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210
The Fairy-Land of Science
·
Arabella B. Buckley
54
Our
next
question
is
as
to
the
weight
of
our
aerial
ocean.
You
will
easily
understand
that
all
this
air
weighing
down
upon
the
earth
must
be
very
heavy,
even
though
it
grows
lighter
as
it
ascends.
The
atmosphere
does,
in
fact,
weigh
down
upon
land
at
the
level
of
the
sea
as
much
as
if
a
15-pound
weight
were
put
upon
every
square
inch
of
land.
This
little
piece
of
linen
paper,
which
I
am
holding
up,
measures
exactly
a
square
inch,
and
as
it
lies
on
the
table,
it
is
bearing
a
weight
of
15
lbs.
on
its
surface.
But
how,
then,
comes
it
that
I
can
lift
it
so
easily?
Why
am
I
not
conscious
of
the
weight?
To
understand
this
you
must
give
all
your
attention,
for
it
is
important
and
at
first
not
very
easy
to
grasp.
you
must
remember,
in
the
first
place,
that
the
air
is
heavy
because
it
is
attracted
to
the
earth,
and
in
the
second
place,
that
since
air
is
elastic
all
the
atoms
of
it
are
pushing
upwards
against
this
gravitation.
And
so,
at
any
point
in
air,
as
for
instance
the
place
where
the
paper
now
is
as
I
hold
it
up,
I
feel
no
pressure
because
exactly
as
much
as
gravitation
is
pulling
the
air
down,
so
much
elasticity
is
resisting
and
pushing
it
up.
So
the
pressure
is
equal
upwards,
downwards,
and
on
all
sides,
and
I
can
move
the
paper
with
equal
ease
any
way.
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