Chapter I: Front Matter

Transcriber’s Note: Italics are enclosed in _underscores_. Additional notes will be found near the end of this ebook.

THE
TELEPHONE, MICROPHONE, & PHONOGRAPH

THE TELEPHONE
THE MICROPHONE & THE PHONOGRAPH

BY
COUNT DU MONCEL

MEMBRE DE L’INSTITUT

_AUTHORISED TRANSLATION
WITH ADDITIONS AND CORRECTIONS BY THE AUTHOR_

WITH 70 ILLUSTRATIONS ON WOOD

_FOURTH EDITION_

LONDON
KEGAN PAUL, TRENCH, TRÜBNER, & CO. LTD.
PATERNOSTER HOUSE, CHARING CROSS ROAD
1892

(_The rights of translation and of reproduction are reserved_)

_CONTENTS._

PAGE

History of the telephone 1

_MUSICAL TELEPHONES._

Reiss’s telephone 11

Wray’s telephone 15

Electric harmonica 18

Gray’s telephone 21

Pollard and Garnier’s singing condenser 26

_SPEAKING TELEPHONES._

String telephones 31

Bell’s electric telephone 35

Gray’s share in invention of telephone 62

_FUNDAMENTAL PRINCIPLES OF BELL TELEPHONE._

Explanation of principles 67

_ORDINARY ARRANGEMENT OF BELL TELEPHONE._

Description and illustrations 71

_BATTERY TELEPHONES._

Edison’s telephone 83

Edison’s chemical telephone 90

Navez’ telephone 93

Pollard and Garnier’s telephone 97

Hellesen’s telephone 100

Thomson and Houston’s telephone 101

Telephones with liquid senders 103

Telephones with voltaic arcs 107

Mercury telephones 110

Friction telephones 113

_MODIFICATION OF BELL TELEPHONES._

Telephones with several diaphragms 114

Gray’s system 118

Phelps’s system 118

Cox Walker’s system 121

Trouvé’s system 121

Demoget’s system 124

Mac Tighe’s system 125

Modifications of telephonic organs 125

Righi’s system 126

Ader’s system 129

Jorgenson’s system 131

_EXPERIMENTS WITH THE TELEPHONE._

On the effects of voltaic and induced currents 132

On the effects of different telephonic organs 139

Edison’s experiments 140

Canestrelli’s experiments 142

Hughes’s and Roy’s experiments 143

Bréguet’s experiments 149

Luvini’s experiments 149

Warwick’s experiments 151

Experiments on the effects of mechanical shocks 154

Des Portes’ experiments 154

Thompson’s experiments 158

Theory of telephone 159

Nature of vibrations 160

Action of diaphragm 163

Action of magnet 167

Action of currents 169

Wiesendanger’s thermophone 171

_OTHER EXPERIMENTS WITH THE TELEPHONE._

D’Arsonval’s experiments 173

Eick’s experiments 175

Demoget’s experiments 176

Sensitiveness of telephone 179

Hellesen’s experiments 180

Zetsche’s experiments 181

_THE MICROPHONE._

History of microphone 182

Different systems 187

Hughes’s microphone 188

Gaiffe’s system 190

Carette’s system 191

Ducretet’s system 192

Ducretet’s speaker 193

Boudet’s speaker 195

Gaiffe’s thermoscope 197

Blyth’s system 199

Microphone as a speaking instrument 200

Hughes’s system 203

Other arrangements of microphones 205

Varcy’s and Trouvé’s microphones 207

Lippens’s microphone 209

Hughes’s experiments 211

Hughes’s theory 215

Microphone used as thermoscope 217

Edison’s thermoscope 219

Experiments in London 220

Experiment at Bellinzona 223

_APPLICATIONS OF MICROPHONE._

Its application to scientific research 226

Application to telephonic relays 229

Application to surgery 232

Various applications 236

_EXTERNAL INFLUENCE ON TELEPHONIC TRANSMISSIONS._

Disturbing influences 239

Confusion of circuits 241

Induced reactions 243

Mr. Preece’s suggestions 245

Effects of heat and moisture 249

_ESTABLISHMENT OF TELEPHONE STATION._

Pollard and Garnier’s system 252

Bréguet and Roosevelt’s system 254

Edison’s system 257

_CALL-BELLS AND ALARUMS._

Weinhold’s system 262

Dutertre and Gouault’s system 264

Puluj’s system 266

Chiddey’s system 267

_APPLICATIONS OF TELEPHONE._

Its application to simultaneous transmissions 270

Bell’s system 273

Lacour’s system 276

Gray’s system 282

_VARIOUS USES OF THE TELEPHONE._

Its use in offices 293

Its use in telegraphic service 294

Its application to military purposes 297

Its application to industry 302

Its application to scientific research 303

_THE PHONOGRAPH._

Edison’s patent 309

Description of phonograph 313

Several systems 322

Theory of phonograph 327

_USES OF PHONOGRAPH._

Account by Edison 333

Lainbrigot’s system 339

_FABER’S SPEAKING MACHINE_ 341

_APPENDIX._

Perrodon’s system of telephonic alarum 351

Varey’s microphone speaker 352

Fitch’s microphone speaker 353

Theory of telephone 353

Pollard’s microphone 356

Ader’s electrophone 357

Gower’s new telephone 358

Transmission of speech by telephones without diaphragm 360

THE TELEPHONE,

_&c._

_HISTORY OF THE TELEPHONE._

