The following documents, drawn from the scientific literature of the time, are placed in chronological order, beginning with the first memoir published by Philipp Reis himself, in the Jahresbericht of the Physical Society of Frankfort, for the year 1860-61. Every care has been taken that the translations here given shall be faithful in every detail to the originals. All notes and comments by the translator are distinguished by being enclosed in square brackets.

[1.] On Telephony by the Galvanic Current.
By Philipp Reis.

[Translated from the Annual Report (Jahresbericht) of the Physical Society of Frankfurt-am-Main, for 1860-1861.]

The surprising results in the domain of Telegraphy, have often already suggested the question whether it may not also be possible to communicate the very tones of speech direct to a distance. Researches aiming in this direction have not, however, up to the present time, been able to show any tolerably satisfactory result, because the vibrations of the media through which sound is conducted, soon fall off so greatly in their intensity that they are no longer perceptible to our senses.

A reproduction of the tones at some distance by means of the galvanic current, has perhaps been contemplated; but at all events the practical solution of this problem has been most doubted by exactly the very persons who by their knowledge and resources should have been enabled to grasp the problem. To one who is only superficially acquainted with the doctrines of Physics, the problem, if indeed he becomes acquainted with it, appears to offer far fewer points of difficulty because he does not foresee most of them. Thus did I, some nine years ago (with a great penchant for what was new, but with only too imperfect knowledge in Physics), have the boldness to wish to solve the problem mentioned; but I was soon obliged to relinquish it, because the very first inquiry convinced me firmly of the impossibility of the solution.

Later, after further studies and much experience, I perceived that my first investigation had been very crude and by no means conclusive: but I did not resume the question seriously then, because I did not feel myself sufficiently developed to overcome the obstacles of the path to be trodden.

Youthful impressions are, however, strong and not easily effaced. I could not, in spite of every protest of my reason, banish from my thoughts that first inquiry and its occasion; and so it happened that, half without intending it, in many a leisure hour the youthful project was taken up again, the difficulties and the means of vanquishing them were weighed,—and yet not the first step towards an experiment taken.

How could a single instrument reproduce, at once, the total actions of all the organs operated in human speech? This was ever the cardinal question. At last I came by accident to put the question in another way: How does our ear take cognizance of the total vibrations of all the simultaneously operant organs of speech? Or, to put it more generally: How do we perceive the vibrations of several bodies emitting sounds simultaneously?

In order to answer this question, we will next see what must happen in order that we may perceive a single tone.

Apart from our ear, every tone is nothing more than the condensation and rarefaction of a body repeated several times in a second (at least seven to eight times[15]). If this occurs in the same medium (the air) as that with which we are surrounded, then the membrane of our ear will be compressed toward the drum-cavity by every condensation, so that in the succeeding rarefaction it moves back in the opposite direction. These vibrations occasion a lifting-up and a falling-down of the “hammer” [malleus bone] upon the “anvil” [incus bone] with the same velocity, or, according to others, occasion an approach and a recession of the atoms of the auditory ossicles, and give rise, therefore, to exactly the same number of concussions in the fluid of the cochlÆa, in which the auditory nerve and its terminals are spread out. The greater the condensation of the sound-conducting medium at any given moment, the greater will be the amplitude of vibration of the membrane and of the “hammer,” and the more powerful, therefore, the blow on the “anvil” and the concussion of the nerves through the intermediary action of the fluid.

The function of the organs of hearing, therefore, is to impart faithfully to the auditory nerve, every condensation and rarefaction occurring in the surrounding medium. The function of the auditory nerve is to bring to our consciousness the vibrations of matter resulting at the given time, both according to their number and their magnitude. Here, first, certain combinations acquire a distinct name: here, first the vibrations become musical tones or discords (MisstÖne).

That which is perceived by the auditory nerve, is, therefore, merely the action of a force affecting our consciousness, and as such may be represented graphically, according to its duration and magnitude, by a curve.

