CHAPTER IV.CONTEMPORARY DOCUMENTS.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 theJahresberichtof 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.ByPhilipp 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.Areproductionof the tones at some distance by means ofthe 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 greatpenchantfor 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 doesour eartake 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” [malleusbone] upon the “anvil” [incusbone] 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 thecochlæa, 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 musicaltonesordiscords(Misstöne).That which is perceived by the auditory nerve, is, therefore,merely the action of aforceaffecting our consciousness, and as such may be represented graphically, according to its duration and magnitude, by a curve.Fig. 24.Let the linea, 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 ordinatescorresponding 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:Fig. 25.In a cube of wood,r s t u v w x, there is a conical hole,a, closed at one side by the membraneb(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. Fromthe binding-screwnthere 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 openinga, they will set the membranebin vibration. At the first condensation the hammer-shaped little wiredwill 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 fromp) againstdonce 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 certainnumber 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 thatthe 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. theknitting 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 betweenFandf''[20].It is, of course, understood that in all researches it was sufficiently ascertained that the directconductionof 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:—Fig. 26.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 (seeFig. 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).Fig. 27.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 hasopened outa 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 discourseson 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 wereaudibleto 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 aspiral 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 becomeas 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 theFreies 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 thisinvention, 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 thequestion, “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 inPlate 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 ofhistelephone. 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.Byv. 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 producingvisiblesignals, but with its application for the production ofaudiblesignals—oftones!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 numberas 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.Let, for example, the length of the linea bbe any definite duration of time, and let the curves above this line denote the condensations (+), and the curves below this line the rarefactions (-); then every ordinate erected at the extremity of an abscissa gives us the strength of the condensation in consequence of which the drum-skin vibrates, at the moment indicated by the position of the foot of the ordinate.Anything more than that which is exhibited in this way or by similar curves our ear cannot in the least perceive, and this is sufficient to bring to our consciousness each single tone and each given combination of tones. For, if several tones are produced at the same time, the sound-conducting medium is put under the influence of several simultaneously acting forces which are subject to the laws of mechanics.If all the forces operate in the same sense, then the magnitude of the motion is proportional to the sum of the forces. If the forces act in opposite directions, the magnitude of the motion is proportional to the difference between the opposing forces.Consequently it is possible out of the condensation-curves of several simultaneously-occurring tones to compound, by theforegoing principles, a condensation-curve which exactly expresses that which our ear experiences on the reception of these simultaneously-acting tones. The objection ordinarily made to this, that a musician, or even any one, is able to hear separately the single tones of which this combined curve is built and constructed, cannot be admitted as a proof to the contrary; for one expert in the science of colour will, for example, in the same way discern in green a mixture of yellow and blue in their various shades: and the one phenomenon equally with the other may be referred back to this; that, to the person concerned, the factors which make up the product of that which reaches his consciousness are well known.According to that which has been already explained, it is easy to construct the condensation-curves of various tones, chords, &c., and for the sake of clearness some examples follow:—Fig. 1, Plate I.,[25]shows a combination curve of three tones, in which all the proportions of the components recur successively.Fig. 2shows such a curve of more than three tones, in which the proportions