Daily globe. [volume] (St. Paul, Minn.) 1878-1884, 1878-09-01
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 vide plain or upon an en-
inence, is obviously likely to determine
lightning discharge, to "attract the light
ming, to use common expression. The
top of the tree is the nearest point to the
cloud, and since the tree is better con-
ductor than the air, a line drawn yerti-
cally through it to the cloud marks the
shortest and easiest cour.e along which
the electrlclties may pass ii, when the
charged cloud arrives directly over this
point, the tension is sufficient to overcome
the resistance along that line, a discharge
VIII take place, and the tree will be struck
But if tire tension be not sufficient the
cloud will pass harmlessly over. Hence
it appears that a person standing during
thunderstorm beneath tree so situat-
ed is exposed to some risk.
On no account, therefore, should the
traveller take refuge under an isolated tree:
generally he will do well TO avoid its
neighborhood altogether; but should he
be overtaken by the storm when on
plain with no shelter near, the tree may
still be made to afford him some protec-
ton If he take up q position near it,
but moi under its branches he will prob
ably escape unhurs 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 influence of the stroke; to remain at
| much greater distance away is to place
ones self in the same conditions of lso-
iation as the tree itself 1t will have
been remarked by ali 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 a numerous group.
When there are many trees together, their
| Collective con6uctivitY 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
| film 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.
| 1t appears, therefore, that the safest
situation during thunderstorm is in the
midst OF wood, partcu arly 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 efectually shielded
from harm. The greatest risk of injury
from Lightning is undoubtedly incurred
by persons Travelling across a wide and
very flat plain, because In such situation
they are the only elevated objects. To
lessen the risk, which may here be some
what serious, advantage hould be taken
of whatever fluctuations of surface may
exist TO keep upon the lowest ground.
No doubt the PROSTATE position would IN
these circumstances afford greater secur-
lty than the erect. 1t happens not unfre-
quently that animals are killed by light
ming under tree to which they had
betaken themselves for shelter In these
cases the tree is struck partly in conse-
quence OF It's isolation, and partly on ac-
count Of the presence of the animals be.
meath it.
Usually there are several and often
/
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.
Who has not noticed the cloud Of vapor
that IN the early morning and in certain
states OF the weather hangs over flock
of sheep or heard OF kine2 The column
OF moist air ascending through the
branches of the tree toward the cloud Of
fers, in consequence of the comparatively
| high conductiyity Of water, favorable
passage of the electricity. A herd of
cattle under an isolated tree is thus ex-
posed to double risk: also it is evident
that these animals are in the open
country less secure from injury than hu.
man being, who cannot affect tie atmos-
phere in like egree.-Cham1er's Jour
nal.