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NEW YORK : »• APPi^ETON A OO MPANY. ^ ^- ^'' ft i8ir9. l/ TKH'S.'^^S Entered, according to Act of Congresp, !n the year 1878, by GEORGE B. PRESCOTT, In the Office of the Librarian of Congress, at Washington, PREFACE. The object which we have had in ™w, in preparing this descuptK,n of the more recent and useful improvementa i„ electncal «c.ence, and especially to explain the principles and opem.on of that marvellous p^ductiou. the Speak^ C phone. In g,vmg particular praminence to this part of the ^m however we have by no mean, lost aight'of an t e rn^tcr an connecfon therewith, of eonside,«ble historical im- portance and wh.ch has also elicited an unusual amount o( limeitra;r°' **■ '" ""^™°"=^ -^ *« -«-«"« stotements that have appeared from time to time, is, to s.v the f::r:o=:hVzc:rtn';:tv:= oMain all the facts as the/lTrd Zr C S". : we have found them, without favor or p^judice. ThrrT^e" I if: ": ^r;' *° t''^ "- '"^'^ ^--^ -•>- -« creait to accord to each of tlio a;^^^ have W„ en.,ed with the irTe'lS^:- xov^tiy -"f^rn'mnw^ n PREFACE. Within a short time past, a veiy extended application of elec- tncity to illuminating purposes has been made, both in thi» country and abroad, and just now public interest in this matter 18 very much excited. It was a long time after Davy's discovery that the electric current was capable of producing the most briDiant light, before the thought was seriously entertained of putting this agency to practical use as a light producing power But with the introduction of Nollet's improved magneto-electric machines the thing soon became an accomplished fact, by which the solution of the great problem is to be attained Later and more efficient machines have rendered this application of elec- tricity much more feasible, and to-day its field of usefulness for .certain purposes is as clearly defined as that of steam itself. Whether the further introduction of electi-icity for domestia lighting will realize the expectations of many who are at present studying the subject, remains yet to be seen. The economical side of the problem is still a debatable subject, and one also of very general interest, so that it is not at all surprising, consider- ing what has already been accomplished, that the public gives, easy credence to many extravagant statements made with regard to it. ° How much ground there may be for the anticipations of suc- cess which are so sanguinely indulged in by friends and pro- moters of the new light it would be difficult to say, as consider- able secrecy is properly maintained in regard to the devices at present. What has been said on the general subject in the chapters on electric lighting will, however, give the reader a fair knowledge of what has already been done, and thus enable him to judge with some degree of confidence what probability of success there is in prospect in the immediate future. y^- aKr!W3!acaa5=2 0. S A. COISTTENTS. I— The Speaking Telephone , ^*"- H.—Bell's Telephonic Researches Iir.~The Telephone Abroad '^^ IV.-Hisiory of the Production of Galvanic Music. ...'.*.*.'.'.'.'.'. ' ^^ v.— Gray's Telephonic Researches Vl.-Edison's Telephonic Researches ^" VII.— Electro-Harmonic Telegraphy VIII-Dolbear's Telephonic Researches , IX.-In,proven,ents of Channing. Blake and others.........''..'.''"*"" ^ X.-Tho Talking Phonograph XL— Quadruples Telegraphy XII.— Electric Call Bells XIII-The Electric Light ...' ''* XIV.— The Electric Light XVI.-DUP,., I„e,„,„, K,e„.,^M.^„, „, ,„,,,„ „^^ ^^^^ ^^^ ^Jll^.^. I u Q . tl G V( th fo en SUj grs by froi eel] beti m a galvanie batter^we.. m^t to' ""T' ""' '"° '^ oeU of water. WhenThr!!! ^'"^'' '*"' ""'<»• *" » between the opp^^ t^ liir nTr ^ ^^ "^"^^ decomposed, and a bubble of h^ri ""^^^^^ ^^s the bubble from ehampt: d^es 1^7 " ''' ^^^^^^' ^ observer, seeing it, knew L a 11 If" ''^'' ^^^ *^« the bubble was the signal But ir ^'^'°^' ""^ *^^t signal. But It was evanescent " ^^« snowfalls in the river A moment white, then melts forever." lu 1820, Oersted discoverpd rKnf u INTRODUCTION. discovered that a piece of iron, surrounded by a spiral wire through which a current of galvanism passed, would become magnetic. From this fact Ampere deduced the hypothesis that magnetism is the circulation of currents of electricity at right angles to the axis joining the two poles of the magnet That was a brilliant deduction ; but no practical result was produced from it until 1825, when the first simple electro-magnet was made by Sturgeon, who bent a piece of wire into the shape of a horseshoe, and wound a fine wire around it in a helix, through which the galvanic current passed ; and he found that the horse- shoe wire was magnetic as long as the current flowed- Then at once an attempt was made with Sturgeon's magnet to produce the electro-magnetic telegraph, but without success. The diffi- cul was that the biagnetic power could not be transmitted from the battery for more than fifty feet with Sturgeon's magnet, which was, therefore, entirely useless for the purposes of a telegraph ; and, in 1829, Professor Barlow published a scientific demonstration in England, which was accepted by the scientific world, that an electro-magnetic telegraph was impossible ; which was true in the then state of knowledge In 1830, Professor Henry deduced from the hypothesis of Ampere the invention now known as the compound electro- magnet He also answered the demonstration of Barlow, and proved that the electro magnetic telegraph was possible. In the same year he set up an electro-magnetic telegraph in Albany, over a line of a mile and a half in length, using a polarized relay, the armature of which was pivoted so as to vibrate between its poles as the current of electricity was reversed, thus transmitting intelligence by sound. In 1831, Professor Faraday made known his discovery of the phenomenon of magnetic induction. P INTRODUCTION. ' ' r ^ in 1834, Gauss and Weber constructed a li . , containing about 15,000 feet of wiLwhrch ^^^'^"^"^ -gneto-electric currents general 'i:';tj7^^^^^^^^ ''' latter was moved un nr a^ ^'^® ^^en the which it .71^^^ " tT "'"''; ''"""'"™' ""^«'. """-d Waiiam Thomson haa »ince 3 ""^^^P^-dence. Sir r^^ »a t.e.v .ivenrrrr^^T^ii!-:'"^ ''^'^- vanometer which beara his name. '""'""^^ ^^^^ In 1837, Steinheil diseovpmrl *\.^ • would .„e . a conduo: t *;ZCr' '"-• *'^ ^ a cireuit: Coolce invented . .^,™S "™ ^'^ >■> forming known as the needle Jeti ''^'''"'•"-^"etic semapho^ 'ace of a dial, iust aTS ro^L V " ^"^"^ "^'^ '"« on the hill tops : Mo.e invenW ht e^ , '""'""'°'^ ^"^S which he put in ope.tio:i^3^:^':":^'»^««o '«'cg«pl. - 18«. and Pj discovered Ztlr^r' '^""'■^'' Panies the disturbance of tb! '^' "°'""^ '«=com. when poised or s^e:deds^'::r::;:tt:r ^ "^' '-■ In 1861, Keiss discovered thr, , f '*'" ^"'ra'iona actuated by the human Xt'^:"'""»\''-P''-g» codd be of vocal sounds to be ^Z^^TZ ^ ' """^ '"'' "■^*- hy electm-magnetism. * *^""' "■"* "^P^-duced »uS;s't:rb?::::^r-r-.w..e.bytwoeom. wi-; and, in 1874, E isl^eZt '"T"^ "^^' <"■« the simultaneous t.nsmissionff^?""'*"'"^^ ^■^^'^» 'or same conductor oommumeations over the IV INTRODUCTION. / ) L and rhythm, could be reproduced at a distance ; and subsequently- conceived the idea of controlling the formation of electric waves by means of the vibrations of a diaphragm capable of responding to all the tones of the human voice, thus solving the problem of the transmission and reproduction of articulate speech over an electric conductor. In 1876, Bell invented an improvement in the apparatus for the transmission and reproduction of articulate speech, in which magneto-electric currents were superposed upon a voltaic cir- cuit, and actuated an iron diaphragm attached to a soft iron magnet During the same ;year, Dolbear conceived the idea of substitut- ing permanent magnets in place of the electro-magnets and battery previously employed, and of using the same instrument for both sending and receiving, instead of employing instru- ments of different construction, as had been previously done. r In 1877, Edison applied to the telephone the discover}- made by hinisielf a few years before, )f the variation of resistance which carbon and certain other semiconductors undergo when subjected to a change of pressure. By this means h') not only succeeded in varying the strength of the battexy current in unison with the rise and fall of the vocal utterances, but, at the same time, also obtained louder articulation. d. X9 /■■^v ■■' ^<.-- THE 1/ SPEAKING TELEPHONE AND ELECTRIC LIGHT, CHAPTER I THE SPEAKING TELEPHONE. # The Speaking Telephone, a recent American invention, which at the present moment is exciting the wonder and admiratfon 5 the cvili^ world, ,s a device for tmnsmitting to a dist^n,^ over an electric cireni^ and accunttely reproducing at any dS place, v»ons kmds of sounds, including those of the tam™ vo,ce The function of the telephone if analogous t^ Sof aspeakmg tube capable of almost infinite extension th™! itTe':""'"" '^' '^ "^^ °" - readily r'wSr;^ sons ID the same room. ^ Before proceeding to give a description of the apDaratus employed for communicating or reproducing articulately at a distance by the telephone, it will be well to devote Xe «>n ^deration to the process by which the ear distinguish Zvibr^; w„ ^ K "^><= V"""""°''<"'''y «<=' "PO" it, for by this means we may be enabled to ascertain the conditions under whiehT rsi:i '--^''^ "■'— -- - ^-^ °^- e«*: It is well known that the sensation which we call sound ia wmveyea Irom the tympanum to the auricular nerves in tl,« w ndS?, *' "":■ "^ ■"^""^ <" ^ mechanical a^^r^tW wonderful deli««:y and precision of action, consisting of TZZ o, bones termed respectively the hammer, Lvil and !t,lp fo ficwSiot '??h°'"°T *""" by eleitro-magnetU^^^a* co"s sC^: of the mechanism of the human L ia employed, to the :f.l\-'''"u^,?™''"™'» - *"?•■«««• corresponding h -..p„nu.„, vvh,eh oy ,te vibrations generates and "controls 6 THE SPEAKING TELEPHONE. an electric circuit extended to a distant station by a metallic conductor. If we analyze the process by which the ear distinguishes a simple sound, we find that a tone results from the alternate ex- pansion and condensation of an elastic medium. If this process takes place in the medium in which the ear is situated, namely, the atmosphere, then at each recurring condensation the elastic membrane or tympanum will be pressed inward, and these vibra- tions will be transmitted, by the mechanism above referred to, to the auricular nerves. The greater the degree of condensation of the elastic medium in a given time, the greater is the amplitude of the movement of the tympanum, and consequently of the mechanism which acts upon the nerves. Hence it follows that the function of the human ear is the mechanical transmission to the auditory nerves of each expansion an(^ contraction which occurs in the surround- ing medium, while that of the nerves is to convey to the brain the sensations thus produced. A series of vibrations, a definite number of which are produced in a given time, and of which we thus become cognizant, is called a tone. The action which has thus reached our consciousness, beino- a purely mechanical one, may be rendered much more easy of comprehension by graphical delineation. If, for example, we assume the horizontal line a i to represent a certain period of time, let the cui-ves extending above the line a b represent the a- -h sn -cessive condensations ( -f ), and the curves below the line the successive expansions ( — ), then each ordinate represents the degree of condensation or expansion at the moment of time cor- responding to its position upon the line a h and also the amplitude of the vibrations of the tympanum. A simple musical tone results from a continuous, rapid and uniformly recurring series of vibrations, provided the number of THE nd th» ear be, i„^p,y^ ^^ appreciating the Z.d.'^ ''' '^ The ear distinguishes three distinct chamcteristics of sound • lo» ^^ '°!'t°;P"°>'. by virtue of which sounds arehi..h or kw and which depends upon the rapidity of the vibratorymove- ment The more rapid the vibrations the more acute wiU beX 2. The intensity, by virtue of which sounds are loud or ,„ff «nd which depends upon the amplitude of the vibrations ^ 8. The quality, by which we are able to distin<.uish a note mounded upon, for example, a violin, from the slme 12 when sounded upon a flute. By a remarkable series of ex^,^ mental mvestigations Helmholtz succeeded in demlSr .hat the different qualities of sounds depend altogethrrrh! number and intensity of the overtones which accomXv ,h! Z7ZTZ "' '"rr"''- '^"^'^'^-n'ow'ristCo :ire7^::s^ri^;^r ^^ ''- '"'~'- lengthlf r::„rHtJ::irret..;d zr - -'''-'" diffei^nt tres St «« T' ""^ "' "^'"'""^ « "" resented bXT urn !hirf'„ "'T *" *"*"' *°™ '^ "'P" i. repiesenid by lYfftt'etTwr ^t^ *« '"^"'""^ " 8 THE SPEAKING TELEPHONE. In fig. 1 three distinct simple tones, c, g and e are represented, the rapidity of the vibrations being in the proportion of 8, 6 and 5. The composite tone resulting from the simultaneous pro- duction of the three simple tones is represented graphically by the fourth line, which correctly exhibits to the eye the effect pro- Piga. 1, 2, 3. duced upon the ear by the three simultaneously acting simple tones. Fig. 2 represents a curve formed of more than three tones, in which the relations do not appear so distinctly, but a musical REISS'S MUSICAL TELEPHONE. \l 9 We may even understand by referenc** tn firr q i, •. • , height above or denth biw tT f *''"' <=<>"P™tive qua.it, b, the foJoT'L ttls Lt^T It""^''^ ''^ easy to underatand that if k ^"^mselves. It la, therefore, W^adein^s^eiTAititoTSSlrG" H. apparatus was constructed in the maLtttttT"''' clearn^ the applil cL W Ih'^ ^/ir °^ ^"^ ""^ -''« "' recipmcal .mnsmission in ole d,W '^'^ T' '' °™"S<='^ «''• omitted. Furthermo,^ i? mav ^ n " " ""' <>"'«'• have bee:, paratus wasconstmcrd'Sfo X '""^ """• "= ">« "P" to a „id„ ci«=,e the dLr ttbtlTJZfrt"^'"""'" the p<«ibility of extending the actbn oTtbl " '''"" ""^^' tonce beyond the I,mi, of the diZT.ltiLln^^'"'"" "' * <"" been taken into , Adoration ^?'. "?'""" »f the current had not ohanieal conatrucfo.,, a?d ts r,~n T™ ''"'^"°" °' ">»" nomena under consideration I'T ^'"""^ "P"" ""o Phe- nsweration. The tone transmitter A &„„! ^ / 10 THE SPBAEING TELEPHONB. is on the one hand connected by a metallic conductor with the tone receiver B at the distant station, and on the other with the battery C and the earth, or the return conductor. It consists of a conical tube, a 6, about 6 inches in length, and having a di- ameter of 4 inches at the larger and 1 J inches at the smaller end. BEISa's MUSICAL TELEPHOKE. , , j. It WM found by experiment that the material of which .!,„ , k. was oonstrttoted had no influence upon the action nf^K *" ratus, and the same is true as to its length An i„l ' ^T diameter of the tube w»s found to irn^r thelffe t TeT " surface of the tube should be made asLoTth f Isibk ThI smaller or rear end of the tube is closed by meaas^ .'n J^ »e.,iic"o:;dult '^ti'rz'h rr* r-^f ^"^'^^ braclcet. The proner llLh „T ^'"^ ' '""' ™PP<>rting respective arms rrandTlpl''7''°"'°"' *° ^ ^iven to thf mechanical coTsidera ,„„s ttJ^^Vt '' ''°'«™'"»'l "^ ^rm „ .shoald C^Zt^llfTf'' '^'""'^'''■'g''' of the necessary ^o..ZTt^ T72'C\t^, " ""-^ ^^''"' "■» force at d The lev,.r ;Lip I, ,fl ' possible exertion of i» order that^^m;i,r ^^ ^L^J. -<<- ''«"' ^ P^-b.e. membrane, as any inaccuLrv in^t -^ movements of the false tone It the ,^cl S^S^^ion W^Tk' ""' «^™ "* '° » Stale of rest the conZ°a, rf° T "^ '^^ *PP'"""' '» '» » maintains the levert^hi^^fitior Th^" ", f,^""*^ ^P™^ « connected „iih one pole of ?he batter/c thT M ° "1""''"^ ^ '' is connected to the earth „" . 1? ''^ ' ""'^'Po'^^f "I''"'' other station. Aflat"rin°„U ,,' T'."™ *'"> leading to the is provided with a oo„!« ° ? ""'""' '" *''« ^"^"'^ /, ™d the'lever „ " TColtn:fT™P°"'''"S '^ «■»' »' <^ »P™ iy meansofasc"wr ^^"'"'=°'"*°'P°"'"'Vbeadjusted of t:™:r:s'x:iVns;mfr" r^^"""^ "^ "■« -•- of the membran J rten maW * "'"'°/P''«f« "?» »!■« back side able ,0 place a^IlcaloTt vL? ^ "PP"^'"'' " '" ""l^'^ tube a i, in the form of rlliro7fl" ^^ '" *'""^'«' "P"" ""e longitudinal axis. " *'"'»*' »' "S^t angles to its mo?nXrat:„i!i^ir:r t "■' «'»°''°-«- •». the circuit of the ele^S^^ J ""' "' ""^ '""^"^^ in -on. ..,-rS---m^the.^^^^^ 12 THE SPEAKING TELEPHONE. which is attached to a broad but thin and light plate, i, which should be made as long as possible. The lever and armature are suspended from the upright support k, in the manner of a pendulum, its motion being regulated by the adjusting screw t and the spring s. In order to increase the volume of sound, the tone receiver may be placed at one of the focal points of an elliptical chamber of suitable size, while the ear of the listener is placed at the other focal point. The operation of the apparatus is as follows: When the different parts are in a state of rest the electric circuit is closed.^ If an alternate condensation and rarefaction of the air in the tube a i is produced by speaking, singing, or playing upon; a musical instrument, a corresponding motion is communicated to the membrane, and from thence to the lever c d, by whick means the electric circuit is alternately opened and closed at d g^ each condensation of the air in the tube causing the circuit to bo broken, and each rarefaction in like manner causing it to be closed. Thus the electro-magnet m m, of the apparatus at B,. becomes demagnetized or magnetized, according to the alternate condensations and rarefactions of the body of air contained in the tube a &, and consequently the armature of the electro-mag- net is thrown into vibrations corresponding to those of the mem- brane in the transmitting apparatua The plate «, to which the armature is attached, transmits the vibrations of the latter to the surrounding atmosphere, which in turn conveys them to the ear of the listener. It must however be admitted, that while the apparatus which has been described reproduces the original vibrations with per- fect fidelity, so far as their number and interval is concerned, it cannot transmit their intensity or amplitude. The accomplish- ment of this latter result had to await the further development of the invention. It was in consequence of this defect in the apparatus that the more inconsiderable differences of the original vibrations were distinguished with great difficulty; — that is to say, the vowel BEISS'S KU8I0AI. TELEPHONli. II 18 sounds were heard wiih more or less indistinotness, for th- jeason that the eharaoter of eaeh tone depends not n,e«l/Jo: the number of the sonorous vibrations, but upon their intensity whZh 1' T ^'^ """^ ^"""^ ''" «"> observed fa, . tZ while chords and melod.es were transmitted and reproduced with a surpr-smg degree of aoeuraey, single words, as pronounced i, ^7 °", '^i^'-^ "'™ *•"' i»*=«™1y h«arf, although in this case, also the inflections of the voice, interrogaWe. exclama tory, etc., couW be distinguished withoui difficult Figure e illustrates another form of Keiss's appmtus. A IS a hollow wooden box, provided with two apertures, one at the top and the other in front The former is coVered with a onembrane S, such ^ a piece of bladder, tightly strotched I a ciroular frame When a person sings into the mouthpiece M which ,s inserted in the front opening, the whole foree of S voice isconcentrated on the tight membrane, wUchTthrown into vibrations corresponding exactly with the vibratiolonle ZZlrf .^"'t"'"'"* "' *« ^"g'^K- A thin piece of pt ! .wi, t^^ *" "" """~ °' ""« >n«mbn»ne and connects «th the binding screw a, in which a wire from the battervTi^ teed. Upon the membrane reste a little tripod e/g, Jlu^ whifrl?'l^"'*"""e'^'''"P^"P°° *•>« <^-nlaf^'rameover which the skm IS stretched. One of them, / rests in a mer oury cup connected with the binding screw J The hirf L7T consKting of a platinum contact point. He» .„ the 4- °°*' ^' _ _e -.1 piau- u THE SP£AKING TELEPHONE. num which is placed upon the centre of the vibrating membrane and hops up and down with it By this means the closed circuit which passes through the apparatus from a to 6 is momentarily broken for every vibration of the membrane. The receiving innrumenc R consists of a coil or helix, enclosing an iron rod and fixed upon a hollow sounding box, and is founded on tha fact, first investigated by Professor Joseph Henry, that iron bars,, when magnetized by means of an electric current, become slightly elongated, and at the interruption of the current are re- stored to their normal length. In the receiving instrument these elongations and shortenings of the iron bar will succeed each other with precisely the same interval as the vibrations of the original tone, and the longitudinal vibrations of the bar will be communicated to the sounding box, thus being made distinctly audible at the receiving station. It will be seen that the result produced by these devices i» not the veritable transmission of sound by means of the electric current, but is simply a reproduction of the tones at some other point, by setting in action at this point a similar cause, and thereby producing a similar effect It is obvious that this J4>pttratus, IiJce the one previously de- scribed, is c^uible of producing only one of the three charac- teristics of sound, viss., its pitch. It cannot produce different degrees of intensity or other qualities of tones, but merely sings the melodies transmitted with its own voice, which is not vety unlike that of a toy trumpet Referring to the graphic repre- sentation of the composite tone in fig. 1, this apparatus would, reproduce the waves at properly recurring intervals, but they would ail be of precisely the same amplitude or intensity, for the reason that they are all produced by an electric current of the same strength. ^ In the spring of 1874 Mr. Elisha Gray, of Chicago, invented a method of electrical transmission by means of which the in- tensity of the tones, as well as their pitch, was properly repro- duced at the receiving station. This was a very important dis- covery—in fact, an essential prerequisite to the development of ". •SfS^^W^-'^'^^^Z'i^-^ GBAT'8 SPBiKINO TELEPHONE. n 15 fte telephone, both in respect to the reproduction o£ hannonie musical tones and of articulate speech, as it enabled any r^Z number ot d,fierent tones .0 be ^produced simulUpeou^w^ out destroying their individuality. In this method the transmitters were so arranged that a seoa- rate series of electrical impulses of varying strength ^ weU ^s ^pidity passed into the line, thus rep Judng at the dbtTnTend the mtensmes of the vibrations, corresponding to the rIw representation on the fourth or bottoiTline of fig fT this means a tune could be reproduced at any distnce JZ perfect accuracy, including its pitch and varying Stvt well as quality of sound. With a i^iving i^s^LeTit mnr E-s- fig. 6. ing of an electro-magnet, having ite armature rigidly fixed to one pole, and separated from the other by a snace of U n/ „ inch, and mounted upon a hollow soundinJ borsch te that of a^ohn, responded to all vibrations whieh wei communicated to It, the tones became very loud and distinct "^^^^^^t^^ Subsequently Mr. Gray conceived the idea of controlling fh« "„d "tL:ef -"i" e^^'e VrrXToTnnls' f 1^ kind tmversrng the atmosphere, so arranged as to reproduce problem oTrr' " '"'!"'°" Whenthiswts accompS Z e.tn^ G^^auuiur was theoretically solved. 16 THE SPEAKING TELEPHONE. The principle and mode of operation of Gray's original telephone are shown in the accompanying fig. 6. The per- son transmitting sounds speaks intx) the mouthpiece T*. D* is a diaphragm of some thin substance capable of respond- ing to the various complex vibrations produced by the human voice. To the centre of the diaphragm one end of a light metallic rod, N, is rigidly attached, the other extending into a glass vessel J, placed beneath the chamber. This vessel, whose lower end is closed by a metallic plug, P, is filled with slightly acidulated ■water, or some other liquid of the same specific resistance, and the metallic plug or end placed in connection with one term>cal of an electric circuit, the other end being joined by a very light ■wire to the rod N, near the diaphragm. It will thus be seen that the water in the vessel forms a part of the circuit through -which the current from a battery placed in this circuit will pass. H^ow, as the excursiuit of the line, which is constantly cha3by a cnn^t from the battery E. The vibmtions of' he Xet » , iSZ B. ^ S^^^^T"""-' '" *'"" °°"' "f *« o'ectro-magnet M, Which travei^e the circuit, and the magnitude of the-VonC «r y^^'^""^ *° *« «P«it7 andLplitude of the 'w tionsof the magnet; thus, for instance, when the small pTrm" nent msg„et is made to move toward M, a current oSiX ZL ^'',■^■°*oity will consist of a single wave or priTc'hof „:. T "i",?''"''"' "P°" «■« velocity^ofrte ap current will move Th. . . T.,^ ^ ■"°™ '""^ ''"'" " ! l"" 'his so that JhltThenr^^. '■'''"'"'"' '" "" "PP*"'" '"■^'i"". den.nI, Pi'sation goes from A to B or from B to A ^lepends simply upon the direction of the motion of H ^ L8 THE SPEA^ISG TELBPFONB. The electricity thus generated in the wire by such vibratory movements varies in strength, as already observed, with the variations in the movement of the armature ; the line wire be- tween two places will, therefore, be filled with electrical pulsa- tions exactly like the serial pulsations in structure. These induced electric currents aic very transient, and their effect upon the receiver B is either to increase or decrease the power of the magnet there, as they are in one direction or the other, and consequently to vary the attractive power exercised upon the iron plate armature. Let a simple sound be made in the tube, consisting of 256 vibrations per second; the membrane carrying the iron will vibrate as many times, and so many pulses of induced elec. tricity will be imposed upon the constant current, which wiU each'act upon the receiver, and cause so many vibrations of the armature upon it;' and an ear held near r will hear the sound with the same pitch as that at the sending instrument If two or more sound waves act simultaneously upon the membrane, its motions must correspond with such combined motion ; that is its motion v/ill be the resultant of all the sound waves, and the corresponding pulsations in the current must reproduce at B the same effect Now, when a person speaks in the tube, the membrane is thrown into vibrations more complex m structure than those just mentioned, differing only in number and inten- sity. The magnet will cause responses from even the minut- est motion, and, therefore, an eat near r will hear what is said in the tube. Consequently, this apparatus is capable of transmitting both the pitch and intensity of the tones which enter the tube T. The receiving instrument consists simply of a tubular electro-magnet R, formed of a single helix with an ex- ternal soft iron case, into the top of which is loosely fitted the iron plate r, which is thrown into vibrations by the action of the macrnetizing helix. The sounds produced in this manner were quite weak, and could be transmitted but a short distance ; but the mere accomplishment of the feat of transmitting electric {ja,>„ia«a nvfir a metallic wire which should reproduce articu- dolbbar's speaking telephone. 19 late speech, even in an imperfect manner, at the farther end ex- cited great interest in a scientific as well as popular point of view, throughout the civilized world. During the ensuing autumn some important changes in the telephone were effected, whereby its articulating properties were greatly improved. Professor A. E. Dolbear, of Tufts Col- lege, observing that the actual function of the battery current with which the line was charged in Bell's method had simply the effect ol polarizing the soft iron cores of the transmitting and receiving instruments, or of converting them into permanent magneto, and that the mere passage of the constant voltaic cur- rent over the Ime had nothing to do with the result, conceived the Idea of maintaining the cores in a permanently magnetic or polarized state by the inductive influence of a permanfnt mag- "UN? fig. 8. net instead of by a voltaic cuiTent He therefore substituted permanent magnets with small helices of insulated co^pe ^'e surrounding one or both poles, in place of the electro-magrto and battery previously employed. '"sui-ra Another important improvement made by him consisted in usmg the same instrument for both sending and relvZ n^d J%::redtctr heJLT'?-"^ T of "ary permanent bar magnet, N S, a single ,^. „ a m....,,],;, uiapuragra, v, consisting of a disk of thin 20 THE SPEAKING TELEPHONE. sheet iron, two and a quarter inches in diameter and one fiftieth of an inch thick, forming an armature to the magnet, N S. The vibratory motions of the air produced by the voice or other cause are directed towards and concentrated upon the diaphragm, D, by means of a mouthpiece, T. It will thus be seen that when vibrations are communicated to the air in front of the mouth- piece the impact of the waves of air against the elastic diaphragm will cause a corresponding movement of the latter. This in turn, by reacting upon the magnet, disturbs the normal magnetic con- dition of the ba", and since any change of magnetism in this tends to generate electrical currents in the surrounding helix, the circuit in which the helix may be placed will be traversed by a series of electrical pulsations or currents. Moreover, as these currents continue to be generated so long as the motion of the diaphragm continues, and as they increase and decrease in strength with the 'amplitude of its vibrations, thus varying with the variations of its amplitude, it is evident that they virtually possess all the physical characteristics of the agent acting upon the transmitting diaphragm. Consequently, by their electra- magnetic action upon the magnet of an apparatus identical with the one above described, and placed in the same circuit at the receiving end, they will cause its diaphragm to vibrate in exact correspondence with that of the transmitting apparatus. During the past year many ingenious persons have turned their attention to the subject of telephones, and by the introduction of various modifications have succeeded in greatly improving the invention, so as to make it available for practical applica- tion. Prominent among these is Mr. G. M. Phelps, mechanician of the Western Union Telegraph Company, to whose ability in the invention of valuable improvements, as well as in the scien- tific arrangement of details in the construction of the apparatus, the public is indebted for some of the most effective telephones yet introduced. The peculiar excellence of these instruments consists in their distinct articulation, combined with a loudness of utterance that is not often met with in the numerous other forms that have appeared up to thb present time. Both of these * PHELPS'S DUPLEX TELEPHOHE. 21 qu^ities, mamfestlyso desirable, a«, developed ia these mstm- mente m a very rem^-kable degree, while the Lance over wS. they may be used is also another of their distinguishing oW ^ns^,c^ ou^aite of over one hundred mUes having b«n worM by them with the most admirable resulta The most essential improvements introduced by Mr. Phelns consist m combining two or more vibmting diaph.4ms and t^ or more corresponding magnetic cores, enveloped in separat^ helices, connected in the same cire„i„ ;ith a single mou^C :i:jm?'™'^' '" """""^8 two magnetic cor^Tta oombmed with sepan.te diaphmgms and <^ls, and?Cle mouthpiece, upon opposite poles of the same permanent m^ Pig. 9. and in subdividing a single continuous induction plate into t wn ^ more separate and distinct a,.as of vibr.tion,lus ^i tu Uy to hp onrn-o/i • "''"">' wiin wnich it permits conversation m.L er,:'b^rsi:rTc"" "^'vr' """"^''^ '»-- '-- of harden^ st^lThi'ch ,TT ""'" P'™™^"' ""^S-o' « occunv but lif^. . ?' ""° »'■ """-g f"™. » as to ne:;fach:the* rh:,.": t„d' H? "; •'°'°' "°"'^"'^""' -pectively upon the north l^^^ ^::X:t ^ THE SPEAKING TELEPHONE. metallic diaphragms, D and D*, and the speaking tube or mouth- piece T, ivhich maj be made of wood, metal, or such other substance as fancy may suggest The diaphragms are placed upon opposite sides of a short cylindrical piece of hard rubber, provided with a lateral opening for the insertion of the mouth- piece, and, together with it, form a sort of chamber, within which the air is alternately condensed and rarefied, in conse- quence of the motion or impulses communicated to its particles by the voice when directed toward the opening of the tube. Hence, it will be seen that edch condensation exerts an outward pressure of its own upon the diaphragm, while each rarefaction causes a corresponding pressure from the external air, and thus a vibratory movement is imparted to both diaphragms at one and the same instant ; consequently, if the helices are so con- nected that the direction of the current pulsations, which are inductively produced by the vibrations of the diaphragms in the manner already explained, are similar when they become united in the line, the magnetic force, as exhibited in the receiving ap- paratus at the distant station, will be augmented considerably above that produced by the action of a single coil and diaphragm alone, and thereby a corresponding increase in the loudness of the sound will be produced. The best effects are obtained when instruments of this form are employed both in transmitting and receiving, the advantages they possess for the latter purpose being quite as marked as for the former, as will appear obvious enough when we consider that every time a current passes through the helices the attractive forces thereby imparted to the cores or magnet poles are such as to cause the centres of the two diaphragms to be drawn directly from each other, thus produc- ing a much greater rarefaction of the air within the chamber than could be obtained by the action of a single diaphragm alone. A corresponding condensation, on the other hand, is pro- duced at each cessation of the current, owing to the return of the diaphragms, in virtue of their elasticity to their normal position. The greater the degree of condensation and rarefaction, how- eveFj the oreatfir the aniDlitude of the sonorous vibrp.tiorss one in coDse- PHBLPS'S DUPLEX TELBPHONB. I ! 23 expression being the equivalent of the other-and, therefore, the greater w, 1 1^ the intensity or loudness of the sound produced. We might add in this connection, that the introduction of a second hehx in the line circuits presents in itself a slight disad vantage. This arises from the inductive action of the pulsatorv cuirents upon themselves in the coils and the reactive influence of the core whereby other and opposing currents are produced which tend to delay, and, in part, neutralize the eflects of the fomer The latter are termed extra currents, to distinguish them from those produced in circuite exterior to that in which lorss one I Fig. 10. pant" I Z, *■" ""^"S- ^^ ""^^ ■"« '■<"""' «<> >«=<»■»■ 13 brought m proximity to another, as is the case iu maene hehc^, ,t „,n readily be seen that ;hey must become the more troublesome as the number of stations am inereasel-it b^in^ ne^ry to keep the vibratory bells at each^Ln i„"^! cuits, m order that calls may be heard. By the use of con densers consisting of alternate sheets of tin foil and par^ffiTed paper placed around the bell coils, wo are enable ,„^!™„r ine UitticuUy the« currents would otherwisep'resenL 'col u THE SPEAKING TELEPHONE. densers, therefore, become almost indispensable in cases where many telephones are employed in one circuit The instrument we have just described is made separate by itself, to be used as a transmitting or receiving instrument, or it is combined in a box represented below, with a call bell and th& oval shaped telephone to be con«dered presently. In the latter case it is usually employed to transmit alone, while &e oyal form serves for receiving ; it can, however, be used for either purpose. Mg. 11. Mr. Phelps also found that the efficiency of the telephone for transmitting the human voice was much improved by reducing the cavity or chamber in which the diaphragm vibrates to the smallest practicable dimensions. Further gain was also made by cushioning the bearings of the diaphragm on both sides with rings of paper. In the form described below the diaphragms are still further cushioned on the side towards the magnets by a PHELPS'S DUPLEX TELEPHONE. ' £6 ato^ quality ch.«c.eristio of m<»t of .tee r ; .fifp W^^^^^^^ i^. 12. exte„"s'!tT "'.^"^ f°™' designed by Mr. Phelps, and now being extensively introduced by the American Telephone Comoanv k nS wth T^ ,? ""^^f ' *"P''"«" """J «°"^ i"'id«- I» con- nection with this there is also n «r"oll m-x-n-^- -1 - - • i ^■ contained in ihf, «ki u ^, "^afen,.tu-ciccincai maebine, ntamed m the oblong box shown in fig. 11, which is used for 26 THE SPEAKING TELEPHONE. operating u call bell when the attention of the correspondent at the distant station is required. The currents generated by this machine, when the crank is turned, are conveyed by the conducting wires through the helices of a polarized mag&et, shown on the under side of the cover, fig. 12, and cause the ham- mer attached to the armature lever to vibrate against the bell, thus producing a violent ringing during the time the crank is turned. By the use of polarized magnets — the latter so named on account of their armatures being permanent magnets — the arma- ture levers are retained in a definite position, depending upon the direction of the current last sent into the line, and no retractile spring whatever is required. At the same time, also, the alter- nating currents produced by the magneto-electrical machine are permitted to act wi^h their maximum power, as the repelling force exercised in one pair of coils urges the armature in the same direction as that of the attractive force in the other, and the two effects are thus added. It is usual to supply two telephones with this apparatus — two being preferable to one — as then one can be held to the ear while the other is being used to speak into. By this means any liability of losing a word while the instrument is being passed from the mouth to the ear, supposing one only to be used, is entirely prevented, and consequently the necessity for repetition avoided. When the telephone is not in use it is placed in a slide, as shown in fig. 11, which causes a spring, shown at the end of the box in fig. 12, to be pressed inward and cut out the instrument, leaving only the magneto machine and call bell in circuit. The spring, when in its normal position, on the other hand, cuts out the machine and call bell and leaves the telephone alone in circuit. Figc 13 represents a somewhat more expensive but at the same time also a more desirable combination of the telephone and its accessoriea The box is intended to be fastened permanently to the wall. It contains in addition to the extra loud telephone Phelps's dhplei telephoitk. ' ' 27 with doable diaphragms, which was described above a call hell andamagneto-electric ..achiao of improved constrain tI^" "« fJ^hatL^r"" '^" °^*'-'PP'-'- " in the mIZ circuit-the magceto machme. unlike that in the boi just noticed being cut out, so as to guard against accidental demag^eto W -%. 13. ^i-h to . r sometimes liable to occur. Wh.n ^e wi^n tosuud a sit;nai. however if i^ ««i 6u»j, However, it 13 only necessary to turn the' 28 THE SPEAKING TELEPHONE. crank of the magneto machine, shown in front of the case, and at the same time press upon the push button 0, which is visible on the left The latter movement, by a change of connection to be more fully described presently, puts the magneto machine in circuit, and thus allows the currents generated by it to pass into the line and act upon the distant call bells. The switch near the top of the case serves for cutting the ap- paratus in and out of circuit When it is turned to the right, and the telephone is in the fork or holder, as represented in the figure — in which case it pn ases against a button correspond- ing to the spring in the former box and cuts itself out of circuit — only the call bell is left in with the main line. When it ia .^::^ Fig. 14. turned to the left hand or opposite side, which should always be done whea left at night, all of the apparatus is cut out of circuit. A lightning arrester is provided in each box for the protection of the apparatus; but during thunder storms, and especially severe ones, it is best to cut the apparatus out of circuit altogetBer by means of the switch, as the best arresters sometimes fail. The accompanying diagrams, showing the internal arrangements of the different boxes, will give a much clearer understanding of the connections. Figure 14 represents the parts and connections of the improved apparatus, which is placed in a portable box, • like the one shown in figure 11, without, however, the additioa MAONSTO-ELEOTRIG BELL CALL. ase, and I visible meotion oaachine ; to pass r the ap- le rigbty sDted in respond- csircuit — len it ia 29 Jways be 3f circuit. )rotectiott especially iltogetBer lail. The ements of anding of nnections Eible box, i addition of what we have called the extra loud Speaking Telephone. In the ordinary working condition of the apparatus the switch S should be placed on the button contact, shown just to the right of it, and the telephone hung in its fork, which causes the spring A to be forced against the inside contact point The telephone and magneto machine are thus cut out of circuit, as will be seen on tracing the connections, but the call currents arriving from a distant station on the line, find a ready path ^g. 15. through the coils of the bell magnet B and spring below the push button C to the spring A, and thence by switfh S trilne again or ground, as the case may be, the final connection de- pending, of course, upon whether the station is located some- where m the centre or at the terminal of the line. A call given aSZh \t'^'°' '"^ *'' ^'^^""^ "'"' *^-^^-^' be heard at all the others, as the connections at each are precisely similar crank of the magneto man-hinp t^ r^».^oo .• _. .,. . , , ^,, _ -« , .„ ^,.^„o ayaiHat. luu push buttOU II! 30 THE SPEAKING TELEPHONE. C, 80 as to bring the adjacent spring in contact with the little connecting piece which is metallically joined to the coils of the machine. Unless this is done no current will be sent into the line, because it is by this means alone that the inductive appa- ratus is placed in the circuit When the button is down, the path opened for the current may be traced from the line terminal of the instrument by way of the bell aud magneto coils to the spring beneath C ; thence by way of spring A and switch S to line or ground. LINE UNE Fig. 16. It will be obvious that the above arrangement supplies the means for giving a variety of calls in case there are several offices in one circuit ; for, while turning the crank, the push button can be used, like a Morse key, to give different signals. The removal of the telephone from its fork or holder puts it in circuit, and cuts everything else out, as will readily be seen by tracing the connections. The manner in which the apparatus is cut out of circuit, by turning the switch S on the left hand con- tact point, will also be seen on referring to the diagram. Figures 15 and 16 show the internal connections and arrange- gray's battery TELEPHONI. qi ment of the large box, figure 16, being the arrangement for a ter m,nal, and figure 16 that for an intermediate stafion The loud spealiiing instrument is shown in both. Fienre 16 »lt? .1. .ho manner of connecting the condenser D a^u:dl ^rX" «. as to avo,d the previously noticed inductive difficulties whch present themselves when many sets of the apparatus .^ riac^ m one c^„^ The lightning arrester is representedTt L ft W.I1 hardly be necessary to say anything farther in re-mrd to the eonnecuons .„ .he last two figures, as the same letter^ hat wete used ,a the preceding figure have been retained for correspInT »g parts m these, and have, therefo,^, been al«adyZXd Fig. IT. Figure 17 represents a form of Gray's SoeaVincr T.i. i, manured by the Western Electric^TeS^^rCo^f;- tXF^r ^\^'^T- " '"="''" "f ""^ ^^i^^. ■■^'d-'oed to about one thn-d the natural s,.e, and designed toshow the internal meohan- len«I 7'°Ik °* *" "" '"""■ "' *"' ^ ^««» "=»' *« core C is fas. tened to the upper end of the curved metallic bar H , 1.^ hTnTeT *M"""" "' *'"> '^'^'P''"-- The 1 er n°' ■■ he handle .s m l,ke manner attached to the metallic brace B To th.s brace .s secured, by means of a stout screw, the iron nm $2 THE SPEAKING TELEPHONE. which holds the diaphragm ; thus the core and the diaphragm form the two ends of a rigid metallic system, every part of which is of sofk iron. Around the core two helices of insulated copper wire are wound. One of these— the polarizing helix— is somewhat longer than the other, and contains wire of larger gauge. In using the telephone, this helix is connected in circuit with a local battery. The soft iron system is in consequence rendered magnetic, the end of the core exhibiting opposite polarity to that of the dia- phragm confronting it By employing the battery current to charge the soft iron core, Mg. 18. a greater degree of magnetism ia thereby secured than could be obtained by the use of a permanent magnet of the same dimen- sions. The difference also of magnetic potential existing between the diaphragm and the core is increased by making these respectively the opposite poles of the same magnet. The other helix is made of very fine wire, and serves to con- vey to the line the undulating currents induced by the vibrating diaphragm. At any point on the line these currents may be reconverted into sound by introducing an instrument similar to the above. gray's speaking telephone. ' 83 In adjusting this telephone advantage is taken of the elasticitv H ^WsTnde'nf-^' has a t,,,,„,^ to approach tie Ct M This tendency ,s checked and regulated by the adiustinff r^Le'froSet: d'f' "^^ °^"^^ ''' '^^^^ ^'-- *--^' or recede trom the handle ; and, consequently, the diaphragm will also move to or recede from the core of the magnet Another of the forms devised by Mr. Gray is shown in fig 10 In this there are two diaphragms, and no battery i ulfd ^ me ngure. Ihe magnet also answers as a handle, by which ■%. 19, the instrument may be held convenientlv Twn c.u • are secured bv scr/w., ir. ti, ^""^«°iemiy i wo soft iron pieces of copper X whl, '^'P"^^''/ ^he magnet and carry helices leadiifg L^fr^J^^^^ ^7f *«g^tl^^r, and terminal wires TKo .^^^"^ ^^^6 to put the instrument in circuit of thif sheetrra^ 'Sirs r;'"Y''^^ f P"™"^ -i-ph^gms cates moti-- 4.^ ^-L- •>' , t^namoers, and thus commnni- - «ot,„. .„ .,„ mapU,^m^ The principle of the aoUon in 34 THE SPEAKING TELEPHONE. this apparatus is, of course, the same as that in the other forms of magneto telephones. It will be observed that all the Speaking Telephones which we have described, possess certain common characteristics em- bodied in Mr. Gray's original discovery, and are essentially the same in principle although differing somewhat in matters of de- tail. All, for example, employ a diaphragm at the transmitting end capable of responding to the acoustic vibrations of the au-; all employ a diaphragm at the receiving end capable of being thrown into vibrations by the action of the magnetizing helix, corresponding to the vibrations of the transmitting diaphragm ; all depend for their action upon undulating electric currents pro- duced by the vibratory motion of a transmitting diaphragm, which increases and decreases the number and amplitude of the electric impulses transmitted over the wire without breaking the circuit; and, fiWly, in all practically operative telephones, whether vocal or harmonic, the cores of the receiving mstru- ment are maintained in a permanently magnetic state by the inductive action, either of a permanent voltaic current or of a permanent magnet Repeated experiments have shown, also, that this permanent magnetic condition of the cores is absolutely essential, in order that the receiving magnet may become prop- erly responsive to telephonic vibrations, especially when these are of great rapidity and comparatively small amplitude. _ Mr. Thomas A. Edison, of Menlo Park, New Jersey, has m- vented a telephone, which, like that of Gray, shown in figure 6, is based upon the principle of varying the strength of a bat- tery current in unison with the rise and fall of the vocal utter- ance. The problem of practically varying the resistance con- trolled by the diaphragm, so as to accoraphsh this result, was by no means an easy one. By constant experimenting, however, Mr. Edison at length made the discovery that, when properly prepared, carbon possessed the remarkable property of changing its resistence with pressure, and that the ratios of these changes moreover corresponded exactly with the pressure. Fig. 20 rep- resents a convenient and ready way of showing the decrease in EDISON'S SPEAKIKO TELEPHONE, i , 35 resistaice of this substance when so subjected The device con- sists of a carbon disk, two or three cells of batterv and T T gent or other form of galvanometer. The carbon^ls ;iac:dt' teT^dTr ° P'''" '""'' '"' i°»«i -i* tte gatano.^ ter and battery in one circuit, through which the batterv Zl; plate the carbon IS subjected to a definite amount of pressure which :s shown by the deflection of the galvanometer nZk M^^\" ;?? """""^ °' <*^^^ As additional we,VM added, the deflection increases more and more so thnt w „ fully noting the deflections correspondingTo' fte Id^T crease of pressure we can thus follow the ^J.L 1! ; distance at our leisure. Here, ^C., ZsluZ^:!X -^ I^. 20. by vibrating a diaphragm with varying de^rep. .f against a disk of carbon, which is made tff ^'"''""^ of an electric circuit, the resistance of tt ^^^^ P^^^^^ preczse accordance with the degree of nl! ^^'^^/^^^^ vary in a proportionate variation woXe occ'a^^^^^^^^ the current. The latter wouM thus " In teT'*^ ^' istiosof the vocal waves and bvif= . , *" oharacter- of an electro-magnerSIt thfn I T°",,*''°"S'' *^ "^dium causing the latteft^ vS and tl ' */"" *" ""o*"' ^isk, Fig. 21 shows Thr t^!;r "' '■'P'''^''™ ""diWe speech -.%he oarC di:^ f .^X^dZT" H ^ "^ ^'"- near the diaphraem A A nU i 1 ^ *" '''*°''^ P»rt>on. B, D and G, whichTcottte'd t thetr "'° "■"""'"» P'^W the lines. A small Jece „f kv, ?""'■'' ""'""'■ "« *ow„ by centre of thtmll hH Lphra™'''' T'"^' »' '^ ''«««hed to thi -ory piece, 0, whioL'^teC'-"-""" "ghtly against an 1 ...__u aire^xj uvxr one oi the platinum 86 THE SPEAKING TELEPHONE. platei Whenever, therefore, any motion is given to the dia- phragm, it is immediately followed by a corresponding pressure upon the carbon and by a change of resistance in the latter, as described above. The object in using the rubber just mentioned is to dampen the movement of the disk, so as to bring it to rest almost immediately after the cause which put it in motion has ceased to act ; interference with articulation, which the prolonged vibration of the metal tends to produce in consequence of its Fig. 21. elasticity, is thus prevented, and the sound comes out clear and distinct It is obvious that any electro-magnet, properly j&tted with an iron diaphragm, will answer for a receiving instru- ment in connection with this apparatus. Fig. 22 shows a sending and receiving telephone and a box containing the battery. In the latest form of transmitter which Mr. Edison has intro- duced the vibrating diaphragm is -done away with altogether, it having been found that much better results are obtained when a EDISOS'a SPEAKING TELEPHOlfll. ' m rigid plate of metal is substituted in its place. With the nM vabmtmg diaphzagm the articulation pK,duced in I"«rt more or ta muffled, owing to slight changes which l^^Z 4sk occasions m the pressure, and which probably resulS ^dampenmg of the vib«>tions after having been ^^ started In the new arrangement, however, the 4o«]ation i^ l^g. 12. IliT^^ exceedingly well rendered that a whisper even m»v readily be transmitted and undei^tood The inSle nW ^ r.«».,,-„ f . - "^ ™"°'' . a much greater deoreo nt ' ■'""'"'-> Pven effort on the part of the^speakerTs thus 138 THE SPEAKING TELEPHONE. brought to bear on the disk tban could be obtained if only its small surface alone were used. The best substance so far discovered for these disks is lamp- black, such as is produced by the burning of any of the lighter hydrocarbons. Mr. Edison has found, however, that plumbago, hyperoxide of lead, iodid'- of copper powdered gas retort car- bon, black oxide of manj^- imorphous phosphorus, finely di- vided metals, and many sii: , .des may be used ; indeed, tufts of fibre, coated with various metals by chemical means and pressed into buttons have also been employed, but they are all less sensi- tive than the lampblack, and have consenuently been abandoned for the latter substance. With the telephone, as with the ordinary telegraphic instru- ments, there is of course a hmit beyond which the apparatus cannot be rendered practically serviceable, but in most cases this limit is sooner reached for the telephone than for other instruments that are employed for the transmission of telegraphic matter. One reason why this is so is probably due to the fact that the current pulsations generated by the vibrating diaphragm are made to follow each other with so much greater rapidity than those that are sent into the line by the ordinary hand manipulation, that less time is allowed for charging and discharging the line, and the phenomenon of inductive retardation thus becomes soonest manifest in the former case. Another reason, however, and perhaps the principal one, is that the disturbances created by the inductive action of elec- trical currents in neighboring wires combine with the signals, and so confuse the latter in many cases, that it becomes altogether impossible to distinguish them. It is necessary, therefore, when we wish to speak over long distances, or over wires in close prox- imity to Morse lines, either to employ some means for neutral- izing these disturbances, or to so increase the loudness of the ar- ticulation that it can be heard above this confused mingling of many sounds. One of the best means so far suggested for overcoming the diffi- culty is the employment of metallic circuits throughout for the Edison's telephonic repeater. SS telephone, placing the two wires forming a single circuit very close together, so as to render the inductive action practically the same in each. The resulting currents would thus neutralize each other and leave the telephone quite free. It is claimed that the inductive disturbances just noticed are much less marked with Mr. Edison's telephone than with any of the other forms, owing to the fact that the signals or sounds in the former are produced by stronger currents, and the re- ceiving instruments are made less sensitive to those fugitive currents that are always met with in telegraph lines. Mr. Edison has recently invented a telephonic repeater, which is designed to be used in connection with his apparatus for in- creasing the distance over which it may be made available. The princ^al parts are shown in fig 23. I is an induction coil, whose Mg. 23. secondary is connected in the main line L', into which the repeat- ing IS to be done; C is a carbon transmitter, included with battery B m the primary circuit, and operated by the magnet M instead of by the voice. The variations In the current pro- duced by speaking against the disk of the instrument at the transmittmg end of the line, cause this magnet to act on the re- peater diaphragm, and thus produce different degrees of pressure on the carbon disk and thereby change its resistance. A coitc- sponding change consequently takes place in the current of the pnmary coil, and thus gives rise to a series of induced currents IQ the seconnarv wlii^li into the line, and, oil reaching 40 THE SPEAKING TBLEPHONK. sation to be carried on r^^r^r.A -l , -^^ ^P^^'^ttedconver- -^'sr. 24. amngement of this kind tTI i • ^^^^^^^^^o^^ for an -;L;'rr£r*" -Si-it' TELEPHONE AND VIBEATING BELL. M 4^ itrr."r* ::-xr Tir '^"-^ p--^ with the ground ^^^epnones, T, also m communication consequently disappear, and the annatS to™ Wk "^"^ occasions a distinct tap upon the bell ^^ ™"°". therefore, and demagnetization a^ efc^^gty ^pTd ^e tal"^'*""*'? succeed each other with suffident%T| y ^k^^uTaT:""^ ous nnging «*i^iuii,_y to Keep up a contmu- distant corespondent placinl^^tat:^ nISuH tXht f m turn causine the hpll at +1.^ * ^- •; • , ^^^^'^") and thereby signal to ring ^ Both sl^ll.! ^'T ^'""'' ""8'°''% g^™ the availab^for the interchange o^ ::rp:rn:. """"" "' "^« When the^th isTr^^H . '.' ""^ «'°^^"^'" t" i«™ the Mo..e appamus t^ W ™* **;' "«'"* '"""^ ^-rt^^' P°i"»t exchange o^~rn;;eTrf^:;taT TrcM "^^ ^°'*'' answcis also for a call to attia,^ ,t7 Z^\- , °'^ apparatus when wanted- the loll W,^\''''" °* * """^^Po^dent When the s^iZ^^:^l72:,^':^-l^\^ ""^ '"^ in circuit """ "" "" ^^"^ tulephoues alone are 42 THE SPEAKING TELEPHONE. Before leaving tlie subject we must more particularly mention one point in connection therewith that is of too much interest to be overlooked. This is in relation to the various characteristics or forms of action that take place in the transmission of articu- late speech, and which furnish us, in the operation of the Speaking Telephone, with a most beautiful illustration of the correlation of forces, or of their mutual convertibility from one form into another. "When we speak into a telephone the muscular efforts exerted upon the lungs force the air through the larynx, within which are situated two membranes called the vocal chords. These can be tightened or relaxed at Mg. 25. will by the use of certain muscles, and, being thrown into vibra- tion by the passage of the air, give rise to a series of sonorous waves or aerial pulsations, varying in pitch with the tension or laxity of the chords. The impact of these pulsations against the metallic diaphragm produces, in turn, corresponding vibrations of the latter, which, as we have seen, is in close proximity to the poles of a permanent magnet. By this means, therefore, the inductive action of the diaphragm on the magnet is called into play, and there is consequently generated in the surrounding helix a series of electrical currents, which the intervening con- COBRELATION OP FOROES. 43 ductor conveys to the distant station, where their further action is then spent in the production of magnetism. The receivlDg diaphragm, being then thrown into vibration by the resulting attractions, responds with faithful accuracy to the vibrations originally produced at the transmitting end of the line, and thus Fig. 26. also reproduces those sonorous waves which reach the ear and give us the sensation of sound. Here, then, we have, first, the mechanical effects of muscular action converted into electricity, then into magnetism, and finally back again into mechanical action. At each transformation, however, a portion of the I 'I |! . 44 THife SPEAKING TELEPHONE. energy is lost, so far as its available usefulness is concerned ; and, therefore, the sound waves which reach the ear, although pre- cisely similar in pitch and quality to those first produced by the vocal organs, are nevertheless much enfeebled — their amplitude, on which alone loudness depends, being diminished by the amount of energy lost in the transformation. Fig. 27. During the past year the articulating or Speaking Telephone has attracted very general interest and attention, not only in this ^ country but also in Europe. It has already been extensively ' introduced here upon many of our short lines, and bids fair to become of almost universal application in a very short time, its I! :.|i 1)11 POPULAHITY OF Tlffi TELEPHONE. 46 extreme simplicity and the reliability of its operation rendering jt one of the most convenient of the many electrical appliances in use. In Germany it has been r.dopted as a part of the tele- graph system of the country, and there, as well as in other foreign countries, it is also being generally introduced for various private l)urposes, for establishing communication with the interior of coal Fig. 28 and iron mines, and for facilitating the carrying on of a multitude of industries of various kinds. The innumerable uses to which the telephone has already been applied shows more forcibly than anything else its practical im- portance, and the advantages it affords for communicating 46 THE SPEAKING TELEPHONE. between places separated even by comparatively long distances • no more convenient or serviceable instrument for this purpose has ever been produced, while at the same time it is capable of ■ being used by every one. It can also be united with the District Telegraph system, so extensively developed here, and thereby the range of the latter system, which is now limited to a few special calls, such as police, fire, hack, etc., may be very much extended and improved. In addition to thi. again, its connection with he general telegraph system will noon greatly increase the usefulness of that service, by bringing many villages and hamlets that are now destitute of any telegraphic facilities whatever into commnnication with the rest of the world Hitherto the great obstacle in the way of accomplishing this object has been the expense of keeping skilled employds at such places, where the business receipts are usually less than would be required to pay the salary of an operator. The application of the telephone however, now provided the means of connecting these places i^ the nearest telegraph office with veryHttle trouble and with little or no outlay for running expenses. We may therefore confidently expect that another year or two will cuffice to establish telegraph communication with nearly every place in the country The apparatus, as at present furnished to the public by the American Speaking Telephone Co., is all contained in a neatly finished oblong box, which has already been described on pages 25 and 26. ' Figs. 11 and 12 show the outfit complete J^ig. 26 gives a large size front view of the telephone, and also shows the manner of holding it when in use. Manu- facturers and others, whose works are situated at some dis- tance from their offices, will hardly need to be told of the advantages that may be derived from the use of the telephone whereby they are at all times practically enabled to oversee and personally superintend the details of affairs at the works • these niust bo evident to everyone. It will also appear equally obvious that large and expensive warehouses may in many cases be dispensed with in cities where rents are always hi^h the telephone rendering it possible to fill orders at a moment's BAILLE'S TELEPHONE PEOPHECY 4^ .itating the p^^ZT^ ^ ^^"T^ '''*''»' "t all neces- phone we feel coiZ^t^tpTodlTer™ ^^ "^^ *^'" telegraphy, he says : ^peaking of the marvels in So»e y^ea.^1" t^l^ S.^Tetli: fT^"^- inventerl tl! , . ^^ ^^' *^^ ^^'^^^tio telegraph been invented, the principle has been discovered nnd if «.,i !« .ender the invention p^cticable aTSili: ^S^^tTwZ 1 r^st >■/■- A'rPrm7„ cw iJil^CricUi, par J. MailU. Paris, 1871. 48 THE SPEAKING TELEPHONR body, traverse the air and reach- our ear. Just as a stone, dropped into a pond, throws off a succession of circular undu- lations or water rings, so a concussion, acting on the air, pro- duces analogous vibrations, though they are invisible, and it is when these vibrations reach the ear that we become sensible of sound. Helmholtz, an eminent German scientist, has analyzed the human voice and determined its musical value. According to him each simple vowel is formed by one or more notes jf the scale, accompanied by other and feebler notes which are harmo- nics of these. He demonstrates that it is the union of all these notes that give quality to the voica Every syllable is formed by the notes of the vowel accomplished by different movements of the organs of the mouth. Helmholtz, reflecting upon this, thinks it would be possible to construct a human voice by artifi- cially producing and combining the elementary sounds of which it is composed. This is not the place to discuss such theories, but if we grant that there is any truth in them, we can under- stand that the acoustic telegraph can be invented and can trans- mit the living voica Already experiments have been made in this direction, A vibrating plate produces a sound, and, according to the rapidity of the vibrations, these sounds are sharp or flat At each of the vibrations the plate touches a small point placed in front of it, and this contact suf^ces to throw the current into the line. When the plate ceases to vibrate and returns to its posi- tion of equilibrium, it no longer touches the metal point and the current is consequently interrupted. By this means is obtained & series of interruptions, more or less rapid, according to the sound, the current being thrown into the line and interrupted once for each of the vibrations. At the extremity of the line the current enters an electro- magnet, which attracts another vibrating plate of size and qual- ity identical with the former. Attraooed and repelled very rapidly, exactly, and as rapidly in fact as the plate mentioned above, this second plate gives forth a sound which will have the same musical value as that of the other, as the number of vibra- tions per second is the same in both cases. baille's telephone prophecy. 49 .11 Should this process be perfected it will be possible to transmit sound bj means of the telegraph-to transmit a series of sounds, a tune, or spoken sentence and conversation. This consumma- to has not, however, been yet attamed Many extierimente have been made, the principle has been applied in divers ways, and eveiything makes us hope that we will yet arrive at a perfect system of acoustic telegraphy. Advances have been made verv far upon the road to succesa A series of vibrating plates, an- swering to the strings of a harp, has been arranged, each of which vibrates when struck by a particular sound, and sends off electricity to create at the end of a line the same vibrations in a corresponding plate, or, in other words, to reproduce the same sound. This system, it must be admitted, is at least very ingenious. Expenments have been made in laboratories, that is to say under conditions entirely favorable, and such as we would not often find m actua practice. Under these conditions a musical air has actual y been successfully transmitted by this acoustic tele- graph. All must admit that this is a promising beginning • but we muBt not make too much haste to exalt the miracle and to extol the advantages of the future machine, or to abandon our- selves to the indulgence in indiscriminate laudation on the strength of this new discoverjr. That would be a gross mistake aiid an mjury to Pcienca True scientific faith is doubt, until the truth appears in uncontrovertible cleamesa Care must be taken not to toke for reality that which is merely a desire on our pajt We must guard against all premature exultation, because It weakens us in the search for truth, and because even one de- ception IS crueL Let us therefore give to doubt, to patience and to perseverance, the place which some too readily give to con- gratulation." CHAPTEE H bell's telephonic KESEAKCHEa ^ In" a lecture delivered before the Society of Telegraph En- gineers, in London, October 31st, 1877, Prol A. G. Bell gave a history of hit; researches in telephony, together with the experi- ments that he waf; led to undertake in his endeavors to produce a practical system oi multiple telegraphy, and to realize also the transmission of articulate speecL As the subject has now be- come of grer.t interest, both in a scientific and popular point of view, we feel varranted in reproducing the lecture in full After the usual introduction. Professor Bell said : " It is to-night my pleasure, as well as duty, to give you some account of the telephoiiic researches in which I have been so long engaged. Many years ago my attention was directed to the mechanism of speech by my father, Alexander Melville Bell, of Edinburgh, who has made a life-long study of the subject Many of those present may recollect the invention by my father of a means of representing, in a wonderfully ac- curate manner, the positions of the vocal organs in forming sounds. Together we carried on quite a number of experiments, seeking to discover the correct mechanism of English and foreign elements of speech, and I remember especially an investigation in which we were engaged concerning the musical relations of vowel sounds. "When vowel sounds are whispered, each vowel seems to possess a particular pitch of its own, and by whispering certain vowels in succession a musical scale can be distinctly perceived. Our aim was to determine the natural pitch of each vowel ; but unexpected difl&culties made their appearance, for many of the vowels seemed to possess a double pitch — one due, probably, to the resonance of the air in the mouth, and the other to the resonance of the air contained in the cavity behind the tongue, comprehending the pharynx and larynx. HEJJtHOLTZ'S EXPSBIMKOTS. r, I hit upon an expedient for determining the piteh which »» that toe, I thought to be origmal with myllt T^lS L vjbjuhng a tumngfork in W of the mouth while t^^c^ of the vocal organ, for the various vowel sounds werj^^^ takea It was found that each vowel position causeftS «f^ forcement of some particular fork or forta! 1 wrote an account of these researches to Mr Alex. T Tflli. of Won; whom I have very g^t pleasure Z'^ t^^ mght Tn reply, he informed me that the expe^Z XtS had abeady been performed by Helmhol^ and in^muorm™ ^ manner than I had don. IndeS. he ^d Zf^. Mtz had not only Maly^ed the vowel sounds inte theiTa^ He had succeeded in producing, artificially, certain of the- vowel sounds by causing tuning forks of diff^nt pi4 L w! brate sunultancously by means of an electric cu.«„t ^ XZ was kmd enough to grant me an interview foTZpurpos^ rf exptomng the apparatus employed by Helmholtz L pZ^int ghtful day with him m mvestigating the subject At that ^Zl-^7^^' ^ ™' '°° ''^sMy acquainted with the taws of of so^ia^d^ :wr,i^z"sru:^; i\s;s possession of a copy of Hehnholte's gn=at 3k . and W^ duct^n J? ^ K° "f """"^ "P^" ^^ possibilities of the pro! duction of sound by electrical means, it struck me that th^ i^^ aneWmagnet might bo applied to the electrical ^Sulion 1 imagined to myself a series of tuning forks of diffensnt P";:Wj>nung ^ to vibrate au teinatically in the manL'sWn 62 THE SPEAKINQ TELEPHONE. I by Helmholtz— each fork interrupting, at every vibration, a vol- taic current — and the thought occurred, Why should not the depression of a key like that of a piano direct the interrupted current from any one of these forks, through a telegraph wire, to a series of electro-magnets operating the strings of a piano or other musical instrument, in which case a person might play the tuning fork piano in one place and the music be audible from the electro-magnetic piano in a distant city ? The more I reflected upon this arrangement the more feasible did it ^eem to me ; indeed, I saw no reason why t^e depression of a number of keys at the tuning fork end oX the circuit should not be followed by the audible production of a full chord from the piano in the distant city, each tuning fork affecting at the re- ceiving end that string of the piano with which it was .in unison. At this time the interest which I felt in electricity led me to study the various sysj«ms of telegraphy in use in this country and in America. I was much struck vrith the simplicity of the Morse alphabet, and with the fact that it could be reud by sound Instead of having the dots and dashes recorded upon paper, the operators were in the habit of observing the duration of the click of the instruments, and in this way were enabled to distinguish by ear the various signala It struck me that in a similar manner the duration of a musi- cal note might be made to represent the dot or dash of the tele- graph code, so that a person might operate one of the keys of the tuning fork piano referred to above, and the duration of the sound proceeding from the corresponding string of the distant piano be observed by an operator stationed there. It seemed to me that in this way a number of distinct telegraph messages might be sent simultaneously from the tuning fork piano to the other end of the circuit by operators, each manipulating a differ- ent key of the instrument These messages would be read by operators stationed at the distant piano, each receiving operator listening for signals of a certain definite pitch, and ignoring all others. In this way could be accomplished the simultaneous transmission of a number of telegraphic messages along a single TELEPHONIC CURRENTS. ,j 53 S listener sear. The idea of increasing the carmng power of a telegmph wuje in this way took complete posseS^n" my n^L and ,t was this practical end that I had in view when Cm- menced my researehes in electric telephony vh^^tS^ of science it is unive«Jly f„„„d that com. ptoty leads to simplicity, and in narrating the history of sden- tao research it is often advisable to begin at the end. in glancing back over my own researcho*. T fin^ ;. „„ :^1^. '^^i' --"^ '^ van^e^T:' S^c'tntl TrT^ attention to several distinct species of what may be termed tek phomc currents of electricity. In order that th'e peoSrife ^f these currents may be clearly understood, I shall ask Mn F™ Mg.29 Tarielr "^'''' *^' """""'' ^ ^^^"^^ iUustotion of the different in I^2?!rf^lT^'^ of representing electrical currents shown ^ % 29 13 the best means I have been able to devise of studying telephonic appamtus. and it has led me to the conception of tiiat tory, which has rendered feasible the artificial production of articulate speech by electi-ical meana proauction of pulses of positive electricity are represented above the 2en> line, and negative impulses below i1^ or vice versa. ^ «nrpH V^"*'.?^ thickness of any electrical impulse (6 or d), mea- fiured from the zero line. indiPi,f^-« ffa- '"tenHt" -' - / ^^ ™ea- dft THE SPEAKING TELEPHONK m current at the point observed, and the horizontal extension of the electric line (6 or d) indicates the duration of the impulse. Nine varieties of telephonic currents may be distinguished, but it will only be necessary to show you six of thesa The three primary varieties designated as intermittent, pulsatory and nndulatory, are represented in lines 1, 2 and 3. Sub- varieties of these can be distinguished as direct or re- versed currents, according as the electrical impulses are all of one kind or are alternately positive and negativa Direct cur- rents may still further be distinguished as positive or negative, according as the impulses are of one kind or of the other. An intermittent current is characterized by the alternate pres- ence and absence of electricity upon the circuit ; A pulsatory current results from sudden or instantaneous, changes in the intensity of a continuous current ; and An undulatory cunrent is a current of electricity, the intensity of which varies in a manner proportional to the velocity of the .motion of a particle of air during the production of a sound : thus the curve representing graphically the undulatory current ifor a simple musical tone is the curve expressive of a simple pendulous vibration — that is, a sinusoidal curve. •t t Intermittent Pulsatory Undulatory Direct Direct Direct i Positive 1 Positive intermittent current. ( Negative 2 Negative " " Reversed 3 Reversed " '* ( Positive 4 Positive pulsatory current. ( Negative 5 Negative " " Reversed 6 Reversed " " I Positive 1 Positive undulatory current I Negative 8 Negative " " Reversed 9 Reversed " " And here I may remark, that, although the conception of the undulatory current of electricity is entirely original with myself, methods of producing sound by means of intermittent and pul- satory currents have long been known. For instance, it was long since discovered that an electro-magnet gives forth a de- page's galvanic music. 88 antaneoua. cided sound when it is suddenly magnetized or demagnetized. When the circuit upon which it is placed is rapidly made and broken, a succession of explosive noises proceeds from the mag- net These sounds produce upon the ear the effect of a musical note when the current is interrupted a sufficient number of tmies per second. The discovery of Galvanic Music by Page,i in 1837, led inquirers in different parts of the world almcit simultaneously to enter into the field of telephonic research; and the acoustical effects produced by magnetization were carefully studied by Marrian,^ Beatson,» Gassiot,* De la Eive,6 Matteucci,« Guillemin,' Wertheim,^ Wartmann," Jan- niar,io Joule, " Laborde,i9 Legat,is Reis,i* Poggendorff,i» 1 a O. Jhge. «' The Production of Galvanic Music." Silliman's Journ,, 1837 xxxiu p. 396 ; SiUiman's Journ., 1888, xxxiii. p. 118 ; Bibl. Univ. (new series), 1889* u. p. 398. " ' * J. P. Marrian. Phil. Mag., xxv. p. 382 ; Inst., 1845, p. 20; Arch, de I'llleotr., V. p. 195. ' « IP. BeaUon. Arch, de l':6lectr., v. p. 197 ; Arch, de 8c. Phys. et Nat. (2d series), ii. p. 118. ^ -" * Gassiot. See"Treati8eonElectricity,"byDelaEive, i. p. 300. » \-^\ ^^-^f"'' "^'•^*"«« o*! Electrici'ty," i. p. 300; Phil. Mag.,'xxxv. p. 422; • Arch, de I'Electr. v. p. 200 ; Inst. 1846, p. 83 ; Comptes Rendus, xx. p. 1287 ; Comp Kend. xxii. p. 432; Pogg. Ann. Ixxv. p. 687: Ann. do Chiin. et de Phys xxvi p. 158. « MaUeucci. Inst., 1845, p. 815 ; Arch, de I'Electr., v. 389. » GuilUmin. Comp. Eend. xxii. p. 264 ; Inst. 1846, p. 30 ; Arch. d. Sc. Phys. (2d series), i. p. 191. s G.WeHheim. Comp. Rend. xxii. pp. 336, 644; Inst. 1846, pp. 65, 100 ; Pogg Ann. Ixviii. p. 140; Comp., Rend. xxvi. p. 505; Inst. 1848, p. 14e ; Ann. do Chim et do Phys. xxiii. p. 302 ; Arch. d. Sc. Phys. et Nat. viu. p. 206 ; Pogg. Ann. Ixxrii p. 43 ; Berl. Ber. iv. p. 121. » ElU Wartmann. Comp. Rend. xxii. p. 644; Phil. Mag. (3d series), xxviii p 644 : Arch. d. Sc. Phys. et Nat. (2d series), i. p. 419 ; Inst. 1846, p. 290 ; Monatscher d. Berl. Akad. 1846, p. 111. 10 Jannair. Comp. Rend, xxiii. p. 819 ; Inst. 1846, p. 269 ; Arch. d. So. Phys et Nat. (2d series), ii. p. 394. ^^ J.K Joule. PhU. Mag. xxv. pp. 76, 225 ; Berl. Ber. iii. p. 489. 1 » Laborde. Comp. Rend. 1. p. 692 : Cosmos, xvii. p. 514. " Ltgat. Brix. Z. 8. ix. p. 125, " Rm. "Td6phonie." Polytechnic Journ. clxviii, p. 186; Bftttger's Notizbl. 1863, No. 6, " ^. C. Paggtndorff. Pogg. Ann. xcviii. p. 198 ; Berliner Monatsber, 1856, p. 188; Cosmos, ix. p. 49; Berl. Ber. xii. p. 241 ; Pogg. Ann. IxxxviL p. 189, 66 THE SPEAKING TELEPHONE. il: i! i ' I' » 1 Du Moncel, * Delezenne' and others. ' It should also be men- tioned that Gore* obtained loud musical notea from mercury, accompanied by singularly beautiful crispations of the sur- face, during the course of experiments in electrolysis; Page* produced musical tones from Trevelyan's bars by the action of the galvanic current ; and further it was discovered by Sullivan" that a current of electricity is generated by the vibration of a wire composed partly of one metal and partly of another. The cur- rent was produced so long as the vnre emitted a musical note, but stopped immediately upon the cessation of the sound. For several years my attention was almost exclusively directed to the production of an instrument for making and breaidng a voltaic circuit with extreme rapidity, to take the place of the transmitting tuning fork \Lsed in Helmholtz* researchea I vrill not trouble you with the description of all the various forms of apparatus that were- deviaed, but will merely direct your atten- tion to one of the best of them, shown in fig. 80. In the trans- mitting instrument T a steel reed a is employed, which is kept in continuous vibration by the action of an electro-magnet e and local battery. In the course of its vibration the reed strikes alternately against two fixed points m, Z, and thus completes alternately a local and a main circuit When the key K is depressed, an intermittent current from the main battery B is directed to the line wire W, and passes through the electro- magnet E of a receiving instrument R at the distant end of the circuit, and thence to the ground G. The steel reed A is placed 1 Du Moncel. Expos^, ii. p. 1 25 ; also, iii. p. 83. * Ddetenne. "Souad produced by magnetization," Bibl. Univ. (new senes), 1841, xvi. p. 406. » See London Journ. xxxii. p. 402 ; Polytechnic Journ. ex. p. 16 ; Cosmos, iv. p. 43; GlOsener Traits gdneral, &o. p. 350; Dovo.-Repert. vi. p. 58; Pogg. Ann. xliii. p. 411 ; Berl. Ber. i. p. 144 ; Arch. d. Sc. Pbya. et Nat. xvi. p. 406 ; Kuhn'a Enoyclopffldia der Physik, pp. 1014-1021. * Gore. Proceedings of Royal Society, xii. p. 217. • C. 0. Jhge. " Vibration ot Trevelyan's bars by the galvanic current." SlUi- man'a Journal, 1850, ix. pp. 105-108. • Sullivan. " Currents of Electricity produced by the vibration of Metals," Phil, Mag. 1845, p. 261 ; Areb. de I'Eleotr. x. p. 480. MULTIPLE TELEGKAPHY. 67 in front of the receiving magnet, and when its normal rate of vibration is the same as the reed of the transmitting instrument It is thrown into powerful vibration, emitting a musical tone of a similar pitch to that produced by the reed of the transmitting iQstrumenl^ but if it is normally of a different pitch it remains silent Aglanceatfigs. 81, 32 and 33 will show the arrangement of raoh mstruments upon a telegraphic circuit, designed to enable a num- ber of telegraphic despatches to be transmitted simultaneously fig. 30. along the same wire. The transmitters and receivera that are numbered alike have the same pitch or rate of vibration. Thus the reed of T' is in unison with the reeds T' and E' at all the stations upon the circuit, so that a telegraphic despatch sent by the man- ipulation of the key K' at the station shown in iig. 31, will be received upon the receiving instruments R' at all the other stations upon the circuit Without going into detaOs, I shall merely say that the great defects of this plan of multiple tele- graphy were found to consist, firstly, in the fact that the receiving operators were required to possess a good musical ear in order to discnmmate the signals; and secondly, that the signals could only pass m one direction along the line (so that two wires would be necessary in order to complete communication in hnth '^^^^^ 11 il 68 THE SPEAKING TELEPHONE. VIBRATORY CIRCUIT BREAKER. 69 tions). The first objection was got over by employing the de- vice which I term a "vibratory circuit breaker," shown in the next diagram, whereby musical signals can be automatically re- corded. Fig. 34 shows a receiving instrument, B, with a vibratory cir- cuit breaker V attached. The light spring lever V overlaps the free end of the steel reed A, and normally closes a local circuit, m which may be placed a Morse sounder or other telegraphic apparatus. When the reed A is thrown into vibration by the passage of a musical signal, the spring arm V is thrown upwards opemng the local circuit at the point 0. When the spring arm Y IS so arranged as to have normally a much slower rate of vibra- tion than the reed A, the local circuit is found to remain perma- Pig. 34. nently open during the vibration of A, the spring arm Y coming mto contact with the point only upon the cessation of the re ceivers vibration. Thus the signals produced hv the vibration of the reed A are reproduced upon an ordinary telegraphic instru- ment in the local circuit Fig. 35 shows the application of electric telephony to auto- graphic telegraphy q, q represent the reeds of transmitting instru- mente of different pitch, s, s the receivers at the distant station of correspondmg pitch, and u, u, etc., the vibratory circuit breakers Jttached to the receiving instruments, and connected ^vith metalhc bnstles resting upon chemically prepared paper w. The message or picture to be copied is written upon a metaUic surface, p, with non-metaUic mk, and placed upon a metallic cylinder connected with the mam battery, c; and the chemically prepared paper, upon which the message is to be received, is placed upon a eo THE SPEAKING TELEPHONE. metallio cylinder connected with the local battery d at the receiving station- When the cylinders at either end of the cir- cuit are rotated — ^but not necessarily at the same rate of speed — a fae simile of whatever is written or drawn upon the metallic surface p appears upon the chemically prepared paper w. The method by means of which musical signals may be sent simultaneously in both directions along the same circuit is shown in our next illustration, figs. S6, S7 and 38. The arrangement i» similar to that shown in figures 31, 32 and 33, excepting that the iiitermittent current from the transmitting instruments is passed ll'li I Fig. 35. through the primary wires of an induction coil, and the receiving instrumenta are placed in circuit with the secondary wire. In thib way free earth communication is secured at either end of the circiiit, and the musical signals produced by the manipulation of any key are received at all the stations upon the lina The great objection to this plan is the extreme complication of the parts and the necessity of employing local and main batteries at every station. It was also found by practical experiment that it was difiicult, if not impossible, upon either of the plans here snowDi to transmiu simuivaneously the nuuiucr of iiiusical tones I MULTIPLE TELEGRAPHY. 61 ry d a\ the d of the cir- te of speed — the metallic ►er w. may be sent suit Is shown rangement i» ting that the snts is passed 't- •53;> ihe receiving vire. Inthib : end of the lipulation of ' lina The ation of the L batteries at eriment that J plans here lusiual tones 62 THE SPEAKING TELEPHONE. that theory showed to be feaaibla Mature consideration re- vealed the fact that this difficulty lay in the nature of the electrical current employed, and was finally obviated by the invention of the undulatory current It is a strange fact that important inventions are often made almost simultaneously by different persons in different paiis of the world, and the idea of multiple telegraphy, as developed in. the preceding diagrams, seems to have occurred independently to no less than four other inventors in America and Europe. Even the details of the arrangements upon circuit — shown in figs. 31, 32, 83 and 36, 37, 38 — are extremely similar in the plana proposed by Mr. Cromwell Varley, of London, Mr. ElisHa Gray, Fig. 89. of Chicago, Mr. Paul La Oour, of Copenhagen, and Mr. Thomas Edison, of Newark, New Jersey. Into the question of priority of invention, of course, it is not my intention to go to-night That the difficulty in the use of an intermittent current may be more clearly understood, I shall ask you to accompany me in my explanation of the effect produced when two musical signals of different pitch are simultaneously directed along the same circuit Fig. 39 shows an arrangement whereby the reeds r r' of two transmitting instruments are caused to interrupt the current from the same battery, B. We shall suppose the musical interval between the two reeds to be a major third, in which case their vibrations are in the ratio of 4 to 6, «" e., 4 vibrations of r are made in the same time as 5 vibrations of /. A and B represent the intermittent currents produced, 4 im- MULTIPLE TELEGRAPHY. 53 pulses Of B being made in the same time as 6 impulses of A. Ihe Ime A + B represents the resultant effect upon the main Ime when the reeds r and r' are simultaneously caused to make and break the same circuit, and from the illustration you wUI perceive that the resultant current, whilst retaining a uniform mtensi^, is less mt^rrupt^d when both reeds are in operation han when one alone is employed. By carrying your thoughts still furthe^ you wiU understand that when a large number of reeds of different pit«h or of different rat^s of vibStion are sir^- ultaneously making and breaking the same circuit, the resultant effect upon the mam hue is practically equivalent to one contin- uous current It will also be understood that the maximum number of Fig. 40. musical signals that can be simultaneously directed along a .vhch the "make" bears to the << break;" the shorter the con- signals that can be transmitted without confusion, and vice versa. The apparatus by means of which this theoretical conclusion has been verified is here to-night, and consists of an ordinary parlor liamiommn, the reeds of which are operated by wind in the usual manner. In front of each reed is'arranged^a metal screw adW t *'' "'""'^^ ^" '''' ^'^^-^ ^''^ -Oration, b'^ adjusting the screw, the duration of the contact can be made IZrv' 71 ^'^ "^'^ "'^ ^^^"^^^^^ -*^^ «- VolJ7l Oattery, and the screws against which thev strike Pnnjm,,^ 64 THE SPEAKING TELEPHONE. with, the line wire, so that intermittent impulses from the battery axe transmitted along the line wire during the vibration of the reeds. We now proceed to the next illustration. "Without entering into the details of the calculation you will see that with a pulsa- Fig. 41. lory current the effect of transmitting musical signals simultane- ously is nearly equivalent to a continuous current of minimum intensity — see A+B, fig. 40; but when undulatory currents are employed the effect is different — see fig. 41. The current Fig. 42. from tne battery B is thrown into waves by the inductive action of iron or steel reeds vibrated in front of electro-magnets placed in circuit with the battery ; A and B represent the undulations caused in the current by the vibration of the magnetized bodies, MULTIPLE TELEGRAPHT. e5 and It will be seen that there are four undulations of B in the same tune as five undulations of A. The resultant effect upon the main line is expressed by the curve A -|-B, which is the alge- braical sum of the sinusoidal curves A and B. A similar effect is produced when reversed undulatorj currents are employed, as " shown m fig. 42, where the current is produced by the vibration ' of permanent magnets in front of electro-magnets united upon a cu'cuit without a voltaic battery. It will be understood from figs. 41 and 42 that the effect of transmitting musical signals of cSf- ferent pitches simultaneously along a single wire is not to ob- hterate the vibratorjr character of the current, as in the case of mtenmttent and pulsatory currents, but to change the shapes of Mg.id. the electrical undulationa In fact, the effect produced upon the current is precisely analogous to the effect produced in the air by the vibration of the inducing bodies. Hence it should be possible to transmit as many musical tones simultaneously through a telegraph wire as through the air. The possibility of using undulatory currents for the purposes of multiple telegraphy enabled me to dispense entirely with the complicated arrange- ments of the circuit shown in figs. 81, 82, 33 and 86, 37, 88, and to employ a single battery for the whole circuit, retaining only the reoeivincr inatrnmRnfa fr^rv^^rl" °1— sr- mi_--_ ■'. . 66 THE SPEAKING TELEPHONE. represented in fig. 43. Upon vibrating the steel reed of a re- ceiver E, R', at any station by any mechanical means, the corre- sponding reeds at all the other stations are thrown into vibration, reproducing the signal. By attaching the steel reeds to the poles of a powerful permanent magnet, as shown in fig. 45, the signals can be produced without the aid of a battery. I have formerly stated that Helmholtz was enabled to produce vowel sounds a,rtificially by combining musical tones of difierent pitches and intensities. His apparatus is shown in fig 44 Tuning forks of different pitch are placed between the poles of electro-magnets (a', a^, &c.), andare keptin continuous vibration by the action of an intermittent current from tho fork h. Beso- Fig. 441. nators 1, 2, 3, etc., are arranged so as to reinforce the sounds in a greater or less degree, according as the exterior orifices are enlarged or contracted. Thus it will be seen that upon Hehnholtz's plan the tmung forks themselves produce tones of uniform intensity, the loud- ness being varied by an external reinforcement ; but it struck rae that the same results would be obtained, and in a much more perfect manner, by causing the tuning forks themselves to vibrate with difierent degrees of amplitude. I therefore devised the apparatus shown in fig. 45, which was my first form of articulat- ing telephone. In this figure a harp of sroel rods is employed, 1 The iuU description of this figure wiii bs foui «,«lRt,ion r,r HelmhoUz'8 work, " Theory f. Tuiid." bp found in Mr. Alexander J. EUIb'b MULTIPLE TELEGRAPHY. 67 ftuder J. EUU'a attached to the poles of a permanent magnet, N. S. When ariy one of the rods is thrown into vibration an undulatory current IS produced in the coils of the electro-magnet E, and the electro- magnet E' attracts the rods of 'the harp H' with a varying force throwing into vibration that rod which is in unison with that vibrated at the other end of the circuit Not only so, but the amplitude of vibration in the one will determine the ampHtude of vibration in the other, for the intensity of the induced current is determined by the ampUtude of the inducing vibration, and the amphtude of the vibration at the receiving end depends upon the intensity of the attractive impulses. When we sing into a piano, certain of the strings of the instrument are set in vibration sympathetically by the action of the voice with differ^ Fig. 45. ent degrees of amplitude, and a sound, which is an approxima- ton to the vowel uttered, is produced from the piano. Theory shows that, had the piano a very much larger number of strings to the octave the vowel sounds would be perfectly reproduced. My idea of the action of the apparatus, shown in fig. 45, was this: Utter a sound m the neighborhood of the harp H and certam of the rods would be tin-own into vibration with dMer- cnt amplitudea At the other end of the circuit the correspond- ing rods of the harp H' would vibrate with their proper relations of force, and the timbre of the sound would be reproduced The expense of constructing such an apparatus as that shown in fig. 45 deterred me from making the attempt, and I sought to sim- plify the apparatus before venturing to have it made. I have before alluded to the invention by iiij xather uf a sys 68 the: speaking telephone. I' I ! tern of physiological symbols for representing the action of the vocal oi^ans, and I had been invited by the Boston Board of Education to conduct a series of experiments with the system in the Boston school for the deaf and dumb. It is well known that deaf mutes are dumb merely because they are deaf, and that there is no defect in their vocal organs to incapacitate them from utter- ance. Hence it was thought that ray father's system of pictorial symbols, popularly known as visible speech, might prove a means whereby we could teach the deaf and dumb to use their vocal organs and to speak. The great success of these experiments urged upon me the advisability of devising methods of exhibit- ing the vibrations of sound optically, for use in teaching the Fig. 46. deaf and dumb. For some time I carried on experiments with the manometric capsule of Kdenig and with the phonautograph of Leon Scott The scientific apparatus in the Institute of Tech- nology in Boston was frccij placed at my disposal for these ex- periments, and it happened that at that time a student of the Institute of Technology, Mr. Maurey, had invented an improve- ment upon the phonautograph. 