covers the earth; another layer rests upon it; and thus layer is piled upon layer, for 50 miles in height. Each layer is a “stratum” of air; and the plural of stratum is strata.
Q. Why do we hear the collapsing of the air nearest the earth first?
A. Because sound takes a whole second of time to travel 380 yards; but the air is ripped from top to bottom instantaneously: if, therefore, the cloud were 1000 yards off, we should hear the collapsing of the lowest strata nearly three seconds, before we heard that in the immediate vicinity of the cloud.
Q. Why is the thunder sometimes like a deep growl?
A. When the storm is far distant, the thunder sounds like a deep growl.
Q. Does not scenery affect the sound of thunder?
A. Yes; the flatter the country, the more unbroken the peal: Mountain scenery breaks the peal, and makes it harsh and irregular.
Q. What is the cause of rolling thunder?
A. The rolling is produced by the reverberation of the thunder along the massive clouds.
Q. What is meant by the reverberation?
A. The echo.
Q. Why is a flash of lightning generally followed by a pouring rain?
A. The cloud collapses, as soon as the electric fluid has left it; and the water it contained is squeezed out.
Q. Why is a flash of lightning generally followed by a gust of wind?
A. The flash rent the air asunder through which it darted; and when the two parts collapse, a rapid motion is produced, which we call wind: the vibration of the thunder contributes also to agitate the air.
Q. What is meant by the “vibration of the thunder?”
A. The quivering motion it gives to the air, by its loud sound.
Q. Why is there no thunder to what is called summer lightning?
A. Because the lightning-clouds are so far off, that the sound of the thunder is lost, before it reaches the earth.
Q. Do thunder-bolts ever drop from the clouds?
A. No; the notion of thunder-bolts falling from the clouds, arises from the globular form, that is sometimes assumed by a 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?
