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1
378
The Story of the Atlantic Telegraph
·
Henry M. Field
232
But
a
conductor
ever
so
perfect,
with
insulation
complete,
was
useless
without
proper
external
protection,
to
guard
it
against
the
dangers
which
must
attend
the
long
and
difficult
process
of
laying
it
across
the
ocean.
The
old
cable
had
broken
a
number
of
times.
The
new
must
be
made
stronger.
To
this
end
it
was
incased
with
ten
solid
wires
of
the
best
iron,
or
rather,
of
a
soft
steel,
like
that
used
in
the
making
of
Whitworth's
cannon.
This
made
the
cable
much
heavier
than
before.
The
old
cable
weighed
but
twenty
cwt.
to
the
mile,
while
the
new
one
reached
thirty-five
cwt.
and
three
quarters.
But
mere
size
and
weight
were
nothing,
except
as
they
indicated
increased
strength.
This
was
secured,
not
only
by
the
larger
iron
wires,
but
by
a
further
coating
of
rope.
Each
wire
was
surrounded
separately
with
five
strands
of
Manilla
yarn,
saturated
with
a
preservative
compound,
and
the
whole
laid
spirally
round
the
core,
which
latter
was
padded
with
ordinary
hemp,
saturated
with
the
same
preservative
mixture.
This
rope
covering
was
important
in
several
respects.
It
kept
the
wires
from
coming
in
contact
with
the
salt
water,
by
which
they
might
be
corroded;
and
while
it
added
greatly
to
the
strength
of
the
cable,
it
gave
it
also
its
own
flexibility--so
that
while
it
had
the
strength
of
an
iron
chain,
it
had
also
the
lightness
and
flexibility
of
a
common
ship's
rope.
This
union
of
two
qualities
was
all-important.
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