CHAPTER XI. The Electric Telegraph

THE ELECTRIC TELEGRAPH

WHEN two persons engage in ordinary conversation, they really use two methods of communication. Both methods are extremely complicated. By means of mouth, tongue, and throat, the speaker changes the current of air issuing from his lungs, and throws it into a great variety of vibrations. These vibrations are communicated to the outside air and find their way into the ears of the other person. Such is speech. At the same time, people when speaking employ signals which appeal to the eye. They move their lips, eyelids, eyebrows, and sometimes their hands, and each motion gives a slightly different quality, or stress, to what they are saying. These motions produce an effect upon the waves of light which are constantly passing to and fro between the two people. In this way speech is assisted by sight.

When two persons are far apart and still wish to communicate they have to shout. When the distance becomes greater, their voices become less and less able to cover it, and, finally, they are driven to communicate by sight only. So, we find them waving their hands, or handkerchiefs, or hags at the end of sticks. When the distance is many miles, this method fails again, and communication becomes very difficult. In ancient times people used to get out of the difficulty by lighting big fires which could be seen for ten or fifteen miles in the dark. The smoke from the fire could be seen for about the same distance in the day-time. Some savage tribes use the same method even now, and manage to convey a great deal of information by it. But nowadays we use the electric telegraph for all such purposes, and the story of its invention is one of great interest.

The immediate predecessor of the electric telegraph was the optical telegraph invented by Hooke, Newton’s assistant. The first occasion on which the optical telegraph was put to practical use was about the time of the French Revolution. In the year 1792 the whole of France was covered by a system of signals. The system consisted of a number of towers on the top of which “semaphores” were mounted which looked very much like the railway signals of the present day. By means of this system a message could be sent from Paris to the end of France in a few hours. When the war broke out in Austria in 1809, the great Napoleon profited by it to fall upon the Austrians unawares, giving them no time to make preparations to meet him.

The Austrians were in alliance with the Bavarians, who suffered greatly by the war with Napoleon, and the Bavarian Government asked one of the professors at Munich to devise a system of telegraphy which should be superior to that used so successfully by Napoleon. The name of the professor was Soemmering.

He started on the work at once, and four days after receiving the request he had devised the first electric telegraph which was capable of transmitting the letters a, b, c, d, e. That was all. The apparatus was quite simple and very ingenious. It consisted of one of Volta’s piles made of fifteen pairs of silver and iron plates separated by layers of felt soaked in salt water.

This arrangement was the source of electricity. At the station to which the signals were to be sent there was a bottle or small tank of water with a large cork in the bottom of it. Through this cork five wires were drawn, and they led into water with which the bottle was filled. The five wires were made very long. They were covered with shellac varnish, and then they could be twisted together without being in actual contact. The strand of wire was stretched between the sending station and the receiving station.

At the sending station the strand of wire was unravelled, and the five loose ends were marked with the letters a, b, c, d, e. The top of the Volta pile placed at the sending station gave positive electricity, and the bottom of the pile gave negative electricity. Now, suppose that the wire marked a was brought into contact with the top of the pile, and the wire marked b was brought into contact with the bottom of the pile. Then an electric current travelled all along the strand, through the pile and the two wires, and through the water between the two wires, thus making a complete circuit. The water in the bottle was then split up into hydrogen and oxygen, and bubbles of hydrogen appeared at the wire b where it entered the water. The observer at the receiving station then understood that his companion at the sending station wanted to telegraph to him the letter b.

Whenever the man at the sending station wanted to telegraph a letter, all he had to do was to bring the corresponding wire into contact with the bottom of the pile, and to bring any other wire into contact with the top of the pile. The wire at the top was usually the wire which came next in the message, so that the two letters could be telegraphed at the same time, the second letter being that which gave off a very small quantity of oxygen gas.

The instrument so constructed was only capable of sending five different letters. In order to send a complete message, it was necessary to have as many wires as there are letters in the alphabet. Twenty-six wires were therefore twisted together in a strand, after being covered with varnish and silk thread. The ends of the wires at the sending station were nailed to a frame by means of nails with perforated heads. A wire was kept touching the top of the Volta pile, and another was kept in contact with the lower end of the pile. These wires ended in small plugs which could be inserted into the perforations of the nails, so that the sender could pick out any two letters he wished to telegraph. At the other end the wires were laid through the bottom of a vessel containing water, and were marked with appropriate letters. The telegraph was then worked on the same principle as the smaller one made for five letters.

