HOW A CABLE IS LAID.

Press, Volume LVIII, Issue 11012, 9 July 1901, Page 5

HOW A CABLE IS LAID.

A VISIT TO THE BRITANNIA. (SPECLSX TO "THE PRESS.") AUCKLAND, July 8. The presence in these v.atexs of the cable steamer Britannia brings home more forcibly to New Zealanders the fact that preparations for laying the Pacilic cable are well in hand, and progH>«»h>g Meiuliiy.

At the present juncture, when public attention is being directed to this important undertaking, some particulars of tin' visiting vessel and her work ;ire of especial interest. A valuable article on this subject appeared a few weeks ago in the "Brisbane Courier." and. as its accuracy is vouched for by the officials ou the Britannia, I do not hesitate to give republicuiion to portions of it: — The Britannia, is a ship of 1800 wins burthen, built on tire lines of a. yanht, and she is the property of the Telegraph Construction «.nd iuaintenmnre Company. The commander is Captain J- l'>- an officer of great experience. On board with ihim are Mr C. W. Clarke, a young and enthusiastic eleetrkul scientist, who specially represents the-"Telegraph. Construction and Maintenance Company ; and Mr R. EPeake, a much-travelled man of the world, I the representative and engineer of the Pacific Cable Company. With, the Australian, site settled generally *at' Southport, » popular seaside resort, we have next to consider the work of the survey for the line of tbe cable, \ and the laying of the girdle which shall flash from the old land to the new its vanying messages. The line will run direct from Vancouver to .Fanning Island, thence to Fiji, and thence to Norfolk Island, where it will bifurcate to Queensland and New Zealand. . .

The present mission of the Britannia is to survey the route of the. cable from Queensland and New Zealand to Fanning Island. She. (has been to Norfolk Island, and next goes to Fiji, and then to Fanning Island; and, her task being completed, sho will return to England, via Singapore Mid the Suez Canal. The work of surveying thesestretches of sea will occupy until the middle of August-, aajd it will be about March next year before the work of Jaymg the cable can be started. In this case the work of laying the cable will be started next year, and a ship will leave London about the 15th. of January, with the first sections. The sections from Queensland and New Zealand will be kid first, an<| the'last section will be laid from Vancouver to the point of junction. How many of those who read tlheir cable news in the daily papers, or who arc able to flash messages round the world for the comfort and Intelligence of their friends, 'realty appreciate what is meant by th* , . services brought so cheaply and so conveniently: to their hands? How is s, cable laid? • The Britannia goes out to sea, auc her first work ia to lay down in black and white the oontours of the uncharted areas of the intervening spaces of the sea's bed. That seems a difficult task, for under the blue flash of the surfaoe waves with their whitecresfced caps, there are great sileut depths of green, wafer, and 'how is the, Lydrographer to get under them, measuring mile by mile the beds tof coral, the rocky promontories of the' ever-covered and seaswept land, the long stretches of golden sand, the depressions which represent truly the valleys of the sea, and the uharj ascents and descents of extinct volcanoes which have long since given up fire and lavai flow, and lie in the dark silence thousands of feet below the rash of the ocean liners which link liwid to land? On the bowa of the ship is the sounding gear and the sheaves for picking up the cable when inspecting or effecting repairs. Let us first talce the work of repairing a cable. Some day a paper amwurs without its foreign intelligence, and a paragraph explains that the cable lias been interrupted. Perhaps it is a break : perhaps insects have fought their way through the covering of hhe cable, and "like our white ants in a wooden house, slowly and by infinitesimal degrees destroyed the means of a clear flow of the electrical current. A ship, say the Britannia., goes out to search for the 'break or the source of the interruption. Grapnels are lowered from the bows, -so nxt-d that, whichever side drops down, there is a rake-like apparatus for catching the ends of the cable, or it may be, if the cable is old, omtd it is feared tfiat it will not stand the strain of being drawn up in a bight, a cutter eevers it, and one end is brought to the surface for examination. How difficult it is from the tfhortv waiting impatiently for the blue flash which indicates restored" eommunieatfcm, to fully realise the trying work of those engaged in picking up the broken ends of a string, stretches along the ocean bed, perhaps, at-' a depth of three miles! Now we come to the survey. In the bows of the ship is a, sounding gear, worked to a' large extent automatically, with a reel of pianoforte wire six and a* half miles in length, and with weights of 501b eacih to carry the connection down to the depths of the ocean. On some of these weights are what are known as "snapper" gears, like two large spoons. These close as they strike the bottom of the sea, and the 601b weight is released und lost, and the "snappere 1 drawn to the surface. In th«> Kpoon-' tike clips is a specimen' of the formation at the bottom of the sea. That is useful to those engaged in laying the cable, for it is well to know the class" of bed that t-'ae line is to rest upon. The weights are too heavy to be hauled up from such a depth, and are abandoned. The Britannia ha<l

over a thousand of them on board, and was therefore prepared to take over a thousand soundings. ' There ia another gear for bringing up samples of! a. soft, oozy {tmttomi and yet another which is used when in shallow water. Shallow water is represented by anything under a thousand fataoms—iOOOft' In the case of the latter the weight is a fixture, and need not be abandoned.

These soundings taken give an idea of the contours of the ocean bed. It seems strange that old mother sea has hbv mountains and valleys, but so it is. When steep grades are met with, or valleys discovered, another line is sought. Probably a mile or Uvo to the right or left will show «a easier frade. Hills are very much objected to v the engineers of a cable-bed, and sharp hollows are considered extermely inimical tv the life of the girdle. And so tho survey, though approximating only t<) exactitude, when compared with a land survey, has its cares, and calk /or the exercise o£ great prudence, based upon experience. Another interesting point in cable-lav-ing is temperature on toe ocean-bed. 'i'fie lower the temperature the 'better are the electrical effects. At 3000 fathoms—do not start, it is only 18,000 ft, and that is a reasonable figure in ocean dv-pths —th« thermometer records about 34deg Fahr., and there is not much fluctuation from that, perhaps not more tlum from half-a-flegiee to a degree, in deep-sea soundings, For taking the temperature a. thermometer is used to -withstand the enormous pressure at deep levels; 501b to the square inch is the capacity of resistance of the ordinary apparatus used on the Britannia. I Sow we come to the eable-laying^wiuSb

h*a* simple* enough process -when one sees hoy it « forked. . Ite gear is extremefy simple. The cable is utored in tanks, ■which embrace a diameter of almost ti< whole of the beam of ,t3ie ship; say 4fi is allowed <m each aide for passage '~ lure mid aft. • The forward movement of th* chip provider th« motive power in pa) (vi/ out, and the cable passea over pulievn,, vrith a regulator in the form of a larger drain, round which a double turn i« taken. A dynamometer indicates the strain pressure, Ami upon ' that the speed of the sliip ta regulated. There is no intricacy. .When paying out cable the Britannia travels at half-speed. The reel ■work of the cable-laying requires no further description. Its very simplicity is n- tribute to the skill of those who, from time to time, have been employed in bringing it to perfection.