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281
Heroes of the Telegraph
·
John Munro
265
It
would
appear
that
the
current,
reduced
in
strength
by
its
passage
through
a
long
wire,
had
failed
to
excite
his
electro-magnet,
and
he
was
ignorant
of
the
reason.
Wheatstone
by
his
knowledge
of
Ohm's
law
and
the
electro-magnet
was
probably
able
to
enlighten
him.
It
is
clear
that
Cooke
had
made
considerable
progress
with
his
inventions
before
he
met
Wheatstone;
he
possessed
a
needle
telegraph
like
Wheatstone,
an
alarm,
and
a
chronometric
dial
telegraph,
which
at
all
events
are
a
proof
that
he
himself
was
an
inventor,
and
that
he
doubtless
bore
a
part
in
the
production
of
the
Cooke
and
Wheatstone
apparatus.
Contrary
to
a
statement
of
Wheatstone,
it
appears
from
a
letter
of
Cooke
dated
March
4,
1837,
that
Wheatstone
'handsomely
acknowledged
the
advantage'
of
Cooke's
apparatus
had
it
worked;'
his
(Wheatstone's)
are
ingenious,
but
not
practicable.'
But
these
conflicting
accounts
are
reconciled
by
the
fact
that
Cooke's
electro-magnetic
telegraph
would
not
work,
and
Wheatstone
told
him
so,
because
he
knew
the
magnet
was
not
strong
enough
when
the
current
had
to
traverse
a
long
circuit.
Wheatstone
subsequently
investigated
the
conditions
necessary
to
obtain
electro-magnetic
effects
at
a
long
distance.
Had
he
studied
the
paper
of
Professor
Henry
in
SILLIMAN'S
JOURNAL
for
January
1831,
he
would
have
learned
that
in
a
long
circuit
the
electro-magnet
had
to
be
wound
with
a
long
and
fine
wire
in
order
to
be
effective.
As
the
Cooke
and
Wheatstone
apparatus
became
perfected,
Cooke
was
busy
with
schemes
for
its
introduction.
Their
joint
patent
is
dated
June
12,
1837,
and
before
the
end
of
the
month
Cooke
was
introduced
to
Mr.
Robert
Stephenson,
and
by
his
address
and
energy
got
leave
to
try
the
invention
from
Euston
to
Camden
Town
along
the
line
of
the
London
and
Birmingham
Railway.
Cooke
suspended
some
thirteen
miles
of
copper,
in
a
shed
at
the
Euston
terminus,
and
exhibited
his
needle
and
his
chronometric
telegraph
in
action
to
the
directors
one
morning.
But
the
official
trial
took
place
as
we
have
already
described
in
the
life
of
Wheatstone.
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