,transcriber's ,note3 ,italics are enclosed in underscores4 ,additional notes will be found near the end of this ebook4 ,,the ,,telephone1 ,,microphone1 ,,phonograph ,,the ,,telephone ,,the ,,microphone ,,the ,,phonograph ,,by ,,count ,,du ,,moncel ,,membre ,,de ,l',,institut ,,authorised ,,translation ,,with ,,additions ,,and ,,corrections ,,by ,,the ,,author ,,with #gj ,,illustrations ,,on ,,wood ,,fourth ,,edition ,,london ,,kegan ,,paul1 ,,trench1 ,,tr,,bner1 ,,co4 ,,ltd4 ,,paternoster ,,house1 ,,charing ,,cross ,,road #ahib 7,the rights of translation and of reproduction are reserved7 ,,contents4 ,,page ,history of the telephone #a ,,musical ,,telephones4 ,reiss's telephone #aa ,wray's telephone #ae ,electric harmonica #ah ,gray's telephone #ba ,pollard and ,garnier's singing condenser #bf ,,speaking ,,telephones4 ,string telephones #ca ,bell's electric telephone #ce ,gray's share in invention of telephone #fb ,,fundamental ,,principles ,,of ,,bell ,,telephone4 ,explanation of principles #fg ,,ordinary ,,arrangement ,,of ,,bell ,,telephone4 ,description and illustrations #ga ,,battery ,,telephones4 ,edison's telephone #hc ,edison's chemical telephone #ij ,navez' telephone #ic ,pollard and ,garnier's telephone #ig ,hellesen's telephone #ajj ,thomson and ,houston's telephone #aja ,telephones with liquid senders #ajc ,telephones with voltaic arcs #ajg ,mercury telephones #aaj ,friction telephones #aac ,,modification ,,of ,,bell ,,telephones4 ,telephones with several diaphragms #aad ,gray's system #aah ,phelps's system #aah ,cox ,walker's system #aba ,trouv's system #aba ,demoget's system #abd ,mac ,tighe's system #abe ,modifications of telephonic organs #abe ,righi's system #abf ,ader's system #abi ,jorgenson's system #aca ,,experiments ,,with ,,the ,,telephone4 ,on the effects of voltaic and induced currents #acb ,on the effects of different telephonic organs #aci ,edison's experiments #adj ,canestrelli's experiments #adb ,hughes's and ,roy's experiments #adc ,brguet's experiments #adi ,luvini's experiments #adi ,warwick's experiments #aea ,experiments on the effects of mechanical shocks #aed ,des ,portes' experiments #aed ,thompson's experiments #aeh ,theory of telephone #aei ,nature of vibrations #afj ,action of diaphragm #afc ,action of magnet #afg ,action of currents #afi ,wiesendanger's thermophone #aga ,,other ,,experiments ,,with ,,the ,,telephone4 ,d',arsonval's experiments #agc ,eick's experiments #age ,demoget's experiments #agf ,sensitiveness of telephone #agi ,hellesen's experiments #ahj ,zetsche's experiments #aha ,,the ,,microphone4 ,history of microphone #ahb ,different systems #ahg ,hughes's microphone #ahh ,gaiffe's system #aij ,carette's system #aia ,ducretet's system #aib ,ducretet's speaker #aic ,boudet's speaker #aie ,gaiffe's thermoscope #aig ,blyth's system #aii ,microphone as a speaking instrument #bjj ,hughes's system #bjc ,other arrangements of microphones #bje ,varcy's and ,trouv's microphones #bjg ,lippens's microphone #bji ,hughes's experiments #baa ,hughes's theory #bae ,microphone used as thermoscope #bag ,edison's thermoscope #bai ,experiments in ,london #bbj ,experiment at ,bellinzona #bbc ,,applications ,,of ,,microphone4 ,its application to scientific research #bbf ,application to telephonic relays #bbi ,application to surgery #bcb ,various applications #bcf ,,external ,,influence ,,on ,,telephonic ,,transmissions4 ,disturbing influences #bci ,confusion of circuits #bda ,induced reactions #bdc ,mr4 ,preece's suggestions #bde ,effects of heat and moisture #bdi ,,establishment ,,of ,,telephone ,,station4 ,pollard and ,garnier's system #beb ,brguet and ,roosevelt's system #bed ,edison's system #beg ,,call-,,bells ,,and ,,alarums4 ,weinhold's system #bfb ,dutertre and ,gouault's system #bfd ,puluj's system #bff ,chiddey's system #bfg ,,applications ,,of ,,telephone4 ,its application to simultaneous transmissions #bgj ,bell's system #bgc ,lacour's system #bgf ,gray's system #bhb ,,various ,,uses ,,of ,,the ,,telephone4 ,its use in offices #bic ,its use in telegraphic service #bid ,its application to military purposes #big ,its application to industry #cjb ,its application to scientific research #cjc ,,the ,,phonograph4 ,edison's patent #cji ,description of phonograph #cac ,several systems #cbb ,theory of phonograph #cbg ,,uses ,,of ,,phonograph4 ,account by ,edison #ccc ,lainbrigot's system #cci ,,faber',s ,,speaking ,,machine #cda ,,appendix4 ,perrodon's system of telephonic alarum #cea ,varey's microphone speaker #ceb ,fitch's microphone speaker #cec ,theory of telephone #cec ,pollard's microphone #cef ,ader's electrophone #ceg ,gower's new telephone #ceh ,transmission of speech by telephones without diaphragm #cfj ,,the ,,telephone1 c4 ,,history ,,of ,,the ,,telephone4 ,strictly speaking1 the telephone is merely an instrument adapted for the transmission of sound to a distance1 and this idea of transmitting sound is as old as the world itself4 ,the ,greeks made use of means which might effect it1 and there is no doubt that these means were sometimes used for the pagan oracles4 ,but such transmission of sound was within somewhat narrow limits1 and certainly did not exceed those of a speaking-tube4 ,mr4 ,preece considers that the earliest document in which this transmission of sound to a distance is distinctly formulated1 dates from #affg3 he refers to a paper by one ,robert ,hooke1 who writes to this effect3 #8,it is not impossible to hear a whisper at a furlong's distance1 it having been already done2 and perhaps the nature of the thing would not make it more impossible1 though that furlong should be ten times multiply'd4 ,and though some famous authors have affirm'd it impossible to hear through the thinnest plate of ,muscovy glass2 yet ,i know a way1 by which 'tis easie enough to hear one speak through a wall a yard thick4 ,it has not yet been thoroughly examin'd how far otacousticons may be improv'd1 nor what other wayes there may be of quickning our hearing1 or conveying sound through other bodies than the air2 for that is not the only medium ,i can assure the reader1 that ,i have1 by the help of a distended wire1 propagated the sound to a very considerable distance in an instant1 or with as seemingly quick a motion as that of light1 at least incomparably quicker than that which at the same time was propagated through the air2 and this not only in a straight line or direct1 but in one bended in many angles4' ,this plan for the transmission of sound is the principle of the string telephones which have attracted attention for some years1 and it remained in the stage of simple experiment until #ahai1 when ,sir ,charles ,wheatstone applied it to his magic lyre4 ,in this instrument1 sounds were transmitted through a long strip of deal1 with one end in connection with a sounding board3 one step more led to the use of the membrane employed in string telephones4 ,it would be difficult to say with whom this idea originated1 since it is claimed1 as if beyond dispute1 by several telephone-makers4 ,if we may believe some travellers1 it has long been used in ,spain for the correspondence of lovers4 ,however this may be1 it was not to be found among the scientific appliances of some years ago1 and it was even supposed by many persons that the cord consisted of an acoustic tube of slender diameter4 ,although the instrument has become a child's toy1 it has great scientific importance1 for it proves that vibrations capable of reproducing speech may be extremely minute1 since they can be mechanically transmitted more than a hundred yards4 ,from the telegraphic point of view1 however1 the problem of transmitting sounds to a distance was far from being solved in this way1 and the idea of applying electricity to this mode of transmission naturally arose as soon as the wonderful effects of electric telegraphy were observed1 that is1 in the years subsequent to #ahci4 ,a surprising discovery made in ,america by ,mr4 ,page1 in #ahcg1 and afterwards investigated by ,,mm4 ,wertheim1 ,de la ,rive1 and others1 must also have led up to it3 for it was observed that a magnetic bar could emit sounds when rapidly magnetised and demagnetised1 and these sounds corresponded with the number of currents which produced them4 ,again1 the electric vibrators devised by ,,mm4 ,macaulay1 ,wagner1 ,neef1 etc41 and adapted to produce musical sounds1 between #ahdg-aheb1 by ,,mm4 ,froment and ,ptrina1 showed that the problem of transmitting sounds to a distance was not insoluble4 ,yet1 up to #ahed1 no one had ventured to admit the possibility of transmitting speech by electricity1 and when ,m4 ,charles ,bourseul published in that year a paper on the electric transmission of speech1 the idea was regarded as a fanciful dream4 ,i confess that ,i myself thought it incredible1 and when ,i produced the paper in the first edition of my account of the applications of electricity1 published in #ahed1 ,i felt bound to add that the scheme seemed more than doubtful4 ,yet1 as the paper was thoughtfully written1 ,i had no hesitation in publishing it1 affixing the signature of ,,ch4 ,b4 ,events justified this daring idea1 and although it did not include the only principle which could lead to the reproduction of articulate sounds1 yet it was the germ of the fertile invention which has made the names of ,graham ,bell and ,elisha ,gray famous4 ,for this reason ,i will again quote ,m4 ,charles ,bourseul's paper4 #8,after the telegraphic marvels which can reproduce at a distance hand-writings1 or even more or less complicated drawings1 it may appear impossible to penetrate further into the region of the marvellous4 ,yet we will try to advance a few steps further4 ,i have1 for example1 asked myself whether speech itself may not be transmitted by electricity--in a word1 if what is spoken in ,vienna may not be heard in ,paris4 ,the thing is practicable in this way3-- #8,we know that sounds are made by vibrations1 and are adapted to the ear by the same vibrations which are reproduced by the intervening medium4 ,but the intensity of the vibrations diminishes very rapidly with the distance3 so that it is1 even with the aid of speaking-tubes and trumpets1 impossible to exceed somewhat narrow limits4 ,suppose that a man speaks near a moveable disk1 sufficiently flexible to lose none of the vibrations of the voice1 that this disk alternately makes and breaks the currents from a battery3 you may have at a distance another disk1 which will simultaneously execute the same vibrations4 #8,it is true that the intensity of the sounds produced will be variable at the point of departure1 at which the disk vibrates by means of the voice1 and constant at the point of arrival1 where it vibrates by means of electricity2 but it has been shown that this does not change the sounds4 ,it is1 moreover1 evident that the sounds will be reproduced at the same pitch4 #8,the present state of acoustic science does not permit us to declare priori if this will be precisely the case with syllables uttered by the human voice4 ,the mode in which these syllables are produced has not yet been sufficiently investigated4 ,it is true that we know that some are uttered by the teeth1 others by the lips1 and so on2 but this is all4 #8,however this may be1 observe that the syllables can only reproduce upon the sense of hearing the vibrations of the intervening medium3 reproduce precisely these vibrations1 and you will reproduce precisely these syllables4 #8,it is1 at all events1 impossible in the present condition of science to prove the impossibility of transmitting sound by electricity4 ,everything tends to show1 on the contrary1 that there is such a possibility4 ,when the application of electro-magnetism to the transmission of messages was first discussed1 a man of great scientific attainments treated the idea as utopian1 and yet there is now direct communication between ,london and ,vienna by means of a simple wire4 ,men declared it to be impossible1 but so it is4 #8,it need not be said that numerous applications of the highest importance will immediately arise from the transmission of speech by electricity4 ,any one who is not deaf and dumb may use this mode of transmission1 which would require no apparatus1 except an electric battery1 two vibrating disks1 and a wire4 ,in many cases1 as for example in large establishments1 orders might be transmitted in this way1 although transmission by electricity will not be used while it is necessary to go from letter to letter1 and to make use of telegraphs which require use and apprenticeship4 ,however this may be1 it is certain that in a more or less distant future1 speech will be transmitted by electricity4 ,i have made some experiments in this direction3 they are delicate1 and demand time and patience1 but the approximations obtained promise a favourable result4' ,this description is certainly not full enough to enable us to discern from it the arrangement which would lead to the solution of the problem1 and if the vibrations of the disk at the receiving station were to follow from making and breaking the current at the sending-station1 under the influence of vibrations caused by the voice1 they would only produce musical1 and not articulate sounds4 ,yet the idea was magnificent1 as ,mr4 ,preece said1 even when he thought it impossible to realise it4 ,besides1 it is easy to see that ,m4 ,bourseul himself was not deceived as to the difficulties of the problem1 as far as articulate sounds are concerned1 for he points out1 as we have seen1 the difference existing between the simple vibrations which produce musical sounds1 and the complex vibrations which cause articulate sounds2 but1 as he justly said3 #8,reproduce at the one end of the line the vibrations of air caused at the other1 and speech will be transmitted1 however complex the mechanism may be by which it is effected4' ,we shall presently see how the problem was solved1 and it is probable that some attempts had already enabled ,m4 ,bourseul to anticipate the solution of the question2 but there is nothing in his paper to show what were the means he proposed1 so that the discovery of the electric transmission of speech cannot reasonably be ascribed to him1 and we do not understand why we should be reproached for having at that time failed to appreciate the importance of a discovery which seemed to be then only within the range of fancy4 ,it was not until #ahgf that the problem of the electric transmission of speech was finally solved1 and the discovery has lately given rise to an interesting controversy as to priority between ,mr4 ,elisha ,gray1 of ,chicago1 and ,mr4 ,graham ,bell1 on which we must say a few words4 ,as early as #ahgd ,mr4 ,elisha ,gray was occupied with a system of musical telephone1 which he wished to apply to manifold telegraphic transmissions1 and the investigations which he made1 in order to establish this system under the best possible conditions1 gave him a glimpse of the possibility of transmitting articulate words by electricity4 ,while carrying on his experiments on the telegraphic system1 he arranged in fact1 about the #aeth ,january1 #ahgf1 a system of speaking telephone1 and he deposited the specification and drawings in the ,american ,patent ,office1 in the form of a caveat or provisional specification4 ,the deposit was made on the #adth ,february1 #ahgf3 on the very same day1 ,mr4 ,graham ,bell also deposited1 in the ,american ,patent ,office1 a request for a patent in which he spoke of an instrument of the same kind1 but with special application to simultaneous telegraphic transmissions by means of a telephonic apparatus2 and the few words which could1 in this specification1 refer to a telephone with articulate sounds1 applied to an instrument which1 by ,mr4 ,bell's own admission1 had not produced any satisfactory results4 ,in ,mr4 ,gray's caveat1 on the contrary1 the application of the instrument to the electric transmission of speech alone is indicated1 the description of the system is complete1 and the drawings which accompany it are so exact1 that a telephone made from them would work perfectly3 this was proved by ,mr4 ,gray himself1 when1 some time afterwards1 he finished his instruments1 which differed in no respect from the one described in ,mr4 ,bell's statement as worked by a battery4 ,on these grounds ,mr4 ,elisha ,gray would certainly have obtained the patent1 if the expiration of his caveat had not been the result of an omission of form in the ,patent ,office1 which1 as we know1 decides the priority of inventions in ,america4 ,an action on the ground of this omission has lately been brought against ,mr4 ,bell1 in the ,supreme ,court of the ,american ,patent ,office1 to set aside the patent granted to him4 ,if ,mr4 ,gray did not appeal before1 it was because he was then wholly occupied with experiments on the system of harmonic telephone1 applied to telegraphic communication1 and he had no time to attend to the matter4 ,however this may be1 ,mr4 ,bell did not begin to give serious attention to the speaking telephone until he had obtained his patent1 and his efforts were soon crowned with success3 a few months later1 he exhibited his speaking telephone at ,philadelphia1 which has from that time attracted so much public attention1 and which1 when perfected in a practical point of view1 reached ,europe in the autumn of #ahgg under the form we know4 ,to complete this summary account of the telephone1 we ought to say that since its success a good many claims of priority have arisen1 as if by enchantment4 ,mr4 ,john ,camack1 of ,english origin1 has among others claimed the invention of the telephone1 not merely relying on the description he gave of the instrument in #ahfe1 but on the drawings he executed2 he even adds1 that if he had not lacked means for its construction1 this would have been the date of the discovery of the telephone4 ,a similar pretension has been put forward by ,mr4 ,dolbear1 a fellow countryman of ,mr4 ,bell1 of whose claim we shall speak presently4 ,signor ,manzetti1 of ,aosta1 says the same thing1 asserting that his telephonic invention was described in several newspapers of #ahfe1 among others in #8,le ,petit ,journal1' of ,paris1 on the #bbnd ,november1 #ahfe2 #8,il ,diritto' at ,rome1 #afth ,july1 #ahfe2 #8,l',echo d',italia1' ,new ,york1 #ith ,august1 #ahfe2 #8,l',italia1' ,florence1 #ajth ,august1 #ahfe2 #8,la ,comuna d',italia1' ,genoa1 #ast ,december1 #ahfe2 #8,la ,verit1' ,novara1 #dth ,january1 #ahff2 #8,il ,commercio1' ,genoa1 #fth ,january1 #ahff4 ,it is true that no description of the system was given1 and that the journals in question only asserted that experiments had been made1 which proved that the practical solution of the problem of transmitting speech by electricity became possible by this system4 ,at any rate ,m4 ,charles ,bourseul must still have the credit of the priority of the idea1 and1 in our opinion1 all claims made after the fact only merit slight consideration4 ,before considering ,bell's telephone1 and the different modifications which have been applied to it1 it seems worth while1 in order to make the reader perfectly familiar with these kinds of instruments1 to study the electro-musical telephones which preceded it1 and especially that of ,m4 ,reiss1 which was made in #ahfj1 and became the starting point of all the others4 ,we shall find that these instruments have very important applications1 and that telegraphy will probably be one day much advanced by their use4 ,,musical ,,telephones4 ,telephone of ,m4 ,reiss4--,this telephone is1 as far as the reproduction of sound is concerned1 based upon ,mr4 ,page's discoveries in #ahcg1 and1 as regards electric transmission1 it is based on the vibrating membrane of which ,mr4 ,l4 ,scott made use in his phonautograph1 in #ahee4 ,this instrument is composed1 like telegraphic systems1 of two distinct parts1 a sender and a receiver1 as represented in fig4 #a4 ,illustration3 ,,fig4 #a4 ,the sender was virtually composed of a sounding box ,k1 having on its upper surface a large circular opening1 across which a membrane was stretched1 and in its centre there was fitted a thin disk of platinum o1 above which a metallic point c was fixed1 and this1 together with the disk1 constituted the contact-breaker4 ,on one face of the sounding-box ,k1 there was a sort of speaking-tube1 for the purpose of collecting the sound1 and directing it to the interior of the box1 in order that it might then react upon the membrane4 ,part of the box ,k is broken away in the plate1 in order that the different parts of which it is made may be seen4 ,the rods a1 c1 which support the platinum point b1 are in metallic contact with a ,morse key t1 placed on the side of the box ,k1 and with an electro-magnet ,a1 which belongs to a telegraphic system1 intended to exchange the signals required to start the action of the two instruments at their respective stations4 ,the receiver consists of a sounding-box ,b1 on which rest two supports d1 d1 bearing an iron rod of the thickness of a knitting needle4 ,an induction coil of insulated wire g is wound round this rod1 and the whole is enclosed by the lid ,d1 which concentrates the sound already increased by the sounding-box3 for this purpose the box is provided with two openings below the coil4 ,the circuit is completed through the primary of this coil by the two terminals #c and #d1 and a ,morse key t is placed at the side of box ,b1 in order to exchange signals4 ,in order to work this system1 the speaking instrument should be placed before the opening ,t1 and this instrument may be a flute1 a violin1 or even the human voice4 ,the vibrations of air occasioned by these instruments cause the telephonic membrane to vibrate in unison1 and the latter1 rapidly moving the platinum disk o to and from the point b1 causes a series of breaks in the current1 which are repeated in the iron wire d d1 and transformed into metallic vibrations1 of which the number is equal to that of the sounds successively produced4 ,according to this mode of action1 the possibility of transmitting sounds with their relative value becomes intelligible3 but it is equally clear that sounds thus transmitted will not have the timbre of those which produce them1 since the timbre is independent of the number of vibrations1 and it must be added that the sounds produced by ,m4 ,reiss's instrument were as shrill as those of a child's penny trumpet1 and by no means attractive4 ,the problem of transmitting musical sounds by electricity was1 however1 really solved1 and it can be said with truth that an air or a melody could be heard at any given distance4 ,the invention of this telephone dates1 as we have seen1 from #ahfj1 and ,professor ,heisler speaks of it in his treatise of technical physics1 published at ,vienna in #ahff2 he even asserts1 in the article which he devotes to the subject1 that although the instrument was still in its infancy1 it was capable of transmitting vocal melodies1 and not merely musical sounds4 ,the system was afterwards perfected by ,m4 ,van der ,weyde1 who1 after reading the account published by ,m4 ,heisler1 sought to make the box of the sender more sonorous1 and to strengthen the sounds produced by the receiver4 ,he writes as follows in the #8,american ,scientific ,journal3' #8,in #ahfh1 ,i caused two telephones to be made1 similar to those ,i have described1 and ,i exhibited them at a meeting of the ,polytechnic ,club of the ,american ,institute4 ,the transmitted sounds were produced at the farthest extremity of the ,cooper ,institute1 quite outside the hall in which the audience sat3 the receiver was placed on a table in the hall itself4 ,the vocal airs were faithfully reproduced1 but the sound was rather weak and nasal4 ,i then tried to improve the instrument1 and ,i first obtained stronger vibrations in the box ,k by causing reverberation from the sides of the box1 by means of hollow partitions4 ,i next intensified the sounds produced by the receiver1 by introducing several iron wires into the coil1 instead of one4 ,these improvements were submitted to the meeting of the ,american ,association for the ,advancement of ,science1 which was held in #ahfi1 and it was considered that the invention contained the germ of a new method of telegraphic transmission which might lead to important results4' ,this opinion was soon afterwards justified by the discoveries of ,bell and ,elisha ,gray4 ,messrs4 ,cecil and ,leonard ,wray's ,telephone4--,this system1 represented in figs4 #b and #c1 is simply an improvement on that of ,m4 ,reiss1 with the object of intensifying the effects produced4 ,the sender is provided with two membranes1 instead of one2 and its receiver1 instead of being formed of a single iron wire covered with a magnetising coil1 is composed of two distinct coils ,h1 ,h 7fig4 #b71 placed in the same straight line1 and within which are two iron rods4 ,these rods are fastened by one of their ends to two copper disks ,a1 ,b2 these disks are maintained in a fixed position by screws ,i1 ,i1 and the two other extremities of the rods1 between the coils1 are opposite each other1 not touching1 but divided by a very small interval4 ,the instrument is set upon a sounding-box1 in which there is a hole ,t in the space corresponding to the interval between the coils3 these coils communicate with four terminals1 which are connected with the electric current in such a way that the adjacent poles of the two rods are of opposite polarity1 thus forming a single magnet1 divided in the centre4 ,it seems that by this arrangement the sound produced becomes much more distinct4 ,illustration3 ,,fig4 #b4 ,illustration3 ,,fig4 #c4 ,the form of the sender also is somewhat different from the one we have previously described3 the upper part1 instead of being horizontal1 is rather inclined1 as it appears in fig4 #c1 and the opening ,e through which the sound has to communicate with the vibrating membrane1 occupies a great part of the upper surface of the box1 which consequently appears to be somewhat oblique4 ,the second membrane ,g1 which is of caoutchouc1 forms a sort of partition which divides the box in two1 starting from the upper end of the opening3 the inventor states that this will protect the outer membrane ,d from the breath and other injurious effects1 while increasing the force of the vibrations produced on the first membrane1 as in a drum4 ,the contact-breaker itself also differs from the one in ,m4 ,reiss's instrument4 ,the platinum disk b is only placed in circuit by means of two slender wires of platinum or steel1 which are immersed in two small cups1 filled with mercury1 and connected with the circuit4 ,in this way1 the movements of the membrane ,d are free1 and its vibration is rendered more easy4 ,the circuit is also broken by a little platinum point resting on a lever with a spring-joint1 ,k ,h1 which is above the disk3 one end of the lever1 which is fixed below a kind of ,morse key ,m ,i1 makes it possible to close the circuit with the hand1 so as to give the signal for setting the apparatus to work4 ,electric ,harmonica4--,long before ,m4 ,reiss's invention1 and consequently still longer before that of ,mr4 ,elisha ,gray1 ,i mentioned a sort of electric harmonica1 and described it as follows in the first edition of my #8,expos des applications de l',electricit1' published in #ahec3-- #8,the power possessed by electricity to set metallic plates in motion and cause their vibration has been used for the production of distinct sounds1 which can be combined and harmonised2 but in addition to this purely physical application1 electro-magnetism has come to the aid of certain instruments1 such as pianos1 organs1 c41 rendering them capable of being played at a distance4 ,so that this extraordinary force may be turned to account in arts which are apparently the least susceptible of any application of electricity4 #8,we have already spoken of ,m4 de la ,rive's contact-breaker4 ,it is1 as we know1 an iron disk1 soldered to a steel spring1 and maintained in a fixed position opposite to an electro-magnet by another spring in connection with one branch of the current4 ,as the other branch1 after passing into the wire of the electro-magnet1 terminates in the iron disk itself1 the electro-magnet is only active at the moment when the disk touches the terminal spring2 at the moment of leaving it1 the magnetism ceases1 and the iron disk returns to its normal position1 and then leaves it again4 ,in this way a vibration is produced1 rapid in proportion to the small size of the vibrating disk1 and to the greatness of the force produced by the approach of the disk to the electro-magnet4 #8,in order to increase the acuteness of the sounds1 one or other of these expedients must be employed4 ,the simplest way is to use a screw which can be tightened or relaxed at pleasure1 and which in this manner removes the vibrating disk to a greater or less distance from the electro-magnet4 ,this is the case in ,m4 ,froment's instrument1 and by this means he has obtained sounds of extraordinary acuteness1 although not unpleasant to the ear4 #8,m4 ,froment has not applied the apparatus to a musical instrument1 but it is evident that it would be easy to do so2 it would only be necessary to make the notes of a key-board act on metallic levers1 of a length corresponding to the position required by the disk for the vibration of different tones4 ,these different levers1 resting on the disk1 would act as a point of contact1 but the point would vary in position1 according to the touch4 #8,if the current were constant1 such an instrument would certainly have many advantages over the pipe instruments which are in use1 since the vibration might be prolonged at will in the case of each note1 and the sounds would be softer2 unfortunately the irregular action of the battery makes it difficult in practice4 ,these kinds of instruments are therefore only used as a means of regulating by ear the force of the battery1 a much more convenient regulator than the rheometers1 since it is possible to estimate by them the variations of the battery during an experiment without any distraction of the mind4' ,in #ahef ,m4 ,ptrina1 of ,prague1 invented an analogous arrangement1 to which he gave the name of electric harmonica1 although1 strictly speaking1 he had not thought of it as a musical instrument4 ,this is what ,i have said on the subject in vol4 iv4 of the second edition of my #8,expos des applications de l',electricit1' published in #ahei3-- #8,the principle of this instrument is similar to that of ,neef's rheotome1 in which the hammer is replaced by slender rods1 whose vibrations produce a sound4 ,four of these rods are placed side by side1 and when moved by keys1 and arrested by levers1 produce combined sounds of which the origin may be easily shown4' ,it is true that nothing is said in this passage of the capability possessed by these instruments of being played at a distance2 but this idea was quite legitimate1 and ,german periodicals assert that it was accomplished by ,m4 ,ptrina even before #ahef4 ,it was the result of what ,i said at the outset3 #8that electro-magnetism may come to the aid of certain instruments1 such as pianos1 organs1 c41 in order to enable them to be played at a distance1' and ,i also pointed out the expedients employed for the purpose1 and even for setting them at work1 under the influence of a small musical box4 ,i did not1 however1 ascribe importance to the matter1 and it is only by way of historical illustration that ,i speak of these systems4 ,telephone by ,mr4 ,elisha ,gray1 of ,chicago4--,this system1 invented in #ahgd1 is in reality only an instrument of the nature of those which preceded it1 but with important modifications1 which made it possible to apply it usefully to telegraphy4 ,in an early model1 he made use of an induction coil1 with two helices1 one over the other3 the contact-breaker1 which was vibrating1 was multiple1 and so arranged as to produce vibrations numerous enough to emit sounds4 ,these sounds may1 as we have seen1 be modified by this arrangement1 according to the mode in which the instrument is adjusted1 and if there are a certain number of such contact-breakers side by side1 with vibrating disks so ordered as to produce the different notes of the scale on several octaves1 it becomes possible1 by a combination of certain notes1 to execute on this new kind of instrument a piece of music such as may be produced by an harmonium1 an accordion1 or any other instrument with blowers4 ,the contact-breakers are set in motion by means of the primary current of the induction coil1 as it circulates through one or other of the electro-magnets of these contact-breakers1 actuated by the lowering of the notes of a key-board connected with them1 and the secondary currents which arise in the coil1 in consequence of the interruptions in the primary currents1 transmit the corresponding vibrations to a remote receiver4 ,there is an analogy between this instrument and the telephones of which we have already spoken by ,reiss and ,wray1 but the effect is increased by ,mr4 ,gray's modifications4 ,we represent in fig4 #d the arrangement of the first system4 ,the vibrators are ,a and ,a1 the key-board ,m and ,m1 the induction coil ,b1 and the receiver ,c4 ,this receiver consists1 as we see1 of a simple electro-magnet ,n ,n3 above its poles there is a metal cylindrical case ,c1 of which the bottom is made of iron1 to serve as an armature4 ,this box1 like a violin1 is pierced with two holes in the form ,s1 to serve as a sounding-board2 and ,mr4 ,elisha ,gray has ascertained that the molecular motion which takes place in the magnetic core and its armature1 under the influence of alternate magnetisation and demagnetisation1 sufficed to produce vibrations corresponding to the velocity of these alternations1 and to emit sounds which became audible when they were magnified by the sounding-board4 ,illustration3 ,,fig4 #d4 ,it is quite intelligible that the effect obtained in this system might be reproduced1 if1 instead of contact-breakers or electric rheotomes1 mechanical contact-breakers were used at the sending station1 so arranged as to furnish the requisite number of breaks in the current which communicates the vibrations of the different notes of the scale4 ,in this way also it would be possible to dispense with the induction coil1 by causing the current which has been broken by the mechanical contact-breaker to react upon the receiver4 ,mr4 ,elisha ,gray has moreover made a different arrangement of this telephonic system1 which he has applied to telegraphy for simultaneous electric transmissions1 of which we shall speak presently4 ,if we may believe ,mr4 ,elisha ,gray1 the vibrations transmitted by the secondary currents would be capable1 by the intervention of the human body1 of causing the sounds to be reproduced at a distance by conducting disks1 which vibrate readily1 and are placed on a sounding-box4 ,in this way musical sounds may be evoked from copper cylinders placed upon a table1 from a metallic disk fastened to a kind of violin1 from a membrane stretched on a drum1 or from any other resonant substance1 by touching any of these objects with one hand1 while holding the end of the line with the other4 ,these sounds1 of which the quality must vary with the substance touched1 would reproduce the transmitted note with the precise number of vibrations which belong to it4#a ,mr4 ,varley's ,telephone4--,this is1 strictly speaking1 merely a musical telephone of the same kind as that of ,mr4 ,gray1 but the arrangement of the receiver is original and interesting4 ,this part of the instrument essentially consists of a drum of large size 7three or four feet in diameter71 within which is a condenser formed of four sheets of tinfoil1 divided by sheets of some insulating material1 and with a surface of about half the size of the drum4 ,the plates of the condenser are placed parallel to the membranes of the drum1 and very little removed from its surface4 ,if an electric charge is communicated to one of the series of conducting plates of the condenser1 those which correspond to it are attracted1 and if they were movable they might communicate to the intervening strata of air a movement which1 on reaching the membranes of the drum1 might1 by a series of charges in rapid succession1 cause the membranes to vibrate1 and thus produce sounds3 these sounds would correspond to the number of charges and discharges which had occurred4 ,since these charges and discharges are determined by the contact of the two plates of the condenser1 at the extremities of the secondary circuit of an induction coil1 of which the primary circuit has been duly broken1 it becomes evident that1 in order to cause the drum to emit any given sound1 it will be enough to produce the number of vibrations in the contact-breaker of the induction coil which are required for this sound4 ,the means employed by ,mr4 ,varley to produce these interruptions are the same which are in use in several electrical instruments1 and especially in chronographs--an electro-magnetic tuning-fork1 regulated so as to emit the sound required4 ,this tuning-fork may1 by acting as contact-breaker1 react on the primary current of the induction coil2 if the number of the tuning-forks equals that of the musical notes which are to be transmitted1 and if the electro-magnets which set them in motion are connected with the key-board of a piano1 it would be possible to transmit a melody to a distance by this system1 as well as by that of ,mr4 ,elisha ,gray4 ,the peculiarity of this system consists in the reproduction of sounds by the action of a condenser1 and we shall presently see that this idea1 adopted by ,messrs4 ,pollard and ,gamier1 led to interesting results4 ,singing ,condenser of ,,mm4 ,pollard and ,garnier4--,this instrument1 which astonishes all who hear it1 attracted public attention in ,london some time ago4 ,it is difficult to say why its fame was not greater1 since much attention has been bestowed on less curious instruments4 ,it is a fact that we have been able1 thanks to ,,mm4 ,pollard and ,garnier1 to hear songs issue from a sort of copy-book1 so as to become audible throughout the room4 ,the songs thus reproduced are certainly not always perfectly true2 yet when the person who sings into the sender is a musician1 and understands how to make use of it1 the condenser in question will emit sounds somewhat resembling those of the violoncello or the hautbois4 ,the singing instrument consists of a condenser ,k1 formed of thirty sheets of paper1 laid one over the other1 from nine to thirteen centimtres in thickness3 between these1 twenty-eight sheets of tinfoil1 from six to twelve centimtres thick1 are intercalated1 so joined as to form the two plates of the condenser4 ,for this purpose the pair sheets are joined together at one end of the copy-book1 and the odd sheets at the other end4 ,this system is fastened to a stiff carton1 after taking care to bind it with a strip of paper1 and the sheets of tinfoil are joined to the two ends of the condenser by two copper rims ,d1 ,d1 which are provided with terminals for the circuit wire1 and in this way the singing instrument is constructed4 ,a somewhat heavy weight1 placed upon the condenser to compress the sheets1 does not in any way prevent it from working2 and this vitiates the theory first put forward to explain its effects1 that the sheets were moved by attraction4 ,illustration3 ,,fig4 #e4 ,the sending instrument consists of a sort of telephone without a handle1 ,e1 of which the vibrating disk is formed of a very thin plate of tin4 ,a cylindrical piece of carbon ,c is fastened to its centre1 and is supported by another cylinder of the same material ,h4 ,this rests on a transverse piece of wood ,a ,b1 jointed on the side ,a1 on the edge opposite to the box1 by means of a regulating screw ,v4 ,an arched spring ,r 7the end of a watch spring7 placed across this piece of wood gives it a certain elasticity beneath the pressure1 and this elasticity is necessary in order that the instrument may act properly1 and it thus becomes a sort of microphone with a diaphragm4 ,the tin plate is put into communication with one pole of a battery ,p1 of six ,leclanch cells1 and the lower carbon cylinder ,h corresponds to the primary helix of an induction coil ,m1 previously connected with the second pole of the battery3 ,finally1 the two extremities of the secondary helix of the coil1 a and b1 are in immediate connection with the two plates ,d1 ,d1 of the condenser4 ,this secondary helix should consist of twenty strands of wire ,no4 #cb1 covered with silk1 and the primary helix is made of five strands of wire ,no4 #af4 ,the length of the coil should not exceed seven centimtres and the diameter of the core of fine iron wire ought to be about one centimtre4 ,in order to produce song on the condenser1 the sender must be so regulated that the two carbons ,c and ,h do not touch each other in their normal condition1 but they should be so close that in singing the vibrations of the disk ,l ,l may effect the needful contacts4 ,the adjustment can be easily made by the touch1 and by uttering the same note until it is repeated by the condenser4 ,if three notes1 given in succession1 are faithfully reproduced1 the instrument may be assumed to be properly regulated1 and1 in order to make it work1 it is enough to apply the mouth to the mouthpiece as it is applied to a reed pipe4 ,in order to obtain a satisfactory result1 the disk of the instrument must be heard to vibrate1 as in a flte l'oignon4 ,instead of carbons1 contacts of platinum may be used2 but when arranged as we have described1 the instrument may be employed for several purposes1 as we shall see presently4 ,this instrument is made by ,,mm4 ,chardin and ,prayer4 ,m4 ,janssens has made the system more portable by fastening the sender1 represented in fig4 #e1 to a handle in which the induction coil is placed3 the instrument then resembles an ordinary telephone1 and the vibration of the diaphragm is made more easy by piercing two holes in it4 ,on the side of the sending-box1 above and below the diaphragm1 there are binding screws in connection with the end of the handle1 since the instrument may be used as an ordinary telephonic sender1 and even as a telephonic receiver4 ,,speaking ,,telephones4 ,we have seen that the telephones just described can only transmit musical sounds1 since they can merely repeat simple vibrations1 in greater or less number1 it is true1 but not in simultaneous combinations like those which reproduce articulate sounds4 ,up to the time of ,mr4 ,bell's invention1 the transmission of speech could only take place with the aid of acoustic tubes1 or of the string telephones of which we have spoken4 ,although these instruments have no connection with the object of our study in this work1 we have thought it necessary to say a few words about them1 since they may sometimes be combined with electric telephones1 and also represent the first stage of the invention4 ,string ,telephones4--,these instruments1 which have flooded the cities of ,europe for several years1 since the date of the invention was #ahfg1 are interesting in themselves1 and we are surprised that they have not hitherto taken a place in the collections of physical science4 ,they are made of two metal or cardboard tubes1 in the form of a cylindrical cone3 one end is closed by a tightly stretched membrane of parchment1 in the centre of which the cord or string intended to connect the two cylinders is fastened by a knot4 ,when two such tubes are connected in this way1 and the cord is tightly stretched1 as in fig4 #f1 it is only necessary to apply one tube to the ear1 while another speaks into the opening of the other tube3 the words spoken by the latter are instantly transmitted1 and it is even possible to converse in quite an undertone4 ,under these conditions the vibrations of the membrane affected by the voice are mechanically transmitted to the other membrane by the string1 which1 as ,robert ,hooke declared in #affg1 is a better transmitter of sound than the air4 ,in this way it is possible to communicate at a distance of #agj yards1 and the size and nature of the cord have some influence4 ,the sellers of these instruments say that the best results are obtained from silken cords1 and the worst from those made of hemp4 ,cords of plaited cotton are usually employed for the sake of cheapness4 ,illustration3 ,,fig4 #f4 ,in some patterns1 the tubes are so arranged as to present1 between the membrane and the mouth1 a diaphragm pierced with a hole1 and the instrument somewhat resembles a bell with its base bored and closed again a little above the parchment membrane2 but ,i have not observed that this pattern is decidedly superior to the others4 ,it has also been asserted that horn-shaped tubes of nickel silver are to be preferred1 of which ,i am equally doubtful4 ,at any rate1 these instruments have produced unexpected results2 and although their practical use is very limited1 they are interesting from a scientific point of view1 and are instructive toys for children4 ,mr4 ,millar1 of ,glasgow1 declares that the effect produced by these telephones depends very much on the nature of the string1 the way in which it is attached1 and the way in which the membrane is fastened to the mouthpiece4 ,improvements made in the ,string ,telephone4--,the amazing effects of the ,bell telephones have lately brought the string telephones1 which were only regarded as children's toys1 again into fashion4 ,since they have made it possible to transmit to several persons the words reproduced by an electric telephone1 means have been sought for combining them usefully with the latter1 and the best mode of making them speak on a string presenting several angles has been sought for3 it has been shown that1 under the usual conditions1 these instruments only speak distinctly when the string is stretched in a right line4 ,to solve this problem1 it occurred to ,m4 ,a4 ,brguet to make use of a sort of tambourine for the supports1 with the string passed through their centre2 the sound conveyed by that part of the string which is in connection with the speaking-horn causes the membrane of the tambourine to vibrate1 which again communicates the vibration to the next portion of string4 ,in this way the angles may be multiplied at will1 and the string may be supported throughout the length compatible with this kind of telephone1 which does not exceed #aab yards4 ,m4 ,a4 ,brguet has also invented a system of relays to accomplish the same object4 ,he makes the strings terminate in two membranes which close the two openings of a brass cylinder4 ,the sounds reproduced on one of these membranes react upon the other1 which vibrates under its influence1 as if it were affected by the voice4 ,the cylinder then acts as an ordinary acoustic tube1 and its form may be varied at pleasure4 ,m4 ,a4 ,badet1 on ,february #a1 #ahgh1 succeeded in making string telephones in an analogous way1 and he used parchment stretched upon frames which acted as resonant boards4 ,the string was fixed in the centre of the membrane1 and made with it the angle desired4 ,several scientific men1 among others ,messrs4 ,wheatstone1 ,cornu1 and ,mercadier1 have long been occupied about these ways of transmission by wire1 and ,messrs4 ,millar1 ,heaviside1 and ,nixon have lately made some interesting experiments1 on which we must say a few words4 ,mr4 ,millar ascertained that by means of a telegraphic wire1 stretched and connected by two copper wires with two vibrating disks1 musical sounds might be conveyed to a distance exceeding #afj yards1 and that by stretching these wires through a house1 and connecting them with mouth-and-ear holes in different rooms1 communication between them became perfectly easy4 ,for the vibrating disks he employed wood1 metal1 or gutta-percha1 in the form of a drum1 with wires fixed in the centre4 ,the sound seems to become more intense in proportion to the thickness of the wire4 ,messrs4 ,heaviside and ,nixon1 in their experiments at ,newcastle-on-,tyne1 have ascertained that the most effective wire was ,no4 #d of the ,english gauge4 ,they employed wooden disks inch in thickness1 and these may be placed in any part of the length of the wire4 ,when the wire was well stretched and motionless1 it was possible to hear what was said at a distance of #bcj yards1 and it seems that ,mr4 ,huntley1 by using very thin iron diaphragms1 and by insulating the line wire on glass supports1 was able to transmit speech for #b1dej feet1 in spite of the zigzags made by the line on its supports4 ,mr4 ,graham ,bell's ,electric ,telephone4--,telephonic instruments were at this stage when ,bell's telephone was shown at the ,philadelphia ,exhibition of #ahgf4 ,sir ,william ,thompson did not hesitate to call it #8the wonder of wonders1' and it instantly attracted universal attention1 although there was at first much incredulity as to its genuineness4 ,this telephone1 in fact1 reproduced articulate words1 a result which surpassed all the conceptions of physicists4 ,in this case it was no longer a conception1 to be treated as visionary until there was proof to the contrary3 the instrument spoke1 and even spoke so loudly that it was not necessary to apply the ear4 ,sir ,william ,thompson spoke to this effect on the subject at the meeting of the ,british ,association at ,glasgow in ,september #ahgf3-- #8,in the department of telegraphs in the ,united ,states ,i saw and heard ,mr4 ,elisha ,gray's electric telephone1 of wonderful construction1 which can repeat four despatches at the same time in the ,morse code1 and1 with some improvements in detail1 this instrument is evidently capable of a fourfold delivery4 ,in the ,canadian department ,i heard 8,to be or not to be8 ,there's the rub10 uttered through a telegraphic wire1 and its pronunciation by electricity only made the rallying tone of the monosyllables more emphatic4 ,the wire also repeated some extracts from ,new ,york papers4 ,with my own ears ,i heard all this1 distinctly articulated through the slender circular disk formed by the armature of an electro-magnet4 ,it was my fellow-juryman1 ,professor ,watson1 who1 at the other extremity of the line1 uttered these words in a loud and distinct voice1 while applying his mouth to a tightly stretched membrane provided with a small piece of soft iron1 which executed movements corresponding to the sound vibrations of the air close to an electro-magnet introduced into the circuit4 ,this discovery1 the wonder of wonders in electric telegraphy1 is due to a young fellow-countryman of our own1 ,mr4 ,graham ,bell1 a native of ,edinburgh and now naturalised in ,new ,york4 #8,it is impossible not to admire the daring invention by which we have been able to realise with these simple expedients the complex problem of reproducing by electricity the tones and delicate articulations of voice and speech2 and it was necessary1 in order to obtain this result1 to find out the means of varying the intensity of the current in the same proportion as the inflections of the sound emitted by the voice4' ,if we are to believe ,mr4 ,graham ,bell1 the invention of the telephone was not due to a spontaneous and fortunate conception3 it was the result of his long and patient studies in acoustic science1 and of the labours of the physicists who preceded him4#b ,his father1 ,mr4 ,alexander ,melville ,bell1 of ,edinburgh1 had studied this science deeply1 and had even succeeded in representing with great ingenuity the adaptation of the vocal organs for the emission of sound4 ,it was natural that he should instil a taste for his favourite studies into his son's mind1 and they made together numerous researches in order to discover the relations which exist between the different elements of speech in different languages1 and the musical relations of vowels4 ,it is true that several of these researches had been made by ,m4 ,helmholtz1 and under more favourable conditions2 but these studies were of great use to ,mr4 ,bell when he was afterwards occupied with the telephone1 and ,helmholtz's experiments1 which he repeated with one of his friends1 ,mr4 ,hellis of ,london1 concerning the artificial reproduction of vowels by means of electric tuning-forks1 launched him into the study of the application of electricity to acoustic instruments4 ,he first invented a system of an electric harmonica with a key-board1 in which the different sounds of the scale were reproduced by electric diapasons of different forms1 adapted to different notes1 and which1 when set in motion by the successive lowering of the keys1 could reproduce sounds corresponding to the notes touched1 just as in an ordinary piano4 ,he next1 as he tells us1 turned his attention to telegraphy1 and thought of making the ,morse telegraphs audible by causing the electro-magnetic organ to react on sounding contacts4 ,it is true that this result had already been obtained in the sounders used in telegraphy1 but he thought that by applying this system to his electric harmonica1 and by employing such an intensifying instrument as ,helmholtz's resonator at the receiving station1 it would be possible to obtain through a single wire simultaneous transmissions which should be due to the action of the voice4 ,we shall see presently that this idea was realised almost at the same time by several inventors1 among others by ,m4 ,paul ,lacour1 of ,copenhagen1 ,mr4 ,elisha ,gray1 of ,chicago1 and ,messrs4 ,edison and ,varley4 ,mr4 ,bell's study of electric telephones really dates from this time1 and he passed from complex to simple instruments1 making a careful study of the different modes of vibration which arise from different modes of electric action4 ,the following is an abstract1 with the omission of more technical details1 of the paper read by ,mr4 ,bell to the ,society of ,telegraphic ,engineers1 ,london1 ,october #ca1 #ahgg4 ,if the intensity of an electric current is represented by the ordinates of a curve1 and the duration of breaks in the current by the absciss1 the given curve may represent the waves of the positive or negative current respectively1 above and below the line of ,x1 and these waves will be more or less accentuated1 just as the transmitted currents are more or less instantaneous4 ,if the currents which are interrupted to produce a sound are quite instantaneous in their manifestation1 the curve represents a series of isolated indentations1 as we see in fig4 #g2 and if the interruptions are so made as only to produce differences of intensity1 the curve is presented under the form of fig4 #h4 ,finally1 if the emissions of current are so ordered that their intensity alternately increases and diminishes1 the curve takes the form represented in fig4 #i4 ,in the first case1 the currents are intermittent2 in the second1 pulsatory2 in the third case1 they are undulatory4 ,illustration3 ,,fig4 #g4 ,illustration3 ,,fig4 #h4 ,illustration3 ,,fig4 #i4 ,these currents are necessarily positive or negative1 according to their position above or below the line x1 and if they are alternately reversed1 the curves present the form given in fig4 #aj1 curves which essentially differ from the first1 not merely in the different form of the indentations1 but especially in the suppression of the extra current1 which is always found in the pulsatory and undulatory currents4 ,illustration3 ,,fig4 #aj4 ,the two former systems of currents have long been in use for the electric transmission of musical sounds1 of which we have an interesting example in ,reiss's telephone already described4 ,but ,mr4 ,bell claims to have been the first to employ the undulatory currents1 which made it possible to solve the problem of transmitting speech4#c ,in order to estimate the importance of this discovery1 it will be enough to analyse the effects produced with these different systems of currents when several notes of varying pitch are to be combined4 ,fig4 #g shows a combination in which the styles a1 a1 of two sending instruments cause the interruption of the current from the same battery ,b1 so that the given vibrations should be between them in the relation of a tierce major1 that is in the relation of four to five4 ,under such conditions1 the currents are intermittent1 and four contacts of a are produced in the same space of time as the five contacts of a1 and the corresponding electric intensities will be represented by the indentations we see in ,a#b and in ,b#b3 the combination of these intensities ,a#b ,b#b will produce the indentations at unequal intervals which may be observed on the third line4 ,it is evident that although the current maintains a uniform intensity1 there is less time for the breaks when the interrupting styles act together than when they act separately1 so that when there are a number of contacts effected simultaneously by styles working at different degrees of velocity1 the effects produced will have the effect of a continuous current4 ,the maximum number of distinct effects which can be produced in this way will1 however1 greatly depend on the relation which exists between the durations of the make and break of the current4 ,the shorter the contacts are1 and the longer the breaks1 the more numerous will be the effects transmitted without confusion1 and vice vers4 ,by the aid of pulsatory currents the transmission of musical sounds is effected in the way indicated in fig4 #h1 and it is seen that when they are produced simultaneously1 the result ,a#b ,b#b is analogous to that which would be produced by a continuous current of minimum intensity4 ,in the case of undulatory currents the result is different1 but in order to produce them it is necessary to have recourse to inductive effects1 and fig4 #i indicates the manner in which the experiment should be made4 ,in this case1 #8the current from the battery ,b is thrown into waves by the inductive action of iron or steel reeds ,m1 ,m1 vibrated in front of electro-magnets e1 e1 placed in circuit with the battery3 ,a#b and ,b#b represent the undulations caused in the current by the vibration of the magnetised bodies1 and it will be seen that there are four undulations of ,b#b in the same time as five undulations of ,a#b4 ,the resultant effect upon the main line is expressed by the curve ,a#b ,b#b1 which is the algebraical sum of the sinusoidal curves ,a#b and ,b#b4 ,a similar effect is produced when reversed undulatory currents are employed1 as in fig4 #aj1 where the current is produced by the vibration of permanent magnets united upon a circuit1 without a voltaic battery4 #8,it will be understood from figs4 #i and #aj that the effect of transmitting musical signals of different pitches simultaneously along a single wire is not to obliterate the vibratory character of the current1 as in the case of intermittent and pulsatory currents1 but to change the shapes of the electrical undulations4 ,in fact1 the effect produced upon the current is precisely analogous to the effect produced in the air by the vibration of the inducing bodies ,m1 ,m4 ,hence it should be possible to transmit as many musical tones simultaneously through a telegraph wire as through the air4' ,illustration3 ,,fig4 #aa4 ,after applying these principles to the construction of a telegraphic system for multiple transmissions1 ,mr4 ,bell lost no time in making use of his researches to improve the vocal training of deaf mutes4 #8,it is well known1' he said1 #8that deaf mutes are dumb merely because they are deaf1 and that there is no defect in their vocal organs to incapacitate them from utterance4 ,hence it was thought that my father's system of pictorial symbols1 popularly known as visible speech1 might prove a means whereby we could teach the deaf and dumb to use their vocal organs and to speak4 ,the great success of these experiments urged upon me the advisability of devising methods of exhibiting the vibrations of sound optically1 for use in teaching the deaf and dumb4 ,for some time ,i carried on experiments with the manometric capsule of ,koenig1 and with