Let us begin, then, by clearly disembarrassing our minds of any
lingering belief in the existence of thunderbolts. There are absolutely
no such things known to science. The two real phenomena that underlie
the fable are simply thunder and lightning. A thunderstorm is merely a
series of electrical discharges between one cloud and another, or
between clouds and the earth; and these discharges manifest themselves
to our senses under two forms--to the eye as lightning, to the ear as
thunder. All that passes in each case is a huge spark--a commotion, not
a material object. It is in principle just like the spark from an
electrical machine; but while the most powerful machine of human
construction will only send a spark for three feet, the enormous
electrical apparatus provided for us by nature will send one for four,
five, or even ten miles. Though lightning when it touches the earth
always seems to us to come from the clouds to the ground, it is by no
means certain that the real course may not at least occasionally be in
the opposite direction. All we know is that sometimes there is an
instantaneous discharge between one cloud and another, and sometimes an
instantaneous discharge between a cloud and the earth.
But this idea of a mere passage of highly concentrated energy from one
point to another was far too abstract, of course, for primitive man, and
is far too abstract even now for nine out of ten of our
fellow-creatures.
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