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Session 1888. PRINTED BY JOHN LOVELL & SON. iw The Society will not hold itself responsible for any statements or opinions ^Yllicll rany Le a(lvir..»''fl iii the followin" i)aue.s. |anabian f orietu of ixM §nmmm. Session 1888. TRANSACTIONS. Cth January, 1888. E. P. HAXNAFOr.D, Vice-President, In the Chair. Paper Xo. 12, THE TELEPHONE. By F. N. GisBORNE, M. Can. Soc. C. E., F.R.S.C, &c,, &c. Many and bitter have been the writings and discussions as to thc' On'guHil Inventor of the Telephone. The earliest reconi, vide copy of the " Jahrc.'bericht," of 18G1, in the British Museun,, proves that Philip Reis, of Berlin, had then experi- mented with the ^A\o^yed ohiQct oi' transmitting speech hy eJactricity, and that musical sounds had been conveyed by his apparatus. 3Iore'over, his original instruments now reproduce speech, when the electrodes are moistened will i drop of water, or oil. Fifteen years lat<..r, 187G, Professor Elisha Gray, while endeavoring' to transmit speech, invented his Jummnic telegraph ,- and Graham Bell" who was in search of a hnrmonic telegraph (vide his original United States Patent of 1S7G), discoveied the simple and beautiful method of transmitting speech, which has since bestowed upon him fame and for- tune. Two years later, 187>^, Professor Hughes gratuitously gave to science and the world, his mierojihone ; and based upon such discovery, viz., the varying resistance of carbon electrodes under more or less pressure, Thomas A. Edison invented and improved telephonic transmitters ; ayd now the combined inventions of Bell, Edison, Gower, Blake and o'thers constitute the commercial value of those Bell Telephone Company's acquired patents which have been upheld by the law courts of the United States and Europe with such liberality of scope as greatly ta astonish the scientists of the world. 4 Gisbmnic on the Tdcphone. Innumerable attempts have coiisfCjuently been made to transmit speech without !n/niig!n/ ajipVud heat; but that when the current first passes through the electrodes, their minute points offer so much resist- •ance, that heat is produced and tluy burn off, .'o that the surface con- tacts become larger and the instruiiinits convey speech; but when too large, silence ensues ; — that when jiroperly adjusted, a rapid bombard- ment of moveable atoms between the t'lectrodes occur, very ([uickly from the positive and more slowly iVoni the negative poles. And lie Gisbovnc on the. Telvplionc. & instanced the Ibllowinj^ curious experiment, under ujicroscopic observa- tion, that when a drop of oil was placed between two j latina poiutod electrodes and a current passed throufrh them, a c. For many practical reasons, the speaker considers this latter stitenicnL ofProreHHor ThonipMon's an important one. I'rofeHsor Thompison tlien exhibited a 'ransmitter, designed with tin! object of dispensinir with the patented diaphragm. At the small end of a speaking tube, a ball or vaU'c of metal rested upon three metallic pointe and the sound waves cuspended, or in part rolieved, the weight of the ball ; but Professor Hughes observed, that if the tube were jdugged below the valve and the air allowed to escape through side holes, the instrument remained equally effective, thus proving that the tube itself became a diaphragm of different form, and that under any circumstances, for well known mcfhanieal reasons, the practical limita- tion of three points of support would render tiie instrument less power- i'ul than many others in use. The experimental transmitter just described will serve in great mea- sure to <'Xplain the broad claim allowed at law in favour of the din- jihragm, as patented by Professor Bell. It appears, however, that a simple grid of small carbon bars, sus- pended upon a platina wire, within a non-vibrating leaden fiame, and acted upon direct by sound waves, proves to be an effectivi. transmitter, and by such device a diaphragm may be totally dispensed with. Professor Hughes stated that if a series of small bars or pencils of carbon were iittaclicd to the inside rim of a bowl, or box, filled with water in order to eliminate the hollow tones of such receptacle, &uch a transmitter would operate with increased power, because every portion of the watei would then be in a state of tremor from the sound waves. This remarkable powf>r of water for conveying sounds has already been utilized for discovering leaks in water pipes; even the leakage of a few drops may be localized by the application of a delicately constructed teleplionic receiver ; and there can be little doubt that under favourable circamstanees distinct signals can be telephonically conveyed througli several miles of water. Magneto-electric transmitters liave, since the introduction of the microphone, been superseded by local circuit battery powor transmitters ; but from the results of practical experiments made with the " Gisborne & Keeley " patented telephone, now owned by the Bell Telephone Co. of Canada, it seems desirable, if possible, to dispense with the always uncertain an'l varying action of introduced galvanic battery power. Professor Thompson suggested a transmitter based upon the principle of a dynamo-electric machine; but the advantages of such mode of increasing the power of the currents would be more than counterbalanced by the increased inertia consequent upon the to and fro movement of the armature. Giaborve on the Telephone. 