News that Russia could be working on plans to sever key internet communications during future wars brings to mind author Tom Clancy and The Hunt for Red October. Indeed, The New York Times first reported in late October that some military sources are worried about a spike in Russian naval activity near the locations of undersea cables. These cables are vital to the Internet's daily operations and move huge amounts of data between continents.

In our world laced with dozens of undersea fiber-optic cables providing Gbps links among continents and remote islands, it is hard to imagine the effort and anguish behind the first transatlantic cable effort.

After all, the current cables are laid by specially designed ships equipped with sonar, sounding gear, detailed undersea charts, GPS and other navigation aids, in addition to weather forecasts, satellite voice/data links and retrieval and repair stations. The cables themselves are optical fibers with all-optical amplifiers that are wrapped in multiple layers of specialized polymers and steel jacketing for protection against ocean floor hazards, sharks, ship anchors and fishing nets. While laying these cables is not routine by any means, it is a carefully planned effort with almost assured success.

A recent BBC report says that Russia watchers have long known of the threat to undersea communications and internet cables. However, they say that cutting the U.S. off from the web would probably be impossible because of the number of connections going into and out of the country.

A Different World

Such was not the case 150 years ago. The story of the first submarine telegraph cable to span the Atlantic Ocean is a throwback to a different world. It is a tale of financial commitment, abortive attempts and major setbacks, renewed commitment and technical innovation within severe limitations, all leading to an eventual—albeit long-delayed—success. The 12-year effort yielded the first message to Europe in July 1866, and shrank the Earth's distances and associated time lags in ways that changed nearly everything about commerce, politics, diplomacy and even war. Many of the technological, material and production advances that the cable-laying venture used remain with us today.

The first cable laying effort was done well before the existence of any instrumentation as we know it, not to mention electric lamps, motors or soldering/welding tools, or the array of engineering materials that now are used for insulation and armoring. Manpower, in the literal sense of the word, was key: although steam engines for power were available, such machines were not suitable for all aspects of the project. As a result, many tasks could only be done by hundreds of laborers working around the clock.

References listed at the end of this article will direct interested readers—and perhaps even an international spymaster or two—to more in-depth studies. However, here are some specific facets of the undertaking that are worth knowing. These include engineering demands and advances in material science, ocean sailing, mass production and at-sea project implementation, all undertaken on a scale that at the time was both inconceivable and yet exciting.

People and Timeline

The project was largely financed by self-made businessman Cyrus Field West and a consortium he put together. He had the idea in 1855 and expected the effort would take a few years and a few million dollars. In fact, the effort required no fewer than four attempts made over more than a decade, and at a cost of tens of millions of mid-19th-century dollars.

Critical to Field's eventual success were a brilliant railroad, tunnel and ship designer, Isambard Kingdom Brunel, and William Thomson (who later became Lord Kelvin), plus workers at the factories that made the cable, those at the plantations that provided the raw insulating substance, master shipbuilders, hundreds of workers who wrapped the miles of cable in the ship's holds, the electrical engineers and craftsmen who could set up and splice (weld) cable at sea, and large sailing crews.

Ocean Route

Little was known about the ocean floor and routes; meaningful charts and mapping did not exist. The estimated maximum depth was said to be about 2½ miles (4 km) with an ocean floor ranging from mud and rock to smooth and sharp. The existence of steep undersea mountain ranges in the mid-Atlantic was just guesswork. A Lieutenant in the U.S. Navy, J.M. Brooke, invented a mechanical device to be attached to a sounding line, which could be dropped to the ocean floor where it collected samples and then was reeled back onboard; this ingenious device provided additional, but still limited, insight into the ocean floor.

The planned ocean route traced a path from St. John's, Newfoundland, to Valentia Bay, Ireland; the path from New York City to St. Johns would make use of land-based cables and several short submarine cables, with similar land-based and short-run submarine links on the Europe side. Navigation was done entirely by compass and star-sighting. As a result, following the planned route and tracing previous locations to find the cable to make repairs, proved to be major challenges.

Sailing Vessels

For each of the four attempts, different ships were used. The first attempt used modified cargo ships. This was followed by a pair of Navy ships that started from opposite sides of the Atlantic and ended with a mid-sea rendezvous and splice. One major issue was the sheer mass and volume of the cable that resulted in many problems, including organizing the cable in the ship so it could be paid out smoothly at sea, and the effect of the volume of cable on ship stability and handling (several times the ships nearly sank during severe storms).

