Evening journal., 1902-09-27
MYSTERIES Oh
LIGHTNING FLASH
How II Is Evolved and The
Energy Which it
Possesses

AVDDCNDOD
Without doubt lightning wsa the first
electrical phenomenon that was obscrv-
ed by human beings. TO this dag lt
remains the least known and least un-
derstood Of natural clccalcal ianaifes-
tatlons except perhaps the aurora.
There Is Il vast deal Of popular mis-.
conception concerning the danger OF
lightning aud the nature cf 1t. The
lightning fash Is a discharge from a
cloud at a high potential with refer
ence TO the earth. When the atmos
phere is charged with water yapor and
some eddy or current in it's colder up
per strata Is detected dowaward. caus-
ing condensation. exceedingly minute
drops Of water are formed, each bear
Ing an electrical charge. The consol-
dation Of these into larger drops results
In a very great Increment Of the potcn-
tlal Of tho charge since the capacity OF
the drop yarles with It's diameter and
the volume Of the drop with the cube
Of the diameter.
The consequence OF this is that II
takes, for example eight drops consoli-
dated tosmake one Of twice the diane
ter Of the constituent drops. and the
charge on the surface Of the consoll-
dated drop win he four times as grea.
as that upon the surfaces Of It's ele-
ments. In this way, as the small wa
ter PARTICLES unite TO form drops which
fall as rain, the potential Of the Charge
they carry increases until it attains
enormous values, and the lightning
flash leaps TO the earth. which may be
regarded simply as a body Of very
great electrostatic capacity The dis
charge. which h called lightning. Is
apt to be more or less destructive. al.
though the energy Of an individual
fash Is perhaps not very great. Often
the conditions are such that the dis
charge takes on an osclllating charac-
ter producing violent surglngs Of cur
rent No very accurate measurements
have been made upon the current in
volved, but It Is taken TO be of the or
der Of 1000 to 5000 ampercs The
electro motive force necessary to cause
n fash a rile long is probably several
million volts ana 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 entralned the attention OF
natural philosophers since franklin
sent up his historic kite. The net re-
suit Of more than century Of attempt
TO secure protection has been the light
ming rod In its more or less inefficient
forms and the discovery that buildings
Of modern construction, having metal
lie roofs and often metallic frames as
well, are practically Immune from at
tack by lightning.
The total number of deaths due to
lightning in any given summer Is com
paratively very small-in the ratio OF
about one to each 100000 population in
the United States. In cities the de-
structive influence Of lightning is ex-
ceedlngly small, although 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 devices
have been constructed for this purpose.
To-day lightning is little feared by the
station superintendent and should be
very little feared by any one. The
time honored rule that It is wisest .
keep In the open and not seek the shell
ter of trees is one which common pru-
dence dictates Recourse 10 the feath-
or bed OF our ancestors, however. Is no
longer necessary except to quiet the
nerves Of tlmorous persons. while the
ancient superstitlors regarding han
ding steel Instruments and sitting In
drafts may he utterly dlsregarded. A
modern building IN a city Is as nearly
absolutely lightning proof and those In
1t are as nearly absolutely protected
from lightning as Is possibie.-ElectrIc-
al Review.