Smyrna times., 1901-10-09
LIGHTNING FLASHES.
HOW THEY ARE EVOLVED AND THE
ENERGY THEY POSSESS.

GNGnOI HEY POSSESS,
Inhabitants of COmpactIy Built
cities Have Little Cause to Fear
These Mysterious and Destructive
Balls From the Clouds.
Without doubt lightning was the first
electrical phepomenOn that was observ-
I'd by human beings. To this dav If
remains the least known and least un-
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 if. The
Hghtnlng flash is discharge from
cloud at a high potential with refer
'nce TO the earth. When the atmos-
phere is charged with water vapor and
some eddy or current in its colder nm
per strata is detected downward. cans
ing condensation, exceedingly minute
drops of water are formed. each bear-
ing an electrical charge. The cOnsoli-
datiOn of these into larger drons results
III very great increment of the DOten-
tlaI OF the charge since the capacity of
the drop varies with it's diameter and
the volume of the drop with the cube
of the diameter.
Ihe consequence of this is that if
takes, for example, eight drops consoIi-
dated TO make one of twice the diame-
ter of the constituent drops. and tbo
charge on the surface of the cOnsOli-
dated drop will be four times as great
as that upon the surfaces of its ele-
mentS. In this way, as the small wa
tor particles unite to form drops which
as rain, the potential of the charge
Aey carry increases until it attains
enormous values, and the lightning
flash leaps to the earth, which NAV 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
Hash 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, but it is taken to be of the or
der Of 1000 to 5000 amperes. The
electro motive force necessary to cause
Il flash 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
natural philosophers since Franklin
sent up his historic kite The net re-
suit of more than a 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-
ceedingly 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.
Today 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 to
keep in 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 ancestors, however, is no
longer necessary except to quiet the
nerves of timOrous persons. while the
ancient superstitions regarding han
ding steel instruments and sitting in
drafts may be utterly disregarded. a
modern building in a city is as nearly
absolutely lightning proof aad those in
it are as nearly absolutely protected
from lightning as is possible.-Electric-
al Review.
Americas Superior Schools.
In spite of excessive decentralization
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