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 phonautograph, and in this way he had been enabled to obtain enlarged tracings upon a plane surface of smoked glass. With this apparatus I succeeded AN AURAL PHONAUTOGRAPH. „ fig in producing very beautiful tracings of the vibrations of the air ; for vowel sounds. Some of these tracings are shown in fig 46 I was much struck with this improved form of apparatus, and ii occurred to me that there was a remarkable Ukeness between the manner m which this piece of wood was vibrated by the membrane of the phonautograph and the manner in which the QSSiGulce of the human ear were moved by the tympanic mem- Mg. 47. brane I determined, therefore, to construct a phonautograph modelled still more closely upon the mechanism of the human ear, and for this purpose I sought the assistance of a distin- guished aurist in Boston, Dr. Clarence J. Blake. He suggested the use of the human ear itself as a phonautograph, instead of making an artificial imitation of it The idea was novel and struck me accordingly, and I requested my friend to prepare 3>Si 70 THE SPEAKING TELEPHONE. , 1] i '■- a specimen for me, which he did. The apparatus, as finally con- structed, is showr. m fig. 47. The stapes was removed and a stylus of hay tiL^.ufc jiu inch in length was attached to the end of the in.-us. Upon moistening the membrana tympani and the ossiculco mth a mixture of glycerine and water the necessary mobility of the parts was obtained, and upon singing into the external artificial ear the stylus of hay was thrown into vibration, and tracings were obtained upon a plane surface of smoked glass passed rapidly underneath. While engaged in these ex- periments I was struck with the remarkable disproportion in weight between the membrane and the bones that were vibrated by it It occurred to me that if a membrane as thin as tissue paper could control the vibration of bones that were, compared to it, of immense size and weight, why should not a larger and thicker membrane be able to vibrate a piece of iron in front of M A_ . J_ ^ an electro-magnet, in which case the complication of steel rods shown in my fii-st form of telephone, fig. 45, could be done away with, and a simple piece of iron attached to a membrane be placed at either end of the telegraphic circuit. Fig. 48 shows the form of apparatus that I was then employ- ing for producing undulatory currents of electricity for the pur- poses of multiple telegraphy. A steel reed. A, was clamped firmly by one extremity to the uncovered leg ft of an electro- magnet E, and the free end of the reed projected above the covered leg. When the reed A was vibrated in any mechanical way the batterjr current was thrown into wavesj and electrical undulations traver-sed the circuit B E W E', throwing into vibra- tion the corresponding reed A' at the other end of the circuit I immediately proceeded to put my new idea to tlie test of practical experiment, and for this purpose I attached the reed bell's inopebative telephonk 71 A (dg. 49) loosely by one extremity to the uncovered pole A of the magnet, and fastened the other extremity to the centre of a stretched membrane of goldbeaters' skin n. I presumed that upon speaking in the neighborhood of the membrane n it would be thrown into vibration and cause the steel reed A to mo, e in a similar manner, occasioning undulations in the electrical cur- rent that would correspond to the changes in the density of the air during the production of the sound ; and I further thought that the change of the intensity of the current at the rec oiving end ,vould cause the magnet there to attract the reed A' in such a manner that it should copy the motiofi of the reed A, in which case its movements would occasion a sound from the membrane n' similar in timbre to that which had occasioned the original vibration. Fig. i9. The results, however, were unsatisfactory and discouraging. My friend, Mr. Thomas A. Watson, who assisted me in this first experiment, declared that he heard a faint sound proceed from the telephone at his end of the circuit, but I was unable to verify his assertion. After many experimente, attended by the same only partially successful results, I determined to reduce the size and weight of the spring as much as possil)le. For this purpose I glued a piece of clock spring, about the size and shape of n thumb nail, firmly to the centre of the diaphragm, and had .t similar instrument at the other end (fig. 60) ; we were t hen ena bled to obtain distinctly audible effects, i I remember thl Patt! frnf !'w"Y^ l«^«. Mr. EUsha Gray, of Chicago, filed a caveat in TurlrT ?r . ^'*«^»»»'«». describing the Speaking Telephone shown in tnitZ'" fl ' '"^ "''''■' "P""^ «'^«»"n'»tion, will be found to be identical with ti u nrp:tl7offl''n'w\.''" ^'^r*' d^yJ^-^-sorBeUfiledan appUoa- «Qn in ine i-atent Office at Washimrton. ' ""^™" "" '^'®'=""y ""^ ^'^Perienoed so long as parallel Imes were not in opemtion. Sunday was chosen a! the day on which it was probabl. other circnit. would be at re^t Conversation was carried on between myself in New York, and Mr, Thomas A. Watson, in Boston, until the L^ of business upon the othcrwirea When this happened thf vo^ ?|S=^t:i^nS;^r:r^t£S I am inforinri by my friend Mr. Preeee tliat eonvemtioa ha., fen successfully earned on thi-ough a submarine cable, sixty mdes m length, extending from Dartmouth to the Island of 82 THE SPEAKING TELEPHONE. Guernsey, by means of hand telephones similar to that shown in fig. 56." At the conclusion of the lecture complimentary remarks were made by the President and various other members who were present, and a cordial vote of thanks was extended to Professor Bell for his very philosophical and entertaining discourse. We reproduce a portion of the remarks made by Mr. Preece : "While on the one part Professor Bell has placed in our hands, to a certain extent, a new power, he has, on the other hand, thrown upon our shoulders an extra weight The poor telegraph engineer has now to master many sciences. Not only must he know something of electricity and magnetism — not only must he know a good deal of chemistry — not only must he pass through various stages of mathematical knowledge, but now, thanks to Professor Bell, he is obliged to be master of the in- tricacies of acoustica ; I do not blame him, because the study of sound is in itself a beautiful occupation, and when it becomes linked to one's profession it becomes almost a luxury. Professor Bell alluded to the fact that expectancy led him in his first telephone to anticipate what was said. I will give you an illustration of the effect of expectancy. It was my pleasure, on a recent occasion, to exhibit the telephone before a veiy large audience. Many learned men were present There is one very remarkable feature of a learned meeting. When you call upon a learned member to make a learned remark he frequently makes a foolish one. Now, I selected one of the leading scien- tific men of the day, and placed the telephone in his hand. It was in connection with a similar instrument fifty-five miles away. Of course we expected xo hear from him some learned axiom, some sage aphorism or some wonderful statement ; but, after son^ hesitation, he said: 'Hey diddle diddle— follow that up.' He rapidly put the telephone up to his ear and an- nounced with much glee, * He savs, cat and the fiddle.' Fift\' miles off my assistant was answenag the question. I asked him next day \i he understood ' Hey diddle diddle.' He said ' No.' * Wlwit did you say ?' ' I asked him to repeat I' " CHAPTER IIL THE TELEPHONE ABROAD. > Op all modem inventions connected with the transmission of telegraphic signals, the telephone, devised by Mr. Alexrder Graham Bell, has excited the most widespread interest and won an account of h.s invention and the researches which havered up to 1^ crowds have assembled to hear him. Nor is thi, astonishing; for the telephone professes not only to onw ntelligvble signals to great distances without the use of a hZ tery but to transmit in fec-simile the tones of the human vofee so that a voice shall be as certainly recognized when hearf ovT,; a distance of a few hundreds of miles as if its owner were spelt mg in the room by our side. And the telephone Z^Ztl short of Its profession. ScientiHc men have had their wonder and curiosity aroused even more than the unscientific pubfo since a scientific man appreciates the enormous diificultie^to te overcome before such an instrument can be realized. Had any hardy speculator a few years ago proposed a telephone which Aould act on the principle, and be constructed in the form of a lunatic » The efEects are so marvellous ; the exciting causes at first sight so entirely inadequate to produce them. FoT^U phonic message differs as widely from an onlinary tele^mnh,; mes^ge as a highly finished oil painting diflei. frL ^^ print In the one you have only white and black-black fym bols on a white ground-the symbols being limited in numC and recurring ag.am and again with mere differences ofTrd^' The pamtmg, on the other hand, discloses every variety of coIo; and arrangement No sharp lines of discontinuity offend the eye ■■on the contrary, the tint, shad e off (rradually and softly ■ From th. W«,min^ It„i„, . g,. B^^MM„,~~ 84 THE SPEAKING TELEPHONE. into each otUer. presenting tone and depth m ^f^^^'^^ The page of print is unintelligible without the aid of a key , the paintinf tells its sto.7 P'-inV e-ough to any one who haa eyes *°Cns inquire for a moment what is the nature of the appar^ .tus which we have been using for the last thirty or onyj^^ for the transmission of telegraphic signals The "Strumente chieflT employed have been the single needle te egraph and the MTrsf instUent, In the former a coil of '™ '"""^f * „ magnetized needle, which is suspended in a vertical pos. lom When an electrical current passes through the cod, the needle j deflected to right or left, according to the direction of the cur- rent The sender, by means of a handle, can pa^ «*^'- P°^''^« or negative currents into the circuit The right ''"d left deflee. tioDS of the needle are combined in various ways to form the letters of the alphabet, and the letters form word^ Thus, at riding s Jon a message is broken up into httle bits, eaeh bit or part of a bit transmitted separately, and the pro«.^ of building these up again performed at *«,--™S;^^°" Some of the letters of the alphabet are indicated by a single movement of the needle, that is, by a single current ; for others, as many as four are required . In the Morse instrument only one current is utilised, which may be either positive or negative, and the requisite vane y Tobtained by allowing the current to pass through the eir- c„if r a llger or shorter interval. The essential part of the iuBtrument consists of an electro-magnet with an iron annature attached to one end of a lever. At die other end Z the lever is a pointer or pencil, and a paper "tto^^T™' *» ■: constant rate in ftont of the end of f P"-'»- J" coils of the electro-magnet are traversed by a «=>^™» ' *" annature is attracted, and the pointer comes in contact with the pa^r ribbon, on which it makes a mark, long or short, iK^coidmg Hhe duration of the cuirent Thus are produced the dots and Thl These are combined in a simila. way to the nght and left lavements of the needle in the ne.dle instrument.' In some UNDULATING CURRENTS. 8S variety, 3y; the as eyes appar- f years uments and the )uiids a )Ositioii. eedle is the cur- positive t deflec- "orm the Thus, at its, each •ocess of station. a single >r others, d, which 3 variety . the cir- tial part an iron ther end moves at ^hen the ;, the iron ; with the according ; dots and right and In some of the more refined instruments lettera are indicated and even printed directly at the receiving station. This is, of course, a great simplification ; but with such arrangements we cannot have more than this. The page of print represents the limit of what such instruments and methods can do for us. It is true that a skilled operator with the Morse instrument can interpret the sig- nals as they arrive without looking at the marks on the paper, si ply by using his ears. Every time the circuit is made or broken a click is heai-d, and long practice has taught him to rely on the evidence of his ears with as much confidence as one less accustomed to the work would trust his eyes. Nevertheless, he hears only a succession of clicks, which must be interpreted before they become intelligible to any one but himself. In these forms of apparatus, it will be observed, the currents are intermittent; each current, circulating through the coil, is followed by an interval of rest They begin and end abruptly, and all perform the same kind of work ; that is, they deflect a needle, or produce marks on a piece of paper. Telephonic cur- rents, on the other hand, rise and fall, ebb and flow, change in intensity within comparatively wid^ limits, but preserve their continuity so long as continuous snuLds are being uttered in the neighborhood of the telephone. They are called undulatory currents, to distinguish them from the intermittent currents of the ordinary telegraphic apparatus ; and their peculiar character is an essential feature of the telephone. No skill or training is required for the effective use of the telephone. The operator has merely to press the instrument to his ear to hear distinctly every sound transmitted from the dis- tant end. For this, it is true, an effort of attention is required, and some persons use the instrument at the first trial with more success than others. Individuals differ in the facility with which they are able to concentrate their attention on one ear, so as to be practically insensible to what goes on around them. But this habit of attention is readily acquired, and when it is once acquired the telephone may be used by any one who has ears to hear and a tongue to speak. In sending a message, the instru* .s^. ^ V^. ..aj 7] /2 ^ ^4 ^ v^;^'*' IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 11.25 I*^ Nig HJUU U 11.6 Photographic Sciences Corporation // ^ .^4^ t Ao instru- ment here given are found to be convenient, but they are by no means essential. Good results have been obtained by means of a magnet only an inch and a half long, and a working instru- ment need not be too large for the waisi^coat pocket There is na difference between the transmitting and the receiving telephone; each instrument serves both purposes. Nevertheless, in order to avoid the inconvenience of shifting the instrument backwards and forwards between the ear and the mouth, it is better to have two on the circuit at each station. The operator then holds one permanently to his ear, while he talks with the other. It will not be supposed that the idea of this marvellously simple piece ot apparatus was evolved ready formed from the inventor 8 brain : very far otherwise. It is the final outcome of a long series of patient researches carried out by Mr. Bell in the most skilful and philosophical manner, in which one modifica- tion suggested another, accessory after accessory was discarded, and finally the instrument was pruned down to its present form and dimensions. Telephones have been long known. A few years «go a simple arrangement whereby articulate sounds could be transmitted over a distance of fifty or sixty yards, or even fur- 90 THE SPEAKING TELEPHONE. ther, could be bought in the streets for a penny. It consisted of a pair of pill boxes, the bottoms of which were connected by a piece of string stretched tight, while over the mouth of each was pasted tissue paper. On speaking to one of the pill boxes the tissue paper and enclosed air were set in vibratioa The vibra- ' tions so produced were communicatee! to the thread and trans- mitted to the distant pill box, which was held close to the ear, where they affected the air in such a way as to reproduce the original sounds. The simple apparatus was more effective than would be at first imagined. Electric telephones were devised in this country about the same time ihat the telegraph was intro- duced, but the best of them differed widely from the modem in- strument They were capable of conveying to a distance sounds of various pitch, so that the succession of notes constituting a melody could be reproduced many miles away, but the special character of the voice by which the melody was originated was entirely lost 1 Now the great interest which attaches to Mr. Bell's telephone, and the intense wonder and curiosity it has aroused, are due to its power of conveying absolutely unaltered every peculiarity of voice or musical instrument A violin note reappears as a violin note ; it cannot be mistaken for anything else. And in the case of a human voice, it is not less easy to distinguish one speaker from another than it would be if the speakers were in the room close by instead of being miles or even hundreds of miles away. This is the charm of the new telephone ; this it is which renders it immeasurably superior to anything of the kind which preceded it Mr. Bell's researches in electric telephony began with the arti ficial production of musical sounds, suggested by the work in which he was then engaged in Boston, viz : teaching the deaf and dumb to speak. Deaf mutes are dumb merely because they are deaf. There is no local defect to prevent utterance, and Mr. Bell has practically demonstrated by two thousand of • Roiss's telephone was the first invention which could accomplish the result here stated, and this was invented in Germany, in 1861. See description of Beisa's telephone, page 9. TRACINGS OF AIR VIBRATIONa 91 his own pupils that when the deaf and dumb know how to con- trol the action of their vocal organs, they can articulate with comparative facility. Striving to perfect his system of teaching It occurred to Mr. Bell that if, instead of presentin / to the eye of the deaf mute a system of symbols, he could make visible the vibrations of the air, the apparatus might be used as a means of teaching articulatioa In this part of his investigations Mr. Bell derived great assistance from the phonautograph. He suc- ceeded in vibrating by the voice a style of wood, about a foot in length, attached to the membrane of the phonautograph ; and with this he obtained enlarged tracings of the vibrations of the air, produced by the vowel sounds, upon a plane surface of smoked glass. Mr. Bell traced a similarity 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 membrane. Wishing to construct an apparatus closely resembling the human ear, it was suggested to him by Dr. CJarence J Blake, a distinguished aurist of Boston, that the human ear Itself would be still better, and a specimen was prepared. Our readers are aware that the tympanic membrane of the ear is con- nected with the internal ear by a series of little bones called res- pectively the malleus, the incus and the stapes, from their pecu- liar shapes, and that by their means the vibrations of the tympanic membrane are communicated to the interna^ ear and the audi- toiy nerves. Mr. Bell removed the stapes and attached to the end of the incus a style of hay about an inch in length. Upon singing into the external artificial ear, the style of hay was thrown mto vibration, and tracings were obtained upon a plane surface of smoked glass passed rapidly underneath. The curves so ob- tained are of great interest, each showing peculiarities of its own dependent upon the vowel sound that is sung. Whilst engaged m these experiments Mr. Bell's attention was arrested by observ- ing the wonderful disproportion which exists between the size and weight of the membrane— no thicker than tissue paper— and the weight of the bones vibrated by it, and he was led to 92 THE SPEAKING TELEPHONE. inquire whether a thicker membrane might not be able to vibrate a piece of iron in front of an electro-magnet. The ei^periment was at oiice tried. A piece of steel spring was attached to a stretched membrane of gold beater's skin and placed in front of the pole of the magnet This answered very well, but it -v^as found that the action of the instrument was improved by in- creasing the afea of metal, and thus the membrane was done away with and an iron plate substituted for it It was important at the same time to determine the effect produced by altering the strength of the magnet ; that is, of the current which passed round the coils. The battery was gradually reduced from fifty cells to none at all, and still the effects were observed, but in a less marked degree. The action was in this latter case doubtless due to residual magnetism ; hence, in the present form of appar- atus a permanent magnet is employed. Lastly, the effect of varying the dimensions of the coil was studied, when it was found that the sounds became louder as its length was dimin- ished ; a certain length was, however, ultimately reached, beyond which no improvement was effected, and it was found to be only necessary to enclose one end of the magnet in the coil of wire. Such was the instrument that Mr. Bell sent to the Centennial Exhibition at Philadelphia. The following is the official report of it, signed by Sir WilUam Thomson and others : Mr. Alexander Graham Bell exhibits an apparatus by which he has achieved a result of transcendent scientific interest — ^a trans- mission of spoken words by electric currents thnaugh a telegraph wire. To obtain this result Mr. Bell perceived that he must pro- duce a variation of strength of current as nearly as may be in exact proportion to the velocity of a particle of air moved by the sound, and he invented a method of doing so — a piece of iron attached to a membrane (fig. 68), and thus moved to and fro in the neighborhood of an electro-magnet, which has proved per- fectly successful The battery and wire of this electro-magnet are in circuit with the telegraph wire and the wire of another electro- magnet at the receiving station. This second electro-magnet has a solid bar of iron for core which is connected at one end by a SIR WILLIAM Thomson's report. 9S thick disk of iron to an iron tube surrounding the coil and bar. The free circular end of the tube constitutes one pole of the electro-magnet, and the adjacent free end of the bar core the other. A thin circular iron disk, held pressed against the end of the tube by the electro-magnetic attraction and free to vibrate through a very small space without touching the central pole, constitutes the sounder by which the electric effect is reconverted i%r. 68. into sound (fig. 59). With my ear pressed against this disk, I heard it speak distinctly several sentencea I need scarcely say 1 was astonished and delighted- So were others, including some judges of our group, who witnessed the experiments and verified with their own ears the electric transmission of speech. This, perhaps, the greatest marvel hitherto achieved by the electric Fig. 59. telegraph, has been obtained by appliances of quite a homespun and rudimentary character. With somewhat more advanced plans and more powerful apparatus, we may confidently ex- pect that Mr. Bell will give us the means of making the voice and spoken words audible through the electric wire to an ear hundreds of miles distant The present form of instrument, which is now being manu- 94 THE SPEAZISTQ TELEPHONE. factured m large numbers by the Silvertown Company, does not essentially differ from that reported on so enthusiastically by Sir William Thomson. Only it ia more simple in construction and more handy. Before attempting any explanation of the action of the tele- phone, It may be well to draw the attention of our readers to the special characteristics of the human voice, and to those pe!. xxxi\,. p. 896, July, 1837. %). %/. TONES PRODUCED BY ELECTRICAL CURRENTS, HI the contact is made and broken ; when the contact is made, the sound emitted is very feeble ; when broken, it may be heard at two or three feet distance. The experiment will hardly succeed with small magnets. The first used in the experiment consisted of three horseshoes, supporting ten pounds. The next one tried was composed of six magnets, supporting fifteen pounds by the armature. The third supported two pounds. In each of these trials the sounds produced differed from each other, and were the notes or pitches pec iliar to the several magneta H a larcre magnet supported by the bend be struck with the knuckle,1t gives a musical note ; if it be slightly tapped with the finger nail, It returns two sounds, one its proper musical pitch, and another an octave above this, which last is the note given in the experi- ment ON THE DISTURBANCE OF MOLECULAR FORCES BY MAGNETISM. 1 A short article on this subject appeared in the last number of this journal under the caption, " Galvanic Music." The followino- experiment (as witnessed by yourself and others not long since") affords a striking illustration of the curious fact, that a ringing sound accompanies the disturbance of the magnetic forces of a steel bar, provided that bar is so poised or suspended as to ex- hibit acoustic vibrations. An electro-magnetic bar four and a half inches in length, making five or six thousand revolutions per minute, near the poles of two horseshoe magnets properly suspended, produces such a rapid succession of disturbances that the sound becomes continuous and much more audible than in the foi-mer expenment, where only a single vibration was pro- duced at a time. . •CONES PRODUCED BY ELECTRICAL CURRENTS. 3 Mr. Page was the first to discover that an iron bar, at the moment it became magnetic through the galvanic current, gave a pecuhar tone, and this fact has since been confirmed by Mr. Delezenne. l?;r ^^"»°' Silliman's Journal, vol. xxxiii.., p. 118, October, 1837. W, Wertheim. Annalen dcr Physio and Chcmic. LXXVII., Juuo, 1849. 112 THE SPEAKING TELEPHONK Without being aware of this discovery, I published, in 1844, a treatise in which I dealt with several questions relating to this bubject. In this work I attempted to prove : 1st That the elsctrical current causes a temporary weakening of the coefficient of the elasticity of iron. 2d That likewise the magnetization is accompanied by a very slight decrease of the coefficient of thp elasticity of the iron, v/hich diminishes only partially when the magnetizing current is inter- rupted, and that thi;j result does not manifest itself at once, but only upon the continued action of the currents. The production of sound through the outside current (that is, a current which passes through a helix in whose axis is an iron bar or extended iron wire) was first accurately noticed by Mr. Marrian. According to these physicists, the sound produced was identical with that obtained by striking the rod on either of its ends in the direction of its axis. Striking the rod sideways, however, did not give the same result Mr. Marrian also noticed that other metals, under the tame con- ditions as iron, did not give any sound, and that the sounds from rods of the same dimensions, whether of iron, tempered steel or magnetized steel, were identical. Mr. Matteucci has repeated these experiments with wires as well as iron bars, attempting especially to establish the relatior between the strength of the current and the intensity of the sounds. He has, however, been in some doubt as to the character and value of the sounds. Messrs. De la Rive and Beatson individually made the dis- covery that the current which passes directly through an iron wire produces a sound therein. In one of his later treatises, Mr. De la Rive has given a minute description of a series of experi- ments with various combined currents or* <1 Afferent metals and under different conditions. Mr. Guillemen made an interesting experiment, the result of which confirms my experiments already mentioned. lie found that a weak iron bar which, surroimded by a helix, is fixed at TONES PRODUCED BY ELECTRICAL CURRENTS. 113 one of its ends in a horizontal, position and at the other end is loaded with a light weight, visibly straightens itself when a cur- rent passes through the helix. Mr. Guillemen attributes this movement to a temporary increase of the elasticity of the iron effected by magnetization. At the same time I delivered to the academy a short note in which, without entering into the details of the experiments I explained the results which I had obtained, and how, according to my opinion, the sounds were to be accounted for. The pres- ent treatise contains developments and proofs to sustain the opinions given by me at that time. It seems superfluous to repeat here the discussion which occurred at the time of writing this note, between Messrs. De la Eive, Guillemen and Wari;mann I desire simply to say that the last named scientist was the first to notice that a current passing through a wire may produce a sound withoat there being, in the wire, a resistance of any amount to oppose. Sound may therefore be produced as well in an iron bar as m an extended iron wire, heat having only an insignifi- cant part to play in the phenomenon. Later on Mr. De la Eive sent a treatise to the Eoyal Society, in London, which dealt with a part of this subject After admit- ting that no sound is produced by a current passing through any metal other than iron, he goes on to describe a new class of facts. All conductors, when exposed to the influence of a powerful electro-magnet, give, at the moment of the, passage of an inter- rupted electrical current, a very distinct sound, similar to that of Savart s cogged wheel. The influence of magnetism on all con- ducting bodies seems to consist in its imparting to the latter similar properties to those possessed by iron in itself ; thus devel- oping in these conductors the property of emitting sounds which are similar to those given by iron and other metals without aid Irom the action of a magnet VIBRATIONS OF TREVELYAN S BARS BY THE GALVANIC CURRENT. " ' The vibrations of Trevelyan's bars by the action of heat is a ^experiment more interes ting tl.nn familiar, and one which 1 Silliman's Journal, 1850. Vol. ix., p. 105. ' ' 114 THE SPEAKING TELEPHONE. has been variously and vaguely explained by most authora It will not be necessary for me to recapitulate the several descrip- tions and solutions of this phenomenon, as the novel experi- ment about to be detailed will embrace substantially the whole subject About a year since, while exhibiting to a class the vibration of these bars by heat, it became inconvenient to prolong the ex- periment, as the vibration ceases as soon ab the temperature of the bar is somewhat reduced, and I was induced to seek for some method by which the vibratory motion could be produced and continued at pleasure without the trouble of reheating the bars for each trial. After various fruitless efforts, I obtained a most beautiful result by using the heating power of a galvanic Pig. 62. current Fig. 62 shows the mode of performing the experi- ment with the battery. A and B are the two forms usually given to Trevelyan's bars, which, when to be vibrated by the action of heat, are made of brass, and weighing from one to two pounds, and after being sufficiently heated are placed upon a cold block of lead, as seen in fig. 63. The two bars may be placed upon the same block, though the vibrations are apt to interfere when two are used. When the bars are to vibrate by the galvanic current, they may be of the same size and form as sliewn, and of any kind of metal— brass, or copper, or iron, how- ever, seeming to bo most convenient One or both of the bars may be placed at once, without reference to temperature, upon the stand, as in fig. 62, the bars resting upon metallic rails E 1\ TREVELYAN'S EXPERIMENT. II5 which latter are made to communicate each with the poles of a galvamc battery of some considerable heating power. Two pairs of Darnell^ of Smee's, or of Grove's battery of large size are sufficient The battery I employ consiste of two pL of Grove s, with platinum plates four inches square. The vibration will proceed with great rapidity as long as the galvanic current is sustained. In fig. 63 one pole of the battery is connected with tiie metallic block, and the other pole with mercury in a little cavity in the centre of the vibrating bar. The experiment succeeds much better with the rails as in fig 62, and quite a number of bars may be kept m motion by increasing the number of rails, and passing the current from one to the other through the bars rest- ing upon them. ^ Fig. 63. The rails are best made of brass wire, or a strip of sheet brass, though other metals will answer-the harder metals which do not oxidate readily, however, being preferred. A soft metal, like lead IS not so favorable to the vibrations in this experi- ment, although in Trevelyan's experiment lead seems to be almost the only metal that will answer to support the bar, which IS usually made of brass. Prof. Graham and other authors have attributed the vibration of Treyelyans bars to the repulsion between heated bodies, and others have classed the phenomenon with the spheroidal state of heated bodies. I do not consider that any repulsive action is manifested or necessary in either of these cases, nor do I know of any instance in which a repulsion has been proved between heated bodies It is obvious some otlier solution is required for this curious phenomenon, and it appears to me that the motion 116 THE SPEAKING TELEPHONE. is due to an expansion of the metallic block at the point of con- tact, and, upon this supposition, it appears plainly why a block of lead is required. That is, a metal of low conducting power and high expansibility is necessary, and lead answers these con- ditions best In a future communication I will analyze this matter and explain more fully. The size of the bars may be very much increased when the galvanic current is employed, and some curious motions are ob- served when long and large cylinders of metal are used. If they are not exactly balanced, which is almost always the case, they commence a slow rolling back and forth, until finally they roll entirely over, and if the rails were made very long they would Fig. 64. go on over the whole length. An inclination of the rails is re- quired in this case, but it may be so slight as not to be percep- tible to the eye. If a long rod of some weight be placed across one of the bars, as shown in fig. 64, the vibrations will become longer, and by way of amusement I have illustrated this with a galvanic see-saw, as it may be termed. It is well known that where mere contact (without metallic continuity) is made by metals conveying the galvanic current, the metals become most heated at the points of contact, and if the current be frequently broken the heat at these points is still more auo-mented. It is for this reason we are able to use various MOLECULAR ACTION OF MAGNETIC BODIES. 117 kinds of metals for the experiment, without reference to their conductmg powers and expansibilities VIBRATORY MOVEMENTS AND MOLECULAR EFFECTS DETER- MINED IN MAGNETIC BODIES BY THE INFLUENCE OF ELEC- TRIC CURRENTS. 1 Afr. Page, an American philosopher, had observed, in 1837 that on brmgmg a flat spiral, traversed by an electric current near to the pole of a powerful magnet, a sound is produced M. Delezenne, m France, also succeeded, in 1838, in producino- a sound by revolving a soft iron armature rapidly before the poles of a horseshoe magnet In 1843, I myself remarked that plates or rods of iron give out a very decided sound when placed m the mterior of a helix whose wire is traversed by a powerful electric current; but only at the moment when the circuit is closed, and when it is interrupted. Mr. Gassiot, in London, and Mr. Marrian, in Birmingham, had also made an analogous experiment in 1844. Attributing this singular phenomenon to a change brought about by the magnetism in the molecular constitution of the magnetized body I went through a great number of experiments, in order to study this interesting subject It is above all things important, in order to obtain a numerous series of vibrations, to be provided with a means of interrupting and of completing, many times in a very short space of time, the circuit of which the wire that transmits the current forms a part • m other words, to render a current discontinuous or continuous.' With this view, I made use of one of the numerous apparatus called rheotomes, or cut-currents, and which are intended, when placed m the circuit, to render a current discontinuous. One of the most convenient (fig. 65) consists of a horizontal rod, carrying two needles, inserted perpendicularly and parallel with 1 Treatise on Electricity in Theory and Practice, by Aug. De Ja Bive. 1858 Vol 18; pa^fesSOOtosyi iuclusiye. »«"«. looo. vol. 118 THE SPEAKING TELEPHONE. eacli other, so arranged that when they are immersed simultane- ously in two capsules filled with mercury, and insulated from each other, the circuit is closed ; and when they are not immersed, it is open. A clock work movement, or simply a winch moved by the hand, gives a rotatory movement to the axis ; whence it follows that, in a given time, a second for example, the circuit may be closed or interrupted a great number of times. The ap- paratus of fig. 65 presents four needles instead of two, and consequently four compartments corresponding with the four needles. We shall have occasion hereafter to see the use of the second system of two needles ; for the present, a single one is suflEicient; and, consequently, in all the experiments that will follow, in order to place it in the circuit, we shall employ indif- ferently either the one that is nearest to the clock work move- Fig. 66. ment or the one that is most distant. There is a risk of the mercury being projected when the movement is too rapid ; to prevent this inconvenience, we must cover the capsules, the needles, and the axis that carries them, with a small glass shade. When the current is very powerful, the mercury is oxidized by the effect of the sparks that occur at the moment when the needles emerge ; in this case it is necessary to remove the oxide, or to change the mercury. We may do without mercury, and supply its place by two elastic metal plates resting on a cylinder, or on the circumference of a varnished wooden or ivory wheel, in the edges of which are inserted small pieces of metal, in me- tallic communication together. When the elastic plates, by means of the rotation of the cylinder or of the wheel upon its axis, come in contact with the metal part of the surface, the cir- ELECTRICAL RHEOTOME. 119 cuit is closed; when the contact with this metal part ceases, which occurs when the contact is with the wood or ivory, the circuit is open. It is necessary in this case that the two plates, as were the mercury cups in the preceding case, shall be in the course of the circuit, that is, to traverse the wire of the helix, and shall press strongly against the circumference. We may also intei-posein the course of the current merely a toothed wheel and an elastic metal plate, which presses upon the teeth of the wheel (fig. 66). By giving the wheel a movement upon its axis, we cause the plate to leap from one tooth to another ; each leap produces a rupture in the circuit, which is closed again immediately afterwards. The musical tone given out by the plate, when we have no other means of measuring it, gives us exactly the number of times that the circuit has been opened and closed, that is to say, interrupted, in a second. I Fig. 66. have dwelt upon these several kinds of rheotomes because we frequently make use of one or the other of them. For the pres- ent, we shall apply them to the study of the vibratory movement experienced by magnetic bodies under the influence of discon- tinuous currents. "When we place a magnetic but unmagnetized body, such as iron or steel, in the interior of a bobbin, this body experiences very remarkable vibratory movements, as soon as we pass a series of discontinuous currents through the wire with which the bobbin is encircled. These movements are made manifest under the form of very decided and varied sounds, when the body has a cylindrical, or even an elongated form. The sound is less de- cided, but more sharp and more metallic, with steel than it is with soft iron. Whatever be the form or the size of the pieces of soft iron, two sounds are always to be distinguished : one a series of 120 THE SPEAKING TELEPHONK blows or sliocks, more or less dry, and very analogous to the noise made by rain when falling on a metal roof ; these blowa exactly correspond to the alternations of the passage and the in- terruption of the current; the other sound is a musical sounds corresponding to those which would be given by the mass of iron, by the effect of the transverse vibrations. We must take care in these sounds to distinguish those that are due to the simple me- chanical action of the current upon the iron — an action which,, being exercised throughout the entire mass, may deform it, and consequently produce, by its very discontinuity, a succession of vibrations. However, this is not sufficient for the explanation of Fig. 67. all the sounds ; and we must admit that there is, in addition, a molecular action, namely thq,t the magnetization determines a particular arrangement of the molecules of the iron, a rapid suc- cession of magnetizations and demagnetizations gives rise to a series of vibrations. How, for example, can we otherwise explain the very clear and brilliant musical sound given out by a cylin- drical mass of iron 4 inches in diameter, and weighing 22 lbs., when placed in the interior of a large helix (fig. 67), while tra- versed by a discontinuous current ? Kods of iron half an inch and upwards in diameter, when fixed by their two extremities, also MOLECULAR ACTION OP MAGNETIC BODIEa 121 give out very decided sounds under the same influence. But the most bnlhant sound is that which is obtained by stretching upon ThTn d -^ r' well annealed wires, one or two twentieth! of an nch in diameter and a yard or two in length. They are placed n the axis of one or several bobbins, the wires of which are. traversed by electric currents, and they produce an assemblage of sounds, the effect of which is surprising, and which greX resembles that to which several church bells give rise when vibrating harmonically in the distance. In order to obtain this effect It la necessary that the succession of the currents be not too i-apid and that the wires be not too highly strained. With LTnTtl nl'"'^'' ^^ ''"°^^' and finches in diameter, I found that the maximum of effect occurs when it is stretched W a weight of from 67 lbs. to 117 lbs., if it is annealed ; and from 64 lb. to 126 lbs., if it is hardened. Beyond these limi'ln 3 portion as the tension increases, the total intensity and the num^ ber of different sounds notably diminish ; and, at a certain degree of tension, we no longer hear the sound due to the transverse vibrations but simply that arising from the longitudinal vibra- tions. The reverse occurs when the wire is slackened Sounds entirely analogous to those we have been describing: may be produced by passing the discontinuous electric current through the iron wire itself. We remark, in like manner, a se- ries of dry blows, corresponding to the interruptions of the cur- rent, and stronger and more sonorous musical sounds, in some cases, than those that are obtained by the magnetization of the wire Itself. This superiority of effect is especially manifested when the wire IS well annealed, and of a diameter of about one twelfth of an inch; for greater or less diameters, the magnetiza- tion by the helix produces more intense effects than those which result from the transmission of the current Moreover, the same circumstances that influence the nature and the force of the sound in the former case, exercise a similar influence in the latter. The transmission of the discontinuous current produces sounds only when transmitted through iron, steel, argentine, and magnetic bodies in general; but in different decrees for each 122 THE SPEAKING TELEPHONE. depending on the coercitive force that opposes the phenom- enon. Wires of copper, platinum, silver, and, in general, any metals, except the magnetic, do not give forth any sound, whether under the influence of transmitted currents, or under that of ambient currents, such as the currents that traverse the convolutions.of a wire coiled into a helix around a bobbin. The sound that is produced when a discontinuous electric current is made to pass in an iron wire, explains a fact that had been for a long period observed, and had been described as far back as 1785, by the Oanon Gottoin de Coma, a neighbor and a contemporary of Yolta This fact is, that an iron wire of at least ten yards in length, when stretched in the open air, spontaneously gives forth a sound under the influence of certain variations in the state of the atmosphere. The circumstances that accompany, as well as those that favor the production of the phenomenon, demonstrate that it must be attributed to the transmission of atmospheric electricity. This transmission, in fact, does not occur in a continuous manner, like that of a current, but rather by a series of discharges. Now, Mr. 3eatson has demonstrated that the discharge of a Leyden jar through an iron wire causes this wire to produce a sound, provided it does not occur too suddenly, but is a little retarded by passage through a moist conductor, such as a wet string. The sounds given out by iron wire and by magnetic bodies, under the circumstances that we have been describing, seem to in- dicate, in an evidenfmanner, that magnetism produced by the in- fluence of an exterior current, as well as by the direct transmis- sion of a current, determines in them a modification in the ar- rangement of their particles, that is to say, in their molecular constitution. This modification ceases and is constantly pro- duced again by the effect of the discontinuity of the current; whence results the production of a series of vibrations, and con- sequently different sounds. A great number of observations, made by different philoso- phers, have in fact demonstrated in a direct manner the influence joule's experiments, 128 tj'^^t'fZ T"" '^^ "'°^""'^^^'- P^^P^rt»«« «f magnetic bodies. M. de Wertheim, in an extensive work on the elasticity of metals, had already observed, that magnetization produced by means of a helix whose wire is traversed by the electric current produces a dimmution in the coefficient of elasticity in iron wire and even m steel; a diminution which, in the latter at least, re- mains in part even after the interruption of the current M. Guillemm has also remarked moie recently, that a bar of soft iron, fixed by one of its extremities whilst the other is free, and which, instead of remaining horizontal, is curved by the eilect of Its own weight, or by that of a small additional weight im- mediately raises itself, when the current is made to pass in the wire of a helix with which it is surrounded, which helix is itself raised up with the bar, all the movements of which it followl since 1 IS coiled around it This experiment possesses this im IT T~^ 'i""^ ''^ magnetization determines a mol fication in the molecular state of iron ; for it cannot be explained by a mechanical action, which, could only occur if the heHx is independent of the bar. Furthennore, an English philosopher, Mr. Joule, succeeded in determining the influence that magnetization can exercise over the dimensions of bodies. By placing a soft iron bar in a well closed tube, filled with water and surmounted by a capilW tube, he first satisfied himself that this bar experienced no vaZ t on of volume when it was magnetized by means of a powerful he IX In fact, the least variation of volume would have been detected by a change of the level of the water in the capilty tube; now not the slightest is observed, however powerful the magnetization may be. This result is in accordance Z^h I t M W^l'^'^'lf i^^'T''^ ^^ ""'^''^ "^^*^°ds, and with what M. Wertheim had also obtained by operating yery nearly in the same manner as Mr. Joule. But if the total volume s not altered, it is not the same for the relative dimensions of the bar which, under the influence of magnetization, experiences an increase m length at the same time as it doe a dim nXn in 124 THE SPEAKING TELEPHONE. diameter, at least within certain limits. It was by means of a very delicate apparatus, similar to the instrument employed in measuring the dilation of solids, that Mr. Joule discovered that a soft iron bar experiences a decided elongation, which is about •tao'^ooo '-'^ o^ ^^ *°*^^ length, at the moment when the current by .which it is magnetized is established, and a shortening at the moment when it is interrupted. The shortening is less than the lengthening, because the bar always retains a certain degree of magnetism. It woiild appear that the lengthening is propor- tional, in a given bar, to the square of the intensity of the magnetism that is developed in it. When we make use of iron wires instead of bars, it may happen that it is a shortening, and not a lengthening, that is obtained at the moment of magnetiza- tion. This change in the nature of the effect is observed when the degree of tension to which the wire is subjected exceeds a certain limit \ Thus an iron wire, 12^ inches in length by | inch in diameter,, distinctly lengthens under the influence of the magnetism, so long as it is not exposed to a greater tension than 772 lbs. ; but the less so, however, as it approaches nearer to this tension. Setting out from this limit, and for increasing tensions, which in one experiment were carried up to 1764 Iba, the wire was con- stantly seen to shorten at the moment when it was magnetized. Tension exercises no influence over highly tempered steel ; sa there is never any elongation, but merely a shortening, which commences when the force of the current exceeds that which is. necessarv to magnetize the bar to saturation. M. Wertheim, on his part, at the close of long and minute researches, succeeded in analyzing the mechanical effects that are manifested in magnetization. He found that, when an iron bar is fixed by one of its extremities, and the bobbin is so placed that its axis coincides with that of the bar, no lateral movement is observed, but merely a very small elongation, which rarely exceeds ,00078 inch. This elongation is the greater as the bob- bin is situated nearer to the free extremity of the bar, and dim- inishes in proportion as it approaches the point by which it is WERTHEIM's RESEARCHEa 125 fixed When the bar cea.es to be within tho axis of the bobbin the elongation still remains; but it is accompanied by a lateral/ move„,ent in the direction of the radius of'the bobbin tS hobbin that was employed by M. Wertheim was 9.84 inches long, and 7 inches in interior diameter; glasses of a magnifying power of about 20 diameters, and containing two steeTwLs! Ten't ^:;t ^ -T'^'' '^'" '^'"^"*^"^ ^"^ '^' ^^t^r-i displace- ment This displacement, or, what comes to the same thing the versed sine of the curvature of the bar, measured at its extremity was determmed for different intensities of cuirent; and it al- peared that it was in general proportional to this intensity, but It vaned for each position of the bar in the interior of the bob- bin However it may be, we are able to find for each of these positions the mechanical equivalent of the unit of the intensity of the current, nanaely, the weight which, when applied at the extremity of the b^-, would produce the same versed sine Thus, for example by calling the length of the part of the ! radius comprised between the axis of the bar and the axis of the bobbin D, the versed sine of the curve/ the weight that would produce the same versed sine P, the following resulte have been obtained by acting successively upon three bars of iron, the respective masses of which were 100, 40 5 and 25 5 • NO. OF BARS. FOB D— 80. 1. 2. ■3. / .4386 feet. 3.0632 " 1.5249 " 98.92 grs. Tr. 41.26 " 22.57 " FOB D— 50. / .2385 feet. 1.5573 " .9360 " 53.86 grs. Tr. 23.04 " 12.55 » We calculate P from the formula P.= /|^, in which/is the rsT7l2f65?if ""? "'^ ' *'' '^^'^^^^"^ °^ ''^''^'y' -^-1^ I ' Ji , avoirdupois per square inch for soft iron, b and c the width and thickness of the bar, and L its length from its fixed point to Its free extremity. Prom the preceding table we "'"')■ ^^ *is result mlht be attributed to a part of the cunmt travelling the iron cnvdone Itself, .n.,tead of cirenlating exclusively through the copper wh^ I insulated the latter by means of a thb covering of sTorwlx so that the iron cylinder that surrounds it is i»t able t^ com Te'riT "'","''■ ""' Tpp-^'- '^"« ^««=' ■'' --«x TZ^ZuJ :^^ °'^' *'"" '^ ^ *'y' "'" di^-ntinuous cuirent that traverses the copper wire determines a series of vi- bra tions ,n the iron envelope, which proves that we may adm"t that he same effect is pr squires a peculiar dry tone which makes it resemble that which steel giv^ out wiZ out being magnetized. ® The very remarkable influence of tension, which, beyond a certain limit, diminishes in soft i«,„ wires their aptitude to le ounds, IS a further consequence of our explanLa In W fL—r-X'^" ^^v' '*»^'°"' -'<'■«<' " po—t derangement in their normal position, and are conaequentlv found crippled in their movements, and are no W awl under the mfluence of exterior or interior causes, to exlute the r&TZr ™' ~"^"-"- ''^ vi^tionsthS in J'rHll'T^h"* a character altogether different from the preced- ing, stm further show that the magnetization of iron is always attended by a molecular change in its mass. ^ The first of these facts was discovered by Mr. Grove It i, that an annature of soft iron experiences an elevation of torn fzed r ,T''' ^'^'' ^'""' '' ^ '^^^i^ and demagne". ^ed several times successively by means of an electro-magnft or even of an ordinaiy magnet set in rotation in front of it ^obal s^i^d "'""v,*"' ""^ phenomenon, but in a some^ha slighter degree; whilst non-magnetic metals, placed underexactly tloTr.rr"^'"' ^^ ''°* P"^"* *'«' ^'^I-tost traces o^ admitting that the development of heat arises from the mole cular changes which accompany magnetization and demagneti- TZ. , T"^ ^""^ *'"'='' '' '"' ^'"^ ™P»*'nt, is due to l)r. Magg,, of Verona, who proved that a oireular plate of verv homogeneous soft iron conducts heat with more f^ility in o7e direction than m the other when it is magnetized by a powerful • electro-magnet ; whilst, when it is in the natural state! its conduc" X84 THE SPEAfcING TELEPHONE. Ability is the same in all directions, and, consequently, perfectly unif onn. The plate is covered with a thin coating of wax melted with oil, and the heat arrives at its centre by a tube that tra- verses it, and in the interior of which the vapor of boiling water is passing. The plate is placed horizontally on the two poles of a powerful electro-magnet, several insulating cards pre- venting contact between it and the iron of the electro-magnet So long as it remains in its natural state, the curves that bound the melted wax assume the circular form which indicates a uni- form conductibility for heat in all directions. But, as soon as the electro-magnet is magnetized, the curves are deformed ; and they are always elongated in a direction pei-pendicular to the line that joins the magnetic poles ; which proves that the con- ductibility is better in the direction perpendicular to the magnetic axis than in the direction of the axis; a result in accordance with the fact that we have established, that the par- ticles of iron approach each other, by the effect of magnetiza- tion, in the direction perpendicular to the length of the magnet, and recede in the direction of that length, which is always the magnetic axis. INFLUENCE OF MOLECULAR ACTIONS UPON MAGNETISM PRODUCED BY DYNAMIC ELECTRICITY. We have seen that heat, tension, and mechanical actions gen- erally facilitate magnetization.* M. Matteucci has found that torsion and percussive and mechanical actions, not only facilitate the magnetization produced upon soft iron by a helix that is traversed by a powerful current, but they also contribute, when the current has ceased to pass, to the destruction of magnetism in a very rapid manner. The same philosopher has likewise observed, that torsion, when it does not pass beyond certain limits, augmented the magnetization produced upon steel needles by discharges of the Leyden jar. 1 M. Lager^jelm observed tliat iron becomes strongly uiagnetio by rupture. MARIA^-INl'S EXPEBIMENTS. 135 M. Marianini, who has made numerous and interesting re- searches upon magnetization, arrived at curious results upon the aptitude that iron bars may acquire of becoming more easily magnetized in one direction than in another, and even in being little or much magnetized by the influence of the same cause. When an iron bar has been magnetized by the influence of an instantaneous current that circulates around it, and when it has lost this magnetization by the action of a contrary Cur- rent, it is more apt to be magnetized afresh in the former case than in the latter. We are able, by contrary currents, to give it even more aptitude to be magnetized in the latter du-ection than in the former. The augmentation of aptitude that it acquires of being magnetized in one direction is equal to the loss of apti- tude that it experiences for being magnetized in the other direc- tion. But, by reiterating the action of the currents upon the same bar, the increase of aptitude in one direction, and the cor- responding diminution in the other, become always more and more feeble. The modifications of aptitude for acquiring mag- netization are accompanied by modifications in the aptitude for losing this magnetization ; but in such direction that the latter is the reverse of the former. Willing to enter more deeply into the study of the effects that we have been relating, M. Marianini subjected iron to differ- ent physical and mechanical actions. First of all, he satisfied himself that neither elevation of temperature, nor especially the cooling by which it is followed, neither percussion nor torsion, nor a violent shock, nor any mechanical action, even the most energetic, are able of themselves to determine magnetization; nor, indeed, does the discharge of a Leyden jar through an iron bar magnetize it But these various operators, incapable of magnetizing, may all serve to destroy the polarity of magnetized bodies ; the quantity of magnetic force that they thus lose, when their aptitude has not been altered, is the greater, as the magnet- ization has been more feeble. But if, after having undergone one of these actions, the bar has still preserved a little magnet- ism, It can no longer lose it by this or by any similar action. 138 THE SPEAKING TELEPHONE. What is very remarkable is, that when the magnetism of a bar has been destroyed, on remagnetizing it in a contrary direction by a succession of instantaneous currents, so tliat its magnetiza- tion is null, we may restore to it its former magnetism by means of a violent shock, by letting it fall, for instance, on the pave- ment from the height of a couple of yards. The greater the height of the fall, the more powerful is the magnetism it re- covers. Thus, a bar, that made a needle deviate 60°, having been brought by a succession of discharges to exercise no devia- tion beyond 0°, gave 14° on falling from a height of 12.8 feet, 15° 80' on falling from a height of 15.0 feet, and 21' on falling from a height of 6.4 feet This new polarity was in the same direction as the primitive one. Even when, by destroying the primitive magnetization of the bar, we have actually imparted to it a new one in a contrary di- rection, we find on letting i;t fall upon the pavement that we re- store to it the first that is possessed. M. Marianini would be dis- posed to believe from this experiment and other similar ones, that the bar had retained its former magnetization while still acquir- ing the contrary one, which neutralized the e£Eect of the first and even surpassed it ; and the shock merely destroyed the second, either in whole or in part, which permitted the former to reap- pear. Flexion, friction, heat, or an electric discharge traversing the iron directly, may take the place of the shock, particularly when very fine wires are in question. The action that is exercised by an instantaneous discharge through the wire of a helix upon a body already magnetized, in- creases or diminishes the magnetism of this body according to the direction in which it is sent ; but this increase or diminution is the less sensible as the iron is more magnetized. In any case, a given instantaneous current produces proportionately more effect when it is made to act with a view of diminishing the polarity in the magnetized bodies than when it is made to act with a view of increasing it M. Marianini, in order to explain the results of these experi- ments, admits a difference between what he calls polarity and MARIANINI S EXPERIMENTS. i3r magnetism. Thus, , the same magnet, although deprived of polarity, may very readily retain magnetism, when magnetized at one time in two contrary directions with an equal force. We must then suppose that contrary magnetic systems producing equihbrmm are able to exist in iron, and that exterior forces such as a current or a mechanical action, do not act with the same energy upon the opposite systems. This opinion, which does, not as yet appear to us to rest upon facts sufficiently numerous has, however, nothing in it that is inadmissible; nothin- in fact opposes there being in the same bar a certain number of mrticles- arranged so as to produce a magnetization in a certain direction and_ others so as to produce magnetization in the opposite di- rection ; as, for example, the interior particles may be found to have in this respect an arrangement the opposite of those on the surface ; and that such exterior action operates propoitionatelv with greater force upon the one than upon the other This point would need to be made clear by further observations, and especially by comparative experiments made upon bars of dif- ferent forms and different dimensions-upon hollow and solid cylinders, for example. But if some doubts still remain upon the conclusions that M. Marianini has drawn from his experi- ments, there are not any upon the new proof which they bring in favor of the connection that exists between magnetic and mole- cular phenomena. The different degrees of aptitude acquired by iron under the influence of certain actions, of becoming more easily magnetized in one direction than in the other, are all quite in har- mony with the disposition with which the particles of bodies are endowed to arrange themselves more easily in one direction than in another. This loss of aptitude, af cer the multiplied repetition of the contrary actions, corresponds with the indifference to arrange themselves m one manner or the other, which is finally presented t)J the particles of bodies, after having experienced numerous derangements in different directions, i Finally the remarkable iWe have a remarkable example of this in the fragUity presented by iron when it 188 THE SPEAKING TELEPHONE. effects of shock, flexion, heat, in fact, of all those actions that change the relative position of the particles, come in support of the relation that we have endeavored to- establish. The whole of the magneto-molecular phenomena that we have been studying, lead us to believe that the magnetization of a body is due to a particular arrangement of its molecules, origin- ally endowed with magnetic virtue ; but which, in the natural state, are so arranged, that the magnetism of the body that they constitute is not apparent. Magnetization would therefore con- sist in disturbing this state of equilibrium, or in giving to the par- ticles an arrangement that makes manifest the property with which they are endowed, and not in developing it in them. The coerci- tive force would be the resistance of the molecules to change their relative positions. Heat, by facilitating the movement of the particles in respect to each other, diminishes, as indeed does every mechanical action, tUis resistance, that is to say, the coerci- tive force. There remains an important question to be resolved. Are mechanical or other actions — disturbers, as they are, of the electri- cal state— able of themselves to give rise to magnetism ? or do they only facilitate the action of an exterior magnetizing cause; for example, terrestrial magnetism, which, in the absence of all others, is ever present? M. Marianini's researches would seem to be favorable to the latter opinion; however, the facts that are known do not appear to us sufficient as yet to establish it in an incontestable manner. Let us remark that, even although it should be established, yet the non-existence of a previous and proper polarity of magnetic bodies, or of electric currents, circu- lating around them in a determinate direction, would not neces- sarily follow. We should merely conclude from it that, in the absence of an exterior acting cause, the particles when left to themselves, constantly arrange themselves so as to determine an equilibrium between their opposed polarities ; whence results the nullity of all exterior action. TONES PRODUCED BY BLEGTRICITy. 189 A NEW METHOD OF PBODUCING TONES BY THE ELECTRIC CURRENT. 1 In 1837 Dr. Page, of Salem, Mass., made the important dis- covery that a horseshoe magnet, before or between whose poles a flat spiral of copper wire was suspended, began to emit tones whenever he passed through the spiral the discontinuous current of a galvanic battery. Other physicists, and especially Delezenne, Beatson, Maman, Matteucci, De la Eive, and Wertheim, in following up the dis- covery, have shown us that it is the interrupted current only which generates this new formation of tones, and that for this purpose it can be applied in two ways, either direct, as when it is passed through the bodies themselves, or again, when conductea through a heUcal wire placed around these bodies. In this manner tone^ have been produced in iron and steel, and in these metals only it would seem, as Wertheim has found from actual experiment, that bars and wires of other metals cannot be made to emit tones by either method ; and although De la Eive says in his first treatise that he has obtained tones by both methods from platinum, silver, copper, brass, lead, tin, and zinc, it will be observed that he modifies this assertion in a aubsequent work by saying that this took place only when a pow( al electro-magnet was acting at the same time on the wira The method which we are now about to describe, and which the writer happened to discover accidentally in the fall of 1854, possesses the advantage of generalizing matters, as it shows that all metals can, under certain conditions, be made to emit tones ; there are also other considerations which render it interesting as regards its connection with the theory of electricity. This method is based upon the interruptions of a battery current, although in reality it is not the latter, but rather the induced currents produced by the interruptions that must be considered as the generator of the tones. In place also of bars or wires as 1 J. C. Poggfendorf. PoggendorPs Annalen, xoviii., p. 193. Monatsborichtoii der Acad. Murz, 1856. 140 THE SPEAKING TELEPHONE. heretofore used for producing the tones, tubes formed of sheet metal are substituted, and surround the coils through which the current is passed. The writer used in his experiments coils five inches in length and about one and one eighth inches in diameter. Both wires of the coils were connected, so that their united length was about 100 feet ; the diameter of the wire was 1.4 millimetres. The coils were maintained in a vertical position by means of a stand provided for the purpose, and so placed that the lower ends could be connected to the battery , which, as a rule, consisted simply of a single Grove cell. The tubes to be examined, which were about five inches long and from two to four inches in diameter, were then placed over the coils. Some of them were left entirely open, some closed by soldering, and others bent together so that the edges just touched each other. The ma- terial of the tubes consisted of platinum, copper, silver, tin, brass, zinc, lead and iron. A Wagener hammer of peculiar construction, so as to deaden the noise of its own vibrations, and thus prevent it from interfer- ing with the investigations, was used for interrupting the current From the experiments made with this apparatus it has been found that none of the metals, except iron, can be made to emit tones when formed into either open or completely closed tubes and placed over the coils. If, however, the edges of the tubes just touch each other, then all metals can be made to emit a very audible tone, which will vary in loudness and quality of sound with the dimensions of the tubes, the elasticity and qual- ity of the material employed, the strength of the current, and certain other minor considerations that will readily suggest themselves. Iron is distinguished from the other metals by the fact, due no doubt to its magnetic properties, that it gives a crackling tone both when made into an open tube which surrounds the coil, and also when placed alongside of it The tone in this case is similar to that heretofore noticed in sheet iron when laid in the coil but it is much weaker than that neard when tbe edges or TONES PRODUCED BY ELECTRICITY. 141 the tube come in contact In the latter case it seems as though a second tone appears with the former one. The sounds obtained in this manner from metallic tubes whose edges just come in contact with each other, are evidently produced by the induced current generated in the mass of the tubes by. the action of the intermittent current in the cqil. They must evidently, therefore, become stronger or weaker as the con- ditions which give rise to them render the induced current stronger or weaker. For example, they are increased when iron wires are placed in the coils, as was done in the experiments made by the writer. They are also increased, but in a smaller degree, when the coil is connected with a condenser, which was also done in all of these experiments. The weakening of the tones, however, may be still more strikingly shown. For this purpose it is only necessary to place between the tube producing the tone and the induction coil another metallic tube, completely closed and of somewhat smaller diameter. As soon as this is done, the tone of the wider tube ceases instantly, and when the smaller tube is withdrawn again the tone recommences at once. Even two tubes of different diameters capable alone of giving out tones will show this weakening, but if placed simultaneously one within the other around the coil, they do not interfere with each other. In place of the smaller closed tube, which, for example, may consist of zinc or any other non-magnetic metal, an open iron tube may be substituted. In this case also the action depends upon the length and thickness of the metal, and weakens or destroys the tones accordingly ; not, however, because an induced current is formed in it, as in the case of the closed zinc tube> but because it becomes magnetized by the action of the coil, just as the core does, and the effects of the coil and core consequently oppose each other. The proof of the connection of the tones with the induced current, if additional proof is necessary, is still further shown by the fact that they are quite independent of the diameter of the 142 THE SPEAKING TELEPHONE. tubes. The writer has obtained tones from tubes of two, four, and eight inches diameter without noticing any difference in the strength of the sound, other than what might be attributed to a change of proportion between the length and diameter of the tubes. With proportionate length, a hollow cylinder of any diameter whatever would obviously be forced by the action of a single cell of battery to emit tones just as well as a tube of only an inch in diameter. Now, while it may be considered sufficiently evident that the tones in question owe their origin to the induced currents which are produced in the tubes parallelly with the convolutions of the coil, and in this respect therefore correspond to the tones gener- ated in steel or iron wires when an intennittent current is passed directly through the latter, we must by no means conclude that they are the result of a molecular action extending throughout the entire mass of the metal, as is certainly the case when iron wires or open iron tubes are used. On the contrary, as the writer is fully convinced, the development of tones first noticed by him, has its origin at the points where the edges of the tubes touch each other, and that, in consequence of this, slight concus- sions occur which set the tubes to vibrating and thus give out tones. The tones, moreover, are only a secondary phenomenon, and may entii'oly fail when the material of which the tubes are made possesses but little elasticity, as, for instance, when lead is used. The real part of the acoustical phenomenon lies in the dull sound or kind of ticking, somewhat similar to that of a watch, which is heard at the points where the edges come in contact simultane- ously with the strokes of the vibrating hammer. It is consequently this ticking alone, and not the tone produc- tion, whose investigation properly comes within the province of electrical science, and which I consequently made the especial subject of study, but up to the present time I am obliged to say I have not yet succeeded in bringing about a complete solution of the problem. TONES PRODUCED BY ELECTBICITY. I43 The ticking tone is not audible in a tube whose edges have been soldered, and thus probably made to resemble more nearly a hollow cast-iron cylinder. Even a soldered tube, which has been so nearly cut in t. o that only a portion of metal of about a hne m width remains, is found to give no ticking sound under the conditions I employed. This shows that a certain separation of the edges is required for the production of the sound; it is furthermore perfectly clear that the adjacent edges of the tube do not come in so close contact as the particles within the mass, and is also proven bv phenomena in other provinces of physical science. With ap- parently the very best contact, also, we must admit the exist- ence of a thin air stratum between the edges of the tube, the same as exists even in the dark centre of Newton's inga The influence which distance between the edges of the tubes has on the ticking is shown by the fact that, the more the edges are pressed together the gi-eater is the decrease in the sound, and It IS not improbable therefore that if the compression were in- creased with force sufficient to press the particles of metal firmly against each other, the sound could be entirely destroyed. On the other hand, again, if a loud sound is wanted it is necessary to make the edges just touch each other loosely. It might be thought an increase of pressure would increase the number of contact points also, and in this manner cause the decrease m the strength of the sound. This could only have been the case when I caused gi-eater portions of the edges of the tubes that were not quite parallel to approach each other, so that in general such a conclusion will hardly be found to hold good It has furthermore been found that when a short piece of wire or a sewmg needle is placed between the edges of the tube, the ticking then becomes very loud, but decreases in like manner with increased pressure, although the needle is never made to touch at all points. Portions of the tube edges may also be in close metallic con- tact without the entire disappearance of the ticking if uiily other portions make but slight contact with each othpr. Hence tubes 144 THE SPEAKING TELEPHONE. -which have been partially cut in two, like those previously mentioned, wiU commence to give out sounds if a needle or wedge-shape piece of metal is inserted in the slit This explains a phenomenon which is observed with tin. When a sheet of this metal is bent around the induction coil and its edges are brought close to each other, they immediately become fastened together as if soldered, and yet the ticking continues to be heard exceed- ingly well. K, however, the neighboring edges are melted together with a spirit flame or soldering iron, the sound ceases. The principal question in this examination is of course this : What causes the ticking sound at the divided edges ? On first consideration it might be attributed to the passage of sparks, but iMs certainly is not the origin of the sound. Sparks may gener- ally be seen by separating the edges of the tubes from each other at the moment the hammer interrupts the battery current They are also noticed, but in a lesser degree, with tubes which have been partially cut in two, when the wedge is allowed to drop into the opening. But so long as the edges remain quietly near each -other no spark is observed, even in perfect darkness, and yet the ticking continues all the time without the slightest inter- ruption. I further placed the induction coil with the metallic tube under the exhausted receiver of an air pump, but even there the ticking was heard without the least spark being visible between the edges of the tube. The sparks, moreover, possess an exceedingly low potential, but this is not to be wondered at when we consider that they are produced in a metallic conductor of only a few inches in length. With easily fusible metals, such as tin for example, sparks are often seen to be projected for a distance of several lines, but these cannot be considered as genuine electrical sparks ; they are caused rather by the projection of particles of melted and glow- ing metal, and their direction also is generally contrary to that of the electrical cuiTcnt, being sometimes towards one side and sometimes towards another. In any case, however, they can never be real electrical sparks, since the electrical potential of the current, as already stated, is too low for their production. It TONES PRODUCED BY ELECTRICITY. I45 made no difference how near I brought the edges together with- out causing absolute contact, I could never preceive the pas- sage of sparKs between them. The slight space might also be S b ' rr^'^' ^"^^"' ^^ *^^ ^P «f *^« *oV^ even 2^ r .?r^ ^'*^''^ '^" '^^S'« ^f *^« ^^bes without feeling the slightest sensation. ^ If sparks were the cause of the sound one would naturally suppose It would disappear in a fluid conductor buwW^ maintammg the tube in a horizontal position, I hav'e dipped iL edges m spring water, and even in diluted sulphuric acid, without being ab e to perceive any decrease in the sound. When how- ever, a thin piece of blotting paper, which has been saturated with diluted sulphuric acid, is placed between the edges, and consequently the metallic contact is broken, the sound disap- pears. It also disappears with zinc tubes when the edges are so thoroughly amalgamated that drops of mercury remain adhering tr^:^;:^^ ^ve, became perfect metallic contact i! On the other hand, again, the sound did not cease when the edges were highly heated by the flame of a spirit lamp, but a decrease in its loudness was certainly noticeable. The question therefore presents itself still more forciblv If s^rks do not produce the sound, what then is the cause that We might attribute it to a kind of repulsion such as that which, as has been shown by Ampdre, exists between different elements of a current for each other. It is possible that during the time the current is being generated this repulsion causes the edges of the tubes to separate a little, and on its disappearance allows them to approach each other again. This alone, however IS not sufficient; it seems hardly possible that these weak cur-' rents could produce such disproportionate mechanical results I have noticed the sound in zinc tubes of two inches diameter and over two and a half lines thickness, which required consider- able effort to brmg the edges together. Besides, however much we mav inchnfi tn the idea t^nf t\a --,-1 i ^ ._ LUC mtjti inai isie auuud results from a me-» 146 THE SPEAKING TELEPHONE. chanical knocking of the edges together, observation so far has given no proof that such is the case. To the unassisted eye the edges seem to remain absolutely at rest, and even when viewed in the microscope, magnifying at least a hundred times, which would seem powerful enough to show any such motion if it existed, we are unable to perceive any change. In addition to this also, the liquids in which the ticking tubes were dipped showed no signs whatever of the slightest tremor or undulating motion, so that the ticking and toning vibrations, if such they really are, must be extremely small. The most natural view of the phenomena is, that notwith- standing the apparent metallic contact of the edges of the tubes, no uniform flow of electricity actually follows, but that as the current is inteirupted, a sudden discharge does take place, with- out, however, the appearance of sparks. This assumption may seem to be a very extraordinary one, but at the same time it cannot be said to contradict the experi- ence heretofore- obtained ; there seems to be no real ground for asserting that the passage of electricity through an exceedingly thin stratum of air should necessarily be accompanied by sparks, while, on the contrary, arguments may be adduced to show that the appearance of sparks under similar circumstances is some- what doubtful. It still remains an open question whether, in the sparks as they appear, we really see the substantial transfer of electricity ; these sparks may just as well be only accompany- ing phenomena of a dark invisible discharge of electricity, and their comparatively slow motion in certain cases would seem to render this view not altogether improbable. I do not, however, purpose forming an hypothesis here, and additional light on the phenomena in question must be derived from future observations ELECTRICAL TRANSMISSION OF SPEECH. ^ I have not thought it desirable to give prominence in this chapter on the Electric Telegraph to a fantastic idea of a cer- i Expose de» uppiloatlons do relootrioitc. Far is, 1857, par L6 Cts. Th, T>\5 Mnnn?.!. PEOPAGATION OF TONES BY ELECTRICITT. W7 tain M. Ch. Bourseilles, who believes that we shall be able to, transmit speech by electricity, for it might be asked why I claas amongst so many remarkable inventions an idea which is at present only a dream of its author. Nevertheless, as I am bound to be faithful to the duty I have undertaken of mentioning every electrical application which has come to my knowledge, I will give you some details which the author has already published on this subject He says: I ask myself, for example, if words themselves cannot be transmitted by electricity ; in other words, if one could not speak at Vienna and make oneself heard in Paris— the thing is practicable, and I will show you how. Imagine that you speak against a sensitive plate, so flexible as to lose none of the vibrations produced by the voice, and that this plate makes and breaks successively the communication with an electric pile; you may have at any distance another plate, which will undergo in the same time the same vibration. It is oLvdous that numberiess applications of high importance would immediately arise out of the transmission of speech by electricity, any one who was not deaf and dumb could make use of this mode of transmission, which would not require any kind of apparatus,— an electric pile, two vibratory plates, and a metallic wire are all that would be necessary. In any case, it is certain that in a future, more or less dis- tant, speech will be transmitted to a distance by electricity. I have commenced experiments with this object ; they are delicate and require time and patience for their development, but the approximations already obtained give promise of a favorable result PROPAGATION OF TONES TO ANY I^ISTANCE BY MEANS OF ELECTRICITY. ^ Previous to 1840, the attempts to transmit signals to great dis- tances by means of electricity were not very successful. Since that time, however, great advancement has been made, and tele- 1 Bnttger'n Polyteohnioal Notesblatt, 1863. 148 THE SPEAKING TELEPHONE. graph wires are now so generally erected throughout the country that it leaves little to be desired. Experiments have been made to transmit tones to any desired distance by means of electricity. The first experiment which was in any degree successful was made by Philip Reiss, professor in natural philosophy at Friedrichsdorf, near Frankfort on the Main, and repeated in the meeting room of the Physical Society, in Frankfort, on the 26th of October, 1861, before a large number of members. One part of his apparatus was set up in the Civic Hospital, a building about three hundred feet distant from the meeting room, the doors and windows of the building being dosed. Into this apparatus he caused melodies to be sung, and Fig. 68. the same were rendered audible to the members in the meeting room by means of the second part of his apparatus. The appa- ratus used to obtain this wonderful result is shown in fig. 68, a small light wooden box in the form of a hollow cube, having a large and a small aperture at each end. Over the small open- ing was stretched a very fine membrane, s, against the centre of which rested a small platinum spring e, which was fastened to the wood. Another strip of platinum/ likewise fastened at one end to the wood, had a fine horizontal peg inserted in the other end, which peg rested on the platinum spring at the point of contact with the membrane. As is well known, tones are generated by the condensation and rarefaction of the air taking place in rapid REISS'S MUSICAL TELEPHONE. 149 succession If these motions of the air, called waves, strike the thin membrane thej cause it to vibrate, which forces the plat- mum spring restmg upon it against the horizontal peg inserted m the second platinum strip, which hops up and down with it. I^ow, If the latter be connected by a wire with one of the poles of a galvanic battery, and the electricity conducted by a wire at tached to theother pole of the battery, to any desired distance, then through a helix, E, six inches long, formed of very fine spun copper wire, and thence back to the platinum spring on the trans- mittmg apparatus-then at every vibration of the membrane an interruption of the electric current will take place. Through the openmg m the helix above described, an iron bar ten inches long IS run, the ends of which project about two inches and rest upon two sticks of a sounding board. It is well known that when an electric current passes through a hehx enclosing an iron rod in the manner described, at each interruption of the current a tone, produced by the elongation of the rod, ,s audible. When the interruptions follow each other at a .moderate rate, a tone is generated (owing to the change in position of the molecules of the rod) which is known as the longitudinal tone of the bar, and which depends upon its length and the strength of the current If, however, the interruptions of the electnc current in the helix take place more rapidly than the movements of the molecules of the iron bar, which are limited by its elasticity, then they are hot able to complete their course, and the movements consequently become smaller and quicker in proportion to the rapidity of the interrup- tions. The iron bar then docs not emit its longitudinal tone but a tone whose pitch is dependent upon the number of inter' ruptions of the current in a given time. It is a well known fact that higher and deeper tones depend upon the number of air waves which succeed each other in a second's time. We have seen heretofore that on these air waves depend the number of interruptions of the electric current of our apparatus, through the agency of the membrane and the platinum strips, and the iron bar consequently should emit tones of the same pitch as 160 THE SPEAKING TELEPHONE. those acting upon the membrane. Tones may thus be repro- duced, with a good apparatus, at almost any distance. It is evident, therefore, that it is by the electric impulses alone, and not by the transmission of the sound waves them- selves through the wire, that the tones become audible at the distant end, for the tones are no longer apparent when the ter- minal wires of the helices are joined by a metallic conductor, and thus the instrument shunted out of circuit The reproduced tones are generally somewhat weaker than the original ones, but the number of vibrations is always the same. Consequently, while we may easily reproduce precisely the same pitch of the tone, it is difficult for the ear to determine the dif- ference in the amplitude of the vibrations, on account of the gradually decreasing vibrations, which limit even the weaker tones. The nature of the tone, however, depends upon the number of the vibrations — that is to say — tones of the same pitch are produced by the same number of waves per second — at the same time each wave, as, for instance, the 4th, 6th, etc., may be stronger than any succeeding wave. Scientists have shown that when an elastic spring is made to vibrate by being struck by the teeth of a cog-wheel, the first vibration is the strongest, and each succeeding one, less. If, before the spring stops, it is again struck, then the next vibra- tion becomes equal to the first vibration of the first stroke — without the spring, however, making more vibrations on that account It may be that the time is still distant when it will be possible for us to hold a conversation with a friend at a distance, and to distinguish his voice as if he were in the same room with us. Still the probability of success in this has become as great as it was during the important experiments of Niepce for the repro- duction of the natural colors by photography. CHAPTEE V. gray's telephonic eesearches. ' 1 "While engaged in studying the phenomena of induced cur- rents, I had noticed a sound proceeding from an electro-magnet connected in the secondarj circuit of a small Ehumkorff coil, which was at that time in operation. This, of course, was not new (it having been observed by Page, Henry and others that the magnetization of iron is accompanied with sound), but it helped to direct my mind to the subject of transmitting musical tones telegraphically. Subsequently I made a discovery that led to a thorough investigation of the subject, and I have de- voted my whole time since then to the study which it suggested. The circumstance was as follows : My nephew was playing with a small induction coil, and, as he expressed it, was " taking shocks " for the amusement of the smaller children. He had connected one end of the secondary coil to the zinc lining of the bath tub, which was dry at that time. Holding the other end of the coil in his left hand, he touched the lining of the tub with the right In making contact, his hand would glide along the side for a short distance. At these times I noticed a sound pro- ceeding from under his hand at the point of contact, which seemed to have the same pitch and quality as that of the vibrat- ing electrotome, which was within hearing. I immediately took the electrode in my hand, and, repeating the operation, to iny astonishment found, that by rubbing hard and rapidly, I could make a much louder sound than the electrotome was making. I then changed the pitch of the vibration, increasing its rapidity, and found that the pitch of the sound under my hand was also changed, it still agreeing with that of the vibration. I then moistened my hand and continued the rubbing, but no sound 1 Esperimental Keaearchoa by Elislia Gray, cal Society, March IT, 18T5. Head before the American Electri- 152 THE SPEAKIKG TELEPHONE. wap produced so long as my hand remained wet ; but as soon as the parts in contact became dry the sound reappeared. The next step was to construct a key board, with a range at first of one octave, similar in appearance to the cut shown in fig. 69, which has two octaves. Each key has a steel reed or electrotome, tuned to correspond to its position in the musical scale. A better understanding of the operation of a key and its corresponding electrotome may be obtained by referring to the detached section shown in fig. 70. Fig. 69. a is a steel reed tuned to vibrate at a definite rate, correspond- ing to its position in the scale. One end is rigidly fixed to the post 6, while the other end is left free, and is actuated by a local battery. Tha magnets e and / are arranged in the same local circrdt, magnet / having a resistance of about thirty ohms and magnet e about four ohms. When the reed a is not in vibration the point ^r is in electrical contact with it, which throws a shunt wire entirely around the magnet/; thus, practically, the whole of the local cuiTent passes through magnet e at the instant of closing the key c. It is well known that when two electro- magnets are placed in the same cii'cuit, the one which has the ORAY'a TELErHONIO BESEAHCaEa Igg higher resistance (other things being equal) will develop the stinger magnetism, and that if the magnet of higher^^iL^ When the key c, being depressed, closes the local circuit at d LT «M *'' "^ " ■" '""o"' = Tl-^ whole of the" u^nl Z T'^-i'- """^ *"/«•> *" ""'^^* ^- -hich attn«t« the t«w.' f '^ 7 " 'T'' °' *°'"'- "^hen Ue reed has moved S ? rl *' """•':"' ""^ *'''°^8h ''°* «l>e magnets. Im! mediately the power m / rises from .ero to five, and that of o ^^m.b. i-BiXA Mg. 70. ■ frSp^r ^' *^.T' ^""^ '^' '''^ '' ^**^^*^d t^^^rds / with the p^::r tT ''"'• ""^^^ ^^^^^^^ ^^ again est^bhsh/d with me point 5^ The .;.eration is repeated at a rate determined by he si.e and length of the reed, and which corresponds with the fundamentol of the note it represents. The figures given above only approximate the facts. The relation of the JgnZ TZ size and resistance, so as to give an equal impulse to the reed in both direcuons, was determined by actual experiment with a battery of a given size. It will be observed that by this arrangement the centre of vibration coincides with the centre of the reed when at rest, so 164 THE SPEAKING TELEPHONE. that the pitch of the tone is not disturbed by any ordinary change of battery, as is liable to be the case when only one magnet is used or when the impulse is not equal in both directions. A second battery, which we will call the main battery, is con- nected as follows : One pole is connected to the ground. The other runs to the instrument, and, entering at binding screw 4 (fig. 70), runs to point A of key c; from key c to point «, which makes contact with the reed a ; from reed a to binding screw 1, and thence to line. It will be seen that when the key is at rest the batteries are open at the points d and h. All the keys in the instrument; whether one or more octaves, have corresponding reeds and actuating magnets, the only differ- ence being in the tuning of the reeds. There is but one main and one local battery used, and the connections to each key are run in branch circuits from the binding screws, as shown in fig. 69. But, since all these branches are open at the key points, neither of the batteries is closed unless a key is depressed. If now the keys are manipulated, a tune may be played which is audible to the player. When any key is depressed, the local battery sets in vibration its corresponding reed, which sounds its own fundamental note according to the law of acoustics. So far the instrument is an electrical organ, the motive power being electricity instead of air. The main battery has had no part whatever in its operation. If, however, the main circuit is closed by connecting the dis- tant end to ground, and the point i is properly adjusted, so that it makes and breaks contact with the reed at each vibration, a series of electric impulses, or waves, will be sent through the line, corresponding in number per second to the fundamental of the reed. Now, as the pitch of any musical tone is determined by the number of vibrations per second made by the substance from which the sound proceeds, it is clear that if these electrical wave^^ can be converted into audible vibrations at the distant end of the line, whether it be one mile or five hundred miles from the player, the note produced will be of the same pitch as that of the sending reed. okay's telephonic BESEABOHEa Bg There are various ways by which these electrical waves may be convert^ mto aadible material vibratlona One of ZS ounous and novel is the one in which anin^rue pCa promment p«rt Following out the idea suggested Wtwlth tub expenmen^ I constructed various d,ricc« wUh mewt plates for receiving the tune by rubbing with the hZl T verv convenient method for doing this is shown in fig 71 ^ Th,s instrument has a metal stand of sufficient weight to keep It m position while being manipulated. Upon the stand a CI zontal shaft IS mounted in bearings, upon one end of which fa a crank, with a handle made of some insulating sutoncT Upon the other end is cent«>d a thin cylindrical sounding!