted); the attics and cellar. It is also dangerous to sit close by the walls; to ring the bell; or to bar the shutters, during a thunder-storm.
Q. Why is it dangerous to sit before a fire, during a thunder-storm?
A. Because the heated air and soot are conductors of lightning; especially when connected with such excellent conductors as the stove, fender, and fire-irons.
Q. Why are the attics and cellar dangerous, during a thunder-storm?
A. Lightning sometimes passes from the clouds to the earth, and sometimes from the earth to the clouds; and therefore, the middle story of a house is always the safest to be in, during a thunder-storm.
Q. When does lightning pass from the earth to the clouds?
A. When the clouds are in a “negative” state of electricity.
Q. When does lightning pass from the clouds to the earth?
A. When the clouds are in a “positive” state of electricity.
Q. What is meant by the clouds being in a “positive state of electricity?”
A. When the clouds contain more electric fluid than they generally do, they are said to be in a positive state of electricity.
Q. What is meant by the clouds being in a “negative state of electricity?”
A. When the clouds contain less electric fluid than they ought to do, they are said to be in a negative state of electricity.
Q. Does the flash proceed from a negative or positive body?
A. Always from a positive body, or one over-burdened with electric fluid.
Q. When lightning flashes from the earth to the clouds, what is the flash called?
A. It is called the “returning stroke;” because the earth (being over-burdened with electric fluid) returns the surplus quantity to the clouds.
Q. Why is it dangerous to lean back against a wall during a thunder-storm?
A. Because the electric fluid sometimes runs down the wall of a house or room; and (as a man is a better conductor than a brick wall), would make him its path, and injure him.
Q. Why is it dangerous to ring a bell during a thunder-storm?
A. Bell-wire is an excellent conductor; and (if a person were to touch the bell-handle), the electric fluid, passing down the wire, might run through his hand and injure it.
Q. Why would the lightning run through a man touching a bell-handle?
A. Because the human body is a better conductor than the wall (between the bell-handle and the floor); and as lightning always chooses the best conductors for its path, it would (in this case) pass through the man, and injure him.
Q. Why is it dangerous to bar a shutter during a thunder-storm?
A. The iron shutter-bar is