The Romance of Modern Invention Part 3

The popularity of the telephone may be judged from the fact that in 1901 the National Telephone Company's system transmitted over 807 millions of messages, as compared with 89 millions of telegrams sent over the Post Office wires. In America and Germany, however, the telephone is even more universally employed than in England. In the thinly populated prairies of West America the farm-houses are often connected with a central station many miles off, from which they receive news of the outer world and are able to keep in touch with one another. We are not, perhaps, as a nation sufficiently alive to the advantages of an efficient telephone system; and on this account many districts remain telephoneless because sufficient subscribers cannot be found to guarantee use of a system if established. It has been seriously urged that much of our country depopulation might be counteracted by a universal telephone service, which would enable people to live at a distance from the towns and yet be in close contact with them. At present, for the sake of convenience and ease of "getting at" clients and customers, many business men prefer to have their homes just outside the towns where their business is. A cheap and efficient service open to every one would do away with a great deal of travelling that is necessary under existing circ.u.mstances, and by making it less important to live near a town allow people to return to the country.

Even Norway has a good telephone system. The telegraph is little used in the more thinly inhabited districts, but the telephone may be found in most unexpected places, in little villages hidden in the recesses of the fiords. Switzerland, another mountainous country, but very go-ahead in all electrical matters, is noted for the cheapness of its telephone services. At Berne or Geneva a subscriber pays 4 the first year, 2, 12s. the second year, and but 1, 12s. the third. Contrast these charges with those of New York, where 15, 10s. to 49, 10s. is levied annually according to service.

The telephone as a public benefactor is seen at its best at Buda-Pesth, the twin-capital of Hungary. In 1893, one Herr Theodore Buschgasch founded in that city a "newspaper"--if so it may be called--worked entirely on the telephone. The publishing office was a telephone exchange; the wires and instruments took the place of printed matter. The subscribers were to be informed entirely by ear of the news of the day.

The _Telefon Hirmondo_ or "Telephonic Newsteller," as the "paper" was named, has more than six thousand subscribers, who enjoy their telephones for the very small payment of eighteen florins, or about a penny a day, for twelve hours a day.

News is collected at the central office in the usual journalistic way by telephone, telegraph, and reporters. It is printed by lithography on strips of paper six inches wide and two feet long. These strips are handed to "stentors," or men with powerful and trained voices, who read the contents to transmitting instruments in the offices, whence it flies in all directions to the ears of the subscribers.

These last know exactly when to listen and what description of information they will hear, for each has over his receiver a programme which is rigidly adhered to. It must be explained at once that the _Telefon Hirmondo_ is more than a mere newspaper, for it adds to its practical use as a first-cla.s.s journal that of entertainer, lecturer, preacher, actor, political speaker, musician. The _Telefon_ offices are connected by wire with the theatres, churches, and public halls, drawing from them by means of special receivers the sounds that are going on there, and transmitting them again over the wires to the thousands of subscribers. The Buda-Pesthian has therefore only to consult his programme to see when he will be in touch with his favourite actor or preacher. The ladies know just when to expect the latest hints about the fashions of the day. Nor are the children forgotten, for a special period is set aside weekly for their entertainment in the shape of lectures or concerts.

The advertising fiend, too, must have his say, though he pays dearly for it. On payment of a florin the stentors will shout the virtues of his wares for a s.p.a.ce of twelve seconds. The advertising periods are sandwiched in between items of news, so that the subscriber is bound to hear the advertis.e.m.e.nts unless he is willing to risk missing some of the news if he hangs up his receiver until the "puff" is finished.

Thanks to the _Telefon Hirmondo_ the preacher, actor, or singer is obliged to calculate his popularity less by the condition of the seats in front of him than by the number of telephones in use while he is performing his part. On the other hand, the subscriber is spared a vast amount of walking, waiting, cab-hire, and expense generally. In fact, if the principle is much further developed, we shall begin to doubt whether a Buda-Pesthian will be able to discover reasons for getting out of bed at all if the receiver hanging within reach of his hand is the entrance to so many places of delight. Will he become a very lazy person; and what will be the effect on his entertainers when they find themselves facing benches that are used less every day? Will the sight of a row of telephone trumpets rouse the future Liddon, Patti, Irving, or Gladstone to excel themselves? It seems rather doubtful. Telephones cannot look interested or applaud.