^ Ftg. 71. made o± wood, the face of which is covered with a cap made of thm metal, spun mto a convex form to give it firmness. This t)ox has an opening in the centre to increase its sonorous quali- ties, ihe metal cap is electrically connected to the metal stand by means of a wire. If the operator connects the cap, through the stand, to the ground, and taking hold of the end of the line with one hand, presses the fingei-s against the cap, which he revolves by means of the crank with the other hand, the tune that is being played at the other «nd of the line becomes distinctly audible, and may OQ Heard thiX)ughout a large audience room. If the conditions I ^^a 156 THE SPEAKING TELEPHONE. are all perfect, the faster tlie plate is revolved the louder -vrill be the music, and the slower the motion the softer will it become. When the motion stops the sound entirely ceases. I have found that electricity of considerable tension is needed to produce satisfactory results, at least that of fifty cells of bat- tery. The necessary degi'ce of tension is most conveniently obtained by passing the line current through the primary circuit (adapted to the circuit wherein it is used) of an induction coil, and connecting the receiver in the secondary circuit The cause of this phenomena has been the source of much speculation and experiment At first, I supposed it to be the quivering of the muscles of the hand, produced by the electric impulses and communicated to the plate and box, making an audible sound, and that the motion was produced through the medium of the nerves. This idea, however, had to be aban- doned. While visiting England, in 1874, I called on Professor Tyndall at the Koyal Institution, and exhibited to him a portion of my apparatus. He experimented with various substances, and found that the same result, in kind if not in degree, could be produced with dead animal tissue. For instance, a bacon rind that had been pickled and smoked until there could be no suspicion of a nervous influence left, would, when sufficiently pliable, produce the sound, the cuticle being used next the plate. While Professor Tyndall's experiments did not explain what the cause of the phenomenon really was, they determined most conclusively that it was not due to nervous influence upon the tissues, acting in sympathy with electrical impulses. It was suggested by some that it might be caused by electrical dis- charges, in the form of a spark, from the hand to the plate; but if this is true, why should motion, as a gliding of the hand over the surface of the plate, be necessary to produce the result ? Others have suggested that the molecules of the substance in contact were disturbed upon the passage of each electrical im- pulse, roughening the surlace, and for the instant producing a sudden increase of friction. If this is true, why should wetting the parts in contact destroy the effect ? gray's telephonic besearohes. 157 But to continue m j experiments : I noticed that when revolv- ing the plate with my finger in contact, the friction was gi-eater when a note was sounding. I then connected a small Euhm- korff coil to a battery, inserting a common telegraphic key in the primary circuit, instead of the self-acting circuit breaker. Icon- nected one end of the secondary coil to the metal plate, and holding the other end in my hand, I rubbed the plate briskly, and had my assistant slowly make dots with the key. I noticed at each make of the circuit a slight sound, and at each break a very much louder one, owing to the fact that the terminal secondary wave is much more intense than the initial. I now held my hand still, and, while I could feel the shock just as distinctly as before, there was no audible sound, proving that the motion was a necessary condition in its production. The sensation when the sound was produced was as though my finger had suddenly ad hered to the plate, and then as suddenly let go, producing a sound. The next experiment was with one hundred cells of gravity batteiy. I connected one pole to the plate and held the other in my hand, pressing my finger against the plate and revolving it as before. I inserted a thin piece of paper between my fingers and the plate to prevent painful effects from the current, and my assistant made dashes with a key in the circuit I was thus able to notice the effect of an impulse of longer duration. When the key closed there was a perceptible increase of the friction, so that my finger took a position farther forward on the plate, where it would remain as long as the circuit remained closed. As soon as the key was opened my finger suddenly dropped back on the plate, making the same noise I had before heard. This operation was repeated so often that there could be no question as to the effect it produced. From the foregoing experiments, I find that the following con- ditions are necessary to reproduce musical tones tlirough the medmra of animal tissue, by means of electric waves transmitted through a telegraph wire. 1st. The electrical impulses must have considerable tension in order to make the effect audible. 168 THE SPEAKING TELEPHONE. 2 A The substance used for rubbing the receiving plate must be soft and pHable, and must be a conductor of electricity up to the point of contact, and there a resistance must be interposed, very thin, neither too great nor too little. 3d. The plate and the hand, or other tissues, must not only be in contact, but it must be a rubbing or gliding contact 4th, The parts in contact must be dry, in order to preserve the necessary degree of resistanca It will be seen that we have here the conditions of a static charge, the plate receiving one polarity from the battery, and the hand the other polarity ; the interposed resistance preventing in a great degree the dynamic effect. It is a well known fact, that Mg. 72. two bodies statically charged with opposite electricities, attract each other. May not this be the whole solution of the pheno- menon, that eabh wave as it arrives at the receiving end becomes for a moment static, which results in a momentary attraction be- tween the plate and the linger, and this immediately ceasing when the wave is gone, releases the finger with a noise or sound ? If, then, sounds are repeated as fast as the sending reed vibrates, the production of a musical tone must follow, accord- ing to well known laws of acoustics, providing the waves are sent to line in musical order. In the winter of 1873-4, I experimented very elaborately, and worked out many new applications of the principle, not only to the transmission of music, but to the transmission of telegraphic messages. gray's telephonic researches. 169 If, instead of the revolving plate and the animal tissue, we place in the circuit an electro-magnet, or a number of them, and have a tune played at the transmitting end, the tune will be heard from all these electro-magnets. The music produced will be loud or low ; 1st, as the battery used is strong or weak ; 2d, as the line offers more or less resistance ; and 3d, as the magnets are mounted more or less favorably for acoustic effects. In this case, as in that of the animal tissue, each impulse pro- duces a sound ; but it is produced differently in the two. It is a well known fact that an iron rod elongates when magnetized and contracts again when demagnetized. The elongation and contraction are so sudden, that an audible sound is produced at each change. In order to convert this sound into a musical tone, Mg. 73. it is only necessary to repeat it uniformly and at a definite rate of speed, which shall not be less than sixteen nor more than four thousand per second. When the electro -magnet is properly mounted the tone may be made very loud. Fig. 72 shows a very good form for mounting a magnet for receiving music. It is a common electro- magnet having a bar of iron rigidly fixed at one pole, which ex- tends across the other pole, but does not touch it by about one sixty-fourth of an inch. In the middle of this armature a short post is fastened, and the whole mounted on a box made of tliin pine, with openings for acoustic effects. One of the earliest discoveries in connection with these experi- ments was the fact that not only simple, but composite tone-s 160 THE SPEAKING TELEPHONE. could be sent through the wire and received, either on the metal plate or on the magnet. Not only could a simple melody be transmitted, but a harmony or discord could be equally well. From that time, I have worked assiduously with the view of making a rapid telegraphic system embodying this discovery. The first step was to analyze the tones at the receiving end, which, if successfully accomplished, would open the way to a multiple Morse, a fast printing, an autographic and other sys- tems. It would be impossible to give in this paper all the experi- ments tried, for they were very many indeed. I accomplished +he analysis in a number of ways. The method which seemed in all respects to give the best satiK/action is as follows : Fig. 73 is a perspective of one form of a receiving instru- Fig. 74. ment called an analyzer. The construction of the instrument is very simple. It consists of an electro-magnet adapted to the resistance of the circuit where it is intended to be used, and of a steel ribbon strung in front of this magnet in a solid metal frame, and provided with a tuning screw at one end, so as to readily give it the proper tension. The length and size of the ribbon depeads upon the note we wish to receive upon it If it is a high note we make it thinner and shorter ; if a low note we make it thicker and longer. If this ribbon is tuned so that it will give a certain note when made to vibrate mechanically, and the note which corresponds to its fundamental is then transmitted through its magnet, it will respond and vibrate in unison with ics trans- mitted note ; but if another note be sent ',';;> ich varies at all from GBAT'S TELEPHOHIC RESEABCHiS. Igl ite fundamental, it will not respond. If a composite tone is sent ae nbbon will respond when its own note is being sent Ta ^Ut Jn'™"'^"^ *"""■ ''"' ^ ^» ^« '«« ""^ «»■«' i« left Milr r"""*"" •'' ''°P- '^''"^ ^ "■» *We to select out and wmch are passing over the line. ^ This method of analyzing tones transmitted through a wire electrically is analogous to Helmholtz's method of LaraW tones transmitted through the air. . ^^Paratmg are^madrZir"^ instmments used in sending composite tones, are made similar m every respect to the one shown in %. ro] Fig. T5. except that each reed is separately mounted. A cut of one of these transmitters, used in telegraph work, is shown in fig 74 i^ig 75 shows a diagi-am view of two transmitters and two receivers, with their connections. The local circuits, with their magnets, are left off to avoid confusion. A and B represent two transmitters, placed at one end of a line, A and B , two receivers at the other end. One end of the mam battery is connected to Hne, and the other end to o-round Each transmitter is placed in a shunt wire, running from L mam battery connections around one half of the battery A 162 THE SPEAKING TELEPHONE. common open circuit key is placed in each of these shunt wires. Suppose now the two reeds of A and B to be sounding, A making 26i vibrations per second, and B 320, just two tones or a major third above A. So long as the keys remain open, all the battery is constantly on the line. If the key of transmitter A is closed, half of the battery is being thrown on and off the line, at the rate of 264 times per second. This causes a succession of electrical waves to flow through the line at the same rate. If now the steel ribb6n of the analyzer A' has been tuned in unison with these electrical waves, it will respond and hum the same note as the transmitter ; but, if it is not in unison, it will remain practically quiescent, so that the note can only be heard by sub- mitting it to the most delicate test To bring it in unison it is Fig. 76, only necessary to turn the tuning screw up or down, as the case may be. When the fundamental of the ribbon corresponds with that of the sending reed, it announces the fact by sounding out loud and full If (having the key of transmitter A still closed, and consequently its corresponding analyzer still soun'mg)we close the key belonging to transmitter B, the other half of the battery -vnll be thrown on and off the line, at the rate of 320 times per second, and another succession of electrical waves will flow through the line, this one being at the rate of 320 times per second. If the analyzer B' is in proper tune, so that its fun- damental is the same as that of its corresponding transmitter B, it will hum its note as long as the key is closed, making a chord ghat's telephonic MSEAKCHEa Jag With A'. In the same way, a great number of diflerent notes Jme, and be heard simultaneously at the other and » J, L*. Bounding upon a diffei^nt receivi4 instrument ' ""** Ihe manner of making these vibrations of the analyzer f JtudtV"""^' ^f ° '' """^ with a eontact point at it« con-ave cup d, upon the extremity of the armature o. When he armature ,s thrown into vihmtion the contact kvcr hoc! sZSfbut J. ., '^ «th sufficient firmness to actuate the S ~ tr V ^'""^"O^^'OP^ tte local circuit is closed. atPd hv < ," °° "P"" *" ^•""l"''. •»" it may be oper- whfch'L;rdrs: ^t'^''^' — -g^liavarionsother^^s fdlows men fr *''""'^^'^'^ The complete operation isL tollows. When the operator, at the sending station, closes his ^ C ZT7 "'"'' """^ -'» -b Jion, and'rem fns s!: I^v when tLf ° '""^"''^''' ^"' """O' *» ^^^t imme- fnlW .r ^ " °P'°"'- ^^ '«™'' "'i not being able to turwr r"^*"™' '^'"'" ''^™' *' with a buzzing sound dit turb ng the eontmuity of the local circuit by th?owin7ira gr^t resistance at the point d. This r^istance is 3^ t^ act upon the sounder the same, practically, as a dead brntk. Bv other tones 4be b^u^hTir J::e,thX~re''o:ht^ and each seeking its own at the receiving end ' A ampler construction of the analyzer, and one which ren- ders the sounder unnecessary, is shown in fig. 77. The Z tro.magnet M M, which has very short core^ls piwidrf witt an armature a, ngidly attached to the lower com, but slparrtcd from the upper one by a space of J, of an inch tLT»! K .nereased or diminished by moving"he uTperti. if: Zl^y means of the screw S. The armature ifmade tl^nnl at\he 164 THE SPEAKING TELEPHONE. point i, being filed down until it vibrates to a certain note, the nicer adjustment being accomplished by adjusting the movable weight W. The whole is mounted upon a sovniding l.^ox B, open at one end, which is termed a resonator. The pi-iSiciple involved in the action of the resonator is this : A volume of air contained in an open vessel, when thrown into vibrations, tends to yield a certain note, and consequently strengthens that note, when the latter is sounded in its neighborhood. By placing the instru- ments upon corresponding resonators, the souud is greatly strengthened, so that an operator may readily read by sound Fig. 77. the telegraphic characters into which the continuous tone ia broken by the transmitting key. By this method not only may different messages be sent simul- taneously, but a tune with all its parts may be sent through hundreds of miles of wire, and be distinctly audible at the receiving end. 1 Grray's electro-harmonic telegraph is founded upon the prin- ciple that an electro-magnet elongates under tlie action of the electric current, and contracts again when the current ceases. 1 American Mechanical Dictionary. Vol. iii. (The invention here described i» & modiflcation of that shown on pages 159 and 160.) gray's electko-harmonic telkphoke. 166 Consequently, a successioa of impulses or interruptions wiU cause the magnet to vibrate, and if these vibrations be of suffi- cient frequency, a musical tone will be produced, the pitch of which will depend upon the rapidity of the vibrations. By interrupting an electric current at the transmitting end of a Ime, with sufficient frequency to produce a musical tone by an instrument vibn. ed by said interruptions, and transmitting the impulses thus induced to an electro-magnet, at the receiving end ' of the line, the latter will vibrate synchronously with the trans- mitting instrument, and thr • produce a musical tone or note of a corresponding pitch. r S - JViiin Fig. 78. The instrument shown in fig. 78 consists of the transmitting apparatus, mounted on a base board, and a receiving apparatus, shown m a position beneath the former. The induction coil Ji has the usual primary an' secondary circuits. An ordinary automatic electrotome c has a circuit-closing spring c'l, so adjusted as, when in action, to produce a given musical tone. A common telegraph key d is placed in the primary circuit a a, to make or break the battery connection. The key being depressed, and the electrotome consequently vibrated, the inter- ruptions of the current will simultaneously produce in the sec- 166 THE SPEAKING TELEPHONE. ondary circuit b h, of the induction-coil, a series of induced cun-ents or impulses corresponding in number with the vibra- tions of the electrotome, and as the receivmg electro-magnet e is connected with this circuit, it will be caused to vibrate by suc- cessive elongations and contractions, thus producing a tone of corresponding pitch, the sound of which may be intensified by the use of a hollow cylinder s, of metal, placed on the poles of 'the magnet When a single electrotome c is thrown into action, its corre- sponding tone will be reproduced on the sounder by the magnet. "When electrotomes c c^, of different pitch, are successively ope- rated by their respective keys dd^, their tones will be corre- spondingly reproduced by the receiver ; and when two or more electrotxjmes are simultaneously sounded, the tone of each will still be reproduced without confusion on the sounder, so that, by these means, melodies or tunes may be transmitted. Another system is founded upon the alternate making and breaking of a telegraphic circuit by means of the vibration of timing forks, or musical reeds, as in Helmholtz's ajiparatus for the production and transmission of vocal sounds. If a. given fork be made to interrupt an electric circuit by its vibrations, and the intermit- tent current thus produced be passed through a series of electro- magnets, each in connection with a fork of different pitch, and consequently different rate of vibration, only that fork will be thrown into vibration which is in unison with the first one. Practically, tlie time required to do this is a small fraction of a second. The advantages of this method are numerous. N'ot only may many receiving instruments at one station, be operated, each by its own key, through a single wire, but many different stations in the same circuit may be operated, that one alone receiving the message which has an instrument with the requisite pitch, so as to vibrate in synchronism. Many signals may, in this way, be transmitted over the same wire at the same time, and many dispatches sent simultaneously to as many stations. All this may be done, too, without affecting the line for its ordinary use. gray's electro-harmonic telephone. 167 COMBINATION OF THE TELEPHONE AND MORSE APPARATUS.* The method of combining the telephonic, or electro harmonic, with the ordinary Morse system of telegraphy, invented by Mr. Elisha Gray, of Chicago, has for its object a meana whereby two communications may be simultaneously transmitted in the same du-ection, or in opposite directions, or, in other words, to double the capacity of a Moi-se circuit, having thereon several inter- mediate stations, so arranged that while a communication is being transmitted from one terminal station to the other by means of the telephonic system, either terminal station or any way station, may at the same time receive a message from or transmit one to either of the terminal, or any one of the way offices by means of the ordinary Morse apparatus. This inven- tion has been subjected to a series of tests upon the lines of the Western Union Telegraph Company, with considerable success. One of the several circuits upon which the system was tested experimentally extends from Chicago to Dubuque— a distance of 184 miles — with seventeen intermediate stations in the cir- cuit, the total conductivity resistance of which, including all of the relays on the line, being about 5,000 ohms. The principle and mode of operation of this invention is shown in fig. 79, which represents the instriunents, in connection with the line, at a terminal station, including both the telephonic, or electro-harmonic, and the ordinary Morse apparatus, the former consisting of transmitter T, key K, local batteries e, e* and e^, vibrator or reed V,. receiving instrument or analyzer A, repeat- ing relay Ai, sounder S, rheostat Ri and main battery B; and the latter consisting of relay D, sounder SS key K*, rheostat R and condenser C, the earth terminal of the line being at G. Each intermediate office is equipped with the Morse apparatus only, including the condenser and rheostat last mentioned ; while at the distant terminal station both the telephonic, or electro- 1 Abstraot ofun iirticlo from the Journal of tho American Electrical Society, Vol. L, No. 2, entitled, A New and Practical Application of the Talephone, hy^Elisha Gray, 8c. D. 16» THE SPEAKING" TELEPHONE. harmonic, and the Morse apparatus are arranged precisely as shown in the diagram. To effect the object sought, viz., the simultaneous transmis- iion of two communications in the same, or in opposite directions, it is obviously essential that sounder S (for example) should respond solely to the movements cf key K and transmitter T of the telephonic apparatus ; while in like manner the sounder S^, which is connected with the Morse instruments at the distant terminal, and at the several intermediate offices, should respond solely to the movements of key K^. The manner in which this is accomplished will be understood by reference to the figure, and the following explanation thereol llllllllllllllll B [G] Fig. 79. The transmitter T, which in principle is similar to that used in connection with the duplex and quadruplex systems, is oper- ated by means of the key K and local battery e. The auxiliary lever J, one end of which rests upon a suitable fulcrum, while the free end rests upon the anvil of transmitter T, serves, in con- nection with the armature a of the latter, to control the local circuit of sounder S in a manner and for a purpose to be herein- after described. The vibrator or reed V (which, with the receiving instrument or analyzer A, are fully illustrated and described on pages 158 and 182) is kept constantly in vibration by means of electro-magnets and a local battery (not ghown in the figure), GEAY'S ELECTRO-HARMONIC TELEPHONE. 16^ well known device for ,.ve,.it tej'Z^oT ■ ^ stmment A, in order thntT * *'' ««e""'g «- t«.nsmitto tTsopI mlrr' ?"\*'" °' ^^^^ ^ -"' having the fe^^ prln^et ^""" ^=''"^"^''°'' "^ '"^^ "^ ^^"S-'^'l '' '"^ .luc'^C"?! tlr. ;Tf ""^ developments attending the intro- .n the1J^ ' T° *"■' '^ P"'*""!^' "°"e ""»■» diking •iiiui loJIows a change in the magnetic condition nf tl,„ receivmg electro-magnet. -onuition of the Very cu-ly in the course of my experiments in tlie matter Hmiply superposing them upon this constnn ^^^^''^t^«»« W varying its i^ower. ^"* ''^"'^°* without To define more clearly what I mean I win «•• -^.X-peHon. which occurred T ]:fl^ZZ TI^H^ 172 THE SPEAKING TELEPHONE. While experimenting at Milwaukee, with my electro -harmonic or electro-acoustic multiple telegraph system, I had with me a set of my apparatus for receiving tunes, known as the musical tele- phone. One evening, after the regular work of the day was closed^ I transmitted a few tunes across the street from the telegraph office to the Newhall House, for the amusement of some friends. Instead of using an independent battery, I simply tapped one of the regular batteries of the North- Western Telegraph Com- pany, which contained two hundred cells of the ordinary gravity form, by connecting my short line wire to the battery, twenty cells from the ground end, without in any way disturbing the other connections. This battery at the same* time supplied three lines, which extended through Wisconsin in various direc- tions to distant points. The few cells which I employed did not in the least interfere with the ordinary working of the lines. A number of familiar tunes were played during the evening, and I was surprified next morning to learn from variouo offices in the State, through which the three lines ran that were supplied by the common battery, that the tunes played were all repro- duced audibly and distinctly by the relays in the various offices along the line. Some of the operators being ignorant of the in- vention of the telephone at that time, were very much amaaed at this new exhibition of the musical powers of their instruments, and I am told that one gentleman, sixty miles from Milwaukee, closed his office that night much earlier than he was accustomed to do. The relation of the instrument to the various circuits is shown in the diagram, fig, 80. E and c represent the battery of two hundred cells used to supply the three telegraph lines L, ex- tending through Wisconsin. T is a musical transmitter placed in the short wire running to the Newhall House, and attached to the battery, twenty cells from the ground end. K is a Morse key ; M is the electro-magnet, and R the armature of the tele- phonic receiver at the Newhall House. It will be readily observed, that each time the transmitting vibrator closed, the PECULIARITIES OF VIBRATORY CURRENTS. 173 twenty cells of battery they would be short circuited tbrouffh the receiverin the Newhall House and ground, thereby proportion- ately dimimshing the power of the whole battery and restorino It again each time the vibrator opened the short circuit, thus sending a series of vibrations superposed upon the uniform cur- rent flowing from the larger battery throughout the lines sup- plied by It I was well aware that twenty cells of this form of battery, connected to the three lines as shown, would not produce such marked effect upon so many magnets and at so great a dis- tance ; and I was naturally led to conclude that the one hundred or more cells of the additional battery, which were not thrown n [£) Pig. 80. into action by the transmitter, in some way played a part in the matter. ' .' c j f At a later date— I think in the latter part of 1875—1 made another experiment at the same place, under the foUowino- cir. cumstances : I had been using a wire two hundred miles in length, and was engaged in transmitting a series of tones simul- taneously over the same wire for th.' p,upose of applyin^r it to a system of multiple telegraphy I h.ul been using one hundred cells of battery, divided into four sections, upon each end of this wire, as shown in my patent for a multiple circuit, filed in the United States Patent Office, January 27, 1876. in which it will 174 THE SPEAKING TELEPHONE. be observed that the batteries are connected to the two ends of the line in the usual way for an American Morse circuit The two batteries were divided into four sections by shunt wires, in each of which was inserted a transmitter or a vibrator and a Morse key, which stood open except when used for trans- mitting signals while the vibrators were in operation. If the key belonging to any vibrator was depressed, it would throw in vibration the section of battery included in its short or shunt circuiL By this arrangement I had as many as eight receivers in operation simultaneously, each receiving a tone differing in pitch from the others, and each having a vibration strength of twenty-five cells. One evening I wished to make an experiment with one tone M IE. El [*] m Fig. 81. only, and for that pui-pose insei-ted only twenty -five cells in the circuit, leaving out the other one hundred and seventy-five, as it did not occur to me at first that the battery cells left out would play any part in a vibration not inchided in the shunt wires belonging to their particular tonea As twenty- five cells were all that were Tised in transmitting any one single tone, I supposed that amount of battery would be sufficient for the experiment that I wished to try. The position of the battery and instru- ment in relation to each other is shown in fig. 81. E is a battery of twenty-five cells. T is the vibrator and K the key inserted in a short or shunt circuit thrown around the twenty-five cells of battery. M R is the telephonic receiver. I was surprised at first to find that no perceptible effect could be felt on the receiver USE OF SUPPLEMENTAL BATTERIES. 176 when the key was closed and the battery thrown into vibra- taon. After working (,ver it for some time, I concluded that there must be some fault in the connections, and proceeded to test the wires by inserting a Morse relay. I found the circuit all right, when a recollection of my former experience caused me to place m the circuit an additional battery of one hundred cells, leaving the vibrator and shunt wires as they were before around the twenty-five cells only. The arrangement after the additional one hundred cells were inserted is shown in fig 82 M R IS the receiving telephone, T the telephonic transmitter, K the Morse key E represents one hundred cells of batterv and e twenty-five cella *^' When the key was now closed, the receiver responded without Mi IR Mg.82. m difficulty. By inserting an additional amount of battery in the cu-cuit at the receiving end, the amplitude of vibration on the receiving reed, which was tuned in unison with the transmitter, was still greater. I have verified this experiment at different times since the above date, and on different lines, varying in length up to five hundred miles and over. It will be oljserred by studying the diagram in fig. 82. that the only effect tiie vibrator could have upon the circuit, when the key was closed, was to throw into vibration the twenty-five cells included in its short circuit at a rate corresponding to the fundamental of the vibrator It would seem that no effect could be had from the one hundred or more additional cells, inasmuch as they were simply inserted m tnat portion of the circuit which was never broken or opened, ■ 176 THE SPEAKING TELEPHONE. except to produce a permanent magnetic efiect in tlie receiving, magnet corresponding to its cun-ent strength. In other words, if the magnetic effect produced by the one hundred cells is repre- sented by twenty, twenty-five additional cells would increase the magnetic effect to a certain point above twenty, and when taken off it would fall to twenty, but not below. If the power of the twenty -five cells is represented by five, why should it not be exerted with equal power without the one hundred cells inserted in the circuit, as described? This was the problem, and, in a measure it is a problem still, although I have satisfied myself in regard to certain facts which help to strengthen the theoiy which I then held in regard to the matter. I supposed at that time I could account for at least part of this effect, upon the theory that the speed of the signal was increased by the additional potential given by the larger number of cells. In other words, the value of any given cell, or number of cells, when fonning part of a large battery, is greater, especially if used on long lines, than when used alone. This theory, how- ever, is entirely inadequate to account for the whole effect, as will appear from what follows. Some very interesting experiments bearing upon this matter were made by me while experimenting with the speaking tele- phone, known as the battery or supplemental-magnet telephone, a diagram of which is shown in fig, 83. In this instrument no permanent steel magnet is used ; nor is there connected with it a battery current flowing through the main line. Instead of a permanent steel magnet, such as is more commonly used in speaking telephones, I used an electro- magnet, B, which is held permanently charged by a local battery. The electro-magnet 0, which is next to the diaphragm, and whiich connects with the line and ground, and a corresponding magnet at the other end of the line, are charged by induction from the core of the magnet B, which, as before mentioned, is charged from the local battery. Before a battery current had been passed through the coils, and while the cores were perfectly neutral, I made the following MAGNETTO CORES FOR TELEPHONES. 177 experiment: I connected the telephones to the two ends of the me as shown in fig. 83, and put on a local batteiy at station No. 1, shown at the right hand of the diagram, connecting the battery with magnet B through the wires 4 4. The local battery at sta- tion No. 2 at the left of the diagram, was for the time left unconnected so that the core of the magnet B, and also that of O were both m a neutral stata I now placed my ear to the telephone at station No. 2, and had my assistant speak in a loud tone into the instrument at station No. 1, which had the local batteiy attached, and was therefore in condition to transmit the electrical vibrati ons produ ced by the motions of the diaphragm 1 ii J •hii-J HI E] Fiy. 83. acting inductively upon the then magnetized electro-magnet 0. Although the vibrations were passing through the circuit, and consequently through the coils of magnet C, at station 2, I could get no audible effect until I put on the local battery and charged the cores of the magnet at the receiving end of the line Im- mediately after this was done I could hear every word loudly and distinctly, making in all respects the best telephone I have ever heard, due to the fact that by the aid of local batteries we can make of soft iron a much stronger magnet than can be made of steel. I then threw off the battery at station 2, when I could hear the words very faintly, and I was able then to transmit vnry faint sounds, due wholly to the residual charge left in the iron after tne battery was taken o£ It is easy to see why no sound 178 THE SPEAKING TELEPHONE. could be transmitted from the apparatus before it had beea charged by the battery, because there was neither electricity nor magnetism present, nor had we any of the conditions necessary to produce either of these forces by simply speaking against the diaphragm. This was not true, however, of the No. 1 station, because the battery was connected and the magnet charged. No doubt there was some effect produced upon the receiving magnet, for the electrical impulses passing through the line must have been the same whether the magnets at the receiving end were charged or in a neutral condition. This one fact, however, was prominently brought out, that in order to make an electro-magnet, which is the receiver of rapid vibrations (such as will copy all the motions made in the air when an articulate word is uttered), sensitive to all the changes necessary in receiving sounds of varying quality, it must be constantly charged by some force exterior to the electrical vibrations sent through the wire from the transmitting station. We were well aware that tins condition is unnecessary where theiorce transmitted is of sufficient magni- tude, or where the signals are of sufficiently long duration. My experiments lead me to the conclusion that a soft iron core is far more susceptible to the slight changes in the electrinai conditions of the wire surrounding it when it is already in a high state of magnetic tension. It is like an individual who, in his more calm and unruffled moments, may be surrounded by little waves of excitement without being affected by them ; when on the other hand, if from any cause whatever, his nervous system is in a state of tension, he is readily affected by every disturbing influence, however slight It will be noticed that the above observations were made in regard to electrical impulses of very short duration ; the longest several hundred per second, and the shortest many thousand. The explanation of the above results may be partly understood when we fully consider the effects of the extra current which is induced in tlie primary circuit itself ; especially when such cir- cuit has included in it the coils of an electro-magnet. The first effect from a current of electricity passing around BEAOTIVE EFTSCT OF INDDOISD OUKBENIB. 179 4o coils Of an electro-magnet is to develop magnetism in its eoft ™n eore; but as soon as the core be^ns tTmaTef'^ H sets up a momentary induced current in the oppositeTSon to the pnma^ „, i a i„g „„^„._ ,,^ ^^, of whiehl" tanl the charge m the first instance. It has kmg been known that this reactiye effect of the induced cite^:lt" "^-ft-^' « " "'"^ '^«'™'"8 °' *^» electrical :^ STl^T Vr;^""! '" ""''^ "o-^toT. i*« duration is ^ iess able to act aa an opposing agent to the flow of the pri- s^ZTh '' ""''""' ""^^ ^'™" *° "" electrcml^et seems to have nn opposite effect upon the secondary impulse from that wh.ch it has upon the primary. For I notfced when expenmentmg with the induction relayf that if I chald the a'ryTnlr: '"*;,^""y l'-™ «'. -7 Ave, the initialflnd! 7fi3 1 "^ ^' '"■■ ^'^''' *™ 'f I ^''ft " """^tant charge of five m the primary and suddenly raised it to ten I have thought that a further possible explanation of thi, molecules of the iron arc in a state of magnetic tension that is tosay, when they have moved from a neutiSpoint up to a g^'en position, there is then less molecular inertia to overcome in mlv n!lot'Tn tr""''- • ^""^ P"™'P'^ ''^ ^gK-*^-! finds an analogy in the superior resonating qualities of a sounding-board ntt W ^ '"^"''-'-' ''^^^' - --P-'' '^'^ one in a JstIucr,l''T *' ^^^T' °"' """^^ "^o^*' ™ '^e^^ to *e resistance to the passage of rapid vibrations through a heliv Wmg inserted in it an i,„n core, that any electro-magnet n mod in the circuit through which rapid vibrations ai-e electri- cally transmitted, wOl either totally absorb them or greatly dton- .h their power. This is found to be true in practice, and it Z a serious problem how to successfully use Bpeakin^telephonS upon hues where more than two stations were ne^ sary In '>. iMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I l^|2£ |25 *ii Ui 12.2 118 L^ IM IIM i y} ''^i w > >> .^ ^^^ Sis. # Photographic Sciences Corporation 23 WEST MAIN STREET WEBSTER, N.Y. MS80 (716) 872-4S03 4 ^ r<^ r \ "9) %"" 180 THE SPEAKING TELEPHONE. order to be able to call the party witb whom we wish to commu- nicate, it is necessary to have bell magnets, or other signaling apparatus involving the use of an electro-magnet, and these magnets must be in circuit when the line is not in use, to be in position to receive a call from any station on the lin& If A, B and C, have offices on the same line, and A should signal to 0, they would both switch out their bell magnets and switch in their telephones ; but B's bell magnet would still remain in cir- cuit and act as a resistance to the passage of vibrations over the line. This difficulty is fully obviated by the use of a condenser, which is placed in a branch circuit passing around the bell mag- nets.' So effectual is the remedy, that even five or six magnets may be inserted in the line without perceptibly diminishing the loudness of the tones over that of a clear wire of the same length. The action of the condenser in this case has been to some extent explained in an article published in the second num- ber of this journal. 1 The effect of a condenser on impulses of short duration is just the reverse of that of an electro-magnet ; the latter offering a momentary opposition to the passage of the impulse by creating a counter one, which to a great extent neutralizes it, while the former offers an easy passage to it so long as the condenser is filling, which occupies a very short space of time. The de- crease in resistance effected by the use of the condenser is only momentary, and will be of no service whatever in prolonged signals. On the other hand, the increase of resistance caused by the insertion of an electro-magnet in circuit is also momentary, and does not act as a retarding influence, where the signal or im- pulse is sufficiently prolonged, more than the same amount of any artificial resistance. I will mention another peculiarity which relates to the con- struction of the speaking telephone, with reference to its ability to accurately reproduce the characteristics of any voice or any sound that may be transmitted through it or received by it 1 For a description of the application of the condenser, see pages 30 and 81. PBODUCTIO» OF VOWEL SO.INDa Igl f! '^ ,*';«" "^"o™ principle in acoustics that that element of mental T . ^"^ '™'^'' '^* "'&■*"<'« ^ the fmiZ menW. For mstonce, a pure tone is made by a given nnXr composa-on, with ^.fe^nce to number knd inteLtrd^teLlne the character of the composite tone as a whole. ''°'^'™~» An approximately pure tone is obtained from a tuning fort constructs with great care, mounted nponaCwhZl^ , , corresponds accurately to the pitch of the fork XZh! a!r column contained within it is thl^wn into vibi^L mt Z fork IS thrown into vibmtion, the sound of the vowel TJ^l^^ the vowel TJ is purity of tone, and may be likeued to one JfZ positive coloi. unshaded by the admLture of any oZ On ae other hand, if we add to this pure tone, or thevlwei U a tone whose vibrations are double the rate anj veiy intele abo any -ngle element of a composite t^ne, eittr in amSe ^ vibration rate or relation to the fundamental tone in the dln» or compt»n, produces a change in the quality of the sound fs, whole. From this it will be ob«erved\ow^im„ ut It the apparahis we use in transmitting and rep^ducing artiou 1 speech shall copy with the greatest accumoy; both in the tmnf mission and repi^duction, all the motions made in the air brthe speaker. Any attempt to .enforce the vibmtions, by mount^J m THE SPEAKING TELEPHONE. the diaphragm on resonant substances, such as wood, and over hollovr air cavities, serves to mutilate the words transmitted, and destroy the peculiar characteristics of the sound. A few mo- ments study of the laws of acoustics will suggest reasons why this is so. Every solid substance of a resonant character — striking ex- amples of which are wood and some of the metals — ^tends to as- sume a fundamental character when thrown into vibration. For instance, when we strike a bell of a given size, it gives a clang of the same character at every stroke. If the size of the bell is changed, the character of the sound or clang will change, so that everything of a solid or massive character may be said to be able to respond more readily to some tones, than otheiu This char- acteristic increases as the body assumes the form of a vibratory reed or tuning fork, and it diminishes as the body is flattened into a thin shape, and assumes the form of a diaphragm, so that it ceases to vibrate more readily as a whole than in its equal parts. It has then more of the characteristics of the air with reference to its ability to take up simultaneously all forms of motion. If, then, the transmitting diaphragm of a speaking tele- 2)lione is so constructed and mounted — with reference to what- ever device is used to transform its mechanical movements into electrical movements of the same quality — that it copies accu- rately the motions of the air, it must transmit perfectly, and reproduce at the receiving end the same characteristics of sound that were transmitted, provided the receiving instrument is equally perfect in its construction. To secure this result, even after the diaphragm is as perfect as possible with reference to size, thickness and quality of material, it must be so mounted as not to excite the resonant qualities of the surrounding material which may be a part of the instrument To this end, the instru- ment should be constructed, especially that portion which is im- mediately above and below the diaphragm, of some non-resonant material, and the diaphragm should be clamped at its edges by something in the shape of a pad or cushion. ^ The air space above ^A device originally suggested by Professor A. £. Dolbear. Brrjicra produced by busohant DEviOEa 188 and -^W the diaphragm should be the smaUest possible. On the ofter hand, J .he body of the instmment is nLe of wo^ andan au- ^vity of considerable size is made under the dial f w J^i J° ""^"^T *" '-^«"l'"i». ""d change the char- aoter of the transmitted sounds. The reason for thiwiU appear ver, plain when we consider the importance of preserri^^ relat.ons of all the simple elements which make up a SosS sound of a given character. These lesonantdevices^wiuZ^te ^Xin;::eJ:rr --^P-Po-^'-'.-deonse.uent.y • In the following pages, which relate especially to the tele graphic transmission of musical and other sounds it tmr hMtory of my own expenmcnte and observations, as they have t^," T /T "■"' *" ''"'^ ^'"<=^ ^ ''^«^" *•>« "vestigationlf thj subject It IS not myintention to enter into the work which has been done by othe.s ; but to furnish as faithful a recorf as us% entitled to priority of invention and discovery iu respect to the various things hereinafter set forth ^^ Atthe time when I began my investigations in connection with the above subject-matter, I had no knowledge that any one C previouslydone anything in this field I wj, howeve^ femiHar with the general fact which had been made k;own by C and Henry in relation to the effect produced upon the ir^n Tre of an electro-magnet at the moment of its charge and discharge I also had some general idea of the natui^ of the experiments of Eeisa, of Germany, which were made about the y^r 1861 but had no knowledge at the time, or until mo«, than a year ^ I had been actively engaged in telephonic Kseai^h, thaLny cue beside myself was devoting any attention to the same sub"! A glance at my antecedents may not be inappropriate at this ' Ab,tr« of M,p,H«mla! i8»^rd«, by Eli.lm Gr.y, So. D. 184 THE SPEAKING TELEPHONE. point, inasmuch as it will help to show how I came to be led into this particular field of physical research. From my earliest recollection I was profoundly interested in all the phenomena of nature, and had an intense desire, whenever I saw any manifestation of physical force, to become acquainted with the secret of its operation. When I saw a piece of ma- chinery of any character whatsoever, I usually attempted to re- produce it Of course I was unsuccessful in most instances, owing to the fact that my facilities for constructing machines were very limited, and my experience as a mechanician at that early age was meagre. However, not all of my attempts were failures ; for, I have in my mind the memory of the operation of many ma- chines constructed by my own hands, ranging from a saw-mUl run by water power to a Morse telegraphic apparatua Among all the phenomena throughout the domain of physics,, nothing took such hold upon my mind as that exhibited in the various effects "produced by the action of electricity. I read whatever I could find relating to this subject, with the same eagerness and interest that most boys would read Eobinson Crusoe or the Arabian Nights ; and many were the scoldings — to say nothing of stronger appeals that were sometimes made — that I received in consequence of my enthusiasm in experi- mental investigations in the various branches of physics. As I look back from this point, however, I feel no disposition to com- plain of what I then not unnaturally regarded as harsh treat- ment ; for I can readily see that it was not altogether pleasant for my mother to find, as she sometimes did, that whole skeins of flaxen thread, which she had spun with her own fingers, had been used up in manufacturing belts to drive machinery which in her eyes promised very small results ; or to discover that her best case-knife had been notched into saw-teeth, with which to equip a miniature saw-milL Neither was it altogether agreeable to her feelings to find her only quart bottle — for quart bottles in those days were rare, and highly prized by the housewife — converted into a cylinder for an electrical machine ; or to have the copper bottom of her wash-boiler cut up to make the plates GBAT'S EAKLY ESPEBIltliNTa ; Igg rf a galvanic pile. I even tMnk 1 would have invaded the Pi^fn^ir ^,- """u ''"'™ "^^^ "" ''°">'™'« ''^"'e a T^„ """"fction with any of my boyish schemes. .f ^ l! ^ * I ^ constructed a Moi^e register, all the parts of wh,ch were made of wood, with the exception rf the maS^^ annature and embossing point in the end of the lever^S Un:lZt7t ««->ganail downtoapoint> Ihadthel^t bent mtoa Uform by a blacksmith, and then wonnd it with brass bell-wire, which was insulated with strips of cotton cTntb wrapped around it by hand. For a battery'l made^se of » candy jar, m which I placed coUs of sheet copper and zinc with a solution of blue vitriol With these materMs I s„cc"!d el t nmbng a very good electro-magnct, which would sustain n«^rv a pound we«hl^ and which, when mounted as a part of the i™tm wrdtt:s:£Ju:re:To::ttr'^^^^^^ edge tools which I made during that time are'^^tni in rH r^ poss^sioa I soon found, however, that this business "71 I therefore rehnqu,shed it, and became an apprentice to a T i ZZTf, *'?j'i ™ <=--«• with point p«,iecti„/th.„ght rj birjitx7''''r'''^ the pipe, was adjusted very near to thp dr t ^ " ^"^* °* had glued to it a thin piece ofXfn f'^Pj™*^ *• The latter """" -.t this fac. to produce a vibration in the dia- 196 THE SPSAKING TBLEPHONE. pbragm J, whicli would make contact at each movement with the screw D. As the condensations and rarefactions of the air in the tube were synchronous with the vibrations necessary to produce a tone corresponding to the fundamental of the pipe, it is plain that the movement of the diaphragm would be the sama By con- BiBcting a battery and receiving instrument through the bind- ing posts and the point D, when the organ-pipe is sounded its proper tone will be produced on the receiving instrument by electro-magnetic action. Fig. 98. I made a series of these transmitters, operating them with a bellows, and when worked with uniform pressure of air, they produced splendid results. In fact, it makes a very good form of transmitter, and other things being equal, would be quite as good as the one we have most generally used- This method of trans- mission, however, involves the employment of a bellows, pro- • vided with some attachment for maintaining a uniform pressure, as well as with power to work it ; so that it seemed, at least for telegraphic purposes, that some form of transmitter having electricity for its motive power would be more appropriate I TELBPHOOTC TRiLNSMHTlRS. j^y ^o« continued .o prosecute my experiment, in ^t ^ compound magnet, « ahown at flHT ^ ' '^'^*^ * nected the piitive ^le otZh^th^f^ *" '''\'^ ^ *»■ «bout eight^ninchlTin Sj^d tL^ t * '"^ °' '*"' "^ ba., ao that when the magXCr^ chS" T'" '° 1 ^"^"^ ^^^ ^^"^ Charged one bar would show I\g. 94. poaitive or north polarity and the other aouth. The mametiam was about equally distributx^d though the length of eS ^ Th,a arrangement enabled me to get a large fumberT.«d^ upon a smaU number of magneta I found, howeve^, "LTtl power ™a too much distributed to produce good ,^;iru™. This ia substantially the same as my transmitter shown in %. 198 THE SPEAKING TELEPHONE. 87, except that I use two and three reeds upon each magnet, all differently tuned. Another form of transmitter invented by me is shown in % 95. It consisted of a revolving shaft, upon which were mounted two eccentric cams, having one or more projections. These actuated two small levers, causing them to vibrate upon their respective break-points, through which points a battery current passed From a pulley on this shaft I connected a belt to one of the wheels of a lathe which was driven by steam power, from which it derived a uniform motion and a definite rate of sp§eA ^■f IKg. 96. I refer to my experiments with this particular apparatus because, although simple in themselves, they were the means of giving my mind a new impulse in another direction, and one which soon conducted me to the solution of the problem in- volved in the transmission of articulate words. I employed, in connection with this transmitter, one of my common receivers which was adapted to the reception of all varieties of sounds. The pressure of the levers upon their contact-points was con- trolled by elastic springs. When this apparatus was put in operation I noticed that a TRANSMISSION OP ARTICULATE SPEECH. 199 sound of peculiar quality, not unlike that of the human voice when in great distress, proceeded from the receiver. By altering the tension of the spring in various ways with my hand, I found that I Was able to imitate many different sounds, involving the vowels only. I succeeded, among other things, in producing a groan, with all its inflections in the greatest perfection. By skilfully manipulating the spring in the manner before men- tioned, a very great] range in the quality of the sounds was pro- duced, using only a single break-point Fig. 96. ITp to the time of making this experiment I had associated in my mind, in connection with transmission of spoken words, a complicated mechanism involving a separate vibrating reed for each separate tone transmitted This experiment produced an entire change in my views, and I came to the conclusion that it could all be done by means of a single transmitter; although, at -liiat time, I did not carry my experiments farther in that direc- tion, being too much absorbed in my multiple telegraph scheme. During the latter part of the spring and early part of the sum- soo THE SPEAKING TELEEHONE. mer of 1875, I was engaged in conatructing and iidapting my system to a type-printing telegraph, an idea which I had con- ceived early in 1874 I had it reduced to practice far enough to demonstrate the applicability of the principles involved. In January or February, 1876, 1 constructed an operative machine, at that time having three letters of the alphabet, together with the mechanism for controlling the printing and moving the paper. An outline view of this machine is shown in figs. 96 and 97. The model of this machine was completed and forwarded to the Patent Office in October, 1876. The patent on it vras issued Fig. 91 July 4th, 1876, to which I refer for a complete description. The general principle of operation may be briefly stated as follows • A particular tone actuates each particular type, so that there is a transmitting vibrator and corresponding receiver for each tona A simple touch of a key prints the letter at the receiving end without the necessity of waiting for a type-wheel to come into positioa The printing is executed upon a sheet instead of a long stnp or ribbon, as in the ordinary step-by-step machine. It ^ will not be necessary to describe the mechanism in detail in this place, as it is fully set forth in the specification of the patent itself. wb( iHvuNTioM or THi sniKma TshspBosm. 20I rrJk ^ . > ""^ '"™8 » *'««'l attoohed to the centre. detemmed to put this into practical shape and file hiniht records of the Patent Offlno t t , , " ^^ *^<^ matter nf tT^lv u . ^ "^^^'^^^ *^a<= this would be a matter of the highest importence in a scientific point of view bu! «ble to what seemed to be the most practical and useM fSw f^toe, and take it up and develop it more completely at another ■ About the 15th of January, 1876, I went to Washington months Th.s required several weeks of time. Whi eT^ I put my speakrng telephone transmitter into the form li d^" ■ngs and spee^cations, and, as my model was not y^ rLdv I determmed to file the specification as a caveat Follo^n JZ ftl SSS rrr"" ^*'"' '^^P''™8» ■"«» Btring of thT W tae motions of the diaphragm electrically, through the lonm tudmal vtations of a light rod attached 'to the tn re infe" d.aphrag„. These electrical vibrations or midulatiZll t 202 THE ft?EAKINO TBLBPHONK. result of the variations in the resistance of the circnit made by the longitudinal motions of the rod, moving in a yielding sub- stance offering a considerable resistance to the passage of the electric current The following is a verbatim copy of the speci- fication, filed in the United States Patent Office, February 14, 1876: gray's specification, filed FEBRUARY 14, 1876. To all whom it may concern : Be it known that I, Elisha Gray, of Chicago, in the County of Cook, and State of Dlinois, have invented a new art of transmitting vocal sounds telegraphi- cal?y, of which the following is a specification : It is the object of my invention to transmit the tones of the human voice through a telegraphic circuit, and reproduce them at the receiving end of the line, so that actual conversations can be carried on by persons at long distances apart I have invented and patented methods of transmitting musical impressions or sounds telegraphically, and my present invention is based upon a modification of the principle of said invention, which is set forth and described in letters patent of the United States, granted to me July 27th, 1875, respectively numbered 166,095 and 166,096, and also in an application for letters patent of the United States, filed by me, February 23, 1875. To attain the objects of my inventipn, I devised an instrument capable of vibrating responsively to all the tones of the human voice, and by which they are rendered audible. In the accompanying drawings I have shown an apparatus embodying my improvements in the best way now known to me, but I contemplate various other applications, and also changes in the details of construction of the apparatus, some of which would obviously suggest themselves to a skilful electri- cian, or a person versed in the science of acoustics, on seeing this application. Fig. 1 represents a vertical central section through the trans- mitting instrument ; ' Fig. 2, a similar section through the receiver; and Fig. 3, a diagram representing the whole apparatus. gray's 8PK0IF1OATIOX. fc&; /•-i >«mJm •Mii—J-Q -a m \^i^»f. ng. 98. 204 THE SFBAKINO TELSPBONE. My present belief is that the most effective method of pro- viding an apparatus capable of responding to the various tonea of the human voice, is a tympanum, drum or diaphragm, stretched across one end of the chamber, carrying an apparatus for producing fluctuations in the potential of the electric current, and consequently varying in its power. In the drawings, the person transmitting sounds is shown as talking into a box, or chamber, A, across the outer end of which is stretched a diaphragm o, of some thin substance, such as parchment or gold-beaters' skin, capable of responding to all the vibrations of the human voice, whether simple or complex. Attached to this diaphmgm is a light metal rod, A', or other suitable conductor of electricity, which extends into a vessel B, made of glass or other insulating material, having its lower end closed by a plug, which may be of metal, or through which passes a conductor i, forming part of the circuit This vessel is filled with some liquid possessing high resist- ance, such, for instance, as water, so that the vibratiors of the plunger or rod A', which does not quite touch the conductor i, will cause variations in resistance, and, consequently, in the potential of the current passing through the rod A'. Owing to this construction, the resistance varies constantly in response to the vibrations of the diaphragm, which, although irregular, not only in their amplitude, but in rapidity, are never- theless transmitted, and can, consequently, be transmitted through a single rod, which could not be done with a positive make and break of the circuit employed, or where contact points are used. I contemplate, however, the use of a series of diapTngnit^ in a common vocalizing chamber, each diaphragm carryin^^ an inde- pendent rod, and responding to a vibration of diffe cfiS /upicuty and intensity, in which case contact points mounted on other diaphragms may be employed. The vibrations thus imparted are transmitted through an elec- tric circuit, +o the receiving station, in which circuit is included an electr: -n-f'guet of ordinary construction, acting upon a dia- phragn- tc v;.ieu is attached a piece of soft iron, and which bill's SPECmOATlOM. 206 diaphragm is gtretohed acm™ « ~™:, ■ somewhat similar to TeZZ^ T^ ^ vocalizing chamber c, The diaphraZ ^ tb„^?°'"''"f ^'^"'''"« <='«">"«r A. i->^ vib jo3Cndtg™ti to:':'!":^ " '"-^ "■'°'"> and audibie sounds of.oj:f;^Zl "^ *""^""'''"« ^-^' to ™:Ue7::orfr'arlr"°r' n.rin.p^.vementwi., be I claim as my invention the art of transmifHr,,, ^ or conve-sations ^.egraphical., througfanS ::^r'' otherparties I will n^^T^ '^vention as between myself and » I aL awtre t^iTs tlffl^f'^''."';.'"^™--'-, thatsofar Mng t^.eph„;ewiiri?ji^ii:CL:wTr^^^^^^^ voice telegraphically by means of eleXicUy BELL'S SPECiriOATIOJf, PILED FEBBUAEY 14, 1876 In order that the claims of Professor A P. B«ii '. .i, • on the 14d. Frt,!irri876 2 f* ^'"'^ ^''"*'" OfH"^ on which Mr. G^;d 1'^^ '*^' " "^ "^ "'^^'^ W dtS medflraot"'! "^ f^'' ^°- ^''^■^««' ' ormo.teleg.pHo ^Sau'sruSr^^^tirgTSn^:^ *™ - othe.. and oTr^gr^r^-^r ^s 206 THE SPILLKISO TBLEFHONE. at wWcli it will be put in vibration to produce ita fundamental note by one only of the transmitting instruments ; and of vibra- tory circuit-breakers operating to convert the vibrat)ry move- ment of the receiving insti-ument into a permanent mak 3 or break (as the case maybe) of a local circuit, in which is placed a Morse sounder, register, or other telegraphic apparatua I have also therein described a form of autograph telegraph based upon the action of the above mentioned instruments. ^ In illustration of my method of multiple telegraphy I have shown in the patent aforesaid, as one form of ti-ansmitting instru- ment, an electro-magnet having a steel spring armature, which is kept in vibration i)y the action of a local battery. This arma- ture in vibrating makes and breaks the main circuit, producing an intermittent current upon the line wire. I have found,' how- ever, that upon this plan the limit to the numbiirof signals that can be sent simultaneously over the same wire is very speedily reached ; for, when a number of transmitting instruments, having different rates of vibration, are simultaneously making and break- ing the same circuit, the effoct upon the main line is practically equivalent to one continuous current In a pending application for letters patent, filed in the United States Patent Office February 25, 1875, 1 have described two ways of producing the intermittent current— the one by actual make and break of contact, the other by alternately increasing and diminish- ing the intensity of the current without actually breaking the circuit The current produced by the latter method I shall term, for distinction sake, a pulsatory current My present invention consists in the employment of a vibra- tory or undulatory current of electricity, in contradistinction to a merely intermittent or pulsatory current, and of a method of, and apparatua for, producing electrical undulations upon the line wire. The distinction bet\ireen an undulating and a pulsatory cur- rent will be understood by considering that electrical pulsations are caused by sudden or instantaneous changes of intensity, and that electrical undulations result from gradual changes of in- tensity exactly analagous to the changes in the density of air bell's specification. 207 ment, like the aenal motion, can be reoreapnt^rl hrr „ • -1 -, "71'" "^ *''' '"'^*-' of seve JZStu^: """°"^ ^intermittent or pulsatoiy and undulatory currents nmv 1» „» two fands, accordingly as the successive impute ha™ ^al^thf same pohmty or are alternately positive and native. " cu^ntt'nK'"""" '°,''"™ ^" *« "^ 'o* ■"■ -'J»l'"o,7 current in place of a merely latennittent one are first that i ^nfoZ'ontr """"""■ "' ^«"="'«'" "^ *™— S^'ul! taneously on the same cffouit; second, that a closed circuit and ^ngle mam battery may be used; thirf, that commuSL fa Mucttror IZT:'.T}^'' '^^ -essityT^iS more raniX th. r ' "f^" ^^*^^^ ^7 be tmnsriitted more rapidly than by means of an intermittent current or bv fl,^ methods at present in use ; for, as it is uaneccs^^t^ dTscAa^^! e cable before anew signal can be made, the la/giW 3e Srr,^iru-ix^-----»-t^ electncitj is induced in the coils of the latter and ihlTT to vibrate 7nTrnn/7!^' ? f ' ^ P^"^^^^^* "magnet is caused w toe viDratious of the magnet, m polarity to the direction of Its motion and m intensity to the amplitude of its viS That the difference between an undulatory and anrtLit n., „,^^^^ ,^^^ ^jjjg_ ^^ ^^^ transmitting im THE SPSLAXING TELEPHONE. instrument in the same time that five makes and breaks are caused by the other. A and B, fig& 1, 2 and 3, represent the intermittent currents produced, four impulses of B being made in the same time as five impulses of A. c e c, etc., show where and for how long the circuit is made, and ddd, etc., indicate the duration of the break^s of the circuit The line A and B shows the total effect upon the current when the transmitting instruments for A and B are caused simultaneously to make and break the same circuit The resultant effect depends very much upon the duration of the make relatively to the break. In fig. 1 the ratio is as 1 to 4 ; in fig. 2, as 1 to 2 ; and in fig. 3 the makes and breaks are of equal duration. The combined effect, A and B, fig. 3, is very nearly equivalent to a continuous cur- rent When many transmitting instruments of different rates of vibration are simultaneously making and breaking the same circuit, the current upon the main lines becomes for all practical purposes continuous. ISText, consider the effect when an undulatory current is em- ployed. Electrical undulations, induced by the vibration of a body capable of inductive action, can be represented graphically, without error, by the same sinusoidal curve which expresses the vibration of the inducing body itself, and the effect of its vibra- tion upon the air ; for, as above stated, the rate of oscillation in the electrical current corresponds to the rate of vibration of the inducing body— that is, to the pitch of the sound produced. The intensity of the current varies with the amplitude of the vibration — that is, with the loudness of the sound; and the polarity of the current corresponds to the direction of the vibrat- ing body — that is, to the condensations and rarefactions of air produced by the vibration. Hence, the sinusoidal curve A or B, fig. 4, represents, graphically, the electrical undulations induced in a circuit by the vibration of a bojiy capable of inductive action. The horizontal line adef, etc., represents the ze -o of current The elevation b bb, etc, indicates impulses of positive electricity. bell's specification. 209 Vft. 17M6Si ■''^>r asiinti-shfMi. ^ -^ - « _ -2^* *« "^ graphic oi^uitrfelec^eal^b^^otoTrff? "T " *«'<^ fested, not by the oblit^,^^^ f .^ 1 '''^'"*''* P««h is mani- ourvesWichr^Xe^tlVndntrr " '"^ '''^ " "^ eieetfS; dep-eXr-S :^r;nh:t::S7 ™"^'"' °^ Of bodies capable of inductive »oS.. Atrjthritr h 7\^,^-»P%«' I Bhall here spetify When a t through which a continuous current nf «1 7 • ■• ^'"^ caused to vibn.te in the nel^ZJi ^f T^ ■' ^'^"8- '^ ia^^ e„n.„t of e.^trici^^l'llXtTeLr ' Wh""'"- o...tncityis-^irrretr^^^^^^^^ h^\^fiTrdi:r''i,r^^^^^^^^^ ucn bodies. Electrical undulations may also be caused 212 THE SPEAKING TELEPHONE. by alternately increasing and diminishing the resistance of the circuit, or by alternately increasing and diminishing the power of the battery. The internal resistance of a battery is diminished by bringing the voltaic elements nearer together, and increased by placing them farther apart. The reciprocal vibration of the elements of a battery, therefore, occasions an undulatory action in the voltaic current The external resistance may also be varied. For instance, let mercury or some other liquid form part of a voltaic circuit, then the more deeply the conducting wire is immersed in the mercury or other liquid, the less resist- ance does the liquid offer to the passage of the current Hence, the vibration of the conducting wire in mercury or other liquid included in the circuit occasions undulations in the current. The vertical vibrations of the elements of a battery in the liquid in which they are immersed produces an undulatory action in the current by alternately increasing and diminishing the power of the battery. In illustration of the method of creating electrical undulations, I shall show and describe one form of apparatus for producing the efTect I prefer to employ for this purpose an electro-magnet A, fig. 5, having a coil upon only one of its legs J. A steel spring armature c is firmly clamped by one extremity to the uncovered leg d of the magnet, and its free end is allowed to project above the pole of the covered leg. The armature c can be set in vibration in a variety of ways, one of which is by wind, and, in vibrating, it produces a musical note of a certain definite pitch. When the instrument A is placed in a voltaic circuit, g b efg, the armature c becomes magnetic, and .the polarity of its friee end is opposed to that of the magnet underneath. So long as the ar- mature c remains at rest no effect is produced upon the voltaic current, but the moment it is set in vibration to produce its mu- sical note a powerful inductive action takes place, and electrical undulations travei-se the circuit g b efg. The vibratory current passing through the coil of the electro-magnet /causes vibration in its armature h, when the armatures c A of the two instruments A I are normally in unison with one another ; but the armature h bell's specification. 213 "ruments is sef in vibration l^^r"!'"^"' ""y"™"* "-e in- circuit which are ,n St^^h it "Tr™'' "P™ '^- have normally a differemralTf .^^ 7^°"^ '"'* ^o'" ^^ioh if A, flg. 6, is set ifvSon Th T ''""" ^'^"'- ^hus, ■ vibrate also but all the „T' I ^™'""«'' °l A- and A» wil BHscausei'toer^^^ ttl^^lt'Th"'"'"'*'""^"''"'- ^^ spond. Thev ennH„„. ■ ^' *" instruments B B^ re- tion of Buf eontX^tte? " '°^^ its motion. The durS^n of r ''. '''* *" "^'^'i™ <>« the dot or dash oftt Morse flTf'"''^.'''"^^'^ *<'■"*««'« dispatch may be iudiLt,:^ t^lSt f' i''f ''"^ ^ '^'^^''P''- mg the sound. When two or r^''"P""S''°d «'«=''■ pitoharesimultaneous^rurtoXraUr'^ f <^"^''"^"* corresponding pitches Lnr. +1. /'^.'^^®' ^^^ ^^^^ instruments of -pcSng toTat onT^n V of r?" """? "'■^''™' -" with which it is in unison Tbt It ^"'"r""^ iustr„men.« peated by Ai and 1"^ J *« ^.gnals of A, fig. 6, are re- by C and O-whether A B» and f. , ' *' ''«""'' "' «' tanconsly caused to vibra e. Henf "^ r°«^'™'^ "^ «»«1- or more telegraphic sianak o, ^ ""' '"»t™ments two neously ovef i s:;*e cir^it r^t "T ^ ^^'" =''"»"-- another. ™" '''"'°"* interfering with one thLtsiut:n:mrLtn?'T""r°*''--'"*ch mission of musical 2e,^ir' '''*,''^*'«* simultaneous trans- and the telegrSe "ran^miSon"*;" '°"'"''" "^ "^" ^ -l'''*, When tl/armatur~6 °: IZZT'^'l "' '"^^'^ responds not only i„ iitfh butt , ^ "' *'""'™^'«"^ * vibrates with little amDHnd. ?'^"'^'- ^'"'■''' when c tion of ;, is consideXi r"i*4dt!'''''' f *'■"'''"'• ' ana thu resulting sound 214 THE SPEAKING TELEPHONE. becomes louder. So, if A and B, fig. 6, are sounded simul- taneously (A loudly and B softly), the instruments A* and A» repeat loudly the signals of A, and Bi B' repeat softly those of B. One of the ways in which the armature c, fig. 5, may be set in vibration has been stated before to be by wind. Another mod^ is shown in fig. 7, whereby motion can be imparted to the arma- ture by the human voice or by means of a musical instrument The armature c, fig. 7, is fastened loosely by one extremity to the uncovered leg d of the electro-magnet h, and its other extremity is attached to the centre of a stretched membrane, a. A cone, A, is used to converge sound- vibrations upon the mem- brane. When a sound is uttered in the cone the membrane a is set in vibration, the armature c is forced to partake of the motion, and thus electrical undulations are created upon the circuit E h efg. These undulations are similar in form to the air vibrations caused by the sound— that is, they are represented graphically by similar curves. The undulatory current passing through the electro-magnet/ influences its armature h to copy the motion of the armature c. A similar sound to that uttered into A is then heard to proceed from I. ^ In this specification the three words, "oscillation," "vibra- tion," and "undulation," are used synonymously, and in con- tradistinction to the terms "intermittent " and " pulsatory." By the term "body capable of inductive action," I mean a body which, when in motion, produces dynamical electricity. I include in the category of bodies capable of inductive action brass, copper, and other metals, as well as iron and steel. Having described my invention, what I claim, and desire to secure by letters patent, is as follows : ^ 1. A system of telegraphy in which the receiver is set in vibration by the employment of undulatory currents of electricity, substantially as set forth. 2. The combination, substantially as set forth, of a permanent magnet or other body capable of inductive action, with a closed circuit, so that the vibration of the one shall occasion electrical BELL'S SPECTFIOATION. ' 21S mdnlatioM ia theother, orinitself, andtUsIoIaim whether*!,, pem«nent magnet be «et in vibration in the neig^rloS^^: WTO be set ,n vibration in the neighborhood of the permanent »^^or whether the conducting wi« and the perlS^ C^ ^-"Itoneously be set in vibration in each oth*'s „^. S. The method of producing undulations in a continuous voltaio cun^nt hy the vibmtion or motion of bodi^^^w ^Zt2 ^ X^r"''''"- <- motion of thTSu^' ^ Thf CI /°f''°?°^ °' ™* '"«"^'- ■« »"' forth. * ToLotLuk b^ °^P^»«'"g undulations in a continuous voitaio circuit by gradually increasing and diminishing fh,. T s«tanceofthecir.ui^orbygraduallyL.^ig"::fZnt^^ the power of the battery, as set forth. uomunislung ^. lOL ^,lf„''''* T*^,'^ "'• ,*"'^ "PParato for, transmitting vocal or other sounds telegraphically, as herein described, by ca^g electncal undulations, similar in form to the vibrltioi of^ft! Z S"^""^^ *» ^-'-J ^^'l » other ^unds, substantially!! We have given in Chapter IL a verbatim copy of a lecture dehvered by Professor Bell, befoi^ the Society of TewC Engineer^ in London, October 31, 1377. On page 71X5^ eedmg cut, fig. 101, is shown, which is the oSy instmn^nt m the patent of Mai.h 7, 1876 (filed February 14, Sor which any pretence can be set up tliat it is a talking telephone Speaking of this instrument, Professor Bell says, thft Mr Wat 2i6 THE SPEAKING TELEPHONE. ■a Fig. 102. gray's caveat. 217 ZnI^LZ:i:;^^ ''•■"' t'»-« <^'-™^'i late utterate A^m The ll ^ '""*? ^'"° '''^^ "'"«"«' "rt^"- through a speaking tube'" ' P'''"'"'™' o"" willbe Jentfitl^tlltelr*"^ ^*? (''8- «">' '* identical in eonstraction wM the s,„e m pnnciple, and almost and described in mTp ' ' --eceiving mstrnment shown Bell itT, .1 ,^': *^™y '^ «'™''t of February 14, 1876. Pro£ Whether or not ftof Ben rvln?tf), ''"'""""'^ ^*™'-^- ofMr.aray,weWn:t~ tirCh:^^^^^^^^ the tot inventor, we think the fiei^tncif; hoi C he been the fl.t to invent it, is the,, any reason why hi' «ho^W not have deserjbed it in his application, filed simultaneol^ Wu Mr. Gray, on the 14th of February, 1876 ? ""*'"^'^ly "th CHAPTER YL Edison's telephonic researches. The following communication from Mr. Thomas A. Edison gives a detailed account of his researches in telephony, and is a valuable contribution to the history of the developmenj; of the speaking telephone. • Some time in or about the month of July, 1875, I began experimenting with a system of multiple telegraphy, which had for its basis the transmission of acoustic vibrations. Being fur- nished, at the same time, by Hon. William Orton, President of the Western Union Telegraph Company, with a translated description from a foreign scientific journal of Reiss'si telephone, I also began a series of experiments, with the view of producing an articulating telephone, carrying on both series simultaneously, by the aid of my two assistants, Messrs. Batchelor and Adams. - With regard to the multiple telegraph I will say that many methods were devised, among which may be mentioned the transfer system. This consisted in combining a large tuning fork with multiple forks, so arranged at two terminal stations, with contact springs leading to different Morse instruments, that the synchronous vibrations of the forks would change the main line wires from one set of instruments to other sets at both sta- tions, at a rate of 120 times per second. With this rate of vibra- tion the wire would be simultaneously disconnected at both ter- minal stations from one set of Morse signalling apparatus, and momentarily placed in alternate connection with three other similar sets of apparatus, and then again returned to the first set, without causing the apparatus to mark the absence of the current otherwise than by a perceptible weakening of the same. 1 Zt it3c>inft des Deutsch-Oesterreicliisclien Telegraphen-Vereins, herausgegeben in desseii Auilrage von der KOniglich Preussischen Telegraphen-Direction. Redi- girt von Dr. P. Wilhelm Brix. Vol. ix., 1862, page 125, (For a deacription of Reiss's apparatus see pages 9 to 13, inclusive.) TILIPHONIO RECEIVEB& jjg Notwithstanding the perfect success of ih. a . artificial line however w).;.K . , ^ ^^^*^"^ ^P^n an «en% perfect compensaUon for the effects of the static ch^ Fig. 103. to allow of the successful use of the svstPn. or, . v * SepteXf W.°''r"'*i""^"^'^^'™' '''''* ™' devised in beptember, 1876, and is shown in iig. 103, two tuning forks, A > 220 THE SPEAKING TELEPHONE. and B, vibrating from 100 to 500 times per second, were Jcept in continuous motion bj a local magnet and batteiy, and the short circuiting was controlled by the signalling keys Kj and K . As will be seen on reference to the figure, this system, like that shown in my patent of 1873, is dependent upon the 'vary- ing resistance occasioned by employing a movable electrode in water, and which thus produces corresponding variations of the battery current in the line. The receivers E^ and Eg, fig. 104, were formed of telescopic tubes of metal, by lengthening or shortening of which the column of air in either could be adjusted to vibrate in unison with the LINE Mg. 104. proper tone of the fork, whose signals were to be received by each particular instmment An iron diaphragm was soldered to one end of these tubes, and the latter placed in such a manner as to bring the diaphragm of each respectively just in front of an electro-magnet, which, in action, would cause them to vibrate. When the column of air in either receiver was properly adjusted to a given tone, the signals due to stopping and starting the vibrations by the distant key were very loud, as compared to other tones not in harmony with the column of air. Flexible rubber tubes, with ear pieces, were connected to the receivers, so MAGNETO-SPEAKING TELEPHONE. 221 that, in using the instruments, the head of the owr«tn^ „.. . required to be held in an unnWral or strlin^ S. " ""' This system worked verj^ well; but one defect in it w„, apparent from the fi:.t, and that was its continual tende'to g^e the operator what is termed the back-stroke, even fern th^ hghtest ca^e such as the opening of a door or the m^il of With a Morse sounder, as is well known, every dot is mad« apparent to the ear by t^o sounds, the fln,t bjing p^duced whl the lever stnkes the anvil, and the other when U sSkel^e upper or back contact. A dash like th. ^„» • i of two sounds, but the interv" of tte betttn tt° "7°"^ of the to, the downward stroke orrndrdTe upVa:?;:^;:; =s what determines ite chamcter. It fi^quently W "^ w' ever when a sounder is so adjusted that the sound Zdu J W signals consequently become unintelligible and the onZ" tr-L-rofte''rd:;ie::--|^^^^^^^ hy ,.ingthe.nger on ^tZt^Z^::^^ my keys so as to transmit two^trttn^ clos T T TT""^ „-.is, .ucn, lor .natanc;o, as the employment of two 222 THE SPEAKING TELEPHONK forks of slightly different pitch, which, at least, promises welL When this is done the system will be of some value. It will be noticed that the receiving instrument shown in fig. 104 contains the diaphragm magnet and chamber of the magneto- speakmg telephone ; and I may say here that I believe I was the first to devise apparatus of this kind, which I intended for use in connection with acoustic telegraphs. I can, however, lay no claim to having discovered that conversation could be carried on be- tween one receiver and the other upon the magneto principle by causing the voice to vibrate the diaphragm. Another system of multiple transmission consisted, partly, ia the use of reeds for receivers, and has been exceedingly well de- veloped in the hands of Mr. Elisha Gray, but I forbear explain- ing It here, owing to its complexity and lack of practical merit My first attempt at constructing an articulating telephone was made with the Eeiss transmitter and one of my resonant receivers described above, and my experiments in this direction, which continued until the production of my present carbon telephone, cover many thousand pages of manuscript. I shall, however^ describe Lore only a few of the more important ones. In one of the first experiments I included a simplified Eeiss transmitter, having a platinum screw facing the diaphragm, in a circuit containing twenty cells of battery and the resonant re- ceiver, and then placed a drop of water between the points; the results, however, when the apparatus was in action, were unsatis- factory—rapid decomposition of the water took place and a de- posit of sediment was left on the platinum. I afterwards used disks attached both to the diaphragm and to the screw, with sev- eral drops of water placed between and held there by capillary attraction, but rapid decomposition of the water, which was im- pure, continued, and the words came out at the receiver very much confused. Various acidulated solutions were then tried, but the confused sounds and decompositions were the only results obtained. With distilled water I could get nothing, probably because, at that time, I used very thick iron diaphragms, as I have since THE OABBON TELEPHOKB. 228 frequendy obtained good recite ; or, possibly, it was because the ««■ was not yet educated for this du^, and the^reT^ ** know what to look for. If this was the case, it f^S^L tLZ' mustmhon of the fact observed by P„,fessor i^TihTt often fsal to istinguish weak sounds in certain ca^ " 1 do not know what to expect Sponge, paper and felting, saturated with various solutions were also used between the disks, and knife edges we^suM tated for the latter with no better ,«suh^ PoinliZ^^^n e «,t,olyt,c cells we^ also tried, and the experimentsT^^rtai" o-« solutions, devices, etc, continued until Februaiy, 1^76 whTn LSr:? t "^'^r''"' "-^-"l-deavorS to ^^th^ resistaiice of the crcmt proportionately with the amplitude of vibration of the diaphragm by the use of a multiplicity ofplaf num pointe, springs and i^istance coils-all of which were de. signed to be continued by the movements of the diaphnZbut none of the devices were successful. "pnragm, but In the spring of 1876, and during the ensuing summer I en- deavored to utilize the gi^t resistance of thin fllL of plumbago ^nd white Arkansas oil stone, on ground glass, and itVas hl^ that I first succeeded m conveying over wires many articulated sentences Springs attached to the diaphmgm and n^m^^^ other devices were made toeut in and out of cii^uit more~ of the plumbago film, but the disturbances which the dcriZ tWlves caused in the true vibiations of the diaphra„ vented the realization of any poetical results. One of ^y'^^. sistante, however, continued the experiments without interrun tion until January, 1877, when I applied the pcculil^ pS which scmi-conducto,^ have of varying their resZn^^l pressu., a fact discovered iy myself in f873, whCns^^ng some rheostats for artificial cables, in whi^h were emplovrf powder«i carbon, plumbago and other materials, in gCtubes For the purpose of making this application, i construe W an Shewing spimg, which was faced with platinum, and in fmnt of this I placed, m a cup secured to an adjustin,; sc:-,w, sticks °f 224 THE SPEAKING TELEPHONE. crude plumbago, combined in various proportions with dry pow- ders, resins, etc. By tbis means I succeeded in producing a telephone which gave great volume of sound, but its articulation was rather poor ; when once famihar with its peculiar sound, however, one experienced but little difficulty in understanding ordinary conversation. After conducting a long series of experiments with solid ma- terials, I finally abandoned them all and substituted therefor tufts of conducting fibre, consisting of floss silk coated with plumbago and other semi-conductors. The results were then very much better, but while the volume of sound was still great, the articulation was not so clear as that of the magneto tele- phone of Prof. BelL The instrument, besides, required very frequent adjustment, which constituted an objectionable feature. Upon investigation, the difference of resistance produced by the varying pressure upon the semi-conductor was found to be exceedingly small, and it occurred to me that as so small a change in a circuit of large resistance was only a small factor, in the primary circuit of an induction coil, where a slight change of resistance would be an important factor, it would thus enable me to obtain decidedly better results at once. The experiment, however, failed, owing to the great resistance of the semi-con- ductors then used. After further experimenting in various directions, I was led to believe, if I could by any means reduce the normal resistance of the semi-conductor to a few ohms, and still effect a difference in its resistance by the pressure due to the vibrating diaphragm, that I could use it in the primary circuit of an induction coil. Having arrived at this conclusion, I constructed a transmitter in which a button of some semi-conducting substance was placed between two platinum disks, in a kind of cup or small containing vessel. Electrical connection between the button and disks was maintained by the slight pressure of a piece of rubber tubing, J inch in diameter and ^ inch long, which was secured to the dia- phragm, and also made to rest against the outside disk. The vibrations of the diaphragm were thus able to produce the THE OABBOS TELEPBOKE. 225 requisite pressure on the platinum disk, and thereby varv the ZTZ:T '"""" ^""'"^^ '" '"^ pHn>ar,oi.^un t el^tl!'" " ''""°° "^""^^ P'"""^"' ™'='' »» i' ^"'Ployed by f^^yV^rs. waa used, and the ..suits obtained we» Lside J ^ellen every^hmg tansmitted coming out moderately dis- tod, but the volume of sound was no greater than that of the magneto telephona IniT'^'V^'''^''''' '^ ^^*"^^ ^'^' ^^ b^**«^«' ^l^^cb, with a ow nonnal resistance, could also be made, bj a slight pressure to vary greatly .n this respect. I at once tried a gre!t varie^ of substances, such as conducting oxides, sulphides and other par- u! WW t f I ^"^^"^ ""^''^ ^"^ ^ «^^11 q^^^tity of lamp- black that had been taken from a smoking petroleum lamp and preserved as a curiosity on account of its intense black color Dht r. ^ ""f^ ""^ f' '^^'*"'^^^' ^^^^ P^^^^d i^ '^^ tele- phone gave splendid results, the articulation being distinct and the vdume of sound several times greater than wi°th telephones worked on the magneto principle. It was soon found upon mvestagation, that the resistance of the disk could be varied from three hundred ohms to the fractional part of a single ohm b' pressure alone, and that the best results were obtained when tJ: resistance of the primary coil, in which the carbon disk was ilt . ;.Tr^^^ ""^ °^"^' ""^ '^' ^°^^^1 ^^^i^tance of the disk Itself three ohins. **■'■ ^''"•y.^ntley, president of the Local Telegraph Com- pany, at Philadelphia who has made au exhaustive serielof expenmente with a complete set of this apparatus upon the wes of the W^tem Union Telegraph Company, has L,u2 succeeded m workmg with it over a wire of 720 ^les in lengtL and has found it a practicable instrument upon wires of 100 t<^ 200 miles in length, notwithstanding the fact that the latter were placed upon poles with numerous other wires, which occasioned sufficiently powerful induced currents in them to entirely destroy the articulation of the magneto telephone. I also learn that he has found the instrument practicable, when included in a Morse i29 THB SPJBiAKlarO TKLKPHONK. drtuit, with & battery and eight or ten stations provided trith the oMinary Morse apparatus; and that several way stations could exchange business telephonically upon a wire which was being worked quadruplex without disturbing the latter, and not- withstanding, also, the action of the powerful reversed currents of the quadruplex on the diaphragms of the receiver. It would thus seem as though the volume of p'> rt/l prGduc,3d by the voice with this apparatus more than comp. i?> ,> for the noise caused by such actions. While engaged in experimenting with my telephone for the pur- itose of ascertaining whether it might not be possible to dispense with the rubber tube which connected the diaphra nr with the rheostatic disk, and was objectionable on account of its tendency to become flattened by continued vibrations, and thus necessitate the readjustment of the instrument, I discovered that my prin- ciple, unlike all other acoustical devices for the transmission of speech, did not require any vibration of the diaphragm — that, in feet, the sound waves could be transformed into electrical pul- sations without the movement of any intervening mechanism. The manner in which I arrived at this result was as follows : I first substituted a spiral spring of about a quarter inch in length, containing four turns of wire, for the rubber tube which connected the diaphragm with the diska I found, however, that this spring gave out a musical tone which interfered somewhat with the effects produced by the voice ; but, in the hope of over- coming the defect, I kept on substituting spiral springs of thicker wire, and as I did so I found that the articulation became both clearer and louder. At last I substituted a solid substance for the springs that had gradually been made more and more inelastic, and then I obtained very marked improvements in the results. It then occurred to me that the whole question was one of pres- sure only, and that it was not necessary that the diaphragm should vibrate at all. I consequently put in a heavy diaphragm, one and three quarter inches in diameter and one sixteenth inch thick, and fastened the carbon disk and plate tightly together, SO that the latter showed no vibration with the loudest tones. THE GAMON TELEPHONE 227 wriS.LV"'"','* '"y^"™^^ verified; the articulation c^ed on m a whisper three feet from the telephone was dearly hearf and understood at the other end of the line. ^ Ita, therefore, is the arrangement I have adopted inmy pres- «at form of apparatus, which I call the carbon tSephone, to dt tufTc^k from othe.. It is fully describedin anVer'part o" The accessories and connections of this apparatus for lonir dr emta are shown in fig. 106. A is an induoUon'coil, whSe pSl^ wre p, having a resistance of seveml ohms, is placed around Iw and!i, ' T"?"* *° *'"' 'l^g™' of ""^oa re- quired and the receiving telephone R consists simply of a ma1 .^^ ^ ""'y *^^ included in the main line men a ping is' inserid tett tn 1 2 anT/t""" T-?- available for telephonic commnn.^tiorf ' *' '^P"™*"^ " ienU:i: wdt;"i.rcan b'rd- ""^ 1 '"r^™«- - Pliiied ar.nge.ent ^^^^^ ^h^S^ ^^ s^^ the induS currei'^rm rd'Tt™'^ ^''- receiver R tJ^ T^ . " *^'^"" =''"™ <«" upon the to bv itin, P S*^f ^^ 1«"«^ i« thmwn into Xation, sonnd XZ7 f ^""^ ""'^ " -^^P-^tively weak sound with the lever resting upon its centre, however a sham ortl'eTvf r~ r ""^'^ '' *" »°°^'»"' -^ -pa ie^unTs or tne lever which thus answers very well for calling purooses at stations where there is comparatively but little nois! ^ ^ uo THE SPEAKING TBIiEPHONB. Among the various other methods for signalUng purposea which I have experimented with, I may mention the sounding of a note, by the voice, in a small Beiss's telephone ; the employ- ment of a self- vibrating reed in the local circuit ; and a break wheel with many cogs, so arranged as to interrupt the circuit when set in motion. Mg. 107. I have also used direct apd induced currents to release clock work, and thus operate a call, and in some of my earlier acoustic experiments tuning forks were used, whose vibrations in front of magnets caused electrical currents to be generated in the coils surrounding the latter. By the further action of these currents on shnilar forks at a distant station, bells were caused to be rung, and signals thus a Fig. 108. given. Fig. 108 shows an arrangement of this kind. A and B are two magnetized tuning forks, having the same rate of vibration and placed at two terminal stations. Electro-magnets m and wi are placed opposite one of the prongs of the forks at each station, while a bell, C or D, stands opposite to the other. The coils of the magnet are connected respectively to the line ELKCTBP-STATIC TfLEPHONB. %9l we and to earth. When one of the forks is set in vibmtion by bj the approach of one of its magnetized prongs towards the TXrs^r '"^ T^\^ tl^erefrom^ass into'the hne a^T^ the further station where their action soon causes the second fork m o m Fig. 109. JZ^^tri T"' ?\""" ''^"^ "^ ^^ ""^"g^d 'hat the one ot the way of the latter'a vibrations. fi/lT^'Trfh "'''"'"""'' ^^'""^ ^ ■""^ "^' i^ represented in wLe raJ^ *f kT*''"''''*""''"''" ""g^'^'i" Pendulums, Whose rates of vibration are the same, are placed in front o Pig. 110. separate electro-magnets, the helices ot which join in the main hue circuit When one of the pendulums is put in motion 2 cuirents generated by its forward and backward swings in front of the eleetro-magnet pass into the line, and at the oppoL ter mma^ acting through the helix there, cause the secondT^M™ to vibrate in unison with the former. P™auium Fig. 110 shows a form of electrophorous telephone which acta 2S2 THE SPEAKING TELEPHONE. by the approach of the diaphragm contained in A or B towards or Its recession from a highly charged electrophorous, C or D 1 he vibrations of the transmitting diaphragm cause a disturbance of the charge at both ends of the line, and thus give rise to faint sounda Perfect insulation, however, is necessaiy, and either apparatus can be used both for transmitting and receiving, but the results are necessarily very weak. Another form of electro- static telephone is shown in fig 111 In this arrangement Deluc piles of some 20,000 disks each are contained in glass tubes A and B, and conveniently mounted on glass, wood or metal stands. The diaphragms, which are in • electrical connection with the earth, are also placed opposite to one pole of each of the piles, while the opposite poles are joined together by the line conductor. Any vibration of either dia- LJNE Fig. 111. phragm is thus capable of disturbing the electrical condition of the neighboring disks, the same as in the electrophorous tele- phones ; and consequently the vibrations, when produced by the voice in one instrument, will give rise to corresponding electrical changes m the other, and thereby reproduce in it what has been spoken into the mouthpiece of the former. With this arrangement fair results may be obtained, and it is not necessary that the insulation should be so perfect as for the electrophorous apparatus. Fig. 112 shows a form of electro- mechanical telephone, referred to near the beginning" of this communication, by means of which I attempted to transmit electrical impulses of variable strength, so as to reproduce spoken words at a distance. Small resistance coils— 1, 2, 3, etc.