Strictly speaking, the telephone is merely an instrument adapted for the transmission of sound to a distance, and this idea of transmitting sound is as old as the world itself. The Greeks made use of means which might effect it, and there is no doubt that these means were sometimes used for the pagan oracles. But such transmission of sound was within somewhat narrow limits, and certainly did not exceed those of a speaking-tube. Mr. Preece considers that the earliest document in which this transmission of sound to a distance is distinctly formulated, dates from 1667: he refers to a paper by one Robert Hooke, who writes to this effect: ‘It is not impossible to hear a whisper at a furlong’s distance, it having been already done; and perhaps the nature of the thing would not make it more impossible, though that furlong should be ten times multiply’d. And though some famous authors have affirm’d it impossible to hear through the thinnest plate of Muscovy glass; yet I know a way, by which ’tis easie enough to hear one speak through a wall a yard thick. It has not yet been thoroughly examin’d how far otacousticons may be improv’d, nor what other wayes there may be of quickning our hearing, or conveying sound through other bodies than the air; for that is not the only medium I can assure the reader, that I have, by the help of a distended wire, propagated the sound to a very considerable distance in an instant, or with as seemingly quick a motion as that of light, at least incomparably quicker than that which at the same time was propagated through the air; and this not only in a straight line or direct, but in one bended in many angles.’

This plan for the transmission of sound is the principle of the string telephones which have attracted attention for some years, and it remained in the stage of simple experiment until 1819, when Sir Charles Wheatstone applied it to his magic lyre. In this instrument, sounds were transmitted through a long strip of deal, with one end in connection with a sounding board: one step more led to the use of the membrane employed in string telephones. It would be difficult to say with whom this idea originated, since it is claimed, as if beyond dispute, by several telephone-makers. If we may believe some travellers, it has long been used in Spain for the correspondence of lovers. However this may be, it was not to be found among the scientific appliances of some years ago, and it was even supposed by many persons that the cord consisted of an acoustic tube of slender diameter. Although the instrument has become a child’s toy, it has great scientific importance, for it proves that vibrations capable of reproducing speech may be extremely minute, since they can be mechanically transmitted more than a hundred yards.

From the telegraphic point of view, however, the problem of transmitting sounds to a distance was far from being solved in this way, and the idea of applying electricity to this mode of transmission naturally arose as soon as the wonderful effects of electric telegraphy were observed, that is, in the years subsequent to 1839. A surprising discovery made in America by Mr. Page, in 1837, and afterwards investigated by MM. Wertheim, De la Rive, and others, must also have led up to it: for it was observed that a magnetic bar could emit sounds when rapidly magnetised and demagnetised, and these sounds corresponded with the number of currents which produced them. Again, the electric vibrators devised by MM. Macaulay, Wagner, Neef, etc., and adapted to produce musical sounds, between 1847–1852, by MM. Froment and Pétrina, showed that the problem of transmitting sounds to a distance was not insoluble. Yet, up to 1854, no one had ventured to admit the possibility of transmitting speech by electricity, and when M. Charles Bourseul published in that year a paper on the electric transmission of speech, the idea was regarded as a fanciful dream. I confess that I myself thought it incredible, and when I produced the paper in the first edition of my account of the applications of electricity, published in 1854, I felt bound to add that the scheme seemed more than doubtful. Yet, as the paper was thoughtfully written, I had no hesitation in publishing it, affixing the signature of CH. B. Events justified this daring idea, and although it did not include the only principle which could lead to the reproduction of articulate sounds, yet it was the germ of the fertile invention which has made the names of Graham Bell and Elisha Gray famous. For this reason I will again quote M. Charles Bourseul’s paper.

‘After the telegraphic marvels which can reproduce at a distance hand-writings, or even more or less complicated drawings, it may appear impossible to penetrate further into the region of the marvellous. Yet we will try to advance a few steps further. I have, for example, asked myself whether speech itself may not be transmitted by electricity--in a word, if what is spoken in Vienna may not be heard in Paris. The thing is practicable in this way:--

‘We know that sounds are made by vibrations, and are adapted to the ear by the same vibrations which are reproduced by the intervening medium. But the intensity of the vibrations diminishes very rapidly with the distance: so that it is, even with the aid of speaking-tubes and trumpets, impossible to exceed somewhat narrow limits. Suppose that a man speaks near a moveable disk, sufficiently flexible to lose none of the vibrations of the voice, that this disk alternately makes and breaks the currents from a battery: you may have at a distance another disk, which will simultaneously execute the same vibrations.