in the drawing can no longer so evidently be given; yet the practised musician would here recognise them, even although in practice it might be difficult for him to single out, in such chords, the separate tones.This method of exhibiting the action of tones upon the human ear offers the advantage of a very clear perception of the process; and that which is exhibited (Fig. 3) shows also why a discord must affect our ear unpleasantly.This apparent digression from the aim set forth was necessary in order to indicate that as soon as it is possible for us to create anywhere, and in any manner whatever, vibrationswhose curves and magnitudes are similar to the vibrations of any given tone, or of any given combination of tones, we shall have the same impression as this original tone or this original combination of tones would have produced upon us.The apparatus hereafter described offers the possibility of creating these vibrations in every fashion that may be desired, and the employment of electro-galvanism gives us the possibility of calling into life, at any given distance, vibrations similar to the vibrations that have been produced, and in this way to reproduce at any place the tones that have been originated at another place.InFig. 4, Plate II.,[26]herewith presented, A is the transmitter (Tonabgeber), and B the receiver (Tonempfänger), which two instruments are set up at different stations. I make, however, the preliminary remark that the manner of joining the instruments for interchangeable use backward and forward is here omitted for the sake of clearness, and the more so because the whole is not here propounded as a final fact, but in order to bring that which has been hitherto accomplished to the knowledge of a wider circle. The possibility of the working of the apparatus to a greater distance than that which at present limits in practice the direct working of the galvanic current may also be left out of consideration, since these points may be easily rendered possible by mechanical precautions, and do not affect the essential part of the phenomena now described.Let us next turn to the transmitter,Fig. A. It is put into communication on one side with the metallic conductor leading to the neighbouring station, and by means of this with the receiver,Fig. B; on the other side it is connected, by means of the electro-motive power, C, with the earth or a metallic return-conductor.The transmitter,Fig. A, consists of a conical tube,a b, ofabout 15 centimetres length, 10 centimetres in the front, and 4 centimetres in the back aperture.(In the practical investigations it has been established that the choice of material for this tube is without influence on the use of the apparatus, and moreover a greater length of the same for the certainty [of action] of the apparatus is without effect. A greater width of the cylinder spoils the usefulness of the apparatus; and it is recommended that the interior surface be as smooth as possible.)The narrow hinder aperture of the cylinder is closed by a membrane,o, of collodion, and on the middle of the circular surface formed by this membrane rests one end,c, of the lever,c d, the fulcrum (point of support),c, of which, supported on a bearing, remains joined to the metallic conductor.The choice of the length of the two arms of the lever,c eande d, is determined by the laws of force of levers. It is recommended that the arm,c e, be constructed longer than the arme d, in order to bring the smallest movement atcinto action atdwith the greatest possible force; but, on the other hand, it is desirable to make the lever itself as light as possible, in order that it may follow the motions of the membrane. An uncertain following of the lever,c d, produces impure tones at the receiving station. In the condition of rest the contact,d g, is closed, and a delicate spring,n, holds the lever firmly in this position of rest.The second part of this apparatus, the pillar,f, consists of a metallic support, which is united with one pole of the battery, C, while the second pole of the battery is carried to the metallic conductor of the other station.Upon the support,f, there is a spring,g, with a contact, which corresponds to the contact atdof the leverc d, and whose position is regulated by a screw,h.In order not to weaken the action of the apparatus by thecommunication of the air-waves which are produced in using the apparatus, against the back of the membrane, it is recommended, in using the apparatus, to place over the tube,a b, at right angles to its longitudinal axis, a screen of about 50 centimetres diameter, which fixes tight upon the outer surface of the tube.The receiver,Fig. B, consists of an electro-magnet,m m, which reposes upon a sounding-box,u w, and whose wire coils are respectively connected with the metallic conductor and with the earth or metallic return-conductor.Opposite the electro-magnet,m m, stands an armature, which is connected with a lever,i, which is long as possible, but light and broad.The lever,i, is fastened, pendulum-wise, to the support,k, and its movements are regulated by the screw,l, and the spring,p.In order to improve the action of the apparatus, this receiver can be placed in one focus of an elliptically arched cavity of corresponding size, in which case, then, the ear of him