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172
Wonderful Balloon Ascents; Or, The Conquest of the Skies
·
Fulgence Marion
27
The
balloon
is
never
entirely
filled,
for
the
atmospheric
pressure
diminishing
as
it
ascends,
allows
the
hydrogen
gas
to
dilate,
in
virtue
of
its
expansive
force,
and,
unless
there
is
space
for
this
expansion,
the
balloon
is
sure
to
explode
in
the
air.
An
ordinary
balloon,
with
a
lifting
power
sufficient
to
carry
up
three
persons,
with
necessary
ballast
and
materiel,
is
about
fifty
feet
high,
thirty-five
feet
in
diameter’
and
2,250
cubic
feet
in
capacity.
Of
such
a
balloon,
the
accessories--the
skin,
the
network,
the
car--would
weigh
about
335
lbs.
To
find
out
the
height
at
which
he
has
arrived,
the
aeronaut
consults
his
barometer.
We
know
that
it
is
the
pressure
of
the
air
upon
the
cup
of
the
barometer
that
raises
the
mercury
in
the
tube.
The
heavier
the
air
is,
the
higher
is
the
barometer.
At
the
level
of
the
sea
the
column
of
mercury
stands
at
32
inches;
at
3,250
feet--the
air
being
at
this
elevation
lighter--the
mercury
stands
at
28
inches;
at
6,500
feet
above
sea
level
it
stands
at
25
inches;
at
10,000
feet
it
falls
to
22
inches;
at
20,000
feet
to
15
inches.
These,
however,
are
merely
the
theoretic
results,
and
are
subject
to
some
slight
variation,
according
to
locality,
&c.
Sometimes
the
aeronaut
makes
his
descent
by
means
of
the
parachute,
a
separate
and
distinct
contrivance.
If,
from
any
cause,
it
appears
impracticable
to
effect
a
descent
from
the
balloon
itself,
the
parachute
may
be
of
the
greatest
service
to
the
voyager
at
the
present
day
it
is
chiefly
used
to
astonish
the
public,
by
showing
them
the
spectacle
of
a
man
who,
from
a
great
elevation
in
the
air,
precipitates
himself
into
space,
not
to
escape
dangers
which
threaten
him
in
his
balloon,
but
simply
to
exhibit
his
courage
and
skill.
Nevertheless,
parachutes
are
often
of
great
actual
use,
and
aeronauts
frequently
attach
them
to
their
balloons
as
a
precautionary
measure
before
setting
out
on
an
aerial
excursion.
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