7 In conclatl'mj? hist observations at tlio nfcotlnj^ reforrej t.), Profcsso'" Thompson stated that in his opinion the progross of lon^ distance tiansmission of «pcooh would d( ;)end upon iiicrcasing the power of tho transmlUcr, and '■educing ilic sensitiveness of receivers to induced sounds from extraneous dii^turbances. To such general conclusion Mr. W. If. Preem^ (electrician to tlio London Post Office and telcf^rnphs) took exception, and stated that clearness of articulation and lon^ distance telephony dej^ended entirely upon the line wireH being freed from electro-static and electro-magnetic induction, and that wlicn the environment was fi'\orable, the most ordinary form of instruments would convey speech as well over long as over sliort circuits. That the law, which determines the transmission of currents through a wire, to produce speed i> precisely the same, in every respect, a» the law which determine'^ the low of currents throur'h submarine cables, and that it is absolutely impossible, to obtain any greater number of signals, along a given conductor, by any alteration or improvement in the instruments. Tliat the ratio values of conductors were as follows: iron 1,000, •coppe- in cables 1,200, copper exposed 1,500. That the difference between iron and copper was due to the self induction of the iron; flud between copper in cables and copper exposed, the difference was entirely due to the insulation of the former ; the leakage from suspended •wire enabling it to discharge its static charge, and still more quickly from a suspended copper than from an iron wire. That experiments showed, ihat when the speed of the currents was .004 to .003 of a second, the transmission of speech was bad ; wlicn .003 to .002, it was fair ; when .002 to .001, it was good ; and if under .001, perfect. That the average number of sonorous vibrations in the human voice, ■was about 1,500 per second. Experiments made upon the Irish cables and lines proved the relative values of the different circuits, and that even with a powerful " Berliner " transmitter, the rate of speaking was neither increased nor varied from the result obtained when ordinary tiausmitters of much less prwerwere used. That Professor Fleeming Jenkin had verified the law of static induc- tion and consequent retardation of signals, through the French Atlantic cable of 2500 miles in length, when he found it possible to obtain 2^ reversals of current, per second ; and that both thc'^'-' and practice demonstrated that speech was limited in such class of > , 3 to a distar-ce not exceeding 96 to 100 miles of its length. That telephonic disturbances arc principally due to secondary cur- rents induced by primary currents in neighboring lines, and that short 8 Gishorne on the Telephone. circuits are more disturbed by such influences than arc^long circuits^ 8ucb disturbances being due, not merely to the strength or potential of neishborins currents, 1: .c to the rate at which the said currents rise CO / and fall. That although the effects of induction might in some measure be neutralized by strengthening the transmitter and weakening the receiver, it would be almost impossible to convey intelligible speech, when very stroLg currents (such for instance a.^ were used in a Wheatstone trans- mitting telegraph) were traversing neighboring lines, the induction effects from said currents being 100,000 times stronger than telephonic currents. Professor Hughes was «f opinion that greater attention should be given to the transmitter induction coils, and that the battery cells and primary wire of the coils should be in proportion to the internal re- sistance of the transmitter ; and he agreed with Professor Thompson, that more powerful transmitters and less sensitive receivers indicated the path of progress in telephony. Mr. Bidwell held, that the constituent elements of a transmitter should be an arrangement in multiple-arc of heavy carbon pencils, with light points of contact, that the resistance of such a microphone should be propc'-tionately as small as the rost of the circuit, and that