the phonautograph of ,lon ,scott4 ,the scientific apparatus in the ,institute of ,technology in ,boston was freely placed at my disposal for these experiments1 and it happened that at that time a student of the ,institute of ,technology1 ,mr4 ,maurey1 had invented an improvement upon the phonautograph4 ,he had succeeded in vibrating by the voice a stylus of wood about a foot in length which was attached to the membrane of the phonautograph1 and in this way he had been enabled to obtain enlarged tracings upon a plane surface of smoked glass4 ,with this apparatus ,i succeeded in producing very beautiful tracings of the vibrations of the air for vowel sounds4 ,some of these tracings are shown in fig4 #aa4 ,i was much struck with this improved form of apparatus1 and it occurred to me that there was a remarkable likeness between the manner in which this piece of wood was vibrated by the membrane of the phonautograph and the manner in which the ossicul of the human ear were moved by the tympanic membrane4 ,i determined therefore to construct a phonautograph modelled still more closely upon the mechanism of the human ear1 and for this purpose ,i sought the assistance of a distinguished aurist in ,boston1 ,dr4 ,clarence ,j4 ,blake4 ,he suggested the use of the human ear itself as a phonautograph1 instead of making an artificial imitation of it4 ,the idea was novel1 and struck me accordingly1 and ,i requested my friend to prepare a specimen for me1 which he did4 ,the apparatus1 as finally constructed1 is shown in fig4 #ab4 ,the stapes was removed1 and a stylus of hay about an inch in length was attached to the end of the incus4 ,upon moistening the membrana tympani and the ossicul with a mixture of glycerine and water1 the necessary mobility of the parts was obtained2 and upon singing into the external artificial ear the stylus of hay was thrown into vibration1 and tracings were obtained upon a plane surface of smoked glass passed rapidly underneath4 ,while engaged in these experiments ,i was struck with the remarkable disproportion in weight between the membrane and the bones that were vibrated by it4 ,it occurred to me that if a membrane as thin as tissue paper could control the vibration of bones that were1 compared to it1 of immense size and weight1 why should not a larger and thicker membrane be able to vibrate a piece of iron in front of an electro-magnet1 in which case the complication of steel rods shown in my first form of telephone1 could be done away with1 and a simple piece of iron attached to a membrane be placed at either end of the telegraphic circuit8 ,illustration3 ,,fig4 #ab4 #8,for this purpose ,i attached the reed ,a 7fig4 #ac7 loosely by one extremity to the uncovered pole h of the magnet1 and fastened the other extremity to the centre of a stretched membrane of goldbeaters' skin n4 ,i presumed that upon speaking in the neighbourhood of the membrane n1 it would be thrown into vibration and cause the steel reed ,a to move in a similar manner1 occasioning undulations in the electrical current that would correspond to the changes in the density of the air during the production of the sound2 and ,i further thought that the change of the intensity of the current at the receiving end would cause the magnet there to attract the reed ,a in such a manner that it should copy the motion of the reed ,a1 in which case its movements would occasion a sound from the membrane n similar in timbre to that which had occasioned the original vibration4 ,illustration3 ,,fig4 #ac4 ,illustration3 ,,fig4 #ad4 #8,the results1 however1 were unsatisfactory and discouraging4 ,my friend ,mr4 ,thomas ,a4 ,watson1 who assisted me in this first experiment1 declared that he heard a faint sound proceed from the telephone at his end of the circuit1 but ,i was unable to verify his assertion4 ,after many experiments attended by the same only partially successful results1 ,i determined to reduce the size and weight of the spring as much as possible4 ,for this purpose ,i fastened a piece of clock spring1 about the size and shape of my thumbnail1 firmly to the centre of the diaphragm1 and had a similar instrument at the other end 7fig4 #ad72 we were then enabled to obtain distinctly audible effects4 ,i remember an experiment made with this telephone1 which at the time gave me great satisfaction and delight4 ,one of the telephones was placed in my lecture-room in the ,boston ,university1 and the other in the basement of the adjoining building4 ,one of my students repaired to the distant telephone to observe the effects of articulate speech1 while ,i uttered the sentence1 8,do you understand what ,i say80 into the telephone placed in the lecture-hall4 ,to my delight an answer was returned through the instrument itself1 articulate sounds proceeded from the steel spring attached to the membrane1 and ,i heard the sentence1 8,yes1 ,i understand you perfectly40 ,it is a mistake1 however1 to suppose that the articulation was by any means perfect1 and expectancy no doubt had a great deal to do with my recognition of the sentence2 still1 the articulation was there1 and ,i recognised the fact that the indistinctness was entirely due to the imperfection of the instrument4 ,i will not trouble you by detailing the various stages through which the apparatus passed1 but shall merely say that after a time ,i produced the form of instrument shown in fig4 #ae1 which served very well as a receiving telephone4 ,in this condition my invention was exhibited at the ,centennial ,exhibition in ,philadelphia4 ,the telephone shown in fig4 #ad was used as a transmitting instrument1 and that in fig4 #ae as a receiver1 so that vocal communication was only established in one direction4 ,illustration3 ,,fig4 #ae4 #8,the articulation produced from the instrument shown in fig4 #ae was remarkably distinct1 but its great defect consisted in the fact that it could not be used as a transmitting instrument1 and thus two telephones were required at each station1 one for transmitting and one for receiving spoken messages4 #8,it was determined to vary the construction of the telephone1 and ,i sought by changing the size and tension of the membrane1 the diameter and thickness of the steel spring1 the size and power of the magnet1 and the coils of insulated wire around their poles1 to discover empirically the exact effect of each element of the combination1 and thus to deduce a more perfect form of apparatus4 ,it was found that a marked increase in the loudness of the sounds resulted from shortening the length of the coils of wire1 and by enlarging the iron diaphragm which was glued to the membrane4 ,in the latter case1 also1 the distinctness of the articulation was improved4 ,finally1 the membrane of goldbeaters' skin was discarded entirely1 and a simple iron plate was used instead1 and at once intelligible articulation was obtained4 ,the new form of instrument is that shown in fig4 #af1 and1 as had been long anticipated1 it was proved that the only use of the battery was to magnetise the iron core of the magnet1 for the effects were equally audible when the battery was omitted and a rod of magnetised steel substituted for the iron core of the magnet4 #8,it was my original intention1 and it was always claimed by me1 that the final form of telephone would be operated by permanent magnets in place of batteries1 and numerous experiments had been carried on by ,mr4 ,watson and myself privately for the purpose of producing this effect4 ,illustration3 ,,fig4 #af4 #8,at the time the instruments were first exhibited in public the results obtained with permanent magnets were not nearly so striking as when a voltaic battery was employed1 wherefore we thought it best to exhibit only the latter form of instrument4 #8,the interest excited by the first published accounts of the operation of the telephone led many persons to investigate the subject1 and ,i doubt not that numbers of experimenters have independently discovered that permanent magnets might be employed instead of voltaic batteries4 ,indeed one gentleman1 ,professor ,dolbear1 of ,tufts ,college1 not only claims to have discovered the magneto-electric telephone1 but ,i understand charges me with having obtained the idea from him through the medium of a mutual friend4 ,illustration3 ,,fig4 #ag4 #8,a still more powerful form of apparatus was constructed by using a powerful compound horseshoe magnet in place of the straight rod which had been previously used 7see fig4 #ag74 ,indeed the sounds produced by means of this instrument were of sufficient loudness to be faintly audible to a large audience1 and in this condition the instrument was exhibited in the ,essex ,institute1 in ,salem1 ,massachusetts1 on ,february #ab1 #ahgg1 on which occasion a short speech shouted into a similar telephone in ,boston1 sixteen miles away1 was heard by the audience in ,salem4 ,the tones of the speaker's voice were distinctly audible to an audience of #fjj people1 but the articulation was only distinct at a distance of about #f feet4 ,on the same occasion1 also1 a report of the lecture was transmitted by word of mouth from ,salem to ,boston1 and published in the papers the next morning4 ,illustration3 ,,fig4 #ah4 #8,from the form of telephone shown in fig4 #af to the present form of the instrument 7fig4 #ah7 is but a step4 ,it is in fact the arrangement of fig4 #af in a portable form1 the magnet ,n ,s being placed inside the handle1 and a more convenient form of mouthpiece provided4 #8,and here ,i wish to express my indebtedness to several scientific friends in ,america for their co-operation and assistance4 ,i would specially mention ,professor ,peirce and ,professor ,blake1 of ,brown ,university1 ,dr4 ,channing1 ,mr4 ,clarke1 and ,mr4 ,jones4 ,it was always my belief that a certain ratio would be found between the several parts of a telephone1 and that the size of the instrument was immaterial2 but ,professor ,peirce was the first to demonstrate the extreme smallness of the magnets which might be employed4 ,the convenient form of mouthpiece shown in fig4 #ag1 now adopted by me1 was invented solely by my friend ,professor ,peirce4' ,illustration3 ,,fig4 #ai4 ,another form of transmitting telephone exhibited in ,philadelphia1 intended for use with the receiving telephone 7fig4 #ae71 is represented by fig4 #ai4 ,a platinum wire attached to a stretched membrane completed a voltaic circuit by dipping into water4 ,upon speaking to the membrane1 articulate sounds proceeded from the telephone in the distant room4 ,the sounds produced by the telephone became louder when dilute sulphuric acid1 or a saturated solution of salt1 was substituted for the water4 ,audible effects were also produced by the vibration of plumbago in mercury1 in a solution of bichromate of potash1 in salt and water1 in dilute sulphuric acid1 and in pure water4 ,mr4 ,bell goes on to say3 #8,i have found also that a musical tone proceeds from a piece of plumbago or retort carbon when an intermittent current of electricity is passed through it1 and ,i have observed the most curious audible effects produced by the passage of reversed intermittent currents through the human body4 ,a rheotome was placed in circuit with the primary wires of an induction coil1 and the fine wires were connected with two strips of brass4 ,one of these strips was held closely against the ear1 and a loud sound proceeded from it whenever the other slip was touched with the other hand4 ,the strips of brass were next held one in each hand4 ,the induced currents occasioned a muscular tremor in the fingers4 ,upon placing my forefinger to my ear a loud crackling noise was audible1 seemingly proceeding from the finger itself4 ,a friend who was present placed my finger to his ear1 but heard nothing4 ,i requested him to hold the strips himself4 ,he was then distinctly conscious of a noise 7which ,i was unable to perceive7 proceeding from his finger4 ,in this case a portion of the induced currents passed through the head of the observer when he placed his ear against his own finger2 and it is possible that the sound was occasioned by a vibration of the surfaces of the ear and finger in contact4 #8,when two persons receive a shock from a ,ruhmkorff's coil by clasping hands1 each taking hold of one wire of the coil with the free hand1 a sound proceeds from the clasped hands4 ,the effect is not produced when the hands are moist4 ,when either of the two touches the body of the other1 a loud sound comes from the parts in contact4 ,when the arm of one is placed against the arm of the other1 the noise produced can be heard at a distance of several feet4 ,in all these cases a slight shock is experienced so long as the contact is preserved4 ,the introduction of a piece of paper between the parts in contact does not materially interfere with the production of the sounds1 but the unpleasant effects of the shock are avoided4 #8,when an intermittent current from a ,ruhmkorff's coil is passed through the arms1 a musical note can be perceived when the ear is closely applied to the arm of the person experimented upon4 ,the sound seems to proceed from the muscles of the fore-arm and from the biceps muscle4 ,mr4 ,elisha ,gray#d has also produced audible effects by the passage of electricity through the human body4 #8,an extremely loud musical note is occasioned by the spark of a ,ruhmkorff's coil when the primary circuit is made and broken with sufficient rapidity2 when two rheotomes of different pitch are caused simultaneously to open and close the primary circuit1 a double tone proceeds from the spark4 #8,a curious discovery1 which may be of interest to you1 has been made by ,professor ,blake4 ,he constructed a telephone in which a rod of soft iron1 about six feet in length1 was used instead of a permanent magnet4 ,a friend sang a continuous musical tone into the mouthpiece of a telephone1 like that shown in fig4 #ag1 which was connected with the soft iron instrument alluded to above4 ,it was found that the loudness of the sound produced in this telephone varied with the direction in which the iron rod was held1 and that the maximum effect was produced when the rod was in the position of the dipping-needle4 ,this curious discovery of ,professor ,blake has been verified by myself4 #8,when a telephone is placed in circuit with a telegraph line1 the telephone is found seemingly to emit sounds on its own account4 ,the most extraordinary noises are often produced1 the causes of which are at present very obscure4 ,one class of sounds is produced by the inductive influence of neighbouring wires and by leakage from them1 the signals of the ,morse alphabet passing over neighbouring wires being audible in the telephone1 and another class can be traced to earth currents upon the wire1 a curious modification of this sound revealing the presence of defective joints in the wire4 #8,professor ,blake informs me that he has been able to use the railroad track for conversational purposes in place of a telegraph-wire1 and he further states that when only one telephone was connected with the track the sounds of ,morse operating were distinctly audible in the telephone1 although the nearest telegraph-wires were at least forty feet distant2 and ,professor ,peirce has observed the most curious sounds produced from a telephone in connection with a telegraph-wire during the aurora borealis4' ,mr4 ,bell went on to describe instances in which airs sung or played upon a musical instrument are transmitted by a telephone1 when it is not known whence they come2 but the strongest proof of the extraordinary sensibility of this instrument consists in its becoming possible by its means to transmit speech through bodies which might be supposed to be non-conductors4 ,thus communication with the earth through the human body can be made in spite of the intervention of shoes and stockings2 and it may even be effected if1 instead of standing on the ground1 the person stands on a brick wall4 ,only hewn stone and wood are a sufficient hindrance to communication1 and if the foot touches the adjoining ground1 or even a blade of grass1 it is enough to produce electric manifestations4 ,mr4 ,bell says in conclusion3 #8,the question will naturally arise1 ,through what length of wire can the telephone be used8 ,in reply to this1 ,i may say that the maximum amount of resistance through which the undulatory current will pass1 and yet retain sufficient force to produce an audible sound at the distant end1 has yet to be determined2 no difficulty has1 however1 been experienced in laboratory experiments in conversing through a resistance of #fj1jjj ohms1 which has been the maximum at my disposal4 ,on one occasion1 not having a rheostat at hand1 ,i may mention having passed the current through the bodies of sixteen persons1 who stood hand in hand4 ,the longest length of real telegraph line through which ,i have attempted to converse has been about #bej miles4 ,on this occasion no difficulty was experienced so long as parallel lines were not in operation4 ,sunday was chosen as the day on which it was probable other circuits would be at rest4 ,conversation was carried on between myself in ,new ,york1 and ,mr4 ,thomas ,a4 ,watson in ,boston1 until the opening of business upon the other wires4 ,when this happened the vocal sounds were very much diminished1 but still audible4 ,it seemed1 indeed1 like talking through a storm4 ,conversation1 though possible1 could be carried on with difficulty1 owing to the distracting nature of the interfering currents4 #8,i am informed by my friend ,mr4 ,preece that conversation has been successfully carried on through a submarine cable1 sixty miles in length1 extending from ,dartmouth to the ,island of ,guernsey1 by means of hand telephones4' ,illustration3 ,,fig4 #bj4 ,mr4 ,elisha ,gray's ,share in the ,invention of the ,telephone4--,we have seen that if ,mr4 ,bell was the first to construct the speaking telephone in a practical form1 ,mr4 ,gray had at the same time conceived the idea of an instrument also capable of reproducing speech1 and the description given of it in his caveat was so precise that if it had been made from his design1 it would have acted perfectly4 ,this was1 in fact1 afterwards proved by him4 ,in order that our readers may judge from their own knowledge of the share which should be ascribed to ,mr4 ,elisha ,gray in the invention of the telephone1 we reproduce in fig4 #bj the drawing which accompanied the caveat in question4 ,the sender1 as we see1 is composed of a sort of tube1 closed at its lower end by a membrane to which a platinum wire is fixed2 this wire dips into a liquid of moderate conducting power1 and an electrode made of platinum1 in communication with a battery1 is fixed at the bottom of the vessel containing the liquid4 ,the receiver is composed of an electro-magnet1 of which the armature is fixed to the centre of a membrane1 stretched on a kind of resonator or ear-trumpet which is held to the ear1 and the two instruments are united by the line wire as we see in the plate4 ,under these conditions1 the undulatory currents necessary for the reproduction of speech were obtained in a mode analogous to that pointed out by ,mr4 ,bell in his specification1 that is1 by the variations of resistance in the liquid layer interposed between the platinum wires of the transmitter2 and their action1 exerted on an electro-magnet1 of which the armature was fixed on the diaphragm of the resonator1 was produced under more favourable conditions than in ,mr4 ,bell's specification 7see fig4 #ac71 since that gentleman regards this arrangement 7represented in fig4 #ad7 as an important improvement on his first conception4 ,the whole importance of the invention rests on the intervention of undulatory currents1 which1 as we have seen1 are indispensable for the reproduction of speech1 and it concerns us to know whether it was ,mr4 ,bell or ,mr4 ,gray who first declared their importance2 for in both the specifications deposited on ,february #ad1 #ahgf1 the use of undulatory currents was declared to be indispensable4 ,mr4 ,gray asserts that he had recognised their importance for the transmission of combined sounds as early as #ahgd2 but ,mr4 ,bell believes that the undulatory currents mentioned by ,mr4 ,gray at that time were only currents analogous to those he had designated under the name of pulsatory currents1 which we have represented in fig4 #h4 ,we have seen that since these currents only represent the abrupt elevations and depressions of intensity1 they are unfit for the reproduction of articulate sounds1 which1 on the contrary1 demand that the variations of intensity should result from successive efforts1 in exact correspondence with all the inflections of the sonorous vibrations effected by the voice4 ,mr4 ,bell's claim to priority on this question has been recognised by the ,american ,patent ,office1 since he has been placed in possession of the patent4 ,however this may be1 ,mr4 ,gray's telephonic system was complete1 and we see in it1 as we have already said1 the origin of the battery telephones1 which have recently produced such important results4 ,let us now consider the relation which this system bears to ,mr4 ,bell's4 ,the ,bell system1 as we have seen1 although making use of a battery in the first instance1 only obtained the diminution and increase of electric force necessary for the articulation of words by means of induction currents produced by the movements of an armature of soft iron1 currents of which the intensity was consequently due to the range and inflections of these movements4 ,the battery only intervened in order to communicate magnetic force to the inducer4 ,this use of induced currents in telephonic transmissions was already of great importance1 since various experiments subsequently made have proved their superiority to voltaic currents for this purpose4 ,but experience soon convinced ,mr4 ,bell that a powerful inductive apparatus worked by a battery was not only unnecessary for the action of this apparatus1 but that a permanent magnet1 very small and weak1 would provide sufficient currents4 ,this discovery1 in which1 as we have seen1 ,mr4 ,peirce had some share1 was of great importance1 since it became possible to reduce the size of the instrument considerably1 so as to make it portable and adapted for sending and receiving2 and it was shown that the telephone was the most sensitive of all instruments in revealing the action of currents4 ,if1 therefore1 ,mr4 ,bell was not the first to employ the successful mode of transmitting articulate words1 it must be said that he sought1 like ,mr4 ,gray1 to solve the problem by means of undulatory currents1 and that he obtained these currents by the effect of induction1 a system which1 as soon as it was perfected1 led to the important results with which we are all acquainted4 ,if he had only given to the astonished world an instrument capable of reproducing speech telegraphically1 his fame would be great2 for this problem had hitherto been regarded as insoluble4 ,mr4 ,gray's claims to the invention of the telephone are given in the following summary from a very interesting work1 entitled #8,experimental ,researches on ,electro-harmonic ,telegraphy and ,telephony3' #8#a4 ,i was the first to discover the means of transmitting compound sounds and variable inflections through a closed circuit by means of two or more electric waves4 #8#b4 ,i assert that ,i was the first to discover and utilise the mode of reproducing vibrations by the use of a magnet receiver constantly supplied with electric action4 #8#c4 ,i also assert that ,i was the first to construct an instrument consisting of a magnet with a circular diaphragm of magnetic substance1 supported by its edge at a little distance from the poles of a magnet1 and capable of being applied to the transmission and reception of articulate sounds4' ,it is a curious fact1 worth recording here1 that ,mr4 ,yates1 of ,dublin1 in #ahfe1 when trying to improve ,reiss's telephone1 realised to a certain extent ,mr4 ,gray's conception of the liquid transmitter2 for he introduced into the platinum contacts of ,mr4 ,reiss's instrument a drop of water which adapted it for the reproduction of articulate sounds4 ,however1 no notice was then taken of this result4 ,,examination ,,into ,,the ,,fundamental ,,principles ,,on ,,which ,,bell',s ,,telephone ,,is ,,based4 ,although the preceding account would suffice to make the principle of ,bell's telephone intelligible to persons acquainted with electric science1 this would not be the case with the majority of our readers1 and we therefore think it necessary to enter into some details as to the source of the electric currents which are employed in telephonic transmissions4 ,these details seem to us the more necessary1 since many persons still believe that ,bell's telephones are not electric1 because they do not require a battery1 and they are often confounded with string telephones1 so that the difference of price between ,bell's instruments and those hawked in the streets seems astonishing4 ,without defining what is meant by an electric current1 which would be too elementary1 we may say that electric currents can be produced by different causes1 and that1 in addition to those which are due to batteries1 strong currents are also produced by the force exerted by magnets on a conducting circuit properly arranged4 ,such currents are called induction currents1 and are used in ,bell's telephone4 ,in order to understand how they are developed under these conditions1 it will be enough to examine what takes place when the pole of a magnet is brought near to1 and withdrawn from1 a closed circuit4 ,to do this1 let us suppose a copper wire attached to a galvanometer in the form of a circle1 and that one pole of a permanent magnet is directed towards the centre of the circle4 ,now observe what happens3 #a4 ,at the moment when the magnet approaches an electric current arises1 causing the galvanometer to deviate to one side4 ,this deviation will be great in proportion to the extent of the movement1 and the tension of the current will be great in proportion to the abruptness of the movement4 ,the current will however be only instantaneous4 #b4 ,at the moment when the magnet is withdrawn1 a fresh current of the same nature will arise1 but it will appear in an opposite direction from the former4 ,it will be what is called a direct current1 because it is in the same direction as the magnetic current of the magnet which produces it1 while the other current is called inverse4 #c4 ,if1 instead of advancing or withdrawing the magnet by means of a single movement1 it is advanced in jerks1 a succession of currents in the same direction is produced1 of which the existence can be ascertained by the galvanometer when there is a sufficient interval between the movements1 but when the intervals are very slight the currents are interfused2 and since inverse effects take place when the magnet is moved in a contrary direction1 the needle of the galvanometer follows the movements of the magnet1 and to a certain extent stereotypes them4 #d4 ,if1 instead of reacting on a simple closed circuit1 the magnet exerts its force on a considerable number of circumvolutions of this circuit1 that is1 on a bobbin of coiled wire1 the effects will be considerably increased1 and they will be still greater if there be a magnetic core within the bobbin1 since the inducing action will then be more effectually exerted throughout the bobbin4 ,as the magnetic core1 when it is magnetised and demagnetised under the influence of its approach to or withdrawal from the inducing magnet1 is subject to the reaction from all the fluctuations which occur in the movements of the magnet1 the induced currents which ensue are perfectly defined4 #e4 ,if1 instead of a movable magnet1 we suppose it to be fixed in the centre of the coil1 the induced currents of which we have spoken may then be determined by modifying its force4 ,in order to do so1 it is enough that an iron armature should react upon its poles4 ,when this armature is brought close to one of the poles1 or to both at once1 it acquires force1 and produces an inverse current1 that is1 a current in the direction which would have corresponded to an approach of the magnet to the closed circuit4 ,on its withdrawal the inverse effect is produced2 but in both cases the induced currents correspond with the extent and direction of the movements accomplished by the armature1 and consequently they may reproduce its movements by their effects4 ,if this armature is an iron plate1 which vibrates under the influence of any sound in this disposition of the electro-magnetic system1 the alternate movements of the plate will be transformed into the induced currents1 and these will be stronger or weaker1 more or less definite1 according to the range and complexity of the vibrations3 they will1 however1 be undulatory1 since they will always result from successive and continuous movements1 and will consequently be in the conditions which1 as we have seen1 are required for the transmission of speech4 ,as for the action produced upon the receiver1 that is1 on the instrument for reproducing speech1 it is somewhat complex1 and we shall have occasion to speak of it presently2 but we can get a general impression of it1 if we consider that the effects produced by the induced currents of variable intensity1 which traverse the coil of the electro-magnetic system1 must determine1 by the magnetisations and demagnetisations which ensue1 the vibrations of the armature disk2 these vibrations1 more or less amplified and defined1 exactly represent those of the disk before which the speaker stands1 and can only be obtained from them4 ,the effects are1 however1 in reality more complex1 although they are produced under analogous conditions1 and we shall have more to say about them when we come to speak of the experiments made with the telephone4 ,it must meanwhile be observed that1 for the reproduction of speech1 it is not necessary that the magnetic core should be of soft iron1 since the vibratory effects may follow from differential as well as from direct magnetisation4 ,,ordinary ,,arrangement ,,of ,,the ,,bell ,,telephone4 ,the arrangement most generally adopted for the telephone is the one represented in fig4 #ba4 ,it consists of a kind of circular wooden box1 fitted to the extremity of a handle ,m1 which is also of wood1 and contains the magnetic bar ,n ,s4 ,this bar is fixed by means of a screw t1 and is so arranged as to be moved forward and backward by tightening or loosening the screw1 a condition necessary in order to regulate the instrument4 ,at the free extremity of the bar the magnetic coil ,b is fixed2 this must1 according to ,,mm4 ,pollard and ,garnier1 be made of wire ,no4 #db1 so as to present a considerable number of spirals4 ,the ends of this coil generally terminate at the lower end of the handle in two copper rods f1 f1 which traverse its length1 and are fastened to two binding-screws ,i1 ,i1 where the line wires ,c1 ,c are fixed4 ,in the instruments made by ,m4 ,brguet there are1 however1 no binding-screws1 but a little twist1 made of two flexible wires covered with gutta-percha and silk1 is fastened to the two rods4 ,a wooden cap is screwed to the end of the handle1 and the twist passes through a hole made in this cap1 so that there is no inconvenience in working the instrument4 ,by laying hold of the ends of the wire twist with pliers it is possible to join them to the circuit4 ,this instrument is represented in fig4 #bb4 ,illustration3 ,,fig4 #ba4 ,by another arrangement1 the wires of the coil end immediately in the binding-screws which are placed below the wooden box1 but this arrangement is inconvenient4 ,above the pole of the magnetic bar is placed the iron vibrating plate ,l ,l1 which is coated either with black or yellow varnish1 with tin or blue oxide1 but which must always be very thin4 ,this plate is in the form of a disk1 and by its rim1 resting on a caoutchouc ring1 it is firmly fixed to the circular edges of the wooden box1 which is for this purpose made in two pieces4 ,these pieces are adjusted to each other1 either by screws or by spirals cut in half the thickness of the wood4 ,this disk ought to be as near as possible to the polar end of the magnet1 yet not so near as to produce contact between the two by the vibrations of the voice4 ,finally1 the mouthpiece ,r ,r 7fig4 #ba71 which is in form of a wide funnel1 terminates the upper part of the box1 and should be so arranged as to leave a certain space between the disk and the edges of the hole ,v1 which is open in its centre4 ,the size of the box should be so calculated as to permit of its acting as a sounding-box1 without however provoking echoes and a confusion of sounds4 ,illustration3 ,,fig4 #bb4 ,when the instrument is properly made1 it will produce very marked effects2 and ,m4 ,pollard1 one of the first ,frenchmen to take up the study of telephones1 has written as follows on the subject3 #8,the instrument which ,i have prepared gives results which are truly astonishing4 ,in the first place1 when considering the resistance1 the introduction into the circuit of five or six persons does not sensibly diminish the intensity of sounds4 ,on putting an instrument to each ear1 the sensation is precisely the same as if the correspondent were speaking some yards behind4 ,the intensity1 the clearness1 the purity of tone are irreproachable4 #8,i can speak to my colleague in quite an undertone1 scarcely breathing as ,i may say1 and persons placed within two yards of me will be unable to catch a single word of our conversation4 #8,on the part of the receiver1 if anyone raises his voice to call me1 ,i hear the call in all parts of my office1 at least when silence prevails there2 at any rate1 when ,i am seated at my table with the instrument some yards off1 ,i can always hear the call4 ,in order to increase the intensity of sound1 ,i fitted the mouthpiece with a copper horn of conical shape1 and under these conditions words spoken in my bureau two or three yards from the mouthpiece can be heard at the other end of the line2 from my station1 a little more than a yard from the tube1 ,i can hear and speak to my colleague without effort4' ,in using the ordinary ,bell telephone1 it is necessary to speak distinctly before the mouthpiece of the telephone which is handled1 while the listener placed at the corresponding station keeps the mouthpiece of the receiver to his ear4 ,these two instruments form a closed circuit with the two wires which connect them1 but one is enough to make the transmission perfect1 if care is taken to place both instruments in connection with the earth1 which thus takes the place of the second wire4 ,m4 ,bourbouze asserts that the intensity of sound in the telephone is much increased by employing this expedient1 but we believe that this increase depends upon the conditions of the circuit1 although he asserts that the fact can be proved in a circuit not exceeding eighty yards4 ,for practical purposes it is necessary to have two telephones at each station1 so as to hold one to the ear while speaking through the other1 as in fig4 #bc4 ,it is also much more easy to hear with a telephone applied to each ear1 in which case they are held as in fig4 #bd4 ,in order not to fatigue the arms1 an arrangement has been made by which they are held before the ears by a strap and spring which goes round the head4 ,illustration3 ,,fig4 #bc4 ,the sending power of the telephone varies with different voices4 ,mr4 ,preece asserts that shouting has no effect1 and that1 in order to obtain a favourable result1 the intonation must be clear1 the articulation distinct1 and the sounds emitted must resemble musical sounds as much as possible4 ,mr4 ,wilmot1 one of the electricians employed by the ,post ,office1 says that he has been able to make himself heard on circuits through which no other voices were audible4 ,the vowel sounds are most readily transmitted1 and among other letters e1 g1 j1 k1 and q are always repeated more imperfectly4 ,the ear requires practice1 and the faculty of hearing varies in a surprising degree in different people4 ,singing is very distinctly heard1 as well as wind instruments1 especially the cornet--piston1 which1 when played in ,london1 was heard by thousands of people in the ,corn ,exchange at ,basingstoke4 ,illustration3 ,,fig4 #bd4 ,according to ,mr4 ,rollo ,russell1 it is not necessary to isolate the circuit of a telephone when the distance is relatively slight2 thus1 with a circuit of about #dcj yards1 it is possible to use a simple copper wire1 laid on the grass1 without destroying the telephonic transmission from a small musical box1 as long as the two wires do not touch each other4 ,transmission took place1 even when the circuit was buried in moist earth for a length of thirty-five yards1 or immersed in a well for a length of forty-eight yards4 ,the words transmitted under such conditions did not differ from those transmitted by an isolated circuit4 ,the telephone may be heard at the same moment by several listeners1 either by connecting the wires which unite the telephones in correspondence 7near the receiving telephone7 with branch wires of other telephones1 which may be done up to the number of five or six1 in short circuits2 or by means of a little sounding-box closed by two thin membranes1 one of which is fixed on the vibrating disk4 ,when a certain number of acoustic tubes are connected with the membrane1 ,mr4 ,m',kendrick asserts that several people can hear distinctly4 ,telephones may also transmit speech to different stations simultaneously1 by inserting them on the same circuit1 and experiments made at ,new ,york showed that five instruments placed in different parts of the same telegraphic line could be made to speak in this way4 ,in the telephonic experiments made on the canal lines in the department of the ,yonne1 it was ascertained that on a wire seven miles and a half in length1 on which several telephones were placed at varying distances1 three or four persons were able to converse with each other through the telephones1 and each could hear what the other was saying4 ,the questions and answers could be understood1 even in crossing4 ,it was also possible1 by placing a telephone on a second wire1 a little over five miles in length1 and half a yard distant from the other1 to hear the conversation exchanged on the first wire by following it to a distance not exceeding a mile and a quarter4 ,even the different voices of the two speakers could be distinguished4 ,since the telephone made its appearance in ,europe1 several inventors have asserted that they are able to make a telephone speak so as to be audible in all parts of a large hall4 ,it has been shown that this was accomplished by ,mr4 ,bell1 and in this respect we do not see that those who have attempted to improve the telephone have attained results of greater importance4 ,it is certain that the ordinary telephone can emit musical sounds which become perfectly audible in a tolerably large room1 while the instrument is still attached to the wall4 ,we should also remember the results obtained by ,,mm4 ,pollard and ,garnier in the experiments made at ,cherbourg to connect the mole with the ,prfecture ,maritime4 ,the mole at ,cherbourg is1 as we know1 a kind of artificial island thrown up before the town in order to make an anchorage4 ,the forts which have been constructed on the mole are connected by submarine cables with the military port and with the ,prfecture ,maritime4 ,on one occasion1 after making experiments in the ,prfet's study on one of the cables applied to a telephone1 several persons were talking together in the room1 and were much surprised to hear the bugle sound the retreat1 the sound appearing to come from one part of the room4 ,it was found1 on examination1 that the telephone hung to the wall was occupied with this performance4 ,on enquiry1 it appeared that one of the manipulators on the mole station had amused himself by sounding the bugle before the telephone on that station4 ,the mole is more than three miles from ,cherbourg1 and the ,prfecture ,maritime is in the centre of the town4 ,yet these telephones had been roughly made in the dockyard workshops2 and we have here another proof of the small amount of accuracy required for the successful working of these instruments4 ,illustration3 ,,fig4 #be4 ,telephones of various construction on the ,bell model are to be seen at ,m4 ,c4 ,roosevelt's1 ,mr4 ,bell's agent in ,paris1 #a1 ,rue de la ,bourse4 ,they are1 for the most part1 constructed by ,m4 ,brguet1 and the model in the greatest request1 exclusive of the one we have described1 is the great square model1 with a horseshoe magnet enclosed in a flat box1 and a horn on its upper side1 which serves as a mouthpiece4 ,this system is represented in fig4 #be1 and it has been neatly constructed at ,boston under the best conditions4 ,in this new model1 made by ,mr4 ,gower1 the magnet is composed of several plates terminated by magnetic cores of iron1 to which the coils are fixed1 and the whole is covered with a thick layer of paraffin4 ,the sounds thus reproduced are much stronger and more distinct4 ,mr4 ,gower1 who is now ,mr4 ,roosevelt's partner1 has made considerable improvements in the different forms of ,mr4 ,bell's instrument4 ,there is one model in the form of a snuff-box1 in which the magnet is twisted into a spiral1 so as to maintain its length in a circular form4 ,the pole1 which is in the centre of the spiral1 is furnished with an iron core1 to which the induction coil is fastened1 and the cover of the snuff-box supports the vibrating disk as well as the mouthpiece3 this model is represented in fig4 #bf4 ,in another model1 called the mirror telephone1 the preceding arrangement is fitted on to a handle like the glass of a portable mirror1 and there is a mouthpiece on one of the lateral faces1 so that the speaker uses the instrument as if he were speaking before a chimney screen4 ,illustration3 ,,fig4 #bf4 ,mr4 ,bailey has different models of telephones worked by a battery or by the ,edison carbon of which we shall speak presently1 and these1 as well as the telephones by ,messrs4 ,gray and ,phelps1 are more successful in conveying sound on a long line of wire4 ,,different ,,arrangements ,,of ,,telephones4 ,the prodigious results attained with the ,bell telephones1 which were at first discredited by many scientific men1 necessarily provoked1 as soon as their authenticity was proved1 innumerable researches on the part of inventors1 and even of those who were originally the most incredulous4 ,a host of improvements and modifications have consequently been suggested1 which are evidently not without interest1 and must now be considered by us4 ,,battery ,,telephones4 ,the ,edison ,telephone4--,one of the earliest and most interesting improvements made in the ,bell telephone is that introduced by ,mr4 ,edison in the early part of the year #ahgf4 ,this system is indeed more complicated than the one we have just considered1 since it requires a battery1 and the sending instrument differs from the receiving instrument2 but it is less apt to be affected by external causes1 and transmits sound to a greater distance4 ,the ,edison telephone1 like ,mr4 ,gray's1 which we have already had occasion to mention1 is based upon the action of undulatory currents1 determined by the variations in the resistance of a conductor of moderate conducting power1 which is inserted in the circuit1 and the vibrations of a diaphragm before which the speaker stands react upon it4 ,only1 instead of employing a liquid conductor1 which is practically useless1 ,mr4 ,edison has attempted to use semi-conducting solid bodies4 ,those which were most suitable from this point of view were graphite and carbon1 especially the carbon extracted from compressed lamp-black4 ,when these substances are introduced into a circuit between two conducting plates1 one of which is moveable1 they are capable of modifying the resistance of the circuit almost in the same proportion as the pressure exerted upon them by the moveable plate1#e and it was seen that1 in order to obtain the undulatory currents necessary for the production of articulate sounds1 it was enough to introduce a disk of plumbago or of lamp-black between the vibrating plate of a telephone and a platinum plate placed in connection with the battery4 ,when the telephone disk is placed in circuit1 its vibrations before the disk of carbon produce a series of increasing and decreasing pressures1 thus causing corresponding effects in the intensity of the transmitted current1 and these effects react in an analogous manner on the undulatory currents determined by induction in the ,bell system4 ,in order to obtain good results1 however1 several accessory arrangements were necessary1 and we represent in fig4 #bg one of the arrangements made in this part of ,mr4 ,edison's telephonic system4 ,illustration3 ,,fig4 #bg4 ,in this figure a section of the instrument is given1 and its form greatly resembles that of ,bell4 ,l ,l is the vibrating disk2 ,o ,o1 the mouthpiece2 ,m1 the opening to the mouthpiece2 ,n ,n ,n1 the case for the instrument1 which is1 like the mouthpiece1 made of ebonite1 and below the disk it presents a rather large cavity1 and a tubular hole which is scooped in the handle4 ,in its upper part this tube terminates in a cylindrical rim1 furnished with a worm on which is screwed a little rod with a ridge on its inner side1 and the rheostatic system is placed within this tube4 ,the system consists1 first1 of a piston ,e1 fitted to the end of a long screw ,e ,f1 and the turning of the button will move the piston up or down within a certain limit4 ,above this piston there is fitted a very thin platinum plate ,a1 connected by a flexible chain and a wire with a binding-screw ,p4 ,another plate ,b1 exactly similar1 is connected with the binding-screw ,p1 and the carbon disk ,c is placed between these two plates4 ,this disk is composed of compressed lamp-black and petroleum1 and its resistance is one ohm1 or #aaj yards1 of telegraphic wire4 ,finally1 an ebonite disk is fastened to the upper platinum plate1 and an elastic pad1 composed of a piece of caoutchouc tube ,g1 and of a cork disk ,h1 is interposed between the vibrating plate ,l ,l and the disk ,b1 in order that the vibrations of the plate may not be checked by the rigid obstacle formed by the whole rheostatic system4 ,when these different parts are in position1 the instrument is regulated by the screw ,f1 and this is easily done by screwing or unscrewing it until the receiving telephone gives out its maximum of sound4 ,illustration3 ,,fig4 #bh4 ,in another model1 represented in fig4 #bh1 which has produced the best results in the distinctness with which sounds are transmitted1 the vibrating plate ,l ,l is supported on the disks of the secondary carbon conductor ,c by means of a little iron cylinder ,a1 instead of the caoutchouc pad1 and the pressure is regulated by a screw placed below e4 ,the mouthpiece ,e of the instrument is more prominent1 and its opening is larger4 ,finally1 the instrument1 which is cased in nickel silver1 is without a handle4 ,the rigid disk b1 resting on the first platinum plate p1 is of aluminium instead of ebonite4 ,illustration3 ,,fig4 #bi4 ,the receiving telephone somewhat resembles that of ,mr4 ,bell1 yet it presents some differences which can be understood from the examination of fig4 #bi4 ,the magnet ,n ,s is horseshoe in form1 and the magnetising coil ,e only covers one of the poles1 ,n3 this pole is precisely in the centre of the vibrating plate ,l ,l1 while the second pole is near the edge of this plate4 ,the size of the plate itself is considerably reduced3 its superficies is about the same as that of a five-franc piece1 and it is enclosed in a kind of circular groove1 which keeps it in a definite position4 ,in consequence of this arrangement the handle of the instrument is of solid wood1 and the vacant space for the electro-magnetic system is somewhat larger than in the ,bell model2 but an arrangement is made for subduing the echo1 and there is a kind of sounding-box to magnify the sound4 ,it is evident that the relation which the electro-magnetic system bears to the vibrating disk must increase the sensitiveness of the instrument2 for as the pole ,s is in close contact with the disk ,l ,l1 the latter is polarised1 and becomes more susceptible to the magnetic influence of the second pole ,n1 which is separated from it by an interval not exceeding the thickness of a sheet of coarse paper4 ,in ,mr4 ,edison's two instruments1 the receiver and sender1 the upper part ,c ,c1 corresponding to the vibrating disk1 instead of being fixed by screws to the handle1 is screwed on to the handle itself1 which makes it much more easy to dismount the instrument4 ,mr4 ,edison has varied the form of his instruments in many ways1 and their cases have of late been made of metal with a funnel-shaped mouthpiece of ebonite4 ,when ,mr4 ,edison had ascertained1 as indeed ,mr4 ,elisha ,gray had done before him1 that induced currents are more favourable to telephonic transmissions than voltaic currents1 he transformed the currents from the battery which passed through his sender into induced currents by making them pass through the primary circuit of a carefully insulated induction coil2 the line wire was then put into communication with the secondary wire of the coil4 ,we shall afterwards describe some experiments which show the advantages of this combination3 for the present we can only point out the fact1 for it is now an integral quality of almost all the systems of battery telephones4 ,edison's ,chemical ,telephone4--,the curious and really useful effects produced by ,mr4 ,edison with his electro-motograph prompted1 about the beginning of the year #ahgg1 his idea of applying the principle of this instrument to the telephone for the reproduction of transmitted sounds2 and he obtained such interesting results that the author of an article on telephones1 published in the #8,telegraphic ,journal1' ,august #ae1 #ahgg1 put forward this invention as one of the finest of the nineteenth century4 ,it certainly appears to have given birth to the phonograph1 which has lately become famous1 and has so much astonished men of science4 ,to understand the principle of this telephone1 we must give some account of ,mr4 ,edison's electro-motograph1 discovered in #ahgb4 ,this instrument is based upon the principle that if a sheet of paper1 prepared with a solution of hydrate of potash1 is fastened on a metallic plate which is united to the positive pole of a battery1 and if a point of lead or platinum connected with the negative pole is moved about the paper1 the friction which this point encounters ceases after the passage of the current1 and it is then able to slide as if upon a mirror until the current is interrupted4 ,now1 as this reaction may be effected instantaneously under the influence of extremely weak currents1 the mechanical effects produced by these alternations of arrest and motion may1 by a suitable arrangement of the instrument1 determine vibrations in correspondence with the interruptions of current produced by the transmitter4 ,in this system the telephonic receiver consists of a resonator and a drum mounted on an axis and turned by a winch4 ,a paper band1 wound upon a reel1 passes over the drum1 of which the surface is rough1 and a point tipped with platinum1 and fitted to the end of a spring which is fixed in the centre of the resonator1 presses strongly on the paper4 ,the current from the battery1 first directed on the spring1 passes by the platinum point through the chemical paper1 and returns by the drum to the battery4 ,on turning the winch1 the paper moves forward1 and the normal friction which is produced between the paper and the platinum point pushes the point forward1 while producing by means of the spring a tension on one side of the resonator2 but since the friction ceases at each passage of the current through the paper1 the spring is no longer drawn out1 and the resonator returns to its normal position4 ,since this double effect is produced by each vibration made in the sender1 a series of vibrations takes place in the resonator1 repeating those of the sender1 and consequently the musical sounds which affected the sender are reproduced to a certain extent4 ,according to the ,american journals1 the results produced by this instrument are astonishing3 the weakest currents1 which would have no effect on an electro-magnet1 become perfectly efficacious in this way4 ,the instrument can even reproduce with great intensity the highest notes of the human voice1 notes which can hardly be distinguished by the use of electro-magnets4 ,the sender nearly resembles the one we have previously described1 except that1 when it is used for musical sounds1 a platinum point is employed instead of the disk of carbon1 and it ought not to be in constant contact with the vibrating plate4 ,according to the #8,telegraphic ,journal1' it consists simply of a long tube1 two inches in diameter1 having one end covered with a diaphragm formed of a thin sheet of copper1 and kept in its place by an elastic ring4 ,a small platinum disk is riveted to the centre of the copper diaphragm1 and a point of the same metal1 fitted with a firm support1 is adjusted before the disk4 ,when the singer stands before the diaphragm1 its vibration causes it to touch the platinum point1 and produces the number of breaks in the current which corresponds to the vibration of the notes uttered4 ,the experiments lately made in ,america1 in order to decide on the merits of various telephonic systems1 show that ,mr4 ,edison's telephone gives the best results4 ,the #8,telegraphic ,journal1' ,may #a1 #ahgh1 states that on ,april #b ,mr4 ,edison's carbon telephone was tested between ,new ,york and ,philadelphia on one of the numerous lines of the ,west ,union4 ,the length of the line was #ajf miles1 and ran parallel to other wires almost throughout its length4 ,the effects of induction caused by telegraphic transmissions through the adjacent wires were enough to make speech inaudible through the other telephones1 but they had no influence on ,edison's telephone1 which was worked with a battery of two cells and a small induction coil1 and ,messrs4 ,batchelor1 ,phelps1 and ,edison were able to converse with ease4 ,mr4 ,phelps' magnetic telephone1 which is considered to be the most powerful of its kind1 did not afford such good results4 ,in the experiments made between the ,paris ,exhibition building and ,versailles1 the jury commission was able to ascertain that the results were equally favourable4 ,telephones by ,colonel ,navez4--,colonel ,navez of the ,belgian ,artillery1 inventor of the well-known balistic chronograph1 has endeavoured to improve the ,edison telephone by employing several disks of carbon instead of one4 ,he considers that the variations of electric resistance produced by carbon disks under the influence of unequal pressure depend chiefly on their surface of contact1 and he consequently believes that the more these surfaces are multiplied1 the greater the differences in question will be1 just as it happens when light is polarised through ice4 ,he adds that these disks act well by their surfaces of contact1 since1 if they are separated by copper disks1 the speech reproduced ceases to be articulate4#f ,i am not surprised to learn that ,colonel ,navez has found a limit to the number of carbon disks1 for the reproduction of speech in this system is due both to the greatness of the differences of resistance in the circuit1 and to the intensity of the transmitted current4 ,if therefore the instrument's sensitiveness to articulate sounds is increased by increasing the number of imperfect contacts in the circuit1 the intensity of the transmitted sounds is diminished1 and thus sounds lose their power4 ,there is consequently a limit to be observed in the number of carbon disks placed upon each other2 and it depends on the nature of the imperfect contacts which are employed1 and on the tension of the electric generator4 ,in order to stop the unpleasant musical vibrations which accompany telephonic transmissions1 ,colonel ,navez employs for the vibrating plate of the sender a silver-plated copper disk1 and for the vibrating plate of the receiver an iron disk lined with brass and soldered together4 ,he also employs caoutchouc tubes with mouthpieces and ear-tubes for the transmission and reception of sound1 and these instruments are placed level on a table4 ,for this purpose the magnetised bar of the receiving telephone is replaced by two horizontal magnets1 acting through a pole of the same nature on a little iron core which carries the coil1 and which is placed vertically between the two magnets4 ,he necessarily makes use of a small ,ruhmkorff coil to transform the electricity of the battery into induced electricity4 ,illustration3 ,,fig4 #cj4 ,illustration3 ,,fig4 #ca4 ,figs4 #cj and #ca represent the two parts of this telephonic system4 ,the carbon battery is in ,c 7fig4 #cj71 the vibrating disk in ,l ,l1 and the mouthpiece ,e1 fitted to a caoutchouc tube ,t ,e1 corresponds at the lower end to the vibrating disk4 ,the carbon battery is placed in metallic contact with the circuit by a platinum rod ,e ,c1 and the vibrating disk also communicates with the circuit through a binding-screw4 ,in the receiving telephone 7fig4 #ca7 the upper part is arranged much as in the ordinary telephones1 except that1 instead of a mouthpiece1 the instrument is fitted with an ear-tube ,t ,o4 ,the two horseshoe magnets1 ,a1 ,a1 which communicate a uniform polarity to the iron core ,n1 support the induction coil ,b4 ,the two terminals of this receiver are connected with the supplementary wire of the induction coil1 and the two terminals of the sender are connected with the two ends of the primary of this coil1 and with the battery which is inserted in the circuit near this instrument4 ,the ,pollard and ,garnier ,telephones4--,the battery telephone made by ,,mm4 ,pollard and ,garnier differs from the foregoing in this particular3 it simply employs two points of graphite1 mounted in metallic porte-crayons1 and these points are directly applied against the vibrating plate with a pressure which must be regulated4 ,fig4 #cb represents the arrangement adopted1 which1 however1 may be infinitely varied4 ,l ,l is the vibrating tin plate1 above which is the mouthpiece ,e1 and ,p1 ,p are the two graphite points with their porte-crayons4 ,there is a screw on the lower part of the porte-crayons which is fixed in a hole pierced in a metallic plate ,c ,c1 and by this means the pressure of the pencils against the disk ,l ,l can be regulated4 ,the metallic plate ,c ,c is made in two pieces1 placed side by side1 but insulated from each other1 so that they may be placed in communication with a cylindrical commutator1 and by its means the circuit can be arranged in different ways4 ,since the commutator consists of five sheets1 the transition from one combination to another is instantaneous1 and these combinations are as follows3 #a4 ,the current enters by the pencil ,p1 passes into the plate1 and so to line4 #b4 ,the current enters by the pencil ,p1 passes into the plate1 and so to line4 #c4 ,the current comes simultaneously by the two pencils ,p and ,p1 goes into the plate1 and thence to line4 #d4 ,the current comes by the pencil ,p1 goes thence to the plate1 then into the pencil ,p1 and so to line4 ,illustration3 ,,fig4 #cb4 ,by this means there are two elements of combination1 which may be employed separately1 or by coupling them for tension or quantity4 ,when the pencils are properly regulated and give a regular transmission of equal intensity1 the effects produced in the transition from one combination to another may be easily studied1 and it has been ascertained3 first1 that in a short circuit there is no appreciable change1 whatever be the combination employed2 secondly1 that when the