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281
Heroes of the Telegraph
·
John Munro
253
The
articulating
telephone
was
the
forerunner
of
the
phonograph
and
microphone,
and
led
to
their
discovery.
They
in
turn
will
doubtless
lead
to
other
new
inventions,
which
it
is
now
impossible
to
foresee.
We
ask
in
vain
for
an
answer
to
the
question
which
is
upon
the
lips
of
every
one-What
next?
The
microphone
has
proved
itself
highly
useful
in
strengthening
the
sounds
given
out
by
the
telephone,
and
it
is
probable
that
we
shall
soon
see
those
three
inventions
working
unitedly;
for
the
microphone
might
make
the
telephone
sounds
so
powerful
as
to
enable
them
to
be
printed
by
phonograph
as
they
are
received,
and
thus
a
durable
record
of
telephonic
messages
would
be
obtained.
We
can
now
transmit
sound
by
wire,
but
it
may
yet
be
possible
to
transmit
light,
and
see
by
telegraph.
We
are
apparently
on
the
eve
of
other
wonderful
inventions,
and
there
are
symptoms
that
before
many
years
a
great
fundamental
discovery
will
be
made,
which
will
elucidate
the
connection
of
all
the
physical
forces,
and
will
illumine
the
very
frame-work
of
Nature.
In
1879,
Professor
Hughes
endowed
the
scientific
world
with
another
beautiful
apparatus,
his
'induction
balance.'
Briefly
described,
it
is
an
arrangement
of
coils
whereby
the
currents
inducted
by
a
primary
circuit
in
the
secondary
are
opposed
to
each
other
until
they
balance,
so
that
a
telephone
connected
in
the
secondary
circuit
is
quite
silent.
Any
disturbance
of
this
delicate
balance,
however,
say
by
the
movement
of
a
coil
or
a
metallic
body
in
the
neighbourhood
of
the
apparatus,
will
be
at
once
reported
by
the
induction
currents
in
the
telephone.
Being
sensitive
to
the
presence
of
minute
masses
of
metal,
the
apparatus
was
applied
by
Professor
Graham
Bell
to
indicate
the
whereabouts
of
the
missing
bullet
in
the
frame
of
President
Garfield,
as
already
mentioned,
and
also
by
Captain
McEvoy
to
detect
the
position
of
submerged
torpedoes
or
lost
anchors.
Professor
Roberts-Austen,
the
Chemist
to
the
Mint,
has
also
employed
it
with
success
in
analysing
the
purity
and
temper
of
coins;
for,
strange
to
say,
the
induction
is
affected
as
well
by
the
molecular
quality
as
the
quantity
of
the
disturbing
metal.
Professor
Hughes
himself
has
modified
it
for
the
purpose
of
sonometry,
and
the
measurement
of
the
hearing
powers.
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