Let the line a, b, indicate any given length of time, and the curve above the line a condensation (+), the curve below the line a rarefaction (-), then every ordinate erected at the end of an abscissa will give [according to the height of it], at a moment indicated by the position of the foot of the ordinate, the strength of the condensation that is causing the drum-skin to vibrate.

Our ear can perceive absolutely nothing more than is capable of being represented by similar curves, and this method is completely sufficient to bring before our clear consciousness every tone and every combination of tones.

If several tones are produced at the same time, then the medium that conducts sound is placed under the influence of several simultaneous forces; and the two following laws hold good:—

If all the forces operate in the same sense, the resultant motion is proportional in magnitude to the sum of the forces.

If the forces operate in opposite senses, the resultant motion is proportional in magnitude to the difference of the opposing forces.

Let us exhibit the condensation-curves for three tones—each singly (Table I.)[16]: then, by adding together the ordinates corresponding to equal abscissÆ, we can determine new ordinates and develop a new curve which we may call the combination-curve [or resultant curve]. Now this gives us just exactly what our ear perceives from the three simultaneous tones. It ought to cause us as little wonder that a musician can recognize the three tones, as that (as is the fact) a person conversant with the science of colour, can recognize in green, blue and yellow tints. The combination-curves of table I. present, however, very little difficulty, since in them all the proportions of the component curves recur successively. In chords consisting of more than three tones (Table II.), the proportions of the components are no longer so easy to recognize in the drawing. But it is also difficult to an accomplished musician, in such chords to recognize the individual notes.

Table III. shows us a discord. Why discords affect us so unpleasantly I leave provisionally to the contemplation of the gentle reader, as I may perhaps return to this point in another memoir.

It follows from the preceding that:—

(1.) Every tone and every combination of tones evokes in our ear, if it enters it, vibrations of the drum-skin, the motions of which may be represented by a curve.[17]

(2.) The motions of these vibrations evoke in us the perception (sensation) of the tone: and every change in the motion must change the sensation.

As soon, therefore, as it shall be possible at any place and in any prescribed manner, to set up vibrations whose curves are like those of any given tone or combination of tones, we shall receive the same impression as that tone or combination of tones would have produced upon us.[18]

Taking my stand on the preceding principles, I have succeeded in constructing an apparatus by means of which I am in a position to reproduce the tones of divers instruments, yes, and even to a certain degree the human voice. It is very simple, and can be clearly explained in the sequel, by aid of the figure:

In a cube of wood, r s t u v w x, there is a conical hole, a, closed at one side by the membrane b (made of the lesser intestine of the pig), upon the middle of which a little strip of platinum is cemented as a conductor of the current [or electrode]. This is united with the binding-screw, p. From the binding-screw n there passes likewise a thin strip of metal over the middle of the membrane, and terminates here in a little platinum wire which stands at right angles to the length and breadth of the strip.

From the binding-screw, p, a conducting-wire leads through the battery to a distant station, ends there in a spiral of copper-wire, overspun with silk, which in turn passes into a return-wire that leads to the binding-screw, n.

The spiral at the distant station is about six inches long, consists of six layers of thin wire, and receives into its middle as a core a knitting-needle, which projects about two inches at each side. By the projecting ends of the wire the spiral rests upon two bridges of a sounding-box. (This whole piece may naturally be replaced by any apparatus by means of which one produces the well-known “galvanic tones.”)

If now tones, or combinations of tones, are produced in the neighbourhood of the cube, so that waves of sufficient strength enter the opening a, they will set the membrane b in vibration. At the first condensation the hammer-shaped little wire d will be pushed back. At the succeeding rarefaction it cannot follow the return-vibration of the membrane, and the current going through the little strip [of platinum] remains interrupted so long as until the membrane, driven by a new condensation, presses the little strip (coming from p) against d once more. In this way each sound-wave effects an opening and a closing of the current.

