History of the Atlantic Cable & Undersea Communications
Laying a Deep-Sea Cable Line - 1923
Laying a Deep-Sea Cable Line
Only Healthiest of Men Can
Join the Sections,
DURING a period of almost three quarters of a century thin strands of copper, resting in the stillness and darkness on the ocean's bed, have been carrying messages between Europe and North America. The electrical impulses passing over these wires have linked the Old and the New World. Time between the two has been abridged to seconds and minutes, as through the Atlantic waters flash the doings and sayings of the people on each side of the ocean.
Few persons who send cablegram have any adequate conception of the work which must be done and the amount of money spent before such messages can be flashed from one continent to the other. The laying of an ocean cable, its manufacture and repair while in service, may be called herculean feats.
This subject is now creating interest for the reason that the Postal Telegraph - Commercial Cables System the other day took the first step in the laying of a new cable between the United States and Europe. This is said to be the largest and fastest in operation of any deep-sea cable ever manufactured. It is the first to be laid between this country and Europe since 1910, and it will establish the sixth transatlantic circuit owned and operated by the Mackay System.
The American end of the cable was connected with the station at Far Rockaway on Aug. 26, and from that point the cableship Faraday will lay the Far Rockaway-Canso section, which terminates at Canso, Nova Scotia. This cable has a length of about 1,000 miles. Meanwhile, the cableship Colonla, the largest of her kind in the world, will begin to lay another section of the new cable, about 1,750 miles in length, from Canso to the Azores Islands.
At the Azores connection will be made with cables reaching London by way of Waterville, Ireland, and later in the Fall a new section of 1,546 miles will be submerged between the Azores and Havre, thus providing a direct circuit to France and the Continent. The sections between New York and. the Azores are expected to be ready for operation by the end of September, and the cable company has hopes of completing the entire job by Nov. 15.
The new cable has the largest copper conductor ever put in a long-distance submarine cable, and its message-carrying capacity is said to far exceed that of any other cable of similar length. The conductor of the main section weighs 1,100 pounds per nautical mile, against 700 pounds in the largest deep-sea cables used heretofore. The working speed of the new system is expected to be 600 letters a minute simultaneously in each direction, or a full capacity of 1,200 letters.
The laying of this new cable recalls the trials and hardships encountered by Cyrus West Field when he labored to get the first cable across the Atlantic. After the. necessary survey of the ocean's bed had been made in 1856 by the United States and the British Governments the historic undertaking was begun in August, 1857. The starting point was at Valentia, on the west coast of Ireland. After the cable ship had covered a distance of three miles from shore the cable broke because it was of weak construction. In June, 1858, attempts to lay the cable were resumed. Time and again a start was made, but each attempt proved unsuccessful. The greatest length laid was 200 miles.
150 Words in 30 Hours
In spite of these disheartening failures Field did not despair, and in July he made another attempt. This time the venture proved successful. The cable reached Nova Scotia [actually Newfoundland], and on Aug. 16, 1858, the first cablegram was sent from America to Europe. This message was a greeting from President Buchanan to Queen Victoria. It contained 150 words and it took thirty hours to send it across. A comparison of this speed with that of today may prove interesting. Now a message of that number of words can be sent to England in one and one-quarter minutes.
The first cable across the Atlantic was in operation until Oct. 20. that year, when it broke down. It was operated by means of large induction coils and batteries with a potential of 500 volts or more. It was thought that this high battery power burned out the insulation of the cable. Engineers of that day believed that such a longdistance cable required a high voltage, but they were mistaken. It takes more voltage to send an overland telegraph message from lower Manhattan to the Bronx than is required to send a cablegram across the Atlantic.
The next attempt to lay a cable was made an 1865. A contract for a new line had been given to an English company. This cable weighed 300 pounds to the mile instead of 107, the weight of the old. The Great Eastern, a large oceangoing steamship, was chartered for the trip. On July 23, 1865, with Cyrus Field aboard, the ship started westward from Valentia. Everything. went well until the vessel was within 600 miles of the Newfoundland coast, when the cable broke. Attempts were made to recover it at the time, but these were unsuccessful. Field and his men had to turn back and report their ill luck.
Preparations were made for a further attempt and on July 13, 1866, the Great Eastern started from Valentia, on her second voyage. This proved to be a triumphant one. The ship reached Trinity Bay, Nova Scotia [Newfoundland], without mishap on July 27, and the two hemispheres were again joined by means of cable communication. On the return trip to Europe the Great Eastern made a search for the cable lost the previous year and luckily enough found it. This was joined to a new section which was laid the remaining distance to Nova Scotia [Newfoundland] and thus two transatlantic cables went into operation in that year.
To give the reader some idea of the cable rates to Europe in those days it night be stated that in 1866 the minimum rate for a twenty-word message was $100. The minimum rate, or deferred service rate, today for a similar message is only $1, and the deferred service message of the present. reaches is destination sooner than did the fast messages in 1866.
Although it is almost three-fourths of a century. since oceanic telegraph communication was established, most people know little about the making and laying of cables. The heart of the cable is the conductor and this, through which the electrical impulses are transmitted is composed of the purest quality of copper. Since cables lie at the bottom of the ocean in depths ranging from two to three thousand fathoms, or between two and three miles deep, and as the lifting of a cable from such a depth involves a great strain upon it and all the materials used in its construction, it will be understood that flexibility must be reckoned with.. This being the case, a single copper wire, while flexible, would not. have the same flexibility, or tensile strength, as a number of smaller copper wires with an aggregate weight no greater than the single wire. Hence the "core" of the cable is composed of a strand of copper wires. This :conductor is. covered with gutta percha insulating material.
