1000 Things Worth Knowing

by Nathaniel C. Fowler

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, Mass. In 1873 the fourth Atlantic cable connected Ireland and Trinity Bay, New Foundland. 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 under water, 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 The system has been entirely superseded by the use of the syphon galvanometer.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 analine 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 imbedded in gutta percha or similar substance, which is one of the best nonconductors 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 imbedded into the insulation, so as to insure 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.