But at every closing of the circuit the atoms of the iron needle lying in the distant spiral are pushed asunder from one another. (MÜller-Pouillet, ‘Lehrbuch der Physik,’ see p. 304 of vol. ii. 5th ed.). At the interruption of the current the atoms again attempt to regain their position of equilibrium. If this happens then in consequence of the action and reaction of elasticity and traction, they make a certain number of vibrations, and yield the longitudinal tone[19] of the needle. It happens thus when the interruptions and restorations of the current are effected relatively slowly. But if these actions follow one another more rapidly than the oscillations due to the elasticity of the iron core, then the atoms cannot travel their entire paths. The paths travelled over become shorter the more rapidly the interruptions occur, and in proportion to their frequency. The iron needle emits no longer its longitudinal tone, but a tone whose pitch corresponds to the number of interruptions (in a given time). But this is saying nothing less than that the needle reproduces the tone which was imparted to the interrupting apparatus.

Moreover, the strength of this tone is proportional to the original tone, for the stronger this is, the greater will be the movement of the drum-skin, the greater therefore the movement of the little hammer, the greater finally the length of time during which the circuit remains open, and consequently the greater, up to a certain limit, the movement of the atoms in the reproducing wire [the knitting needle], which we perceive as a stronger vibration, just as we should have perceived the original wave.

Since the length of the conducting wire may be extended for this purpose, just as far as in direct telegraphy, I give to my instrument the name “Telephon.”

As to the performance attained by the Telephone, let it be remarked, that, with its aid, I was in a position to make audible to the members of a numerous assembly (the Physical Society of Frankfort-on-the-Main) melodies which were sung (not very loudly) into the apparatus in another house (about three hundred feet distant) with closed doors.

Other researches show that the sounding-rod [i.e. the knitting needle] is able to reproduce complete triad chords (“DreiklÄnge”) of a piano on which the telephone [i.e. the transmitter] stands; and that, finally, it reproduces equally well the tones of other instruments—harmonica, clarionet, horn, organ-pipes, &c., always provided that the tones belong to a certain range between F and f''[20].

It is, of course, understood that in all researches it was sufficiently ascertained that the direct conduction of the sound did not come into play. This point may be controlled very simply by arranging at times a good shunt-circuit directly across the spiral [i.e. to cut the receiving instrument out of circuit by providing another path for the currents of electricity], whereby naturally the operation of the latter momentarily ceases.

Until now it has not been possible to reproduce the tones of human speech with a distinctness to satisfy everybody. The consonants are for the most part tolerably distinctly reproduced, but the vowels not yet in an equal degree. Why this is so I will endeavour to explain.

According to the researches of Willis, Helmholtz, and others, vowel sounds can be artificially produced by causing the vibrations of one body to reinforce those of another periodically, somewhat after the following scheme:—

An elastic spring is set in vibration by the thrust of the tooth of a cog-wheel: the first swing is the greatest, and each of the others is less than the preceding one (see Fig. 26).

After several vibrations of this sort (without the spring coming to rest) let another thrust be given by the tooth; the next swing will again be a maximum one, and so on.

The height or depth of the sound produced in this fashion depends upon the number of vibrations made in a given time; but the quality of the note depends upon the number of variations of amplitude (Anschwellungen) occurring in the same time.

Two vowels of equal pitch may be distinguished from each other somewhat after the manner represented by the curves (1) (2): while the same tone devoid of any vowel quality, is represented by curve (3).

Our organs of speech create the vowels probably in the same manner by a combined action of the upper and lower vocal chords, or of the latter and of the cavity of the mouth.

Now my apparatus gives the number of the vibrations, but with far less strength than the original ones; though also, as I have cause to think, always proportional to one another up to a certain degree. But because the vibrations are throughout smaller, the difference between large and small vibrations is much more difficult to recognize than in the original waves, and the vowel is therefore more or less indefinite.

Whether my views with respect to the curves representing combinations of tones are correct, may perhaps be determined by aid of the new phonautograph described by Duhamel. (See Vierordt’s ‘Physiology,’ p. 254.)

