William Frazer, Esq., M. D.,

“20, Harcourt Street, Dublin,

“March 13, 1883.

“Dear Sir,

“I have a distinct recollection of the Telephone. We had a small private club meeting once each month for scientific purposes. On referring to my note-books, I find that there was a meeting on Thursday evening, October 5th, 1865. It was held in Nassau Street, at the residence Mr. Horatio Yeates, now in Australia, and brother of Mr. Stephen Yeates. The Telephone was upstairs, in the third story of the house, and the voice heard in the hall. Mr. Vereker, of the Bank of Ireland, Mr. John Rigby, of rifle celebrity, the two Mr. Yeates, and, I think, Mr. Tuke, were present with myself. There were some others, whom I cannot now recollect, but our club was small.

“Rigby sang ‘Patrick’s Day’ and ‘God save the Queen,’ and various questions were asked and answered. The separate words were most distinct, the singing less so; but there was no difficulty in recognising the individual who spoke by his voice.

“Being much interested in the subject, I got Mr. Yeates to allow the apparatus to be shewn at a Conversazione (Presbyterian Young Men’s) at the Rotunda on October 12, at 8 P.M. His assistant, Mr. Tuke, took charge of it that night. It was placed in a side room off the main round room of the buildings.

“I exhibited at the October 5th meeting of our club a specimen termed ‘Locust gum,’ probably derived from some Robinia, but really can tell you nothing more about it. There is merely a brief note of it in my private memoranda.

“Yours, dear Sir,
Believe me very truly,
“William Frazer,

“Fellow and Examiner, Royal College of Surgeons, Ireland, Member of Council, Royal Irish Academy, &c.”
“Silvanus P. Thompson, Esq., University College, Bristol.”

APPENDIX I.
Comparison of Reis’s Transmitters with Recent Instruments.

Any one who compares together the many different forms of Reis’s Transmitters cannot fail to notice that amidst the great variety of form, two essential points are preserved throughout, the presence of which is fundamental. These two essentials are, firstly, the tympanum to collect the voice-waves, and, secondly, an electric mechanism, consisting of two or more parts in loose or imperfect contact with each other, and so arranged in combination with the tympanum that the motions of the latter should alter the degree of contact, and consequently interrupt, to a greater or less degree, the current of electricity flowing between the contact-pieces. It was of course familiar to all electricians, long before Reis, that a bad, or imperfect, or loose contact in a circuit offered a resistance and interrupted the flow of an electric current. In all ordinary telegraphic and electric apparatus great care was taken to avoid loose and imperfect contacts by using clamping-screws and solid connectors. But Reis, having made up his mind (see p. 77) that the action due to the magnetising current must vary in a manner corresponding with, and therefore proportional to, the vibrations of the voice, utilised this property of imperfect contacts which alter their resistance according to the degree of contact, by arranging his mechanism so as to apply the voice to vary the degree of contact. This was the essence of his transmitters. In other words, he applied the voice to control or moderate the strength of the current generated by a battery. His “interruptors” may therefore with propriety be called “electric current contact regulators;” and put into technical language, the essence of this part of his invention lay in the combination with a tympanum of electric current regulators working upon the principle of variable contact.

In another appendix is discussed the precise nature of that which occurs at a point of variable or imperfect contact, and which results in a corresponding change of electrical resistance when the degree of contact is varied. Suffice it to say here that it is impossible to vary the degree of contact between two bodies which are lightly pressing one against the other, and through which an electric current is flowing, without altering the resistance offered to the current by this joint in the circuit. If the two surfaces are pressed together, so that there is a good contact, the current flows more freely, finding less resistance. If, on the other hand, by altering the pressure or the amount of surface exposed, we change the degree of contact and cause fewer atoms of one piece to touch those of the other piece, the current meets with greater obstruction and cannot flow with such strength as before: it is partially “interrupted,” to use the expressive term employed by Reis.

Now this operation of varying the degree of pressure in order to vary the resistance of the interrupter or contact regulator, was distinctly contemplated by Reis. We find his definite instructions, for example (see p. 75), for arranging the relative lengths of the two parts of the curved lever in one of his transmitters, so that the movement of one contact-piece may act on the other contact-piece with the greatest possible force; in other words, he shortened his lever at the working end, sacrificing its range of motion in order to get a greater range of pressure at the contact-point.

It has often been said, but incorrectly, that Reis intended his “interruptors” or contact regulators to make and break the electric circuit abruptly in the manner of a telegraphic key worked by hand. No doubt in the mouth of a professional telegraph operator the words “interrupting” the circuit, and “opening” and “closing” the circuit, do now-a-days receive this narrow technical meaning. But Reis was not a professional telegraph operator: he did not (see p. 87) even know the signals of the Morse code, and it is self-evident that he did not use the terms in any such restricted or unnatural sense as abrupt “make-and-break,” because he proposed at the outset to interrupt the current in a manner represented by the gradual rise and fall of a curve, stating emphatically in his very first memoir on telephony (p. 55), that to reproduce any tone or combination of tones all that was necessary was “to set up vibrations whose curves are like those” of the given tone or combination of tones. Moreover, in the construction of almost all his transmitters, even in the very first—the model of the human ear—he purposely introduced certain parts which could have no other effect than to prevent the occurrence of complete breaks in the continuity of the current. In fact, instead of using rigid supports for his interruptor, he mounted one or both of the contact-parts with springs, so that one should follow the movement of the other with a gentle pressure never amounting to absolute break, except perhaps in the accidental case of a too loud shout. By employing these following-springs, he introduced, in fact the element of elasticity into his interruptor; and clearly he introduced it for the very purpose of avoiding abrupt breaking of the contact. In the first form Fig. [5], p. 16 (the “ear”), there was one spring; in the fourth form, Figs. [9] and [10], p. 21 (the “bored block”), there were two springs, one of steel, curved, and one, a straight but springy strip, of copper; in the eighth form (the “lever” form), [Fig. 14], p. 25, there were two springs; in the ninth form, [Fig. 15], p. 26, there was a springy strip of brass. In the final form, Figs. [17] and [18], p. 27 (the “square-box” pattern), there was, it is true, a springy strip of copper, but the light adjustment of contact was in this form obtained, not by a spring, but by the inertia of the upper contact-piece which by its own weight pressed gently upon the lower contact-piece. In every one of these forms, except the last, there was moreover an adjusting-screw to determine the exact degree of initial pressure between the contact surfaces. Doubtless the difficulty of adjusting this screw to give the exact degree of contact, enhanced as that difficulty was in consequence of the liability of the membraneous tympanum to become flaccid by the moisture of the breath, induced Reis to think that the later form of the apparatus in which this adjustment was no longer retained would be more easy to use, or, as he says in his Prospectus, more accessible to others. Yet undoubtedly the absence of the spring at the contacts led some persons to fancy that the instrument was intended to be shouted or sung to so loudly that every vibration should make the upper contact-piece jump up from the lower, and as Professor Müller even suggests (p. 98), produce a spark! But such a manner of using the instrument would entirely defeat Reis’s most fundamental principle, that the interruptions should be such as to correspond to the undulating curve which represents the pressure due to vibration of the sound-wave; the possibility of representing the degree of pressure by a curve being one of the two principles set forth in his paper “on Telephony” (p. 55), in which he remarks, that “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 ... even to a certain degree the human voice.” Reis was perfectly well aware, as his curves show, that a complicated sound-wave does not consist invariably of one condensation followed by one rarefaction, but that there are all sorts of degrees of condensation which may follow one another, and all capable of being represented by a curve. If all sounds consisted of one rarefaction following immediately after each one condensation there might be some propriety in proposing that after each “make” of contact there should be a “break” in the sense of an abrupt or complete breach in the continuity of the current. But, obviously, the fact that one condensation may follow another without a rarefaction between (which Reis’s curves show that he knew) must be amply sufficient to prove that on Reis’s own principle his interruptor was meant to produce variations in the degree of contact in exact correspondence with the variations in the degree of pressure, whatever these might be. Had he not meant this, he could not have talked about “taking his stand” on the principle of representing varying pressures by an undulatory curve. Now, from what has been adduced, the following points are clear:—

Firstly, that the contact-regulator which Reis combined with the tympanum was meant to interrupt the current, more or less, according to the varying movements imparted to it by the voice.

Secondly, that Reis intended such interruptions or variations of contact to be proportional to, or to “correspond” with, the variations indicated by the undulatory curve of varying pressures.

Thirdly, that for the purpose of preventing the occurrence of abrupt breaks in the continuity of the circuit, he used springs and adjusting screws, and in one form availed himself of the inertia of the moving parts to attain a similar end.

It is also clear from his own prospectus, that he was aware that for the simpler and ruder purpose of transmitting musical airs, in which the number of the vibrations is the only consideration and where each single condensation is actually followed by a rarefaction, actual abrupt breaks in the continuity of the circuit are admissible. Reis chose this simple case as the one capable of being readily grasped by a general audience, though it was obviously only a partial explanation of the action of the apparatus in the simplest case that could be presented.

Turning now to some of the more modern transmitters, we will inquire how far Reis’s fundamental principles are involved in their construction. We will first take Berliner’s transmitter, of which [Fig. 43] is a drawing, reproduced from the sketch in the specification of his British Patent. This transmitter consists of a tympanum of thin metal to collect the sound-waves, and behind it is attached an interrupter or current regulator, identical in almost every respect with that of Reis. One of the contact-pieces, marked E, circular in form, is fixed to the centre of the tympanum, and vibrates with it, precisely as in Reis’s latest, and in some also of his earlier instruments. Against this there rests in light contact a second contact-piece, in the form of a small blunt spike, F, screwed into a short arm, loosely jointed to the part N, where the circuit is connected. As in Reis’s latest transmitter ([Fig. 17], p. 27), so here, the contact-pieces are kept in contact by gravity. When any person talks to the tympanum it vibrates, and, as a result, the degree of contact between the two surfaces is varied, resulting in a greater or less interruption of the current, the inertia of the upper contact-piece, serving to prevent complete abrupt “break” of the circuit, except under unusually strong vibrations. In fact, if the speaker talks too loudly when speaking into Berliner’s transmitter, he will cause abrupt breaks to occur instead of partial interruptions; and a rattling noise comes in to confuse the speech at the receiving end of the line. But this is precisely what occurs in a Reis’s transmitter if one talks too loudly to it. It is obvious that if Berliner’s transmitter is a “make-and-break” instrument, so is Reis’s, because the principle of action is identical: and it is also obvious that if Berliner’s instrument is capable of varying the resistance at the contact-points by interrupting the current in a manner corresponding to the pressures of the air in the sound-waves, so also is Reis’s instrument.

Fig. 43.

It is a fact that in Berliner’s instrument it is usual to make the contact-pieces, or one of them, of hard artificial coke-carbon, as this substance will neither fuse nor rust. But Berliner’s transmitter will transmit speech perfectly if the contact parts be of brass, silver, platinum, carbon, or almost any other good conductor. In most of Reis’s instruments the contact-pieces were usually of platinum; but they work quite as well if artificial coke-carbon is substituted. In fact, Reis’s principle of variable and elastic contact is applicable to contact-pieces of any material that is a good enough conductor of electricity and hard enough for the purpose. The main improvement in Berliner’s transmitter is the substitution of the metal tympanum for the membraneous one, which was liable to become flabby with moisture.

Fig. 44.

We pass on to Blake’s transmitter, which is the one more generally used in Great Britain than any other. The drawing, [Fig. 44], of this instrument is taken from the specifications of Blake’s British Patent, and shews all that concerns the contact-parts. It does not show the accessories, the induction-coil, or the form of adjusting screw and frame peculiar to this instrument. Inspection of the figure shows that this transmitter consists of a mouthpiece in the form of a conical hole bored through a stout plank of wood, and closed at the back by a metal tympanum of exactly the same size as that of Reis, behind which the interruptor is placed, precisely as in some of Reis’s instruments. In this interruptor both the contact-parts are supported on springs, resembling, even in the curve given to them, the springs Reis used. The first of the contact-pieces is a small metal spike. Concerning it Mr. Blake remarks (page 4 of Specification):—“It is desirable that it should be formed of, or plated with, some metal, like platinum or nickel, which is not easily corroded. It may be attached directly to the diaphragm, but I prefer to support it independently, as shewn, upon a light spring.” ... “This method of supporting the electrode ensures its contact with the other electrode under some circumstances when otherwise they would be liable to be separated and the circuit broken.” In fact this spring serves functions precisely identical with those of the springs used by Reis. The second of the contact-pieces may be described as a mass of metal at the end of a spring. Of it the patentee remarks:—“This weight may be of metal which may serve directly as the electrode, but I have obtained better results by applying to it, at the point of contact with the other electrode, a piece of gas-coke or a hard-pressed block of carbon.” As a matter of fact, a mass of silver or of nickel or of platinum will transmit talking perfectly, but these metals, though better conductors, are more liable to corrode and fuse, and may require therefore more frequent renewal, than gas-coke. Since, then, it is immaterial to the action of a Blake transmitter what substance is used for the contact-pieces, it is clear that the principle of employing an interruptor mounted on springs is the real feature of the instrument. Reis also mounted his interrupters with springs, and for the very same purpose. The function of the weight on the second spring of the Blake transmitter is to resist the movement of the tympanum, and to “modify by its inertia the variations of pressure” between the two contact-pieces. In other words, it acts partly as Berliner’s transmitter, by inertia. So did one of Reis’s instruments, as we have seen. In the Blake instrument there is the happy idea of applying both the spring-principle and the inertia-principle at once. Yet, in spite of this, if the speaker shouts too loudly into a Blake transmitter, he will cause abrupt breaks between the contact-pieces instead of producing partial interruptions in the contact, and in that case speech will, as heard at the other end of the line, be spoiled by a rattling noise. It is possible, also, with Reis’s instruments to spoil the articulation by shouting too loudly, and causing actual abrupt breaks in the continuity. If Blake’s interruptor can be worked as a make-and-break in this sense, so can Reis’s: for there is not one of the features which is essential to Blake’s instrument that cannot be found in Reis’s also.