What is inside the simple-looking receiver that hangs on the wall beside a small mahogany case, or rests horizontally on a couple of crooks over the case? In the older type of instrument the transmitter and receiver are separate, the former fixed in front of the case, the latter, of course, movable so that it can be applied to the ear. But improved patterns have transmitter and receiver in a single movable handle, so shaped that the earpiece is by the ear while the mouthpiece curves round opposite the mouth. By pressing a small lever with the fingers the one or the other is brought into action when required.

The construction of the instrument, of which we are at first a little afraid, and with which we later on learn to become rather angry, is in its general lines simple enough. The first practical telephone, constructed in 1876 by Graham Bell, a Scotchman, consisted of a long wooden or ebonite handle down the centre of which ran a permanent bar-magnet, having at one end a small coil of fine insulated wire wound about it The ends of the wire coil are led through the handles to two terminals for connection with the line wires. At a very short distance from the wire-wound pole of the magnet is firmly fixed by its edges a thin circular iron plate, covered by a funnel-shaped mouthpiece.

The iron plate is, when at rest, concave, its centre being attracted towards the pole of the magnet. When any one speaks into the mouthpiece the sound waves agitate the diaphragm (or plate), causing its centre to move inwards and outwards. The movements of the diaphragm affect the magnetism of the magnet, sometimes strengthening it, sometimes weakening it, and consequently exciting electric currents of varying strength in the wire coil. These currents pa.s.sing through the line wires to a similar telephone excite the coil in it, and in turn affect the magnetism of the distant magnet, which attracts or releases the diaphragm near its pole, causing undulations of the air exactly resembling those set up by the speaker's words. To render the telephone powerful enough to make conversation possible over long distances it was found advisable to subst.i.tute for the one telephone a special transmitter, and to insert in the circuit a battery giving a much stronger current than could possibly be excited by the magnet in the telephone at the speaker's end.

Edison in 1877 invented a special transmitter made of carbon. He discovered that the harder two faces of carbon are pressed together the more readily will they allow current to pa.s.s; the reason probably being that the points of contact increase in number and afford more bridges for the current.

Accordingly his transmitter contains a small disc of lampblack (a form of carbon) connected to the diaphragm, and another carbon or platinum disc against which the first is driven with varying force by the vibrations of the voice.

The Edison transmitter is therefore in idea only a modification of the microphone. It acts as a _regulator_ of current, in distinction to the Bell telephone, which is only an _exciter_ of current. Modern forms of telephones unite the Edison transmitter with the Bell receiver.

The latter is extremely sensitive to electric currents, detecting them even when of the minutest power. We have seen that Marconi used a telephone in his famous transatlantic experiments to distinguish the signals sent from Cornwall. A telephone may be used with an "earth return" instead of a second wire; but as this exposes it to stray currents by induction from other wires carried on the same poles or from the earth itself, it is now usual to use two wires, completing the metallic circuit. Even so a subscriber is liable to overhear conversations on wires neighbouring his own; the writer has lively recollections of first receiving news of the relief of Ladysmith in this manner.

Owing to the self-induction of wires in submarine cables and the consequent difficulty of forcing currents through them, the telephone is at present not used in connection with submarine lines of more than a very moderate length. England has, however, been connected with France by a telephone cable from St. Margaret's Bay to Sangatte, 23 miles; and Scotland with Ireland, Stranraer to Donaghadee, 26 miles.

The former cable enables speech between London and Ma.r.s.eilles, a distance of 900 miles; and the latter makes it possible to speak from London to Dublin _via_ Glasgow. The longest direct line in existence is that between New York and Chicago, the complete circuit of which uses 1900 miles of stout copper wire, raised above the ground on poles 35 feet high.

The efficiency of the telephone on a well laid system is so great that it makes very little difference whether the persons talking with one another are 50 or 500 miles apart. There is no reason why a Cape-to-Cairo telephone should not put the two extremities of Africa in clear vocal communication. We may even live to see the day when a London business man will be able to talk with his agent in Sydney, Melbourne, or Wellington.

A step towards this last achievement has been taken by M. Germain, a French electrician, who has patented a telephone which can be used with stronger currents than are possible in ordinary telephones; thereby, of course, increasing the range of speech on submarine cables.

The telephone that we generally use has a transmitter which permits but a small portion of the battery power to pa.s.s into the wires, owing to the resistance of the carbon diaphragm. The weakness of the current is to a great extent compensated by the exceedingly delicate nature of the receiver.

M. Germain has reversed the conditions with a transmitter that allows a very high percentage of the current to flow into the wires, and a comparatively insensitive receiver. The result is a "loud-speaking telephone"--not a novelty, for Edison invented one as long ago as 1877--which is capable of reproducing speech in a wonderfully powerful fashion.