There may probably remain much more yet to be done for the utilisation of the telephone in practice (zur praktischen Verwerthung des Telephons). For physics, however, it has already sufficient interest in that it has opened out a new field of labour.

Philipp Reis.

Friedrichsdorf, near Frankfort-on-the-Main,
in December 1861.

[Though the foregoing memoir, as printed in the ‘Jahresbericht,’ of the Physical Society of Frankfort-on-the-Main, is dated “December 1861,” it was delivered verbally on October 26th preceding, as the ‘Proceedings’ of the Society show. From the ‘Jahresbericht’ for the succeeding year we learn that three weeks after the delivery of this communication Reis made a second communication to the Society on a kindred matter. The entry is as follows (‘Proceedings’ of the Society, p. 13): “On the 16th November, by the same: Explanation of a new Theory concerning the Perception of Chords and of Timbre (‘Klangfarben’), as a Continuation and Supplement of the Memoir on the Telephone.” So far as can now be learned, the substance of this communication was embodied in the latter part of the paper “On Telephony,” when written out in December for publication. On the 8th of January, 1862, the formal thanks of the Society were voted to Reis for the manuscript which he had contributed to the ‘Jahresbericht.’

It is of interest, moreover, to note that the matter did not immediately drop. Professor BÖttger, who as one of the regular lecturers of the Physical Society, held fortnightly discourses on matters of scientific novelty, took occasion on the 7th of December to recur to the subject then attracting so much attention. The title of his discourse (see ‘Proceedings’ of the Society, p. 11) was “Application of an Experiment relating to the Transmission of Musical Tones to any desired distance by means of the Galvanic Current.” It is not quite certain whether Reis was present on this occasion. Early in the spring of 1863, appeared in BÖttger’s ‘Polytechnisches Notizblatt’ (No. 6 of that year) an article which contains in condensed form BÖttger’s discourse. This article was copied into Dingler’s ‘Polytechnisches Journal’ for May 1863. vol. clxviii. p. 185, and also into the ‘Polytechnisches Centralblatt’ for July 1863, vol. xxix. p. 858. An extract of Reis’s own paper, condensed from the ‘Jahresbericht’ by Dr. Roeber (now President of the Physical Society of Berlin), appeared in the ‘Berliner Berichte’ (i. e. the ‘Fortschritte der Physik’) for 1861, vol. xvii. pp. 171-173. It is interesting to note that Reis’s paper was then deemed worthy to stand in the pages of the ‘Fortschritte’ by the side of the classic researches of Thomson on Regelation, and of Maxwell on Magnetic Lines of Force. The following is a translation of BÖttger’s notice mentioned above.]

[2.] On the Transmission of Tones to a Distance as far as desired, by the help of Electricity (Telephony).

[Translated from the original notice by Professor BÖttger, which appeared in BÖttger’s ‘Polytechnischen Notizblatt,’ 1863, No. 6, p. 81, in Dingler’s ‘Polytechnisches Journal,’ 1863, vol. clxviii. p. 185, and in the ‘Polytechnisches Centralblatt,’ 1863, t. xxix. p. 858.]

Two decades ago we had not yet gone beyond the first attempts to give signals at a great distance by the aid of electricity. Since then telegraphy has attained such a completeness, and the telegraph wire has reached such a universal extension, that there seems little left for even the boldest wish to desire.

