The Savannah morning news., 1901-09-19
LIGHTNING AND ITS DANGERS.
Inhabitants of COmpacitys Built
Cities Have Little Cause to Fear.


From the Electrical Review.
Without doubt lightning was the first
electrical phenomenon that was OBJ
served by human beings. To this day
it remains the least known and least
understood of natural electrical mani
festations except, perhaps, the aurora.
There is vast deal of popular mis-
conception concerning the danger of
lightning and the nature of it. The
lightning flash is a discharge from a
cloud at a high potential with refer
ence to the earth. When the atmos-
phere is charged with water vapor and
some eddy or current in its colder up
per strata Is DETECTED downward,
causing condensation, exceedingly mi
mute drops of water are formed, each
bearing an electrical charge. The
consolidation of these into larger drops
results in q very great increment of
the potential of the charge, since the
capacity of the drop varies with its
diameter and the volume of the drop
with the cube of the diameter
The consequence of this is that 1t
takes, for example, eight drops con-
solidated to make one of twice the d.
ameter of the constituent drops, and
the charge on the surface of the con-
QIOP Will ne Jour times as
great as that upon the surfaces of it's
elements. In this way, as the small
water particles unite to form drops
which fall as rain, the potential of the
charge they carry increases until 1t at
tains enormous values and the light
ming flash leaps to the earth, which
may be regarded simply as a body of
very great electrostatic capacity. The
discharge takes on an oscillating
Oh 80
of current. No very accurate measure
ments have been made upon the cur
rent involved. but it is taken to be of
the order of 1000 to 5 900 amperes. The
electro motive force necessary to cause
a flash a mile long is probably several
million volts, and of course the power
of the flash measured in watts Is very
great, but its duration is correspond
ingly short.
Protection of property and life from
lightning flashes has been a subject
that has entrained the attention of nat
ural philosophers since Franklin sent
up his historic kite. The net result of
more than century of attempt to Sc
cure protection has been the lightning
rod.in its more or less inefficient forms,
and the discovery that buildings of
modern construction. having metallic
roofs and often metallic frames as
WClls dlC III dSOlSduJ ITO1n at
tack by lightning.
The total number OF deaths due to
lightning is exceedingly small, al
though occasional fires are caused by
it, especially where gas pipes abound
Protection of electric circuits from
lightning has been an interesting sub
ject for research for a number of
years. and several highly efficient de-
vices have been constructed for this
purpose. To-day lightning is little fear.
ed by the station superintendent and
should be very little feared by any one
The time-honored rule that It is wis
est to keep in the open and not seek
the shelter of trees is one which com
mon prudence dictates. Recourse to the
feather-bed of our ancestors, however,
is no longer necessary except to quiet
the nerves of timorous persons. while
the ancient superstitions regarding
handling steel Instruments and sitting
in draughts may be utterly disregard
ed A modern building in city is as
nearly absolutely lightning proof and
those in II are as nearly absolutely
protected from lightning as possible.