All of these men are retired Cable & Wireless employees. They sketched in for us the history of this strange compound of white buildings. Like any old-time cable station, it housed the equipment for receiving and transmitting messages as well as lodgings and support services for the telegraphers who manned it. But in addition it served as the campus of a school where Cable & Wireless foreign service staff were trained, complete with dormitories, faculty housing, gymnasium, and dining hall.
The whole campus has been shut down since 1970. In recent years, though, the gentlemen we met in the pub, with the assistance of a local historical trust, have been building and operating the Museum of Submarine Telegraphy here. These men are of a generation that trained on the campus shortly after World War II, and between them they have lived and worked in just as many exotic places as the latter-day cable guys we met on Lan Tao Island: Buenos Aires, Ascension Island, Cyprus, Jordan, the West Indies, Saudi Arabia, Bahrain, Trinidad, Dubai.
Fortunately, the tiny hut above the beach is not the museum. It's just the place where the cables are terminated. FLAG and other modern cables bypass it and terminate in a modern station up at the head of the valley, so
all of the cables in this hut are old and out of service. They are labeled with the names of the cities where they terminate: Faial in the Azores, Brest in France, Bilbao in Spain, Gibraltar 1, Saint John's in Newfoundland, the Isles of Scilly, two cables to Carcavelos in Portugal, Vigo in Spain, Gibraltar 2 and 3. From this hut, the wires proceed up the valley a couple hundred meters to the cable station proper, which is encased in solid rock.
During World War II, the Porthcurno cable nexus was such a painfully obvious target for a Nazi attack that a detachment of Cornish miners were brought in to carve a big tunnel out of a rock hill that rises above the campus. This turned out to be so wet that it was necessary to then construct a house inside the tunnel, complete with pitched roof, gutters, and downspouts to carry away the eternal drizzle of groundwater. The strategically important parts of the cable station were moved inside. Porthcurno Bay and the Cable & Wireless campus were laced with additional defensive measures, like a fuel-filled pipe underneath the water to cremate incoming Huns.
Now the house in the tunnel is the home of the museum. It is sealed from the outside world by two blast doors, each of which consists of a foot-thick box welded together from inch-thick steel plate. The inner door has a gasket to keep out poison gas. Inside, the building is clean and almost cozy, and except for the lack of windows, one is not conscious of being underground.
Practically the first thing we saw upon entering was a fully functional Kelvin mirror galvanometer - the exquisitely sensitive detector that sent Wildman Whitehouse into ignominy, made the first transatlantic cable useful, and earned William Thomson his first major fortune. Most of its delicate innards are concealed within a metal case. The beam of light that reflects off its tiny twisting mirror shines against a long horizontal screen of paper, marked and numbered like a yardstick, extending about 10 inches on either side of a central zero point. The light forms a spot on this screen about the size and shape of a dime cut in half. It is so sensitive that merely touching the machine's case - grounding it - causes the spot of light to swing wildly to one end of the scale.
At Porthcurno this device was used for more than one purpose. One of the most important activities at a cable station is pinpointing the locations of faults, which is done by measuring the resistance in the cable. Since the resistance per unit of length is a known quantity, a precise measurement of resistance gives the distance to the fault. Measuring resistance was done by use of a device called a Wheatstone bridge. The museum has a beautiful one, built in a walnut box with big brass knobs for dialing in resistances. Use of the Wheatstone bridge relies on achieving a null current with the highest attainable level of precision, and for this purpose, no instrument on earth was better suited than the Kelvin mirror galvanometer. Locating a mid-ocean fault in a cable therefore was reduced to a problem of twiddling the dials on the Wheatstone bridge until the galvanometer's spot of light was centered on the zero mark.
The reason for the ink on Ron Werngren's fingers became evident when we moved to another room and beheld a genuine Kelvin siphon recorder, which he was in the process of debugging. This machine represented the first step in the removal of humans from the global communications loop that has culminated in the machine room at cable landing stations like Ninomiya.
After Kelvin's mirror galvanometer became standard equipment throughout the wired world, every message coming down the cables had to pass, briefly, through the minds of human operators such as the ones who were schooled at the Porthcurno campus. These were highly trained young men in slicked hair and starched collars, working in teams of two or three: one to watch the moving spot of light and divine the letters, a second to write them down, and, if the message were being relayed down another cable, a third to key it in again.
It was clear from the very beginning that this was an error-prone process, and when the young men in the starched collars began getting into fistfights, it also became clear that it was a job full of stress. The stress derived from the fact that if the man watching the spot of light let his attention wander for one moment, information would be forever lost. What was needed was some mechanical way to make a record of the signals coming down the cable. But because of the weakness of these signals, this was no easy job.
Lord Kelvin, never one to rest on his laurels, solved the problem with the siphon recorder. For all its historical importance, and for all the money it made Kelvin, it is a flaky-looking piece of business. There is a reel of paper tape which is drawn steadily through the machine by a motor. Mounted above it is a small reservoir containing perhaps a tablespoon of ink. What looks like a gossamer strand emerges from the ink and bends around through some delicate metal fittings so that its other end caresses the surface of the moving tape. This strand is actually an extremely thin glass tube that siphons the ink from the reservoir onto the paper. The idea is that the current in the cable, by passing through an electromechanical device, will cause this tube to move slightly to one side or the other, just like the spot of light in the mirror galvanometer. But the current in the old cables was so feeble that even the infinitesimal contact point between the glass tube and the tape still induced too much friction, so Kelvin invented a remarkable kludge: he built a vibrator into the system that causes the glass tube to thrum like a guitar string so that its point of contact on the paper is always in slight motion.
Dynamic friction (between moving objects) is always less than static friction (between objects that are at rest with respect to each other). The vibration in the glass siphon tube reduced the friction against the paper tape to the point where even the weak currents in a submarine cable could move it back and forth. Movement to one side of the tape represented a dot, to the other side a dash. We prevailed upon Werngren to tap out the message Get Wired.The result is on the cover of this magazine, and if you know Morse code you can pick the letters out easily.
The question naturally arises: How does one go about manufacturing a hollow glass tube thinner than a hair? More to the point, how did they do it 100 years ago? After all, as Worrall pointed out, they needed to be able to repair these machines when they were posted out on Ascension Island. The answer is straightforward and technically sweet: you take a much thicker glass tube, heat it over a Bunsen burner until it glows and softens, and then pull sharply on both ends. It forms a long, thin tendril, like a string of melted cheese stretching away from a piece of pizza. Amazingly, it does not close up into a solid glass fiber, but remains a tube no matter how thin it gets.