Now there crops up a first serious research to reproduce tones at any desired distance by the aid of electricity. This first experiment which has been crowned with some success, has been made by the teacher of Natural Science at Friedrichsdorf, not far from Frankfort-on-the-Main, Herr Ph. Reis, and has been repeated in the Auditorium of the Physical Society in Frankfort, before numerous assembled members on the 26th of October, 1861. He caused melodies to be sung not very loudly into one part of his apparatus, which was placed in a building (the BÜrger-Hospital), about 300 feet distant, with closed windows and doors. These same melodies were audible to the members in the meeting-hall by means of the second part of the apparatus. These wonderful results were attained with the following simple pieces of apparatus. A little light box, a sort of hollow cube of wood, has a large opening at its front side, and a small one at the back on the opposite side. The latter is closed with a very fine membrane (of pig’s smaller-intestine) which is strained stiff. A narrow springy strip of platinum foil, fixed at its outer part to the wood, touches the membrane at its middle; a second platinum strip is fastened by one of its ends to the wood at another spot, and bears at its other end a fine horizontal spike, which touches the other little platinum strip where it lies upon the membrane.

As is known, tones arise from rarefactions and condensations of the air following quickly after one another. If these motions of the air, known as waves, strike upon the thin membrane, they press it against the little plate of platinum with which it is in contact, and immediately let it vibrate back again into the hollow cube (or so-called artificial ear): they act so that the membrane now takes a form hollowed toward the cube, now bulged toward the outside. The little plate of platinum touching it thereby acquires a vibrating motion, so that it now is pressed against the spike of the second [platinum plate], now leaves the same.

If now one little plate of platinum be united by a wire with one pole of a voltaic battery, and the electricity be led, by a wire fastened to the other pole of the battery, to any desired distance; there carried through a spiral, about six inches long, made of a six-fold winding of very thin covered copper wire; thence led back to the second platinum strip on the wooden cube through a second insulated wire; then at every vibration of the membrane an interruption in the current of electricity takes place because the platinum point no longer touches the other little strip of platinum. Through the hollow of the wire-spiral there is stuck a thin iron wire (a strong knitting-needle), which is ten inches long, and which rests upon two bridges of a sounding-board by its ends which project on both sides about two inches out of the spiral.

It is known[21] that if an electric current be led through a spiral which surrounds an iron rod in the manner described, at every interruption of the same a tone is audible arising from the vibration of the rod. If the closings and interruptions of the circuit follow one another relatively slowly, then there is produced by the changes of position of the molecules of the rod, evoked by the electricity, a tone,—the so-called longitudinal tone of the rod,—which is dependent upon the length and stoutness of the rod. But if the closings and interruptions of the electric current in the spiral follow one another more rapidly than the vibrations of the smallest particles of the iron rod,[22] which vibrations are determined by its elasticity, then these particles cannot complete their paths, receive new impacts, their vibrations become smaller, but quicker, and follow one another as frequently as the interruptions. The iron rod then no longer gives its longitudinal tone, but a tone, which is higher according as the interruptions are more frequent in the given time, or lower, as they are less frequent. It is known that the height and depth of tones depends only on the number of air-waves which follow one another in a second. We have seen above that by this is determined the number of interruptions of the electric current of our apparatus by means of the membrane and the platinum strip. The iron wire must therefore give out the tone in the same height or depth as that which struck the membrane. Now since a very far leading of the electricity makes it suffer scarcely any weakening in proper apparatus, it is intelligible that one can make the tone which acts on the membrane at one place audible, by means of the iron rod, at any desired distance.

That the tone is made audible at a distance by the electric agitations, and not by direct conduction of the sound-waves through the wires is proved in the most evident way of all, because one instantly hears no more the tone through the spiral when a good short circuit is made, as, for example, by laying upon the two wires which conduct the electricity a strip of sheet metal right in front of the spiral.

The reproduced tones are, of course, somewhat weaker than the original ones, but the number of vibrations is similar. If thus the reproduction [of tones] in exactly similar height and depth is easily attained, it is however difficult for our ear, amidst the always smaller vibrations, to which the diminished strength of the tone is due, to evaluate exactly the magnitude of the vibrations. But the character of the tone depends upon the number of variations of amplitude (Anschwellungen), that is to say, depends upon whether, for example, in the tones which have similar pitch and therefore a similar number of waves per second, the fourth, sixth, eighth, tenth, or sixteenth wave is stronger than the others. For physicists have shown that an elastic spring is set in vibration by the thrust of the teeth of a cog-wheel; the first vibration is the greatest, all those that follow being less. If there comes, before the spring comes to rest, a fresh thrust from a cog, then the next vibration is again equal to the greatest first vibration without the spring making any more vibrations on that account; and by this means vowel-tones may be artificially produced.

