- Historic Sites
“i’ll Put A Girdle Round The Earth In Forty Minutes”
It took a decade of effort, heart-breaking disappointments, and the largest ship afloat before Cyrus Field could lay a successful cable across the Atlantic
October 1958 | Volume 9, Issue 6
Fortunately for the progress of the telegraphic art, this effect was of no practical importance in the early days of land lines. Their capacity was so low that messages passed through them without any appreciable delay, and it was not until the first submarine cables were laid across the linglish Channel and the North Sea that signal-retardation became a source of trouble. Its prime cause is the presence of the conducting sea water which surrounds a cable and tints greatly increases its capacity. Because of this effect, a cable may need twenty times as much electricity to charge it up when it is submerged as it would require if suspended in air.
Thomson’s analysis led him to his famous “law of squares,” which states that the speed with which messages can be sent through a given cable decreases with the square of its length. In other words, if one multiplies the length of a cable ten times, the rate of signaling will be reduced a hundredfold. This law is obviously of fundamental importance in long-distance submarine telegraphy; the only way of circumventing it is to increase the size of the conducting core.
This was not appreciated by all telegraph engineers, and was even denied by some—including, unfortunately, Dr. Whitehouse. He had carried out experiments purporting to refute the law of squares; these had also led him to condudc (and the same views had been expressed by Faraday and Morse) that a small conducting wire might be better than a large one, which was the exact reverse of the truth. When stich confusion prevailed among the “experts” it is hardly surprising that the first Atlantic cable was badly designed. It had about as much chance ol success as a bridge built by engineers svho did not understand the laws governing the strength ol materials.
Thomson was only one of the company’s directors, and had no authority—beyond his scientific prestige— over the men who were in charge of its technical allairs. because of their determination to lay the cable during the summer of 1857, the promoters of the scheme had left no time for the experiments and tests which were essential for its success. The dynamic energy of Cyrus Field was partly responsible for this, and when Thomson arrived on the scene, he discovered that the specifications for the cable had already been sent out to the manufacturers and that it was now too late to alter them. What was more, when he had an opportunity of testing the completed article, he was shocked to discover that the yuality of the copper varied so much that some sections conducted twice as well as others. There was nothing that could be done, except to insist that future lengths be made of the purest possible copper and to hope that the existing cable would be good enough for the job.
The conductor itselt consisted of seven strands of copper wire twisted together and insulated by three separate layers of gutta-percha. If there was a hole or imperfection in one layer, the other two would still provide adequate protection. Only in the extremely improbable event of three (laws occurring in exactly the same place would there be danger of an electrical failure.
The insulated core was then covered with a layer of hemp, which in turn was armored with eighteen strands of twisted iron wire. The resulting cable was about five-eighths of an inch in thickness and weighed one ton per mile. This at once raised a serious problem, for the length needed to span the Atlantic weighed 2,500 tons—far too great a load to be carried in any single ship of the time.
The total cost of the cable was £224,000—at least £1,000,000 by today’s standards, though it is about as difficult to relate our present currency to the Victorian pound’s real purchasing power as to that of the Russian ruble.
The cable was completed within the remarkably short time of six months, and by July, 1857, it was ready to go to sea. By rights, Whitehouse should have sailed with it, but at the last moment he pleaded illhealth and Thomson was asked to fill the breach. It says much for the scientist’s greatness of character that he agreed to do this, without any payment. This misshapen infant dumped on his doorstep was certainly not his baby, but he would give it the best start in life he could.
To share the enormous weight of the cable between them, the warships Niagara and Agamemnon had been provided by the United States and British governments respectively. The Niagara was the finest ship in the American Navy; the largest steam frigate in the world, she had lines like a yacht and her single screw could drive her with ease at twelve miles an hour. The Agamemnon , on the other hand, would not have looked out of place at Trafalgar; she was one of the last of the wooden walls of England, and though she had steam power as well as sail, one would not have guessed it by looking at her.
Both ships had been extensively modified to allow them to carry and pay out their 1,250 tons of cable. Their holds had been enlarged into circular wells or tanks in which the cable could be coiled; even so the Agamemnon was forced to carry several hundred tons of it on deck—a fact which later brought her to the edge of disaster.