tlie cur- rent should be as strong as the number of contacts and amount of pres- i-ure would warrant. With due regard to the foregoing views and experiments of eminent electricians, the speaker ventures to express the opinion: — That clearness of articulation and natural tones are best obtainable from magneto-electric transmitters, which are free from the disturbing and varying action of local galvanic cells. That loudness, and progress in long-distance telephony, will depend in great measure upon increased power in the transmitter and decreased sensitiveness in the receiver. That whereas it is impracticable to control the environments of tele- phone wires, attention must be given to the elimination of induced dis- turbing currents, by utilizing twisted all-metallic circuits, or some equi- valent device. That economy in line construction can be eflfected by utilizing one such twisted all-metallic circuit, of low resistance, for several exchange connections. In conclusion the author begs to state that this paper has been compiled with the sole object of inviting discussion upon one of J.e most important inventions of the nineteenth century, by the members and associates of the Canadian Society of Civil Engineers. DISCUSSIOX., Mr. Keeley explained that his presence was due to th« fact that Mr. Glsborne was unable to travel i'. agh illness. He further stated that Mr, Gisborne Lad considered it advisable that he should bring some apparatus, in order to make clear any points that might be brought into question, such apparatus was now on the table, and Mr. Keeley thus continued : — It occurred to Mr. Gisborne, that as tliis paper would be the first one *'•■' Ke«iej on tha subject of Telephony brought before the Society, it should be made as comprehensive as possible; and for that reason he has in it set forth his own ideas and the views of the several prominent electricians who participated in the discussion at a meeting of the Society of Telegraph Engineers and Electricians, when the whole subject was thoroughly considered. Having read the full report of that discussion, and noticed what an amount of acrimony was exhibited by some of the participants, it might be stated, that Mr. Gisborne has given ia his paper, all of the valuable information elicited, just as one wouM serve up honey, without a hint of the stings that had been associated! with it. Without entering into a discussion of the question as to the in of the telephone, but simply dealing with the subject as we (in now find it, the speaker would direct attention to one particularly im- portiint point that to his mind is ccospicuous amongst the many other discussable points with which Mr. Gisborne's paper fairly bristles. Papers treating broad subjects of this character in a general way are necessarily provocative of much discussion ; and unless it be lor purposes of criticism, little good is derivable from an attempt on the part of any single individual to discuss such a paper, clause by clause or point after point, where numbtrs of points are discernable. Attentioa will therefore be directed to one important point. It is pretty generally admitted that the British electricians, whose names figure so prominently in Mr. Gisborne's paper, are authorities upon the subject of telephony. If they be so, the importance of the point which the spo<\ker desires to consider is beyond doubt. It is this : — The Question as to the possibility of improvement ia telephony. Now, one would hardly believe this possible with advanced scientists, in view of the fact that it was only a little while ago the telephone was- introduced, and almost daily the journals remind us that the thing i» M Discussion on the Tdepltone. jct in its infancy. Nevertheless, there appears to be good ground for the doubt that has arisen ; and an atteKipt will be made to shew wherein it lies. Every question has neccssarilv two sides. In this instance we have as representatives of the contrary views, Prof. Sylvanus Thompson on the one hand, and Mr. W. Tl. Preece on the ether. Both of these gentlemen have actually experimented ; they opeak aathoritativoly from the results of their experiments ; and they are agreed that the real impediment to uniformly successful operation con- sists in circuit induction. They are not agreed, however, as to what is requisite for the elimin- ation of this difficulty. Each claims the other's conception to be erroneous and impracticable. Hence, if each is an authority and if both are wrong in their concep- tions, as the speaker has reason to believe they are, the future of tlie telephone is still problematical. To be more explicit Prof S. Thoirpson considers the apparatus at pre- sent in use to be at fault ; it is far too sensitive. He conceives vne require- ment