Part 17

M. Mauborgne, the electrician attached to the Northern Railway of France, has lately used the telephone instead of the galvanometer to ascertain the condition of the circuits in correspondence with the instruments in use for electric signals. The reactions produced on the galvanometer needle by the pieces of iron which are placed at the sides of the railway often make its indications uncertain, and a strong wind produces irregular movements in the instrument which interfere with observations. It was also necessary to place the galvanometer with due regard to the points of the compass, and to wait for the needle to settle, which involved loss of time. The operation is easily accomplished with the telephone, since the strokes of the call-bell are distinctly reproduced; it is made to ring by working the contacts which need verification, and in the same way the condition of the battery can be ascertained.

_Application to military purposes._--Since the telephone was invented, numerous experiments have been made in different countries to ascertain whether it would be of use in military operations. These experiments have hitherto been only moderately satisfactory, on account of the noise inseparable from an army, which generally makes it impossible to hear the telephone, and every means of intensifying its sounds has been eagerly sought. It was at first supposed that the discovery of the microphone had solved the problem, and I received many enquiries from military schools on the subject, but I have not been able to see that anything has been gained from this point of view. The telephone is, however, of great use in schools of artillery and rifle practice. Now that firearms carry so far, it has become necessary to be informed by telegraph of the points hit on the target, in order to judge of the accuracy of aim, and for this purpose telegraphic targets were suggested; but telephones are much to be preferred, and they are now used with good effect.

If the telephone is unsuited for the service of the flying telegraph in the field, it may be of great use in the defence of towns, to transmit the orders of the commandant to different batteries, and even for the exchange of correspondence with captive balloons sent to hover over fields of battle.

In spite of the difficulties attending its use, the experiment was made by the Russians in the late war: the cable wire of communication was 500 or 600 yards long, and so light that it could be laid by one man. The ‘Telegraphic Journal’ of March 15, 1878, states that the bad weather did not interfere with the working of the instruments; but the noise made it difficult to hear, and it was necessary to cover the head with a hood to intercept external sounds. This cannot be considered a satisfactory result, yet the telephone may be of great service to an army by intercepting the enemy’s messages: a bold man, provided with a pocket telephone, who placed himself in a retired spot, might divert the current of the enemy’s telegraphic wire into his telephone, and get possession of all his despatches, as we saw was the case at Clermont. He might even do this by diverting the current to earth or to a rail of the railway line. These are suggestions for future research, and it is probable that they may some day be turned to practical account.

_Its application to the navy._--The telephone may be of the greatest use in naval matters, for the service of electro-semaphores, for island forts and ships at anchor. M. Pollard says that ‘experiments made between the Préfecture Maritime at Cherbourg, the semaphores and the forts on the mole, demonstrate the advantage there would be in establishing telephones at these stations, since they would ensure an easy communication between the vessels of a squadron and the land they are approaching. By sinking small cables which come to the surface of the water along mooring chains, and terminate in buoys or cases which remain permanently in the harbour, the ships of war may in this way place themselves in communication with the Préfecture Maritime as they cast anchor, and, by temporarily connecting the vessels together with light cables, the admiral may communicate freely with the whole squadron.’

The telephone has been tried on board ship for transmitting orders, but without success, on account of the noise always going on in a vessel.

The telephone may be usefully applied to the service of submarine torpedoes. We have already seen how it may be applied in connection with the microphone, but it may also be used in firing the torpedoes after the exact position of the enemy’s ship has been ascertained from two reconnaissances taken from different parts of the coast.

The telephone, again, makes it possible to verify the condition of torpedoes, and to ascertain if there is any fault in the circuit within the explosives. For this purpose a very weak current has been used, and a galvanometer is not always able to indicate the fault, while the extreme sensitiveness of the telephone will do so in the simplest way.

Captain M’Evoy, of the American Army, suggested a way of ascertaining, while on shore, the condition of torpedoes under water, by connecting the buoys which support them with the land by means of a telephonic line. By inserting, in the buoy which supports the torpedo, metallic disks, so arranged as to vibrate with every movement caused by the waves upon the buoy, a continuous noise will be heard in the telephone, after the circuit has been completed by the metallic disks; and the noise will go on as long as the disks continue to oscillate, and will cease as soon as the buoy is completely covered by the water. When it ceases, therefore, if not affected by some accidental cause, it may be supposed that the enemy’s ship is passing over the buoy.

