KINKS IN THE CABLE.

Auckland Star, Volume LVI, Issue 246, 17 October 1925, Page 10

KINKS IN THE CABLE.

PACIFIC SINGULARLY IMMUNE.

MARVELLOUS SPEEDING ,UP.

WITH THE SAME OLD CABLE.

If you send a cablegram this evening to a friend in London he found it lying on his plate this morning when he went down to breakfast! So that in terms of "morning and evening of the same day" he really knew about your message before you sent it. This is one of the curiosities that exist owing to this incorrigible habit of the moderns to annihilate distance. Sir Thomas Browne, you may remember, in a certain passage, is talking about getting to bed (it is midnight) and postponing further cogitation; he sounds a drowsy note, and then suddenly says, "But the hunter is up in-America, and in Persia they are already half through their first sleep." That is the sort of surprise you get when you go delving into this cable business.

Besides confounding the meaning of "this evening" and "this morning" as between you and your London friend, the fact that the sun never sets on the British Empire means that someone is always tapping at the cable, and this means that the man at tbe other end has to be on duty also. As a result the cable is humming away every minute of the twenty-four hours, seven days a week, not omitting the 29th of February as often as it happens. There is nothing in Auckland more nearly akin to perpetual motion. The only thing that interrupts the cable is a break. Fortunately for us the Pacific cable has been singularly free from mishaps, and another distinction is that the long stretcli between Vancouver and Fanning Island, the longest cable in the world, is for working speed in proportion to length the best working in the world. Talking Over Nearly 4000 Miles.. It was this 3458-mile stretch that used to dismay the experts years ago when the Pacific cable was first suggested. Many of them thought the length was too great for the cable to be able to work quick enough to pay its way—the longer the line the more the signals are "delayed," as they say technically, and the slower the working— but enthusiasm and constant improvement have triumphed. When the Pacific started 75 letters a minute was the highest speed over this great stretch between Vancouver and Fanning, the first "leg" of the Pacific cable, but to-day the letters go singing over the bed of the ocean at a rate of 145 letters a minute.

By next September the duplication cable with thq new special metal insulation will be down over this stretch, and then the capacity of the line will be four or five times greater than it is today. If you happen to be discussing this with a cable man he will smile in a way that suggests that he will then begin to admit that they are "doing pretty well." These cable people are never resting, always looking for something to make cabling faster and more accurate. Incidentally, of course, the advent of wireless "bucked everybody up," but the cablemen have not the slightest fear of having to pull up their deep-sea cables and sell them for second-hand hawsers. Alongside this amazing speed with which one talks to one's friends on the other side of the world, and the wonderful improvements that have been made in the mechanical transmission of messages, we are still using, the same style of cable that was dropped overboard from the Great Eastern when she laid the first trans-Atlantic cable away back in 1858. A section of that old cable with jts copper cores, gutta-percha insulation, and sheathing of steel wires, like a ship's hawser, looks for all the world like a bit from the shore-end of the Pacific cable of to-day. One cannot help admiring the genius of those old-time electricians who right away hit on the best type of cable to circumvent old ocean's perils.

Safe on Ocean's Floor Contrary to what the common run of. landlubbers would imagine, the cable lying at the bottom of the ocean could hard°lv be in a safer place. The ooze, formed of the discarded bodies of myriads of infinitesimally small crustaceans seems a natural* «pr eservative of tne , steel-protected cable, for in Davy Jones' Locker there is neither rust to corrode not moth to corrupt. An compared with the common idea of a heavy ponderous sea cable the deep-sea cable is a very slender affair —about an inchc in dia-

meter. - It is near the land on rocky shores that the cablemen .begin to get anxious. As a general rule wave-action does not go much below ten fathoms, so there is complete quiet at the bottom of the ocean. In Cook's Strait, however, where the whole of the water is in motion and the tide going at several miles an hour, the cable is subject to wear in spite of the fact that it is in places fifty or sixty fathoms below the surface. On the Pacific Cable the most expensive area is that off Norfolk Island where the comparatively shallow water on a rocky bottom works havoc. There is, in the Auckland office, a piece of this shore end (much heavier and thicker, of course, than the usual deep-sea cable) which was chafed right through by constant rubbing, but the process was a long one, this particular bit of cable having been down twenty three years.

Three Miles Deep. As far as this question of deep-sea cable is concerned, the landsman is rather surprised to know that the only thing essential is tensile strength—the cable must be able to bear its own weight if it should ever happen that occasion should arise to bring it to the surface in the event of a break. When you know that they once picked up a Lisbon cable in the Bay of Biscay at 2700 fathoms, or about three miles—from Auckland post office nearly out to Epsom tram barn—you can realise that there must be some weight in th e "bight" as the loop picked up is called. This immunity of the cable was not achieved without much research and ceaseless watchfulness. In the old days cablemen were much troubled by the teredo, especially in tropical waters. This tiny little borer could sneak through an invisible chink in the: steel sheathin" and once he penetrated the rubber insulation the cable was out of action. A thin strip of brass, not as thick as writingpaper, is now wound round the rubber insulater copper wire, and the teredo has to go nosing elsewhere for a habitation. As an .instance of the great age to which n cable can attain when once it reaches the kindly ooz on the ocean's bed, it may be mentioned that the cable that was picked up in the Bay of Biscay mentioned above, was thirty years old when fished up, and was then practically as good as new. And it was not a new cnble when laid in the first instance, hay- , in< r been a part of one of the old Atlantic 5 cables that had been relaid. It was

in 1901 that this great feat of lifting the cable from a depth of 2700 fathoms was achieved, and for a cable to have lasted until then shows not only its durability but what exceedingly good workmen the old first cable-makers must have been.

: Real Girdle Round the Earth. ! One other rather astonishing thing—to the layman at least—about submarine cables is that they use an earth return, As most people know the telephones we use in| Auckland have what is called a metallic circuit, that is to say, there is an endless metal "chain" between your instrument and the post office. In the old days they used the "earth return," that is to say there was only one wire, and the circuit was completed by the earth. How the thing happened the experts don't quite know, even in 1925. ; This earth return is still used by the submarine cables, but they take care not to "earth" near such an electrically lively spot as the Auckland tram seri vice and the Auckland power station— i factors which made the metallic circuit necessary in the telephones. The Auck-land-Sydney cable goes to earth about a j mile out to sea from Muriwai Beach, j and the earthing is effected by a simple ! but ingenious method of connecting the copper wire with the outside steel sheath- , ing, which of course comes in contact i with the earth at the bottom of the sea.

When the experts tell you that this "earth return" is used between that 3458-mile' stretch between Vancouver and Fanning Island, the non-technical mind is quite incapable of grasping all it means. And to cap your electrical astonishment they inform you that the Pacific cable is so nearly perfect and the earth return is so good, that when tested the loss is found to be practically nil; in other words, the current is practically the same as if there were a copper wire round the whole circuit.

Submarine cabling is to-day so sure, so tireless, and so continuous, that wireless can never oust it from its commanding position, however useful it may be as an incentive, or an ally. And to the man in the street the most picturesque thing about the whole business is that we are still to-day using practically the same cable as the one that made the name of the Great Eastern famous.