One may also be yet far removed from being able to carry on a conversation with a friend dwelling a hundred miles distant, and recognise his voice, as if he sat near us; but it can no longer be maintained that this is impossible. Indeed the probability that this will be attained[23] is already become as great as the probability of the reproduction of natural colours in photography has become through the notable researches of Niepce.

[The second public exhibition which Reis made of the telephone was, like the first, in Frankfort-on-the-Main, but this time before a Society known as the Freies Deutsches Hochstift, or Free German Institute, a kind of AthenÆum Club for the city of Frankfort, now for many years established in the well-known house where the poet Goethe was born, in the Grosse Hirschgraben. In 1862, however, the Free German Institute held its meetings in another building known as the Saalbau. And on May the 11th of that year Philipp Reis lectured upon and exhibited the Telephone. A journal which appeared then, and still appears, in Frankfort, with the title of ‘Didaskalia,’ devoted to light literary and artistic news, popular science, and general intelligence of an informing character, ordinarily inserted notices of the chief meetings of the Hochstift. On this occasion a preliminary paragraph was inserted in the following terms:—]

[3.] Telephony, i.e. Sound-Transmission
[Translation from ‘Didaskalia,’ May 8th, 1862.]

The excellent physicist, Mr. Phil. Reis, of Friedrichsdorf, calls by this name his surprising invention for using the telegraph line to transmit really audible tones. Our readers will perhaps remember having heard some time since of this invention, the first trials with which Mr. Reis performed here in the Physical Society. Since then the invention has been constantly developed, and will, no doubt, become of great importance.

[The lecture which followed this announcement was duly given on the 11th of May. In the Saalbau there is a suite of four rooms. The Lecture to the assembled members of the Hochstift was delivered in the Auditorium, at one end of the suite: the wires were passed through the two intervening rooms to the fourth chamber, where the transmitter was placed, the doors being closed. The battery and wires were borrowed from the Physical Society for this occasion, permission for their use having been granted on May 2nd, as appears in a formal entry in the minute-book. The following notice of Reis’s discourse, believed to have been written by Dr. Volger, Founder and first President of the Hochstift, appeared in ‘Didaskalia’ for May 14th.]

[4.] Translation from ‘Didaskalia,’ 12th May, 1862.

Yesterday’s meeting of the Free German Institute was a very numerously attended one from the fact that the subject in the order of business, “Telephony by Transmission of the Galvanic Current,” as explained by the inventor himself, Mr. Phil. Reis, excites so great an interest that it rightly deserves the most general attention.

In a lecture exceedingly interesting, universally understood, clear, and concise, Mr. Reis gave a historical outline of the origin and development of his idea of the practical possibility of the transmission of tones in a galvanic way.

His first attempts were mostly unsuccessful in solving the cardinal question propounded by him. “How is it possible that a single instrument can reproduce at once the total action of all the organs operated in human speech?” Until finally it occurred to him to seek the solution of the problem in the question, “How does our ear take cognisance of the total vibrations of all the organs of speech acting at once?” or “How do we perceive the vibrations of several bodies sounding at once?”

In order to answer this question the lecturer went more closely into the anatomy of the ear and into the formation of tones in general. After this was determined, he took up again his experiments in reference to the transmission of tones by means of galvanism.

Afterwards Mr. Reis constructed considerably enlarged the parts of the ear necessary for hearing, by which it was finally possible for him to transmit the tones brought to the mechanically-imitated ear.

The experiments by him some months ago in the Physical Society, were, to the astonishment of all, exceedingly plain and clear, whereas the experiment following the lecture of yesterday was less successful. This was due partly to the poor conductivity of the wires, partly to the locality.