M. Trève, again, has shown that the telephone might be used with advantage for the telegraphic communication between vessels in tow, and M. des Portes has applied it with good effect to diving operations. In this instance, one of the glass panes in the helmet is replaced by a copper plate in which the telephone is framed, so that the diver need only make a slight movement of his head in order to receive or address communications to those in charge of the apparatus. With this system the keels of vessels may be examined, and an account given of their condition, without bringing up the divers, which has hitherto been necessary.

M. de Parville, the able and learned editor of the _Journal Scientifique_ and the science department of the _Journal des Débats_, has suggested a new and interesting application of the telephone. It concerns the possibility of making use of it to determine the precise position of the magnetic meridian, that is, the true direction of the magnetised needle.

For this purpose a Bell telephone is necessary, of which the magnetic core is formed of an iron rod a mètre in length, kept, by a suitable suspension, at nearly the same angle of inclination as a dipping-needle. This rod will be magnetised under the influence of terrestrial magnetism, and the telephone will be able to transmit the sounds produced by some sort of vibrator placed near its mouthpiece. These sounds will be strong in proportion to the degree of magnetisation of the bar; and if the telephone is turned round the horizon, keeping the bar at the same angle of inclination, the sounds transmitted to the receiving telephone will be greatest when the axis of the bar is in the plane of the magnetic meridian, and least when it is at 90°. It will therefore be possible to ascertain from the direction of the axis at the moment when the sounds are no longer heard, the exact inclination of the magnetic needle from north to south, for it will be given by the perpendicular to the line which is followed by the axis of the iron bar at that moment.

It is possible that, with this system, the disturbing influence on the magnetic needle of the mass of iron in iron-plated vessels might be almost destroyed, and a more exact orientation than that of the compass might be obtained. The same process may make it possible to estimate and measure the variations of terrestrial magnetism. M. de Parville has not himself tried to apply this system; but Mr. Blake’s experiments, of which we spoke in an early part of this work, make it probable that it might be done with advantage.

_Application to industry._--One of the earliest and most important applications of the telephone is that which was first made to the service of mines in England and America in the autumn of 1877. The great length of the galleries is well known, and had already involved the use of the electric telegraph for transmitting orders; but the miners did not understand how to work these instruments, and the service was ill performed. Thanks to the telephone, through which the first corner can send and receive a message, there is no longer any difficulty in the communication between the galleries and the surface of the mine.

The ventilation of mines can also be regulated by the aid of telephones. If one of these instruments is placed near a wheel kept in motion by the air which passes through the ventilating shaft, and another is placed in the inspector’s office he can ascertain by the sound if the ventilation is duly carried on, and if the machine works regularly.

_Application to scientific research._--M. d’Arsonval’s experiments, which we have already mentioned, show that the telephone can be used as an extremely sensitive galvanoscope; but since it can only produce sounds under the influence of broken currents, the circuit on which the experiment is made must be divided at rather close intervals. It has been seen that it is not even necessary to insert the telephone in the circuit: it may be influenced, when at a distance, either immediately or by the induction of the broken current on a circuit placed parallel to the first, and the force of these effects may be increased by the reaction of a core of iron, round which the inducing circuit is wound. The drawback to this system is that the direction of the current is not ascertained, so that it cannot be used as a measuring instrument; but, on the other hand, it is so sensitive, so easy to arrange, and so inexpensive, that it might be of the greatest use as a galvanoscope.

Mr. Warren de La Rue has also made use of the telephone in his researches into the electric discharges of high-tension batteries, in order to follow the different phases of the discharge during the luminous phenomena which it produces. In this way he ascertained that when a condenser is placed in connection with a battery formed of a considerable number of insulated elements, and is gradually discharged through a Geissler tube, a dull and faint sound is heard in the telephone, as long as the stratifications of light appear to be perfectly stable; but the sound becomes considerably stronger, and sometimes even piercing, in proportion to the diffusion of these stratifications, and to their approach to the point of extinction: whence it is shown that the discharge of a battery into tubes in which a vacuum has been made is intermittent.

Mr. Spottiswoode has repeated the same experiments with the discharges of Holtz machines, and with large condensers, and he found that the most piercing sounds produced by the telephone coincided with the greatest development of the stratifications. These sounds, however, sometimes ceased for a moment. It was even possible to ascertain, from the intensity of the sounds produced, the differences of tension which might be manifested in the charge of the condenser and the slackening of the machine’s motion, and the differences of intensity in these sounds might in some cases exceed an octave. The fall in the scale generally appeared in half-tones instead of gradually, and the introduction of resistances into the circuit modified the sounds very much: they might even be intensified by approaching the finger to the discharging tube.