By way of further carrying out the comparison between Reis’s methods of combining his tympanum with his contact-regulator, and the methods adopted by later inventors, we give, in [Fig. 45], ten comparative sketches, the first five of which illustrate Reis’s methods. In these sketches the only liberty taken is that of representing no more of the instruments than the actual parts wanted in the comparison. No. 1 represents the working-parts of Reis’s first model ear, with its curved lever, platinum-tipped spring, and adjusting screw. No. 2 shows the springs, screw, and contact-pieces of Reis’s bored-block transmitter (“fourth form:” compare Figs [9] and [10], p. 21). No. 3 shows the curved lever, the springs, and the adjusting screw of Reis’s eighth transmitter (“lever” form). No. 4 gives the working parts of Reis’s ninth transmitter, described in detail on p. 27. No. 5, in which the tympanum is placed in a vertical position, merely for convenience of comparison with the other figures, shows the working parts of Reis’s final form of instrument, in which gravity and the inertia of the upper contact-piece enabled him to dispense with the adjustment of spring and screw. No. 6 shows in profile Berliner’s transmitter, which may be instructively compared with No. 5. No. 7 shows the working part of Blake’s transmitter, which should be compared with Nos. 2 and 4: even the curve of the springs imitates that adopted by Reis. Nos. 8, 9, and 10 are forms of transmitter devised by Edison. No. 8 is copied from [Fig. 10] of the specification of Edison’s British Patent. It will be seen that here there is an interruptor placed on each side of the tympanum, and that each interruptor consists of a short spike mounted on a spring and furnished with an adjusting-screw. “Platina foil disks,” says the inventor, are to be secured to each side of the diaphragm, and against these disks, as in Reis’s instruments, press the contact-points of the interruptors. The patentee also states (p. 7 of his Specification), that for these contact-points “any substance not liable to rapid decomposition” may be used. This term includes all the substances used by Reis, and a great many others. It will therefore be seen that this whole device is nothing more than a Reis transmitter with the contact parts duplicated. Yet this instrument was intended by Edison to transmit speech, and will, like Reis’s instrument, transmit speech if properly used. No. 9 of the set of sketches is taken from [Fig. 25] of Edison’s British Specification, but omits the induction-coil and other accessories, retaining the parts wanted for comparison. The patentee thus describes the parts figured. “The tension-regulator [meaning thereby the interruptor or contact-regulator] is made of platina-foil upon the surface of two soft rubber tubes; one on the diaphragm, the other on the adjusting-screw.” It is interesting to note here how the ingenuity of the later inventor led him to vary the construction adopted by the original inventor in substituting an elastic cushion of soft rubber for the springs of the older instruments. But the principle of combining a tympanum with a contact-regulator, which was Reis’s fundamental notion, is here also the leading idea; and the further idea of obviating abrupt breaks in the current by applying elastic supports is also carried out. Edison even copies Reis in having an adjusting-screw, and he applies the very same substance—platinum foil—which Reis used in his very first and his very last transmitter. Edison’s transmitter transmits speech very fairly, even without any of such later accessories as induction-coils; and why should it not? It is constructed on the very lines, nay, with details almost identical with those prescribed by Reis in describing his invention. It embodies those fundamental ideas which Reis set before him when he said, “Taking my stand upon the preceding principles, I have succeeded.”

Fig. 45.

The last of the ten sketches of [Fig. 45] is taken from Edison’s first American Patent specification [No. 203,014, filed July 20, 1877], and shows a duplicated interrupter with springs and adjusting-screws combined with a tympanum. Further comment on this arrangement is needless, save to remark that in this patent for “speaking telegraphs,” Edison himself describes the contact-apparatus which Reis termed an “interrupter,” as a “circuit-closer,” or in another place as “circuit-breaking connections,” and, in his British Patent quoted above, as a “tension-regulator.” It is evident that if Reis could transmit speech by an interrupter which closed and opened the circuit (always in proportion to the vibrations) there is no reason why Edison seventeen years afterwards should not accomplish the same result by a similar means. But it has lately been fashionable to deny that any such device as an interrupter mounted on springs can transmit speech at all!

We have now compared with Reis’s transmitters several of the more modern inventions. It would be possible to carry comparison further were that course needed. We have not thought it worth while to rake up Edison’s now discarded lamp-black button transmitter; and we have not yet spoken of Crossley’s transmitter nor of Theiler’s transmitter, nor of their parent the Hughes’ microphone, nor of dozens of other forms. In some of these there is no specific “tympanum,” but only a sounding-board of pine-wood, and in most of them the points of loose-contact, where interruption more or less complete may occur, are multiplied. But they all come back in the end to Reis’s fundamental idea, namely that of setting the voice to vary the degree of contact in a mechanism which he called an interruptor, and which others have called a current-regulator (or, less correctly, a tension-regulator) which, because the degree of contact between its parts was varied, caused those parts to offer more or less resistance to the flow of the current, and thereby threw it into vibrations corresponding to those of the sound-wave impressed upon the tympanum. There is not a practical transmitter used in any of the telephone exchanges of Great Britain to-day that does not embody this principle.

Reis did, indeed, penetrate to the very heart the principles necessary to be observed in a successful telephone. He was master of the situation. For, as in every practical transmitter in use to-day, so in his transmitter, there was a loose contact in the circuit so arranged that the voice could act upon it, and thereby regulate the strength of the current. If you eliminate this part of the apparatus,—screw up the loose-contacts of your transmitters, so that your voices cannot affect them,—what will your telephones be worth? No: the essential principle of the transmitter—“Das Telephon” emphatically as its inventor styled it—is variable contact; and that all-essential principle was invented and applied for the purpose of transmitting speech by Philipp Reis in 1861.

If this does not suffice as a claim for the invention of the Telephone transmitter, it may well be wondered what will. We can dispense with all other features save this one. We can even dispense with the tympanum or diaphragm which Reis introduced, and can operate on the contact-parts without the intervention of this part of the combination. We can use the very metals which Reis used, and dispense with lamp-black and all the fallacious rubbish that has been subsequently devised about semi-conductors, whatever that term may mean. We can even dispense with springs and adjusting screws. But with the principle of variable contact we can not dispense. That which alone is indispensable Philipp Reis discovered.

APPENDIX II.
On the Variation of Electric Resistance at a Point of Imperfect Contact in a Circuit.

Ever since electricians had experimented with voltaic currents, and especially since the introduction of the electric telegraph, it had been a familiar fact that a loose or imperfect contact in the circuit caused a resistance to the flow of the current and interrupted it more or less completely. To obviate the occurrence of loose or imperfect contacts, binding-screws were invented; and many were the precautions taken to make tight contacts at joints in the line, the resistance of which it was desirable to maintain at a minimum. Young telegraphists were particularly instructed to press their keys well down in signalling, because a light contact would offer some resistance which, on an increase of pressure, would disappear. In fact, it was generally well known that the resistance of two pieces of metal or other conducting material in contact with one another might be made to vary by varying the goodness or badness of the contact with the application of more or less force. This fact was known to apply to good conductors, such as copper and other metals, and it was known to apply also to non-metallic conductors, such as plumbago. Plumbago points were used by Varley for the contacts of relays; it having been found that points of platinum were liable to become fused together with the passage of the current, and by so sticking rendered the instrument useless. Since plumbago was known to be infusible, it was hoped that a plumbago contact would prove more reliable. In practice, however, the plumbago relay did not turn out so well. True it did not fuse, or stick, or rust; but it was even more liable than platinum to form imperfect contacts, the resistance of the light contact being so high that a sufficient current did not pass. It is not known whether other non-metallic substances were tried; probably not, because of non-metallic substances plumbago is one of the few that are good conductors.

According to Edison (British Patent, No. 792, 1882), compressed graphite is a substance of great conductivity. According to Faraday (‘Exp. Res.’ vol. i. p. 24), retort-carbon is an excellent conductor. Both graphite and retort-carbon agree with the metals in the property that the electric resistance offered at a point of contact between them varies when the pressure at the contact is varied. It is indeed remarkable through what wide ranges of resistance the contact between two good conductors may vary. The resistance of contact between two pieces of copper may be made to vary in a perfectly continuous manner by changes of pressure through a range, according to Sir W. Thomson, from a small fraction of one ohm, up to a resistance of many thousand ohms. The same is true of silver, brass, and many other good conductors, including graphite and retort-coke, though with the latter materials the range of resistances is not so great. With partial conductors, such as oxide of manganese, sulphide of copper, sulphide of molybdenum, &c., and with bad conductors, such as lamp-black and selenium, whose conductivity is millions of times less than that of graphite, copper, and other good conductors, it is impossible to get equally wide variations of resistance, as the amount of pressure at a point which will bring the bad conductors into intimacy of contact, will not turn them into good conductors. Platinum being in the category of good conductors, is amongst those substances which yield a very wide range of electrical resistances at the contact-points which are submitted to varying pressures.

With the very highest conductors, such as silver and copper, the electrical range of contact-resistance is higher than with those of lesser conductivity, such as lead, platinum, graphite, and retort-coke.

But though the range of variation in electrical resistance at contacts is highest for the best conductors, there comes in another element, namely, the range of distance through which the contact-pieces, or either of them, must be moved in order to pass through the range of variations of resistance. This is quite a different matter, for here the best conductors have the smallest range, and some that are not so good a greater range. In any case the available range of motion is very small—to be measured in minute fractions,—millionth-parts, perhaps,—of an inch. So far as experiments go, however, silver has the smallest range of all, then gold, then copper. Platinum and nickel have a considerably wider range, plumbago and retort-coke a still wider one.

It is an extremely difficult matter to decide what is the precise nature of that which goes on at a point of contact between two conductors when the pressure at the point is altered. The principal suggestions hitherto advanced have been that the change of resistance observed is due:—

It is admitted that this last suggestion, though it might account for a difference between different substances, in so far as they differ from one another in the effect of heat upon their specific resistance, implies as a preliminary fact that the amount of surface in contact shall be varied by the pressure. No convincing proof has yet been given that the alleged layer of air or other gases has any real part to play in the phenomena under discussion. Nor can the hypothesis, that minute voltaic arcs are formed at the contact be regarded as either proven or probable.

The only two theories that have really been investigated are (a) and (b) of the above series. Of these two (b) is certainly false, and (a) is probably, at least to a very large extent, true.

It is often said by persons imperfectly acquainted with the scientific facts of the case, that carbon is used in telephone-transmitters, because the resistance of that substance varies with the pressure brought to bear upon it, whilst with metals no such effect is observed. This statement, taken broadly, is simply false. Mr. Edison has, indeed, laid claim to the “discovery” (vide Prescott’s ‘Speaking Telephone,’ p. 223), that “semi-conductors,” including powdered carbon and plumbago, vary their resistance with pressure. All that Mr. Edison did discover was that certain substances, whose properties of being conductors of electricity had been known for years, conducted better when the contact between them was screwed up tightly than when loose. The experiments made to test this alleged “property” of carbon are absolutely conclusive. The author of this book has shown[39] that when a rod of dense artificial coke-carbon, such as is used in many forms of telephone transmitters, such as Crossley’s for example, is subjected to pressure varying from less than one dyne per square centimetre up to twenty-three million times that amount, the resistance of the rod did not decrease by so much as one per cent. of the whole. In this case any doubt that might have been introduced by variable contact was eliminated at the outset by taking the precaution of electro-plating the contacts.

In 1879, Professors Naccari and Pagliani, of the University of Turin, published an elaborate series of researches[40] on the conductivity of graphite and of several varieties of coke-carbon, and found, even with great changes of pressure, that the changes of electric resistance were practically too small to be capable of being measured, and that the only changes in resistance appreciable were due to changes of contact.

In January 1882, Mr. Herbert Tomlinson communicated to the Royal Society[41] the results of experiments on a number of electric conductors. The change of conductivity by the application of stress was found to be excessively small. For carbon it was less than one-thousandth part of one per cent. for an increase of fifteen lbs. on the square inch in the pressure. For iron it was slightly greater, and for lead nearly twice as great, but with all other metals less. If this alleged property were the one on which the action of telephone transmitters depended, then lead ought to be twice as good a substance as graphite; whereas it is not nearly so good.

Professor W. F. Barrett, in 1879,[42] made some experiments on the buttons of compressed lamp-black used in Edison’s transmitter, and found that when an intimate contact was satisfactorily secured at the beginning, “pressure makes no change in the resistance.”

In the face of all this precise evidence, it is impossible to maintain the theory that the electric resistance of plumbago or of any other such conductor varies under pressure. The only person who has seriously spoken in favour of the theory is Professor T. C. Mendenhall, but in his experiments he took no precautions against variability of contacts, so that his conclusions are invalid.

More recently still, Mr. O. Heaviside and Mr. Shelford Bidwell have experimented on the variations of resistance at points of contact.[43] Mr. Heaviside’s experiments were confined to contacts between pieces of carbon, and though extremely interesting as showing that the resistance of such contacts are not the same, even under constant pressure, when currents of different strength are flowing, do not throw much light on the general question, because they leave out the parallel case of the metals. Mr. Bidwell’s very careful researches were chiefly confined to carbon and bismuth. The choice is unfortunate, because bismuth the most fusible and worst conductor amongst metals (save only quicksilver) is the one metal least suited for use in a telephone transmitter. Mr. Bidwell’s conclusions, so far as they are comparative between carbon and “the metals,” are therefore necessarily incomplete.

Professor D. E. Hughes, whose beautiful invention, the Microphone, attracted so much attention in 1878, has lately thrown the weight of his opinion in favour of the view that with carbon contacts the effect is due chiefly to an electric discharge or arc between the loosely-contiguous parts. But Professor Hughes’s innumerable experiments entirely upset the false doctrine that a “semi-conductor” is necessarily required for the contact-parts. Speaking recently,[44] he has said: “I tried everything, and everything that was a conductor of electricity spoke.” In 1878, in a paper “On the Physical Action of the Microphone,” Professor Hughes stated:[45] “the best results as regards the human voice were obtained from two surfaces of solid gold.” Hughes also found carbon impregnated with quicksilver in its pores to increase its conducting power to work better than non-metallised carbon of inferior conductivity. Quite lately Mr. J. Munro has constructed successful transmitters of metal gauze, having many points of loose-contact between them.

It seems, therefore, much the most probable in the present state of investigations, that the electric resistance of a contact for telephonic purposes is determined solely by the number of molecules in contact at the surface, and by the specific conductivity of those molecules. The element of fusibility comes in to spoil the constancy of the surfaces in action; and hence the inadmissibility of general conclusions with respect to all metals drawn from the behaviour of the most fusible of them. At a mere point in contact physically with another point, there may be hundreds or even millions of molecules in contact with one another, all acting as so many paths for the flow of the electric current. An extremely small motion of approach or recession may suffice to alter very greatly the number of molecules in contact, and the higher the specific conductivity of the substance, and the denser its molecules, the shorter need be the actual range of motion to bring about a given variation in the resistance offered. Just as in a system of electric lamps in parallel arc, the resistance of the system of lamps increases when the number of lamps through which the current is flowing is diminished, and diminishes when the number of lamps connecting the parallel mains is increased; so it is with the molecules at the two surfaces of contact. Diminishing the number of molecules in contact increases the resistance, and vice versâ. Each molecule as it makes contact with a molecule of the opposite surface diminishes, by so much relatively to the number of molecules previously in contact, the resistance between the surfaces. Each molecule as it breaks from contact with its opposite neighbour adds to the resistance between the contact-surfaces. It may therefore be that the variations of resistance which are observed at contacts between all conductors, from the best to the worst, are all made up, though they appear to pass through gradual and continuous changes, of innumerable minute makes-and-breaks of molecular contact. The very minuteness of each molecular make-or-break, and the immense number that actually must occur at every physical “point” of contact, explain why the effect seems to us continuous. We owe, moreover, to Mr. Edison[46] the experimental proof that actual abrupt makes-and-breaks of contact can produce an undulating current when they recur very rapidly. Whether the heating action of the current itself may not also operate in changing the conductivity of the molecules which happen at the moment to be in contact is another matter. It may be so; but if this should hereafter be demonstrated, it will but confirm the contact-theory of these actions as a whole.