The SS Great Eastern at low tide. Image source: The SS Great Eastern at low tide. Image source: Then there was the SS Great Eastern, the ship that laid the cable on the ultimately successful attempt. She was unlike any other ocean-going vessel, custom-designed and built for this one task at enormous expense. This iron ship was roughly the size of one of today's larger cruise ships: it was nearly 700 feet long, had a beam of 120 feet and displaced 22,500 tons. Rather than use the space-wasting rib-based structure of other ships, it used a double hull for strength, and was among the first to include watertight compartments.

A ship of this size and displacement needed a huge amount of thrust to carry the cable load, especially in strong seas. In addition to sails, the Great Eastern had side paddlewheels and a stern screw propeller (that was 24-feet in diameter) for propulsion. Each had its own steam power plant (3,800 horsepower for the paddles, and 6,800 horsepower for the screw) because there was as yet no steam engine powerful enough to drive a stern screw and yet be small enough to fit within the ship's available space.

Construction of the Great Eastern required nearly all of the heavy plate-steel production capacity in the United States. New techniques had to be developed for assembling and fastening the plates, because the sheer size and required strength of the final ship placed extreme demands on construction. And, because refrigeration had not yet been perfected, the ship carried live animals to feed the crew of 500. Loading the cable onto the ship took three months.

The Cable

Managing the cable and rolling it out smoothly with the proper tension so it would not snap with the ship's motion and ocean swells was another problem to be solved. The first attempts had a manually operated tensioner wherein a crewman read a tension gauge and controlled a brake as needed. However, the complexity and size of the undertaking, along with the ocean swells, made this unreliable, leading to cable breaks followed by retrieval attempts and splicing. The successful attempt made use of a radical design, which was not only smaller and lighter than predecessors, but also had a more accurate way of measuring tension in real time and automatically adjusting a controlling brake.

The central section and armor layer of the successful cable, with outer protective layer removed. Image source: central section and armor layer of the successful cable, with outer protective layer removed. Image source: The cable for the first attempt was made of seven strands of copper wire (each 0.028 inch in diameter) twisted to make a core 0.083 inch in diameter. This core, which weighed about 100 pounds per nautical mile, was covered with three separate layers of processed gutta-percha (a latex-like secretion from tropical trees. This, in turn, was covered by hemp saturated with a mix of tar, pitch and linseed oil.

The electrical core was protected by an armored layer of 18 iron wires, each made of seven strands. The entire cable was covered with another layer of tar. The final cable measured about 5/8-inch in diameter, weighed about one ton per nautical mile and had a tensile strength of about 6,500 pounds. Due to the limited understanding of metallurgy, the cable's conductivity was inconsistent, and ranged by more than a two-to-one ratio.

The project consumed nearly the entire worldwide production of gutta-percha. Indeed, transforming the raw liquid into final cable insulation was a major industrial-processing task. The cable was tested for electrical conductivity and also was subjected to a hydraulic-pressure test to simulate ocean-depth pressure and verify the integrity of the insulation.

With each successive submarine attempt, the cable was improved and strengthened. The cable carried by the Great Eastern on the successful run used the same type of copper core with seven strands, but was three times heavier overall. The copper used was more highly refined and purified to ensure good and consistent conductivity. The three layers of gutta-percha were increased to four, and supplemented with an intermediate layers of an insulating compound developed specifically for the project.

The iron cladding also was upgraded to a newly developed form of steel called charcoal iron. More pitch-soaked hemp also was used, and the cladding was galvanized to inhibit rust and corrosion. This cladding, in particular, had an additional benefit: the outermost hemp layer did not have to be impregnated with pitch to resist corrosion. This meant the cable was no longer sticky and thus did not attract and hold tiny bits of metal, which caused problems. Techniques were developed to test the electrical and insulation integrity of the cable as it was being spooled out so that defective sections would not be used.

The final cable weighed about twice as much as the one used on the first attempt and was twice as strong. However, due to its larger overall diameter (1.1 inches), it was less dense and effectively lighter in water. This, in turn, reduced load on the above-surface cable as it was spooled out.

Test and Repair

The 19th century was a world of passive circuits. Amplifiers as we know them did not exist; any signal sent down a cable had to arrive and be sensed at the far end without benefit of repeaters. Although electromechanical relays were used as repeaters in land-based telegraphy, they were not feasible for submarine use due to reliability issues and the need to provide DC power for them.