M. Germain, with the help of special tubular receivers, has actually sent messages through a line having the same resistance as that of the London-Paris line, so audibly that the words could be heard fifteen yards from the receiver in the open air!

The Telephone

WIRELESS TELEPHONY.

In days when wireless telegraphy is occupying such a great deal of the world's attention, it is not likely to cause much astonishment in the reader to learn that wireless transmission of _speech_ over considerable distances is an accomplished fact. We have already mentioned (see "Wireless Telegraphy") that by means of parallel systems of wires Sir William Preece bridged a large air-gap, and induced in the one sounds imparted to the other.

Since then two other methods have been introduced; and as a preface to the mention of the first we may say a few words about Graham Bell's _Photophone_.

In this instrument _light_ is made to do the work of a metal connection between speaker and listener. Professor Bell, in arranging the Photophone, used a mouthpiece as in his electric telephone, but instead of a diaphragm working in front of a magnet to set up electric impulses along a wire he employed a mirror of very thin gla.s.s, silvered on one side. The effect of sound on this mirror was to cause rapid alterations of its shape from concave to convex, and consequent variations of its reflecting power. A strong beam of light was concentrated on the centre of the mirror through a lens, and reflected by the mirror at an angle through another lens in the direction of the receiving instrument. The receiver consisted of a parabolic reflector to catch the rays and focus them on a selenium cell connected by an electric circuit with an ordinary telephone earpiece.

On delivering a message into the mouthpiece the speaker would, by agitating the mirror, send a succession of light waves of varying intensity towards the distant selenium cell. Selenium has the peculiar property of offering less resistance to electrical currents when light is thrown upon it than when it is in darkness: and the more intense is the light the less is the obstruction it affords. The light-waves from the mirror, therefore, constantly alter its capacity as a conductor, allowing currents to pa.s.s through the telephone with varying power.

In this way Professor Bell bridged 800 yards of s.p.a.ce; over which he sent, besides articulate words, musical notes, using for the latter purpose a revolving perforated disc to interrupt a constant beam of light a certain number of times per second. As the speed of the disc increased the rate of the light-flashes increased also, and produced in the selenium cell the same number of pa.s.sages to the electric current, converted into a musical note by the receiver. So that by means of mechanical apparatus a "playful sunbeam" could literally be compelled to play a tune.

From the Photophone we pa.s.s to another method of sound transmission by light, with which is connected the name of Mr. Hammond V. Hayes of Boston, Ma.s.sachusetts. It is embodied in the Radiophone, or the Ray-speaker, for it makes strong rays of light carry the human voice.

Luminous bodies give off heat. As the light increases, so as a general rule does the heat also. At present we are unable to create strong light without having recourse to heat to help us, since we do not know how to cause other vibrations of sufficient rapidity to yield the sensation of light. But we can produce heat directly, and heat will set atoms in motion, and the ether too, giving us light, but taking as reward a great deal of the energy exerted. Now, the electric arc of a searchlight produces a large amount of light _and_ heat. The light is felt by the eye at a distance of many miles, but the body is not sensitive enough to be aware of the heat emanating from the same source. Mr. Hayes has, however, found the heat accompanying a searchlight beam quite sufficient to affect a mechanical "nerve" in a far-away telephone receiver.

The transmitting apparatus is a searchlight, through the back of which run four pairs of wires connected with a telephone mouthpiece after pa.s.sing through a switch and resistance-box or regulator. The receiver is a concave mirror, in the focus of which is a tapering gla.s.s bulb, half filled with carbonised filament very sensitive to heat. The tapering end of the bulb projects through the back of the mirror into an ear tube.

If a message is to be transmitted the would-be speaker turns his searchlight in the direction of the person with whom he wishes to converse, and makes the proper signals. On seeing them the other presents his mirror to the beam and listens.

The speaker's voice takes control of the searchlight beam. The louder the sound the more brilliantly glows the electric arc; the stronger becomes the beam, the greater is the amount of heat pa.s.sed on to the mirror and gathered on the sensitive bulb. The filament inside expands. The tapering point communicates the fact to the earpiece.

This operation being repeated many times a second the earpiece fills with sound, in which all the modulations of the far-distant voice are easily distinguishable.

Two sets of the apparatus above described are necessary for a conversation, the functions of the searchlight and the bulb not being reversible. But inasmuch as all large steamers carry searchlights the necessary installation may be completed at a small expense. Mr. Hayes'

invention promises to be a rival to wireless telegraphy over comparatively short distances. It can be relied upon in all weathers, and is a fast method of communication. Like the photophone it ill.u.s.trates the inter-relationship of the phenomena of Sound, Light, and Heat, and the readiness with which they may be combined to attain an end.