Assuming, then, broadly, that the observed resistance at a point of contact is due to the number of molecules in contact and to their individual resistances, it is evident that the property of varying resistance at contact ought to be most evident, ceteris paribus, in those substances which are the best conductors of electricity. Unfortunately, the cetera are not paria, for the question of fusibility comes in to spoil the comparison; and carbon, which has less fusibility than the metals, is commonly credited with giving a better result than any. This common opinion is, however, based on comparisons made without taking into consideration the question of range of motion between the parts in contact, and without taking into consideration the point that whilst some forms of carbon are excellent conductors, others do not conduct at all. In a telephonic transmitter so arranged that the actual range of motion shall be very small, the metals are just as good as carbon—some of them better. I have heard from a transmitter with contacts of pure bright silver better articulation than with any carbon transmitter. And this is exactly what theory would lead one to expect. As to the suggestion that plumbago makes a successful transmitter, because it is a “semi-conductor”—whatever that term may mean[47]—it is one of those suggestions which are peculiarly fitted to catch the unscientific mind as affording an easy explanation for an obscure fact; unfortunately, like a good many other similarly catching suggestions, it is not true. The very best conductor—silver—will serve to transmit articulate speech: and so will the one of the very worst conductors—lamp-black! So much for this fallacious doctrine of semi-conductors!

Reis used for his contact-points substances which, by reason of their non-liability to fuse or oxidize, were customary in electrical apparatus, and chiefly platinum. In his earliest transmitter (model ear), and in his last, platinum was used. In his lever-form of transmitter, so minutely described by von Legat, the material is not specified. The lever-shaped contact-piece was to be a conductor, and as light as possible, and since all metallic parts are particularly described as metallic, whilst this is not so described, the obvious inference is that this was non-metallic. The number of light, non-metallic conductors is so few that the description practically limits choice to some form of hard carbon. No other materials are named by Reis, but Pisko says (p. 103) that brass, steel, or iron might be used for contacts. Any one of these materials is quite competent, when made up into properly-adjusted contact-points, to vary the resistance of a circuit by opening and closing it in proportion to the vibrations imparted to the contact-points. That is what Reis’s transmitter was intended to do, and did. That is what all the modern transmitters—Blake’s, Berliner’s, Crossley’s, Gower-Bell’s, Theiler’s, Johnson’s, Hunning’s do, even including Edison’s now obsolete lamp-black button transmitter. Mr. Shelford Bidwell has very well summarized the action of the current-regulator in the following words: “The varying pressure produces alterations in the resistance at the points of contact in exact correspondence with the phases of the sound-waves, and the strength of a current passing through the system is thus regulated in such a manner as to fit it for reproducing the original sound in a telephone.”

Reis constructed an apparatus consisting of a tympanum in combination with a current-contact-regulator, or “interruptor,” which worked on this principle of variable contact, and he called it “The Telephone” (see pp. 57, 85). The very same apparatus we now-a-days call a “Telephone-transmitter,” or simply a “transmitter.” It is curious to note that Reis seems to have regarded his receiver or “reproducing-apparatus” as no new thing. He says explicitly (p. 56) that his receiver might be replaced by “any apparatus that produces the well-known galvanic tones.” “The Telephone” was with Reis emphatically the transmitter. Bell in 1876 invented an instrument which would act either as transmitter or receiver, and which, though never now used as transmitter, is still called “a Telephone.” Edison’s “sound-telegraph,” or “telegraphic apparatus operated by sound,” was patented in 1877. In his specification he never called his transmitter a “telephone;” that name he reserved exclusively for his receiver. He found it, however, convenient a year later to rechristen his transmitter as the “carbon telephone,” though throughout the whole of his specification neither “carbon” nor “telephone” are mentioned in connection with the transmitter! Within that year Hughes had brought out another instrument—“The Microphone”—which, like Reis’s instrument, embodied the principle of variable contact. Hughes’s instrument, usually constructed with contacts made of loose bits of coke-carbon, was simply a Reis’s Telephone minus the circular tympanum; and the really important new fact it revealed, was that very minute vibrations, such as those produced by the movements of an insect, when transmitted immediately through the wooden supports, sufficed to vary the resistance of a telephonic circuit, though far too slight in themselves to affect it if they had to be first communicated to the air and then collected by a tympanum. Put a specific tympanum to a Hughes’s microphone, and you get a Reis’s telephone. Take away the tympanum from a Reis’s telephone, and you get a Hughes’s microphone. Hughes is not limited to one material, nor is Reis. But the fundamental principle of the electrical part of each is identical. The Blake transmitter ([Fig. 44]), and the Berliner transmitter, and also Lüdtge’s microphone,[48] which was even earlier than that of Hughes, are all embodiments of the same fundamental principle of variable contact which Reis embodied in his “Telephone.”

The numerous experiments which Reis made, and the many forms of instruments which he devised, prove his conviction of the importance of his invention to have been very deeply rooted. He had indeed penetrated to the very soul of the matter. He did not confine himself to one kind of tympanum, he tried many, now of bladder, now of collodion, now of isinglass, and now of thin metal. He varied the forms of his instruments in many ways, introducing the element of elasticity by springs and adjusting-screws. Though he chiefly employed one metal for his contact-pieces, he did not limit himself to that one, but left us to infer that the principle of variable contact was applicable to any good conductor, metallic or non-metallic. He knew better, indeed, than to limit himself in any such fashion; better, indeed, than some of the eminent persons who are now so willing to ignore his claims. Modern practice has taught us to improve the tympanum part of Reis’s invention, and to obviate the inconveniences to which a membrane is liable: in that part we have gone beyond Reis. But in the question of contact-points for opening and closing the circuit in correspondence with the vibrations, we are only beginning to find how much Reis was a-head of us. We have been thrown off the track—blinded perhaps—by the false trail of the “semi-conductor” fallacy, or by the arbitrary and unnatural twist that has been given by telegraphists to Reis’s expression, “opening and closing the circuit,” forgetting that he practically told us that this operation was to be proportional to, “in correspondence with,” the undulations of the tympanum. When we succeed in freeing ourselves from the dominance of these later ideas, we shall see how much we still have to learn from Philipp Reis, and how fully and completely he had grasped the problem of the Telephone.

APPENDIX III.
Comparison of Reis’s Receivers with Recent Instruments.

The receivers invented by Reis for the purpose of reconverting into audible mechanical vibrations the varying electric currents transmitted from the speaking end of the line were of two classes, viz.:

(1.) Those in which the magnetic expansion and contraction of a rod of steel or iron, under the influence of the varying current, set up mechanical vibrations and communicated them to a sound-board.

(2.) Those in which the current by passing round the coils of an electro-magnet caused the latter to vary the force with which it attracted its armature, and threw the latter into corresponding mechanical vibrations.

The first of these principles is embodied in the “knitting-needle” receiver described above and depicted in figures 22 & 23 on page 33. This receiver differs wholly from the later instruments of Bell, and others, and depended for its action upon the phenomenon of magnetic expansion discovered by Page and investigated by Joule. It was well known before Reis’s time that when a needle or bar of iron was magnetised it grew longer, and when demagnetised it grew shorter. Page detected the fact by the “tick” emitted by the bar during the act of magnetisation or demagnetisation. Joule measured the amount of expansion and contraction. To these discoveries Reis added two new facts; first, that if the degree of magnetisation be varied with rapid fluctuations corresponding to those of the sound waves impressed on the transmitter, the expansion and contraction of the rod followed these fluctuations faithfully, and therefore emitted at the receiving end sounds similar to those uttered at the transmitter. Secondly, by employing a needle of steel instead of the bar of iron used by Page, Reis obtained an instrument which once used could never become completely demagnetised on the cessation of the current; it was thenceforth a permanent magnet, and all that the fluctuating currents could do was to vary its degree of magnetisation. Reis carefully explained in his memoir “On Telephony,” how the frequency of such fluctuations in the magnetising current could act in reproducing the pitch, and further, how the amplitude of the fluctuations set up vibrations of corresponding amplitude in the rod: he added with significance, that the quality of the reproduced note depended upon a number of variations of amplitude occurring in a given time. His theory of these actions was that the atoms (or perhaps our modern word molecules would more correctly represent what Reis spoke of as atoms) of the rod or needle were pushed asunder from one another in the act of magnetisation, and that on the cessation of the magnetising influence of the current, these same atoms strove to return to their previous position of equilibrium, and thus the oscillations of the atoms led to the vibration of the needle as a whole. Whether all Reis’s speculations as to the behaviour of the atoms under varying degrees of magnetising force are justified in the present aspect of science or not, is, however, not of any great importance; the important point is, that, whether his theory be right or wrong, the instrument he devised will perform the function he assigned to it: it will reproduce speech, not loudly, but in reality far more articulately than many of the telephonic receivers in use under the names of Bell, Gower-Bell, &c.

One very curious point in connection with this “knitting-needle” receiver of Reis, is its extremely bad acoustical arrangements. It was laid horizontally upon a small sounding-box covered by a lid. If the end of the needle had been made to press on the resonant-board (as indeed appears to have been done at first with the violin, p. 29) the vibrations would have been much more directly reinforced. But when merely supported by two wooden bridges the direct communication was largely lost. The pressure of the lid downwards upon the spiral, as recommended by Reis, is no doubt an important matter acoustically. It is strange that a man who had grappled in so masterly a way with the acoustical problem of the transmitter, and had solved it by constructing that transmitter on the lines of the human ear, should not have followed out to the same extent those very same principles in the construction of his receiver. An extended surface he did employ, in the shape of a sounding-board; but it was not applied in the very best manner in this instrument.

The second principle applied by Reis in the construction of his telephone-receivers, was that of the electro-magnet. He arranged an electro-magnet so that the fluctuating currents passing round the coils set up corresponding variations in the degree of force with which it attracted its armature of iron, and so forced the latter to execute corresponding mechanical vibrations. This principle is common both to the receiver of Reis, and to the later receivers of Yeates, Bell, and Edison. Reis’s armature was an iron bar of oval section; Yeates’s an iron strip screwed to a sound-board, Bell’s was an iron plate, and Edison’s an iron plate also.

For the better comparison of Reis’s electro-magnetic receiver with those of more modern date, we here present in [Fig. 46] a comparative view of a number of different forms of receiver in which Reis’s principle of causing an electro-magnet to set up vibrations in an armature is applied. In this set of figures, A and B are the suggested forms mentioned in the letter of Mr. Horkheimer, p. 119, and show an electro-magnet, opposite the poles of which is placed an armature (a bar) which must be of iron or other metal capable of having magnetism induced in it, and which, by reason of its attachment to an elastic spring, is capable of being made to oscillate to and fro when attracted with a varying force. Reis clearly recognised the necessity of further providing a sufficient resounding surface by means of which the surrounding air could be set in motion: for in the case of these two suggestions the electro-magnet and its elastically-mounted armature were placed within a cigar box. C is a plan of the receiving instrument previously described and figured in Plate II. and in figures 21 and 34 on pages 32 and 109. In this instrument the electro-magnet was horizontal, the armature, a bar of iron of oval section (which in the original drawing in plate II. appears to have been in reality a hollow bar or tube) attached to a thin lever described as a plank, pivoted like a pendulum to an upright support, but prevented by a set-screw and a controlling spring from vibrating in the manner of a pendulum. Such an arrangement, in fact, vibrates in perfect correspondence with any vibrations that may be forced upon it by the electro-magnet. The broad flat surface of the lever—he specially directed that it should be broad and light—transfers the vibrations to the air, and is aided by the surface of the sounding-board on which the apparatus stands. This apparatus has, therefore, all the elements of a successful receiver, except only that its shape renders it inconvenient for portability. But by reason, firstly of its armature of iron, secondly of the elastic mounting of that armature, thirdly of the extended surface presented, it is admirably adapted to serve as an instrument for reproducing speech.

Fig. 46.

[Fig. 46] D represents the excellent electro-magnetic receiver devised in 1865 by Yeates (compare [Fig. 42], p. 128) to work with the Reis transmitter, and is in many respects identical with the preceding form. The armature, a strip of iron, was attached at one end by a very stiff steel spring to a pine-wood sounding-board over a hollow box, from the base of which rose the metal pillar which supported the electro-magnet. This receiver also contains all the elements of a successful receiver, the armature being of a material capable of inductive action, and elastically supported; whilst the sound-box provided adequate surface to communicate the vibrations to the air.

We now come to the more modern instruments of Gray, Bell, and Edison. So far the receivers of Reis and of Yeates were intended for reproducing any sound; but now for the first time, ten years after the date of these early telephonic receivers, we meet with instruments devised with the express purpose of receiving only certain selected tones.

For the purposes of multiple acoustic telegraphy, that is to say for the purpose of signalling the “dots” and “dashes” of the Morse code in a number of different fixed musical notes, each of which is to be signalled out and repeated by a receiver adapted to vibrate in that note alone, it is clear that the instruments of Reis, adapted as they were to transmit and receive any sound that a human ear can hear, would not answer. Accordingly those experimenters, who from about the year 1873 to the year 1870, applied themselves to multiple telegraphy—foremost amongst them being Mr. Elisha Gray and Prof. Graham Bell—dropped the use of the tympanum in the transmitter and devised new transmitters and new receivers, in most of which the ruling idea was that of employing a vibrating tongue or reed, tuned up to one particular note. Now it is obvious that a receiver which, like those of Reis, is adapted to receive any tone, can also receive a musical note. But for the operation of “selective” reception, a receiver must be employed, not only tuned to one note, but tuned to the very note emitted by the particular transmitter with which it is to be in correspondence. Elisha Gray found this out very early in his researches. In the winter of 1873-4[49] he was transmitting musical tones by a sort of tuning-fork interruptor, and received them on an instrument shown in [Fig. 46] E, which represents a form of electro-magnet mounted for the purpose. It was “a common electro-magnet, having a bar of iron rigidly fixed at one pole, which extends across the other pole, but does not touch it by about one sixty-fourth part of an inch. In the middle of this armature a short post is fastened, and the whole is mounted on a box made of thin pine, with openings for acoustic effects.” It was, in fact, very similar to Yeates’s receiver just described, and Gray found it capable of receiving not only simple musical tones but composite tones, and even harmonies and discords. In fact, like Reis’s and Yeates’s receivers, it could receive anything that the transmitter sent to it, even including speech. Now this did not suit Gray, who wished to have selective receivers, one to take up note A, another note C, &c. Accordingly in 1870 we find Gray taking out a fresh patent[50] for selective receivers, which he also called harmonic analysers, each of which consisted of “a tuned bar or reed suitably attached to an electro-magnet, and the whole mounted upon a resonant box.” [Fig. 46] F is reproduced from Gray’s British patent. “A vibrating tongue reed, or bar” of steel “is united with one pole of the magnet. The free end of the reed passes close to, but does not touch the other pole of the magnet.” Gray further says that the reed is made with parallel sides and tuned by cutting it away at one point, as this mode prevents false nodal vibrations from occurring.

Selective receivers for multiple telegraphy were also invented by Graham Bell. The form shown in [Fig. 46] I is transcribed from Fig. 15 of Bell’s Specification to his British Patent, No. 4765, of the year 1876 (dated 9th December), which the inventor thus describes: “It is preferable to employ for this purpose an electro-magnet E, Fig. 15, having a coil upon only one of its legs. A steel spring armature A is firmly clamped by one extremity to the uncovered leg h of the magnet, and its free end is allowed to project above the pole of the covered leg.” In fact the arrangement was almost identical with, but not quite as good mechanically as that patented seven months previously by Gray. The inventor further said that a number of these instruments might be placed on one circuit, and that if one of them were set in vibration, only those would respond which were in unison with its note; and further that “the duration of the sound may be used to indicate the dot or dash of the Morse alphabet, and thus a telegraphic despatch may be indicated by alternately interrupting and renewing the sound.”

Anything more totally different from Reis’s telephone than these selective harmonic telegraphs with their tuned tongues can hardly be imagined. Reis was not aiming at selective harmonic telegraphy; he wanted his one instrument to transmit every sound that a human ear could hear. He did not dream of using a tuned bar or reed; his typical structure was the tympanum of the ear. In fact, as we have seen above, the tuned reed or tongue was introduced into telegraphy for the purpose of transmitting single selected notes to the exclusion of all others.

