The Progress., 1888-09-22
AERIAL PHoTooRApHY.
~ lngsni0a4 PROCESS Recently Pat0ntoA
by Chicae0 Artist.

AERIAL PHOTOGRAPHY.
~ lnssnioss Process Recently PatSneeA
bys Chicago Artist.
During the war of the Rebellion,
While the contending armies lay SO
long between Richmond and the Poto-
mac, various efforts were made by
Northern engineers to obtain photo
graphs from aerial elevations of the
positions OF the Southern troops. The
attempts were made from balloons, but.
they were far from being successful.
The art of instantaneous photography
had not been pefected, if indeed it had
been more than thought Of, and the
danger OF exposure to the almost un-
erring rifle of the sharpsho hooter was so
great that few were willing to- essay
the operation except upon the most
favorable conditions of wind, weather
and situation. During the Franco
Prussian war, a few years later par
ticularly In the neighbOrhood of Paris
both French and German scientists
undertook the enterprise of securing
photographs of the opposing hostile
camps and movements, but only with
partial success. Since then photo
graphic departments have been at
tached to nearly all the Europeans
armies, and numerous discoveries have
been made i'm the management of bal
looms at elevations of from 5000 to-
10. 600 feet.
NJ. j. Steffens, photographer Of this
city, has recently secured letters,
patent for O. new system of aerial
photography, which promises to be Of
value both for military and CONNER
cial purposes It is combination Of
instantaneous photography controlled
by electricity, and a hydrogen-filled
balloon capable.of supporting weight
OF not more than thirty Or forty pounds
at an elevations of 8. 900 or 10000 feet.
The balloon is, composed of a film of
pure rubber, something like that used
in the manufacture of the little toy
articles which street fakirs sell at q
nickel apiece, and is filled with hydro
gen gas made from the decomposition
OF zinc by sulphnric acid and passed
through bath of silrEcate of soda, so az
to remove all traces of oxygen. To the
balloon is attached the camera, the me-
chanism of suspension being arranged
so as to allow of angular or rectangular
field of vision: Between the balloon
and the camera is a wind-fan to re-
duce oscillation to a, minimum, and to
keep the camera in the desired position
an ingenious arrangement has been de-
vised whereby it will remain constant
in the arbitrary relation in which it
was placed to: alarge: compass which
was delicately adjusted to it. The
camera is constructed somewhat upon
the general plan of those used in TAX
ing photographs of horses running at
full speed, and the delicate machinery
for making the exposure and moving
on the rollers the sensitized paper is
manipulated from the. ground by the
operator through the means of an or
dinary telegraph key. The cord by
which the balloon is allowed to ascend
has within it two fine threads of cop
per, which are not allowed to touch
each other. On the ground, connec-
tion is made with a battery of three
or four cells, or as, many as may be
needed. All that the operator has to
do is to insert a roll of sensitized paper
in the camera, adjust the angle OF
vision and the relation of the camera
to the compass, attach lit to the balloon.
and then let it go aloft to the height
required. A click, on the key causes
an instantaneous exposure; the ma
chinery in the interior of the camera
at the same moment begins to operate,
and when the exposure is completed
eight inches of the sensitized paper,
on which the picture has been taken,
is transferred to a second and smaller
roller in the opposite side of the camera.
The instrument is then ready for a
second view, and SO, on until the sensi-
tfzed paper a roll of forty or fifty feet
has been used;, If SO much be re-
quired. The, apparatus is then hauled
down, the gas expelled from the bal
loon, and every thing used in connec-
ton with the experiments packed
away in a box not much larger than an
ordinary valise. The lens used is of
the globular Variety recent inven-
ton and will take picture without
any disturbance at any distance be-
yond a, focus, of seventy feet. At an
elevation of about $500 feet, the lens.
having a. visual angle of 60 degrees,
the field of observation would be a.
circle. having a diameter of one mile..
If a agreater field of observation were.
required at the same height it would
become necessary to use a lens having
a greater visual angle than 60 degrees.
- Chicago Tribune
How to Measure Ones Growth. i
One may measure his own growth by
looking back upon his own record Of
his Likes and dislikes, his thoughts and
convictions, his moods and humors.
Have you an old scrap-book of your
o1-S. i r - =