The morning news. [volume] (Savannah, Ga.) 1887-1900, 1892-09-03
LIGHTNING NOT zIGzAG.
Popular Errors Corrected by the Pho
tographic l. ans
From the Neto Haven PaHadt,,i

From the Neto HGUer Palladium.
Several traits of lightning have been dis
covered by photography that were not pre-
vtously suspected. This is particularly
true Of the course taken by a thuuderbols .
So ephemeral is the flash-it seldom lasts
over two-huudredth part of a second. and
some authorities say that occasionally il en-
dures only millionth-thAt the eye can dis
tlnguish little beyond the general route
traversed. The poetic ana popular concep-
ton OF the path of lightning is that il
Is series OF zigza2s much sharper than
those OF a Virginia rail fence. Photography
proves, however, that the track does not
contain single angle, but is sinuous, like
a river 1t is curious fact that In 1855.
before this fact was thus established, James
Nasmith declared to the British Association
Tor the Advancement OF Science that he
had never observed the zigzag form of
lightning, but that to his eve the fash
always appeared as in a diagram which be
offered, showing only curves, and with or
without branches or forks
1t is now evident that he was an excep-
uonslly keen observer. Photographs reveal
not only the sinuosity of the track. but also
the ramihed character Of many flashes,
Sometimes the filaments diverging from
the main line are as numerous and delicate
EFlDu-
tarfes to river. Whether these branches
flow into or out of the principal stream il is
not easy to say; yet electricity often dis
charges itself by a number of routes. the
quantity OF fluid taking each one being in
proportion to the conductivity of the air
or other substance through which the cur
rent at that point passes The photographs
OF ramihed lightning render much more in
telligiole than was formerly the case some
OF the stories Of thunderbolt freaks. I'M
questtonably instead Of one solitary cur
rent skipping to and fro around a room or
among several buildings, as has been sup
posed was the case In several instances, the
stream has divided into several, each taking
tolerably direct course to the earth.
Besides the sinuous and ramified types,
photography shows the existence of ribbon
like streak. fiat, thin and wavy, quite dis
tinct from other forms. Then, too, there
is the "meandering" variety, which wanders
all over creation without any distinct aim
Still another record made by photography
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 sug-
gestion is thatit Is due to over exposure of the
Photographic plate. A similar result is OBJ
tanned with the sun sometimes, where the
very intensity Of the light reverses the
effect. 1t might also, It is thought be pro
duced by previous flash occurring lust
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 illumine 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 reproduced
in knowledge, British scientific periodical.
1t was taken with lens attached to the
vibrating clapper Of a small electric bell
whicn made nine strokes to the second. The
picture gives three distinct traces, sinuous
but parallel, and indicating that within a
twentieth Of second three discharges oc-
CURED over precisely the same route. To
the observer these probably seemed to be
one fash. possibly with q little quiverine.
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 obs
servers, however, are to be COMPOUNDED with
TIE electric oscillations between sky and
earth which sometimes occur. These latter.
says Prof. Elihu Thomson, are too rapid to
be perceived.