‘It is true that the intensity of the sounds produced will be variable at the point of departure, at which the disk vibrates by means of the voice, and constant at the point of arrival, where it vibrates by means of electricity; but it has been shown that this does not change the sounds. It is, moreover, evident that the sounds will be reproduced at the same pitch.

‘The present state of acoustic science does not permit us to declare _à priori_ if this will be precisely the case with syllables uttered by the human voice. The mode in which these syllables are produced has not yet been sufficiently investigated. It is true that we know that some are uttered by the teeth, others by the lips, and so on; but this is all.

‘However this may be, observe that the syllables can only reproduce upon the sense of hearing the vibrations of the intervening medium: reproduce precisely these vibrations, and you will reproduce precisely these syllables.

‘It is, at all events, impossible in the present condition of science to prove the impossibility of transmitting sound by electricity. Everything tends to show, on the contrary, that there is such a possibility. When the application of electro-magnetism to the transmission of messages was first discussed, a man of great scientific attainments treated the idea as utopian, and yet there is now direct communication between London and Vienna by means of a simple wire. Men declared it to be impossible, but so it is.

‘It need not be said that numerous applications of the highest importance will immediately arise from the transmission of speech by electricity. Any one who is not deaf and dumb may use this mode of transmission, which would require no apparatus, except an electric battery, two vibrating disks, and a wire. In many cases, as for example in large establishments, orders might be transmitted in this way, although transmission by electricity will not be used while it is necessary to go from letter to letter, and to make use of telegraphs which require use and apprenticeship. However this may be, it is certain that in a more or less distant future, speech will be transmitted by electricity. _I have made some experiments in this direction_: they are delicate, and demand time and patience, but _the approximations obtained_ promise a favourable result.’

This description is certainly not full enough to enable us to discern from it the arrangement which would lead to the solution of the problem, and if the vibrations of the disk at the receiving station were to follow from making and breaking the current at the sending-station, under the influence of vibrations caused by the voice, they would only produce musical, and not articulate sounds. Yet the idea was magnificent, as Mr. Preece said, even when he thought it impossible to realise it. Besides, it is easy to see that M. Bourseul himself was not deceived as to the difficulties of the problem, as far as articulate sounds are concerned, for he points out, as we have seen, the difference existing between the simple vibrations which produce musical sounds, and the complex vibrations which cause articulate sounds; but, as he justly said: ‘Reproduce at the one end of the line the vibrations of air caused at the other, and speech will be transmitted, however complex the mechanism may be by which it is effected.’ We shall presently see how the problem was solved, and it is probable that some attempts had already enabled M. Bourseul to anticipate the solution of the question; but there is nothing in his paper to show what were the means he proposed, so that the discovery of the electric transmission of speech cannot reasonably be ascribed to him, and we do not understand why we should be reproached for having at that time failed to appreciate the importance of a discovery which seemed to be then only within the range of fancy.

It was not until 1876 that the problem of the electric transmission of speech was finally solved, and the discovery has lately given rise to an interesting controversy as to priority between Mr. Elisha Gray, of Chicago, and Mr. Graham Bell, on which we must say a few words.

As early as 1874 Mr. Elisha Gray was occupied with a system of musical telephone, which he wished to apply to manifold telegraphic transmissions, and the investigations which he made, in order to establish this system under the best possible conditions, gave him a glimpse of the possibility of transmitting articulate words by electricity. While carrying on his experiments on the telegraphic system, he arranged in fact, about the 15th January, 1876, a system of _speaking telephone_, and he deposited the specification and drawings in the American Patent Office, in the form of a _caveat_ or provisional specification. The deposit was made on the 14th February, 1876: on the very same day, Mr. Graham Bell also deposited, in the American Patent Office, a request for a patent in which he spoke of an instrument of the same kind, but with special application to simultaneous telegraphic transmissions by means of a telephonic apparatus; and the few words which could, in this specification, refer to a telephone with articulate sounds, applied to an instrument which, by Mr. Bell’s own admission, had not produced any satisfactory results. In Mr. Gray’s _caveat_, on the contrary, the application of the instrument to the electric transmission of speech alone is indicated, the description of the system is complete, and the drawings which accompany it are so exact, that a telephone made from them would work perfectly: this was proved by Mr. Gray himself, when, some time afterwards, he finished his instruments, which differed in no respect from the one described in Mr. Bell’s statement as worked by a battery. On these grounds Mr. Elisha Gray would certainly have obtained the patent, if the expiration of his _caveat_ had not been the result of an omission of form in the Patent Office, which, as we know, decides the priority of inventions in America. An action on the ground of this omission has lately been brought against Mr. Bell, in the Supreme Court of the American Patent Office, to set aside the patent granted to him. If Mr. Gray did not appeal before, it was because he was then wholly occupied with experiments on the system of harmonic telephone, applied to telegraphic communication, and he had no time to attend to the matter.

