oceanic laying
Contenido
El cable se componía de siete alambres de cobre, cada uno pesaba 26 kg/km (107 libras por milla náutica), cubierto con tres capas de gutapercha, con un peso de 64 kg/km (261 libras por milla náutica), y terminó con el asfaltado de cáñamo, sobre el cual una vaina de 18 hilos, cada uno de siete alambres de hierro, se colocó en forma de espiral. Pesaba cerca de 550 kg/km (1.1 toneladas por milla náutica), era relativamente flexible y capaz de soportar una fuerza de varias decenas de kN (varias toneladas). Fue realizado conjuntamente por dos empresas inglesas: Glass, Elliot & Co., de Greenwich, y RS Newall & Co., de Birkenhead. Al final de la fabricación se descubrió que las secciones respectivas se habían realizado con los filamentos retorcidos en direcciones opuestas. Aunque resultó una simple cuestión de unir las dos secciones, la opinión pública magnificó posteriormente este error.[7].
El Gobierno británico concedió a Field un subsidio de 1400 £ al año y prestó los barcos necesarios. Field solicitó la ayuda del Congreso de los Estados Unidos. La votación fue muy ajustada, con una serie de senadores anglófobos oponiéndose a cualquier concesión, y el proyecto de ley se aprobó por un solo voto de diferencia. En la Cámara de Representantes se encontró con una hostilidad similar, pero en última instancia, fue firmado por el presidente Franklin Pierce.
The first attempt
The first attempt, in 1857, was a failure. The ships chosen for the installation of the cable were converted warships: HMS Agamemnon&action=edit&redlink=1 "HMS Agamemnon (1852) (not yet drafted)") and USS Niagara&action=edit&redlink=1 "USS Niagara (1855) (not yet drafted)"). The cable began near Ballycarbery Castle, County Kerry, on the south-west coast of Ireland, on 5 August 1857.[8] The cable broke on the first day at almost 3.2 km depth, and the operation was abandoned that year.
Second attempt
The following summer, the Agamemnon and the Niagara, after several trials in the Bay of Biscay, tried again. The ships were to meet in the middle of the Atlantic, where the two halves of the cable were to be spliced together, and while the Agamemnon would unwind eastward to the island of Valentia, the Niagara would unwind west toward Newfoundland. On June 26, the center splice was made and the cable sank. Once again the cable broke, first after less than 5.5 km (three nautical miles), again after about 100 km (54 nautical miles), and for the third time when about 370 km (200 nautical miles) of cable had been left outside each vessel.
Third attempt
The expedition returned to Queenstown to depart again on 17 July with little enthusiasm among the crews. The center splice was completed on July 29, 1858. The cable ran easy this time. The Niagara reached Trinity Bay, Newfoundland, on August 4, and the next morning the end of the shore came ashore. The Agamemnon had an equally successful career. On 5 August, she reached Valentia Island, with the shore end coming ashore at Knightstown and then connecting with the nearby local cable.[9].
First message
On August 16, 1858, the first message sent over the cable was a congratulatory telegram that Queen Victoria sent to American President James Buchanan and expressed her hope that there would result "an additional bond between nations whose friendship is based on their common interest and mutual esteem." The president responded that “it is the most glorious triumph, because it is much more useful to humanity, than was ever won by the conqueror on the battlefield. That the Atlantic telegraph, under the blessing of heaven, will become a link of perpetual peace and friendship between sister nations, and an instrument destined by Divine Providence to spread religion, civilization, liberty and law throughout the world.
Those messages generated an explosion of enthusiasm. The next morning a celebration of 100 guns resounded through New York City, the streets were decorated with flags, church bells rang, and at night the city was illuminated.[12] The Atlantic cable was a subject of countless sermons and a prodigious amount of storytelling.
First cable failure
Operation of the new cable was problematic because the company's two senior electrical engineers had very different ideas about how the cable should be operated.[13] Additionally, Lord Kelvin and Dr. Whitehouse were at opposite ends of the cable and could only communicate over the cable itself.
Lord Kelvin, who was at the western end, believed that it was only necessary to generate a low voltage to detect the peak rise of the current coming out of the wire, and once this had been done, nothing would be gained by further monitoring (Morse code uses a positive current for a dot and a negative current for a dash). Lord Kelvin invented the mirror galvanometer, precisely to quickly observe the change of current.
At the eastern end of the cable stood Dr. Whitehouse. He was the company's chief electrician and a medical doctor, but his knowledge of electricity was self-taught. Whitehouse believed that, in order to obtain a change in current at the receiving end as quickly as possible, the cable must be connected to a high voltage source (several thousand volts via induction coils). The situation was made worse because whenever intelligible Morse code was received on the mirror galvanometer at the eastern end, Whitehouse insisted that the galvanometer be disconnected and replaced with his own patent recording telegraph, which was much less sensitive.
The effects of poor handling and design of the cable, along with Whitehouse's repeated attempts to operate the cable at high voltages, led to deterioration of the cable's insulation. It took more and more time to send messages. Towards the end, sending a half-page text message took a day.
In September, the isolation continued to deteriorate. On October 20, the cable stopped working. In total 732 telegrams had been transmitted.
The reaction to this news was tremendous. Some writers even suggested that the telegraph cable was a hoax, and others thought it was stock market speculation. In the subsequent investigation, Dr Whitehouse was held responsible for the failure, but the company did not escape criticism for employing an electrical engineer without recognized qualifications. Although the handling and conservation of the cable also had its influence: the part of the cable that was not used in the first attempt was left outdoors while the remaining section was built. This deteriorated the gutta-percha insulation.
Reconsideration of the plan
Because of repeated failures, shareholders stopped investing. Furthermore, the following year the Red Sea cable also ended in failure. Submarine cable companies were forced into a fundamental review. In 1859, the British government established a special committee which issued a report that believed that the Atlantic cable was possible.
Cyrus Field was not discouraged by the failure. He was eager to return to work, but the public had lost confidence in the system and his efforts to revive the company were futile. Field received the report: "we decided to try the cable operators again across the Atlantic." Until 1864, with the help of Thomas Brassey and John Pender, he was unable to raise the necessary capital. A start-up company Telcon, later part of BICC, was engaged to manufacture and lay the new cable.
In addition, Field fired Whitehouse as chief electrician and replaced him with Thomson. Thomson took the above observations into account and increased the cross-sectional area of the copper wire and insulation to allow for an increase in transmission intensity. The cable was designed under careful research and many experiments were carried out. The cable design was improved thanks to those experiments. The core consisted of seven strands of very pure copper stranded, weighing 300 pounds per nautical mile (73 kg/km), coated with a Chatterton compound. It was then covered with four layers of gutta-percha, alternating with four thin layers of the cementing compound of the set, and bringing the weight of the insulator up to 400 pounds/NMI (98 kg/km). This core was covered with hemp saturated in a preservative solution, and on the hemp were spirally wound eighteen single chains of high tension steel produced by Webster & Horsfall Ltd of Hay Mills of Birmingham, each covered with fine manila threads also impregnated in the preservative. The weight of the new cable increased to 35.75 quintals (4,000 pounds) per nautical mile (980 kg/km), almost double the weight of the old one. The Haymills site successfully manufactured wire (1600 tonnes), employing 250 workers for over eleven months.
Cable repair
The broken cables required an elaborate repair procedure. The approximate distance where the break had occurred was determined by measuring the resistance of the broken cable. Repair ships sailed to that location. The cable was hooked with a grappling hook and hoisted on board to check electrical continuity. Buoys were deployed to mark the ends of the good cable and a new splice was made between the two ends.[14][15].