The Red Cloud chief., 1888-09-14
AERIAL P~HorocRAPrY.

AERIAL PHOTOGRAPHY.
An Ingenious Process Recently Patented
by . Chicago Ar;ist.
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. bu,
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 sharpshOOtcr 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 a few years later-par-
ticularly in the ncighbOrhOOd of Paris
both French and German scientists
undertook the enterprise Of securing
photographs of the opposing hostile
calnps and movements. but only with
partial success. Since then photo
graphic departments have been at
tached to nearly all the European
armies, and numerous discoveries have
been made in the management of bal
looms ut elevations of from 5000 to
10000 feet.
II. j. Steffens. photographer of this
city, has recently secured letters
patent for a new system of aerial
photography, which promises to be OF
value both for military and CONNER
-cial purposes. 1t is a combination Of
instantaneous photography controlled
by electricity. and Il hydrOgen-illed
balloon capable of supporting a weight
of not more than thirty or forty pounds
at an elevation of 5000 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 =
nickel apiece. and is filled with hydro
gen gas made from the decomposition
Of zine by sulphuric acid apd passed
through Il bath of sillicate ofsOda. SO as
to remove all traces of oxygen. To the
balloon is attached the camera. the me-
chanism of suspension being arranged
sOas 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
keen 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 a large compass which
vas ~de.icately adjusted to it. The
camcra is constructed somewhat upon
the general plan of those used in TAX
ing photographs of horses running ut
full speed. and the delicate machinery
for making the exposure and moving
on the rollers the scnsitiZed paper il
manipulated from the ground by the
operator through the means OF an Or
binary 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-
ton is made with a battery of three
Or four cells. or rs 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 Gamers
to the compass. attach it to the balloon.
and then let it 60 alOft to the height
required. A click on the key AUS
an instantaneous exposure; the ma
chinery in the interior of the Gamers
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
rOllerin 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-a recent inven-
tion-and will take a picture without
any disturbance at any distance be-
yOnd a focus OF seventy feet. At al
elevation Of about $500 feet, the lens
having u visual angle of 60 degrees.
the field of observation would he a
circle having a diameter OF n mile.
II agreater field of observation were
required at the same height it would
become necessary to S a lens having
a greater visual angle than GO degrees.
Chicago Tribune.
How to Measure Ones Growth.
One may measure his " growth by
looking back upon his own record Of
his likes and dislikes. his thoughts and