Strange though it may seem, a tongue receiver like those of Graham Bell and of Gray just described can be used for receiving speech! It is true, as Gray remarks, that a thick bar of steel, cut away as described, is best adapted for its own tone only. But Bell’s thin steel tongue, though it has its own fundamental note (and so has every tympanum, for that matter) when left free to vibrate in its own time, will reproduce any other note or sound that may be forced upon it by the varying attraction of the electro-magnet. There is, indeed, the whole difference between “free” and “forced” vibrations. One of the strangest delusions that has somehow grown up in recent telephonic discussions is the almost incredible proposition that a tongue cannot talk because it is a tongue. It would be equally veracious to affirm that an ear (i.e. a tympanum) cannot hear because it is an ear.

But leaving harmonic telegraphy and its “tuned bars,” both Gray and Bell applied themselves to the old problem of transmitting human speech. What was their very first step? They threw away their “tuned bars” and “steel springs,” and returned to the tympanum! Elisha Gray devised the receiver shown in [Fig. 46], G, taken from his caveat of date February 14, 1876.[51] In that document Gray says: “My present belief is that the most effective method of providing an apparatus capable of responding to the various tones of the human voice, is a tympanum, drum, or diaphragm,” stretched across one end of a chamber. He adds that in the receiver there is (see [Fig. 46], G) an electro-magnet, acting upon a diaphragm to which is attached a piece of soft iron, and which diaphragm is stretched across a vocalising chamber.

Graham Bell’s receiver (the American specification of which was filed the same day as Gray’s caveat) is shown (in the form patented in Great Britain, Dec. 9, 1876) in [Fig. 46] H, which is taken from Fig. 19 of Bell’s British patent. “The armature,” says the inventor, “is fastened loosely by one extremity to the uncovered leg, h, of the electro-magnet E, and its other extremity is attached to the centre of a stretched membrane.” The armature, in fact, was capable of vibrating like a pendulum on its pivot, but was elastically restrained by its attachment to the tympanum; the armature would therefore vibrate in perfect correspondence with any vibrations forced upon it by the electro-magnet. This instrument as also that of Gray, was admirably adapted to receive speech, for it embodied the three essential points which Reis had already discovered: viz., firstly, that the armature must be of iron, or capable of being acted upon by magnetic induction; secondly, that it must be elastically mounted; thirdly, that it should present an extended surface. Bell’s form of receiver had the advantage over Reis’s (compare p. 158), that its extended surface was a true tympanum of membrane, and not a mere broad thin plank. Being a tympanum, it therefore realised Reis’s fundamental notion of imitating the human ear more fully than even Reis’s own receiver did.

Figures [46], J, K, and L represent the more recent types of receiver of Bell and Edison. [Fig. 46] J is reproduced from Fig. 20 of Bell’s British Patent, and shows the substitution of a thin steel plate, attached to a frame, in front of the electro-magnet, for the membrane and iron armature. This form of instrument also embodies Reis’s three principles—but with this improvement, the armature capable of inductive action, the elastic mounting, and the extended surface, are here all united in one organ, the thin flexible tympanum of steel. Apart from this unification of parts there is absolutely nothing in this form of Bell’s receiver, that Reis did not invent fourteen years before. Bell’s great and most signal improvement was not this beautiful mechanical modification of the Reis receiver, but lay in the entirely new suggestion to use such a receiver as a transmitter to work by magneto-electric induction. Two of Reis’s receivers ([Fig. 21]) if coupled up with a battery will talk together as transmitter and receiver: but Reis did not know and never suggested this. Two of Yeates’s receivers ([Fig. 42]) if coupled up with a battery will talk together as transmitter and receiver; but Yeates did not know and never suggested this. Bell did discover this, and thereby invented a transmitter which, though now abandoned as a transmitter, for want of loudness, was more reliable than the anterior transmitters of Reis had been. He made another discovery, presently to be alluded to—that of putting a permanent magnet into the transmitter, to enable him to dispense with the battery; but beyond this and the other mechanical simplifications previously mentioned, all that he discovered may be summed up by saying that he found out that a receiver constructed on Reis’s principles could work as a transmitter also. That was Bell’s really great and important discovery which took all the world by storm at the Centennial Exhibition of 1876.

Bell subsequently added to his claims the substitution of a permanent magnet with an iron pole-piece, in place of the simple electro-magnet, thus enabling him to transmit his fluctuating currents without the trouble of using a battery, and the Bell transmitter, thus modified, is used to this day as a receiver, Reis had in his “knitting-needle” telephone, employed a permanent magnet of steel to serve as a receiver, he had not, however, applied it as Bell did to attract a plate of thin steel.

[Fig. 46], K, exhibits a form of electro-magnetic receiver described in Edison’s British Specification, No. 2909, 1877, Fig. 24. This instrument, though patented seven months after Bell’s instrument, differs from it in no point of importance. Its armature was a thin plate of iron, elastic, and having an extended surface; being, in fact, a tympanum.

No one can examine the set of receiving instruments collected in [Fig. 46] without being struck with the extraordinary similarity of design which pervades the entire series. In every one of the set there is an electro-magnet, the function of which is to set an armature[52] into vibration by attracting it with a variable force. In every one the armature is of a material capable of magnetic induction; that is to say, iron, steel, or equivalent material. In every one of them the armature is either elastically mounted, or is in itself elastic. In every one of them (save only the two quite recent forms, F and I, which were intended not to speak, but to emit only one fixed musical note) there is an extended surface (either a sound-board or a tympanum) to communicate the vibrations to the air. Lastly, every one of these forms, when connected with the line through which the telephonic currents are being transmitted, is perfectly capable of reproducing articulate speech. But the inventor who had the genius to discover all these essential points, and to combine them in an instrument, and to use it to reproduce articulate speech, is surely the true inventor of the system. The inventor of the system embodying these essential points was Philipp Reis.

APPENDIX IV.
On the Doctrine of Undulatory Currents.

“In this Specification the three words ‘oscillation,’ ‘vibration’ and ‘undulation,’ are used synonymously.”—Graham Bell, U.S. Patent, No. 174,465, filed Feb. 14, 1876.

In the preceding appendices it has been demonstrated that all that is essential in both transmitter and receiver of a Telephonic system was to be found existing in 1863 in the Telephone of Reis. There yet remains to be met the doctrinaire objection that as Reis never explicitly mentions an undulatory current as distinguished from an intermittent one, he never intended to use such a current. This objection is advanced only by those persons who have committed themselves to the idea that speech cannot be transmitted by a transmitter which opens and closes the circuit.

It is certain that Reis did not in any of his writings explicitly name an undulatory current: but it is equally certain that, whether he mentioned it or not, he both used one and intended to use one. He did not concern himself as to the precise manner in which the current fluctuated provided only he attained the end in view—namely, that the vibrations of the armature of the receiver should be similar to those of the transmitter. This he did lay down with great clearness and emphasis as his guiding principle; and he cared not about the intermediate question as to how the current did the work. He told the world that the electromagnet at the receiving end must be magnetised and demagnetised correspondingly with the vibrations imparted by the air to the tympanum of his transmitter, in order that the armature might be set into vibrations similar to those of the speaker’s voice. If the tympanum of the transmitter vibrated or oscillated or undulated—the terms are synonymous—so must the armature of the receiver. Graham Bell has told us precisely the same thing: “The current traversing the coils of the electromagnet E occasions an increase and diminution in its intensity” [that is to say, magnetises and demagnetises it], “and the armature A1 is thrown into vibration” ... “and thus imparts to the air at n1 a facsimile copy of the motion of the air that acted upon the membrane n.” Bell agrees then absolutely in every detail with what Reis said on this point. That sound-waves should be transmitted by a Telephone requires indeed a process of several stages. (1.) The sound-waves must strike upon the tympanum of the transmitter and make it undulate, or, oscillate, or vibrate—whichever term you please—in a corresponding manner. (2.) The undulating tympanum must act upon the circuit, and either itself induce undulating or vibrating currents (Bell’s plan, by magnetic induction), or else throw a current already flowing there, into undulations, or vibrations, or oscillations (Reis’s plan, by varying contact-resistance), but in either case these undulations of the current must correspond to the original undulations of the air-waves. (3.) The undulating, or vibrating, or oscillating current must run round the coils of the electromagnet and cause its magnetic force to undulate, or oscillate, or vibrate by demagnetising it and then magnetising it, but this also must be in a manner corresponding to the original undulations. (4.) Further, the armature of the receiver must be set into undulations, or vibrations, or oscillations corresponding to those of the force of the electromagnet, and therefore to the undulations of the current that is magnetising and demagnetising it, and therefore identically corresponding with the original undulations of the sound-waves. (5.) The armature must communicate its vibrations to the air and to the ear of the listener. Of these successive stages Reis explicitly told the world that his instrument was to do the first one and the last three, and he several times emphasized the statement, that the final undulations of the last stage were to be similar to the original undulations of the first stage. The air at the listening end, the armature of the receiver, and the magnetism of the magnet, were all to be set by the fluctuations of the current into undulations corresponding with those of the tympanum at the speaker’s end, and of the waves of his voice. It is perfectly clear therefore, that he regarded as self-evident the intermediate stage, and he did not dwell upon the necessity of the point, that his transmitting-current must also vibrate, because this was obviously so, and was only an intermediate matter of secondary moment. He chose rather to point out the necessity of unification between the first and last stages, leaving it to common sense to see that the “interruption” or the “opening and closing” of the circuit must be effected in a manner corresponding to the undulations of the impressed sound-wave. Had the “interruptions” not been of the nature of corresponding variations of contact, the current could not have been set into corresponding vibrations, and the armature of the electromagnet could not have reproduced the vibrations of the transmitter. Clearly Reis’s whole conception of telephony included as a minor and intermediate step the fact that the current was, by the action of the transmitter, caused to vary in strength in correspondence with the undulations of the tympanum—that, in fact, it was made to undulate by the action of the tympanum and of the interruptor which opened and closed the circuit in obedience to the undulations of the tympanum and in proportion to them.

A difficulty has been raised by telegraph operators that opening and closing the circuit means opening and closing the circuit in abrupt alternations of make-and-break. Reis never said so. Reis never used the phrase in this restricted and technical sense. He was not a professional telegraphist, and, as pointed out in Appendix I., he so arranged his contacts with the following springs and other contrivances, that the “opening and closing” of the circuit should not and could not be abrupt. A Reis transmitter is no more a “make-and-break” instrument than the Blake transmitter is. Both will give undulatory currents by opening and closing the circuit to a greater or less degree, if spoken gently to. Both will give abrupt makes-and-breaks of the circuit if shouted to, in spite of the following-springs, which are used to prevent abrupt interruptions. The term “opening and closing” which Reis applied to his transmitter, is used by him in exactly the same way as the phrase is used by engineers in describing the action of the governing throttle-valve of a steam-engine. The function of the governor, we are told in treatises on engineering, is to open and close the throttle-valve in a manner corresponding to the fall or rise of the governor-balls. No one in his senses imagines that the opening and closing action here referred to means an absolutely abrupt intermittence in the supply of steam. If the governor-balls rise a little by increase of speed, there is a corresponding closing, proportionate in amount to the amount of rise. If any person were to impress an oscillatory motion of rise and fall upon the governor, the supply of steam would be thrown into corresponding undulations. The matter stands precisely so with Reis’s “interruptor” or “regulator;” it opens and closes the circuit in a manner corresponding with the undulations communicated to it. If it did not, it would violate the principle of correspondence so emphatically laid down by Reis.

It is, however, true that Reis’s instruments, in spite of springs and adjusting screws, and other devices to prevent abrupt make-and-break occurring, were prone, by reason of the very lightness of the parts, to break contact, if too loudly spoken to. They share this fault with the more perfect transmitters of Blake and Berliner which are used to-day so generally. The undulatory currents of these transmitters are, like those of Reis’s transmitters, liable to an occasional abrupt interruption, which, though it may not seriously affect the intelligibility of the words, does, to some extent, mar the perfection of the articulation. Still, in practice, to judge by the instruments used in the telephone exchanges of Great Britain, the Blake transmitter with its liability to make-and-brake abruptly is a more satisfactory instrument than the Bell transmitter, which is not used at all. Now the Bell transmitter working on the principle of which Bell is the first and undisputed inventor, is one in which the degree of contact in the circuit is never changed: for it works by the principle of “induction,” whereby currents are set up in a circuit that is never opened or closed, either partially or wholly. Nevertheless the Blake transmitter, which opens and closes the circuit in proportion to the undulations of the tympanum, is the more satisfactory instrument for producing the undulating currents required to procure the all-essential correspondence between the undulations of the tympanum of the transmitter and those of the armature of the receiver. To sum the matter up, it appears that an instrument which opens and closes the circuit on Reis’s principle of transmitting is in practice a more satisfactory transmitter of undulatory currents than Bell’s transmitter which cannot open or close the circuit in the least. Reis, with his instruments, transmitted speech—as Herr Hold tells us (p. 126)—when the words spoken were not too loud. That is a proof that he did really use, whether he knew it or not, undulatory currents of electricity: and an undulatory current is none the less an undulatory current, even if occasionally abruptly interrupted. A speech is none the less a speech, even if the orator sneeze once or twice while speaking. Nay, we may go further, and say that an undulatory current is an undulatory current, even though the finer ripples of the waves are lost in transmission. This is what seems to have been the case with Reis’s instruments as they were in 1861 and 1862. The consonants were satisfactorily transmitted, and so were all musical tones within the range of the instrument. But the finer ripples of the vowels were lost somehow in transmission. Reis, whose innate honour and modesty led him always rather to understate than overstate the facts, most frankly acknowledged this, nay even invited attention to the fact, and discussed the imperfection from a high scientific standpoint. He proposed to rely for the correctness of his views upon the actual recorded curves of sound-waves, as taken down automatically by the then newly-invented phonautograph of Scott (see p. 60). It is perfectly marvellous how precise his views were upon the correspondence between the graphic curve or wave-form of a sound and the actual sound itself; a precision amply justified by the experience and the discoveries of the last ten years.

This matter of representing sounds—or rather the varying density of the air in the sound-wave—by a graphic curve, was a vital one to Reis. Had he had a less clear view of the nature of sound-waves than that afforded by a graphic curve, I doubt whether he would ever have grasped the problem of the telephone—that the final vibrations, or undulations, or oscillations of the armature in the receiver must correspond with—must be the very counterpart of—those of the tympanum of the transmitter. The clearness with which Reis saw this is only surpassed by the clearness with which he expressed himself upon it. For him a sound was simply a complicated series of variations in the density of the air, and capable, in all its complexity, of being represented by the rise and fall of an undulatory curve. “Every tone, and every combination of tones, evokes in our ear vibrations ... the motions of which may be represented by a curve” (p. 54). “That which is perceived by the auditory nerve ... may be represented graphically according to its duration and magnitude by a curve” ... (p. 53). “Our ear can perceive absolutely nothing more than is capable of being represented by similar curves” (p. 53). The curves with which he accompanied his original memoir—and now reproduced in facsimile, from Legat’s plates, at the end of this volume—are evidence of the thoroughness of his grasp on the undulatory principle. And he explicitly states this principle amongst “the various requisite conditions which must be fulfilled by the transmitting and receiving apparatus for the solution of the problem that has been set” (Legat’s Report, p. 71). He declared that so soon as it should become possible “at any place, and in any prescribed manner” (that is to say, whether by electric undulations or by mechanical undulations, as in the string of the toy telephone, or by any other means), “to set up vibrations whose curves are like those of any given tone or combination of tones,” we should then receive the same impression as that tone or combination of tones would have produced upon us.