who is listening to the reproduced tones may be placed at the second focus of this cavity.The action of the two apparatuses here described, is the following:—In a condition of rest the galvanic circuit is closed.In the apparatus,Fig. A, by speaking (singing, or leading into it the tones of an instrument) into the tubea b, in consequence of the condensation and rarefaction of the air present in this tube, there will be evoked a motion of the membrane closing the tube at its narrow end, corresponding to this condensation or rarefaction. The lever,c d, follows the motion of the membrane, and opens and closes the galvanic circuit atd g, so that by each condensation of the air in the tube an opening, and at each rarefaction a closing of the galvanic circuit ensues.In consequence of this process, the electro-magnet ofFig. B(the receiver) will be demagnetised and magnetised correspondingly with the condensations and rarefactions of the mass of air in the tube A,a b[the mouth-piece of the transmitter], and the armature belonging to the magnet will be set into vibrations similar to those of the membrane in the transmitting apparatus. The plank,i, connected with the armature, conveys these similar vibrations to the air surrounding the apparatus,Fig. B, which finally transmits to the ear of the listener the tones thus produced.We are not, therefore, dealing here with a propagation of sound through the electric current, but only with a transference to another place of the tones that have been produced, by a like cause being brought into play at this second place, and a like effect produced.Here, however, it must not be overlooked that the preceding apparatus reproduces, indeed, the original vibrations in equal number, but that equal strength in the reproduced vibrations has not yet been attained, and the production of these is reserved for a completion of the apparatus.One consequence of this temporary incompleteness of the apparatus, is that the slighter differences of the original vibrations are more difficult to discern: that is to say, the vowel appears more or less indistinct, the more so since each tone is dependent, not only on the number of vibrations of the medium, but also on the condensation or rarefaction of the same.By this it is also explained, that, in the practical investigations heretofore carried on, chords, melodies, etc., were transmitted with marvellous fidelity; while single words uttered as in reading, speaking, and the like, were perceptible more indistinctly. Nevertheless, here also the inflexions of the voice, the modulations of interrogation, exclamation, wonder, command, &c., attained distinct expression.There remains no doubt, that before expecting a practical utilisation with serviceable results (praktische Verwerthung mit Nutzen), that which has been here spoken of will require still considerable improvement, and in particular mechanical science must complete the apparatus to be used; yet I am convinced by repeated practical experiments that the prosecution of the subject here explained is of the highest theoretical interest, and that our intelligent century will not miss the practical utilisation (Verwerthung) of it.[This article was also reprinted verbatim in Dingler’s Polytechnisches Journal, vol. clxix. p. 29, 1863.][A peculiar interest is attached to the foregoing article, partly on account of the unique nature of the instruments therein described, partly because of the mystery attaching to the author of the article. Wilhelm von Legat was Inspector of the Royal Prussian Telegraphs at Cassel. How or when he became acquainted with Philipp Reis is not known—possibly whilst the latter was performing his year of military service at Cassel in 1855. None of Reis’s intimate friends or colleagues now surviving can give any information as to the nature of von Legat’s relations with Reis, as not even his name is known to them, save from this Report. Yet he was for one year only (1862), the year in which this Report was made, a member of the Physical Society of Frankfort-on-the-Main. It is possible that he may have been present at Reis’s discourse in the preceding October. It is probable that he was present at Reis’s subsequent discourse in May, 1862, to the Freies Deutsches Hochstift. Dr. Brix, then editor of the ‘Journal of the Telegraph Union,’ informs me that Inspector von Legat based his article upon information derived direct from Reis, whom he knew, and that the article was submitted to Reis before being committed to the‘Journal.’ The particular form of transmitter described in von Legat’s Report (see also p. 25,ante) has also some important points in common with that believed to have been used by Reis at the Hochstift. Neither of the specific forms described by Inspector von Legat are now known to be extant. Inquiries made in Frankfort and in Cassel have failed to find any trace of them. Neither at the local Naturalists’ Society, nor anywhere else in Cassel, did von Legat describe the invention. He met with a tragic end during the Bavarian War in 1866, in the battle near Aschaffenburg, having, according to some, been shot, or, according to others, fallen from his horse.][The next extract is from an article entitled ‘Telephonie,’ which appeared in a journal of science published at Leipzig, under the title ‘Aus der Natur.’ This article is essentially a paraphrase of Reis’s memoir read to the Physical Society in the preceding December (see p. 50), and contains the same illustrations, including a cut of the transmitter identical withFig. 9, p. 20.][6.]Aus der Natur.(Vol. xxi. 1862. July-October. pp. 470-474.)“Until now, however, it was not possible to reproduce human speech with a distinctness sufficient for every person. The consonants are mostly tolerably distinctly reproduced, but the vowels not in an equal degree.”[About this time there arose a Correspondence in the ‘Deutsche Industrie Zeitung’ (‘German Journal of Industry’) concerning the telephone. In No. xvi. p. 184 (1863), a correspondent who signs himself “K” asks whether the account of the telephone is true? In No. xviii. p. 208, there is given a brief answer; and No. xxii. contains, onp. 239, an extract from Legat’s Report, on Reis’s Telephone (see p. 70 of this work), together with an editorial remark to the effect that he had received a letter from Herr J. F. Quilling, of Frankfort-on-the-Main, who gives the information that in the transmission of singing in the telephone, the singer could be recognized by his voice.][7.][Extract From the Annual Report of the Physical Society of Frankfort-on-the-main (1863).]...; “and on the 4th of July, 1863, by Mr. Philipp Reis, teacher, of Friedrichsdorf,On the Transmission of Tones to any desired Distance, by the help of Electricity, with the production of an Improved Telephone, and Exhibition of Experiments therewith.”[This was Reis’s second occasion of bringing his Telephone before the Physical Society. The instrument had now-assumed the “square-box” pattern described at p. 27 of this work.][8.]Letter of Philipp Reis.[In July 1863, Mr. W. Ladd, the well-known instrument-maker of London, bought one of Reis’s Telephones of Messrs. J. W. Albert and Son of Frankfort. Philipp Reis wrote to Mr. Ladd the following letter of instructions, having heard that Mr. Ladd proposed to exhibit the instrument at the approaching meeting of the British Association. The autograph letter, written in English, is still preserved, and has been presented by Mr. Ladd to the Society of Telegraph Engineers and of Electricians of London.]“Institut Garnier,“Friedrichsdorf.“Dear Sir!“I am very sorry not to have been in Francfort when you were there at Mr. Albert’s, by whom I have been informed that you have purchased one of my newly-invented instruments (Telephons). Though I will do all in my power to give you the most ample explanations on the subject, I am sure that personal communication would have been preferable; specially as I was told, that you will show the apparatus at your next sientifical meeting and thus introduce the apparatus in your country.“Tunes[27]and sounds of any kind are only brought to our conception by the condensations and rarefactions of air or any other medium in which we may find ourselves. By every condensation the tympanum of our ear is pressed inwards, by every rarefaction it is pressed outward and thus the tympanum performs oscillations like a pendulum. The smaller or greater number of the oscillations made in a second gives us by help of the small bones in our ear and the auditory nerve the idea of a higher or lower tune.“It was no hard labour, either to imagine that any other membrane besides that of our ear, could be brought to make similar oscillations, if spanned in a proper manner and if taken in good proportions, or to make use of these oscillations for the interruption of a galvanic current.“However these were the principles wich (sic) guided me in my invention. They were sufficient to induce me to try the reproduction of tunes [i.e., tones—see footnote.—S. P. T.] at any distance. It would be long to relate all the fruitless attempts, I made, until I found out the proportions of the instrument and the necessary tension of the membrane. The apparatus you have bought, is now, what may be found most simple, and works without failling when arranged carefully in the following manner.“The apparatus consists of two separated parts; one for the singing station A, and the other for the hearing station B.[28]
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 theJahresberichtof 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.
[Translated from the Annual Report (Jahresbericht) of the Physical Society of Frankfurt-am-Main, for 1860-1861.]
[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.
Areproductionof the tones at some distance by means ofthe 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 greatpenchantfor 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 doesour eartake 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” [malleusbone] upon the “anvil” [incusbone] 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 thecochlæa, 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 musicaltonesordiscords(Misstöne).
That which is perceived by the auditory nerve, is, therefore,merely the action of aforceaffecting our consciousness, and as such may be represented graphically, according to its duration and magnitude, by a curve.
Fig. 24.
Fig. 24.
Let the linea, 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 ordinatescorresponding 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:
Fig. 25.
Fig. 25.