However this may be, Mr. Bell did not begin to give serious attention to the speaking telephone until he had obtained his patent, and his efforts were soon crowned with success: a few months later, he exhibited his speaking telephone at Philadelphia, which has from that time attracted so much public attention, and which, when perfected in a practical point of view, reached Europe in the autumn of 1877 under the form we know.

To complete this summary account of the telephone, we ought to say that since its success a good many claims of priority have arisen, as if by enchantment. Mr. John Camack, of English origin, has among others claimed the invention of the telephone, not merely relying on the description he gave of the instrument in 1865, but on the drawings he executed; he even adds, that if he had not lacked means for its construction, this would have been the date of the discovery of the telephone. A similar pretension has been put forward by Mr. Dolbear, a fellow countryman of Mr. Bell, of whose claim we shall speak presently.

Signor Manzetti, of Aosta, says the same thing, asserting that his telephonic invention was described in several newspapers of 1865, among others in ‘Le Petit Journal,’ of Paris, on the 22nd November, 1865; ‘Il Diritto’ at Rome, 16th July, 1865; ‘L’Echo d’Italia,’ New York, 9th August, 1865; ‘L’Italia,’ Florence, 10th August, 1865; ‘La Comuna d’Italia,’ Genoa, 1st December, 1865; ‘La Verità,’ Novara, 4th January, 1866; ‘Il Commercio,’ Genoa, 6th January, 1866. It is true that no description of the system was given, and that the journals in question only asserted that experiments had been made, which proved that the practical solution of the problem of transmitting speech by electricity became possible by this system. At any rate M. Charles Bourseul must still have the credit of the priority of the idea, and, in our opinion, all claims made after the fact only merit slight consideration.

Before considering Bell’s telephone, and the different modifications which have been applied to it, it seems worth while, in order to make the reader perfectly familiar with these kinds of instruments, to study the electro-musical telephones which preceded it, and especially that of M. Reiss, which was made in 1860, and became the starting point of all the others. We shall find that these instruments have very important applications, and that telegraphy will probably be one day much advanced by their use.

MUSICAL TELEPHONES.

_Telephone of M. Reiss._--This telephone is, as far as the reproduction of sound is concerned, based upon Mr. Page’s discoveries in 1837, and, as regards electric transmission, it is based on the vibrating membrane of which Mr. L. Scott made use in his phonautograph, in 1855. This instrument is composed, like telegraphic systems, of two distinct parts, a sender and a receiver, as represented in fig. 1.

The sender was virtually composed of a sounding box K, having on its upper surface a large circular opening, across which a membrane was stretched, and in its centre there was fitted a thin disk of platinum _o_, above which a metallic point _c_ was fixed, and this, together with the disk, constituted the contact-breaker. On one face of the sounding-box K, there was a sort of speaking-tube, for the purpose of collecting the sound, and directing it to the interior of the box, in order that it might then react upon the membrane. Part of the box K is broken away in the plate, in order that the different parts of which it is made may be seen.

The rods _a_, _c_, which support the platinum point _b_, are in metallic contact with a Morse key _t_, placed on the side of the box K, and with an electro-magnet A, which belongs to a telegraphic system, intended to exchange the signals required to start the action of the two instruments at their respective stations.

The receiver consists of a sounding-box B, on which rest two supports _d_, _d_, bearing an iron rod of the thickness of a knitting needle. An induction coil of insulated wire _g_ is wound round this rod, and the whole is enclosed by the lid D, which concentrates the sound already increased by the sounding-box: for this purpose the box is provided with two openings below the coil.

The circuit is completed through the primary of this coil by the two terminals 3 and 4, and a Morse key _t_ is placed at the side of box B, in order to exchange signals.

In order to work this system, the speaking instrument should be placed before the opening T, and this instrument may be a flute, a violin, or even the human voice. The vibrations of air occasioned by these instruments cause the telephonic membrane to vibrate in unison, and the latter, rapidly moving the platinum disk _o_ to and from the point _b_, causes a series of breaks in the current, which are repeated in the iron wire _d d_, and transformed into metallic vibrations, of which the number is equal to that of the sounds successively produced.

