Thus, assuming the cloud to be charged with positive electricity,
the subjacent earth will be in the negative state. The two
electricities[3] exert a strong tendency to combine or to produce
neutrality, whence there is a species of stress applied to the intervening
air. Possibly the cloud will be drawn bodily toward the earth more or less
rapidly, according as the charge is great or small. Or, on the other hand,
the cloud may roll on for leagues, carrying its influence with it, so that
the various portions of the earth underneath become successively charged
and discharged as the cloud progresses on its journey.
[Footnote 3: We may speak of two electricities or two electric states
without necessarily implying adherence either to the single or the double
"fluid" theory. Whether electricity be of two kinds or no, the fact
remains that there are two conditions, and all the features of this paper
may be explained with equal facility by the supporters of either
hypothesis.]
Should the cloud be near the earth, or should it be very highly charged,
the tension of the two electricities may be so great as to overcome the
resistance of the intervening air; and if this resistance should prove too
weak, what happens? How does the discharge show itself? It takes place in
the form of a lightning flash, and passing from the one surface to the
other--or, maybe, simultaneously from both--produces neutrality more or
less complete.
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