So much for Reis’s principle of correspondence of undulations between the transmitter and the receiver; we have seen how clear and precise, yet how comprehensive it was, and how the general proposition necessarily included within itself, as an intermediate step, the particular minor proposition that the undulations of the current must also be in correspondence with the voice.

Keeping these points in mind, it is very remarkable that when Graham Bell, fourteen years later, followed Reis “into the field of telephonic research,” he selected the very same method of expressing the relations between sounds and the undulations which corresponded with them. To show how remarkably in agreement the views of Reis and Bell are upon this question of representing by a curve the undulations which correspond to the voice, we select the following paragraphs and place them in parallel columns.

Reis.Bell.
That which is perceived by the auditory nerve ... may be represented graphically, according to its duration and magnitude by a curve.—(Memoir ‘On Telephony’ in the Jahresbericht of the Physical Society of Frankfurt-a.-M. 1860-61, p. 59.) [p. 53.]
The height or depth of the sound produced ... depends upon the number of vibrations made in a given time.—(Ib. p. 63.) [p. 59.]		Electrical undulations, induced by a body capable of inductive action, can be represented graphically, without error by the same sinusoidal curve which expresses the vibration of the inducing body itself, and the effect of its vibration upon the air; for, as stated above, the rate of oscillation in the electrical current corresponds to the rate of vibration of the inducing body—that is, to the pitch of the sound produced.—(Specification of U. S. Patent No. 174,465, dated March 7, 1876.)
The greater the condensation of the sound-conducting medium at any given moment, the greater will be the amplitude of vibration of the membrane.—(Ib. p. 58.) [p. 52.] The intensity of the current varies with the amplitude of the vibration—that is, with the loudness of the sound;—(Ib.)
... each tone is dependent not only on the number of vibrations of the medium, but also on the condensation or rarefaction of the same.—(Legat’s Report, Zeitschrift des D.-Oesterr. Telegr. Vereins, 1863, p. 125.) [p. 77.]and the polarity of the current corresponds to the direction of the vibrating body,—that is, to the condensations and rarefactions of air produced by the vibration.—(Ib.)
Let us exhibit the condensation curves for three tones—each singly (Plate I): then, by adding together the ordinates corresponding to equal abscissæ, we can determine new ordinates and develop a new curve which we may call the combination-curve. Now this gives us just exactly what our ear perceives from the three simultaneous tones.—(Memoir ‘On Telephony,’ p. 59.) [p. 54.] The combined effect of A and B, when induced simultaneously on the same circuit, is expressed by the curve A + B, Fig. 4, which is the algebraical sum of the sinusoidal curves A and B. This curve A + B also indicates the actual motion of the air when two musical notes considered are sounded simultaneously.... (Ib.) The electrical movement, like the aerial motion, can be represented by a sinusoidal curve, or by the resultant of several sinusoidal curves.—(Ib.)

The very remarkable agreement of the preceding passages receives a most striking confirmation by comparing the curves respectively drawn by Reis and by Bell. These are facsimiled below, Reis’s “combination”-curve ([Fig. 47]) from Plate I. of his Memoir (also [Plate I.] of this volume), and Bell’s “resultant”-curve ([Fig. 48]) from Fig. 4 of his United States Patent Specification No. 174,465.

The most casual observer cannot fail to notice here that the three lines of undulatory curves of Bell’s specification are practically identical with the three lower lines of undulatory curves of Reis’s memoir. They are, moreover, in each case introduced for the sake of showing how a complex curve corresponds to a compound undulation.

Reis..

Fig. 47.

Bell..

Fig. 48.

Far be it from me even to hint that either curve was plagiarised from the other. Bell tells us that his curve is to represent electrical oscillations, which, he adds, have the same curve as that both of the vibrating body and of the air. Reis tells us that his curve is to represent the oscillations of a tympanum, or of the air, or of the magnetisation of the magnet, or of the armature at the receiving end. How the magnetization of the electro-magnet was made to vary “correspondingly with the condensations and rarefactions of the air,” as represented by such a curve, Reis did not explicitly say, but left to the common sense of his readers to infer. Though the inference was obvious, Bell, who possibly had not then read Reis’s researches, seized upon this intermediate stage of the process employed by Reis, and probably quite unconscious that Reis had already employed it, announced it as a discovery of his own; and then, losing sight of the point that all that was wanted was to secure correspondence between the initial and final stage, he magnified to an absurd and unwarranted importance this intermediate correspondence of the vibrations of the current with those of the tympanum, which correspondence any one reading Reis’s papers would know at once Reis had implicitly assumed and actually employed when he transmitted articulate speech.

If we pass from the method of graphically representing undulations by curves, and proceed to compare the language in which Reis described the action of his machine in reproducing the undulations imparted to the transmitter, with that in which Graham Bell described the action of his machine some fourteen years later, we shall find[53] an agreement even more precise.

Reis.Bell.
The electromagnet ... will be demagnetised and magnetised correspondingly with the condensations and rarefactions of the mass of air, ... and the armature ... will be set into vibrations similar to those of the membrane in the transmitting apparatus.—(Legat’s Report, Zeitschrift, p. 128, 1862.) [p. 77.] The current traversing the coils of the electromagnet E, occasions an increase and diminution in its intensity, and the armature A1 is thrown into vibrations ... and thus imparts to the air at n1 a facsimile copy of the motion of the air that acted upon the membrane n.—(Specification of British Patent, No. 4765, Dec. 9th, 1876, p. 17.)
The transmitter, Fig. A, consists of a conical tube ... closed by a membrane ... by speaking ... into the tube ... there will be evoked a motion of the membrane ... (op. cit.) A cone A is used to converge sound vibrations upon the membrane.
When a sound is uttered in the cone the membrane a is set in vibration....
The apparatus ... 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.—(Legat’s Report, op. cit.) ... and thus electrical undulations are created upon the circuit E b e f g.... The undulatory current passing through the electromagnet f influences its armature h to copy the motion of the armature c.... These undulations are similar in form to the air undulations caused by the sound.
>As soon therefore as it shall be possible ... 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.—(Memoir ‘On Telephony,’ p. 60.) [p. 55.] —that is, they are represented graphically by similar curves....
A similar sound to that uttered into A is then heard to proceed from I.—(Specification of U. S. Patent, No. 174,465.)
Any sound will be reproduced, if strong enough to set the membrane in motion.—(Letter to Mr. Ladd, 1863.) [p. 84.] There are many other uses to which these instruments may be put, such as ... the telegraphic transmission of noises or sounds of any kind.—(Ib.)
the armature belonging to the magnet will be set into vibrations similar to those of the membrane in the transmitting apparatus.—(Legat’s Report, 1862.) [p. 77.] I would have it understood that what I claim is:—... Tenth. In a system of electric telegraph or telephony consisting of transmitting and receiving instruments united upon an electric circuit, I claim the production in the armature of each receiving instrument of any given motion by subjecting said armature to an attraction varying in intensity, however such variation may be produced in the magnet, and hence I claim the production of any given sound or sounds from the armature of the receiving instrument by subjecting said armature to an attraction varying in intensity in such manner as to throw the armature into that form of vibration that characterizes the given sound or sounds.—(Specification of British Patent, No. 4765, Dec. 9, 1876.)

One cannot help thinking that some claims to great inventions are just a little “too previous.”

If it should still be said that Reis’s method of transmitting speech, whether it did its work by undulatory currents or no, was avowedly imperfect, and that therefore such a claim as that quoted above is justified by the subsequent invention of an instrument the articulation of which was more reliable, let us compare what each inventor has said about the imperfections[54] of his own instrument.

Reis.Bell.
That which has here been spoken of will still require considerable improvement, and in particular mechanical science must complete the apparatus to be used.—(Legat’s Report, 1862.) [p. 78.] It is a mistake, however, to suppose that the articulation was by any means perfect.... Still the articulation was there, and I recognized the fact that the indistinctness was entirely due to the imperfection of the instrument.—(‘Researches in Telephony,’ Journal of Soc. of Telegr. Engineers, Dec. 1877.)

If it should be said that Bell is here speaking only of an early and experimental form, and not of his real invention, it should be remembered that Bell here refers to the apparatus with cone and membrane, identical with that exhibited at Glasgow in September, 1876, by Sir William Thomson (who had received it from Bell) and by him described as the very “hardihood of invention,” and “by far the greatest of all the marvels of the electric telegraph.” It certainly worked upon the principle of undulatory currents,[55] whether it articulated or not. Bell had himself, speaking in May 1876, before the American Academy of Arts and Sciences upon his researches, even more explicitly admitted the imperfections of his own instrument.

The effects were not sufficiently distinct to admit of sustain ed conversation through the wire. Indeed, as a general rule, the articulation was unintelligible, excepting when familiar sentences were employed.—(Proceedings of American Academy of Arts and Sciences, vol. xii. p. 7.)

Yet this most imperfect machine, of which the articulation was, as a general rule, unintelligible, had, two months previously, had a patent granted to it as a new invention, the claim being for “the method of, and apparatus for, transmitting vocal or other sounds telegraphically, as herein described, by causing electrical undulations similar in form to the vibrations of the air accompanying the said vocal or other sounds, substantially as set forth.”

If then mere mechanical imperfections do not make an invention any the less a true invention capable of legal recognition, it would be dishonest to the last degree to deny to Philipp Reis the honour of his invention, of which he honestly and openly stated both the successes and the imperfections. He told the world what he aimed at, and in what measure success had crowned his aims. His claim to be the inventor of the Telephone he considered to be justified by that measure of success. If he was so far in advance of his time that the world was unprepared to receive or use the splendid discovery which he gave freely to it, that was not his fault; nor does neglect or apathy make him in one single degree the less entitled to the credit of his inventions. Tulit alter honores has not unfrequently been truly said concerning the men of genius who have had the misfortune to live in advance of the age.

But posterity does not let the names of such truly great ones perish in the dust. The inventor of the Telephone will be remembered and honoured in the coming if not in the present age.

Schedule of Authorities

Key to Title of Work

A. ‘Jahresbericht des Physikalischen Vereins zu Frankfurt-am-Main’
B. ‘Fortschritte der Physik’ (Krönig and Beetz)
C. Dingler’s ‘Polytechnisches Journal’
D. ‘Polytechnisches Central-Blatt’(Schnedermann and Böttcher)
E. Böttger’s ‘Polytechnisches Notizblatt’
F. ‘Didaskalia’
G. ‘Zeitschrift des Deutsch-Oesterreichischen Telegraphen Vereins’ (Dr. Brix)
H. Kuhn’s ‘Handbuch der angewandten Elektricitätslehre’
I. Pisko’s ‘Die Neueren Apparate der Akustik’
J. (Pisko’s) ‘Hessler’s Lehrbuch der Technischen Physik’
K. Müller Pouillet’s ‘Lehrbuch der Physik’
Title of Work.Place of Issue. Date. Volume and
Page.		British Museum.
A. Frankfurt-a.-M. {1860–1
{1863		p. 57
p. 129		}
}		 Ac. 4428
B. Berlin {1861
{1863		 xvii. p. 171-173
——? p. 96		}
}		 Ac. 3775
C. Stuttgart1863{clxviii. p. 185-187
{clxix. p. 23
{clxix. p. 399		}
}
}		 Pp. 1780
D. Cassel1863 xxix. p. 858 Pp. 1615 b.
E.Mainz1863 {No. 6
{No. 15		}
}		 Pp. 1787
F. Frankfurt-a.-M.1862 May 8, May 14 ..
G.Berlin 1862 ix. p. 125 ..
H.Leipzig1866 p. 1017-1021 2244 i
I.Vienna 1865{p. 94-103
{p. 241-243		}
}		 8705 cc.
J. Vienna1866 Vol. I. p. 648 ..
K.Brunswick1868 Vol. II. p. 386-388 ..

Key to Table of References
R.S.Royal Society.R.L.Ronald’s Library.
I.C.E.Institution Civil Engineers.R.I.Royal Institution.
G.S.P.O.Great Seal Patent Office.S.M.School of Mines.
U.C.L.University College, London.B.L.O.Bodleian Library, Oxford.
K.C.King’s College.O.U.M.L.Oxford University Museum Library.
For "Title of Work" see keys in previous table.

and References.

Title of Work.R.S.R.L.I.C.
E.		R.I.G.S.
P.O.		S.M.U.C.L.B.L.O.K.C.O.U.
M.L.
A.1846-1860..................
B.✔..✔✔6546, 118 E✔✔..✔✔
C.✔..✔✔1296, 94 A✔........
D.........1132, 94 I..........
E.....................
F.....................
G.....✔..9511, 24 E..........
H...✔..✔13146, 163 C....198 e 133....
I.✔................✔
J...✔................
K.......A newer
edition
(1872)		..✔(Ed.
1876)		....✔

ADDITIONAL PREFERENCES CONCERNING REIS’S TELEPHONE.

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, STAMFORD STREET AND CHARING CROSS.

Plate 1.
REPRODUCTION OF TONES IN THE ELECTRO-GALVANIC WAY.

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REPRODUCTION OF TONES IN THE ELECTRO-GALVANIC WAY.

THOs. KELL & SON. LITH 40, KING St. COVENT GARDEN

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Section I. On the Equality and Distribution of Forces—Section II. Resistance of Timber—Section III. Construction of Floors—Section IV. Construction of Roofs—Section V. Construction of Domes and Cupolas—Section VI. Construction of Partitions—Section VII. Scaffolds, Staging, and Gantries—Section VIII. Construction of Centres for Bridges—Section IX. Coffer-dams, Shoring, and Strutting—Section X. Wooden Bridges and Viaducts—Section XI. Joints, Straps, and other Fastenings—Section XII. Timber.

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Gold: Its Occurrence and Extraction, embracing the Geographical and Geological Distribution and the Mineralogical Characters of Gold-bearing rocks; the peculiar features and modes of working Shallow Placers, Rivers, and Deep Leads; Hydraulicing; the Reduction and Separation of Auriferous Quartz; the treatment of complex Auriferous ores containing other metals; a Bibliography of the subject and a Glossary of Technical and Foreign Terms. By Alfred G. Lock, F.R.G.S. With numerous illustrations and maps, 1250 pp., super-royal 8vo, cloth, 2l. 12s. 6d.

Progressive Lessons in Applied Science. By Edward Sang, F.R.S.E. Crown 8vo, cloth, each Part, 3s.

Part 1. Geometry on Paper—Part 2. Solidity, Weight, and Pressure—Part 3. Trigonometry, Vision, and Surveying Instruments.

A Practical Treatise on Coal Mining. By George G. André, F.G.S., Assoc. Inst. C.E., Member of the Society of Engineers. With 82 lithographic plates. 2 vols., royal 4to, cloth, 3l. 12s.

Sugar Growing and Refining: a Comprehensive Treatise on the Culture of Sugar-yielding Plants, and the Manufacture, Refining, and Analysis of Cane, Beet, Maple, Milk, Palm, Sorghum, and Starch Sugars, with copious statistics of their production and commerce, and a chapter on the distillation of Rum. By Charles G. Warnford Lock, F.L.S., &c., and G. W. Wigner and R. H. Harland, FF.C.S., FF.I.C. With 205 illustrations, 8vo, cloth, 30s.

