heroes of the telegraph-第32节
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eed had been set in vibration by the magneto…electric currents induced in the line by the mere motion of the distant reed in the neighbourhood of its magnet。 This discovery led him to discard the battery current altogether and rely upon the magneto…induction currents of the reeds themselves。 Moreover； it occurred to him that； since the circuit was never broken； all the complex vibrations of speech might be converted into sympathetic currents； which in turn would reproduce the speech at a distance。
Reis had seen that an undulatory current was needed to transmit sounds in perfection； especially vocal sounds； but his mode of producing the undulations was defective from a mechanical and electrical point of view。 By forming 'waves' of magnetic disturbance near a coil of wire； Professor Bell could generate corresponding waves of electricity in the line so delicate and continuous that all the modulations of sound could be reproduced at a distance。
As Professor of Vocal Physiology in the University of Boston； he was engaged in training teachers in the art of instructing deaf mutes how to speak； and experimented with the Leon Scott phonautograph in recording the vibrations of speech。 This apparatus consists essentially of a thin membrane vibrated by the voice and carrying a light stylus； which traces an undulatory line on a plate of smoked glass。 The line is a graphic representation of the vibrations of the membrane and the waves of sound in the air。
On the suggestion of Dr。 Clarence J。 Blake； an eminent Boston aurist； Professor Bell abandoned the phonautograph for the human ear； which it resembled； and； having removed the stapes bone； moistened the drum with glycerine and water； attached a stylus of hay to the nicus or anvil； and obtained a beautiful series of curves in imitation of the vocal sounds。 The disproportion between the slight mass of the drum and the bones it actuated； is said to have suggested to him the employment of goldbeater's skin as membrane in his speaking telephone。 Be this as it may； he devised a receiver； consisting of a stretched diaphragm or drum of this material having an armature of magnetised iron attached to its middle； and free to vibrate in front of the pole of an electro…magnet in circuit with the line。
This apparatus was completed on June 2； 1875； and the same day he succeeded in transmitting SOUNDS and audible signals by magneto…electric currents and without the aid of a battery。 On July 1； 1875； he instructed his assistant to make a second membrane…receiver which could be used with the first； and a few days later they were tried together； one at each end of the line； which ran from a room in the inventor's house at Boston to the cellar underneath。 Bell； in the room； held one instrument in his hands； while Watson in the cellar listened at the other。 The inventor spoke into his instrument； 'Do you understand what I say？' and we can imagine his delight when Mr。 Watson rushed into the room； under the influence of his excitement； and answered；'Yes。'
A finished instrument was then made； having a transmitter formed of a double electro…magnet； in front of which a membrane； stretched on a ring； carried an oblong piece of soft iron cemented to its middle。 A mouthpiece before the diaphragm directed the sounds upon it； and as it vibrated with them； the soft iron 'armature' induced corresponding currents in the cells of the electro…magnet。 These currents after traversing the line were passed through the receiver； which consisted of a tubular electro…magnet； having one end partially closed by a thin circular disc of soft iron fixed at one point to the end of the tube。 This receiver bore a resemblance to a cylindrical metal box with thick sides； having a thin iron lid fastened to its mouth by a single screw。 When the undulatory current passed through the coil of this magnet； the disc； or armature…lid； was put into vibration and the sounds evolved from it。
The apparatus was exhibited at the Centennial Exhibition； Philadelphia； in 1876； and at the meeting of the British Association in Glasgow； during the autumn of that year； Sir William Thomson revealed its existence to the European public。 In describing his visit to the Exhibition； he went on to say： 'In the Canadian department I heard； 〃To be or not to be 。 。 。 there's the rub；〃 through an electric wire； but； scorning monosyllables； the electric articulation rose to higher flights； and gave me passages taken at random from the New York newspapers： 〃s。s。 Cox has arrived〃 （I failed to make out the s。s。 Cox）； 〃The City of New York；〃 〃Senator Morton；〃 〃The Senate has resolved to print a thousand extra copies；〃 〃The Americans in London have resolved to celebrate the coming Fourth of July！〃 All this my own ears heard spoken to me with unmistakable distinctness by the then circular disc armature of just such another little electro…magnet as this I hold in my hand。'
