The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1900-05-26
Speaking by Sunlight.

duSSlnlJH uuTlllS IHS siege was transmitted
from the beleaguered town to General
Butler by means of either the heliograph
or fashlight.
Eight hundred years ago North Africa
had a system of wireless telegraphy by
which places hundred miles apart could
exchange messages in a few seconds. In
Algiers buildings were erected on promi-
nent sites over the land, with adjustable
mirrors on the roofs. The suns rays fall
ing on these mirrors were flashed in the
sky, and were visible at great distances
1t was easy to arrange plan by which the
flashes off different length should mean
various letters, and so make it possible to
exchange conversation.
Then the world went to sleep, and it
was not till the time of the Crimean war
that the possibility of talking by sunfash
began to arouse attention. The Russians
used mirrors for this purpose largely when
they were besieged at Sebastopol, and this
led the English army to examine the mat
ter, but 1t was not until thirty years later
that the mirror telegraph, as some call
ed it. was adopted by the Indian army
In 1885 experiments were begun by the
English army with the heliograph, and
they were so satisfactory that four years
later every regiment and battalion in the
service was supplied with two
Since then there has not been military
campaign without abundant demonstrations
Of its usefulness
In the recent campaigns against native
tribes in Northern India the heliograph
was invaluable, and by it the most outlying
posts were kept in constant touch with
headquarters. Your enemy can cut the
wire Of your field telegraph line; he cannot
intercept the flashes of your mirrors.
Many years before this, in the Transvaal
war of 1850, one of the besieged British
garrisons tried by every possible means to
open up communication with other British
forces many miles off Runners were in
tercepted, messages never got through.
At last bright idea struck one of our
officers. There was no heliograph with
our troops, but the officer got shaving
mirror and used an ordinary cloth cap as a
shade. He put the mirror at an angle to
reach where he thought the British relief
column might be, and started flashing in
the SKY by quickly covering and exposing
the mirror with his cloth cap. At first
came no response.
The work was continued, the signal word
being flashed around all likely places.
Then there came fash back from the far
distance With strainiug eyes and beating
hearts the besiesed men read out the
signals, sent from scores of miles away:
''All well Reliefquiokly coming.
What Is the heliograph? Briefly, ii is
circular adjustable mirror or mirrors,
usually mounted on a tripod stand, and
with sighting arrangement attached
The mirror is adjusted until the shadow
from the sighting rod { the rod which stands
out in front Of the glass; falls exactly on
an unsiivered spot in the centre of the
glass, The unsilvered spot, the point of
the sightrod. and the distant object which
it is wanted to reach have to be brought in
the same line of sight
There is also a rear screw arrangement
by which the mirror can be moved to the
right or left, without disturbing the sight
ing, so as to follow the apparent motion of
the sun A shutter is 50 placed that it
intercepts the DETECTION from the mirror,
which Is operated by key at the bottom
Of the mirror.
The operator, by depressing, the key,
moves the mirror, and so permits the flash
of the hight to be reflected \ short de
preston reflects a short fash, and long
depression longer flash This enables
the Morse alphabet to be used-the ordi-
nary dot and dash system of the telegraphic
instrument.
The distance which these sun flashes
will travel is hardly credible The record
was made by Captain w A. Glassford, of
the United States Army Signalling Corps,
who in some experiments in Western
America, succeeded in opening up and
maintaining communication between Mount
Ellen Utah, and Mount Uncompahgre,
Colorado hundred and eighty-three
miles apart He used an eight inch
mirror.
The larger the mirror the farther it is
possible TO flash. The ordinary English
service pattern is five inches in diameter.
1t is only in very clear sunshiny country
that long distances can be covered. In
England it would probably be impossible to
send message more than twenty miles,
save under unusual conditions Our climate
makes the hehograph comparatively use
less here
When it is required to send message
to a place in such direction that the opera
tor stands with the sun behind him, a
duplex mirror has to be used, so that the
sun's rays are caught on one glass and
sent back on the other. This involves
careful adjustment, and is more compli
.atal tb,n ,rhau tho c,n - IN front