— were so arranged with connecting springs near a platinum 'faced lever THERMO-ELECTRIC TELEPHONE. 288 B, in connection with the diaphraffm in A tlmf «« to act urSZl,"""*^" ''™' ""'J ''^W tl-en be made to act upon au ori.naiy receiving telephone. By arranging Z ^g. 112. .ae.b,e™Hation :.t -t-J^--^^^^^^ -Pis'. 113, and c. ^ *"^ '° *" Mstrument at a I am now conducting experiment with a thermo-electric tele- 284 THB SPBAEINQ- TELEPHONE. plione, which gives some promise of becoming serviceable. In this arrangement a sensitive thermopile is placed in front of a diaphragm of vulcanite at each end of a line wire, in the circuit of which are included low resistance receiving instruments. The principle upon which the apparatus works depends upon the change of temperature produced in the vibrating diaphragm, which I have found is much lower as the latter moves forward, and is also correspondingly increased on the return movement Sound waves are thus converted into heat waves of similar characteristic variations, and I am in hopes that I may ultimately be able, by the use of more sensitive thermo-piles, to transform these heat waves into electrical currents of sufficient strength to produce a practical telephone on this novel principle. Before concluding, I must mention an interesting fact con- nected with telephonic transmission, which was discovered during some of my experiments with the magneto-telephone, and which is this, that a copper disk may be substituted for the iron dia- phragm now universally used. The same fact, I believe, has also been announced by Mr. W. H. Preece, to the Physical Society, at London. If a piece of copper, say one sixteenth of an inch thick and three fourths of an inch in diameter, is secured to the centre of a vulcanite diaphragm, the effect becomes quite marked, and thQ apparatus is even more sensitive than when the entire diaphragm is of copper. The cause of the sound is due, no doubt, to the production of very weak electrical currents iu the copper disk. CHAPTEB VH. ELEOTRO-HARMONIO TELEGBAPHY.» Mian City of pl-tcit^wt "'"^' ^^"^ ^ *■■« »«'«» • arehitechiral wonder of T. ,^ „ oentunes among the the g.at catTXr.l^^:^ JXh 'H^r"''^"^'""*"' ty a slender sUver chain 1^ i ? ohaodelier, suspended -the™ b:^j:i:?:;:;,:;r4°tt'fa^r tr^ station in the channel i^l^r of ^ 4. .1 ^ arcnes. J^ronl his timea Our choir Kn« oUi. i. ^ ' ' periormea in equal reflections upon the remaricabltf^ tl^S ,' Ti ^" ™'''^«™* attn^ted Ws'attention Tef C Sttt 'he d " ""'""'^"^ of the most comprehensive an^ far^chW , T'^ "^ <"'"' -the law of isochronous vibration tt„„^ ""physical laws derived f.m the Greek, LTCn"?. ^e^ Jt^e^ "^^ ^^ ^!!!!!:i:!!^^i^^^^;^t^f^>^^ X^ tiioal Society, vol. i., No. S. ''J' ^- ■^- Pope. Journal of the A.nericfln Elco- f 236 THE SPEAKING TELEPHONE. have justly rendered the name of Galileo forever immortal in the annals of science and of history. In order that we may arrive at a clear understanding of the principles underlying the different varieties of the telephonic, or, in more general terms, the electro- harmonic system of teleg- raphy, and that we may be able to trace intelligently its origin and development, it is essential that we should first become somewhat acquainted with the laws and leading phenomena of vibratory or undulatory motion in general. Haying done this, we shall find no difficulty in passing to the consideration of the special practical applications of these laws, which have recently been made in the domains of electro-telegraphy and electro- acoustics, and which have been attended with such remarkablv brilliant and successful results. Let us consider for a moment some of the peculiar properties of a body freely suspended from a fixed point — in other words, a pendulum, 1 suppose there are not many here present who do not treasure among the happiest memories of childhood the associations connected with the swing. It was simply a seat suspended by two ropes, perhaps from' the horizontal branch of some overshadowing tree. I shall probably be safe in assuming that you all have a tolerably vivid recollection of most of the phenomena presented by this mechanical contrivance when in active operation ; a very fortunate circumstance, inasmuch as it will enable me to place clearly before your minds some of the most important of the fundamental laws of vibration. When our friend the school-boy, having seated one of his youthful favorites in the swing, and by a series of judiciously timed impulses gradually increased the amplitude of her oscilla- tions from zero to perhaps 120° of arc, proceeds, in compliance with her breathless request, to discontinue his exertions, and, in the classic language of the play-ground, to ** let vje old cat die," it is hardly surprising that, not being another Galileo, our young -friend has utterly failed to grasp the great physical truth that the vibrations of the little maiden are isochronous. Still less does he probably suspect that, even were he to subject the very PROPERTIES OF THE PENDULUM. 237 propertj which is verj well illustrated htZ i / "". ' ^ to which I have just referrer iT t ;^^ A T^?^^ '"^'"^' body even if if i! ^eten-ed. It is this : A freely suspended ^ ^«i .aws or rxDratOij motion, for the reason THlLaEBAKINQ TELEPHONE. t^t its phenomena are familiar to you all, not merely because „gh the medium of the eye iH um-:^ «. that it would .ark u^ a ZZ^^^ S^t .ufflcrent wdth, moving „„ifon„ly beneath it at ri?ht aSto 4e plane of ,t, oscillation, a wavy line would be pSee^ Th» wavy Ime once drawn would remain na a pennanirr^ of the kmd of motion performed by the oendnlZT^ • part of its oscillation. Kg 119 reore..If JTr v "^ ^^'^ ^^^^^^^&^^epiesents a line such as would be J^. 119. produced by the process we have just describeA It i, „„t diffl wira"un^r:i:^:r2rn :rr *° ''--'t endof threetweir:;^'ri-;t::;roXtct 246 THE SPEAKING TELEPHONE. descend gmdually, till at the end of six twelfths of a second it had reached its mean position b, and then it continued descending on the o])posite side till the end of nine twelfths of a second, and so on. We can also easily determine where the vibratory point was to be found at the end of any fraction of this twelfth of a second. A diagram of this kind, therefore, shows at a glance at what point of its path a vibrating particle is to be found at any given instant, and thus gives a complete image of its motion. ^ Although we are not yet able to make all vibrating bodias automatically record their movements on paper in this manner, yet we may ourselves construct curves whic-li truthfully represent their vibration when the law of their motion is known; that is, when we know how far the vibrating point will be from its mean position at any given moment of time. We set off on a horizontal line, such as a &, fig. 119, lengths corresponding to the interval of time, and let fajl perpendiculars, or, in mathematical language, ordinatea to it, on either side, making their lengths equal or proportional to the distance of the vibrating point from its mean position, and then by joining the extremities of these perpendiculars, we obtain a curve such as the vibrating body would actually have drawn, if it had been possible to make it do so. Physicists, therefore, having in their minds such curvilinear forms, representing the law of the motion of vibrating bodies, are accustomed to speak as a matter of convenience of the form of vibration of such bodies, ^ a term which I shall hereafter employ when referring to the subject. We are now ready to return to the consideration of the phenomena of compound vibrations. To illustrate in a general way the characteristics of this kind of motion, we conveniently refer again to the waves formed upon a calm surface of water. We have seen that if this surface is agitated by a pebble dropped upon it, that the agitation is propagated by concentric waves extending in every direction from the centre to a greater and '" ' ' ' ' " 'I ■' ■■ 1 Helmholtz— 2>j« Zehn von den Tonernpfindumjen (English Translation, by A. J. Ellis), p. 31. » Ibid., p. 3a PROPAGATION or COMPOUND VIBRATIONS. 247 greater distance. Now, if we drop two pebbles at two points some little distance from each other, we shall produce two separate centres of agitation. Each will set in motion.a separate set of concentric waves, and these two, gradually expanding, will finally meet and overlap each other. When this happens, It IS 3asy to see that not only the water, but any floating body upon its surface as well, will be set in motion by both kinds of agitation at the same time, but this fact will in no wise interfere with the separate propagation of both sets of wavea Each of these will continue to advance further and further over the sur- face precisely as if the other had no existence. As they pro- ceed, those parts of both rings which have just coincided appear again, distinct and unchanged in form These little systems of waves may be accompanied by other and larger systems, caused by the action of the wind, but they will continue to spread out over the surface thus agitated, with the same systematic regu- larity that they did upon a perfectly calm surface. The action of the vibrations or undulations of the atmosphere, which produce the sensation of sound, is strictly analogous to that of the waves of water. There is practically no limit to the number of distinct sets of vibrations which may be going on at the same time, without mingling with each other; but, hi cases where there are many of these, the resulting motion of each separate particle of air is necessarily complex, almost beyond the power of the mind to conceive. The principle, hcvvcver, may be understood perfectly well by studying the composition of two or three sets of simple vibrations, and this may be readily done by the aid of the method of graphic projection, which has been before explained. Thus in fig. 120, we may suppose the horizontal length of the diagram to represent a unit of time. The curve A will then represent the undulation in the atmosphere caused by the vi- brations of a tuning-fork in action. The horizontal distances measured on the straight line will represent the passing time, and the vertical heights the corresponding displacements of the particles of air. Now, suppose a second fork is set in action. 248 THE SPEAKING TELEPHONK which is tuned an octave higher than the first, and, conse- quently, makes twice as m^nj vibrations in the sametimi. The undulations produced by the second fork will be represented by the curve B. In such case, the curves above the horizontal line represent the compression of the air, and those below the line its rarefaction. Now, according to the laws of mechanics, if two different forces act in the same direction, the total force is repre- sented by their sum, while if they act in opposite directions it is represented by their difference. If, therefore, we combine these two simple curves, according to this principle, we shall have a composite curve C, which represents the effect produced by the superposition of one set of waves upon another. The line c^ . is the sum of the lines a^ and b^, while Cg is exactly equal to ttj. On the other hand, the line Cg represents the difference between the lines a^ and b^, one being above the horizontal line and the other below it. Every point in the curve may be found in the same manner, and, by tlie same method of con- struction, the resultant curve, corresponding to any xiumber of simple curves combined together, may also be found, as you will readily understand. The simple vibrational form is always the same. It is only FOURIER'S LAW OP VIBRATIONAL FORMa 249 ite wave height or amplitude, and its wave length or periodic time which IS susceptible of change. But the number of vibra- tional forms which may arise from the composition of simple forms are mathematically infinite. The converse of this prop, option IS also true, which is, that any fonn of vibration, no matter how complex, may be expressed as the sum of simple vibrations. This was first mathematically demonstrated by Fourier, but its experimental proof is due to the labors of the ^eat German physicist, Helmholte, who, after a most elaborate series of investigations, succeeded in separating from each other the several simple sounds whichform the constituents of a com- irZZiL ^*^^^,°*^«,«««^ryhere to enterinto a description of the methods employed by Helmh. tz in accompHshing this beautiful result 1 although we shall have occasion to refer here- alter to some of the analogous means which have been emploved m telegraphy for the same purpose, that is to say, the analysis of composite vibratory motions. "^ The idea of synchronizing the movements of the two instru- ments at widely separated points for telegraphic purposes by making us3 of the principles of isochronous vibration, was employed in telegraphy at a very early period. Thus Eonalds=» in 1861, and Vail3 in 1837, employed isochronous pendulums to control their machinery, while at a later date the printing telegraph of Hughes,* and the automatic telegraph of Casselli and others, have embodied most ingenious and beautiful appli- cations of the same principle, with which I presume you are all more or less familiar, and therefore I need not dwell upon them. In 1861, Mr. Philip Eeiss, of Germany, made the first apparatus of which we have any account, for reproducing musical sounds atadist ance, by means of electro-magnetism . Ilis devices were Bee\S:Sll;trin."'''° "^'•"'^^"' '"^''"^^'^''^ e.np7o,cdi„ these experiments, » See Shuffner-" Telegraph Munuul," p. Ul p. ; J'''^-"^^««*-'"'^«?-tio Telegraph," p. 159 ; Shaffner-" Telegraph Manual - * Prescott-" History, Theory and Practice of Electric Telegraph " i, ixi, Al„„ Ba,ne author's " Electricity and El.ctrio Telegraph," p. 600. ' ^ 250 THE SPEAKING TELEPHONE. very ingenious and beautiful, and it is evident, from descriptions and papers published at that time,i one of which has recently been reproduced in the Journal of the Telegraph, that Reiss had made a thorough study, both of the laws of electro-magnetism and of acoustics, and understood perfectly the conditions of the problem with which he undertook to deaL Sound is simply a sensation resulting from the action of vibrations upon the nerves of the ear. If the same vibrations are felt by the touch, they produce a certain peculiar fluttering sensation ; but this is not sound. Therefore, although all sounds are necessarily the result of vibrations, all vibrations do not necessarily produce sound. The vibratory motions proceeding from sounding bodies are usually conducted to the ear through the medium of the atmosphere. Therefore, to produce any given sound, of whatever character, at a distance, it is evidently only necessary to throw the ^.tmosphere at this point into vibration precisely similar in every respect to those which would be pro- duced by the action of the original source of sound, whatever it may be. It is found that all the characteristics of sound which are appreciable by our senses depend upon three things : First, the rapidity of the vibrations, which determines what we call the pitch of the sound, whether, for example, it is high or low; second, the amplitude of the vibrations, which determines the loudness or power of the sound ; and, third, the form of vibra- tion, as represented by the curve corresponding to the movement of the vibrating body, which determines the quality of the sound. The apparatus of Reiss consisted of a thin, stretched mem- brane, rigidly supported at the edges, and free to vibrate in the middle. The mathematical theory of the vibration of such a. membrane, having a uniform tension in all directions, shows 1 Roiss -Dingler's Iblyteohnic Journal, Vol. CLXVIII.,p, 185 ; Leg&t^Zeitachri/t dt» Deutschosterreichigchen Telegraphen Vereins, Vol. IX., p. 125. An oxc!olloiit trans- lation of this last paper may be found in the Journal of the Telegraph, Vol. X., p. £63. BEISS'S APPARATUS. 251 that vibrations produced in any part of the membrane will pro- duce nearly as strong vibrations (disregarding individual nodal Imes) m all other parts of it A thin, hght membrane is not only susceptible of sympathetic vibration when vibrating air is aUowed to act upon it, but this vibration is not limited to any particular pitch, and it is therefore capable of responding to sonorous vibrations of every character, traversing the atmos- phera A delicate circuit-breaker, attached to the membrane was arranged to break the circuit of a telegraph line at the vibmtion, and thus the armature of an electro-magnet at the receivmg station was easily adjusted to respond to those vibra- tions, and, when mounted upon a proper sounding-board, gave them out to the atmosphere, which conveyed them to the ear of the listener. Now, if the form of vibration in this sounding-board could have been made to coincide in all respects with that of the membrane at the station from which the vibrations had been transmitted, Reiss would have had a perfect sound telegraph or telephone. But this was far from being the case. The piteh and rhythm of the sounds were perfectly preserved ; their loud- ness or intensity, also, to a very small extent ; but the quality was entirely lost It is not difficult to understand the reason of this. Every vibration of the membrane caused a pulsation of electocity to traverse the w-re and act upon the electro-magnet but as each and every vibration of the armature was produced by a current of precisely the same strength, the only difference m the amplitude of these vibrations would be that due to the more complete magnetization or demagnetization of the electro- magnet, when the time allowed for the process was increased by the greater play of the circuit-closer, under the influence of stronger vibrations at the transmitting station. The form of the vibrations was of course altogether lost Any simple musical tone, consisting of a regular succession of uniform vibrations or any series of such tones, could, however, be reproduced with the greatest accuracy. The next important step in flio r\r~rr^^- r • I ---^-iL su.|. uv tne progress of mveuiiou was 252 THE SPEAKING TELEPHONE. <., obviously the discovery of some means whereby the proper amplitude of each vibration, or succession of vibrations, either simple or compound, could be directly reproduced by means of the electric current ; and when this was once done, the genei-al problem of harmonic telegraphy may be said to have been solved. This having been accomplished, ii was not difficult to foresee^ that two important practical applications might be expected to follow, namely, multiple transmission, and vocal transmission. I believe that this discovery of the true method of transmitting- composite vibrations was first publicly announced in the Journal of this society,! in a paper contributed by Mr. Elisha Gray, it having been made by him in December, 1874. It consists in causing the effective strength of the electric current, by which the transmission is effected, to rise and fall with the varying amplitude of the vibrations or waves which are to be reproduced. Nothing could be mor^ simple and beautiful in a theoretical point of view, but the practical exemplification of the method, as is usual in such cases, presented considerable difficulty. At the time of making this important improvement, Mr. Gray had already been engaged for more than a year in endeavor! r^r to devise a practical means of transmitting and simultaneoi-^iy reproducing a number of tones, so as to utilize them for the pui-pose of multiple telegraphy. Let us briefly glance at what he had already accomplished. It was observed in 1837, by Dr. Page,« that a musical sound was produced by a magnet, between the poles of which a flat spiral was placed. The sound was heard whenever contact was made or broken between the coil and the battery. These obser- vations were confirmed and extended by De la Eive, Wert- heim* and many others. The apparatus employed by these 1 Gray, Journal of American Electrical Society, vol. i., p. 18, This apparatv.s and its mode of operation will be found described in detail in Gray's patents, No. 1,874, of May 4, 1876 (Groat Britain), and 186,340, of January 16, 1877 (United States). ' Pago— Amerioan Journal of Seience (tiist series), vol. xxxii., p. 869; ibid., vol. xxxiii., p. 354. » De la Rive—" Traiti oP Electricite, thtorique et applique^' (English Translation, by v. C. Wallier, vol. i., p. 800); also, "Knight's Mechanical Dictionary," Arti- culating "Telephone." *Ibid.,vol. i.,p. 807. SOUNDS PRODUCED BY MOLECULAR CHANGES. 268 experimenters may be described in general terms as an electro- magnet with a self -interrupting break-piece attached to its anna, ture and another magnet in the same circuit for producing the sounds. The sounds proceed from the core of the magnet itself and are caused by the molecular change which takes place in ^e iron at the moment of magnetization or demagnetization. When the current is interrupted a sufficient number of times per second, the successive sounds produce upon the ear the effect of a musical nota The method by whick Gray at first sought to accomplish the desired result of multiple transmission was by arranging two or more self-inten-upting magnets, adjusted to different rates of vibration, so as to close the circuit of the same line at the sending station, while at the receiving station all the currents passed through a series of electro-magnets, equal in number to the transmitters, and having armatures severally adjusted to their respective rates of vibration. As Mr Gray has already described this apparatus at length in a preceding number of the Journal,! I need not enter into further particulars con- cerning Its construction and arrangement, but will in a few ^ords point out the reason why it failed to answer its intended purpose, except to a very limited extent Suppose we have two self-interrupting transmitters, one of which, a, makes six vibra- tions m the same time that the other one, b, makes five. If we now set them m operation, first one and then the other, and record the pulsations on chemical paper at the receiving station we should obtain the results shown in fig. 121 at a and b. But if both are set in operation simultaneously, we get the result shown in the third line of the figure, at c. Now, it is obviously quite possible, by insuring a proper relation between the times of vibration of two or even more transmitters, to avoid any material mterference between the different sets of pulsations, but a limit IS very quickly reached, because, as you will readily perceive, 1 Qnj— Journal Amwican Electrical Sociav, vol i on K « Vr.^ a^.^u a fiirthor description nee spedflcations of Gray'^'^.ate t ,' Wz* ^L ofJufv2 18^4 and on, of Mard. 16, 1875 (Groat Britain) ; also No. 166:095 of :i.t,;fr'it.' nlj^ b«teB; ; also, - Kaijfht's Meohanioal Dictionary," Articulating " Telephone.''" 254 THE SPEAKING TELEPHONE. any considerable number of transmitters, acting in this manner to open and close the same circuit, would .produce a continuous current, and no analysis of the separate sets of vibrations at the receiving station would be possible. I will now proceed to describe in general terms the nature of the improvement by means of which Mr. Gray was enabled to transmit an indefinite number of different series ©f vibrations, without destroying their individuality. The details of his sys- tem, and the particular application of it to multiple telegraphy, having been already made known in a preceding number of the JoumaV I shall not attempt to enter into them at any lengtL The strength of current in any circuit may be varied in two ways : by employing a constant electromotive force, and varying Mg. 121. the resistance of the circuit, or else by varying the electromotive force, and allowing the resistance to remain constant Gray employed the latter process in his method of multiple telegraphy. Each series of vibrations at the transmitting station, when added to the existing ones by the depression of its proper key, carried with it its own section of battery, and, therefore, its electromotive force was superposed upon that abeady in the circuit The effect of this was to produce a resultant current of varying strength, which would be properly represented by a curve ident- ical with that representing the resultant of the several sets of simple vibrations at the sending station. The analysis of the composite vibrations at the receiving station was effected by a I 1 Gtblj— Journal American Electrical SocieCy, vol. 1, pp. 13 et teg. ; also see patents of Great Britain and Uuitt. i h^tates, referred to in note 2. HELMHOLTZ'S ANALYSIS OF VOCAL SOUNDS. 265 series of electro-magnets, the several armatures of which wer© bars or plates adjusted to a certain rate of vibration, the normal rate of each armature bar differing from that of the other. Each armature bar will respond to its corresponding set of vibrations only, and it makes no difference whatever whether these vibra- tions are transmitted alone, or whether they form a constituent part of a composite series of vibrations. Each set of vibrations IS broken up into dots and dashes by the action of a key, just as if It was an ordinary continuous current But as a matter of fact, the main circuit is never broken, although the strength of the current is constantly varied. The manner in which these armatures are thrown into vibration by the properly timed impulses of the electric current acting upon the electro-magnet IS, as you will readily perceive, strictly analogous to that of the swing, which can only be set in action by properly timed impulses ; or that of the tuning fork, set in vibration by the tiny blows of the little atmospheric waves, in the manner which has already been explained. The reproduction of. articulate vocal sounds at a distance, depends upon precisely the same fundamental principle as multiple harmonic transmission, namely, the transmission of composite vibrations. This will become evident from a consid- eration of the character of articulate sounds, such as those of the human voica The analysis of vocal sounds was first accomplished by Helmholtz. i It would occupy too much space to detail the experiments by which he succeeded in establish- ing the fact that the different vowel sounds are produced by the presence of a fundamental note, mingled with higher har- monics in various proportions, a harmonic tone being a weak or partial tone, caused by a rate of vibration twice, three times, four times, and so on, greater than that of the fundamental! The several vowels, therefore, belong to the class of sustained tones which can be used in music, while the character of conso- nants mainly depends upon brief and transient noises. The 1 Helmholtz-2«fl Lth.rt ton dem. TonrnpAnd^nntn (EHis' Tran;^ktion), Chap. HI. 256 THE SPEAKING TELEPHONE. problem in this case was to reproduce at the receiving station precisely the same vibrations in the atmosphere as those pro- duced by the voice of the speaker at the transmitting station. "We have seen why Reiss was unable to accomplish this. Let ns see wherein later inventors and discoverers have been more fortunate. Some time prior to February, 1876, Gray conceived the idea of attaching to a stretched membrane, such as that used by Eeiss, a resistance apparatus, which should be placed in a con- stant circuit, and caused to vary with the vibrations of the mem- brane in response to the sonorous waves traversing the atmo- sphere and impinging upon it Of course, if this could be done, it would be easy to attach an electro-magnet with an armature formed of a circular plate, which would respond to vibrations of every character, and thus reconvert the waves of electricity into aerial sound wavesj A caveat, describing this invention, was filed by Gray in February, 1876, and himself and others have since been engaged in perfecting and elaborating it, with a very satisfactory degree of practical succesa ^^ "We will now turn to the labors of another inventor in the same field, Mr. Alexander Graham Bell. Like Gray, he had been for some time at work upon the problem of multiple tele- graphic transmission by means of harmonic vibrations, and when we consider that each of them appears to have been, at least as late as October, 1874, in entire ignorance of the labors of the other, the singular coincidence in the results which they finally attained was not a little remarkable. Gray had approached the 1 Since the above was written, Mr. Thomns A. Edison, of Menlo Park, New Jersey, is said to have obtained very satisfactory results with a telephono con- structed upon the general plan set forth in Gray's caveat, i. «., a variable resistance controlled by the vibrations of a diaphragm. Edison made the discovery that plumbago possessed the curious property of altering its electrical resistance in pro- portion to the pressure to which it is subjected, and availed himself of this dis- covery in the construction of his telephone. More recently the same experimenter is said to have obtained still better results by the use of carbon in the form of lamp- black, from the smoke of an ordinary hydrocarbon xamp, compressed into- a cylin- drical button. No details of this apparatus have yet been made public. bell's experiments. 257 subject from the stand-point of an electrician. Bell, on the other dW;ir.''^f''T^ *'"'' \"'^ '" "PProached it from the opposite d«-ection,< If I may use the expression. As early as 1867, he became interested in the researches of Helmholtz, because of the,r bearmg upon the subject of his professional study, vocal physiology, or, m other words, the mechanism of human speech. Kis earliest expenments appear to have been made in Boston in iv tJ 1 ,,T^ ^-bstantially repetitions of tho.,e already made by Helmholtz. In November, 1878, he completed an experi taental instrument with two self-interrupting tLsmitting reeds, md two correspondrag receiving i-eeds, the transmittei? beint Fo™ '""f ■?!« -0. exactly as in Gray's fi,.t method For reasons which ha,e ali-eady been given in speaking of Gray's apparatus it is possible to transmit two separafe series of vib^ tions without material interference in this manner, yet a limit U mZr% r"™"^ "■'' experiments in multiple trans- tITr t""^ f" ^""" ^^^* ""^ 1875, but it does not appear that anything of practical importance in that direction resulted te tl S""'l ^' ''r\ "" ^""" *" ''-^ '--'i Ws atten &„ to he development of the speakmg telephone, and in the spring of 18 , 6 be arrived at some important Results. In a communica- K„^l ' P"","'"'* " *« proceedings of the society,. Mr. Bell gives a somewhat detailed account of his researches in telegraphy up to tliat date. I quote from this paper the foIW mg description of an experiment in vocal tmnsmission, probabry W„ ™ rVI-*"^ ''fSree successful, which appears to have inte J ^ " ""''' " ""^ ^P™= "■ '''"' -'1 « <" g-='t ten'I™?'"^'^'^°'' '''^f °-""«°ets, each having a resistance of ten ohms, were arranged upon a circuit with a battery of five !!:^!^^lf;:^^nt^_The_toton^e^^ the circuit, Exclusive B«ll-iWi<»j. c/A^„n A,,dm.y ^ AH. a^'Ll^, v.l. XH., p. 1. 258 THE SPEAKING TELEPHONE. of the battery, was about twenty-five ohms. Drum-heads of gold- beaters' skin, seven centimetres in diameter, were placed in front of each electro-mag.; :, •.. . ,. ircular piece of clock-spring, one centimetre in dif!^oeter, \t.!S glued to the middle of each mem- brane. The telephones, so constructed, were placed in different rooms. One was retained in the experimental room and the other taken to the basement of an adjoining house. Upon sing- ing into the telephone, the tones of the voice were reproduced by the instrument in the distant T-om. \vucn two persons sang sunultaneously into the instrument, two notes were emitted sim- ultaneously by the telephone in the other house. A friend was sent into the adjoining building to note the effect produced by articulate speech. I placed the membrane of the telephone near my mouth, and uttered the sentence : ' Do you understand what I say?' Presently an answer was returned through the instru- ment in my hand. Articulate words proceeded from the clock- spring attached to the membrane, and I heard the sentence: 'Yes ; I understand you perfectly.' The articulation was some- what muffled and indistinct, although in this case it wa<5 Intel- ligible. Familiar quotations were generally understood after a few repetitions. The effects were not sufficiently distinct to admit of sustained conversation through the wire. Indeed, as a general rule, the articulation was unintelligible, excepting when familiar sentences were employed. Occasionally, however, a sentence would come out with such startling distinctness as to render it difficult to believe the speaker was not close at hand." i There is reason to suppose that Bell had formed some idea of the possibility of this result as early as 1874, although its practical exemplification does not appear to have taken place until shortly before the date of the paper from which the above extract is taken. It will be observed that his method differs from that of Gray, inasmuch as the lattar varies the resistance in the circuit without changing the electromotive force, while Bell varied the electromotive force, the resistance remaining constant The bat- 1 Ibid., Vol. XII., p. r. See, also, Telegraph Jour/uil, vol. V,, p. 277. APPLICATION OF PERMANENT MAGNETS. 269 go.„g .„„> verj, extensive use. to artiouIationZrc^s Lt k not very Joud, altho„gh sufflciontly so in a 1^00;! 'l. anstrument to admit of lengthy sustined convnltn!^ tltt the Bl,,,.tost misunderstanding or repetition. Of conr.;.' ,T I n'" to be e.peeted that the loudness of bis f«, ,„ of t^U^Z„. T mereased very greatly beyond its present vo umt f^r I ^ " at best only get from it the meohan cal equivalent of ,h\ voice, dedneting the loss inseparabl flZt onv^^iot^r; r^lte are ,o be'lool 'T" '"?" "°"°"- '^'■'^ "o^' »«k^ng Mr Grn fl th .'" *" '"'■''="°" fi'-'*' pointed out by Mr tria , for the reason that, if an effectual method of con pwm ITT "' ''/ r™* "^ "^"^ of -^ v"-4 d : pnragm can be discovered, the source of power whi^h i^ ti case as the battery, may be augmented to an™ ed extlnf It as not to be denied that the problem thus present dt onr„f exceeding mechanical difficulty : but there uT^T V pose thatitmaynot be suece Ju ly ^ed It is toSrd T^' thatof themagneto-instrument, that inventors will find it mo^ advantageous to.tnrn their attention, for I hazard t.lll that the latter has alre-xdv rei,.|,„^ i ""^""l/'™ ^ saying „ffi ■ , aneaay reached such a surpris nff d.3"rpB of efficiency as to leave ccmparatively little more to be done wUhL ti|^neees,= ly limitations which have been pointed 'J^ . Dolbear-.. The Tel.phone,.. p. „.. jg,, .,„ j,,,,,^^ ^,^^ ^^^^ CHAPTER YITL dolbear's telephonic researches. 1 During the year 1854, while at work in Allen & Thurber's pistol factory, in Worcester, Massachusetts, I began to make ex- periments in electricity and magnetism, I introduced at that time the use of a permanent magnet to pick up the small parts of the locks of pistols from the cases. This had previously been done by the employes with their fingers, which were often made sore by the nails being worn oflE too short The magnet was adopted by those having that kind of work I also tried to make a perpetual motion machine, which should derive its power from permanent magneta I also constructed a trough battery of six cells, with which I tried many experi- ments. 1855. —During this year I made a magneto-electric machine, of the common pattern. Was frequently with Henry M. Paine, who was then trying to construct a successful electromotor. 1859. — Made another magneto-electric machine. Also in- vented a steam whistle, which was designed to play any tune. This was while employed in Mason's locomotive works, at Taun- ton, Massachusetts. 1861. — ^Invented and constructed a gyroscope to run by electro- magnetism, consisting of a small electro-magnet revolving be- tween the poles of a permanent magnet, shaped like the letter C. 1864. — Made for the Ohio Wesleyan College, at Delaware, O., a large compound permanent magnet ; also an electro-magnet for lecture purposes. I invented a magneto-electric telegraph, in which the current of electricity was generated by the action of a permanent magnet when thrust into or withdrawn from a hollow bobbin. This was designed to move a needle. Also proposed to 1 Abstract from "Researches in Telephony," by Professor A. E. Dolbear, of Tufts College. DOLBEAK'S TELEPHONIC HESEARCHES. 261 receiving magnet vvas to be fnr^.^\ t^e/^rst instrument The - the ^ovoLnjo, tttiz Sr' %'':rr '^ -^^- ments of the seconr] wm„i^ ^ • '^^ ^'^^^ *'ie move- tbe fi.t, but rdrtrfttXo'ar'^"^'*' '^°- -^ ^cond would be so feeble aa it actu, Tlv k ^^ "o™"-™' of the number of persons in thi. i„ "f' "7.'' '^ I '"ed to interest a had no me^rand was 11°"' ^"' *'' "°' '"^^^^ As I con,pe.led to aCndrth^'^^^^.r^i:^, ^^^h t'^«^' ' ''- whrdemtr^rsr/re^^r^^^^^^ was a student in Michigan Unive lltv Tl7 ' T '""'" ^ structed by Eitehie, was exhibited, T/l^'f^ This machine, eon- 1868.-Conducted a serit f e™ '""'"' ^•■^'"Wtion. qnantityof matter trans7err«i bv tr'T!"'' *° '*'^"=™'"'= *« carried out was as folTow. o ^^ ?'° "P"* T'"' Pla" electrical machire w rreeetd -7"^ ".^'' ^P»*sfrom'an chloric acid from a ba o ~ The .1""?"' '"'"' ''^*°- bj the addition of ammonia 3 ;>, ^""i "'■" ""•■"''' ""<> solution which was ^uc^/,r;r°'"r'''* '''*'' ^tondard jndged to be al^ I^W ' "°'"'^ °* "'« '™ ''^.^ copper for that nlbl tf ^^J '''^r:'^'^ ^ '™^'^-'' with iron, silver lead .„,! 7 T' , ^™ P'"" was tried different k.^^^ wth 1^ " °*" ^"'^""<="' "^<"' "* -«-■ Ts n^f '^Z -r com,^' S Selr^ner-'^" _^^;^^;;^^^°-^to^a small mir,.r upon the long arm of 262 THE SPEAKIISG TELEPHONK a lever while the bar acted upon the short arm. A beam of light was projected upon the mirror, and reflected to a distance of fifty feet. The angle of its displacement then admitted of convenient measurement Repeated experiments proved that the result of the magnetization of an iron rod was an average elongation of j^^ part of its length. I tried to cause a fine ratchet-wheel to revolve by a recipro- cating motion derived from this slight molecular movement, making and breaking the circuit with an interrupter. 1872. — Made some very large forks, capable of vibrating strings twenty feet in length, for class demonstration. 1873. — Made some large tuning forks for projecting sound- curves upon a screen ; also discovered a method of very much amplifying these vibrations, i A pair of these forks was ex- hibited at the Philadelphia Exposition. At the same time in- vented an attachment to the whirling-table, for accomplishing the same thing. 3 Discovered convertibility of sound-vibrations into electricity. Using a tuning fork in connection with a thermo-pile and gal- ' vanometer, I noticed that when the fork vibrated the needle was deflected. Further observed the effect of a vibrating tuning fork, which was also a magnet, upon the current from a thermo-pile. At the Portland meeting of the American Association, in 1873, read a short paper in regard to the first of these experi- ments, which I thought was new ; but said notliing about the second, as I considered it was only a particular case of magneto- currents, which were well known. Nevertheless, it was pre- cisely the same thing as the undulatory current which Professor Bell claims to have invented or discovered. While engaged in making a manometrio flame capsule, I in- vented the opeidoseope. ^ I also proved that the sheet of air issuing from a sounding 1 8oe Journal of IVanhUn Institute, 1 873. * Seo proceeding's of Americun Association, 1873. « Seo Journal of Franklin Institute, 1878. Appoudix I. DOLBEAB'S MAGNETO-ELEOTBIO TELEPHONE. 268 organ-pipe vibrates like a reed. This waa done by fllW an organ W 0^3 with smoke, and examining it throngh a ZC soopic disk while escaping from the pipe. 1876.-.Commenced my investigation and experiments in telephony, using at first a Helmholt. interrupter^T„d etet:^ ^t. r^^ "'"^ ^Perimente in transmitting speTl tned that of a conical point of iron fastened to t'Le'^Tddle of an opeidoseope membmne, the point being attached toa movement. 1 his point dipped into a mercury cup and the id«, TIT A r , "^"-^ " ™'^'J ?■■'««■>' " "otably lamer sur with rr *" '''"*"'"= ""■°"8'' *'''<=l> I <=™W get a signal :" Jikrr J :— ^" ^-« - -°^«" ^ s! nhonZithre^n-"' '""^'""^ a patent upon the speakin. tele- ^none with pe.munont magnets, and began constructing suitable 264 THE SPEAKING TELEPHONE. instruments to serve as a patent model, but before th-^ !e instru- ments were completed, I was informed that Professor A. Graham Bell had declared that he had secured a patent upon the same thing two or three years before. On the 12th of February, 1877, Professor Bell gave a lecture and exhibition, at Salem, Mass. Within a day or two I called upon him to see his fixtures. He was not in, but his assistant, Mr. Watson, showed them to me. They were substantially like mine. I invited Messrs. Watson and Bell to come to College Hill and see my apparatus. J-ig. 122. Mg. 123. Mr. Watson said Professor Bell wished to know what the resiotance of the human body was, and asked if I could measure it. I promised to do scj, and in a few days sent him the meas- urement of the resistance of the bodies of about twelve students, for which I received a letter of thanks. About the first of March, 1877. I chanced to see the official gazette of the Patent Office, containing Professor Bell's patent of January 30th, 1877, and found that I had been deceived ii*. regard to his having patented the application of permanent mag' nets to the telephone previous to my invention, and accordingly went to consult a lawyer about it. I was considerably difi- couraged on account of his statement of the probable cost of an attempt to secure my rights. I tried to interest several per- sons in my case, but without sucqess. DOLBEAR ASSERTS HIS RIGHTS. 265 challenged hi. statement, informing him wW T '^ / """'^ telephony, smce he desired to do iustice to nil T .1 ''' i'Vfl^. 124. him the particulars of my work. He acknowledged that I had mvenW the telephone independently of himself^ "" ..tl: ' ™' "'"'^^'^ '° "'"''O farther investigation into the ZTZt^m''°'f '^'^^"P'™ *-"^-^- »'" ftereTukl th ^'"* '"°™'''' ""'^ inventions to report a^ tne result of these investigations: arntlit°udf of *°'i "l' "'^''"'"S *^PWm, by which greater eZte Tel "''™"°"/ .*^-^% 1.0 I.I 2.5 I2i^ mil 2.2 1.8 L25 |||||_U_ .6 ^A V] //j. ^ '^^^ r Hiotographic Sciences Corporation 23 WEST ma:n street WEBSTER, N.Y. 14580 (716) 872-4303 q^ m \ ^\ V rv 'js. ^. ^O ^^■* ^ ""« « by the Providence experTmenC^™^,!'"f \"^ ^^^ '"tented strument thus referred toTan.. ! "^^^ "'**«*' ^e in- handle telephone of DrChaui^l''?':^'' f Presentation of the so wide a ^.eer, anrdifft Sjl • i '""f """'^ "^^ '-' mental instnune;t of P of Bd liff '^ ^™" *he experi- Prof Bell, intheaboveSmct w 1 T" ^'^^ '■"» ^e. of the handle ...cpho:; wSht "ZlrZ, t "'t"*" has a recogni^ place in the history SspTtin! t^,' T" t""" he also implies that he gave t» tL , J'^ *^ telephony, but thus ignoriuff one of tll^ , telephone portable form dencef^periLntel ' """ "-«''««»- of the Pro™! It happened with the telephone a, witl, ♦!, nr In the beginning it was supposed that the n ? t^'^^^ mentswas pmportioned to thel ste "^',,P°''«'- "^ *« instru- shown in both that more del Late l,t ''^"""'"'' '"'™ effective. ^"""'^ instruments are the most 278 THE SPEAKING TELEPHONE. It will be observed tbat Professor Bell is criticised here, not for claiming tbat he had made a straight magnet telephone, but for claiming this in combination with the handle, and figuring this combination, which constitutes the well known handle in- strument, as his own. His real claim is to the independent experiment of putting a U magnet in a handle, subsequent to the construction of the genuine handle instrument in Providence. Another practical result obtained in Providence as early as June, was the glass plate telephone of Henry W. Yaughan, State assayer. A disk of soft iron, about the size and shape of a nickel cent, was cemented with shellac to the centre of a very thin glass plate, 2^ inches in diameter. This, with Peirce's mouth-piece and the usual magnets, gave the loudest and clear- est articulation attained at that or at a later time, and may be the germ of important improvements. Mr. Yaughan also made, before the telephone had been seen in France, what has since been described as the multiple telephone of M. Trouvd In this telephone, plates form the sides and ends of a cubical or poly- hedral chamber, a magnet and coil being behind each plate. Among other scientific observations with the telephone. Prof. Peirce heard the auroral sounds early in the summer of 1877, and Dr. Channing noticed the characteristic telephonic sound of lightning, even when distant, preceding the visible flash. Prof. E. W. Blake made the capital experiment, imperfectly reported in Prof. Bell's lecture, of substituting a soft iron bar for the magnet of the telephone. Whenever this bar was turned in the direction of the dipping needle, the telephone would talk by the earth's magnetism ; but when swung up into a position at right angles with the dipping needle, the telephone became perfectly silent Prol Blake also talked with a friend by telephone for a short distance, using the parallel rails of the same railroad track as conductors, and hearing at the same time, by induction, the Morse operating from the telegraph wires overhead. This illus- trates the apparent indi£Eerence of the telephone, at times, to insulation. Prof. Blake also originated the responsive tuning forks, in which two forks of the same musical pitch are magnet- ce cs o < IS SIPHON BECOBDIiB TEMPHONE. £79 ^; a short iron core, surrounded with a spool of wire is ,ud ^^t^ Tol":' poles o.p of eao£ The^rbS^ eonnecM rt one tur^g toA ,3 struck the other «=spond3 at I .J^^^ '^'^^ °* ^^"^ ^"'^ "'^- Clarke and Charles E Austin should be mentioned among the oorj« of Providence expS^ •T.r.r^'"""" *° *''"' "''"P'^-- of W-Phonic p„>»Z With the object of stimulating inquiry into the m!^ of nnprovrng the telephone, which is the most\ea„tiful aSIprtion fl II. > hi ea s ^ ^^ < s •N y J S 1- «. 1 ■• 1- H >,.. ^;ia^^2 S ^— »lfl («*"i DC b. ^. 132. p^acticabihty , for no one having witnessed its performance can fell to see a great future before it readv mTnf :? °^ ^k ^^ '^5°™'™' '''°™ " % 1«2, afforfs a ready means of speakmg, and gives out such clear tones as to lt:^:^TTfl' -™>™'»"ly look behindteinTtr^ f:!!:!^:^^l!P!^Wwhojnaybe miles away). It suffices to 1 John Gott. Journal Society TeUgraph Engineers. Nos. XV. and XVI. isrr. 280 THE SPEAKING TELEPHONE. take a tube two inches in diameter, and stretch over one end a membrane of parchment or thin gutta percha (the latter is less affected by the breath, the former becoming somewhat flaccid after a time). To the centre of the membrane cement a straw and fix the tube in front of the instrument, about six inches from the movable coil h ; cement the other end of the straw to the coil at the point where the silk fibre k is usually fixed. This is all thai is necessary for both speaking and receiving. Six or eight cells of battery connected in circuit with the electro-mag- nets suffice. ' A pair of these tubes may also be connected 'in a similar manner with the tongues of two polarized relays. The tube is to be fixed in a convenient position, at right angles to the tongue, and the free end of the straw cemented to the tongue, taking care that the latter is free from its ordinary contact points. No battery is required for speaking with this arrange- ment ! Or a pair of these speaking tubes may be connected with the ordinary armatures of any instrument or relay, and a current kept on the line. The armature should, however, not be too heavy, and should be carefully adjusted. The best adjustment gives the loudest sound. In sending, be careful that the arma- ture in vibrating does not touch the cores of the electro-magnet. A plate- of thin iron, such as is used for stove pipes, fixed to an upright board, the latter hollowed out on the side on which the plate is fastened, and a hole made in the board in front for inserting a convenient tube for speaking, may be used as an armature, and a pair of coils placed in front of the iron plate through which a current from a battery is flowing, the cores to be adjusted as close as possible to the plate ; this answers for sending and receiving. The battery need not be strong; if it be so, the armatures have to be removed further away from the coils. On a short line the resistance of the coils, with a suitable battery, is of little importance. I have spoken as well with small coils of three ohms as with 400 ohms. If a pair of coils at the receiving end be placed on a violin, and connected to the line on which there is a permanent current BEMABKABLE TELEPHONIC PHENOMENA. 281 and a sending instrument aa described, singing and speaking into .t;rof tit^iSjagrer ^■^'^-'-^^p'''-^ ^-o. the^r^tr f "'''' "«'"*-»'i th«y a«= »eleeted as being within the reach of many-may be demonsa^ted the possibility of speakmg over miles of teleg„.ph line. The sound onhe ™fce in the tube .s not that of a whisper, but of a voice at a diZce and Jhe nearer you seem to bring the sound the bettT^^ adjustment, and vice versa. * I have spoken through four knots of buried cable without sensible diminution of effect wicnout When the instruments are not well adjusted, some words will come clear when others do not; and I have fo^nd the sentence tZJZr:^' ^"^^^^^^' '^''^^•^^^^' '^^^^'^^^'^ when The object to be sought for is to augment the strength of the variations of cun-ent At present it is limited by the power of the voice to move an armature or coil; and unless it can be magnified by putting in play a reserve of force, as compressed air, etc., improvement cannut go far. The most hopeful field seems to be the effecting a variation through a sensible range of resistance at the sending^TvaT; he strength of current in a.primary coil by shunting or' v^rZ he resistance of a batteiy circuit ; a^, for example a fine wirf inserted more or less in mercury a KEMAEKABLE TELEPHONIC PHENOMENA.! During five evenings in the latter part of Aueust an,! fl™, pa« of September, 1877, performer stationed i^^^ Wes'^ Un.on buUdmg in New York, sang or played into an Edt," musical telephone, actuated by a powerful battery, and Z B. ^■f^r^urzzT.%r^;:^'zzi,''^T^^' ~- 282 THE SPEAKING TELEPHONK nected with one or more cities by a No. 8 gauge wire, with return through the ground. In Providence, on the evening of the ^rst of these concerts (August 28), Henry W. Vaughan, State assayer, and the writer, were conversing through magneto telephones over a shunt made by grounding one of the American District Telegraph wires in two places, about a quarter of a mile apart, through suitable resistance coils, At about half past eight o'clock we were sur- prised by hearing singing on the line, at first faint, but afterward becoming distinct and clear. At the same moment, apparently, Clarence Rathbone, talking with a friend through telephones over a private line in Albany, was interrupted by the same sounda Afterv.'ard, during that and subsequent concert even- ings, various airs were heard, sung by a tenor or soprano voice, or played on the cornet The origin of these concerts remained a mystery for some time in Providence, and the lines were watched for music many evenings. The programmes heard proved to be precisely those of the Edison concerts performed in New York, the singers being Signor Tagliapietro, D. W. McAneeny and Madame Belle Cole. The question how this music passed from the New York and Albany wire to a shunt of the District wire in Providence, is of scientific importance. The Edison musical telephone consists of an instrument converting sound waves into galvanic waves at the transmitting station, and a different instrument reconverting galvanic into sound waves at the receiving station. The batteiy used in sending the music from New York to Saratoga con- sisted of 125 carbon cells, with from 1,000 to 3,000 ohms resist- ance interposed between the battery and line connections in New York. The wire used in these concerts extended from the Western Union building, corner of Broadway and Dey Street, through Park Row, Chatham Square, the Bowery and Third Avenue to One Hundred and Thirtieth Street, and thence via the Harlem Railroad to Albany. On the same poles with this Albany wire, for sixteen miles, are supported no less than four wires running REMARKABLE TELEPHONIC PHENOMENA 283 mMmmm Wirt! N:rt3rr6'2°r ^'z ""'^ ^-^r" ^-'°» TT„- „ 1 ., ,. ' . ' '^' "> -^^ and 28 east, run into the Western here >s a d,3toct featoe. The District wire beClto " nclud mg several hundred ohms resistance, so as not to imna^ the galvan,c insulation of the lina The telephone talked thrXh tbs pc^fectb;, and the sounds of atmospheric electricity were Sd m remarkable perfection. "'y were Heard It will be seen that the music from the Albany wire passed denTe' andtt;^?. ''! '" f P"'"""' "'^'™' "'"^ '^ P'ovi- ^s;;:het:^;rtht'' ^"'■" °' *" ^'^'™' »"^"" •'^*- .nCYoSb?'''"'^Tr''^'^^'^'«^'°^''"*''«-'in«'-nee^ in ^ew rork, by a crowded ground conductor. In the transfer in Providence f«>m the New York and Boston o Z oltS Wire, ther« was no common ground connection, and it is difficuU 284 THE SPEAKING TELEPHONE. to suppose that sufficient leakage took place on the three brackets and three poles, which were common to the New York and the local wire, to account for the transfer in Providence. The mag- neto-telephone has also proved itself abundantly capable of pick- ing up signals in an adjoining wire by induction alone. Without rejecting wholly, therefore, the other modes of transfer, I should ascribe to induction the principal part in the transfer of the con- certs from wire to wire between New York and Providence. What proportion, then, of the electrical music, set in motion in New York, could have reached the listeners on the shunt in Providence? Whether induction, leakage, or crowded ground was concenied, will any electrician say that the New York and Providence wires situated as described, could have robbed the Albany wire of one tenth or even one hundredth of its electrical force or - lotion ? When this one te.ith or one hundredth reached Providei ^, will any , electrician say that the wires from New York, in the course of 975 feet, could have given up to the parallel Pistrict wire one tenth or one hundredth of their elec- trical wave motion ? Lastly, when the District circuit had secured this minute fraction of the original music bearing electric waves, will any electrician say that the shunt as described (containing 600 ohms resistance, while the shunted quarter of a mile of Dis"^ trict wire contained only 5 ohms resistance) could have diverted one tenth of the electric motion from the District circuit ? The music heard plainly in Providence did not, therefore, require or use one ten thousandth, hardly one hundred thou- sandth, of the electro-motive force originally imparted to the Albany wire. This startling conclusion suggests, first, the wonderful delicacy of the magneto-telephone, on which point I shall venture to enlarge, and second, the as yet unimagined capacity of electricity to transport sound. The magneto-telephone is probably the most sensitive of elec- troscopes for galvanic, magneto-electric, and atmospheric or free electricity, and will be used extensively in science and the arts, in this capacity. In the French Academy, on the 6th of Novem- SENSITIVENESS OF THE TELEPHONE. £86 "ber, Mr. Breguet introduced the telenhone n« J oii i ies8 than one hundred thousandth part of the ouirent ZZ Z ^,r'?f !""• '" '^'""8 --'^'--- with a Whelle bndge, the telephone k more sensitive than the galvanomer ^eetHea. discha^-iftr:; Tz^:j ::^:^ .r„r it^r s:;r n^^i;dtH^^^ v»es a™ not products of the m^neto-telepC S Zt^ galvamc currenta The delicate magneto-electr o cu^m rf te telephone .s not genendly exposed to ea.esdroppinHn l j d« ferent sete of wires actually come in contact i-roi Peirce has observed that if one screw ^„„ „f «.op>o deheacy of the telephone is this: Prof. E. W Blat^f Brown University, talked with a friend for some d stance awf ^.Iroad, uamg the two lines of ..ils for the telephtic c "uit At the same time he heard the ooeratino- o„ ti. .1 ,■ TS ""^n"^^ ''r -"^ pSr;s; ■nt«ir''' -"^ The ateence of insulation in this experiment recalls another onnoua observation. The telephone works better r^me stt of the atmosphere than in othei^. A north-east win "ap„e^ specially favorable When a stonn is approachingTe S 286 THE SPEAKINa TELEPHONE. are sometimes weak ; bit the talking is often loud and excellent in the midst of a storm, when insulation is most defective. I have just verified this by talking over a short line where the wire is without insulation, and its only support between two houses, the trunk of a tree, just now sheeted with water from falling rain. This apparent indifference to insulation in a telephone which will overcome a resistance of eleven tho: sand ohms is not easily explained. This 'j only one of a multiJiude of paradoxes, presented by the telephone. The sound produced in the telephone by lightning, even whea so distant that only the flash can be seen in the horizon, and no thunder can be heard, is very characteristic, something like the quenching of a drop of melted metal in water, or the sound of a distant rocket The most remarkable circumstance is that this sound is always heard just before the flash is seen— that is, there is a probable disturbance (inductive) of the electricity overhead^ due to the distant conbentration of electricity preceding the dis- ruptive discharge. On Sunday, November 18, 1877, these sounds were heard and remarked upon in Providence the first time for several weeks. The papers on Monday moriiing explained it by the report of thunder storms in Massachusetts on the preceding day. Frequent sounds of electrical discharge similar to that of lightning, but much fainter, are almost always heard several hours before a thunderstorm. This has just been exemplified in Providence. The sounds produced in the telephone by the auroral flashes or streamers were observed in Providence by Prof. John Peii'ce in Mayor June, 1877. I will give one further illustration of the delicacy of the tele- phone, this time in relation lio magnetism. In June, 1877, Prof. E. W. Blake substituted for the magnet of the telephone a bar of soft iron, free from magnetism. When this was held in the line of the dipping needle, the telephone talked readily by the earth's magnetism. But when the telephone was swayed into a position at right angles with the line of the dipping needle (in the same vertical plane), it was absolutely silent ; and the bkequet's telephone, feld^Z*^, '"' ^"^ r '" P"'P°'«°'' "« *o telephone wa« directed towarf or receded from the pole of the dipping needk It remins only to speak of the quality of the con^r^^l ov^Aearf m Providence. The rendering of the 0.^"^ Perfect, bnt arbculation waa deficient or absent, both Tn S songs and m some sentences which a,« said to have beln de Saratoga and elsewhere. The papers of the day reportXuhe words were undistinguishable in Saratoga. ThereT the^foro no reason to suppose that the sounds losf anything iJqXS ae course of their indirect transmission to Providence. ^ BEEGUET'S TELEPHONE. M. Breguet has invented an entirely novel telephone based on the pnncxple of Lippnxann's electro-capillary elj^^orne Jr I^g. 133. sl^nw""*'? ™'' ""^r" "' '^^"y *!*«. ^"d «»A consists wW?^fl^ , ^r ^T' """"^'"'"S a layer of mercury, over which floats a layer of acidulated water. Into this water diS the pomt of a glass tube containing mercury ^ ihe upper part of the glass tube contains air and mav h. ri^a nr™S'"^ ""'-/ byaplateordia;hr:gte"a IbM 01 vmratmg. The circuit is formed by connecting the mer hih. !f !.. . ""i'"'"'- ^''™ o"" ^P^""^' over the top of the :;t M :rrt\t^^^™"°"rtf ^""^'^''— ^^ u.^ ^^ ta« ^„,^, y^ jjjQ ^ylj^ ^^^^,^ ^j^^ mercury 288 THE SPEAKING TELEPHONK makes contact \vith the acidulated water of the vessel bj the fine capillary bore of the tube. Here the electro-capillary action takes place, the vibratory motions of the mercury generating electro-capillary currents, which traverse the circuit to the re- ceiver, and by a reverse process reproduce the air vibrations at the top of the tube of the receiver. M. Breguet says that this telephone, unlike Prof. Bell's, is capable of reproducing not only oscillatory motions of the air, but of reproducing the exact range of the most general movements of the vibratory plate. A port- able form of this instrument, constructed by M. Lippmann, con- sists of a fine glass tube, several centimetres long, containing alternate drops of mercury and acidulated water, so as to form an electro-capillary series. It is sealed at the ends, by which two platmum wires make contact with the terminal mercury drops. A rondelle of firwood is fixed normally to the tube by its centre, and gives a larger surface for the voice to act against, so as to furnish more njiotion to the tube when it acts as a trans- mitter, and be easily applied to the ear when it is a receiver. M. Breguet claims for this telephone that it will act through submarine cables with instantaneous effect, because it will only establish variations of potential at the sending end of the line, and, unlike other telephones, will not generate currents to flow through the line. But this claim does not appear to us to be justifiable, since currents must result in the line from the varia- ' tions of potential set up ; and, if there is to be any communica- tion at all, they must travel throughout the length of the cable from end to end. REMARKS ON THE THEORY OF THE TELEPHONE. 1 It is generally admitted that the audition of speech in the tele- phone IS the result of repetitions, by the diaphragm in the receiv- ing instrument, in consequence of electro-magnetic effects, of the vibrations produced in the transmitter when the voice is 1 By Th. du Monoel. Extract from Comptes Rendus of the French Academy of Sciences. ' BEKARZ8 ON THE THEOBr OF THE TEI,EPflOJ,E. 289 recent exp^menteffntfTl'''"'''."' '^**'°" *° «H "" to show Lltl^zrtc^^rf^''''r'' ''"-' that not only can the vCt It' '*'' '^"' •'""""strated ceiver be repC^ W "''""""f .^V"^'" of the telephone re- tHat the vib.tCpirt:rfntfh:i>^^^^^^^^ ci,y ui d, srring teiephone, as shown bv Mr A Hr.^ e.ect..„agnetic\!rThrVfhS;rri^^^^^^^^ tViQT, +v,„+ 4! . ^^ "J •-"« voice, Has no other role to fill ^ri:S:zrri:irh;;tro:^nrrT the vari^ions in the electro-magnetirit ^tfe ptee\S pli«.e w,th increased nipidity as its mass is redu^d it\Sf K^ vlr .•'r"';"*^'^ *^y '' i^ important toT^' ve^' tin 290 THE SPEAKING TELEPHONE. tions of magnetization determining the sounds are rendered sharp and clear, and there is consequently an advantage in both cases. This hypothesis, it will also be observed, in no wise excludes the phonetic effects of such mechanical vibrations as may be produced, and whose action would therefore be added to that in the magnetic corea In the telephones of Messrs. Eeiss, Wray and Gray, the mag- netic cores have no armatures at all, sonorous boxes alone being used for increasing the sounds; but in Bell's telephone it is more particularly the vibrating disks in the receivers which determine the sound effect, and the permanent magnet is used solely for the purpose of rendering the apparatus capable of being used both as a transmitter and receiver. In the Bell model, shown at Philadelphia, the receiver consisted simply of a tubular magnet, whose cylindrical pole was provided with a vibrating plate. We have now to Ascertain what the physical effects are to which the vibrations of the magnetic core, under the influence of variations in tlie strength of the current in the bobbin, should be attributed, and for this purpose it is necessary to refer to the experiments of Messrs. Page, Henry and Wertheim. From these it would appear that they are due entirely to the contractions and dilations of the magnetic molecules of the core, under the influ- ence of successive magnetization and demagnetization ; and this assumption receives additional confinnation from the changes that have been observed to take place, by certain physicists, in the length of a bar of iron when submitted to energetic magnetic action. As to the more efficacious action of induced currents in tele- phonic transmission, I do not find it difficult to believe that they owe this advantage directly to their instantaneous character or the suddenness of their production. For this reason, they are not, like voltaic currents, dependent upon the duration of the vibrations in the transmitter ; and, as they do not have to pass through a variable period either, which increases as the square of the length of the circuit, their action simply depends upon CUBBENTS PRODUCED IH THE TELEPHONE. .29X their Strength alone. They are, consequently, much more favor able for the production of phonetic vibmtion than vZo ™r «nte; «„d he fact that the invce currents which foUowZ inrtial pulsation tend to discharge the line promptly contributed sfU more toward rendering their action shaker and moret^f If we consider also, that the currents produced b^Z Sn of the voice on the diaphiugm of an ordinary telephone dTn^ exceed that from a single Daniell cell in a cLitTloO m^ WMren de la Rue to be the case, we can readily underetand that the greater or less st^ngth of these curi^nte is of IMe jmportance m the phonetic effects produced, and, unde o^ nary cmumstances, would be incapable of podu ing mL^™ like that of the telephone to produce the sounds we hear. ' CHAPTER X. THE TALKING PHONOGRAPH. The Talking Phonograph, invented by Mr. Thomas A. Edi- son, is a purely mechanical invention, no electricity being used. It is, however, somewhat allied to the telephone, for, like the latter, its action depends upon the vibratory motions of a metal- lic diaphragm, capable of receiving from and transmitting to the air sound vibrations. The term phonograph, or sound-recorder, includes, besides Mr. Edison's, a large number of instruments, which, though they are not able to reproduce sound, are capable of graphically represent- ing it Before treating of thesb instruments, it might be well to recall what has been said in an earlier part of this work on the nature of sound. Bearing in mind that sound is and has for its origin motion, we will see that a vibrating body, situated in an elastic medium like our atmosphere, becomes the central source of a peculiar form of action, which is ever propagated outward- This is known as wave motion, and if the number of vibrations causing it be within certain limits, the wave motion becomes perceptible to the ear, and is called sound. Any change in the original vibrations will cause a change in the nature of the sound emitted. Thus, if their amplitude be increased, the sound becomes louder, and can be heard at a greater distance, or, in other words, intensity is dependent on the extent of the vibrations. Again, should the number of vibrations in equal portions of time be varied, the note will rise or fall in the musical scale ; or, pitch depends on the number of vibrations occurring in a given time. A third and, in this connection, more important characteristic 0HAKA0TEBISTI08 OP SOUKD. 293 Im tjf '^V^"' "" unchanging fundamental tone is oove^d with 'r^'^i^i^ir^^^:^;:'^:^^:::- - paniment and predominance of certain^? rt„ V " they are called^ that giver to a^^ ^l ! hannomcs, as Whereby it may he distSgr^h^d ^111.7^^1 H^ and pitch. This characteristic i. often called the ZbL o^^ of the note, but is known equally well as its quahty. shape of th^ cavity maybe so varied that it will resmmd to luTlT ^ ™f/'*''- ^^ '■"^ °* «^= l-'*^' poweT^ are able to produce the vowel ^o la™ ta^ta stylus, which also participates in the motion, and records it nmn the blackened paper. The hmnan voice, th; tonesT^ mS «^tnlmen^ and even the rumbling of istant ZnZaTZl graphically presented on paper represents the quiet membrane, according to the force of tl.« pressure, different articulate sounds varying greatly in len^h consists in the relative abruptness of the rising and falhnff inflec tions, which makes curves of various shapes The sZthnI, or ruggedness of a sound has thus ite own .r«.l,;. XT." ' 296 THE TALKING PHONOGRAPH. independent both of its actual intensity and its length. The logograph consists of a small speaking trumpet, having an ordi- nary mouth-piece connected to a tube, the other end of which is widened out and covered with a thin membrane of gold beater's skin or gutta percha. A spring presses slightly against the membrane, and haa a light arm of aluminium, which carries the marker, consisting of a small sable brush inserted in a glass tube containing a colored liquid. An endless strip of paper ia German r proltmged Tromhont oo in mood Fig. 137. caused to travel beneath the pencU, and is marked with an irregular curved line, the elevations and depressions of which correspond to the force, duration and other characteristics of the vocal impulses. The lines thus traced exhibit remarkable uni- formity when the same phrases are successively pronounced Incomprehennbility Fig. 138. Fig. 137 shows curves obtained by the interposition of a light lever between the membrane and the smoked glass, which is drawn along beneath the style, whose excursions are much mag- nified by the lever. The curves show respectively the tongue trill or German r prolonged, the mark produced by the sound of a trombone, and by the sound of oo in mood. Fig. 138 shows a tracing from the utterance of the word incomprehensibility, with different degrees of effoi-t It will be LOGOGRAPHIC JIECORD& 297 The Wer 21"ra. XT'" "P'"'™ °' ""«°^ '^■"i- ..an., w HoSrw:: t^rr """^ '"" ''" ^»-'"- A much mor. delicate instrument' for «corfi„g ,„„„,„, I_/La^-^_JvX1_ JVntoMw ■DxftlcKiiy ■^ ton* and tnunptt /a,t "rrayad. And/uriau4 oMry larger neighed. «*» y<»« the drta4fia rwHry, ^. 139. moist by a mix^rte™^?™?' "Tl'"^^ '^ '^^P' attached to a perpendicuirCsh^^^raS "^'ri t T^'""^ ° **" apn^at pudt, ana 298 THE TALKING PHONOGRAPH. moved by a ratchet wheel. To the upright is attached, horizon- tally, a metallic stage six inches in length, upon which slides a carriage with a glass plate, and having a regular movement given to it by wheel and cord. A bell shaped mouth-piece is inserted in the external auditory meatus and luted in position. The vibrations of the membrane, due to a musical tone sounded in the bell, may be observed by means of a ray of light thrown Mg. 140. upon small specula of foil attached to the malk^i.:, ineug, or to different portions of the membrana tympani, 01 nia^ be lecorded on smoked glass by a stylus fastened to the descending process of the malleus or incus by means of glue, in a line with the long axis of the process, and extending downward, so as to reach the plate of smoked glass, which is moved at a right angle to the excTiw'cTi of tlie stylus ; the latter then traces a wave line cor- KONIg'S MONOMETKIO FLAMEa a99 responding to the character and pitch of the musical tone sounded into the ear. As the glass plates present plane surfaces, and as the point of the vibrating style sweeps through the segment of a circle, the curves obtained are apt to be discontinuous, especially when the amplitude is great To obviate this difficulty a sheet of glass is employed, having a curved surface, the concavity being presented to the stylus. The sheet of glass is a section of a cylinder whose semi-diaraeter is equivalent to the length of the style. In this way the point of the stylus never leaves the surface of the glass and the curve resulting from its vibration is continuous. The carbon film is preserved by pouring collodion upon it As soon as this is dry, the film may be floated off with water, and placed upon a plane sheet of glass, or upon paper, and varnished in the ordinary way. Numerous other methods of rendering sound-vibrations visible ' to the eye might be cited In general these methods are of two kmds. They either aim at producing a lasting record on paper, glass, etc., which may be preserved and examined at leisure, or they present to the eye in a vivid way the sound vibrations as they are actually transpiring Of the latter class, one devised by Kdmg deserves a passing notice. A hollow chamber is divided by a thin membrane of caoutchouc into two compartments : one of which communicates through a tube to the mouth-piece, in front of which the sounds are generated ; the other is supplied from a pipe with ordinary coal gas, which issues from the com- partment through a fine burner, where it is ignited. Any motion of the diaphragm will change the pressure on the gas, and either lengthen or shorten the jet The movements of the flame when viewed directly are scarcely perceptible. To render them dis- tinct, they are received on a four-sided mirror, which is made to revolve. The image of the flame is thus lengthened out into a luminous band. When the membrane vibrates, the upper edge of the band becomes serrated, each elevation being due to one sound-vibration. The instruments thus far described, while able to produce -^L^'. 800 THE TALKING PHONOGRAPH. records undoubtedly correct, could go no farther. The records thus made suggested no way of reproducing the sound. Nor was this effected until Mr. Edison produced his wonderful talk- ing j)honograplL In its simplest form the talking phonograph consists of a mounted diaphragm (fig. 141), so arranged as to operate a small steel stylus placed just below and opposite its centre, and a brass cylinder, six or more inches long by three or four in diameter, which is mounted on a horizontal axis, extending, each way, beyond its ends for a distance about equal to its own length. A spiral groove is cut in the circumference of the cylinder from one end to the other, each spire of the groove being sepa- rated from its neighbor by about one tenth of an inch. The I Fig. 141. shaft, or axis, is also cut by a screw thread corresponding to the spiral groove of the cylinder, and works in screw bearings ; con- sequently, when the cylinder is caused to revolve by means of a crank that is fitted to the axis for the purpose, it receives a for- ward or backward movement of about one tenth of an inch for every turn of the same — the direction, of course, depending upon the way the crank is turned. The diaphragm is supported by an upright casting capable of adjustment (fig. 142), and so arranged that it may be r'^moved altogether when necessary ; when in use,, however, it is clamped in a fixed position above or in front of the cylinder, thus bringing the stylus always opposite the groove as the cylinder is turned, A small flat snrino- attached to the castinf* MOUNTING OF THE PHONOGEAPH. 301 extends underneath the diaphragm as far as its centre, and car- ries the stylus ; and between the diaphragm and spring a small piece of India rubber is placed to modify the action, it having been found that better results are obtained by this means than when the stylus is rigidly attached to the diaphragm itself. The action of the apparatus will now be readily understood from what follows. The cylinder is first very smoothly covered with tmfoil, and the diaphragm securely fastened in place by clamp- ing its support to the base of the instrument When thiJ has been properly done, the stylus should lightly press against that part of the foil over the groove. The crank is now turned, while, at the same time, some one speaks into the mouth-piece of Fig. 142. the instrument, which will cause the diaphragm to vibrate ; and, as the vibrations of the latter correspond with the movements of the air producing them, the soft and yielding foil will become marked along the line of the groove by a series of indentations of different depths, varying with the amplitude of the vibrations of the diaphragm ; or, in other words, with the inflections or modulations of the speaker's voice. These inflections may, there- fore, be looked upon as a sort of visible speech, which, in fact, they really are. If now the diaphragm is removed by loosening the clamp, and the cylinder then turned back to the starting 802 THE TALKING PHONOGRAPH. point, we have only to replace the diaphragm and turn in the same direction as at first to hear repeated all that has been spoken into the mouth-pieCe of the apparatus, the stylus, by this means, being caused to traverse its former path ; and, conse- quently, rising and falling with the depressions in the foil, its motion is communicated to the diaphragm, and thence through the intervening air to the ear, where the sensation of sound is produced. As the faithful reproduction of a sound is, in reality, nothing more than a reproduction of similar acoustic vibrations in a given time, it at once becomes evident that the cylinder should be made to revolve with absolute uniformity at all times, otherwise a difference, more or less marked, between the original sound and the reproduction will become manifest To secure this uni- formity of motion, and produce a practically working machine for automatically recording speeches, vocal and instrumental music, and perfectly , reproducing the same, the inventor Las devised an apparatus in which a plate replaces the cylinder. This plate, which is ten inches in diameter, has a volute spiral groove cut in its surface, on both sides, from its centre to within one inch of its outer edge. An arm, guided by the spiral upon the under side of the plate, carries a diaphragm and mouth-piece at its extreme end. If the arm be placed near the centre of the plate, and the latter rotated, the motion will cause the arm to follow the spiral outward to the edge. A spring and train of wheel-work regulated by a friction-governor, serves to give uni- form motion to the plate. The sheet upon which the record is made is of tinfoil This is fastened to a paper frame, made by cutting a nine-inch disk from a square piece of paper of the same dimensions as the plate. Four pins upon the plate pass through corresponding eyelet-holes punched in the four comers of the paper when the latter is laid upon it, and thus secure accurate re- gistration, while a clamping-frame hinged to the plate fastens the foil and its paper frame securely to the latter. The mechanism is so arranged that the plate may be started and stopped in- stantly, or its motion reversed at will, thus giving the greatest convenience to both speaker and copyist TRACINGS FROM PHONOGRAPHIC RECORDS. 303 Mr. Edison iias found that the clearness of the instrument's articulation depends considerably upon the size and shape of the opening in the mouth-piece. When words are spoken against the whole diaphragm, the hissing sounds, as in shall, fleece, etc., are lost These sounds are rendered clearly when the hole is small and provided with sharp edges, or when made in the form of a slot surrounded by artificial teetL Beside tinfoil other metals have been used. Impressions have been made upon sheets of copper, and even upon soft iron. "With the copper foil the instrument spoke with sufficient force to be heard at a distance of two hundred and seventy-five feet in the open air. By using a form of pantograph, Prof. A. M. Mayer has ob- tained magnified tracings on smoked glass of the record on the Fig. 143. foiL The apparatus he used consisted of a delicate lever, on the under side of which is a point, made as nearly as possible like the point under the thin iron plate in the phonograph. Cemented to the end of the longer arm of this lever is a pointed slip of thin copper foil, which just touches the vertical surface of a smoked -^lass plate. The point on the short arm of the lever rests in the furrow, in which are the depressions and elevations made in the foil on the cylinder. Eotating the cylinder with a slow and uni- form motion, while the plate of glass is slid along, the point of copper foil scrapes the lampblack off the smoked glass plate and traces on it the magnified profile of the depressions and eleva- tions in the foil on the cylinder. In fig. 143, A represents the appearance to the eye of the impressions on the foil, when the sound of a in hat is sung against the iron plate of the phono- 304 THE TALKING PHONOGRAPH. graph. B is the magnified profile of these impressions on the smoked glass obtained as just described. C gives the appear- ance of Kdnig's flame when the same sound is sung quite close to its membrane. It will be seen that the profile of the impres- sions made on the phonograph, and the contours of the flames of Kdnig, when vibrated by the same compound sound, bear a close resemblance. Mr. Mayer finds that. the form of the trace obtained from a point attached to a membrane vibrating under the influence of a compound sound, depends on the distance of the source of the sound from the membrane, and the same compound sound will form an infinite number of different traces as the distance of its place of origin from the membrane is gradually increased ; for, as you increase this distance, the waves of the components of the compound sound are made to strike on the membrane at differ- ent periods of their swings. For example, if the compound sound is formed of six, harmonics, the removal of the source of the sonorous vibrations, from the membrane to a distance equal to ^ of a wave length of the 1st harmonic, will remove the 2d, 3d, 4th, 6th and 6th harmonics to distances from the mem- brane equal, respectively, to J, f, 1, 1^ and 1^ wave-lengths. The consequence evidently is, that the resultant wave-form is entirely changed by this motion of the source of the sound, though the sonorous sensation of the compound sound remains tmchanged. This is readily proved experimentally by sending a constant compound sound into the cone of Kdnig's apparatus, while we gradually lengthen th-e tube between the mouth-piece and the membrane. The articulation and quality of the phonograph, although not yet perfect, is full as good as the telephone was six months ago. The instrument, when perfected and moved by clock work, will undoubtedly reproduce every condition of the human voice, including the whole world of expression in speech and song. The sheet of tinfoil or other plastic material receiving the impressions of sound will be stereotyped or electrotyped, so as to be multiplied and made durable ; or the cylinder will be made of APPLICATIONS OP THE PHONOGRAPH. 305 a material plastic when used, and hardening afterward. Thin sheets of papier- mach^, or of various substances which soften by heat, would be of this character. Having provided thus for the durability of the phonograph plate, it will be very easy to make it separable from the cylinder producing it, and attachable to a cor- responding cylinder anywhere and at any time. There will doubt- less be a standard of diameter and pitch of screw for phonograph cylinders. Friends at a distance will then send to each other phonograph letters, which will talk at any time in the friend's voice when put upon the instrument How startling, also, it will be to reproduce and hear at pleasure the voice of the dead I All of these things are to be common, every-day experiences withm a few years. It will be possible a generation hence to take a file of phonograph letters, spoken at different ages by the same person, and hear the early prattle, the changing voice, the manly tones, and also the varying manner and moods of the speaker— so expressive of character— from childhood up! These are some of the private applications. For public uses, we shall have galleries where phonograph sheets will be pre- served as photographs and books now are. The utterances of great speakers and singers will there be kept for a thousand years. In these galleries spoken languages will be preserved from century to century with all peculiarities of pronunciation, dialect or brogue. As we go now to see the stereopticon, we shall go to public halls to hear these treasures of speech and song brought out and reproduced as loud, or louder, than when first spoken or sung by the truly great ones of earth. Certainly, within a dozen years, some of the great singers will be induced to sing into the ear of the phonograph, and the electrotyped cylmders thence obtained will be put into the hand organs of the streets, and we shall hear the actual voice of Christine Nilsson or Miss Cary ground out at every corner. In public exhibitions, also, we shall have reproductions of the sounds of nature, and of noises familiar and unfamiliar. Nothing will be easier than to catch the sounds of the waves on the beach, the roar of Niagara, the discords of the streets, S06 THE TALKING PHONOGRAPH. the noises of animals, the puflang and rush of the railroad train, of the rolling thunder, or even the tumult of a battle. When popular airs are sung into the phonograph and the notes are then reproduced in reverse order, very curious and beautiful musical effects are oftentimes produced, having no ap- parent resemblance to those contained in their originala The instrument may thus be used as a sort of musical kaleidoscope, by means of which an infinite variety of new combinations may be produced from the musical compositions now in existence. The talking phonogi-aph will doubtless be applied to bell- punches, clocks, complaint boxes in public conveyances, and to toys of all kinds. It will supersede the shorthand writer in taking letters by dictation, and in the taking of testimony before refereea Phonographic letters will be seat by mail, the foil be- ing wound on paper cylinders of the size of a finger. It will re- cite poems in the voice of the author, and reproduce the speeches of celebrated orators. Dramas will be produced in which all the parts wiU be " well spoken — with good accent and good dis- cretion;" the original matrice being prepared on one machine provided with a rubber tube having several mouth-pieces : and Madame Tussaud's figures will hereafter talk, as well as look, like their great prototypes I 1 The phonograph has quite passed the experimental stage, and is now practically* successful in every respect, and must be regarded as instrumental in opening a new" field for scientific research, and making one more application of science to industry. Its aim is to record and reproduce speech, to make a permanent record ot vocal or other sOnorous vibrations, and to recreate these vibrations in such a manner that the original vibrations may be again imparted to the air as sounds. The talking phonograph is a natural outcome of the tele- phone, but unlike any form of telephone, it is mechanical, and not electrical, in its action. In using the phonograph, it is found best to speak in a loud, clear voice, and with distinct enuncia- * Scribntr'a Monthly Magcudne, for AprU, IS^a, CHAEAOTKBISncs OP THE PHOlfOGRAPa 807 the handle, spt^r pZl „£ ITT to the movement of be uniform and steady. ^ '' """'"' ""^ "'yl"« "" the Pitch Of thet^rsrhT:nrrrs;:z:rir JeTch oTtl,. t T '"""^^tance, in connection with Z and it . p4::a I'^Lfke IZ^^'t^ of te l" "'•"^' out iWn^, o. eanrd;;S:Tb^«rl-;f *~^ -'*; the phonograph is usually uther shrill anfe^ ^ t^V feet will undoubtedly be corrected hv ;m„. T ^' *'" ^*- must be obse^ed thft, r..ry7^l'Z'Z^ZT:T .^ quite new. and it is imnossible tn ,.„ * "^™™*' w, it is stUl tion it may yet be cai.^1: LXd^'^ ^^^''^t ^ea^h out-yet .^ L tttl T^.^-*,- 808 THE TALKING PHONOGRAPH. gested many valuable uses in trade, manufactures and sodal life, and it will he the aim of this department to report the progress of this, one of the most remarkable inventions of this century, and its applications to science and industry. ^ FBO!^ THE 1. A /or fBOMTHE CHAPTER XI. EDISON'S QUADRUPLEX TELEGRAPH. The quadruplex system of telegraphy, by means of which four commumcations, two in each direction, may be simultaneously transmitted over a single wire, has, within a few years, found very extensive practical application upon the lines of the Western Union Telegraph Company, and is at the present time operated apon sixty lines, between almost all of the principal cities in the country. The distinguishing principle of this system consists in com- bmingat two terminal stations, two distinct and unlike methods of single transmission, in such a manner that they may be earned on independently upon the same wire, and at the same time, without interfering with each other. One of these methods of single transmission is known as the double current system, and the other is the single current or open circuit system. In the double current system the battery remains constantly in connection with the line at the sending stations, its polarity being completely reversed at the beginning and at the end of every signal, without breaking the circuit The receiving relay is provided with a polarized or permanently magnetic armature but has no adjusting spring, and its action depends solely upon the reversals of polarity upon the line, without reference to the strength of the current In the single current system, on the other hand, the transmission is effected by increasing and decreasing the current, while the relay may have a neutral or soft iron armature, provided with a retracting spring A better form, however, for long circuits, is that of the polarized relay especially adapted to prevent interferences from the reversals sent into the line to operate the double current system. In this system, therefore, the action depends solely upon the strength 310 QUADRUPLEX TELEGRAPHY. of the current, its polarity being altogether a matter of indiffer- ence It will thus be apparent that by making use of these two distinct qualities of the current, viz., polarity and strength, com- bined with the duplex principle of simultaneous transmission in opposite directions, four sets of instruments may be operated at the same time, on the same wir& This method possesses, more- over, the important practical advantage that the action of each of the receiving relays is perfectly independent Each receiving operator controls his own relay, and can adjust it to suit himself without interfering with the other. Fig. 144 shows the quadruples apparatus, as arranged upon the bridge plan, which was at first employed by the Western Union Telegraph Company in 1874, when the system was placed upon its hnea Ti is a double current transmitter or pole-changer, operated by an electro-magnet, local battery e^ and finger key K^. The office of the transmitter Ti is simply to interchange the poles of the main battery E^, with respect to the line and ground wires, whenever the key Kj is depressed; or, in other words, to reverse the polarity of the current upon the line by reversing the poles of battery E^. By the use of properly arranged spring contacts, «j Sjj, this is done without at any time interrupting the circuit Thus the movements of the transmitter T^ cannot alter the strength of the current sent out to line, but only its polarity or direction. The second transmitter, Tj, is operated by a local circuit and key Kg in the same manner. It is connected with the battery wire 12, of the transmitter T^ , in such a way that when the key Kg is depressed, the battery Ej is enlarged by the addition of a second battery, Eg, of two to three times the number of cells, by means of which it is enabled to send a current to the line of three or four times the original strength, but the polarity of the current with respect to the line of course still remains, as before, under control of the first transmitter T^. At the other end of the line are the two receiving instruments El and Eg. Hi is a polarized relay with a permanently mag- BRIDGE METBOIX 511 i ^ ^liaLJ j 812 QUADRUPLEX TELEGRAPHY. netic armature, which is deflected in one direction by positive, and in the other by negative currents, without reference to their strength. This relay consequently responds solely to the move- ments of key Kj, and operates the sounder Sj by a local circuit from battery Lj in the usual manner. Relay Rg is placed in the same main circuit, and is provided with a neutral or soft iron armaturf". It responds with equal readiness to currents of either polarity, provided they are strong enough to induce sufficient magnetism in its cores to overcome the tension of the opposing armature spring. The latter, however, is so adjusted that its retractile force exceeds the magnetic attraction induced by the current of the battery E^, but is easily overpowered by that of the current from E^ and Ea combined, which is three or four times as great Therefore, the relay Rj responds only to the movements of key K^ and transmitter T,. The same difficulty which troubled former inventors arises again in this connectidn. When the polarity of the current upon the line is reversed daring the time in which the armature of Rj, is attracted to its poles, the armature will fall oflE for an instant, owing to the cessation of all attractive force at the instant when the change of polarity is actually taking place, and this would confuse the signals by false breaks if the sounder were connected in the ordinary way. By the arrangement shown in the figure, the armature of the relay R, makes contact on its back stop, and a second local battery L, operates the receiving sounder S3. Thus it will be understood that when relay R, attracts, its armature, the local circuit of sounder S3 will be closed by the back contact of local relay S ; but if the armature of R3 falls off, it must reach its back contact, and remain there long enough to complete the, circuit through the local relay S and operate it before the sounder S, will be affected. But the interval of no magnetism in the relay R^, at the change of polarity, is too brief to permit its armature to remain on its back contact long enough to affect the local relay S, and through the agency of this ingenious device the signals from Kg are properly ^responded to by the movements of sounder S,. BKIDGB METHOD. 