to be a receiver insufficiently sensitive to be affected by currents induced from extraneous sources; and a transmitter sufficiently powerful to produce currents to modify any oxtraneously induced, and conse- quently sufficiently strong to be effectual in the receiver. Mr. Preece, on the other hand, considers tha apparatus at present in use as faultless. He conceives the difficulty rests with the circuit, and that uniform results can only be secured by its isolation, or, as he would <;xpress it, by getting rid of its mischievous environment. Each of these gentlemen combats the other's view, and with good reason. It is quite certain there would be a limit, a low one, to the power of Prof. Thompson's tiansmitter; whereas, the strength of currents in- duced from adjacent wires (electric-light circuits, for instance) is practi- cally unlimited. It is also evident that the isolation of any one of a number of adja- cent wires is physically impossible without the interposition of an invul- nerable screen between it and the others throughout its length ; and as the material for such a screen has yet to be discovered, Mr. Preeco's idea is less hopeful than Prof Thompson's. It therefore follows that as these gentlemen arc recognized authori- ties, that as both are decided as to the impediment existing, and that as they are mutually skeptical as to each other's conception of what is needful to remove it, the development of the telephone is at a stand- still, anc it is actually questionable with them whether any further improvement is possible. Discussion on the Telephone, 11 Now, assuminc; that it will be considered tins point is well taken, it may be stated, for the comfort of those who have the future of the telephone at heart, that there is no good cause for alarm. It can be borne in mind that the mere fact of a standard time-piece, coming to a full stop, docs not necessarily throw the entire time service of a com- munity out of gear. Further, it may be said that perhaps there is another way out of the difficulty that has not occurred to the minds of our British colla- borators other than that advocated by Mr. Gisborne, who proposes the use of twisted ail-mctHlHc circuits, an expedient that would cort;iinly bridge the difficulty, and whose only dlsadvaatage consists in the cost. The way the speaker would suggest is one that will involve neither the abandonment of the apparatus tit present in use nor the reconstruction of the circuit ; it has reference soLly to the disposition of the appiratus in the circuit. In order to convey a clear understanding of this idea, v. ill you recall the explanations given in the text books with reference to the origin of the quadruples in telegniphy. It will be remembered the duplex was in existence, the duplex enables us to operate a wire from botlx onds simultaneously — that is a system of double transmission, but the trans- mission is in opposite directions; the problem was to devise a system whereby we should have double transmission in the same direction. At that time, as at present, the open-circuit syiitem of I4«i««' telegraphy was in existence in England, and the closed-circuit system in America. The former is operated by reversals of the transmitting battery, and the Jatter is operated by the introduction and withdrawal of the battery. The idea occurred to two electricians (experimentalists they were, too), Messrs. Edison & Prescott, that these sy;jtems might be combined. That idea was the solution of the problem. Now, it was in a somewhat analogous manner the speaker viewed this telephone difficulty. The apparatus is worked in the one way all the world over ; but if there are not two continents to look to, wo have two departments in the system itself, the Primary and Secondary cir- cuits ; the former 13 operated by the variation of resistance, and the latter is operated by induction. Suppose we combine these two, and arrange the whole so that the induction currents will be neutralized, while the direct current will control the instrument. It seems pro- bable that it can be done. Same time ago the speaker conceived that the receiver and battery might be so disposed in the circuit, that, while cur- rents induced in the circuit from extraneous sources would traverse the receiver in opposite divections, thus producing no effect in it, the latter, having the battery current conducted through it in one direction, would 12 Discussion, oil the Telephone. be responsive to the fluctuations in the current strength occasioaed by viuiationS of resistance in the circuit. But, exacdy how this result is to be secured, cannot be said. The speaker has made a large num- ber of* experiments, the results of which, if not satisfactory as regards the solution of the problem, are yet