In addition to these letters, the inventor devised a mechanism by which a bell could be sounded in order to attract the attention of the man at the receiving end. This apparatus was extremely ingenious. It consisted of a lever to which a spoon was attached.

The spoon lay in the water, just above two of the wires, with its open surface down. When the current was sent through these two wires, the hydrogen and oxygen collected in the spoon, and raised it. This set a little ball rolling down into a funnel. Through the funnel it dropped into a small pan, and removed the catch of an alarm clock. This set the alarm going and attracted the attention of the man at the receiving station. When the message was finished, the man had to put back the ball to its original place, and wind up and set the alarm clock as before.

It was not long before the Emperor Napoleon heard of the Bavarian invention. One of his officials told him about it and asked leave to explain it to him. The Emperor listened to the explanation, but then swept it aside as worthless. “It’s only a German idea,” he said. He considered it impossible to lay a strand of wire across country and to preserve it from damage. He preferred to rely on his optical telegraph which had done him such good service.

The electric telegraph did not come into real use until the magnetic needle was adopted as an indicator. Ten years after the first telegraph was invented, a Danish electrician made a very important discovery, which exercised a far-reaching effect upon electric science. He was trying to discover some connection between electricity and magnetism, and made all sorts of experiments with magnetic compasses. He found at last that a magnetic needle is affected powerfully by a current passing in a wire close by. When a wire bearing an electric current is stretched along a table from north to south, and a magnetic compass is placed on the top of the wire pointing in the same direction, the needle swings round every time the current is sent through the wire, and swings back into its ordinary position as soon as the current is interrupted. So long as the current flows, the needle tends to set itself at right angles to the wire, and will do so almost exactly when the current is very strong.

This discovery made a great impression on the scientific world, and many men of science proposed to use it for the purpose of telegraphy. But it was not until the year 1833 that the first telegraph was constructed on this principle. Two professors in Heidelberg, whose names were Gauss and Weber, established a telegraph of this kind between the Physical Institute and the Observatory. The wire had a total length of nearly two miles, and they produced at the receiving station a deflection of a magnetic needle to the right or left. This arrangement was afterwards improved by a young student, who attached pens to two magnetic needles, and made them write dots on a strip of paper passing along under them. Using two different inks, he got different sets of coloured dots for each letter. These could be easily recognised afterwards and read off the paper.

The current used in these experiments was not a steady current from a Volta pile or electric battery. It was a so-called induction current. The induction current had been discovered in 1831 by a great Englishman of the name of Michael Faraday, who found that when a wire is placed by the side of another wire through which electricity can pass, then as soon as the current is sent through this wire by connecting it with the battery, a momentary current flows in the opposite direction through the other wire.

For this to happen, however, it is necessary that the second wire should also form a closed circuit, and not have any free ends. Such an induction current, or induced current, can also be obtained by means of a large magnet. All that is necessary is to take a coil of wire and suddenly slip it upon a bar magnet, or suddenly slip it off. The more rapidly the slipping on or off is done the stronger is the current. In this way, therefore, it is possible to produce an electric current without any piles, or batteries, or chemicals.

This kind of current was found very effective for telegraphy, especially as the magnet was always ready, whereas the electric batteries, or cells, were liable to get exhausted and useless. It was only when the electric battery was improved greatly and made more trustworthy that it was adopted again for telegraphy, and it is used for that purpose at the present day.

A great improvement was introduced into telegraphy by S. E. B. Morse, who invented the alphabet known as the “Morse Code” and also a recording machine which writes down the message in dots and dashes. The alphabet is as follows:--

a • — h • • • • o — — — u • • —

b — • • • i • • p — — • v • • • —

c — • • • • j • — — — q — — • — w • — —

d — • • k — • — r • — • x — • • —

e • l • — • • s • • • y — • — —

f • • — • m — — t — z — — • •

g — — • n — •

The word “alphabet” appears on the paper strip like this:--

• — • — • • — — • • • • • • — — • • • • — a l p h a b e t

For work in which no record is required, the needle telegraph is employed usually. But the Morse code is used in this case also, the needle moving to the right when a dot is intended, and to the left when a dash. Telegraph clerks get after a while to understand a message by simply listening to the sound of the needle. Nowadays the needle is a stout magnet, which as a rule rests against a piece of iron belonging to an electromagnet. When the current passes, it knocks against a different piece of iron, and the operators learn to read the message from the sound of the knocks. The instrument is therefore called a sounder.