According to this mode of action, the possibility of transmitting sounds with their relative value becomes intelligible: but it is equally clear that sounds thus transmitted will not have the _timbre_ of those which produce them, since the _timbre_ is independent of the number of vibrations, and it must be added that the sounds produced by M. Reiss’s instrument were as shrill as those of a child’s penny trumpet, and by no means attractive. The problem of transmitting musical sounds by electricity was, however, really solved, and it can be said with truth that an air or a melody could be heard at any given distance.

The invention of this telephone dates, as we have seen, from 1860, and Professor Heisler speaks of it in his treatise of technical physics, published at Vienna in 1866; he even asserts, in the article which he devotes to the subject, that although the instrument was still in its infancy, it was capable of transmitting vocal melodies, and not merely musical sounds. The system was afterwards perfected by M. Van der Weyde, who, after reading the account published by M. Heisler, sought to make the box of the sender more sonorous, and to strengthen the sounds produced by the receiver. He writes as follows in the ‘American Scientific Journal:’

‘In 1868, I caused two telephones to be made, similar to those I have described, and I exhibited them at a meeting of the Polytechnic Club of the American Institute. The transmitted sounds were produced at the farthest extremity of the Cooper Institute, quite outside the hall in which the audience sat: the receiver was placed on a table in the hall itself. The vocal airs were faithfully reproduced, but the sound was rather weak and nasal. I then tried to improve the instrument, and I first obtained stronger vibrations in the box K by causing reverberation from the sides of the box, by means of hollow partitions. I next intensified the sounds produced by the receiver, by introducing several iron wires into the coil, instead of one. These improvements were submitted to the meeting of the American Association for the Advancement of Science, which was held in 1869, and it was considered that the invention contained the germ of a new method of telegraphic transmission which might lead to important results.’ This opinion was soon afterwards justified by the discoveries of Bell and Elisha Gray.

_Messrs. Cecil and Leonard Wray’s Telephone._--This system, represented in figs. 2 and 3, is simply an improvement on that of M. Reiss, with the object of intensifying the effects produced. The sender is provided with two membranes, instead of one; and its receiver, instead of being formed of a single iron wire covered with a magnetising coil, is composed of two distinct coils H, H′ (fig. 2), placed in the same straight line, and within which are two iron rods. These rods are fastened by one of their ends to two copper disks A, B; these disks are maintained in a fixed position by screws I, I′, and the two other extremities of the rods, between the coils, are opposite each other, not touching, but divided by a very small interval. The instrument is set upon a sounding-box, in which there is a hole T in the space corresponding to the interval between the coils: these coils communicate with four terminals, which are connected with the electric current in such a way that the adjacent poles of the two rods are of opposite polarity, thus forming a single magnet, divided in the centre. It seems that by this arrangement the sound produced becomes much more distinct.

The form of the sender also is somewhat different from the one we have previously described: the upper part, instead of being horizontal, is rather inclined, as it appears in fig. 3, and the opening E through which the sound has to communicate with the vibrating membrane, occupies a great part of the upper surface of the box, which consequently appears to be somewhat oblique. The second membrane G, which is of caoutchouc, forms a sort of partition which divides the box in two, starting from the upper end of the opening: the inventor states that this will protect the outer membrane D from the breath and other injurious effects, while increasing the force of the vibrations produced on the first membrane, as in a drum. The contact-breaker itself also differs from the one in M. Reiss’s instrument. The platinum disk _b_ is only placed in circuit by means of two slender wires of platinum or steel, which are immersed in two small cups, filled with mercury, and connected with the circuit. In this way, the movements of the membrane D are free, and its vibration is rendered more easy.

The circuit is also broken by a little platinum point resting on a lever with a spring-joint, K H, which is above the disk: one end of the lever, which is fixed below a kind of Morse key M I, makes it possible to close the circuit with the hand, so as to give the signal for setting the apparatus to work.

_Electric Harmonica._--Long before M. Reiss’s invention, and consequently still longer before that of Mr. Elisha Gray, I mentioned a sort of electric harmonica, and described it as follows in the first edition of my ‘Exposé des applications de l’Electricité,’ published in 1853:--

‘The power possessed by electricity to set metallic plates in motion and cause their vibration has been used for the production of distinct sounds, which can be combined and harmonised; but in addition to this purely physical application, electro-magnetism has come to the aid of certain instruments, such as pianos, organs, &c., rendering them capable of being played at a distance. So that this extraordinary force may be turned to account in arts which are apparently the least susceptible of any application of electricity.

‘We have already spoken of M. de la Rive’s contact-breaker. It is, as we know, an iron disk, soldered to a steel spring, and maintained in a fixed position opposite to an electro-magnet by another spring in connection with one branch of the current. As the other branch, after passing into the wire of the electro-magnet, terminates in the iron disk itself, the electro-magnet is only active at the moment when the disk touches the terminal spring; at the moment of leaving it, the magnetism ceases, and the iron disk returns to its normal position, and then leaves it again. In this way a vibration is produced, rapid in proportion to the small size of the vibrating disk, and to the greatness of the force produced by the approach of the disk to the electro-magnet.

