Heroes of the Telegraph

by John Munro

The 'duplex' system, or method of telegraphing in opposite directions at once through the same wire, has of late years been applied, in connection with the recorder, to all the long cables of that most enterprising of telegraph companies—the Eastern—so that both stations may 'speak' to each other simultaneously. Thus the carrying capacity of the wire is in practice nearly doubled, and recorders are busy writing at both ends of the cable at once, as if the messages came up out of the sea itself.

We have thus far followed out the recorder in its practical application to submarine telegraphy. Let us now regard it for a moment in its more philosophic aspect. We are at once struck with its self-dependence as a machine, and even its resemblance in some respects to a living creature. All its activity depends on the galvanic current. From three separate sources invisible currents are led to its principal parts, and are at once physically changed. That entering the mouse-mill becomes transmuted in part into the mechanical motion of the revolving drum, and part into electricity of a more intense nature—into mimic lightning, in fact, with its accompaniments of heat and sound. That entering the signal magnet expends part of its force in the magnetism of the core. That entering the signal coil, which may be taken as the brain of the instrument, appears to us as INTELLIGENCE.

The recorder is now in use in all four quarters of the globe, from Northern Europe to Southern Brazil, from China to New England. Many and complete are the adjustments for rendering it serviceable under a wide range of electrical conditions and climatic changes. The siphon is, of course, in a mechanical sense, the most delicate part, but, in an electrical sense, the mouse-mill proves the most susceptible. It is essential for the fine marking of the siphon that the ink should neither be too strongly nor too feebly electrified. When the atmosphere is moderately humid, a proper supply of electricity is generated by the mouse-mill, the paper is sufficiently moist, and the ink flows freely. But an excess of moisture in the air diminishes the available supply of EXALTED electricity. In fact, the damp depositing on the parts leads the electricity away, and the ink tends to clog in the siphon. On the other hand, drought not only supercharges the ink, but dries the paper so much that it INSULATES the siphon point from the metal tablet and the earth. There is then an insufficient escape for the electricity of the ink to earth; the ink ceases to flow down the siphon; the siphon itself becomes highly electrified and agitated with vibrations of its own; the line becomes spluttered and uncertain.

Various devices are employed at different stations to cure these local complaints. The electrician soon learns to diagnose and prescribe for this, his most valuable charge. At Aden, where they suffer much from humidity, the mouse-mill is or has been surrounded with burning carbon. At Malta a gas flame was used for the same purpose. At Suez, where they suffer from drought, a cloud of steam was kept rising round the instrument, saturating the air and paper. At more temperate places the ordinary means of drying the air by taking advantage of the absorbing power of sulphuric acid for moisture prevailed. At Marseilles the recorder acted in some respects like a barometer. Marseilles is subject to sudden incursions of dry northerly winds, termed the MISTRAL. The recorder never failed to indicate the mistral when it blew, and sometimes even to predict it by many hours. Before the storm was itself felt, the delicate glass pen became agitated and disturbed, the frail blue line broken and irregular. The electrician knew that the mistral would blow before long, and, as it rarely blows for less than three days at a time, that rather rude wind, so dreaded by the Marseillaise, was doubly dreaded by him.

The recorder was first used experimentally at St. Pierre, on the French Atlantic cable, in 1869. This was numbered 0, as we were told by Mr. White of Glasgow, the maker, whose skill has contributed not a little to the success of the recorder. No. 1 was first used practically on the Falmouth and Gibraltar cable of the Eastern Telegraph Company in July, 1870. No. 1 was also exhibited at Mr. (now Sir John) Pender's telegraph soiree in 1870. On that occasion, memorable even beyond telegraphic circles, 'three hundred of the notabilities of rank and fashion gathered together at Mr. Pender's house in Arlington Street, Piccadilly, to celebrate the completion of submarine communication between London and Bombay by the successful laying of the Falmouth, Gibraltar and Malta and the British Indian cable lines.' Mr. Pender's house was literally turned outside in; the front door was removed, the courtyard temporarily covered with an iron roof and the whole decorated in the grandest style. Over the gateway was a gallery filled with the band of the Scots Fusilier Guards; and over the portico of the house door hung the grapnel which brought up the 1865 cable, made resplendent to the eye by a coating of gold leaf. A handsome staircase, newly erected, permitted the guests to pass from the reception-room to the drawing-room. In the grounds at the back of the house stood the royal tent, where the Prince of Wales and a select party, including the Duke of Cambridge and Lady Mayo, wife of the Viceroy of India at that time, were entertained at supper. Into this tent were brought wires from India, America, Egypt, and other places, and Lady Mayo sent off a message to India about half-past eleven, and had received a reply before twelve, telling her that her husband and sons were quite well at five o'clock the next morning. The recorder, which was shown in operation, naturally stood in the place of honour, and attracted great attention.

The minor features of the recorder have been simplified by other inventors of late; for example, magnets of steel have been substituted for the electro-magnets which influence the swinging coil; and the ink, instead of being electrified by the mouse-mill, is shed on the paper by a rapid vibration of the siphon point.

To introduce his apparatus for signalling on long submarine cables, Sir William Thomson entered into a partnership with Mr. C. F. Varley, who first applied condensers to sharpen the signals, and Professor Fleeming Jenkin, of Edinburgh University. In conjunction with the latter, he also devised an 'automatic curb sender,' or key, for sending messages on a cable, as the well-known Wheatstone transmitter sends them on a land line.

In both instruments the signals are sent by means of a perforated ribbon of paper; but the cable sender was the more complicated, because the cable signals are formed by both positive and negative currents, and not merely by a single current, whether positive or negative. Moreover, to curb the prolongation of the signals due to induction, each signal was made by two opposite currents in succession—a positive followed by a negative, or a negative followed by a positive, as the case might be. The after-current had the effect of curbing its precursor. This self-acting cable key was brought out in 1876, and tried on the lines of the Eastern Telegraph Company.

Sir William Thomson took part in the laying of the French Atlantic cable of 1869, and with Professor Jenkin was engineer of the Western and Brazilian and Platino-Brazilian cables. He was present at the laying of the Para to Pernambuco section of the Brazilian coast cables in 1873, and introduced his method of deep-sea sounding, in which a steel pianoforte wire replaces the ordinary land line. The wire glides so easily to the bottom that 'flying soundings' can be taken while the ship is going at full speed. A pressure-gauge to register the depth of the sinker has been added by Sir William.

About the same time he revived the Sumner method of finding a ship's place at sea, and calculated a set of tables for its ready application. His most important aid to the mariner is, however, the adjustable compass, which he brought out soon afterwards. It is a great improvement on the older instrument, being steadier, less hampered by friction, and the deviation due to the ship's own magnetism can be corrected by movable masses of iron at the binnacle.