Union County courier. [volume] (Elk Point, Union County, D.T. [S.D.]) 187?-1913, 1878-07-31
LIGHTNING.

Conditions Favorable for its Attraction
Safeguards Against Injury from
Electric Bolts.
Under what conditions is damage from
lightning possible, and what are the
means by which the risk may be lessen
ed or avoidedY An isolated tree, stand
ing either upon a wide plain or upon an
emneince, is obviously likely to determine
a lightning discharge, to attract the
lightning" TO use a common expression.
The top of the tree is the nearest point
to the cloud, and since the tree is a
better conductor than the air, a line
drawn vertically through it to the cloud
marks the shortest and easiest course
along which the electricities may pass.
If, when the charged cloud arrives d.
rectly ove this point, the tension is suf-
ficient to overcome the resistance along
that line, a discharge will take place,
and the tree will be struck But if tn
tension be not sufficient, the cloud Will
pass harmlessly over. Hence it appears
that a person standing during a thunder
storm beneath a tree so situated is ex-
posed to some risk. QQfno account,
therefore, should the traveller take refuge
under an isolated tree; generally he will
do well to avoid its nelghborkood alto
gether; but should he be overtaken by
the storm when on a plain with no
shelter near, the tree may still be made
to afford him some projection. If he
take up a position neal it, but not under
its branches, he will probably escape
unhurt should the lightning descend
upon it. The safest distance from the
tree is that which is equal to its height.
To approach much nearer than this is to-
incur the risk of being within the in-
fluence of the struke; to remain at i
much greater distance away is to place
ones self in the same conditions of isola-
ton As the tree itself. 1t will have been re-
marked by all observers of the phe-
nomenon that whenever a tree has been
struck by lightning it has generally
occupied an isolted position. In de-
scribing the position as one of isolation,
however, it is not meant that the tree
is necessarily standing alone, but that il
is not n of a numerous group. When
there are many trees together, their col
lective conductivity is often sufficient TO
cause an indestructive discharge of the
electricity. This is especially likely to
happen when the trees are wet with
rain, for then their surfaces are covered
with a film of water, which is a good
conductor. For this reason, the danger
from lightning is much less after rain
has begun to fall, than before, when
everything is dry. Itappears, therefore,
that the safest situation during a thun-
der-storm is in the midst of a wood, par
ticularly if the neighborhood of the
tallest tress be avoided. In such a place
OF shelter, the traveller may take refuge
in full assurance that he will there be
etfectually shielded from harm. The
greatest risk of injury from lightning is
undoubtedly incurred by persons travel
ing across a wide and very fat plain,
because in such a situation they are the
only elevated objects. To lessen the
risk, which may here be somewhat
serious, advantage should be taken of
whatever undulations of surface may
exist, to keep upon the lowest ground.
No doubt the PROSTATE position would
in these circumstances afford greater
security than the erect. 1t happens not
u~nfrequently that animals are killed
by lightning under a tree to which they
had betaken themselves for shelter. In
these cases the tree is struck partly in
consequence of its isolation, and partly
on accoun of the presence of the animals
beneath it. Usually there are several,
and often many of them assembled to-
gether, huddled probably by terror into
contact one with another. The air,
heated by their bodies, rises above them
laden with moisture. derived mainly
from their breath. Who'll has not noticed
the cloud of vapor hat in the early
morning and in certain states of the
weather hangs yer a flock of sheep or Il
herd of kline? The column of moist air
ascending through the branches of tie
tree toward the cloud, offers, in conse-
quence of the comparative high conduc-
tivity of water, a favorable passage for
the electricity. A herd of cattle under
an isolated tree is thus exposed to n
double risk; also it is evident that these
animals are in the open country less Sc
cure from injury than human beings,
who cannoe affect the atmosphere in a
like degree.-Chambers' journal.