‘In order to increase the acuteness of the sounds, one or other of these expedients must be employed. The simplest way is to use a screw which can be tightened or relaxed at pleasure, and which in this manner removes the vibrating disk to a greater or less distance from the electro-magnet. This is the case in M. Froment’s instrument, and by this means he has obtained sounds of extraordinary acuteness, although not unpleasant to the ear.

‘M. Froment has not applied the apparatus to a musical instrument, but it is evident that it would be easy to do so; it would only be necessary to make the notes of a key-board act on metallic levers, of a length corresponding to the position required by the disk for the vibration of different tones. These different levers, resting on the disk, would act as a point of contact, but the point would vary in position, according to the touch.

‘If the current were constant, such an instrument would certainly have many advantages over the pipe instruments which are in use, since the vibration might be prolonged at will in the case of each note, and the sounds would be softer; unfortunately the irregular action of the battery makes it difficult in practice. These kinds of instruments are therefore only used as a means of regulating by ear the force of the battery, a much more convenient regulator than the rheometers, since it is possible to estimate by them the variations of the battery during an experiment without any distraction of the mind.’

In 1856 M. Pétrina, of Prague, invented an analogous arrangement, to which he gave the name of electric harmonica, although, strictly speaking, he had not thought of it as a musical instrument. This is what I have said on the subject in vol. iv. of the second edition of my ‘Exposé des applications de l’Electricité,’ published in 1859:--

‘The principle of this instrument is similar to that of Neef’s rheotome, in which the hammer is replaced by slender rods, whose vibrations produce a sound. Four of these rods are placed side by side, and when moved by keys, and arrested by levers, produce combined sounds of which the origin may be easily shown.’

It is true that nothing is said in this passage of the capability possessed by these instruments of being played at a distance; but this idea was quite legitimate, and German periodicals assert that it was accomplished by M. Pétrina even before 1856. It was the result of what I said at the outset: ‘that electro-magnetism may come to the aid of certain instruments, such as pianos, organs, &c., _in order to enable them to be played at a distance_,’ and I also pointed out the expedients employed for the purpose, and even for setting them at work, under the influence of a small musical box. I did not, however, ascribe importance to the matter, and it is only by way of historical illustration that I speak of these systems.

_Telephone by Mr. Elisha Gray, of Chicago._--This system, invented in 1874, is in reality only an instrument of the nature of those which preceded it, but with important modifications, which made it possible to apply it usefully to telegraphy. In an early model, he made use of an induction coil, with two helices, one over the other: the contact-breaker, which was vibrating, was multiple, and so arranged as to produce vibrations numerous enough to emit sounds. These sounds may, as we have seen, be modified by this arrangement, according to the mode in which the instrument is adjusted, and if there are a certain number of such contact-breakers side by side, with vibrating disks so ordered as to produce the different notes of the scale on several octaves, it becomes possible, by a combination of certain notes, to execute on this new kind of instrument a piece of music such as may be produced by an harmonium, an accordion, or any other instrument with blowers. The contact-breakers are set in motion by means of the primary current of the induction coil, as it circulates through one or other of the electro-magnets of these contact-breakers, actuated by the lowering of the notes of a key-board connected with them, and the secondary currents which arise in the coil, in consequence of the interruptions in the primary currents, transmit the corresponding vibrations to a remote receiver. There is an analogy between this instrument and the telephones of which we have already spoken by Reiss and Wray, but the effect is increased by Mr. Gray’s modifications.

We represent in fig. 4 the arrangement of the first system. The vibrators are A and A′, the key-board M and M′, the induction coil B, and the receiver C. This receiver consists, as we see, of a simple electro-magnet N N′: above its poles there is a metal cylindrical case C, of which the bottom is made of iron, to serve as an armature. This box, like a violin, is pierced with two holes in the form S, to serve as a sounding-board; and Mr. Elisha Gray has ascertained that the molecular motion which takes place in the magnetic core and its armature, under the influence of alternate magnetisation and demagnetisation, sufficed to produce vibrations corresponding to the velocity of these alternations, and to emit sounds which became audible when they were magnified by the sounding-board.

It is quite intelligible that the effect obtained in this system might be reproduced, if, instead of contact-breakers or electric rheotomes, mechanical contact-breakers were used at the sending station, so arranged as to furnish the requisite number of breaks in the current which communicates the vibrations of the different notes of the scale. In this way also it would be possible to dispense with the induction coil, by causing the current which has been broken by the mechanical contact-breaker to react upon the receiver. Mr. Elisha Gray has moreover made a different arrangement of this telephonic system, which he has applied to telegraphy for simultaneous electric transmissions, of which we shall speak presently.

