Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1901-10-18
LIGHTNING FLASHES.
HOW THEY ARE EVOLVED AND THE
ENERi3Y THEY POSSESS.

Cities Have Little Cause to Fear
These Mysterious and Destructive
Balls From the Clouds.
Without doubt lightning was the first
electrical phenomenon that was observ-
ed by human beings. To this day it
remains the least known and least I'M
derstoOd Of natural electrical manifes-
tations 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 Il discharge from Il
cloud nj high potential with refer
ence to the earth. When the atmos-
phere Is charged with wafer vapOr and
some eddy or current in It's colder up
per strata is DETECTED downward. caus-
ing condensation. exceedingly minute
drops OF water are formed. each bear
ing an electrical charge. The CONSOLE
dalton OF these into larger drops results
in very great increment of the poten-
tial 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 it
takes, for example. eight drops cOnsoli-
dated TO make one of twice the diane
ter of the constituent drops. and the
charge on the surface of the CONSOLE
dated drop will be four times as great
as that upon the surfaces of its ele-
ments. In this way. as the small wa
ter particles unite to form drops which
fail as rain, the potential of the charge
they carry increases until ii attains
enormous values. and the lightning
fash leaps TO the earth. which may be
regarded simply as a body of very
great electrostatic capacity. The dis
charge. which is called lightning, is
apt to be more or less destructive, al
though the energy of an individual
flash is perhaps not very great. Often
the conditions are such that the dis
charge takes on an oscillating charac-
ter, producing violent surgings of cur
rent. No very accurate measurements
have been made upon the current in
volved. hut IL is taken To- be of the or
der of 1000 TO 5000 amperes. The
electro motiv9iorce necessary to cause
u fash mile long is probably several
million volts, and of course the power
of the flash measured in watts is very
great. but fits duration is correspond
ingly short
Protection of property and life from
lightning flashes has been a subject
that has entrained 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-
oeedingly small, although occasional
fires are caused by it. especially where
gas pipes abound.
Protection of electric, circuits from
lightning has been an interesting SUBJ
feet for research for a number of years.
and several highly efficient devices
have been constructed for this purpose.
Today lightning is little feared by the
station superintendent and should re
very little feared by any one. The
time hOnored rule that 1t is wisest to
keep i'm the open and not seek the shell
ter of trees is one which common pru-
dence dictates. Recourse to the feath-
er bed of our ancestor however. is no
longer necessary exc TO quiet the
nerves OF timorous persons. while the
ancient superstitiOns regarding han
ding steel instruments and sitting in
drafts may be utterly disregarded. \
modern building in Il city is as nearly
absolutely lightning proof and those in
it are as nearly absolutely protected
from lightning as is possible.-Electric-
al Review.