In a cube of wood,r s t u v w x, there is a conical hole,a, closed at one side by the membraneb(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. Fromthe binding-screwnthere 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 openinga, they will set the membranebin vibration. At the first condensation the hammer-shaped little wiredwill 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 fromp) againstdonce 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 certainnumber 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 thatthe 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. theknitting 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 betweenFandf''[20].
It is, of course, understood that in all researches it was sufficiently ascertained that the directconductionof 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:—
Fig. 26.
Fig. 26.
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 (seeFig. 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).
Fig. 27.
Fig. 27.
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 hasopened outa 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 discourseson 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.]
[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.]
[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 wereaudibleto 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 aspiral 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 becomeas 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 theFreies 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:—]
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 thisinvention, 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.]
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 thequestion, “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 inPlate 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 ofhistelephone. 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.]
[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.)]
[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 producingvisiblesignals, but with its application for the production ofaudiblesignals—oftones!
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 numberas 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.
Let, for example, the length of the linea bbe any definite duration of time, and let the curves above this line denote the condensations (+), and the curves below this line the rarefactions (-); then every ordinate erected at the extremity of an abscissa gives us the strength of the condensation in consequence of which the drum-skin vibrates, at the moment indicated by the position of the foot of the ordinate.
Anything more than that which is exhibited in this way or by similar curves our ear cannot in the least perceive, and this is sufficient to bring to our consciousness each single tone and each given combination of tones. For, if several tones are produced at the same time, the sound-conducting medium is put under the influence of several simultaneously acting forces which are subject to the laws of mechanics.
If all the forces operate in the same sense, then the magnitude of the motion is proportional to the sum of the forces. If the forces act in opposite directions, the magnitude of the motion is proportional to the difference between the opposing forces.
Consequently it is possible out of the condensation-curves of several simultaneously-occurring tones to compound, by theforegoing principles, a condensation-curve which exactly expresses that which our ear experiences on the reception of these simultaneously-acting tones. The objection ordinarily made to this, that a musician, or even any one, is able to hear separately the single tones of which this combined curve is built and constructed, cannot be admitted as a proof to the contrary; for one expert in the science of colour will, for example, in the same way discern in green a mixture of yellow and blue in their various shades: and the one phenomenon equally with the other may be referred back to this; that, to the person concerned, the factors which make up the product of that which reaches his consciousness are well known.
According to that which has been already explained, it is easy to construct the condensation-curves of various tones, chords, &c., and for the sake of clearness some examples follow:—
Fig. 1, Plate I.,[25]shows a combination curve of three tones, in which all the proportions of the components recur successively.
Fig. 2shows such a curve of more than three tones, in which the proportions in the drawing can no longer so evidently be given; yet the practised musician would here recognise them, even although in practice it might be difficult for him to single out, in such chords, the separate tones.
This method of exhibiting the action of tones upon the human ear offers the advantage of a very clear perception of the process; and that which is exhibited (Fig. 3) shows also why a discord must affect our ear unpleasantly.
This apparent digression from the aim set forth was necessary in order to indicate that as soon as it is possible for us to create anywhere, and in any manner whatever, vibrationswhose curves and magnitudes are similar to the vibrations of any given tone, or of any given combination of tones, we shall have the same impression as this original tone or this original combination of tones would have produced upon us.
The apparatus hereafter described offers the possibility of creating these vibrations in every fashion that may be desired, and the employment of electro-galvanism gives us the possibility of calling into life, at any given distance, vibrations similar to the vibrations that have been produced, and in this way to reproduce at any place the tones that have been originated at another place.
InFig. 4, Plate II.,[26]herewith presented, A is the transmitter (Tonabgeber), and B the receiver (Tonempfänger), which two instruments are set up at different stations. I make, however, the preliminary remark that the manner of joining the instruments for interchangeable use backward and forward is here omitted for the sake of clearness, and the more so because the whole is not here propounded as a final fact, but in order to bring that which has been hitherto accomplished to the knowledge of a wider circle. The possibility of the working of the apparatus to a greater distance than that which at present limits in practice the direct working of the galvanic current may also be left out of consideration, since these points may be easily rendered possible by mechanical precautions, and do not affect the essential part of the phenomena now described.
