The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1901-11-17
THE COLOR OF LIGHTNING
SUCCESSFUL PHOTOGRAPH OF SPEC
TRUM AT HARVARD
A New Field Opened to the Physicist
-ScIentihc value eft These Ex-
periments with the Camera.

~
CAMBRIDGE, Mass, Nov l6--The hrst
successful experiments IN photographlng
the spectrum OF ughtning-the divisions of
color which combine 10 produce the white
glare OF the lightning fash and offer the
physicist his opportunity TO anaiyze the
elements that compose it's announced IN
a circs'ar sent out to-day by Prof. E. G
Pickering. ne director Of the Harvard OBJ
servatory.
The photographs were obtained at the OBJ
servatory last summer with the same appa-
ratus that IS used in photographing the
spectra Of the stars, consisting of a big
eight-inch or ~eleven-inch telescope with a
camera at one end and a prism at the 9TH
er. the latter being placed in front of the
objective lens so as to break up the object
photographed into parallel bands of color.
which are seen in the photograph by diff
ferences in degree of black and white. The
effect will be familiar to anyone who re-
calls the colored border produced by the
pendant glass prisms on the old-fashiOned
lamps. Photographic spectra, however,
range only from yellow 10 blue. the ex-
IRENE colors. violet at one end and red at
the other, as seen in the rainbow, which
s. the spectrum of the sun. being impos-
sible 70 record by the camera.
The scientific value Of these spectra arises
from the fact that the various elements of
the atmosphere, as well as the various ele-
ments Of solid bodies under the influence
OF intense heat. give off different colors,
by which they can be differentiated. The
element OF hydrogen, which is found in
the spectra Of nearly all stars. produces a
series Of well-marked lines quite different
from those made by the element Of iron,
for example, found In some but not all
stellar spectra. The photograph Of a star
spectrum is not so much a photograph of
the star as Of the luminous vapor immedi-
ately surrounding it, from which it is posi-
bic TO deduce the constitution of the burn
ing mass of the star itself.
NEW FIELD OF STUDY.
The successful photographing OF the spec
trum OF lightning is an achievement that
opens a new field of comparative study.
The photographs s~ecured-three of them
taken in July by Mr.. J. II. F~reese, OF Har-
ward, and one by the same observer in
September-include several flashes. and
naturally suggested immediate comparison
with the stars. These comparisons are given
at length in Professor chickering's circular.
Briefly. it may be said that the hydrogen
lines are found 10 be very much like those
shown by the spectra of new" stars, such,
for example. as Nova Persei, the discovery
of which by the Edinburgh astronomer.
DR.. Anderson. is still fresh in the public
mind. The chief difference is that the
spectrum OF the Nova Persei shows dark
lines. proving the presence of a solid body.
while the lines of the spectrum of lightning.
which is simply a fash in the sky. are all
49, .-aN-- g-4a-m-4ga-
shows that the hydrogen lines CT a light
hing flash that illuminated the whole heav-
rms correspond almost exactly with those
Of a little quarter of an inch fash Of light
ping produced artifcially in a small tube
81 in the open air.
Photographic star spectra is. CT course.
nothing new at the Harvard Observatory,
shere stellar photography has been more
fully developed. perhaps, than anywhere
else, so that it may seem strange at 1rst
glance that the Harvard Photographic tel
escapes should not have been earlier
utilized in the study of lightning. The main
difficulty lies in the fact that lightning is
almost always accompanied by rain and
that the rain interferes with the use of the
telescope. Last summer. however. there
were several opportune dry showers
clouds and lightning without rama con-
dition which made it possible to secure the
much desired pictures.
\ LIGHTNING SPECTRUM.
The process by which the lightning spec
trum has thus been finally captured. as
described by Mr.. King of the observatory.
who directed the work, is not unlike that
of taking a snapshot with a pocket camera,
with the important exception that the APP
paratus is larger than the photographer.
When the stars are photographed, this APP
paratus sometimes weighing several tons,
moves by cIockwork. following the move
ment OF the celestial bodies. The rate OF
speed. however. Is a very small fraction
faster than that of the star itself, in order
that the star may trail somewhat in the
photograph. thus producing a spectrum in
which the colors are spread out more
conveniently than if the star were secured
IN a seemingly stationary position
Lightning Is an obviously different mat
ter. Where the flash will come can only be
guessed at, and the instrument Is con-
trolled. therefore. not by and
electrical attachments, but by the hand of
the operator. The fash itself. once II
comes in the field OF the telescope, is an
automatic, or natural, flash light.
The situation. however. is further compli-
Gated by the fact that the prism refracts
the ightning-thEt is to say. the lightning
enters and leaves the prism at an angle
and the telescope must be aimed not at
the flash but at a certain number of de-
grces. according 10 the prism in use, TO
one side of it. There is. of course, no pos
sibiIitv of "A time exposure. and the sue
cess of the photograph depends upon the
good luck as we'll as the good Judgment OF
the man behind the telescope.