The Wichita daily eagle., 1892-10-20

LIGHTNING NOT zIGZAo.
Popular Errors Corrected BY tho Photo.
YraDhSc Lana


LIGHTNING NOT ZIGZAG.
Popular Errors Corrected BY tho Photo
graphic Lens.
Several traits of lightning have been
discovered by photography that were
not previously suspected. This is par
ticularly true of the course taken by a
thunderbolt. So ephemeral is the fash
it seldom lasts over a two hundredth
part of second, and some authorities
say that occasionally it endures only a
millionth--that the eye can distinguish
beyond the general route traversed
The poetic and popular conception OF
the path of lightning is that
it is a series of zigzigs much
sharper than those OF Vir-
ginia rail fence. Photography, proves,
however, that the track does not con-
tain single angle, but is sinuous, like
river. 1t is curious fact that in 1855.
before this fact was thus esta bllshed,
Mr.. James Nasmith declared to the
British Association for the Advance
ment of Science that he had never OBJ
served the zigzag form of lightning, but
that to his eye the fash always ap-
peared as in diagram which he offered,
showing only curves, and with or with
out branches or forks.
1t is now evident that he was an ex-
ceptionally keen observer. Photographs
reveal not only the sinuosity of the
track, but also the ramifed character of
many flashes. Sometimes the ilaments
diverging from tho main line are as
numerous and delicate as the rootlets of
a tree or the small tributaries to river.
Whether these branches flow into or
out of the principal stream it is not
easy to say; yet electricity often dis
charges itself by number of routes,
the quantity of fluid taking each one
being in proportion to the conductivity
of tho air or other substance through
which the current at that point passes.
Those photographs of ramified light
ming render much more Ineligible
than was formerly the case In some of
the stories of thunderbolt freaks Un-
questionably, instead of one solitary
current skipping to and fro around
room or among several buildings, as
has been supposed was the case in sew
cral instances, the stream has divided
into several, each taking tolerably
direct course to the earth.
Besides the sinuous and ramifed
types, photography shows the exist
ence of ribbon-like streak, fat, thin
and wavy, quite distinct from other
forms Then, too. there is the mean
dering' variety, which wanders all
over creation without any distinct aim.
Still another record made by photogra-
ply is called dark" lightning, because
the streak produced, when a print is
made from the negative, is black and
not white. Precisely how this effect
is caused has not yet been satisfactorily
explained One suggestion is that
1t is due to over-exposure of the
Photographic plate. A similar result is
obtained with the sun sometimes, where
the very intensity of the light reverses
the effect. 1t might also, it is thought,
be produced by previous fash occur
ring just before the plate was exposed,
and leaving a line of nitrous oxide in
the air along its route. A subsequent
flash, slightly further away, would IL
illuminate the whole field, but fail to
penetrate this streak. Absorption of
the rays would occur somewhat as in
the case of gas in the spectrum.
An interesting photograph is repro
duced in knowledge, a British scientific
periodical. 1t was taken with a lens
attached to the vibrating clapper of a
small electric bell which made nine
strokes to the second. The picture
Eives three distinct traces, sinuous but
parallel, and indicating that within a
twentieth of a second three discharges
occurred over precisely the same route.
To the observer these probab bly, seemed
to be one fash, possibly with little
quivering. The eye can, however,
sometimes detect three or four separate
flashes like these in close succession and
following the same path. Neither those
which this photograph records nor
those distinguished by keen observers,
however, are to be confounded with the
electric oscillations between sky and
earth which sometimes occur. These
latter, SAYS Prof. Elihu Thomson, are
too rapid to be perceived. New Haven
Palladium.