What is a Cable Made of?
A submarine telegraph cable as usually made consists of a core in the
center of which is a strand of copper wire which varies in weight from
seventy to four hundred pounds to the mile. Strands of copper wire
instead of one thick wire of copper are used, because the former is
more flexible. The copper conductor is covered with several coatings of
rubber of equal weight to the copper wires. After this comes a coating
of jute serving, then a layer of galvanized iron wires and finally a
layer of yarn and compound which forms the outer covering of the cable.
In addition to this where the cable lays among rocks that might injure
it, chains are securely wrapped around it, so as to prevent wear and
tear as much as possible.
You may not have known it, but the cable which lies on the bottom
where the water is deepest is never so large as nearer the shore or
in shallow water. Little by little the men who lay and look after
cables have found that it is best to have a specially constructed outer
covering for different depths and character of bottoms so as to provide
the least possible danger of damage through the action of the water on
the bottom.
How is a Cable Laid?
When the cable of sufficient length is completed, it is carried to
a specially equipped vessel which has a great tank for holding the
cable and the necessary machinery for lowering it over the end of the
ship into the water. The cable is carefully coiled in the tank, the
different coils being prevented from adhering by a coat of whitewash.
First then, a sufficient length of cable is paid out to reach the cable
house or shore. Here it is finally tested to see that the entire length
of cable is in working order. If satisfactorily tested, the vessel
steams slowly away on the course outlined, paying out the cable as she
goes.
[Illustration: STORING A CABLE LONG ENOUGH TO CROSS THE OCEAN
Here we see a cable coiled round and round in the tank which holds it
on board the cable ship.]
[Illustration: In the front of the picture we see the cable coming from
the tank in which it is coiled. It goes over the drum of the paying-out
machine and thence to the bow of the ship, where it passes over big
sheaves or pulleys and down into the ocean.]
[Illustration: THE MACHINERY ON A CABLE SHIP
The paying-out machine. The cable makes a couple of turns around the
big drum, which is connected to the dial, so that the dial indicates
the length of cable which has been paid out into the sea.]
[Illustration: The upper forward deck of the cable steamship
“Telconia,” showing the gear which is used in paying out the cable.
Away in the bow are the big sheaves over which the cable goes into the
sea. Nearer is a dynamometer which measures the tension on the cable.]
[Illustration: HOW THE CABLE IS DROPPED INTO THE OCEAN
Here we see the cable on the lead, as it is called, passing over the
big bow sheave from which it dives into the depths of the sea.]
The vessel must pay out more than a mile of cable for every mile she
travels because there must be enough slack allowed at the same time
to provide for the unevenness of the bottom of the sea. For this
purpose the amount of cable paid out must be measured. This is done
by the paying-out machine, which is shown in one of the pictures.
The difference between the speed of the ship and the amount of cable
paid out gives the amount of slack. Too much slack would also be bad,
so that it is a very pretty problem to pay out just enough and both
the speed of the vessel and the rate of paying out the cable must be
watched carefully.
One of the greatest wonders accomplished by the ingenuity of man is the
ocean telegraph, by which we flash messages back and forth under the
sea between the continents and completely around the world.
Hardly had the telegraph become an established fact, before Professor
Morse, who made the telegraph practical, expressed the belief that a
telegraph line to Europe by means of a wire laid on the bottom of the
ocean was easily possible at some future time. Mr. Cyrus W. Field, the
first to lay an ocean cable successfully, heard him and in his own
mind said “Why not now?” The idea fixed itself so thoroughly in his
resolute mind that he soon said to himself “It shall be done,” and
went to work, and labored incessantly through twelve years of failure
and discouragement before he accomplished his task, which was a great
compliment to this giant of American stick-to-it-iveness.
While many doubted the feasibility of the project and others thought
it the dream of a disordered brain, Mr. Field found many who believed
in him and his idea and who loaned him their financial support for the
undertaking.
[Illustration: THE CABLE ARRIVES ON THE OTHER SIDE
Landing the shore end of a cable. The cable is supported on several
boats and this picture shows the inshore boat with the end of the cable
reaching the beach with the seas breaking over her.]
[Illustration: THE MEN WHO MADE THE OCEAN CABLE POSSIBLE