SECTIONS OF CABLES (REDUCED). 1. Main cable of 1858. 1a. Shore end, abandoned cable of 1858. 2. Main cable of 1866. 2a. Shore-end, recovered cable of 1865. 3. Shore end of cable of 1866.
Copper is one of the best conductors of electricity known, and hence the wires in the center are made of that metal. Water, too, is an excellent conductor, and if the wires were not closely protected, the electricity would pass from them into the sea, instead of carrying its message the whole length of the line. Therefore, the wires must be encased or insulated in some material that will not admit water and is not itself a conductor. Gutta-percha meets these needs, and the hemp and galvanized wire are added for the strength and protection they afford to the whole.
It was an American who first thought of laying such an electric cable as this under the turbulent Atlantic. Some foolish people laughed at the idea and declared it to be impracticable. How could a slender cord, two thousand miles long, be lowered from an unsteady vessel to the bottom of the ocean without break? It would part under the strain put upon it, and it would be attacked by marine monsters, twisted and broken by the currents. At one point the bed of the sea suddenly sinks from a depth of two hundred and ten fathoms to a depth of two thousand and fifty fathoms. Here the strain on the cable as it passed over the ship's stern would be so great that it certainly must break. More than this, the slightest flaw—a hole smaller than a pin's head—in the gutta-percha insulator would spoil the entire work, and no remedy would be possible. A great many people spoke in this way when the Atlantic cable was first thought of, as others, years before, had spoken of Watt and Stephenson. But Watt invented the steam-engine, Stephenson invented the locomotive, and Cyrus Field bound Great Britain to the United States by telegraph.
Early in 1854, Mr. Field's attention was drawn to the scheme for a telegraph between Nova Scotia and Newfoundland, in connection with a line of fast steamships from Ireland to call at St. John's, Newfoundland. The idea struck him that if a line were laid to Ireland, lasting benefit would result to the world. So he called together some of his intimate friends, including Peter Cooper, Moses Taylor, Chandler White, and Marshall O. Roberts, and they joined him in organizing the "New York, Newfoundland, and London Telegraph Company," which was the pioneer in the movement to connect the two continents by a telegraph cable, and without whose aid its consummation would have been indefinitely delayed.
The work was costly and difficult. The first part consisted in surveying the bottom of the sea for a route. This was done by taking "soundings" and "dredgings." As some of you are aware, "sounding" is an operation for ascertaining the depth of the sea, while "dredging" reveals what plants and living creatures are at the bottom. After much patient labor, a level space was found between Ireland and Newfoundland, and it seemed to be so well adapted to the surveyor's purposes that it was called the "Telegraphic Plateau."
Two or three large vessels were next equipped, and sent out with several thousand miles of cable on board, which they proceeded to lay. But the fragile cord—fragile compared with the boisterous power of the waves—broke in twain, and could not be recovered. A second attempt was made, and that failed, too. Brave men can overcome adversity, however, and the little band of scientific men and capitalists were brave men and were determined to succeed. Each heart suffered the acute anguish of long-deferred hope, and each expedition cost many hundred thousands of dollars. Nevertheless, the promoters of the Atlantic cable sent out a third time, and when failure met them again, it seemed to common minds that their scheme was a settled impossibility. Not so with the heroes. Each failure showed them some faults in their plans or machinery. These they amended. Thus, while they were left at a distance from the object of their ambition, they were brought a little nearer to its attainment.
Guided by the light of past experience, they equipped a fourth expedition. The "Great Eastern" was selected, and her interior was altered for the purpose. She was, and is still, the largest vessel afloat. Her length is six hundred and ninety-five feet; her breadth eighty-five feet, and her burthen twenty-two thousand tons. One of the principal causes of failure in previous expeditions was the inability of the cable to endure the severe strain put upon it in stormy weather as it passed from an ordinarily unsteady vessel into the sea. The "Great Eastern," from her immense size, promised to be steady in the worst of gales. Her hold was fitted with three enormous iron tanks—-a "fore" tank, a "main" tank, and an "after" tank. The main tank was the largest, and eight hundred and sixty-four miles of cable were coiled in it. Eight hundred and thirty-nine miles in addition were coiled in the after tank, and six hundred and seventy miles in the fore tank, making in all two thousand three hundred and seventy-four miles of cable. The food taken on board for the long voyage in prospect consisted of twenty thousand pounds of butcher-meat, five hundred head of poultry, one hundred and fourteen live sheep, eight bullocks, a milch cow, and eighty tons of ice.
What is called the shore-end of the cable—i.e., that part nearest the shore, which is thicker than the rest—was first laid by a smaller steamer. It extended from Valentia to a point twenty-eight miles at sea. Here it was buoyed, until the great ship arrived. On a wet day in July, 1866, it was joined with the main cable on board the "Great Eastern," and on the same day that vessel started on her voyage to Newfoundland.
It may seem a simple matter to distribute or "pay out" the cable, but in practice it is exceedingly difficult. Twenty men are stationed in the tank from which it is issuing, each dressed in a canvas suit, without pockets, and in boots without nails. Their duty is to ease each coil as it passes out of the tank, and to give notice of the marks painted on the cable one mile apart. Near the entrance of the tank it runs over a grooved wheel and along an iron trough until it reaches that part of the deck where the "paying out" machine is placed. The latter consists of six grooved wheels, each provided with a smaller wheel, called a "jockey," placed against the upper side of the groove so as to press against the cable as it goes through, and retard or help its progress. These six wheels and their jockeys are themselves controlled by brakes, and after it has been embraced by them the cable winds round a "drum" four times. The drum is another wheel, four feet in diameter and nine inches deep, which is also controlled by powerful brakes; and from it the cable passes over another grooved wheel before it gets to the "dynamometer" wheel. The dynamometer is an instrument which shows the exact degree of the strain on the cable, and the wheel attached to it rises and falls as the strain is greater or less. Thence the cable is sent over another deeply grooved wheel into the sea.