interesting, in that they throw more light upon the subject, and afford abetter understanding of the actions obtaining in the premises. it would hardly be in order to go into a further explanation of this idea now ; but the experiments in connection with it are nearly com- pleted, and if the matter is considered of sufficient interest, the details may be coinmuuieated to the Society at one of its future meetings. Mr.Thornberry Very little of any thinu' can be added to the very clear explanations and remarks, as given by Mr. Iveeley. A few remarks, respecting the delicate character of the Blake transmitter, may now be made. It is interesting to know jnst how delicate an instrument the Blake transmitter is ; and when it is stated that it is possible ta use but 10 or 15 per cent, of the current supplied by one cell, such as you see on the table, you can comprehend its delicacy. By the expression " use but 10 or 15 per cent, of the current," it is meant that the variation of the contact caused by the voice waves causes a varia- tion of only 1 to 15 per cent, of the current supplied to the instruments. A word might be added in raference to the instrument designated, the Draubaugh. This instrument has been very much improved in the States. The Bell Telcplione Co. has adopted it on its lines between New York and Philadelphia, and between New York, Boston and Albany. When the first experiments were made by the American Bell Telephone Co. witli this transmitter, the speaker was connected with that company^ and has frequently whispered between New York and Boston. The line between Boston and New York is about 300 miles long, and cost in the neighborhood of $30,000. Conversation is now carried on between Boston and Philadelphia, 350 miles, and the line also goes to Albany. Perhaps a few remarks in reference to the underground question may not be out of place. An expression very frequently heard io to the effect that " the telephone wires are a nuisance and should go under ground."' The remarks Mr. Keelcy read in his paper when he said, telephony is impossible on sub-marine cables, except within 95 to 100 miles, illustrated the difficulty to be contended with in an underground cable ; and th.it is the effect of the charge the cable has a capacity for. The charge referred to of is the capacity of the metal of the conductor^ and the metal surrounding the cable in connection with the earth to Discussion on the Tdei^hone. 13 take on a charge of electricity, which charge opposes the currents sent out • • by the speaker and so retards his fonversntion. This is what n.akes underground work so unsatisfisictoiy . Then the expense is so great that necessarily the rate must be rais<'d. Few would wish for this, espe- cially as the present rate is thought to be too great, while the service is also as good as it can be made. A misapprehension is prevalent respecting tht- way in which a Blake transmitter should be spoken, to and should be corrected. No advantage is gained by talking in a loud tone of voices that only does an injury, and " breaks up the conversatioii '' so that it is misunderst'iod. A full even voice, three or four inches away from the instrument, is the best. In reply to the remarks of Professor Bovey, a humming noise heard in the telephone at night, which is often so loud as to drown at a time all conversation, the spenker stated it to be due to induction caused by the Electric Light. The Electric Light Co. runs its wires regardless of ours. Mr. L. B. McFarlane said: Tliere seems to be a statement made MrMaiauan© in Mr. Gisborne's paper, to the effect that Prof. Thompson had found platinum and copper treated with selenium the best microphonic con- tact for Transmitters. It will be asked, by those not familiar with the telephone business, why this contact is not used in practice. For their information it might be explained that platinum and copper so treated will answer fcr a short time only. The Telephone companies are constantly experimenting in this direction, and have found nothing to equal what they now use. In reply to the question that has been asked, with reference Mr. Keeley. to a form of telephone in which the south pole of the magnet is bant round and fixed to the outer edge of the diaphragm, it may bo said that the object of that arrangement is to strengthen the magnetic field by bringing the north and south poles as nearly as possible toge- ther. The object can harJly be said to be attained, however, as the mass of iron in the diajjhragm is too little to conduct the lines of force. A great many instruments have been constructed in which that feature is found. The Crown telephone has a system of eight magnets, each with its south pole in contact with the outer edge of the diaphragm, and all of the north poles directed towards its centre. In the Gisborne- Keoley instrument (Fig. 8), there are four magnets on each side of the diaphragm similaily disposed. The speaker has handled a good many instruments with and without this feature. In some forms the magnet is arranged in that way for convmienoo. or for neatness in design ; bi'yond that it has no advantage. llt.Uannaford, Mr. Kecley. 