Although much is still left to be done for the practical utilisation (Verwerthung) of the telephone, yet a new and interesting field of labour is hereby opened to physics.

[No more complete report than the foregoing is to be found, and it is believed that the discourse, which like all those given by Reis was delivered extempore, was never committed to writing. Its resemblance to the discourse of the preceding autumn before the Physical Society is great; and indeed it may be said that all Reis’s discourses upon the telephone were practically identical in their contents. A few months after this lecture, Reis presented a pair of instruments, transmitter and receiver, to the Hochstift. These instruments were not the same as those used by Reis at his lecture, but were of the “improved” type, whilst those used by Reis at his lecture to the Hochstift, were, so far as respects the transmitter at least, more like the form described by W. von Legat, and figured in Plate II., Fig. A;[24] and according to Mr. Horkheimer, who helped Reis on this occasion, the transmitter was provided with a conical mouthpiece of wood. The transmitter presented later by Reis is of the “square-box” form (Fig. 17), and is stamped, “1863, Philipp Reis, 2,” and the receiver is of the “knitting-needle” form (Fig. 23). These instruments are carefully preserved by the Hochstift in the “Goethehaus,” amongst their archives “in everlasting remembrance” of the inventor. A few months later, in 1863, the Emperor of Austria and the late king Max of Bavaria were residing at Frankfurt and visited the “Goethehaus;” and on this occasion Reis’s instruments were shown to these distinguished visitors by the Founder and President of the Hochstift, Dr. Volger.

In honour of his brilliant invention Reis was, shortly after his lecture, elected an honorary member of the Freies Deutsches Hochstift.]

[The next document in order is a Report by Wilhelm von Legat, communicated to the Austro-German Telegraph Union (Verein) in 1862, and printed in the ‘Journal’ of that Society. It was reprinted verbatim in Dingler’s ‘Polytechnisches Journal,’ for 1863, vol. clxix. p. 29. This Report is of great importance. It is quoted by Graham Bell, in his earliest account of his telephone. It was this Report, moreover, which in 1875 or 1876, in a translated manuscript form, was put into Mr. Edison’s hands by the then President of the Western Union Telegraph Company, and which formed the starting-point of Edison’s subsequent work.]

[5.]On the Reproduction of Tones in the Electro-Galvanic Way.
By v. Legat, Inspector of the Royal Prussian Telegraphs in Cassel.

[Translated from the Journal of the Austro-German Telegraph Society (edited by Dr. Brix), vol. ix. p. 125, 1862. (Zeitschrift des deutschÖsterreichischen Telegraphen-Vereins, 1862.)]

It might not be uninteresting to make known to wider circles the following ideas concerning the reproduction of tones in an electro-galvanic way, which have recently been put forward by Herr Philipp Reiss [sic] of Friedrichsdorf, before the Physical Society, and before the meetings of the Free German Institute (Freies Deutsches Hochstift) in Frankfort-on-the-Main; also to state what has hitherto been attained in the realisation of this project, in order that building upon the collected experiences and the efficacy of the galvanic current, what has already been made serviceable to the human intellect for the advancement of its correspondence, may in this respect also be turned to profit.

In what is here announced we are concerned not with the action of the galvanic current in moving telegraphic apparatus of whatever construction for producing visible signals, but with its application for the production of audible signals—of tones!

The air-waves, which by their action within our ears awaken in us the sensation of sound, by first of all setting the drum-skin into a vibrating motion, are thence, as is known, conveyed to the inner part of the ear and to the auditory nerves lying there by a lever apparatus of the most marvellous fineness,—the auditory ossicles (including “Hammer,” “Anvil,” and “Stirrup”). The experiment for the reproduction of tones is based upon the following: viz. to employ an artificial imitation of this lever-apparatus and to set it in motion by the vibrations of a membrane like the drum-skin in the ear, and thus to open and close a galvanic circuit which is united by a metallic conductor with a distant station.

