A Story of the Telegraph

by John Murray

The cost of the cable before laying depends upon the dimensions of the cars, or conducting wire, which is copper; gutta percha, which still forms the only trustworthy insulating material, constituting the principal item of expense.

For an Atlantic cable of the most recent construction, the cost may be taken at £250 to £300 per nautical mile.

The system of submarine cables originating in Great Britain has continued to develop in her hands, until the world has been covered with a veritable network of cables, which has hitherto done much to prevent the decline of her commercial supremacy. During the last few years, however, other maritime nations in Europe have begun to realize the importance of submarine cable enterprise in this respect, and France and Germany have made some progress towards freeing themselves from British monopoly; both are now connected with America by cables which are owned in their respective countries, though their manufacture and submergence was effected by an English Company.

This spread of the cable system has naturally followed trade routes, and thus, with the exception of the cables to America, their trend has been eastwards as far as Australia and Japan. During the year 1902 the Dominion of Canada was connected by cable with New Zealand and Australia, the total length of cable, 8,272 miles, and cost £1,795,000.

An agreement was entered into between the Imperial Government and the Governments of Canada, Victoria, New South Wales, New Zealand and Queensland, and it was through the persistent efforts and advocacy of Sir Sandford Fleming that this great work was accomplished.

Owing to the experience gained with many thousand miles in all depths and under varying conditions of weather and climate, the risks, and, consequently, the cost of laying, has been greatly reduced, but the cost of effecting a repair still remains a very uncertain quantity, success being dependent on quiet conditions of sea and weather.

The modus operandi is briefly as follows: The position of the fracture is determined by electrical tests from both ends with more or less accuracy depending on the nature of the fault, but it can be located within a few miles. The repair steamer, on reaching the given position, lowers one or perhaps two mark buoys, mooring them by mushroom anchors, chain and rope, using these buoys to guide the direction of tow. Grapnel, a species of five pronged anchors attached to a strong compound rope formed of strands of steel and manilla, is lowered to the bottom and dragged at a slow speed, as it were ploughing a furrow in the sea-bottom in a line at right angles to the cable route until the behavior of the dynamometer shows that the cable is hooked. The ship is then stopped and the cable gradually hove up towards the surface; but in deep water, unless it has been caught near a loose end, the cable will break on the grapnel before it reaches the surface, as the catenary strain on the bight will be greater than it will stand. Another buoy is put down marking this position, fixing at the same time the actual line of the cable. Grappling will then be recommenced so as to hook the cable near enough to the end to allow of its being hove to the surface. When this has been done an electrical test is applied, and, if the original fracture is between the ship and shore, the heaving in of the cable will continue until the end comes on board. Another buoy is then lowered to mark the spot, and the cable on the other side of the fracture grappled for brought to the surface, and, if communication is found perfect with the shore, buoyed with sufficient chain and rope attached to allow of the cable itself reaching the bottom. The ship now returns to the position of original attack and by similar operations brings on board the end which secures communication with the shore. The gap between the two ends has now been closed by splicing on new cable and paying out until the buoyed end is reached, which is then hove up and brought on board. After the “final splice,” as it is termed, between these ends has been made, the bight made fast to a rope is lowered overboard, the slip rope cut and the cable allowed to sink by its own weight to its resting place on the sea-bed. The repairs being thus completed the various mark buoys are picked up and the ship returns to her usual station.

The grappling of the cable and raising it to the surface from a depth of 2,000 fathoms seldom occupies less than twenty-four hours, and, since any extra strain due to the pitching of the vessel must be avoided, it is clear that the state of the sea and weather is the predominating factor in the time necessary for effecting the long series of operations which, under the most favorable circumstances, are required for a repair. In addition the intervention of heavy weather may mar all the work already accomplished and require the whole series of operations to be undertaken de novo.

As to cost, one transatlantic cable repair cost £75,000.

The repair of the Aden Bombay cable, broken in a depth of 1,900 fathoms, was effected with the expenditure of 176 miles of new cable, and, after a lapse of 251 days, 103 being spent in actual work, which for the remainder of the time was interrupted by the monsoon. A repair of the Lisbon Porthcarrow cable broken in the Bay of Biscay in 2,700 fathoms, eleven years after the cable was laid, took 215 days with an expenditure of three hundred miles of cable.