14 Discussion on the Telephone. Mr. Hannaford next ixMjULstcd Mr. Kcclcy to describe the appa- ratus. Two or three years azo au impression Sjomehow got abroad that the Superintendent vi Government Telegraphs (Mr. Giaborne) wanted to get hold of a telephone that would beat everything of the kind in existence. The result wa3 that a great many inventions were sent or brought to hiui by the inventors or their representatives, and each claimed that his was the best In the world. All inyeutors do that. In the midst of ail .this there Avas a certiiinty, and that was the necessity for a standard for comparison. Mr. Gisborne examir.ed all the instruments that were sent to him. It was the speaker's privi- lege to assist him in his examination and tests. The instruments of the Bell Telephone Company were taken as the standard — the same that you are all familiar with, and which you make use of every day. Here flftj Fic2 Fig5 they are — the Blake transmitter (Fig. 1) and the JSell receiver (Fig. 2). These were our standards. Few of the i.istruments tried wore as good, crone were better. There was one form of transmitter, .somewhat different from the Bl:ike, and possessing some good feature* that held our attention. It is this one (Fig. 3), made by the Consoli- dated Tfk'phono Company of Loudon, England. It is a first rate instrument. You observe there is a number of carbon pencils and blocks Fic.4 Tie S here (Fig. 4, plan of microphone of in.strumont shewn in Fig. 3), urranged radially liko the spokes of a wheel , the hub Gxed to the centre Discussion on the Telephone. 15 of a mica diaphragm (d). Half of the mumbar of blocks (h) are fixed to a semi-eixcle of metal, E, on one side, and the other half similarly fixed on the other side of the annular space (a) back of the diaphragm. This device seems to have originated with Dr. Herz, of "V ienna, and was independently inventec' by Mr. Crossky, in Scotland. It is a form of instrument used very extensively in England and France. (They have a mouth-piece on it there ; this open-faced diaphragm is an improvement, suggested to the makers of the instrument by Mr. Gis- borne.) It seems that the Bell Telephone Company's patents cover this instrument, and it may be interesting to shcv how it compares with the Blake transmitter, in order that you may conceive why it is not made use of in this country. In this Blake transmitter (Fig. 1) the microphone (Fig. 5, plan of microphone of instrummt shown in Fig. 1) consists in a carbon button (c) and a platinum point (j)) ; that is what is called a single contact. You see these parts are hung In a very pretty piece of mechanism ; a wonderfully nice system of springs, whose appearance alone clearly proclaims the scientific construction of the instrument. By means of these springs (s, s', s",) the adjustment o^ this transmitter is practically unlimited ; it can be made extremely sensitive, and the reverse. In practice, as you are all aware, it is so adjusted that it is possible to communicate through it in ordinary conver- tional tones. Now, look at this English instrument. The mieiophone consists in these pencils and blocks of carbon (Fig. 4) ; this is called multiple contact. You perceive there is nothing adjustable about this ; it is put together, once and for all; su that what is true of almost everything else made in England is true of this transmitter, — it is substantial and reliable. Comparing the two, thercfo;.", one would iiardly expect to find this one so sensitive as the Blake — and it is not so. Consequently, when we approach a Blake transmitter, we are disposed to say, in a tone as low as possible: "Do you hear me now?" Wherfias wore we using this multiple contact microphone we would in a louder tone entjuire: ^' Are yon there — / — ! ■ " However, this laktcr instrument has one great advantage : it is possible to talk loudly into it with perfect success, the louder the better ; and sometimes it is a great satisfaction to a man to talk loud. This cannot be done with the Blaks as ordinarily adjusted ; it. must be spoken to quietly, naturally, and without effort at precise utterance. For this reason it is preeminently fitted for the field it occupies. If you want to put up a telephone out in the country far beyond the reach of the experts who adjust the Blake instruments lor exchange work, and far away from people iuquainied with