Nelson Evening Mail FRIDAY, MARCH 28, 1919. THE SUBMARINE CABLE.

Nelson Evening Mail, Volume LIII, Issue 74, 28 March 1919, Page 4

Nelson Evening Mail FRIDAY, MARCH 28, 1919. THE SUBMARINE CABLE.

WHEN reading cable news from various parts of the world few people stop to think of the wonderful work performed by the submarine cable. The cable itself • consists of a central core of copper conductors or wires that carry the current. As one authority says, in giving these details, it is. convenient to speak of it as “current,” but it should be said that what electrical energy really is no man ; knows. No one, indeed, knows how the conductors convey it for certain—that is, whether it passes round them or through them. One theory is that it takes a spiral path round them. But though it has an affinity for a good conductor, such as copper, It would escape en route if it had the chance. To prevent this as much as possible—it cannot be prevented entirely—the conductors are surrounded, by gutta-percha, \yhich serves to keep the wayward current to the conductors. Bound the guttapercha there is a coating of hemp. Then comes a sheathing of iron or steel wire, which acts as. an armoured protection, for however carefully a cable is laid it is subjected to considerable strains. The| • outer coating consists of tarred canvas j i for deep water, but at depths not exceeding 300, fathoms a, binding of brass tap© is supplied. This is to discourage that persevering pest, the teredo, which . otherwise would bore its way through : the tarred canvas and leave the armourling exposed to the corrosive action of | the water. At great depths the cable is j exposed to very high water pressure^ ! At 1800 fathoins; which is not an ex- | 7 ; treme depth, this would be considerably over two tons to the square inch. And 1 yet there are fish which are adapted •. to live . only under these most oppres- , sive .conditions. Their extraordinary j muscular organism, always exerted j against the water pressure, prevents them from being crushed; but if that pressure is removed, as it is when they: | are brought to the surafee, it is their 1 undoing, for then they burst asunder or 1 “implode,” to use the technical word, j And but for these strange fish,, the cable , at such depths : would rest in eternal | darkness—a darkness made visible, perhaps, when the sun in shining in bis I strength by "just the Rainiest glimmer | of , green. But these fish—or some of | them, at any rate, carry their own electric light. It is, maybe, a single light suspended by a thin ligament attached to the head; sometimes the fish are lighted up by little lamps, which glow like the portholes of a steamer at night, and sometimes they emit an undefined glow. This provision is not that they may find their way about, but that they may earn an easy living. They lie quiet, • and; their foolish prey, attracted by the light, swim into their mouths, and so pqrish, But at these still depths the 1 cable has no foes, and it will last for many years; it is only in shallow waters made uneasy by currents that it is subjected to, much wear and tear. Prom these and other causes it may cost many thousjands a year .to keep a long cable ; in - yepair, ; If a fault occurs after the cable has been laid, a repair ship must proceed to the spot and fish the broken ends up with grapnels. It is possible - to-; determine the position if the fault is within close limits. Where breaks occur in deep water this

is usually due to some shifting of, the bed\of the ocean, by a seismic disturbj aric‘6, ’ One of the broken ends is grapf pled for, and is then raised to the surface in order that a new piece may be spliced on., Tjie , second broken end is j brought to ■, the surface and spliced in similar manner. In, deep water repairs > may . take ■; a long time, and the expense, of is very heavy. Some years ago one of the Atlantic cables broke at great- depth; to effect repairs . took many months, and the expenditure was £75,000;