Chapter 2
Section 2 of A Thousand Things Worth Knowing. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by Pamela Nagami.
A Thousand Things Worth Knowing by Nathaniel C. Fowler, Jr. Atlantic Cable. The original, or rather the first permanent cable, was laid in July 1866 connecting Ireland with Newfoundland, but an earlier cable was laid between the foregoing points, which was lost in construction.
This lost cable, however, was recovered and completed. In 1868, a cable was laid from France to Duxbury, Massachusetts. In 1873, the fourth Atlantic cable connected Ireland and Trinity Bay, Newfoundland. Several cables have been subsequently laid and are maintained. Considerable difficulty was experienced in obtaining the right kind and a sufficient
current of electricity, which would carry the message several thousand miles underwater and not pass from the cable into the water itself. Two keys are used, which when depressed, transmit respectively positive and negative currents coming from the connected batteries. The current does not pass directly into the cable, but enters what is known as a condenser
and from there reaches the wire itself. This increases the force of the current and overcomes interfering earth currents. Originally, the messages were received by a reflecting galvanometer. Upon the magnet of this instrument was placed a small curved mirror and in front of it was a lighted lamp behind a frame with a vertical slit.
The light from the lamp passed through the slit and fell upon the surface of the mirror. The flashes of light moving with the movements of the suspended needle indicated the message sent. Because of the delicacy of the instrument, it was difficult to translate the telegraphic code. The system has been entirely superseded by the use of the siphon galvanometer. This needle is affected by the currents and moves in response to the opening and closing
of the telegraphic key. It consists of a small hollow needle which swings between two fixed magnets. A very soluble aniline ink is allowed to flow through the tube. The mouth of this tube is suspended, a very small fraction above a strip or roll of white paper which moves automatically.
The vibration or movements of the needle allow the ink to flow in irregular lines or curves upon the moving paper. These irregularities or curves indicate letters which are easily read by the receiving operator. Cable dispatches now are recorded, when formerly they had to be read as they were seen, with the impossibility of retaining an automatic record of them.
Professor Morse, the inventor of telegraphy, may be considered the inventor of the cable, although he had little to do with its mechanical construction. To Mr. Cyrus W. Field, must be given much of the credit for its accomplishment was largely due to his foresight and energy. The cable consists of several copper wires embedded in gutter-percha or similar substance
which is one of the best non-conductors of electricity. The cable with its several wires and coverings or insulation has a circumference equal to that of the old-fashioned three-cent piece. Several wires are embedded into the insulation so as to ensure better connection. The cable is laid by steamers built for the purpose.
They travel over a charted route and unscientifically speaking throw the cable overboard. Of course, no cable could be constructed of a length that would reach across the ocean. New pieces are therefore spliced in as conditions require. If the sea is too rough for the laying of the cable, the end is buoyed and picked up when the weather changes.
The cable lies upon the bottom of the ocean, and as the bottom of the ocean is as irregular as the surface of the earth with its mountains, plateaus and valleys, there is always danger of the cable being broken or injured, although there is of course absolute quiet at the bottom of the ocean. Then, many feet or even a mile of cable may be stretched between two projecting points
and the strain may part it in time. The process of locating a break or injury is very interesting. The cable fails to work. The operator stationed at either end discharges electricity into the cable and although it doesn't reach the other side, he can, by a delicate instrument, locate approximately
the place of parting or where injury has occurred. The repair steamer sails for the place. With grappling irons it brings the cable to the surface, but as the location of the break cannot be determined accurately, the electrician on board must determine which way to sail to locate the place of the trouble.
He attaches the cable to a battery on board and opens connection with the land. If the break, for example, is between him and Europe, the European operator will not respond, but he will receive a reply from the American operator. He then directs the vessel's course toward Europe. The cable, when it is taken on board, is run on pulley wheels, one in the bow and one in
the stern of the vessel, and the vessel sails slowly under the cable. As the vessel is two or three hundred feet long, several hundred feet of cable will be exposed. The cable is watched carefully and the break or injury will be easily located. When it is, the operator connects the cable with the batteries and then telegraphs in
the direction opposite to that from which he received a reply. If his message goes through, the receiving operator will respond. If a reply comes, he knows he has located the break. If no reply is received, there must be other breaks in the same direction. The break is repaired and the steamer sails on until it finds another break or injury.
I have attempted to explain this in the simplest words. It is obvious that a scientific explanation would be unintelligible to the average reader. End of Section 2.