circuit is long1 or of great resistance1 the tension arrangement is the best1 and this in proportion to the length of the line4 ,this telephonic system1 like the two preceding ones1 requires an inducing machine to transform voltaic into induced currents3 we shall presently speak of this important accessory of these instruments4 ,besides this arrangement1 ,,mm4 ,pollard and ,garnier have employed the one we have represented in fig4 #e1 which has given better results4 ,we shall see presently that it can be used as the receiving organ of sounds4 ,in each case the two carbons must be placed in contact1 and subjected to a certain initial pressure1 which should be regulated by the screw fitted to the support of the lower carbon4 ,as for the receiving telephone1 the arrangement adopted by ,,mm4 ,pollard and ,garnier is the same as ,bell's1 except that they employ tin plates and helices of greater resistance4 ,this resistance ranges in fact from #ajj to #abe miles4 #8,we have always held1' these gentlemen say1 #8that whatever may be the resistance of the outer circuit1 there is an advantage in increasing the number of spirals1 even when using wire ,no4 #db1 which is the one we prefer4' ,illustration3 ,,fig4 #cc4 ,m4 ,hellesen's ,reaction ,telephone4--,m4 ,hellesen believed that the vibrations produced by the voice on the carbon of a telephonic sender would be magnified if the moveable part of the rheotome were subjected to an electro-magnetic action resulting from the vibrations themselves1 and he has contrived a sender1 which is based on the principle shown in fig4 #cc1 and which has the merit of forming in itself the inducing apparatus intended to transform the voltaic currents employed4 ,this instrument is composed of a vertical iron tube1 supported on a magnetic bar ,n ,s1 and surrounded by a magnetising coil ,b ,b1 above which is fixed an inducing helix of fine wire ,i ,i1 communicating with the circuit4 ,within the tube there is a lead pencil ,c1 held by a porte-crayon which can be raised or lowered by means of a screw ,v fixed below the magnetic bar4 ,finally1 above this pencil1 there is an iron vibrating plate ,l ,l1 with a platinum point in communication with the battery in its centre2 the local circuit communicates with the pencil by means of the magnetising helix ,b1 and for this purpose one end is soldered to the iron tube4 ,from this arrangement it follows that the vibrations of the plate ,l ,l1 at the moment when it comes nearest to the pencil1 tend to become greater in consequence of the attractive force exerted on the plate1 and as the pressure of the lead pencil is increased1 it increases the differences of resistance which result from it1 and consequently causes greater variations in the intensity of the transmitted currents4 ,reaction ,telephone of ,messrs4 ,thomson and ,houston4--,the telephonic arrangement we have described has lately been adopted by ,mr4 ,elihu ,thomson and ,mr4 ,edwin ,j4 ,houston1 who1 on ,june #ba1 #ahgh1 two months after ,m4 ,hellesen explained his system to me1#g published an article in #8,the ,english ,mechanic and ,world of ,science' about an instrument very similar to that of ,m4 ,hellesen4 ,in their instrument1 the current1 which passes through a body of moderately conducting capacity1 acts on an electro-magnet provided with an induction coil1 and this electro-magnet reacts on the diaphragm1 in order to increase the range of its vibrations1 and to create at the same moment two electric actions in the same direction3 the only difference lies in the arrangement of the contact of this indifferent conductor with the vibrating plate4 ,instead of a simple contact effected by pressure between this plate and a carbon pencil1 a fragment of the same substance with a sharpened point is fixed on the vibrating plate1 and it dips into a drop of mercury which has been poured into the receptacle made for it at the upper end of the electro-magnet4 ,in other respects1 the arrangement of the instrument is that of an ordinary telephone1 and the iron rod of the electro-magnet represents the magnetised bar of the ,bell telephone4 ,the inventors assert that this instrument can be used both as a sender and receiver1 and it is in the following manner that it is worked in each case4 ,when the instrument is transmitting1 the morsel of carbon dips more or less into the mercury1 and consequently differences are produced in the surfaces of contact1 according to the range of vibrations made by the plate2 the current varies in intensity in proportion to this range1 and induced currents in the induction coil result from these variations2 the induced currents react on the receiving telephone1 as in ,bell's instrument1 and are further strengthened by those which are produced electrically by the movement of the diaphragm before the induction coil1 and the iron of the electro-magnet4 ,when the instrument is used as a receiver1 the usual effects are displayed1 for since the iron of the electro-magnet is magnetised by the current1 its conditions are precisely those of the ordinary ,bell telephone1 and the induced currents reach it in the same manner1 only with greater intensity4 ,messrs4 ,thomson and ,houston assert that their system has produced excellent results1 and that by it the sound of the voice is much less altered than in other telephones4 ,telephones with batteries and liquid senders4--,we have seen that in #ahfg ,mr4 ,gray conceived the idea of a telephonic system based on the differences of resistance effected in a circuit completed by a liquid1 when the layer of liquid interposed between the electrodes varies in thickness under the influence of the vibrations of the telephonic plate which is in communication with one of these electrodes4 ,this system has since been the subject of study by several inventors1 among others by ,,mm4 ,richemond and ,salet2 and ,i give some of the accounts which have been published respecting their researches4 ,another telephone for the reproduction of articulate sounds1 which ,m4 ,richemond terms the electro-hydro telephone1 has been recently patented in the ,united ,states4 ,it resembles that of ,mr4 ,edison in some respects1 but instead of making use of carbon disks to modify the resistance of the circuit1 water is employed1 and this water is placed in communication with the circuit and battery by means of two platinum points1 one of which is fixed on the metallic diaphragm which vibrates under the influence of the voice4 ,as the vibrations of the diaphragm transport the point which is attached to it to different parts of the interpolar layer of liquid1 they diminish or increase the electric resistance of this layer1 and cause corresponding variations in the intensity of the current traversing the circuit4 ,the receiving telephone is of the usual kind4 7,see #8,telegraphic ,journal1' ,september #ae1 #ahgg47 ,m4 ,salet writes3 #8,i thought it would be interesting to construct a telephone in which there should be absolute solidarity in the movements of the two membranes1 and for this purpose ,i have availed myself of the great resistance of liquids4 ,mr4 ,bell had already obtained some results by attaching to the vibrating membrane a platinum wire communicating with a battery1 and dipping more or less into a metallic vessel1 itself connected by the line with the receiving telephone and containing some acidulated water4 ,i have substituted for the platinum wire a small aluminium lever supporting a disk of platinum1 and at a very slight distance from it there is a second disk in connection with the line4 ,the vibrations of the membrane1 tripled or quadrupled in their range1 are not altered in form1 thanks to the small size and light weight of the lever3 they cause variations in the thickness of the liquid layer traversed by the current1 and consequently in its intensity1 and these variations cause corresponding differences in the attractive force of the receiving electro-magnet4 ,under its influence the receiving membrane executes movements which are identical with those of the sending membrane4 ,the sound transmitted is very distinct1 and its timbre is perfectly maintained1 a result which might have been anticipated4 ,the consonants1 however1 are not so clearly pronounced as those transmitted by ,mr4 ,bell's instrument4 ,this inconvenience is most apparent when the lever is heavy1 and might easily be obviated4 ,the electrolysis also produces a continual murmur1 but this does not interfere with the distinctness of the sound4 #8,since on this system the voice is not required to produce1 but only to direct the electric current generated by a battery1 the intensity of the sound received might in theory be increased at pleasure4 ,i have in fact been able to make the receiver emit very powerful sounds1 and ,i think that this advantage greatly counterbalances the necessity of employing a battery1 and a somewhat delicate sending instrument4 ,unfortunately it can only be used for moderate distances4 ,assuming that any displacement of the transmitting membrane increases the resistance to a degree equivalent to five or six hundred yards of wire3 if the line is five hundred yards long1 the intensity of the current will be reduced by one half1 and the receiving membrane will take up a fresh position1 considerably differing from the first2 but if the line is three hundred miles in length1 the intensity of the current will only be modified by a thousandth part4 ,an immense battery must therefore be employed in order that this variation may be translated by a sensible change in the position of the receiving membrane4' 7,see #8,comptes ,rendus de l',acadmie des ,sciences1' ,february #ah1 #ahgh47 ,m4 ,j4 ,luvini1 in an article inserted in #8,les ,mondes1' ,march #g1 #ahgh1 has suggested a system of rheotome by means of a current1 for battery telephones1 which1 although complicated1 possibly offers some advantages1 since it produces currents alternately reversed4 ,in this system1 the vibrating disk of the sender1 which should be in a vertical position1 reacts on a moveable horizontal wire1 turned back at a right angle1 and supporting on each of its branches two platinum points which dip into two bulbs1 filled with a liquid of moderate conducting capacity4 ,the two branches of this wire1 insulated from each other1 are placed in communication with the two poles of the battery1 and the four cups into which the platinum wire dips communicate inversely with the line and the earth by means of platinum wires immoveably fixed in the cups4 ,it follows from this arrangement1 that when the distances are duly regulated between the fixed and moveable wires1 two equal currents will be opposed to each other across the line circuit when the diaphragm is motionless2 but as soon as it vibrates1 the respective distances of the wires will vary1 and it follows from this that there will be a differential current1 of which the intensity will correspond with the extent of the displacement of the system1 or with the range of vibrations1 and the direction will vary with the movements above or below the line of the nodes of vibration4 ,in this way the advantage of the induced currents is obtained4 ,telephones with a battery and voltaic arcs4--,in order to obtain variations of resistance of still greater sensitiveness than is the case with liquids or pulverised substances1 the idea has been suggested of employing conductors of heated gas1 and several arrangements of battery telephones have been made in which the circuit was completed by a stratum of air1 separating the vibrating disk from a platinum point1 which serves to excite an electric discharge of high tension4 ,under these conditions1 the stratum of air becomes the conductor1 and the intensity of the current which traverses it corresponds to its thickness4 ,this problem has been solved1 either by means of voltaic currents of high tension1 or by a ,ruhmkorff coil4 ,the former system was arranged by ,m4 ,trouv1 and he writes as follows on the subject in the journal #8,la ,nature' of ,april #f1 #ahgh3 #8,a metallic vibrating membrane forms one of the poles of a high tension battery2 the other pole is fastened before the disk by a micrometer screw which can be adjusted so as to vary the distance from the disk according to the tension of the battery1 but without ever coming in contact with it4 ,the distance must not in any case exceed that to which the discharge of the battery can extend4 ,under these conditions1 the membrane which vibrates under the influence of the waves of sound has the effect of constantly modifying the distance between the two poles1 and thus of continually varying the intensity of the current3 consequently the receiving instrument 7a ,bell telephone1 or telephone with an electro-magnet7 is subjected to magnetic variations1 corresponding to the variations of the current which affect it1 and this has the effect of making the receiving instrument vibrate at the same moment4 ,this kind of telephonic instrument relies1 therefore1 on the possibility of varying within wide limits the resistance of the outer circuit of a high-tension battery1 in which the poles are not in contact4 ,in order to vary the conditions of this resistance1 it is also possible to interpose some vapour or other medium1 such as air1 or gas of greater or less rarity4' ,m4 ,trouv thinks that he was successful with his battery of small disks1 moistened with sulphate of copper and sulphate of zinc1 arranging these elements1 to the number of five or six hundred1 in glass tubes of small diameter4 ,it is well known that it is unnecessary for the elements to be of large size in order to obtain tension currents4 ,m4 de ,lalagade has suggested an analogous mode by employing for the formation of the arc a current of which the tension is increased by inserting a strong electro-magnet into the circuit4 ,this electro-magnet acts on a ,hughes magnet in order to produce induction currents capable of making the receiving instrument act4 ,m4 de ,lalagade says that a ,bunsen battery1 or one of six cells with bichromate of potash1 will be enough to produce a continuous voltaic arc between the vibrating plate of a telephone and a platinum point which is sufficiently remote to avoid contact4 ,it is necessary1 however1 to begin with a contact1 in order to produce the formation of this arc4 ,in ,m4 de ,lalagade's system1 the vibrating plate should have in its centre a small platinum plate1 in order to obviate the oxidising effects of the spark4 ,the inventor asserts that sounds transmitted in this way1 and reproduced in a telephone of which the electro-magnetic system is set upon a sounding-box1 will have greater intensity than the sounds transmitted by an ordinary telephone1 and the speaker will appear to be close to the ear4 ,mercury ,telephones4--,these systems are based on the physical principle discovered by ,m4 ,lippmann1 that if a layer of acidulated water is placed above mercury1 and connected with it by an electrode and wire1 every mechanical action which exerts pressure on the surface of the mercury1 and alters the form of its meniscus1 will cause an electric reaction1 capable of producing a current with a force which corresponds to the mechanical action exerted4 ,conversely1 every electric action produced on the circuit of such a system will occasion a displacement of the meniscus1 and consequently its movement1 which will be more marked in proportion to the smallness of the tube in which the mercury is placed1 and to the greatness of the electric action4 ,this electric action may result from a difference of potential in the electric condition of the two extremities of the circuit1 which communicate with the electric source employed1 or with some electric generator4#h ,illustration3 ,,fig4 #cd4 ,in accordance with these effects1 it is intelligible that if two tubes ,t ,t1 pointed at the end1 and containing mercury1 are plunged into two vessels ,v ,v 7fig4 #cd7 containing acidulated water and mercury1 and metallic wires1 ,p ,p1 ,q ,q1 are used1 first to connect the columns of mercury in the tubes1 and secondly the layers of mercury at the bottom of the two vessels1 the tubes being a little removed from the surface of the mercury in the vessels1 we shall then have a metallic circuit1 completed by two electrolytes1 one of which will be subjected to the mechanical or electrical effects produced in the other4 ,if two vibratory plates ,b ,b are placed above the tubes1 and one of these is caused to vibrate1 the other will reproduce these vibrations1 influenced by the vibratory movements communicated by the corresponding column of mercury4 ,the vibrations themselves will be in connection with the electrical discharges resulting from the movements of the column of mercury in the first tube1 which are mechanically produced4 ,if an electric generator is introduced into the circuit1 the effect which we have just analysed will be caused by modifications in the potential of this generator1 in consequence of electro-capillary effects4 ,but if no generator is employed1 the action will result from electric currents determined by the electro-capillary attraction itself4 ,in the latter case1 however1 the instrument must be more delicately made1 in order to obtain more sensitive electric reaction1 and ,m4 ,a4 ,brguet describes his instrument as follows4 #8,the instrument consists of a tube of thin glass1 a few centimtres in length1 containing alternate drops of mercury and acidulated water1 so as to constitute so many electro-capillary elements1 connected in tension4 ,the two ends of the tube are fused together1 yet so as to allow a platinum wire to touch the nearest drop of mercury on each side4 ,a small circle of thin deal is fixed at right angles to the tube by its centre1 thus providing a surface of some extent1 which can be applied to the ear when the instrument is a receiver1 and to make the tube more mobile under the influence of the voice when the instrument is a sender4 ,the following are the advantages offered by instruments of this construction3-- #8#a4 ,they do not involve the use of a battery4 #8#b4 ,the disturbing influence of the resistance of a long line is almost destroyed in these instruments1 although it is still appreciable in the ,bell telephone4 #8#c4 ,two mercury telephones1 coupled together as we described above1 are absolutely correlative1 in this sense1 that even different positions in the equilibrium of the mercury in one of them produce different positions of equilibrium in the opposite instrument4 ,it is therefore possible to reproduce at a distance1 without a battery1 not merely faithful indications of oscillatory movements1 which is done by the ,bell telephone1 but also the exact image of the most general movements4' ,friction ,telephones4--,mr4 ,e4 ,gray has quite recently applied the principle of producing sounds by the friction of animal tissues to the construction of a speaking telephone which may be heard through a whole room1 like the singing condenser4 ,he obtains this result by means of clockwork1 which causes the rotation of the metallic disk of which we have spoken 7p4 #bc71 and on which a piece of skin is so arranged as to produce friction4 ,a carbon or liquid telephone is placed at the sending station1 in such a way as to react on an induction coil1 as in the systems of ,edison1 ,navez1 or ,pollard1 and speech is reproduced on the rotating disk1 and is audible1 as we have said1 without the necessity of approaching the ear to the instrument4 ,the best arrangement of the metallic disk on which the animal tissue rubs is that of a cylindrical box1 of which the outer lid is made of a thin sheet of zinc with a highly polished1 slightly oxidised surface2 for the agent of friction1 glove-leather slightly moistened with acidulated water may be used1 or a sinew of an ox1 or skin taken from the ear or tail of a pig4 ,,modifications ,,introduced ,,in ,,the ,,construction ,,of ,,the ,,bell ,,telephones4 ,the modifications which we have been considering relate to the principle of the instrument2 those which we have now to consider are only modifications in the form and arrangement of the different organs which form the ,bell telephone itself1 and which have been designed with the object of increasing the intensity and distinctness of the sounds produced4 ,telephones with several diaphragms4--,when we remember that the induced currents caused in a magnet result from the vibratory movements of the diaphragm1 and that these are produced by the vibrations of the stratum of air interposed between this diaphragm and the vocal organ1 it necessarily follows that if these vibrations of the air react on several diaphragms1 each attached to its electro-magnetic organ1 several induced currents might be caused simultaneously1 and if these were properly connected1 their effects on the receiver would be so much the more intense1 since the sounds produced would result from the combination of several sources of sound4 ,several inventors1 starting from this argument1 have planned instruments of varying ingenuity1 which we will now describe1 but without being able to declare who was the first to realise this idea4 ,it is in fact so simple1 that it probably suggested itself to the minds of several inventors at the same time1 and we see that while ,m4 ,trouv proposed this improvement in ,france in ,november #ahgg1 it was tried in ,america and discussed in ,england1 where indeed it was not expected to produce very favourable results4 ,mr4 ,preece wrote on the subject in a paper entitled #8,on some ,physical ,points connected with the ,telephone1' which was published in ,april #ahgh4 ,he observes that all the attempts to improve the telephone have ended in disappointment and failure4 ,one of the first attempts of the kind was made by ,mr4 ,wilmot1 who expected to obtain favourable results by augmenting the number of diaphragms1 helices1 and magnets1 connecting the helices in a series1 and causing them to act simultaneously1 so as to increase the energy of the currents developed by the influence of the voice2 but experience showed that when the instrument acted directly1 the vibratory effect of each of the diaphragms decreased in proportion to their number1 and the general effect remained the same as with a single diaphragm4 ,mr4 ,wilmot's instrument was made in the beginning of ,october #ahgg1 and that of ,m4 ,trouv was only an imitation of it4 ,on the other hand1 we see that if the telephones with several membranes were not successful in ,england1 this was not the case in ,america1 for the telephones which experience has shown to give the best results in that country are those of ,mr4 ,elisha ,gray and ,mr4 ,phelps1 and these have several diaphragms4 ,it is evident that there are details of construction in these instruments which may appear insignificant in theory1 and which are notwithstanding very important from a practical point of view1 and we believe that it is to this circumstance that instruments of this kind owe their success or failure4 ,thus1 for example1 it seems that the vibrations of air caused in the mouthpiece ought to be immediately directed on the surface of the diaphragms by means of distinct channels2 it is necessary that the empty space round each diaphragm should be sufficiently limited to prevent echoes and interruptions1 unless the case is so large that there is no danger of such effects4 ,above all1 it is necessary that the organs should be fixed in some material unsusceptible of reverberation1 and for this reason a preference is given to iron or ebonite4 ,it is certain that when the instrument is properly made1 its effects are superior to those of the ,bell telephones1 and it is asserted in the #8,telegraphic ,journal' that experiments were made with one of these instruments before the ,royal ,society1 in ,london1 ,may #a1 #ahgh1 and that the intensity of sound was in proportion to the number of diaphragms4 ,this instrument was designed by ,mr4 ,cox ,walker1 of ,york1 and possessed eight diaphragms4 ,he considers that this is the arrangement which gives the best results4 ,illustration3 ,,fig4 #ce4 ,mr4 ,elisha ,gray's ,system4--,mr4 ,elisha ,gray's last system1 which we represent in fig4 #ce1 is one of those which have given the best effects4 ,it is made1 as we see1 of two telephones1 side by side1 to which correspond two tubes1 issuing from a common mouthpiece ,e4 ,one of these telephones is seen in section in the plate1 the other in elevation1 and they correspond to the two branches of a nickel-plated horseshoe magnet ,n ,u ,s1 which may serve as a suspension ring4 ,in that part of the plate which represents the section1 the induction coil is shown in ,b1 and the magnetic core1 of soft iron1 in ,a1 which is screwed to the polar end of the magnet ,s2 the vibrating plate is in ,l ,l1 and1 as we see1 the tube of the mouthpiece terminates on its surface4 ,in another model there are four telephones side by side1 instead of two1 and the effects produced are still more marked4 ,mr4 ,phelps's ,system4--,this system is only deduced from the last1 but there are two models of it4 ,in the larger one1 which makes it possible to hear as distinctly as if the person with whom conversation is held were speaking in a loud voice in the same room1 the two telephones are placed parallel to each other1 and so as to present their diaphragms vertically2 the space between these two diaphragms is occupied by a vertical tube1 terminating at its lower end in a horizontal tube corresponding to the centres of the two diaphragms1 and on this tube the mouthpiece is fitted1 which projects outside the box in which the instrument is enclosed4 ,the induction coils1 and the magnetic cores which traverse them1 follow the axis of the system1 and seem to constitute the axis of a wheel which is polarised by the poles of a horseshoe magnet1 of which the position with reference to the surface of the diaphragms can be regulated by moveable screws4 ,the appearance of the instrument somewhat resembles a gyroscope1 resting by a horizontal axis on two shafts which issue from a flattened horseshoe magnet4 ,above this system there is the electro-magnetic apparatus of the call-bell1 in which there is nothing peculiar1 and which is like the ,german alarums of which we shall speak at the end of this account4 ,this instrument is remarkable for strength and clearness of sound1 and especially for its freedom from the ,punch and ,judy voice so displeasing in other telephones4 ,mr4 ,phelps's small model is in the form of an oblong or elliptical snuff-box1 of which the two centres are occupied by two telephonic systems1 influenced by the same magnet4 ,this magnet is placed in a horizontal position below the snuff-box1 and its poles correspond to the magnetic cores of the coils4 ,these cores are made of iron tubes1 split longitudinally in order to destroy irregular induction reactions1 and the iron diaphragms rest on five spiral springs1 which raise them above the magnetic system4 ,on their other surface the diaphragms are provided with rings of some semi-elastic substance1 which prevent the central vibrations of the disks from becoming complicated by those of their edges4 ,the lid1 hollowed out in very shallow cavities1 is next placed upon the disks1 and there are channels of communication in it to serve as a sounding-box4 ,the mouthpiece corresponds to one of these cavities1 and the other is closed by a small metallic stopper1 which can be withdrawn to regulate the instrument when necessary4 ,since the vibrations of air are transmitted by the channels to both cavities1 the two telephones act together1 although at first sight only one of them seems to be required to produce the effect4 ,mr4 ,phelps praises the simultaneous effects produced on the two instruments1 which he ascribes1 first1 to the semi-elastic ring surrounding the rim of each disk1 and acting as the hammer of the ear1 that is1 as a damper2 then1 to the longitudinal splits of the magnetic core1 and lastly to the small size of the cavities left above the vibrating disks4 ,the instrument is made of ebonite1 grooved on the surface in order to give a better grasp to the hand4 ,mr4 ,phelps has a new model1 called the crown telephone1 which is now in use in ,america1 together with ,mr4 ,edison's carbon sender4 ,in it each of the two systems of the large model we have described is worked by six horseshoe magnets radiating round the magnetic core1 and so arranged that the north poles correspond to this core1 and the other poles to the circular rim of the diaphragm4 ,in this way the magnetic field is considerably enlarged1 and the sound much intensified4 ,in experiments recently made at ,dr4 ,wells's church1 ,new ,york1 an assembly of three hundred people were able to hear speech and vocal or instrumental music distinctly in different parts of the hall4 ,mr4 ,cox ,walker's ,system4--,this system1 on which we have already said a few words1 has exactly the arrangement of that by ,mr4 ,elisha ,gray4 ,the magnets which act upon the diaphragms are horseshoe1 and separate pipes1 issuing from a common mouthpiece1 direct the vibrations of air on the diaphragms4 ,these1 indeed1 are only defined parts of one diaphragm1 bounded in a circle by mouthpieces corresponding to the air-pipes1 and sufficiently restricted on their edges to limit the field of vibration4 ,m4 ,trouv's ,system4--,m4 ,trouv has simplified the arrangement of telephones with a double diaphragm1 by designing the instrument so as to make ,bell's bar magnet react by both poles at once on several disks4 ,for this purpose1 he employs a tubular magnet1 and winds a helix throughout its whole length1 as we see in fig4 #cf4 ,this magnet is maintained in a fixed position in the centre of a small cylindrical box1 of which the base is slightly funnel-shaped1 thus acting as a mouthpiece and acoustic tube4 ,it is consequently pierced in the centre with a hole larger at a1 the station for speaking1 than on the opposite side b4 ,between the base and the poles of the magnet there are two vibrating iron plates1 ,m1 ,m1 one of which1 ,m1 is pierced with a hole a of the same diameter as the hollow part of the magnet1 and consequently smaller than that of the mouthpiece4 ,finally1 several other plates n1 n1 n1 are ranged in parallel lines between these two plates1 so that the magnet and its helix may pass through them4 ,illustration3 ,,fig4 #cf4 ,when anything is said before the mouthpiece a1 the waves of sound encountering the edges of the plate ,m place it in vibration1 and1 continuing their passage inside the tubular magnet1 they cause the plate ,m to vibrate at the same time as ,m4 ,a double inducing action therefore takes place on the tubular magnet1 and this is translated by the induced currents developed in the helix1 which have greater energy since each of the plates intensifies the magnetic effects produced at the pole opposite to the one they influence1 which is always the case with bar magnets when the inactive pole is provided with an armature4 ,this advantage may even be obtained in the case of ordinary telephones1 if the screw which holds the magnet is placed in contact with a mass of soft iron4 ,in ,m4 ,trouv's arrangement1 the induced currents therefore possess greater energy2 but he adds that the sounds reproduced will also be strengthened by the multiplicity of vibratory effects1 and by the enlargement of the magnetic effects1 which results from a better arrangement of the magnets4 #8,when the ear is placed at a1' ,m4 ,trouv writes1 #8it perceives immediately the sounds produced by the first plate ,m1 and those of the second plate reach the ear through the interior of the magnet4 ,this new arrangement is well adapted for an experimental comparison of the results produced by a telephone with a single membrane 7a ,bell telephone71 and those produced by a telephone with several membranes4 ,it is in fact enough to listen at the two faces of the telephone alternately1 in order to perceive at once the difference of intensity in the sounds produced4 ,those collected at a1 on the side of the pierced iron plate1 appear manifestly doubled in intensity compared with those collected at b on the side of the simple membrane which forms the ordinary telephone4 #8,the difference is still more striking if1 in transmitting or receiving a sound of invariable intensity through a multiple telephone1 the unbroken membrane ,m is repeatedly prevented from vibrating4' ,before making this arrangement ,m4 ,trouv had planned another1 which he presented to the ,acadmie des ,sciences1 ,november #bf1 #ahgg1 and which we have glanced at in the beginning of this chapter4 ,he describes it in these terms3-- #8,in order to increase the intensity of the effects produced in the ,bell telephone1 ,i have substituted for the single membrane a cubic chamber1 of which each face is1 with one exception1 formed of a vibrating membrane4 ,each of these membranes1 put in vibration by the same sound1 influences a fixed magnet1 which is also provided with an electric circuit4 ,in this way1 by connecting all the currents generated by the magnets1 a single intensity is obtained1 which increases in proportion to the number of magnets influenced4 ,the cube might be replaced by a polyhedron1 of which the faces might be formed of an indefinite number of vibrating membranes1 so as to obtain the desired intensity4' ,m4 ,demoget's ,system4--,several other systems of telephones with multiple membranes have been proposed4 ,one of them1 planned by ,m4 ,demoget1 consists in placing before the vibrating disk of the ordinary ,bell telephone1 separated by the space of a millimtre1 one or two similar vibrating disks1 taking care to pierce in the centre of the first a circular hole of the same diameter as that of the bar magnet1 and to pierce a larger hole in the second membrane4 ,the inventor asserts that the distinctness as well as the intensity of sounds is increased in this way4 #8,by this arrangement1' says ,m4 ,demoget1 #8since the vibrating magnetic mass is larger in proportion to the magnet1 the electro-motive force of the currents generated is increased1 and consequently the vibrations of the disks of the second telephone are more perceptible4' ,mr4 ,mc,tighe's ,telephone4--,in this telephone1 which has several diaphragms1 there is a horseshoe magnet1 and instead of placing the coils upon the poles1 there is a single coil fastened to an iron core1 which is inserted between wide polar appendices fitted to the two poles of the magnet4 ,these appendices consist of thin plates1 which act as vibrating plates4 ,modifications in the arrangement of ,telephonic ,organs4--,we see that the forms given to the ,bell telephone are very varied1 and this is still more the case with its constituent organs1 without1 however1 producing any remarkable improvements4 ,mr4 ,preece observes that little has been gained by varying the size and strength of the magnets1 and the best effects have been obtained by using the horseshoe magnets directed by ,mr4 ,bell himself4 ,the telephone was certainly introduced into ,europe with the arrangement which is theoretically the best1 although ,mr4 ,bell is still occupied in improving it4 ,this is also the opinion of ,m4 ,hellesen1 who1 like ,mr4 ,preece1 has made many experiments on this point2 but this has not deterred several people from declaring that they have discovered the way of making a telephone speak so as to be audible to an assembly of people4 ,of the different instruments made with this object1 that of ,m4 ,righi seems to be the most important4 ,it was lately tried with success at the ,acadmie des ,sciences1 the ,conservatoire des ,arts et ,mtiers1 and the ,press pavilion of the ,exhibition4 ,illustration3 ,,fig4 #cg4 ,the receiver is only a ,bell telephone of large size1 with a diaphragm of parchment ,l ,l 7fig4 #cg71 in the centre of which there is a sheet-iron disk ,f4 ,this membrane is stretched on a large funnel ,e1 which is fixed on a box ,c ,c1 containing the electro-magnetic coil ,b3 and the magnet ,n ,s1 much larger than in the ordinary instruments1 issues from the box1 and serves as its support4 ,illustration3 ,,fig4 #ch4 ,the sender resembles the one represented in fig4 #ai1 except that1 instead of liquid1 ,m4 ,righi employs plumbago mixed with powdered silver1 and the platinum needle is replaced by a metallic disk ,d 7fig4 #ch74 ,the receiver ,i1 which contains the powder1 is supported on a spring ,r1 which can be pushed up and down by a regulating screw ,v1 and the whole is fitted into a box ,c ,c1 and supported on a foot ,p4 ,the speaker places himself above the mouthpiece ,e1 and the vibrations transmitted to the membrane ,l ,l cause the variations of resistance in ,i which are necessary for the transmission of speech1 as in the ,edison system4 ,two ,bunsen cells are enough to set the instrument at work1 and it will make the sound of a trumpet or flute audible throughout a room4 ,vocal music1 which is less intense1 is necessarily transmitted to a rather less distance1 and words spoken in the natural voice are heard by those standing about two yards and a half from the instrument4 ,the maximum distance at which the instrument has been worked with the battery only is twenty-eight miles1 the distance between ,bologna and ,ferrara1 and for greater distances it is necessary to have recourse to induction coils4 ,in this case1 an induction coil is introduced into the circuit at each station1 and its primary wire is traversed by a current from the local battery1 and so also is the sender1 which is elsewhere connected with the receiver by a commutator4 ,the secondary circuit of these coils is completed through the earth and line wire4 ,from this arrangement it follows that the induced current which influences the receiver in correspondence1 only produces its effect after a second induction1 produced on the primary wire of the local coil1 and it appears that this is a sufficient effect2 but the advantage of this arrangement is1 that it is possible to receive and transmit sounds without the aid of anything but the commutator4 ,among other arrangements which have been suggested1 we may mention one in which1 instead of the bar magnet1 a horseshoe magnet is used1 with a vibrating plate placed between its poles4 ,for this purpose the poles are tipped with iron1 and one of them is pierced with a hole which corresponds to the mouthpiece of the instrument4 ,the two branches of the magnet are also furnished with magnetising helices4 ,when anything is spoken before the hole1 the vibrating plate causes induced currents in the two helices3 these currents would be of opposite direction if the poles were of like nature1 but1 since the magnetic poles are of contrary nature1 they are in the same direction4 ,the vibrating plate then acts like the two plates of ,m4 ,trouv's instrument1 which we have described above4 ,in another arrangement1 lately made by ,ader1 the receiver is only an ordinary two-branched magnet1 of which the armature is supported1 at about two millimtres from its poles1 by a glass plate to which it is glued1 and the plate itself is fastened to two rigid supports4 ,in order to hear it is only necessary to apply the ear to the plate4 ,the sender is a moveable rod of iron or carbon1 which rests on a fixed piece of carbon1 with no pressure except its own weight1 and it supports a concave disk1 to which the speaker applies his mouth4 ,these two parts are so arranged as to move horizontally1 so that1 when the instrument is suspended1 the circuit is forcibly disconnected by the fact of its position1 and is therefore closed until anyone takes it up to speak4 ,speech is well reproduced by this system1 and may be transmitted to some distance if it is made on a larger scale4 ,again1 an anonymous inventor1 in a little note inserted in #8,les ,mondes1' ,february #g1 #ahgh1 writes as follows3 #8,since the intensity of the currents produced in the telephone is in proportion to the mass of soft iron which vibrates before the pole of the magnet1 and since1 on the other hand1 the plate is sensitive in proportion to its tenuity1 ,i employ1 instead of the ordinary plate1 one reduced by nitric acid to the least possible thickness1 and ,i fix it to a circle of soft iron1 which keeps it stretched and forms part of the same substance4 ,this circle is placed in a circular opening made inside the compartment4 ,the intensity of a telephone is much increased when such a system replaces the ordinary plate1 even at one end of the line4' ,in order to obtain vibrating plates of extreme tenuity1 ,m4 ,e4 ,duchemin thought of employing very thin plates of mica1 sprinkled with pulverised iron fixed to the plate by a layer of silicate of potash4 ,the inventor asserts that it is possible to correspond in a low voice with the aid of this system2 but it has this inconvenience1 that the plate will be broken by speaking too loud4 ,professor ,jorgenson1 of ,copenhagen1 has also made a ,bell telephone which produces very intense sounds1 and which has permitted him to observe some curious effects4 ,in this instrument1 the magnet is made in a mode analogous to ,nickls' tubular magnets4 ,there is first a cylindrical magnet with a core of soft iron at its upper end1 to which the coil is fitted2 next1 a magnetised tube1 formed of a steel ring1 which encloses the first magnetic system1 and is connected with it by an iron tube4 ,finally1 above the polar extremities of this system1 there is the vibrating disk1 with the same arrangement as that of ordinary telephones1 and of which the superficies is large4 ,if this plate is only a millimtre in thickness1 the words spoken can be heard throughout a room2 but the sounds lose their clearness when the ear is approached to the vibrating plate1 the words are confused1 and there is the reverberation which is observed on speaking in a place apt to produce echoes3 the listener is1 in fact1 stunned by the sounds produced4 ,on using a thicker plate--one1 for example1 of three or four millimtres--the telephone only produces the effect of the ordinary instruments1 and it is necessary to apply the ear to it4 ,m4 ,marin ,maillet1 of ,lyons1 has suggested that the sounds reproduced by the telephone might be increased by reflecting them through a certain number of reflectors1 which1 by concentrating them in a focus on a resonator1 would considerably enlarge them4 ,since this idea was not accompanied by experiments1 it can hardly be regarded as serious4 ,,telephonic ,,experiments4 ,since ,mr4 ,bell's experiments of which an account has been given in the early part of this work1 much study has been given by men of science and inventors to the effects produced in this curious instrument1 so as to ascertain its theory and deduce improvements in its construction4 ,we will take a glance at these researches in succession4 ,experiments on the ,effects produced by ,voltaic and ,induced ,currents4--,the comparative study of the effects produced in the telephone by voltaic and induced currents was one of the first and most important4 ,in #ahgc1 as we have seen1 ,mr4 ,elisha ,gray converted the voltaic currents1 which he employed to cause the vibrations of his transmitting plate1 into induced currents by means of an induction coil1 such as ,ruhmkorff's4 ,the voltaic currents then traversed the primary helix of the coil1 and the induced currents reacted on the receiving instrument1 producing on its electro-magnetic system the vibrations excited at the sending station4 ,when ,mr4 ,edison designed his battery telephone1 he had recourse to the same means to work his receiving telephone1 since he had ascertained that induced currents were superior to voltaic currents4 ,but this peculiarity of ,mr4 ,edison's arrangement was not clearly understood from the descriptions which reached ,europe1 so that several persons believed that they had invented this arrangement--among others1 ,colonel ,navez and ,,mm4 ,pollard and ,garnier4 ,colonel ,navez1 in an interesting paper on the new telephonic system1 presented to the ,belgian ,royal ,academy1 ,february #b1 #ahgh1 only suggests this arrangement as a mode of reproducing speech at a great distance2 but he quotes no experiment which distinctly shows the advantages of this combination4 ,twenty days later1 ,,mm4 ,pollard and ,garnier1 unacquainted with ,colonel ,navez's researches1 sent to me the results they had obtained by similar means1 and these results appeared to me so interesting that ,i communicated them to the ,acadmie des ,sciences1 ,february #be1 #ahgh4 ,in order that the importance of these results may be clearly understood1 ,i will repeat the text of ,m4 ,pollard's letter1 addressed to me on ,february #bj1 #ahgh3 #8,with the object of increasing the variations of electric intensity in the ,edison system1 we induce a current in the circuit of a small ,ruhmkorff coil1 and we fix the receiving telephone to the extremities of the induced wire4 ,the current received has the same intensity as that of the inducing current1 and consequently the variations produced in the current which works the telephone have a much wider range4 ,the intensity of the transmitted sounds is strongly increased1 and the value of this increase depends upon the relative number of spirals in the inducing and induced circuits4 ,our attempts to determine the best proportions have been laborious1 since it is necessary to make a coil for each experiment2 we have hitherto obtained excellent results with a small ,ruhmkorff coil reduced to its simplest form1 that is1 without condenser or contact-breaker4 ,the inducing wire is ,no4 #af1 and is wound in five layers2 the induced wire is ,no4 #cb1 and in twenty layers4 ,the length of the coil is seven centimtres4 #8,the following is the most remarkable and instructive experiment3 ,when setting the sender to work with a single ,daniell cell1 there is no appreciable effect at the receiving station1 at least in the telephone which ,i have made1 when it is in immediate connection with the circuit2 after inserting the small induction coil1 sounds become distinctly audible1 and their intensity equals that of good ordinary telephones4 ,since the battery current is only moderately intense1 the points of plumbago are not worn down1 and the regulating apparatus lasts for a long while4 ,when a stronger battery is used1 consisting of six cells of bichromate of potash 7in tension7 or twelve ,leclanch cells1 sufficient intensity is obtained by the direct action to make sounds nearly as audible as in ordinary telephones2 but when the induction coil is inserted1 the sounds become much more intense1 and may be heard at a distance of from fifty to sixty centimtres from the mouthpiece4 ,songs may1 under such circumstances1 be heard at a distance of several yards2 but the relative increase does not appear to be so great as in the case of the single ,daniell cell4' ,on the other hand1 #8,les ,mondes1' ,march #g1 #ahgh1 contains an account of a series of experiments made by ,signor ,luvini1 ,professor of ,physics at the ,military ,academy of ,turin1 which proved that the introduction of electro-magnets into the circuit which connects the two telephones sensibly increases the intensity of sound4 ,the maximum effect is produced by placing one close to the transmitting1 and the other close to the receiving telephone1 and the introduction of other magnets is of no use4 ,the inducing wire of a ,ruhmkorff coil1 when introduced into such a circuit1 excited no sensible effects of induction in the induced circuit1 and consequently could not set the telephone in connection with this circuit at work4 ,but the current of a ,clarke machine produces sounds resembling the beats of a drum1 which are deafening when the ear is applied to the instrument3 they become very faint1 however1 at the distance of a mtre4 ,the currents of a ,ruhmkorff machine are still more energetic1 and the sound fills a whole room4 ,by modifying the position of the lever of the coil1 the sound passes through different tones1 which are always in unison with the breaks of the current1 at least up to a certain pitch4 ,this property of currents induced by the ,ruhmkorff coil has enabled ,m4 ,gaiffe to obtain by their means a very simple mode of regulating telephones1 so as to produce in them the maximum amount of sensibility4 ,for this purpose he places the telephone he proposes to regulate in the circuit of an induction instrument with moveable helices and graduated intensities4 ,the sounds which result from the vibrator are then reverberated from the telephone1 and are audible at a distance from the instrument2 by using a screw-driver1 it is possible to adjust the screw to which the free end of the bar magnet of the instrument is fixed4 ,it can be tightened or loosened1 so as to advance or withdraw the other end of the magnet from the vibrating plate of the telephone1 and the process is repeated until the maximum intensity of sound is obtained4 ,on the other hand1 as the sounds given out by the two telephones in correspondence are intense in proportion to the degree of unison in the vibrations produced by them1 it is necessary to select those which emit the same sounds for the same given note2 and the mode we have just described may be employed with advantage1 since it will be enough to observe what instruments give the same note in the condition of maximum sensibility1 when regulated in the same way by the induction machine4 ,it is very important that the telephones in correspondence should be well matched1 not only to ensure clear transmissions1 but also with reference to the tone of voice of those who are to use it4 ,the sound becomes more audible when the tone of voice corresponds to the telephonic tone2 and for this reason some telephones repeat the voices of women and children better than those of men1 and with others the reverse takes place4 ,the telephonic vibrations vary in different instruments1 and these variations may be noted in the way we have indicated4 ,the advantages of induced currents in telephonic transmissions may be easily understood1 if we consider that the variations of resistance in the circuit1 resulting from the greater or less range in the vibrations of the transmitting plate1 are of constant value1 and can only manifest their effects distinctly in short circuits2 consequently the articulate sounds which result from them can only be really appreciable in circuits of great resistance4 ,according to ,mr4 ,warren de la ,rue's experiments 7reported in the #8,telegraphic ,journal1' ,march #a1 #ahgh71 the currents produced by the vibrations of the voice in an ordinary telephone represent in intensity those of a ,daniell cell traversing #ajj megohms of resistance 7or #aj1jjj1jjj kilomtres72 and it is plain that the simple question of greater or less intensity in the currents acting on the receiving telephone is not the only thing we have to consider4 ,with an energetic battery1 it is evident1 in fact1 that the differential currents will always be more intense than the induced currents produced by the action of the instrument4 ,i myself am inclined to believe that induced currents owe the advantages they possess to the succession of inverse currents and their brief duration4 ,these currents1 of which ,m4 ,blaserna considers that the duration does not exceed #a_/bjj of a second1 are much more susceptible than voltaic currents of the multiplied vibrations which are characteristic of phonetic vibrations1 and especially since the succession of inverse currents which take place discharge the line1 reverse the magnetic effects1 and contribute to make the action more distinct and rapid4 ,we cannot therefore be surprised that the induced currents of the induction coil1 which can be produced under excellent conditions at the sending station1 since the circuit of the voltaic current is then very short1 are able to furnish results1 not only more effective than the voltaic currents from which they take their origin1 but even than the induced currents resulting from the action of the ,bell telephone1 since they are infinitely more energetic4 ,as for the effects produced by the currents of ,bell telephones1 which are relatively great when we consider their size1 they are easily explained from the fact that they are produced under the influence of the vibrations of the telephone plate1 so that their variations of intensity always maintain the same proportion1 whatever may be the resistance of the circuit1 and consequently they are not effaced by the distance which divides the two telephones4 ,experiments on the part taken by the different telephonic organs in the transmission of speech4--,in order to introduce all the improvements of which a telephone is capable1 it is important to be quite decided as to the effects produced in the several parts of which it is composed1 and as to the part taken by the several organs which are at work4 ,to attain this object several men of science and engineers have undertaken a series of experiments which have produced very interesting results4 ,one of the points on which it was most important to throw light was that of ascertaining whether the vibrating plate used in their telephone receivers by ,messrs4 ,bell and ,gray is the only cause of the complex vibrations which reproduce speech1 or if the different parts of the electro-magnetic system of the instrument all conduce to this effect4 ,the experiments made by ,mr4 ,page in #ahcg on the sounds produced by the resonant electro-magnetic rods1 and the researches pursued in #ahdf by ,messrs4 de la ,rive1 ,wertheim1 ,matteucci1 c41 on this curious phenomenon1 allow us to state the question1 which is certainly more complex than it at first appears4 ,in order to start from a fixed point1 it must first be ascertained whether a telephone can transmit speech without a vibrating plate4 ,experiments made by ,mr4 ,edison#i in ,november #ahgg1 with telephones provided with copper diaphragms1 which produced sounds1 make the hypothesis credible2 and it received greater weight from the experiments made by ,mr4 ,preece and ,mr4 ,blyth4 ,the fact was placed beyond a doubt by ,mr4 ,spottiswoode 7see the #8,telegraphic ,journal' of ,march #a1 #ahgh71 who assures us that the vibrating plate of the telephone may be entirely suppressed without preventing the transmission of speech1 provided that the polar extremity of the magnet be placed quite close to the ear2 and it was after this that ,i presented to the ,acadmie des ,sciences my paper on the theory of the telephone1 which led to an interesting discussion of which ,i shall speak presently4 ,at first the authenticity of these results was denied1 and then an attempt was made to explain the sounds heard by ,mr4 ,spottiswoode as a mechanical transmission of the vibrations1 effected after the manner of string telephones2 but the numerous experiments which have subsequently been made by ,messrs4 ,warwick1 ,rossetti1 ,hughes1 ,millar1 ,lloyd1 ,buchin1 ,canestrelli1 ,wiesendanger1 ,varley1 and many others1 show that this is not the case1 and that a telephone without a diaphragm can transmit speech electrically4 ,colonel ,navez himself1 who had first denied the fact1 now admits that a telephone without a diaphragm can emit sounds1 and even1 under certain exceptional conditions1 can reproduce the human voice2 but he still believes that it is impossible to distinguish articulate words4 ,this uncertainty as to the results obtained by the different physicists who have studied the matter shows that at any rate the sounds thus reproduced are not clearly defined1 and that in physical phenomena1 only appreciable to our senses1 the appreciation of an effect so undefined must depend on the perfection of our organs4 ,we shall presently see that this very slight effect can be largely increased by the arrangement adopted by ,messrs4 ,bell and ,gray1 and we shall also see that1 by a certain mode of magnifying the vibrations1 it has been decisively proved that a telephone without a diaphragm can readily reproduce speech4 ,i proceed to give the description of such a telephone1 which was shown by ,mr4 ,millar at the meeting of the ,british ,association at ,dublin in ,august #ahgh4 ,this instrument consists of a small bar magnet1 three inches in length and #e_/af of an inch in width and thickness1 and a copper helix 7,no4 #cj7 of about six mtres in length is wound round the bar4 ,it is fixed in a box of rather thick pasteboard1 fitted above and below with two zinc plates1 which render it very portable4 ,with a telephonic battery sender and a single ,leclanch cell1 speech can be perfectly transmitted2 the whistling of an air1 a song1 and even the act of respiration become audible4 ,it seems also that the instrument can act without a magnet1 merely with a piece of iron surrounded by the helix2 but the sounds are then much fainter4 ,signor ,ignace ,canestrelli obtained the same results by making one of the carbon telephonic senders react on a telephone without a diaphragm1 by means of an induction coil influenced by two ,bunsen cells4 ,he writes as follows on the subject3 #8,with this arrangement ,i was able to hear the sound of any musical instrument on a telephone without a diaphragm3 singing1 speaking1 and whistling were perfectly audible4 ,whistling could be heard1 even when the telephone without a diaphragm was placed at some distance from the ear4 ,in some cases1 depending on the pitch of the voice1 on the distance of the sending station1 and on the joint pressure exerted by the carbons1 ,i could even distinguish words4 #8,i finally discharged the currents of the transmitter into the coils of insulated copper wire with which the two poles of a magnet were provided4 ,this magnet was placed on a musical box1 made of very thin slips of wood1 and on placing the ear at the opening of the box ,i obtained the same results as with the ordinary telephones without a diaphragm4' ,m4 ,buchin1 after repeating experiments of the same kind as the above1 intimates that it is easy to hear the sounds produced by a telephone without a diaphragm1 by introducing into the ear the end of an iron rod1 of which the other end is applied to the active pole of the bar magnet of the telephone4 7,see #8,le ,journal d',electricit1' ,october #e1 #ahgh47 ,i repeat finally the account of some experiments made by ,mr4 ,hughes and ,m4 ,paul ,roy which are interesting from our present point of view4 #a4 ,if an armature of soft iron is applied to the poles of an electro-magnet1 with its two branches firmly fixed on a board1 and if pieces of paper are inserted between this armature and the magnetic poles1 so as to obviate the effects of condensed magnetism2 if1 finally1 this electro-magnet is connected with a speaking microphone1 of the form given in fig4 #ci1 it is possible to hear the words spoken in the microphone on the board which supports the electro-magnet4 #b4 ,if two electro-magnets are placed in communication with a microphone1 with their poles of contrary signs opposite to each other1 and if their poles are separated by pieces of paper1 speech will be distinctly reproduced1 without employing armature or diaphragm4 ,these experiments are1 however1 delicate1 and demand a practised ear4 #c4 ,if1 instead of causing the current produced by a microphone to pass through the helix of a receiving telephone1 it is sent directly into the bar magnet of this telephone in the direction of its axis--that is1 from one pole to another--the words pronounced in the microphone may be distinctly heard4 ,this experiment by ,m4 ,paul ,roy indicates1 if it is exact1 that the electric pulsations which traverse a magnet longitudinally will modify its magnetic intensity4 ,the experiment1 however1 demands verification4 ,another point was obscure4 ,it was important to know whether the diaphragm of a telephone really vibrates1 or at least if its vibrations could involve its displacement1 such as occurs in an electric vibrator1 or in wind instruments which vibrate with a current of air4 ,m4 ,antoine ,brguet has made some interesting experiments on the subject1 which show that such a movement cannot take place1 since speech was