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.