The Hartford herald. [volume] (Hartford, Ky.) 1875-1926, 1912-07-31
1t is the Result of Voltage
Inequalities.
WHICH FORM IN THE CLOUDS
A Scientific Dissertation Pur-
porting to Enlighten
Investigators.
LIGHTNING RODS ALL RIGHT

In a recent paper read before the
Electrical Section of the Franklin
Institute DR.. Charles Proteus Stein
metz, the electrical genius of the
General Electric Company, disclos-
| ed some very interesting facts
! about lightning. and thunder in gen.
eral.
I'm the early days lightning was
explained as the discharge of the
Clouds" says DR.. Steinmetz. THE
clouds were thought to be positive
ly charged and the ground mega
lively charged, the sparks jumping
from the cloud to the ground. Spec
ulations were made as to how the
clouds became charged and as then
the only method of producing cleo
/ tricity was by friction, II was said it
might be the friction of the vapor
! through the air, or the raindrops
| through the air, or some other form
of friction. That explanation used
to appear satisfactory, but with our
present knowledge of dielectric
phenomena, it is not satisfactory
any more.
ut was thought that lightning
was the discharge from the cloud
! to the ground. That means that
the electric field between the cloud
| he ha hp
breakdown strength of the air. In
uniform field the breakdown
strength of air is about $4,000
| volts per inch, or nearly million
volts per foot. Even if the cloud
is only 1000 feet above ground,
this would require a thousand mil
lion volts. If there were an cleo
,trostatic field between the cloud
and the ground of a thousand mil
lion volts extending over the whole
area of the thunder cloud, this
would represent such an immense
amount of electric energy that 1t
is inconceivable how any reason
able source of energy can produce
it: how il can exist without hav-
ing a destructive effect far beyond
anything known of lightning. Fur
thermore, a uniform field cannot
we'll exist between clouds and
ground. on account OF the uneven
ness of the ground surface.
I'VE cannot consider the light
ming discharge as a simple electric
rupture in the same way that an
overloaded beam may break me-
chanically. but as an equalization
of internal stresses, such as a piece
of hot glass that is rapidly chilled
and thereby full of internal COM
preston and tension strains, sud-
denly breaking all over by the in
ternal stresses. So with our pres
ent knowledge we must consider
this as the most probable eXplana-
tion-although not certain by any
means-that the lightning dis
barge is the phenomenon of the
equalization of internal electric |
stresses in the cloud, and is analo-
gous to the splintering o rbreaking
of an unevenly stressed brittle ma
terial, like glass. Lightning dis
charges are the result of the volt
age inequalities, produced in the
clouds by the unequal rate of con-
glomeration of rain particles, due |
to the unequal cloud density.
"Tn agreement with this is that
heavy lightning strokes are usually
followed by heavy downpour OF |
rain; in reality they are preceded |
and caused by it, but 1t takes time
for the raindrops to come down.
THE lightning rod is a great pro-
lection, and l would not like to be
in an exposed place without such
protection. But you must not ex-
pect that one rod on the end of the
building will completely protect the
other end a hundred or more feet
away. There must be sufficient rods
to extend their protective zone over
the entire area; the apex of the
roof and other projecting edges
must be protected by connecting
wires, &C. That is. like any other
apparatus, the lightning rod protec-
ton must be installed intelligently
and properly to be elective. But
the general principle is correct
only 1t must be nationally applied"
t Electrical News.