The central portion of Lord Kelvin's galvanometer; this version was intended for use at a land station. Image source: central portion of Lord Kelvin's galvanometer; this version was intended for use at a land station. Image source: The only way to test the cable’s integrity both at manufacturing and after its underwater placement was to send a pulse down the cable and look for a minuscule output at the far end. This is where Lord Kelvin played a role. In addition to advising on the cable construction and electrical aspects, he developed a highly sensitive galvanometer that would visibly indicate if even a tiny current flow existed and, thus, an intact cable (versions of this device are still in use). Lord Kelvin wound an electromagnetic coil around a lightweight core, to which he attached a mirror. By shining a lightbeam on this mirror, any minute deflection due to current flow could be seen as a movement of the reflected beam.

Repairing the cable meant that the break first had to be found. Today, time-domain reflectometry (TDR) is routinely used to locate cable breaks with high accuracy and precision. For breaks of the first transatlantic cable, however, the cable-laying ship stumbled around blindly; crews used a grappling hook that was dragged along the ocean floor in an effort to snag the cable then bring it to the surface for splicing. The splicing itself was a major project requiring special fixtures, onboard welding, skilled labor and re-insulating over the splice and all of this done, in most cases, on board a rolling ship.

For invisible breaks of the copper conductor within the cable, sections were pulled up from the sea floor, sliced off a piece at a time until the break was located and then spliced. Special grappling and lifting techniques, using a helper ship and an intermediate subsurface buoy, were developed so the weight of the cable being hauled on board did not snap the onboard cable.

On one attempt to locate a break, the chief electrical engineer sought to boost signal strength by increasing the voltage supplied by batteries via induction coils to several thousand volts from the nominal level of several hundred volts. This may have burned out the cable and created many internal short circuits, which likely resulted in failure of the overall attempt. (To be fair, our present technical understanding and consistent definitions of voltage, current, resistance and insulation breakdown, plus an electrical model of a cable, did not exist at the time.)

Success, then Scrap

The first successful connection was established in 1866. Messages could be sent between North America and Europe without the need for physical transport by ship and associated time lags. However, the telegraph signaling rate was on the order of one character per minute due to the inherent series inductance and parallel capacitive loading within the cable, neither of which was well understood. The cost to transmit a message was an astonishing $1 per letter in an era when a workingman's pay might be a few dollars per week.

The Great Eastern was celebrated as a man-made wonder, and rightfully so. However, it was good at only one thing and was costly and complicated to operate. The ship was so large that there were only few places for it to dock, and it needed a squadron of smaller ships to ferry supplies, crew and fuel to it. It was soon replaced by smaller ships that used new techniques, and it was no longer viable. Suggestions were made to turn it into an ocean liner, or to hollow it out and use it as a floating drydock; after a few decades of passing from one owner to another it was sold for scrap.


The successful deployment of this first transatlantic submarine did more than provide a way for news and diplomatic messages to reach the other side with a speed that we consider laughingly slow now, but which was orders of magnitude faster and with greater reliability than even the best alternative. Like many such projects, it relied on the latest in technology, but also spurred advances that other projects soon leveraged. These advances included material science and metallurgy, large-scale manufacturing, ocean-going operations, large-vessel design and construction, principles of cable-based media and testing and repair techniques.

Within a few years of this success, additional transatlantic cables were deployed and operated on parallel submarine routes. This added capacity and redundancy linked many far-flung locales. For example, at the time of the historic volcanic explosion at Krakatoa in 1883 (which killed over 300,000 people), the Dutch trading post about 10 miles away was linked to nearby islands and in turn to Europe and North America so that news of the eruption reached those places within hours.

It is hard to imagine that a private investor group (admittedly with some technical help and modest financial support from the U.S. and British governments) would literally sink so much time, energy and money into such an audacious project, nor give up even after several costly and frustrating failures. Although their immediate goal was clearly defined, the investors had little idea of the full range of resources they would need, the problems they would face, the innovations their project would require, and the advances it would inspire for others to use. That the group continued is a tribute to their spirit, vision, commitment, perseverance and willingness to take major risks even at great cost. The current international community would do well to take note of this engineering marvel.


  1. John Steele Gordon, "A Thread Across the Ocean: The Heroic Story of the Transatlantic Cable," Walker & Co, NY, 2002.
  2. Chester G. Hearn, "Circuits in the Sea: The Men, The Ships, and the Atlantic Cable," Praeger Publishers, Westport Conn., 2004.
  3. "The Great Transatlantic Cable," (video), PBS American Experience, 2005,