reproduced with great distinctness from telephones with vibrating plates of various degrees of thickness1 and he carried the experiment so far as to employ plates fifteen centimtres in thickness4#aj ,when pieces of wood1 caoutchouc1 and other substances were laid upon these thick plates1 the results were the same4 ,in this case it cannot be supposed that the plates were moved to and fro4 ,i have moreover ascertained1 by placing a layer of water or of mercury on these plates1 and even on thin diaphragms1 that no sensible movement took place1 at least when the induced currents produced by the action of speaking were used as the electric source4 ,no ripples could be seen on the surface of the liquid1 even when luminous reflectors were employed to detect them4 ,and indeed it can hardly be admitted that a current not more intense than that of a ,daniell element1 which has traversed #aj1jjj1jjj kilomtres of telegraphic wire--a current which can only show deviation on a ,thomson galvanometer--should be powerful enough to make an iron plate as tightly stretched as that of a telephone vibrate by attraction1 even if we grant that the current was produced by laying a finger on the diaphragm4 ,very nice photographic experiments do1 however1 show that vibrations are produced on the diaphragm of the receiving telephone2 they are indeed excessively slight1 but ,mr4 ,blake asserts that they are enough to cause a very light index1 resting on the diaphragm1 to make slight inflections on a line which it describes on a register4 ,yet this small vibration of the diaphragm does not show that it is due to the effect of attraction1 for it may result from the act of magnetisation itself in the centre of the diaphragm4#aa ,an interesting experiment by ,mr4 ,hughes1 repeated under different conditions by ,mr4 ,millar1 confirms this opinion4 ,if the magnet of a receiving telephone consists of two magnetised bars1 perfectly equal1 separated from each other by a magnetic insulator1 and they are so placed in the coil as to bring alternately the poles of the same and of contrary signs opposite to the diaphragm1 it is known that the telephone will reproduce speech better in the latter case than in the former4 ,now1 if the effects were due to attraction1 this would not be the case2 for the actions are in disagreement when the poles of contrary signs are subjected to the same electric influence1 while they are in agreement when these poles are of like signs4 ,on the other hand1 it is known that if several iron plates are put together in order to form the diaphragm of the receiver1 the transmission of sounds is much stronger than with a simple diaphragm2 and yet the attraction1 if it has anything to do with it1 could only be exerted on one of the diaphragms4 ,it further appears that it is not merely the magnetic core which emits sounds1 but that they are also produced with some distinctness by the helices4 ,signor ,rossetti had already ascertained this fact1 and had even remarked that they could be animated by a slight oscillatory movement along the bar magnet1 when they were not fixed upon it4 ,several observers1 among others ,m4 ,paul ,roy1 ,herr ,wiesendanger1 and ,signor ,canestrelli1 have since mentioned similar facts1 which are really interesting4 #8,if1' writes ,m4 ,paul ,roy1 #8a coil of fine wire1 which is at the extremity of the bar magnet of a ,bell telephone1 receives the pulsatory currents transmitted by a carbon telephone1 it is only necessary to bring the coil close to the ear in order to hear the sounds4 #8,the sounds received in this way are very faint1 but become much stronger if a piece of iron is introduced into the circuit coil4 ,a magnet acts with still greater force1 even when it consists of a simple magnetised needle4 ,finally1 the sound assumes its maximum intensity when an iron disk is inserted between the ear and the coil4 #8,by placing the end of the coil to the ear1 and sending a current through it from the bar magnet1 it is ascertained that the sound is at its minimum when the neutral line of the magnet is enclosed by the coil1 and that it increases until attaining its maximum1 when the magnet is moved until one of its poles corresponds to the coil4 #8,this fact of the reproduction of sounds by a helix is universal4 ,every induction coil and every electro-magnet are capable of reproducing sound when the currents of the sender are of sufficient intensity4' ,signor ,canestrelli writes as follows3 #8,with the combination of a carbon telephone and one without diaphragm or magnet--that is1 with only a simple coil--,i was able to hear whistling through the coil1 placed close to the ear4 ,this coil was of very fine copper wire1 and the currents were produced through an induction coil by two ,bunsen elements4 ,the contacts of the telephone were in carbon1 and it was inserted in the primary circuit4 #8,i fastened the coil to the middle of a tightly stretched membrane which served as the base of a short metal cylinder4 ,when a magnet was placed near this part of the coil1 the sounds were intensified1 and when ,i fixed the magnet in this position1 ,i could hear what was said4 #8,i afterwards substituted for the magnet a second coil1 fastened to a wooden bar1 and on causing the induced currents to pass into both coils at once ,i was able to hear articulate speech1 although not without difficulty4 #8,under these latter conditions ,i found it possible to construct a telephone without a magnet1 but it required a strong current1 and it was necessary to speak into the sender in a special manner1 so as to produce strong and concentrated sounds4' ,another very interesting experiment by ,m4 ,a4 ,brguet shows that all the constituent parts of the telephone--the handle1 the copper rims1 and the case1 as well as the diaphragm and the electro-magnet--can transmit sounds4 ,m4 ,brguet ascertained this fact by the use of string telephones1 which he attached to different parts of the telephone on which the experiment was made4 ,in this way he was not only able to establish a correspondence between the person who worked the electric telephone and the one who was listening through the string telephone1 but he also made several string telephones act1 which were attached to different parts of the electric telephone4 ,these two series of experiments show that sounds may be obtained from different parts of the telephone without any very appreciable vibratory movements4 ,but ,signor ,luvini wished for a further assurance of the fact1 by ascertaining whether the magnetisation of any magnetic substance1 followed by its demagnetisation1 would involve a variation in the form and dimensions of this substance4 ,he consequently caused a large tubular electro-magnet to be made1 which he filled with a quantity of water1 so that1 when its two ends were corked1 the liquid should rise in a capillary tube fitted to one of the corks4 ,in this way the slightest variations in the capacity of the hollow part of the electro-magnet were revealed by the ascent or descent of the liquid column4 ,he next sent an electric current of varying intensity through the electro-magnet1 but he was never able to detect any change in the level of the water in the tube2 although by this arrangement he could measure a change of volume of #a_/cj of a cubic millimtre4 ,it appears from this experiment that the vibrations produced in a magnetic substance under the influence of successive magnetisations and demagnetisations1 are wholly molecular4 ,yet other experiments made by ,m4 ,canestrelli seem to show that these vibrations are so far sensible as to produce sounds which can be detected by the microphone4 ,he writes as follows on the subject3 #8,when the broken currents of an induction coil are discharged into a coil placed on a sounding-box1 it is possible to hear at a little distance the sounds produced by the induced currents thus generated4 ,on approaching the magnet to the opening of the coil1 these sounds are intensified1 and the vibrations of the magnet become sensible to the touch2 this vibration might even be made visible by suspending the magnet inserted into the coil to a metallic wire1 which is fitted to a membrane stretched on a drum1 and the latter will then reproduce sounds4 ,when the same magnet is suspended to a microphone1 it is possible1 with the aid of a telephone1 to ascertain the same effects1 which are then increased4' ,we shall presently consider how these different deductions are to be interpreted1 so as to render the true theory of the telephone intelligible2 but1 before doing so1 we will mention some other experiments which are not without interest4 ,we have seen that the experiments of ,messrs4 ,edison1 ,blyth1 and ,preece1 show that sounds may be reproduced by a telephone with a diaphragm made of some unmagnetic substance1 and they also show1 which is still more curious1 that these sounds may be transmitted under the influence of induced currents produced by these diaphragms when they are placed in vibration before the magnet4 ,messrs4 ,edison and ,blyth had already adduced this fact1 which was received with incredulity1 but it has been confirmed by ,mr4 ,warwick in an article published in the #8,english ,mechanic4' ,he writes that in order to act upon the magnet1 so as to produce induced currents1 something possessed of greater energy than gas must first be made to vibrate4 ,it is not1 however1 necessary that this substance should be magnetic1 for diamagnetic substances act perfectly4#ab ,mr4 ,preece sought for the cause in the induced currents developed in any conducting body when a magnet is moved before it1 currents which give rise to the phenomenon discovered by ,arago and known by the name of magnetism by rotation4 ,yet these facts do not appear to us to be sufficiently well established to make the theory worthy of serious consideration1 and it is possible that the effects observed resulted from simple mechanical transmissions4 ,to conclude the account of these experiments1 we will add that ,mr4 ,w4 ,f4 ,barrett thinks it somewhat difficult to define the mode of vibration of the diaphragm1 since1 while a certain amount of compression exerted on the iron destroys the sounds resulting from the peculiar effects of magnetisation1 a still stronger compression causes them to reappear4 ,it is certain that the question is full of obscurity1 and demands great research3 it is enough to have shown that the theory hitherto held is insufficient4 ,on the other hand1 ,colonel ,navez considers that the intensity of sound reproduced in a telephone depends not only on the range of vibrations1 but also on the vibrating surface and the effect it produces on the stratum of air which transmits the sound4 7,see paper by ,colonel ,navez in the #8,bulletin de l',acadmie de ,belgique1' ,july #g1 #ahgh47 ,experiments on the ,effects which result from ,mechanical ,shocks communicated to different parts of a ,telephone4--,if a piece of iron is applied to the screw which holds the magnet of the ordinary telephone1 it is observed that the transmitted sounds are more distinct1 owing to the force supplied to the active pole of the magnet2 but at the moment when the piece of iron is applied to the screw a distinct noise is heard1 which seems to be due to the mechanical vibrations caused in the magnet at the moment of the shock4 ,m4 des ,portes1 a lieutenant in the ,french navy1 has lately made some interesting experiments on this class of phenomena4 ,he has observed that if1 in a telephonic circuit of #ij yards completed by the earth1 the sending telephone is reduced to a simple magnet1 provided with the coil which constitutes its electro-magnetic organ1 and if this magnet is suspended vertically by a silken thread1 with the coil above it1 a blow struck upon the magnet1 either by a copper rod or a piece of wood1 will cause distinct sounds to be produced in the receiving telephone--sounds which will increase in intensity when the blow is struck close to the coil1 and which will become still stronger1 but less clear1 if a vibrating plate of soft iron is placed in contact with the upper pole of the magnet4 ,when the striking instrument is made of iron1 the sounds in question are more strongly marked than if it is of wood1 and when the magnet has a vibrating disk applied to its active pole1 a vibration of the disk takes place at the moment when the shock is heard4 ,if the striking body is a magnet1 the sounds produced resemble those obtained when it is of iron1 if the effect is produced between poles of the same nature2 but if the poles are of contrary natures1 a second noise is heard after each blow1 which is produced by drawing away the magnet1 and which appears to be a blow struck with much less force4 ,the sound is of course increased if the magnet is provided with its vibrating disk4 ,if words are uttered on the vibrating disk of the sending telephone1 when it is applied to the pole of the magnet1 various sounds are heard on the receiving telephone1 somewhat similar to those produced by vibrating one of the strings of a violin1 and the sound made in withdrawing the disk from contact with the magnet is distinctly heard in the receiver4 ,the person who applies his ear to the vibrating disk of the sender when it is arranged as above1 may hear the voice of anyone who speaks into the receiver1 but cannot distinguish the words1 owing1 no doubt1 to the condensed magnetism at the point of contact between the magnet and the vibrating disk1 which slackens the magnetic variations and makes it more difficult for them to take place4 ,a coil is not necessary in order to perceive the blows struck upon the magnet with a rod of soft iron4 ,it is enough to wind three turns of naked conducting wire1 which acts as line wire1 round one end of the magnet1 and the sounds perceived cease1 as in other experiments1 when the circuit is broken1 plainly showing that they are not due to mechanical transmission4 ,it is a still more curious fact that if the magnet is placed in the circuit1 so as to form an integral part of it1 and if the two ends of the conducting wire are wound round the ends of the magnet1 the blows struck upon the latter with the soft iron rod are perceived in the telephone as soon as one pole of the magnet is provided with a vibrating disk4 ,i have myself repeated ,m4 des ,portes' experiments by simply striking on the screw which1 in ordinary telephones1 fastens the magnet to the instrument1 and ,i have ascertained that1 whenever the circuit was complete1 the blows struck with an ivory knife were repeated by the telephone3 they were1 it is true1 very faint when the vibrating disk was removed1 but very marked when the disk was in its place4 ,on the other hand1 no sound was perceived when the circuit was broken4 ,these sounds were louder when the blows were struck upon the screw than when they were struck on the pole of the magnet itself above the coil3 for this reason1 that in the first case the magnet could vibrate freely1 while in the second the vibrations were stifled by the fixed position of the bar magnet4 ,these effects may be to some extent explained by saying that the vibrations caused in the magnet by the shock produce undulatory displacements of the magnetised particles in the whole length of the bar1 and that induced currents would1 according to ,lenz's law1 result in the helix from these displacements--currents of which the force would increase when the power of the magnet was further excited by the reaction of the diaphragm1 which acts as an armature1 and also by that of the striking instrument when it also is magnetic4 ,yet it is more difficult to explain ,m4 des ,portes' later experiments1 and the effect may be produced by something more than the ordinary induced currents4 ,these are not the only experiments which show the effects produced under the influence of molecular disturbance of various kinds4 ,mr4 ,thompson1 of ,bristol1 has observed that if a piece of iron and a tin rod placed perpendicularly on the iron are introduced into the circuit of an ordinary telephone1 it is enough to strike the tin rod in order to produce a loud sound in the telephone4 ,he has also shown that if the two ends of a bar magnet are enclosed by two induction coils which are placed in connection with the circuit of a telephone1 and if the flame of a spirit lamp is moved below the magnet in the space dividing the two coils1 a distinct sound is heard as soon as the flame exerts its influence on the bar magnet4 ,this effect is undoubtedly due to the weakening of the magnetic force of the bar which is produced by the action of heat4 ,i have myself observed that a scratching sound on one of the wires which connect the telephones is heard in both of them1 at whatever point in the circuit the scratch is made4 ,the sounds produced are indeed very faint1 but they can be distinctly heard1 and they become more intense when the scratch is made on the binding-screws of the telephone wires4 ,these sounds cannot result from the mechanical transmission of vibrations1 since they are imperceptible when the circuit is broken4 ,from these experiments it appears that some sounds which have been observed in telephones tried on telegraph stations may arise from the friction of the wires on their supports--a friction which produces those very intense sounds which are sometimes heard on telegraphic wires4 ,theory of the ,telephone4--,it appears from the several experiments of which we have spoken that the explanation generally given of the effects produced in the telephone is very imperfect1 and that the transmission of speech1 instead of resulting from the repetition by the membrane of the receiving telephone 7influenced by electro-magnetism7 of vibrations caused by the voice on the membrane of the transmitting membrane1 is due to molecular vibrations produced in the whole electro-magnetic system1 and especially on the magnetic core contained in the helix4 ,these vibrations must be of the same nature as those which have been observed in resonant electro-magnetic rods by ,,mm4 ,page1 de la ,rive1 ,wertheim1 ,matteucci1 c41 and these have been employed in telephones by ,reiss1 by ,cecil and ,leonard ,wray1 and by ,vanderweyde4 ,according to this hypothesis1 the principal office of the vibrating plate consists in its reaction1 in order to produce the induced currents when the voice has placed it in vibration1 and by this reaction on the polar extremity of the bar magnet it strengthens the magnetic effects caused in the centre of the bar when it vibrates under the electro-magnetic influence1 or at least when it is affected by the magnet4 ,since the range of these vibrations for a single note is great in proportion to the flexibility of the note1 and since1 on the other hand1 the variations in the magnetic condition of the plate are rapid in proportion to the smallness of its mass1 the advantage of employing1 as ,mr4 ,edison has done1 very thin and relatively small plates is readily understood4 ,in the case of transmission1 the wider range of vibration increases the intensity of the induced currents transmitted4 ,in the case of reception the variations in the magnetising force which produces the sounds are rendered clearer and more distinct1 both in the armature membrane and in the bar magnet3 something is gained1 therefore1 in each case4 ,this hypothesis by no means excludes the phonetic effects of the mechanical and physical vibrations which may be produced in the armature plate under the influence of magnetisation and demagnetisation to which it is subjected1 and these join their influence to that of the magnetic core4 ,what is the nature of the vibrations sent into the receiving telephone8 ,this question is still obscure1 and those who have studied it are far from being in agreement3 as early as #ahdf it was the subject of an interesting discussion between ,,mm4 ,wertheim and de la ,rive1 and the new discoveries render it still more complex4 ,m4 ,wertheim considers that these vibrations are at once longitudinal and transverse1 and arise from attractions exchanged between the spirals of the magnetising helix and the magnetic particles of the core4 ,m4 de la ,rive holds that in the case we are considering the vibrations are simply longitudinal1 and result from molecular contractions and expansions produced by the different combinations assumed by the magnetic molecules under the influence of magnetisation and demagnetisation4 ,this appears to us to be the most natural explanation1 and it seems to be confirmed by the experiment made by ,m4 ,guillemin in #ahdf4 ,m4 ,guillemin ascertained that if a flexible iron rod1 surrounded by a magnetising helix1 is kept in position by a vice at one end1 and bent back by a weight at the other1 it can be made to return instantly to its normal position by sending a current through the magnetising helix4 ,this recovery can in such a case be due to nothing but the contraction caused by the magnetic molecules1 which1 under the influence of their magnetisation1 tend to produce intermolecular attractions1 and to modify the elastic conditions of the metal4 ,it is known that when iron is thus magnetised it becomes as hard as steel1 and a file makes no impression on its surface4 ,it is at any rate impossible to dispute that sounds are produced in the magnetic core1 as well as in the armature1 under the influence of intermittent electric action4 ,these sounds may be musical or articulate2 for as soon as the sender has produced the electric action required1 there is no reason why vibrations which are effected in a transverse or longitudinal direction should transmit the one more than the other4 ,these vibrations may1 as we have seen1 be termed microscopic4 ,signor ,luvini1 who shares our opinion of the foregoing theory1 does not1 however1 think it wholly satisfactory1 unless account is taken of the reaction caused by the bar magnet on the helix which surrounds it4 #8,there cannot1' he says1 #8be action without reaction1 and consequently the molecular action produced in the magnet ought to cause corresponding variations in the helix1 and these two effects ought to contribute to the production of sounds4' ,he supports this remark by a reference to ,professor ,rossetti's experiment1 of which we have spoken above4 ,we believe1 however1 that this double reaction of which ,signor ,luvini speaks is not indispensable1 for we have seen that insulated helices can produce sounds2 it is true that the spirals1 reacting on each other1 may be the cause of this4 ,the difficulty of explaining the production of sounds in an electro-magnetic organ destitute of armature caused the authenticity of the experiments we have described to be at first denied1 and ,colonel ,navez started a controversy with us which is not likely to be soon terminated2 yet one result of this controversy is that ,colonel ,navez was obliged to admit that the sound of the human voice may be reproduced by a telephonic receiver without a disk4 ,but he still believes that this reproduction is so faint that it is not possible to recognise articulate words1 and he maintains that the transverse vibrations of the disk1 which are due to effects of attraction1 are the only ones to reproduce articulate speech with such intensity as to be of any use4 ,it is certain that the articulation of speech requires a somewhat intense vibration which cannot easily be produced in a telephone without a diaphragm2 for it must be remembered that in an instrument so arranged1 the magnetic effects are reduced in a considerable ratio1 which is that of the magnetic force developed in the magnet1 multiplied by itself1 and that so faint an action as that effected in a telephone becomes almost null when1 in consequence of the suppression of the armature1 it is only represented by the square root of the force which produced it4 ,it is therefore possible that the sounds which are hardly perceptible in a telephone without a diaphragm become audible when the cause which provokes them is multiplied by itself1 and when there are in addition the vibrations produced in the heart of the armature itself1 influenced by the magnetisations and demagnetisations to which it is subjected4 ,in order to show that the action of the diaphragm is less indispensable than ,colonel ,navez seems to imagine1 and that its vibrations are not due to electro-magnetic attractions1 it will be enough to refer to ,mr4 ,hughes's experiments1 which we have mentioned above4 ,it is certain that if this were the effect produced1 we should hear better when the two bar magnets present their poles of the same nature before the diaphragm1 than when they present the poles of contrary natures1 since the whole action would then converge in the same direction4 ,again1 the more marked effects obtained with multiple diaphragms in juxtaposition completely exclude this hypothesis4 ,it is1 however1 possible that in electro-magnetic telephones the iron diaphragm1 in virtue of the rapid variations of its magnetic condition1 may contribute to render the sounds clearer and more distinct2 it may react in the way the tongue does2 but we believe that the greater or less distinctness of the articulate sounds must be chiefly due to the range of vibrations4 ,thus ,mr4 ,hughes has shown that the carbons of metallised wood employed in his microphonic speakers were to be preferred to retort carbons for the transmission of speech1 for the very reason that they had less conductivity1 so that the differences of resistance which result from differences of pressure are more marked1 and consequently it is easier to seize the different degrees of vocal sounds which constitute articulate speech4 ,it must be clearly understood that what we have just said only applies to the ,bell telephone1 that is1 to a telephone in which the electric currents have such a faint intensity that it cannot be supposed there is any external attractive effect4 ,when these currents are so energetic as to produce such an effect1 a transverse electro-magnetic vibration certainly takes place1 which is added to the molecular vibration1 and helps to increase the sounds produced4 ,but it is no less true that this transverse vibration by attraction or by movement of the diaphragm is not necessary for the reproduction of sounds1 whether musical or articulate4 ,we are not now concerned with the discussion of magnetic effects2 there has been an advance in science since ,colonel ,navez started the controversy1 and we must ask how his theory of the movements of the telephone diaphragm by attraction will explain the reproduction of speech by a receiving microphone destitute of any electro-magnetic organ1 and ,i can assert that my experiments show that there can be no mechanical transmission of vibrations1 since no sound is heard when the circuit is broken or deprived of its battery4 ,colonel ,navez must therefore accept the molecular vibrations4 ,this certainly gives us a new field for study2 but it is because ,european men of science persist in remaining bound by incomplete theories that we have allowed the ,americans who despise them to reap the glory of the great discoveries by which we have lately been astonished4 ,the experiments quoted above show that sounds may be reproduced not only by simple helices without an electro-magnetic organ1 but also by the plates of a condenser1 in spite of the pressure exerted upon them2 and when we add to this the effects ,i have just pointed out1 it may be supposed that vibrations of sound must result from every reaction between two bodies which has the effect of producing abruptly and at close intervals modifications in the condition of their electric or magnetic equilibrium4 ,it is known that the presence of ponderable matter is necessary for the production of electric effects1 and it is possible that the molecular vibrations of which ,i have spoken may be the result of molecular movements1 due to the variations of the electric force which holds the molecules in a special condition of reciprocal equilibrium4 ,in conclusion1 the theory of the telephone and microphone1 considered as reproductive organs of speech1 is still far from being perfectly clear1 and it would be imprudent to be too positive on questions of such recent origin4 ,the theory of the electric transmission of sounds in electro-magnetic telephones is somewhat complex4 ,it has been seen that they can be obtained from diaphragms of non-magnetic substance1 and even from simple mechanical vibrations produced by shocks4 ,are we to ascribe them in the first case to the inductive reaction of the magnet on the vibrating plate1 and in the second case to the movements of magnetic particles before the spirals of the helix8 ,the matter is still very obscure2 yet it is conceivable that the modifications of the inducing action of the magnet on the vibrating diaphragm may involve variations in the magnetic intensity1 just as we can admit an effect of the same kind due to the approach and withdrawal of the magnetic particles of the spirals of the helix2 ,m4 ,trve1 however1 believes that there is in the latter case a special action1 which he has already had occasion to study under other circumstances1 and he sees in the current thus caused the effect of the transformation of the mechanical labour produced amidst the magnetic molecules4 ,the question is complicated by the fact that these effects are often produced by purely mechanical transmissions4 ,there is another point to consider1 on which ,colonel ,navez has made some interesting remarks2 that is1 whether the effects in the receiver are stronger with permanent than with temporary magnets4 ,in the first model of the telephone1 exhibited by ,mr4 ,bell at ,philadelphia1 the receiver was1 as ,i have said1 made of a tubular electro-magnet1 furnished with a vibrating disk at its cylindrical pole2 but this arrangement was abandoned by ,mr4 ,bell1 with the object1 as he states in his paper1 of rendering his instrument both a receiver and a sender4#ac ,yet ,colonel ,navez maintains that the magnet plays an important part1 and is even indispensable under the present conditions of its form4 #8,it is possible1' he says1 #8under certain circumstances1 and by making the instrument in a special way1 to make a ,bell receiver speak without a permanent magnet1 yet with an instrument of the usual construction the sound ceases when the magnet is withdrawn and replaced by a cylinder of soft iron4 ,in order to restore the voice of the telephone1 it is enough to approach the pole of a permanent magnet to the cylinder of soft iron4 ,it follows from these experiments that a ,bell telephone cannot act properly unless the disk is subjected to an initial magnetic tension obtained by means of a permanent magnet4 ,it is easy to deduce this assertion from a consideration of the theory4' ,the assertion may be true in the case of ,bell telephones1 which are worked by extremely weak currents1 but when these currents are relatively strong1 all electro-magnets will reproduce speech perfectly1 and we have seen that ,m4 ,ader made a telephone with the ordinary electro-magnet which acted perfectly4 ,the action of the currents sent through the helix of a telephone can be easily explained4 ,whatever may be the magnetic conditions of the bar1 the induced currents of different intensity which act upon it produce modifications in its magnetic state1 and hence the molecular vibrations follow from contraction and expansion4 ,these vibrations are likewise produced in the armature under the influence of the magnetisations and demagnetisations which are produced by the magnetic action of the core1 and they contribute to the vibrations of the core itself1 while at the same time the modifications in the magnetic condition of the system are increased by the reaction of the two magnetic parts upon each other4 ,when the bar is made of soft iron1 the induced currents act by creating magnetisations of greater or less energy1 followed by demagnetisations which are the more prompt since inverse currents always succeed to those which have been active1 and this causes the alternations of magnetisation and demagnetisation to be more distinct and rapid4 ,when the bar is magnetised1 the action is differential1 and may be exerted in either direction1 according as the induced currents corresponding to the vibrations which are effected pass through the receiving coil in the same or opposite direction as the magnetic current of the bar4 ,if these currents are in the same direction1 the action is strengthening1 and the modifications are effected as if a magnetisation had taken place4 ,if these currents are of opposite direction1 the inverse effect is produced2 but1 whatever the effects may be1 the molecular vibrations maintain the same reciprocal relations and the same height in the scale of musical sounds4 ,if the question is considered from the mathematical point of view1 we find the presence of a constant1 corresponding with the intensity of the current1 which does not exist in mechanical vibrations1 and which may possibly be the cause of the peculiar tone of speech reproduced by the telephone1 a tone which has been compared to the voice of ,punch4 ,m4 ,dubois ,raymond has published an interesting paper on this theory1 which appeared in #8,les ,mondes1' ,february #ba1 #ahgh1 but we do not reproduce it here1 since his remarks are too scientific for the readers for whom this work is intended4 ,we will only add that ,mr4 ,c4 ,w4 ,cunningham asserts that the vibrations produced in a telephone cannot be manifested under precisely the same conditions as those which affect the tympanum of the ear1 because the latter has a peculiar funnel-shaped form1 which excludes every fundamental note1 specially adapted to it1 and this is not the case with the bars and magnetic plates which possess fundamental notes capable of greatly altering the half-tones of the voice4 ,he considers the alteration of the voice observed in the telephone must be ascribed to these fundamental notes4 ,m4 ,wiesendanger's ,thermophone4--,m4 ,wiesendanger1 in an article inserted in the #8,english ,mechanic and ,world of ,science1' ,september #ac1 #ahgh1 ascribes the reproduction of speech in certain telephones to vibratory movements resulting from molecular expansions and contractions produced by variations of temperature1 and these variations would follow from the currents of varying intensity which are transmitted through the telephonic circuits4 ,he was conscious of one objection to this theory1 namely1 that the movements of expansion and contraction due to heat are slowly produced1 and consequently are not capable of substantial action1 rapid enough to produce vibrations2 but he considers that molecular effects need not take place under the same conditions as those which are displayed in the case of material substances4 ,m4 ,wiesendanger believes that this hypothesis will explain the reproduction of speech in the receiving microphones of ,mr4 ,hughes1 and that it may even be applied to the theory of the electro-magnetic telephone1 if we consider that a magnetising helix1 as well as a magnetic core1 round which an electric current circulates1 is more or less heated1 according to the intensity of the current which traverses it1 especially when the wire of the helix and the core are bad conductors of electricity and of magnetism4 ,pursuing this idea1 ,m4 ,wiesendanger has sought to construct telephones in which calorific effects are more fully developed1 and with this object he used very fine wire of ,german silver and platinum to make the coils4 ,he ascertained that these coils could produce sounds themselves1 and1 to increase their intensity1 he put them between disks of iron1 or on tin tubes1 placed on resonant surfaces close to the disks4 ,in this way he says that he was able to make a good receiving telephone without employing magnets4 ,he afterwards arranged the instrument in different ways1 of which the two following are the most noteworthy4 ,in the first1 the electro-magnetic system was simply formed by a magnetic disk with a helix wound round it1 of which the wire was in connection with the circuit of a microphone1 and which was fastened to the centre of the parchment membrane of an ordinary string telephone2 the disk consisted of two iron plates separated by a carbon disk of smaller diameter1 and the whole was so compressed as to form a solid mass4 ,in the second1 the helix was wound on a tin tube1 six inches long and five-eighths of an inch in diameter1 which was soldered by merely a point to the centre of the diaphragm of an ordinary telephone4 ,the inventor asserts that the tube and diaphragm only act as resonators1 and that the sounds produced by this instrument are nearly the same as those obtained from the ordinary string telephone3 the tunes of a musical box were heard1 and the reproduction of speech was perfect1 both in intensity and in distinctness of sound2 it even appeared that telephonic sounds were audible with the tin tube alone1 surrounded by the helix4 ,m4 ,wiesendanger says that #8these different receiving telephones show clearly that the diaphragm and magnet are not essential1 but merely accessory1 parts of a telephone4' ,,various ,,experiments ,,made ,,with ,,the ,,telephone4 ,we must now consider a series of experiments which demonstrate the wonderful properties of the telephone1 and which may also give some indication of the importance of the influences by which it is liable to be affected4 ,experiments by ,m4 d',arsonval4--,we have seen that the telephone is an extremely sensitive instrument1 but its sensitiveness could scarcely be appreciated by ordinary means4 ,in order to gauge it1 ,m4 d',arsonval has compared it to the nerve of a frog1 which has hitherto been regarded as the most perfect of all galvanoscopes1 and it appears from his experiments that the sensitiveness of the telephone is two hundred times greater than that of the frog's nerve4 ,m4 d',arsonval has given the following account of his researches in the records of the ,acadmie des ,sciences1 ,april #a1 #ahgh3 #8,i prepared a frog in ,galvani's manner4 ,i took ,siemens' instrument of induction1 used in physiology under the name of the chariot instrument4 ,i excited with the ordinary pincers the sciatic nerve1 and ,i withdrew the induced coil until the nerve no longer responded to the electric excitement4 ,i then substituted the telephone for the nerve1 and the induced current1 which had ceased to excite the latter1 made the instrument vibrate strongly4 ,i withdrew the induced coil1 and the telephone continued to vibrate4 #8,in the stillness of night ,i could hear the vibration of the telephone when the induced coil was at a distance fifteen times greater than the minimum at which the excitement of the nerve took place2 consequently1 if the same law of inverse squares applies to induction and to distance1 it is evident that the sensitiveness of the telephone is two hundred times greater than that of the nerve4 #8,the sensitiveness of the telephone is indeed exquisite4 ,we see how much it exceeds that of the galvanoscopic frog's leg1 and ,i have thought of employing it as a galvanoscope4 ,it is very difficult to study the muscular and nervous currents with a galvanometer of #cj1jjj turns1 because the instrument is deficient in instantaneous action1 and the needle1 on account of its inertia1 cannot display the rapid succession of electric variations1 such as are effected1 for example1 in a muscle thrown into electric convulsion4 ,the telephone is free from this inconvenience1 and it responds by vibration to each electric change1 however rapid it may be4 ,the instrument is therefore well adapted for the study of electric tetanus in the muscle4 ,it is certain that the muscular current will excite the telephone1 since this current excites the nerve1 which is less sensitive than the telephone4 ,but for this purpose some special arrangement of the instrument is required4 #8,it is true that the telephone can only reveal the variations of an electric current1 however faint they may be2 but ,i have been able1 by the use of a very simple expedient1 to reveal by its means the presence of a continuous current1 also of extreme faintness4 ,i send the current in question into the telephone1 and1 to obtain its variations1 ,i break this current mechanically with a tuning-fork4 ,if no current is traversing the telephone1 it remains silent4 ,if1 on the other hand1 the faintest current exists1 the telephone vibrates in unison with the tuning-fork4' ,professor ,eick1 of ,wurzburg1 has also used the telephone for physiological researches1 but in a direction precisely opposite to that explored by ,m4 d',arsonval4 ,he ascertained that when the nerves of a frog were placed in connection with a telephone1 they were forcibly contracted when anyone was speaking into the instrument1 and the force of the contractions chiefly depended on the words pronounced4 ,for instance1 the vowels a1 e1 i produced hardly any effect1 while o and especially u caused a very strong contraction4 ,the words ,liege still1 pronounced in a loud voice1 only produced a faint movement1 while the word ,tucker1 even when spoken in a low voice1 strongly agitated the frog4 ,these experiments1 reminding us of those by ,galvani1 were necessarily based on the effects produced by the induced currents developed in the telephone1 and they show that if this instrument is a more sensitive galvanoscope than the nerve of a frog1 the latter is more susceptible than the most perfect galvanometer4 ,experiments by ,m4 ,demoget4--,in order that he might compare the intensity of the sounds transmitted by the telephone with the intensity of original sounds1 ,m4 ,demoget placed two telephones in an open space4 ,he held the first to his ear1 while his assistant withdrew to a distance1 constantly repeating the same syllable with the same intensity of tone in the second instrument4 ,he first heard the sound transmitted by the telephone1 and then the sound which reached him directly1 so that comparison was easy1 and he obtained the following results4 ,at a distance of #ic yards the original and the transmitted sounds were received with equal intensity1 while the vibrating disk was about #e centimtres from the ear4 ,at this moment1 therefore1 the relative intensity was as #be to #ha1jjj1jjj4 ,in other words1 the sound transmitted by the telephone was only #a_/cjjjjjj of the emitted sound4 #8,but1' said ,m4 ,demoget1 #8since the stations at which we worked could not be regarded as two points freely vibrating in space1 the ratio may be reduced by one half on account of the influence of the earth1 and the sound transmitted by the telephone may be supposed to be #a1ejj1jjj times weaker than that emitted by the voice4 #8,again1 since we know that the intensity of the two sounds is in proportion to the square of the range of vibrations1 it may be concluded that the vibrations of the two telephone disks were in direct proportion to the distance1 that is1 as #e to #i1jjj1 or that the vibrations of the sending telephone were eighteen hundred times greater than those of the receiving telephone4 ,these latter may therefore be compared to molecular vibrations1 since the range of those of the sending telephone was extremely small4 #8,without in any degree detracting from the merit of ,bell's remarkable invention1' continues ,m4 ,demoget1 #8it follows from what ,i have said above that the telephone1 considered as a sending instrument1 leaves much to be desired1 since it only transmits the #ah_/ajj part of the original power2 and if it has produced such unexpected results1 this is due to the perfection of the organ of hearing1 rather than to the perfection of the instrument itself4' ,m4 ,demoget considers this loss of power which takes place in the telephone to be chiefly owing to the eight transformations in succession to which sound is subjected before reaching the ear1 setting aside the loss due to the electric resistance of the line1 which might in itself suffice to absorb the whole force4 ,in order to estimate the force of the induced currents which act upon a telephone1 ,m4 ,demoget has attempted to compare them with currents of which the intensity is known1 and which produce vibrations of like nature and force3 for this purpose he has made use of two telephones1 ,a and ,b1 communicating through a line #bb yards in length4 ,he placed a small file in slight contact with the vibrating disk of the telephone ,a1 and caused friction between the file and a metallic plate3 the sound thus produced was necessarily transmitted by the telephone ,b1 with an intensity which could be estimated4 ,he then substituted a battery for the telephone ,a1 and the file was introduced into the circuit by connecting it with one of the poles4 ,the current could only be closed by the friction of the file with the plate1 which had a spring1 and was in communication with the other end of the circuit4 ,in this way broken currents were obtained1 which caused vibration in the telephone ,b1 and produced a sound of which the intensity varied with the strength of the battery current4 ,in this way ,m4 ,demoget endeavoured to find the electric intensity capable of producing a sound similar to that of the telephone ,a1 and he ascertained that it corresponded in intensity to that produced in a small thermo-electric battery formed of an iron and a copper wire1 two millimtres in diameter1 flattened at the end1 and soldered to the tin3 the faint current produced by this battery only caused a short wire galvanometer to deviate two degrees4 ,this estimate does not appear to us to unite so many conditions of accuracy as to enable us to deduce from it the degree of sensitiveness possessed by a telephone1 a sensitiveness which the experiments of ,messrs4 ,warren de la ,rue1 ,brough1 and ,peirce show to be much greater4 ,mr4 ,warren de la ,rue1 as we have seen1 used ,thomson's galvanometer1 and compared the deviation produced on the scale of this galvanometer with that caused by a ,daniell cell traversing a circle completed by a rheostat3 he ascertained that the currents discharged by an ordinary ,bell telephone are equivalent to those of a ,daniell cell traversing #ajj megohms of resistance1 that is1 #f1bjj1jjj miles of telegraphic wire4 ,mr4 ,brough1 the ,director of ,indian ,telegraphs1 considers that the strongest current which at any given moment causes a ,bell telephone to work does not exceed #a_/ajjjjjj of the unit of current1 that is1 one ,weber1 and the current transmitted to the stations on the ,indian telegraphic line is #djj1jjj times as strong4 ,finally1 ,professor ,peirce1 of ,boston1 compares the effects of the telephonic current with those which would be produced by an electric source of which the electro-motive force should be #a_/bjjjjj part of a volt1 or one ,daniell cell4 ,mr4 ,peirce justly remarks that it is difficult to estimate the real value of these kinds of currents at any precise sum1 since it essentially varies according to the intensity of the sounds produced on the transmitting telephone2 but it may be affirmed that it is less than the #a_/ajjjjjj part of the current usually employed to work the instruments on telegraphic lines4 ,signor ,galileo ,ferraris1 who has recently published an interesting treatise on this question in the #8,atti della ,reale ,accademia delle ,scienze di ,torino' 7,june #ac1 #ahgh71 states that the intensity of the currents produced by the ordinary ,bell telephone varies with the pitch of the sound emitted4 ,experiments by ,m4 ,hellesen1 of ,copenhagen4--,in order to estimate the reciprocal effects of different parts of a telephone1 ,m4 ,hellesen has made telephones of the same size with three different arrangements which act inversely to each other4 ,the first was of the ordinary form1 the second like that of ,bell's first system1 that is1 with a membrane supporting a small iron armature on its centre1 instead of a vibrating disk1 and the third telephone consisted of a hollow cylindrical magnet1 with the vibrating disk fixed to one of its poles1 and the disk was adapted to move before a flat1 snail-shaped spiral1 of which the number of spirals equalled those of the two other helices4 ,in this last arrangement1 the induced currents resulting from the vibrations of the voice might be assimilated to those which follow from the approximation and withdrawal of the two parallel spirals1 one of which should be traversed by a current4 ,it is this last arrangement which ,mr4 ,bell has adopted as producing the best effects1 and it is rare in the history of discoveries that an inventor hits at once on the best arrangement of his instrument4 ,experiments by ,m4 ,zetsche4--,there are always a few perverse minds1 impelled by a spirit of contradiction to deny evidence1 and thus they attempt to depreciate a discovery of which the glory irritates them4 ,the telephone and the phonograph have been the objects of such unworthy criticism4 ,it has been said that electric action had nothing to do with the effects produced in the telephone1 and that it only acted under the influence of mechanical vibrations transmitted by the conducting wire1 just as in a string telephone4 ,it was in vain to demonstrate to these obstinate minds that no sound is produced when the circuit is broken1 and in order to convince them ,m4 ,zetsche has made some experiments to show1 from the mode in which sound is propagated1 that it is absurd to ascribe the sound produced in a telephone to mechanical vibration4 ,he wrote to this effect in an article inserted in the #8,journal ,tlgraphique1' ,berne1 ,january #be1 #ahgh3 #8,the correspondence by telephone between ,leipzig and ,dresden affords another proof that the sounds which reproduce words at the receiving station are due to electric currents1 and not to mechanical vibrations4 ,the velocity with which sound is transmitted by vibrations on the wire1 in the case of longitudinal undulations1 may be estimated at three miles one furlong a second1 so that the sound ought to traverse the distance from ,leipzig to ,dresden in #be seconds4 ,the same time ought to elapse before receiving the answer4 ,consequently there should be an interval of more than three-quarters of a minute allowed for each exchange of communication1 which is by no means the case4' ,experiments which may be made by anyone4--,we will conclude this chapter1 devoted to the account of the different experiments made with the telephone1 by the mention of a singular experiment1 which1 although easily performed1 has only been suggested a few months ago by a ,pennsylvanian newspaper4 ,it consists in the transmission of speech by a telephone simply laid on some part of the human body adjacent to the chest4 ,it has been asserted that any part of the body will produce this effect1 but according to my experience1 ,i could only succeed when the telephone was firmly applied to my chest4 ,under such conditions1 and even through my clothes1 ,i could make myself heard when speaking in a very loud voice1 from which it appears that the whole of the human body takes part in the vibrations produced by the voice4 ,in this case1 the vibrations are mechanically transmitted to the diaphragm of the sending telephone1 not by the air1 but by the body itself acting on the outside of the telephone4 ,,the ,,microphone4 ,the microphone is in fact only the sender of a battery telephone1 but with such distinctive characteristics that it may be regarded as an original invention which is entitled to a special name4 ,the invention has lately given rise to an unfortunate controversy between its inventor1 ,mr4 ,hughes1 and ,mr4 ,edison1 the inventor of the carbon telephone and the phonograph--a controversy which has been embittered by the newspapers1 and for which there were no grounds4 ,for although the scientific principle of the microphone may appear to be the same as that of ,mr4 ,edison's carbon sender1 its arrangement is totally different1 its mode of action is not the same1 and the effect required of it is of quite another kind4 ,less than this is needed to constitute a new invention4 ,besides1 a thorough examination of the very principle of the instrument must make us wonder at ,mr4 ,edison's claim to priority4 ,he cannot in fact regard as his exclusive possession the discovery of the property possessed by some substances of moderate conductivity of having this power modified by pressure4 ,in #ahef1 and often subsequently1 as for example in #ahfd1 #ahgb1 #ahgd1 and #ahge1 ,i made numerous experiments on this point1 which are described in the first volume of the second edition of my #8,expos des applications de l',electricit1' and also in several papers presented to the ,acadmie des ,sciences1 and inserted in their ,comptes rendus4 ,m4 ,clarac again1 in #ahfe1 employed a tube made of plumbago1 and provided with a moveable electrode1 to produce variable resistances in a telegraphic circuit4 ,besides1 in ,mr4 ,edison's telephonic sender1 the carbon disk1 as we have seen1 must be subjected to a certain initial pressure1 in order that the current may not be broken by the vibrations of the plate on which it rests1 and consequently the modifications of resistance in the circuit which produce articulate sounds are only caused by greater or less increase and diminution of pressure1 that is1 by differential actions4 ,we shall presently see that this is not the case with the microphone4 ,in the first place1 the carbon contact is effected in the latter instrument on other carbons and not with platinum disks1 and these contacts are multiple4 ,in the second place1 the pressure exerted on all the points of contact is excessively slight1 so that the resistances can be varied in an infinitely greater ratio than in ,mr4 ,edison's system2 and for this very reason it is possible to magnify the sounds4 ,in the third place1 a microphone can be made of other substances besides carbon4 ,finally1 no vibrating disk is needed to make the microphone act2 the simple medium of air is enough1 so that it is possible to work the instrument from some little distance4 ,we do not therefore see the grounds for ,mr4 ,edison's assertions1 and especially for the way in which he has spoken of ,messrs4 ,hughes and ,preece1 who are well known in science and are in all respects honourable men4 ,i repeat my regret that ,mr4 ,edison should have made this ill-judged attack on them1 since it must injure himself1 and is unworthy of an inventor of such distinction4 ,if we look at the question from another point of view1 we must ask ,mr4 ,edison why1 if he invented the microphone1 he did not make us acquainted with its properties and results4 ,these results are indeed startling1 since the microphone has in so short a time attracted general attention2 and it is evident that the clear-sighted genius of this celebrated ,american inventor would have made the most of the discovery if it were really his4 ,the only justification for ,mr4 ,edison's claim consists in his ignorance of the purely scientific discoveries made in ,europe1 so that he supposed the invention of the microphone to be wholly involved in the principle which he regards as his peculiar discovery4 ,in ,mr4 ,hughes's instrument which we are now considering1 the sounds1 instead of reaching the receiving stations much diminished1 which is the case with ordinary telephones1 and even with that of ,mr4 ,edison1 are often remarkably increased1 and it is for this reason that ,mr4 ,hughes has given to this telephonic system the name of ,microphone1 since it can be employed to discover very faint sounds4 ,yet we must add that this increase really takes place only when the sounds result from mechanical vibrations transmitted by solid substances to the sending instrument4 ,the sounds propagated through the air are undoubtedly a little more intense than in the ordinary system1 but they lose some of their force1 and therefore it cannot be said that in this case the microphone has the same effect upon sounds as the microscope has on objects on which light is thrown4 ,it is true that with this system it is possible to speak at a distance from the instrument1 and ,i have even been able to transmit conversation in a loud voice1 when standing at a distance of nine yards from the microphone4 ,when close to the instrument1 ,i was also perfectly able to make myself heard at the receiving station while speaking in a low voice1 and even to send the sounds to a distance of ten or fifteen centimtres from the mouthpiece of the receiving telephone by raising the voice a little2 but the increase of sound is not really very evident unless it is produced by a mechanical action transmitted to the standard of the instrument4 ,thus the steps of a fly walking on the stand are clearly heard1 and give the sensation of a horse's tread2 and even a fly's scream1 especially at the moment of death1 is said by ,mr4 ,hughes to be audible4 ,the rustling of a feather or of a piece of stuff on the board of the instrument1 sounds completely inaudible in ordinary circumstances1 are distinctly heard in the microphone4 ,it is the same with the ticking of a watch placed upon the stand1 which may be heard at ten or fifteen centimtres from the receiver4 ,a small musical box placed upon the instrument gives out so much sound1 in consequence of its vibratory movements1 that it is impossible to distinguish the notes1 and in order to do so it is necessary to place the box close to the instrument1 without allowing it to come in contact with any of its constituent parts4 ,it therefore appears that the instrument is affected by the vibrations of air1 and the transmitted sounds are fainter than those heard close to the box4 ,on the other hand1 the vibrations produced by the pendulum of a clock1 when placed in communication with the standard of the instrument by means of a metallic rod1 are heard perfectly1 and may even be distinguished when the connection is made by the intervention of a copper wire4 ,a current of air projected on the system gives the sensation of a trickle of water heard in the distance4 ,finally1 the rumbling of a carriage outside the house is transformed into a very intense crackling noise1 which may combine with the ticking of a watch1 and will often overpower it4 ,different ,systems of ,microphones4--,the microphone has been made in several ways1 but the one represented in fig4 #ci is the arrangement which renders it the most sensitive4 ,in this system1 two small carbon cubes1 ,a1 ,b1 are placed one above the other on a vertical wooden prism2 two holes are pierced in the cubes to serve as sockets for a spindle-shaped carbon pencil1 that is1 with the points fined off at the two ends1 and about four centimtres long3 if of a large size1 the inertia will be too great4 ,one end of this pencil is in the cavity of the lower carbon1 and the other must move freely in the upper cavity which maintains it in a position approaching to that of instable equilibrium1 that is1 in a vertical position4 ,mr4 ,hughes states that the carbons become more effective if they are steeped in a bath of mercury at red heat1 but they will act well without undergoing this process4 ,the two carbon cubes are also provided with metallic contacts which admit of their being placed in connection with the circuit of an ordinary telephone in which a ,leclanch battery has been placed1 or one1 two1 or three ,daniell cells1 with an additional resistance introduced into the circuit4 ,illustration3 ,,fig4 #ci4 ,in order to use this instrument1 it is placed on a table1 with the board which serves to support it1 taking care to deaden any extraneous vibrations by interposing between this board and the table several folds of stuff so arranged as to form a cushion1 or1 which is better1 a belt of wadding1 or two caoutchouc tubes3 what is said by a person standing before this system is immediately reproduced in the telephone1 and if a watch is placed on the stand1 or a box with a fly enclosed in it1 all its movements are heard4 ,the instrument is so sensitive that words said in a low voice are most easily heard1 and it is possible1 as ,i have already said1 to hear