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1036
Enquire within upon everything
·
Robert Kemp Philp
375
Because
the
weight
on
the
surface
of
the
mercury
frequently
leans
against
the
side
of
the
tube,
and
does
not
move
freely.
And,
also,
the
mercury
clings
to
the
sides
of
the
tube
by
capillary
attraction;
therefore,
tapping
on
the
face
of
the
barometer
sets
the
weight
free,
and
overcomes
the
attraction
which
impedes
the
rise
or
fall
of
the
mercury.
978.
Why
does
the
Fall
of
the
Barometer
denote
the
Approach
of
Rain?
Because
it
shows
that
as
the
air
cannot
support
the
full
weight
of
the
column
of
mercury,
the
atmosphere
must
be
thin
with
watery
vapours.
979.
Why
does
the
Rise
of
the
Barometer
denote
the
Approach
of
Fine
Weather?
Because
the
external
air,
becoming
dense,
and
free
from
highly
elastic
vapours,
presses
with
increased
force
upon
the
mercury
upon
which
the
weight
floats;
that
weight,
therefore,
sinks
in
the
short
tube
as
the
mercury
rises
in
the
long
one,
and
in
sinking,
turns
the
hand
to
Change,
Fair,
&e.
980.
When
does
the
Barometer
stand
highest?
When
there
is
a
duration
of
frost,
or
when
north-easterly
winds
prevail.
981.
Why
does
the
Barometer
stand
highest
at
these
Times?
Because
the
atmosphere
is
exceedingly
dry
and
dense,
and
fully
balances
the
weight
of
the
column
of
mercury.
982.
When
does
the
Barometer
stand
lowest?
When
a
thaw
follows
a
long
frost,
or
when
south-west
winds
prevail.
983.
Why
does
the
Barometer
stand
lowest
at
these
Times?
Because
much
moisture
exists
in
the
air,
by
which
it
is
rendered
less
dense
and
heavy.
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