If we may believe Mr. Elisha Gray, the vibrations transmitted by the secondary currents would be capable, by the intervention of the human body, of causing the sounds to be reproduced at a distance by conducting disks, which vibrate readily, and are placed on a sounding-box. In this way musical sounds may be evoked from copper cylinders placed upon a table, from a metallic disk fastened to a kind of violin, from a membrane stretched on a drum, or from any other resonant substance, by touching any of these objects with one hand, while holding the end of the line with the other. These sounds, of which the quality must vary with the substance touched, would reproduce the transmitted note with the precise number of vibrations which belong to it.[1]

_Mr. Varley’s Telephone._--This is, strictly speaking, merely a musical telephone of the same kind as that of Mr. Gray, but the arrangement of the receiver is original and interesting. This part of the instrument essentially consists of a drum of large size (three or four feet in diameter), within which is a condenser formed of four sheets of tinfoil, divided by sheets of some insulating material, and with a surface of about half the size of the drum. The plates of the condenser are placed parallel to the membranes of the drum, and very little removed from its surface.

If an electric charge is communicated to one of the series of conducting plates of the condenser, those which correspond to it are attracted, and if they were movable they might communicate to the intervening strata of air a movement which, on reaching the membranes of the drum, might, by a series of charges in rapid succession, cause the membranes to vibrate, and thus produce sounds: these sounds would correspond to the number of charges and discharges which had occurred. Since these charges and discharges are determined by the contact of the two plates of the condenser, at the extremities of the secondary circuit of an induction coil, of which the primary circuit has been duly broken, it becomes evident that, in order to cause the drum to emit any given sound, it will be enough to produce the number of vibrations in the contact-breaker of the induction coil which are required for this sound.

The means employed by Mr. Varley to produce these interruptions are the same which are in use in several electrical instruments, and especially in chronographs--an electro-magnetic tuning-fork, regulated so as to emit the sound required. This tuning-fork may, by acting as contact-breaker, react on the primary current of the induction coil; if the number of the tuning-forks equals that of the musical notes which are to be transmitted, and if the electro-magnets which set them in motion are connected with the key-board of a piano, it would be possible to transmit a melody to a distance by this system, as well as by that of Mr. Elisha Gray.

The peculiarity of this system consists in the reproduction of sounds by the action of a condenser, and we shall presently see that this idea, adopted by Messrs. Pollard and Gamier, led to interesting results.

_Singing Condenser of MM. Pollard and Garnier._--This instrument, which astonishes all who hear it, attracted public attention in London some time ago. It is difficult to say why its fame was not greater, since much attention has been bestowed on less curious instruments. It is a fact that we have been able, thanks to MM. Pollard and Garnier, to hear songs issue from a sort of copy-book, so as to become audible throughout the room. The songs thus reproduced are certainly not always perfectly true; yet when the person who sings into the sender is a musician, and understands how to make use of it, the condenser in question will emit sounds somewhat resembling those of the violoncello or the hautbois.

The singing instrument consists of a condenser K, formed of thirty sheets of paper, laid one over the other, from nine to thirteen centimètres in thickness: between these, twenty-eight sheets of tinfoil, from six to twelve centimètres thick, are intercalated, so joined as to form the two plates of the condenser. For this purpose the pair sheets are joined together at one end of the copy-book, and the odd sheets at the other end. This system is fastened to a stiff _carton_, after taking care to bind it with a strip of paper, and the sheets of tinfoil are joined to the two ends of the condenser by two copper rims D, D, which are provided with terminals for the circuit wire, and in this way the singing instrument is constructed. A somewhat heavy weight, placed upon the condenser to compress the sheets, does not in any way prevent it from working; and this vitiates the theory first put forward to explain its effects, that the sheets were moved by attraction.

The sending instrument consists of a sort of telephone without a handle, E, of which the vibrating disk is formed of a very thin plate of tin. A cylindrical piece of carbon C is fastened to its centre, and is supported by another cylinder of the same material H. This rests on a transverse piece of wood A B, jointed on the side A, on the edge opposite to the box, by means of a regulating screw V. An arched spring R (the end of a watch spring) placed across this piece of wood gives it a certain elasticity beneath the pressure, and this elasticity is necessary in order that the instrument may act properly, and it thus becomes a sort of microphone with a diaphragm.

The tin plate is put into communication with one pole of a battery P, of six Leclanché cells, and the lower carbon cylinder H corresponds to the primary helix of an induction coil M, previously connected with the second pole of the battery: Finally, the two extremities of the secondary helix of the coil, _a_ and _b_, are in immediate connection with the two plates D, D, of the condenser.