Next we turn from air to earth, and to the consideration of the work of Mr. A. F. Collins of Philadelphia. This electrician merely makes use of the currents flowing in all directions through the earth, and those excited by an electric battery connected with earth. The outfit requisite for sending wireless spoken messages consists of a couple of convenient stands, as many storage batteries, sets of coils, and receiving and transmitting instruments.

The action of the transmitter is to send from the battery a series of currents through the coils, which transmit them, greatly intensified, to the earth by means of a wire connected with a buried wire-screen.

The electric disturbances set up in the earth travel in all directions, and strike a similar screen buried beneath the receiving instrument, where the currents affect the delicate diaphragm of the telephone earpiece.

The system is, in fact, upon all fours with Mr. Marconi's, the distinguishing feature being that the ether of the atmosphere is used in the latter case, that of the earth in the former. The intensity coils are common to both; the buried screens are the counterpart of the aerial kites or balloons; the telephone transmitter corresponds to the telegraphic transmitting key; the earpiece to the coherer and relay. No doubt in time Mr. Collins will "tune" his instruments, so obtaining below ground the same sympathetic electric vibrations which Mr. Marconi, Professor Lodge, or others have employed to clothe their aerial messages in secrecy.

THE PHONOGRAPH.

Even if Thomas Edison had not done wonders with electric lighting, telephones, electric torpedoes, new processes for separating iron from its ore, telegraphy, animated photography, and other things too numerous to mention, he would still have made for himself an enduring name as the inventor of the Phonograph. He has fitly been called the "Wizard of the West" from his genius for conjuring up out of what would appear to the mult.i.tude most unpromising materials startling scientific marvels, among which none is more truly wizard-like than the instrument that is as receptive of sound as the human ear, and of illimitable reproducing power. By virtue of its elfishly human characteristic, articulate speech, it occupies, and always will occupy, a very high position as a mechanical wonder. When listening to a telephone we are aware of the fact that the sounds are immediate reproductions of a living person's voice, speaking at the moment and at a definite distance from us; but the phonographic utterances are those of a voice perhaps stilled for ever, and the difference adds romance to the speaking machine.

The Phonograph was born in 1876. As we may imagine, its appearance created a stir. A contributor to the _Times_ wrote in 1877: "Not many weeks have pa.s.sed since we were startled by the announcement that we could converse audibly with each other, although hundreds of miles apart, by means of so many miles of wire with a little electric magnet at each end.

"Another wonder is now promised us--an invention purely mechanical in its nature, by means of which words spoken by the human voice can be, so to speak, stored up and reproduced at will over and over again hundreds, it may be thousands, of times. What will be thought of a piece of mechanism by means of which a message of any length can be spoken on to a plate of metal--that plate sent by post to any part of the world and the message absolutely respoken in the very voice of the sender, purely by mechanical agency? What, too, shall be said of a mere machine, by means of which the old familiar voice of one who is no longer with us on earth can be heard speaking to us in the very tones and measure to which our ears were once accustomed?"

The first Edison machine was the climax of research in the realm of sound. As long ago as 1856 a Mr. Leo Scott made an instrument which received the formidable name of Phonautograph, on account of its capacity to register mechanically the vibrations set up in the atmosphere by the human voice or by musical instruments. A large metal cone like the mouth of an ear-trumpet had stretched across its smaller end a membrane, to which was attached a very delicate tracing-point working on the surface of a revolving cylinder covered with blackened paper. Any sound entering the trumpet agitated the membrane, which in turn moved the stylus and produced a line on the cylinder corresponding to the vibration. Scott's apparatus could only record.

It was, so to speak, the first half of the phonograph. Edison, twenty years later, added the active half. His machine, as briefly described in the _Times_, was simple; so very simple that many scientists must have wondered how they failed to invent it themselves.

A metal cylinder grooved with a continuous square-section thread of many turns to the inch was mounted horizontally on a long axle cut at one end with a screw-thread of the same "pitch" as that on the cylinder. The axle, working in upright supports, and furnished with a heavy flywheel to render the rate of revolution fairly uniform, was turned by a handle. Over the grooved cylinder was stretched a thin sheet of tinfoil, and on this rested lightly a steel tracing-point, mounted at the end of a spring and separated from a vibrating diaphragm by a small pad of rubber tubing. A large mouthpiece to concentrate sound on to the diaphragm completed the apparatus.