Union County courier. [volume] (Elk Point, Union County, D.T. [S.D.]) 187?-1913, 1892-09-02
THE HELI0uRAPn:
How Communicable Hetwcea DlItAnt
Points IL Reached Dy Reflectins ~
SUMS Rays

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Heliography Is the name applied 70 ths
method Of commnniating between. dis.
tant points in N6le Gsual signals are
obsaiasd by Esaad pg Ga 1 RI. ], q 81 ~ =
mirrors ID the right direction. AZ !
matter of course, the method can only
be employed where the sky is free from
clouds and the atmosphere clear for con-
siderable periods of time, and the fact
that no place is free from sudden atmo-
spheric changes makes the establishment
Of permanent photographic stations unad.
In military signalling heliog-
raphy has been found to possess great
over other methods, particu-
larly on account of the portability of the
and in coast and geodetic
surveys it has been found invaluable.
TO those who have not studied the
phenomena attending the reflection Of
sunlight it is quite astonishing, under
favorable atmospheric conditions, at
what great distance the flash can be seen,
bright and distinct as a planet, which in
appearance it very much resembles. Only
the clouds and intervening obstacles adj
NIT the possibilities of photography.
Equipped with the proper telescope and
suitable mirrors, and stationed at the
requisite elevation, with favorable con-
ditions of atmosphere, and there is prac-
tically no limit to the distance at which
signaling can be carried ON. A little
Of certain facts will make
the truth of this statement plainly appar-
ent. The suns rays reach the
earth after travelling $4,000, 900
miles: Striking mirror simply al
ters their course, but makes very little
difference in their energy, and hence it
does not seem remarkable that they
should preserve sufficient vital force to
carry them hundred or two hundred
miles further. The moon, which is not
perhaps the best reflector, projects the
suns rays to us from distance of 232. 900
miles. The discovery of the principle in
volvcd in photography is as old as the
time of Alexander the Great, whose fleet
is said to have been piloted along the
Persian Gulf by mirrors. The aborigines
of North America long ago adopted the
policy of sun-tlashing from polished sur
faces, and the Russians made use of sun
for important signaling at the
siege of Sebastopol.
The two instrument generally used in
photography are the hcliograph and the
hcliotropc. The latter is sometimes con-
founded witls-t4el,ciioetat, but a hello
stat proper is an instrument operated by
clockwork in such a way as to reflect the
-, =. Exol l;r,,t:,r +bo
use of this instrument, the mirror is 50
adjusted that, ct a particular hour Of the
day, arranged beforehand, the light of
the sun is reflected to the surveyors sta
tion. The hcliotropc, however, is. opc-
rated by hand, and it is the instrument
which, in its moro or less improved
forms, is used by Prof. Davidson in coast
survey work. Hcliotropcs are usually
placed upon stand or table and adjust
cd to the distant signal station by the
sights over the uprights. The centre
ring is a triflc larger than one at the
end. SO that when the shadow of the
centre rim shows upon the rim of the
outer ring, the flash may be said to be in
focus, and when the sun is in front Of
the operator, that is all there is to it.
When the sun is in the rear, however, it
is necessary to make use Of another mir
ror, placing it where it will reflect the
sun on to the heliotropic mirror and
thence through the rings.
This creates steady light which has
already been described as like bright
star, but in order to keep it continuous,
the operator has to adjust the mirror
every moment or two with his hands to
conform to the motion of the earth. In
the operator usually begins
work at sunrise, and keeps his hcliotrope
in focus until the days work is practically
over. The triangulator, having that
bright daylight star for his basis, has by
that time been able to lay out considerable
drawing, and he signals the hcliotropist
to shut up shop by passing his hat over
the rays Of his own instrument given
number of times. Each party on survey
work prearranges its own signals. There
is no regular code made use of in this
work, but in the army it is quite differ
net.
The heliotrope had been in use nearly
half a century when, in the autumn Of
1889 at the Jack telegraph station in
Beloochistan, Henry c. Nance, now Sir
Henry, adapted the principle of the
heliotrope, or heliostat, to the modern
instrument since then known as the hello
graph. He conceived the idea Of con-
vcrting the fascicle Of reflected suns rays
which had previously been regarded, In
. signaling sense, as entirely passive,
into active speaking agents. This he ac-
complishcd by adapting to mirror the
means Of imparting to the reflections the
character of pulsations Of varied dura-
tions, in accordance with the Morse code.
Nance's heliograph, as now perfected for
field signaling, is the one now used in
the United States army. The mirrors are
not always Of the same size. The greater
the mirror the more powerful the flash.
There are usually two tripods,
one bearing the mirror to reflect
the sun to the signaling mirror
when necessary. The stand for the sig
mailing mirror has q sighting bar. by
means Of which perfect alignment can
be made By looking through hole made
BY scraping of little Of the silver from
the centre Of the back Of the mirror.
The obstruction Is obtained by giving a
small angular motion TO the screen mirror,
or shutter, causing the reflected beam to
travel through twice tho angle and com
pletely disappear from the distant point.
IT. working q made very similar to that
Of Morse key. Several important i'm
provements on the heliograph have been
made BY Lieut.. John r. Finlay, United