Alexandria gazette. [volume] (Alexandria, D.C.) 1834-1974, 1886-05-18
LIGHTNING.

LIGHTNING.
The researches of Professor von PetZold
Karsten, Weber, and others have proved
that the number of damaging strokes o
lighting has considerably increased during
the last fifty years, and this increase cannot
be explained by the theory that owing to
the growing number of houses, factories,
ETC., tho number oflightning strokes ircreas
cd proportionately; to the contrary, this
number ought to decrease, as every building
even when not protected by a alightning-rod
effects au equilibrium of the opposite elec.
trio potcntials, and, therefore, the number
OF lightning strokes ought relatively TO de-
crease with the growing number of build
ings. This, indeed, is proved BY the fact
that in the space OF one year among 100000
buildings there occurred but thirteen cases
of lightning strokes in cities, against twenty.
three strokes on buildings in the country.
We, therefore, have to take this natural
phenomenon from another point of view,
and to consider the ratio of damaging or
other strokes to the number of buildings in
certain district. This ratio, called by the
German naturalists blitzgefahr danger from
lightning), increased in the kingdom oil
Bavaria from 1914 to 1882 threefold (accord.
ing To records of insurance companies even
ivefold) and other countries show the
same increase. As in nature each phe-
nomenon must have its cause, the
question arises: To what cause is
due the above mentioned facts?
And this question not only is of scientific
interest, but also of great practical import
ance. A great many theories have already
been advanced to explain this phenomenon /;
among others, that, owing to the decrease OF
the woodland, houses are more and more
made the projecting points of Il certain area,
and, therefore, attract the lig ghtning beside,
this decrease effects q greater rise of tenn
perature in summer, aud, in consequence,
moro numerous thunder storms. Others
find the cause of it in the large increase of
such constructions as gas and water works,
weather. cocks, etc. But this theory does
not explain why, especially, country houses,
which commonly lack these kind OF con.
structions, are mostly exposed to danger by
lightning. Admitting that these causes
may to some extent explain the increase of
danger from lightning, they arc not sufi-
cient TO fully show the surprising increase
of strokes during 80 short period. There
must be moro genera! and fundamental
cause. Through what car the electrical
intensity during a thunderstorm be so strong
ly increased that a larger number of light
ming strokes pass over to the earth than was
the case heretofore 1t is not so much the
increasing number Of thunderstorms as
their greater force which produces the in.
creased danger
As the main cause we now point out the
enormous increase during the last fifty
years of factories, railroads, steamboats-in
short, of all constructions filling the atmos.
phere with smoke, vapors and PARTICLES of
dust of every description. When we con
slider that every day thousands of locomo-
tives. thousands of steamers go around the
earth, that thousands of factories of all
kinds daily emit enormous quantities of
smoke, vapor, and dust into the air, that,
especially in cities, the large number OF
houses produce immense quantities of smoke
and dust, the assertion will not seem in
credible, that there is certainly hundred
times the smoke, dust and gases absorbed
in the atmosphere that there was fifty years
ago. Already with the naked eye the i'm
pure state of the atmosphere may be no.
tced. Gro through the coal districts of Man.
chester, England, through those of Penn
sylvania, through the cities of Essen, Ger.
many, and Pittsburg, Pa, and you will no
tice layer of vapor constantly lowering
over them; the air is filled with foul gases
and every object is more or less covered
with the settling particles of dust.
These conditions being established, we
have to consider their relations to the vic
| lence of thunder storms. To give the read
er better conception of this relation We
will briefly discuss the theory of thunder
storm and the origin of electricity thereby
developed. Friction is now generally ac'
cepted to be the cause of the electricity in s
thunder storm. Friction between air anC
particles of ice according to Luvine) or be-
tween air and molecules of water (accord
ing to Andries) Is the main cause of that cleo
tricity. When beside these factors particles
of dust are filling the atmosphere the devel
opment of electricity is highly increased.
is the election of steam and ashes common tt
the phenomenon which causes the thunder
storms attending to it assume an exceeding
ly violent character.
That the pyramid of Cheops is rendered
electrical by the whirling dust of the deser
may here also be mentioned. It is nothin.
but the friction of the grains of sand on th
surface of the pyramid that causes electrici
ty to originate.
The author of this essay claims that tn
rapid, enormous, and lasting development
of electricity during thunder storms canno
be otherwise explained than by a purel.
mechanical cause, analogous to the nechan
icaI force of the hydro-electrical machine
Now, as our atmosphere contains 40 mucl
more dust than in former years, the fac
must be of great influence regarding the in
tensity of electrical phenomena during thun
der storms from the same reasoning or
explained volcanic eruptions. That Ibis in
creased force of thunder storms must mani
fest itself in the greater violence and NOR
dangerous character of lightning stroke