Delicate Work Involved
The copper core is manufactured in lengths of about three miles and is coiled temporarily on drums. These lengths of core later are joined together and the jointing is of the greatest importance. It is done by hand and requires skillful workmanship. If any dust or gases are allowed to remain or to form in the gutta percha while making a joint it may mean the loss of thousands of dollars, because this weakness will not become apparent until the cable is submerged and thus placed under great pressure, when the most minute impurity or gas bubble in the joint would manifest itself and cause faulty electrical continuity. The deep-sea cable jointer must be a man of temperate habits and in good health. It may seem almost inconceivable, but numerous joints made by skilled but intemperate or unhealthy jointers have proved faulty through what was believed to be the injurious exudations from the pores of the fingers. This will give some idea of the extreme delicacy and importance of perfect jointing.
Over the gutta percha insulation a brass tape is wound which protects the insulation against attacks of an aqueous worm, known as the teredo. This worm, if given the chance, would bore holes in the gutta percha to the copper conductor and cause faulty transmission. The completed core with brass taping is covered with jute yarn, steeped in a tarry preservative. This yarn serves also as a bedding for the outer protecting galvanized iron wires. These wires vary in thickness according to the depth of the water in which the cable rests.
In the manufacture of the new cable for the Mackay system more than 4,000,000 pounds of copper were required or its conductor and 2.000,000 pounds of gutta percha for insulation. At the same time upward of 80,000 miles of steel and iron wires of varying sizes were needed to protect the copper conductor and the gutta percha insulation.
Near landing places the armor wires of the cable are large and heavy. The shore end of the new cable weighs about twenty tons to the mile. It tapers down as the cable runs into deep water, where the weight is about two tons a mile. The shore end of the cable is something over four inches in diameter and the deep-sea portion is not much more than an inch and a quarter. It will lie at depths anywhere from 10,000 to 17,000 feet below the surface. The cost and the laying of the cable will amount to something more than $15,000,000.
The laying of long submarine cables is not an easy matter. It is a well-known fact that the contour of the ocean's bottom varies similarly to that of dry land. It has its rolling and steep hills, its valleys and plateaus. It therefore is necessary to know the contour of the ocean bed before the cable is laid. This is essential to avoid suspending the cable between two hills, where it would hang in a festoon, or like a clothesline between two poles. Such suspension soon would cause the cable to wear because of its own weight.
The route over which the cable will lie must be more carefully surveyed than the course for a new railroad over prairies, through forests and across mountain passes. The ocean survey consists of a series of deep-sea soundings which not only furnish the depth of the water and samples of the water, but also produce specimens of the ocean bottom and the temperature of the water, all of which are important factors in the laying of submarine cables. If by chemical analysis it should transpire that there is any mineral deposit on the bottom of the ocean which would injuriously affect the cable, or if the temperature should show that there was volcanic action at certain places, these must be avoided. Deep-sea sounding machines have been invented to obtain this information. Samples of the sea water along the ocean bed and also the earth deposits are brought to the surface for examination. A specially constructed thermometer that will withstand the terrific pressure at great depths is used in this connection.
Always Dangerous Task
One of the most interesting spots on a cable ship is the testing room. Here sits an electrician in front of a table, glistening softly with polished ebonite and brass terminals of testing apparatus. He is watching a spot of light as it sways to and fro on a graduated scale. This spot is the reflection from the mirror of the galvanometer, and the swaying movement is caused by the induced currents set up in the coiled cable by the rolling of the ship. By the end of every fifth minute the spot gives a kick sideways on the scale and the man properly notes its magnitude. The kick is caused by a signal from shore, having been sent by the electrician in the cable hut which holds the terminal of the cable, and it proves that the continuity of the conductor is still preserved. If the galvanometer indicates that there is something wrong the ship is stopped, the cable cut and, if the fault is near, picking up is begun. If the fault is some distance away the cable is buoyed and the vessel steams to the faulty portion.
The men in charge of cable laying say that under the most favorable conditions it is anxious work. At any time during the paying out, some ten or fourteen days, a storm may arise and raise havoc with the work. One can imagine what a strain is placed on the cable reeling from the stern of the vessel as this is whipped about on mountainous waves. The cable is very likely to break under such conditions and it may be lost in a depth of 2,000 fathoms.
It is hard to predict the time of recovery. It may take three or four days and it may take weeks and months. Should a cable break and be lost, in spite of the best precautions, a mark buoy is lowered at once to guide the ship in grappling operations. Then the dragging is done at right angles to the line in which the cable lies. The grappling iron used to drag the ocean bottom looks like a four-pronged anchor, and if it once catches the cable it will hold it securely until raised to the surface.
Close to the shore where the cables lie in shallow water they suffer from corrosion and the anchors of ships. There are cases on record where cables have been broken by icebergs grounding and crushing them. Some time ago, when the Commercial Cable Company's vessel, the Mackay-Bennett, was on a repair trip, she counted as many as 100 icebergs. In order to carry on her work she had to tow an iceberg to sea so as to take it off the line of cables that needed repair. Cables have been broken in the deeper waters of the Atlantic by submarine slides, which have buried the lines for many miles. A whale one time put an Alaskan cable out of commission. The line was broken and the decomposed carcass of the whale found encircled by the cable when it was recovered during repair. There was an instance where one of the cables in southern waters was damaged by a shark's tooth, which was imbedded in the gutta percha insulation.
Source: New York Times; Sep 2, 1923
Last revised: 20 February, 2011