From experiments made with the telephone between Calais and Boulogne, it appears that this instrument might be applied with advantage to the science of projectiles. In fact, in some artillery practice which took place on the shore at Boulogne, a telephone was placed close to the gun, and the explosion was heard at a distance of nearly two miles, where the projectile fell. It was possible to estimate its velocity by measuring the lapse of time between the moment when the projectile left the gun, and its fall. This calculation is usually made by observing the flash from the cannon’s mouth; but in some cases, as in a fog or in practice at long ranges, the telephone may be usefully substituted for ocular observation. On the field of battle, an observer, provided with a telephone and placed on a hill, might rectify from a distance the aim of his battery, which is generally established in a sheltered and less elevated place.

THE PHONOGRAPH.

Mr. Edison’s Phonograph, which has for the last year attracted so much attention, is an instrument which not only registers the different vibrations produced by speech on a vibrating plate, but reproduces the same words in correspondence with the traces registered. The first function of this instrument is not the result of a new discovery. Physicists have long sought to solve the problem of registering speech, and in 1856 Mr. Leo Scott invented an instrument well known to physicists under the name of Phonautograph, which completely solved the difficulty: this instrument is described in all the more detailed treatises on physics. But the second function of the Edison instrument was not realised nor even mentioned by Mr. Scott, and we are surprised that this able inventor should have regarded Mr. Edison’s invention as an injurious act of spoliation. We regret on his own account, since no one has wished to deprive him of the credit he deserves, that he should have published a pamphlet on the subject, couched in terms of such asperity, which proves nothing, and only states facts which were well known to all physicists. If any other person could claim the invention of the phonograph, at least in its most curious property of reproducing speech, it would certainly be M. Charles Cros; for in a sealed paper deposited at the Académie des Sciences, April 30, 1877, he pointed out the principle of an instrument by means of which speech might be reproduced in accordance with the marks traced on a register like that of the phonautograph.[19] Mr. Edison’s patent, in which the principle of the phonograph is first indicated, is dated July 31, 1877, and he was still only occupied with the repetition of the Morse signals. In this patent Mr. Edison described a mode of registering these signals by means of indentations traced with a stylus on a sheet of paper wound round a cylinder, and this cylinder had a spiral groove cut on its surface. The tracings thus produced were to be used for the automatic transmission of the same message, by passing it again under a stylus which should react on a current breaker. In this patent, therefore, nothing is said of the registration of speech or of its reproduction; but, as the ‘Telegraphic Journal’ of May 1, 1878, observes, the foregoing invention gave him the means of solving this double problem as soon as it was suggested to him. If we may believe the American journals, this suggestion soon came, and it was the result of an accident.

In the course of some experiments Mr. Edison was making with the telephone, a stylus attached to the diaphragm pierced his finger at the moment when the diaphragm began to vibrate under the influence of the voice, and the prick was enough to draw blood. It then occurred to him that if the vibrations of the diaphragm enabled the stylus to pierce the skin, they might produce on a flexible surface such distinct outlines as to represent all the undulations produced by the voice, and even that the same outlines might mechanically reproduce the vibrations which had caused them, by reacting on a plate capable of vibrating in the same way as that which he had already used for the reproduction of the Morse signals. From that moment the phonograph was discovered, since there was only a step between the idea and its realisation, and in less than two days the instrument was made and tried.

This is an ingenious story, yet we would rather believe that the discovery was made in a more serious spirit. In fact, such an inventor as Mr. Edison, who had discovered the electro-motograph, and had applied it to the telephone, was already on the way to discover the phonograph, and we think too well of his powers to attach much credit to this American romance. Besides, Mr. Edison was well acquainted with Mr. Scott’s phonautograph.