3ia By placing the two receiving instruments R^ and Rj in the bridge wire of a Wheatstone balance, and duplicating the entire apparatus at each end of the line, the currents transmitted from either station do not affect the receiving instruments at that station. Thus in fig. 144 the keys K^ and K^ are supposed to be at New York, and their movements are responded to only by the receiving relays Rj and R^ at Boston. The duplicate parts which are not lettered operate in precisely the same manner^ but in the opposite direction with respect to the lina In applying this system of quadruplex transmission upon lines of considerable length, it was found that the interval of no mag- netism in the receiving relay R3 (which, as before stated, takes place at every reversal in the polarity of the line current) was greatly lengthened by the action of the static discharge from the line, so that the employment of the local relay S was not suffi- cient to overcome the difficulties arising therefrom. A rheostat or resistance Xj was therefore placed in the bridge wire with the receiving instruments Rj and R3, and shunted with a condenser c of considerable capacity. Between the lower plate of the con- denser and the junction of the bridge and earth wire an addi- tional electro-magnet r was placed, acting upon the armature lever of the relay R^, and in the same sense. The effect of this arrangement is, that when the current of one polarity ceases, the condenser c immediately discharges through the magnet r, which acts upon the armature lever of relay R3, and retains it in posi- tion for a brief time before the current of the opposite polarity arrives, and thus serves to bridge over the interval of no mag- netism between the currents of opposite polarity. It will be seen that the combination of transmitted currents in this method differs materially from any of those used in previous inventions. They are as follows : 1. When the first key is closed and the second open, -f 1 2. When the second key is closed and the first open— 3 or— 4 3. When both keys are closed _j_3 or 4-4 4. When both keys are open 1 814 QUADKUPLEX TELEGRAPHY. Here we discover another very important practical advantage in the system under consideration, which is due to the fact that the difference or working margin between the strengths of cur- rent required to produce signals upon the polarized relay and upon the neutral relay, respectively, may be increased to any extent which circumstances render desirable. Within certain limits, the greater this difference the better the practical results, for the reason that the range of adjustment of the neutral relay increases directly in proportion to the margin. The ratio of the respective currents has been gradually increased from 1 to 2 to as high as 1 to 4, with a corresponding improvement in the practical operation of the apparatus. From what has been said, therefore, it will be seen that before it became possible- to produce a quadruples apparatus capable of being worked at a commercial rate of speed upon long lines, it was essential that its component parts should have arrived at a certain stage of de^felopment When, in the early part of 1872, simultaneous transmission in opposite directions was for the first time rendered practicable upon long lines by the combination therewith of the condenser, the first step was accomplished. It now only remained to invent an equally successful method of simultaneous transmission in the same direction, which, as we have seen, was done in 1874. The application of one or more of the existing duplex combinations to the new invention, to form a quadruplex apparatus, soon followed as a matter of course. The following method of simultaneous transmission in the same direction was invented in December, 1875. Fig. 145 is a diagram of the apparatus as arranged for quadru- plex transmission. The lever t^, with its appendages, constitutes the first or single-point transmitter, which is the same as that of the Stearns duplex, being operated by an electro-magnet Tj, local battery i and key Kj. The second or double-point transmitter consists of a quadrangular plate of hard rubber, E, mounted upon an axis, and capable of being oscillated by the arm «, which is rigidly attached to it By means of a spring e^, the DIFFBHENTIAL METHOD. 315 am e presses upon a roller fixed upon one end of the lever d which forces the other end of the lever against the stop d. The lever d carries the armature of the electro-magnet T„ which, like the single point transmitter, is operated by a local battery and key K, The oscillating plate E has four insulated contact F>mte/ g,f^, g^, upon its respective angles. The contact levers ± and G are mounted on axes at each end of the plate E and txr 3a SB JAl. Fig. 146. are pressed against it by sprmgs s^ a^. When the transmitter is in a position of rest, as shown in the figure, P is in contact with /and a- with/j, and the parts are kept in this position by the action of the spring e^. When key K, is depressed, the arm e is raised by the action of the electro-magnet Tg upon the bent lever d; this turns the plate E upon its axis, and brings F into contact with^ and G with g^ 316 QUADEUPLEX TELEGRAPHY. In this apparatus, as in the one previously described, there are four diflEerent electrical conditions possible when transmitting two simultaneous despatches in the same direction, as follows : 1. Bolh keys in a position of rest. This position is represented - in fig. 146. Disregarding for the present the receiving instru- ments and their connections, the circuit may be traced as follows : From the earth at Gr through wires 9 and 8, contact spring &,, lever t^, wire 7, contact point /^ and lever Gr, wires 6 and 5, and thence through the receiving instruments to the line L. Thus the line wire is connected to earth without any battery, and there is no current upon the line. 2. The first key closed and the second key open. The route is the same as before from the earth at G to contact spring h. From this point it now diverges through contact lever F, wires 12, 13, and battery B to wire 7, and thence to the line as before. The battery B is now in circuit and sends a -f- current to line. 3. The second key closed and the first key open. The route is now from the earth at G, through wires 9 and 8, contact spring 6 and lever t^, as in the first instance, thence through battery B, wires 13, 12, contact lever G, wires 6, 5, and through the receiving instruments to line. The same battery B now sends a — current to the line. 4. Both keys closed. The route is now from the earth at G, by wires 9 and 8 to contact spring b ; thence by contact point a and wire 14 to battery 3B ; thence by wire 15, through g to lever F, wire 12 and g^ to contact lever G, and finally through wires 6 and 5 to the line. The battery 3B, which contains about three times as many elements as B, now sends a -f- current to the line. It will thus be seen that the two batteries B and 3B are never thrown together on the line at the same time, as in the previous arrangement The receiving apparatus consists of two sounders, S^ and Sg, which are controlled by two relays, K^ and Kg, fig. 145. The line wire L, on entering the receiving station, passes through the coils of both relays, and thence to earth through the transmitting apparatus Both relays are provided with polarized armatures, DIFFERENTIAL METHOD. 317 and are preferably constructed with two electro-magnets mm^, arranged with their poles facing each other, with a permanently^ magnetized armature between the opposite polea The arriving current, entering the relay K^, passes through the wire 2 and coil h^ of magnet m and Ag of m^, which are so arranged that a + current will cause the polarized armature n to be attracted by m^ and repelled by w, while with a — current the opposite effect will be produced. The armature of relay E^ is provided with a retracting spring r^, and operates the sounder S^ by means of a local battery Z^, in the ordinary manner. The relay Eg consists of two electro- magnets p and jOj, and its armature is also provided with a re- tracting spring 7-3 ; but it differs materially from the other relay in the arrangement of its local connections. The polarized arma- ture is held by the tension of the spring r^, not against a fixed stop, but against the free end of a movable contact lever r, the opposite end of which turns upon an axis. The contact lever r is itself held against a fixed stop g' by a spring q^, the tension of which considerably exceeds that of spring r^. The local battery w is placed in the wire 22, leading from the contact lever r to the differential sounder S3. The manner in which the receiving instruments operate in each of the four different electrical conditions of the line is as follows : 1. No current. The local circuit of sounder S^ is kept open by the action of spring r^ on armature w, and it remains inactive. The opposing branch circuits 23 and 24 of sounder S3 are both closed by relay E3, which render it also inactiva 2. Current of -\. B. The relay E^ (which is affected by positive currents of any strength) operates sounder S^. The armature of relay Eg is pressed more strongly against contact lever r, but not with sufficient power to overcome the spring q^. Sounder S3 is therefore unaffected. 3. Current of— B. The armature of relay E^ is attracted toward its back stop, and S^ is not affected. The armature of E, is uttmctcd to the right, and opens wire 24, which permits 318 QUADRUPLEX TELEGRAPHY. the local battery w to operate the sounder S3 by way of wires 22 and 28. 4. Current 0/+ 3B. The armature of relay E^ operates as m the second case. The increased power of the current from, the battery of many elements causes the armature of Eg to over- come the resistance of spring q^-^ and break the local circuit of wire 22, leaving the sounder S^ free to operate by way of whea 22 and 24. Thus the + 3B current operates both sounders. In order to adapt this system to quadruplex transmission, addi- tional helices h h^ and A3 h^ are placed upon the receiving relays E^ and E3, which are placed in the circuit of an artificial line, arranged according to Stearns's differential duplex method, which diverges at the point 6 and goes by way of 16, 17, 18 19* 20 and 21 to the earth at G, and is provided with the usual rheostat X and condenser C. The small rheostat x is employed to regulate the time of (discharge from the condenser. By the arrangement of the contact lever r, in connection with the armature lever o of relay E3, and the local circuits as above described, the reversal of polarity upon the line takes place without interrupting the signal upon sounder S3, for the reason that when the armature o is acted upon by the reversal it goes directly over from one extreme position to the other, without stopping at the intermediate position long enough to affect the sounder S3, even if there is a considerable interval between the successive currents. An improvement upon the above an-angement was subse- quently invented, in which an entirely novel combination of currents upon the line was employed, and which does not require the polarity of the current to be reversed during the transmission of a signal In fig. 146, T^ is a local electro-magnet, which oper- ates the single point transmitter t^, under control of the key K^. The key K3 in Hke manner controls the double point trans- mitter t^. The four electrical conditions of the line in the dif- ferent positions of the keys are as follows : 1. Both keys open. This is the position represented in the figure. The route of the current is from the earth at Q- throu^-h DIFFERENTIAL METHOD. 319 wire 1, spring h, lever i^, wires 2 and 3, contact point o, spring O, wires 4 and 6, battery B, wires 6 and 7, contact point n, and spring N, thence by wire 8 to line L. The battery B sends a -f current to line. 2. First hey chsed and second hey open. The route is now Fig. 146. from earth at G, .by wire 1 and spring h to point a, wires 12 and 7 and thence as before to the line. In this case there is no battery in circuit, and no current goes to line. 8. Second hey closed and first hey open. The route is now from earth at G by wire 1, spring b and lever i^, wires 2 and 320 QUADRUPLEX TELEGRAPHY. 13, battery 3B, wire 14, point o^, spring O, wires 4 and 15, con- tact point n^, spring N and wire 8 to the line. The large bat- tery 3B sends a — current to the line. 4. Both keys closed. The route is from earth at G by wire 1, spring b, contact point a, wires 12 and 6, main battery B, wires 5 and 15, contact point Wj, spring N, and wire 8 to line L, In this case the lesser mai^i battery se^ids a — current to line. The receiving apparatus cons. jl two sounders S^ and Sj, controlled by two relays R^ and Rg, both of which have polar- ized armatures, and are constructed in the same manner as those described in connection with the last method. The armature of relay Rg is provided with a retracting spring r^, and operates the sounder Sg by means of a local battery l^, in the usual man- ner. The polarized armature j\ when no current is passing through the line, is l^eld by a spring r^ against the free end of £* contact lever r, which is in turn held against the fixed stop q by the tension of a spring q^, which considerably exceeds that of the spring r^. The manner in which the receiving instruments operate in each of the four conditions of the line is as follows: 1. Cur- rent of-\-B. The local circuit of sounder S^ is kept open by the action of the positive current upon the polarized armature of relay R^, which is sufficient to overcome the tension of spring rj, and it therefore remains inactive. The local circuit of sounder Sg is kept open by the action of the positive current upon the armature h of relay Rg, in addition to the action of spring r^. 2. No current The armature j of relay Rj is drawn by the tension of spring r^ over against the contact lever r, thus completing the local circuit of sounder S^. The armature of Rg is held back by spring r^, thus breaking local circuit of Sg 3. Current of — 3B. In this case the action of the negative current from the gi-eater battery causes the polarized armature to press against the contact lever r and overcomes the tension of spring g'j, and thus, although the local circuit is still closed between the armature j and contact lever r, it is now broken COMBINED DIFFERENTIAL AND BMDGE METHODa 321 tetween the latter and the fixed stop q, and hence sounder S ■ remains inactive. On the other hand, the negative current carrie the armature h of relay E, to the left, closing the local eircui and actuating the sounders,, i. Current of- B ThiW . ™nt IS not sufficient to overcome the tension of spring Tanl herefore, the contact lever . continues to i^st against slop ; and tCf r sZrv ^°' "'^°^'' "'°^ ^'^ ^"^^^ '''™'' unon a' ';™"8e>nent it will be seen that a revei-sal of polarity upon the line cannot occur while a signal is being given by either key. This method may be readily united wifhLy su^ able duplex method to form a quadruplex combkation. i,n™ ,i I '^ " ?™? illustrating a quadruplex method, based ^poa that shown in fig. 144, but embodies several important medications and improvements not shown there. This aLnge- ^em was extensive yemployedforsome time upon the Western Unmn hues, especially upon the longer eircuifa, and was found to be m many respecte, far superior to that first introduced. It will be seen that no changes w.re made in the principle of the t^nsmitting portion of the appanitus, or the combination of eur! rents sent to line m the different positions of the keys but portions of the receiving apparatus were materially altS JIa^' ^*^"«' P.*"-<=d 'e% E„ and its accompanying sounder, are placed in the bridge 5, 6, as before. The neS ^lay, which was formerly placed in the bridge wire Z k polarized lelay B,. This is inserted, not in the bridge wire but in the line and earth wires ; these respectively form th°e tSa„d fourth sides of the bridge, of which A and B are the fi .t and second side^ Thus, when the resistances A and B are mtde equa^^the outgoing currents will divide equally between the bne lt^.Tn' Th t" "'""^^ ""* °"'- '" *- effect i": tne relay B^. The latter consists of two eleotro-ma.nets facing each other, with a polarized armatme between them When nf ouiTcnt IS passing, the polarized armature is held in a ceil^ 322 QUADRUPLEX TELEGRAPHr. position between two spring contact levers N Nj, and the cir- cuit of the local relay S is completed through these and the armature lever. The springs of the contact levers N N^ are adjusted with sufficient tension to prevent them from responding to the current of the small battery E^ at the sending station, but the additional current from battery E^ will overcome the spring LINE QROUNO Fig. 147. of N" or of Nj, according to its polarity, and thus break the circuit of the local relay S, which by its back contact will operate the sounder Sg. • The electro-magnets r r are arranged to act in con- junction with Rg Rg upon the same armature lever, and are connected with a condenser c and a rheostat Xj in the bridge wire, for reasons which have been fully explained on page 313. DIPPKBEHMAL METHOD. ' gog Pig. 148 shows the connections of another form of quadruolei Waratas, embodying seveml important improvementTthTa™ ^ ':« :L R ''PP^-'-i-'ofo-descriL.. Bothreceting relays B, and B, are provided with differential helices and n„l»f a«rf armatu,^ and in general the differential methyl i":S^ Mg. 148. throughout in place of the bridge. The relavs R «..! P adop^u .u all Ae more recent apparatus. The combinatbn of ! I 824 QUADRUPLEX TELEGRAPHY. the outgoing currents differs from that employed in the original quadruplex, and is as follows : Kj open and Kj open, current traversing line -{-4cB Ki open and Kg closed, " " " + B Kj closed and K^ open, " » " — 4 B Ki closed and K^ closed, " " " '. — B As in the original quadruplex, key K^ controls the polarity of the current going to line, but the depression of K3 decreases the outgoing current, irrespective of its polarity, from 4 B to B ; or, in other words, cuts off the battery 3 B altogether. The only matter requiring detailed explanation is the action of the relay Eg. When both keys are at rest, the positive cur- rent of both batteries (-}- 3 B + B) is passing over the line, and the polarized armature is pressed against the contact lever Wj, which yields, thus allowing it to separate from the contact lever n,, and the circuit of the sounder S3 is broken. When K^ is closed, the polarity of the entire battery upon the line is reversed, and the armature passes over to the other side and presses against rig in the same manner, so that the sounder S3 cannot be operated by the stronger currents of either polarity. But the depression of the key Kg in either case decreases the current, until it is unable to withstand the tension of the springs of the contact levers n^ n^, and thus the local circuit through the sounder Sg is completed, and the latter consequently responds to the movements of key Kg. On circuits exceeding 200 miles in length, the sounder Sg is preferably operated through the medium of a local relay, arranged as in fig. 147. The combination of the outgoing cur- rents in different positions of the keys is also rearranged, so as to conform to the original plans (figs. 144 and 147), and is as follows : K^ open and Kg open, current traversing line . . / + B Ki open and Kg closed, " " " +4B Ki closed and Kg open, " " " — B Ki closed and Kg closed, » « " — 4 B ■ cui^ showing the rela'^e ;Xro(TheTff "* °" " '°"« '^"■ apparatus. I„ fl„ 149 th. „ 1 different parta of the is lor receivto" atd tlfet^T T' "' """ '"P "' *e figure sending ope atol pi^'^lf^^-^'-S ' -''"-° %• 150°the -ceiving operator rCer one P^The^Zr"^"; "-"^ *« leierence will be explained elsewlipm T^^ whtsirrLre:Lrurtirrt "*^- ''-™- transmitted over one eo„d,^t !f "■^ ''^ sunultaneously binedwith an7 utobk onetf\V" *' "*?' * ration, or com"^ . simultaneous douCtinlLf '''"^' ''''''™ "^'"^ <>* fourdistinetcommun eTon Zr^P""''" *'^°"™'' ^° *"* without interfering SelSr-tT''*^ -multaneousty, make use of a double ael„ ' ^'^ '^" necessary to -eiving statiottCel ofTZreTeT ' "' "' v"^ two or more armatures, or else of tto '''^*™-™''?''^' •'"ving receiving instalments. "" "^ '"'»•'' "dependent thauKctTveS: 7t: 'f "^°*»"^^ ''™"g--' - two or more "ma^stltelur r'""^"^*^''"^ °- "^ the othcK is ateadvTn eo^lT ^ T"^ whenever one of polea Thus armovLT: ' the ""''^ " '=°'"^<='' -"^ '«« sarily interfere with eXaerll^/'''^'' ''™*"'«'^ "«*»• tee the signals. ThTseo^*,' ""<"^<»-»ce tends to con- independeft4i''g^:rm:rs:^,^^^^^^^^^^^ above mentioned obiections i<, linKi^ + ^ "^°"^ *^® the prindipal of w^r « 1 ol ws • wCth °*" ''^*"*^ arranged for the simultaneous tZsmLioI of / '''''"'™'™ '" tions. two in each d;r»„t;™ -I f , ' '°" oommunica- equating -irnttrc^rnsltp^itfef""' n ""''-T '^« «.e two receiving instruments a^T ST^ ^^^ ^^ 826 QUADRUPLEX TELEGRArHY. Fig. 149. EXPLANATION OP FIGS. 149 AND 150. Ki, Key of No. 1 sending operator. Ti, Double current transmitter, operated by K, or fcj. «i, Transmitter local, of tbree cells. ki. Key of No. 1 receiving operator. Bn Single polarized relay. Sj, Beceivfng sounder operated by ditto. (,, Sounder local, of two cells. K,, Key of No. 2 sending operator. T,, Single current transmitter, operated by K, or k^. 6i, Transraitter local, of three cells. jfc,, Key of No. 2 receiving operator. Rj, Compound polarized relay. S, Local relay or repeating sounder of ditto. I, Local of repeating sounder (two cells). 8,, Receiving sounder, operated by 8. l~, Sounder local, of two cells. B, Smaller division of main battery. 8 B, Larger division of main battery. Q, Switcu for cutting out main battery and connecting line to earth while balancing. X, Large rheostat for balancing resistance of lino. ARRANGEMENT Of APPARATUS ioR LONG CIHCUI-ra. tl|l|l{l|l|l|l{l{lll{|||{|{|||||||||l-— ^' iRTH 3!b 'III EARTH Fig. 150. y. Rheostat for compensating resistance of battery SB. z. Rheostat for compensating resistance of entire main battery 8 B + B. c. Equalizing condenser placed between main and artificial line. «i Cj, Condensers for compensatins? static dis- charge from main line. The quantity and duration of the condenser discharse are regulated by means of the adjurt- able rheostats r and r^. Thn nrran<»- ment shown is employed only on Unes i tww L** obtained, c, should have about twice as many sheets as c^ (both being ad- \Zr^ll^- ?^}'^ condenser cVshould refeive rlnnlrp^f *l"'.1»'' S''°"' ^a^f the resistance Tiirf'^^J '"'*''•, For example, If the num- 60 (total 90) and the resistance required for and7f^^'*S ohms, c, would require 1,000 and c, l,iOOO._ On lines of less than 400 miles -n.. arrangemcut shown in fig. 148 answers every purpose. * ouuwers 828 QUADBUPLEX TELEGRAPHY. the strength or polarity of the outgoing currents ; as the changes necessary to effect the proper adjustment or balance of one receiving instrument destroy the balance of the other, and much care and skill are, at times, required to accomplish the desired result Again, when two receiving instruments are used, one must be sufficiently sensitive to respond readily to weak currents. The other must be much less sensitive, responding only to cur- rents of greater strength. The current required to actuate the latter instrument sometimes affects injuriously the working of the more delicate one. To meet these difficulties, a somewhat novel and ingenious arrangement has been devised, which is shown in fig. 151. The principal part of the improvement consists in the use of a new form of double acting relay, composed of a double eleotro-magnet DOUBLE ACTING RELAY. 82» and a single armature, the latter capable of being placed, by tha the Z „ br"'" '""' '"*"'" P"''""- oiLpon'ding I Bv min VKr""'"* ** '"° ^'^' "' *^« ^-^ding statin. By means of suitably arranged contact-levers, two independent local crcmts are brought into action by the same armatu^ inl different position^ so as to actuate two independent sonnde,^ tZ fjT '''T *' •^^'™g i'-'trument or relay at one Older to effect the simultaneous transmission and Option of ^ruZ™"^"™;- "' *' -^^ "' *" oppo^'^ *-««™^ or ootd, upon one conductor. With the exception of the arrangement of contact.point3 and their respective local connections with the leve,^ N and N and amaature a by means of which the latter controls the loc^ cir the J. "?'""'' *""' '°'""^''' ^' "■"* S" 'l'^ constriction of the receiving instrument is precisely the same as that used in the quadruplex system, which we have just considered, and which is fully described on page 824. As shown in the figure' Ae con tact-leveiB N and N, of the receiving instmmenlTm fi::^ upon suitable fulcrums at their lower ends, while their f^e S TXZ 1 ''''' "«'/?"'«»-* *"« adjustable contact ^'^'nS « ?. by the tension of the adjustable springs rr,. A contact point IS upon the upper extremity of the contact leveTN^ 1 everT Th?^ T?''''' * eori.sponding position 'upon am a„ which ,s ngidly attached to the armature a, to play between the stops „ and „, upon the contact levers, w4h limU aZT^Jl "^l ""''"'' '"'""P' "* «"* "»^« ^ ^l-o a™"'"™ sprinT.r ™ rr ""'l' "" °™™"»^ "'^ '■^t™'""'' i"^ of sol^L ^°''*' ""'" " *"^"^^ '^■"»* tl^^ adjustable .n J^ ''T?^'°'' ''V^^ ^'^^ independent transmitters or keys K, Hp«1 ' !. . ''x'^''^ '*^*^^"' ^^^"^ "^^^ *° f««^ different elee- S Xtr^^^^^^^ !:ri^^.^_^^!r^ *« ^'^^ -p-t- positions each other, as fol tuwH : 880 QUADRUPLEX TELEGBAPHY. 1. First and second keys both open. This is the position of the apparatus shown in the figure. In this position of the keys both main batteries are in eft-cuit, sending to line a positive or 4- current of4-B-|-3B = 4.4B, 2. First key closed and second key open. In this position both main batteries are also in circuit, sending to line a negative or — current of — 8B — B = — 4B. 8. Second key closed and first key open. In this position the smaller of the two main batteries only is in circuit, sending to line a positive or -|- current of a strength of -|- B. 4. First and second keys both closed. In this position the smaller battery only is in circuit, sending to line a negative or — current of a strength of — B. At the distant terminal of the line L, the apparatus is arranged precisely as shown in the figure. It is essential that one sounder (for example, S^) should respond solely to the riiovements of the key K^, and the other sounder, Sg, in like manner to the movements of the key K^ ; while both should respond when both keys are simultaneously depressed. The manner in which this result is accomplished will be understood by the following explanation of the effect of each of the above mentioned electrical conditions of the line upon the receiving instrument 1. Positive current from both batteries (4- 4 B). The local circuit of sounder S^ is open between the point o and arm a^, and that of Sg between the lever N^ and the stop jj, because the action of the current upon the armature a, tending to attract it toward M^, is strong enough to overcome the tension of the spring r^, and force the lever N^ against the stop y^. 2. Negative currents from both batteries ( — 4 B). The local circuit of sounder S^ is closed at the point of contact between arm a^ and contact lever N ; but that of sounder Sg is broken between the contact lever N and th - stop q^ because the strength of the current upon the line is so great as to overcome the tension of the spring r, and force the lever N against the stop ^, DOUBLE ACTING RELAY. tsi S. PMitive current from batteiy B onlv(4- Bl IT, , , ' ^^ »ot Aom the st^p7 ^" '"""^ '' "'"» ^"^ ^P'^-'e the lever N electrical conS^orlfThrre!"""''""''"^^*''''^""'^-"' When the armature is in either nf u. ^ ^ local cu-cuit of the sounder s;*b™ken meTr'*'""*^ passes directly over from nn.L! °""^™'. When the armature oou^e, closes trioTZlr'''"'''"" *" *° °*^'' ''• "« An mdependent condenser is armna„r„ I poles in connection with the n^in CT J f "1" '"' °* "^ the artificial line A ^ *■"* ""^ °*''^'' ^«' ^^i cu^'ufrth: Slrif: "-"^'^r ''^ "^^ ™'«-^ on each sida ° '*""■ '^ ™bstantially the same the'i^siZ:::! treTrrvM^'r' ^"«°"' »^^""« -''" condenser, vhwh rem wL ^" T """ """^ '='«"-e«« the takes place up:n triin^ itft .V^n^vTt " *" ™™"' , in^r..ntij diHuhargea itself and 532 QUADBUPLEX TELEGRAPHY. sends a momentary pulsation through the electro-magnets M M^y thus tending to hasten the action of the receiving magnet upon its armature at each reversal, thereby improving the signals upon, long lines. The eflEective action of this condenser may be much increased if desired, by augmenting the resistance of the helices M M^, or by inserting additional resistances between these and the junction of the wires leading to the condenser on each side. The double acting receiving instrument here described, and shown in the figure, is equally serviceable in connection with the arrangement of main batteries illustrated and described on pages 314 and 318. The apparatus has been tested in practical service upon all of the longest circuits on which the quadruplex system is worked from the Western Union Telegraph Company's New York office^ and continued in constant use for one week on the New York, and Albany circuit with very satisfactory results. In regular practice, however, it has been found preferable to use two inde- pendent relays, thus enabling each operator to adjust his own instrument. On February 7, 1877, a test was made on a direct circuit between New York and Chicago, via Pittsburgh, Pa., a dis- tance of 913 miles, and the simultaneous reception of two com- munications in the same direction was accomplished at a speed of thirty words a minute on each of the respective sounders Sf and Sg. Fig. 152 shows a general plan of the quadruplex apparatus now in use on the lines of the Western Union Telegraph Com- pany, and which embodies the more recent improvementa The transmitting devices, both in construction and mode of operation, are precisely similar to those referred to in connection with fig. 151, so that it will be necessary here to refer only to the effect produced by the operation of the two independent transmit- ters or keys, which is as follows : 1. Key Kj and Kg both open. In this position the entire battery is in circuit, sending to the line a negative or — current of — 13 — 3 B = — 4 B. IMPROVED RELAY. 333 2. Key K^ open and Kg closed. In this case battery B only is in circuit, sending to the line a negative or — current of 3. Key K^ closed and Kg open. The entire battery is again in circuit, but in this case with the positive or + pole to the line, sending a current of 4- 3 B + B = 4- 4 B. 4 Key K^ and K^ both closed. In this position the battery :8* B only is in circuit, sending to the line a positive or + current of + B. ^ Thus it will be understood that the line is caused to assume four distinct electrical conditions, corresponding with the four possible positions of the keys at the transmitting station. The receiving apparatus consists of two sounders, S^ and Sj, .. _ Li !.^ rviajn i«.j ana j-v^. iuuconsiruction oi li. 384 QUADRUPLEX TELEGRAPHY. is the same in everjr particular as that heretofore described • it being, m fact, simply a polarized relay capable of responding to positive and negative currents. The relay Eg, however, differs materially from relay E^ in the arrangement of its local circuit connections, by means of which the sounder S3 is operated ; and the improvement upon the form of relay heretofore used consists chiefly in dispensing with one of the supplementary contact levers, whereby the apparatus is not only simplified, but made to work with greater f acihty and certainty through long circuita The normal position of the apparatus, when neither key at the transmitting station is depressed, is that shown in the diagram. The manner in which the relays E^ and E^ operate in each of the four electrical conditions of the line mentioned, so as to muse he sounder S^ to respond solely to the movements of key Ki, and the sounder S3 in like manner to the movements of key K^, and both in respdnse to a simultaneous depression of keys Ki and K3, will be understood by reference to the following explanation: 1. Kj and K^ both open, A negative or — current from both batteries (— 4B> The local circuit of sounder S^ is kept open, because the polarity of the line current tends to hold the armature h of relay E^, on its back stop p. The local circuit of sounder S3 is also open between armature J and lever r, because the current on the line is sufficiently powerful to over' come the spring r^, and hold armature / against stop 0; thus sounder S3 remains inactive. 2. K^ open and K3 closed. A negative or — current from battery B only (— B). The local circuit of sounder S^ re- mains open between stop p^ and armature h, because the polarity of the current is such as to hold the latter against stop p. '1 he action of this current upon relay E, is to cause its arma- ture y, assisted by spring r^, to move to the left and make con- tact with the lever r, but not with sufficient force to overcome the retractile spring q^, thus leaving armature / in a central position between stops o and Oj, thereby closing the local circuit and operating sounder Sg. IMPROVED RELAY. 336 3. Ki closed and Kg open. A positive or + cun-ent from both batteries (+ 4 B). This current causes the armature h of relay E^ to move to the left, thus closing the local circuit at stop p^ and actuating sounder S^. The armaturey of relay Rj, is also strongly attracted toward the left, pressing against the yielding lever r with sufficient force to overcome the spring q^, and press the former against the stop o^, thus opening the local circuit of sounder Sg. 4. Keys K^ and K^ both closed. Positive or + current from battery B only (+ B). Relay R„ which is arranged to close Its local circuit by positive currents of any strength, actuates the sounder S^ precisely as in the third case. The current upon the line in this case is not of sufficient strength to hold the armaturey of relay Rg against stop o^; consequently it moves, together with lever r, assisted by spring ^,, to a central position, thus closing the local circuit between armature j and stop a through lever r. thereby operating sounder S^. When the arma- ture; of relay Rg passes directly over from one extreme position to the other: for example, from stop o to o^; it will be observed that the local circuit is closed for an instant, but not long enough to produce any effect whatever upon the lever of sounder Sg. It is therefore obvious that, with the apparatus as arranged above, two communications may be simultaneously transmitted over a single conductor, and the signals recorded' with facility and accuracy. In order that four communications may be made to pass simultaneously over a single conductor, it is only necessary to combine the apparatus here described with any one of the several known methods of simultaneous transmission in opposite direc- tions. The aiTangement in general use for the accomplishment of this purpose upon the Western Union Telegraph Company's lines is that known as the differential method. A system 'of duplex telegraphy known as the bridge method may be used instead of the differential, or, instead of either of these, a com- bmation of the differential and bridge methods. In practice the latter has been found preferable, more especially on the longer S36 QUADRUPLEX TELEGRAPHY. circuits, where the signals have to be retransmitted automatically over an adjoining circuit, in which case it is absolutely essential that the signals should be recorded perfectly at the repeater station. The last named plan is in operation on the New York and Ohicago quadruplex circuit, arranged so that signals from New York and Chicago are at Buffalo automatically retransmitted in either direction. Before considering the arrangement for repeat- ing from one circuit into another, however, it will first be well to describe the different instruments more in detail than we have yet done. A few words also regarding the setting up and adjustment of the apparatus will not be out of place here. DIRECTIONS FOR SETTING UP THE QUADRUPLEX. The diagram, figs. 149 and 150, will sufficiently explain the manner in which the instrument should be set up and connected. The smaller section of the battery B usually contains about one third the number of cells that the larger section 8 B does. The rheostat z should be as nearly as possible equal to the internal resistance of (B-|-3B)=4B. The resistance of y should be equal to the internal resistance of the portion 3 B of the battery. THE DOUBLE CURRENT TRANSMITTER. This is represented at T^ in figs. 148, 149 and 150, and is operated by the key K^ and a local battery e^, usually of three cells. The double current transmitter is sometimes constructed as shown in fig. 153, but a simpler and far better arrangement has been recently introduced, which is shown in fig. 154. The draw- ing is an end view of the transmitter, and shows the pole changing apparatus distinctly. The adjustable contact screws a and a^ are supported by and are in electrical connection with the post P, which is in turn connected with the line wire. The post also supports two contact springs S^ and Sg, which are insulated from it and connected by wires 1 and 12 with the zinc and copper DOUBLE CURRENT TRANSMITTER 337 poles of the main battery, respectively. The lever t, of the transmitter is connected with the earth. The proper adjustment of this transmitter is a matter of the Fig. 153. greatest importance to ensure the successful working of the apparatus. In order that it may follow the movements of the Fig. 154. key with promptness, the play of the lever t^ between*fts limit- ing stops near the electro-magnet should not exceed ^ of aa mch. The contact screws must be so adjusted that at a point 388 QUADRUPLBI TELEGRAPHY. about midway of the stroke of the lever t^ the springs S and S, will both be in contact with it at the same time, but for the shortest possible periv^d- The easiest way is to first temporarily adjust the upper limiting stop at the opposite end of the trans- mitter lever t^, so as to reduce the play of the lever to ,V of an inch, or about half the ordinary distance allowed for a sounder. Then gradually raise the contact screw a until the spring S^ barely touches the lever ^«. Hanty of the ou„en, and the oth^r by c^nges^ti: Z^7;Z!Zyt " "^"""^ ''^''" electro-magnet T., lo.^ Of the po.a„ty of .. ^^.^l^ ^^ fearrS Station, A. StaUcn B. %. 158. ~eotstf tn^K'rafSrr "°^'^^"^"'« *° «>« .f.r4^^^dldt7eTlhSr'• - '-- four t,mes as great as that of the line A W K L ^ w.th the line in such a manner as to shut th'e ^hCaTxt Circuit of nmn.f;naiu,«< •.__- , ^"'' ine rtieostat A. by a ^"~ '''-^ ^"^ ^^^isuiuce each time the key is depressed. r 848 QUADBUPLEX TELEGRAPHY. ^Illlllllllllllll^ COMBINED DIPLEX AND CONTBAPLIX SYSTEMS. 349 thus shunting he S X .nZ " T*^' 1*'' *''^ ''"P ''• The o.d™.;oo„tae\7S t fe7a? '^n3^ ,1 r™ ^ ^me, strikes upon its anvil, and doL^hH^'^ft:^ Z focal r:jt;f Xtt^L" '■ -' «■- OupHcates'thti^:,' ar^trrdtdrusirriLf^Tpte?^^^ Sr^u *f'thr'""f 'T™^"'B» opens and closes the local cmmt of the sounder S„ m the ordinary manner The sCnd'uoTo"^ "■ ffi *' """"« i-trnment'^R,, should L rettrT^erShrrCst:?'""' ^^ ""r'" "^ -tion, while i! wi., be e^^L? ;;iTra:d":; the hue current, which results from the slfunting o7 the rheltTt Changed, and consequently its armature has no tendency to fall off when the current is reyen,ed upon tl,. line ^ It IS obvious that any required number of receiving instru mente similar to R„ accompanied with the other apparlTus of he hue at way or intermediate stations, all of which w" Zlt^t' "^^'^'" " ''' ''"''' ^'™" '' ''' '^y^' »" Kg. 159 is a modification and extension of the system so arranged as to be «ipable of either transmitting ^0;™ fl the keys K, and K, are operated at the same time, the 350 QUADRUPLEX TELEGRAPHY. former will control the polarity and the latter, the strength of the current going to line from the battery E. At the terminal station B, as well as at the intermediate station 0, receiving instruments K^ and R^ are made use of, the construction and operation of which are fully described on pages 838 and 340. The polarized armature a plays between two contact levers JN and Ni, which are held against the stops q and q^ by springs r and ri ; these springs being strained up to a tension sufficient to resist the electro magnetic action of the weak current, which traverses the line when the rheostat X^ is put in circuit by the opening of key K4, but which will readily be overcome by the stronger current which passes when the rheostat is cut out, by the depression of key K4. The local relays M M, between the receiving instruments R4 and R5, and their respective sounders S^ and S5, at stations B and C, when arranged in this manner, is a well known device for reversing the signals of the relays, in order that they may appear correctly upon the sounder. Thus it will be understood that the sounding or recording instruments S4 and S5 at stations B and C, will respond each time the key K4, at station A, is depressed, while in like manner the sounders S^ and S3, at stations B and C, will respond each, tune the key K^, and transmitter t^, at station A, is operated The rheostats X, X3, and X4, are cut 01. S of the circuit when the operators at the respective stations are not using the line by means of the switches W^, W3 and W4, precisely as in the case of the ordinary closed Morse circuit In order to transmit communications in opposite directions at the same time, the operator at station A will use key K^, and the operator at station B or C will use key Kg or Kg. With the apparatus constructed and arranged as in fig. 159, the operation may be briefly summed up as follows : When key K^ is operated sounders S^ and S3 will respond. When either Kg, K3, or K4 is operated by first opening the switches attached, sounders Sg, S4 and Sg will respond COMBINED DIPLEX AND CONTRAPLEX SYSTEMa 361 It Will, therefore, be readily understood that the followino- results may be obtained : loiiowing 1. Station A may send a message to C, and C at the same time send one to A, fcoth of which may be read at B one to aT.w ^?T^^ *° ^' ^"^ ^ ^* *^« '^^^ time send one to A, both of which may be read at C «Pr!i ^ T^f ^d,\°^f ^'-'ge to C, and at the same time B may send one to A, which latter may also be read at C A ""^^/^^^ ^ "message to B, and at the same time C mav send one to A. which latter may also be read at B ^ Uh , ^"T- ? ""^^ simultaneously send messages to B the latter of which may be read at A ul \ ^1"? ? ""^^ simultaneously send messages to C, the latter of which may be read at A. 7. A may send messages to B and C at the same time. » A may send two messages simultaneously to B, both of which may be read at C. . J' "^ ■". "oza ot 9 A may send two messages simultaneously to 0. both of which may be read at B. ' ^ 10. B and C can work together singly precisely as in the ordinary closed circuit, Morse system ; and 11. When it is not required to work duplex, A can signal B or C with either of his two keys. ^ All the results which have been described are accomplished Fig 160 represents a combination of the above system with the quadruplex at a common terminal station, at which the connections are so arranged as to allow of the repetition of signals from one circuit into the other. ° Taking an actual case, as before, we will suppose the repeating apparatus to be located at New London, which, for convenience Z Yot^f2^^" Tr ^l- "^'^ '^ ^^ communication with New Yoik 126 miles distant, by a quadruplex wire L, and with m length, the former being an intermediato and th^ latter a 352 QUADEUPLEX TELE&BAPHY. terminal office, which we will designate respectively as stations B and 0. . i x 4. ^# The api^ax? us lu station A consists of a complete set ol quadru-.u-k in. laments and a set of the instruments shown m fig. 168 both of which have already been described; conse- quently,' it will only be necessary now to show the manner in which they are worked conjointly. -S-E Fig. 160. The switeh or button ». is bo pW between t"^^ teries B, and e„ that when dosed it forms a par of eadi of the to local circdte eontaining the sounder S and tr— er ^ but when open the separate oiromts are combined mto one , and a LI key I be closed, the relay E. then operates both sounder COMBINATION or QUADRUPLEX AND DIPLEX SYSTEMS. 863 S, and transmitter t,, and thus repeats the signals coming from line L into hneLi, and to stations B or 0. The local circuit containing the sounder s, is, in a similar manner separated from or combined with that containing the transmitter T, bj means of the button W,. In th< utter case . relay r, operates transmitter T, as well a. sounder .„ and th^by i-epeats the signals from L, over line L to New York" The sounder S,, which is operated by the r "lay E, of line L may be arranged in connection with wires 1 and 2 and button w^, so that when the latter is closed and ' , opened the shunt around the rheostat X is thereby exteudeo rid It A read aflald C.""^' ""' *° ^' ^ '^ ^«" ^»^' -<• '«"' -- , 3 New York may send to, C, and be read at A and B Tt A and G ""' ^ """' ""^ '° """^ ^°^^' ""-J ""'^ 4 New York may send to B, and be read at A and while C may send to New York, and be read at A and B ' 5 New York may send to B, and be read at A and C wh,le also may send to B, and be read at A and at New York 6 New York may send to C, and be read at A and B and N^w Yo'r '""' ^ "'^ "''" '""' '" ^' "■«* *>« '^ ^' ^ 7. New York may send to B, and be read at A and C and Ne!VT *""' ^ "^^ "''" '""^ *" ^' =""1 "^ '^ »' C and if 864 QUADRUPLEX TELEGRAPHY. ,i|| 8. New York may send to C, and be read at A and B, and at the same time A may also send to C, and be read at B and New York. 9. New York and station A may work duplex continu- ously, without regard to what is passing between stations A, B and 0. 10. New York may send two messages simultaneously to A, one of which may he read at B and C, and at the same time two communications may pass over the line to New York, one from A and the other from C, the latter of which may be read at A and B. 11. New York may send two messages simultaneously to A, one of which may be read at B and C, and at the same time two may pass simultaneously over line L to New York, one from A and the other from B, the latter of which may be read at A and C. « 12. New York may send two messages simultaneously to B, both of which may be read at A and C, and at the same time receive two from A. 13. New York may send two messages simultaneously to C, both of which may be read at A and B, and at the same time receive two from A. 14. New York may send two messages simultaneously, one to A and the other to C, the latter of which may be read at A and B ; and, at the same time, receive two, one from A and one from C, the latter of which may be read at A and B. 16. New York may send two messages simultaneously, one to A , the other to B, and the latter be read at A and C ; and, at the same time, receive two, one from A and the other from B, the latter of which may be read ai A and 0. 16. New York may receive two messages simultaneously from A, and, at the same time, transmit two distinct communi- cations, one to B and one to C, or both to either station sep- arately, and both may be read at A. Finally, 17. Station A may, by properly arranging the buttons w^, w. and Wi, divide the two lines L and L^, and operate each QUADRUPLED REPEATEa ' «,. oOO - to ^peat from one inTThe „th"r 'w!""^ f """'^ ^ station to be Cleveland, and thatT ^ *'" '"PP"^ *« wire extending from tCZIn^l il"^"^ * quadraplex "iles, and L, ^ simL tt'tteen n "'?' "i '"^'^™<' "^ ^^^ adistance,of250miles ™?, '*'''*<"' C'«™'»d and Cincinnati, to two complete ZofoZlT"^ """P™^'' '" «'*tion switches, W, W,, W a"d w 't™'"™'^ *' '"^ '"'"°" through com'mun'ii betwi'n' bJmo""', ^ «'™8 *-' d.vidi„g the wes and thus IlTowing 1 °h „?th Tl""' °' '"^ separately. ^iowmg each of them to be worked i»« the artificial hrh:rbt::m-r'^"'"™'^"--'^^^ bmed with those of transmitter^ Jt^T^Tr °'-~'"- by means of the buttons W, W W \„d w " '^^P^'^t'^Iy. same as that shown in fi.T iw *" ^"' "^a- '^ precisely the ^t::!ST1^'^^^^^^ ^- one .uadru. said! z :tt brnsr:;t or ^ "-;' ^-^ ■'^-^^ "- *, and ., closed, Bui^I ra; ^^H "/*» '^'^^ ^" ^" simultaneously over the line 1 m ■ . «"n»"n«=ation8 then be auto^ically "t "nsm^Ld ^n'^^V^^'^ ^^^ «" fitter T„ the other bv rekv ? '1'. ^ '^^''^ ""■ ""^ trans- to Cincinnati. The htL Ltlon "?' "^^ ^=' °™^ ""^ L, pendent messages at h same le?"r, °, """'"" ''<> '"<'<' they will be ^tr.n.XZ.TCtZTf\ f "^' ■" *""' and the other by relav R -.Jl 7 ^ ' ™'' transmitter / , Buffalo. ^ ^ ' ™'' transmitter t„ over line L, to By simply closing the buttons W, W w „„j w .,. ci^uits may be divided at Clevela;d'^a;d'^:ored''s:p^:^r 1 • 356 QUADRUPLEX TELEGRAPHY. Mg. 161. Q^^DRUrMX REPEATER 357. In regular practice, however, the circuits are worked in thr. foT • Wh ,^"°°' ^' """^ ^» ""^ "^o^ and W and W onenM When thus arraneed Biiffnln on,] n- ■ .• » opened. together duplex ^^r"fl°™'^<^™»"*'^ enabled to work The transmitter (. and rew" 'fl^ ?""""'*" °™' ""^ ^»- desk or table with J^Tl 2 ' "^ '° ■°'='"«' "" *« Quad^piex repeate. TZ^:Z^ CZZ., A combination of the two niethnrl^ r.f /i i "^'^"/;^®^^^' known as the bridge and diCnt a TysS^f S'"' matenally in aTangement from that showTon pL gP f?,^ used m practice AfR„fl?„i ^ ^"'" "^ page rfii is also these pointa ^' ^'°^^^ '^'^^' between A second wire between New Yorlr m^rl ni.,-^ are sueh tha while its office and Chicago are working dunJ, - one s,de, the latter may also work duplex on ?he ofhertde with any one of two or more branch offices in New York The ~l2V ^ 7'"^ explanation, which relate to the for the Chicago hue, however, is just the same : Iff* 858 QUADRUPLEX TELEGRAPHY. i . The complete quadruplex set in connection with the line L is supposed to be at the New York main office, sounders 5^ and S4, and key h^^ at a branch office in the city, which we will call station A ; and the apparatus consisting of sounders s^ and S3, repeating relay wig, key k^ and local battery 64, at a second branch office, which we will call B. In order to provide for the simultaneous reception of two independent communications over line L, from Boston, one of which shall be received upon relay E^ and sounder S^, and, at the same time, also, upon sounder s^ at station A, and that the other shall be received upon relay K3, sounder S3 and upon sounder Sg at station B as well, while separate communications are at the same time being sent to Boston from each of the two stations A and B, it is only necessary to connect the local or branch lines with the relaja and transmitters of the quadruplex apparatus at the main office in the : lanner shown in the diagram (fig. 162). Here the route of the local or branch wire of the relay E^ m.ay be traced from the earth plate G^, at the main office, to battery e, wire 1 aad armature of relay E^ to sounder S^, and thence by wire 1^ to sounder s^ and earth G-g at station A. The route of the branch circuit of relay Eg is from earth plate Gg to battery e^, wire 2, armature of repeating sounder M and sounder Sg, and thence by line I3 to sounder Sg and earth G4 at station B. The routes of transmitters T^ and Tg may be similarly traced. It will be noticed, however, that the arrangement of the branch line, as well as local connections of transmitter Tg, differ materially from those of T^, as in its nor- mal position the former should remain open, and thus leave only the smaller portion of the main battery on the line. The keys Kg and k^ are not provided with circuit closing switches, and contact is made at the back point, instead of the front, as in the ordinary form. The normal position of these keyi is that shown in the figure, in which they close the branch circuit and cause the armatures a and a^ of repeating relays m^ artd TWg to be attracted, and thus break the local circuits of transmitter Tg at the main office, and sounder S3 Pt B. By depressing Kg or ARBAJSTGEMENT FOR BRANCH OFFICES. ^5^ *3, and consequently breaking the branch circuit, the armatures of the repeating relays m^ and m^ will be rele- sed, and the local circuite of transmitter T^ and sounder S3 will be closed simultaneously. The operator at B is thus enabled to hear his own or other signals that are being transmitted by the main or other office on the branch line. EDg. Fig. 162 It w:ll therefore be sufficiently obvious that the signals received from the line L upon relay R, and sounder S, at the mam office can, with equal facility, be read from sounder ., at station A while the latter office at the same time may, by depress- ing the key ^j, and consequently operating sounder S, and tmnsmitter T, be sending signals to Boston or to some branch office at that place. In a similar manner and at the same time •dlw sea QUJLDBUPLEX TELEGRAPHY. station B may work duplex witK another branch office at Boston, of which at that place the.-e are five on one side of the quadru- plex and two on the other. The balancing and adjusting of the quadruplex, it will, of covirse, be understood, is all done at the main office. Fig. 163. The quadruplex is also arranged to work in connection with a single direct circuit containing any number of offices, and the plan has been found to servo an excellent pui-pose in practice, as communication can thereby be maintained between a distant QUADSHPLffiC AND SINOLE OIBCUIT COMBINATION. 86], t^r^et^tr'^^ "'"""' ""^ ™^ °"^ °^ *" »™^» 0" Fig. 163 shows the details of the arrangement as adopted at ol^th e fr*"™"""^ "P""""« ^"» °- circuit into the oth.r, he outfit consisting of one complete set of quadrapW apparatus and portions of a Milliken repeater. The line lII tendmg to Chicago, 280 »iles distan^s connect with th" quadruplcK relays; and line L„ extending to ZansT CiV Atehson Leavenworth and St. Joseph, witt the Sen '^ nled JZrf 7T' °' ""' "■"'"y '^ '^P'''*"'d f™» or con- nected with that of the transmitter T. by means of the switeh W m precisely the same manner as in the precedingTas^ and by means of the switch W„ the local circuit of rflay E ' may be extended through the transmitter („ or di connTctrf herefrom at pleasure. With the switch W, turned 1070 right IZTr'^ir ''T '" *" «e™' "^-^ 'oc-l circuit may be terv F b f r,T ^V *™°'' ^^ "™ ^' ^o'"'Jcr S. and bat- S. 't?^ '"""'""'■■ "S™- When it is turned to theleft battery E and transmitter t, arc thrown out of circuit and relay front end of transmitter <, are shunted out when desired bv means of the button or switch », ; and the main cont tpoin^ at the opposite end of the lever are in like manner cut out bv meana of button W. When,, therefore, the switches W ^ and J are open W, turned to the right and keys K, ^ni^' closed, as shown in the figure, Chicago may exchange Cness with any one of the oflices on L„ the signals being automati^llv i*ansm,tted at St Louis by lelays R., r, andlansmiSf and (,. At the same time St Louis and Chicago may also work duplex, using key K, and E, for that purpos; By closing .witehes W„ u;, and W and turning W, to the fcfr,_a,„ two hues L and L„ as will readily be len, nl be Jon.cd separately, the former as a quadruplex and the lattTr a^ a 6inglo Morse circuit 862 ABRANQEMENT FOR NEUTRALIZING CURRENT INDUCTION. CURRENT INDUCTION. The interference between well insulated telegraph lines, known as current induction, has from the first done a great deal toward preventing the proper working of the quadruplex system, and the question as to how the disturbing effecte due to this cause might be overcome has, therefore, become one of considerable importance. . ., Mr Charles H. Wilson, of Chicago, who has given consider- able attention to the subject, has devised a plan for diminishing the difficulties just referred to. Mr Wilson seeks to accomplish his object by establishing a counter current in the disturbed conductor at the same moment and of the sii me strength and duration as that of the induced cur- Mg. 164. rent which is generated in it by the sudden change of potential in a neighboring wire. . , • i tvt Fig 164 shows the application of the method to a single Morse line but here it is of comparatively little practical importance from the fact that these lines, as a general thing, can be supplied with strong cuiTcnts, so that there is always sufficient worlang margin to cover the difficulties arising from induction. The primary wire of the induction coil C is in the circuit of one line and the secondary coil in that of the other. The coils are so wound or connected to the lines that either will induce m the other currents of opposite direction to those induced by the remaining parts of the circuit. The electro-magnets represented at a, a\ b and 6', are employed for producing the proper retard- ing effect on the counter or neutralizing currents which are generated in the coils surrounding C, and the adjustable resist- INDUCTION BETWEEN PARALLEL LINES. 868 ZZ^,^ °1*' t""' «'^"' ««nre to still further modify these ~ of », pouHt, is .entity, jjrxrc;:'^? ■Fig. 165. :teTtif;ttetL\vt:t tt*^ "-^ "• --^-^ '^ "^ cun^nt will Jo be indu3i^ the lil t Tt •"*""' ' """'"^ as the oo,=aeetion is so arlld th,? .^ " " ^ '^' ''"^' i>o arranged that this current opposes that zaiE J^. 1B6. e proper action of the instruments will not be disturbed ae ena m view, is to cause the two artificial lines to act I! 864 DOUBLE TRANSMISSION IN THE PAME DIRECTION. upon each other in a manner similar to the action of the actual lines, and for this purpose an induction coil and system of mag- nets, similar to that just described, is inserted in the path of the two artificial lines at I. Fig. 166 shows an arrangement of condensers substituted for the induction coils, which has been in extensive use on some of the long lines in the central division of the Western Union Telegraph Company. If the inductive effect of the two wires are equal, the condenser E is alone necessary to effect the neu- tralization; but when unequal, the two condensers F and (x are required in connection with E, EARLY METHODS OF SIMULTANEOUS TRANSMISSION IN THE SAME DIRECTION. In October, 1855, A. B.ernstein, of Berlin, devised a plan for the simultaneous transmission of two messages in the same direction, which is shown in fig. 167. ' The transmitting apparatus consists of two independent cir- cuit preserving keys K^ and Kg in connection with batteries Bi and Bg, the former composed of, say 10, and the latter 20 cells, as shown in the figure at station A. The movements of these keys produce three different electrical conditions in the line, according to their respective positions with reference to each other, as follows : 1. First and second keys open. The route of the circuit may be traced as follows: From the earth plate G, through wire 6, adjustable stops 5 and 4, wire 3, to adjustable stops 1 and 2 and line L. This may be considered the normal condition of the keys, in which position no current passes to the line. 2. First key closed and second key open. The route is from earth plate G to wires 6, 7, main battery B^, thence to lever l^ of key Ki, and wire 3 to stops 2 and 1 and line L to distant station as before. In this position of the keys the smaller battery B^ only is in circuit, sending to the line a positive or -|- current of -f- 10. • . 3. Second key closed and first key open. The route now is bebnstein's methods. 855 f^r/°j! If *l^: "'^'' '" ''°F^ ^ »■"* * ' *«»=« by wires 8 ae keys the larger battery fi, only is in circuit, sending to line a positive or + current of + 20. ei^uif^'tv** ''""'' ^^' '"'* '^'P'''^"^ The ™ute of the r W r' '' "■" '"■^'^ P'""^ «■ ™« «. 7, to battery -Ba, iever ;, ; thence to stop 4, and wires 3, 8, and battery ute now IS %. 167. B, to lever l„ wire 9 to stop 1 ; thence to the line L and distant station as before. In this position of the keysboth batter.^ are m circmt, sending to line a positive or +' „ At station B a receiving instrument or relay is made use of •Ki, Kg and R„ to each (,f which are attached retractile sprinirs r r and . respectively, with local circuite and sounders I ana fcg, as shown m the figure. ^ 866 DOUBLE TRANSMISSION IN THE SAME DIRECTION. Sounder Sj should respond solely to the movements of key Ki, and sounder S3, in like manner, to the movements of key Kg, while both should respond when keys K^ and Kj are simultaneously depressed. The manner in which this result is attained will be under- stood by reference to the following explanation of the effect of each of the previously mentioned electrical conditions of the line upon the receiving instrument M at station B : 1. The normal condition of the transmitting apparatus. No current to line, 'J'he local circuit of sounder S^ is open at point 0, armature El being held against its back stop by the retractile force of spring r^. Armature R, is, in a like manner, held against its back stop. Armature B3 rests \ipon its back stop, owing to the retractile force of spring rg, in which position it will be observed that a local circuit is completed, in which are included sounder 83 and both local batteries, but as the two latter have like poles together, their effect upon sounder S3 is substantially neutralized ; con- sequently, the latter remains inactive. - 2. Positive current from battery B^ only = -f- 10. The local circuit of sounder Sj is closed between the point o and armature Ri, because the actir»n of the current upon the relay M is strong enough to overcome the' -spring r^, and force armature E^ against the stop o. Armature E3 remains on its back stop, because the power of the current upon the line is not sufficient to overcome the tension of spring r^^. Armature Eg rests upon its' back stop because the current is not strong enough to overcome the spring r^. As in the first case, it will also be observed here that armature Eg, in this posi- tion, completes a local circuit in which is included sounder Sg. The latter^ however, remains inoperative, for the reasons before explained. 3. Positive current from battery Bg = + 20. BEKNSrem'S 1U.TH0DS. gg. The local circuit of sounder S, is closed between the contact point and armature B„ because the power of the line cu^nM» sufficen .oove.com,. the spring r„ and move the 2.131 stop, because the cun-ent upon the line is not of sufficient stanch to ove«=omc the tension of spring r. In onler to prTenS ngnal from b<«ng given by sounder S„ it is obviously e^entill .n ths case, that armature K, should make contZ ^tl, h. point osimAltoneously with armature E„ b^ wT^^m"* Z Jrr!:%tt^-"- ^' '^ ^''°-— ' *>>- '=. t 4. Positive current from both batteries (B, and B,) - 4. 30 The current upon the line in this case is sufficientlf « +4i to overcome the tension of the retractile springs r, r andr and force the armatures R T> r,r.A n ■ =, .i-'a^^r,, front stons » nnrlT .■' , " "8"'"'" *''^"' respective iront stops o and o operating the sounders S, and S,. Thus will be understood the manner in which the respective a matures of the ..eeiving instrument are made to oasuTSd different positions with relation to the electrical condTtLn o the hue, so as to record the proper signals upon souidrs' Instead of the receiving ii,,-trument as devised by Mr Bern stem, V,. : a single electro-magnet, with three sepLte frma" tnres, of different adjustments, tlirec independent Sys may bt A second method was also invented by Bernstein in which he made use of both positive and negative currents ' Beferrmg to the diagram, flg. 168, it will be observed that tl,e ^nsm, te., or keys are ch-cuit preserving, the ske^h differ ng from the ongmal in form, but not in principle ^ eu rent upon the line, according to their respective positions with reference to each other, as follows • positions, ,%. ^a. IMAGE EVALUATION TEST TARGET (MT-S) 1.0 I.I 1.25 "^1^ Ml ■5.0 "^" in^s NlUu IE IM 1116 Photographic Sdeiices Corpordtion 73 WiST MAIN STRHT WEBSTiR.N.Y. M580 (716) 872-4503 'V'" A ^ 868 DOUBLE TRANSMISSION IN THE SAME DIRECTION. The route of the circuit, in each of the before mentioned posi- tions of the kejs K^ and K,, may be readily traced by reference to the drawing. Key Ki alone sends a positive or + current of, say, 10 cells from battery B. Key K3 alone sends a negative or — current from the same battery ==, — 10. When both keys are simultaneously depressed, the negative Fig. 168. pole of the smaller battery is insulated, and the larger battery ±$1 sends a positive, or -(- current =, -f 20. Bernstein's receiving apparatus, in this case, is composed of three independent relays, polarized by means of the auxiliary local coils Bi, R3 and R,, the two former being constant, and the latter controlled by the armature a, of relay M„, as shown m the figure at station B. The sounders S^ and S^ are opemted by shunting, instead of opening and closing the circuit •N. 'ned posi- reference i 10 cells tbe same negative Bernstein's methods. 869 battery osed of ixiliarj nt, and shown «ad of The strength of the current in each of the anxiliaiy local cir- cuits before mentioned may be changed at will, by varying the adjustable resistance coils r^, r^ and r^. It should noi, how-' ever, be of suificient power to overcome the tension of springs ^11 « and s. The current from auxiliary local E^, circulating in Mj, is, say, = + 10, and that of auxiliary local Eg, circulating in Mg, = — 10. That of relay Mg is brought into action only when armature a^, of relay M3, makes contact with stop 0, at which time a current of -f 10 circulates through Mg. Bearing this in mind, it will be readily understood by the fol- lowing explanation how the armatures o^, a^ and a^ of the receiving instruments M^, Mg and Mg, respectively, are made to assume positions, with relation to the three electrical condi- tions of the line, so as to cause sounder S^ to respond solely to the movements of key K^, and sounder Sg, in like manner, to the movements of key Kg, while both respond when K^ and Kg, at the sending station, are simultaneously depressed. 1. Ki alone depressed, a positive or -f- current to the line of + 10. The strength of this current, supplemented by that of the auxiliary local E^, is sufficient to overcome the spring s^, and move the armature a^ forward, thus breaking the shunt between stop P^ and armature o^, and leaving sounder S^ to be actuated by local battery l^. The action of the line current upon relay Mg, in this case, tends to partially neutralize the eifect of the auxiliary coil Ej ; consequently, the armature a^ is held more firmly by spring «, in the position shown. Armature a^, of relay Mg, also remains on its back stop Pg, because the line cun-ent (viz. : + 10 :) is not of sufficient strength to overcome the spring Sg. Thus the shunt around sounder Sg remains unbroken, and the latter is inoperative. 2. Key Kg, depressed. A negative or — current of — 10. In this case, the polarity of the line current is such as to partially neutralize the effect of the auxiliary local Ej. The armature a^ is, in consequence, held 870 DOUBLE TRANSMISSION IN THE SAME DIRECTION. more securely by spring s^ against stx>p Pi, thus preventing a signal being given on sounder S^. Armature a^ of relay Mg is carried from stop Pg to o, because the strength of the line current, viz. : — 10, added to that of the auxiliary local (— 10), is sufficient to overcome the tension of retractile spring 53, thus breaking the shunt, and causing local battery l^ to operate the sounder S3. It will here be observed that when armature a 3 connects with stop o, the auxiliary local of relay Mg is closed, the strength of which (viz. : -j- 10) being the same as that from the line, but of opposite polarity, it only serves to substantially neutralize the eflfect of the latter upon relay Mg, and armature a, is held inactive by the retractile spring Sg. 3. Keys K^ and Kg, both depressed. A positive or -j- current of -\- 20. Armature a^ of relay Mj is caused to move forward, thus breaking the shunt, and allowing a current from local battery l^ to operate sounder Sj. The line current in this case is of a polarity, and sufficiently powerful to completely neutralize the effect of the auxiliary local Rg and exert a force upon relay Mg, tending to attract its armature ag ; but the latter is held in the position shown, against stop Pg, by the retractile spring Sg. The armature a 3 of relay Mg is carried from stop Pg to stop Oi, because the line current is sufficiently powerful to overcome retractile spring Sg, thus breaking the shunt and permitting sounder Sg to respond. Practically, the method of using one receiving instrument having three armatures is a very unsatisfactory one, for the reason that the effective attraction of the electro-magnet for any one of two or more armatures is materially lessened whenever one of the others is in contact, or nearly in contact, with its poles. The" manner of operating a register, or sounder, by closing and breaking a shunt, as in the system above described, would render it impossible to receive and record the signals with accu- racy at any considerable degree of speed. BERNSTEIN'S METHODa 37* ous transmission in the samA .Ur^nf ' .^ ^^ simultane- and Siemens, in 1866 andTwch C ri - ^^ ^"^'^ insurmounteble. ^^ *^' ^^*^' ^^'^ considered THE ELECTRO-MOTOGRAPH. The salient feature in this discovery is the T.m^n.« r motion and of sound, by the stylus of Z Bain ll^ T '''' ^^ ment, without the in ervention of « ml "^/^^^ ^legraph instru. the motion thus produced anv of th. ? 'f "'^^*"^«- % printing or sounL^rslZnt o ^f ^^^^^«^«^« ^i telegraph making it possibti ":z:i " T "ri'^ "^^'^.^' *^- thousands of miles of wte ^fl^l i' ^'''* transmission over ing, delay, or Sc^ of-y W ''"' ^^"'' "^*^^^* ^-^^*' More than this, the apparatus operates in a hi^hlv .ff .• manner under the weaKest electric current rendewlf k? to receive and transmit messages bv lu^lT ^ ^""'''^^^ ordinary magnetic instrument ifcrn^^^ "7 ^'^^ *^^ mdication of the passage of electricity ZTZnlZ ^'" '" mstruments stand still, owing to thf fpi.1 "'^^j' *^« «o^mon platina, resting upon a atrip of moistened paper wul^f^ ™!^ Tlie spnng R is to draw the lever to the Uft .„^ point X. L is a main batter. K a kev Tht T"" ** battery is eonneeted to the p;int F^Thile the TaXt ° *'" connected to the metallic drum G, thriughle Xk VC K 872 THE ELECTRO-MOTOGRAPH. is closed, the chemicals with which the paper is saturated are decomposed by the passage of the current through the paper, and the lever rests against the point X, closing the local circuit containing the sounder AX and local battery LB. If the key K is opened, the normal friction of the platina point F upon the paper is so great that the spring R is insufficient to keep it against the point X, and it is carried forward by the rotation of the drum to the point D, where it remains until the key K is again closed ; then, by the passage of the current, the friction is reduced so as to be imperceptible, and the spring R easily pulls the lever against X, where it remains as long as the current is allowed to pass. As will be seen from this brief description, the Mg. 169. lever is moved backward and forward by a difference in frictions, caused by the decomposition of the chemicals (a solution of chloride of sodium and pyrogaUic acid), with which the paper is moistened, by the passage of the current. Why the paper becomes so extremely slippery on the pas- sage oJE the purrent, the inventor is unable to state. The apparatus is extremely sensitive, and can be worked over a circuit of two hundred miles with two cells of battery. Some idea of its wonderful sensitiveness may be formed from the statement that by employing a delicate construction of mechan- ism and using clock work to actuate the same, a movement of the lever has been obtained, sufficient to close a local circuit, THE POLARIZED MOTOGRAPH. 373 With a current that was incapable of discoloring paper, mois- tened with potassic iodide, or of moving the needle of an 3 - nary galvanometer. Unlike a magnet, no secondary currents are set up, upon opening and closing the circuit, to delay the movements of the lever ; neither ha. it cores to consume more time, in charging and discharging, but moves with a maximum effect instantly The plan shown m fig. 170 is called a polarized motograph. The key K alternately connects the batteries A and B to the lever of the motograph, one sending a positive and the other a negative current The current from the battery A passes to the Fig. ITO. point X, thence through the paper to the point G, up through « back to the other end of the battery A. Thus hydrogen is generated on the point F, which becomes slippery, while oxvgei IS generated on the point G, which retains its normal friction- hence the point G is carried to the right by the rotation of the druno^ If the direction of the current be reversed by putting on the battery B, hydrogen is generated on the point G, which becomes slippery, and oxygen on P, which retains its normal fnction, ana the lever is thrown to the left. The diagram is arranged merely to illustrate the principle of the invention. ^ In practice, a single battery and reversing key are used. 874 THE ELEGTRO-MOTOOBAPH. Mr. Thomas A. Edison, the inventor of the electro-motograph, states that he has a machine in operation in his laboratory con- structed upon the principle shown in fig. 169, with which he has succeeded in repeating automatic signals from one circuit into another, at the rate of one thousand two hundred words per minute, an average of six thousand letters, or twenty-four thousand waves per minute, compelling the lever A (fig. 169) to move backward and forward from the point on the left to the point D on the right four hundred times per second. By attaching an ink wheel to the extremity of the lever, opposite a continuous strip of paper moved by clock work, mes- sages transmitted at a speed of several hundred words per min- ute may be recorded in ink ; and by attaching a local circuit to the repeating points and adding a sounder thereto, as shown in the figure, the apparatus may be used as a Morse relay to work long lines of telegraph. CHAPTER XIL ELECTRIC CALL BELLS. The introduction of call bells or alarms, which have now be- come of such extensive application in hotels, factories, elevatore, and wherever else their service has been desirable, or where it has been found convenient to employ electricity for operating them, followed, as a matter of course, with the early introduction of the electric telegraph. The invention of these instruments may, therefore, be said to date as far back as that of the tele- graph itself. It will readily be understood that, whatever may be the sys- tern of telegraphy employed for correspondence between places distant from or near to each other, it is important, first of all, to have some means at command by which the attention of the correspondent with whom we wish to communicate may be ob- tamed ; and this, of course, for cases under consideration, includes the means of producing a noise of some kind within his hearing A wide field has thus been allowed for the exercise of man's constructive faculties ; and the devices which have been succes- sively introduced to meet the want have consequently been exceedingly numerous. Their general development, however, has been very much the same as that of the telegraph Prof essor Wheatstone, in his earliest telegraph experimente, made use of a call which was run by clock work, the movement of the latter bemg controlled by the action of an electro-magnet. Ihis seems to have been about the first really practical instru- ment of the kind introduced, and even it w'as not considered altogether satisfactory in its operation at that time. Since then however, the apparatus has been so much improved and simpU- lied m one way and another, and the various domestic uses to which it has been applied have given rise to so many different forms, that a knowledge of their details becomes desirable We 376 ELECTRIC CALL BELLS. have, therefore, thought it worth our while to devote a chapter to the consideration of the more important of this class of instru- ments. . The push button or key used in short circuits serves to close the latter in a very simple and elfectual manner. Its general plan wUl be mado apparent by reference to figs. 171 and 172. Fig. 171. The former shows the case T of wood or other insulating sub- stance, within which are secured the two metallic strips p and g, one above the other. In its normal state the upper strip is separated from the other by a steel or spiral spring. When, therefore, such a key is inserted in the circuit the latter remains open, but may be closed when desired by. pressing upon the Fig. 172. knob p\ which brings the points p and g together Upon the removal of the pressure the circuit is again opened by the re- tractile force of the spring. , ^.«. Various patterns of keys are made to suit the different pur- poses for which they are to be used. The form shown m fig. 171 is the ordinary one. Fig. 173 represents another form, used for electric door bells, in which the circuit closer is contained COMBINATION KEY& 377 within a hollow in the base, the latter being usually of marble and provided with screws for securing it wherever desired. Fig. 174 is a con venient form for combining a number of keys within a small compass; eight push buttons, corresponding to as many distinct circuits, are arranged at equal distances around a cylindrical case, within which the connections between the metallic strips and wires are made. Each wire is separately msulated by a silk covering, and the whole wound together into a single strand, where they leave the case. COMBINATION KEYS. With the keys above described it is evident that the signals last only so long as the button is depressed by the operator: it will also be observed that the operator has no means of knowino- with certainty that a signal has been given, and that he must therefore be still less sure of its having been noticed. To meet this defect, and provide a suitable arrangement for every require- ment, a special combination is needed, such as is shown in % 878 HJJLCtmC CALL BELLS. 176. This consists of a case containing a magnetic needle, an electro-magnet, and the metallic contact springs a b and c d. One end of the coil of the electro-magnet E is attached to the screw c, the other to the line wire by the insulated screw V. The spring a i is connected to the binding screw r lead- ing to the battery, the other, c c?, to the plate at e, b}> which communication with the line is made through the coil of the 6lectro-magnet. To the axis of the magnetic needle, A, is fas- tened a pin g, which presses against the platinum contact r, when the lower pole is attracted by the electro-magnet, and the needle Mg. 176. thus made to take up the position represented by the dotted lines opposite which, on the cover, is the word understood, or here. The axis of the needle is also in electrical connec- tion with the metallic back of the instrument, to which are attached the metallic plate p and binding screw q, so that all three are electrically connected. The small plate connecting with C, a and r is insulated from the back, and a spiral wire n m joins q with the binding screw e and coil of E. In its normal position the pin g rests against a stop not shown. The operation of the key will now be readily understood. APPARATUS FOR GIVING THE SIGNALS. iJ7^ Id !St!" ^""aI^ '" uT^'"''^ *^' current from C passes along ab andcrftoeand through the coil ofEtoV,thence to lineLandofher apparatus, where an audible or visible signal is to be givea ThI ZZtZ '''')Tf'' ^ '^ ^'^ elect,x,-magnet E,^ulg i^: former to pomt to the word here on the cover, enabks the opem tor to see that the key has properly performed its office. Auhe with r so that thecurrentnowhasasecond route through sprinf^s -and^,andthe„eedle remains deflected after thefinge^hafbeS withdrawn from B. Thus a continuous signal is given^until no^ IVu^l ""^^r '' " '"*^"^^^' ^^« ^^^" i-t-r-Pts the Dose wTw w ^. ^^ '"'^ "^^'"^ ^ ''' P^-^ided for the pur- fts norrn^ n V ^^^T^,*^^^ "^ '^^ ^^^°^^* *^« ^^^le return^s to f o l^it ol ' r^""*^"^ ^'"' '" ^^ described presently, is used needt ^V T''*''^^ '°"*^'^'^""^ *^ ^^^ ^'^ ^^^ement of the needle takes place as long as the circuit remains uninterrupted. APPARATUS FOR GIVING THE SIGNALS. The ordinary form of bells used for giving single taps is shown in figure 176. It consists of an electro-mag- net MM, opposite whose poles, ' n s, is placed the armature with its clapper, Jc. The latter, in its normal position, is held back from the bell G by a spiral spring attached to the movable •upright d, which serves to regu- late its tension. The stroke of the armature is limited by the set screw r. Another form devis- ed by Breguet, in which the pro- longation of the armature lever Fig. 176. 880 ELECTRIC CAL- BELLS. is a rather stiff spring, is shown iu figure 177. When such an apparatus is placed in circuit with a battery and one of the push button keys already described, a ringing tap is given every time the button is depressed. By combining a certam number of taps with proper intervals between them, it is possible tx) com- Mg. 117. municate words and sentences, and thus, besides being a simple call, the apparatus becomes a veritable telegraph. THE VIBRATING BELL. Tl e principle employed in this arrangement is shown in figure 178 MM are the coils of an electro-magnet, which are so con- nected that one end of the wire leads to the binding post B and the other to the post C. To the latter is also attached a straight Bpring which carries the armature e, and, when the current is not ucli an le push L every nber of 10 com- THE VIBRATING BELU S8t a simple in figure 3 so con- ist B and a straight ent is not circulating, tends to keep it withdrawn from the poles of the magnet and against another spring, r ; this again is in electrical communication with the binding post D, and both B and D are connected respectively to A and E by brass strips. When such an apparatus is included in the circuit with the battery and push button, and the button is depressed, the cur- rent arriving at h passes through the coils to the post C and arma- Mg. 178, turee, thence via the spring r to post E and wire c, completing the circuit The soft iron coves consequently become magnetized and attract the armature which interrupts the current at r this causes the cores to become demagnetized again and the armature falls back against the spring, when the circuit is once more estab- lished aiid an attraction follows as befoi-e. Thus a rapidly vibra- ting movement is set up and continued as long as the button is depressed or the circuit remains closed by the needle pin before referred to. 382 ELECTBIG CALL BELL& S'' t : By a slight modification of tlie connections in the bell instra* ment the apparatus can be used both as a vibrator and as an in- strument to give simple taps. The general plan is shown in fig. 179, in ■which M and e refer to the same parts as in the last. S is a switch which can be turned on B or E at pleasure. When it is on E the connections are precisely the same as those just described and the apparatus becomes a vibrating instrument ; when turned on B there is no interruption of the current with Fig. 179. the attraction of the armature, and the instrument simply re- sponds by single taps to each closing of the circuit by the push button. The path of the current, when the switch is on B and E^ is sufficiently evident from the figure without further description. I DOUBLE BELLS. When it is desirable to produce a very loud sound, double bells and double electro-magnets are usually employed in the vibrating apparatus. Figure 180 represents an arrangement of this kind. The current, arriving at the binding post 0, follows the metallic strips in connection therewith to D and D', thence through the coils M M' and strips H V, H' Y' to the contact springs R li' and armature A. From A the continuation of the circuit may be traced by way of B and binding post Z, which DOUBLE BELL& 38a leads back to the battery. One of the bobbins, M for instance IS wound so as to produce a greater magnetic effect than that produced by the other M'; this causes the armature A to be drawn towards M until the circuit of the latter is broken at K • M now acts alone untU interrupted in turn by the break at K, when the same alternation is begun anew. Thus, at each Fig. 180. Vibration of the armature, one of the two bells is struck with considerable violence, and the noise, with rapidly recurring strokes, IS well calculated to arrest the attention. In double bells of this kind the line circuit is never broken by the vibrating armature— the effect of tliis movement being merely to shift tho current from one coil to the other. This, in 884 ELECTBIO CALL BELLS. fiome particular cases, is an advantage of considerable import- ance. In general, the principle of all vibrating bells is that of the self-acting make and break; but, when the contacts are rigid points, the vibrations of the armature take place only vrithin narrow limits, and the arrangement cannot very well be utihzed for ringing a bell. Siemens has devised a plan, in his dia,l in- struments, which answers the purpose much better, by giving the armature a greater range of movement ; but the adaptation of this device to the ringing of bells for simple calls is a little troublesome, and, in fact, for general use, would be altogether too complicated. By far the most preferable way of obtaining the desired range of stroke is that already described, in which a spring of some kind forms part of the path for the current, and Jii Hin Fig. 181. which, with the attraction of the armature, follows the latter for such a distance as may be required. When one battery is to serve for operating several of the bells above described, the vibrators cannot all be placed in one circuit, as each one interrupts the circuit independently of the others; and it is impossible, or rather impracticable, to make the arma- tures of the various instruments so that they will all vibrate in exactly the same time, or always be in unison. The plan generally adopted for such cases is shown in figure 181, where each bell, I, II, III, has a separate conducting wire of its own, as represented by the numerals 1, 2, 3, and a return wire, L L, serves for all. If, now, one of the bells is operated by the pressure of a push button in 1, 2 or 3, as the case maybe, NON-INTEEKUPTING CIBCUIT BELLS. 386 I'^n o'^utTV" '7 ^'^ '"*^^^""S "^^h '^- Others, as they are all quite independent of the circuit thus interrupted. ^ SINGLE BELI^ TO ^E WORKED WITHOUT INTEKEtTPTi™ THE CIRCUIT. to which the oUpZkl't.tTT"'"^"''' "•*'>'=»■•'»«'«'« •-"pper A 13 attached by means of a rather stiff '^. 182. %. 183. toa!!^';""^-^'"''''^'""' "^' 'P-'-a '^■Wcl' readily follows the ^^'m7:rT' *»,rr'"-f- » short diJoi L ■ugure i»j, the armature itself forms nart nf n oi,„ * • , which the current is withd^n iZZl A l," beT'' ^ « arriving at passes through thc^ire ^rirrid /Tnd I J r ^ ' '^' f ™"'"''« '^ «'»' """"''rf to the sT,r!n^ /, and a second route made for the current by way of a r. TT the re^stance of this route is exceedingly smf^rpar^d to that of he hehce, almost the entire current passes iy the new path and the cores become dema;:.,- ri.ed. The ret Jtile force ofth« sprmg now preponderates, and the armature fll s^rnsftL back stop, breaking the shunt circuit on its way Bv ,V means thflma£rPet^''m -^t" -i-- • . ^ ^"^ way. ±jy this - _ uia^net^om vx ^.n^ cores is again renewed, and a con- 886 ELBCTRIC CALL BELLS. stant vibration kept up. In figure 188, the forward movement of the armature brings a spring / against a cont83t c, and forma the shunt quite independent of the armature. As either of these arrangements does not break the main cir- cuit, any desired number of them can be placed in the same line and worked without interfering with each other. When the bell system is to be used for long distances, or when a very loud ringing is desired, for which purpose the main line current,, as a rule, is not sufficient, a relay and local battery are 2!>:sr. 184. generally used; and with the heaviest apparatus, requiring still more power, the ringing is done by means of weights. ^ Figure 184 represents an arrangement devised by Aubme, m which a single set of electro-magnets, M M, serve both for the relay and the call. A small projection on the upper end of the armature a, when the latter is in its normal position, supporte the lever 3, keeping it from making contact with spnng 4, and, at the same time, holding it firmly against spring 2. When now a current is sent into the line, it passes along the connection 1 to BLEOTBIC ALiRK WITH BELAYS. ggf This causes an a'tt^tila of .r ""."'""?'' *« <=oUstoeaSL magnetization of the core -S,,' ^ "'■J* again resnits in a i» the n,anner already dLriW™'"'«."*«^.»«i<> to vibrate which continues nntiCb—t on Vtt '^"^^ '^ '^' "?' »ised and suppo^ Xa^r™ p^S ™' ' '^ "^ ^. 186. cientlv apparent with nnf/Vi. , "''"'' ^'"^ ^^''c^it is suffi. spiral sprint rfl A ITt'V "f '^ '^^"^^ "P™^ by the Matter is' not LateTCZT^'''''^ '^ With the arrival of the h. ?P *^' '^^ ^ ^ ^^P^essed. of the line current the armature is attracted and ssa ELECTRIC CALL BELLS. the rod rel ased; this allows the spring d to act, and close the local circuit at c 6 when the ringing is commenced. By pressing on the knob F the lower end c£ the rod is caused to engage with the projecting armature pin, and the apparatus is once more ready for auother call SIEMENS AND HALSKE'S STATION ALARM. This is shown in figure 186, and consists of an ordinary relay and bell magnet, wiih an automatic make and break arranged upon the same principle as Siemens' dial instrument, m m are the coils of the relay magnet, and 1^ and l^ its terminal wires, one of which leads to line, the other to earth. The poles only of the bell magnet are shown at M M, one of its coils is connected to the binding post Z, the other to a V shaped piece of metal, termed the shuttle, which, in its normal position, rests with one end against an adjustable screw i:i the plate E, the lattsr also in metalho connection with the relay lever a. The local battery is joined to the binding posts Z and K When a current is sent into the main line the armature a is attracted and closes the local circuit ; this charges the magnet M M and actuates armature A, but after passing a little distance the lung projecting arm on the latter moves the shuttle against the stop r and breaks the local circuit ; the spring F, being no longer restrained, now withdraws the armature, but in doing so causes the shuttle to close the cir- cuit once more, and thus a constant ringing is maintained as long as the main line is closed. BREGUET's alarm or CALL. With most of the apparatus heretofore described the call or alarm is only maintained for such a period of time as the circuit may be closed by the person giving the signal, or, as with the arrau'^ement shown in fig. 184, until the messenger called stops the ringing by depressing the knob. Various other combinations have been°suggested by Aubine, Breguet and other?, by means of which a single signal is made to give any number of taps. lose the pressing i,ge with je more BBEGUET'S ALARM OR CALL. 889 ry relay irranged m in are al wires, s only of )n Dec ted I metal, with one r also in >attery is t is sent the local ature A, m on the bhe local ithdraws 3 the cir- d as long e call or be circuit with the [led stops binations by means • of taps. 890 ELECTRIC GALL BELLS. Breguet'a arrangement is shown in figure 187, and it3 operation may be described as follows : The line current arriving at L in consequence of the key being depressed, passes to the contact screw S, thence by way of the lever C c, pivoted at C, through the coils of the electro-magnet E to the armature a and contact b to earth. The armature is thus drawn forward for a short dis- tance, but returns immediately afterward, owing to the break in the circuit occasioned by the movement, and closes the circuit again. In this manner a vibratory motion is set up, and with each backward movement of the armature the toothed wheel R Fig. 187. is forced forward one cog, so that the lever c C is soon released from the pin g and falls on the contact screw d, placing the local batt .ry in circuit The continued vibration of the armature keeps the wheel in motion, the arm D is thus brought against the hammer lever, and the latter carried forward a certain dis- tance and then released, when the hammer strikes against the bell with considerable force. With the complete revolution of the wheel the pin g engages with the lever c again, and one© more closes the main current COMBINATION OF CALL BELL AND BELAYS, 891 COMBINATION OP A SINGLE CALL BELL WITH TWO OR MOBE RELAYS FOR SEVERAL LINKS. .oi]?!^ ^''''t.''' """'^ ""'"^^ terminate at one place a single ^U bel may be made to answer for them all, but in such caS Zfm17"\^^ P'' u^'^ ^^'^^°°^^ an^ngement such as the ~d FM m fig. 185 to show on which of the lines the signal has been sent. Fig. 188 shows an arrangement of this kind aZ the electro-magnet of the relay, whose armature ends in a bent ^.^ur'a ;7v.'°? ^°f ^"^ ""''^ '^^ '^^ FI; ^ and n are two «rew8 attached to the upright, D K. and serve to limit the plaj -%. 188. Of the amature. This upright is made in two parts, insulated from each other; the one marked D is connected to one pole of the local battery ; the other, K, is connected by a wire S to the interrupting spring M. of the vibrating bell already described. When the armature of the relay magnet is attracted, its upper part IS brought m contact with the screw n and the local circuit IS completed, at the same time the attraction of the armature releases the rod F I, which is raised by the action of the spring d and thus shows, when attention is called by the bell, which line has given the signal. 892 ELECTRIC CALL BELLS. '1 n' Each of the several relays are connected with the bell magnet in the manner shown in the figure, so that there are virtually as many distinct keys for closing the local circuit as there are re- lays After the call has been observed the knob F is again de- pressed when it engages with the armature and is held until released by another signal. It is frequently desirable that the bell should continue to ring after the main line current has ceased ; and, in order that this may be the case, the upper part of the pillar D K, fi,^. 188, is made the same as its lower part, in two sections, P and Q, and each insulated from the other. Two wires, S' Z', shown by the dotted lines, connect Q and P respectively to the wires S and Z when, therefore, the rod F I is released, the action of the spring d brings the small platinum tipped piece e against a similar contact on Q and forms a second closing of the local circuit, so that the bell continues to ring until the call has been observed and the knob depressed. SIEMENS AND HALSKE'S RELAY WITH ANNUNCIATOR PLATE. These instruments are made in a very perfect manner, and are much used on the German Fire Alarm Telegraph. Fig. 189 rep- resents a perspective, and fig. 190 a sectional view of the relay, which does not differ materially from the ordinary forms, except in the addition of the annunciator disk and lever bed, pivoted ate. The relays are made for both open and closed circuits, the one represented being designed for closed circuits. The line connections are made at 1 and 2. K and B connect with the Morse recording apparatus, while the alarm ball is joiixcu t. A and the metallic piece "W V. In its normal state the V --. ^' the disk is held in a horizontal position by the hooK ou the lever a a, but with any interruption of the main circuit the ar- mature is drawn off by the action of spring/ and releases the disk, which is now raised to a vertical position by the weight 6; this closes t^e call ciredt at i at t'je same time that the armature on tise Lsiok contact m, actuates the Morse recording a a, fallin RELAY WITU ANNUNCIATOR PLATE. 39a iVg. 189. Sdi SLEGTRIC GALL BUhLB. Fig. 190. CLOCK WORK ALARM. 395 instrument. When the automatic vibrating bell is ««.H .1. J^. 190. CLOCK WqRK ALARM. . operated by wdght orlril T'!,"' ^-"^ ""' ''="»»»^ « for eaeU ^u.! o^^ZT^ir^C-TtTt strokes are repeated a certain number of tmL'- n, 1 ^ !u' r.nging is oontinnons; but in all case^ the ™ has^X' *'" r rat2;tii ;St?L^ -:. tit:- Hagendorff -s, which ^ive. h,n aTw J- "" '^'''V' *"' °* &'" otiOLc lur eacn depression • 896 ELECTRIC CALL BELLS. I of tho signaling key, and which is therefore preferable to the vibrating "bells for many purposes, especially in places where the rattle of the latter is likely to be more or less annoying. The use of weights or springs for causing the separate bell taps is also to be preferred to the tapping from a clapper cariied by the armature lever, as with the latter arrangement, owing to an occasional tardy withdrawal of the hammer, the signals are not always very distinct. Fig. 19L J^. 192. Figures 191 to 194, inclusive, show the principnl parts of HagendorfPs apparatus; the letters refer to the same parts in. each figure. Figure 191 gives an interior view of the works. B B is part of the brass frame to the back of which is attached an electro- magnet M ; fig. 193 represents the inside view of tbe same plate. The wheel I, fig. 191, is loose on the axis n' and carries a disk CLOCK WORK ALARM. 