A Guide to the Scientific Knowledge of Things Familiar. Ebenezer Cobham Brewer
lightning condenses the air, in the immediate advance of its path; it keeps flying from side to side, in order to pass where there is the least resistance.
Q. How does lightning condense the air in the immediate advance of its path?
A. The air is condensed by the rapidity of the lightning-flash.
Q. Why is forked lightning more dangerous than a straight flash?
A. Whatever resists the flash, diverts its course; and when terrestrial objects offer resistance to the current, they are in great danger of being destroyed.
Q. Why are there sometimes two flashes of forked lightning at the same moment?
A. Sometimes (in very severe storms) a flash of lightning will divide into two or more parts; and then each branch assumes the zig-zag form.
Q. Why is the flash sometimes quite straight?
A. When the lightning-cloud hovers near the earth, as the flash meets with very little resistance, it is not diverted; or (in other words) the flash is straight.
Q. What is the cause of sheet lightning?
A. It is only the reflection of distant flashes, not distinctly visible: and sometimes several flashes (from different clouds) intermingle, and form one vast blaze or sheet of lightning.
Q. Which form of lightning is the most dangerous?
A. The ball of fire is by far the most dangerous; and the zig-zag lightning is next in danger. Sheet lightning is not often attended with danger.
Q. Why are balls of fire so very dangerous?
A. Because (whenever they fall) much mischief is occasioned by their bursting, which they always do, with an explosion like that of a cannon.
Q. Do these balls of lightning ever run along the ground?
A. Yes; they often run a considerable way along the ground, then stop for a little time, and burst in numberless pieces: sometimes each of these pieces will explode; and at other times, the whole ball will burst at once, producing most mischievous consequences.
Q. What mischief will these balls of fire produce?
A. They will set houses and barns on fire; and kill all cattle and human beings, which happen to be in their course.
Q. Why does lightning sometimes kill men and beasts?
A. When the electric current passes through a man or beast, it produces so violent an action upon the nerves, that it destroys life.
Q. When is a person struck dead by lightning?
A. Only when his body forms a part of the lightning’s path: i.e. when the electric fluid (in its way to the earth) actually passes through his body.
Q. Why are men sometimes maimed by lightning?
A. Because lightning strikes with amazing force, whatever opposes it: and if a man stand in the way, it strikes him such a blow, as to maim him.
Q. What is thunder?
A. Lightning parts the air through which it passes; and when the parted air closes again, the noise made by the concussion, is called Thunder.
Q. Why does lightning part the air through which it passes? It does not part a rod of iron.
A. Iron is a conductor, and therefore allows the fluid to go freely through it: but air being a non-conductor, resists the lightning; which, therefore, rips it open, in order to pass through it.
Q. Why is thunder sometimes one vast crash?
A. When the lightning-cloud is near the earth, as the flash is straight—the whole volume of air (through which it passes) collapses at once; and produces one unbroken sudden crash.
Q. What is meant by the air collapsing?
A. When the rent air closes again, it is said to collapse.
Q. Why is the peal sometimes an irregular mangling broken roar?
A. When the lightning-cloud is a long way off, as the flash is zigzag, the air does not collapse all at once; and as we hear the concussion of one part after another, the peal is broken, protracted, and irregular.
Q. Which part of the collapsing air do we hear first?
A. That part nearest the earth; then the strata above; and last of all, that in the immediate vicinity of the cloud.
Q. What is meant by “strata of air?”
A. If a board were laid upon the earth, and several other boards were piled upon it, this pile would represent strata of wood.
Q. How does this illustration apply to the air?
A. A layer of air 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