the speaker when he is standing nine yards from the microphone4 ,yet some precautions are necessary in order to obtain good results with this system1 and besides the cushions placed beneath the instrument to guard it from the extraneous vibrations which might ensue from any movements communicated to the table1 it is also necessary to regulate the position of the carbon pencil4 ,it must always rest on some point of the rim of the upper cavity2 but as the contact may be more or less satisfactory1 experience alone will show when it is in the best position1 and it is a good plan to make use of a watch to ascertain this4 ,the ear is then applied to the telephone1 and the pencil is placed in different positions until the maximum effect is obtained4 ,to avoid the necessity of regulating the instrument in this way1 which must be done repeatedly by this arrangement1 ,,mm4 ,chardin and ,berjot1 who are ingenious in the construction of telephones on this pattern1 have added to it a small spring-plate1 of which the pressure can be regulated1 and which rests against the carbon pencil itself4 ,this system works well4 ,illustration3 ,,fig4 #dj4 ,m4 ,gaiffe1 by constructing it like a scientific instrument1 has given the instrument a more elegant form4 ,fig4 #dj represents one of his two models4 ,in this case1 the cubes or carbon dice are supported by metallic holders1 and the upper one ,e is made to move up and down a copper column ,g1 so as to be placed in the right position by tightening the screw ,v4 ,in this way the carbon pencil can be made to incline more or less1 and its pressure on the upper carbon can be altered at pleasure4 ,when the pencil is in a vertical position1 the instrument transmits articulate sounds with difficulty1 on account of the instability of the points of contact1 and rustling sounds are heard4 ,when the inclination of the pencil is too great1 the sounds are purer and more distinct1 but the instrument is less sensitive4 ,the exact degree of inclination should be ascertained1 which is easily done by experiment4 ,in another model ,m4 ,gaiffe substitutes for the carbon pencil a very thin square plate of the same material1 bevelled on its lower and upper surfaces1 and revolving in a groove cut in the lower carbon4 ,this plate must be only slightly inclined in order to touch the upper carbon1 and under these conditions it transmits speech more loudly and distinctly4 ,i must also mention another arrangement1 devised by ,captain ,carette of the ,french ,engineers1 which is very successful in transmitting inarticulate sounds4 ,in this case the vertical carbon is pear-shaped1 and its larger end rests in a hole made in the lower carbon2 its upper and pointed end goes into a small hole made in the upper carbon1 but so as hardly to touch it1 and there is a screw to regulate the distance between the two carbons4 ,under such conditions1 the contacts are so unstable that almost anything will put an end to them1 and consequently the variations in the intensity of the transmitted current are so strong that the sounds produced by the telephone may be heard at the distance of several yards4 ,illustration3 ,,fig4 #da4 ,fig4 #da represents another arrangement1 devised by ,m4 ,ducretet4 ,the two carbon blocks are at ,d ,d1 the moveable carbon pencil is at ,c1 the telephone at ,t1 and the binding screws at ,b ,b4 ,an enlarged figure of the arrangement of the carbons is given on the left4 ,the arm which holds the upper carbon ,d is fastened to a rod1 bearing a plate ,p1 of which the surface is rough1 and a little cage ,c1 made of wire netting1 can be placed upon the plate1 so as to enable us to study the movements of living insects4 ,when speech is to be transmitted with a force which can make the telephone audible in a large room1 the microphone must have a special arrangement1 and fig4 #db represents the one which ,mr4 ,hughes considers the most successful1 to which he has given the name of speaker4 ,illustration3 ,,fig4 #db4 ,in this new form1 the moveable carbon which is required to produce the variable contacts is at ,c1 at the end of a horizontal bar ,b ,a1 properly balanced so as to move up and down on its central point4 ,the support on which the bar oscillates is fastened to the end of a spring plate in order that it may vibrate more easily1 and the lower carbon is placed at ,d below the first4 ,it consists of two pieces laid upon each other1 so as to increase the sensitiveness of the instrument1 and we represent the upper piece at ,e1 which is raised so as to show that when it is desired only one of these carbons need be used4 ,for this purpose the carbon ,e is fastened to a morsel of paper1 which is fixed to the little board and contributes to the articulation4 ,a spring ,r1 of which the tension can be regulated by the screw t1 serves to regulate the pressure of the two carbons4 ,mr4 ,hughes recommends the use of metallised charcoal prepared from deal4#ad ,the whole is then enclosed in a semi-cylindrical case ,h ,i ,g1 made of very thin pieces of deal1 and the system is fixed1 together with another similar system1 in a flat box1 ,m ,j ,l ,i1 which1 on the side ,m ,i1 presents an opening before which the speaker stands1 taking care to keep his lower lip at a distance of two centimtres from the bottom of the box4 ,if the two telephones are connected for strength1 and if the battery employed consists of two cells of bichromate of potash1 it is possible to act so strongly on the current1 that1 after traversing an induction coil only six centimtres long1 a telephone of ,bell's square model can be made to speak1 so as to be heard from all parts of a room2 a speaking tube1 about a yard long1 must indeed be applied to it4 ,mr4 ,hughes asserts that the sounds produced by it are nearly as loud as those of the phonograph1 and this is confirmed by ,mr4 ,thomson4 ,m4 ,boudet de ,paris has lately invented a microphone speaker of the same kind1 with which it is possible to make a small telephone utter a loud sound4 ,an induction coil1 influenced by a single ,leclanch cell1 must be employed4 ,suppose that a very small carbon rod with pointed ends is placed at the bottom of a box1 of about the size of a watch4 ,one end of the rod rests against a morsel of carbon1 which is fastened to a very thin steel diaphragm1 placed before a mouthpiece which acts as a lid to the box1 and is screwed above it4 ,next suppose that a small piece of paper1 folded in two1 in the shape of the letter ,v1 is fixed above that part of the carbon in contact with the carbon of the diaphragm4 ,this constitutes the instrument1 and in order to work it1 it must be held in a vertical position before the mouth1 at a distance of about three centimtres1 and it is necessary to speak in the ordinary tone4 ,if the telephone is placed in direct communication with this instrument1 it will send the voice to a distance4 ,without employing a ,leclanch cell1 the voice may be heard at the distance of ten yards1 if one of the carbons used for the phonograph is placed before the mouthpiece of the telephone4 ,in this system1 the sensitiveness of the instrument is entirely due to the slightness of the contact between the two carbons1 and the slight elasticity of the folded paper constitutes the contact4 ,perhaps the paper itself has some influence2 at any rate the most delicate spiral spring is incapable of producing the same effect1 and it is necessary to suspend the instrument vertically1 in order that the weight of the moveable carbon may not affect it4 ,it can be regulated by depressing or elevating that part of the paper which rests on the carbon rod4 ,although it is possible to work all telephones with this instrument1 some are more effective than others4 ,the mouthpiece must be concave1 and the diaphragm must be close to its rim1 and must be made of a particular kind of tin4 ,the ordinary diaphragm does not act well1 and ,m4 ,boudet de ,paris has tried several1 so as to obtain the maximum effect4 ,it is certain that when the instruments are as well regulated as those which the inventor has deposited with me1 their results are really surprising4 ,it is even possible1 by using several microphones at the sending station1 to obtain the reproduction of duets1 and even of trios1 with remarkable effect4 ,with this kind of microphone speaker ,m4 ,boudet de ,paris is able to transmit speech into a snuff-box telephone1 merely consisting of a flat helix of wire1 placed before a slightly magnetised steel plate1 and without insertion of a magnetic core4 ,a single ,leclanch cell was enough4 ,an experiment of the same nature was tried in ,england1 but it was found necessary to use six ,leclanch cells4 ,illustration3 ,,fig4 #dc ,illustration3 ,,fig4 #dd4 ,the microphone may also be made of morsels of carbon pressed into a box between two metallic electrodes1 or enclosed in a tube with two electrodes represented by two elongated fragments of carbon4 ,in the latter case the carbons ought to be as cylindrical as possible1 and those made by ,m4 ,carr for the ,jablochkoff candles are very suitable4 ,fig4 #dc represents an instrument of this kind which ,m4 ,gaiffe arranged for me1 and which1 as we shall see1 serves as a thermoscope 7fig4 #dd74 ,it is composed of a quill filled with morsels of carbon1 and those at the two ends are tipped with metal4 ,one of these metal tips ends in a large-headed screw which1 by means of its supports ,a ,b1 is able to press more or less on the morsels of carbon in the tube1 and consequently to establish a more or less intimate contact between them4 ,when the instrument is properly regulated1 speech can be reproduced by speaking above the tube4 ,it is therefore a microphone as well as a thermoscope4 ,mr4 ,hughes has remarked one curious fact1 namely1 that if the different letters of the alphabet are pronounced separately before this sort of microphone1 some of them are much more distinctly heard than others1 and it is precisely those which correspond to the breathings of the voice4 ,a microphone of this kind may be made by substituting for the carbon powders of more or less conductivity1 or even metal filings4 ,i have shown in my paper on the action of substances of moderate conductivity1 that such power varies considerably with the pressure and the temperature2 and as the microphone is based on the differences of conducting power which result from differences of pressure1 we can understand that these powders may be used as a means of telephonic transmission4 ,in a recent arrangement of this system ,mr4 ,hughes has made the powder adhere together with a sort of gum1 and has thus made a cylindrical pencil which1 when connected with two electrodes which are good conductors1 can produce effects analogous to those we have just described4 ,as ,i have said1 it is possible to use metal filings1 but ,mr4 ,hughes prefers powdered charcoal4 ,mr4 ,blyth states that a flat box1 about #ae inches by #i1 filled with coke1 and with two tin electrodes fixed to the two ends1 is one of the best arrangements for a microphone4 ,he says that three of these instruments1 hung like pictures against the wall of a room1 would suffice1 when influenced by a single ,leclanch cell1 to make all the sounds produced in a telephone audible1 and especially vocal airs4 ,mr4 ,blyth even asserts that a microphone capable of transmitting speech can be made with a simple piece of coke1 connected with the circuit by its two ends1 but it must be coke3 a retort carbon1 with electrodes1 will not act4 ,it is a remarkable property of these kinds of microphones that they can act without a battery1 at least when they are so arranged as to form a voltaic element for themselves1 and this can be done by throwing water on the carbons4 ,mr4 ,blyth1 who was the first to speak of this system1 does not distinctly indicate its arrangement1 and we may assume that his instrument did not differ from the one we have already described1 to which water must have been added4 ,in this way1 indeed1 ,i have been able to transmit not only the ticking of a watch and the sounds of a musical box1 but speech itself1 which was often more distinctly expressed than in an ordinary microphone1 since it was free from the sputtering sound which is apt to accompany the latter4 ,mr4 ,blyth also asserts that sounds may be transmitted without the addition of water1 but in this case he considers that the result is due to the moisture of the breath4 ,certainly much moisture is not required to set a voltaic couple in action1 especially when a telephone is the instrument of manifestation4 ,the ordinary microphone may be used without a battery1 if the circuit in which it is inserted is in communication with the earth by means of earthen cakes2 the currents which then traverse the circuit will suffice to make the tickings of a watch placed upon the microphone perfectly audible4 ,m4 ,cauderay1 of ,lausanne1 in a paper sent to the ,acadmie des ,sciences1 ,july #h1 #ahgh1 informs us that he made this experiment on a telegraphic wire which unites the ,htel des ,alpes at ,montreux with a chlet on the hill--a distance of about #eej yards4 ,the ,microphone used as a ,speaking ,instrument4--,the microphone can not only transmit speech1 but it can also under certain conditions reproduce it1 and consequently supply the place of the receiving telephone4 ,this seems difficult to understand1 since a cause for the vibratory motion produced in part of the circuit itself can only be sought in the variations in intensity of the current1 and the effects of attraction and magnetisation have nothing to do with it4 ,can the action be referred to the repulsions reciprocally exerted by the contiguous elements of the same current8 ,or are we to consider it to be of the same nature as that which causes the emission of sounds from a wire when a broken current passes through it1 so that an electric current is itself a vibratory current1 as ,mr4 ,hughes believes8 ,it is difficult to reply to these questions in the present state of science2 we can only state the fact1 which has been published by ,messrs4 ,hughes1 ,blyth1 ,robert ,courtenay1 and even by ,mr4 ,edison himself4 ,i have been able to verify the fact myself under the experimental conditions indicated by ,mr4 ,hughes1 but ,i was not so successful in the attempt to repeat ,mr4 ,blyth's experiments4 ,this gentleman stated that in order to hear speech in a microphone it would be enough to use the model made from fragments of carbon1 as we have described1 to join to it a second microphone of the same kind1 and to introduce into the circuit a battery consisting of two ,grove elements4 ,if anyone then speaks above the carbons of one of the microphones1 what is said should be distinctly heard by the person who puts his ear to the other1 and the importance of the sounds thus produced will correspond with the intensity of the electric source employed4 ,as ,i have said1 ,i was unable by following this method to hear any sound1 still less articulate speech2 and if other experiments had not convinced me1 ,i should have doubted the correctness of the statement4 ,but this negative experiment does not in fact prove anything1 since it is possible that my conditions were wrong1 and that the cinders which ,i employed were not subject to the same conditions as ,mr4 ,blyth's fragments of coke4 ,illustration3 ,,fig4 #de4 ,with respect to ,mr4 ,hughes's experiments1 ,i have repeated them with the microphone made by ,,mm4 ,chardin and ,berjot1 using that by ,m4 ,gaiffe as the sender1 and ,i ascertained that with a battery of only four ,leclanch cells1 a scratch made on the sender1 and even the tremulous motion and the airs played in a little musical box placed on the sender1 were reproduced--very faintly1 it is true--in the second microphone2 in order to perceive them1 it was enough to apply the ear to the vertical board of the instrument4 ,it is true that speech was not reproduced1 but of this ,mr4 ,hughes had warned me2 it was evident that with this arrangement the instrument was not sufficiently sensitive4 ,a different arrangement of the microphone is required for the transmission and the reproduction of speech by this system1 and a section of the one which ,mr4 ,hughes found most successful is given in fig4 #de4 ,it somewhat resembles ,mr4 ,hughes's microphone speaker1 placed in a vertical position1 and the fixed carbon is fastened to the centre of the stretched membrane of a string telephone4 ,the ear or mouth tube is at ,a1 the membrane at ,d ,d1 the carbon just mentioned at ,c3 this carbon is of metallised charcoal prepared from deal1 and so also is the double carbon ,e1 which is in contact with it and is fastened to the upper end of the little bar ,g ,i4 ,the whole is enclosed in a small box1 and the pressure exerted on the contact of the two carbons is regulated by a spring ,r and a screw ,h4 ,the tube of the telephone serves as an acoustic tube for the listener1 and ,mr4 ,hughes's speaker1 described above1 acts as sender4 ,it is hardly necessary to say that the two instruments are placed at each end of the circuit1 that the carbons are connected with the two poles of a battery of one or two cells of bichromate of potash1 or two ,bunsen or six ,leclanch cells1 and the two instruments are connected by the line wire4 ,under such conditions1 conversation may be exchanged1 but the sounds are always much less distinct than they are in a telephone4 ,i was able to ascertain this fact with a roughly made instrument brought from ,england by ,mr4 ,hughes4 ,,mm4 ,berjot1 ,chardin1 and de ,mritens1 who were also present at the experiments1 were able with me to hear speech perfectly1 and ,i have since successfully repeated the experiment alone1 but it does not always succeed1 and under its present conditions the instrument has no importance in a scientific point of view4 ,it is evident that the instrument can dispense with any support1 and the little box then forms the handle of the instrument2 in this case the two binding screws are placed at the end of this handle1 as in a telephone4 ,the microphone speaker with a disk1 represented in fig4 #e1 which acts as sender to the singing condenser1 can be used1 when properly regulated1 as a receiving microphone4 ,m4 ,berjot has obtained good results from a little instrument of the same kind as that in fig4 #de1 but with a metal diaphragm1 and the microphonic system consists of a cylindrical piece of carbon resting on a small disk of the same substance1 which is galvanised and soldered to the diaphragm4 ,the whole is enclosed in a small round box1 with its upper part cut in the form of a mouthpiece4 ,it seems that all microphone senders with disks can reproduce speech more or less perfectly2 it is a question of adjusting and refining the carbon points of contact4 ,a weak battery1 consisting of a single ,leclanch cell1 is better for these instruments than a strong battery1 precisely because of the effects of oxidation and polarisation1 which are so energetically produced at these points of contact when the battery is strong4 ,the effects of the microphone receiver explain the sounds1 often very intense1 produced by the ,jablochkoff candles when they are influenced by electro-magnetic machines4 ,these sounds always vibrate in unison with those emitted by the machine itself1 and they result1 as ,i have already shown1 from the rapid magnetisations and demagnetisations which are effected by the machine4 ,these effects1 observed by ,m4 ,marcel ,deprez1 were particularly marked in ,m4 de ,mritens' first machines4 ,other ,arrangements of ,microphones4--,an arrangement such as we have just described has been employed by ,m4 ,carette to form an extremely powerful microphone speaker4 ,the only difference is that the stretched membrane is replaced by a thin metallic disk3 he fastens one of the carbons to the centre of this disk1 and applies to it the other carbon1 which is pointed1 and held by a porte-carbon with a regulating screw1 so that the pressure which takes place between the two carbons may be regulated at pleasure4 ,by this arrangement speech may be heard at a distance from the telephone4 ,in other respects it resembles the telephone sender represented in fig4 #e4 ,m4 de ,mritens has executed the system represented1 fig4 #de1 on a large scale1 forming the tube ,a ,b of a zinc funnel a yard in length1 and in this way he has been able to magnify the sounds1 so that a conversation held in a low voice1 three or four yards from the instrument1 has been produced in a telephone with more sonorous distinctness4 ,the instrument was placed on the floor of the apartment1 with the opening of the funnel above1 and the telephone was in the cellars of the house4 ,the form of the microphone has been varied in a thousand ways1 to suit the purposes to which it was to be applied4 ,in the #8,english ,mechanic and ,world of ,science1' ,june #bh1 #ahgh1 we see the drawings of several arrangements1 one of which is specially adapted for hearing the steps of a fly4 ,it is a box1 with a sheet of straw paper stretched on its upper part2 two carbons1 separated by a morsel of wood1 and connected with the two circuit wires1 are fastened to it1 and a carbon pencil1 placed crosswise between the two1 is kept in this position by a groove made in the latter4 ,a very weak battery will be enough to set the instrument at work1 and when the fly walks over the sheet of paper it produces vibrations strong enough to react energetically on an ordinary telephone4 ,the instrument must be covered with a glass globe4 ,when a watch is placed on the membrane1 with its handle applied to the morsel of wood which divides the two carbons1 the noise of its ticking may be heard through a whole room4 ,two carbon cubes placed side by side1 and only divided by a playing-card1 may also be used instead of the arrangement of carbons described above4 ,a semicircular cavity1 made in the upper part of the two carbons1 in which are placed some little carbon balls1 smaller than a pea and larger than a mustard seed1 will make it possible to obtain multiple contacts which are very mobile and peculiarly fit for telephonic transmissions4 ,this arrangement has been made by ,mr4 ,t4 ,cuttriss4 ,several other arrangements of microphones have been devised by different makers and inventors1 such as those of ,messrs4 ,varey1 ,trouv1 ,vereker1 de ,combettes1 ,loiseau1 ,lippens1 de ,courtois1 ,pollard1 ,voisin1 ,dumont1 ,jackson1 ,paterson1 ,taylor1 c41 and they are more or less satisfactory4 ,the instruments of ,,mm4 ,varey1 ,trouv1 ,lippens1 and de ,courtois are the most interesting1 and we will describe them4 ,m4 ,varey's microphone consists of a sounding box of deal1 mounted in a vertical position on a stand1 and two microphones are arranged on either side of it1 with vertical carbons united for tension4 ,a small ,gaiffe cell of chloride of silver1 without liquid1 is applied to the standard of the instrument1 and is enough to make it work perfectly4 ,this system is extremely sensitive4 ,m4 ,trouv's microphones1 represented in figs4 #df1 #dg1 #dh1 are extremely simple1 so that he is able to sell them at a very moderate price4 ,they generally consist of a small vertical cylindrical box1 as we see in the figure1 with disks of carbon at its two ends1 which are united by a carbon rod1 or by a metallic tube tipped with carbon4 ,this rod or tube turns freely in two cavities made in the carbons1 and the box1 while acting as a sounding box1 becomes at the same time a prison for the insects whose movements and noises are the objects of study4 ,illustration3 ,,fig4 #df4 ,these boxes may be suspended on a cross-bar 7fig4 #dg7 by the two communicating wires1 so as to be completely insulated4 ,in this case the ticking of a watch placed upon the board1 friction1 and external shocks are hardly heard1 but on the other hand the sound vibrations of the air alone are transmitted1 and they acquire great distinctness4 ,we have often repeated these experiments1 and have always found that the tones of the voice were perfectly preserved4 ,the model represented fig4 #dh is still more simple1 and appears to be the latest development of this kind of instrument4 ,it consists of a stand and a disk united by a central rod4 ,the upper disk moves round the central rod1 and permits the vertical carbon to assume any inclination which is desired4 ,it is evident that the instrument will become less sensitive when the carbon is more oblique4 ,illustration3 ,,fig4 #dg4 ,we must also mention a very successful microphone devised by ,m4 ,lippens4 ,it is a slightly made box1 like that of ,m4 ,varey1 and on its opposite faces there are applied1 on two frames left empty for the purpose1 two thin plates of hardened caoutchouc1 in the centre of which inside the box1 two carbons are fastened1 and on their outer surface a half-sphere is hollowed4 ,illustration3 ,,fig4 #dh4 ,the interval between the two carbons hardly amounts to two millimtres1 and a carbon ball is inserted into the two cavities which form its spherical case4 ,this ball is supported by a spiral spring which can be extended more or less by means of a wire wound on a windlass which is fixed above the instrument1 like the spring of an electric telegraph instrument4 ,by means of this spring1 the pressure of the carbon ball against the sides of the cavity which contains it can be regulated at pleasure1 and the sensitiveness of the instrument and its capacity for transmitting speech can be adjusted4 ,under these conditions1 the vibrations of the caoutchouc plates directly affect the microphone1 and the currents of air have no influence on it1 so that the effects are more distinct4 ,it is so sensitive that it is best for the speaker to place himself at the distance of at least #ej centimtres from the instrument4 ,m4 ,lippens' instrument is a pretty one1 mounted on a wooden stand1 which is neatly turned4 ,in order to put an end to the sputtering usual in microphones1 it occurred to ,m4 de ,courtois to prevent any cessation of contact between the carbons by keeping them close together1 and to effect the variations of resistance necessary for articulate sounds by making them slide over each other1 so as to insert a shorter or longer portion of the carbon in the circuit4 ,for this purpose a vibrating disk is placed in a vertical position in a rigid frame1 and a small conducting rod1 terminated by a pointed carbon1 is applied to it1 with this carbon point resting on another flat piece of carbon placed below it4 ,influenced by the vibrations of the disk1 the carbon point moves to and fro1 effecting more or less extensive contacts with the lower carbon1 and thus producing variations of resistance which almost correspond to the range of vibrations on the disk4 ,experiments made with the ,microphone4--,i must now mention the interesting experiments which led ,mr4 ,hughes to the invention of the remarkable instrument of which we have spoken1 as well as those undertaken by other scientific men1 either from a scientific or a practical point of view4 ,believing that light and heat can modify the conductivity of bodies1 ,mr4 ,hughes went on to consider whether sound vibrations1 transmitted to a conductor traversed by a current1 would not also modify this conductivity by provoking the contraction and expansion of the conducting molecules1 which would be equivalent to the shortening or lengthening of the conductor thus affected4 ,if such a property existed1 it would make it possible to transmit sounds to a distance1 since variations in the conductivity would result from variations corresponding to the intensity of the current acting on the telephone4 ,the experiment which he made on a stretched metal wire did not1 however1 fulfil his expectation1 and it was only when the wire vibrated so strongly as to break1 that he heard a sound at the moment of its fracture4 ,when he again joined the two ends of the wire1 another sound was produced1 and he soon perceived that imperfect contact between the two broken ends of wire would enable him to obtain a sound4 ,mr4 ,hughes was then convinced that the effects he wished to produce could only be obtained with a divided conductor1 and by means of imperfect contacts4 ,he then sought to discover the degree of pressure which it was most expedient to exert between the two adjacent ends of the wire1 and for this purpose he effected the pressure by means of weights4 ,he ascertained that when the pressure did not exceed the weight of an ounce on the square inch at the point of connection1 the sounds were reproduced with distinctness1 but somewhat imperfectly4 ,he next modified the conditions of the experiment1 and satisfied himself that it was unnecessary to join the wires end to end in order to obtain this result4 ,they might be placed side by side on a board1 or even separated 7with a conductor placed crosswise between them71 provided that the conductors were of iron1 and that they were kept in metallic connection by a slight and constant pressure4 ,the experiment was made with three ,paris points1 and arranged as it appears in fig4 #di1 and it has since been repeated under very favourable conditions by ,mr4 ,willoughby ,smith with three of the so-called rat-tail files1 which made it possible to transmit even the faint sound of the act of respiration4#ae ,illustration3 ,,fig4 #di4 ,he afterwards tried different combinations of the same nature1 which offered several solutions of continuity1 and a steel chain produced fairly good results1 but slight inflections1 like those caused by the timbre of the voice1 were not reproduced1 and he tried other arrangements4 ,he first sought to apply metallic powders to the points of contact2 powdered zinc and tin1 known in commerce under the name of white bronze1 greatly increased the effects obtained2 but they were unstable1 on account of the oxidation of the contacts2 and it was in seeking to solve this difficulty1 as well as to discover the most simple means of obtaining a slight and constant pressure on the contacts1 that ,mr4 ,hughes was led to the arrangement1 previously described1 of carbons impregnated with mercury1 and he thus obtained the maximum effect4#af ,mr4 ,hughes considers that the successful effects of the microphone depend on the number and perfection of the contacts1 and this is doubtless the reason why some arrangements of the carbon pencil in the instrument described above were more favourable than others4 ,in order to reconcile these experiments with his preconceived ideas1 ,mr4 ,hughes thought that1 since the differences of resistance proceeding from the vibrations of the conductor were only produced when it was broken1 the molecular movements were arrested by the lateral resistances which were equal and opposite1 but that if one of these resistances were destroyed1 the molecular movement could be freely developed4 ,he considers that an imperfect contact is equivalent to the suppression of one of these resistances1 and as soon as this movement can take place1 the molecular expansions and contractions which result from the vibrations must correspond to the increase or diminution of resistance in the circuit4 ,we need not pursue ,mr4 ,hughes's theory further1 since it would take too long to develope it1 and we must continue our examination of the different properties of the microphone4#ag ,carbon1 as we have said1 is not the only substance which can be employed to form the sensitive organ of this system of transmission4 ,mr4 ,hughes has tried other substances1 including those which are good conductors1 such as metals4 ,iron afforded rather good results1 and the effect produced by surfaces of platinum when it was greatly subdivided was equal1 if not superior1 to that furnished by the mercurised carbon4 ,yet since the difficulty of making instruments with this metal is greater1 he prefers the carbon1 which resembles it in being incapable of oxidation4 ,we have already said that the microphone may be used as a thermoscope1 in which case it must have the special arrangement represented in fig4 #dc4 ,under these conditions1 heat1 reacting on the conductivity of these contacts1 may cause such variations in the resistance of the circuit that the current of three ,daniell cells will be annulled by approaching the hand to the tube4 ,in order to estimate the relative intensity of the different sources of heat1 it will be enough to introduce into the circuit of the two electrodes ,a and ,b1 fig4 #dc1 a battery ,p1 of one or two ,daniell cells1 and a moderately sensitive galvanometer ,g4 ,for this purpose one of #abj turns will suffice4 ,when the deviation decreases1 it shows that the source of heat is superior to the surrounding atmosphere2 and conversely1 that it is inferior when the deviation increases4 ,mr4 ,hughes says that the effects resulting from the intervention of sunshine and shadow are shown on the instrument by considerable variations in the deviations of the galvanometer4 ,indeed it is so sensitive to the slightest variations of temperature that it is impossible to maintain it in repose4 ,i have repeated ,mr4 ,hughes's experiments with a single ,leclanch cell1 and for this purpose ,i employed a quill1 filled with five fragments of carbon1 taken from the cylindrical carbons of small diameter which are made by ,m4 ,carr for the electric light4 ,i have obtained the results which are mentioned by ,mr4 ,hughes1 but ,i ought to say that the experiment is a delicate one4 ,when the pressure of the fragments of carbon against each other is too great1 the current traverses them with too much force to allow the calorific effects to vary the deviation of the galvanometer1 and when the pressure is too slight1 the current will not pass through them4 ,a medium degree of pressure must therefore be effected to ensure the success of the experiment1 and when it is obtained1 it is observed that on the approach of the hand to the tube1 a deviation of #ij will1 after a few seconds1 diminish1 so that it seems to correspond with the approach or withdrawal of the hand4 ,but breathing produces the most marked effects1 and ,i am disposed to believe that the greater or less deviations produced by the emission of articulate sounds when the different letters of the alphabet are pronounced separately1 are due to more or less direct emissions of heated gas from the chest4 ,it is certain that the letters which require the most strongly marked sounds1 such as ,a1 ,f1 ,h1 ,i1 ,k1 ,l1 ,m1 ,n1 ,o1 ,p1 ,r1 ,s1 ,w1 ,y1 ,z1 produce the greatest deviations of the galvanometric needle4 ,in my paper on the conductivity of such bodies as are moderately good conductors1 ,i had already pointed out this effect of heat upon divided substances1 and ,i also showed that after a retrograde movement1 which is always produced at once1 a movement takes place in an inverse direction to the index of the galvanometer when heat has been applied for some instants1 and this deviation is much greater than the one which is first indicated4 ,in a paper published in the #8,american ,scientific ,journal1' ,june #bh1 #ahgh1 ,mr4 ,edison gives some interesting details on the application of his system of a telephonic sender to measuring pressures1 expansions1 and other forces capable of varying the resistance of the carbon disk by means of greater or less compression4 ,since his experiments on this subject date from ,december #ahgg1 he again claims priority in the invention of using the microphone as a thermoscope2 but we must observe that according to ,mr4 ,hughes's arrangement of his instrument1 the effect produced by heat is precisely the reverse of the effect described by ,mr4 ,edison4 ,in fact1 in the arrangement adopted by the latter1 heat acts by increasing the conductivity acquired by the carbon under the increased pressure produced by the expansion of a body sensitive to heat3 in ,mr4 ,hughes's system1 the effect produced by heat is precisely the contrary1 since it then acts only on the contacts1 and not by means of pressure4 ,therefore the resistance of the microphone-thermoscope is increased under the influence of heat1 instead of being diminished4 ,this contrary effect is due to the division of some substance which is only a moderate conductor1 and ,i have shown that under such conditions these bodies1 when only slightly heated1 always diminish the intensity of the current which they transmit4 ,i believe that ,mr4 ,edison's arrangement is the best for the thermoscopic instrument1 and makes it possible to measure much less intense sources of heat4 ,indeed he asserts that by its aid the heat of the luminous rays of the stars1 moon1 and sun may be measured1 and also the variations of moisture in the air1 and barometric pressure4 ,this instrument1 which we give fig4 #ej1 with its several details1 and with the rheostatic arrangement employed for measuring1 consists of a metallic piece ,a fixed on a small board ,c1 and on one of its sides there is the system of platinum disks and carbons shown in fig4 #bh4 ,a rigid piece ,g1 furnished with a socket1 serves as the external support of the system1 and into this socket is introduced the tapering end of some substance which is readily affected by heat1 moisture1 or barometric pressure4 ,the other extremity is supported by another socket ,i1 fitted to a screw-nut ,h1 which may be more or less tightened by a regulating screw4 ,if this system is introduced into a galvanometric circuit a1 b1 c1 i1 g1 provided with all the instruments of the electric scale of measure1 the variations in length of the substance inserted are translated by greater or less deviations of the galvanometric needle1 which follow from the differences of pressure resulting from the lengthening or shortening of the surface capable of expansion which is inserted in the circuit4 ,illustration3 ,,fig4 #ej4 ,the experiments on the microphone made in ,london at the meeting of the ,society of ,telegraphic ,engineers on ,may #be1 #ahgh1 were wonderfully successful1 and they were the subject of an interesting article in the #8,engineer' of ,may #ca1 which asserts that the whole assembly heard the microphone speak1 and that its voice was very like that of the phonograph4 ,when the meeting was informed that these words had been uttered at some distance from the microphone1 the ,duke of ,argyll1 who was present1 while admiring the important discovery1 could not help exclaiming that this invention might have terrible consequences1 since1 for instance1 if one of ,professor ,hughes's instruments were placed in the room in ,downing ,street1 in which ,her ,majesty's ministers hold their cabinet council1 their secrets might be heard in the room in which the present meeting took place4 ,he added that if one of these little instruments were in the pocket of ,count ,schouvaloff1 or of ,lord ,salisbury1 we should at once be in possession of the secrets for which all ,europe was anxiously waiting4 ,if these instruments were able to repeat all the conversations held in the room in which they stood1 they might be really dangerous1 and the ,duke thought that ,professor ,hughes1 who had invented such a splendid yet perilous instrument1 ought next to seek an antidote for his discovery4 ,dr4 ,lyon ,playfair1 again1 thought that the microphone ought to be applied to the arophone1 so that by placing these instruments in the two ,houses of ,parliament1 the speeches of great orators might be heard by the whole population within five or six square miles4 ,the experiments lately made with the microphone at ,halifax show that the ,duke of ,argyll's predictions were fully justified4 ,it seems that a microphone was placed on a pulpit-desk in a church in ,halifax1 and connected by a wire about two miles long with a telephone placed close to the bed of a sick person1 who was able to hear the prayers1 the chanting1 and the sermon4 ,this fact was communicated to me by ,mr4 ,hughes1 who heard it from a trustworthy source1 and it is said that seven patients have subscribed for the expense of an arrangement by which they may hear the church services at ,halifax without fatigue4 ,the microphone has also lately been applied to the transmission of a whole opera1 as we learn from the following account in the #8,journal ,tlgraphique1' ,berne1 ,july #be1 #ahgh3-- #8,a curious micro-telephonic experiment took place on ,june #ai at ,bellinzona1 ,switzerland4 ,a travelling company of ,italian singers was to perform ,donizetti's opera1 8,don ,pasquale10 at the theatre of that town4 ,m4 ,patocchi1 a telegraphic engineer1 took the opportunity of making experiments on the combined effects of ,hughes's carbon microphone as the sending instrument1 and ,bell's telephone as the receiver4 ,with this object he placed a ,hughes microphone in a box on the first tier1 close to the stage1 and connected it by two wires1 from one to half a millimtre in thickness1 to four ,bell receivers1 which were placed in a billiard-room above the vestibule of the theatre1 and inaccessible to sounds within the theatre itself4 ,a small battery of two cells1 of the ordinary type used in the ,swiss telegraphic service1 was inserted in the circuit1 close to the ,hughes microphone4 #8,the result was completely successful4 ,the telephones exactly reproduced1 with wonderful purity and distinctness1 the instrumental music of the orchestra1 as well as the voices of the singers4 ,several people declared that they did not lose a note of either1 that the words were heard perfectly2 the airs were reproduced in a natural key1 with every variation1 whether piano or forte1 and several amateurs assured ,m4 ,patocchi that by listening to the telephone they were able to estimate the musical beauty1 the quality of the singers' voices1 and the general effect of the piece1 as completely as if they had been among the audience within the theatre4 #8,the result was the same when resistances equivalent to #aj kilomtres were introduced into the circuit1 without increasing the number of cells in the battery4 ,we believe that this is the first experiment of the kind which has been made in ,europe1 at least in a theatre1 and with a complete opera2 and those who are acquainted with the delicacy and grace of the airs in 8,don ,pasquale0 will be able to appreciate the sensitiveness of the combined instruments invented by ,hughes and ,bell1 which do not suffer the most delicate touches of this music to be lost4' ,although experiments with the microphone are of such recent date1 they have been very various1 and among other curious experiments we learn from the ,english newspapers that the attempt has been made to construct an instrument on the same principle as the telephone1 which shall be sensitive to the variations of light4 ,it is known that some substances1 and particularly selenium1 are electrically affected by light1 that is1 that their conductivity varies considerably with the greater or less amount of light which is shed upon them4 ,if1 therefore1 a circuit in which a substance of this nature is inserted1 is abruptly subjected to a somewhat intense light1 the increase of resistance which results from it ought to produce a powerful sound in a telephone inserted in the circuit4 ,this fact has been verified by experiment1 and ,mr4 ,willoughby ,smith infers from it1 as we have already suggested1 that the effects produced in the microphone are due to variations of resistance in the circuit1 which are produced by more or less close contacts between imperfect conductors4 ,in order to obtain this effect under the most favourable conditions1 ,mr4 ,siemens employs two electrodes1 consisting of network of very fine platinum wire1 fitting into each other like two forks1 of which the prongs are interlaced4 ,these electrodes are inserted between two glass plates1 and a drop of selenium1 dropped in the centre of the two pieces of network1 connects them on a circular surface large enough to establish sufficient conductivity in the circuit4 ,it is on this flattened drop that the ray of light must be projected4 ,,applications ,,of ,,the ,,microphone4 ,the applications of the microphone increase in number every day1 and in addition to those of which we have just spoken1 there are others of really scientific and even of practical interest4 ,among the number is the use which can be made of it as a system of relays for telegraphy1 in science for the study of vibrations imperceptible to our senses1 in medicine and surgery1 and even in manufactures4 ,its application to ,scientific ,research4--,we have seen that several physicists1 including ,messrs4 ,spottiswoode1 ,warwick1 ,rossetti1 ,canestrelli1 ,wiesendanger1 ,lloyd1 ,millar1 ,buchin1 and ,blyth1 have been able to hear what is said in a telephone which has no iron diaphragm1 but it was so difficult to establish the fact that it has been often disputed4 ,more certain evidence was desirable1 and the microphone is an opportune agent for affording it4 ,the #8,telegraphic ,journal' of ,september #a1 #ahgh1 observes that ,m4 du ,moncel1 in order to claim the victory in his controversy with ,colonel ,navez1 had still to show that the sounds which appeared to be inarticulate in telephones without a diaphragm might become intelligible if they were intensified4 ,this has been done for him by the use of ,mr4 ,hughes's microphone1 and the following experiments were made for the purpose4 #a4 ,if a magnetising coil1 surrounding a bar of soft iron1 is inserted in the circuit of a microphone1 with a battery of three cells1 the ticking of a watch and other sounds of the same kind may be heard on approaching the ear to the electro-magnet which has been thus constituted4 ,it is true that these sounds are very faint when they are not amplified1 but if the electro-magnet is fastened to a board1 and a second microphone is fixed to the same board1 the sounds produced by the electro-magnet are magnified1 and become distinctly audible in the telephone which is placed in connection with this second microphone4 #b4 ,these sounds may be further amplified by resting one of the extremities of the core of the electro-magnet on one of the poles of a permanent magnet1 which is fixed upon the board4 ,articulate speech may then be heard in the telephone which is placed in connection with the microphone resting on the board1 and the point at issue between ,,mm4 ,navez and ,du ,moncel is completely decided in this way3 for the auxiliary microphone can only propagate and amplify the vibration of articulate sounds1 which are communicated by the bar magnet of the coil to the board on which the two instruments are placed4 ,in this way it would be possible to render articulate sounds perceptible to ,m4 ,navez1 when transmitted by the bar magnet of a telephone without a diaphragm4 #c4 ,when a second bar magnet rests on the free pole of the electro-magnet1 so as to present to it a pole of the same nature as the one with which it is already in communication--in a word1 if a bar is placed between the two poles of a horseshoe electro-magnet1 the effects are still more marked1 and hence it may be assumed that the bar reacts as an armature1 by concentrating the lines of magnetic force in the vicinity of the helix4 #d4 ,when the two poles of a horseshoe magnet are inserted together inside a coil1 their effects are equally energetic1 although by this arrangement one of the poles might be expected to neutralise the effect of the other3 but the most important effects have been obtained by placing an armature of soft iron across the poles of the magnet which has been already inserted in the coil4 ,under these conditions articulate sounds are distinctly heard4 ,these experiments were confirmed by ,mr4 ,f4 ,varley1 in a letter published in the #8,telegraphic ,journal' of ,september #ae1 #ahgh1 and among the fresh experiments mentioned by him1 we will quote those which he made with an iron tube inserted in a helix1 in which the two opposite poles of two bar magnets are introduced4 ,these poles are only separated from each other by the interval of an inch1 so that the centre of the iron tube may be strongly magnetised4 ,mr4 ,varley says that this last arrangement reproduces the articulate sounds which issue from a sending microphone1 and this experiment is more decisive than that of ,professor ,hughes1 in which case it might be supposed that the bar magnet1 resting on the polar end of an electro-magnetic bar1 was only a modification of the disk in the ,bell telephone1 set in vibration by the alternate currents passing through the helix1 and that these vibrations were communicated to the board1 and became sensible when enlarged by the microphone4 ,but such an objection cannot be alleged in the case of the arrangement described above1 for since the sound is produced between the current passing into the helix and the magnetic current of the bar1 it can only be the result of a vibration produced by a disturbance of the reciprocal relations subsisting between these two elements4 ,mr4 ,varley adds that these experiments confirm ,m4 du ,moncel's researches1 which have thrown considerable light upon the causes which are at work in the action of the speaking telephone1 and with which we have hitherto been imperfectly acquainted4 ,its application to ,telephonic ,relays4--,in ,february #ahgh1 ,i first began to consider the mode of forming telephonic relays1 but ,i was checked by the discovery that there was no vibration in the receiving telephone1 and ,i made the following communication on the subject to the ,acadmie des ,sciences on ,february #be3--#8;,if the vibrations of the disk in the receiving telephone were the same as those of the sending telephone1 it is easy to see that if a telephone with a local battery1 acting both as sender and receiver1 were substituted for the receiving telephone1 it might1 by the intervention of the induction coil1 act as a relay1 and might therefore not only amplify the sound1 but also transmit it to any distance4 ,it is1 however1 doubtful whether the vibrations of the two corresponding disks are of the same nature1 and if the sound be due to molecular contractions and expansions1 the solution of the problem becomes much more difficult4 ,here is therefore a field for experiments4' ,these experiments have been successfully made by ,mr4 ,hughes1 who acquainted me with them early in ,june #ahgh1 and they led to the discovery of a most interesting system of microphonic relays4 ,on a wooden board of moderate size1 such as a drawing board1 he placed a microphone with a carbon brought to a fine point at each end1 and fixed in a vertical position4 ,one or more telephones were placed in the circuit1 with their membranes facing the board1 and a continuous sound was heard1 sometimes resembling a musical note1 sometimes the singing of boiling water in an oven2 and the sound1 which could be heard at a distance1 went on indefinitely1 as long as the electric force was exerted4 ,mr4 ,hughes explains this phenomenon in the following way4 ,the slightest shock which affects the microphone has the effect of sending currents1 more or less broken1 through the telephones1 which transform them into sound vibrations1 and since these are mechanically transmitted by the board to the microphone1 they maintain and even amplify its action1 and produce fresh vibrations on the telephones4 ,thus a fresh action is exerted on the microphone1 and so on indefinitely4 ,again1 if a second microphone1 in connection with another telephonic circuit1 be placed upon the same board1 we have an instrument which acts as a telephonic relay1 that is1 it transmits to a distance the sounds communicated to the board1 and these sounds may serve either as a call1 or as the elements of a message in the ,morse code1 if a ,morse manipulator is placed in the circuit of the first microphone4 ,mr4 ,hughes adds that he has made several very successful experiments with this system of instruments1 although he only employed a ,daniell battery of six cells without any induction coil4 ,by fastening a pasteboard tube1 #dj centimtres in length1 to the receiving telephone1 he was able to hear in all parts of a large room the continuous sound of the relay1 the ticking of a watch1 and the scratching of a pen upon paper4 ,he did not try to transmit speech1 since it would not have been reproduced with sufficient distinctness under such conditions4 ,since this first attempt1 ,mr4 ,hughes has arranged another and still more curious system of microphonic relays1 for which two microphones with vertical carbons are required4 ,he places two microphones of this description on a board1 and connects one of them with a third microphone1 which acts as a sender1 while the second is in communication with a telephone and a second battery3 in this way the words uttered before the sender are heard in the telephone1 without employing any electro-magnetic organ for the telephonic relay4 ,in ,august #ahgh1 ,messrs4 ,houston and ,thomson likewise arranged a system of telephonic relays which only differs from that of ,mr4 ,hughes in the particular of having the microphone fixed on the diaphragm of the telephone1 and not on the board beside it4 ,the system consists of three vertical microphones1 which can be combined for tension or quantity1 according to the conditions for which they are required4 ,the model of this instrument was represented in the #8,telegraphic ,journal' of ,august #ae1 #ahgh1 to which we must refer our readers1 if they wish for further information on the subject4 ,its application to ,medicine and ,surgery4--,the extreme sensitiveness of the microphone suggested its use for the observation of sounds produced within the human body1 so that it might serve as a stethoscope for listening to the action of the lungs and heart4 ,dr4 ,richardson and ,mr4 ,hughes are now busy in the attempt to carry out this idea1 but so far the result is not very satisfactory1 although they still hope to succeed4 ,meanwhile1 ,m4 ,ducretet has made a very sensitive stethoscopic microphone1 which we represent in fig4 #ea4 ,it consists of a carbon microphone ,c ,p1 with a simple contact1 of which the lower carbon ,p is fitted to one of ,m4 ,marais' tambourines with a vibrating membrane ,t4 ,this tambourine is connected with another ,t1 by a caoutchouc tube1 which is to be applied to the different parts of the body which demand auscultation1 and which is therefore termed the tambour explorateur4 ,the sensitiveness of the instrument is regulated by means of a counterpoise ,p ,o1 which is screwed upon the arm of a bent lever1 and to this the second carbon ,c is fixed4 ,the extreme sensitiveness of ,m4 ,marais' tambourines in transmitting vibrations is well known1 and since their sensitiveness is further increased by the microphone1 the instrument becomes almost too impressionable1 since it reveals all sorts of sounds1 which it is difficult to distinguish from each other4 ,such an instrument can only be of use when entrusted to experienced hands1 and a special education of the organ of hearing is needful1 in order to turn it to account4 ,illustration3 ,,fig4 #ea4 ,in a work lately published by ,m4 ,giboux on the application of the microphone to medicine1 this stethoscopic system is rather severely criticised1 and not without reason if1 as ,m4 ,giboux asserts1 it is only sensitive to the movements which take place on the surface of the body1 and those which are internal are either lost or altogether changed in character4 ,but without pronouncing on the improvements which may ultimately be made in the instrument1 ,m4 ,giboux thinks that its most important use in medical practice consists in its allowing a certain number of students to observe with the professor the different sounds of the body1 to study them with him in their different phases1 and thus to profit more readily by his teaching4 ,a microphonic circuit might bifurcate between several telephones1 so that each person might hear for himself what is heard by others4 ,the most important application of the instrument to surgical purposes has lately been made by ,sir ,henry ,thompson1 aided by ,mr4 ,hughes1 for the examination of the bladder in cases of stone4 ,it enables him to ascertain the presence and precise position of calculi1 however small they may be4 ,for the purpose of research1 he uses a sound1 made of a ,maillechort rod1 a little bent at the end1 and placed in communication with a sensitive carbon microphone4 ,when the sound is moved about in the bladder1 the rod comes in contact with stony particles1 even if they are no larger than a pin's head1 and friction ensues1 producing in the telephone vibrations which can be easily distinguished from those caused by the simple friction of the rod on the soft tissues of the sides of the bladder4 ,the arrangement of the instrument is shown in fig4 #eb4 ,the microphone is placed in the handle which contains the sound1 and is the same as that given in fig4 #db1 but of smaller size1 and the two conducting wires e which lead to the telephone1 issue from the handle by the end a opposite to that bb to which the sound dd is screwed4 ,as this instrument is not intended to reproduce speech1 retort carbons instead of wood carbons may be used4 ,illustration3 ,,fig4 #eb4 ,some deaf people1 whose sense of hearing is not completely destroyed1 have been able to hear by an expedient based upon the principle of the microphone4 ,for this purpose two telephones1 connected by a metallic crown1 which is placed on the temples1 are applied to the ears of the deaf person1 and the telephones are placed in communication with a battery microphone1 which hangs to the end of a double conducting wire4 ,the deaf man keeps the microphone in his pocket1 and presents it as an acoustic tube to the person who wishes to converse with him4 ,mr4 ,hughes's speaker1 represented fig4 #db1 is the one used4 ,various ,applications4--,the microphone may be used in many other ways1 some of which are suggested in the #8,english ,mechanic' of ,june #ba1 #ahgh4 ,the article states that by means of this instrument1 engineers will be able to estimate the effects of the vibrations caused on old and new buildings by the passage of heavy loads2 a soldier will be able to discover the enemy's approach when he is several miles off1 and may even ascertain whether he has to do with artillery or cavalry2 the approach of ships to the neighbourhood of torpedoes may be automatically heralded on the coast by this means1 so that an explosion may be produced at the right moment4 ,it has also been proposed to use the microphone to give notice of an escape of gas in coal-mines4 ,the gas1 in escaping from between the seams of coal1 makes a whistling noise1 which might1 with the aid of the microphone and telephone1 be heard at the top of the shaft4 ,again1 it has been suggested that the microphone might be used as a seismograph to reveal the subterranean noises which generally precede earthquakes and volcanic eruptions1 and which would be much intensified by this instrument4 ,it might even be of use to ,signor ,palmieri for his observations in the ,vesuvius ,observatory4 ,the microphone has also been used by ,mr4 ,chandler ,roberts to render the diffusion of gaseous molecules through a porous membrane sensible to the ear4 ,as might have been expected1 the acclamation with which ,mr4 ,hughes's invention was received led to the assertion of other claims to priority1 and in addition to that of ,mr4 ,edison1 on which we have already given our opinion1 there are several others1 showing that if some microphonic effects were discovered at different times before the date of ,mr4 ,hughes's discovery1 they could not have been considered important1 since they were not even announced4 ,among the number was that of ,mr4 ,wentworth ,lascelles ,scott1 specified in the #8,electrician' of ,may #be1 #ahgh1 and that of ,m4 ,weyher1 presented to the ,socit de ,physique1 ,paris1 in ,june #ahgh4 ,another1 made by ,m4 ,dutertre1 is of somewhat greater importance1 for his experiments were reported in the ,rouen papers in ,february of the same year3 yet there is no just ground for such claims1 since the earliest date of his experiments is subsequent to the experiments first made by ,mr4 ,hughes4 ,these began early in ,december #ahgg1 and in ,january #ahgh they were exhibited to officials of the ,submarine ,telegraph ,company1 as ,mr4 ,preece declared in a letter addressed to the several scientific men4 ,,external ,,influence ,,on ,,telephonic ,,transmissions4 ,the obstacles which occur in telephonic transmissions proceed from three causes3 #a4 ,the intensity of sound is diminished by the loss of current in transmission--a loss which is much greater in the case of induced currents than in those received from a battery4 #b4 ,confusion is caused by the influence of adjacent currents4 #c4 ,the induction from one wire to another4 ,this last influence is much greater than is usually supposed4 ,if two perfectly insulated wires are placed side by side1 one in communication with the circuit of an electric bell1 and the other with the circuit of a telephone1 the latter will repeat the sounds of the bell with an intensity often great enough to act as a call without applying the instrument to the ear4 ,,mm4 ,pollard and ,garnier1 in their interesting experiments with the induced currents of the ,ruhmkorff coil1 have ascertained that in this way not merely sounds may be obtained which correspond with the induced currents resulting from the action of the primary current1 but also those which result from the action of the secondary current on other helices1 which are termed currents of the second order4 ,these different reactions frequently cause the telephonic transmissions made on telegraphic lines to be disturbed by irregular sounds1 arising from the electric transmissions on adjoining lines2 but it does not appear that these influences altogether neutralise each other1 so that conversation held in the ordinary way and a message sent in the ,morse code may be heard simultaneously4 ,at the ,artillery ,school1 ,clermont1 a telephonic communication has been established1 for the sake of experiments1 between the school and the butts1 which are at a distance of about eight miles4 ,another communication of the same kind has been established between the ,clermont ,observatory and the one at ,puy-de-,dme1 which is nearly nine miles from the former4 ,these two lines are carried on the same posts for a course of six miles1 together with an ordinary telegraphic wire1 and for a distance of #ccj yards there are seven other such wires4 ,the two telephonic wires are separated from each other by a space of #he centimtres4 ,the following facts have been observed under these conditions4 #a4 ,the school telephone is perfectly able to read off from their sound the ,morse messages which pass through the two adjacent telegraph wires1 and the ticking of the instrument does not at all interfere with the vocal communication of the telephone1 nor render it inaudible4 #b4 ,the two adjacent telegraphic lines1 although not in contact1 confuse their messages together1 and it has sometimes been possible to hear messages from ,puy-de-,dme at the school through the wire which runs to the butts1 although the distance between the two lines is nowhere less than #he centimtres4 ,these inconveniences have been in some degree remedied by inserting strong resistances in the circuit1 or by putting the current to earth at some distance from the telephonic stations4 ,m4 ,izarn1 ,professor of ,physics at the ,lyce1 ,clermont1 holds that telephonic electric currents may readily be turned aside by the earth1 especially if in the course of their passage they encounter metallic conductors1 such as gas or water pipes4 ,he writes as follows on the subject1 in a paper addressed to the ,acadmie des ,sciences1 on ,may #ac1 #ahgh3--#8;,i set up a telephone in the ,clermont ,lyce with a single wire1 more than #ej yards in length1 which crosses the court-yard of the ,lyce1 and goes from the laboratory1 where it is suspended to a gas-burner1 to a room near the porter's lodge1 where it is suspended to another gas-burner4 ,when ,i applied my ear to the telephone1 ,i could distinctly hear the telegraphic signals1 ,morse or otherwise1 which came either from the telegraph office at ,clermont1 or from the telephone office which was at work between the ,school of ,artillery and the butts below ,puy-de-,dme1 a distance of eight miles4 ,i could overhear words1 and especially the military orders issued at the butts for the purpose of being heard at the school4 ,yet my wire is perfectly independent of those used for signalling1 and is even very remote from them2 but as the wires of the telegraph office and of the ,school of ,artillery go to earth at a little distance from the gas-pipes1 it is probable that this phenomenon is caused by a diversion of the current produced in my wire1 by means of the earth and the network of metal pipes4' ,mr4 ,preece made the same remark in his notice of #8some physical points connected with the telephone4' ,again1 we read in the #8,telegraphic ,journal' of ,june #ae1 #ahgh1 that in a telephonic concert transmitted from ,buffalo to ,new ,york1 the singers at ,buffalo were heard in an office placed outside the telegraphic circuit in which the transmission was effected4 ,on enquiry1 it was ascertained that the wire through which the telephonic transmission took place1 was at one point in its course close to the one which directly transmitted the musical sounds1 but the distance between the two wires was not less than ten feet4 ,when the circuits are altogether metallic1 there is much less risk of confusion1 and ,m4 ,zetzche declares that sounds proceeding from other wires are in this case little heard1 and then only momentarily1 so that it is much more easy to hear with this arrangement than with the one in ordinary use4 #8,it is not1' he says1 #8the resistances of the wire1 but rather the diversions of the current near the posts1 which interfere with telephonic correspondence on long lines above ground4 ,this was proved by the following experiments3--,i connected the telegraphic line from ,dresden to ,chemnitz with a line from ,chemnitz to ,leipzig 7#ed miles71 which made a circuit of #ajc miles1 going to earth at its two extremities4 ,there was no communication between ,dresden and ,leipzig1 but ,leipzig and ,dresden could communicate with ease1 in spite of the greater extent of line4 ,i broke the connection with earth1 first at ,leipzig1 then simultaneously at ,leipzig and ,dresden1 and ,i observed the following effects4 ,when insulation took place at ,leipzig only1 the telephone could be heard at the stations of ,dresden1 ,riesa1 and ,wurzen2 when the line was insulated at both ends1 the communication was good between the two latter stations1 but it was observed that at the intermediate station the words spoken at ,wurzen were more distinctly heard than the words spoken at ,riesa were heard at ,wurzen4 ,since the distance from ,wurzen to ,leipzig is little more than half that from ,riesa to ,dresden1 there are consequently nearly twice as many posts on the latter line1 which carry the currents to earth1 and hence ,i conclude that these diversions of current explain the possibility of conversing on an insulated line1 and also why sounds are more distinctly heard at the ,riesa station in consequence of the greater intensity of current still remaining on the line4' ,some vibrations also result from the action of currents of air on telegraphic wires1 which produce the humming sound so well known on some lines1 and these may also react on the telephone2 but they are in this case generally mechanically transmitted1 and they may be distinguished from the others1 if the sounds which ensue are heard after the telephone is excluded from the circuit by a break with a short circuit and after the communication to earth established behind the telephone has been broken4 ,the induced reactions caused by the line wires on each other are not the only ones which may be observed on a telephonic circuit3 every manifestation of electricity near a telephone may produce sounds of greater or less force4 ,of this we have already given a proof in ,m4 d',arsonval's experiments1 and others by ,m4 ,demoget demonstrate the fact still more clearly4 ,in fact1 if a small bar magnet provided with a vibrator be placed before one of the telephones of a telephonic circuit1 and the vibrating plate of the telephone be removed1 in order to draw away the sound produced by the vibrator1 its humming noise may be distinctly heard on the second telephone of the circuit2 a noise which attains its maximum when the two extremities of the electro-magnet are at their nearest point to the telephone without a diaphragm1 and it is at its minimum when this electro-magnet is presented to it along its neutral line4 ,m4 ,demoget supposes that the action which is exerted in this instance is that of a magnet exerting two inducing actions which are opposite and symmetrical1 with a field limited by a double paraboloid and with an axis1 according to his experiments1 which extended #ee centimtres beyond the magnetic core1 and a vertical diameter of #fj centimtres4 ,he believes that in this way it would be easy to telegraph on the ,morse system1 and that1 in order to do so1 it would only be necessary to apply a key to the inducing electro-magnet4 ,mr4 ,preece points out three ways of overcoming the difficulty presented by the induced reactions caused by the wires on each other4 #a4 ,by increasing the intensity of the transmitted currents1 so as to make them decidedly stronger than the induced currents1 and to reduce the sensitiveness of the receiving telephone4 #b4 ,to place the telephonic wire beyond the range of induction4 #c4 ,to neutralise the effects of induction4 ,the first mode may be effected by ,edison's battery system1 and we have seen that it is very successful4 ,in order to put the second mode in practice1 ,mr4 ,preece says that it would be necessary to study the two kinds of induction which are developed on telegraphic lines3 electro-static induction1 analogous to that produced on submarine cables1 and electro-dynamic induction1 resulting from electricity in motion4 ,in the former case1 ,mr4 ,preece proposes to interpose between the telephone wire and the other wires a conducting body in communication with the earth1 capable of becoming a screen to the induction by itself absorbing the electro-static effects4 ,he says that this might be accomplished by surrounding the telegraphic wires adjacent to the telephonic wire with a metallic envelope1 and then plunging them in water4 ,he adds that the effects of static induction are not completely destroyed in this way1 since the substance used is a bad conductor1 but they are considerably reduced1 as he has proved by experiments between ,dublin1 ,holyhead1 ,manchester1 and ,liverpool4 ,in the second case1 ,mr4 ,preece admits that an iron envelope might paralyse the electro-dynamic effects produced by absorbing them1 so that if insulated wires were employed1 covered with an iron case1 and communicating with the earth1 the two induced reactions would be annulled4 ,we will not follow ,mr4 ,preece in his theory as to these effects--a theory which seems to us open to question1 but we content ourselves with pointing out his proposed mode of attenuation4 ,in order to carry out the third expedient1 it might be thought that it would be enough to employ a return wire instead of going to earth1 for under such conditions the currents induced on one of the wires would be neutralised by those resulting from the same induction on the second wire1 which would then act in an opposite direction2 but this mode would only be successful when there is a very small interval between the two telephone wires1 and they are at a considerable distance from the other wires4 ,when this is not the case1 and they are all close together1 as in submarine or subterranean cables1 consisting of several wires1 this mode is quite inefficient4 ,a small cable1 including two conductors1 insulated with gutta-percha1 may be successfully carried through the air4 ,the use of two conductors has the further advantage of avoiding the inconvenience of stray currents on the line and through the earth1 which1 when the communications to earth are imperfect1 permit the line current to pass more or less easily into the telephonic line4 ,in addition to the disturbing causes in telephonic transmission we have just mentioned1 there are others which are also very appreciable1 and among them are the accidental currents which are continually produced on telegraphic lines4 ,these currents may proceed from several causes1 at one time from atmospheric electricity1 at another from terrestrial magnetism1 at another from thermo-electric effects produced upon the lines1 at another from the hydro-electric reactions produced on the wires and disks in communication with the earth4 ,these currents are always very unstable1 and consequently they are likely1 by reacting on the transmitted currents1 to modify them so as to produce sounds upon the telephone4 ,mr4 ,preece asserts that the sound proceeding from earth currents somewhat resembles that of falling water4 ,the discharges of atmospheric electricity1 even when the storm is remote1 produce a sound which varies with the nature of the discharge4 ,when it is diffused and the clap takes place near at hand1 ,dr4 ,channing1 of ,providence1 ,u4,s41 says that the sound resembles that produced by a drop of fused metal when it falls into water1 or1 still more1 that of a rocket discharged at a distance3 in this case it might seem that the sound would be heard before the appearance of the flash1 which clearly shows that the electric discharges of the atmosphere only take place in consequence of an electric disturbance in the air4 ,mr4 ,preece adds that a wailing sound is sometimes heard1 which has been compared to that of a young bird1 and which must proceed from the induced currents which terrestrial magnetism produces in the metallic wires when placed in vibration by currents of air4 ,m4 ,gressier1 in a communication made to the ,acadmie des ,sciences on ,may #f1 #ahgh1 has spoken of some of these sounds1 but he is totally mistaken in the source to which he ascribes them4 #8,in addition to the crackling sound caused by the working of telegraph instruments on the adjacent lines1 a confused murmur takes place in the telephone1 a friction so intense that it might sometimes be thought that the vibrating disk was splitting4 ,this murmur is heard more by night than by day1 and is sometimes intolerable1 since it becomes impossible to understand the telephone1 although nothing is going on in the office to disturb the sound4 ,the same noise is heard when only one telephone is used4 ,a good galvanometer inserted in the circuit reveals the presence of sensible currents1 sometimes in one direction1 sometimes in another4' ,i studied these currents for a long time with the galvanometer1 and made them the subject of four papers which were laid before the ,acadmie des ,sciences in #ahgb1 and ,i am convinced that they have in general nothing to do with atmospheric electricity1 but result either from thermo-electric or hydro-electric influence4 ,they take place constantly and in all weathers on telegraph lines1 whether these lines are insulated at one end1 or in contact with the earth at both ends4 ,in the first case1 the polar electrodes of the couple are formed by the telegraph wire and the earth plate1 generally of the same nature1 and the intermediate conducting medium is represented by the posts which support the wire and the earth which completes the circuit4 ,in the second case1 the couple is formed in almost the same way1 but the difference in the chemical composition of the ground at the two points where the earth plates are buried1 and sometimes their different temperature1 exert a strong influence4 ,if only the first case be considered1 it generally happens that on fine summer days the currents produced during the day are inverse to those which are produced by night1 and vary with the surrounding temperature in one or the other direction4 ,the presence or absence of the sun1 the passage of clouds1 the currents of air involve abrupt and strongly marked variations1 which may be easily followed on the galvanometer1 and which cause more or less distinct sounds in the telephone4 ,during the day1 the currents are directed from the telegraph line to the earth plate1 because the heat of the wire is greater than that of the plate1 and these currents are then thermo-electric4 ,during the night1 on the other hand1 the wire is cooled by the dew1 which causes a greater oxidation on the wire than that which takes place on the plate1 and the currents then become hydro-electric4 ,i say more about these currents because1 in consequence of a mistaken belief as to their origin1 it has been supposed that the telephone might serve for the study of the variations of the atmospheric electricity generally diffused through the air4 ,such an application of the telephone would1 under these conditions1 be not only useless1 but also misleading1 by inducing the study of very complex phenomena1 which could lead to nothing more than ,i have already stated in my different papers on the subject4 ,certain local influences will also produce sounds in the telephone4 ,thus the distension of the diaphragm by the moist heat of the breath1 when the instrument is held before the mouth in speaking1 causes a perceptible murmur4 ,from the electro-static reactions1 so strongly produced on the submarine cables1 in consequence of electric transmissions1 it might be supposed that it would not be easy to hold telephonic correspondence through this kind of conductor1 and1 to ascertain the fact1 an experiment was made on the cable between ,guernsey and ,dartmouth1 a distance of sixty miles4 ,articulate speech1 only a little indistinct1 was1 however1 perfectly transmitted4 ,other experiments1 made by ,messrs4 ,preece and ,wilmot1 on an artificial submarine cable1 placed in conditions analogous to those of the ,atlantic cable1 showed that a telephonic correspondence might be kept up at a distance of a hundred miles1 although the effects of induction were apparent4 ,at the distance of #aej miles1 it was somewhat difficult to hear1 and the sounds were very faint1 as if some one were speaking through a thick partition4 ,the sound diminished rapidly until the distance of #bjj miles was reached1 and after that it became perfectly indistinct1 although singing could still be heard4 ,it was even possible to hear through the whole length of the cable1 that is1 for #c1jjj miles1 but ,mr4 ,preece believed this to be due to the induction of the condenser on itself3 he holds1 however1 that singing may be heard at a much greater distance than speech1 owing to the more regular succession of electric waves4 ,mr4 ,preece also made experiments on the subterranean telegraphs between ,manchester and ,liverpool1 a distance of #cj miles1 and found no difficulty in exchanging correspondence2 and it was the same with the cable from ,dublin to ,holyhead1 a distance of #fg miles4 ,this cable had seven conducting wires1 and when the telephone was connected with one of them1 the sound was repeated through all the others1 but in a fainter degree4 ,when the currents of the telegraphic instruments passed through the wires1 the induction was apparent1 but not so great as to prevent telephonic communication4 ,,establishment ,,of ,a ,,telephonic ,,station4 ,although the telephonic system of telegraphy is very simple1 yet certain accessory arrangements are indispensable for its use4 ,thus1 for example1 an alarum call is necessary1 in order to know when the exchange of correspondence is to take place1 and information that the call has been heard is likewise necessary4 ,an electric bell is therefore an indispensable addition to the telephone1 and since the same circuit may be employed for both systems1 if a commutator is used1 it was necessary to find a mode of making the commutator act automatically1 so as to maintain the simple action of the system which constitutes its principal merit4 ,,mm4 ,pollard and ,garnier's ,system4--,with this object1 ,,mm4 ,pollard and ,garnier devised a very successful arrangement last ,march1 which employs the weight of the instrument to act upon the commutator4 ,for this purpose1 they suspended the instrument to the end of a spring plate1 fastened between the two contacts of the commutator4 ,the circuit wire corresponds with this plate1 and the two contacts correspond1 the one with the telephone1 the other with the bell4 ,when the telephone hangs below the spring-support1 that is1 when it is not at work1 its weight lowers the spring plate on the lower contact1 and the communication of the line with the bell is established3 when1 on the other hand1 the telephone is raised for use1 the spring plate touches the higher contact1 and communication is established between the line and telephone4 ,in order to make the bell sound1 it is only necessary to establish1 on the wire which connects the line with the bell contact of the commutator1 a breaker which can both join and break the current1 and which communicates on one side with the contact of the bell1 and on the other with its battery4 ,the ordinary push of an electric bell will be sufficient1 if it is supplied with a second contact1 but ,,mm4 ,pollard and ,garnier wished to make this action also automatic1 and consequently they devised the arrangement represented in fig4 #ec4 ,illustration3 ,,fig4 #ec4 ,in this system1 as well as in those which have since been devised1 two telephones are employed1 one of which is constantly applied to the ear1 and the other to the mouth1 so as to make it possible to speak while listening4 ,the telephones are supported by three wires1 two of which contain flexible conductors1 while the third only acts as a support4 ,two of the four wires of the two telephones are connected with each other1 and the other two are connected with the two binding screws of the commutator t1 t3 the wires without conductors are suspended to the extremities of the two flexible plates l1 l1 which correspond with earth and line4 ,when at rest1 the weight of the telephones presses the two plates l1 l1 on the lower contacts ,s1 ,s1 but when the instruments are taken up these plates press against the higher contacts4 ,the two bell wires terminate on the lower contacts1 those of the telephones on the higher contacts1 and one of the poles of the battery is connected with the lower contact on the left ,s1 the other with the higher contact on the right ,t4 ,when at rest1 the system is applied to the electric bell1 and the current sent from the opposite station will follow the circuit ,l l ,s ,s ,s l ,t1 so that the call will be made4 ,on taking up the two telephones1 the circuit of the bell system is broken1 and that of the telephones is established1 so that the current follows the course ,l l ,t t t ,t l ,t4 ,if only one telephone is held at a time1 the current is sent into the bell system of the opposite station1 and follows the route ,p ,s l ,l ,t l ,t t ,p --4 ,in this way the three actions necessary for calling1 corresponding1 and enabling the corresponding instrument to give a call1 are almost involuntarily made4 ,system by ,,mm4 ,brguet and ,roosevelt4--,in the system established by the ,paris agents of the ,bell company1 the arrangement resembles the one just described1 except that there is only one spring commutator1 and the call is made with the push of an ordinary electric bell4 ,a mahogany board is suspended from the wall1 and on it are arranged1 first1 the ordinary electric bell system1 with a sending push fixed below it2 second1 two forks supporting two telephones1 one of which is fastened to the bar of a commutator1 arranged as a ,morse key4 ,the two telephones are connected by two conducting wires1 so arranged as to be capable of extension1 and two of their four binding screws are in immediate connection with each other1 and the other two with the earth1 line1 and battery1 by means of the commutator1 the sending push1 and the bell system4 ,the arrangement is shown in fig4 #ed4 ,illustration3 ,,fig4 #ed4 ,the commutator ,a consists of a metallic bar a c1 bearing the suspension fork of one of the telephones ,f below its point of articulation3 it ends in two pins a and c1 below which the two contacts of the commutator are fixed1 and a spring compresses the lower arm of the bar1 so as to cause the other arm to rest constantly on the higher contact4 ,for greater security a steel tongue a b is fastened to the lower end of the bar1 and rubs against the small shaft b1 which is provided with two insulated contacts1 corresponding to those of the board4 ,the bar is in communication with the line wire by means of the call-push1 and the upper of the two contacts we have just described corresponds with one of the telephone wires which is inserted in the same circuit1 while the other corresponds with the bell system ,s1 which is in communication with earth4 ,it follows from this arrangement1 that when the right telephone presses its whole weight on the support1 the bar of the commutator is inclined on the lower contact1 and consequently the line is in direct communication with the bell1 so that the call can be made4 ,when1 on the other hand1 the telephone is removed from its support1 the bar rests on the higher contact1 and the telephones are connected with the line4 ,pressure on the sending push serves to call the corresponding station3 the connection of the line with the telephones is then broken1 and it is established with the battery of the sending station1 which sends its current through the bell of the corresponding station4 ,in order to obtain this double effect1 the contact spring of the sending push generally rests upon a contact fastened to a piece of wood shaped like a joiner's rule1 which covers it in front1 and below this spring there is a second contact1 which communicates with the positive pole of the station battery4 ,the other contact corresponds with the line wire1 and a connection takes place between the earth wire and the negative pole of the station battery1 so that the earth wire is common to three circuits3 #ast4 ,to the telephone circuit4 #bnd4 ,to that of the bell system4 #crd4 ,to that of the local battery4 ,the second fork1 which supports the telephone on the right1 is fixed to the board1 and is independent of any electric current4 ,it is clear that this arrangement may be varied in a thousand ways1 but the model we have just described is the most practical4 ,edison's ,system4--,the problem becomes more complex in the case of battery telephones1 since the battery must be common to both systems1 and the induction coil must be inserted in two distinct circuits4 ,fig4 #ee represents the model adopted in ,mr4 ,edison's telephone4 ,illustration3 ,,fig4 #ee4 ,in this arrangement1 there is a small stand ,c on the mahogany board on which the bases of the two telephones rest4 ,the bell system ,s is worked by an electro-magnetic speaker ,p1 which serves1 when a ,morse key is added to the system1 for exchange of correspondence in the ,morse code1 if there should be any defect in the telephones1 or to put them in working order4 ,above the speaker there is a commutator with a stopper ,d to adapt the line for sending or receiving1 with or without the bell2 and below the stand ,c the induction coil1 destined to transform the voltaic currents into induced currents1 is arranged in a small closed box ,e4 ,when the commutator is at reception1 the line is in immediate correspondence either with the speaker or with the receiving telephone1 according to the hole in which the stopper is inserted2 when1 on the other hand1 it is at sending1 the line corresponds to the secondary circuit of the induction coil4 ,under these conditions the action is no longer automatic2 but since this kind of telephone can only be usefully employed for telegraphy1 in which case those who work it are acquainted with electric apparatus1 there is no inconvenience in this complication4 ,,call-,,bells ,,and ,,alarums4 ,the call-bells applied to telegraphic service have been arranged in different ways4 ,when the vibrating bells are in use1 like those of which we have just spoken1 it is necessary to use a battery1 and the advantages offered by telephones with induced currents are thus sensibly diminished4 ,in order to dispense with the battery1 the use of the electro-magnetic bell has been suggested4 ,in this case there are usually two bells1 with a hammer oscillating between them1 and a support formed of the polarised armature of an electro-magnet4 ,the electro-magnetic instrument is placed below this system2 it is turned by a winch1 and sends the currents1 alternately reversed1 which are necessary to communicate the vibratory movement to the hammer1 and this movement is enough to make the two bells tinkle4 ,below the winch of this electro-magnetic instrument there is a commutator with two contacts1 which adapts the instrument for sending or receiving4 ,m4 ,mandroux has simplified this system1 and has reduced it to small dimensions by the following arrangement4 ,he fixes two magnetic cores1 furnished with coils1 on each of the two poles of a horseshoe magnet1 composed of two bars connected by an iron coupler1 and between the poles expanded by these four cores he inserts an armature1 within which there is a steel spring fastened to one of these poles4 ,in this way the armature is polarised1 and oscillates under the influence of the reversed currents transmitted by an instrument of the same kind provided with an induction system4 ,these oscillations may have the effect of producing the sound of a call-bell1 and the induction system may consist of a manipulating key1 fastened to a duplex system of armature1 regularly applied to the magnetic cores1 taken in pairs4 ,on communicating a series of movements to this manipulator1 a series of induced currents in an inverse direction are produced1 which cause the armature of the corresponding station to act as we have already seen1 and which may even1 when necessary1 furnish a series of ,morse signals for a suitable manipulation4 ,on account of the small size of this system1 it might be applied to the telephonic service of the army4 ,the ,bell ,telephone ,company in ,paris has arranged another little call-system which is quite satisfactory and has the advantage of acting as a telephone at the same time4 ,the model resembles the one we have termed a snuff-box telephone1 and it has a button commutator by means of which the instrument is placed in communication with the electro-magnetic system of the instrument1 or with a battery which is able to make the telephone vibrate with some force4 ,to make a call1 the button must be pressed1 and the battery current is communicated to the corresponding instrument1 which begins to vibrate when the call is made2 and when notice is given of the receipt of the signal1 the pressure on the button is removed1 and it becomes possible to speak and receive as in ordinary telephones4 ,illustration3 ,,fig4 #ef4 ,m4 de ,weinhold's ,system4--,m4 ,zetzche speaks highly of an alarum devised by ,professor ,a4 de ,weinhold1 which resembles that by ,m4 ,lorenz1 represented in fig4 #ef4 ,its organ of sound consists of a steel bell ,t1 from #ac to #ad centimtres in diameter1 and toned to give about #dbj double vibrations in a second4 #8,its diameter and tone1' he says1 #8are important1 and any great departure from the rule laid down diminishes the effect4 ,the opening of the bell is below1 and it is fixed on a stand by its centre4 ,a slightly curved bar magnet1 provided at its two ends with iron appendices enclosed in a coil1 traverses the stand4 ,the bar magnet of the telephone also terminates in an iron appendix enclosed in a coil4 ,in both cases the changes produced in the magnetic condition appear to be more intense than they are in magnets without appendices4 ,the bar magnet is placed within the bell in the direction of one of its diameters1 so that the appendices almost touch its sides4 #8,when the bell is struck on a spot about #ij from this diameter with a wooden clapper ,m1 which acts with a spring1 and is withdrawn by stretching the spring and then letting it go1 as in a bell for the dinner-table1 the vibrations imparted to it send currents into the coils1 and these currents produce identical vibrations on the iron disk of the telephone1 which are intensified by a conical resonator fitted to the telephone1 so as to be easily heard some paces off4 ,for ordinary use1 the bell coil is broken into a short circuit by means of a metallic spring ,r1 and consequently1 when the bell is struck1 the spring must be opened so as not to break the circuit4 ,an instrument of the same kind has also been devised by ,herr ,w4 ,e4 ,fein at ,stuttgardt4' ,illustration3 ,,fig4 #eg4 ,illustration3 ,,fig4 #eh4 ,,mm4 ,dutertre and ,gouault's ,system4--,one of the most ingenious solutions of the problem of making the telephone call has recently been proposed by ,,mm4 ,dutertre and ,gouault4 ,figs4 #eg and #eh represent the opposite faces of the instrument4 ,it consists of a kind of snuff-box telephone1 like the one shown in fig4 #bf1 and it is so arranged as to send or receive the call1 according to the way in which it is placed on its stand1 which is only an ordinary bracket fastened to the wall4 ,when it is placed on the bracket so as to have the telephone mouthpiece on the outside1 it is adapted for receiving1 and can then give the call4 ,when1 on the other hand1 its position on the bracket is reversed1 it permits the other station to make the call1 by producing vibrations on a vibrator under the influence of a battery1 and these vibrations reverberate in the corresponding instrument with sufficient force to produce the call4 ,if the instrument is taken up1 and the finger is placed on a small spring button1 it may then be used as an ordinary telephone4 ,in this instrument1 the magnet ,n ,s 7fig4 #eg7 is snail-shaped1 like others we have mentioned1 but the core of soft iron ,s1 to which the coil ,e is fastened1 can produce two different effects on its two extremities4 ,on the one side1 it reacts on a small armature which is fastened to the end of a vibrating disk ,c1 fig4 #eh2 the armature is placed against a contact fastened to the bridge ,b1 and constitutes an electro-magnetic vibrator4 ,for this purpose the bridge is in metallic communication with the coil wire1 of which the other end corresponds with the line wire1 and the spring ,c is mounted on an upright ,a1 which also supports another spring ,d ,g acting on two contacts1 one placed at ,g1 and corresponding to the earth wire1 the other at ,h1 and connected with the positive pole of the battery4 ,a small moveable button1 which passes through a hole in the lid of the box1 and projects beyond it1 is fixed at ,g1 and all this part of the instrument faces the bottom of the box4 ,the upper part consists of the vibrating disk and the mouthpiece1 so that the mechanism we have described is all mounted on an inner partition forming a false bottom to the box4 ,when the box rests upon its base1 on the side shown in fig4 #eh1 the button at ,g presses on the spring ,d ,g1 and raises it so as to break the connection with the battery2 the coil of the instrument is then united to the circuit1 and consequently receives the transmitted currents1 which follow this route3 line wire1 coil ,e1 bridge ,b1 spring ,c1 spring ,d ,g1 earth contact4 ,if these currents are transmitted by a vibrator1 they are strong enough to produce a noise which can be heard in all parts of a room1 and consequently the call may be given in this way4 ,if the currents are due to telephonic transmission1 the instrument is applied to the ear1 care being taken to put the finger on the button ,g1 and the exchange of correspondence takes place as in ordinary instruments2 but it is simpler and more manageable to insert a second telephone in the circuit for this purpose4 ,when the box is inverted on its mouthpiece1 and the button ,g ceases to press on the spring ,d ,g1 the battery current reacts on the vibrator of the instrument1 and sends the call to the corresponding station1 following this route3 ,i ,d ,a ,c ,b ,e1 line1 earth and battery2 and the call goes on until the correspondent breaks the current by taking up his instrument1 thus warning the other that he is ready to listen4 ,system of ,m4 ,puluj4--,there is yet another call system1 devised by ,m4 ,puluj4 ,it consists of two telephones without mouthpieces1 connected together1 and with coils placed opposite the branches of two tuning-forks1 tuned as nearly as possible to the same tone4 ,a small metal bell is fixed between the opposite faces of the tuning-forks1 and a wire stretched near them is provided with a small ball in contact with their branches4 ,when the tuning-fork at the sending station is put in vibration by striking it with an iron hammer covered with skin1 the tuning fork at the other station vibrates also1 and its ball strikes upon the bell4 ,as soon as the signal is returned by the second station1 mouthpieces with iron diaphragms are fastened to the telephones1 and the correspondence begins4 ,it seems that1 by the use of a resonator1 the sound which reaches the receiving station may be so intensified as to become audible in a large hall1 and the bell signal may be heard in an adjoining room1 even through a closed door4 ,mr4 ,alfred ,chiddey's ,system4--,this arrangement consists of a slender copper tube1 eight inches long1 and with an orifice of #a_/cj of an inch1 of which the lower end is soldered to the diaphragm of a telephone4 ,a branch joint1 to which an india-rubber tube is fitted1 connects it with a gas jet1 which is lighted and surrounded with a lamp shade1 in such a way as to make it produce1 under given conditions1 sounds resembling those of the singing flames4 ,a perfectly similar system is arranged at the other end of the line1 in such a way that the sounds emitted in each case shall be precisely in unison4 ,if the two systems are so regulated as not to emit sounds in their normal condition1 they can be made to sing by causing a tuning-fork in the vicinity of one or the other to vibrate the same note1 and then the corresponding flame will begin to sing1 producing a vibration in the diaphragm of the telephone with which it is in correspondence1 and hence will follow the vibration of the diaphragm of the other telephone1 and consequently the vibration of the flame of the calling instrument4 ,in this way the call signal may be made without the intervention of any battery4 ,,applications ,,of ,,the ,,telephone4 ,the applications of the telephone are much more numerous than might be supposed at the first glance4 ,as far as the telegraphic service is concerned1 its use must evidently be rather limited1 since it cannot register the messages sent1 and the speed of transmission is inferior to that of the improved system of telegraphs2 yet in many cases it would be very valuable1 even for a telegraphic system1 since it is possible to work it without any special telegraphic training4 ,the first comer may send and receive with the telephone1 and this is certainly not the case even with the simplest forms of telegraphic instruments4 ,this system is therefore already in use in public offices and factories1 for communication in mines1 for submarine works1 for the navy1 especially when several vessels manuvre in the same waters1 some towed by others2 finally1 for military purposes1 either to transmit orders to different corps1 or to communicate with schools of artillery and rifle practice4 ,in ,america the municipal telegraphic service and that of telegraphs limited to the area of towns are conducted in this way1 and it is probable that this system will soon be adopted in ,europe4 ,indeed1 a service of this kind was established in ,germany last autumn at the telegraph offices of some towns1 and the ,london ,post ,office is now thinking of establishing it in ,england4 ,but1 besides its use for the purposes of correspondence1 the telephone can be useful to the telegraphic service itself by affording one of the simplest means of obtaining a number of simultaneous transmissions through the same wire1 and even of being combined in duplex with the ,morse telegraphs4 ,its applications in the microphonic form are incalculable1 and the proverb which declares that #8walls have ears' may in this way be literally true4 ,it is alarming to think of the consequences of such an indiscreet organ4 ,diplomatists must certainly redouble their reserve1 and tender confidences will no longer be made with the same frankness4 ,on this point we cannot think that much will be gained1 but on the other hand the physician will probably soon make use of this invention to ascertain more readily the processes going on within the human body4 ,,application ,,of ,,the ,,telephone ,,to ,,simultaneous ,,telegraphic ,,transmissions4 ,the simultaneous transmission of several messages through the same wire is one of the most curious and important applications of the telephone to telegraphic instruments which can be made1 and we have seen that it was this application which led ,messrs4 ,gray and ,bell to the invention of speaking telephones4 ,the admiration which these instruments have excited has thrown the original idea into the background1 although it has perhaps a more practical importance4 ,we will now consider these systems4 ,an articulating telephone is not necessary in order to obtain simultaneous transmission3 the musical telephones devised by ,,mm4 ,petrina1 ,gray1 ,froment1 c41 are quite sufficient1 and a brief explanation of their principle will make this intelligible4 ,suppose that there are seven electro-magnetic vibrators at the two corresponding stations1 which are tuned with the same tuning-fork on the different notes of the scale1 and suppose that a key-board1 resembling the ,morse telegraph key1 is arranged so that1 by lowering the keys1 electric reaction takes place on each vibrator3 it is easy to see that these vibrators may be made to react in the same way on the corresponding vibrators of the opposite station2 but they must be tuned on the same note1 and the sounds emitted will continue while the keys are lowered4 ,by keeping them down for a shorter or longer time1 the long or short sounds which constitute the elements of telegraphic language in the ,morse system may be obtained1 and consequently an audible transmission becomes possible4 ,let us now suppose that a telegraphist accustomed to this mode of transmission is placed before each of the vibrators1 and that they transmit different messages at the same moment in this way3 the telegraphic wire will be instantaneously traversed by seven currents1 broken and massed upon each other1 and they might be expected to produce a medley of confused sounds on the vibrators at the receiving station2 but since they each harmonise with the corresponding vibrator1 they have no sensible influence except on those for which they are intended4 ,the dominant sound may be made still more distinct by applying a ,helmholtz resonator to each vibrator1#ah that is1 an acoustic instrument which will only vibrate under the influence of the note to which it is tuned4 ,in this way it is possible to select the transmitted sounds1 and only to allow each employ to hear that which is intended for him4 ,consequently1 however confused the sounds may be on the receiving vibrators1 the person to whom do is assigned will only receive do sounds1 the person to whom sol is assigned will only receive sol sounds1 so that correspondence may be carried on as well as if they had each a special wire4 ,in the mode we have described1 this telegraphic system only admits of audible transmissions1 and consequently cannot register messages4 ,to supply this defect1 it has been suggested to make the receiving vibrators react on registers1 so arranging the latter that their electric organ may present such magnetic inertia1 that1 when it is influenced by the vibrations of sound1 its effect may be maintained throughout the time of vibration4 ,experiments show that a ,morse receiver1 worked by the current of a local battery1 will be enough for this purpose2 so that if the musical vibrator is made to react as a relay1 that is1 on a contact in connection with the local battery and the receiver1 the dots and dashes may be obtained on it which are the constituent elements of the ,morse code4 ,on these principles1 and considering that the musical spaces separating the different notes of the scale are such as may be easily distinguished by the resonator1 seven simultaneous transmissions may be obtained on the same wire2 but experience shows that it is necessary to be content with a much smaller number4 ,yet this number may easily be doubled by applying the mode of transmission in an opposite direction to the system4 ,mr4 ,bell states that the idea of applying the telephone to multiple electric transmissions occurred simultaneously to ,m4 ,paul ,lacour of ,copenhagen1 to ,mr4 ,elisha ,gray of ,chicago1 to ,mr4 ,varley of ,london1 and to ,mr4 ,edison of ,new ,york2 but there is some confusion here1 for we have already seen1 from reference to the patents1 that ,mr4 ,varley's system dates from #ahgj1 that of ,m4 ,paul ,lacour from ,september #ahgd1 that of ,mr4 ,elisha ,gray from ,february #ahge1 and those of ,messrs4 ,bell and ,edison were still later4 ,yet it appears from ,mr4 ,gray's specification that he was the first to conceive and execute instruments of the kind4 ,in fact1 in a specification drawn up on ,august #f1 #ahgd1 he distinctly put forward the system we have described1 and which is the basis of those of which we have still to speak4 ,this specification was only an addition to two others made out in ,april and ,june #ahgd4 ,mr4 ,varley's system has only an indirect relation to the one we have described4 ,it appears from what ,mr4 ,bell said on the subject in a paper addressed to the ,society of ,telegraphic ,engineers in ,london1 that he himself only attaches a secondary interest to this invention4 ,he said that he had been struck with the idea that the greater or less duration of a musical sound might represent the dot and dash of the telegraphic alphabet1 and it occurred to him that simultaneous telegraphic transmissions1 of which the number should only be limited by the delicacy of the sense of hearing1 might be obtained by suitable combinations of long and short sounds1 and that these should be effected by a keyboard of tuning-forks applied to one end of a telegraphic line1 and so arranged as to react electrically on electro-magnetic instruments striking on the strings of a piano4 ,for this purpose it would be necessary to assign an employ to each of the keys for the service of transmission1 and to arrange that his correspondent should only distinguish his peculiar note among all those transmitted4 ,it was this idea1 ,mr4 ,bell adds1 which led to his researches in telephony4 ,for several years he sought for the best mode of reproducing musical sounds at a distance by means of vibrating rheotomes3 the best results were given by a steel plate vibrating between two contacts1 of which the vibrations were electrically produced and maintained by an electro-magnet and a local battery4 ,in consequence of its vibration1 the two contacts were touched alternately1 and the two circuits were alternately broken2 the local circuit which kept the plate in vibration1 and the other which was connected with the line1 and reacted on the distant receiver1 so as to effect simultaneous vibrations in it4 ,a ,morse key was placed in the latter circuit near the sending instrument1 and when it was lowered1 vibrations were sent through the line2 when it was raised1 these vibrations ceased1 and it is easy to see that1 by lowering the key for a longer or shorter time1 the short and long sounds necessary for the different combinations of telegraphic language could be obtained4 ,moreover1 if the vibrating plate of the receiving instrument were so regulated as to vibrate in unison with the sending instrument in correspondence1 it would vibrate better with this sender than with another whose plate was not so adjusted4 ,it is evident that different sounds might be simultaneously transmitted with several plates by this arrangement of contact breaker1 and that at the receiving station the sounds might be distinguished by each employ1 since the one which corresponds to the fundamental note of each vibrating plate is reproduced by that plate4 ,consequently1 the sounds produced by the vibrating plate of do1 for example1 will only be audible at the receiving station on the plate tuned to do1 and the same will be the case with the other plates2 so that the sounds will reach their destination1 if not without confusion1 yet with sufficient clearness to be distinguished by the employs4 ,mr4 ,bell sums up the defects still existing in his system as follows3--#ast4 ,the receiver of the messages must have a good musical ear1 in order to distinguish the value of sounds4 #bnd4 ,since the signals can only take place when the transmitted currents are in the same direction1 two wires must be employed in order to exchange messages on each side4 ,he surmounted the first difficulty by providing the receiver with an instrument which he called the vibrating contact breaker1 and which registered automatically the sounds produced4 ,this contact breaker was placed in the circuit of a local battery1 which could work a ,morse instrument under certain conditions4 ,when the sounds emitted by the instrument did not correspond with those for which it had been tuned1 the contact breaker had no effect on the telegraphic instrument3 it only acted when the sounds were those which were to be interpreted1 and its action necessarily corresponded to the length of the sounds4 ,mr4 ,bell adds that he applied the system to electro-chemical telegraphs2 but we need not dwell on this part of the invention1 since1 as we have said1 it is no longer his special study4 ,system of ,m4 ,lacour of ,copenhagen4--,m4 ,lacour's system was patented on the #bnd ,september1 #ahgd1 but his experiments were commenced on the #eth ,june of the same year4 ,since ,m4 ,lacour believed that the vibrations would be imperceptible on long lines1 his first attempts were made on a somewhat short line2 but in ,november #ahgd fresh experiments were made between ,fredericia and ,copenhagen on a line #bbe miles in length1 and it was ascertained that vibratory effects could be easily transmitted1 even under the influence of a rather weak battery4 ,illustration3 ,,fig4 #ei4 ,in ,m4 ,lacour's system1 the sending instrument is a simple tuning-fork1 placed in a horizontal position1 and one of its arms reacts on a contact breaker1 which can produce precisely the same number of discharges of currents as there are vibrations of the tuning-fork4 ,if a ,morse manipulator is inserted in the circuit1 it is evident that if it is worked so as to produce the dots and dashes of the ,morse alphabet1 the same signals will be reproduced at the opposite station1 and the signals will be manifested by long and short sounds1 if an electro-magnetic receiver is connected with the circuit4 ,this sender is shown fig4 #ei4 ,fig4 #fj represents ,m4 ,lacour's receiver4 ,it consists of a tuning-fork ,f made of soft iron1 not of steel like the sending tuning-fork1 and each of its branches is inserted in the bobbin of an electro-magnetic coil ,c ,c2 two distinct electro-magnets ,m ,m react close to the extremities of the fork1 in such a way that the polarities developed on the two branches of the fork under the influence of the coils ,c ,c should be of contrary signs to those of the electro-magnets ,m ,m4 ,illustration3 ,,fig4 #fj4 ,if this double electro-magnetic system is inserted in a line circuit1 it follows that1 for each discharge of the transmitted current1 a corresponding attraction of the branches of the tuning-fork will take place1 and consequently there will be a vibration1 producing a sound1 if the discharges are numerous4 ,this sound will naturally be short or long in proportion to the duration of the sender's action1 and it will be the same as that of the tuning-fork in that instrument4 ,again1 if one branch of the tuning-fork reacts on a contact ,p inserted in the circuit of the local battery communicating with a ,morse receiver1 traces will be produced on this receiver of length varying with the duration of the sounds1 for the ,morse electro-magnet will be so quickly affected by the successive breaks in the current that its armature will remain stationary throughout each vibration4 #8,i have not yet been able1' said ,m4 ,lacour in an address delivered before the ,danish ,academy of ,science in #ahge1 #8to calculate the time necessary for the production of definite vibrations in the tuning-fork4 ,different factors have to be considered1 but experiment has shown that the time which elapses before the local circuit is broken is such a small fraction of a second as to be almost inappreciable1 even when the current is very weak4 #8,since intermittent currents only affect a tuning-fork on condition that it vibrates in unison with the one which produces them1 it follows that if a series of sending tuning-forks1 tuned to the different notes of the scale1 is placed at one end of a circuit1 and if a similar series of electro-magnetic tuning-forks1 in exact accordance with the first1 is placed at the other end of the circuit1 the intermittent currents transmitted by the sending tuning-forks will be added to each other without becoming confused1 and each of the receiving tuning-forks will only be affected by the currents emitted by the tuning-fork in unison with it4 ,in this way the combinations of elementary signals representing a word may be telegraphed simultaneously4' ,m4 ,lacour enumerates the ways in which this system may be applied as follows3 #8,if the keys in connection with the sending tuning-forks are placed side by side1 and are lowered in succession1 or two or three together1 it will be enough to play on the keys as on a musical instrument1 in order that the air may be heard at the receiving station1 or the signals transmitted simultaneously may each belong to a different message4 ,this system will therefore allow the furthest station on a line to communicate with one or several intermediate stations1 and vice versa1 without disturbing the communication at other stations4 ,in this way two stations can exchange signals1 unperceived by the rest4 ,the power of sending many signals at once affords a good means of improving the autographic telegraph4 ,in the instruments now in use1 such as those of ,caselli and ,d',arlincourt1 there is only one tracing stylus1 and this stylus must pass over the whole surface of the telegram in order to obtain a copy of it1 but with the telephone a certain number of styli may be placed side by side in the form of a comb1 and this comb need only be drawn in a certain direction to pass over the surface of the telegram4 ,in this way a more faithful copy will be obtained in a shorter time4' ,m4 ,lacour also observes that his system possesses a merit already pointed out by ,mr4 ,varley1 namely1 that the instruments permit the passage of ordinary currents without revealing their presence1 whence it follows that the accidental currents which often disturb telegraphic transmissions will have no effect on these systems4 ,m4 ,lacour began without applying an electro-magnetic system to his instrument in order to maintain the movement of the tuning-fork1 but he soon saw that this accessory was indispensable1 and he made the tuning-forks themselves electro-magnetic4 ,it also occurred to him to convert the transmitted currents into pulsatory currents by inserting an induction coil in the circuit1 which was also done by ,mr4 ,elisha ,gray4 ,finally1 in order to obtain the immediate action of the tuning-forks and the immediate cessation of their action1 he constructed them so as to reduce their inertia as much as possible4 ,this was effected by inserting the two branches of the tuning-fork in the same coil and by lengthening its handle1 and turning it back so that it might pass through a second coil1 dividing into two branches and embracing the two vibrating branches1 but without touching them4 ,when a current traverses both coils1 it produces1 in the kind of horseshoe magnet formed by the two systems1 opposite polarities which provoke a double reaction in the vibrating branches--a reaction by repulsion exerted by the two branches in virtue of the same polarity1 and a reaction by attraction by the other two branches in virtue of their opposite polarities2 and this double action is repeated by the movements of a contact breaker applied to one of the vibrating branches of the tuning-fork4 ,illustration3 ,,fig4 #fa4 ,mr4 ,elisha ,gray's ,system4--,according to the system originally patented1 each sender1 represented fig4 #fa1 consists of an electro-magnet ,m ,m resting below a small copper tablet ,b ,s1 in such a way that its poles pass through this tablet and are on a level with its upper surface4 ,a steel plate ,a ,s is fixed above these poles2 its tension can be regulated by means of a screw ,s2 and another screw c is placed on the plate1 and is in electric communication with a local battery ,r by means of a ,morse key4 ,below the plate ,a ,s there is a contact d connected with the line wire ,l2 this contact is met by the plate at the moment of its attraction by the electro-magnet1 and breaks the current of a line battery ,p1 which acts on the receiver of the opposite station4 ,finally1 the electric communication established between the local battery ,r and the electro-magnet1 as may be seen in the figure1 produces vibrations in the steel plate ,a ,s at each lowering of the key1 as in the case of ordinary vibrations--vibrations which1 with a suitable tension of the plate and a given intensity of the battery ,r1 can produce a definite musical note4 ,moreover1 since at each vibration the plate ,a ,s meets the contact1 discharges of the line current take place through the line ,l1 and react on the receiving instrument1 causing it to reproduce exactly the same vibrations as those of the sending instrument4 ,illustration3 ,,fig4 #fb4 ,the receiving instrument represented fig4 #fb exactly resembles the one we have just described1 except that there is no contact d below the vibrating plate ,a ,s1 and the contact c1 instead of communicating with the line wire1 is in electric connection with a register ,e and a local battery ,p4 ,it follows from this arrangement that when the plate ,a ,s vibrates under the influence of the broken currents passing through the electro-magnet ,m ,m1 similar vibrations are sent through the register2 but if the electro-magnetic organ of this register is properly regulated1 these vibrations can only produce the effect of a continuous current1 and hence the length of the traces left on the instrument will vary with the duration of the sounds produced4 ,in this way the registration of the dashes and dots which constitute the signs of the ,morse vocabulary will be effected4 ,if it is remembered that the plate ,a ,s vibrates under the influence of electro-magnetic attractions more readily in proportion to their approximation in number to the vibrations corresponding to the fundamental sound it can emit1 it becomes clear that if this plate is tuned to the same note as that of the corresponding instrument1 it will be rendered peculiarly sensitive to the vibrations transmitted by the sender1 and the other vibrations which may affect it will only act faintly4 ,moreover1 a resonator placed above the plate will greatly increase this predisposition2 so that if several systems of this kind1 tuned to different notes1 produce simultaneous transmissions1 the sounds corresponding to the different vibrations will be in a certain sense selected and distributed1 in spite of their combination1 into the receivers for which they are specially adapted1 and each of them may retain the traces of the sounds emitted by adding the register1 which may be so