397 ^, better shown in figure 192 ; this is provided with a detent S and spnng F F, which presses the former into the teeth of the ratchet wheel Z, thus preventing the latter, as well as the wheel R, which IS fastened to it, from turning in the direction indicated by the arrow without at the same time causing the wheel 1 to ' turn with it The wheel R is provided with radial pins which catch m a chain passing over it and attached to the weight P Mg. 193. • fig 194, the pins serving to prevent the chain from slipping As will be seer, the ratchet allows the wheel Z and R to be freelv turned m a direction opposite that indicated by the an-ow; thfs raises the weight P, which, in descending again, sets the whole tram m motion, wheel 1 communicating its movement to wheel 11, and the latter, in turn, acting on axis g' and stop lever / connected to it. r j 898 ELECTRIC CALL BELLS. The wheel 11, fig. 193, carries near its circumference eight or ten projecting pins, h h, which raise the arm 1 on the axis k. A powerful spring, S, surrounding this axis and in communication .with it and with the frame of the apparatus, tends continually to keep the arm depressed. When, therefore, the latter is raised by the revolution of the wheel the spring is subject to considerable tension, and as soon as a pin passes from under the arm, causes Fig. 194. the latter to descend, and the hammer K, attached to the axis h by the arm «, strikes the bell with some violence. The pin m serves to limit the play of the arm n. Figure 191 represents the relay armature attracted. When no current passes in the coils of the magnet the armature re- mains down and the train work is arrested by the arm / which catches in the escapement d' e e'. The ends e e' of the escapement are so made that the back one e is a little nearer than the front a, causes CJLOCK WORK ALARM. 899 one e to the plate B B, but the two are attached to one piece ^eration of the apparatus will now be readily understock IS attracted, the front point e' of the escapement ZToi one complete .vo,„«o„, wtt;tlS ^inbir s-Jl'r CHAPTER XIII. THE ELECTRIC LIGHT. When the terminal wires of a battery containing a number of ceils are brought together, and then separated slightly, there results, as is well known, an intense, bright light between them, and to this, on account of its curve'd form, the name electric arc has been given. If the circuit is not immediately broken, the ends of the wires rapidly become heated, and, in a very short time, melt and drop ofE in glowing globules. Portions are even volatilized and pass off as vapor, whose color varies with the kind of metals (employed, and with the medium in which the experiment is made. The distance between the ends conse- quently increases rapidly, and a point is soon reached at which the light is interrupted, the electro-motive force of the battery being then no longer sufficient to maintain a current against the opposing resistance. If, however, the wires are again brought together, and then separated as before, the arc is once more established, but, as we have just seen, it will last only for the very short time during which the electro-motive force is suffi- cient to overcome the resistance between the points. When two pointed pieces of hard, conducting carbon are used for the terminals, as shown in fig. 195, the light becomes of dazzling brightness, too intense, by far, if the number of cells is considerable, to be carelessly regarded by the unprotected eye alone. By viewing it through colored glass, however, or by projecting an image of it upon a screen, it may be studied without danger. As the number of cells is augmented, the light becomes not only more intense, but the arc may be materially lengthened, while its temperature, at the same time, is still further increased. In the brilliant experiments of Davy, which were performed at the beginning of the present century, with some 2,000 cells of TEMPEKATUBE OP THE ELECTBIO ARC. 401 ^^Vl I,"f ""^ ^' '''"' "«" "^^ """lo °» » extended seaH an are of four mehes in length wa3 obtained ia the open ZZfZrZ'' '"^^^'^ 'o ^™» '"^es. Sinee then, Ir^ powerful elemente, and greater number have been emp o3 and the resutang effects have been on a corresponding Z7 ' ,11 1 '^"^T "^ ™" "^ brightness, the voltaic are exceeds all other ar«fle,al sources of heat; by its means the mL^frac tory substances are fused and volatilized, includinHven the dramond itself, which Desp„tz succeeded i'n redudng t! ™po^ ■f^g. 195, As the light continues, the positive carbon is found to waste nZ: "^^VT;^^^ ^^-- *^e negati.e-a fact first observed by Silhman-and although the latter is first to become heated Its temperature in the end is less th-xn thnt of fV, / ' be 9PPn xxrl.o,. +1, r w *°^* ^* *"® former, as may ara This transport of particles can be rendered visible to a illifl 402 THE ELECTRIC LIGHT. large number of persons at one time by throwing an image of the heated points upon a screen, with the aid of a lena On watching the image for a few minutes, incandescent particles will be observed traversing the length of the arc, sometimes in one direction and sometimes in the other, the prevailing direc- tion being, however, that of the positive current. This circum- stance, which appears to be connected with the higher tempera- ture of the positive terminal, explains the difference between the forms assumed by the two carbons. The point of the posi- Fig. 19G. tive carbon becomes concave, while the negative remains pointed, and, as stated above, wears away less rapidly. In vaxjuo the difference is still more marked. A kind of cone then grows upon the negative carbon, while a conical cavity is formed m the positive. . Fig. 196 shows a convenient apparatus for experimentmg with the light in vacuo and in various gases. It consists of a bell shaped receiver of glass, provided with three tubular open- ings, two, d and 0, opposite each other, and the third, 6, on top. DUBOSCQ'S EEGULATOR. 4^3 besides, a scale o, by L:>^^rwLhl: i^T'"" "'"'"■ With the arrangement shown in figs. 195 an,! iqa +k t t. as we have already seen, i, «oo„ eSiSd owl. tote increased distance between the noint« w Ti, r ' ^ ^ *"^ away of the carbons; co^tZ il ™'"« "' ^'^'^"^ continuously for an; oSrlt'^rof Zelttc"" '' necessaiy to employ some mechanical meana fekl^r pencils at the right distance anart «, f„ i, ""^ J^eepmg the again automatic^, i^f^r^^^^^^^^^^^^^ become separated sufficiently to cJuse the li^ht to Xt t great many forms of apparatus have been demised f of r pose, some exceedingly simple an I otW , ' ^'^' cated. ^ ' ''*^^'^^ "^^^^ °^ less compli- Fig. 197 shows a form of lamp deviserl hv Bni.^ ated by the combined action of the currL '^^^^^^^ "^ 'P'" wheel work, driven bv a snrin^^n ! ! ^ ^^'^^"^ °^ wheels ^ ^ connection with one of the that may be given to it. ihe lower end! l"ro7/nr «ded with a rack F, which engages with the wh^l G andTe latter again ,s p,.ssed on to the axis of another whedH^d 404 THE ELECTBIO LIGHT. firmly held in place by friction. Within a barrel connected with wheel H there is a powerful spring, which serves as the motive force for actuating the mechanism of the lamp. A double rack J, terminating above in the rod O, which passes throngh aa Fig. 197. insulating guide in the cover, and is provided with a socket for holding the lov/er carbon, engages on one side with the wheel H, and on the other with the axis of wheel K. This wheel, in like manner, engages with the pinion of wheel L, better shown DnBOSCQ'3 KEGULATOR. ^qj in fig. 198, and the latter again, with an endte, screw M on 4e p,„lo„gat,™of the axi^ carrying the cog wheel N an" wnn Its helix of insulated copper wire, is placed in the base of the I^p ; and one end of the wire of the helix is connect^ to lower end of the rack J, which moves up and down in the hollow of the oora A cupula.- piece of ii^n'q, attached u> the benT Fig. 198. lever EST, serves as an armature to the ma^npt anrl ^Ko« attn^ted by the latter, causes the pallet of t^eTuppfe™ the wheel N, and thus arrest its motion and that of the train ot wheels with which it is in eonnectioa There is also a Su o rod m connection with the apparatus, that can be pushed in from the outside, and made to start or stop the train work wZ When the lamp is t» be used, the rod D is raised. This causes 406 THE ELKCTRIO LIGHT. the wheels G and H to revolve, and thus at the same time lowers the rod O, so that the carbons can be inserted. If allowed to act now, the spring within the barrel connected with H will cause the carbons to approach and touch each other. The battery can then be connected; the positive pole to the post V, the negnHve to C. With the passage of the current through the coil surrounding the core, the armature will be attracted and the train thus locked ; but the points may be properly separated again by raising the rod carrying the upper carbon, and the light will then shine out in all its brilliancy. As the carbons burn away the current necessarily becomes weaker, on account of the increased resistance of the arc, and a time soon comes when the magnet is no longer strong enough to retain the armatura The retractile spring then prevails, and releases the wheel N, and thus allows the spring in the barrel of H to act and bring the points once more near each other. With the decrease in the distance between the points, the current becomes stronger and the armature is again attracted. A moment more, it is again released and again attracted, and so its position con- tinues to vary from time to time with the changes in the strength of the current. It therefore becomes possible, by the use of the lamp, to maintain the light for a very long time without inter- ruption. As will be observed, the diameter of wheel H is double that of wheel G, and consequently the carbon connected with the holder O moves through twice the distance of that in the upper holder. The object of this is to compensate for the more rapid wasting away of the positive carbon, which, as has been found, consumes about twice as fast as the negative. The use of wheels of different diameters thus furnishes the means for keeping the light at a given point, which is a matter of consider- able importance in almost all of the uses to which it is applied ; and when a reflector is used, is absolutely necessary, as other- wise it would be all but impossible to keep the light properly focused. Fig. 199 shows another form of lamp, devised by Foucault In this there are two systems of wheel work, one for bringing the foucault's beoulatob. 407 ne time ted If ted with h other. 3 to the current ■will be properly carbon, As the aker, on me soon stain the tases the I to act ^ith the becomes ; more, it ;ion con- strength se of the )ut inter- sel H is onnected i that in J for the b, as has re. The aeans for consider- applied ; as other- properly Foucault iging the Fig. 199. 40» THE ELECTRIC LIGHT. carbons together and the other for separating them, and it is prin- cipally in the addition of this last arrangement that the lamp differs from that of Duboscq, there being, in the latter form, no provision for automatically relighting the lamp in case it should accidentally go out. L' is a barrel driven by a spring inclosed within it, and driving several intermediate wheels, which trans- mit its motion to fly o. L is the second barrel, driven by a stronger spring, and driving in like manner the fly o'. The racks which carry the carbons work with toothed wheels attached to th'e barrel L', the wheel for the positive carbon having double the diameter of the other, the same as in the Duboscq lamp. The current enters at the binding screw C, on the base of the apparatus, traverses the coil of the electro-magnet E, and passes through the wheel work to the rack D, which carries the positive carbon. From tl^e positive carbon it passes through the voltaic arc to the negative carbon, and thence, through the support H, to the binding screw connected with the negative pole of the battery. When the armature F descends toward the magnet, the other arm of the lever F P is raised, and this movement is resisted by the spiral spring E, which, however, is not attached to the lever in question, but to the end of another lever, pressing on its upper side and movable about the point X. The lower side of this lever is curved, so that its point of contact with the first lever changes, giving the spring greater or less leverage, according to the strength of the current In virtue of this arrangement, which is due to Robert Houdin, the armature, instead of being placed in one or the other of two positions, as in the ordinary forms of apparatus, has its position accurately regulated, according to the strength of the current The anchor T < is rigidly connected with the lever F P, and follows its oscil- lations. If the current becomes too weak, the head t moves to the right, stops the fly o' and releases o, which accordingly revolves, and the carbons are moved forward. If the current becomes too strong, o is stopped, o' is relea;^3d, and the carbons are drawn back. When the anchor T t is exactly vertical, both flifis nrfi nrrfistfid. and the narbons remain stationarv. Thfl p.nrva- PARMER'a AUTOMATIC LAMP. 409 ture Of the lever on which the spring acte being very sliRht, the ti? tht""^'' '" '}" f ""«"' "^ ">' ™"^'" »d brilliancy o^ the Jight are immediately corrected lamp, in which the weight of the rod in which the carbon is fixed supplies- the place of the clock work in the lamp just dc scribecl, and an elcctro-magnet lets it descend, or locks it^ the carbons are consumed. ^ Mr. Farmer, of Newport, R. L, has also invented an automatic kmp containing but little tiuin work, and whose actionTcr Mled by a regulator or relay, consisting of an axial magnet or m a branch of tne same, and a delicately poised lever from one end o which the axis bar of the coil is suspended ' Tte achon of the current, when too strong, tips the bar in one dir.« t^n and when too weak a ..tractile spring tips it in the othTr tt lamoT °^t °' ''" "'^^ *" "P^'^^ *^ mechanisL of the lamp, through the intervention of local or branch circuits Of the other forms of lamps now in use. The train of wheel Z ' 1"'T ^^ u 'P'''"8' '^"'^^ '^ """^^ *^ <=''^bons to approach each other, but the motion is arrested if the armature of a smaU ckctro-magnet, forming part of the apparatus, is attracted. ?he i^lting bar of the regulator closes the local circuit of this rele^! mg magnet whenever the current is of the proper strength but as soon as the current weakens, by the burning away o the points the retraotUe spring of the regulator cans! s the W to Z of th T« T"'*n^ "" '"'""'"S magnet, and the arma- ture of the latter then allows the train to move. The carbons consequently, approach each other until the main current a^ain becomes of such strength that the regulator closes the bra°nch circuit of the detaining magnet, and thus, once more, stops the motion of the train. 1^ When the points run into actual contact, after the arc, has been brokGn. tho lirr},+ ,•= — :„ __x-i_t i j i - . _ * , ^n.. ,.^ agaui csuxuiisned Ly a third electro- 410 THE ELECTBIO LIGHT. magnet, also in the main circuit, which withdraws the lower car- bon from contact with the upper, and holds it in position until the arc is again broken. The movement of the carbon holders is caused by the action of two screws so geared together that one pencil, the positive, moves twice as rapidly as the other. There are, besides, conveniences attached to each of the car- bon pencil-holders, so that they can be disengaged from the screws and moved independently to any required position at pleasure. The holders, also, admit of separate adjustments on a vertical axis, so that by this means the carbons can be placed in a perpendicular line, one above the other. The spring does not need rewinding oftener than new carbons are supplied, and the p^-rformance of the lamp is very satisfactory. It has been run for hours when required, and no reason exists why it should not run contin,uously until the pencils are consumed, provided it be properly adjusted at first. Within the last two years a new form of electric light appa- ratus has been introduced in France and elsewhere, which, from the remarkable properties that have been attributed to it, has attracted a great deal of attention. The invention is due to M. Jablochkoff, a Bussian engineer, and is known as JablochkofE's candle. It consists of two carbons placed side by side, and sep- arated by an insulating and fusible substance. No clock work whatever is required, and the light is very soft and steady. Fig. 200 shows the arrangement as originally designed. The carbons a, b, some four inches in length and one quarter of an inch square, are imbedded in an insulating substance c; the carbon slips being also separated from each other some three sixteenths of an inch, and the whole moulded into the shape of a candle. In order to facilitate the early action of the current, a small piece of carbon, about the size cf the lead of an ordinary lead pencil, is placed across the top of the electrodes. A series of experiments with candles of this description were carried out at Chatham some time since, and, it is stated, the power then obtained was some fifty per cent greater than that obtained previously from the recognized electric light JABLOOHKOFF'S candle. 41J +>,^ u "^ / Prececling. His first proceedinff was to divest tb rxv (tvr rr^' '"™« »°*'^"« ''"^*" Don Slips a 6 (fig. 201), and the intervening substance, kaoline U^ 7\°V' ''?'* " * ™»" ''-^ *«be ci; ., ie lowe^ portions of which are left vacant, so that they may fi over two metal pins, attached to which a.^ the wires fa,m the mLZ IT T\ These tubes are insulated one fromfeotherand the whole bound together by a band of insulaHng materia / The latest modification embraces the removal ItT^rins oMmh Fig. 200, Fig. 201. and ae replacement of them by a carbon paste, a sort of nrim ma the object of which is to reduce the LisLce wh ch Te' kaoUne when cold, inteqioses to the passage of the c" ■With this arrangement a splendid band of Lht, constant^!ft and steady, is obtained. ^^ constant, soft The principal advantages of the candle appear to be due to ^e fact that it is neither darling nor blading, and does not the«=fore, surround the various objects iUumfnat^d wi h the disagreeable ha., and ghastly shadows that are observTwhen the ordmaiy electric light is used. It is, however, somewha" more expensive, but, as a compensation, L said to Jiow of a 412 THE ELECTBIC LIGHT. greater subdivision of tlie current — as many as fifty lights having been maintained from a single source by its use. A novelty in electric lamps has just been brought out by Mr. Wallace, and, we learn, will soon be placed in the market at a very low figure. It consists principally 'of a substantial metallic frame and an electro-magnet There are two slides in the frame, each capable of holding, in a horizontal position, the two carbons, which are made in the form of plates, twelve inches long by two and a half wide, and half an inch thick. The upper and lower parts of the framework are insulated from each other, and in electrical connection with two binding posts, on the upper part, serving to connect them with the magneto machine. The electro-magnet, through whose helices the main current circu- lates, is placed in the centre of the frame above the carbons, and, by its action on an armature, serves to separate the upper carbon from the lower, to any distance desired. When the lamp is joined with a magneto machine by means of the binding posts and conducting wires, the circuit is com- pleted through the carbons, which touch each other, and the armature is attracted, thus separating and holding them apart so long as the current is maintained. The light bums toward the opposite end from which it started, then changes and burns back again, always burning toward the place where the carbons are nearest If, from any cause, the light goes out, the circuit is broken, and, of course, the electro-magnet ceases to act Bat the instant the upper carbon falls the circuit is again closed, and the carbons are once more separated and relighted. The advantages of this lamp are that it contains no combina- tion of wheels or springs, and, consequently, there is no winding up of the apparatus to look after. The carbons, again, are so large that they will last for ten nights, of ten hours each, and the lamp requires no care except for their renewal. The practical disadvantage that suggests itself is its lack of means for main- taining the light at a given point, so as to use it in connection with a reflector. Figs. 202 and 203 show two forms of the Brush electric lamp, as MAGNETO-EL ECTEIO MACHIlTteS. 418 manufaured by the Telegraph Supply Company, of Cleveland, -t^ig. 2Ui IS a hanging lamp, intended for factory usd : fio- 203 an adjustable table lamp. ° There are also a great many other lamps, such as Serrin's, Brownmgs, Siemens's, etc., and all of which are more or less employed when it is desired to maintain the constancy of the light for long continuous working; but the apparatus we have just described contain most of the principal characteristics and conveniences embodied in these, and it will, therefore, be un- necessary to give more attention to this part of the subject at present. is nowTf "'^f'" ^"''T' ^^"'' employment for light purposes IS now almost exclusively confined to the illustration of lecture- room experiments, and physical demonstrations in class rooms. or to the production of luminous effects in theatrical exhibitions -places where it is seldom convenient to employ a steam en- used, and their advantages over the battery are very marked in a great many particulars. Of late years, dynamo machines have also been extensively introduced in electro-plating establish- ments, to take the place of batteries, but in such cases their con- ^ .tion IS considerably modified, in order to adapt them to tm. particular kind of work. As ordinarily constructed for ight purposes, the machines would have an electro-motive force far too high for plating, where, as a general thing,. two or three volts are all that are required. Large magnoet-electric machines, for 'light purposes, appear o have been first suggested by Professor Nollet, of Brdssds, 1 1850, but since then a great many modifications and improve- ments have been mtrocluced, so that the machines of to-dav although depending for their action, like the earlier ones, upon he same inductive principle by which mechanical force is trLs- Wed into electricity, are nevertheless far superior to them both as regards economy and effectiveness when in action. ' .nn f ^?V^P'??'' ""''^ ^^ *^^" ^'''' ^^'-"^^ «f t^^^^« "machines as constructed by Holmes, of London, and the Compa^nic 1' 4iranec 414 THE ELECTRIC LIGHT. m I HI Fig. 202. brush's automatic EEGULATOB& 415 Fi'j. 203. 416 THE ELECTRIC LIGHT. of Paris, and which at one time promised to become of very extensive application for light-house purposes. In this machine there are eight rows of compound horseshoe magnets fixed symmetrically around a cast iron frame. They are so arranged that the opposite poles always succeed each other, both in each row and in each circular set. There are also seven of these circular sets, with six intervening spaces. Six bronze wheels, mounted on one central axis, revolve in these intervals. IHg. 204. the axis being driven by steam power, transmitted by a pulley and belt. The speed of rotation is usually 350 revolutions of the axis per minute. Each of the six bronze wheels carries, at its circumference, sixteen coils, corresponding to the number of poles in each circular set. The core of each coil is a cleft tube of soft iron, this form having been found peculiarly favorable to rapid demagnetization. Each core has its magnetism reversed sixteen times in each revolution, by the influence of the sixteen succes- SIEMENS'S ARMATURE. 4^7 of currents m alternately opposite directions, are generated in the coda The cods can be connected in different ways, accord mg as great electro-nrotive force or small resistance il eqXd The positive ends are connected with the axis of the machine Itoda ^'^'^'^^ '"" ^^' ^^ ^"^P^^^^^ - *^« -native In 1854 Siemens devised a very effective armature, which has smce been much employed by other manufacturers ndi^eren resul s from its occupymg but little space for rotation. Conse- sTrnttt: r -t' ^^ " ^ ^^^^ ^*^«"^ -^-^- ^^1^; ^tTe same t.me also its form renders it well adapted for rotat on It consists of a peculiarly shaped electro-magn'et, such Is wouW be formed by cutting two wide and deep longitudinal grooves oppo si^e each other m a cylindrical bar of iron, and the^n continufng them around the ends. The wire is wound lengthwise around the core in he groove, like thread upon a shuttle, and brass caps, provided with axes and a pulley, are then screwed on to the ends of the magnet When this armature is mounted between the poles of a series of permanent horseshoe magnets and rotated mpidly, very strong currents are produced. The two ends of the wire are connected with a commutator, formed by fastening two semicircular pieces of brass to an ivory ring on the axis, and springs bearing upon these brass piece., and in metallic con- nection with the binding posts of the apparatus, supply the means for collecting and conducting away the electricity produced in the wire coils. By employing two of these armatures and taking advantage of the property which soft iron possesses of receiving a much higher degree of magnetism than steel, and consequently, there- tore, of Its capability of producing stronger currents by induc- tion in movable coils within its field, Mr. Wilde, of Manchester iLngland,has succeeded in constructing very energetic machines and which are well adapted for producing the electric light 418 THE ELECTRIC LIGHT. The apparatus in reality consists of two machines combined in one. The current from one of the Siemens's armatures, pro- duced by its rapid rotation in the strong magnetic field of a series of permanent magnets, is employed to charge a large and power- ful electro-magnet, between whose poles the second armature is made to revolve, and the current from the latter is utilized for the light . . Two armatures for the electro-magnet are sometimes f urmsnea Fig. 205. with the machine, one with wire coils for the production of cur- rents of rather high electro-motive force, to be used for light purposes alone, and the other with coils of sheet copper strips, which give currents of less electro-motive force, but more espe- cially adapted for plating. With the interchangeable armatures, which are driven by belts running on pulleys on their axis, the machines can be used either for lighting or for plating at pleas- ure, and this, in some particular cases, is a very desirable feature. ladd's dynamo-electric machine. 419 Numerous other machines are constructed with interchangeable armatures, on the same plan and for the same purposa Another form of magneto apparatus is that known, from the Buhlllv '""'ZT"' "I '^' ^'^^ ™"^^^"^- This was first publicly exhibited at the Paris Exposition of 1867. It is machine two Siemens's armatures, but it differs from the latter pnncipallyin not havmg any permanent magnets whatever to charge the armature which supplies the horizontal field coils B B attached to the iron castings or pole pieces MM, NN, which are turned out just large enough for the armatures to fit inside of them and rotate without touching. Thick strips of brass or other non-magnetic metal are also placed between the upper and lower castings M and N, to keep them separate from efch other, and thus subject the armatures between them to the full lorce of their inductive action. The connections of the coils are such as to produce opposite polarities m M and N; and the armature at the left of the ma etrti? t H:hr ''''^ ^'^" ''-' " ''' ''''' '-^^'- ^'^ One of the most remarkable properties of these machines is that by nrtue of which they become capable of producing exceed- mgly powerful currents from the smallest beginnin-s • the sint)le reac.ve effectof the veiy slight residual magnetismtWema^ m cores after they have once been charged being,m fact, all that IS required, on revolving the armatures, for their produc- tion ; and to operate a new machine, it is only necessary to place ^ in. such a way that the armatures will stand in the magnetic meridian, and then cause the one which supplies the field coils to rotate rapidly This, of course, causes the convolutions of wire surrounding the latter to cut through the lines of force due to terrestrial magnetism, and produces in them electrical currents of greater or less magnitude, depending upon their velocity of rotation, which, on traversing the larger coils B B, render the cores and pole pieces M N slightly magnetic. The reactive 420 THE ELECTRIC LIGHT. effect of the magnetism in the pole pieces on the armature is thus added to that produced by the earth's magnetism, and an in- creased current flows into the field coils. A greater degree of mag- netism is consequently produced in the pole pieces, which causes the latter to react once more on the armatures, and the result of which is a corresponding increase in the current, and increased magnetism. By this means, therefore, the current, in an exceed- ingly brief interval of time, increases from nothing to a maxi- mum of strength, at which it remains practically constant for a uniform velocity of armature rotation. It is usually better, how- ever, and much more convenient in charging a machine for the first time, to use the current from a battery, or from another machine already charged, than to depend alone, for this effect, upon terrestrial magnetism. The machines thus far described furnish only momentary currents of varying strength and polarity. If currents of but one direction are required, these intermittent currents must be recti- fied, as we have already seen, by means of a commutator, and this causes a diminution in the strength of current, and is fre- quently accompanied by the production of sparks. Mr. Z. J. Gramme has, however, invented a machine in which these objec- tions are not met with, as the current obtained from it flows continuously, and in one direction only. The mao-netic field in this, as in other machines, is created by a powerful magnet, of such a shape that its poles confront each other, and its characteristic feature, therefore, lies wholly in the construction of the armature. This consists of a ring of soft iron, surrounded by an endless coil of wire, and is rigidly attached to an axis, so that it can be made to revolve ; one half of the ring being under the influence of the north pole, and the other under that of the south pole of the magnet. As the ring revolves, every portion of it changes position in the magnetic field ; but no current is developed in the wire, con- sidered°as a whole, as the latter entirely surrounds the ring, and the magnetic state of this, as a whole, remains unchanged. A point on the ring considered by itself, however, changes polarity gbamme's machine. 421 frmra^h? 3urrou„dmg wire an electro-motivo foi^e, he »am6 as that generated when it appmachcs the other pole and tHe7ura:r;re:a e:rir ' ''"''''' ^^'"-" *^-' In practice, the ring consists of a bnndle of soft iron wire and ™>un, the correspondmg bra^ strips touc. a couple of „cX i^. 206. rre;xvrst:tronT:ht- gt^htn^' T^^^^^^^ t72L tre^,^r:t^;:r ^ ''- ^^^-^ ^"-'^ -''-^- oountiy, but, perhaps, hy none on a scale so large as that 422 THE ELECTBIC LIGHT. carried on by Messrs. "Wallace & Sons, of Ansonia, Conn. This firm began the construction of these machines for the market in the spring of 1875, and since that time there is hardly any form of magneto machine that has not been built and tested at their works. The machine which they finally decided upon manufacturing, as possessing the greatest merit, is the invention of Moses G. Farmer, formerly of Boston, but now and for the last three years electrician at the Government Torpedo Station, at Newport, E. L Fig. 207. This machine, which has been somewhat modified and im- proved upon from time to time by Mr. "William Wallace, is, in many respects, unlike any of the other forms that we have con- sidered. It consists of two large electro-magnets, an armature, two commutators and four brushes, the latter forming part of the circuit, and serving, when the machine is in operation, to collect the currents generated in the armature coila The two magnet", are mounted upon a cast iron frame, similar to that of PAEMEK'S DYNAMO-ELECTEIO MACHINE. 423 winch consists of an iron casting of varying diameter, according to the size of the machine, is mounted upon a shaft, knd placed SZr r^'*^ The shaft also carries pulle;s at each of ite ends, and is made to rest in bearings in the yokes of the electro-magneta The annature disk cafries on efch sde and near Its penphery, twenty-five wedge shaped pro^tions of which there are fifty in all, that face the poles of he elec ro magneH and on which coils of wire are placed. The teltl of these coils are jomed together, and a wire, connected with the the tZ' t.T *^^^«"^°^^^*^*«^' ^it^ated on the same side of the plate-all the coils on ope side connecting with one com- mutator and all on the opposite side with the other The commutators are placed upon the shaft, between the legs of the two magnets, and consist of wood or other more durable insulating substance, on which strips of brass, connecting whL the wires from the armature coils, are secured. The connections of the machine are so arranged that when the external circuit which may consist of the light apparatus or depositing vats wTth their leading wires, is completed, the armature and field of force coils are combined with it in one-an arrangement for which Mr Parmer obtained a patent in 1872, and which, when the external resistance is low, is of very great advantage. < rr^^ll^^^^ inch niachine, so palled from the length of its electro- magnet, and which IS the one most commonly employed, will pro- duce two lights of about two tliousand candle power kch and IS so arranged that the two may be combined in one if desired It weighs SIX hundred pounds, and requires to drive it about one horse power for every twelve hundred cr.ndle light Tho machines made by Messrs. Wallace & Sons weigh from one hundred and twenty-five to three thousand pounds each, and are capable of producing alight equal to that of from one hou- mndtoforty thousandcandles. Some of them will evenmaintain the arc with the carbons three and a half inches apart Fig 208 ^Ir "- '^ '?™ ^^ 'l^l!'^^^ --^--' - constructed by the ..^u.fi.u^a ouppij Co., oi uieveiaud, on a plan devised by Mr. C. BRUSH'S DYNAMO-ELECTBIC MACHIKE 426 o^her™mLin^"L'J ':: "f f '^''-'<- between this and effeot in ..^rl^w "^ ' ^P^®^' ^^*^ corresponding eliK s in r« ^'"'"V"'"™"^ ""^"""S. The second diile^ ae magnetjc Md they are cut out one after theoST .nd thus while adie, do not tend to weaken the effects of the mrhinl bv ■ affording a path to divert the current genenited in t^e a„ti™ sections irom 1(8 proper channel. " me active It would be an interesting mattei, if the effieiency of all th» Merent Machines employed in the p^duetion of fte elecwl Lght could be obtained and published, .0 as to be ..aily a^^ 426 THE ELECTBIO LIGHT. able. A general comparison could then be made which, would, in a measure, settle the ever-recurring question in regard to the superiority of this or that machina Undoubtedly, this infor- mation exists for many of the machines, as numerous measure- ments of them have been made by different experimenters, but the results have in most cases never been made public, and are, therefore, to be found only in the hands of the individual experimenters themselves. It may be stated, however, from such information as we have found available, that the amount of energy obtainable as electricity from the best machines probably does not exceed, or if so, only in a slight degree, two thirds that of the mechanical force required to drive them. The expense of maintaining the electric light is much less than that incurred by the employment of any of the ordinary methods of illumination. Mr. Farmer states that where a large amount of light, say from five thousand to ten thousand candle light, is required, it can be produced from a suitable machine at the rate of one thousand candle light per horse power; but, smaller amounts — say two hundred to three hundred candle light — are relatively more expensive, probably about one half horse power for two hundred to two hundred and fifty candle light This is much more economical than when produced from any of the ordinary forms of galvanic battery. One horse power may be reckoned as costing from two to six cents per hour, which would give the cost of ten thousand candle light as sixty cents per hour, simply for power. Of course some other items, such as oil, attendance, interest and depreciation, also cost of carbons consumed, would increase this amount somewhat, but even at twice or three times this cost it is still much less expen- sive than gas light at three candle light to the cubic foot per hour, at $2.50 per thousand for gas. The difliculty of procuring carbons that would bum uni- formly has been a source of a great deal of annoyance. If the carbon is taken just as it comes from the gas retorts and sawed into shape, it is found to contain many impurities, and, when BRUSH'S IMPROVED CARBONS. 43? »ell t,5den over by Xt ."! •^S^^t^ ^^ *» be pUtty «Iosely,has,webelifiv» =7 ^ . • ' "'"' '"'^ «""J'^ it very «arbo„; but we a^ r rr "^ ■nproducmg yery satisfaoto^ The L^IT ^ ^^ "Moquainted with the process ^nd the rapid eonsumS f '^""*,'f '^"^'^ '''S'^ «'-^ton»« air on thei^ hi^hrh^T eudrT Bthtt^ ""Tt " *« Tiate these difficulties and nt tj,! "'^•^f ™'>.'' ™3 sought to ob- ating power of the ShT 1 1 T' """ ™P''°™ *« "'""i- ^ubstances wi h the So- » /.- "™ "' **'"'™' ^'''^''S" ».echa„icaIW by el^tTnl ? ^ ™rrounding the stick eith^ P'-"""''''! appear, boTsolJ^i^jT " *" ''^'^ '"^'^ ^^ ™»I'">-hen he substituted gas retort earbonforthe thmfe r T."'. " r'"™ °' '™ ™P>--ement than a„y- Ihmg else and did not solve the question eompletely, since i th.s day r occupies the attention of practical men. ' some"exte*nt'istnr" "f °'''°' ''"'^'"''^ ""'^""^ ="«' ''^ to some extent is st.ll used, consists in first reducing coke to a verv fine powder and mixingit with syrup, with whichltis thor™,!^^ 430 THE ELECTBIO LIGHT. incorporateA The mixture is then strongly compressed in moulds and baked, and afterwards placed in a concentrated solution of sugar or molasses until saturated. It is then placed in an oven and raised to a white heat, at which it is maintained for an hour or more. By this means moisture is all driven off and a compact mass is formed, which may be rendered still more solid by repeated saturation aud baking. The disadvantage of carbons prepared in this manner, however, is that they con- tain all the impurities of the coke, no means being taken to- exclude these injurious matters. A purer material, capable of giving a very steady light, is made by placing pencils of gas retort carbon in caustic potash or soda, melted and raised to a white heat, and in which they are allowed to remain a quarter of an hour or more. The sticks are then washed in hot water, and placed in a porcelain or refractory earthen tube, through which a current of chlorine is passed, while the whole is maintained at a red heat for several hours. Many of the impurities that are not removed by the potash or soda are thus changed into volatile chlorides and driven off. Another way of procuring very pure carbons, according to M. Fontaine, from whom we borrow liberally on this point, has been suggested by M. Jacquelin, a French chemist, of the Central School, at Paris. This consists in imitating the condition of things that is brought about in gas retorts during the manufac- ture of gas, which is the reduction of the material and contact of the heated and very dense hydrocarbon matter with the sides of the retort Part of the matter is thus volatilized, while the rest is decomposed, and leaves a deposit of carbon. In the retorts of gas works the hydrocarbon matters carry with them much of the impurities contained in the coal ; but, by taking tar, pro- duced by actual distillation, which is consequently free from all non-volatile impurities, and reproducing the above conditions in specially prepared apparatus, it would seem possible to pro- duce carbon of great purity, and such has actually been found to be the case. Plates obtained in this manner, and sawed into sticks of the proper dimensions, give a perfectly steady light that CJLSR&'a CAEBOHS. 481 fweMlr'^ '''"'"'■ *"" """^ '"'^ ^ well-something like whleyet so ft, are placed in a horizontal position onl bed of After the first bakmg, which should be continued at a cherrv red heat for four or five hours at least, the carbons are 1 1 en out and placed in a vessel of boiling hoi and verrconcentntd jup of sugar cane, or oammel, and left for two or Tree Ws ^lowmg also, two or th,.e coohng intervals of som du^Z' 8o that the pores may become filled. The carbon, ,™ .. darned by opening a stop cock at the bottom JttlCtd 432 THE ELECTRIC LIGHT. allowing the liquid to run out They are then stirred a few moments in boiling water, to dissolve any sugar that may remain on the surface. When dried, they are again replaced and baked once more, after which they may be packed in the crucible in a standing position, with sand between them, the above operation being repeated until they have acquired the density and solidity required. They are then dried slowly, the drying process being terminated in a drying oven, whose temperature gradually attains eighty degrees centigrade, in twelve or fifteen hours, and to pre- vent their change of shape in drying, the sticks are placed in T-shaped pieces of metal. The Carrd carbons are more tenacious and rigid than retort carbon, and are remarkably straight and regular. Sticks two fifths of an inch in diameter may be used, eighteen inches in length, without 'fear of breaking; and their cylindrical form, joined to their homogeneity, causes their ends to remain as per- fectly sharpened as if they were turned. They are also better conductors than retort carbon. The only inconvenience that appears to accompany the use of carbons prepared in this man- ner, consists in their rapid wasting away, the production of small sparks and the irregularity of the luminous e£Eect "We learn from M. Fontaine's work, that the admixture of foreign substances with the carbon, of which mention has been made on page 427, has also been carefully studied by M. Carr^, within a few years past, with very interesting results; and, from a large number of experiments made by him, he has been able to deduce the following important facts : 1. That potash and soda at least double the length of the arc, rendering it also free from the hissing sound so peculiar to it when carbon alone is used, while, at the same time, by combining with the silicates that are usually present, they eliminate these substances from the pencil points, causing them to fuse into clear, vitreous and often colorless globules just outside of the arc, and that they increase the illuminating power in the ratio of 1.23 to 1. GAUDOIN'a CARBON& 433 2. That lime magnesia and strontium increase the light in the proportion of 1.40 to 1, and color it variously. ^ 3. That iron and antimony enhance the illuminating eilect to 1.60 and even to 1.70. matenal from the oxygen and the air, increase, the durability of the carbon matenally, though without augmenting the light ^^umerous experiments have also been made by M. Gaudoin with carbons containing borate, chloride, phosphate and silicate of Imie, pure precipitated silex, borate of magnesir, magnesia abjminum and silicate of aluminum, the proportions being call oulated so as to give about five per cent, of oxide after the baking o the carbons; but, although the light is about double that from the f" f "''^"^' *^^ ^^'^^ ^"^ ^P^ suiting from the use of carbons prepared in this manner, is, aside from llt'T'!' ?™''' "^ '^' ^'^"^^^' ^ g'-^^^ -b«<^«l« to their practical introduction, and for this reason chemically pure Sstr ^' '""^^^^'^ ^^''' continuous light is The dust of retort carbon, although containing but a small pro- portion of foreign matters, is, nevertheless, not sufficiently pure for this use, and Its employment presente some inconvenlem-es while washing m acids or alkalies, to which the carbonaceous matters may be submitted, with the aim of extracting the ^mpuriUes they contain, is a costly and insufficient opemtion. ai^en^di^^^^^^^^^^ ^^^^^'' '" ^^ ^'^ '' '^^^ -^ ^^ — M. Gaudoin, however, has found a solution of the problem in decomposing, by heat in closed vessels, the dried pitches, fats or liquids, tars resins, bitumens, natural or artificial essences or oiJs, and other organic matters, capable of leaving behind sufficiently pure carbon after their decomposition by heat The^apparatus employed for effecting this decomposition con- sist of closed retorts or crucibles of plumbago, and these are placed m a furnace capable of being heated to a bright red Ihe lower parts of the crucibles are furnished with two tubes' 484 THE ELEOTKIC LIGHT. i I one serving for the disengagement of gas and volatile matters, and the other for the introduction of the primary material. The volatile products of decomposition may be conducted under the hearth of the furnace and there burnt for heating the crucibles, but it is more advantageous to conduct them into a condensing chamber or into a copper still, and thus recover, after condensa- tion, the tars, oils, essences and hydrocarbons that are produced in the operation. M. Gaudoin also utilizes these different subproducts in the manufacture of his carbons, and he takes great care to avoid the use of iron, zinc, or any substances susceptible of being attached by these tars to the worms of the receiver, as the whole value rests in purity. Whatever the primary material employed for the manufacture of this carbon may be, the decomposition by heat should be capable of beiAg conducted either slowly or quickly, according ,to the nature of the subproducts to be obtained. For operating slowly, it is sufficient to fill the retort two thirds full and heat gradually up to a clear red, avoiding as much as possible the boiling over of the substances. For operating quickly, the empty retort is first heated to a deep red, and the primary material thrown into the bottom in small quantities, in a thin stream, if it is liquid, and in small fragments if it is solid. The slow distillation gives most tars and heavy oils and little gas. The quick decomposition more light oils and gas. When, then, the primary material has been properly chosen, a carbon, more or less compact, remains in the retort This is pulverized as finely as possible, and then agglomerated either alone or with a certain quantity of lamp black, by means of the carbides of hydrogen obtained as secondary products. The car- bides thus prepared are completely free from iron, and much preferable to those found in commerce, not only for agglomer- ating the carbon, but also for impregnating or soaking the manu- factured objects. The last operation, when effected with com- mercial products, introduces oxide of iron in the pores. Objects made in agglomerated carbon are, for the same variety of car- GAUDOIN'S CARBON& ^gg beet' tuS *: thTmt!:^"'""? "^^P'"'"""'' ««" •- '»"« . may also be usrf in C" , ' "^ "'^^''y S^P^^''^ «"»«"» %h' M. GauT^nht added rr °' -•»- '"r the electric that make the appa^trll '^'" '""P""''*"' improvemen^ the work. Th\7f^!^ 7 " ™'"*''^ "■"> *-««- "d^P^d to top to tatom vert 'ut ./ T""? "■" "'"''""'^ *° '=^™ *'»»' bons form, with the 'hort„ Td ' "T'' *''^' *'" '"»'"« "=*- seventy degrees. ^^ZTZ^'^^^UT "i TT' "^ bj tubes or ffutter^ Th;« ^ *^^ ^^°^® length whole of theCTr coniSeT\?"r"P^^^^ *^« ing the work • and a. t^!? u ^^""^"^ "^'^^^^^ interrupt- nof brearunde t r';^^^^^^^^ ^r^^' ^^ d^ issuing vertically. ^ ' ""^'"^ frequently happens when We have made, at different times savs M Fnn.o- ous trials with all Vinria «* """^N says M. J^ontame, numer- ^nanufaotr \i^t :^ct:' r j^ ;;^t r ^^^^^ necessitated much tim^ ur.A . -7 ff^^- -^^ has, however, »— „re J^tr mfr^;— ^ zz: r:^ *^' c^ironr: o'fthr^ *" ^^- o.'°thf t™.^: 'tor., Archereau Zrlnd LIT™?' ""* '""'""^ ""O 436 THE ELECTRIC LIGHT. No. 1. TABLE OF EXPERIMENTS MADE NOVEMBER 6, 1876, WITH DIFFERENT KINDS OF CARBONS. Name of Carbon. Consumption. Dimenilons. Retort. Arcbereau. Carr6. Oandoin. 9m. m. square, 9m. m. Bquare 10m. m. diam. 10m. lU. diam. m.m, 800 9S0 800 920 10 4m. m. diam. 800 10 4m. m. diam. 930 in.m *19 23 20 30 18 11 3m. m. diam. 11 Sm. m. diam, 800 920 48 60 «0 20 38 60 80 38 50 in, III 65 71 80 90 78 106 Kegularlty. j „„ { I Irregular. >63-^ Sufflciently H 58 1 73 regular. Sufflciently regular. Sufflciently regular. Irregular. Regular enough. Very regu lar. Very regu lar. ObMrvattona. Scintillating, eclipsed for a short time, a slight disaggregation. A slight disaggregation, a few sparks, cinders of oxide of iron in rather large quantities. White light. Cones good. A slight disaggregation, a few sparks, more cin- ders than the pre- ceding, reddened for a greater length. Neither disaggregation nor sparks; less cin- ders than the Cai re and Archereau carbons. The light produced with the retort carbons was equal to one hundred and three burners, that by the artificial carbons varied between one hundred and twenty and one hundred and eighty burners for the Archereau and Carr<5 carbons, and between two hundred and two hundred and ten for the Gaudoin carbons. The mean of one hundred and fifty burners may be applied, without appreciable error, to the Archereau and Carre carbons, and that of two hundred and five to the Gaudoin carbons. Keduced to a uniform section of 0.0001 square m6tre, the consumption of the carbons was, respectively : For the retort carbons 51 millimetres (about 2 inches). " Archereau carbons *>" "'•° '■ Gaudoin " r:^ " " 2-8^ " .. Carre " " " " ^ " • To convert milllmdtres into inches, multiply by .03937 OOMPASISON OF BirFEBENT CARBONa m In proportion to .he light produced, the consumption wa. • retort 49 1.93 A gramme machine, constructed bj M. Br^euet «n.1 . p a lamp by the same maker, were used in LT ! ' f ^^""^ ments, and the carbons ^r" rkenatT.! '^'" ^"P'"' several metres for each series "^^'"^ ^'""^ " ^°* «^ tiofof'triralr a^Vl^ ^"^^"*^^^' ^^^ ^^^^ ^^^ ^^P- xnents were made Xalr^^^^^^^^ ^^^^^^^ -P- Serrin lamp. ^ ^"^^^ ^"'^"'"^^ ^^^hine and a No. 2. EESULTS OF A SERIES OF EXPERIMENTS MADE APRIL 4 1877 UPON SEVERAL DIFFERENT KINDS OF CARBONS ' Name of OsrboD. Splinters numerous. Sena, ration of small piedS: Scintillation. Carbons were shaped very irregu. Retort car- Square, 9 m. m ^if^Uf^^l "> 'he side, quality. Archereau's carbons, now speci- men. Carry's car- 1 Round, 9 m. m bons, newj diam. specimen. Gaudoin's, Type No. 1 Gaudoin's Ajtglomera- tion of Wood car- bon. Disaggregation. Sparks. Liglit very variable In Intensity at periods, uhap. Ing into small facets. Small sparks. Light run. ning round. Very varla- ole in intensity. Good shaping of the carbons. Neither sparks nor splln- ters. Light a little red. but pretty constant. 830 Sufficiently JLight vertr white. Lest good. I steady than with G»a. ooln's carbons, No. i No sparks. Small varla- none. I i 488 THE ELECTRIC LIGHT, The preceding table (No. 2) gives the mean of three series of these experiments, made with the greatest precision. The elec- tric lamp was placed vertically and on the same level with the oil lamp and photometer, and every precaution was taken to prevent any sensible error in the measarements of the lumin- ous intensity. The rate of consumption of the carbons in these experiments, and reduced to a uniform section of .0001 square metres, was respectively : For the Carre carbons *44 millimetres. " retort '« 49 " " Archereau carbons 53 " " Gaudoin (wood carbon) 61 " " Gaudoin, No. 1 78 In proportion to the light produced, the consumption was as follows : ' For the Gaudoin (wood carbon) .32 millimetres per 100 burners. " Archereau carbons 39 " " " " Carre carbons 40 " " " " Gaudoin, No. 1, carbons 40 " " " » retort carbons ...-. 50 " " " The light given by the Gaudoin carbons was a little less regular than that observed on November 6, 1876. That given by the Carr^ carbons varied in less than a minute from one hundred to two hundred and fifty burners; the arc rotated positively round the points, the same as if alternating currents were being used. The Archereau carbons appeared to be less effective than at the first trial ; they were consumed slowly, but produced a light so variable that it was difiicult to take photo- metric measurements. Only the retort carbons maintained their durability, luminous intensity, and, unfortunately, also their irregularity. We cannot do better, while on this subject, than describe the later improvements that M. Gaudoin has made in his process, and which were patented April 7, 1877. * To convert millim^trea Into inches, multiply by .03937. gaudoin's oaebons. 439 ju was as .n Wh . ^^^bonizing wood, reducing it to powder, and then submitting ,t to mixture, the inventor takes dried and properly chosen wood, to which he gives the definite form the carbon is to possess, and then converts it into hard carbon, and finaUy soaks It m the manner before described. The distillation of the wood is effected slowlj, so as to drive out the volatile substances, and the final desiccation is made in a reducing atmosphere, at a very high temperature. A previous washmg, m acids or alkalies, removes from the wood any im- punties that it possessed. M. Gaudoin points out also the means of filling up the pores of the wood, by heating to redness, and submitting it to the action of chloride of carbon and different carbi'i.s of hydrogea He hopes by this >neans to produce electric carbons of small consumption, and giving an absolutely steady light Smce the first edition of this work was printed, a series of expenments has been made by a committee of the Franklin Institute, with several of the machines now used for light pur- poses. Having also been conducted with the greatest care and skill, and including, as they do, accurate measurements of the vanous factors which affect the general question of electric lighting, these experiments will necessarily possess a great deal • of mterest for persons whose attgntion may be directed to the subject, and we, therefore, give a large share of the committee's report m regard to them complete. Previous to the commencement of the labors of the commit- tee, an invitation was extended to makers of dynamo-electric machines, with a request that they should furnish machines for competitive trial. The machines supplied were two each of the Brush and Wallace-Farmer types, and a Gramme machine which had formed a part of the exhibit of M. Breguet, at the Centennial exhibition. In measuring the power used, indicator diagrams were taken from the engine, as a check on the dynamometer readings, although the latter were relied upon in making our calculations,' except ill the case of the large Wallace machine. This machine 440 THE ELECTRIC LIGHT. requiring more power thaa could be supplied by the institute's engine, or safely transmitted by the dynamometer, it was taken to tbe works of the I. P. Morris Co., and driven by an engine of 9" bore and 18" stroke, and the amount of power consumed de- termined from the indicator diagrams. This determination was sufficient to demonstrate the fact that this machine possesses no economical advantages over the smaller one of the same make, but the power consumed is omitted from the table of results, as FHg. 209. comparisons based on the different methods would be obviously unsatisfactory. The following is a descriptio-» of the machines submitted to examination. Their dimensions are given in Table III. The Gramme machine, fig. 209, consists of two cylindrical electro-magnets, with their combined poles extended by pieces of such shape as nearly to envelop the aimature which rotates TABLE OF MECHANICAL DETAILS. 441 ilea ruu»< CO o o 00 r— 1 »o 00 o 05 OS o CO CO CO iZ2 02 O 442 THE ELECTRIC LIGHT. between them, figs. 210 and 211. The armature is composed of a ring of soft iron, with insulated copper wire wound over its entire surface. This wire is divided into sixty coils, connected successively at their ends, and the loops thus formed between each pair of coils are connected to the copper strips of the com- mutator. Fig. 211 represents the mode of winding this wire on the ring, only a few turns, however, being shown. The commutator consists of copper stiips equal in number io the armature coils, placed radially edgewise around the shaft of the machine, and insulated from each other and the shaft, thus forming a cylinder, the surface of which is composed of alter- nate strips of opper and insulating material. Upon the sur- Fig. 210. Fig. 211. face of the commutator rest bundles of soft iron wire, by which the currents generated in the ai-mature coils are conducted to the external circuit As the armature is rotated between the poles of the field magnets, currents of electricity are generated. These machines are also constructed with two commutators, each connected respectively to alternate armature coils, in which case the external circuit can be divided ; but it is usual to pass both currents through the field coils, and then join them in the external circuit. This machine runs smoothly and very quietly, with few or no sparks at the commutator, and very littM ' h sating, the temperature of the armature being about 98° iahr. after runnihg nearly five hours. brush's dynamo machine. 443 are almost coUlete ' X W ' "^"^ ^'"''^ *^ ""'^ thus e^posin, C/urf^ ol Zl^^X t f?' pation of heat, due to its constantlvTlT ^ ^ ^''''■ the Pacinotti riachme. ^ '^'°^^°^ magnetism, as in J%. 212, The ring revolves between the poles of two We field ma. nets, the two positive poles of which are nt TL! f ^" of the diflmpfo,. ^1^+1. ^* *^® ^^"^^ extremity ot the diameter of the armature, and the two negative poles at he opposite extremity, each pair constituting practLaUy ex tended poles of opposite character practically ex- The coils on the armature ring are eight in number, opposite on being connected end to end, and the terminals cair'ed oul to the commutator. Figs. 213 and 214 show this arraZment necteo. in order to place tho nommutofo- i- - ^- • r ""iiiiuwiox lu a cuuvenient posi-^ 444 THE ELECTRIC LIGHT. tion, the terminal wires are carried through tlie centre of the shaft, to a point outside the bearings. The commutators are so arranged that, at any instant, three pairs of coils are interposed in the circuit of the machine, work- ing, as it were, m multiple arc, the remaining pair being cut out at the neutral point; while in the Gramme machine, the num- erous armature coils being connected end to end throughout, and connections being made to the metal strips composing the commutator, two sets of coils in multiple arc are at one time in- terposed in the circuit, each set constituting one half of the coils on the armature. The commutator consists of segments of brass, secured to & -■E Fig. 213. Mg. 214. ring of non-conducting material, earned on the shaft These segments are divided into two thicknesses, the inner being per- manently secured to the non-conducting material, and the outer ones, which take all the wear, are fast.':ed to the inner in such a, manner that they can be easily removed when required. The commutator brushes, which are composed of strips of hard brass, joined together at their outer ends, are inexpensive and easily renewed. The high speed at which these machines are run, together with the form of the armature, cause the rota- tion of the latter to be considerably resisted by the air, and pro- duce a humming sound, but otherwise they run smoothly; the heating of the armature being inconsiderable, not exceeding WALLACE-FARMER MACHINE. 445 one hundred and twenty degrees Fahrenheit after four and three quarter hours run. They are simple in construction, all the Tnce W ''''^^ accessible, and the cost of mainte- Fig. 212 represents the smaller Brush machine, which is iden- former there are two commutators, each of which is connected Tvitli alternate armature coils. J^g. 215. By this arrangement connections can be so made as to produce ■electric currents of high or low electromotive force (fifty-five to one hundred and twenty volts, as will hereafter be shown) or the conductor can be divided into two circuits, each of which can te ^utihzed for producing its own light, or for performing other In the Wallace-Farmer machine, fig 216, the magnetic field is also produced by two horseshoe electro-magnets, but with poles of opposite character facing each other. Between the arms of the magnets, and passing through the uprights supporting them, IS the shaft, cairying at its centre the rotating armature. 446 THE ELECTBIC LIGHT. This consists of a disk of cast iron, near the periphery of which, and at right angles to cither face, are iron cores, wound with insulated wire, thu.. c<:>5.^i;ituuug a double series of coils. These armature coils jigs. 513 aud 217) being connected end to end, the loops so forinod are connected in the same manner, and to a commutator of the same construction, as that of the Gramme. As the armature rotates, the cores pass between the opposed north and south poles of the fie'd magnets, and ^he current gene- rated depends on the change of polarity of the corea It will be seen that this constitutes a double machine, each series of coils, with its commutator, being capable of use quite independently of the other; but in practice the electrical connections are so Fig. 216. Fig. 217. made, that the currents generated in the two series of armature coils pass through the field magnet coils, and are joined in one external circuit This form of armature also presents consider- able uncovered surface of iron to the cooling effect of the air, but its external form, in its fan-like acdon on the air, like that of the Brush, presents considerable resistance to rotation. In the "Wallace- Farmer machine there was considerable heating of the armature, the temperature being sufficiently high to melt sealing wax. The Brush and Wallace-Farmer machines were accompanied by lamps, or carbon holders, which were thought by their makers to present advantages, if not for all machines, at least to be espe- BRUSH'S AUTOMATIC REGULATOR. 447 ■%. 218. This lami .3 shown in flga 218 and 219, in which a is a hnll, o msulateu copper w.r^ resting upon an'insulated pl^ e 6 t held by fte metalho post c. Loosely fitted within the hdik is he eore d, partially supported by the adjustable springs e Tl e md / passes freely through the eentre of the eore'^i, a^d has at ite lower end a damp for holding the earbon peneil. A wa her h, of brsss, surrounds the rod / jast below L eore d, ZTZ Il It ' w 448 THE ELECTRIC LIGHT. one edge resting on the lifting finger attached to the latter, while the other edge ia overhung by the head of an adjustable screw ^^'r'he^etal post c is supported and guided by a tubular post ^• secured to a suitable base plate. Attached to the lower end of the post c, and passing out through a slot in t, is the arm y, supporting an insulated holder for the lower carbon If, now? one conducting wire, from the machine, ^e connected to the base plate, and the other to the lower carbon holder the current of electricity will pass up through the posts t and c, Fig. 219. through the helix a, rod/, and the carbons k k, thus completing the circuit , ,. .„ . .1 ^ The axial magnetism produced in the hehx will draw up the core d, and it, by means of the lifting finger, will raise one edge of the washer h, which, by its angular impingement against the rod/, clamps and lifts it to a distance controlled by the adjust- able stop X, but separating the carbon points far enough to ^llLtalfnsburn away, the increased length of the electnc arc increases its resisl^nce and weakens the magnetism of the brush's automatic bequlatoh. 449 helix and, therefore the eoil, rod and carbon move downward by the force of gravity, nntU, by the shortening of the are the mrtrs;S*'^4r",''-"«'''«-'^-^''''^'°wnwirit ment arrested. When, however, the downward movement i, sufficient to bring the clatch washer A to the snpZTft wi be re.eased from the clamping effect of the lifting Zor, and tl oflh^eTllCttl'"""' T'""" "^'"^ -PwJmovlfn or tne core, due to the increased magnetism of the helix. The normal position of the clamp washer is with the edire u^der the adjustable stop, just touching the support a the offife I ho;:™: J,^-S'''-g^»»'«*eslippfngof thf rod'igh t points thus contm^ued at .t^;^; Z:L^2:tt:^'' ■ In the lamp used in these experiments, the helix was ^om SIS s-rr *jr;t :r -i?* -' • "2 with varying the weight to be Uft!^ ;,. ' '" ™™«>=''<>n hel^x.eitLVl„adinf:hrco:eo:tl^^^ In order to make 'he measurements as accurate as possible it o? itsrfrh:To^''f^r^\*^ ^pp^^^"- *^' - - -^,o A «l and twenty g,a J Were much higher intenaities of ]i'«"*■ "-»' ^^ferences by which aC expS; ' establishing standarf were connected. e^Penments upon the different points t^-ons made at intervals, care befal lu ^? ''°""' ""^ <"»erva. and other conditions noC ZTL ":'"'"" *^ ^P^^ drtions necessary to insure con-«^t u °" ""P"rtant con- tion of the carbon po"! G^ """ ™'' *" '^"»«ve posi. of the two sticks or pencUs of ^b ""* "'".'"'^™ '^' ^^^ a^es liat the light producXwd Z^^^Z Z * n^ ""^ ""«' ^ tiona Were the axes of the carboTn^ T^^^ '" "" '^^■ line, a much greater quant y oTtefL T '"' *' ^« one direction, and the result of . T ^ I"'°i*<"ed in duced, based on the inve^ "' l'™ " T f ""= "k''' P™" photometer, would be Jg^t^o"™!'';^ *«'»"»« f.^om the adjustment was in the one'orTor Str" "^'^ "^ ""^ J:i:t'':t\: x:rtif,™ff rr'r'^'*^ focussing len, with its aL t right'at^erfo'tt t"'™ '"'"P' ^ to the photometer, and a,, ima^e ,fro IcteTu *"""" °* ''sH the observ r to see the condit 1? , '^^ " '™"" ''"""ing points without fatig„i*tI^evrPh!f ^"f " "^ «» ^^^o? from *ir-- + +• ^fei'iieeje. I'liotoffraphi^ w^,.« „i„„ +.7 *-- an. to trme, at the moment of makfng the;;:;^^' ^2 THE ELECTRIC LIGHT. observations-tlius securing a permanent record of the conaition of the carbon points. ^ • ' i ,^ Another difficulty in determining the exact photometric value of the electric light is the fluctuation, or rather, the moving from side to side, of the electric arc, and great care was taken so to adinst the conditions, that the arc or flame should be steady, and equally distributed about the ends of the carbon pencila Figs 221 to Q28 are full size, exact reproductions of the photo- graphs taken, and fairly represent the average condition of the carbon when observations were made. ^ It was found, that although there was a slow consumption ot the negative carbon, there was, at the same time, a constant " stalagmatic" growth of particles carried from the positive car- bon by the action of the electric current ^hese stalagmites assumed different forms, as shown in the cuts, but no particular form seemed to be produced by the current from the difl^erent machines, except that the deposits on the negative carbon won d be^^ome greater with increased current These deposits would build up gradually until they had assumed the forms shown in fisB 226 and 228 ; then growing narrower near the base, until, by a weakening of the current by this and the consumption of tne upper carbon, the lamp would readjust itself, and the piece would drop oft The effect of these growths on the intensity of the light was scarcely appreciable, except for a few seconds before and after the readjustment of the lamp. , , , ,, Experiments were also made to determine what would be the efiect on the amount of light produced by so adjusting the carbons, that the front edge of the upper one was m hne with the centre of the lower one. Fig. 229 shows such an adjustment, and is from a photograph taken while measuring the light pro- duced from the small Brush machine, running at twelve hundred and fifty revolutions per minute, and resulting as follows: „ , 2218 candles. ^.7* : 578 " ^f ::::::::::::::::::: ^s - Back • ^^^ 3486-^4=871. TABIATION IN AMOUNT OF LIGHT PEODUCED. 453 conllonf eCtTht '\*^^ T' "^^^^^'^^^ ^^^ *^^ -- line, was^quaf V^y^^^^^^^ ^^^^^ - -e vortical candles. TMs would l 1 ^^ ^^"^''^ "^^ twenty-five mmimmJ '""''' ^ ^^'^'«^t« t^at nearly sixty-six tig, 221. i^i?. 222. -^■(7 223. ■Rj?. 224. ""'■"'■' ^^'■^=- «^.2«. .^.„e. per cent more light was produ^d by this adjustment of th^ carbons; but a close study of the conditions sa Z us thtt ™«^^^no»he»se^™d«>at^^ ,^1 TJy^ „.*uT^®:'°^*a^« arc Should have been shown in fl., 09r „- .•_ ...TZ rT— •-aiuuiis used were couted with copper. " ~° "^ '" "'f' -''• ^" ^^e 454 THE ELECTBIC LIGHT. from such adjustment, except when the light is intended to be used in one direction only. We would here call the attention of those who may compare our results with those obtained at the recent experiments at South Foreland, England, to the following statement upon this point, in the report of Mr. Jas. N. Douglas, engineer to the Trinity House, page sixteen of the official report: I have found this arrangement of the carbons (the axis of the bottom carbon nearly in the same vertical plane as the front of the top carbon), and assuming the intensity of the light with the carbons having their axis in the samci vertical Ime to be represented by one hundred, the intensity of the light m four Fig 229, directions in azimuth, say east, west, north and south, will be nearly as follows : East or front intensity 287 to 100 „ ,, .,„ 116 to 100 North or side „ ,, „ 116 to 100 South or " „- ^ , , 38 to 100 West or back • •• 661-7-4=139 to 100 ^ * * * ^ * * In measuring the csindle power of the light produced by each machine, I have given the mean intensity obtained in the ^r option of the photometer, the carbons in lamp working with i to be lompare lents at pon this ■ to the axis of he front ^ht with le to be in four will be * )duced by led in the rking with COMPARISON WITH RESULTS OBTAINED BY MR. DOUGLAS. 466 the Holmes and Alliance max5hinv.s being always arranged with the axes in the same vertical line, and the carbons in the lamp workmg the Gramme and Siemens machine being always ar- ranged with the front edge of the top carbon nearly on the centre of the bottom carbon. It is, therefore, evident tbat the results given by Mr. Douglas must be divided by 2-87 in making a comparison with those obtained by ua Thus in the table on page 31 of the official report, in the column headed light produced by horse power in standard candles he gives for the Gramme machine condensed beam twelve hundred and fifty-seven; but if this be divided by 2-87 we have four hundred and thirty-eight candles, which is, no doW still too high, our result of three hundred and eighty-three can- dles per horse power for the Gramme being obtained under the careful and rigid conditions before named. In many battery circuits a high external resistance may be employed, and the electromotive force remain comparatively constant, while in dynamo-electric macldnes, in which the re- action principle is employed, the introduction of a very hi^h external resistance into the circuit must be necessarily attended by decided variations in the electromotive force, due to changes in the mtensity of the magnetic field in which the currents have their origin. Moreover, a considerable difficulty is experienced in the great variations in the behavior of these machines when the resistance of the arc, or that of the external work, is changed. Changes, due to loss of conductivitv by heating also take place in the machine itself. " ' _ The variations above mentioned are also attended by changes m the power required to drive the machine, and in the speed of running, which as:ain react on the current generated. There are certain normal conditions in the running of dy- namo-electrio machines designed for light, under which all measurements must be made, viz. : 1. The circuit must be closed, since, on opening, all electrical manifestations cease. 456 THE ELECTRIC LIGHT. 2. The circuit must be closed through an external resistance equal to that of the arc of the machine. 3 The arc taken as the standard must be the normal arc of the machine. This condition can only be fulfilled brnoticing the behavior of the machine while running, as to the absence of sparks at the commutator, the heating of thfe machine the regu- larity of action in the consumption of carbons in the lamp, etc. 4. The speed of the machine must be, as nearly as possible, constant . ^ t ^a rv„-.af ■ 6. The power required to maintam a given rate of speed must be, as nearly as possible, constant The machines submitted to us for determinations were, as already stated : j.„ 1 Two machiues of different size, and of somewhat difierent detailed constructioi. , ]>ailt according to the invention of Mr. L. F. Brush, and styled respectively in our report as AS the larger of the two machines, and A^, the smaller. 2 Two machines known as the Wallace-Farmer machines, differing in size, and in minor details of construction, and desig- nated respectively as BS the larger of the two, and B^ the smaller In the case of the machine B\ the experiments were discontinued after the measurement of the resistances was made, insufficient power being at our disposal to maintain the machme at its proper rate of speed. 3 A Gramme machine of the ordinary construction. All the above machines are constructed so that the whole cur- rent traverses the coils of the field magnets, being single current machines, in which the reaction principle is employed. In the case of the machine designated A^ the commutators are so arranged as to permit the use of two separate circuits when For the purpose of preserving a ready measure of the current T>roduced by each machine, under normal conditions, a shunt was constructed by which an inconsiderable but definite proportion of the current was caused to traverse the coils of a galvanometer thus giving with each machine a convenient deflection, which ELECTRICAL RESISTANCE OF MACHINES. 4g7 .tof; tZ *'•'"' .^,.7'°"l«<=''i ^ *e inte-position of this shunt m the circuit d.d not appreciably increase its resistance the normal conditions of running were preserved As indicating the preservation of norm.al conditions in any case, the speed of running and the resistances being the same L m any previous run, it was found that when there was an equal expenditme of power as indicated by the dynamometer, theTu ! ZlLl::!' " "''"^'^ "' '"« galvanometer, w. in each Certain of the naachines experimented with heated consider- ably on a prolonged run ; most of the tests, therefore, were made when the machines were as nearly as possible at about the tern perature of he surrounding air. It is evident that no oZr taudard could be well adopted, as under a prolonged run the temperature of the different parts of the machine wof Id inc^ase very unequally; and, moreover, it would be impossible Tmake paL ""'asurements of the temperatures of many^uch brite^Xi"^-^^' «3is<«nceof the machines, a Wheatstone's br dge, with a slidmg contaet, was used in connection with a deh- eate galvanometer and a suitable voltaic battery. In tokine the rcsistaces of the machines, several measurements wem^ 'de with the armatures in different positions, and the mean of fee measurements taken as the true resistance It was, of course, a matter of the great..t importance to obtain a value for the resistance of the arc in any ca^e, since upon the i^ative values of this resistance, and that of tie machine L efficiency would in any given case, to a great extent, depend In each case the arc of which the resistance was to betaken wa that which was obtained when each machine was giving its a™ age results as to steadiness of light and eonstency of the galvan ometer deflection. gaivan- The method adopted for the measurement of the are was that of substitution, in which a resistance of german silver Zim mersed m water was substituted for the arc, without altering a^y of the conditions of running. This substituted resistance wal 458 THE ELECTBIC LIGHT. afterwards measured in the ' ?oal w«y, and gave, of course, the resistance of the arc. It coul« , therefore, when so desired, serve as a substitute for the arc. IFo other method of obtammg the arc resistance appeared applicaole, since the constancy of the re- sistance of the arc required the passage of the entire current through the carbons. It maybe mentioned, as an interesting fact in this connection, that when the current flowing was great, the arc coiTespoudmg thereto had a much lower resistance than when the current was small This fact is, of course, due to increased vaporization, consequent on increased temperature in the arc. In determining the true arc resistance, the resistance of the Fig. 230. electric lamp controlling the arc was measured separately, and deducted from the result obtained with the german silver wire substitute. . For ease of obtaining a resistance of german silver wire equal in any case to that of the arc, a simple rheostat was constructed, by winding, upon an open frame, such a length of wire as was judged to be in excess of the resistances of any of the arcs to be measured. By means of a sliding contact, successive lengths of the wire were added, until the conditions a<^ above stated were reproduced. Fig. 230 shows the arrangement of the rheostat With this arrangement, no difficulty was experienced in repro- ducing the same conditions of normal run^^ng as when the are MEASUREMENT OF CURRENT. 459 was used. The same conducting wires were used throughout these experiments. Being of heavy copper, their resistance was low, VIZ.: about -016 ohm. Having thus obtained the circuit resistances, we proceeded to determme the value of the current Here the choice of a num- ber of methods presented itself. , We selected two methods, one leased on the production of heat in a circuit of known resistance ^nd the other upon the comparison of a definite proportion of the current with that of a Daniell's batterv. In the application of the first method, "eight litres of water at a known temperature, were taken and placed in a suitable non- conductmg vessel. In this was immersed the german silver wire before mentioned, and the sUding contact so adjusted as to afford a resistance equal to that of the normal arc of the machine under consideration. This was now introduced into the circuit of the machine. All these arrangements having been made, the tem- perature of the water was accurately obtained, by a delicate ther- mometer, reading readily to quarter degrees Fahrenheit. The current from the machine running under normal conditions was allowed to pass, for a definite time, through the calorimeter so provided. From the data thus obtained, after making the nec- essary corrections as to the weight of the water employed, the total heating effect m the arc and lamp, as given in Table lY was deduced. ' Since the heat in various portions of an electrical circuit is directly proportional to the resistance of those portions, the total heat of the circuit was easily calculated, and is given in Table v., m English heat units. For ease of reference, the constant has been given for conversion of these units into the now com- monly accepted units of heat. _ Haying thus obtained the heating effect, the electrical current IS readily determined by the well known formula, R t c ' where C= the veber current per ohm, TTthe weight of water In, 460 THE ELECTRIC LIGHT. CO » (-1 M o 1^ o l-t « o » I o P o o EH 01 I o H O P O W a o c3 d -U M-l 4i to OS - ^ bO O :: ID bD r <1 "o'S d) o •sniqo JO 80uw»si9e'a l«»ox DQ OS QQ g a •duiBT: — OiY JO O 00 ■rii OS 10 t- •JoionpnoQ — euiipBH JO CO CO 00 05 •oay JO 9Aisnpxa 'daiBi JO oouwjsjse'a; CO CO o o Hi PQ •eai^ Sui^onp -uoo JO eou'BiBisffa m H o !zi » •draB^+ OiV JO •joionpnoo+ OUll1 eo 10 CO o CO CO tH i-H o o 00 CO 10 05 05 "+• '^ cc ^ 00 cq o »p CO o CO CO rH i-H o o . > 00 T-l 1 O 1:3 '2 2 00 -* op CN b- 00 T^ CO

o 1—1 -• f— H N IN <^<} <1<1 Wpq Wpq TABLE OF THEKMK; EFFECTS. 461 "1^ o 6 a p o 03 Eh o a 93 O ^ 5 H Is p^ o fe w w >. rU o CO KH d 1^ o Oh bs W a W S EH i Snipnpui 'Sni -p«aa aaleuiouiBUifd •sjnuim Jed •ab'^ •euiqoBui JO paedg CO o o 8^ r-4 o A a:> cq o CO 8S ■4" -H Tt^ 00 CO o •pUOOBS J9d 'oiqo jed !)Be|{ 00 00 CO cq t Oi (M 00 O •^ ol 'o'h spunod ai iinojp aq; JO :>Baq"iwjox 55 00 »p 00 lb O Oi Tt4 t- CO CO OD t1i o -* -5*^ O OH epunod ni 'doIBI pUB OJB U[ ;b9JJ 00 CO op CO b- IT) 00 tH CO CO CO >* »0 00 tH 00 (>l o b- lb o 1— I 1— I c^ ■OJB o^ iTjnba ja^eoi -laoiBQ JO eouB^sisaa 00 oo 1:^ t- 00 qp GO qq ? CO »0 10 Tji G CO 10 OS a o a o P^ " j "j v\ ^ <^ 6^ 'rfSk-^ ^ "Sfc .^ A^ '^ 6 ^ 462 THE ELBGTBIG LIGHT. pounds, h the increase of temperature in degrees Fahrenheit, seven hundred and seventy-two Joule's constant, B the resistance in ohms, t the time in seconds, and c the constant, "TSTSSS the equivalent in foot pounds of one veber per ohm per second. The currents so deduced for the different machines are given in Table VI. The other method employed for obtaining the current, viz., the comparison of a definite portion thereof, with the current from a Daniell's battery, was as follows : a shunt was constructed, of which one division of the circuit was 12 ohm, and the other three thou- sand ohms. In this latter division of the circuit was placed a. low resistance galvanometer, on which convenient deflections were obtained. This shunt being placed in the circuit of the machine, the galvanometer deflections were carefully noted. To- the resistance afforded by the shunt, such additional resistance was added as to make the whole equal to that of the normal are of the machine. These substituted resistances were immersed in water, in order to maintain an equable temperature. Three Daniell's cells were carefully set up and put in circuit, with the same galvanometer used above, and with a set of stand- ard resistance coils. Eesistances were unplugged sufficient to produce the same deflections as those noted with the shunt above mentioned. The shunt ratio, as nearly as could conveniently be obtained, was yrfu-ir* Then the formula, 5 n X 1 "079 (?= -j^ . where G equals the veber current, s the reciprocal of the shunt ratio, n the number of cells employed, 1-079 the assumed normal value of the electro-motive force of a Daniell's cell, and R the re- sistances in the circuit with the battery, gives at once the current In comparison with the total resistances of the circuit, the inter- nal resistance of the battery was so small as to be neglected. The results obtained were as follows : MEASUBEMENT OF ELECTKO-MOTIVE FORCE. 463 Name of Machine. Large Brush Small Brush Wallace-Farmer ] Gramme ■STyrr li & U 0' 1 s i ff 3 3 3 3 3 Resistances Unplugged. 2710 ohms. 3700 " 8320 " 6980 " 4800 ■< Speed of Machine. 1340 rev. 1400 " 844 " 1040 " 800 " • From the results thus derived, the electromotive force was deduced by the general formula, E=GXR Statements are frequently made, when speaking of certain dy- namo-electnc machines, that they are equd to a VenTumber however that no such comparison can properly be made, .since he electro-motive force of a dynamo-electric machine, in ^hlh the reaction principle is employed, changes considerably with any change in the relative resistances of the circuit of which it forms a part, while that of any good form of battery, disregard- ing polarization, remains approximately constant The internal resistance of dynamo-electric machines is, as a rule, very much lower than that of any ordinary series of battery cells, as gener- ally constructed; and, therefore, to obtain with a battery condi- tions equivalent to those in a dynamo-electric machine,' a suffi- cient number of cells in series would have to be employed to give the same electro-motive force; while, at the same time the size of the cells, or their number in multiple arc, would require to be such that the internal resistance should equal that of the machine. Suppose, for example, that it be desired to replace the large Brush machine by a battery whose electro-motive force and in- ternal and external resistances are all equal to that of the 464 THE ELECTRIC LIGHT. n EH Hi Si! I c K 1^ o O o 5 S 1 si II 2 ■* ■* ^ -^ oa *• ^ ^51 ^n ^5^ 1 CO (N rt4 00 00 00 tH 1-1 tH T-l I n3 p 00 S :^ 05 •8oni«j\^ ^ OS oiJ!(onioaiBni((j CO S :g OS SatpaodsaiJOQ rH^ OS • (M CD .-H 1— tH • r-i •OJB eq* uj Saused 00 • • «3 00 ■ OS 03 • ip $ -dB !^aaj ino jo ^ijoa^. ; cb »b ! 00 1—1 eqi JO "ineo jaj^ l» :io CO , cO »o H 5 i^ § 00 • CO OS • to 1-t ^ 65 - • tH • OS • «••§! CO . «5 t- , OS ■» t^ ill g s ^ U5 T-H OS 00 cq Oi pTt< ip-^ tH OS 9 65 10 (M 1-1 »0 K5 OS .2 S'ffl CO kO OOt- 00 ^ w 08 j3 S n M "11 t- • t- CO • '^o _j 5i n t- CO (M St £ 1 <1 1 EPriOIENOr OF DYNAMO-ELEOTBIO MACHINES. 465 machine, and that we adopt a8 a stodard a Daniell's cell of ah .ntemal reactance of, say, one ohm. Beferriog to Table VLtte eWmoUve iorceof this machine ia about thirtynine vor4 to pn>duce whch about thirtyseveu ceUs, in aerie^^wov^d te re rf \ t^ u^ ^""^ ^^- *''« '■"^"l "Stance of t^rm^hi^e ^a^ut -49 ohm Tojeduce the resistance of our standarfceU to th«, figure when thirtyseven cells are employed in serie hundredT^!^ Jl^^y-seven by seventy-six, or two thousand eight Mica It must be borne m mind, however, that although the ' maehme above mentioned is equal to two thousand eighfhun dred and twelve of the cells taken, that no other ~ jem^f . Ind tov' *"' "^'"'°""*- ^^' -^"'7-- i" muSrire and m^r ..'" '"■"'• "^'^ '-Produce the same cond tionl' and, moreover, the external resistances must be the same S «.me pnncples, applied to the other machines, wouM when fe mtemal resistance was great, require a lai^e number of ll W «n."ged m ,„eh a way as to be extremei; wastofu from "y fe tis^frbL:;^^ ^'- "- ^-^4^^^ The true comparative measure of the efficienov of ,1^no«. wort derived from electrical currents, whether as light heat or lsumedtrr"°"' "^ ^""IV comparing the unt o;:'ork otxiTn* trthirctrii^rLTnT"''^^ *- «■« data are aiven. T„ *!,? « , , ™" ""' ""mparative Kiv^re t^W noJ ?'""" "'^ dynamometer reading gives the total power consumed ; from which are to be dednctpf he flguresgiven in thesecond column, being the w^kextntd m fnetion, and in overeoming the resistance of the air Xutl of course, It must be borne in mind th^t ti,", . • .^ ' most economical in ^>.^K oZZ^XiT'^TZT'': anee of the air and the friction are the ieasr Th.?.,- f T g-vea the total power expended in pr:dX It 'tf e^t": 466 THE ELECTRIC LIGHT. portion only of which, however, appears in the eflEective circuit, the remainder being variously consumed in the production of local circuits in the different masses of metal composing the machines. This work eventually appears as heat in the machine. Columns four, five and six give respectively the relative amounts of power variously appearing as heat in the arc, in the entire circuit, and as heat due to local circuits in the conducting masses of metal in the machine, irrespective of the wire. This latter consumption of force may he conveniently described as due to the local action of the machine, and is manifestly comparable to the well known local action of the voltaic battery, since in each case it not only acts to diminish the effective current produced, but also adds to the cost We desire to call attention to the fact, that in all the determi- nations condu9ted by us, we have been particularly careful to insure a definite relation between the external and internal re- sistances in each case— a condition of paramount importance in the effective working of these machines. It is evident, indeed, that no determinations made with an unknown or abnormal ex- ternal resistance can be of any value, since the proportion of work done, in the several portions of an electrical circuit, depends upon, and varies with, the resistances they offer to its passage. If, therefore in separate determinations with any particular machine, the resistance of that part of a circuit of which the work is meas- ured be, in one instance large, in proportion to that of the re- mainder of the circuit, and in another small, the two measure- ments thus made would give mdely different lesulte, since in the case where a large resistance was interposed m this part of the circuit, the percentage of the total work appearing there would be greater than if the small resistance had been used. When an attempt has been made to determine the efficiency of a single machine, or of the relative efficiency of a number of machines, by noting the quantity of gas evolved in a voltameter, or by the electrolysis of copper sulphate in a decomposing cell, when the resistance of the voltameter or decomposing cell did not represent the normal working resistance, it is mamfest that CONDITIONS OP ECONOMICAL WOSKINO. 497 ^r^^ cannoe p„,pe.„ be .aken aa a .easu™ of the actual it was also hSh burttvlt I ""' "■■" '^'^'»°=« n"™"' «o each other. The am res LJe T "^T^^"'^ ^^P^--^^"' "PP" current, the natnZ/ZTZt'^t "^ t"- ""^-^of the Other conditions being the ^mrrt; .°" *•"='■• *''««<=« »P«n^ when the current is Xt ' '^'*"°" °^ "■« «« ^^^ wi.frdn"berntr„twr' r "-"' ^-''^•'"-s.'* is the most economlalL whlh'^r^ ''?! *'!»'"• *»' "^oWne a considemble prop^^on tot.,' ™* t°" '" *« ^"^ ^ea^ since, with any^vCa^^t the v " ""= '''°'« '=™»''. ^d ^stance, wc havfin T,\Te iV^^,!''*''?"^"'''™''' *° *^« '^• regard. For example in the J„ .7*. comparison in this large Brush maehi,tX LisUnl o/t ™'"^''°" °* ^*' *« siderablymo.^ than one h^f the t„M "'""' "°"''""*«= «""- circuit, while in B», thesmafl wtlf J*^"*^""" °' *^ «■>''« ^itutes somewhat momThal T-S™"' ■"■"="»«• " con- These relative Jstanrsle of" "* ^ *°*' '^«'='«''«^ the cum^nt genemted.tbSh is u n' ™'{ *' P"P°^<» <>* heat, the conditions of' ^owt ~^^" '^ "" '^ '«^' »'' not being there expressed """"^ *° P-'^d'^ce the current m^ht^iSrii;:; trer^.-v-"^ -'^^ <" *« auction from those parte rf the -,?^ T '"*'"="^ ^""^ «>°- aa explained in afomerpartlf tht -'""f ^^ ■'^'" ""ti"". distance, and a 00^:;^ fl^^Te T f" '"'''^'' Thus, in Table IV., at the temperlre of 8^0 f^ Z'T - ohn. Thle .«erenr :lir„:~ -; >: ™^ ^Jr-^r-rrt-s^:---- 468 THE ELECTRIC LIGHT. These correspond to different connections, viz., the resistance, 1-239 ohms, being the connection at the commutator for low re- sistance, the double conducting wires being coupled in multiple arc, while 5*044: ohms represent the resistance when the sections of the double conductor are coupled at the commutator in series. Eeferring to Table Y., the numbers given in the column headed "Heat in arc and lamp," are the measure of the total heating power in that poifcion of the circuit external to the machine. They do not, however, in the case of any machine, represent the energy which is available for the production of light, which depends also on the nature and the amount of the resistance over which it is expended. For example, the heat in arc and lamp are practically the same in each of the Brush machines, if the measurement of the smaller of these machines be taken ,«.t the higher speed. The amount of light produced, however, is not 'the same in these two instances, being consider- ably greater in the case o£ the larger machine. The explanation of this apparent anomaly is undoubtedly to be found in the dif- ferent resistances of the arcs in the two cases. In the large Brush machine the carbons are nearer together than when the small machine is used. This suggests the very plausible expla- nation, that the cause of the difference is to be attributed to the fact, that, although the total heating effect is equal in each case, when the large machine is used, the heat produced is evolved in a smaller space, and its temperature, and consequent light giving power, thereby largely increased. It would seem, indeed, that any future improvements made m the direction of obtaining an increased intensity of light from a given current, will be by concentrating the resistance normal to the arc in the most limited space practicable, thereby increas- ing the intensity of the heat, and, consequently, its attendant light It may be noted, in this connection, that in all the cases in which the resistance of the arc was low, the photometric inten- sity was high. This, indeed, might naturally be expected, since a great intensity of heat would, under existing conditions of the use of the arc, admit of increased vaporization, and consequent lowering of the resistanca ENERGY OP CURRENT IN HEAT UNITa 469 In the column headed "Total heat of circu-* " are given the quantities of heat developed in the whole circuit, which num- ber, compared with those in the preceding column, furnish us ^ith the relative proportions of the work of the circuit, which appear in the arc and lamp. The column headed "Heat per ohm per second," gives the relative work per ohm of resistance in each case, and these num- bers, multiplied by the total resistance, give the total energv of the current expressed in heat units per second. In Table VI. are given the results of calculation and measure- ment, as to the electric work of each machine. It is evident to those acquainted with the principles of electrical science, that in the veber current and the electro-motive force, we have the data for comparing the work of these machines with that of any other machine or battery, whether used for light, heat, electrolysis or any other form of electrical work. As might be supposed, the values given in Table YI, of the veber current, approximate relatively to the photometric values, as will be seen from an examination of that part of the general report of the committee relating to photometric measuiementa The values of the veber current, as deduced from the heat developed, and from the comparison with a Daniell's cell, do not exactly agree; -nor could this have been expected, when the difficulty of minutely reproducing the conditions as to speed, resistance, etc., is considered. By comparison of the electro-motive force of the different machines, it appears that no definite unit seems to have been aimed at by all the makers as that best adapted to the produc- tion of light Table VIL is designed especially to permit a legitimate com- parison of the relative efficiency of the machines, as well as their actual efficiency in converting motive power into current. The actual dynamometer reading for which we are indebted to the subcommittee on the measurements of power, is given in the first column. On account of differences of construction, and differences in speed of running, the friction and resistance of the :i \m m 470 m P a a o •a i THE ELEGTRIO LIQHT. ■noipuj Smionp CO <>J CO OCO rH rH JO -ijueo aaj •OJB ut V peziipu JSMod }o 1-1 00 00 o «0 (M 00 •jjno CO to :^ ^ OS CO CO •jp eioqM ni Sat ■^ CO lO 00 »O00 t^ 00 CO CO t- 00 CO O OS Tt4 •»«9q lO -* tH 00 «o 00 B« ajv ni -* -H \0 1>- -^ CO SaiJBai^dv -j -^ CO CO <» CO o CO «o (N 0» 00 'M o •noipuj ^ *-t^ <© t^ Saipnpep ja^jv OS CO . s 'paninBaoa -^ -j 00 oo CO rH »o o 00 "-O O (N (M o oa t^ O t^ r-* 'JIB }0 80a«lB188I 05 coos 00 o to pu« uopoia j "-;:> tH «o O 00 00 -* oq 'pamneuoo o o ^ <» TJ4 OS d '3. SaipTOj CO O lO OS 00 OS o j9:)8aioniBaif(x o T-l (M 1-H tH OS s « a S .9 a o "e i COMPARATIVE MERITS OF DIFFERENT MACHINES. 