The Story of the Atlantic Telegraph

by Henry M. Field

Thus after infinite toil, the wreck of old disasters was cleared away, and the mighty task begun anew. The works of the Telegraph Construction and Maintenance Company were the largest in the world, and all their resources were now put in requisition. Never did greater care preside over a public enterprise. It was a case in which the motive of interest was seconded or overborne by pride and ambition. A cable was to be made to span the Atlantic Ocean, and to join the hemispheres; and they were determined to produce a work that should be as nearly perfect as human skill could make it. The Scientific Committee, that had so long investigated the subject, had approved a particular form of cable, as "the one most calculated to insure success in the present state of our experimental knowledge respecting deep-sea cables," but at the same time recommended the utmost vigilance at every stage of the manufacture. These precautions deserve to be noted, as showing with what jealous care science watches over the birth of a great enterprise, and prescribes the conditions of success. They recommended:

That the conductivity of the wire should be fixed at a high standard, certainly not less than eighty-five per cent; that the cable should be at least equal to the best ever made; that the core should be electrically perfect; that it should be tested under hydraulic pressure, and at the highest pressure attainable in the tanks at the Company's works; that after this pressure, the core should be examined again, and before receiving its outer covering, be required to pass the full electrical test under water; that careful and frequent mechanical tests be made upon the iron wire and hemp as to their strength; that special care be given to the joints, where different lengths of cable were spliced together; and that when completed, the whole be tested under water for some length of time, at a temperature of seventy-five degrees.

This was higher by forty degrees than the temperature of the Atlantic. The insulation is improved by cold; so that, if it remained perfect in this warm water, it could not fail in the icy depths of the ocean.

OLD ATLANTIC CABLE, 1858.

NEW ATLANTIC CABLE, 1865.

After passing through such elaborate tests, all will be glad to see the final product of so much care and skill. As the long line begins to reel off from the great wheels and drums, we may examine it in its completed and more perfect form. It is only necessary to compare it with the cable laid in 1858, to show its immense superiority. A glance at the two as they appear on the preceding page will show that the cable had grown since first it was planted in the ocean, as if it were a living product of the sea. This growth had been in every part, from core to circumference.

First, the central copper wire, which was the spinal cord, the nerve along which the centre current was to run, was nearly three times as large as before. Prof. Thomson had long seen that this was a condition of success. While joining heartily in the attempts of 1857-58, he felt that an error was committed in the smallness of the cable; that the copper conductors and the gutta-percha covering should both be much larger. The old conductor was a strand consisting of seven fine wires, six laid round one, and weighed only one hundred and seven pounds to the mile. The new was composed of the same number of wires, but weighed three hundred pounds to the mile. As it was made of the finest copper that could be obtained in the world, it was a perfect conductor. Next, to secure insulation, it was first imbedded for solidity in Chatterton's compound, a preparation impervious to water, and then covered with four layers of gutta-percha, which were laid on alternately with four thin layers of Chatterton's compound. The old cable had but three coatings of gutta-percha, with nothing between. Its entire insulation weighed but two hundred and sixty-one pounds to the mile, while that of the new weighed four hundred pounds.

But a conductor ever so perfect, with insulation complete, was useless without proper external protection, to guard it against the dangers which must attend the long and difficult process of laying it across the ocean. The old cable had broken a number of times. The new must be made stronger. To this end it was incased with ten solid wires of the best iron, or rather, of a soft steel, like that used in the making of Whitworth's cannon. This made the cable much heavier than before. The old cable weighed but twenty cwt. to the mile, while the new one reached thirty-five cwt. and three quarters. But mere size and weight were nothing, except as they indicated increased strength. This was secured, not only by the larger iron wires, but by a further coating of rope. Each wire was surrounded separately with five strands of Manilla yarn, saturated with a preservative compound, and the whole laid spirally round the core, which latter was padded with ordinary hemp, saturated with the same preservative mixture. This rope covering was important in several respects. It kept the wires from coming in contact with the salt water, by which they might be corroded; and while it added greatly to the strength of the cable, it gave it also its own flexibility—so that while it had the strength of an iron chain, it had also the lightness and flexibility of a common ship's rope. This union of two qualities was all-important. The great problem had been to combine strength with flexibility. Mere dead weight was an objection. The new cable, though nearly twice as heavy as the old in air, when immersed in water, weighed but a trifle more; so that it was really much lighter in proportion to its size. This increased lightness was a very important matter in laying the cable, as it caused it to sink slowly. The old cable, though smaller, was heavy almost as a rod of iron, so that, as it ran out, it dropped at an angle which exposed it to great danger in case of a sudden lurch of the ship. Thus in 1857 it was broken by the stern of the Niagara being thrown up on a wave just as the brakes were shut down. Now the cable, being partially buoyed by the rope, would float out to a great distance from the ship, and sink down slowly in the deep waters.