apparatus of this kind, then send the English style of instrameut. Mr. Gisborne sent a pair of them out to the North-Wcst, J 6 Diacu8»ion on the Telephone. •durin- the trouble there in 1885 ; they were put up and operated by parties who had never handled such appaiatus before. On the other Uhand, if you wanted connections in town or in any place where if required the apparatus could be adjusted, it would be better to put in the Blake. The peculiarity of the Blake transmitter is that you cannot operate it successfully with more than a single cell of battery. In these transmitters you know the arrangement consists of an induction .coil (I Fic' (i), the primary wire (p) of which is in circuit with a battery ^i' as low ns possible. It is princi^,iilly to secure a low internal resistance thut the single cells ofLe (Jlaneho used with the telephone apparatus are so large. The internal resistance is increased as the size of the plates and volume of fluid is decreased. In reply to Mr. McFarlane's romaiks, coneorningMie u^". of electrodes composed of selenium and copper, it may be that he is r* ht as to the failure of the ccmibination to act fur any considerable period ; thesf 'akor had no knowledge '^f the coniposition in question and was not aware that it had ever been used excepting in an experimental way. It will be noticed that in Mr. Gisborne'y paper refercacci is made only to the rnultof experiments made by Prof. Tiiompson. Besides, Mr. Gisborno reuiirks thut the combination req-* '.res a greater initirl pressure than requi- red in the carbon microphones. From this it a ay be inferred that it is not so sensitive as the latter, and in that case it would i^eed to bespoken to loudly. The member who enquired as to whether the coldness of those nights liud any eficct on telephones a.ust have misunderstood his i iformant as to the kind of telephone referred to. The buzzing sound heard in the electric telephone is due to induction from the electric light wires. Tt is probable reference was had to an acoustic telephone ; it is not unlikely that effects would bo produced ou it on a cold nigiit that would not be produced on any other night, for the reason that the wire, already tightly strung and under tension, would be contracted by the frost, and be thereby subject to such a high tension that the least thing would vibrate it. As electric currents produce heat, it is not at all impossible that currents induced from neighboring electric light wires would obtiin in this tightly strung wire, and each pulsation would in a minute degree vary the temperature of the wire; a constant repe- tition of this effect would vei'y soon create a vibration in the wire, unat would produce in tlie aeaustif telephone precisely the same sounds we get in the electric telephone from the same prip>\ry sourej. With reference to Mr. Thoruberry's remarks relative to the operation of the metallic circuit between Boston ahd New York, it niijrht perhaps be explained how it is that the instruments on such a circuit arc not affected in any way by induction from neighb jriag wires. &uppo80 m A 6 c Discussion on the Telephone. FlO II this line (A, Fig. 11) is a telegraph wire, with an intermittent current traversing it in the direction of the plain arrow, and this other line (B), below, is a telephone wire, it is known Ihat currents flowing in one direction induce currents in the onposite direction ; so there is an induced current in this telephone wire, in the direction of the t I I \ ♦ tl t i feathered arrow. Suppose this third line (C) is another telephone wire ; in it an iaduced current from the telegraph wire is also set up in the direction of the feathered arrow. Suppose now these two telephone wires are connected into one round circuit through the telephones (T and T,' Fig. 12), at either end of the line. Is it not quite evident that the current induced in the wires will he opposed in the instruments, and will mutually neutralize each other ? Now, that is just what does occur ; hence the telegraph current doos not affect the telephone at all. But a current sent out from the transmitter at one end will circulate round in one direc- tion (plain arrows) in the circuit, and the ** receiver at the other end will respond to it. lu If it were not for the expense and inconve- nience of the thing, the metallic circuit, and Mr. Ginborne's twisted mctiiUic circuit in particular, might be considered as the solution of all telephone difficulties. Electricians are however looking for other means for getting rid of the trouble. The speaker has idrendj? stated what his own idea is in this connection ; and as so much attention is now being given to the matter in iiU quarters, no doubt there .vill be sonic furtlier interesting developments before long. N