Spons’ Information for Colonial Engineers. Edited by J. T. Hurst. Demy 8vo, sewed.

No. 1. Ceylon. By Abraham Deane, C.E. 2s. 6d.

Contents:

Introductory Remarks—Natural Productions—Architecture and Engineering—Topography, Trade, and Natural History—Principal Stations—Weights and Measures, etc., etc.

No. 2. Southern Africa, including the Cape Colony, Natal, and the Dutch Republics. By Henry Hall, F.R.G.S., F.R.C.I. With Map. 3s. 6d.

Contents:

General Description of South Africa—Physical Geography with reference to Engineering Operations—Notes on Labour and Material in Cape Colony—Geological Notes on Rock Formation in South Africa—Engineering Instruments for Use in South Africa—Principal Public Works in Cape Colony: Railways, Mountain Roads and Passes, Harbour Works, Bridges, Gas Works, Irrigation and Water Supply, Lighthouses, Drainage and Sanitary Engineering, Public Buildings, Mines—Table of Woods in South Africa—Animals used for Draught Purposes—Statistical Notes—Table of Distances—Rates of Carriage, etc.

No. 3. India. By F. C. Danvers, Assoc. Inst. C.E. With Map. 4s. 6d.

Contents:

Physical Geography of India—Building Materials—Roads—Railways—Bridges—Irrigation—River Works—Harbours—Lighthouse Buildings—Native Labour—The Principal Trees of India—Money—Weights and Measures—Glossary of Indian Terms, etc.

A Practical Treatise on Casting and Founding, including descriptions of the modern machinery employed in the art. By N. E. Spretson, Engineer. Third edition, with 82 plates drawn to scale, 412 pp., demy 8vo, cloth, 18s.

The Clerk of Works: a Vade-Mecum for all engaged in the Superintendence of Building Operations. By G. G. Hoskins, F.R.I.B.A. Third edition, fcap. 8vo, cloth, 1s. 6d.

Tropical Agriculture; or, the Culture, Preparation, Commerce, and Consumption of the Principal Products of the Vegetable Kingdom, as furnishing Food, Clothing, Medicine, etc., and in their relation to the Arts and Manufactures; forming a practical treatise and Handbook of Reference for the Colonist, Manufacturer, Merchant, and Consumer, on the Cultivation, Preparation for Shipment, and Commercial Value, etc., of the various Substances obtained from Trees and Plants entering into the Husbandry of Tropical and Sub-Tropical Regions. By P. L. Simmonds. Second edition, revised and improved, 515 pages, 8vo, cloth, 1l. 1s.

Steel: its History, Manufacture, and Uses. By J. S. Jeans, Secretary of the Iron and Steel Institute. 860 pages and 24 plates, 8vo, cloth, 36s.

American Foundry Practice: Treating of Loam, Dry Sand, and Green Sand Moulding, and containing a Practical Treatise upon the Management of Cupolas, and the Melting of Iron. By T. D. West, Practical Iron Moulder and Foundry Foreman. Second edition, with numerous illustrations, crown 8vo, cloth, 10s. 6d.

The Maintenance of Macadamised Roads. By T. Codrington, M.I.C.E, F.G.S., General Superintendent of County Roads for South Wales. 8vo, cloth, 6s.

Hydraulic Steam and Hand Power Lifting and Pressing Machinery. By Frederick Colyer, M. Inst. C.E., M. Inst. M.E. With 73 plates, 8vo, cloth, 18s.

Pumps and Pumping Machinery. By F. Colyer, M.I.C.E., M.I.M.E. With 23 folding plates, 8vo, cloth, 12s. 6d.

Tables of the Principal Speeds occurring in Mechanical Engineering, expressed in metres in a second. By P. Keerayeff, Chief Mechanic of the Obouchoff Steel Works, St. Petersburg; translated by Sergius Kern, M.E. Fcap. 8vo, sewed, 6d.

Girder Making and the Practice of Bridge Building in Wrought Iron, illustrated by Examples of Bridges, Piers, and Girder Work, etc., constructed at the Skerne Iron Works, Darlington, by Edward Hutchinson, M. Inst. M.E. With 35 plates, demy 8vo, cloth, 10s. 6d.

Spons’ Dictionary of Engineering, Civil, Mechanical, Military, and Naval; with technical terms in French, German, Italian, and Spanish, 3100 pp., and nearly 8000 engravings, in super-royal 8vo, in 8 divisions, 5l. 8s. Complete in 3 vols., cloth, 5l. 5s. Bound in a superior manner, half-morocco, top edge gilt, 3 vols., 6l. 12s.
See page 15.

A Treatise on the Origin, Progress, Prevention, and Cure of Dry Rot in Timber; with Remarks on the Means of Preserving Wood from Destruction by Sea-Worms, Beetles, Ants, etc. By Thomas Allen Britton, late Surveyor to the Metropolitan Board of Works, etc., etc. With 10 plates, crown 8vo, cloth, 7s. 6d.

Metrical Tables. By G. L. Molesworth, M.I.C.E. 32mo, cloth, 1s. 6d.

Contents.

General—Linear Measures—Square Measures—Cubic Measures—Measures of Capacity—Weights—Combinations—Thermometers.

A Handbook of Electrical Testing. By H. R. Kempe, Member of the Society of Telegraph Engineers. New edition, revised and enlarged, with 81 illustrations. Crown 8vo, cloth, 12s. 6d.

Electro-Telegraphy. By Frederick S. Beechey, Telegraph Engineer. A Book for Beginners. Illustrated. Fcap. 8vo, sewed, 6d.

Handrailing: by the Square Cut. By John Jones, Staircase Builder. Fourth edition, with seven plates, 8vo, cloth, 3s. 6d.

Handrailing: by the Square Cut. By John Jones, Staircase Builder. Part Second, with eight plates, 8vo, cloth, 3s. 6d.

The Gas Consumer’s Handy Book. By William Richards, C.E. Illustrated. 18mo, sewed, 6d.

Steam Pleating for Buildings; or, Hints to Steam Fitters, being a description of Steam Heating Apparatus for Warming and Ventilating Private Houses and large Buildings; with Remarks on Steam, Water, and Air in their relation to Heating; to which are added miscellaneous Tables. By J. W. Baldwin, Steam Heating Engineer. With many illustrations. Second edition, crown 8vo, cloth, 10s. 6d.

A Pocket-Book of Useful Formulæ and Memoranda for Civil and Mechanical Engineers. By Guilford L. Molesworth, Mem. Inst. C.E., Consulting Engineer to the Government of India for State Railways. With numerous illustrations, 744 pp. Twenty-first edition, revised and enlarged, 32mo, roan, 6s.

Synopsis of Contents:

Surveying, Levelling, etc.—Strength and Weight of Materials—Earthwork, Brickwork, Masonry, Arches, etc.—Struts, Columns, Beams, and Trusses—Flooring, Roofing, and Roof Trusses—Girders, Bridges, etc.—Railways and Roads—Hydraulic Formulæ—Canals, Sewers, Waterworks, Docks—Irrigation and Breakwaters—Gas, Ventilation, and Warming—Heat, Light, Colour, and Sound—Gravity: Centres, Forces, and Powers—Millwork, Teeth of Wheels, Shafting, etc.—Workshop Recipes—Sundry Machinery—Animal Power—Steam and the Steam Engine—Water-power, Water-wheels, Turbines, etc.—Wind and Windmills—Steam Navigation, Ship Building, Tonnage, etc.—Gunnery, Projectiles, etc.—Weights, Measures, and Money—Trigonometry, Conic Sections, and Curves—Telegraphy—Mensuration—Tables of Areas and Circumference, and Arcs of Circles—Logarithms, Square and Cube Roots, Powers—Reciprocals, etc.—Useful Numbers—Differential and Integral Calculus—Algebraic Signs—Telegraphic Construction and Formulæ.

Spons’ Tables and Memoranda for Engineers; selected and arranged by J. T. Hurst, C.E., Author of ‘Architectural Surveyors’ Handbook,’ ‘Hurst’s Tredgold’s Carpentry,’ etc. Fifth edition, 64mo, roan, gilt edges, 1s.; or in cloth case, 1s. 6d.

This work is printed in a pearl type, and is so small, measuring only 2½ in. by 1¾ in. by ¼ in. thick, that it may be easily carried in the waistcoat pocket.

“It is certainly an extremely rare thing for a reviewer to be called upon to notice a volume measuring but 2½ in. by 1¾ in., yet these dimensions faithfully represent the size of the handy little book before us. The volume—which contains 118 printed pages, besides a few blank pages for memoranda—is, in fact, a true pocket-book, adapted for being carried in the waistcoat pocket, and containing a far greater amount and variety of information than most people would imagine could be compressed into so small a space.... The little volume has been compiled with considerable care and judgment, and we can cordially recommend it to our readers as a useful little pocket companion.”—Engineering.

Analysis, Technical Valuation, Purification and Use of Coal Gas. By the Rev. W. R. Bowditch, M.A. With wood engravings, 8vo, cloth, 12s. 6d.

Condensation of Gas—Purification of Gas—Light—Measuring—Place of Testing Gas—Test Candles—The Standard for Measuring Gas-light—Test Burners—Testing Gas for Sulphur—Testing Gas for Ammonia—Condensation by Bromine—Gravimetric Method of taking Specific Gravity of Gas—Carburetting or Naphthalizing Gas—Acetylene—Explosions of Gas—Gnawing of Gaspipes by Rats—Pressure as related to Public Lighting, etc.

A Practical Treatise on Natural and Artificial Concrete, its Varieties and Constructive Adaptations. By Henry Reid, Author of the ‘Science and Art of the Manufacture of Portland Cement.’ New Edition, with 59 woodcuts and 5 plates, 8vo, cloth, 15s.

Hydrodynamics: Treatise relative to the Testing of Water-Wheels and Machinery, with various other matters pertaining to Hydrodynamics. By James Emerson. With numerous illustrations, 360 pp. Third edition, crown 8vo, cloth, 4s. 6d.

The Gas Analyst’s Manual. By F. W. Hartley, Assoc. Inst. C.E., etc. With numerous illustrations. Crown 8vo, cloth, 6s.

Gas Measurement and Gas Meter Testing. By F. W. Hartley. Fourth edition, revised and extended. Illustrated, crown 8vo, cloth, 4s.

The French-Polishers Manual. By a French-Polisher; containing Timber Staining, Washing, Matching, Improving, Painting, Imitations, Directions for Staining, Sizing, Embodying, Smoothing, Spirit Varnishing, French-Polishing, Directions for Repolishing. Third edition, royal 32mo, sewed, 6d.

Hops, their Cultivation, Commerce, and Uses in various Countries. By P. L. Simmonds, Crown 8vo, cloth, 4s. 6d.

A Practical Treatise on the Manufacture and Distribution of Coal Gas. By William Richards. Demy 4to, with numerous wood engravings and 29 plates, cloth, 28s.

Synopsis of Contents:

Introduction—History of Gas Lighting—Chemistry of Gas Manufacture, by Lewis Thompson, Esq., M.R.C.S.—Coal, with Analyses, by J. Paterson, Lewis Thompson, and G. R. Hislop. Esqrs.—Retorts, Iron and Clay—Retort Setting—Hydraulic Main—Condensers—Exhausters—Washers and Scrubbers—Purifiers—Purification—History of Gas Holder—Tanks, Brick and Stone, Composite, Concrete, Cast-iron, Compound Annular Wrought-iron—Specifications—Gas Holders—Station Meter—Governor—Distribution—Mains—Gas Mathematics, or Formulæ for the Distribution of Gas, by Lewis Thompson, Esq.—Services—Consumers’ Meters—Regulators—Burners—Fittings—Photometer—Carburization of Gas—Air Gas and Water Gas-Composition of Coal Gas, by Lewis Thompson, Esq.—Analyses of Gas—Influence of Atmospheric Pressure and Temperature on Gas—Residual Products—Appendix—Description of Retort Settings, Buildings, etc., etc.

Practical Geometry and Engineering Drawing; a Course of Descriptive Geometry adapted to the Requirements of the Engineering Draughtsman, including the determination of cast shadows and Isometric Projection, each chapter being followed by numerous examples; to which are added rules for Shading, Shade-lining, etc., together with practical instructions as to the Lining, Colouring, Printing, and general treatment of Engineering Drawings, with a chapter on drawing Instruments. By George S. Clarke, Lieut. R.E., Instructor in Mechanical Drawing, Royal Indian Engineering College. 20 plates, 4to, cloth, 15s.

The Elements of Graphic Statics. By Professor Karl Von Ott, translated from the German by G. S. Clarke, Lieut. R.E., Instructor in Mechanical Drawing, Royal Indian Engineering College. With 93 illustrations, crown 8vo, cloth, 5s.

The Principles of Graphic Statics. By George Sydenham Clarke, Lieut. Royal Engineers. With 112 illustrations. 4to. cloth, 12s. 6d.

The New Formula for Mean Velocity of Discharge of Rivers and Canals. By W. R. Kutter. Translated from articles in the ‘Cultur-Ingenieur,’ by Lowis D’A. Jackson, Assoc. Inst. C.E. 8vo, cloth, 12s. 6d.

Practical Hydraulics; a Series of Rules and Tables for the use of Engineers, etc., etc. By Thomas Box. Fifth edition, numerous plates, post 8vo, cloth, 5s.

A Practical Treatise on the Construction of Horizontal and Vertical Waterwheels, specially designed for the use of operative mechanics. By William Cullen, Millwright and Engineer. With 11 plates. Second edition, revised and enlarged, small 4to, cloth, 12s. 6d.

Aid Book to Engineering Enterprise Abroad. By Ewing Matheson, M. Inst. C.E. The book treats of Public Works and Engineering Enterprises in their inception and preliminary arrangement; of the different modes in which money is provided for their accomplishment; and of the economical and technical considerations by which success or failure is determined. The information necessary to the designs of Engineers is classified, as are also those particulars by which Contractors may estimate the cost of works, and Capitalists the probabilities of profit. Illustrated, 2 vols., 8vo, 12s. 6d. each.

The Essential Elements of Practical Mechanics; based on the Principle of Work, designed for Engineering Students. By Oliver Byrne, formerly Professor of Mathematics, College for Civil Engineers. Third edition, with 148 wood engravings, post 8vo, cloth, 7s. 6d.

Contents:

Chap. I. How Work is Measured by a Unit, both with and without reference to a Unit of Time—Chap. 2. The Work of Living Agents, the Influence of Friction, and introduces one of the most beautiful Laws of Motion—Chap. 3. The principles expounded in the first and second chapters are applied to the Motion of Bodies—Chap. 4. The Transmission of Work by simple Machines—Chap. 5. Useful Propositions and Rules.

The Practical Millwright’s and Engineer’s Ready Reckoner; or Tables for finding the diameter and power of cog-wheels, diameter, weight, and power of shafts, diameter and strength of bolts, etc. By Thomas Dixon. Fourth edition, 12mo, cloth, 3s.

Breweries and Maltings: their Arrangement, Construction, Machinery, and Plant. By G. Scamell, F.R.I.B.A. Second edition, revised, enlarged, and partly rewritten By F. Colyer, M.I.C.E., M.I.M.E. With 20 plates, 8vo, cloth, 18s.