Let us next turn to the transmitter,Fig. A. It is put into communication on one side with the metallic conductor leading to the neighbouring station, and by means of this with the receiver,Fig. B; on the other side it is connected, by means of the electro-motive power, C, with the earth or a metallic return-conductor.
The transmitter,Fig. A, consists of a conical tube,a b, ofabout 15 centimetres length, 10 centimetres in the front, and 4 centimetres in the back aperture.
(In the practical investigations it has been established that the choice of material for this tube is without influence on the use of the apparatus, and moreover a greater length of the same for the certainty [of action] of the apparatus is without effect. A greater width of the cylinder spoils the usefulness of the apparatus; and it is recommended that the interior surface be as smooth as possible.)
The narrow hinder aperture of the cylinder is closed by a membrane,o, of collodion, and on the middle of the circular surface formed by this membrane rests one end,c, of the lever,c d, the fulcrum (point of support),c, of which, supported on a bearing, remains joined to the metallic conductor.
The choice of the length of the two arms of the lever,c eande d, is determined by the laws of force of levers. It is recommended that the arm,c e, be constructed longer than the arme d, in order to bring the smallest movement atcinto action atdwith the greatest possible force; but, on the other hand, it is desirable to make the lever itself as light as possible, in order that it may follow the motions of the membrane. An uncertain following of the lever,c d, produces impure tones at the receiving station. In the condition of rest the contact,d g, is closed, and a delicate spring,n, holds the lever firmly in this position of rest.
The second part of this apparatus, the pillar,f, consists of a metallic support, which is united with one pole of the battery, C, while the second pole of the battery is carried to the metallic conductor of the other station.
Upon the support,f, there is a spring,g, with a contact, which corresponds to the contact atdof the leverc d, and whose position is regulated by a screw,h.
In order not to weaken the action of the apparatus by thecommunication of the air-waves which are produced in using the apparatus, against the back of the membrane, it is recommended, in using the apparatus, to place over the tube,a b, at right angles to its longitudinal axis, a screen of about 50 centimetres diameter, which fixes tight upon the outer surface of the tube.
The receiver,Fig. B, consists of an electro-magnet,m m, which reposes upon a sounding-box,u w, and whose wire coils are respectively connected with the metallic conductor and with the earth or metallic return-conductor.
Opposite the electro-magnet,m m, stands an armature, which is connected with a lever,i, which is long as possible, but light and broad.
The lever,i, is fastened, pendulum-wise, to the support,k, and its movements are regulated by the screw,l, and the spring,p.
In order to improve the action of the apparatus, this receiver can be placed in one focus of an elliptically arched cavity of corresponding size, in which case, then, the ear of him who is listening to the reproduced tones may be placed at the second focus of this cavity.
The action of the two apparatuses here described, is the following:—
In a condition of rest the galvanic circuit is closed.
In the apparatus,Fig. A, by speaking (singing, or leading into it the tones of an instrument) into the tubea b, in consequence of the condensation and rarefaction of the air present in this tube, there will be evoked a motion of the membrane closing the tube at its narrow end, corresponding to this condensation or rarefaction. The lever,c d, follows the motion of the membrane, and opens and closes the galvanic circuit atd g, so that by each condensation of the air in the tube an opening, and at each rarefaction a closing of the galvanic circuit ensues.
In consequence of this process, the electro-magnet ofFig. B(the receiver) will be demagnetised and magnetised correspondingly with the condensations and rarefactions of the mass of air in the tube A,a b[the mouth-piece of the transmitter], and the armature belonging to the magnet will be set into vibrations similar to those of the membrane in the transmitting apparatus. The plank,i, connected with the armature, conveys these similar vibrations to the air surrounding the apparatus,Fig. B, which finally transmits to the ear of the listener the tones thus produced.
We are not, therefore, dealing here with a propagation of sound through the electric current, but only with a transference to another place of the tones that have been produced, by a like cause being brought into play at this second place, and a like effect produced.