arranged as to act as an ordinary ,morse receiver4 ,mr4 ,gray states that the number of sending instruments and independent local circuits may be equal to that of the tones and semitones of two or more octaves1 provided that each vibrating plate be tuned to a different note of the scale4 ,the instruments may be placed side by side1 and their respective local keys1 arranged like the keys of a piano1 will make it easy to play an air combining notes and chords2 there may also be an interval between the instruments1 which may be sufficiently far from each other to allow the employs to work without being distracted by sounds not intended for them4 ,in a new arrangement1 exhibited at the ,paris ,exhibition1 #ahgh1 ,mr4 ,gray considerably modified the way of working the various electro-magnetic organs which we have just described4 ,in this case1 the plates consist of tuning-forks with one branch kept in continual vibration at both stations1 and the signals only become perceptible by intensifying the sounds produced4 ,this arrangement follows from the necessity of keeping the line circuit always closed for multiple transmissions of this nature1 so as to react with pulsatory currents1 which are alone able1 as we have already seen1 to retain the individual character of several sounds simultaneously transmitted4 ,illustration3 ,,fig4 #fc4 ,under these conditions1 the sender consists1 as we see 7fig4 #fc71 of a bar tuning-fork1 a1 which is grooved for the passage of a runner1 heavy enough to tune the fork to the desired note1 and it oscillates between two electro-magnets e and f and two contacts ,i and ,g4 ,the difference of resistance in the electro-magnets is very great3 in the one f the resistance is equal to #b miles of telegraphic wire1 in the other it does not exceed #ddj yards4 ,when electric communication is established as we see in the figure1 the following effect takes place4 ,since the current of the local battery through the two electro-magnets is broken by the rest-contact of the ,morse key ,h1 the plate a is subject to two contrary actions2 but since the electro-magnet f has more turns than the electro-magnet e1 its action is preponderant1 and the plate is attracted towards f1 and produces a contact with the spring ,g1 which opens a way of less resistance for the current4 ,since the current then passes almost wholly through ,g1 b1 #a1 #b1 ,b1 the electro-magnet is now able to act2 the plate a is then attracted towards e1 and1 by producing a contact on the spring ,i1 it sends the current of the line ,b ,p through the telegraphic line1 if the key ,h is at the same time lowered on the sending contact3 if not1 there will be no effect in this direction1 but since the plate a has left the spring ,g1 the first effect of attraction by the electro-magnet f will be repeated1 and this tends to draw the plate again towards f4 ,this state of things is repeated indefinitely so as to maintain the vibration of the plate1 and to send out signals corresponding with these vibrations whenever the key ,h is lowered4 ,the elastic nature of the plate makes these vibrations more easy1 and it ought also to be put in mechanical vibration at the outset4 ,the receiver1 represented fig4 #fd1 consists of an electro-magnet ,m1 mounted on a sounding-box ,c1 and having an armature formed by a tuning-fork ,l ,l firmly buttressed on the box by a cross bar ,t4 ,there is a runner ,p on the armature1 sliding in a groove1 which makes it possible to tune the vibrations of the tuning-fork to the fundamental note of the sounding-box ,c1 which is so arranged as to vibrate in unison with it4 ,under these conditions1 the box as well as the tuning-fork will act as an analyser of the vibrations transmitted by the currents1 and may set the register at work by itself reacting on a breaker of the local current4 ,to obtain this result1 a membrane of gold-beater's skin or parchment must be stretched before the opening of the box1 and a platinum contact must be applied to it1 so arranged as to meet a metallic spring connected with any kind of register or a ,morse instrument1 when the membrane vibrates4 ,as1 however1 in ,america the messages are generally received by sound1 this addition to the system is not in use4 ,illustration3 ,,fig4 #fd4 ,the instrument is not only regulated by the runner ,p1 but also by a regulating screw ,v which allows the electro-magnet ,m to be properly adjusted4 ,the regulating system is made more exact by the small screw ,v1 and the instrument is connected with the line by the binding screw ,b4 ,of course this double arrangement is necessary for each of the sending systems4 ,as ,i have already said1 seven different messages might theoretically be sent at once in this way1 but ,mr4 ,gray has only adapted his instrument for four2 he has1 however1 made use of the duplex system1 which allows him to double the number of transmissions1 so that eight messages may be sent at the same time1 four in one direction1 and four in another4 ,mr4 ,hoskins asserts that this system has been worked with complete success on the lines of the ,western ,union ,telegraph ,company1 from ,boston to ,new ,york1 and from ,chicago to ,milwaukee4 ,since these experiments were made1 fresh improvements have rendered it possible to send a much larger number of messages4 ,mr4 ,gray has also1 aided by ,mr4 ,hoskins1 devised a system by which telephonic messages may be sent on a wire previously used for ,morse instruments4 ,mr4 ,varley had already solved this problem1 but ,mr4 ,gray's system seems to have produced important results1 and has therefore a claim to our attention4 ,we do not1 however1 describe it here1 since it is not within the lines marked out for us1 and those who are interested in the subject will find all the necessary details in a paper inserted in the #8,journal of the ,society of ,telegraphic ,engineers1 ,london1' vol4 vi4 ,mr4 ,varley's ,system4--,this system is evidently the earliest in date1 since it was patented in #ahgj1 and the patent describes the principle of most of the arrangements which have since been adopted by ,messrs4 ,lacour1 ,gray1 and ,bell4 ,it is based upon the use of his own musical telephone1 which we have already described1 but with some variations in its arrangement1 which make it somewhat like the ,reiss system4 ,it was ,mr4 ,varley's aim to make his telephone work in conjunction with instruments with ordinary currents1 by the addition of rapid electric waves1 incapable of making any practical change in the mechanical or chemical capacity of the currents which serve for the ordinary signals1 yet able to make distinct signals1 perceptible to the ear and even to the eye4 ,he says3 #8,an electro-magnet offers at first a great resistance to the passage of an electric current1 and may consequently be regarded as a partially opaque body with respect to the transmission of very rapid inverse currents or of electric waves4 ,therefore1 if a tuning-fork1 or an instrument with a vibrating plate1 tuned to a given note1 be placed at the sending station1 and so arranged as to be kept in constant vibration by magnetic influence1 the current which acts upon it must be passed into two helices placed one above the other so as to constitute the primary helix of an induction coil3 in this way it will be possible to obtain in two distinct circuits two series of rapidly broken currents1 which will correspond to the two directions of the vibrations of the tuning-fork1 and we shall also have the induced currents produced in the secondary helix by these currents1 which may act on a third circuit4 ,this third circuit may be placed in connection with a telegraphic line previously used by an ordinary telegraphic system1 if a condenser is applied to it1 and in this way two different transmissions may be obtained simultaneously4' ,illustration3 ,,fig4 #fe4 ,fig4 #fe represents the arrangement of this system4 ,d is the vibrating plate of the tuning-fork designed to produce the electric contacts necessary to maintain it in motion4 ,these contacts are at ,s and ,s1 and the electro-magnets which affect it are at ,m and ,m4 ,the induction coil is at ,i1 and the three helices of which it is composed are indicated by the circular lines which surround it4 ,there is a ,morse manipulator at ,a1 another at ,a1 and the two batteries which work the system are at ,p and ,p4 ,the condenser is at ,c1 and the telephone is at the end of the line ,l4 ,when the vibration of the plate ,d tends to the right1 and the electric contact takes place at ,s1 the current of the battery ,p1 after traversing the primary helix1 reaches the electro-magnets ,m ,m1 which give it an impulse in the contrary direction4 ,when1 on the other hand1 it tends to the left1 the current is sent through the second primary circuit1 which will be balanced by the first4 ,consequently there will be a series of reversed currents in the induced circuit corresponding to the key ,a1 which will alternately charge and discharge the condenser ,c1 thus sending into the line a corresponding series of electric undulations which will react on the telephone placed at the end of the line2 and as the duration of the transmitted currents will vary with the time that the key ,a is lowered1 a correspondence in the ,morse code may be obtained in the telephone1 while another correspondence is exchanged with the key ,a and the ordinary ,morse receivers4 ,in order to render the vibratory signals visible1 ,mr4 ,varley proposes to use a fine steel wire1 stretched through a helix and facing a narrow slit1 to reproduce the vibrations4 ,a light1 which is intercepted by the wire1 is placed behind the slit4 ,as soon as a current passes1 the wire vibrates and the light appears4 ,a lens is placed so as to magnify the image of the luminous slit1 and project it on a white screen while the wire is in vibration4 ,,various ,,uses ,,of ,,the ,,telephone4 ,its domestic application4--,we have seen that telephones may be used with advantage in public and private offices3 they can be set up at a much less expense than acoustic tubes1 and in cases where the latter would never be employed4 ,with the aid of the calls we have described1 they offer the same advantages1 and the connection between the instruments is more easily concealed4 ,the difference of price in establishing them is in the ratio of one to seven4 ,for this purpose electro-magnetic telephones are evidently the best1 since they require no battery and are always ready to work4 ,they are already in use in many ,government offices1 and it is probable that they will soon be combined with electric bells for the service of hotels and of large public and private establishments3 they may even be used in private houses for giving orders to servants and porters1 who may thus save visitors from the fatigue of a useless ascent of several storeys4 ,in factories1 telephones will certainly soon replace the telegraphic communication which has already become general4 ,they may not only be used for ordinary messages1 but to call for help in case of fire1 and they will become an integral part of several systems already established for this purpose4 ,in countries which have free telegraphic communication1 the telephone has already replaced in great measure the private telegraph instruments which have hitherto been in use2 and if the same privilege is extended to ,france1 no other mode of correspondence will be used4 ,its application to telegraphic service4--,the advantage to be derived by the telegraphic service from the telephone is rather limited1 since1 as far as the speed of transmission is concerned1 it is of less value than many of the telegraphic instruments now in use1 and the messages which it produces cannot be registered4 ,yet in municipal offices not overburdened with messages they offer the advantage of not requiring a trained service4 ,on longer lines their use would be of little value4 ,the #8,berne ,telegraphic ,journal' has published some interesting remarks on this subject1 of which the following is a summary4 #ast4 ,in order to send a message with the special advantages of the system1 the sender ought to be able to address his correspondent without the intervention of an official4 ,those who are acquainted with the network of wires know this to be impossible4 ,intermediate offices for receiving messages are essential1 and the public cannot be admitted to those set apart for sending and receiving2 consequently the sender must deliver a written message4 #bnd4 ,if the message is written1 the chief advantage of the instrument is lost1 since it must be read and uttered aloud1 which could not be done if expressed in a language with which the employs were unacquainted4 #crd4 ,the instruments now in use at the telegraph offices can transmit messages more quickly than if they were spoken4 ,in ,germany1 however1 a telephone service has been established in several telegraph offices1 and its possible advantages are enumerated as follows in the official circular which created it3 #8,the offices which will be opened to the public for the service of telephonic messages in ,germany will be regarded as independent establishments2 yet they will be in connection with the ordinary telegraph offices1 which will undertake to send telephonic messages through their wires4 #8,the transmission will take place as follows3 ,the sending office will request the receiving office to prepare the instrument2 as soon as the tubes are adjusted1 the sending office will give the signal for despatching the verbal message4 #8,the sender must speak slowly and clearly1 without raising his voice2 each syllable must be distinctly pronounced2 the final syllables especially must be well articulated1 and there must be a pause after each word1 in order to give the receiver time to write it down4 #8,when the telegram has been received1 the employ at the receiving office must verify the number of words2 then he must repeat through the telephone the whole message without pausing1 so as to make sure that there is no mistake4 #8,in order to ensure secrecy1 the telephones are placed apart1 where persons unconnected with the service cannot hear the verbal message1 and the employs are forbidden to reveal to anyone the names of the correspondents4 #8,the charge for telephonic messages1 as for the ordinary telegraphic services1 is at the rate of so much a word4' ,the use of the telephone has also been suggested for verifying the perfect junction of telegraphic wires4 ,it is certain that1 if the junction is complete1 no abnormal sounds will be heard1 or only those which result from accidental currents2 but if the junction is bad1 the imperfect contacts which take place produce variations in electric intensity which are translated into the more or less marked sounds observed in the telephone4 ,m4 ,mauborgne1 the electrician attached to the ,northern ,railway of ,france1 has lately used the telephone instead of the galvanometer to ascertain the condition of the circuits in correspondence with the instruments in use for electric signals4 ,the reactions produced on the galvanometer needle by the pieces of iron which are placed at the sides of the railway often make its indications uncertain1 and a strong wind produces irregular movements in the instrument which interfere with observations4 ,it was also necessary to place the galvanometer with due regard to the points of the compass1 and to wait for the needle to settle1 which involved loss of time4 ,the operation is easily accomplished with the telephone1 since the strokes of the call-bell are distinctly reproduced2 it is made to ring by working the contacts which need verification1 and in the same way the condition of the battery can be ascertained4 ,application to military purposes4--,since the telephone was invented1 numerous experiments have been made in different countries to ascertain whether it would be of use in military operations4 ,these experiments have hitherto been only moderately satisfactory1 on account of the noise inseparable from an army1 which generally makes it impossible to hear the telephone1 and every means of intensifying its sounds has been eagerly sought4 ,it was at first supposed that the discovery of the microphone had solved the problem1 and ,i received many enquiries from military schools on the subject1 but ,i have not been able to see that anything has been gained from this point of view4 ,the telephone is1 however1 of great use in schools of artillery and rifle practice4 ,now that firearms carry so far1 it has become necessary to be informed by telegraph of the points hit on the target1 in order to judge of the accuracy of aim1 and for this purpose telegraphic targets were suggested2 but telephones are much to be preferred1 and they are now used with good effect4 ,if the telephone is unsuited for the service of the flying telegraph in the field1 it may be of great use in the defence of towns1 to transmit the orders of the commandant to different batteries1 and even for the exchange of correspondence with captive balloons sent to hover over fields of battle4 ,in spite of the difficulties attending its use1 the experiment was made by the ,russians in the late war3 the cable wire of communication was #ejj or #fjj yards long1 and so light that it could be laid by one man4 ,the #8,telegraphic ,journal' of ,march #ae1 #ahgh1 states that the bad weather did not interfere with the working of the instruments2 but the noise made it difficult to hear1 and it was necessary to cover the head with a hood to intercept external sounds4 ,this cannot be considered a satisfactory result1 yet the telephone may be of great service to an army by intercepting the enemy's messages3 a bold man1 provided with a pocket telephone1 who placed himself in a retired spot1 might divert the current of the enemy's telegraphic wire into his telephone1 and get possession of all his despatches1 as we saw was the case at ,clermont4 ,he might even do this by diverting the current to earth or to a rail of the railway line4 ,these are suggestions for future research1 and it is probable that they may some day be turned to practical account4 ,its application to the navy4--,the telephone may be of the greatest use in naval matters1 for the service of electro-semaphores1 for island forts and ships at anchor4 ,m4 ,pollard says that #8experiments made between the ,prfecture ,maritime at ,cherbourg1 the semaphores and the forts on the mole1 demonstrate the advantage there would be in establishing telephones at these stations1 since they would ensure an easy communication between the vessels of a squadron and the land they are approaching4 ,by sinking small cables which come to the surface of the water along mooring chains1 and terminate in buoys or cases which remain permanently in the harbour1 the ships of war may in this way place themselves in communication with the ,prfecture ,maritime as they cast anchor1 and1 by temporarily connecting the vessels together with light cables1 the admiral may communicate freely with the whole squadron4' ,the telephone has been tried on board ship for transmitting orders1 but without success1 on account of the noise always going on in a vessel4 ,the telephone may be usefully applied to the service of submarine torpedoes4 ,we have already seen how it may be applied in connection with the microphone1 but it may also be used in firing the torpedoes after the exact position of the enemy's ship has been ascertained from two reconnaissances taken from different parts of the coast4 ,the telephone1 again1 makes it possible to verify the condition of torpedoes1 and to ascertain if there is any fault in the circuit within the explosives4 ,for this purpose a very weak current has been used1 and a galvanometer is not always able to indicate the fault1 while the extreme sensitiveness of the telephone will do so in the simplest way4 ,captain ,m',evoy1 of the ,american ,army1 suggested a way of ascertaining1 while on shore1 the condition of torpedoes under water1 by connecting the buoys which support them with the land by means of a telephonic line4 ,by inserting1 in the buoy which supports the torpedo1 metallic disks1 so arranged as to vibrate with every movement caused by the waves upon the buoy1 a continuous noise will be heard in the telephone1 after the circuit has been completed by the metallic disks2 and the noise will go on as long as the disks continue to oscillate1 and will cease as soon as the buoy is completely covered by the water4 ,when it ceases1 therefore1 if not affected by some accidental cause1 it may be supposed that the enemy's ship is passing over the buoy4 ,m4 ,trve1 again1 has shown that the telephone might be used with advantage for the telegraphic communication between vessels in tow1 and ,m4 des ,portes has applied it with good effect to diving operations4 ,in this instance1 one of the glass panes in the helmet is replaced by a copper plate in which the telephone is framed1 so that the diver need only make a slight movement of his head in order to receive or address communications to those in charge of the apparatus4 ,with this system the keels of vessels may be examined1 and an account given of their condition1 without bringing up the divers1 which has hitherto been necessary4 ,m4 de ,parville1 the able and learned editor of the ,journal ,scientifique and the science department of the ,journal des ,dbats1 has suggested a new and interesting application of the telephone4 ,it concerns the possibility of making use of it to determine the precise position of the magnetic meridian1 that is1 the true direction of the magnetised needle4 ,for this purpose a ,bell telephone is necessary1 of which the magnetic core is formed of an iron rod a mtre in length1 kept1 by a suitable suspension1 at nearly the same angle of inclination as a dipping-needle4 ,this rod will be magnetised under the influence of terrestrial magnetism1 and the telephone will be able to transmit the sounds produced by some sort of vibrator placed near its mouthpiece4 ,these sounds will be strong in proportion to the degree of magnetisation of the bar2 and if the telephone is turned round the horizon1 keeping the bar at the same angle of inclination1 the sounds transmitted to the receiving telephone will be greatest when the axis of the bar is in the plane of the magnetic meridian1 and least when it is at #ij4 ,it will therefore be possible to ascertain from the direction of the axis at the moment when the sounds are no longer heard1 the exact inclination of the magnetic needle from north to south1 for it will be given by the perpendicular to the line which is followed by the axis of the iron bar at that moment4 ,it is possible that1 with this system1 the disturbing influence on the magnetic needle of the mass of iron in iron-plated vessels might be almost destroyed1 and a more exact orientation than that of the compass might be obtained4 ,the same process may make it possible to estimate and measure the variations of terrestrial magnetism4 ,m4 de ,parville has not himself tried to apply this system2 but ,mr4 ,blake's experiments1 of which we spoke in an early part of this work1 make it probable that it might be done with advantage4 ,application to industry4--,one of the earliest and most important applications of the telephone is that which was first made to the service of mines in ,england and ,america in the autumn of #ahgg4 ,the great length of the galleries is well known1 and had already involved the use of the electric telegraph for transmitting orders2 but the miners did not understand how to work these instruments1 and the service was ill performed4 ,thanks to the telephone1 through which the first corner can send and receive a message1 there is no longer any difficulty in the communication between the galleries and the surface of the mine4 ,the ventilation of mines can also be regulated by the aid of telephones4 ,if one of these instruments is placed near a wheel kept in motion by the air which passes through the ventilating shaft1 and another is placed in the inspector's office he can ascertain by the sound if the ventilation is duly carried on1 and if the machine works regularly4 ,application to scientific research4--,m4 d',arsonval's experiments1 which we have already mentioned1 show that the telephone can be used as an extremely sensitive galvanoscope2 but since it can only produce sounds under the influence of broken currents1 the circuit on which the experiment is made must be divided at rather close intervals4 ,it has been seen that it is not even necessary to insert the telephone in the circuit3 it may be influenced1 when at a distance1 either immediately or by the induction of the broken current on a circuit placed parallel to the first1 and the force of these effects may be increased by the reaction of a core of iron1 round which the inducing circuit is wound4 ,the drawback to this system is that the direction of the current is not ascertained1 so that it cannot be used as a measuring instrument2 but1 on the other hand1 it is so sensitive1 so easy to arrange1 and so inexpensive1 that it might be of the greatest use as a galvanoscope4 ,mr4 ,warren de ,la ,rue has also made use of the telephone in his researches into the electric discharges of high-tension batteries1 in order to follow the different phases of the discharge during the luminous phenomena which it produces4 ,in this way he ascertained that when a condenser is placed in connection with a battery formed of a considerable number of insulated elements1 and is gradually discharged through a ,geissler tube1 a dull and faint sound is heard in the telephone1 as long as the stratifications of light appear to be perfectly stable2 but the sound becomes considerably stronger1 and sometimes even piercing1 in proportion to the diffusion of these stratifications1 and to their approach to the point of extinction3 whence it is shown that the discharge of a battery into tubes in which a vacuum has been made is intermittent4 ,mr4 ,spottiswoode has repeated the same experiments with the discharges of ,holtz machines1 and with large condensers1 and he found that the most piercing sounds produced by the telephone coincided with the greatest development of the stratifications4 ,these sounds1 however1 sometimes ceased for a moment4 ,it was even possible to ascertain1 from the intensity of the sounds produced1 the differences of tension which might be manifested in the charge of the condenser and the slackening of the machine's motion1 and the differences of intensity in these sounds might in some cases exceed an octave4 ,the fall in the scale generally appeared in half-tones instead of gradually1 and the introduction of resistances into the circuit modified the sounds very much3 they might even be intensified by approaching the finger to the discharging tube4 ,from experiments made with the telephone between ,calais and ,boulogne1 it appears that this instrument might be applied with advantage to the science of projectiles4 ,in fact1 in some artillery practice which took place on the shore at ,boulogne1 a telephone was placed close to the gun1 and the explosion was heard at a distance of nearly two miles1 where the projectile fell4 ,it was possible to estimate its velocity by measuring the lapse of time between the moment when the projectile left the gun1 and its fall4 ,this calculation is usually made by observing the flash from the cannon's mouth2 but in some cases1 as in a fog or in practice at long ranges1 the telephone may be usefully substituted for ocular observation4 ,on the field of battle1 an observer1 provided with a telephone and placed on a hill1 might rectify from a distance the aim of his battery1 which is generally established in a sheltered and less elevated place4 ,,the ,,phonograph4 ,mr4 ,edison's ,phonograph1 which has for the last year attracted so much attention1 is an instrument which not only registers the different vibrations produced by speech on a vibrating plate1 but reproduces the same words in correspondence with the traces registered4 ,the first function of this instrument is not the result of a new discovery4 ,physicists have long sought to solve the problem of registering speech1 and in #ahef ,mr4 ,leo ,scott invented an instrument well known to physicists under the name of ,phonautograph1 which completely solved the difficulty3 this instrument is described in all the more detailed treatises on physics4 ,but the second function of the ,edison instrument was not realised nor even mentioned by ,mr4 ,scott1 and we are surprised that this able inventor should have regarded ,mr4 ,edison's invention as an injurious act of spoliation4 ,we regret on his own account1 since no one has wished to deprive him of the credit he deserves1 that he should have published a pamphlet on the subject1 couched in terms of such asperity1 which proves nothing1 and only states facts which were well known to all physicists4 ,if any other person could claim the invention of the phonograph1 at least in its most curious property of reproducing speech1 it would certainly be ,m4 ,charles ,cros2 for in a sealed paper deposited at the ,acadmie des ,sciences1 ,april #cj1 #ahgg1 he pointed out the principle of an instrument by means of which speech might be reproduced in accordance with the marks traced on a register like that of the phonautograph4#ai ,mr4 ,edison's patent1 in which the principle of the phonograph is first indicated1 is dated ,july #ca1 #ahgg1 and he was still only occupied with the repetition of the ,morse signals4 ,in this patent ,mr4 ,edison described a mode of registering these signals by means of indentations traced with a stylus on a sheet of paper wound round a cylinder1 and this cylinder had a spiral groove cut on its surface4 ,the tracings thus produced were to be used for the automatic transmission of the same message1 by passing it again under a stylus which should react on a current breaker4 ,in this patent1 therefore1 nothing is said of the registration of speech or of its reproduction2 but1 as the #8,telegraphic ,journal' of ,may #a1 #ahgh1 observes1 the foregoing invention gave him the means of solving this double problem as soon as it was suggested to him4 ,if we may believe the ,american journals1 this suggestion soon came1 and it was the result of an accident4 ,in the course of some experiments ,mr4 ,edison was making with the telephone1 a stylus attached to the diaphragm pierced his finger at the moment when the diaphragm began to vibrate under the influence of the voice1 and the prick was enough to draw blood4 ,it then occurred to him that if the vibrations of the diaphragm enabled the stylus to pierce the skin1 they might produce on a flexible surface such distinct outlines as to represent all the undulations produced by the voice1 and even that the same outlines might mechanically reproduce the vibrations which had caused them1 by reacting on a plate capable of vibrating in the same way as that which he had already used for the reproduction of the ,morse signals4 ,from that moment the phonograph was discovered1 since there was only a step between the idea and its realisation1 and in less than two days the instrument was made and tried4 ,this is an ingenious story1 yet we would rather believe that the discovery was made in a more serious spirit4 ,in fact1 such an inventor as ,mr4 ,edison1 who had discovered the electro-motograph1 and had applied it to the telephone1 was already on the way to discover the phonograph1 and we think too well of his powers to attach much credit to this ,american romance4 ,besides1 ,mr4 ,edison was well acquainted with ,mr4 ,scott's phonautograph4 ,mr4 ,edison's phonograph was only patented in ,january #ahgg4 ,consequently1 when we look at the principle of the invention1 ,m4 ,cros undoubtedly may claim priority2 but it is a question whether the system described in his sealed paper1 and published in the ,semaine du ,clerg1 ,october #h1 #ahgg1 would have been capable of reproducing speech4 ,our doubt seems justified by the unsuccessful attempts of the ,abb ,leblanc to carry out ,m4 ,cros' idea4 ,when we have to do with such undulating and complex vibrations as those involved in the reproduction of articulate words1 it is necessary that the stereotyping should in some sense be effected by the words themselves1 and their artificial reproduction will necessarily fail to mark the slight differences which distinguish the delicate combinations of speech4 ,besides1 the movements performed by a point confined to a groove that follows a sinusoidal curve cannot be effected with all the freedom necessary for the development of sounds1 and the friction exerted on the two edges of the groove will often be of a nature to stifle them4 ,a distinguished member of the ,socit de ,physique1 when ,i exhibited the phonograph to that society1 justly said that ,mr4 ,edison's whole invention consisted in the thin metallic sheet on which the vibrations are inscribed2 this sheet permits the movements of the vibrating plate to be directly stereotyped1 and thereby the problem is solved4 ,it was necessary to find such an expedient1 and it was done by ,mr4 ,edison1 who is therefore the inventor of the phonograph4 ,after ,m4 ,cros1 and before ,mr4 ,edison1 ,,mm4 ,napoli and ,marcel ,deprez attempted to make a phonograph1 but with so little success that they believed at one time the problem to be insoluble1 and threw doubts on ,mr4 ,edison's invention when it was announced to the ,socit de ,physique4 ,they subsequently resumed their labours1 and lead us to hope that they may eventually produce a phonograph of more perfect construction than that of ,mr4 ,edison4 ,we shall have more to say on this subject4 ,in conclusion1 the mechanical reproduction of speech was first effected by ,mr4 ,edison1 and in so doing he has accomplished one of the most curious and important discoveries of our time1 since it has shown that this reproduction was much less complicated than had been supposed4 ,yet the theoretical consequences of the discovery must not be exaggerated1 since ,i do not consider it by any means proved that our theories on the voice are incorrect4 ,there is in fact a great difference between the reproduction of a sound which has been uttered1 and the mode in which the same sound was produced4 ,the reproduction may be easily effected1 as ,m4 ,bourseul has remarked1 as soon as a mode has been discovered of transmitting the vibrations of air1 however complex they may be2 but in order to produce the complex vibrations of speech by the voice1 several special organs must be exercised--first1 the muscles of the throat2 secondly1 the tongue1 the lips1 and even the teeth--and for this reason an articulating machine is necessarily very complex4 ,surprise was expressed that the speaking machine1 which was brought from ,america two years ago1 and exhibited at the ,grand ,htel1 ,paris1 was so extremely complicated1 since the phonograph solved the problem in such a simple way4 ,this is because the latter instrument only reproduces speech1 while the former utters it1 and the inventor of the speaking machine had to employ in his mechanism all the organs which are necessary in our organism for the reproduction of speech4 ,the problem was infinitely more complex1 and this invention has not attracted all the attention it deserved4 ,we shall speak of it presently4 ,we must now describe the phonograph and the different applications which have been1 or which may be1 made of it4 ,description of ,phonograph1 and mode of using it4--,the first and best known model of this instrument1 which we represent in fig4 #ff1 simply consists of a registering cylinder ,r1 set in motion with the hand by a winch ,m1 before which a vibrating plate is placed1 furnished on its face with a telephone mouthpiece ,e1 and on the reverse side with a tracing point4 ,this tracing point1 which is seen at s in the section of the instrument given in fig4 #fh1 is not fixed directly on the plate2 it rests on a spring r1 and a caoutchouc pad c is placed between it and the vibrating disk4 ,this pad is formed of the end of a tube which is designed to send the vibrations of the plate to the point s without stifling them4 ,another pad a1 placed between the plate ,l ,l and the rigid support of the point1 moderates in some degree these vibrations1 which1 without this precaution1 would generally be too powerful4 ,illustration3 ,,fig4 #ff4 ,the cylinder1 of which the axis ,a ,a 7fig4 #ff7 is cut at one end like a screw1 to enable it to make a lateral progressive movement simultaneously with the rotatory movement effected on itself1 has on its surface a narrow screw-thread coinciding with that of the axis1 and when the tracing point is inserted1 it is able to pass along it for a distance corresponding to the time occupied in turning the cylinder4 ,a sheet of tinfoil or of very thin copper is carefully applied to the surface of the cylinder1 and it should be slightly pressed down upon it1 so as to show a faint tracing of the groove1 and to allow the point of the vibrating disk to be placed in a proper position4 ,the point rests on the foil under a pressure which must be regulated1 and for this purpose1 as well as to detach the cylinder when it is desired to place or take away the tinfoil1 there is the articulated system ,s ,n which sustains the support ,s of the vibrating disk4 ,this system consists of a jointed lever in which there is a nut screw for the screw ,r4 ,the handle ,n at the end of the lever allows the tracing system to be turned aside when the screw ,r is loosened4 ,in order to regulate the pressure of the tracing point on the sheet of tinfoil1 it is enough to turn the screw ,r loosely in its socket1 and to tighten it as soon as the right degree of pressure is obtained4 ,this is the simple system by which speech can engrave itself on a plate in durable characters1 and it works in the following manner4 ,illustration3 ,,fig4 #fg4 ,the speaker stands before the mouthpiece ,e1 as before a telephone or an acoustic tube1 and speaks in a strong1 emphatic voice1 with his lips pressed against the walls of the mouthpiece1 as we see in fig4 #fg2 at the same moment he turns the handle of the cylinder1 which is provided with a heavy fly-wheel in order that the movement may be regular4 ,influenced by the voice1 the plate ,l ,l begins to vibrate1 and sets the tracing point at work1 which presses on the tinfoil at each vibration1 and produces a furrow whose depth varies along its course in correspondence with the unequal vibrations of the disk4 ,the cylinder which moves at the same time presents the different parts of the groove of which we have spoken to the tracing point in succession2 so that when the spoken sentence comes to an end1 the design which has been pricked out1 consisting of a succession of reliefs and depressions1 represents the registration of the sentence itself4 ,the first part of the operation is therefore accomplished1 and by detaching the sheet from the instrument the words may be put away in a portfolio4 ,we have now to see how the instrument is able to reproduce what has been so easily inscribed4 ,for this purpose it is only necessary to repeat the process1 and the identical effect will be reproduced in an inverse sense4 ,the tracing stylus is replaced at the end of the groove it has already traversed1 and the cylinder is again set in motion4 ,when the engraved track passes again under the point1 it has a tendency to raise it and to impart to it movements which must necessarily be the repetition of those which first produced the tracing4 ,the vibrating plate is obedient to these movements1 and begins to vibrate1 thus producing the same sounds1 and consequently the same words2 yet since there is necessarily a loss of power in this double transformation of mechanical effects1 the speaking tube ,c is attached to the mouthpiece ,e in order to intensify the effects4 ,under these conditions the words reproduced by the instrument may be heard in all parts of a hall1 and it is startling to hear this voice--somewhat shrill1 it must be admitted--which seems to utter its sentences from beyond the grave4 ,if this invention had taken place in the middle ages1 it would certainly have been applied to ghostly apparitions1 and it would have been invaluable to miracle-mongers4 ,illustration3 ,,fig4 #fh4 ,as the height of the notes of the musical scale depends on the number of vibrations effected by a vibrating substance in a given time1 speaking will be reproduced in a tone of which the pitch will depend on the velocity of rotation given to the cylinder on which the tinfoil is wound4 ,if the velocity is the same as that which was used in registration1 the tone of the words reproduced is the same as that in which they were uttered4 ,if the velocity is greater1 the tone is higher2 if less1 the tone is lower2 but the accent of the speaker may always be recognised4 ,owing to this peculiarity the reproduction of songs is nearly always defective in instruments turned by the hand2 they sing out of tune4 ,this is not the case when the instrument is moved by a well-regulated system of clockwork1 and in this way a satisfactory reproduction of a duet has been obtained4 ,the words registered on tinfoil can be often reproduced2 but the sounds become fainter and more indistinct at each repetition1 since the tracings in relief are gradually effaced4 ,the reproduction on copper is more successful1 but if intended to be permanent the sheets must be stereotyped1 and in this case the instrument must be differently arranged4 ,an attempt has been made to obtain speech from the phonograph by taking the words registered inversely to their true direction4 ,in this way the sounds obtained were necessarily quite unlike the words uttered2 yet ,messrs4 ,fleeming ,jenkin and ,ewing have observed that not only are the vowels unchanged by this inverse action1 but consonants1 syllables1 and even whole words may be reproduced with the accent they would have if spoken backwards4 ,the sounds produced by the phonograph1 although fainter than those of the voice which produced the registered tracing1 are strong enough to react on the ordinary string telephone1 and even on a ,bell telephone2 and as in this case the sounds do not go beyond the instrument1 and can only be heard by the person who is using it1 it is easy to ascertain that the sound has not been produced by trickery4 ,mr4 ,edison presented his phonograph to the ,acadmie des ,sciences through me1 ,march #aa1 #ahgh1 and when his agent1 ,m4 ,puskas1 caused the wonderful instrument to speak1 a murmur of admiration was heard from all parts of the hall--a murmur succeeded by repeated applause4 ,a letter appeared in the newspapers from one of the persons present1 in which he said that #8the learned ,academy1 generally so cold1 had never before abandoned itself to such enthusiasm4 ,yet some members of a sceptical turn of mind1 instead of examining the physical fact1 ascribed it to moral causes1 and a report soon ran through the room which seemed to accuse the ,academy of having been mystified by a clever ventriloquist4 ,certainly the spirit of ancient ,gaul is still to be found among the ,french1 and even in the ,academy4 ,one said that the sounds emitted by the instrument were precisely those of a ventriloquist4 ,another asked if the movements of ,m4 ,puskas' face and lips as he turned the instrument did not resemble the grimaces of a ventriloquist4 ,a third admitted that the phonograph might emit sounds1 but believed that it was much helped by the manipulator4 ,finally1 the ,academy requested ,m4 du ,moncel to try the experiment1 and as he was not accustomed to speak into the instrument1 it was unsuccessful1 to the great joy of the incredulous4 ,some members of the ,academy1 however1 desiring to ascertain the real nature of the effects1 begged ,m4 ,puskas to repeat the experiments before them in the secretary's office under such conditions as they should lay down4 ,m4 ,puskas complied with this request1 and they were absolutely satisfied with the result4 ,yet others remained incredulous1 and it was necessary that they should make the experiment for themselves before they accepted the fact that speech could be reproduced in so simple a way4' ,the anecdote ,i have just related cannot be interpreted to the discredit of the ,acadmie des ,sciences1 since it is especially bound to preserve the true principles of science intact1 and only to accept startling facts after a careful examination4 ,owing to this attitude1 all which emanates from the ,academy can be received with complete confidence2 and we cannot approve too highly of reserve which does not give way to the first impulse of enthusiasm and admiration4 ,the failure of my experiment at the ,academy was simply due to the fact that ,i spoke at too great a distance from the vibrating disk1 and that my lips did not touch the sides of the mouthpiece4 ,some days later1 at the request of several of my colleagues1 ,i made repeated trials of the instrument1 and ,i soon succeeded in making it speak as well as the supposed ventriloquist2 but ,i learned at the same time that practice is necessary to ensure success4 ,some words are reproduced more readily than others2 those which include many vowels and many r's come out better than those which abound in consonants1 and especially in s's4 ,it is therefore not surprising that1 even in the case of an experienced manipulator like ,mr4 ,edison's agent1 some of the sentences uttered by him are more audible than others4 ,the simultaneous repetition of several sentences in different languages by registering one over the other is one of the most surprising effects of the phonograph4 ,as many as three different sentences have been obtained2 but in order to distinguish them through the confused sounds which result from placing one over the other1 it is necessary that different persons1 giving special attention to a particular sentence1 should thus separate them and understand their sense4 ,vocal airs may1 in the same way1 be registered over the word tracings1 and in this case it is more easy to distinguish them4 ,there are several models of phonographs4 ,the one represented in fig4 #ff has been chiefly used for public experiments1 but there is a small model1 generally sold to the public1 in which the cylinder is much longer1 and serves at once for register and fly-wheel4 ,this instrument gives good results1 but can only be used for short sentences4 ,in this model1 as indeed in the other1 the words are more easily registered by fastening a small tube in the form of a prolonged speaking-trumpet to the mouthpiece2 the vibrations of the air are thus concentrated on the vibrating disk1 and act with greater energy4 ,the tenuity of the vibrating disk adds to the efficiency of the instrument1 and the tracing point may be fitted directly to this disk4 ,illustration3 ,,fig4 #fi4 ,i need not describe particularly the phonograph which acts by clockwork4 ,the instrument resembles the one represented fig4 #ff1 except that it is mounted on a rather high table1 to give room for the descent of the weight which moves the clockwork2 the mechanism is applied directly to the axis of the cylinder1 supplying the place of the winch1 and is regulated by a small fly-wheel4 ,the wheel used in an ,english system has been adopted1 but we prefer that of ,m4 ,villarceau1 which has small wings4 ,since it is always difficult to fit the tinfoil to the cylinder1 ,mr4 ,edison has tried1 with good success1 to obtain the tracing on a plane surface of tinfoil1 by means of the arrangement represented fig4 #fi4 ,in this new model1 the plate on which the tin or copper sheet is to be applied has a spiral grooving1 of which one end corresponds to the centre of the plate1 and the other to its outer edges4 ,the plate is set in motion by a powerful system of clockwork1 of which the velocity is regulated with reference to the length of the turns of the spiral4 ,the vibrating disk is arranged as in the former instrument1 and is placed above this plate2 the tracing point may1 by means of a movement of progression imparted to the system1 follow the spiral groove from the centre of the plate to its circumference4 ,it must not be supposed that all the tinfoil used for phonographic registration is equally good4 ,the foil must be of a definite thickness1 and combined with a definite amount of lead4 ,that which is used for wrapping chocolate1 and indeed all foil of ,french manufacture1 is too thin and too exclusively made of tin to produce good results1 and ,m4 ,puskas was obliged to import some from ,america to continue his experiments4 ,the relative proportion of lead and tin has not yet been defined1 and the selection of foil has been made empirically2 but as the use of the phonograph becomes more general1 this proportion must be ascertained1 and it may easily be done by analysing the composition of the foil which gives the best results4 ,illustration3 ,,fig4 #gj4 ,the arrangement of the tracing point is also of much importance for the successful action of the phonograph4 ,it must be very slender and very short 7not exceeding a millimtre in length71 so as to register distinctly the smallest vibrations of the vibrating disk without deviating from the normal direction of the cylinder1 which might be the case1 if it were long1 on account of the unequal friction exerted on the tinfoil4 ,it must also be made of a metal which has no tendency to tear the metallic sheet4 ,iron appears to combine most of the conditions demanded4 ,the phonograph is still in its infancy1 and it is probable that it may soon be enabled to register speech without the necessity of speaking into a mouthpiece4 ,according to the newspapers1 ,mr4 ,edison has already discovered a way of collecting1 without the aid of an acoustic tube1 the sounds uttered at a distance of three or four feet from the instrument1 and of printing them on a metallic sheet4 ,from this there is only a step to the power of inscribing a speech uttered in a large hall at any distance from the phonograph2 and if this step is taken1 phonography may be substituted with advantage for shorthand4 ,we add in a note the instructions given by ,m4 ,roosevelt to the purchasers of phonographs1 so as to enable them to work the instrument4#bj ,considerations on the theory4--,although the explanation we have given will make the effects of the phonograph intelligible1 it leads to a curious question which has greatly interested physicists--namely1 how it is that the tracing made on so yielding a surface as tin can1 when retraced by the stylus1 of which the rigidity is relatively great1 produce a vibratory movement without being completely destroyed4 ,to this we reply that the retracing is effected with such extreme rapidity that the effects of active force which are developed only manifest themselves locally1 and that under these conditions the mechanical effects exerted are as energetic in soft as in hard substances4 ,the curious experiment1 related in so many books on physics1 must be remembered1 of a plank pierced when a candle serves as the projectile of a gun4 ,the various accidents caused by the discharge of paper waddings must also be remembered4 ,under such conditions the motion imparted to the molecules which receive the shock has not time to be transmitted to the whole mass of the substance to which they belong1 and these molecules are compelled to separate from it1 or at any rate to produce1 when the substance is capable of vibration1 a centre of vibration which diffuses waves throughout its surface1 and produces sounds4 ,several scientific men1 among others ,messrs4 ,preece and ,mayer1 have carefully studied the form of the tracing left by the voice on the tinfoil of the phonograph1 and they observe that it greatly resembles the outline of the singing flames so well shown by ,herr ,koenig's instruments4 ,mr4 ,mayer wrote on this subject in the #8,popular ,science ,monthly ,review' of ,april #ahgh4 ,he said that he had been successful in reproducing a splendid tracing on smoked glass1 which gave in profile the outline of the vibrations of sound registered on the tinfoil with their varying curves4 ,for this purpose he fastened to the spring support of the tracing point of the phonograph a slender rod1 terminating in a point1 which pressed obliquely against the plate of smoked glass1 and1 since the latter was in a vertical position1 a movement imparted to the rod enabled it to produce a sinusoidal tracing4 ,by this arrangement1 when the phonograph was at work1 two systems of tracings were produced at the same moment1 of which one was the profile of the other4 ,mr4 ,mayer had not1 at the time he wrote1 been long enough in possession of the instrument to make many experiments with it1 but from a study of some of its curves it appeared to him that the registered outlines bore a strong resemblance to those of ,koenig's singing flames4 ,illustration3 ,,fig4 #ga4 ,fig4 #ga represents the tracing which corresponds to the letter a when pronounced as in bat1 in the three systems of registration4 ,that corresponding to line ,a is an enlarged reproduction of the tracing left on the tinfoil2 that corresponding to line ,b represents its profile on the sheet of smoked glass4 ,finally1 line ,c shows the outline of ,koenig's singing flames1 when the same sound is produced quite close to the membrane of the register4 ,it must be quite close1 since the form of the tracing produced by a pointer attached to a vibrating membrane1 when influenced by composite sounds1 depends on the distance intervening between the membrane and the source of sound1 and an infinite variety in the form of the tracing may be obtained by modifying the distance4 ,in fact1 when this distance is increased1 the waves of sound which result from composite sounds react on the membrane at different moments of their emission4 ,for example1 if the composite sound is formed of six harmonics1 the displacement of the source of vibration from the first harmonic by the length of a wave will respectively remove the second1 third1 fourth1 fifth1 and sixth harmonics 1 1 #a1 #a1 #a the length of a wave1 and consequently the outline resulting from the combination of waves will no longer be the same as it was before the displacement of the source of sound1 although the perception of the sounds remains the same in both cases4 ,this principle is clearly demonstrated by ,koenig's instrument1 by lengthening and shortening an extensible tube1 inserted between the resonator and the vibrating membrane1 which is placed close to the flame2 and this explains the disagreement of physicists as to the composition of vocal sounds which they have analysed by means of the singing flames4 ,mr4 ,mayer adds that these facts further show that we cannot hope to read the impressions and tracings of the phonograph1 which not only vary with the nature of the voice1 but also with the different moments at which the harmonics of the voice are emitted1 and with the relative differences in the intensities of these harmonics4 ,notwithstanding this assertion1 we reproduce 7fig4 #gb7 an extremely curious tracing sent to us by ,mr4 ,blake1 which represents the vibrations produced by the words #8,brown1 ,university3 how do you do8' ,they were photographed by means of an index fastened to a vibrating disk on which a ray of light was thrown4 ,the word #8how' is particularly remarkable for the combined forms of the inflections of the vibrations4 ,recent experiments seem to show that the more the vibrating membrane of the phonograph resembles the human ear in its construction1 the better it repeats and registers the sound vibrations3 it should be stretched1 as far as possible1 in the same way as the tympanum is stretched by the hammer of the ear1 and moreover it should have the same form1 since the vibrations of air are in this case much more effective4 ,illustration3 ,,fig4 #gb4 ,mr4 ,edison considers that the size of the opening of the mouthpiece has considerable influence on the distinct articulation of speech4 ,when the sounds are pronounced before the whole surface of the diaphragm1 some hissing sounds are lost4 ,they are1 on the contrary1 intensified when these sounds reach the diaphragm through a narrow orifice with sharp rims4 ,if the opening is toothed on its flattened rims1 the hissing consonants are delivered more clearly4 ,speech is reproduced more perfectly when the mouthpiece has a covering of some thickness1 so arranged as to deaden the sounds arising from the friction of the tracing point on the tin4 ,mr4 ,hardy has rendered the registration of phonographic tracings more easy by adding a small ebonite tube1 resembling the mouthpiece of a wind instrument1 to the mouthpiece of the phonograph4 ,,uses ,,of ,,the ,,phonograph ,,and ,,its ,,future4 ,mr4 ,edison has lately published in the #8,north ,american ,review' of ,may-,june #ahgh an article on the future of the phonograph1 in which he himself discusses the different applications which may be made of this instrument4 ,without sharing all his anticipations1 which appear to us to be very premature1 we think that some extracts from his paper may be interesting4 #8,in order to furnish a basis on which the reader may take his stand 444 a few categorical questions and answers are given upon the essential features of the principle involved4 #8#a4 ,is a vibrating plate or disk capable of receiving a complex motion which shall correctly represent the peculiar property of each and all the multifarious vocal and other sound waves8 #8,the telephone answers affirmatively4 #8#b4 ,can such complex movement be transmitted from such plate by means of a single embossing point attached thereto1 to effect a record upon a plastic material1 by indentation1 with such fidelity as to give to such indentations the same varied and complex form8 ,and if so1 will this embossing point1 upon being passed over the record thus made1 follow it with such fidelity as to transmit to the disk the same variety of movement1 and thus effect a restoration or reproduction of the vocal or other sound waves1 without loss of any property essential to producing on the ear the same sensation as if coming direct from the original source8 #8,the answer to this may be summed up in a statement of the fact that 444 the writer has at various times during the past weeks reproduced these waves with such degree of accuracy in each and every detail as to enable his assistants to read1 without the loss of a word1 one or more columns of a newspaper article unfamiliar to them1 and which were spoken into the apparatus when they were not present4 ,the only perceptible loss was found to be in the quality of the utterance1 a non-essential in the practical application of the instrument4 ,indeed1 the articulation of some individuals has been perceptibly improved by passage through the phonograph1 the original utterance being mutilated by some imperfection of lip and mouth formation1 and these mutilations corrected or eliminated by the mechanism of the phonograph4#ba #8#c4 ,can a record be removed from the apparatus on which it was made1 and replaced upon a second without mutilation or loss of effective power to vibrate the second plate8 #8,this is a mere mechanical detail1 presenting no greater obstacle than having proper regard for the perfect interchangeableness of the various working parts of the apparatus--not so nice a problem as the manufacture of the ,american watch4 #8#d4 ,what as to the facility of placing and removing the second sheet1 and as to its transportation by mail8 #8,but ten or fifteen seconds suffice for such placing or removing4 ,a special envelope will probably be required1 the weight and form of which1 however1 will but slightly increase the cost of postage4 #8#e4 ,what as to durability8 #8,repeated experiments have proved that the indentations possess wonderful enduring power1 even when the reproduction has been effected by the comparatively rigid plate used for their production4 ,it is proposed1 however1 to use a more flexible plate for reproducing1 which1 with a perfectly