A Practical Treatise on the Manufacture of Starch, Glucose, Starch-Sugar, and Dextrine, based 011 the German of L. Von Wagner, Professor in the Royal Technical School, Buda Pesth, and other authorities. By Julius Frankel; edited by Robert Hutter, proprietor of the Philadelphia Starch Works. With 58 illustrations, 344 pp., 8vo, cloth, 18s.

A Practical Treatise on Mill-gearing, Wheels, Shafts, Riggers, etc.; for the use of Engineers. By Thomas Box. Third edition, with 11 plates. Crown 8vo, cloth, 7s. 6d.

Mining Machinery: a Descriptive Treatise on the Machinery, Tools, and other Appliances used in Mining. By G. G. André, F.G.S., Assoc. Inst. C.E., Mem. of the Society of Engineers. Royal 4to, uniform with the Author’s Treatise on Coal Mining, containing 182 plates, accurately drawn to scale, with descriptive text, in 2 vols., cloth, 3l. 12s.

Contents:

Machinery for Prospecting, Excavating, Hauling, and Hoisting—Ventilation—Pumping—Treatment of Mineral Products, including Gold and Silver, Copper, Tin, and Lead, Iron, Coal, Sulphur, China Clay, Brick Earth, etc.

Tables for Setting out Curves for Railways, Canals, Roads, etc., varying from a radius of five chains to three miles. By A. Kennedy and R. W. Hackwood. Illustrated, 32mo, cloth, 2s. 6d.

The Science and Art of the Manufacture of Portland Cement, with observations on some of its constructive applications. With 66 illustrations. By Henry Reid, C.E., Author of ‘A Practical Treatise on Concrete,’ etc., etc. 8vo, cloth, 18s.

The Draughtsman’s Handbook of Plan and Map Drawing; including instructions for the preparation of Engineering, Architectural, and Mechanical Drawings. With numerous illustrations in the text, and 33 plates (15 printed in colours). By G. G. André, F.G.S., Assoc. Inst. C.E. 4to, cloth, 9s.

Contents:

The Drawing Office and its Furnishings—Geometrical Problems—Lines, Dots, and their Combinations—Colours, Shading, Lettering, Bordering, and North Points—Scales—Plotting—Civil Engineers’ and Surveyors’ Plans—Map Drawing—Mechanical and Architectural Drawing—Copying and Reducing Trigonometrical Formulæ, etc., etc.

The Boiler-maker’s and Iron Ship-builder’s Companion, comprising a series of original and carefully calculated tables, of the utmost utility to persons interested in the iron trades. By James Foden, author of ‘Mechanical Tables,’ etc. Second edition revised, with illustrations, crown 8vo, cloth, 5s.

Rock Blasting: a Practical Treatise on the means employed in Blasting Rocks for Industrial Purposes. By G. G. André, F.G.S., Assoc. Inst. C.E. With 56 illustrations and 12 plates, 8vo, cloth, 10s. 6d.

Surcharged and different Forms of Retaining Walls. By J. S. Tate. Illustrated, 8vo, sewed, 2s.

A Treatise on Ropemaking as practised in public and private Rope-yards, with a Description of the Manufacture, Rules, Tables of Weights, etc., adapted to the Trade, Shipping, Mining, Railways, Builders, etc. By R. Chapman, formerly foreman to Messrs. Huddart and Co., Limehouse, and late Master Ropemaker to H.M. Dockyard, Deptford. Second edition, 12mo, cloth, 3s.

Laxton’s Builders’ and Contractors’ Tables; for the use of Engineers, Architects, Surveyors, Builders, Land Agents, and others. Bricklayer, containing 22 tables, with nearly 30,000 calculations. 4to, cloth, 5s.

Laxton’s Builders’ and Contractors’ Tables. Excavator, Earth, Land, Water, and Gas, containing 53 tables, with nearly 24,000 calculations. 4to, cloth, 5s.

Sanitary Engineering: a Guide to the Construction of Works of Sewerage and House Drainage, with Tables for facilitating the calculations of the Engineer. By Baldwin Latham, C.E., M. Inst. C.E., F.G.S., F.M.S., Past-President of the Society of Engineers. Second edition, with numerous plates and woodcuts, 8vo, cloth, 1l. 10s.

Screw Cutting Tables for Engineers and Machinists, giving the values of the different trains of Wheels required to produce Screws of any pitch, calculated by Lord Lindsay, M.P., F.R.S., F.R.A.S., etc. Royal 8vo, cloth, oblong, 2s.

Screw Cutting Tables, for the use of Mechanical Engineers, showing the proper arrangement of Wheels for cutting the Threads of Screws of any required pitch, with a Table for making the Universal Gas-pipe Threads and Taps. By W. A. Martin, Engineer. Second edition, royal 8vo, oblong, cloth, 1s., or sewed, 6d.

A Treatise on a Practical Method of Designing Slide-Valve Gears by Simple Geometrical Construction, based upon the principles enunciated in Euclid’s Elements, and comprising the various forms of Plain Slide-Valve and Expansion Gearing; together with Stephenson’s, Gooch’s, and Allan’s Link-Motions, as applied either to reversing or to variable expansion combinations. By Edward J. Cowling Welch, Memb. Inst. Mechanical Engineers. Crown 8vo, cloth, 6s.

Cleaning and Scouring: a Manual for Dyers, Laundresses, and for Domestic Use. By S. Christopher. 18mo, sewed, 6d.

A Handbook of House Sanitation; for the use of all persons seeking a Healthy Home. A reprint of those portions of Mr. Bailey-Denton’s Lectures on Sanitary Engineering, given before the School of Military Engineering, which related to the “Dwelling,” enlarged and revised by his Son, E. F. Bailey-Denton, C.E., B.A. With 140 illustrations, 8vo, cloth, 8s. 6d.

Treatise on Valve-Gears, with special consideration of the Link-Motions of Locomotive Engines. By Dr. Gustav Zeuner. Third edition, revised and enlarged, translated from the German, with the special permission of the author, by Moritz Müller. Plates, 8vo, cloth, 12s. 6d.

A Pocket-Book for Boiler Makers and Steam Users, comprising a variety of useful information for Employer and Workman, Government Inspectors, Board of Trade Surveyors, Engineers in charge of Works and Slips, Foremen of Manufactories, and the general Steam-using Public. By Maurice John Sexton. Second edition, royal 32mo, roan, gilt edges, 5s.

The Strains upon Bridge Girders and Roof Trusses, including the Warren, Lattice, Trellis, Bowstring, and other Forms of Girders, the Curved Roof, and Simple and Compound Trusses. By Thos. Cargill, C.E.B.A.T., C.D., Assoc. Inst. C.E., Member of the Society of Engineers. With 64 illustrations, drawn and worked out to scale, 8vo, cloth, 12s., 6d.

A Practical Treatise on the Steam Engine, containing Plans and Arrangements of Details for Fixed Steam Engines, with Essays on the Principles involved in Design and Construction. By Arthur Rigg, Engineer, Member of the Society of Engineers and of the Royal Institution of Great Britain. Demy 4to, copiously illustrated with woodcuts and 96 plates, in one Volume, half-bound morocco, 2l. 2s.; or cheaper edition, cloth, 25s.

This work is not, in any sense, an elementary treatise, or history of the steam engine, but is intended to describe examples of Fixed Steam Engines without entering into the wide domain of locomotive or marine practice. To this end illustrations will be given of the most recent arrangements of Horizontal, Vertical, Beam, Pumping, Winding, Portable, Semi-portable, Corliss, Allen, Compound, and other similar Engines, by the most eminent Firms in Great Britain and America. The laws relating to the action and precautions to be observed in the construction of the various details, such as Cylinders, Pistons, Piston-rods, Connecting-rods, Cross-heads, Motion-blocks, Eccentrics, Simple, Expansion, Balanced, and Equilibrium Slide-valves, and Valve-gearing will be minutely dealt with. In this connection will be found articles upon the Velocity of Reciprocating Parts and the Mode of Applying the Indicator, Heat and Expansion of Steam Governors, and the like. It is the writer’s desire to draw illustrations from every possible source, and give only those rules that present practice deems correct.

Barlow’s Tables of Squares, Cubes, Square Roots, Cube Roots, Reciprocals of all Integer Numbers up to 10,000. Post 8vo, cloth, 6s.

Camus (M.) Treatise on the Teeth of Wheels, demonstrating the best forms which can be given to them for the purposes of Machinery, such as Mill-work and Clock-work, and the art of finding their numbers. Translated from the French, with details of the present practice of Millwrights, Engine Makers, and other Machinists, by Isaac Hawkins. Third edition, with 18 plates, 8vo, cloth, 5s.

A Practical Treatise on the Science of Land and Engineering Surveying, Levelling, Estimating Quantities, etc., with a general description of the several Instruments required for Surveying, Levelling, Plotting, etc. By H. S. Merrett. Third edition, 41 plates with illustrations and tables, royal 8vo, cloth, 12s. 6d.

Principal Contents:

Part 1. Introduction and the Principles of Geometry. Part 2. Land Surveying; comprising General Observations—The Chain—Offsets Surveying by the Chain only—Surveying Hilly Ground—To Survey an Estate or Parish by the Chain only—Surveying with the Theodolite—Mining and Town Surveying—Railroad Surveying—Mapping—Division and Laying out of Land—Observations on Enclosures—Plane Trigonometry. Part 3. Levelling—Simple and Compound Levelling—The Level Book—Parliamentary Plan and Section—Levelling with a Theodolite—Gradients—Wooden Curves—To Lay out a Railway Curve—Setting out Widths. Part 4. Calculating Quantities generally for Estimates—Cuttings and Embankments—Tunnels—Brickwork—Ironwork—Timber Measuring. Part 5. Description and Use of Instruments in Surveying and Plotting—The Improved Dumpy Level—Troughton’s Level—The Prismatic Compass—Proportional Compass—Box Sextant—Vernier—Pantagraph—Merrett’s Improved Quadrant—Improved Computation Scale—The Diagonal Scale—Straight Edge and Sector. Part 6. Logarithms of Numbers—Logarithmic Sines and Co-Sines, Tangents and Co-Tangents—Natural Sines and Co-Sines—Tables for Earthwork, for Setting out Curves, and for various Calculations, etc., etc., etc.

Saws: the History, Development, Action, Classification, and Comparison of Saws of all kinds. By Robert Grimshaw. With 220 illustrations, 4to, cloth, 12s. 6d.

A Supplement to the above; containing additional practical matter, more especially relating to the forms of Saw Teeth for special material and conditions, and to the behaviour of Saws under particular conditions. With 120 illustrations, cloth, 9s.

A Guide for the Electric Testing of Telegraph Cables. By Capt. V. Hoskiœr, Royal Danish Engineers. With illustrations, second edition, crown 8vo, cloth, 4s. 6d.

Laying and Repairing Electric Telegraph Cables. By Capt. V. Hoskiœr, Royal Danish Engineers. Crown 8vo, cloth, 3s. 6d.

A Pocket-Book of Practical Rules for the Proportions of Modern Engines and Boilers for Land and Marine purposes. By N. P. Burgh. Seventh edition, royal 32mo, roan, 4s. 6d.

Table of Logarithms of the Natural Numbers, from 1 to 108,000. By Charles Babbage, Esq., M.A. Stereotyped edition, royal 8vo, cloth, 7s. 6d.

To ensure the correctness of these Tables of Logarithms, they were compared with Callett’s, Vega’s, Hutton’s, Briggs’, Gardiner’s, and Taylor’s Tables of Logarithms, and carefully read by nine different readers; and further, to remove any possibility of an error remaining, the stereotyped sheets were hung up in the Hall at Cambridge University, and a reward offered to anyone who could find an inaccuracy. So correct are these Tables, that since their first issue in 1827 no error has been discovered.

The Steam Engine considered as a Heat Engine: a Treatise on the Theory of the Steam Engine, illustrated by Diagrams, Tables, and Examples from Practice. By Jas. H. Cotterill, M.A., F.R.S., Professor of Applied Mechanics in the Royal Naval College. 8vo, cloth, 12s. 6d.

The Practice of Hand Turning in Wood, Ivory, Shell, etc., with Instructions for Turning such Work in Metal as maybe required in the Practice of Turning in Wood, Ivory, etc.; also an Appendix on Ornamental Turning. (A book for beginners.) By Francis Campin. Second edition, with wood engravings, crown 8vo, cloth, 6s.

Contents:

On Lathes—Turning Tools—Turning Wood—Drilling—Screw Cutting—Miscellaneous Apparatus and Processes—Turning Particular Forms—Staining—Polishing—Spinning Metals—Materials—Ornamental Turning, etc.

Health and Comfort in House Building, or Ventilation with Warm Air by Self-Acting Suction Power, with Review of the mode of Calculating the Draught in Hot-Air Flues, and with some actual Experiments. By J. Drysdale, M.D., and J. W. Hayward, M.D. Second edition, with Supplement, with plates, demy 8vo, cloth, 7s. 6d.

Treatise on Watchwork, Past and Present. By the Rev. H. L. Nelthropp, M.A., F.S.A. With 32 illustrations, crown 8vo, cloth, 6s. 6d.

Contents:

Definitions of Words and Terms used in Watchwork—Tools—Time—Historical Summary—On Calculations of the Numbers for Wheels and Pinions; their Proportional Sizes, Trains, etc.—Of Dial Wheels, or Motion Work—Length of Time of Going without Winding up—The Verge—The Horizontal—The Duplex—The Lever—The Chronometer—Repeating Watches—Keyless Watches—The Pendulum, or Spiral Spring—Compensation—Jewelling of Pivot Holes—Clerkenwell—Fallacies of the Trade—Incapacity of Workmen—How to Choose and Use a Watch, etc.

Spons’ Engineers’ and Contractors’ Illustrated Book of Prices of Machines, Tools, Ironwork, and Contractors’ Material; and Engineers’ Directory. Third edition, 4to, cloth, 6s.

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FOOTNOTES:

[1] An autograph letter of Philipp Reis to Mr. W. Ladd, the well-known instrument maker of Beak Street, London, describing his telephone, is still preserved, and is now in possession of the Society of Telegraph Engineers and Electricians of London. It is reproduced at p. 81.

[2] As to the difference in quality of the instruments, see the testimony of the maker, Albert of Frankfort, on p. 44. Prof. Pisko (see p. 101) seems to have had a peculiarly imperfect instrument.

[3] Dr. Messel, F.C.S., a former pupil of Reis, and an eye-witness of his early experiments, makes, in a letter to Professor W. F. Barrett, the following very interesting statement: “The original telephone was of a most primitive nature. The transmitting instrument was a bung of a beer-barrel hollowed out, and a cone formed in this way was closed with the skin of a German sausage, which did service as a membrane. To this was fixed with a drop of sealing-wax a little strip of platinum corresponding to the hammer of the ear, and which closed or opened the electric circuit, precisely as in the instruments of a later date. The receiving instrument was a knitting needle surrounded with a coil of wire and placed on a violin to serve as a sounding board. It astonished every one quite as much as the more perfect instruments of Bell now do. The instrument I have described has now passed into the hands of the Telegraph Department of the German Government.” [The instrument now in the museum of the Reichs Post-Amt in Berlin is not this, but is the first of the “Improved” Telephones described later by Reis in his “Prospectus” (see p. 85), and is stamped “Philipp Reis,” “1863,” “No. 1.”] S.P.T.