This secondary helix should consist of twenty strands of wire No. 32, covered with silk, and the primary helix is made of five strands of wire No. 16. The length of the coil should not exceed seven centimètres and the diameter of the core of fine iron wire ought to be about one centimètre.

In order to produce song on the condenser, the sender must be so regulated that the two carbons C and H do not touch each other in their normal condition, but they should be so close that in singing the vibrations of the disk L L may effect the needful contacts. The adjustment can be easily made by the touch, and by uttering the same note until it is repeated by the condenser. If three notes, given in succession, are faithfully reproduced, the instrument may be assumed to be properly regulated, and, in order to make it work, it is enough to apply the mouth to the mouthpiece as it is applied to a reed pipe.

In order to obtain a satisfactory result, the disk of the instrument must be heard to vibrate, as in a _flûte à l’oignon_. Instead of carbons, contacts of platinum may be used; but when arranged as we have described, the instrument may be employed for several purposes, as we shall see presently. This instrument is made by MM. Chardin and Prayer. M. Janssens has made the system more portable by fastening the sender, represented in fig. 5, to a handle in which the induction coil is placed: the instrument then resembles an ordinary telephone, and the vibration of the diaphragm is made more easy by piercing two holes in it. On the side of the sending-box, above and below the diaphragm, there are binding screws in connection with the end of the handle, since the instrument may be used as an ordinary telephonic sender, and even as a telephonic receiver.

SPEAKING TELEPHONES.

We have seen that the telephones just described can only transmit musical sounds, since they can merely repeat simple vibrations, in greater or less number, it is true, but not in simultaneous combinations like those which reproduce articulate sounds. Up to the time of Mr. Bell’s invention, the transmission of speech could only take place with the aid of acoustic tubes, or of the string telephones of which we have spoken. Although these instruments have no connection with the object of our study in this work, we have thought it necessary to say a few words about them, since they may sometimes be combined with electric telephones, and also represent the first stage of the invention.

_String Telephones._--These instruments, which have flooded the cities of Europe for several years, since the date of the invention was 1867, are interesting in themselves, and we are surprised that they have not hitherto taken a place in the collections of physical science. They are made of two metal or cardboard tubes, in the form of a cylindrical cone: one end is closed by a tightly stretched membrane of parchment, in the centre of which the cord or string intended to connect the two cylinders is fastened by a knot. When two such tubes are connected in this way, and the cord is tightly stretched, as in fig. 6, it is only necessary to apply one tube to the ear, while another speaks into the opening of the other tube: the words spoken by the latter are instantly transmitted, and it is even possible to converse in quite an undertone. Under these conditions the vibrations of the membrane affected by the voice are mechanically transmitted to the other membrane by the string, which, as Robert Hooke declared in 1667, is a better transmitter of sound than the air. In this way it is possible to communicate at a distance of 170 yards, and the size and nature of the cord have some influence. The sellers of these instruments say that the best results are obtained from silken cords, and the worst from those made of hemp. Cords of plaited cotton are usually employed for the sake of cheapness.

In some patterns, the tubes are so arranged as to present, between the membrane and the mouth, a diaphragm pierced with a hole, and the instrument somewhat resembles a bell with its base bored and closed again a little above the parchment membrane; but I have not observed that this pattern is decidedly superior to the others.

It has also been asserted that horn-shaped tubes of nickel silver are to be preferred, of which I am equally doubtful. At any rate, these instruments have produced unexpected results; and although their practical use is very limited, they are interesting from a scientific point of view, and are instructive toys for children.

Mr. Millar, of Glasgow, declares that the effect produced by these telephones depends very much on the nature of the string, the way in which it is attached, and the way in which the membrane is fastened to the mouthpiece.

_Improvements made in the String Telephone._--The amazing effects of the Bell telephones have lately brought the string telephones, which were only regarded as children’s toys, again into fashion. Since they have made it possible to transmit to several persons the words reproduced by an electric telephone, means have been sought for combining them usefully with the latter, and the best mode of making them speak on a string presenting several angles has been sought for: it has been shown that, under the usual conditions, these instruments only speak distinctly when the string is stretched in a right line. To solve this problem, it occurred to M. A. Bréguet to make use of a sort of tambourine for the supports, with the string passed through their centre; the sound conveyed by that part of the string which is in connection with the speaking-horn causes the membrane of the tambourine to vibrate, which again communicates the vibration to the next portion of string. In this way the angles may be multiplied at will, and the string may be supported throughout the length compatible with this kind of telephone, which does not exceed 112 yards.

M. A. Bréguet has also invented a system of relays to accomplish the same object. He makes the strings terminate in two membranes which close the two openings of a brass cylinder. The sounds reproduced on one of these membranes react upon the other, which vibrates under its influence, as if it were affected by the voice. The cylinder then acts as an ordinary acoustic tube, and its form may be varied at pleasure.