471 air vary greatly, being least with the Gramme, as might be ex- pected, since the form of the revolving armature, and the speed of the machme, conduce to this result This is, of couree. a pomt greatly m favor of the Gramme machina That portion of the power expended available for producing current is given in the third column, being the remainder, aftel deductmg the fnction, as before mentioned ; but this power is not m any case fully utilized in the normal circuit This is lound to be the case by comparing calculations of the total work of the circuit in foot pounds, as given in the appropriate column, with the amount expended in producing such current For instance, in the case of Ai, the large Brush machine, the available force for producing current is 89656 f. p. per minute, of which only 63646 reappear as heat in the circuit The ball ance is most probably expended in what we have termed heal ac ^, that is, the production of local currents in the various con- ducting masses of metal composing the machine. The amount thus expended in local action is given in the column designated F. p. unaccounted for in the circuit" A comparison of the figures m this column is decidedly in favor of the Gmmme machine, it requiring the smallest proportion of power expended, to be lost in local action. When, however, we consider ^at the current produced by the large Brush machine is nearly double that produced by the Gramme, the disproportion in the local ac- tion is not so great The columns containing the percentages of Power utihzed m the arc," and "Useful effecte after de- ducting fnction," need no special comment The determination which we have made, as described in the foregomg part of this report, have enabled us to form the follow- ing opinions as to the comparative merite of the machines sub- mitted to us for examination • 1. The Gramme machine is the most economical, considered as a means for converting motive power into electrical cur- rent, giving in the arc a useful result equal to thirty-eight per cent., or to fori;y-one per cent after deducting friction and the resistance of the air. In this machine the loss of power in friction 472 THE ELECTRIC LIGHT. and local action is the least, the speed being comparatively low. If the resistance of the arc is kept normal, very little heating of the machine results, and there is an almost entire absence of sparks at the commutator. 2. The large Brush machine comes next in order of eflBciency, giving in the arc a useful effect equal to thirty-one per cent of the total power used, or thirty-seven and one half per cent, after deducting friction. This machine is, indeed, but little inferior in this respect to the Gramme, having, however, the disadvantages of high speed an'd a greater proportionate loss of power in friction, etc. This loss is nearly compensated by the advantage this machine possesses over the others, of working with a high external, compared with the internal resistance, thus also insuring compara- tive absence of heating in the machine. This machine gave the most po" "erful current, and consequently the greatest light. 3. TL ?mall Brush machine stands third in efficiency, giving in the aw a useful result equal to twenty-seven per cent, or thirty-ono per cent after deducting friction. Although some- what inferior to the Gramme, it is, nevertheless, a machine admir- ably adapted to the production of intense currents, and has the advantage of being made to furnish currents of widely varying electro-motive force. By suitably connecting the machine, as be- fore described, the electro-motive force may be increased to over one hundred and twenty volts. It possesses, moreover, the ad- vantage of division of the conductor into two circuits, a feature which, however, is also possessed by some forms of other machines. The simplicity and ease of repair of the commutator are also advantages. Again, this machine does not heat greatly. 4. The Wallace-Farmer machine does not return to the effect- ive circuit as large a proportion of power as the other machines, although it uses, in electrical work, a large amount of power in a small space. The cause of its small economy is the expendi- ture of a large proportion of the power in the production of local action. By remedying this defect, a very admirable machine would be produced. Within a short time past a new dynamo machine, invented MAIIM'3 MACHINE AND LAMPS. ^73 by Mr. Hiram Maxim, o( this city, has been brouelit out ,.H ■ now bemg mtroduced by the United States Ekotric Lil^ " of I.>ndon, but the armatu,^, or revoWnKportion if "- design, which is said to be free from m7,^v k . ' " "*'' to other machines. The onTv n^L 7 °^"'"°"' """"""' wear takes place on tZti^l' ^\rtt:'" ""''^"""^ ^rvinV^r- -- -"- - " rnr'tre In some machines this portion has been hnilt ;„*„*!, so that when it is worn the whok Z. .. '"*f 'he maohme, bvulding in case ofreLl Mr t "'' ™"''^ '""J"™ '«" »achinf so that ^C'^Zl, ouJ^Zenr^.^TT'^.'^ to wear, so that they may be renl,!!^ T P""^ '"'''«'=' trifling cost ^ P^^ '" ^ *«" """"'««. »nd at a the'i"Lf:;ry!rg a^^'r/siT ""^' '"''"'' '^ ^'"'- - flg, 232, a'pe^p^ivT^e/^rrZra:: ^tf T^ A « the positive carbon holder and B the lZ,tit. 4 "*"■ tion of this lamp is as follows : ^"^ ^^^ "P™" The negative carbon, which may be siy i„.,t„ i , . secured in the lower ho der B the L Lw '""''^ '™a being as the pinion that g J Lto t S. ° LTo t '"™ "P' direction without driving the train Tgli T2T '",""" mches long may now be inserted in *e'"p holtr andij pj:: foftiaS^frrurn^r-tfgCrwi^ar the weigh, of the positive carrier to ™tate fheZ^'orj^p: and by winding up a cord, to driw the negative upwarfS the combined movement of both causes the potets oil t.!^ carbons .to meet This will estabUsh an elecS 1^^ 2 - ■■1 k y ■ 1 ■ -1 '" ' \ \ 1 4: 474 THE rLECTBIO LIGHl'. Fig. 231. maxim's automatic lamps. 476 -fwff. 2, ■ifs. sa,i ana 233. 476 THE ELECTRIC LIGHT. carreiit will at once commence to pass, and the electro magnet in the bottom of the lamp will become excited and draw down- ward the two armatures, one of which draws down one end of the cord that supports the negative carbon, and the other locks the gearing. The separation of the carbons by this downward movement of the negative establishes the voltaic arc, when the light comes out in all its splendor. As the carbons waste away the arf^ becomes longer, and the resistance to the passing current becomes greater, its power to excite the electro magnet corre- spondingly decreasing. The armature E is drawn away from the magnet by a retractile spring, the tension of which is ad- justed by thumb screw D. When the magnetism is so much reduced that the pull of the spring is greater than the pull of the magnet, the spring will force the armatures upward and re- move the detent from the ratchet wheel F, thus allowing the train of gears to 'move so that the carbons slowly approach each other, until a point is reached where the arc is shortened sufficiently to again bring the magnet up to its original strength^ when it will again pull down the armature and lock the gearing. A too rapid movement of the parts is prevented by a small fan, shown in fig. 233. When the carbons are drawn apart to a con- siderable distance and then allowed to approach, this fan will revolve with great speed, and its wings will be spread by cen- trifugal action to their fullest extent ; but when the carbons touch, and the electrical current is established, its speed is much reduced, as the larger armature C is drawn down, and it remains in that position while the circuit is complete. The armature has an attachment which is brought within the field of the ex- tended wings, but it cannot reach them when they are closed. The lan, when engaged by the attachment, can revolve only a quarter turn at a time and at a very slow speed. When the ratchet F, on the fan shaft, is unlocked, it can re- volve rapidly only when the current is broken, and when it is ^ released to feed the carbons to an already established arc, it can * only turn at a speed a little faster than the actual consumption 'of the carbons. Should the arc be broken, or the light be maxim's automatic LAMPa 477 ignet in 7 down- 1 end of er locks wnward hen the to away current jt corre- ay from. \i is ad- much. 1 pull of and re- ring the ,pproach. lortened strength^ gearing, nail fan, a con- fan will by cen- carbons IS much remains armature 1 the ex- e closed, e only a it can re- hen it is re, it can sumption light be cxbnguished, from a high wind or other cause, the large arma- ture C will be liberated, and by bringing the lower carbon agamst the upper carbon, it reestablishes the arc instantly A too rapid movement is prevented by a controlling chamber or dash pot in the bottom of the lamp. All the comparatively heavy work of separating the carbons and reestabhshing the oun-ent is done by the armature C, while the smaUer armature E has only to lock and unlock the train of gearing As the distance to be travelled is very alight, and the work to be done so light, but very little change in the electro-motive force of the current is required to stop or start the feeding of the carbons The tension of the spring that opposes the mag- netism can be adjusted from the outeido of the case to balance Its pressure against a current of any strength Where great nicety and steadiness are required, this lamp seems well adapted to meet all requirements. It is small and compact, and appears a very substantial and beautiful piece of mechanism. Fig 234 is a side elevation of a less expensive kind of lamp devised by the same in.^entor. In this lamp both carbon holder are supported by a cord. As the upper or positive holder de- scends it draws the cord over a pulley and raises the negative just one half the distance travelled by the positive. When the wires are properly connected and the carbons are in position, the top holder may be allowed to run down until the two carbons meet This establishes the circuit and excites the axial magnet in the bottom of the case, when the core is drawn into the helix and the two carbons, through the medium of levers, are drawn ipart until the magnetism and tension of the spring balance each other; and as the carbon is burned away the arc is lengthened the magnetism reduced, when the core is drawn out of the spool,' thus feeding the carbons together as they are consumed until the parts have reached a position where the ratchet on the lower lever is beyond the reach of the pawl ; then the core descends and the ratehet revolves, when the carbons take a new position and the feeding goes on as before. The ratehet wheel is prevented from turning more than one tooth at a time by a I 1 478 THE ELECTRIC LIGHT. end of the lower lever. The pull of the rack is opposed to 'the spring, and when the pull is reduced by the disengagement of a ratchet tooth the lever, and with it the ratchet, are forced down- ward, and the succeeding tooth is caught on the pawl. The core on which the magnetism operates is connected with the rack by Fig. 234. compound levers, so that by changing the position of the con- necting link the leverage can be readily adjusted. Adjustments may also be made with the thumb nut on the top of the case, which is attached to a retractile spring. While this lamp is not so susceptible of a very fine adjustment, still, for maxim's automatic lamps. 479 to 'the at of a down- 1© core ick by le con- m the While ill, for some purposes, it is better than the more expensive one just de- scribed. In places where the speed of the dynamo machine varies much, or where the machine is of poor quality, it is better than the regular clock work lamp. A new lamp, which is quite different from anything before made, is shown m fig. 235. This lamp is in two paits, connected by vertical tubes. The upper portion has a device for feeding the carbons, and the lower portion conteins a device for separa tmg them The focus or source of light is always at the same S' 'li t!-""^ r^°^' ^''^ '^^''^y i^ proportion to the ra- pidity with which they are consumed. This lamp will accom- modate iteelf to widely vaiying currents. Should a slackening of the speed allow the carbons to come completely together, thev would at once draw apart on the increase of speed, and they will do this any number of times in succession; or the current may be broken and established any number of times without dis- arrangement of the parte. This feeding has positive movement, and IS so nicely balanced that a very slight change in the length of the arc allows the carbons to feed, and should the current be broken, the lower carbon, by a very rapid movement, reestablishes It before the heat of the carbons is perceptibly diminished, and before the magnetism of the machine is discharged The light from the naked carbon points is dazzling to the eyes, and casts very distinct shadows. The light is of wonder- ful intensity. To diffuse the light without reducing it very much, and to make the small point appear as large as possible, have been the aim of the inventor in constructing this lamp Above the focus is a silvered reflector, of suitable shape to throw the beams that would be wasted above in a horizontal or down- ward direction, and from this reflector two rows of prisms are suspended. One half of the prisms are arranged with their flat side to the light, and the other half have their angular side toward the light Below the focus is a bowl shaped glass having a zone : .nd just wide enough to be always between the eye of a near observer and the luminous arc. The point from which the light is emitted appears from a distance diamond 480 THE ELECTRIC LIGHT. Fig. 236. STREET ILLUMINATING BY ELECTBIOITY. 481 shaped and quite large. Thus atwith^^nf . vi . '"^°^^fi®<^'t^e light can be looked at with perfect ease, while its brilliancy does not seem to be at all impaired, the ground glass portion of the globe only being between he eye and the luminous point The prisms and glas! bowl enclose the light and protect it from the wind. The bow s suspended by two cords that pass over pulleys and are aV Uched to the reflector. By pulling the bowl dowUrd th re flector IS raised up, thus opening a space through which the carbons may be viewed. A pair of carbons | x f inch Tn these lamps last about three hours, and afford a very sidy Hght Carbons ^ x 1 J inch last about ten hours ^ ^ f aHo^lil ^'^^' T^ ^" ""'^'"'^ '"^ *^^ ways-either by power- ful foci Illuminating at great distances, or by less intense foci giving a more diffused light, suitable for all kinds of nigltwor^ bus including lighthouse service, fortifications, maritim^e serv ce stores, annies m action; and for manufactories, show room! open air use, large workshops, railroad depots and yards' rtm 7,^^^' «*--^«^*«' ---, theatres, large halls, reading rooms, streets, squares, and many other placea For these pur poses electnc light is superior to all othei. and much cheape Mechanical workshops have been among the first to make u- of the electnc light, also dyers and sugar refinei., who need L;7a/o;:dt ^'"^ ''''' ^^^ -^^ -''^- -^ ^-^^^f In the matter of street illuminating by electricity, Paris has TeW Lf 'V'' lead of the world, though the example is now being followed in other cities, and notably in Si Petersburg Madrid and Brussels. The great development of the plrfi system, however, gives it a degree of importance that has not yet been equalled elsewhere ; and the following remarks by Mr P h. 1 ope who has investigated the system during the past sum^ mer, will, therefore, not be without interest : P ^r sum There are at the present time some three hundred electric lamps nightly m successful operation, illuminating the boule- vards, gardens and public buildings of Paris, and arrangements for h^ht,n. nil .1.. principal boulevards and places ; progress. now in 482 THE ELECTRIC LIGHT. The magneto-electric apparatus employed is a Gramme ma- chine, arranged for producing alternating currents, the field of force being fed by a smaller machine of the continuous current variety. The candle employed is the double carbon construction of JablochkoflE. Owing to the peculiar arrangement of this alter- nating machine, it is possible to divide the current so as to fur- nish sufficient electricity to sixteen, or more, separate candles. That this system, in a scientific and practical point of view, is literally a brilliant success is sufficiently evident to any one who has carefully watched its operation, night after night, m the streets and public places of Paris. The quality of the light is pure, soft and white, the general effect being not un- like that of an unusually powerful moonlight, but differs from- the latter in the absence of the heavy, black shadows. These are avoided, partly by placing the candles within globes of opal glass, and partly by placing the lamps at a considerable eleva- tion above the ground, perhaps twenty feet or more. The gas- lights in the vicinity of the Place de I'Opera present an unusually red, smoky and flickering appearance in contrast with the abso- lute clearness and steadiness of the electric light. That the system is equally successful in an economical point of view, in some of its applications at least, would seem to admit of very little doubt It is possibly premature to assert that it is destined speedily to supersede the employment of gas for all purposes of public and general illumination on a large scale, yet it must be said that such a result seems exceedingly probable. The construction of the alternating current magneto" machine will be understood by reference to figs. 236 and 237, the former being a longitudinal vertical section taken in the plane of the dotted line A B C, in fig. 237 and the latter an end elevation (partly in section) of the same. An exterior induction ring or armature of soft iron is securely bolted to the frame of the machine, and is wound with insulated copper wire in eight sec- tions, each of which consists of four coils or subsections, abed (see fig. 237). By reference to the figure it will be seen that the wire, although continuous, is wound in the reverse direction GRAMME'S ALTERNATING CURRENT MACHINE. 483 484 THE ELECTRIC LIGHT. upon each alternate one of the eight sections. The inducing magnet T revolves within the induction ring, and consists of eight soft iron cores, K K, etc., projecting radially from a central hub, H, which is fixed upon a horizontal axis, F, revolving in bearings, and provided with a pulley, which receives its motion Fig. 237. from a belt driven by steam or other power. Like the sections of the external ring, these radial cores are alternately wound with right and left handed coila The outer poles of the cores are fitted with enlarged projecting pole pieces, as seen in fig. 237, m 1 GRAMME'S ALTERNATING CURRENT MACHINE. 485 .ng compound ,«Jial magnet, when the nTX^t in oZtl" T f^f .<^''™°>« machine of the onlinary well known tZ. oi coutse, be produced by the action of a voltaic battery of ,„f floient power. Thi, inducing cur„,nt is conduc^totl ^vl mg magnet by means of brushes of silver plated copZX P It has been stated that the eight section, of .1,. ** • annature are each provided with Zr^^ { ""^ '~" d, all wound in the irTat:^^''"'i^'X^''^'"^ " ' ' erjr r'^, ". ^^^!- <" *e ™:^xreffe:s°f; only nec^ssar, to connect in one series all he t WkX for Th« principle of operation of the machine is, of courae snffl oently obvious. When the shaft, with its radial ma^etlsma^e to revolve, powerful alternating eun^nts arc induXn the^k force of which depends upon the intensity of the magnetTsm in Tiere are at present three sizes of this machine made, of 486 THE ELECTRIC LIGHT. which the one shown in the illustration is the largest. The weight, capacity, and other particulars of these are shown in the following table : Partioulars op Maohinb. Motive power required (horse power) , Revolutions per minute Weight of machine (kilogrammes) " " copper wire (kilogrammes) Number of Jablochkoff candles operated Cost of machine, including small continuous current machine (francs) Size op Machine. 16 600 650 103 16 10,000 6 700 280 40 6 5,000 4 800 190 28 4 3,500 The dimensions of the machine shown in the figures are as follows: Length, incl,uding shaft and pulley, thirty-five inches, width thirty inches, and height nearly the same. The extreme size of the base plate is twenty-eight inches by thirty, and as the drawings are made to scale, the dimensions of any ^.f the other parts of the machine may be estimated without difficulty. It will be seen that the power required is one horse power for each electric candle, each candle being calculated to be equal to one hundred ordinary gas burners. I was informed that the" re- sults of the operation for one year, at the Magazin du Louvre, showed that this estimate is very nearly correct. Several hun- dreds of these machines have been at work in Paris during the past year, and so far as my inquiries extended, I could not learn that any of them had required repairs or had involved any expense whatever, except that of lubrication. I was informed that M. Gramme was at work era anot' t and still smaller machine, intended to supply two cauaieb only, which is quite different in construction from those which have just been described, and from which he expects to realize a material saving in the relative expense both of first cost and power consumed in man );f<. There is also a Gramme machine shown in the Expo- siticii vvi' .ch vfeighs four hundred and forty-one pounds, and is JABLOCHKOFF'3 CAJiDLE. 497 • S'thi't"'"' ," "f ' "l™' *" '^'"^ *"""'"'• ™~"-. "'e cost of which IS only^bout 1,500 francs. For practical purposes mors e r ""T :' r "^"'"^'^ '^ ^"^ <--. - " *" »-h more hable to get out of order than the standard pattern. The electric candle of M. Paul JablochkofI, which is so ex wuh the magneto-electric apparatus of M. Gramme, is a very sample device; so simple, indeed, that, as is frequently tto ^sl IL lorutn""""-*"'/"' ""' O"^'""' -™"«°-- "•«"-" sid?hv T""", """f '^ ''""P'y ™ P'^™S t™ ''^'•t'on pencils side by side, and insulating them from each other by means of a thin plate of some refractory material inserted beL^en them ^h.ch IS a non-conductor at ordinary temperaturerbu" wh ch e^nt The most suitable material yet discovered for this pur- Z.Z On7 ft' ""f '^ ""^ ■" "" '"« «""lles nowTn hS2t t th?r t , "^"'•'^ "^ *' ""^ °* *"' """-rial is to unpart to the light a famt tinge of rose color, which is by no means unpleasant to the eye. ■' SI;,- ^*2^^''//eP"'^™tation,half in elevation and half m «,ction, of one of the lanterns in the Avenue de I'Opera. Ea^h lanteru contains four candles, which are brought into opeiTtbn successivdy, only one candle burning at a timl ThisTs nee" each night, a single candle as now made lasting only one and a half hours. Fig 239 is an enlai^ed sectional view, sWnt the candles and devices for holding them in position. The,e° arl mounted upon a circular base of white onyx. A, which serves not only to support the parts, but to insulate them f«,m each other 1 he four candles are placed in a corresponding number of cliD.s or caudle-holders, arranged in the form of a cross. The candled 488 THE BLECTBIC LIGHT. Fig. 238. jablochkoff's candle. i89 f BO:^ THE LA20nAT0aY 0? T. A. SBIS^J, J \ JDBNLO P A]^ N. ft. J US. A. Fig. 239, 490 THE ELECTRIC LIGHT. The candle itself is shown on a small scale in fig. 289. The two cylindrical pencils of compressed carbon, c c, are each two hundred and twenty-five mm. (8-8 inches) in length and four mm. (0.167 inches) in diameter. The distance apart is three mm (0.118 inches). Fig. 240 shows the tip of a candle of its natural size, in elevation and in section. The candle holder or clip con- sists of two jaws, B B* (^ig. 239), one of which, B, is fixed, and the other, B*, is movable. The opposite faces of these jaws are provided with vertical grooves of semicircular form, for grasping the candle. The four fixed jaws, B, in each lantern are mounted Mthe ne^ti^e ^^ °" arranged m the same way, so that when in operation there are IS>. *n all "™"^' "* '"" '■«'*^ '" -'='''--'■ - -ti" . %. 241 will serve to give an idea of the general arrangement of the apparatus. The alternate current magneto machine wMcl supphes the current for operating the lamp^ is seen at thMowe nght hand corner of the figure, to the left of which is the co" tmuous current machine which supplies the field of force The arrangement of the switch in connection with the ei,.ui,« leading to the four candles w,II be readily undei^tood from the figure 18 R W r ™'°"^ ""f "'" <^°"*™w of a strand of seven No a rettacLT^l^ 1 '»"i,-=°P'«'-' '^'-d together, and have a resistance of about one ohm to one tho„s»p^ fr,,. i,,..j_.. ieet These conducU^rs are insulated wiS strip" T'l^Sl^ 492 THE ELECTRIC LIGHT. rubber, several thicknesses of which are wound on spirally and united by india rubber cement Thesg are placed underground, in tubes similar to the vitrified drain tile used in this country. Some arrangement of insulators (which was not seen) is em- ployed to keep the wires from touching the interior of the pipes. HI Hi Fig. 241. It should have been mentioned in its proper place, that each candle is provided with a conducting tip, as shown at c^ in fig. 240, consisting of a piece of powdered plumbago and gum, com- AUTOMATIC SWITCH FOR JABLOCHKOFP'S CANDLE. 493 pr^ed into a little cylinder about as large as a No. 18 wire and attached to the candle by a strip of asbestos. The object of this IS to complete the circuit when the machine starts, and mamtam it until the fusion of the plaster of paris commences when the latter becomes sufficiently conducting, as before mentioned. The number of lamps now in operation in the Place de I'Opera and the avenue of the same name is forty-six ; but as the two lamps directly in front of the opera house are arranged to burn two candles at a time, in order to increase the brilliancy of the illumination, it will be seen that forty-eight candles are in opera- tion at once. The average distance apart of the lamps on each siae of the avenue is about one hundred and fifteen feet These forty- eight candles are fed by three separate machines of the kind which has been described. The greatest distance to which the current of any one machine is transmitted is said to be two hundred metres (about six hundred and fifty feet). At first it was necessary to employ a man to go round to the different lamp posts at intervals of an hour and a half, and switch the current to a fresh candle as the old one burned out ; but an auto- matic apparatus has been invented for doing this, which is now being applied, and which will be understood by reference to fig. 242. A and A 1 are two candle holders, in which are placed the candles C C^. An upright angular lever, L, is pivoted to a standard, l^, upon the base. A spring, s, presses against this and tends to throw it into such a position as to bring the short arm I of the lever into contact with the metallic block m, but this movement is prevented by a platinum wire, w, which is attached to the top of the lever L, and rests against the insulating portion of the candle C, at a point near its socket. This arrangement forms an automatic shunt, for when the candle C is burned down far enough to release the wire w, the spring s throws the lever L over, making contact between I and m, and thus bring- ing the candle C^ into circuit. This is in like manner arranged to bring the third candle into circuit at the proper time, and ^fio on. Ihe suustitution of one cauulc for another produces scarcely any visible interruption of the illumination. 494 THE ELECTEIC LIGHT. A few words in reference to the cost of illumination by this system may be of interest by way of conclusion. The items of expenditure, other than that of interest on first cost, are almost entirely for motive power, candles and attendance. The cost of Jablochkoff candles is given as about fifteen cents each. Mr. Stay ton, who examined the apparatus and system in Paris, in behalf of the vestry of Chelsea, a parish of London, gives the total running expense of thirty -two candles as sixteen shillings (nearly four dollars) per hour. His estimate includes wages, coal. Fig. 242. oil, waste, eta, as well as electric candles. This would make tlie expense per light per hour about twelve cents. The system now in operation in the Place and Avenue de rOpera was put up under a contract with the director of public works in Paris, by the General Electricity Company, which under- took to provide all the apparatus, and light the lamps for a term of six months, covering the period of the Exposition, for one franc and forty-five centimes (twenty-nine cents) per light per DE MEKITENS' DYNAMO MACHINE. 495 hour. The amount of light produced by each electric candle is vanously stated from five hundred to seven hundred wax candles. The principal difficulties in the way of the general adoption of this light for street purposes, aside from the original outlay which IS a pretty serious item, is the amount of power required for each lamp, and the difficulty of conveying the current to any considerable distance from the machine without seriously re- ducing Its strength. These are really the same difficulties in two different forma At present, however, it certainly seems admira- bly adapted for lighting large squares, places and public build- ings, and It does not seem unreasonable to expect that it will ere long be utilised for other purposes, when we consider what a number of inventors, some of them of exceptional abilitv are now at work upon the problem. Another machine for use in electric lighting, and somewhat resembling the Brush machine in construction, has just been brought out m France, and is highly spoken of there. One of these machines, with eight magnets only (of the same dimen- sions as those m the Alliance machines^, will, it is said, illumin- ate from three to four of the JablochkofF candles with an expen- diture of but little over one horse power for driving purposes This IS considerably better than the Gramme. • It gives reversed currents and experienced scarcely any heating. Its dimensions, besides, are very small, and the elementary parts simple in con- struction and easy of adjustment. A description of this machine for which we are indebted to the Telegraphic Journal, is given below : ° The enhanced effect of this class of machines is due to the fact that to the induction currents produced in the coil of the Gramme machines are added those produced in ordinary mag- neto electric machines. In order to understand this, let us imagine a Gramme ring, fig. 243, divided, for example, into four sections, insulated magnetically the one from the other, and forming, consequently four electro-magnets, placed end to end. Let us suppose that 496 THE ELECTRIC LIGHT. I I the iron core of each of these sections is terminated at each end 1 by a piece of iron, A Ji, forming expanded prolongations of the poles ; and let us suppose all these pieces to be joined by pieces of copper, C D, to form one solid ring, around which are placed permanent magnets, N S, with poles alternating with each other. Let us examine what will take place when this ring accom- plishes a revolution upon itself ; and let us see, in the first place, what will happen on the approximation of the expanded pole B, as it travels from left to right, to the pole N. At this moment it will develop in the electro-magnetic helix an induced current. as in the Clark machine. This current will be instantaneous, and in a contrary direction to the Amperian currents in the inducing magnet. It will be very powerful, by reason of the proximity of B to the pole N ; but the ring, in passing on, causes a series of magnetic displacements between the pole N and the core A B, which give rise to a series of currents, which may be called currents of polar introversion, from B to A. These cur- rents will be direct iu relation to those in N, but they are not instantaneous, and they increase in energy from B to A. DE MERITENS' DYNAMO MACHINE. 497 To these currents will be joined simultaneously the currents (of dynamic mduction) resulting from the passage of the helix before the pole N. When A leaves N a demagnetization cur- rent IS produced, equal in energy, and in the same direction, as the magnetization current due to the approximation of B to N Ihus we get reverse induced currents through the approach and recession of B and A; direct induced currents during the passage of the core A B before the inductor; direct induced currents resulting from the passage of the helix in front of N All these inductive effects are thus accumulated in this combina- tion; there are also currente resulting from lateral reaction of A a upon neighboring poles. To still further augment the effects of induction, M. de Mdntens the inventor, makes the core and appendages of thin plates of iron, cut out and placed together, to the number of fifty, each one millimetre thick. The coils are so arranged that they can be connected in series or for quantity In fig. 243 we have considered only four sections, but there are, m fact, more than this ; the model to which we have referred possessing sixteen, which are mounted on a bronze wheel centred on the motor shaft The inductor magnets are placed above the wheel and strongly fi.xed horizontally to two bronze frames. A little consideration will show that the ring is constructed under the best possible condition. In fact, as each section is separate, it may be dismounted singly, and consequently, the wire can be wound on without difiiculty Those who know the difficulty of winding a Gramme ring will readily appreciate this advantage. On the other hand, the core being composed of plates which can be at once removed by releasing the key piece IS an enormous advantage, for it obviates the precision necessary to the construction of solid rings, which are always difficult to keep perfectly true. Lastly there is neither commutator nor collector, and, consequently, no loss of current. T ^^^^^^^ ^^'^ ^^""^ *^^' "^^^^^"^ ^^^ feed three or four Jablochkoff candles applied to an electric light regulator • but / 498 THE ELECTBIO LIGHT. it has also been found competent to illuminate regulators, even when the carbons were separated by a distance of three and a half centimetres. It is certain that these results are very important, and we may safely argue a future for this machine. As is well known, when an electrical current, which flows through a conductor of considerable length, is suddenly broken, a bright flash, called the extra spark, appears at the point of separation. The extra spark will appear, although the current is not sufficient to sustain an arc of any appreciable length at the point of separation. In the system proposed by Professors '^Lhomson and Houston, one or both of the electrodes, which may be the ordinary carbon electrodes, are caused to vibrate to and from each other. The electrodes are placed at such a distance apaii; that in their motion towards each other they touch, and afterwards recede a distance apart which can be regulated. These motions or vibrations are made to follow one another at such a rate, that the effect of the light produced is continuous; for, as is well known, when flashes of light follow one another at a rate greater than twenty- five to thirty per second, the effect produced is that of a con- tinuous light. The vibratory motions may be communicated to the electrodes by any suitable device, such, for example, as mechanism operated by a coiled spring, a weight, compressed air, etc. ; but it is evident that the current itself furnishes the most direct method of obtaining such motion, as by the use of an automatic vibrator or an electric engine. In practice, instead of vibrating both electrodes, it has been found necessary to give motion to one only; and since the negative electrode may be made of such size as to waste very slowly, motion is imparted to it in preference to the positive. The carbon electrodes may be replaced by those of various substances of sufficient conducting power. In this system, when desired, an independent battery circuit is employed to control the extinction and lighting of each lamp. The following is a description of one of the forms of the elec- tric lamp devised to be used in connection with the system. THOKSOK ^^.„ HOUSTON'S KLKar„„ ,,„. 499 Oft X^'^l'lL-ilfi"^- 2«. '' «™'y »t^hed at one «»re, a, placed opposite 2 be'"^M its other end an iron arma- "««neti. A E':' collar, c, supports the negative electrode, Fig. 244. the positive electrode bein^ suDDorfPrl h,r n tbe pillar p. ^ supported by an arm, y, attached to The pillar » is divided by insulation at^into two sections, the 600 THE ELECTRIC LIGHT. upper one of which conveys the current from the binding post marked -f , to the arm j, and the rod K, supporting the positive electrode. The magnet m is placed, as shown by the dotted lines, in the circuit which produces the light The pillar p is hollow, and has an insulated conducting wire enclosed, which connects the circuit closer v to the binding post mariied — . The current is conveyed to the negative electrode, through b and the coils of the magnet m. When the electrodes are in contact, the current circulating through m renders it magnetic and attracts the armature a, thus separating the electrodes, when, on the weakening of the current, the elasticity of the rod b again restores the contact During the movement of the negative electrode, since it is caused to occur many times per second, the positive electrode, though partially free to fall, cannot follow the rapid motions of the negative electrode ; and, therefore, does not rest in permanent contact with it The slow fall of the positive electrode may be insured either by properly proportioning its weight, or by partly counterpoising it. The positive electrode thus becomes self-feeding. The rapidity of movement of the negative carbon may be controlled by means of the rigid bar I, which acts, practically, to shorten or lengthen the part vibrating. In order to obtain an excellent, but free contact of the army with the positive electrode, the rod r, made of iron or other suit- able metal, passes through a cavity, s, fig. 245, filled with mer- cury, placed in electrical contact with the arm / Since the mercury does not wet the metal rod r, or the sides of the open- ino- through which it passes, free movement of the rod is allowed without any escape of the mercury. We believe that this feature could be introduced advantageously into other forms of electric lamps. In order to prevent a break from occurring in the circuit, when the electrodes are consumed, a button, «, fig. 244, is attached to the upper extremity of the rod K, at such a distance that when the carbons are consumed as much as is deemed desirable, it comes into contact with a tripping lever, t, which then allows two BEYNIER'S ELECTRIC LAMP. gQj conducting plugs, attached to the bar v to fall intn fV,n- Another form of electrical lamp, devised recentlv'hv M Reynier, is shown in figs. 246 to 249 ThT! .• f {• T ^' a vivm light The pnncpal difficulty to be overcome in Fig. 245. '^ sp^, on .cconnt of the .o^.^ZZ';^ T^^.X:tr^. carbon pencils ; and which is greatly accelerated iTTv, by the rapid combustion of th! incaLt^b:' ' """ "' points is performed in VmL^^::'''^^C2''r'"^ pencil is placed in the circuit »,-,V, fl ^ '"«">descent part of th'e same until\rC\7ti ^1"' ^^Lrhf ^ *e. e.t.nguish«i. The cur.n^ now^sud"assZt'f tL?: 602 THE ELECTRIC LIGHT. carbon to another, which is consumed, the circuit broken in its turn, and so on. This method is open to many objections; there is an inter- ruption of the current, accompanied by an extinction of light at every rupture of the pencil. The luminous intensity varies continually on account of the gradual thinning of the carbon. The conductor only gives its maximum of light at the moment next to that of rupture. Finally, the proposed apparatus can scarcely work except in an enclosed space. In the new system here referred to the renewal of the carbon is progressive. The carbon, incandescent a part of its length, advances almost continuously, till the whole available part has been consumed. The system can operate in the open air. The following is the principle : A cylindrical or prismatical pencil of carbon, C, fig. 246, between i and y, forms part of an electrical circuit (continuous or alternate), sufficiently intense to render this part incandescent. The current enters or leaves at the point of contact I; it leaves or enters at the point of contact B; The contact ?, which is elastic, compresse? the pencil laterally ; the contact B touches it at its end. Under these conditions the carbon is consumed at its extremity sooner than at any other place, which tends to diminish its length. Consequently, if the carbon is steadily forced in the direction of the arrow, it will gradually advance as it is consumed, sliding through the lateral contact \ so as to press continuously on the point of contact at B. The heat developed by the passage of the current is greatly increased by the combustion of the carbon. In practice, a revolving contact, B, fig. 247, which carries off the cinders of the carbon, is substituted for the fixed contact. The rotation of the contact is made dependent on the progressive movement of the carbon, so that the weight of the latter, exerted at its end, acts as a brake on the mechanism of the motion. The principle of this new system once established, simple apparatus to realize it could easily be devised. The specimens submitted to the Society of Physics may be understood at the first glance. The advance of the carbon C, fig. 248, and revolv- HEVNIEB'S ELECTKIO LAMP. gflS he!vvr„Tp" t' ""^ ?**"*' ''^ ""^""^ of the descent of the this rod. 1 he earbon peneil is placed in its position without any adjustment The luminous point remains fixed, Jk^^t elements. W.th a more powerful electrical source, seveml ^. 246. n i^. 247. i*¥j/. 248. lamps of this system may be operated, and thus « a subdivision of the electncal light may be obtained." The following experiments were made before the Society of Physics: With a battery of thirtysix elements of eSLn centimetres, grouped in two series of eighteen each, four ^8 were operated when placed in a single circuit, and jl f "^r we^' repeatedly extinguished and relighted at will. Each of the lo^ 604 THE ELECTEIC LIGHT. lamps could be extinguished and relighted ^'individually," the three others continuing unaffected. Light was also obtained Fig. 249, from one of these lamps by means of tlio current of a small Gramme machine, for the laboratory, with treadle attachment. REYNIER'S ELECTRIC LAMP. 5Q5 (JJ^'f^'^ Y' ^^' ^^^'^"^ ^i*^ ^ battery of three Plants (secondary) elemente, which were charged LLltL IZ noon, at the establishment of M Brdcrnet Tn/ ^^ ? ^'' to the hall of the society Thif . ' ''''"'^' ^^^"^^^' The following is a more recen t arrangement r,f ti>„ In this arrangement the revolut on ofrt!? ^^"^"^ ' ob^ined W the tangential ^Ip^enf of heTrelroTt* carbon pencil on the cireumference of the disk Thu, the 1 < the peneil never leaves the revolving cont^t Jd«, ''1 insularity in the light are obviatid ' '" '^'^ °^ The brake, always indispensable, is operated fi<, wo • .> following manner: The disk B is <^vriSTl' 1 ' *^ this event- on an extended Jle is i ot falltant C°",^' I C.:c::nr:bZ7rrtr;„tf ht'-' wanted and that the cireumstanceu"ferS^,e ijlf's " be used has a modifying influence in re„,r^ 7 . , ^ A place already provided with power „f^nch I "^i?''"'''""- receive it without necessitating eZpr^Wsio;s,o,T" "' *" decreases, the economy at„becote-''"°"".' f ''^'' ''"l""^'* uy ai..o oecOineH very much less m-rked. 506 THE ELECTRIC LIGHT. Platinum and iridium, as already explained on page 428, and gas retort, or other carbon pencils when rendered incandescent by the passage of sufficiently powerful currents, serve very well for illuminating small spaces and apartments, but the difficulties attending the use of these substances are considerable, and no extended practical application of them, so far as we are aware, has yet been made. The subject has, however, been taken up anew by Messrs. Edison, Sawyer and Man — the former working independently and the two latter together — and the results so far obtained, it is said, promise very well for their ultimate success. Considered from a theoretical standpoint alone, carbon is even better adapted for lighting purposes than platinum or iridium, since its radiating power for equal temperatures is greater and its capacity for heat, referring, of course, to equal volumes, is less than that of either of these metals ; thin sticks of this material would consequently be raised to a much higher temperature for a given current than equal volumes of the metals. Carbon also possesses the advantage of remaining intact at the highest tem- perature, while the metals become fused and are even defla- grated ; its disadvantage, on the other hand, aside from a tend- ency to volatilize at high temperatures, is the ready combination of its heated particles with the oxygen of 'the air, but this in a measure has been overcome by confining the incandescent carbon in an atmosphere of some non-oxidizing gas, such as nitrogen. The Sawyer-Man lamp comprehends the use of this gas for the above mentioned purpose, but the idea is certainly not a new ne. We shall refer to this lamp again presently. It has been announced quite recently that Mr. Edison has dis- covered a means for subdividing the electric current indefinitely, thereby making it possible to use electricity for lighting small areas, and the statement has had a marvellous effect in bringing down the value of gas stock abroad. It is somewhat remarkable, too, that although gas Shares de- preciated greatly and suddenly in England, on this announcement, few persons in that country had the slightest idea of what the alleged improvement consisted ; they had, however, seen the light, LIGHTING BY INCANDESCENCE. 507 ae m otber directions, and that seemed quite sufficient <=lmissionr'oTleZT'''''' "," *' "^""^ °* *« ^^S"''' 23 1S7S „ A- ^ ? ' ''^^nngdate of Wednesday, October rent tL t^"* t, f ^ "'^ ""''""'^^ -"division o"^^ the cup " Method J ?^ ^ **°^ "f *« P«*«it, is as follows' iiSn \SriSr Wetrr ^'"'^"' ''"™"'^ »^' idea is included therefn T^^iT^l u ^"^ '^"""' "■"* *« aection to note as weH ' thi ° r^' "'" °' P'""^ ™ ""^ <=»»- English patet'offlcl on OcTobe"- ^ tT ™.' "'" ''^<' '" *» Charles E. Shea for a " Me hM ^/' "'.*'*<' ^^J^ I^'er, by Mr. force " How many oth^ pelns iTngc^ed upon'r's! " -bii!;yTirinfl* ThXiir f^zr '"" *^ --• of c^e invention. More thin i n>,o,.f^ * pnncipal part was the liability „f the wire to fuse. This M^ MU '' e.xpand the instant the wire reaches within a few degrees of Z £.08 THE ELECTRIC LIGHT. steady glow of pure light. If this is done economically, and the practical limit of the subdivision is sufficiently extended, it is obvious that a marked advance has been made in artificial illu- mination. Actual trial, however, must determine whether the action of the automatic bar regulator will do all that is claimed for it. A somewhat similar arrangement, or one which, .it first sight, might be thought to involve the sa: .oiple, was exhibited before the Koyal Society in June, 187b, . . ±Jr. Siemens ; and the method with which Mr. Farmer experimented some years since might not appear altogether dissimilar. As early as 1859 — nine- teen years ago — Mr. Farmer also demonstrated the possibility of subdividing the electric current for illuminating purposes, and at the same time showed its application to private dwellings by actually lighting one of the dwelling houses in Salem, Mass.^ every evening during the month of July of that year. This was undoubtedly the first private dwelling ever lighted by electricity. The current used for the purpose was supplied by three dozen six gallon battery jars. In 1875, he carried the subdivision still further, by making forty-two divisions in the current from a single dynamo-electric machine, and producing as many separate lights. The machine used in this case did not weigh over eight hundred pounds, and was driven by a small steam engine. While, therefore, a casual observer might discover a marked similarity between the invention of Mr. Edison and those of Messrs. Farmer and Siemens, a more careful one would scarcely fail to note the difference which, in one sense, is quite distinctive. In both of the latter it is the current which is regulated, while in the former it is the temperature of the incandescent substance, each lamp being entirely independent of the strength of current above a certain amount, and each also independent of the other. The new form of electric light produced by what is known as the Sawyer-Man lamp, has been publicly exhibited in New York lately by the Electro-Dynamic Light Company, and its appear- ance alone certainly impresses the observer very favorably. We have, however, no reliable data in regard to the photometric value BAPIEFr'S SYSTEM. 509 of the lights, the current required for each, nor the practical limit to the subdms.o„ of tl.e principal current. Undoubtedly ub - other that has been brought out-it may be further But there for each Lp "°' ^ ™7.'"«°»« ^erable one either, is required neceia^v to le f ff "^ 'l" ^°' ™»" "'"°™*'- >' b«ng only «" are equal, the cur^nts in el ^ , t '^ rBuT: ' ^^ "4:":d reth r " rr'" <"""°" ?»'"-'« wbt\:: .i.ZtiS;^p™i: r^ora'-^utir- -^ *^^' - ^ne great advantage of this li^ht k thuf u i, for a whole n,-D->.f if ^ , ^* ^* ^^" ^^ sustained .s effected by means of a lead weight or counterpoise W,.h carbons twenty inches long and two tenths of a f i^h in^ia meter the hght ,s maintained for seven or eight hou'and It carbons twenty.four hundredths of an inch^hiek it is W ,. handed te :: r7 /'". ■«'' -^ «^»'™'™' «» fr'™ » - hundred to one hundred and twenty gas flames, or about one 610 THE ELECTRIC LIGHT. Kip thousand candles, but a smaller form of the lamp is made which is estimated to give five gas flames. The resistance of the arc i». only two or throe ohms. The Sawyer- Man lamp consists of two conductors enclosed in a sealed glass vessel of about eight inches in height by two and a half in diameter, containing nitrogen, and a very thin carbon pencil, probably one tenth of an incli thick and three quarters- long, which is the source of the light when rendered incandescent, by the passage of the current Every precaution has been taken in the construction of the lamp to modify or remove even the slightest thing that could tend to interfere with its use in a prac- tical way. The glass is made very clear, to prevent undue absorp- tion both of light and heat ; the wires are large and long, so as to form ready conductors for the dissipation of useless heat that is always generated, and, finally, a diaphragm of some non- absorbing substance is placed immediately below the carbon pencil to prevent radiation' downward, which, if allowed to take place, might seriously interfere with the sealing. The conductors are also wound in a spiral form to economize space. Consider- able secrecy has been maintained by the inventors in regard to some substance contained in the base of the lamps ; but this is believed to be metallic potassium, placed there to absorb any oxygen that may chance to leak through. We have seen five or more of these lamps in operation at one time, and were much pleased with their performance. Our inves- tigation of the various details connected with their construction and practical maintenance was, however, too limited to enable us to judge of them from an economical standpoint. One or two things which catne under our observation did not impress us quite so favorably as we had reason to anticipate from what we had heard of them. Possibly a poor adaptation of means to ends, which is so often noticeable with new and hastily introduced apparatus, is in part responsible for this, but it is certainly remark- able that the continuance of the light on the occasion of our visit was not prolonged beyond five minutes at the most ; and this fact, taken in connection with the sound from the dynamo- SAWYERMAN LAMP. g^. J^g. 250. in ihoonntyifZl\7Tvf'''^ ''"'^ and factories we have there sLid hLT '"»'" '" " ™''" ™7- What and economical ■ * ^ '"' ""* advantageous Messrs. Wallace & Sons, of Ansonia, Conn., have been amon. ,12 THE ELECTRIC LIGHT. the first here to introduce the light in a practical way, and their extensive rolling mills have been very successfully lighted with four lamps for months together. Fig. 250 shows one form of the lamp which they use ; it has already been described on page 412. Various other applications of the light have also been made elsewhere in this country, but we are, unfortunately, not in possession of any detailed statement of the cost of the same, compared with that of gas used under similar circumstances. Mr. Schuyler informs us, however, that the cost of lightmg one of the corridors in the Equitable building, New York, by two Maxim lamps, like that shown in fig. 235, and one of the Farmer- Wallace machines, is a trifle over fifteen and a half cents per hour for running expenses alone, as against fifty-one cents per hour for gas, and that the quantity of light furnished by the two lamps, which replace fifty^one gas burners, is three times greater. It is confidently hoped by Mr. Schuyler and his associates that the advantages of the electric light will be even more marked, both iis regards steadiness and economy, when the Farmer-Wallace machine is replaced by one of the new Maxim machines, asjs proposed to be done shortly. This machine is shown in fig. 251, and, it is claimed, will furnish a very large amount of current for the comparatively small amount of material used in its con- struction. Its tendency to become heated is, at the same time, very small, on account of the manner of arranging the armature and field magnets, whereby a constant circulation of air among all the parts is secured. The Maxim machine and lamp, we understand, have been adopted by the Russian government for the steamships which are being constructed for it in this country, the trial on one of the vessels having given so much satisfaction that all will now be similarly equipped. In England, the Lontin machine and lamp have been some- what extensively introduced, but it is difficult to get really accu- rate statements 'in regard to the cost of operating them. The machine, which has not been noticed in the preceding pages, is -H~ "-io.tion.ua of 1 -:sr:retrwfcr r " -^*" "=" --'- appear to differ materia .yZTeVr' f"'' '"'''^'' ''°"=^ "<" ^taces in this country, iZZll „ , ^'"''^^«»i'"^ ei«=um. I'ghting oa a la^e scale in tl,,^' ^ '"'°"'" ''^""P'o of electric light can^be'^pCd ,ot ^' " ''''°"' ^'"'^- «■« the illumination of sZnTt '^e greatest advantage. For However, where, compT^tiver""? ""'' '"' l-vate' houses, -anted, and *»; at ^S JteT " ^™" "«'" ""'^ '^ not so apparent It would h„„^' "'t*"'*^'""^ advantages a«i the numberwho are dTv"tin. Z ?, ?'™"""^' ^"-^'dering the consequent rapidly I^ Si; "'r"''"" *" *'^ ^"'^i*'- »"! -u«e of illumin'atio';, to^^ert P&" <" ^'-'™ty as a »lt.mately be made to yield co^J i^" ''«'™<^^ »ay „o, r»" ^eale, though it is'^one thTT'' I '"'""'='8^' »" » uoprovements will first have t^ be maTe. "" ""^ '""* °*" information CnC LT, ^^r^l"- »7™* of geL., «nde« hin. so eminen'tly aWe to gt " "^^ '''^"''"^ eitnZrp^/t^Tt'i^s platinum wire whi.l, „?, , , J' ""'' ''S"" <'™''<=d by a «tru=k by™e'i' "^, ^T'' ^^'•" "'-t™ cun-ent, I was the >r^'^:^:^az^:^r'' "t obtained fror t I "L n^tw' r^ •"""*'" '«'" ^'"'^ "^ electro-magnets, r^^J^H^l^j^Zi: -""'-'i™ of desired result and oarlv -•-- ^^-^ r * "^""^^^ ^'^^^ thn —t, oarly .a xooy I pufc the idea into successful 516 THE ELECTRIC LIGHT. i and practical execution, and we had a beautiful light in use in my house in Salem. I at once entered upon a protracted investigation of the con- ditions which govern the management of the current, the con- struction of rheostats, the arrangement of lamp, etc., and the best proportion of length, width and thickness of the lUumm- ator. I tried various substances in the course of my investiga- tion, such as copper, aluminum, platinum, iridium, palladium, iron, nickel, carbon, etc. Pure iridium gave the best results of any of the metaia Alloys of iridium and platinum gave next best results, and next to this, platinum and palladium. Carbon, when inclosed in an atmosphere free from oxygen, also gave satisfactory resulta Nitrogen, carbonic oxide and hydrogen are all suitable gases to surround the incandescent carbon. A vacuum is, perhaps, better, were it not for the difficulty of maintaining it The important point is, that the higher the temperature of the incandescent substance, the greater the amount of light; and it is very noteworthy, that it requires nearly half as much current to make platinum shine in the dark as it does to fuse the wire or ribbon. Three quarters of the fusing current will not give one half the light that will be given off by seven eighths of the fusing current A flat ribbon of platinum will give nearly one hundred candle lights per square inch, if it be maintained within two hundred degrees Falirenheit of the melting point, and I have been able to keep it at this temperature for hours and days. A bar of pure iridium, owing to its higher melting point, will give several times as much light as an equal and equally exposed surface of platinum ; but, since pure iridium is neither malleable nor ductile when cold, it is costly to work it into convenient shape ; hence, I have had recourse to alloys of ])latinum and iridium, which, although they do not give so much light as pure iridium, are yet superior to pure platinum. The platinum does not seem to waste perceptibly, yet I think I have detected a tendency to volatilization. The resistance of platinum, at the melting point, is nearly MR. PARMER'S EXPERIMENTO. '' 5^7 platinum when the proper constants are supplied three of the branches were .^mo™f Tc„t ^ff i ' T "' electricity would be so curtailedrto 1"' 't th7^'^ "' temperature, the l„,„ps i„ the remaining ^4 "'"'^^ . My regulator, as I used it in 1866, 1867 and 18BS sit ve as to feel the p„™„„. i . "•/.°'" """ lo88, was so sen- shutting of Tdoo' oTthe 1"'^™»'"? f™™ tte opening and placed *' ~°'" ■" "'"'='' *« Waratus was I had this apparatus on exhibition if ino n„. ^ c^ Boston, during the years 1865 1Sfi« iLf ^ ,2? "^ ^"''*'*' '" Xost "^^-""-'-'rio -cWnes best adapted to Z mo tve force, or polarizing force, is encountered in the n^s "^ of the current between the electrodes, and this polari JZ f! often as great in amount as twenty or thirty .„!,, P°'"^*™ '» The resistance to condnctiyity in the arc "yaries also, being less 618 THE ELECTRIC LIGHT. as the cross section of the arc increases, less as the temperature increases, also as the length of the arc diminishes, following the laws of conduction in fluids and liquids. With carbon, one quarter inch square, and a current of from twelve to twenty vebers, the resistance of the arc may be set down at ten to tliir- teen ohms per linear inch of arc, varying, however, between wide limits. With carbon one half inch square, and current of fift> or more vebers, it is much less. The best prepared carbon weighs more than an avoirdupois ounce per cubic inch. The resistance of carbon, unlike that of metals, does not vary greatly with the changes of temperature. The resistance of some specimens, which I have tested, is about fifteen hundred or sixteen hundred times that of pure copper, at thirty-two degrees, while the specific resistance of other specimens is at least twice as great The light evolved is due in considerable measure to the oxida- tion of the carbon by the atmosphere. Much of the light is, however, due to the energy of the current, and this depends on the density of current in the arc. A second method of producing electric light is by rendering a continuous bar of carbon incandescent in the air by the pas- sage of a current of sufficient density to raise its temperature to a white heat. Here much of the light is due to the superficial oxidation of the carbon bar, and this may perhaps prove to be the most economical method of producing it. The third method is by enclosing the carbon bar in a closed transparent globe free from oxygen. In this case the carbon is not consumed, but the light is wholly due to the energy (ES^) of the current acting on the bar. The fourth method is that of rendering some of the metals, with high melting points, incandescent by the passage of a cur- rent of great density. This is the method to which I have given most attention, and which promises to be the most convenient for minutely sub- dividing and widely distributing electric light, especially for MR PARMEB'S EXPERIMENTS. " 519 W nrf ^^ " "'"'='' "•" accumulated stock of W ledge will be most usefuUj employed «=cSi^mrJ° "^ investigations, Gardiner and Blossom had natea by a coil of platinum wire, heated by the passaee of » cu^nt of electricity from a galvanic battery "^^ * King, Staite and others had studied the use of carbon h»~ m sealed globes, and had proposed methods tir^Ti^dht^ been applicable and useful had there been on, oZ a venient source of electricity. I fid thaT ^Zt^ftrj galvanic battery increased the cost of electric liglT to th^or SdiSv/tre^'''^'''/"''"^-' andtoremULt.^' t if^^T ?^ ™y attention to the thermo-electric battery Ber in ?' ^ 1. ™ '""'« ^'°"«^' '"'° -oW™ by Marcus o^ "^m::: wh- hi Sd "^'"^"^ f ^ '°™ °' -4--— machine which I had conceived of in 1859, namely, one in which of force in which it revolved, and also perform the useful work in the external part of the circuit. I succeeded in ISRr so far perf«,ti„g this apparatus as to be ^^k to give ^^ni: account of its performance to Mr. H Wilde nf m' i, . England in October, 1866, and an e.tract^m m^ 1^ eTtolSS zcx^- "■« "-"■>-- ^-p"'-. Magai::n From all my researches, I conclude that when light is nro duccd in large amount^say, five thousand, ten thousand l!^;, thousand candle lights-from one lamp, as much as eght ™ dred to twelve hundred candle lights can be obtained from the expenditure of one horse power upor .suitable ZamoXtric machine and properly prepared and utilised carbon ^ Now, while It is remembered that as much as two tho,„.nd or three thousand foot pounds of enei^y per minute ,«r caiTdle 520 THE ELECTRIC LIGHT. light is consumed in the production of light from ordinary illuminating gas, it will be apparent that a large field is opened for the introduction and utilization of the electric light, which often requires the expenditure of less than one hundred foot pounds of energy per minute per candle light A great deal has been said and written about the difficulty of subdividmg the electric light Now, there is really no difficulty except that which arises from inexperience and the lack of skill. If a wire of pure platinum five inches long and one hundredth of an inch in diameter be traversed by a current of electricity somewhat more than five and less than six vebers in strength, it can be maintained at a temperature quite near to the point of fusion, and while in this condition, it will, in the common at- mosphere, emit something more than three candle lights, and just below the melting point the light will be between four and five cnndle lights. If the light be enclosed in a glass globe and surrounded by hydrogen gas it will radiate less light The resistance of the wire at the melting point will not be far from one and a quarter ohms if the platinum be pure ; hence the energy active in the wire with a current of five and a half vebers (which it will ordinarily withstand) will not be far from 44:JX(oi)^Xl-2ij= 1673 foot pounds per minute, and if it give four and a half candle lights, which it will do if the surface of the platinum be highly polished) we should require ^|.3^'=say 370 foot pounds of energy per minute per candle light Now, if one hundred such wires be put in series in a circuit, the sum of this resistance would be one hundred and twenty-five ohms, and it would require a difi'erence of potential equal to 125X5^ =687-i- volts to maintain this strength of current of five and a half vebers and we should get in the aggregate five hundred or more candle lights. If, further, we shoald arrange ten such circuits in multiple arc, having one hundred lights in each of the ten branches, we should find the joint resistance of this part of the circuit re- duced to twelve and a half ohms ; but it would now require SUBDIVISION OF THE CURRENT. 1 1 521 one htlnd tw r/^P"'^"" '•^<1»™<' «» "aintaL the be s * iZdf .d* 1' ""^ ^"'" *'''^'' *" *^« '="«<=^. ^""W -till n!,^ Welve r ''■e^'y-^'^r "i => 1'"" volts, b^twe should now have five thousand candle lights instead of five hundred and the -m, a, W this part of the oireuit would be' equal to fZif^XlfiOX^ - a3,000 =more than fifty hoi-se power to iTZ'tr We™ ''"""^ ™°*"' '«!* or one hundred candle n?t aluL r ^°'"'- ^"* '' ""^' ^ remembered, that tl.is is and^is„?:i!:^:,^^^^^^^^^^ e..triomachi„es^rwT;tet:reTr;tA ''"^^^^^^ inJ™:.Snc?oT:hf,v ' ' ^''^"" « ^^p---"*^ *« an^allasoneCe Li5!':i,or°"""°'°'' '""' ™ "'' -"« ^ iTo^^ntThKrbfr r ""^^■''- ^^-«--- hundred eandie S '"'''" "'".'™ «»«J'«= i and if only one TfTou'tr ' ? "'* *" ""' ■""*'- "- '-- ..u/rei-f ^^hrc:it:^^^^^^^^ the cost of production was on ih^ n, • '^^^ threehundredthnf r? ' ^'^'^^^' '"^ ^^^^^^^ of one tnree Hundredth of a horse power per candle light; and thi. too IZT Zr\T^. ^'''' ''^''' '- greater L^unttkn tn fifteen or fifty candle lights per lamp. Now, it is well known hat the greater the amount of light at any s;urce, Z g^arer he economy, and so a five or ten thousand candid hJT^ less per candle than does a ten. fifteen or .went- c 'd^-^^^^^^ 522 THE ELECTRIC LIGHT. If next we consider the incandescent carbon, in an atmos- phere free from oxygen, as in King's, Staite's, Kosloff's, and other lamps of this class, we shall find that a carbon rod three eighths of an inch in length and one thirtieth of an inch in diameter will offer a resistance of not far from half an ohm, whether it be cold or hot, and such a bar will bear a current of from ten to fifty vebers' strength for a time, without injury, and will give a soft, mild and very pleasant light, not too con- centrated, but very desirable ; and, as with the platinum lamp, many of these lamps can be put in one circuit, and many branch circuits in multiple arc can be heated simultaneously by one source of electricity, provided it have sufficient electro-mo- tive force and conductivity, and the light will be more economi- cal than from platinum, because the carbon, when thus protected, "will withstand a higher temperature than will the platinum. Next, we will consider the electric light produced by the arc between carbon points. If we have two suitable carbon rods, each, say, five sixteenths of an inch diameter, and separated to the distance of about one sixteenth of an inch, and apply to these electrodes a source of electricity, which has an electro-mo- tive force of, say seventy volts, and an internal resistance of, say three ohms, we shall, after establishing the arc, find a current developed of about eight or ten vebers, and a light produced equal to from one hundred to four hundred candle lights. If the resistance (four ohms) of the circuit were all metallic, the current developed would be in amount equal to sixteen or seventeen vebers ; but the electric arc behaves like an electro- lyte, and offers a counter electro-motive force, and so the actual electro-motive force in the circuit may be thus represented : E - - c, where E is the electro-motive force of the machine, and — c the counter or polarizing force of the arc. If, now, I rep- resent the resistance to conductivity of the arc, B the internal resistance of the battery or machine, and r that of the leading wires, then the strength of current active in the circuit will be f\ E — e ^ B + r+Z The value of e varies, and all the conditions of its variation SUBDIVISION OP THB CURHBNT. ^.^ are not yet well underetood It is suffioim,+ f Mi an internal resistanrof .». f ™ °* ^^-^'^ ™"«. between carbon Zt a„d wtr ""t" "'" ■"^'"'*'° ™ ""= exeeedone^ixteS 'f anCur";^rrtr \^ "t "^ tion, even three aiv«, ,.™,i.i i, , " - " mampula- snch a ^achinl ^ ^^ultaneonaly maintained with sevtTXdtr""''™ ',?"^ '^" ™^^ <" - - — of would need to Twdl eln tmlrao M rendered sensitive iTlv Z ^r ^"""■at^'y ad usted, and current **"* ^'""""-^ '" "'^ ^'^'"'Sth of the 024 THE ELECTRIC LIGHT. I! To sum up, then, the electric light question, there are manj good and well known magneto-electric machines free to the pub- lic to use, for instance, the Saxton, the Siemens, Carpenter, Shepard, and many others; then, too, there is the platinum lamp of Gardiner and Blossom ; the incandescent carbon lamps of King, Staite, and others. Besides these there are the carbon point lamps of Browning, Dubosque, Serrin, Siemens, and many more, which are all free to the public, and hampered by no patents ; no carbon point lamp need be better than the Serrin, when properly constructed, as it can be run for hours without flickering, or going out, if the carbons be good, the lamp well made and properly adjusted, and if the machine, which supplies the current, be of ample power. Light to the amount of from one hundred to one thousand candles per horse, power can be obtained from some of these machines and lamps, while at best not more than twenty-five or thirty candle light can be obtained from one horse power's worth of gas. So let me here repeat what I in substance published in the Scientific American, a few years since, namely, that one pound of coal, if used for making gas, would yield enough to supply a candle light or its equivalent for about fifteen hours. One pound of the gas, when made and burned, yields a candle light for seventy-five hours. Further, one pound of coal, burned in a good furnace under a good boiler, will furnish sufficient steam to drive a good steam engine, and if a magneto-electric machine, for a sufficient length of time, to furnish an electric light, which in intensity and duration shall be the equivalent of one candle light for one thousand hours. But if all the energy locked up in one pound of carbon could be liberated and converted wholly into light, it would be equiva- lent to that given by one candle during one and a half years, if all concentrated in one source. 'Hence, let experimenters take courage, and try to fill this ■chasm between one thousand hours and one and a half years ! When we shall see the electric light distribute J in our dwell- COST OF ELEOTBIO LIGHTING. , gJS T.eed not consume more than two Sd 1 1 plundf "^ nte per candle light So it mi„l,t Z? ^ P^"' """■ poet that onepo/ndo^Ss^^turcoX::^^^^^^^ bo le ,?r r " " P"P" ^''""'■■' ''"'' ^"=«» be taken Som Te S I ir;piX^Te^r;^^ I CHAPTER XV. Edison's recent telephonic and acoustic inventions. The most important advance that has been made in the appli- cation of the telephone to business, manufactures and medical science dates from the discovery of the varying electrical re- sistance of certain bodies when submitted to pressure. The car- bon telephone is based on this fact, and more recent discoveries prove that any mass of metal that is not continuous, like a heap of shot, a coil of chain, or charcoal impregnated with iron, will produce changes in an electrical current when submitted to pres- sure. This pressure may be the impact of sonorous waves of all kinds, and thus such a mass of metal may become the transmit- ter of a telephonic circuit In Chapter VI. we have already described a few of the discov- eries and inventions made by Mr. Edison in his researches which culminated in the invention of the carbon telephone. We now propose to present a more complete description of the important forms of telephone upon which he then experimented, as well as to describe his more recent acoustic inventions. The carbon telephone is only one of many contrivances for reproducing articulate speech at a distance, but owing to its clear and truth- ful articulation, its simplicity of construction, and the far greater volume of sound which it creates, it is likely to be the most extensively used. Other instruments of Mr. Edison's inven- tion, however, are not far behind it, and may by improvement be luade equally effective. As a rule, Mr. Edison has succeeded better with those telephones which produce a variation in the resistance of the circuit than with such as depend for their action upon a variation of the electromotive force or static charge. An instrument very similar to the carbon transmitting tele- phone is shown in fig. 252 (devised November 19, 1877), the BIBULOUS PAPER TRANSMITTING TBLEPHONE. 527 essential difference being that the carbon is replaced bv bih„ Fig. 252. Fig. 263 .8 vaned by speaking into the mouth of the veL^ Th«2h 255 (devised August 12, 1877) the pulverised plumbago p| floated upon mereaiy, M, and is eompressed betweenT°suL« 628 Edison's keoent telephonic and acoustic inventions. Still another form of the Edison transmitter is shown in fig. 256 (devised July 5, 1877). The carbon C rests upon the dia- phragm, which, iu this instrument, is a horizontal j)late forming the top of a vocalizing chamber, the mouth piece being at the side. Three fine cords attach the carbon to the framework of the diaphragm, and prevent it from being displaced when the diaphragm is vibrating. In appearance this instrument resem- bles the Reiss telephone, and in principle it would be much the ^''Jijk^^iHfiir Fig. 254. Pig. 266. same were it not that, in vibrating, the carbon never actually leaves the plate upon which it rests, but simply, for an instant, releases its pressure. It is evident that the resistance of the cir- cuit depends upon the electric connection between the carbon and the diaphragm, and that this connection depends upon the pressure of the carbon, vvhich is constantly changing when the diaphragm is in vibration. This apparatus is too sensitive to extraneous sound? to be useful in telephony. Fi(j. 25G. Another form acting on much the same principle is illustrated by fig. 257 (devised Sept 30, 1877) ; it is called the inertia tele- phone, though it is hardly certain that its action is to be attrib- uted solely to inertia. The carbon C is placed between two metallic plates, one of which is fastened to the diaphragm, and the other is held by a screw bearing in a framework, attached to the diaphragm by insulating supports. When vibrating, the EDISON'S CAKBON TRANSMITTKR. 628 whole system moves, instead of tl,e plate P alone, as in the ordi. mry carbon tmnsm.tter. Mr. Edisons explanation of its mode ^ acfon ,s, that the degree of pressure with which the carbon rests against the plates is varied during the vibration. Thu. after a movement toward the right, the diaphragm suddenf; stop,^and the carbon p,.sses in virtue of i^ inertia on S!e An aJvantage which the magneto-telephone has over the earlier forms of Mr. Edison's telephone is° that its diaphC Fig. 257, ^oes not touch anything, and can therefore vibra e with peri^ect xreedom. On the other hand, the diaphragm of tue carbon tele phone, used before his adoption of the present non-vibrating ngid plate, presses with considerable force upon the carbon and thus causes it to njake false vibration. In the form shown in % 258 (devised June 25, 1877), this difficulty is not encoun- tered ihe diaphragm carries an armature. A, of soft iron which confronts but does not touch the magnet B. A and B are opposite poles of the same magnet, being connected at P and polaiized by a local circuit. The magnet B presses upon 680 emson's recent telephonic and acoustic inventions. the carbon at C, the pressure bemg regulated by the screw S. The attraction between A and B varies with the distance be- tween them. When, in vibrating, A moves toward B, the at- traction rapidly increases, and B lessens its pressure upon C. During a motion in the opposite direction, the attraction dimin- ishes, and B, drawn by the spring S, increases its pressure upon C. A similar contrivance is illustrated in fig. 259. (Devised April 10, 1877.) The diaphragm carries an armature. A, which, by its motioij, changes the potential of two electro-magnets. These changes in magnetism cause a bar, situated in their mag- netic fields to reproduce the original vibrations. The ends of the bar are held by the magnetic force against two pieces of carbon, c and c. These and the bar are included in the primary circuit of an induction coiL The resistance of the circuit Fig. 259, decreases when the bar is drawn up, and increases as the bar descends. Of all substances which have thus been tested in the tele- phone for increasing and decreasing the resistance of the circuit by the effect of the sonorous vibrations, lamp black from the lighter hydrocarbons proves the best It is very essential that the lamp black should be deposited at the lowest temperature poasible, and the flame of the lamp should not be allowed to play upon the deposit ; otherwise the product is of high re- sistance and wholly unsuitable for this purpose. Commercial lamp black of the best quality, scarcely allows a current to pass through it, while that obtained by the process herein described offers but slight resistance. The lamp black as it comes from the burning apparatus is MANUFACTURING CARBON BUTTONS. 681 nf all fi«,>i J- -J 1 '*^'^i"j' explained, when we consider that of all finely divided substances obtained either hJT t • ! ticle« flt +1,/^ : ^ ^ ^^^^^^ o^ ^ess number of par- ticles at the junction or surfaces ^ are b«>ughiitf:sthThrx;t:r'rfr "•""" pomta representing the disturbance of the cu„™I h. ,h V ' of the parades themselves. Now if the but^! J '*"' carbon be renkced K„ „„. . I- *'"'' °* S^s retort much smJeTpal?i w" h no^™^'"'' """'' '^ '°°'P°-<' »* the waves wi^r:::^rJVl:t^as'^:,:rt^''^h'• pomte will be seareely pe.x=eptib[e, a°d these ^1 1 *" m.„„^ a^ beyond the Aer of th^ tellw t.T±'"^-'" *" "'"*"' " P»- ™-. but these gaps' weaken the wavT:: 632 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. a whole by their effect on the self-induction of the telephone receiver. But in the case of lamp black, the particles are in- finitely finer than graphite, and, moreover, the button is some- what elastic ; hence the line representing the form of the wave will be perfectly straight, although theoretically there are gaps. They are infinitely small as compared to graphite or other con- ducting material, therefore we not only prevent harsh sounds, but obtain a stronger wave, owing to the absence of gaps and their effect on the self-induction of the magnet Lamp black when moulded into buttons possesses another property differing from all other conducting material, and that in its elasticity. For instance, if we subject buttons of different materials to pressure, the greatest difference of resistance with a given weight will be produced on the lamp black button ; again, if we increase the weight on all the buttons, a point will be reached where any additional weight ceases to reduce the resistance appreciably, except in the case of the lamp black, which continues to show decrease of resistance by additional weight placed upon it long after the other buttons cease to be affected, as all the particles that can come in contact will be brought in contact by a slight weight owing to the inelastic nature. Mr. Edison has en- deavored to obtain an approximation as to the number of points of contact on the lamp black button now used. In order to accomplish this purpose hp first placed a Rutherford dif- fraction grating under the microscope having 17,291 lines ruled on speculum metal within a space of one inch, and by the side of this a button of lamp black, then by changing from one to the other, he calculated that there were not less than 10,000,000 of points upon the surface of the button, nearly all of which were constantly in use when subjected to the sonorous vibra- tions. Had the Rutherford grating been ruled both ways there would have been 298,000,000 of points, and there is little doubt that a buiiton of platina ruled double in this manner would give good results in the telephone, but would not equal the lamp black, owing to its want of elasticity. The elasticity of the lamp black button has another advantage, ELASTICITY OF THE LAMP-BLACK BUITOn" 533 must be exceedm^W i,-„i,* ^ , wiiere tne initial pressure adjusted in thTs t!/ner tCd '"'^'^ "^ ^^"^™"^- ^l'- circuit, and the ZnZZr\ f .'^''^ " ^"^^ '" *« sparks to occur whl in f »* 'iisagreeable, and allow -inue to >as;:iirt'LstitiTL?d:nnT!j the instrun,en:2WeVi 'Len '"""" 'f.™"^ '«''' ^^ being dropped onXflLwhe b^tonTT ^°' '"^'^"'*' "^ the lamp-black jrC Z anti "I '""""^ '^ "'^'"S ilie value of different substances to be used n^ ].„*. • Lamp-black, Hjperoxide of lead, Iodide of copper, Graphite, Gras carbon. Platinum black. Finely divided materials which do not oxidize in ih. .■ a. osmium, ruthenium, silicon, boron/i^'fr ^H ti'l "'' 634 Edison's recent telephonic and acoustic inventions. give results proportionate to this minute division, but many of them are such good conduct? rs that it is necessary to mix some very fine non-conducting material with them before moulding. All the conducting oxides, sulphides, iodides, and nearly every metal finely divided has been tried by Mr. Edison, in vari- ous states of divisibility and mixed with various substances. Liquids in porous buttons of finely divided non-conducting material, render these particles conducting, and they, conse- quently, act in the same manner, but, of course, owing to the formation of gas, polarization, etc., they are objectionable. Mg. 260. THE MICROPHONE. The device of using several pieces of the semi-conductor instead of one was early tried by Mr. Edison. He found, in general, tb it the loudness of the sound was increased by thus multiplying the number of contact surfaces, but also that the articulation was impaired. Instruments of this nature have since become known as microphones, though it is not probable that faint sounds were ever augmented through their agency so that they could be easily recognized at a distance from their source. Fig. 260 shows one of the first forms, invented by Mr. THE MIOBOPHONE. SS6 Ediso^ Apnl 1, 1877. Four pieces of charcoal are used, C P^ rf cZ'^f ■* "" "" 7"«'" ^P™8' - "* S and S'. ' Th Th„ ^r' '^/^tened to the cent:^ of the diaphragm. nC*^ ^/"^ °' *^ "'*"'"'»'' <=°a are attached to^hrS tw?*^!*"™" "" '■''"'" ^^ ^g^ 261 and 262. The former has nrusTrraiL^^'^'^"^ »-^ -^^ '- -^-^ !■«. 268 (devised Sept 21, 1877) illustmtes a microphone, J^. 261. Ji^. 262. having ten plates of silk ; a mixture of dextrine and lamp-black having been previously Avorked into the porea ^ In fig. 264 (devised June 7, 1877), fifty disks T) w^'fi, • protoxidized on the surface. are'shown^ncksedt^gCtbr A novel form of transmitter used bv Mr Edllt V periments is shown in fig. 266 (devi^J Aug t^lS 7) C wuu plumbago. It can be used with or without a diaphia™. The .nstmment shown in fig. 266 (devised Aug, 24,1877) S both a. a transmitter and receiver, the lattcf fac bJ2 dt soUd carbon of the transmitter is here replaced by silk fibres coated w.th gz^phite. Its action as a receiver is p^"du 686 Edison's recent telephonic and acoustic inventions. to the attraction of parallel currents ; the volume of the whole being contracted during the passage of a current through F. In May, 1878, Mr. Hughes, of London, published some inter- esting experiments, based upon Mr. Edison's discovery of the variable resistance of solid conductors when subjected to pres- sure. Mg. 263. Fig. 264. In fig. 267, A is a glass tube filled with a mixture of metallic tin and zinc, commonly known as white silver powder. This powder is slightly compressed by two plugs of gas car- Fig. 265 Mg. 266, bon inserted at the ends, to which are attache^i wires, hav- ing a battery, B, nod galvanometer, Q-, in ciiTriit The plugs are cemented in their place by being covered o , r with ordinary ..^^ THE MICROPHONE. " gg^ one another so "3 to^"°°';f .<'" T''"^ ^^^ ^"''^ Awards tion. In tU3 case *!,« fi„T J- 7 , '''^ opposite direo- the oontenrofTe tube a"!i f "^ ""'*^''" P^'"'^ f<>™i»g tion of exSn ° n'd In, th """'' ""P"^'^ ''""■^S *« "P^-^" increasing thTeuCt XVT'^r "' ""' °'^<'"' '^ ^^^d, the second. D tWW t Tt"""' ""^ "^^"-^""g ** i° vanometer ne«ile LtZ ^ ?' ' ■"°™°'^'>' "f the gal- needle m the reverse direction cannot be calM a /IV7. 267. would be a remarkable .7 ^f '^'ff- Tbs expenment alone of the teIeph"tdetT^ °^*' "^""""^ .ensitivenesa force, for i? is haSi! „ ,^' °^ """"'^ ^^""on^ of electrical that teki pC i^'2 ff'";, *° "^"eive the minute increment three inchiw wht iT^'f^K^f ^ "' » ^"^ '»>». ^-""e this sensitive tuttrf ^ P""'"® '''* *" "■^^'^ »«* named explrim^t ^TsenT- ""'' f'" '^ ^"^"^ ''^ the last up sono«,r"b:Lns and 't ^^'o '^' '^' ""'""^ "^ "^-^-^ influence it tmnsmiteCil pT T ''*"^'""'' under their P>^one, undulato, ^^^7:^^^^^^ 688 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS the sounds by which thej were produced, and with even greater perfection than would be attained if a telephone were the trans- mitting insti-ument By attaching one of these tubes to a small resonating box, as shown in fig. 268, we have one of the very simplest electric articulating telephones that has ever been pro- duced. It consists of nothing more than a tube of glass filled with a powder whose electric conductivity can be varied by varia- tions of compression, wires being led from the two ends, and this little apparatus attached to a little box opened at one end, which serves as the mouth piece of the instrument. The wires are attached to a distant telephone, and have a battery of three Fig. 268. small Daniell cells in circuit With this simple telephone the sounds are so loud that it is po&sible to sing into one instrument, and hear at the same time singii.^ from a distant station in another. This duplex arrangement with a single circuit works perfectly, the one communication in no way interfering with the other. When a stick of pure vegetable carbon, such as is used by artists, is employed instead of the tube, no effect is produced, because of its very high resistance making it to all intents and purposes a perfect non-conductor ; but by heating it to incan- descence, and suddenly plunging it into a bath of mercury, it THE MICROPHONE. 689 ployed, it must not be homLn^T^ T ' " ""' increase or decreaae of pressure bvnj^ T~' "" ^^ distant union between iuCdu '^.Srf^'X ^ T of varymg the st^ngth of the cu^n't Cl^^, '^^'^ZX Fly. 269. i an insulating oxfde beS,^!^ l^." ^'' '" ""^q-^oe of ceases to co1.v^ tie ^^7 po"" w" T^"' "' ^^ *"'' " Fig. 269 represents a perspective view of a ain«n ^.^ t, open at one end, and resembling the Wes .tT ^""^ J^ningforka AconvenientsiXnt^hL^e eiX:'''""^ long' and seven inches deep. On this is a 1^^^ "°''f ' open at boa. ends, and fas Jed downtthltCwal'^^i.t: 640 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. tube are a number of pieces of willow charcoal that have been metallized with " ';\. prepare this charcoal, take sticks (pencils) of charcoal uixi pack them loosely in an iron box with a loose cover, and bring the box slowly to a white heat This tends to drive out the water that may be held in the pores of the charcoal, and it is replaced by the vapor of iron, so that, when cool, the sticks of charcoal are loaded with iron and have a decided metallic ring. Sm;,; pieces of the metallized char- coal are placed in the glass tube and closely pressed together till it is full and a portion of the charcoal projects at either end, as shown in the figure. The wires of a telephonic circuit are wound round these projecting ends, and the ends of the tube Pig. 270. are then closed with sealing wax. This apparatus, simple as it is, makes a telephonic transmitter of most remarkable sensitive- ness. On holding an ordinary magneto-electric telephone to the ear (with a battery in the line), the mere rubbing of the finger on the box, the trace of a pencil, or the footsteps of a house fly walking on or near the box will be heard with perfect distinctness. So sensitive is this mstrument that sounds that cannot be heard by the ear become clear in the telephone, A watch placed on the box gives all the sounds of its works— the grinding of the wheels, the sonorous ring of the spring and the minutest tick of the gearing. Words spoken in the box sound with the power of a trumpet in the telephone, and the blowing of the breath resembles the roar of the wind in a forest Fig. 2 vsameprii used in t the uprigh wooden pla a small block (sealing wax) THE MTGROPHONE. '' ^, ■% 271. J^g. 212. f «'«all block of the metallized charcoal restino- nn a« • i (sealing wax^ X on^ v /'"'^^^^a^ resting on an insulator iseaiing wax). X and Y are the two wires of a telephonic ^Ime. 542 sdison's recent telephonic and acoustic inventions. This appamtus shows the effect of varying pressure on electrical resistance. On lifting the lower end from the mass of charcoal the circuit is broken. On pressing it down on the charcoal the electrical resistance will vary with the pressure, however mi- nute it may be. The pressure exerted by sonorous vibi-ations even though they may be caused by the tread of a fly or the pressure of a fingef, cause so great changes in the electrical status of the line that when the telephone receiver is placed at the ear these minute movements are distinctly heard. Fig. 271 represents a thin pine board about six inches square, placed upright on a suitable support To this are attached, by Fig. 273. means of sealing wax, two pieces of common gas carbon, C, C. (See detail sketch, fig. 272.) In each piece is hollowed out a shal- low cup, and supported between them is an upright spindle of gas carbon, A, the pointed ends just touching the cups. This spindle is placed in a telephonic circuit by twisting the wires round the carbon cups; as shown in the drawing. "Words spoken before this sounding board, even at a distance of several yards, are distinctly heard in the telephone. These transmitters, rou^^h and crude as they may appear, plainly show that a most import- ant advance has been made in telephony. With instruments of more delicate construction, even more remarkable results may ' THE MICBOPHONE. " ^^ made 1^; rl?„ T ," '"'" """='''™ "" " ^■"'^l ^h-" are pmbably le to^l ^ ! "^ °'^"" ""^^ *« phenomena would call faulte wh.Vh "'■"'the telegraph engineer though variattlrpttu^l ™::te " "f" '^"'"''-' conducting structure 17™ . *^ ^^P''™'^ P""^ "f «he theless a te That we nlT '""" "™"^"' """^ ^^^ '' '^ ■'«™>- ci«)uit and Lulat^ 2™ 7 T"? """^ ™ " '^'^P'"'"!" thirfnail „po7hl to l^'°/'^'l°*"' """^ "'^ P''^"' "• mitter is at »1 ttde The *''.r"'*' " "^P""! '-ns- nail, will be rerrZced in ,h ??T "''""'°°'' '""'»« ™ *^ are fastened down to a i^oriZuZJ^ZTSr ^' attached to them leadi*n«y tr. o k„** ^ , ^^^ ^ ^^^ a manner that^^ „ai 1™ ,.e 7V ' T^ " *''°P''°"« '" ^^h can be closrf by kv,„l i^ '^"^'^ '" ""» <^""*"'' ''Woh When a thW n^l if ll ^ °°1"'=""« °"'*^"''' '«=^°^ "x'"'- (aa a eylindlr can ol , t"^ ?' °*'' *™' " '« »'«"' ^at parallel wUhitlr^-r ""°*f °^''"'*^'- "''"^ «=='^ ^ not Lperf cI on "eel: Tie n^^'t' */ ''"'"° "™'* ""^ ^ ^"^ and it is to .hrM^ttection th t'tr' ^^'^^ *« "''"^' arrangement is due. "°'"'"="™ """ *« sensitiveness of this In the accounts which have been nnH;«h.^ t with the microphone, the ^tatemLThrfttntlv Zr^'^ that minute sounds are actually ma^rbT ^jX ™^'' ^nse that minute objects are ma^^^^ the ^iZ^Tl tele reflechon will show, hoWever, that there is T^^, m the action of the two in*,n.en... The soundIush^"1^ 644 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS the operator's fingers tapping lightly and, it may be, inaudibly upon the key. This view of the subject readily explains why the microphone has failed to realize the expectations of many per- sons, who, upon its first exhibition, enthusiastically announced that by its aid, we should be able to hear many sounds in nature which had hitherto remained wholly inaudible. SHORT CIRCUITING TELEPHONES. A number of the telephones invented by Mr. Edison may be classed together as short circuiting, or cut out telephonea The principle upon which they act might thus be briefly stated : In vibrating, the diaphragm cuts from the circuit resistances, which Pig. 274. Mg. 275. are proportional to the amplitude of the vibrations. A transmitter constructed upon this principle is shown in fig. 274 (devised March 20, 1877). A lever, L, of metal, vibrating in a vertical plane, rests at one end upon a strip of carbonized silk, C, which is part of the primary circuit of the induction coil I. In the course of its vibrations the lever cuts from the circuit parts of the silk, the current passing temporarily through the lever. Another, acting on the same principle, but differing consider- ably in construction, is shown in fig. 275 (devised August 21, 1877). A fine wire, W, of high resistance, is wrapped around a cylinder in a spiral groove. The wire forms part of the primary circuit of the coil C. A spring, S, of metal, in the form of an 3HPET CIBOUITING TELEPHONES. "545 ellipse, is fastened at one side to the diaphragm while the nth», '^rr '^™' *^ '"''^'''^ ^™ u^on the' o^i^t rSkin^it ■?"' " """""^ *°^'^ "^^ "8H flattens the'^^rring; TwJd fZT"P°''"«':'''^'^ -""»'«' of convolutionfthat : would If the mobon were in the opposite direction. The re s^tanee of the circuit depend., therefore, upon the position ^f ment is, that either a wnole convolution or none at all is «,! In fig. 276 (devised October 21, 1877), a similar sprine rest, .pon a nam>w strip of metal, on the surface of a ^^pC J^ig. 276. f^g. 2T7. The film is shown in perspective at F, and consists of a fine strio menJthtri: flg'ir ^^^^^ ' ^™"^^ '° *•>''' °' "^^ -'^«- fig'277:d:tdNrv °/i877i "r:«"V''-'"'°r ^"°™'" — acid th,^,--2gm"^^^^^^^^^ »ohler aI?' '!\°™™'««™^ Wroach or recede from to cause the nrst few coils to come together; and, in general the number of coils that thus touch each other is denenlT the amplitude of thn diar.|>™„.n'.. _-i J ^pendent upon u-uiaj.i..„gtn„ „,„t,„„^ ine wire is included 646 EDISON'S HECENT TELEPHONIC AND ACOUSTIC INVENTIONS. in the primary circuit of an induction coil, so that the r^distance of the circuit fluctuates as the diaphragm vibratea This wire has also been used as the primary of the induction coil itself with better results. CONDENSER TELEPHONES. Telephones in which static charge, instead of current strength, is made to vary in unison with the vocal utterances, have also been tried with success by Mr. Edison. The forms shown in figs. 278 and 279 (devised February 9 and December 10, 1877) differ only in construction, not in principle. Fig. 278. Fuj. 279. The former consists of a circular vocalizing chamber with mouth piece at Y. The chamber is surrounded with plates, which are connected with each other and with the ground These plates are free to viljrate, and are shown in the figure in section, as at P'. Immediately behind each of these stands a similar plate as at P, held at its centre by an adjusting screw. The outside row of plates are electrically connected with each other and with the battery which goes to line. When the inside row of plates vibrates under the influence of a jound, the distance between the plate varies and changes their static capacity. CONDENSER TELEPHONEa ' ' g^- bearing i„ the sZC^.^T^^ f "P°" ^^-^ ^7 a o:^w in vibrnting varies th?7 I ""^t^ment The diaphragm ^ The resiatenof of a ^Xtr *V''*'""'™-°'' "f ^e line. H an isometric UcckoT^^Tl 1 ''''P^"'^^"' "P"" i^ shapa basis of se/eralWeninn^+^i f''^'^^^.^^- This fact lies at the The one shown TnT 280 rT" "IT^ '^ ^^- ^^-- exceedingly si^;:::^^:!