[4] Or sometimes “tension-regulators,” though the latter term is acknowledged by most competent electricians to be indescriptive and open to objection.

[5] See Die Geschichte und Entwickelung des Elektrischen Fernsprechwesens (issued officially from the Imperial German Post-office, 1880), p. 7.

[6] The name “Telephone” had already been applied by Sir C. Wheatstone (1831) to an acoustic arrangement for transmitting sounds through wooden rods to a distant place in a purely mechanical manner. It is needless to observe that speech as well as music can be thus transmitted; and though Wheatstone gave telephonic concerts, this does not prove (nor do telephonic concerts given through Reis’s instrument prove) that speech could not be transmitted also. The name “Fernsprecher,” now used in Germany for the Telephone, was only suggested in 1877 by Dr. Stephan, Postmaster of the German Empire, in obedience to the absurd fashion which has raged since 1871 in Germany of rejecting words of classic derivation.

[7] See proceedings in U. S. Court (Dowd suit), Edison’s second answer, and Prescott’s ‘The Speaking Telephone,’ p. 218.

[8] Published volume of Proceedings in the United States Patent Office, before the Commissioner of Patents. Evidence for A. G. Bell, p. 6.

[9] Proc. Soc. Telegr. Engin. and Electr. vol. xi. p. 134, 1882.

[10] ‘Electrical Review,’ July 22, 1882, p. 49.

[11] Mr. E. Albert, of the firm of J. W. Albert and Sohn, of Frankfurt, to whom Reis entrusted the manufacture of Telephones for public sale, thus writes: “The most important part was the membrane, because the delicacy of the apparatus depended principally upon that part. As it was not possible to make every membrane equally good, so it came about that instruments of different degrees of superiority came into use, and various decisions were arrived at as to the ability of the instrument to perform the functions for which it was designed. Those who happened to have a poor instrument were able to hear but little; while those who possessed a good instrument were astonished at its performances. A good instrument reproduced the words sung into it in such a manner that not only the pitch but also the words of the song were perfectly understood, even when the listener was unacquainted with the song and the words.”

M. St. Edmé, of Paris, who contributed to ‘Cosmos,’ vol. xxiv. p. 349, 1864, an article on Reis’s Telephone, of which he had seen an example in König’s atelier, said that when the scale was sung it needed a trained ear to distinguish the notes amidst the noises of the receiver. He must have got hold of an uncommonly bad transmitter with a flabby tympanum to have failed so completely.

[12] Letter of Dr. Messel to Professor W. F. Barrett quoted, in Professor Barrett’s memoir, ‘On the Electric Telephone,’ read Nov. 19, 1877, to the Dublin Royal Society. Vide Proc. Roy. Soc. Dubl. 1877.

[13] See Barrett’s ‘Telephones Old and New’ (1878), p. 12.

[14] See Reis’s own remark at bottom of p. 57.

[15] [This was the number formerly accepted on the authority of Despretz as the minimum number of vibrations that could evoke the sensation of a tone in the human ear. The limit now more usually recognized is that of Helmholtz, who assigns from thirty to forty double vibrations per second as the minimum.]—S. P. T.

[16] [The three plates or tables with which Reis accompanied his Memoir, containing a variety of undulatory curves corresponding to various combinations of tones, both of musical concords and of dissonant sounds, are not reprinted in this book in their entirety. Table I. contained three sets, the first of which is reproduced by photo-lithography in reduced facsimile in [Fig. 47], p. 173. It was also reproduced by W. von Legat in his Report from which [Plate I.] at end of this book is copied, Fig. 1 of that plate being the same as Fig. 1 of Reis’s Table I. Fig. 2 of Plate 1, was in like manner copied by Legat from the first figure of Reis’s Table II., and Fig. 3 of Plate I., which represents the curves of a non-harmonious combination is the same as Reis’s Table III., the only difference being that in Reis’s Table III. the irregular undulations of the resultant curve were emphasised by being labelled ‘Dissonanz.’]—S. P. T.

[17] [This is true for speech-tones as well as for musical tones. Each kind of tone may be represented by its own characteristic curve.]—S. P. T.

[18] [This is the fundamental principle, not only of the telephone, but of the phonograph; and it is wonderful with what clearness Reis had grasped his principle in 1861.]—S. P. T.

[19] [That is, at any single demagnetisation of the needle, it vibrates and emits the same tone as if it had been struck or mechanically caused to vibrate longitudinally.]—S. P. T.

[20] [This range was simply due to the degree of tension of the tympanum; another tympanum differently stretched, or of different proportions, would have a different range according to circumstances.]—S. P. T.

[21] [The so-called “galvanic tone” heard on opening or closing the circuit was well-known, and Wertheim had shown that this tone was, for any given rod of iron, identical with its “longitudinal tone,” i.e. the tone produced by striking it on the end so as to produce longitudinal vibrations. But it was one of the most important discoveries in Reis’s researches that such a rod could take up any tone in obedience to the vibrations forced upon it by periodic interruptions in the magnetising current in the spiral of any degree of rapidity within very wide limits. The translator has had occasion to examine this point, and has found iron, steel, and cobalt wires varying from 4 to 10 inches in length, including some used by Reis himself as receivers, to be capable of taking up vibrations from as slow as 40 per second to the very shrillest whistle audible to human ears, or exceeding 36,000 per second. It is sometimes also mistakenly supposed that such a wire can respond only to the vibrations of tones that are musical, not to those that are articulate, including both consonants and vowels. This, however, is an entire mistake. For, using such a wire as a receiver (surrounded by its proper coil and mounted with an appropriate sounding board, or, better still, tympanum), in conjunction with a well-adjusted transmitter, the articulation transmitted surpasses that obtainable with any of the ordinary magnetic receivers in distinctness, though not in loudness. This discovery of Reis’s is of the greatest importance, especially as some who ought to know better have very unjustly denied the capability of this part of the apparatus to act as a telephone receiver for articulate sounds.]—S. P. T.

[22] [This limit is a mistake of Professor Böttger’s. The longitudinal tone of an unstrained iron or steel wire 10 inches long would be a note about four octaves above the middle c of the piano; whereas, in fact, any note of the whole piano-gamut down to the lowest note, can be reproduced by such a wire, as stated in preceding footnote.]—S. P. T.

[23] [Professor Böttger had not to wait long for the fulfilment to a very large degree of this anticipation; for within six months Dingler’s Journal, in which this article appeared, contained Legat’s report on Reis’s instruments, in which not only were various modifications in their construction made known, but also the transmission of voice-tones, not yet perfectly but with recognisable modulations and intonations, was recorded. Reis had, indeed, succeeded nearly as well as this with his first instrument, as his memoir of 1861 shows. See p. 58.]

[24] [Compare ‘Die Geschichte und Entwickelung des Fernsprechwesens,’ a pamphlet issued officially in 1880 from the Imperial German Post-Office in Berlin, p. 6.]

[25] [Plate VIII. of the original in Vol. IX. of the Zeitschrift.]

[26] [Plate IX. of the original Memoir.]

[27] [This word, as the context and ending of the paragraph shows, should have been spelled tones. The letter, written in English by Reis himself, is wonderfully free from inaccuracies of composition; the slip here noted being a most pardonable one since the plural of the German “ton” is “tönen,” the very pronunciation of which would account for the confusion in the mind of one unaccustomed to write in English. So far as is known, this is the only piece of English composition ever attempted by Reis.—S. P. T.]

[28] [Reis here sketched a figure identical in all its parts with that which a fortnight later was issued in his ‘Prospectus.’ His sketch is reproduced in facsimile in Fig. 28.]

[29] [This was the little auxiliary signalling apparatus at the side of the box, placed there for the same reasons as the auxiliary call-bell attached to modern telephones.]

[30] [This word is underscored in Reis’s original letter.]

[31] [Compare Böttger Polyt. Notizbl. 1863, p. 81, the notice translated at p. 61 preceding.]—S. P. T.

[32] [This rather obscure passage refers to the call-key or communicator fixed to the side of the instruments, and which as the inventor explains in his Prospectus (see p. 87), to be intended, like the call-bell or communicator of modern telephones, as a means of sending signals to the speaker, and which, as the Prospectus says, can also be used—as any call-bell can—for telegraphing words by a pre-arranged code of signals.]—S. P. T.

[33] [Fig. 30 of this book.]

[34] [References.] Telephon von Reis im Jahresbericht des physikalischen Vereins zu Frankfurt-a.-M. für 1860-1861, pag. 57 bis 64. Müller-Pouillet, Physik, 1863, 6. Auflage, II pag. 352, Fig. 325. Berl. Ber. für 1861, xvii. pag. 171 bis 173. Der Musiktelegraph in der “Gartenlaube” 1863, Nr. 51, pag. 807 bis 909. Aus der Natur 1862, xxi. pag. 470 bis 484; König’s Catalog, 1865, pag. 5.

[35] [This part of the apparatus is in fact a “call,” serving precisely the same function as the call-bell attached to ordinary telephones, by which the subscriber can be “called up” to listen to the instrument. It is not without importance to observe that this function was perfectly well-known at the time; for it was gravely argued during a former telephone law-suit in England that the presence of this “signal-call” at the side of the Reis Transmitter was a proof that it was intended to transmit singing only and not speech, or “else there would not have been that little Morse-instrument at the side by which to talk”! This suggestion is, however, self-evidently absurd, because if this had been the case the little electromagnetic Morse telegraph would have been fixed, not on the side of the transmitter but on that of the receiver. Reis himself explains the use of the “call” (see p. 87) in his “Prospectus.”]—S. P. T.

[36] [Professor Pisko seems to have got hold of an unusually unfortunate specimen of the instrument if he could make it neither speak nor sing. His transmitter must have been in exceedingly bad condition to fail so completely.]

[37] This error has been copied by Count du Moncel, along with the other defects of the article, into the fifth volume of his ‘Applications of Electricity,’ published in 1878. It is rather amusing now to read, at p. 106, of Du Moncel’s treatise that “Heisler” (sic) “pretends” that the telephone of “Reuss,” which “appears” to have been invented “anterior to the year 1866,” was capable of transmitting vocal melodies! Count du Moncel, though he has since posed as an authority on the telephone, did not in 1878 shine in that capacity, for on the very same page of the Count’s book may be found the following astounding sentiment:—“If it is true, as Sir W. Thomson has assured us, that at the Philadelphia Exhibition of 1876 there was a telegraphic system transmitting words, we may recognize,” &c. Count du Moncel has since found out that it is true that there was a Telephone in Philadelphia in 1876: perhaps he will next discover that “Reuss” did, “anterior to the year 1866,” actually “appear” to transmit not only what “Heisler” “pretends” he did, but that he also transmitted spoken words.—S. P. T.

[38] Ueber Fortpflanzung der Töne auf wilkührlich weite Entfernungen, mit Hülfe der Elektricität (Telephonie). Polyt. Journ. clxviii. 185; aus Böttger’s Notizbl. 1863, Nr. 6. [See translation on page 61.]

[39] ‘Philosophical Magazine,’ April 1882.

[40] ‘Atti del R. Istituto Veneto di Scienze,’ vol. vi. ser. 5.

[41] Proc. Roy. Soc. No. 218, 1882.

[42] See Proc. Roy. Dubl. Soc. Feb. 17, 1879.

[43] Vide ‘The Electrician,’ Feb. 10, 1883.

[44] Journal Soc. Telegr. Engin. and Electricians, vol. xii. p. 137.

[45] Proc. Physical Soc. vol. ii. p. 259, 1878.

[46] ‘Journal Soc. Telegraphic Engineers,’ vol. iv. p. 117, 1874.

[47] The term “semi-conductor” is very rarely used by electricians, who prefer the term “partial conductor” as being more correct. Moreover, electricians, from Faraday downwards, are practically agreed in calling plumbago a good conductor, and worthy of being classified by reason of its high conductivity along with the metals. The substances known as “semi-conductors” are those given in Ferguson’s ‘Electricity,’ p. 49 (edition of 1873), namely, alcohol, ether, dry-wood, marble, paper, straw, and ice. Mascart and other eminent authorities agree in this classification. It would tax even Mr. Edison’s unrivalled ingenuity to make of these materials a transmitter that should alter its resistance by pressure!

[48] Lüdtge’s German Patent, dated Jan. 12, 1878,describes a “Universal Telephone” in which a tympanum was applied to convey vibrations to an interruptor made of hard coke-carbon.

[49] See Prescott’s ‘Speaking Telephone,’ p. 158.

[50] ‘British Patent,’ No. 1874, of the year 1876 (dated 4th May).

[51] Prescott, ‘Speaking Telephone,’ p. 203.

[52] Yet Bell’s claim (British Patent Specification) runs: “I claim the production of any given sound or sounds from the armature of the receiving instrument.”

[53] In making these comparisons in parallel columns, I wish to repudiate in the most emphatic way any sinister inference that might be drawn as to Graham Bell’s use of descriptions and curves identical in so many points with those of Reis. For, in the first place, I believe Professor Bell to be incapable of such contemptible appropriations, and the candour with which he has himself invited comparison by giving various references to Reis’s papers, itself precludes such inference. In the second place, I do not think that at the date of these quotations Bell understood German sufficiently well to comprehend Reis’s very precise statement of the problem of the Telephone. I simply exhibit these parallel extracts to show the thoroughness with which Reis had grappled with the problem with which, fourteen years later, Bell also grappled; and to prove in the most irrefragable manner, from the necessary identity in the terms selected for expressing the facts of the solution of the problem, that the problem to which each found a solution was identical. The circumstance that does, however, puzzle me, and which does not appear in these parallel extracts, is that, whilst in his original memoir, Reis speaks in detail of the auditory ossicles and their movements as having suggested his transmitter, and casually mentions the phonautograph of Scott in support of his views, Bell, in his original lecture before the American Academy, speaks in detail of Scott’s phonautograph as having suggested his transmitter, and casually refers to the auditory ossicles and their movements.

[54] Reis’s failures were chiefly with the vowels, Bell’s more particularly with the consonants. Reis’s contacts were liable to break, and the following-springs of his contact-regulators too little pliable. Bell’s transmitter could not open and close the circuit proportionally with the motions of the tympanum, and owing to the sluggishness due to self-induction in the coils of his telephone, the induced undulations of the current failed to come up in suddenness to those of the tympanum. In consequence whip sounded like whim, and kiss like kith, even in the perfected Bell Telephones made two years after Bell’s first “improvements” in telephony were patented.

[55] The following very remarkable passage occurs in the evidence given by Professor Graham Bell concerning Reis’s Telephones. (See published volume of ‘Proceedings in the United States Patent Office before the Commissioner of Patents.’ Evidence for A. G. Bell, p. 14.)

Question 37. “If a Reis Telephone, made in accordance with the descriptions published before the earliest dates of your invention, would in use transmit and receive articulate speech as perfectly as the instruments did which were used by you on June 25, 1876, at the Centennial, would it be proof to you that such Reis’s Telephones operated by the use of undulatory movements of electricity in substantially the same way as your instruments did upon the occasion referred to?”

Answer by Bell. “The supposition contained in the question cannot be supposed. Were the question put that if I were to hear an instrument give forth articulate speech transmitted electrically as perfectly as my instruments did on the occasion referred to in the question, I would hold this as proof that the instrument had been operated by undulatory movements of electricity, I would unhesitatingly answer, Yes.”

Surely no better authority is needed to support the proposition that if Reis made his Telephone speak, as he said he did, he employed undulatory currents.

Transcriber's notes:

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