Here, however, it must not be overlooked that the preceding apparatus reproduces, indeed, the original vibrations in equal number, but that equal strength in the reproduced vibrations has not yet been attained, and the production of these is reserved for a completion of the apparatus.
One consequence of this temporary incompleteness of the apparatus, is that the slighter differences of the original vibrations are more difficult to discern: that is to say, the vowel appears more or less indistinct, the more so since each tone is dependent, not only on the number of vibrations of the medium, but also on the condensation or rarefaction of the same.
By this it is also explained, that, in the practical investigations heretofore carried on, chords, melodies, etc., were transmitted with marvellous fidelity; while single words uttered as in reading, speaking, and the like, were perceptible more indistinctly. Nevertheless, here also the inflexions of the voice, the modulations of interrogation, exclamation, wonder, command, &c., attained distinct expression.
There remains no doubt, that before expecting a practical utilisation with serviceable results (praktische Verwerthung mit Nutzen), that which has been here spoken of will require still considerable improvement, and in particular mechanical science must complete the apparatus to be used; yet I am convinced by repeated practical experiments that the prosecution of the subject here explained is of the highest theoretical interest, and that our intelligent century will not miss the practical utilisation (Verwerthung) of it.
[This article was also reprinted verbatim in Dingler’s Polytechnisches Journal, vol. clxix. p. 29, 1863.]
[A peculiar interest is attached to the foregoing article, partly on account of the unique nature of the instruments therein described, partly because of the mystery attaching to the author of the article. Wilhelm von Legat was Inspector of the Royal Prussian Telegraphs at Cassel. How or when he became acquainted with Philipp Reis is not known—possibly whilst the latter was performing his year of military service at Cassel in 1855. None of Reis’s intimate friends or colleagues now surviving can give any information as to the nature of von Legat’s relations with Reis, as not even his name is known to them, save from this Report. Yet he was for one year only (1862), the year in which this Report was made, a member of the Physical Society of Frankfort-on-the-Main. It is possible that he may have been present at Reis’s discourse in the preceding October. It is probable that he was present at Reis’s subsequent discourse in May, 1862, to the Freies Deutsches Hochstift. Dr. Brix, then editor of the ‘Journal of the Telegraph Union,’ informs me that Inspector von Legat based his article upon information derived direct from Reis, whom he knew, and that the article was submitted to Reis before being committed to the‘Journal.’ The particular form of transmitter described in von Legat’s Report (see also p. 25,ante) has also some important points in common with that believed to have been used by Reis at the Hochstift. Neither of the specific forms described by Inspector von Legat are now known to be extant. Inquiries made in Frankfort and in Cassel have failed to find any trace of them. Neither at the local Naturalists’ Society, nor anywhere else in Cassel, did von Legat describe the invention. He met with a tragic end during the Bavarian War in 1866, in the battle near Aschaffenburg, having, according to some, been shot, or, according to others, fallen from his horse.]
[The next extract is from an article entitled ‘Telephonie,’ which appeared in a journal of science published at Leipzig, under the title ‘Aus der Natur.’ This article is essentially a paraphrase of Reis’s memoir read to the Physical Society in the preceding December (see p. 50), and contains the same illustrations, including a cut of the transmitter identical withFig. 9, p. 20.]
“Until now, however, it was not possible to reproduce human speech with a distinctness sufficient for every person. The consonants are mostly tolerably distinctly reproduced, but the vowels not in an equal degree.”
[About this time there arose a Correspondence in the ‘Deutsche Industrie Zeitung’ (‘German Journal of Industry’) concerning the telephone. In No. xvi. p. 184 (1863), a correspondent who signs himself “K” asks whether the account of the telephone is true? In No. xviii. p. 208, there is given a brief answer; and No. xxii. contains, onp. 239, an extract from Legat’s Report, on Reis’s Telephone (see p. 70 of this work), together with an editorial remark to the effect that he had received a letter from Herr J. F. Quilling, of Frankfort-on-the-Main, who gives the information that in the transmission of singing in the telephone, the singer could be recognized by his voice.]