^^^^^^ f ' ^^^^) ^« of rests upon a slightly concave ^«f. / I °^ "''''""^' ^' the diaphragn. LentsT ^p^ ^r/^^^^^^^^ ^^^^^^ ^-- lipper surface, and as it vibrates ■Pig. 280. J^ig. 281. slightly alters the shape of the ^lobulp TV. • u • exceedingly small, is Efficient f va^ the r^i^^^^^^^^^ f^^f phonic current considerably. resistance of the tele- It is a peculiar characteristic of a dobnl« ^^ changes its original shape duriL fh. """'"'^ '^^ ^' tHroughit. MifEdisonh^LadTaLp^^^^^^^^^ ^'^^ ena in the telephone receiver shown in % 281 M '^^^P^"«°^• 19, 1877). The globule of mcrcZ Vt f ^^"'"''^ "^"^^^ a conducting solution, in a TshTpfci fub ' Tl ' *°''^'" "^*^ Which is faLned ^ T^J"^^^^ ^'^ ^oat I, 648 Edison's recent telephonic and acoustic inventions the voltaic pile telephone. . We have shown in fig. 282 (devised August 25, 1877) an instrument known as the pile telephone. A piece of cork, K, fastened to the diaphragm, presses upon a strip of platinum which is attached to a plate of copper. The latter is one of the termi- nal plates of an ordinary voltaic pile. The otiier terminal plate presses against the metallic frame of the instrument. When the pile is included in a closed telephonic circuit it furnishes a con- tinuous current The strength of this currant depends upon the internal resistance of the pile and its polarization, and these Are varied by vibrating the diaphragm. Fig. 282. Fig. 283. A convenient and peculiar form of receiver used by Mr. Edison is shown in fig. 283 (devised August 30, 1877). It is like the ordinary magneto telephone, except that the circular diaphragm is replaced by a strip of thin iron, the edges having been bent so as to render it stiff. We mention it simply because it demon- strates the fact that it is not essential that a circular diaphragm be used. A novel and purely mechanical telephone is illustrated by fig. 284 (deviocd August, 1877). In place of a line wire, the illuminating gas contained in gas pipes is used. It is calculated MECHANICAL TELEPHONE. 549 for short distances only, as it is essential that the eas used m ened by ite anet +n t/ ' instrument is merely a cone fast- W end Zl VI' ^'\?^P^ ^" P^^°« «f tl^e burner. The larger end 13 closed by a thin circular diaphragm. The vibra ^droTS^^"^-^^^^^^-^- toUerthl^ht The phonograph and telephone, when combinpri ir.^ • u august 1/^, 1877) IS a representation. The drum nf +1,0 raverae the hehx H, and which onginate at a distant statioa ^ig. 284 desired. ^^ converted mto sound when THE MOTOGRAPH. .wr^aL^s!^oTSi-tra^T'°"d^ flcation beoomo an articulating telephone ^ " "* '"°'''- moved .howmg ,t. .^nstraetioa. Withb the drum D^con" tamed the decomposing solution, and the coveringl™"„a7 "« the d.-am ,s kept constantly moist by capillary aelion 12 mo spnng attached to the oen,™ of the diap'hragmlt: ,.Z 550 EDISON'S KECENT TELEPHONIC AND ACOUSTIC INVENTIONS. the drum. While receiving, the drum is revolved by turning the milled screw at A. >' a Mr. Edison's musical transmitter is shown in fig. 287. The /%. 285. Fig, 286. point P, projecting from the centre of the diaphragm, impinges upon a wrapping oi platinafoil covering a small drum of rubber capable of adjustment bj a thumb screw. ' Fig. 287. THE CARBON RHEOSTAT. A very important application of the property possessed by semi-conductors, of changing their resistance under varying pres- sure, is shown in fig. 288. The outs represent the new Edison THE CARBON RHEOSTAT. 651 carbor. rheostat The instrument is designed to replace the ordinary adjustable rheostats whenever a resistance is to be inserted in a telegraph line, as, for example, in balancing quadruples circuits, and where accuracy is not required. Fig. 289 is a vertical section. It shows a hollow cylinder of vulcanite, containing fifty disks of silk that have been saturated with sizing, and well filled with fine plumbago and dried. These are sunnounted by a plate of metal, C, which can be raised or lowered by turning the screw D. The carbon disks can thus be Mg. 288. subjected to any degree of pressure at pleasure. When inserted in the line, it is a matter involving no loss of time to obtain any desired resistance. The resistance can be varied from four hundred to six thousand ohms. THE MICRO-TASIMETER The micro-tasimeter is the outcome of Edison's experiments with his carbon telephone. Having experimented with dia- phragms of various thickness, he ascertained that the best results were secured by using the thicker diaphmffms-. At this 552 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. Stage he experienced a new difficulty. So sensitive was the carbon button to changes of condition, that the expansion of the rubber telephone handle rendered the instrument inarticulate, and finally inoperative. Iron handles were subsLituted, with a similar result, but with the additional feature of musical and creaky tones distinctly audible in the receiving instrument. These sounds Edison attributed to the movement of the mole- cules of iron among themselves during expansion. He calls them molecular music. To avoid these disturbances in the telephone, the handle was dispensed with, but it had done a great service in revealing the extreme sensitiveness of the carbon button, and this discovery opened the way for the inventicn of the new and wonderful instrument. The micro-tasimeter is represented in perspective in figs. 290 and 291, in section in fig. 292, and the plan upon which it is arranged in the electric circuit is shown in fig. 293. The instrument consists essentially in a rigid iron frame for holding the carbon button, which is placed between two platinum surfaces, one of which is fixed and the other movable, and in a THE MICRO-TASIMETER. 553 664 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. device for holding the object to be tested, so that the pressure resulting from the expansion of the object acts upon the carbon button. Two stout posts, A, B, project from the rigid base piece C. A vulcanite disk, D, is secured to the post A, by the platinum Mgs. 291, 292, 293. beaded screw E, the head of which rests in the bottom of a shallow circular cavity in the centre of the disk. In this cavity, and in contact with the head of the screw E, the carbon button P is placed. Upon the outer face of the button there is a disk THE MICKO-TASIMETER. I ! 566 -ployed .o operate*: LstltV'"" °' '''^'^™^ ■"■"^"^' '^ tain;: mtdtcrr:;:^- *" ^°''^' »'• - which and ,,e cud G i , T,1 a "*' " ""P' I' ^'^'weea expa„.Mit, H rdCd%Sbrx:tT'"^"T "'■"^ <=ommunicatio„ with a galvanometer and S '^ '" connected with the batterv. The 2io of H ^^f"™""' '^ tested is nut nndpr j . i • "^""/"'P "* '"« substance to be galvanomeC ne d l a few T "T""' ""<='■ ■^''^A-"^ "^o When the needle col^.*^''>"' *' ■'™'™' P™"*- est subsequent exprnl?''''r''°"""°"- '^''^^ht- indieatedVtheZ™ ° to°,'r T''°° °* '^' ='"P ""•"'<' strip of hard rubrer pllee^t ,h' ?''™°"'^<-'- "^^dle. A thin sensitiveness, ^in^e^^^A ^yV^^tZXT,^ ^■^"•™^ "ove through several degrees fteneedle o ' ' "."" '" galvanometer, which is ,J »ff! Tl Z ?" ^ '""'^ ordinary tHennoplIe f-ingtr^rtrd W i t'thTh'T^ "i^ -per,„cn^ is held a few inches from he .bber sti T , of mica IS sensiblviffpotori T, *t, i. ^ ' ^^"otr stnp. A strip of gelatine, placed fe tt ^ "' "' '^' '^•"^' ""d » *ip mofature f^om a daml J '"J' "' ""'"""^ <'^P'""'«d by inches away ^ ""^ """"^ "* P'P"^ ''<'M 'wo or three mX^Z^ZT'Zv ?' ''"*™"^"' '' "-g"^ - - % Thomson's refiretiltar T'"™f "' '' -"nected with °a by a Wheats^ret^^rC aJI rh . ."' "r"' '^ ^"''"^'^ on both sides of th. c^,I "^*' "° '"'^^ *« resistance fromtheittllf T'^fl'^r-T:'''^"^'''''^""" "• at^ratrrT^*^^ ' i '• ^-^ '^^ *-~ At «, * and c the SneT'is'r^Z^'^' 1'^" """^ ■^^'»'="'- nution of theprcssu.on the ctbT ut^^^CrTnl -Lt!, IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 1.25 ■"US I2£ |50 "^^ ■■■ u tm 4^ 12.0 12.2 It! Ki U 1.8 1.4 6" Photographic Sciences Corpcration 23 WE!^T MAIN STREET WE6»TER,N.Y. 145«C (716) 873-4503 560 edison's recent telephonic and acoustic inventions^ expansion or contraotion of the substance under test is indicated on the scale of the galvanometer. The carbon button may be compared to a valve, for, when it is compressed in the slightest degree, its electrical conductivity is increased, and when it is allowed to expand it partly loses its conducting power. The heat from the hand, held six or eight inches from a strip of vulcanite placed in the instrument — when arranged as last described — is sufficient to deflect the galvanometer mirror so as Fig. 294. to throw the light beam completely off the scale. A cold body placed near the vulcanite strip will carry the light beam in the opposite direction. Pressure that is inappreciable and undiscoverable by other means is distinctly indicated by this instrument Mr. Edison proposes to make application of the principle of this instrument to numberless purposes, among which are deli- ' cate thermometers, barometers and hygrometera Fig. 294 shows in perspective the latest form of the Edison M THE MICRO-TASIMETER. 557 micro-tasimeter, or measurer of infinitesimal pressure. The value of the instrument lies in ita ability to detect small varia- ' tions of temperature. This is accomplished indirectly. The change of temperature causes expansion or contraction of a rod of vulcanite, or other material which changes the resistance of an electric circuit, by varying the pressure it exerts upon a carbon button included in the circuit During the total eclipse of the sun, July 29, 1878 It successfully demonstrated the existence of heat in the corona! It IS also of servace in ascertaining the relative expansion of substance due to rise of temperature. fHg. 295. In fig. 295 the important parts are represented in section, affording an insight into its construction and mode of operation. The substance whose expansion is to be measured is shown at A. It IS firmly clamped at B, its lower end fitting into a slot in the metal plate M, which rests upon the carbon button. The latter is in an electric circuit, which includes also a delicate gal- vanometer. Any variation in the length of the rod chan<.es the' pressure upon the carbon and alters the resistance of the circuit Ihis causes a deflection of the galvanometer needle ; a movement in one direction denoting expansion of A, while an opposite 668 EDISON'S BECENT TELEPHONIC AND ACOUSTIC INVENTIONS. motion signifies contraction. To avoid any deflection which might arise from change in strength of batterj, the tasimeter IS mserted m an arm of the Wheatstone bridge, whHe the galvanometer is used in the bridge wire of the same. In order to ascertain the exact amount of expansion in deci- mals of an inch, the screw S, seen in front of the dial, is turned until the deflection previously caused by the change of tempera- ture IS reproduced. The screw worJis a second screw, causing the rod to ascend or descend, and the exact distance through which the rod moves is indicated by the needle N, on the dial. The mstrument can also be advantageously used to measure changes m the humidity of the atmosphere. In this case the stnp of vulcanite is ttsphced by one of gelatine, whitAi changes itB volume by absorbing moisture. The delicacy of the appa- ratus to heat is remarl^able, and far exceeds that of any other apparatus. When adjusted moderately delicate, the heat of the hand placed in line with the cone of the tasimeter thirty feet dis- tant, causes the spot of light of the galvanometer to leave the scale. THE AEROPHONE. The aerophone, an invention of Mr. Edison's for amplifying sound, has already attracted considerable attention, though as- yet ?t has not been perfected. Its object is to increase the loudness of spoken words without impairing the distinctness of the articulation. The working of the instrument is as follows : The magnified sound proceeds from a large diaphragm, which IS vibrated by steam or compressed air. The source of power is controlled by the motion of a second diaphragm vibrating under the influence of the sound to be magnified. There are three distinct parts to the instrument : A source of power. An instrument to control the power. A diaphragm vibrating under the influence of the power. The firat of these is usually compressed air, supplied from a THE AEROPHONE. 55^ J-ne second, shown in section at flg. 296 consists »f » ^i & -d -uth piece like those ufed L'the^fphon: 1" Ptol '-?;, r !""'f ''^ " '"^ to the centred the dit ptogn. The cyhnder and its chamberE wUI, therefore, vibmte •^V. 296. With the diaphragm. A downward movement lets the chamber Jhl V ^°^P^«««^d air enters at A and fills the chamber which m Its normal position has no outlet Every dZZ^ vibi^tion of the diaphragm will thus condense the ^T^ ^>. 297. pipe C, at the same time allowing the air in B (» escaoe vi„ If oniina., en,n^ The P^toCdX"; ^^ t^ ^L^^^^ 560 Edison's recent telephonic and acoustic inventions. large diaphragm, D. The pipes C and B are continuations of those designated in fig. 34 by the same letters. The pipe C communicates with one chanaber of the cylinder and B with the other. The piston, moving under the influence of the compressed air, moves also the diaphragm, its vibrations being in nmuber and duration identical with those of the diaphragm in the mouth piece. The loudness of the sound emitted through the directing tube F is dependent on the size of the diaphragm and the power which moves it. The former of them is made very large, and the latter can be increased to many hundred pounds pressure. Fig. 298. THE HARMONIC ENGINE. This instrument is shown in fig. 298. Mr. Edison claims that ninety per cent of the power derived from the battery is utilized through its agency. The chief part of the machine is a tuning fork of large dimensions, vibrating about thirty-five times a second, and carrying on each arm a weight of thirty-five pounds. The amplitude of the vibration is about one eighth of an inch, and the vibrations are sustained by means of two very small THE MEGAPHONE. 661 electro-magnets placed lear the end of each arm. These maffnets are connected in circuit with each other and with a 6omm?tator worked by one of the arms. Small branches extend from the fork arms into a box con- taamng a miniature pump having two pistons, one attached to each arm. Each stroke of the pump raises a very small quan- TfL M ' ^'J^V' ^«^P«"sated for by the rapidity of the strokes. Mr. Edison's proposal is to compress air with the bar- ■•>„ m ii. amicrophoneffiir 8nn!l: I!! ^3 ***™y' ^ ~"P'«d *« of the fnZrubb!r2C\ f'^'''^''^'''*'^"g'»*»'»«di»>a T, and, consequtX o^ ttf "'"'" *^"' "P°° «■« '"-^o" n^s of whichTan trjt;^^''^; "r"'":^ ^^ *"-« ^»^«™- miemphone termina Jl° a !fnc«^c . r"^*^'^'"" ^' '^'" of plumbago, which restTon „ ^u , v "^ '^^^ '=«''""> "^ the^^coiviL CbouT Th„ t^* '*"" '""'"™' ^^^ o" mng tambour. The whole fonns a complete circuit, in 564 Edison's rboent telephonic and acoustic inventions which is a Daniell or Leclanch^ battery of one to three elements, and the telephones through which are heard the pulsation from the searching tambour T. Th;s microphone is susceptible of modification, and will un- doubtedly be the means of more extended physiological obser- vations. By substituting a small funnel for the tambour T, speech may be transmitted. Fig. 301. Mr. Edison, in his telephonic experiments, discovered that the vibrations of the vocal organs were capable of producing con- siderable dynamic effect Acting on this hint, he b^an experi- ments on a phonomoter, or instrument for measuring the me- chanical force of sound waves produced by the human voice. In the course of these experiments he constructed the machine t J' ^.r^:yi j7^ -^%^:W.\:' EDISON'S PHONOMOTBR. I ' 666 . shown in fig. 302, which exhibits the dynamic force of the voice 1 he instrument has a diaphragm and mouth piece similar to a phonograph. A spring, which is secured to the bed piece reste on a piece of rubber tubing placed against the diaphragm. ' This spnng carries a pawl that acts on a ratchet or roughened wheel on the fly wheel shaft A sound made in the mouth piece creates ^brations in the diaphragm, which are sufficient to pro- pel the fly wheel with considerable velocity. It requires a sur- prising amount of pressure on the fly wheel shaft to stop the machine while a continuous sound is made in the mouth piece We have already referred, on page 86 and elsewhere, to the later improvements made by Mr. Edison in the carbon tele- phona The subject, however, has by no means been exhausted and we, therefore, return to ite reconsideration the more ml- Jmgly now-, as the opportunity thus afforded enables us to say IvT M^f f '"^ "^"^ ^ '^^ ^^P"'^ "^e^^ telephones which Mr. Phelps constructs for working in connection with the carbon transmitter. The contmued use of these improved transmitters, in a practi- ^ way, for a number of months past, has shdwn them to be the Dest adapted of any of the forms now in use for real effective »emce ; and if the necessary use of a battery in comiection with them IS, after all, so much of an inconvenience as some would amagme, their rapid introduction, in spite of this fact, and to the exclusion of other instrumenH is sufficienc evidence that the Above mentioned drawback is fully compensated for by coii«- sponding advantages in other directions. On page 36 it has been stated that in the more recent forms of the carbon telephone Mr. Edison had done away with die vibrating diaphragm altogether, replacing the same by an in- flexible plate of metal, whose sole function was to collect and concentrate a larger portion of the sonorous waves upon the limited carbon surface. This form of transmiti;er is shown in fig. 303. The prepared carbon represented at C, is contained in a hard rubber block open clear through, so tiiat one side of the former is made i^ 666 EDISON'S BECBNT TELEPHONIC AND ACOUSTIC INVENTIONS EDISON'S CABBON TELEPHONE. 667 rest upon the metallic part of the frame which forms one of the connections of the circuit The opposite side of the carbon is covered with a circular piece of platinum foil, P, which leads to a binding post insulated from the frame, and forming the other connection for placing the instrument in circuit A glass disk, G, upon which is placed a projecting knob. A, of aluminum, is glued to the foil ; and the diaphragm D, connecting with the knob, serves, when spoken against, to communicate the resulting pressure to the carboa A substantial metallic frame surrounds the carbon and its connections, and their complete protection agamst injuiy, to which they are liable from careless handling is thereby secured. Fig. 303. The same instrument, in perspective, is shown in fig 304, mounted upon a projecting arm with a joint at each end, only one of which, however, is shown in the cut The lower end of the arm is secured by means of the joints to a desk shown m fig 305, and thus, as will readily be seen— the motion being in a vertical direction— permits of placing the telephone in a convenient position for speaking purposes, and, consequently, rendering it easily adapted for the accommodation of persons of various heighta w 661 EDISON'S HBCEAT TELEPHONIC AND ACOUSTIC INVENTIONS. The Edison telephone, it should be distinctly understood relies yrholly upon the battery for its power, and not upon the voice, as is the case with other telephones. Consequently it is nnnecessary to shout into the apparatus, and thus destroV the privacy of conversation. All that is requiiod ia that the worda should be spoken distinctly and in an ordinary tone of voice One great drawback to the univenml introduction of the tele- phone, that has thus far been experienced, is the disturbing influence of current pulsations in neighboring conductora when t^e latter are m use, and which produces a rattling noise within Hie telephone. This phenomenon, to which we have before I^g. 304. referred, under the hr^ad of induction, page 28, and elsewhere, IS effectually overcome by using the Edison telephone, as the power of this instrument is so great that it can be operated with perfect success on lines having the greatest amount of inductive action, and where no other form could be used. Figs. 806 and 307 represent two forms of the magneto tele- phone, as devised by Mr. Phelps, which give surprisingly good results, both whan used singly and in combination with the Edi- son transmitter. In shape they somewhat resemble a single and double crown, and owing to this fact, have been designated respectively single and double crown instruments. '■^itT^^^T. '^f-y'^^^^'-:'^W^'*':^^^^^^0f-: EDISON'S CARBON TELEPHONE. . gg^ plat of &oZu ZlZ^,""'^'^ '" '^^ '"^'™"'»« io core wUoh i^e^r ^i J»'^. joined to one end of the oames the magnetizing helix, and radiate from it io ■%. 306. as many different direotiona. Th» «•,„«.•. iJie double crown instrument is shown in R^ qn7 7 will be seen, consists of two sinde cmwn . i \ ' ''^' ** together, witl, a oomn.onyJlZt.XrV''T ^'"^^ coils on ea«h of t.h« .^..= „J^"^^_"g«^.»^ber between them. The - -a_ _.^ «,^ wiiaoci«a m such a way that the 570 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONa currents generated in them, when the diaphragms are made to vibrate, mutually strengthen each other, or, when used in combination with the Edison transmitter, that the action of the pulsating current in each coil contributes to a single result, and thus enhances the effectiveness of the apparatus- Some idea of the performance of these improved instruments will be conveyed by mentioning the results obtained at a recent exhibition of them in the Sunday school room of Dr. Wells' church, Brooklyn. Mr. Edison's carbon transmitter was used for sending and Mr. Phelps' single crown telephone for receiving. Fig. 306. The sound was also reenforced at the receiving end by the use of a large paper cone, whose smaller extremity was held to the mouth p\.ce of the instrument. The circuit extended from the resi- dence of Dr. Wells, near the church, to the lecture room. Speech from the telephone was distinctly heard in all parts of the room by an audience of about three hundred persons, while the sing- ing of a vocal quartette, solo singing, and guitar playing were transmitted with surprising clearness and loudness. It should be observed, moreover, that the performance in this case was very different from the so called musical telephones, by means of " > i ij,^ -< « ' V>Jw** I ■ EDISO^-'S CARBON TELEPHONE. 57^ was exacUy reproduced This is one of ,^„ t °* """"^ magneto telepLne-eyerytS^Tflh^ ,? "°''™'''^<'' ^^ WeUs addre^ the aS^ ^™\^^"^ -^P^^uced. Dr. phone, and not oZ^M^W^i^^^^?'' *■»« <*'- also instantly reeoffjized. ^ """^eratood. but h« voice was Fig. 308 shows a convenient way rf ananging the telephone JFig. 301. apparatus for shop, counting room, and various other purposes. ^erator, serves as the t^nsmitter, and the P^rol" ment as the recenrer the caU being given by an o^X- graph sounder and a key for interrupting the cireuit ^ The switch shown at the back serves for putting the telenhon, .n and out of circuit The small induction coif used wfh the apparatus .s placed beneath the desk aad in a posi^n :^1*: 4 ^^i 672 Edison's recent telephonic and acoustic inventions. is not liable to damage. When the switch is turned as rep- resented in the cut, the apparatus is in the proper condition for speaking purposes. When it is turned to the opposite buttons, which is its normal position when not in use, the telephones are cut out of circuit, the sounder, battery and key alone being then included. By depressing the key now, wldch in the normal position keeps the circuits closed through a back contact, the battery current is interrupted and the sounder armature released. Fig. 308. thus furnishing the call, to indicate that telephonic communi- cation is desired. It will be understood, of course, that the same battery is used both for signalling and talking purposes. In the former case the battery current traverses the line and produces the signal directly, while in the latter it merely passes through the telephone and primary wire of the induction coil and the induced currents, produced in the secondary coil by the variations of the battery Edison's oabbon telephone. 678 tmrrent when the telephone is spoken into, traverses the line and produces the articulation heard in the receiver at the distant! station. This apparatus, mounted as in fig. 808, is much used, m fact, almost universally, in the merchants' exchange system. to which we shall refer presently. F^g. 309. The form of cal] here shown, however, is intended only for short lines, as the cuxi ;nt from the small battery employed would not be sufficiently powerful to operate a sounder placed some miles away. For long lines the magneto machine is used to generate the call currents. The combination shown in fi- S09 I'f 574 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. and which contains a machine of this kind, is somewhat similar m arrangement to the one given on page 27, but of a more improved pattern. The call bell and duplex telephone are the same, and the principal difference consists only in the arrange^ ment of circuit connections, within the box, and in the addition of the smgle crown instrument, by which greater effectiveness is obtamed. The switch at the upper right hand side of the box is used to put the apparatus in and out of circuit, as desired, while that on the left serves for connecting or disconnecting the bell magnets. When placed as represented in the figure, the latter is m circuit, and will cause the bell to ring both at the home and didtant stations, if the button marked C is pushed in repeatedly while the crank shown in front, and which operates the magneto machine, is turned at the same time. Fig. 310 represents the same form of call box, with an Edison transmitter attached to replace the duplex instrument in the combination just described. The internal connections are the same in both, so that it will be unnecessary to describe them again. Fig. 311 shows acall box, devised by Mr. Grav, and much used m the Western States in combination with the bipolar telephone. A stiU later form has been arranged by Mr. Phelpa This also contains the magneto call apparatus and switeh connec- tions of the combinations referred to above, and in addition to these it is provided with an ingenious device, first sug- gested and applied by Mr. Henry Bentley, of Philadelphia, by means of which the carbon telephone, and, consequently, the battery also, is cut out of circuit at all times, except when actually in use for transmitting purposes. This device consists of a small spring placed on top of the handle of the instrument, or at the side, as the case maybe, and which, in its normal position, keeps the telephone circuit disconnected, but immediately establishes it whenever the handle is grasped by the hand, being then pressed down upon the contact button, and thus allowing the battery current to pass through the telephone and primary wire of the induction coil. As the result of this arrangement, Mr. ■-«w^W':-a»;*'^?#«*% .■ bentley's telephonic improvement. 575 ; Beutley has been enabled to introduce the Leclancb^ battery for ^kmg p . ,^^ ^j^p,^^^ ^^^^^^ .^ J or gravity battery heretofore used, and thereby has paved the wav for grea ly reducing the expense of maintenance in W systems, hke that of which we intend to speak directly, asTh^ Fig. 310. exe ntT, ^'f "°- '^P'""" """^ ^ '"<="■«* for attendance, m<71 ' -^ ""g mtervals. Altogether this .eems U> be the most economic^ and practical combination that has yet been brought ouMnd its very general introduction would a~° oo aii Dut assured. «i-i-car i^ ! / 676 Edison's becent telephonic and acoustic invention& During the past summer the Gold and Stock Telegraph Com- pany have organized a merchants' exchange system in New York and elsewhere, which, besides being of great convenience to sub- acribers, has also been the means of giving a marked impetus ^g'. 311. to the already widely extended and continually increasing appli- cation of the telephone to business purposes. In this system a central office is connected by wires with the house, office, count- ing room or other place of business of each of the subscribers, I THE TELEPHONIC EXCHANGE SYSTEM. 677 I a ^parate wire, as a general thing, being used for each ona Each individual subscriber is also provided with a list of all the sub- scnbers to the system, and when at anytime desiring to com- municate with any particular one of the members, has mei-.ly to notify the central office of the fact, when the two corresponding wires are immediately connected and direct correspondence is established. Attendants sufficiently numerous are, of course, always kept on duty at the central office during business hour^ to attend to this work of switching and to see that everything IS maintained in proper working condition. A brief review of the arrangement in this office may not be ^thout interest. Near the centre of a large room an oblong frame is erected, and enclosed and within this all the wires of the system are connected and separately led to small sections of what collectively may be caUed a switch board. These sections are arranged alongside of each other, facing outwards and in two -or more parallel rows, one above the other, but all within con- venient reach of an attendant standing upon the floor. Refer- ring to a single section, as the connections are similar in all, the line wire after its introduction within the frame or back of the switch is connected to a screw passing through the section and m electiical connection with a metallic piece in front, which also carries a key provided with both front and back contacts. In its normal position the key is held on the back contact, which IS simply a slight projection from a metallic plate, and thus establishes a good electrical path for a current arriving from the line to this plate, and when a plug is inserted between this and a brass disk beneath it, which is also in electrical connection through a small relay with the earth, the circuit for the call current is completed. A catch on the end of the armature lever which extends through the wooden part of the section, engages with an annunciator disk and keeps it in a vertical position so long as the armature remains unattracted or during the normal condition of the line when idla If, however, a current is sent into the line from the other terminal station, by the depression of a key hke the one shown in fig. 308, the armature lever is 678 EDISOfi'S BEOENT TELEPHONIC AND ACOUSTIC INVENTIONS. attracted, and thus releases the annunciator disk, which, being hinged below, now falls by its own weight, and indicates not only that a call has been sent, but also at what particular station it originated. This the attendant acknowledges by pressing upon the proper key and causing it to touch the front contact, which is connected to a battery of two or three cells, and by means of which a current is sent to line to actuate the correspondent's sounder or bell. The telephones are then placed in circuit and verbal communication established, when the wants of the calling station may be made known. The central office acquaints the station asked for that correspondence is desired and then switches the two lines together. It may also be added, in further explanation of the system, that some one in the central office always takes the precaution to see that communication is really established after the switching has been done. To facilitate this and provide for the contingency of simultaneous calls, telephone desks with their complete outfits are arranged along the sides of the room and connected by wires with the switch board. The number of desks, of course, varies somewhat, a certain number being always provided for a given number of lines, and these are continually increasing. Heretofore, when through communication had been established it has been necessary for an attendant at the central office to listen from time to time, so as to know when to disconnect the lines again ; but a device is now being introduced which will render this proceeding unnecessary. This consists of a short core relay, which is placed in the telephone circuit and adjusted so that its armature remains unattracted or upon the back stop while the telephones are in circuit, but immediately responds to the increased strength of current occasioned by the withdrawal therefrom of one or the other of these instruments. A local battery and call bell are connected with the relay, and serve to attract the attendant's attention when the armature is attracted. A single bell in conjunction with the annunciator disks is also used for some of the sections of the switch at the central office, but it has been found in practice that the fall of the disks alone EXPEBIMENTB WITH EDISOn's OABBON TELEPHONE. 679 make sufficient noiae to call attention to them, and the bell for tw"""^?" w I, therefore, be dispensed with for any new wire, that may hereafter be added to the system Prmtiag iastameats, to a very limited extent, are likewise "ed on some of the TOB rf the ewiMge system, but their em. &i".rf "* with c„osid:::^™oi oo^pii^'jz iZ, ° *•;« t^'ephon^ and correspondence is, at the same ti»i fi^ ?!^ ^'^ ^ *"* "^^ ""'"'"^^ 0* *^« instruments is con- ^e p^^ir ' '' ^""^ '""^""^ '"'"'« '"' '^•«P''°- -- Jll"^ ^^^ '° ^^"^ "^-^ ^- B^i^^'. of the Uni- ^ty rf Ptaa8ylvi«,a, for the folWng interesting partiou- km m relation to the exp«fa»n1« a,ade with the Edison carbon telephone, between Philadelphia a.d Washington, in Ap^ 1878 These expenments originated in the foltowing way: Whfe makmg plans to exhibit to the National AcademPof Seienl at ite spring session, in Washington, the collection of telephones which tie kmdness of my friends, Mess... Bentley, EdiZ Gmy and Phelps, had placed at my disposal for m/iecture °f ' Apnl 15, It occuned to me that it would be a pleasant thing if the oo««,on could be made an opportunity of Xrding Pref^, Joseph Hemy the distinguished president of the aJemy,X had watched with so much interest the progress of the telephone ^TZA'^V^ "" '^ir' '^"■'^™''«°° with some distan point, and thus of personally verifying the latest triumph of electacd Bcience. The matter meeting with the corfial approv^ I ^'^ T'' ^f'^' "^ /"'"d^lpWa, I suggested it inater I was then writing to Hon. William Orton, president of thi Western Union Tel^iaph Company As this^great and goS aZj7 rrr^. ^r "--S -^. I ^ay b^ pe..mittrfX quote that part of his letter in which he replies to my sugges. bon, because it shows the kindliness of his nature and the warm appreciation which he had of Professor Henry's scientific inves- tigations. In his letter, which is dated April 11 he says- "I note what you say concerning the meeting of the Academv of Science, at the Smithsonian Institution, on Tuesday and I 580 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONS. sympathize most warmly with you in your desire to exhibit to Professor Henry the latest wonders of that science to which he has devoted so much of his priceless life, and for which he has received so little reward. But if the world is slow, as it often seems to be, in doing justice to those who have done most to promote the interests of science, and thereby the welfare of man- kind, I believe that justice is sure to be done in the end, and so believe that the time will come when all men everywhere will recognize his services in connection with the grand resiilts of his noble life. Any service that I can render toward making the occasion to which you refer interesting to all who may partici- pate in it will be rendered most cheerfully." In pursuance of this kind offer, I received, a few days afterward, an official letter from Mr. James Merrihew, the superintendent of the Western Union Telegi*aph Company, at Philadelphia, saying that he would be glad to do anything in his power to facilitate the proposed plan. Manager Eobinson, too, was equally courteous. On reaching "Washington and reporting on Wednesday morn- ing to Manager Whitney, of the Western Union office there, I, learned that Superintendent Merrihew had himself come on to assist at the experiments, and that they would be ready for the preliminary tests that evening. Early in the evenmg the wires worked badly, and it was with some difficulty that we could get Menlo Park. But about ten o'clock the induction lessened, and I carried on a conversation with one of Mr. Edison's assist- ants with considerable ease, the distance being two hundred aiid five miles. For the experiments at the Smithsonian Institution, on Thursday, April 18, it was judged best ., \ 1.^ attsmpt con- versation beyond Philadelphia Mr. Edisor snif' .V Bachel »:• had arrived that morning, and had brougui, ,vith them some improved instruments. In the morning Mr. Edison exhibited the phonograph to Professor Henry in his own parlor. At three in the afternoon the telephonic apparatus was arranged in the sa'riv V lace. Mr. Edison being absent. Professor Henry, Mr. ]\I.!! v.-ew raid myself seated ourselves at the table, upon which, L-eside the Edison transmitter and induction coil, were the EXPERIMENTS WITH EDISON's CARBON TELEPIlONE. 581 magneto telephones of Phelps, Gray and Bell, to be used as receivera The Morse instrument in circuit told us when all was ready ; and, on cutting in the telephone, we leeognized at once Mr. Bentley's well known voice, calling " Hallo I hallo I" Ordinary conversation was then carried on with perfect ease, and Mr. Bentley's elocutionary efforts, detailing the personal charac- teristics of the little girl whose forehead was adorned with a curl in its centre, were most highly appreciated, the articulation being clear and distinct. Professor Henry said he heard every word, and expressed to Mr. Bentley, through the transmitter, the pleasure 'and gratification which he deeply felt, and which his manner showed to every one present Doubtless, his memory carried him back to 1830, when in the laboratory of the Albany academy he made the early researches of which the interesting experiments he had now assisted at, and which showed that men could converse through one hundred and forty miles of inter- vening distance, were the outcome. The friends who had gathered to witness the trials were now afforded an opportunity to test the question for themselves, Mr. Bentley most generously assisting them in every way. At four o'clock, the hour which the academy had fixed for the phonograph and telephone experiments, the apparatus was taken down stairs into the office of the secretary, where the meeting was in progress. Mr. Edison was presented to the academy, and was welcomed by the chairman, Vice-President Marsh. Mr. Bachelor then exhibited the phonograph. I then read my communication on the telephone, exhibiting and describing the various forms, and closed by placing them on the Philadelphia wire, so that the members could hear the words spoken one hundred and forty miles away. The academy expressed itself highly gi-atified, and passed a resolution of thanks to the Western Unioa Telegraph Company, and especially to Mr. Edison, Mr. Bentley, Mr. Merrihew and Mr. Whitney for the courtesies shown. The result of this experiment, the most important made in telephony up to that time, showed that it was entirely possible ■i ;:82 EDISON'S BECENT TELEPHONIC AND ACOUSTIC INVENTIONS. to converse with ease between stations one hundred and forty miles apart, and this over a wire surrounded by twenty or more wires, air in active use, and carried under firee rivers m its course, in insulated cables. The first proof of this fact must ever be a source of gratification to all who were concerned in establishing it ; and to none, I am su/e, more than to Mr. Henry Bentley, through whose intelligent and well directed efi'orts the carbon telephone, the conception of Edison's genius, first became practically successful. In a work which has been so largely occupied in considering the discoveries recently made by Mr. Edison, it does not seem inappropriate to add a few words in regard to the man himself, and to this end the concluding portion of the present chapter will be devoted. For the information respecting the early years of the great inventor we ^re indebted to an interesting paper entitled "A Night with Edison," written by William Bishop' , and published in Scribners Monthly, November, 1878. Thomas Alva Edison was born at Milan, in Erie County Ohio February 11, 1847. An obscure canal village of the smallest size, it was not the place where the advent of a genius would be looked for, if this elusive spark had the habit of appearing anv- where according to prescribed formulas. The village of Port Huron, Michigan, to which' his lamily removed soon'after, and where the gi-eater pgrt of his youth was passed, could not have afforded a better prospect His family was an average one of the humbler sort There was no unusual talent in any of its members upon which a claim to heredity of ability could be based. Of a number of brothers and sisters, none have shown an inclination towards pursuits like the inventor's own. He may have taken from his father— who was in turn tailor, nur- seryman, dealer ingrain, in lumber and in farm lands— some of the restlessness which has impelled him to activity in so many different directions. He took, also, from him a good constitu- tion. This parent of Dutch descent, a hale old gentleman, still living atthe age of seventy-four, had two immediate ancestors' who lived, one to the age of one hundred and twn +.h« ^+ho^ + Edison's eakly life. 1! 683 -hundred and three. It is a point not altogether unimportant to note in passing, since it holds out the prospect, in the ordinary course of time, for the matured completion of the wonderful programme the inventor has laid out for himself already, at the comparatively youthful age of thirty-one. His mother, of Scotch parentage, though born in Massachusetts, was of good education, and had formerly been a school teacher in Canada. She im- parted to him about all the instruction from outside sources he ever received. Of regular schooling he had no more than two months in his life ; and his school mates of this brief period do not remember him as brilliant, nor are there preserved family records of phenomenal infantile doings. But he was a child who amused himself much alone, and doubtless, if his quiet plays had been noted, there would have been detected indica- tions of the faculty in which his extraordinary future career was involved. He had the intense curiosity about the world we in- herit, and its great names and great deeds, which will be found an early tr^it in common in almost all the lives that have his- tories of their own to leave behind them. At ten, he was read- ing Hume's England, Gibbon's Home, the Penny Encyclopaedia, and even some books of chemistry, which came in his way, with the rest, and gave, as it seems, the direction to his future action. While it will thus be observed, that his school opportunities were of a very limited nature, the statement that he is an un- educated man, which has appeared in some of the daily journals, is by no means true. During the whole of his life the habit, so ■early acquired, of reading everything that came within his reach has been continued, and much has, consequently, been gained in this manner, as he possesses a most retenti - memory. As an i n- dication of his thirst for knowledge, the naive ignoring of enor- mous difficulties and the completeness with which the shaping of his career was in his own hands, it may be stated that at one time he formed the project of reading through the whole public library of Detroit! There was no one to tell him that all human knowledge may be found in a certain moderate number of volumes, nor to point out to him approximately what they are^ 584 EDISON'S RECENT TELEPHONIC AND ACOUSTIC INVENTIONSL Each book was, in his view, a distinct part of the great domain, and he meant to lose none of it He began with the solid treatises of a dirty lower shelf, and actually read, in the accomplishment of his heroic purpose, fifteen feet in a line. He omitted no book and skipped nothing in the book. The list contained, among others, Newton's Principia, Ure's Scientific Dictionaries and Burton's Anatomy of Melancholy. When Edison was fourteen years old he entered the telegraph service, and remained in it until he was twenty-three, becoming in the meantime an accomplished operator. His experience as a practical telegraphist has been of the greatest value to him in the prosecution of his electrical inventions, particularly those relating to telegraphy. The great number and variety of subjects to which Mr. Edison has given his attention is scarcely less suiprising than the marked success with which his labors have been crowned. Electricity alone, although receiving the most attention, has fur- nished but a single field for the display of his versatile powers. His path has been through extended portions of physics and chemistry, and is clearly marked by characteristic inventions in these vast domains. Not less remarkable, too, is the originality of his ideaa Many of his inventions, to be sure, are but im- provements upon the methods of previous investigators, but many others have been produced while pursuing a line quite outside of that followed by these earlier pioneere, and in some in- stances, also, without any knowledge whatever that the subjects had been considered by them. As illustrations of this faculty for original research, we have only to mention his chemical sys- tem of telegraphy, the electro-motograph, the system of double transmission in the same direction, the quadruplex telegraph and the carbon telephone, in all of which this faculty is con- spicuously displayed. Stark, it is true, invented a method of simultaneous transmission in the same direction, in 1856, and at that time had the idea of quadruplex telegraphy in mind. Kramer, shortly afterwards, improved hpon this method, and subsequently the idea was also taken up by Bernstein, Schreder. X EDISON'S ORIGINALITY. '' 535 , Wartman and others ; but all, with only slight modifications, fol- lowed a similar line of investigations, and in the end only suc- ceeded in working imperfectly upon Unes of very short length. Mr. Edison, however, instead of employing three relays, or their Zr .*' ^^r^-f ^'^"^ *^^^ °^^'^^*' - ^^« P-dec.:sors had misir H ".f ,^^^ *« *-' -- for receiving each trans- signals which a change in the polarity of the battery current pro- duced ; and by the addition of a simple device, never thought of by previous experimenters, and which was made directly opera- tive by the line current, and independently of the relays them- Sr TT"t " '""P^'*"^-^ '""^''^^ '^' q^^^tion of multiple telegraphy for all cases, making the quadruplex, in consequence a practical apparatus for the longest circuit^^ sequence, .i,^ri!r'rf''^.^ ""''^ beneficial results attended his labors in the field of chemical telegraphy With this system, after care- fully studying the problems involved, he succeeded in vastly Thatevlr^ '^^^"^ ""^ transmission for circuits of any length His originality is also shown to good advantage in the inven- tion of the carbon telephone. During the time that Gray was occupied with the problem of transmitting articulate speech by means of vanations in the current strength, produced by a mov- able electrode in a liquid conductor, and Bell sought to realize his Idea of reproducing speech at a distance by the magneto prin- ciple, Edison directed his attention to the attainment of the same object in quite another way, and soon succeeded in furnishing the true solution of the difficulties to be overcome, and of securing the best practical results, by following out a principle previously discovered by himself, and in which the current variation waa produced by the variable resistance of solid conductors when subjected to pressure. The result of this novel departure is seen m the carbon telephone, justly considered the best transmittino- instrument yet introduced. ^ We might thus go on and enumerate other invention ssfcavcc!." 586 Edison's recent telephonic and acoustic inventions. less calculated to show his manner of investigation in the line of original research, but enough has already been said to make this point apparent ; we will, therefore, conclude our very brief sketch with a few words regarding his great capacity and still greater inclination for work. Without doubt, Mr. Edison is more than usually endowed with what the world terms genius. His intellectual powers are of no ordinary kind, and the potentiality of his brain is very much above the average ; but it should be clearly understood that his great success is the result, not so much of the divine gift of genius alone as of his ceaseless activity and indomitable perseverance under all circumstances. These are un- questionably the most remarkable characteristics of his nature and the real elements of his success. The author can state from personal knowledge what is now becoming more generally known regarding Mr. Edison's extraordinary propensities for work. No person with whom he has ever met has exhibited anything like it, and very few, if favored with like power of endurance, would be found willing to apply themselves so assiduously in any given direction. During the early experiments with the quadruplex system of telegraphy, which took place under Ins own supervision, and which required a vast amount of time and application for its perfection, it was a very common thing to find Mr. Edison work- ing through the entire night, his only rest being such as a brief interval of sleep just before day might afford, taken in the ex- perimental rooms. Night after night he has worked in this manner, and been found in the morning with nothing but his coat for a pillow and the table or desk for a couch, makino- thus a lame apology to nature for the most reckless disregard of her requirements. Mr. Edison still keeps up the habit of working long into the night, at his laboratory in Menlo Park, and probably will con- tinue to do so as long as his physical powers will sustain him. The accompanying fig. 812 represents him after a night spent in some absorbing work, as he takes his solitary way homeward through the surrounding darkness that precedes the dawn of an- other day. Entreaty and remonstrance with him on this point EDISON'S ENOKMODS CAPAOIIT TOB WORK. 687 are alike in vain ; not that he is unmindful of friendly counsel or studiously neglects it, but because, when engaged upon any subject, his whole energies for the time being are con magnet is termed a bar magnet, and usually acts by means of one of its poles only, but if the core is bent in such a manner that both its extremities may act upon the same armature, it is termed a horse shoe or U magnet. The same result may also be obtained by uniting several pieces together. Thus two cores of iron connected together by a yoke or bridge piece of the same metal, each core being surrounded by a bobbin, constitutes an Mg. 315. Fig. 316. electro-magnet with two branches, this being, in fact, the form in which electro-magnets are usually constructed, but many other forms are .^Iso employed, to a greater or less extent When the electro-magnet just described is without a helix or coil upon one of its cores, it is termed a single coil magnet. Figs. 315 and 316 represent two forms of this kind of electro-magnets. The earliest experiments which were made with the view of improving and perfecting the electro-magnet, demonstrated that the effective force of an electro-magnet is proportional to the strength of the magnetizing current and to the number of con- volutions in the magnetizing helix ; and that in order to produce the most advantageous effect, the resistance of the helix should * Abstract from Expose des Application de I'Electricite, by Ct. Th. Du Moncel. MAXIMUM or MAGNETIZATION. " 593 be equal to that of the portion of the circuit not included in i the hehx. Subsequent experiments proved that a mass of iron is suscep- tible of acertam maximum of magnetization only, and only with- in certam limits is the force of the electro-magnet proportional to the square root of the diameter of the iron cores, or simply to the diameters, if we take into account their action on the ar- matures. These experiments also proved that in order to de- velop m two electro-magneta of different diameters the same proportional part of their maximum magnetism, the product of the current multiplied by the number of evolutions must be proportional to the square roots of the cubes of the diameters A still later series of carefully conducted experiments showed that the magnetic force not only increases as the squai^ root of the diameter of the core, but is also proportional to the square of the length. The attraction which results from this force, how- Tl ^^"!?!f ^^^ i^ *^« ratio of tlie square root of the distance of the middle or neutral point of the core from the armature. Ihe result of these experiments shows that the attractive force ^xerted by an electro-magnet upon its armatuje is proportional to the diameter of the core and to the square root of its lengtL The investigation of the question of magnetic saturation proves that the maximum of saturation depends solely upon the mass of iron contained in the electro-magnet, irrespective of Its form; and that the maximum degree of magnetization, of which a mass of soft iron is susceptible under the influence of the electric current, is more than five times as great as that which a corresponding mass of hardened steel is capable of retaining. ^ When the electro-magnet exerts its attraction on an armature Of soft iron, it creates a new magnet, which, reacting in turn on the first induces a similar action, thus proving that the attractive force of electro-magnets is proportional to the square of the strength of current for a like number of convolutions, and to the square of the number of convolutions for like strength of cur- rent This law can, however, only be considered as rigorously 594 DUPLEX TELEGBAPHS AND ELECTRO-MAGNETS. exact when the electro-magnet and the armature contain about the same mass, and their magnetic state is near the point of saturation ; that is to say, that which these magnetic pieces would retain if, being of tempered steel, they were magnetized to a maximum. We will only add, that it follows from the preceding law, that if the strength of current (acting on the electro-magnet), and the number of convolutions in the helix vary at the same time, which is nearly always the case, since by increasing the number of convolutions without changing the battery, we in- crease the resistance of the circuit, the attractive force of the electro -magnet becomes proportional to the square of the strength of current multiplied by the square of the number of convolu- tions. When the electro-magnet, instead of acting on an arma* ture of soft iron, exerts its action upon another electro- magnet, the attraction is propo^ional to the sum of the products of the strength of current by the number of convolutions in the two helicea Finally, when the electro-magnet acts upon a steel armature magnetized to saturation, the attractive force is simply proportional to the product of the strength of current by the number of convolutions. It will be observed at the same time that the nature and diameter of the wire of the magnetizing helices exert no influence, provided the strength of current doea not vary. In the laws of the electro- magnet which have thus far been gummed up, the armature has been assumed to be of sufficient dimensions to render it capable of receiving the same amount of magnetism as the core itself — a condition which is necessary in case the attraction exerted upon the armature is represented by the square of the force proper of the electro-magnet. In order that the law may hold good in the case of an electro magnet which has arrived at its maximum point of saturation, it is evidently necessary that this armature should present a mass nearly equal to that of the core which is directly magnetized by the helix, . while in order to satisfy the conditions of the law of proportionality of the forces, with respect to the diameters and lengths, the armature should be of about the same dimen- PROPORTION OF FORCES TO DIAMETERS. II 696 sions as the electro-magnet Hence we arrive at the conclusion that the maximum of force of which an electro-magnetic svstem composed of a helix, core and armature, is capable, is devdoped when the dimensions of the two latter in respect to their length and surface are equal. ° The proportion of the forces to the diameters indicates that the former depends more upon the surfaces than upon the magnetic masses. It follows from this principle, that if a second armature IS attached to the inactive pole of a straight electro- magnet, the effective force of the combined system ought to be considerably augmented ; for the reason that the electro-magnet with ite first armature constitutes, in point of fact, an electro- magne of double length. Therefore, the maximum of force ought to be developed when the length of the second armature 28 also equal to that of the electro-magnet If we consider the system with reference to the first armature, we arrive at the following general law : In a straight electro-magnet, the length of whose core exceeds that of the magnetizmg helix, at the end opposite the armature the force progressively increases with the length of the core, until the total length becomes three times that of the bobbin This result IS confirmed by experiment We are now able to estab- lish other conditions of maxima in respect to double electro- magnets In fact, since the length of the magnetic core which projects beyond the magnetizing helix becomes more and more ^vorable to the development of magnetic force until the core becomes three times the length of the helix, we can readUy understand that the force can be still further augmented bv causing this mass of iron to react on the armature, and bv enveloping the latter in a second helix. Now, if this second helix IS of the same length as the first, we then have two elec- tro-magnets, each of which is placed in its condition of maxi mum, and of which the part without the coils-which is usuall, termed the yoke-of the double electro-magnet should be equa^ in length to one of the cores, if it is desired to keep it within the maximum conditions already established. We may, therefore m DUPLEX TELEGRAPHS AND ELECTBO-MAGNETS. lay down the equality of the four constituent parts of the system, as the condition of maximum of double electro-magnets. This conclusion, which experience has shown to be correct, explains several phenomena exhibited by electro-magnets, to which we shall have occasion to refer in another place. The problem now under consideration is that of determining the best construction of the armature. If we only take into consideration the ques- tion of force without concerning ourselves with practical require- ments, which are sometimes directly opposed to the conditions of maximum-— as in cases where the utmost rapidity of motion is required, for example, when the mass of the armature should be as small as possible— it is obvious that the flat prismatic form is the best ; for, inasmuch as the centre of the magnetic action in the armature coincides with its axial line, it is clear that the greater the thickness in the normal direction of the action of the magnet, the greater will be the distance between the latter and the mid- dle point of the armature, and, therefore, the less the force. Con- sequently, the cylindrical form and the prismatic form of equal dimensions should be rejected. The best results will be attained by means of the thinnest possible armature placed broadside in front of the poles of the electro-magnet, for the reason that in that case the distance from the magnetic centre of the armature to either pole of the electro -magnet will be at its minimum. In fact, experiment shows that with an armature one inch in breadth and one eighth of an inch in thickness, the difference in the respective forces resulting from the position of the armature, whether flat or edgewise, is the ratio of ninety-two to fifty-nine. * 1 The form and mass of the armatures should depend upon several consider- ations, but principally upon the functions which they are required to fulfil. In respect to force alone, these armatures ought always to be a little broader than the poles which act upon them ; the length ought to exceed by four or five lines the polar extremities of the magnet, and their thickness ought to vary accordmg to the force of the magnet. It is even asserted that for a given magnetic force this thickness is susceptible of a maxima -?, beyond which there is a loss of power when the thickness is still further augmented. It is easy to understand that this condition of force cannot always be realized, for if we require a very rapid move- aiODt of the armature, we ought to make the latter m light as "cssibls. MOVEMENT OF THE ABMATURE. )' 597 On the other hand, it is easy to understand, that in order to allox^ the greatest possible amount of play with the least loss of power, It is preferable to pivot the armature in such a way that one of it^ extremities is in contact with one of the magnetic cores, and the other end alone movable. In this manner the armature moves angularly, and the force which is developed, compared with that which IS obtained from the same armature moving parallel to the axi^ of the cores, is nearly double, being in fact, in the ratio of one hundred and twenty-five to sixty-four. The reason of this is obvious, when we consider that the distance through which the attractive force is exerted is by this arrangement diminished nearly one bat From the comparison which we have already made, with the yoke uniting the cores of the double electro-magnet with itsar- mature we can readily see that when these four parts are equal to each other they constitute a double system, in which each one of the magnetic cores composing a special electro-magnet has a dis- tinct armature, which armature being of the same length and siirf ace as the magnetic core which acts upon it, may give rise to a magnetic reaction under conditions analogous to those of the action produced by the magnetic core itself. ,But this is no lonagr the case when the armatures as well as the yokes are of greater^r less dimensions. In this case it may happen, either that these armatures cannot furnish the sum of magnetism necessary to enable them to respond to the action, or, on the other hand, that the cores themselves do not possess sufficient magnetic mass to re- spond fully to the reaction which would otherwise be produced. In this case the forces depend upon the shortest parts constituting the magnetic system, but as the proportion of the total force which they are individually able to furnish is proportional to the square root of their length, and as one of these parts cannot vary m length unless the other also does, the result is, that when the different parts of a double electro-magnet are not equal, the force is proportional to the length of the shortest part This fact was long since discovered and made known by Dub. As corollaries to this law, the latter gives the following deductions, which mav wdiljr couipi-chciidod without further explanation : 598 DUPLEX TELEGRAPHS AND ELECTEO-MAGNETS. 1. The attractive force of an electro-magnet is proportional to its length, when the lengths of all the different parts of which it is composed increase in the same ratio. 2. The maxima of attractive force are proportional to the various lengths of the systems, of which the component parts are respectively of equal length. 8. The attractive force remains constant when the shortest parts are equal to each other, whether these are represented by the electro-magnet or the armature. According to the British Association committee, electro-mag- netic forces should be measured by the method of repulsion, and the unit of electro-magnetic force is represented by the repulsion exerted between two like magnetic poles placed at a distance of one m^tre apart, and acting on each other with a force repre- sented by -y.-^ (gramme-m^tre). Nevertheless, as the greater part of the experiments which have been made up to the present time with electro-magnets have been made by means of a balance and weights, the existing ratio between the two systems of measures still remains to be ascertained. The accompanying plate shows the various forms of electro- magnets generally used for electrical purposes. Figs. 1, 2, 3, 4, 5, 6 and 7 are electro-magnets, whose poles are straight, bevelled, tapering or flattened, according to the purpose needed. In fig. S the copper disks or end pieces are soldered to the core of the electro-magnet In fig. 4 the core is hollow, with two iron disks at the extreme ends to increase the polar surfaces, and to serve as end pieces for the bobbins. Fig 6 represents Bonelli's electro- magnet, in which the armature forms a part of the magnetized core, and by receiving from the helix a direct magnetization, makes the attraction between the two parts more powerful. Fig. 7 represents an electro-magnet provided at both ends with two iron pallets. This plan is used to adva,ntage as an armature of an electro-magnet, in which case the pallets correspond to the poles of the electro-magnet This arrangement has been adopted by Mr. Maroni for the Italian Morse instruments. Figs. 8, 9, 10, 11, 12, 13, 17, 18 and 20 show the various forms which have been VARIOUS FORMS OF ELECTRO-MAGNETa 699 , given to the double branched electro-magnets. Fig. 9 represents ' the best known and more generally used form. Fig. 10 shows an electromagnet in which the helix is wound around the iron core without retaining disks at the ends ; the various spirals are wound so as to form two truncated cones in opposite direction to their base. This form of electro-magnet is especially made use of in Clark's instruments, to favor the effects of induction, which is more energetic in the centre of the cores than at the extreme ends. Fig. 12 represents an electro-magnet with hollow cores and iron end piecea Fig. 11 represents an electro-magnet with one coil. By bringing near together the two branches of such an electro-magnet, and bending the free branch around, as is shown in fig. 13, we may bring the two poles of the electro- magnet very near together, and hence make them react at the same time on an armature placed endwise, and of very small size. A similar form, and devised for the same purpose, has been adopted by Mr. Hughes for the two bobbin electro-magnets of his telegraphs, the branches, however, being bent back, as in fig. 17. If a soft iron cylindrical case is placed around the bobbin and soldered to the circular end piece of a straight electro-magnet, this cylinder will share the magnetism of the end piece, and will present a like pole to its free end ; hence there would be at one of the ends of the electro-magnet a circular pole, in the centre of which the other pole would be found, as shown in fig. 15. Manufacturers of these tubular electro-magnets claim a great superiority for them in strength over the other forms. Electro- magnets of this style have been used in electro-motors, the poles being oblong instead of circular, as shown in fig. 21. If we place over an iron tube electro-magnet like that shown in fig. 4, two soft iron cylindrical cases, leaving between them, towards the middle of the electro-magnet, a small open groove,' we shall obtain a circular electro-magnet having a different pole on each of the two iron cases which surround it, and hence acting through its two poles at the same time on a longitudinal or circular armature, on which it rests. This form of magnet, as 600 DUPLEX TELEGRAPHS AND ELECTRO-MAGNETS. shown in figs. 16 and 28, has been proposed for magnetizing the wheels of locomotives on railroads, and as an electro-transmitter of motion to supply gears. By bending the yoke at right angles the two opposite poles of an electro-magnet may be made to face each other, as shown in fig. 18 ; and by cuttmg the yoke in two, and sliding the two free , parts in a groove made in a plate of soft iron, the distance of the poles from each other may be regulated at will. When it is desired that an armature should oscillate between the two poles of an electro-magnet, in which case magnetic armatures are , usually employed, there are three ways that may be followed- the poles of the electro-magnet may be bent in such a way as to stand opposite to one another at any desired distance apart or the two cores are brought sufiiciently near each other %i allow the oscillation to ^ke place between them ; or, lastly the cores themselves are indined at the proper angle to brino-' the poles near to each other. The latter method possesses a s%ht advantage over the others, in not requiring any marked lengthen- mg of the cores, which is always detrimental ; and at the same time It allows a direct attraction on the armature, which is more powerful than lateral attractions. Fig. 20 represents a magnet of this description. ° Electro-magnets, with multiple poles, as shown in fig. 19 are sometimes employed for large electro-motors. These magnets con- sist of an iron bar, carrying eight, ten and twelve, or even more iron cores, on which the magnetizing helices are placed ; the even branches are all magnetized alike, or are of the same polarity while the uneven are of the other. The result is, that any one of these poles always stands between two poles, whose magnet- ism IS opposite to that of the one considered. Electro-magnets of this construction are very powerful, and consequently of consider- able importance in the construction of electro-motors. Attempts have also been made to magnetize iron plates in different ways. Fig. 22 shows one arrangement of this kind constructed by Joule^ in which the plate is rolled into a cylindrical form, and the wire wound around it in the direction of the length of the cylinder ELECTHO-JtAGNETS WITH MULTIPLE POLEa'^ 601 ful • bat n, t>,r however, these magnets are not very power- ful , out, as thej occupy but very little mom *\.^- "V ^ be multiplied considerably. Zmak n'T' "T^"' "^^^ the projection thicker, th"^^ wfre may b°e tn' TrV"^" '°^ of magnetic p^we^^;htV ' '"■ *"7'"8 " '""-S^ "»<"»' consist! in ^^gX Ite IZro7t ™''^^^P-- I* twenty-iifth of an inch tWlT i ^ ^' """ ''^"'J^' ""^ ARRANGEMENT OF ARMATURES quent,y,thea:t::tt':;th fwVp'r;::!:"'' "'' '=°""^- both ends. It „ay be articuIaW by o"e end airfi': Tl °' in which case the movement Ml™ „r ^- ^^' •"* with .spect to the a ™S ^td tlTacZtf th^^ ^"rtfe;zi:ri;rc:ir rn^^^^ articulated between *V ^^li- - * ' ''"' ^^'*^^' ^* "^^^ be - e_n „n. p.i.. ;,, ,uc eiectro-magnet by means of 602 DUPLEX TELEGRAPHS AND ELECTBO-MAGNETa a pivot parallel to the branches of the latter, as in fig. 86. The movement then partakes of a tilting motion, and the attraction is effected in a lateral direction This arrangement of armatures, however, applies only to the direct action of electro-magnets, which may be either normal or lateral. When we desire to employ the forQC of the latter. on their armatures, through their reciprocal magnetic reacti arrangement of the armatures may be modified in three a . ant waya They may be fixed flatwise, with regard to the poles of the electro-magnet, to the end of a lever, whose opposite end is hinged near* the yoke of the electro-magnet, and whose motion is, consequently, in a direction at right angles to the line joining the polea The armature, being then placed about one twenty- fifth of an inch above the polar ends of the electro-magnet, is carried over the poles^ by the magnetic action of the latter until its centre coincides with the axial line of the magnet This is, as remarked elsewhere, one of the best means of obtaining a large excursion of the armature ; but, when the magnet is some- what powerful, there is some risk of bending the supports. Fig. 37 sufficiently indicates this arrangement The second way of arranging armatures to obtain a similar magnetic reaction is to pivot them so as to tilt, as shown in fig. 86, above the ends of the magnet, which is provided with soft iron pole pieces. Siemens employed this method, in 1848, for his dial telegraph. The third arrangement consists in pivoting them in such a way ss to allow of their turning between the poles of the electro, magnet, the edges of which have been hollowed out in order that the armature may turn freely through nearly half of a cir- cumference, as in fig 38. This is evidently the best arrange- ment, as the normal attraction of the poles, which is not con- cerned in the angular displacement of the armature, is in this case exerted at the two extreme ends of the armature, and in opposite directions. There is, consequently, no injurious results to be apprehended either to the pivoting or from any flexion of the armature or pieces that support it One advantage in employing electro-magnetic arrangements of ARRANGEMENT OP THE ARMATURE& 603 ment, which is T)rf»P,-««i^ ^ ! *^® armature's move- instances are so marked T™ meThod 'of '''™''?^g^ ,■" '^V tares, and aUowinR the ustTf T , ^"■'"'g"'g &« "ma- double branched mZ^.r ^ ^l«=tfo-niagnets in place of were flrat emp WdT ' , '^T" " ^Ss- 29 to 31. These 1855 ^nZ!7 """P'" °' electr^-motora exhibited in magnet; thf;fe:~':;^ruir'"'"^'*''r'"'™' axis of the electro m«^n J^^7 '*.^*^^<^« perpendicular to the «>30 car^ anlSrSr.^ Ci^tt ^n'T r and the^atu^^^ort r ' Y ^? '"''''^ *^^ ^^ "^'i^der, action of .SttoTrntrr ""'T'' *' "'""'"'■"-g^et; the infer sides 7t^":^i,f ZZuftZ " ^^ "*^' °^ ''^ simplicity of the arrangement^? thf ^ °" '^"°"''* °' ""^ figs. 30 and 31 in S^n 1? "■ V"™"^ P^rts, are shown in magnets. ' '^ "' "^^""^ ''^f' '« given tK> the electro- it i^w^^hXr IrL^^r't "'"'''"f™^ ''- -'-^^ *». for which purpoirifroX il '"™' *' "™"'"'-^^ ™ P°»W in the framework Som^ ^"'^ "" ""^'"^ """'"^ ^"PP""^ nsed instead*" whrch tr'th!"™'' ?""« ^P?"''^ "^ "« ^tractile springs to wuL^r^f^ *'■' "'"'' '"'^^ '^ ^«"« «« been interrupt!. "tJ^'^T"'"^ ^'^ *^ ""^nt has yince oursel™ bj ,n,pe„!7. 315. he eterio teU tl T '^ u^"^ "' Washington thmngh eieotno tell tale shown at the left end of the t^,H» fi„ ,,7 608 THE ELEGTKIC TIME SEUVICE. Owing to the great height of the ball when raised, it is visible' for many miles around ; and directly or indirectly the clocks and watches of some two millions of people are thereby kept from straying far from the true time. Even as far off as Bayonne, N. J., according to a local paper, the principal of a public school regulates his clock daily by the falling ball. The ball and its discharging apparatus were designed by Mr. George M. Phelps, superintendent of the Western Union manufactory. The pub- lic service thus rendered by the Western Union Telegraph Com- pany is wholly gratuitous, and affords not only a notable illus- tration of the public spirit of this great corporation, but also an illustration of the far reaching indirect benefits which applied Pig. 318. science is constantly conferring upon modem life, free of ex- pense to the recipients. But the time service does not end here. To reap the full benefit of the time ball, a great number of people must watch for its fall ; that takes time, and time is money. It is cheaper to employ one man with a little machinery to regulate the time of all, and the service is much more surely attended to. Ac- cordingly, Mr. J. Hamblet has introduced a system of constant time service, by which our clocks may be kept constantly under the electrical control of a central regulator or standard clock, whicb is kept in exact time with the clock of the National Observatory, at Washington, due allowance being made, of course, for the difference in geographical position. DROPPING THE WESTERN UNION TIME BALL. 609 wmmNh ii'fifilA i Fig. 317. 610 THE ELECTBIC TIME SERVICE. The central regulator is stationed in the Western Union Tele- graph Company's building, and is so constructed as to keep time with the highest attainable accuracy. In addition, it is every day compared with the clock of the National Observatory, at Washington, and checked by the daily time observations made at the observatories at Allegheny, Pa., and Cambridge, Mass., with which it is in telegraphic connection. By this it must not be inferred that the clock in question is kept in exact accord with either or all of the observatory clocks, that being a me- chanical impossibility. The range of variation, however, is kept within a few hundredths of a second. It is possible to measure and record the hundredth part of a second. Fig. 318 will make clear how it is done. It shows a section of the paper tape of the chronograph, which is used in comparing the standard clock with the clock of the Washington Observatory. The chrono- N£W-YORK aoCK |ii ii| i i i Hi ii i |iiii |i i ii|n ii ]u i i| i i ii ]ii i n ii ZO 40 60 SO 100 Fig. 318. wASKmroif ciocK graph is electrically connected with both clocks, and records the pendulum beats of each on the strip of paper. If the beats are exactly synchronous, the dots stand side by side. If the beats are not synchronous, the dots will be separated by an interval, long or short, according to the difference of the clocks— that is^ the difference in time between the beginnings of corresponding beats— and the speed of the chronograph. Supposing the clock to be beating seconds, and the chronograph to discharge an inch of tape each second, it is obvious that the dots recording the beats of each clock will stand one inch apart. It is obvious, too, that the lineal space between the recording dots of two clocks not beating exactly together can easily be measured, as shown by the scale placed below the dots in the. cut (fig. 318), and thereby the difference in time exactly determined. | The next step in the time service is to distribute the accurate m DISTKIBHTIOir OF TIME SlflNALS. || gu &»e thus maintained to ™oh as want it, wliioh is done through an eleotncal attachment to the standard cl«=k. This oontoS dock was constmcted by E, Howard & Company of S from des,gns by Mr. Hamblet, and has a oZion ^^ty e^apement The front cl(«k plate and the electrical mecCm are shown ,n fig. 819. The wheel in the centre withZsTnd hand evolves once a minute. One of its thirty teeth hX» Fig. 319. whfch II'h ..™°""' 'P""" '=""^™S *« o™^'"" of the tick mfnute th/ """' ™* *" «*y^«hth second of the wS br Jv! """?'"? *^'* ""' "P°" » •'<=■''=»"' i^'^^M spring. Th twowt?" T° "'T' ■•" *^ ^'^S' "f -=><>•' ^oth Ihe two wires connecting with this spring and its banking oner ate the relay, at the left of the %u«., and "through it the sound" 'H< 'ftAk 1 612 THE ELECTBIC TIME SERVICE. which indicates the beginning of each minute by a pause of two seconds. The beginning of each five minutes is identified by a pause of twenty seconds, obtained through the agency of the five minute wheel to the left of the seconds wheel. At eack revolution of the five minute wheel the lever at the top drops into the notch in the wheel, making electric connection between the two wires governing the relay, thus preventing the minute wheel from breaking the circuit for the space of twenty seconds. At the right, near the top of the figure, is shown a sounder, which may be located at any point on the lines. It is by means of these sounders, with which the recipients of the service are supplied, that their time pieces are regulated. The practical advantages of this constant and trustworthy time service will appear to any one who has to do with important commercial or industrial affairs. One of the great sources of friction in social and business intercourse is time variation and uncertainty. The maintenance of a common and authoritative standard will go far to lessen such friction, to the great time saying of all classes, and the prevention of many mistakes and misunderstandings. Where thousands are engaged, delays of no more than a minute at a time amount in practical effect to the loss of hours, days, even months of individual labor. In a factory employing only three hundred men, a variation of one minute in the signal for starting and stopping means the loss of one man's work for a whole day. ,;;'^!H!«TW- .,!' INDEX. I ABBOAD, the telephone, 88. „.SSf*t'?'''*.? *°^ connections of the carbon telephone, 28?. Anvil, haminer and stirrup, 6, ^jrSf**"/*'® repulsion of different ele- *«„« ®1i* **' a current for each other. 146 aSS **?.*•"'« S' '•>• Plionograph, 805 ' phSne,°8S9 P*""*"*"*' ""'g"^'* '« »«!«- Apparatus' for producing undulatory cur- Articulating telephone, 68. ■r»H'^"^'*J® ^Peech, transmission of, 199. Atmospheric vibrations, S. Atlantic cable, resistance of, 86. Autographic telegraphy, 60. Auditory nerves, 8. "^"ft ^""*^* *•• *«'«P'»o»»lc experiments. B*^^7?'j^j!^h^?-i"P^u"°S telephone, ^oa'^ 'telephonic researches, 818 : Carbon ^lc8irsM^^^''*''*^^P''**°y>'>"'238- *l''P''°"f. 8^; talking phonoCTaphT^ Bell call, 84. "*''phones"a2?'' *^P«'^«'«'"« wll»i tele ^ m?'ia2^^'^''®* '" telephony, 66, 112, ^^^^llf}jf2^ ^i' ^- contributions to the tMcl^fof *;Jf P*'*"^«' 2« ; u«e of railway ^^'^1;„^f;,F'*'"®°5* J-. experiments with a £ll°^n"'**S"P'^ n»ade out of a human B^?f'^-. ®S ?'?'"Je8.,Propo8ed telephone, 147. Bottger'rt Polytechnical Notezolatt, 147. Breguet's telephone and telephonic Investi- CAMION telephone, 85: measuring resist- n.Ki *''"* ?t' ^5 ! .invention of, 223. Cable, working telephone throigh, 87 Centennial exEibitlon of telephone, 73. UonsfVtf '874 """^ *■•• '«'«Pi»«nic inven- Characterls^s of sound, 95; of the phono- rnmfe^^i' application to telephone, 31. Combination of the Morsa and harmonic teiupuone, 187. Constructlan of the telephone, 83. 293 Correlation of forces, 42 Clarke, Louis W., researches and experl- ments In telegraphy, 76, 279. ^ current induction, urrangeuients . r neu- tralizing, 392. Currents, intermittent, pulsatory and undu- latory, 54. r ., Currents produced la the telephone, 291. D^?17f m'" rosearches In telephony, 86, ^ W?*^^' '*^*'*"'»~ ^ telephony, 66, 118, Diaphragm, vibrating, 16. Discharge of a LeySen jar through an iron wbe causes the wire to produce a sound" Dolbear's, Professor A. B., speaWne tele- P,l">ne, 19, 76 ; researches, atofmalnetor |i«ctric teephone, 263;' electroSS, S^f,VP^;!?il5fPP*"'«?-.«l»: coSvertl-' 146; E^ gratres!' ®°*P^°y"* " » Phonauto- ^'""^ ' ?"i^^'^ automatic regX tors, 412; cosljof the light, 428; Davy's experiments, llOO; Duboscq's regulator; w^r'„»,'^'"5'®'" * automatic lamp, 409 Farmer 9 dynamo-electric machine, 423; Poucault's regulator, 406; Gramme's ™«cWne, 421; Hart's lamp, 409rJab. lochkofl 8 candle, 410; Lady's dynamo- electric machine, 419 ; magneto-electri^ 'nach'nes, 413; Siemens's a?mature, 417 ; subdivision of the light, 427; tempera^ turo of tlie arc, 401. «»"i»«ri*- ■■'*tt*teSS^SiW3«' '""mrmmminmr- 614 ■" ^ '■Vj>iiI5r--s INDEX f Bleciric light, «9 • urangement of drcnit for street Hghttag, 481 ; Mitomatic switch ior.rablochkoff candle, 498; alternatfnK current machine, 488 : Archereau's car- bons, 486 ; armatare of the Gramme niachine, 448; Bmsh dynamo machine, i^' ^V '^••''s antomatlc regulator, 418, «7 ; Hansen's photometer, 460 ; cost of Jablochkoffs candle, 4B4 ; cost of electric light with Jablochkoff's can- « ulPfi.***"""' *^ i <"»» of the eiectrlc Iteht, 486, 487. 610, 516 ; Carry's carbons, 4W ; comparison of different carbons, 487; comparative merits of different magneto-electric machines, 471 ; com- parison with results obtained by Mr Douglas, 466; current and electro- motive force of dynamo-electric ma- chines, 464 ; condition of economical working, 467 ; current for illnminatlnff house iTrst used, 808; Dncommun foun- dries at Mulbouse lighted by electric iMnpg, 614 ; De Mfiritens' dynamo-elec- trio machine, 4B5 ; Douglas' report on electric lighting, 464; electrical resist- ance of dynamo-electric machines, 457 ; efficiency of dynamo-electric machines, 466; energy of current in heat units, 469 ; effects of dynamo-electric currents In foot pounds per minute, 470 ; electric light in the Place de I'Opera, 498 ; elec- tric lamps with continuous conductors, 601 ; experiments before the Stoclety of Physics, 608 ; Edison's Invention, m ; Blectro-Dynamlc Light Company, 608 ; Fanner, Hoses G., subdivision of the electric current for illuminating pur- poses, 608; Farmer's magneto-electric machine, 488, 446 ; Farmer's automatic !^J'','*^i fl«L°''"^*n8f illnminated with electric liffht, 608; Foucault's gas retort carhop, 439; Franklin Institute experiments, 489; Gramme ring, 495; Gramme machine, 440 ; Gramme's alter- nating current machine, 482-486 ; great- est distance to which the current of one machine is transmitted in Paris, 493; Gandoin's carbons, 488 ; Gramme's ma- chine and Carry's lamp, 487; incandes- cent pencil, 601; Jacquelin's carbon, 480 ; Jablochkoff's candle, 410, 487-^90 ; light obtained from a small Gramme mach^e, 604; Lontin's machine and lamp. 613: measurement of current, 459 ; measure- ment of electro-motive force, 468; Max- im's machine and lamp, 473-480, 518- measure of the total heating power, 468 • Plante 8 secondary elements employed for prodncinB light, 505 ; platinum and Irfdinm used for electric lighting, 606 ; Ppotometric measurements, 451 ; power utilized in the electric arc, 470 ; 81111- man's observation on the waste of car- bon, 401 ; Sawyer-Man lamp, 608 ; Shea, Charies E., title of invention, 607 ; Sie- mens' arrangement for controlling the current, 508; KaplelTs system of electric lijghting, 600 ; Reynier's electric lamp, 501 ; retort carbon, 436 ; revolving con- tact, 50iJ ; renewal of carbon, 502 ; street Illumination by electricltj, 481 ; table of reslstancei? of dynamo-electric machine, 460 ; thermic cflTects of dynamo-electric machines, 461 ; table of mechanical de- tidlB relating to el«otric lighting, 441 r Thomson and Houston's inichlMS and lamp, 498 ; variationa In the amount of light produced, 465; WaUace-Farmer machine, 463 ; Wrmw'a electric light, 616; Kdlson'a indefinite eubdivlalonofl 806 ; JBdison'a applicmtion for patent for. ""Ti *~!»2n "method of overcomlngdim- wAt^3^ **' ftadon of platinum wli» for, 607. Edison's recent telephonic und acoustic in- ventjpns, 686; aerophone, 668; action of microphone not analogous to mlcro- Xio?S: ^ vSi*"^J?'"' P*P«' tronsmitting^ telephone, 627 ; button made of gas re- j£2'„h"*'*'"' '?i5 ^^^ transmitting telephone r«Kiniring no a4}natment, 687 : carbon telephone with sQft iron arma- ture, 689, 680 ; carbon button, 681 ; char- coal microphone, 585; cork and plum- bago microphone, 686; condenser tele- phone, 646; Carbon rheoatot, 660; car- bon telephone, 888, 667; luiability of the carbon button, 638; elasticity of lamp-blMk buttons, 633; experiment vrith a Rutherford difli-aotlon grating, 682; electro-static telephone. 8^ ; elec- tro • harmonic telegraph, 1«7; electro- motograph, 871: experiment* with Edi- son 8 carbon telephone by Prof. Barker and Henry Bentley, 579 ; Gray's combi- nation, 576; grapliite buttons, 681 ; har- monic engne. 666 ; Hughes' experiments on Edison's discovery of the variable re- sistance of conducting substances under pressure, 581, 686; rnertla telephone, K J '"™P;]?lack used in making carbon °ii?«'j°2Pj mercury telephone, 627- modified Meiss telephone. 5SH; manufao ture of carbon buttons, 681 ; microphone, 684; metallized charcoal transmitter, 640; mechanical telephone, 648 ; moto- graph, 649; musical transmitter, 640: micro-tasimeter, 667; megaphone, 561 • phonometer, 565; phonograph, 292; Phelps' combination, 576 ; qnadruplex telegraph, 810; pulverized black lead telephone, 627 ; number of points of con- .A**" a carbon button, 638 ; nail trans- mitter, 6^ ; carbon silk coated micro- phone, 585; short circuiting telephone, 544; stethOBCOpic microphone, 663: thermo-electric telephone, 238; tele- SPii ".*■ «»:hanM system. 576; voltaic lie telephone, 648 ; undulatory cuirent, »9; value of dilTerent substances to be used as buttons, 688. Edison's early life, 582 ; enormous capacity for work, 686 ; originality and genius' Electro-magnetism and duplex telegraphy. 688; arrangement of annatures, 5oi | Boscha's duplex, 6S9; form and mass of the armature, 596; laws of the electro- magnet, 594 ; maximum of magnetiza- tion, 593; movement of the armature, r2I ' gfopo'^on of forces to diameter. 595 ; Schreder's duplex, 5£0 ; single coil e ectro-iiiaienet, 593; various forms of electro-magnets, 589. Electric time service. 606 ; comparison of clock of the National Observatory, at Washmgton, with daily time observa- tions made at observatories in Alleehenv and Cambridge, 610. ' INIMSX. 615 XpouRMa's law of vibrational formB, 240. GALVANIC mnsic, 110. ^^ Qasslot's resairches in telephony, 66, -Oalileo's observations, S26 Oay-Lussac's discoveries, 188, •<3ore'g researches, 66. ^wer's, P. A., experiments, 80. «ottoinde Comma's observations, 122 ■wray, Blisha, telephonic researches, 161 171 • electro-harmonic telephone, IBr : earlv experiments in telephony, 185 ; bitth-tub experiments, 187; violin experiment, 1«) ; phenomena attending the trjns- mlssion of vibratory currents, 171 ; dls- covsry of the speaijing telephone, 15; transmission of composite tones, 189 • telephonic specifications filed in the ?A^^a «J2'®* *'"'^"' 0*ce, February 1*, iOTO, id 1 7. ' 'x'*P'*'*'*' method of physicists, 245. •Graham, Professor, theory of vibration of Trevelyan's bars, 115. •Grove's experiment demonstrating the ten- dency of the particles of magnetic bodies to group themselves under the Influence of magnetism in a longitudinal or axial direction, 188. ■QnU'erain's researches in telephony, 55, 118, HENKT, Professor Joseph, telephonic re- searches, 14. Belmholtz on the human voice, 48 ; ana- lysis of tlie vowel sounds, 51, 8S ; of vocal sounds, 355 ; method of analyzing tones tninsraltted through a wire, 161 -Humorous example of telephonic expectancy related by W. H. Preece, 82. *""'""'*'J' INDDOTiON currents, 87, 104. Influence of molecular actions upon ""gnet'sm, produced by dynamic electri- cyi 184. Induced currents, reactive effect of, 179. invention of the spealiing telephone, 201 Improvements by Channirig, Bluke, Peirce, Jones and Austin, 275. JANNiAR's telephonic researches, 65. Joule's researches in telephony, 55 , influence of magnetism over dimensions of bodies, 123. -Jone*. Edison S., invention of telephone handle, 876. K'"«u°'^'*'^?''*'*^ dictionary, cuts from, o», 296, 297. KOnlg's researches, 68 ; phonograph, 895 • monometriu flames, 2U9. f . ■'""i LA CouB's telephone, 02. Laborde's telephonic researches, 55 iegat s telephonic Investigations aud pub- iications, 65. ^ ^&2^'"«P'i invented by W. H. Barlow, P. R. »., 295. -^Sogra^lc records, 897 ; wich the human MAOoi's heat experiments, 188. Marianini's experiments, 185. Magttetic cores for telephones, 177. Magnetic speakinff telephone, 281. MauoOMtric capsule, 68. Maurey'ii experiments, 68. Matteuccl"8 expeHments, M. 118. Marrian's wsearches, 66, 112, 117. Magneto-electric machine, 88. Membrane, elutlc, 6. Morse telegraph contrasted with the tele- Molecular 'forces disturbed by magnettam. M. iJ. i' "c"on of magnetic bodies, 117, 181. Multiple telegraphy, 67. Mayer s, ProTessor A. M., magnified tracings on smoked glass of the talking phono- graph record on the foil, 808 ; what the lorm of the trace depends upon, 804. •JlTiOLB's tubular electro-mignet, 101. OHM, or nnit of resistance, 103. On the disturbance of molecular forces bv magnetism. 111. «™riun,oB tricity^arl.'""''""^ **' *"'""* *"'" *'^««^- P'%y, Kt h '''«^"'='>- »° *«!*- *''''5lmCXs^5'"' ''^P«'"»-'« «"d in- Picullaritles of vibratory currents 173 • of compound vibrations; 317. ' ' Phelps's telephone, 81. Phonogranh, the talking, 898; mounting of the, 301 ; what clearness of articulation depends upon, 303. »"jouiauon Phonautograph, Barlow's, 895 ; KOnl" 295 • p. Scott's, 296; experiments with, "a ' ' Phonographic records, tracings from; 803- driinas ; letters, 805. ' ' Pill bos telephone, 90. Plate, inflexible, 87. Poggendorff's researches in telenhonv S3 Providence experimentalists 76, 274^' phU7:^' observations on1he tele- Production of vocal sounds, 181 Properties of the pendulum, 237 Producing the record of sound, 294. ,3&riri^a]aireihod^» combined differential aud bridge ilieth-' pds, 321 ; arrangement of apparatus for long circuits, ^; double acting relay' 329 ; single current twiusoiltter, 338 339 • wi"H""'"'i'" ','»'' quadruplex, 341 ;'com- b ued quadruplex and duplex circuiis 845 ; arrangement for contraplex transl mission, 811' ; combined dlplex and mu- traplex sydtoms, 849 ; combined diplex bin^JII'T*"^ iy«'?™«' 3«. 851 ; com ?«m, ?-a °' quadruplex and duplex sys- tems, 3j3 ; quadruplex repeater, 835, 857 ; tu^'Z^n '•*-''*>\83«; direction's for setl tiug up ihe luadruplex, 836 ; the double current transmitter, m ; tl.'e compound Pt»'"'^«d relay, 338 ; the'single polSrlzed relay, 810 ; adjustment of the apparatus for working, 841 ; combination Sfquad- Q ■"•»msi^«piMsff!{s 616 f^U; INDEX. Sfc """l. ''lP»« systems, 858; ar- rangement for branch offices, 859 ; quad- i^it f„'3'°ff"®'" '"f neutralizing cur- M^n-i'^n""""'-.'®* : induction between RfS-!^ ""!?,• ^^.5 ''o"'''« transmission in the same direction, 864 ; early methods d Sn"°,^"'iL*"*?'f4«« In thfstal «irecuon, 364 ; Bernstein's method, 865. E"f ^al^dtfce^".'^^^^^^^^^^^^ '^' ReTss!66!Vl''''^™^*'^ ^^ ^^'""^ 218; Relss's telephone, J851. Bheotome, 78. ilahmkorff's coll, 78. S^«?iH.i^?'"'® reported by telephone, 76. Iilini„^^°"' phonograph. 68, 295. li^nH^nS "PPJ^tus for telephones, 39, 289 Hound, characteristics of 7 ns an? • ntfA vertibillty Into elec?Hc iVy, gVaphil; reS" 5!«f,nf t'pnoo'. 8 ; velocity oWtvE-" vffliSto'w?' *^: Bound 'wav^s con- verted into heat waves, 284 ; vibrations flonnd'sof the human voice, 97; Helmholtz analysis of vocal, 255; produced^n Iron AnllK^^^^'iS^ P' electricity, 122; pro" dnced by molecular changes, 253 * «onoTOU8 UQduIations, 99. ''^in ?he nniJl*Sl^P'*"S.*<' inventions flled rnarv iyf«^«* States Patent Office, Peb- ruary 14, 1876 ; Orav's. 202- R«il'n otk l?mn,'?h« Jf '"Phone, im^nll* VaOl. ' ^^• Sympathetic vibrations, 67. niALKiNo phonograph, 202. Telephone, articulating, 15; audibility of W, American spealilngiompanr 46 • ao- plication of permanent magneti to^2^# accessories and connectloSs of th'« P,.r' to.^U^|]'«' 17.50 305° battery 32 •" ^ B«;hUv'^^""V«' 287 ; Boursefc|?s; X47, Bentley's experiments, 285 • correlal reIear?h«s^?^9.V^', ®f*y'« teleplionio researches, 152 ; Gray's electro-harmonic 167 ; Gray's caveat, 217 • handle s^fi. innumerable uses of, 45ViIlu8?r^at%f of Si hvVh •'"'?•'' ^^*'»«' ^ ; Improve. llmi?or^?JihnW^o/'"'«*- handle, 276; on^h?„.",?'^'"J 'y- 38 ; musical, 9 ; korse x>„.- , • 1'' Phelp'8 dnplex. 21 • Peirce's mouthpiece for. 275 ; piF box. 90 Reiss's, 9, 148, 251 • reneatpr «o • r- 28l"""sir' 2"' r^^ricab WenomJnt ■iai , siphon recorder, 279 • siMialllnff sXh'2S'.29-«»i aensithTeness^fS; Thimo^^' speaking, Invention of 201 bvX^l" '■«P'"-t.98; tones produced by electric currents 111, 189 ; theory of, Srri„^"'«""'^vhe». 41 ; vibrating dial PnJ^S™' ^1= vibratory plate, 48; wor£ T«„'°?''"".°"8h cable, 81. ' TraM'S' ^i""?^* *"•* composite, 8. Jr^h''' air vibratlon8V91 ; from phono- graph records, 803. vuuuu- rSSfiSufi'"" °' composite tones, 189. ^™nsinittlnK reeds, 191. sound, ^.'"'"*°'*' ^'^^' '«<='"«« ««» TTsM of the phonograph, 3a5. uVlve«uJrtenrw.'"'' ''' *^' '^• ■yABLBT. Cromwell P., researches, 62. 101 .1°}** u*""?* "' transmitting reeds, ml«ers?'l?7'"°'*' "'''''''• ^^^i trans! Velocity of sound, 243. Vibrating plate, 48 : rods, 289. Vibratory circuit breaker, 59 ; movements tl-flT'S?"'l' effects determined in mag- netic bodies by the Influence of electrfc ?S,"®"'^'h"'^ ' ';"."??t8. peculiarities of, -„. I'S ' "notions of fluids, 241. ' Vibrations, propagation of compound, 247 • ?' T''?r|'y'"i's hars by the galvanic cur^ rent, 118; of sound, optically exhibited, Vibrational forms, Fourier's law of, 849 Visible speech, 68, "IITaoener's hammer, 140. nn..f^H*°".K' Thomas A., assistance in perfecting the speaking telephone, 71, 77 Wartmann's researches inteleohonv 55 lis Wertheim's researches in teleKy,' t;"on the elasticity of metals, 123 ; analysis of the mechanical effecto manifested in magnetism, lai, 128, 139. Western Electric Manufacturing Company telephonicapparatus, 81, 32,33. ' Working telephones over artificial lines, 103. WheatHone's instruments, 104. Wilson's, Charles H.. method for overcom- ing current laduction, 862. -wp^psewK* J l-=.»:£^RcSiMJ ELECTRO-MAGNETS. /■ .* MM W r K c //>■ Iff 3s y/ ¥~ 3^ '.0 ^ 18 e 3lf 4" A MM r" r ^:^S- m mm wmm^m^^^'^ 0-MA6NETS. fi S=T^^ it U t ct: J Hoi 4" A il .7.7 4/ ^o^iio; I'.l ^J' ajjniu ^# o ( 1 \_|fflilj_^' o a* J 1 mmmm ^.y-