Before the description of the necessary apparatus is followed out, it might be necessary, however, to go back to the point how our ear perceives the vibrations of a given tone, and the total vibrations of all the tones simultaneously acting upon it; because by this means will be determined the various requisite conditions which must be fulfilled by the transmitting and receiving apparatus for the solution of the problem that has been set.

Let us consider first the processes which take place in order that a single tone should be perceived by the human ear; so shall we find that each tone is the result of a condensation and rarefaction several times repeated in a certain period of time. If this process is going on in the same medium (the air) in which our ear is situated, the membrane will at every condensation be forced toward the hollow of the drum, and at every rarefaction will move itself in the opposite direction.

These vibrations necessitate a similar motion of the auditory ossicles, and thereby a transference to the auditory nerves is effected.

The greater the condensation of a sound-conducting medium at any given moment, the greater also will be the amplitude of vibration of the membrane and of the auditory ossicles and of their action; and in the converse case the action will be proportionally less. It is, therefore, the function of the organs of hearing to communicate with fidelity to the auditory nerves every condensation and rarefaction occurring in the surrounding medium; whilst it remains to be the function of the auditory nerves to bring to our consciousness the number as well as the magnitude of the vibrations ensuing in a given time.

Here in our consciousness a definite name is given to a certain composition, and here the vibrations brought to the consciousness become “tones.”

That which is perceived by our auditory nerves is consequently the effect upon our consciousness of a force which, according to its duration and magnitude, may for the sake of better comprehension, be exhibited graphically.

“The apparatus A, a square box of wood, the cover of which shows the membrane (c) on the outside, under glass. In the middle of the latter is fixed a small platina plate to which a flattened copper wire is soldered on purpose to conduct the galvanic current. Within the cercle you will further remark two screws. One of them is terminated by a little pit in which you put a little drop of quiksilver; the other is pointed. The angle, which you find lying on the membrane, is to be placed according to the letters, with the little whole [hole] (a) on the point (a) the little platina foot (b) into the quicksilver screw, the other platina foot will then come on the platina plate in the middle of the membrane.

“The galvanic current coming from the battery (which I compose generally of three or four good elements) is introduced at the conducting screw near (b) wherefrom it proceeds to the quicksilver, the movable angle, the platina plate and the complementary telegraph to[29] the conducting screw (s). From here it goes through the conducter to the other station B and from there returns to the battery.

“The apparatus B, a sonorous box on the cover of which is placed the wire-spiral with the steel axis, wich will be magnetic when the current goes through the spiral. A second little box is fixed on the first one, and laid down on the steel axis to increase the intensity of the reproduced sounds. On the small side of the lower box you will find the correspondent part of the complementary telegraph.

“If a person sing at the station A, in the tube (x) the vibrations of air will pass into the box and move the membrane above; thereby the platina foot (c) of the movable angle will be lifted up and will thus open the stream at every condensation of air in the box. The stream will be re-established at every rarefaction. For this manner the steel axis at station B will be magnetic once for every full vibration; and as magnetism never enters nor leaves a metal without disturbing the equilibrium of the atoms, the steel-axis at station B must repeat the vibrations at station A and thus reproduce the sounds which caused them.

“Any[30] sound will be reproduced, if strong enough to set the membrane in motion.

“The little telegraph, which you will find on the side of the apparatus is very usefull and agreable for to give signals between both of the correspondents. At every opening of the stream and next following shutting the station A will hear a little clap produced by the attraction of the steel spring. Another little clap will be heard at station (B) in the wire-spiral. By multiplying the claps and producing them in different measures you will be able as well as I am to get understood by your correspondent.

“I am to end, Sir, and I hope, that what I said will be sufficient to have a first try; afterward you will get on quite alone.

“I am, Sir,
“Your most obediant Servant,
“Ph. Reis.

“Friedrichsdorf, 13/7, 63.”