smooth stone point--diamond or sapphire--will render the record capable of from fifty to one hundred repetitions1 enough for all practical purposes4 #8#f4 ,what as to duplication of a record and its permanence8 #8,many experiments have been made1 with more or less success1 in the effort to obtain electrotypes of a record1 and the writer is informed that it has very recently been successfully accomplished4 ,he can certainly see no great practical obstacle in the way4 ,this1 of course1 permits of an indefinite multiplication of a record1 and its preservation for all time4 #8#g4 ,what is the requisite force of wave impinging upon the diaphragm1 and the proximity of the mouth to the diaphragm1 to effect a record8 #8,these depend in great measure upon the volume of sound desired in the reproduction4 ,if the reproduction is to be made audible to an assembly1 considerable force is requisite in the original utterance2 if for the individual ear1 only the ordinary conversational tone 7even a whisper has been reproduced74 ,in both cases the original utterances are delivered directly in the mouthpiece of the instrument4 ,an audible reproduction may1 however1 be had by speaking at the instrument from a distance of from two to three feet in loud tone4 ,the application of a flaring tube or funnel to collect the sound waves1 and the construction of an especially delicate diaphragm and embossing point1 c41 are the simple means which suggest themselves to effect this4444 #8,the foregoing presentment of the stage of development reached by the several essential features of the phonograph demonstrates the following faits accomplis3 #8#a4 ,the captivity of all manner of sound waves1 hitherto designated as 8fugitive10 and their retention4 #8#b4 ,their reproduction with all their original characteristics1 without the presence or consent of the original source1 and after the lapse of any period of time4 #8#c4 ,the transmission of such captive sounds through the ordinary channels of commercial intercourse and trade in a material form1 for purposes of communication4 #8#d4 ,indefinite multiplication and preservation of such sounds1 without regard to the existence or non-existence of the original source4 #8#e4 ,the captivation of sounds1 with or without the knowledge or consent of the source of their origin444 #8,the apparatus now being perfected in mechanical details will be the standard phonograph1 and may be used for all purposes1 except such as require special form of matrix1 such as toys1 clocks1 c41 for an indefinite repetition of the same thing4 ,the main utility of the phonograph being1 however1 for the purposes of letter-writing and other forms of dictation1 the design is made with a view to its utility for that purpose4 #8,the general principles of construction are1 a flat plate or disk1 with spiral groove on the face1 worked by clockwork underneath the plate2 the grooves are cut very closely together1 so as to give a great total length to each length of surface--a close calculation gives as the capacity of each sheet of foil nearly #dj1jjj words4 ,the sheets being but ten inches square1 the cost is so trifling that but a hundred words might be put on a single sheet economically4444 #8,the practical application of this form of phonograph is very simple4 ,a sheet of foil is placed in the phonograph1 the clockwork set in motion1 and the matter dictated into the mouthpiece without other effort than when dictating to a stenographer4 ,it is then removed1 placed in suitable form of envelope1 and sent through the ordinary channels to the correspondent for whom it is designed4 ,he1 placing it upon his phonograph1 starts his clockwork1 and listens to what his correspondent has to say4' ,since this paper by ,mr4 ,edison appeared in ,june #ahgh1 he has applied the phonograph to several other purposes1 among which we may mention that of registering the force of sounds on railways1 and especially on the metropolitan atmospheric railway in ,new ,york4 ,the instrument which he has made for this purpose resembles that by ,mr4 ,leo ,scott1 and bears the same name4 ,it is described and represented in the #8,daily ,graphic' of ,july #ai1 #ahgh1 as well as the aerophone1 the megaphone1 and the microtasimeter1 which is adapted for astronomical observations4 ,we should exceed the limits laid down for this volume1 if we were to give a more detailed account of these inventions4 ,m4 ,lambrigot1 one of the officials on the telegraphic lines in ,france1 and the author of various improvements in the ,caselli telegraph1 has shown me a phonographic system of his own invention in which it is reduced to its simplest form4 ,he sent me the following description of his system4 #8,the instrument consists of a wooden slab placed vertically on a stand and firmly fixed upon it4 ,there is a round opening in the middle of the slab1 covered by a tightly stretched sheet of parchment bearing a steel knife1 which1 like the tracing point of the phonograph1 is intended to trace the vibrations4 ,a solid block rises from the stand to the middle of the slab1 and supports a slide on which a runner can move in front of the slab4 ,there is a strip of glass on this runner1 of which one side is covered with stearine4 ,when the runner is moved to and fro1 the stearine comes in contact with the knife and takes the mould of its form1 which is curved throughout4 #8,a sound places the sheet of parchment in vibration1 and imparts its movement to the knife1 which traces various lines on the surface of the stearine4 #8,the reproduction thus obtained on the strip of glass is subjected to the ordinary processes of metallisation4 ,by galvanism a deposit of copper is obtained which reproduces the lines in an inverse way4 ,in order to make the metallic plate speak1 it is necessary to pass a point of ivory1 wood1 or horn lightly over the signs1 and1 by moving it more or less quickly1 the different tones can be heard1 just as they were spoken4 #8,since copper is relatively harder than lead1 the copper plate on which the vibrations are traced will afford an unlimited number of reproductions4 ,to obtain this result1 a lead wire must be applied to the plate1 and due pressure must be exerted on it4 ,the wire is flattened and takes the impression of all the traces which then appear in relief4 ,if the edge of a card is passed through this impressed tracing1 the same sounds are produced as those which are obtained from the copper plate4' ,m4 ,lambrigot suggests that the speaking plates might be useful in many ways3 for example1 they might make it easy to learn the correct pronunciation of foreign languages1 since a sufficient number might be collected to make a sort of vocabulary which would give the accent of the words most in use in a given language4 ,by this simple process ,m4 ,lambrigot has been able to obtain a strong impression1 within a copper groove1 of the vibrations caused by the voice1 and they are so distinctly engraved that whole sentences may be heard1 if they are retraced by the sharpened point of a match4 ,it is true that the reproduction is imperfect1 and that those words are only to be distinguished which were previously known2 but it is possible that better results will be obtained from improvements in the system1 and at any rate the distinct impression of the vibrations of the voice on a hard metal is a really interesting discovery4 ,i have made one somewhat important observation in the working of the phonograph--namely1 that if speech is registered on the instrument in a very hot room1 and it is then carried to a colder room1 the reproduction of speech is imperfect in proportion to the difference of temperature4 ,this is probably owing to considerable modifications in the elasticity of the caoutchouc pad which is inserted between the tracing point and the vibrating disk3 perhaps differences of expansion in the tinfoil have also some effect4 ,,faber',s ,,american ,,speaking ,,machine4 ,about two years ago the newspapers announced with some pomp that a speaking machine had reached ,paris1 which far surpassed ,vaucanson's duck1 and which would attract general attention4 ,unfortunately the invention was not in the first instance brought forward with any scientific authority1 and was soon relegated to take a place among the curiosities exhibited by conjurors4 ,in a country so essentially critical and sceptical as ,france1 there are always those who profess incredulity1 and who will even resist evidence1 and it was asserted that the machine only spoke because its exhibitor was an able ventriloquist4 ,this is an old assertion which has lately been made with reference to the phonograph4 ,some scientific papers echoed the absurdity1 and the speaking machine was so discredited that it is now unnoticed1 although it is a most ingenious and interesting conception4 ,when will our country be cured of the error of denying everything without due examination8 ,since we ourselves only judge of things after having seriously considered them1 we think it just to vindicate the truth as to ,mr4 ,faber's machine1 and this can only be done by an exact description of it4 ,as ,i said in the last chapter1 there is a great difference between the production and the reproduction of a sound1 and a machine like the phonograph1 adapted for the reproduction of sound1 may differ essentially from a machine which really speaks4 ,in fact1 the reproduction even of articulate sounds may be very simple1 as soon as we possess the means of stereotyping the vibrations of air necessary to transmit these sounds2 but in order to produce them1 and especially to emit the complex vibrations which constitute speech1 it is necessary to set in motion a number of special organs1 fulfilling more or less exactly the functions of the larynx1 the mouth1 the tongue1 the lips1 and even the nose4 ,for this reason1 a speaking machine is necessarily very complicated1 and this is precisely the case with the machine we are now considering4 ,such a machine is not now made for the first time1 and the ,academy has lately been reminded of a speaking head which was in the possession of the philosopher ,albertus ,magnus in the thirteenth century1 and which was destroyed by ,st4 ,thomas ,aquinas as a diabolical invention4 ,mr4 ,faber's speaking machine was exhibited two years ago at the ,grand ,htel1 and may now be seen in the room adjoining ,m4 ,robert ,houdin's theatre1 the same room in which ,mr4 ,giffard exhibited the telephone4 ,it consists of three distinct parts3 #ast1 of a large bellows worked by a pedal1 which produces the currents of air necessary for the production of sounds1 and to some extent acts as the lungs2 #bnd1 a vocal instrument1 consisting of a larynx accompanied by diaphragms of various forms to modify the sounds1 of a mouth with caoutchouc lips and tongue1 and of a tube with an outlet somewhat resembling the nasal cavities2 #crd1 of a system of jointed levers and of pedals1 terminating in keys like those of a piano4 ,the most interesting part of the machinery1 of which we represent the principle fig4 #gc1 is the vocal apparatus1 which involved the severest study of physics in order to succeed in the production of articulate sounds4 ,it consists1 first1 of a rather thick caoutchouc tube1 within which there is a kind of whistle ,l1 as in a clarionet4 ,the whistle consists of a small caoutchouc cylinder with a longitudinal slit1 and before this is placed a very thin ivory plate lined with caoutchouc4 ,this plate is fixed at one end to the cylinder1 and deviates slightly from it at its free end1 so as to permit the current of air projected from the bellows ,s to penetrate between the two parts1 and to cause the vibrations in the ivory plate necessary for the production of a sound4 ,the extremity of the caoutchouc cylinder is closed on this side1 and is fitted to an iron rod t which comes out of the pipe1 and is connected with a system of bars1 corresponding to the keyboard of a piano1 by which the force of sounds can be regulated4 ,this force depends on the width of the opening between the tongue and the cylinder4 ,illustration3 ,,fig4 #gc4 ,the whistle1 which plays the part of the larynx1 is necessarily placed opposite the opening of the bellows1 and a sort of tourniquet ,m is fastened to the opening itself1 which is able to move on certain conditions1 so that it may produce the rolling sound of r4 ,this is done by fastening before the opening a diaphragm in which there is a somewhat wide and long slit1 and this slit can be almost closed by a little bar of the same size ,m1 revolving on a transverse axis which supports it by its centre4 ,in its normal condition1 this little bar is kept in a slanting position by cords attached to the keyboard1 and the air ejected by the bellows readily traverses the slit in order to reach the larynx2 but two dampers are fastened to the rods which transmit movement1 with which the cords just mentioned are also connected4 ,on lowering the notes of the key-board1 the passage of air is contracted1 and the little plate begins to oscillate and to press against a band of leather1 producing by its vibration an action similar to that produced by the cricket4 ,this little tourniquet only begins to act when the dampers are lowered by a pedal worked by the hand2 and this is also the case with the iron rod t1 which modifies the acuteness of the sounds passing through the larynx4#bb ,below the larynx tube1 which is only five centimtres in length1 there is another pipe ,g1 also of caoutchouc1 which terminates in a spherical cavity connected with the outer air by a caoutchouc tube ,i1 slightly raised1 and closed by a valve1 of which the movements are regulated by a pedal worked by the keyboard4 ,when the valve is open1 the sounds emitted through the larynx are somewhat nasal4#bc ,the larynx communicates with the mouth through a square funnel-shaped pipe1 to which six metallic diaphragms ,d are fastened2 the diaphragms are placed in a vertical position behind each other1 and have indentations on their lower end1 which are intended to diminish more or less the orifice for the current of air1 and to impede its passage with greater or less force4 ,the diaphragms1 which we represent separately fig4 #gd1 are connected with the keyboard by jointed iron rods t1 and1 for the emission of most articulate sounds1 several of the diaphragms are moved at the same moment and at different heights4 ,we shall return to this subject4 ,illustration3 ,,fig4 #gd4 ,the mouth consists of a caoutchouc cavity ,o1 somewhat resembling the human mouth1 and forming a continuation to the channel we have just described4 ,the tongue ,c1 likewise modelled on the human tongue1 is placed within the mouth1 and connected with two jointed rods t1 t1 fastened to its two opposite ends1 so as to enable the tongue to raise its tip1 or touch the palate1 in obedience to the notes of the keyboard4 ,the lower caoutchouc lip ,a can also be more or less closed1 according to the action of the keyboard on its special rod4 ,finally1 a circular metallic piece ,e1 following the shape of the mouth1 is placed above the upper lip1 with a small opening in it to admit of the pronunciation of the letter f4 ,the keyboard has fourteen notes1 of different lengths1 producing the following letters when lowered1 a1 o1 u1 i1 e1 l1 r1 v1 f1 s1 ch1 b1 d1 g4 ,the longest corresponds to g1 and the shortest to a4 ,there are two pedals below the g note and those of b and d1 corresponding with the opening of the tube which produces nasal sounds1 and to the rod which regulates the opening of the larynx1 and this makes it possible to obtain p1 t1 and k from the notes b1 d1 g4 ,the mechanical effects produced by lowering the different notes in succession are as follows3-- #a4 ,the a note moves the first five diaphragms4 #b4 o also moves these five diaphragms1 but varies the pitch1 and closes the mouth a little4 #c4 u does the same1 only further closing the mouth4 #d4 t moves a single diaphragm1 raises the tip of the tongue1 and opens the mouth more widely4 #e4 e moves six diaphragms1 throws the tongue further back1 and opens the mouth still more4 #f4 l moves five diaphragms1 sends the tongue against the palate1 and further opens the mouth4 #g4 r moves six diaphragms and the tourniquet1 lowers the tongue1 and somewhat closes the mouth4 #h4 v moves five diaphragms1 almost closes the mouth1 and keeps the tongue down4 #i4 f lowers the circular appendix of the upper lip1 and almost entirely closes the mouth4 #aj4 s moves three diaphragms1 half closes the mouth1 and half raises the tongue4 #aa4 ch moves three diaphragms1 keeps the mouth half closed1 and further lowers the tongue4 #ab4 b moves five diaphragms1 closes the mouth1 and keeps the tongue completely down4 #ac4 d moves six diaphragms1 keeps the mouth three parts closed1 and raises the tongue a little4 #ad4 g moves five diaphragms1 keeps the mouth three parts closed1 and the tongue completely down4 m is produced by lowering note b and opening the valve of the pipe which gives nasal sounds4 n is obtained by lowering note d and opening the same valve4 h is obtained from note s by lowering the pedal which acts upon the larynx1 and half closing it4 ,since the other letters of the alphabet are compound sounds1 they can be produced by combinations of the preceding letters4 ,although the words pronounced by this machine are distinct1 they are spoken in a uniform1 drawling tone1 which might1 ,i should have thought1 have excluded the idea of imposition4 ,some of them are indeed far from distinct1 yet the results are not less remarkable2 and when we consider the amount of study and experience which must have been applied to the combination of all these arrangements1 it seems surprising that physicists have not given more attention to such an interesting machine4 ,as for the mechanical execution1 it is impossible to admire too highly the simple and ingenious manner in which all the complicated movements of the different vocal organs have been connected with the keyboard1 of which the mechanism has been so calculated as only to produce the precise action of the organ which is required for any given effect4 ,for this purpose1 the notes of the keyboard regularly increase in length1 so as to produce at a single touch different mechanical effects on the rods which act upon the mechanism2 and since most of the notes are required to react simultaneously on the whole mechanism1 the rods which transmit the movement are fastened to a series of jointed levers which cross the notes of the keyboard at right angles4 ,pegs of different length are fastened to the notes at this junction1 so as to produce the simultaneous action of the different organs of the machine4 ,the public will believe that the assertions of ventriloquism are unfounded when ,i add that ,i myself have made the machine speak4 ,,appendix4 ,the ,perrodon ,system of ,telephonic ,alarum4--,captain ,perrodon1 of the ,french ,artillery1 has lately improved the system invented by ,,mm4 ,dutertre and ,gouault1 by a self-acting call4 ,for this purpose he has fastened a spring contact before the diaphragm1 combined with the diaphragm and the electro-magnetic system so as to form a vibrator4 ,the vibrations thus produced are strong enough to resound in an ordinary telephone1 so as to make the call audible in spite of external noises4 ,the system has been arranged in different ways4 ,in one arrangement1 a small plate of tinfoil is glued to the outer surface of the diaphragm1 and the end of the telephone coil wire is connected1 below the inner surface of the mouthpiece1 with a silver wire soldered to a spring plate1 which constitutes the contact of the vibrator4 ,this spring plate1 slightly curved1 is fixed below one of the binding-screws of the telephone1 and terminates at its free end in a regulating screw by which the interval between the contacts can be regulated1 and the instrument can be arranged as a telephonic organ4 ,to do this1 the screw can be withdrawn1 and inserted in a nut which establishes direct connection between the line and the telephone coil4 ,it is easy to adapt an ordinary telephone to this system4 ,in another arrangement ,m4 ,courtot's mirror telephone has been employed1 and a sort of spring pedal is inserted in the wood of the mouthpiece1 which terminates in a bent silver wire1 supporting an index adapted to make a contact with a square plate soldered to the diaphragm4 ,the battery is placed in connection with the spring of the pedal1 and one end of the telephone coil-wire communicates as before with the diaphragm4 ,when a call is to be made1 the pedal must be pressed1 and the battery immediately communicates with the silver wire which1 with the diaphragm1 constitutes the vibrator1 and an electric vibration is sent through the circuit1 and produces the call4 ,for receiving1 the pedal is allowed to revert to its normal position1 and the index of the pedal1 touching the contact in connection with the diaphragm1 establishes direct communication between the two telephones1 while breaking the contact of the silver wire with the diaphragm1 so that the battery cannot act4 ,it appears that experiments made at the musketry school at ,orleans for a distance of #cgj miles have been very successful4 ,m4 ,varey's ,microphone ,speaker4--,m4 ,varey has recently arranged a successful microphonic speaker1 in which the principle of the microphone represented in fig4 #ci is maintained4 ,the system of three vertical carbons is arranged inside a sort of snuff-box1 of which the lid is made of a thin plate of mica1 horn1 or ebonite4 ,the snuff-box is provided with two hinged arms1 so that it may be placed in the most convenient position for speaking1 and at the same time the sensitiveness of the instrument can be regulated4 ,a small battery1 consisting of two ,gaiffe cells of chloride of silver1 is placed in the pedestal on which the instrument stands1 and sets the microphone at work without further trouble4 ,in this way the speaker can be used like an ordinary telephone1 and is not affected by vibrations of air4 ,only vibrations of sound react upon it4 ,microphonic ,speaker by ,fitch4--,mr4 ,pope states that this speaker has produced excellent results in ,america4 ,it is merely ,edison's carbon telephone reduced to its simplest form4 ,it consists of a small cylindrical box1 which has a mouthpiece like the one represented fig4 #bh4 ,the box contains two carbon disks of the same diameter as itself1 and is lined with a kind of felt4 ,metal wires1 inlaid in a groove scooped on the circumference of the carbons1 place them in communication with the circuit and battery1 and transmission takes place by means of the vibrations of the upper carbon1 which is directly influenced by the voice without the intervention of any diaphragm4 ,these vibrations1 which can be freely developed in consequence of the elasticity of the felt pad which supports the lower carbon1 produce on the surface of contact of the two carbons the modifications of intensity of current necessary for the reproduction of speech1 in the same way as other microphones4 ,an induction coil is necessarily employed for a long circuit1 and the effects of induction in the adjacent wires are modified by two rheostats introduced into the circuit at its two extremities4 ,further remarks on the theory of the ,telephone4--,following the example of a certain sceptic in the ,acadmie des ,sciences1 ,colonel ,navez continues to maintain the theory first formed as to the mode in which the telephone acts1 in spite of the clearest proofs of its insufficiency2 but most scientific men who consider the question have come round to our opinion1 and admit the concurrence of several causes in the reproduction of speech by this remarkable instrument4 ,mr4 ,fleeming ,jenkin writes to this effect in the new edition of a treatise on ,electricity and ,magnetism4 ,he observes that a singular fact has been discovered by several persons1 who have ascertained that not merely non-magnetic and non-conducting bodies can be substituted for the diaphragms of receiving telephones1 but that they will act without a diaphragm at all4 ,in this case it is evident that we have to do with the sounds discovered by ,page1 and that they are produced by the magnet itself1 in which each molecular movement constitutes the source of the sound produced4 ,this sound becomes articulate as soon as its increase and decrease can follow the increasing or decreasing action of the voice which produces it at the sending station4 ,it is certain that when the transmitted currents are due to the action of the ,bell diaphragm1 the sounds due to the ,page effects ought to correspond with those which would be given by iron diaphragms adapted to the receiving instruments2 so that1 when a telephone has an iron diaphragm1 there are in fact two voices1 that of the diaphragm1 which is strong1 and that of the magnet1 which is weak4 ,when a disk of wood is substituted for one of iron1 it acts as a sounding board for the ,page effect1 and when the disk is of metal1 induction is developed by the magnetic modifications1 and tends to produce vibration1 thus developing a third source of sound1 which may be called the ,ampre effect4 ,finally1 a fourth source of sound may result from the induced effects produced in the wire itself in consequence of changes in the intensity of current4 ,these sounds1 first observed by ,m4 de la ,rive1 have since been studied by ,mr4 ,fergusson of ,edinburgh 7vide #8,telegraphic ,journal' of ,november #a1 #ahgh74 ,mr4 ,fleeming ,jenkin's opinion only differs from mine in his ascribing the energy of sound acquired by a telephone with an iron diaphragm to the preponderance of sounds in the latter1 whereas ,i consider it to be chiefly due to the increase of energy in the whole magnetic system produced by the reaction of the two magnetic parts on each other4 ,if the two effects could be taken singly1 it is probable that the sounds produced by each of them separately would be similar1 since in magnetic effects the reaction and action are equal4 ,but as they are combined1 it becomes difficult to assign to each the share which belongs to it in the general effect observed4 ,besides1 it is quite possible that the sounds of the diaphragm may appear to be stronger and more distinct because it is nearer to the ear than the magnet1 and because the effects of magnetisation and demagnetisation are then more easily produced in consequence of the mass of the magnetic body being smaller4 ,mr4 ,fleeming ,jenkin goes on to say that the question of the displacement of surface in the diaphragm and magnet is very complex1 but that he thinks it impossible to deny the existence of such displacement1 since the air which acts as the vehicle of sound between the ear and the source of sound is placed in vibration2 yet this displacement maybe effected quite otherwise than by flexion4 ,suppose that the magnetic molecules of these bodies are drawn together by magnetisation1 which tends to diminish the intermolecular space which separates them1 the points of surface of the substance corresponding to these intervals will be elevated in a manner equivalent to a displacement of surface1 and the effect of this will be the same as a flexion movement4 ,at the moment of demagnetisation a depression instead of an elevation will take place1 and the vibratory movements will thus be produced without any electro-magnetic attraction1 and it is precisely these vibrations which ,mr4 ,fleeming ,jenkin terms molecular vibrations4 ,he evidently does not mean that such attractions cannot take place3 they may react1 together with the molecular vibrations1 when the electric force is capable of producing them4 ,he adds that the reproduction of sounds by a condenser1 by simple coils1 and by a carbon microphone1 has convinced him that the action just analysed requires generalisation4 ,we have recently seen an article by ,mr4 ,hughes in the #8,telegraphic ,journal1' ,nov4 #ae1 #ahgh1 in which1 to our surprise1 he not only opposes all the theories he has hitherto held1 but cites experiments which are quite inconclusive1 since they were performed under conditions in which electro-magnetic effects must necessarily be displayed4 ,he made use of voltaic currents produced by a battery of three ,daniell cells4 ,in order to estimate the transverse effects resulting in such a case from attraction1 the experiments he mentions are wholly unnecessary3 they may be felt with the hand4 ,on the other hand1 he has evidently forgotten that the currents employed in a ,bell telephone have no influence on a very sensitive galvanometer4 ,m4 ,pollard's ,microphone4--,this microphone1 which has been arranged in several ways1 essentially consists of a carbon rod kept in a horizontal position by a wire1 and resting on two other vertical carbons4 ,the upright of the arm which holds the wire can revolve together with this arm1 and is thus able to regulate the pressure of the horizontal carbon on the two vertical carbons4 ,it appears that this instrument is extremely sensitive1 and that the regulation effected on the two contacts is better than when it is effected on one only4 ,it is fair to add that ,m4 ,voisin previously sent me the sketch of a somewhat similar arrangement4 ,m4 ,dutertre has also made use of such an arrangement in what he calls the ,dolmen microphone4 ,three pieces of coke in the form of a dolmen1 that is1 two uprights1 supporting a third and horizontal carbon1 are placed in circuit4 ,m4 ,gouault has informed me that speech was well transmitted by this instrument1 and it is1 like that of ,mr4 ,blyth1 which succeeded it1 of wonderful simplicity4 ,this microphone1 as well as one composed of two pieces of lead-pencil placed in a watch-case1 and connected by a piece of money1 were exhibited to the ,industrial ,society at ,rouen1 ,february #a1 #ahgh1 of which an account was published in the ,bulletin of that society4 ,m4 ,ader's ,electrophone4--,m4 ,ader has recently constructed a remarkable telephonic instrument1 which reproduces speech and song in a quite exceptional and simple way4 ,it consists of a drum #ae centimtres in diameter1 covered with parchment at one end only4 ,six small tin armatures1 one centimtre in length and two millimtres in width1 are fixed in the centre of the parchment in a circle six centimtres in diameter4 ,six microscopic electro-magnets1 whose distance from the armatures can be regulated by a screw1 are placed opposite the armatures within a wooden circle4 ,the magnets are horseshoe1 with branches #ab millimtres long and #d millimtres in diameter1 including the coils1 and the magnetic core is #a millimtre thick4 ,they are all in connection1 and act simultaneously under the sole influence of the battery current4 ,the sender is the same as that of ,m4 ,ader described before4 ,with this instrument speech may be heard at a distance of six or seven yards1 and songs are much more distinctly heard than in the singing condenser4 ,owing to the simplicity of the arrangement1 the instrument is not costly4 ,the extraordinary effects of this telephone are due to the small size of the electro-magnets1 which1 as we believe1 produce much more rapid magnetic effects than those of larger size4 ,m4 ,ader has also made a small ordinary telephone based on this principle1 of which the sounds are much stronger than in others4 ,modification of ,bell ,telephone4--,mr4 ,gower has recently made a new system of telephone without a battery1 which not only reproduces speech loudly enough to be heard at the distance of eight or nine yards from the instrument1 but will also transmit it when the speaker is at a moderate distance from the sending instrument4 ,in this latter case1 indeed1 the receiving telephone must be brought close to the ear4 ,although this double problem had already been solved by the use of telephones with microphonic senders1 the results furnished by the instruments in question are still more curious1 since they are obtained without batteries1 and are even more distinct4 ,in this new system1 which is only an improvement on ,bell's square model1 the horseshoe magnet is of a peculiar form1 which renders it more powerful4 ,it is formed of a kind of half-circle of magnetised steel1 with its two ends turned back1 so as to form a diameter of the circle1 only this diameter is divided in the centre3 so that the two poles of the magnet are placed one before the other1 as in ,faraday's electro-magnet4 ,the poles are tipped with iron1 terminating in front in two thin iron plates1 on which are placed the electro-magnetic coils1 which are oblong1 and constitute the magnetic core4 ,the diaphragm1 thicker than the ordinary diaphragms1 is of tin1 and is fixed firmly to the edges of the circular box which encloses the whole1 and which forms a kind of sounding-box4 ,the box is made of copper1 and the diaphragm is so firmly fastened to it as to become homogeneous with it1 and to give out a sound when the box is touched1 which is not the case in ordinary telephones4 ,this is one of the conditions which make the instrument a better conductor of sound4 ,the magnet is also much more powerful4 ,it is magnetised by a current from a powerful ,gramme machine1 which acts upon it for almost twenty minutes4 ,the instrument has1 strictly speaking1 no mouthpiece3 the lid of the box which supports the diaphragm1 and is separated from it by a space of two millimtres1 has merely a hole bored in it above the centre of the diaphragm1 and into this hole either a tin trumpet1 #ej centimtres in length1 is screwed1 when the instrument is required to reproduce or transmit speech to a distance1 or an acoustic tube when it is to be used like an ordinary telephone4 ,the remarkable part of the system is that the instrument can itself give a very loud call by only breathing into it instead of speaking4 ,for this purpose a small oblong opening is made in the diaphragm at a half diameter from its centre1 and behind this the reed of an harmonium is applied to a square copper plate fixed on the diaphragm itself4 ,on using the bellows the expelled air passes through this little hole1 and1 on reaching the reed1 sets it in vibration1 and produces a sound of which the acuteness depends on the conditions of the vibrating plate4 ,this addition to the diaphragm in no way alters its properties in the reproduction of speech1 so that1 after using the bellows1 conversation may begin1 and the receiving telephone repeats what is said after emitting a sound somewhat resembling the note of a bugle4 ,the instrument is then provided with the speaking tube of which we have spoken4 ,nothing can be more remarkable than this power of listening to conversation while seated in an armchair six or seven yards from the instrument1 nor is it necessary to move in order to reply4 ,the correspondent1 indeed1 must be close to the acoustic tube in order to speak and listen1 and he must speak rather loud in order to be heard at any distance from the other station4 ,but the listener receives the sounds so amplified that it might be supposed that a giant was speaking1 and conversation held in a low tone may even be distinguished4 ,these results are really extraordinary1 and even to those familiar with such effects this incessant progress is surprising4 ,these results may be ascribed to the following causes3-- #a4 ,first1 that the conditions of the magnet are better than those of ordinary instruments4 #b4 ,that the diaphragm is also thicker1 larger1 and better stretched4 #c4 ,that the box is of metal1 and calculated to act as a sounding-box4 #d4 ,the speaking trumpet magnifies the sounds4 #e4 ,the acoustic tubes concentrate the sound waves on the centre of the diaphragm4 ,note on some fresh ,experiments with ,telephones without any ,diaphragm4 ,in a paper published ,march #d1 #ahgh1 ,i made some suggestions on the theory of the sounds produced in the telephone1 and on the contradictory assertions of physicists as to the transmission of speech by ordinary telephones when devoid of diaphragm4 ,these remarks induced ,m4 ,ader to undertake some experiments which not only demonstrate the truth of my opinion1 but bring to light some fresh facts which may be of great importance to acoustic science4 ,m4 ,ader has in fact not only succeeded in making a telephone without a diaphragm speak1 but he has made it speak more loudly and with less alteration of the voice than we find to be the case with a small model of the ordinary telephone4 ,no one1 therefore1 can now maintain that the sounds produced by the magnetic cores are so faint that they cannot be taken into account among the effects produced1 and that it is at any rate impossible for them to reproduce articulate sounds4 ,to obtain this result1 ,m4 ,ader reduced the size of the magnetic core to that of a simple iron wire1 one millimtre in diameter1 and he fastened it by one of its ends to a small wooden board4 ,under these conditions1 it was enough to fasten a small helix of fine wire on this iron wire1 and to apply the board to the ear in order to hear speech distinctly1 with the aid of a microphonic speaker actuated by a voltaic current4 ,but the range of sound was considerably increased if a mass of metal was applied to the free end of the iron wire3 in this case it was possible to hear when the wooden board was removed to a distance of ten or fifteen centimtres from the ear4 ,if the wire is in contact with masses of metal at each end1 the effect is further increased2 but the two masses must not be in metallic communication with each other1 and must be to some extent insulated by a more or less elastic medium4 ,if the metallic masses are soldered to the wire1 the effects are still greater4 ,m4 ,ader was also able to reproduce speech by using a simple coil without a magnetic core1 but in this case the spirals must be open1 and not pressed together4 ,if they are steeped in gum1 no sound is heard1 but speech will become instantly audible if a wire or a magnetised needle is inserted in the coil1 or even if a second metallic helix is placed in the circuit3 always provided that one of the ends of these magnetic organs rests upon1 or is fastened to1 the board on which the coil is fixed4 ,m4 ,ader has likewise obtained a very distinct reproduction of speech at a distance of two or three yards from the instrument by inserting between the two stretched membranes of two tambourines a bent wire which acts as a spring and passes through an electro-magnetic coil4 ,under these conditions1 magnetisation of the wire in a greater or less degree affects its elasticity and causes vibrations which are magnified by the membranes1 and transmitted sounds are reproduced with intensity4 ,unfortunately articulate speech is less distinct with this system than with the one ,i described before4 ,m4 ,ader has often had occasion to make one curious remark1 namely1 that the timbre of the voice and its high or low key varies with the degree of tension given to the wire2 but if the fundamental note of the wire is deadened by pressing it between the fingers1 the sounds reproduced then become dull and monotonous4 ,they are also somewhat fainter4 ,signor ,carlo ,resio has also observed that in a telephone sender the variations of intensity in the current correspond with the vibrations caused by speech1 and these are reproduced by corresponding variations in a liquid column1 which may thus act as a telephone receiver1 and consequently may reproduce speech without any electro-magnetic organ1 as in a microphone speaker4 ,under these conditions1 however1 a layer of water is inserted between the platinum electrodes and the surrounding air1 and consequently this liquid layer must be put in vibration under the influence of varying intensities of current4 ,mr4 ,edison has also now made a practical application of the chemical telephone we have mentioned before4 ,the trials made with it have been very satisfactory1 showing that sounds transmitted in this way can be heard in a large room4 ,,printed ,,by ,,spottiswoode ,,and ,,co41 ,,new-,,street ,,square ,,london ,,footnotes #a ,mr4 ,gray1 in an article inserted in the ,telegrapher of ,october #g1 #ahgf1 enters into full details of this mode of transmitting sounds by the tissues of the human body1 and he gives the following as the conditions in which it must be placed to obtain a favourable result3 #a4 ,the electricity must be of a high tension1 in order to have an effect perceptible to the ear4 #b4 ,the substance employed to touch the metallic plate must be soft1 flexible1 and a good conductor1 up to the point of contact3 it must then interpose a slight resistance1 neither too great nor too small4 #c4 ,the disk and the hand1 or any other tissue1 must not only be in contact1 but the contact must result from rubbing or gliding over the surface4 #d4 ,the parts in contact must be dry1 so as to maintain the required degree of resistance4 #b ,he cites the following names in his account of electric telephony3--,page1 ,marrian1 ,beatson1 ,gassiot1 ,de la ,rive1 ,matteucci1 ,guillemin1 ,wertheim1 ,wartmann1 ,janniar1 ,joule1 ,laborde1 ,legat1 ,reiss1 ,poggendorf1 ,du ,moncel1 ,delezenne1 ,gore1 c4 ,vide ,mr4 ,bell's paper1 in the ,journal of the ,society of ,telegraphic ,engineers in ,london1 vol4 vi4 pp4 #cij1 #cia4 #c ,this statement is disputed by ,mr4 ,elisha ,gray1 owing1 as we shall see1 to a misunderstanding as to the word undulatory current4 #d ,elisha ,gray4 ,eng4 ,pat4 ,spec4 ,no4 #bfdf1 ,aug4 #ahgd4 #e ,this property has long been known1 but not applied4 ,in #ahef1 in the second edition of my ,expos des applications d',electricit1 ,i pointed them out in speaking of the contact-breakers4 ,i also spoke of them in a paper on electro-magnets 7published in the ,annales tlgraphiques1 #ahfe71 and in several articles laid before the ,acadmie des ,sciences in #ahgb and #ahge on the conductivity of filings and conducting powders4 ,m4 ,clrac1 in #ahfe1 also used them to obtain variable resistances4 #f ,in #ahfe ,i was able to verify this observation when tightening the spirals of an electro-magnet on a naked wire4 ,the greater the number of spirals under pressure1 the more definite were the differences of resistance in the magnetising helix4 #g ,m4 ,hellesen communicated the plan of his instrument to me on ,may #c1 #ahgh1 and his experiments were made in ,copenhagen three weeks earlier4 #h ,m4 ,m4 ,j4 ,page had already noticed that if a telephone is placed in the circuit of the primary helix of an induction coil1 while the secondary helix of this instrument is placed in the circuit of one of ,m4 ,lippmann's capillary electrometers1 a movement of the mercurial column of the electrometer takes place at each word1 and this movement is effected towards the capillary end of the tube1 in whatever direction the current is sent by the telephone4 ,this is because the mercury always tends to move more rapidly at its capillary end than at the other extremity4 #i ,mr4 ,edison1 in a letter written ,november #be1 #ahgg1 writes that he has made two telephones which act with copper diaphragms1 based on ,arago's effects of magnetism by rotation4 ,he ascertained that a copper diaphragm might replace the iron plate1 if its thickness did not exceed #a_/cb of an inch4 ,the effect produced is slight when the copper diaphragm is placed between two corresponding instruments2 but when the sender only is furnished with the copper diaphragm1 and the receiver is arranged as usual1 communication becomes easy4 ,mr4 ,preece repeated these experiments1 but he only obtained very slight and indistinct effects3 he consequently believes that they are of no practical use1 although very interesting in theory4 #aj ,mr4 ,bell had previously made a like experiment1 which suggested to him that molecular vibrations had as much to do with the action of the telephone as mechanical vibrations4 #aa ,m4 ,bosscha1 who has published in the ,archives nerlandaises an interesting paper on the intensity of electric currents in the telephone1 says that the minimum intensity of currents necessary to produce a sound in a telephone by the vibration of its diaphragm may be less than #ajj_/ajjj of a ,daniell element1 and the displacement of the centre of the diaphragm would then be invisible4 ,he was unable to measure exactly the range of movements produced in the diaphragm by the influence of the voice1 but he believes it to be less than the thousandth part of a millimtre2 and from this it follows that1 for a sound of #hhj vibrations1 the intensity of the induced currents developed would be #jjjjjgib of the unit of electro-magnetic intensity4 #ab ,mr4 ,warwick describes his experiments as follows3 #8,the magnets employed were nearly of the usual size1 #a inch in diameter1 and nearly eight times as long4 ,at first ,i employed iron disks1 but ,i found them to be unnecessary4 ,when ,i had discarded them1 ,i tried several substances3 first a thin disk of iron1 which answered perfectly both for sender and receiver4 ,a disk of sheet iron1 about of an inch in thickness1 did not act so well1 but all that was said was quite understood4 ,in making experiments with the disks1 ,i simply placed them above the instrument1 without fixing them in any way3 the wooden cover and the conical cavity were also laid aside1 because the transmission and reception could be effected as well without them4 ,this part of the instrument seems to be superfluous1 since1 when the disk is simply placed level to the ear1 the sound seems to be increased by being brought nearer4 ,although iron acts better than anything1 it appears that iron disks are not absolutely necessary1 and that diamagnetic substances also act perfectly4 ,i wished that my assistant1 who was at some distance1 and could not hear any direct sound1 should continue his calculations4 ,i took away the iron disk and placed across the instrument a wide iron bar1 an inch thick4 ,on applying my ear to it1 ,i could hear every sound distinctly1 but somewhat more faintly4 ,a piece of copper1 three inches square1 was substituted for it3 although the sound was still distinct1 it was fainter than before4 ,thick pieces of lead1 zinc1 and steel were alternately tried4 ,the steel acted in almost the same way as the iron1 and1 as in the other cases1 each word was heard faintly but distinctly4 ,some of these metals are diamagnetic1 and yet the action took place4 ,some non-metallic substances were next tried2 first a piece of window-glass1 which acted very well4 ,the action was faint with a piece of a wooden match-box2 but on using pieces of gradually increasing thickness the sound was sensibly increased1 and with a piece of solid wood1 #a inch in thickness1 the sound was perfectly distinct4 ,i next replaced it by an empty wooden box1 which acted very well4 ,a piece of cork1 inch thick1 acted1 but somewhat faintly4 ,a block of razor-stone1 #b inches thick1 was placed upon the instrument2 and1 on applying the ear to it1 it was quite easy to follow the speaker4 ,i then tried to hear without the insertion of any substance1 and1 on applying my ear quite close to the coil and magnet1 ,i heard a faint sound1 and on listening attentively ,i understood all that was said4 ,in all these experiments the sounds were perceived1 but the sounds transmitted or attempted did not act precisely alike4 ,the sound of a tuning-fork1 placed on the iron disk itself or on the case of the instrument1 was clearly heard3 thin iron disks were more effective for articulate speech4 ,with other substances1 stone1 solid wood1 glass1 zinc1 c41 the sound of the tuning-fork was heard1 whether it rested upon them1 or the vibrating fork was held above them4 ,these substances were not adapted for transmitting the sound of the voice4 ,these were all laid aside1 and the sounding instrument was held directly above the pole of the magnet3 the sound was clearly heard1 although there was nothing but air between the end of the magnet and the tuning-fork4 ,the sound was perhaps less intense when the tuning-fork was held directly above the pole1 than when it was at the end of the magnet4 ,i next tried if my voice could be heard with this arrangement4 ,the result was rather doubtful1 but ,i think that some action must have taken place1 for the tuning-fork was heard when it was simply vibrated near the pole4 ,the effect of the voice can only have differed in the degree of intensity3 it was too faint to be heard at the other extremity4 ,i repeated these effects2 ,i assured myself of them1 and ,i succeeded in transmitting sounds distinctly on the pole without a disk1 and1 on the other hand1 by applying my ear to the instrument1 ,i was able to hear distinctly all that was said1 although there was no disk4' #ac ,these are his own words3 #8,the articulation produced from the instrument was remarkably clear1 but its great defect consisted in the fact that it could not be used as a sending instrument1 and thus two telephones were required at each station1 one for transmitting and one for receiving spoken messages4' #ad ,these carbons are made by heating1 in a temperature gradually raised to white heat1 fragments of deal of a close fibre1 which is enclosed in an iron tube or box hermetically sealed4 #ae ,mr4 ,willoughby ,smith varied this experiment by placing a packet of silk threads coated with copper on the disconnected ends of the circuit1 which were arranged at right angles with each other4 ,under these conditions the instrument became so sensitive1 that the current of air produced by a lamp placed above the system1 caused a decided crackling noise in the telephone4 #af ,mr4 ,hughes observes on this subject that carbon is a valuable material for such purposes1 since it does not oxidise1 and its effects are greater when combined with mercury4 ,he takes the prepared charcoal used by artists1 brings it to a white heat1 and suddenly plunges it in a bath of mercury1 of which the globules instantly penetrate the pores of charcoal1 and may be said to metallise it4 ,he also tried charcoal coated with a deposit of platinum1 or impregnated with chloride of platinum1 but this was not more successful than the former method4 ,if the charcoal of fir-wood is brought to a white heat in an iron tube1 containing tin and zinc1 or any other metal which readily evaporates1 it is metallised1 and is adapted for use if the metal is subdivided in the pores of charcoal and not combined with it4 ,when iron is introduced into carbon in this way it is one of the most effective metals4 ,the charcoal of fir-wood1 in itself a bad conductor1 may thus acquire great conducting power4 #ag ,mr4 ,hughes remarks that the vibrations which affect the microphone1 even in speaking at a distance from the instrument1 do not proceed from the direct action of the sound waves on the contacts of the microphone1 but from the molecular vibrations produced by it on the board which serves to support the instrument2 he shows1 in fact1 that the intensity of sounds produced by the microphone is in proportion to the size of the surface of this board1 and when the sending microphone is enclosed in a cylindrical case1 its sensitiveness is not much diminished if the surface of the box enclosing the whole is sufficiently large4 ,from this point of view he has sought to increase the sensitiveness of his instruments by fixing the frame on which the moveable parts of the sender and receiver revolve on a spring plate4 #ah ,helmholtz's resonator is based upon the principle that a volume of air contained in an open vase emits a certain note when placed in vibration1 and that the height of the note depends on the size of the vase and of its opening4 ,helmholtz makes use of a globe with a large opening on one side and a small one on the other1 and the small one is applied to the ear4 ,if a series of musical notes take place in the air1 the one which is in harmony with the fundamental note of the globe is intensified1 and can be distinguished from the rest4 ,the same effect takes place when1 on singing to a piano accompaniment1 some strings are heard to vibrate more strongly than others1 namely1 those which vibrate in unison with the sounds emitted4 ,the resonators are made in various ways2 those most generally used are cases of different lengths which also serve as sounding-boxes4 #ai ,i give the text of ,m4 ,cros' sealed paper1 opened by his request1 at the ,acadmie des ,sciences1 ,december #c1 #ahgg3--#8,speaking generally1 my process consists in obtaining traces of the movement to and fro of a vibrating membrane1 and in using this tracing to reproduce the same movements1 with their intrinsic relations of duration and intensity1 either on the same membrane or on one adapted to give out the sounds which result from this series of movements4 #8,it is therefore necessary that an extremely delicate tracing1 such as may be obtained by passing a needle over a surface blackened by fire1 should be transformed into a tracing1 capable of sufficient resistance to guide an index which will transmit its movements to the membrane of sound4 #8,a light index is fastened to the centre of a vibrating membrane2 it terminates in a point 7a metallic wire or tip of a feather7 which rests on a surface which has been blackened by fire4 ,this surface forms part of a disk1 to which the double action of rotation and rectilinear progression has been given4 ,if the membrane is at rest1 the point will trace a simple spiral2 if the membrane vibrates1 there will be undulations in the spiral1 and these undulations will represent the precise movements of the membrane in their duration and intensity4 #8,by a well-known photographic process a transparent tracing of the undulations of the spiral can be represented by a line of similar dimensions on some resisting substance1 tempered steel for example4 #8,when this is done1 this resisting surface is placed in a turning machine which causes it to revolve and advance with a velocity and motion similar to those by which the registering surface was actuated4 ,a metallic point if the tracing is concave1 or a grooved index if it is in relief1 is kept upon the tracing by a spring1 and the index which supports this point is connected with the centre of the membrane which produces the sounds4 ,under these conditions1 the membrane will be actuated not by the vibrating air1 but by the tracing which guides the index1 and the impulses will be precisely similar in duration and intensity to those to which the registering membrane was subjected4 #8,the spiral tracing represents equal successions of time by increasing or decreasing lengths4 ,there is no inconvenience in this1 since the turns of the spiral are very close together1 if only the circumference of the turning circle is used2 but then the central surface is lost4 #8,in all cases the tracing of the helix on a cylinder is much more satisfactory1 and ,i am now trying to make this idea practicable4' #bj ,never make a contact between the stylus and the cylinder until the latter is covered with the tinfoil4 ,do not begin to turn the cylinder until assured that everything is in its place4 ,take care1 when the stylus returns to the point of departure1 to bring the mouthpiece forward4 ,always leave a margin of from five to ten millimtres on the left and at the beginning of the sheet of tinfoil2 for if the stylus describes the curve on the extreme edge of the cylinder1 it may tear the sheet or come out of the groove4 ,be careful not to detach the spring of the caoutchouc pad4 ,to fix the tinfoil1 apply varnish to the end with a paint-brush2 take this end between the finger and thumb of the left hand1 with the sticky part towards the cylinder2 raise it with the right hand and apply it quite smoothly to the cylinder2 bring round the sticky end1 and join them firmly4 ,to adjust the stylus and place it in the centre of the groove1 bring the cylinder to the right1 so as to place the stylus opposite the left extremity of the tinfoil2 bring forward the cylinder gently and by degrees1 until the stylus touches the tinfoil with force enough to imprint a mark4 ,observe if this mark is quite in the centre of the groove 7in order to do this1 make a mark with the nail across the cylinder71 and if it is not1 adjust the stylus to the right or left by means of the little screw placed above the mouthpiece4 ,the depth of the impression made by the stylus should be millimtre1 just enough for it to leave a slight tracing1 whatever the range of vibrations may be4 ,to reproduce the words1 the winch must be turned with the same velocity as when they were inscribed4 ,the average velocity should be about eighty turns a minute4 ,in speaking1 the lips must touch the mouthpiece1 and deep guttural sounds are better heard than those which are shrill4 ,in reproducing1 the tightening screw must be loosened and brought in front of the mouthpiece1 the cylinder must be brought back to its point of departure1 the contact between the stylus and the foil must be renewed1 and the cylinder must again be turned in the same direction as when the sentence was spoken4 ,to increase the volume of reproduced sound1 a tube of cardboard1 wood1 or horn may be applied to the mouthpiece2 it must be of a conical form1 and its lower end should be rather larger than the opening of the mouthpiece4 ,the stylus consists of a ,no4 #i needle1 somewhat flattened on its two sides by friction on an oiled stone4 ,the caoutchouc pad which connects the plate with the disk serves to weaken the vibrations of the plate4 ,if this pad should come off1 heat the head of a small nail1 apply it to the wax which fastens the pad to the plate or to the spring1 so as to soften it2 then press the caoutchouc lightly1 until it adheres to the place from which it was detached4 ,the pads must be renewed from time to time1 as they lose their elasticity4 ,care must be taken in replacing them not to injure the vibrating plate1 either by too strong a pressure or by grazing it with the instrument employed to fix the pad4 ,the first experiments should be with single words or very short sentences1 which can be extended as the ear becomes accustomed to the instrument's peculiar tone4 ,the tone is varied by accelerating or slackening the rotatory movement of the cylinder4 ,the cries of animals may be imitated4 ,instrumental music may be reproduced by placing a cardboard tube before the mouthpiece4 ,the airs should be played in rapid time1 since1 when there is no system of clockwork1 they will be more perfectly reproduced than those which are played slowly4 #ba ,we confess that we find it difficult to believe in this property of the phonograph1 from which we have only heard the harsh and unpleasant voice of ,punch4 #bb ,the action of this pedal is effected by two little rockers1 so connected that the upper damper is lowered a little before the lower damper is raised--a condition necessary to produce the quivering motion of the plate which furnishes the rolling r4 #bc ,the arrangement of this part of the instrument is remarkable in this particular1 that in the case of certain letters the air is ejected with more or less force through the pipe ,i1 while in the case of other letters the air is drawn into the same tube4 ,since ,i was unable to see the internal arrangement of these cavities1 ,i can only give an imperfect account of the mechanism at work4 ,transcriber's ,notes ,punctuation1 hyphenation1 and spelling were made consistent when a predominant preference was found in the original book2 otherwise they were not changed4 ,simple typographical errors were corrected2 unbalanced quotation marks were remedied when the change was obvious1 and otherwise left unbalanced4 ,illustrations in this e,book have been positioned between paragraphs and outside quotations4 ,footnotes1 originally at the bottoms of the pages that referenced them1 have been collected1 sequentially renumbered1 and placed near the end of the book4 ,the ,table of ,contents is not well-coordinated with the actual text4 ,the ,transcriber has not added missing entries1 but has attempted to correct page number discrepancies4 ,several diagrams use labels with prime marks1 but the accompanying explanations do not always include the prime marks4