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210
The Fairy-Land of Science
·
Arabella B. Buckley
127
But
why
then
do
we
not
hear
all
sounds
as
music?
Why
are
some
mere
noise,
and
others
clear
musical
notes?
This
depends
entirely
upon
whether
the
sound-waves
come
quickly
and
regularly,
or
by
an
irregular
succession
of
shocks.
For
example,
when
a
load
of
stones
is
being
shot
out
of
a
cart,
you
hear
only
a
long,
continuous
noise,
because
the
stones
fall
irregularly,
some
quicker,
some
slower,
here
a
number
together,
and
there
two
or
three
stragglers
by
themselves;
each
of
these
different
shocks
comes
to
your
ear
and
makes
a
confused,
noisy
sound.
But
if
you
run
a
stick
very
quickly
along
a
paling,
you
will
hear
a
sound
very
like
a
musical
not.
This
is
because
the
rods
of
the
paling
are
all
at
equal
distances
one
from
another,
and
so
the
shocks
fall
quickly
one
after
another
at
regular
intervals
upon
your
ear.
Any
quick
and
regular
succession
of
sounds
makes
a
note,
even
though
it
may
be
an
ugly
one.
The
squeak
of
a
slate
pencil
along
a
slate,
and
the
shriek
of
a
railway
whistle
are
not
pleasant,
but
they
are
real
notes
which
you
could
copy
on
a
violin.
I
have
here
a
simple
apparatus
which
I
have
had
made
to
show
you
that
rapid
and
regular
shocks
produce
a
natural
musical
note.
This
wheel
(Fig.
34)
is
milled
at
the
edge
like
a
shilling,
and
when
I
turn
it
rapidly
so
that
it
strikes
against
the
edge
of
the
card
fixed
behind
it,
the
notches
strike
in
rapid
succession,
and
produce
a
musical
sound.
We
can
also
prove
by
this
experiment
that
the
quicker
the
blows
are,
the
higher
the
note
will
be.
I
pull
the
string
gently
at
first,
and
then
quicker
and
quicker,
and
you
will
notice
that
the
note
grows
sharper
and
sharper,
till
the
movement
begins
to
slacken,
when
the
note
goes
down
again.
This
is
because
the
more
rapidly
the
air
is
hit,
the
shorter
are
the
waves
it
makes,
and
short
waves
give
a
high
note.
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