To hear the immortal words of Shakespeare uttered by the small inanimate voice which had been given to the world must indeed have been a rare delight to the ardent soul of the great electrician。
The surprise created among the public at large by this unexpected communication will be readily remembered。 Except one or two inventors； nobody had ever dreamed of a telegraph that could actually speak； any more than they had ever fancied one that could see or feel； and imagination grew busy in picturing the outcome of it。 Since it was practically equivalent to a limitless extension of the vocal powers； the ingenious journalist soon conjured up an infinity of uses for the telephone； and hailed the approaching time when ocean…parted friends would be able to whisper to one another under the roaring billows of the Atlantic。 Curiosity； however； was not fully satisfied until Professor Bell； the inventor of the instrument； himself showed it to British audiences； and received the enthusiastic applause of his admiring countrymen。
The primitive telephone has been greatly improved； the double electro… magnet being replaced by a single bar magnet having a small coil or bobbin of fine wire surrounding one pole； in front of which a thin disc of ferrotype is fixed in a circular mouthpiece； and serves as a combined membrane and armature。 On speaking into the mouthpiece； the iron diaphragm vibrates with the voice in the magnetic field of the pole； and thereby excites the undulatory currents in the coil； which； after travelling through the wire to the distant place； are received in an identical apparatus。 ＇This form was patented January 30； 1877。＇ In traversing the coil of the latter they reinforce or weaken the magnetism of the pole； and thus make the disc armature vibrate so as to give out a mimesis of the original voice。 The sounds are small and elfin； a minim of speech； and only to be heard when the ear is close to the mouthpiece； but they are remarkably distinct； and； in spite of a disguising twang； due to the fundamental note of the disc itself； it is easy to recognise the speaker。
This later form was publicly exhibited on May 4； 1877 at a lecture given by Professor Bell in the Boston Music Hall。 'Going to the small telephone box with its slender wire attachments；' says a report； 'Mr。 Bell coolly asked； as though addressing some one in an adjoining room； 〃Mr。 Watson； are you ready！〃 Mr。 Watson； five miles away in Somerville； promptly answered in the affirmative； and soon was heard a voice singing 〃America。〃。。。。Going to another instrument； connected by wire with Providence； forty…three miles distant； Mr。 Bell listened a moment； and said； 〃Signor Brignolli； who is assisting at a concert in Providence Music Hall； will now sing for us。〃 In a moment the cadence of the tenor's voice rose and fell； the sound being faint； sometimes lost； and then again audible。 Later； a cornet solo played in Somerville was very distinctly heard。 Still later； a three…part song floated over the wire from the Somerville terminus； and Mr。 Bell amused his audience exceedingly by exclaiming； 〃I will switch off the song from one part of the room to another； so that all can hear。〃 At a subsequent lecture in Salem； Massachusetts； communication was established with Boston； eighteen miles distant； and Mr。 Watson at the latter place sang 〃Auld Lang Syne；〃 the National Anthem； and 〃Hail Columbia；〃 while the audience at Salem joined in the chorus。'
Bell had overcome the difficulty which baffled Reis； and succeeded in making the undulations of the current fit the vibrations of the voice as a glove will fit the hand。 But the articulation； though distinct； was feeble； and it remained for Edison； by inventing the carbon transmitter； and Hughes； by discovering the microphone； to render the telephone the useful and widespread apparatus which we see it now。
Bell patented his speaking telephone in the United States at the beginning of 1876； and by a strange coincidence； Mr。 Elisha Gray applied on the same day for another patent of a similar kind。 Gray's transmitter is supposed to have been suggested by the very old device known as the 'lovers' telephone；' in which two diaphragms are joined by a taut string； and in speaking against one the voice is conveyed through the string； solely by mechanical vibration； to the other
