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1
1036
Enquire within upon everything
·
Robert Kemp Philp
374
[NOR
BREAK
THE
TIES
OF
FRIENDSHIP
NEEDLESSLY.]
973.
Hints
on
the
Barometer.
974.
Why
does
a
Barometer
indicate
the
Pressure
of
the
Atmosphere?
Because
it
consists
of
a
tube
containing
quicksilver,
closed
at
one
end
and
open
at
the
other,
so
that
the
pressure
of
air
upon
the
open
end
balances
the
weight
of
the
column
of
mercury
(quicksilver);
and
when
the
pressure
of
the
air
upon
the
open
surface
of
the
mercury
increases
or
decreases,
the
mercury
rises
or
falls
in
response
thereto.
975.
Why
is
a
Barometer
called
also
a
"Weather
Glass"?
Because
changes
in
the
weather
are
generally
preceded
by
alterations
in
the
atmospheric
pressure.
But
we
cannot
perceive
those
changes
as
they
gradually
occur;
the
alteration
in
the
height
of
the
column
of
mercury,
therefore,
enables
us
to
know
that
atmospheric
changes
are
taking
place,
and
by
observation
we
are
enabled
to
determine
certain
rules
by
which
the
state
of
the
weather
may
be
foretold
with
considerable
probability.
976.
Why
docs
the
Hand
of
the
Weather
Dial
change
its
Position
when
the
Column
of
Mercury
rises
or
falls?
Because
a
weight
which
floats
upon
the
open
surface
of
the
mercury
is
attached
to
a
string,
having
a
nearly
equal
weight
at
the
other
extremity;
the
string
is
laid
over
a
revolving
pivot,
to
which
the
hand
is
fixed,
and
the
friction
of
the
string
turns
the
hand
as
the
mercury
rises
or
falls.
977.
Why
does
Tapping
the
Face
of
the
Barometer
sometimes
cause
the
Hand
to
Move?
Marker
Marker
Fine marker
White-out
Fine white-out
Circle
Paint
Unmarker
Hand
Scalpel
Dice
Sieve
Purify
Undo
Redo
Start over