Mr. Edison’s phonograph was only patented in January 1877. Consequently, when we look at the principle of the invention, M. Cros undoubtedly may claim priority; but it is a question whether the system described in his sealed paper, and published in the _Semaine du Clergé_, October 8, 1877, would have been capable of reproducing speech. Our doubt seems justified by the unsuccessful attempts of the Abbé Leblanc to carry out M. Cros’ idea. When we have to do with such undulating and complex vibrations as those involved in the reproduction of articulate words, it is necessary that the stereotyping should in some sense be effected by the words themselves, and their artificial reproduction will necessarily fail to mark the slight differences which distinguish the delicate combinations of speech. Besides, the movements performed by a point confined to a groove that follows a sinusoidal curve cannot be effected with all the freedom necessary for the development of sounds, and the friction exerted on the two edges of the groove will often be of a nature to stifle them. A distinguished member of the Société de Physique, when I exhibited the phonograph to that society, justly said that Mr. Edison’s whole invention consisted in the thin metallic sheet on which the vibrations are inscribed; this sheet permits the movements of the vibrating plate to be directly stereotyped, and thereby the problem is solved. It was necessary to find such an expedient, and it was done by Mr. Edison, who is therefore the inventor of the phonograph.

After M. Cros, and before Mr. Edison, MM. Napoli and Marcel Deprez attempted to make a phonograph, but with so little success that they believed at one time the problem to be insoluble, and threw doubts on Mr. Edison’s invention when it was announced to the Société de Physique. They subsequently resumed their labours, and lead us to hope that they may eventually produce a phonograph of more perfect construction than that of Mr. Edison. We shall have more to say on this subject.

In conclusion, the mechanical reproduction of speech was first effected by Mr. Edison, and in so doing he has accomplished one of the most curious and important discoveries of our time, since it has shown that this reproduction was much less complicated than had been supposed. Yet the theoretical consequences of the discovery must not be exaggerated, since I do not consider it by any means proved that our theories on the voice are incorrect. There is in fact a great difference between the reproduction of a sound which has been uttered, and the mode in which the same sound was produced. The reproduction may be easily effected, as M. Bourseul has remarked, as soon as a mode has been discovered of transmitting the vibrations of air, however complex they may be; but in order to produce the complex vibrations of speech by the voice, several special organs must be exercised--first, the muscles of the throat; secondly, the tongue, the lips, and even the teeth--and for this reason an articulating machine is necessarily very complex.

Surprise was expressed that the speaking machine, which was brought from America two years ago, and exhibited at the Grand Hôtel, Paris, was so extremely complicated, since the phonograph solved the problem in such a simple way. This is because the latter instrument only reproduces speech, while the former utters it, and the inventor of the speaking machine had to employ in his mechanism all the organs which are necessary in our organism for the reproduction of speech. The problem was infinitely more complex, and this invention has not attracted all the attention it deserved. We shall speak of it presently. We must now describe the phonograph and the different applications which have been, or which may be, made of it.

_Description of Phonograph, and mode of using it._--The first and best known model of this instrument, which we represent in fig. 66, simply consists of a registering cylinder R, set in motion with the hand by a winch M, before which a vibrating plate is placed, furnished on its face with a telephone mouthpiece E, and on the reverse side with a tracing point. This tracing point, which is seen at _s_ in the section of the instrument given in fig. 68, is not fixed directly on the plate; it rests on a spring _r_, and a caoutchouc pad _c_ is placed between it and the vibrating disk. This pad is formed of the end of a tube which is designed to send the vibrations of the plate to the point _s_ without stifling them. Another pad _a_, placed between the plate L L and the rigid support of the point, moderates in some degree these vibrations, which, without this precaution, would generally be too powerful.

[Illustration: FIG. 66.]

The cylinder, of which the axis A A (fig. 66) is cut at one end like a screw, to enable it to make a lateral progressive movement simultaneously with the rotatory movement effected on itself, has on its surface a narrow screw-thread coinciding with that of the axis, and when the tracing point is inserted, it is able to pass along it for a distance corresponding to the time occupied in turning the cylinder. A sheet of tinfoil or of very thin copper is carefully applied to the surface of the cylinder, and it should be slightly pressed down upon it, so as to show a faint tracing of the groove, and to allow the point of the vibrating disk to be placed in a proper position. The point rests on the foil under a pressure which must be regulated, and for this purpose, as well as to detach the cylinder when it is desired to place or take away the tinfoil, there is the articulated system S N which sustains the support S of the vibrating disk. This system consists of a jointed lever in which there is a nut screw for the screw R. The handle N at the end of the lever allows the tracing system to be turned aside when the screw R is loosened. In order to regulate the pressure of the tracing point on the sheet of tinfoil, it is enough to turn the screw R loosely in its socket, and to tighten it as soon as the right degree of pressure is obtained.

This is the simple system by which speech can engrave itself on a plate in durable characters, and it works in the following manner.

[Illustration: FIG. 67.]