The Princeton union. [volume] (Princeton, Minn.) 1876-1976, 1878-09-04
DANGER FROM LIGHTNING.

Under what conditions is damage from
lightning possible, and what are the
means by which. the risk May be lessened
or avoided? An isolated tree, standing
either upon wide plain or upon an en-
inence, is obviously likely to determine
lightning discharge, to ''attract the light
ming" to use a common expression. The
top Of the tree is the nearest point to the
cloud, and since the tree is a better con-
ductor than the air, line drawn verti-
cally through it to the cloud marks the
shortest and easiest course along which
the electricities rpay pass. If, when the
charged cloud arrives directly over this
point, the tension is sufficient to overcome
the resistance along that line, discharge
will take place, and the tree will be struck.
But if the tension be not sufficient, the
cloud will pass harmlessly over. fence
it appears that person standing during
thunderstorm beneath tree so situat-
ed is exposed to some risk. .4.N~
On nc account, therefore, should the
Traveller take refuge under an isolated tree;
generally he will do we'll to avoid it's
neighborhood altogether; but should he
be overtaken by the storm when on q
plain with no shelter near, the tree may
still be made to afford him some protec-
ton. If he take up position near it,
but NOT under its branches, he will prob
ably 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 anhuence of the stroke; to remain at a
much greater distance away is to place
ones self in the same conditions of iso-
latien as the tree itself. 1t will have
been remarked by all observers of the
phenomenon that whenever tree has
been struck by lightning it has generally
occupied an isolated position as one Of
isolation, however, it is not meant that
the tree is necessarily standing alone, but
that it is not one of numerous group.
When there are many trees together, their
objective 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
tilm of water, which is good conductor.
For this reason, the danger from light
ming is much less after rain has begun to
fall. than before, when every thing IS dry.
It appears, therefore, that the safest
situation during thunderstorm is in the
midst Of a wood, particularly if the
ncighborhood of the tallest trees be avoid
ed. In such place of shelter the tray
eller may take refuge in full assurance
that he will there be effectually shielded
from harm. The greatest risk of injury
from lightning is undoubtedly incurred
by persons Travelling across wide and
very fiat plain, because in such situation
they are the only elevated objects. To
lessen the risk, which may here be some
what serious, advantage should be taken
of whatever undulations of surface NAV
exist to keep upon the lowest ground.
No doubt the PROSTATE position would in
these circumstances afford greater secur-
ity than the erect. It happens not unfre-
quently that animals are killed by light
ming under a tree TO which they had
betaken themselves for shelter. In these
cases the tree is struck partly in conse-
quence of its isolation, and partly on ac-
count of the presence of the animals be-.
meath it. aa ai4su 19 5dsa ree
Usually there are several, and often
many of them assembled together, hudl 4
died probably by terror into contract one
with another. The air, heated by their
bodies, rises above them laden with ,nois-
ture, derived mainly from their breath. !