River Falls journal. [volume] (River Falls, Pierce County, Wis.) 1872-2019, 1915-06-17
THUNDERSTORMS.
Simple Scientific Explanation of
How They Occur.
ELECTRICITY IN THE CLOUDS.
The Processes by Which the Masses of
UnequalIy Charged vapor Are
United, the Lightning Flashes Gen.
Grated and the Downpour Started.


United, the Lightning Flashes Gen.
Grated and the DownPour Started.
charges from the clouds, says the Elec-
trical Experimenter in printing what
it calls "a thunderstorm primer"
Every cloud, like every other object,
contains electricity. This makes no
disturbance SO long as the quantity
contained is normal. When the guam
tity becomes greater than normal the
object is positively charged; when it
becomes less than normal the object is
negatively charged. The equilibrium
of the electric force in the clouds is
disturbed by corporations from the
surface of the earth, by changes of
temperature in the atmospheric vapor,
bv chemical action on the earth'S sur
face and. by the friction of volumes of
air Of different densities against each
other.
When clouds charged with the oppo-
site electricities approach, the forces
rush toward each other and combine to
restore the state of equilibrium, for all
bodies charged with opposite electrici-
ties attract each other. Between the
clouds is air, an excellent nonconduc-
tor, through which the electricity has
to force a passage The violence with
which it does this produces the light
ming and the accompanying crash of
thunder.
Clouds are good conductors, while the
air about them is a nOnconductor;
therefore the electricity accumulates in
the clouds. 1t is probably this cleo
tricity which prevents the particles of
water from uniting together and falling
down in the form of rain.
Imagine two clouds near to each 9th
er in the sky, one positively and the
other negatively electrified, for there
cannot in all nature be such a cOndi-
ton as that of one body positively eX-
cited without the coeXistence of an
other body negatively excited. If the
positively charged cloud were all alone
in the sky the circumjacent atmOs-
phere would assume the negative func-
ton. But as the other cloud is near by
it becomes negative, and both are mu-
tually attracted. They approach each
other until the space of air between
them can no longer resist their electric
tension, when the discharge takes
place.
The equilibrium of the clouds being
thus restored, there is nothing to keep
the particles of water apart; they Goa
Lessee into drops and fall as rain.
When only the clouds are involved
the equilibrium is quickly restored by
a few flashes and the storm is over.
When the air also is involved it con-
tinues to charge the clouds with cleo
tricity, and the discharges continue un-
til the various strata q air are brought
into their normal state. Nsss.< s''sA",,-.
Sometimes, when the clouds are
charged with an opposite electricity to
that Of the earth, a discharge takes
place from clouds to earth or from
earth to clouds. 1t is only when there
is q great disturbance of the electrical
forces that the lightning flashes to the
earth or vice versa.
The fash and the thunder peal are
simultaneous, and we see the one be-
fore we hear the other because light
waves move far more swiftly than
sound waves. The peal of thunder is
instantaneous, but comes to us as a
roll through being echoed from clouds
or mountains. The noise is caused by
the vibrations Of the air rushing to fill
I'D the spaces where the electrical dis
charge has rarefied it and condensed
its vapors.
Lightning is zigzag when it travels
through a long distance, because it
congresses the air, which interferes
with its direct course. 1t is straight
when it passes through only short
distance 1t is forked when. being re-
sisted Dy the air, it divides into two or
three points. 1t is sheet when the fash
is too distant to be visible, and its re-
Election alone is seen.
By remembering that sound travels
a quarter Of a mile in a second, while
light travels so swiftly that we see it
instantaneously, we can tell how far
off q thunder clap is. If we hear a
thunder clap four seconds after seeing
the flash we know it is a mile away.
For such calculations our own pulse is
a sufficiently accurate measure of time,
for the pulse of an adult beats about
once a second. A person under forty
should count five beats to the mile; a
person under twenty should count six
beats to the mile.
A Rough Criticism.
Lord Houghton's epigram on "Sor-