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281
Heroes of the Telegraph
·
John Munro
94
The
minor
features
of
the
recorder
have
been
simplified
by
other
inventors
of
late;
for
example,
magnets
of
steel
have
been
substituted
for
the
electro-magnets
which
influence
the
swinging
coil;
and
the
ink,
instead
of
being
electrified
by
the
mouse-mill,
is
shed
on
the
paper
by
a
rapid
vibration
of
the
siphon
point.
To
introduce
his
apparatus
for
signalling
on
long
submarine
cables,
Sir
William
Thomson
entered
into
a
partnership
with
Mr.
C.
F.
Varley,
who
first
applied
condensers
to
sharpen
the
signals,
and
Professor
Fleeming
Jenkin,
of
Edinburgh
University.
In
conjunction
with
the
latter,
he
also
devised
an
'automatic
curb
sender,'
or
key,
for
sending
messages
on
a
cable,
as
the
well-known
Wheatstone
transmitter
sends
them
on
a
land
line.
In
both
instruments
the
signals
are
sent
by
means
of
a
perforated
ribbon
of
paper;
but
the
cable
sender
was
the
more
complicated,
because
the
cable
signals
are
formed
by
both
positive
and
negative
currents,
and
not
merely
by
a
single
current,
whether
positive
or
negative.
Moreover,
to
curb
the
prolongation
of
the
signals
due
to
induction,
each
signal
was
made
by
two
opposite
currents
in
succession--a
positive
followed
by
a
negative,
or
a
negative
followed
by
a
positive,
as
the
case
might
be.
The
after-current
had
the
effect
of
curbing
its
precursor.
This
self-acting
cable
key
was
brought
out
in
1876,
and
tried
on
the
lines
of
the
Eastern
Telegraph
Company.
Sir
William
Thomson
took
part
in
the
laying
of
the
French
Atlantic
cable
of
1869,
and
with
Professor
Jenkin
was
engineer
of
the
Western
and
Brazilian
and
Platino-Brazilian
cables.
He
was
present
at
the
laying
of
the
Para
to
Pernambuco
section
of
the
Brazilian
coast
cables
in
1873,
and
introduced
his
method
of
deep-sea
sounding,
in
which
a
steel
pianoforte
wire
replaces
the
ordinary
land
line.
The
wire
glides
so
easily
to
the
bottom
that
'flying
soundings'
can
be
taken
while
the
ship
is
going
at
full
speed.
A
pressure-gauge
to
register
the
depth
of
the
sinker
has
been
added
by
Sir
William.
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