...; “and on the 4th of July, 1863, by Mr. Philipp Reis, teacher, of Friedrichsdorf,On the Transmission of Tones to any desired Distance, by the help of Electricity, with the production of an Improved Telephone, and Exhibition of Experiments therewith.”
[This was Reis’s second occasion of bringing his Telephone before the Physical Society. The instrument had now-assumed the “square-box” pattern described at p. 27 of this work.]
[In July 1863, Mr. W. Ladd, the well-known instrument-maker of London, bought one of Reis’s Telephones of Messrs. J. W. Albert and Son of Frankfort. Philipp Reis wrote to Mr. Ladd the following letter of instructions, having heard that Mr. Ladd proposed to exhibit the instrument at the approaching meeting of the British Association. The autograph letter, written in English, is still preserved, and has been presented by Mr. Ladd to the Society of Telegraph Engineers and of Electricians of London.]
“Institut Garnier,“Friedrichsdorf.“Dear Sir!“I am very sorry not to have been in Francfort when you were there at Mr. Albert’s, by whom I have been informed that you have purchased one of my newly-invented instruments (Telephons). Though I will do all in my power to give you the most ample explanations on the subject, I am sure that personal communication would have been preferable; specially as I was told, that you will show the apparatus at your next sientifical meeting and thus introduce the apparatus in your country.“Tunes[27]and sounds of any kind are only brought to our conception by the condensations and rarefactions of air or any other medium in which we may find ourselves. By every condensation the tympanum of our ear is pressed inwards, by every rarefaction it is pressed outward and thus the tympanum performs oscillations like a pendulum. The smaller or greater number of the oscillations made in a second gives us by help of the small bones in our ear and the auditory nerve the idea of a higher or lower tune.“It was no hard labour, either to imagine that any other membrane besides that of our ear, could be brought to make similar oscillations, if spanned in a proper manner and if taken in good proportions, or to make use of these oscillations for the interruption of a galvanic current.
“Institut Garnier,“Friedrichsdorf.
“Dear Sir!
“I am very sorry not to have been in Francfort when you were there at Mr. Albert’s, by whom I have been informed that you have purchased one of my newly-invented instruments (Telephons). Though I will do all in my power to give you the most ample explanations on the subject, I am sure that personal communication would have been preferable; specially as I was told, that you will show the apparatus at your next sientifical meeting and thus introduce the apparatus in your country.
“Tunes[27]and sounds of any kind are only brought to our conception by the condensations and rarefactions of air or any other medium in which we may find ourselves. By every condensation the tympanum of our ear is pressed inwards, by every rarefaction it is pressed outward and thus the tympanum performs oscillations like a pendulum. The smaller or greater number of the oscillations made in a second gives us by help of the small bones in our ear and the auditory nerve the idea of a higher or lower tune.
“It was no hard labour, either to imagine that any other membrane besides that of our ear, could be brought to make similar oscillations, if spanned in a proper manner and if taken in good proportions, or to make use of these oscillations for the interruption of a galvanic current.
“However these were the principles wich (sic) guided me in my invention. They were sufficient to induce me to try the reproduction of tunes [i.e., tones—see footnote.—S. P. T.] at any distance. It would be long to relate all the fruitless attempts, I made, until I found out the proportions of the instrument and the necessary tension of the membrane. The apparatus you have bought, is now, what may be found most simple, and works without failling when arranged carefully in the following manner.“The apparatus consists of two separated parts; one for the singing station A, and the other for the hearing station B.[28]
“However these were the principles wich (sic) guided me in my invention. They were sufficient to induce me to try the reproduction of tunes [i.e., tones—see footnote.—S. P. T.] at any distance. It would be long to relate all the fruitless attempts, I made, until I found out the proportions of the instrument and the necessary tension of the membrane. The apparatus you have bought, is now, what may be found most simple, and works without failling when arranged carefully in the following manner.
“The apparatus consists of two separated parts; one for the singing station A, and the other for the hearing station B.[28]