Page:The American Cyclopædia (1879) Volume XV.djvu/651

 TELEPHONE 622^ id cadence, even the character of the speaker's tones being so faithfully reproduced that voices easily distinguished ; but the tones are in a measure ventrilo- quial, and seem to come from a great distance. No pre- vious training is re- quired to enable any one to use the tele- phone. The instru- ment has merely to be held to the ear to enable the oper- ator to hear distinct- ly any message sent from the other end. The same instrument is then placed to the mouth and the an- swer returned. To facilitate the trans- mission and recep- tion of messages, two instruments are gen- erally used by each operator, one of Fl0t 2. which may be held to the ear and the other used for speaking. If several telephones are connected with one wire, the sounds sent over the circuit are reproduced by each, so that any number of persons may listen to the same message ; many sounds may also be transmitted at the same time, like the singing of the differ- ent parts of a song, in which case each per- former sings into a separate instrument. The tones of a musical instrument, or of a collection of instruments, may be conveyed and repro- duced in the same manner. A telephonic con- cert was given in Steinway hall, New York, April 2, 1877, in which all the music, instru- mental and vocal, was executed by performers in Philadelphia, and transmitted over the ordi- nary telegraph wires. The principle of the telephone has long been known ; all that is new about it is its adaptation to practical uses. Electric telephones, devised not long after the introduction of the tele- graph, were capable of conveying to a dis- tance musical tones ; but the other charac- teristics of sound, intensity and quality or timbre, were entirely wanting. In 1837 Prof. Charles G. Page, of Washington, discovered .that the rapid magnetization and demagnetization of iron bars pro- duced a molecular change of sufficient in- tensity to cause a sensible sound. Be la Rive, of Geneva, increased these musical effects in 1843, by operating on long stretched wires. In 1854 Charles Bourseulle, under-inspector of the telegraphic lines at Auch, France, suggested the practicability of transmitting speech by electricity in almost precisely the way in which it has been accom- plished by the telephone of to-day; but, al- though his plan was published in the Count du Monoel'a Expose des applications de Velec- tricite, it does not appear to have been tested practically. The first to utilize Page's discov- ery was Philip Reis, of Friedrichsdorf, Ger- many, who in 1861 constructed a telephone in which a vibrating diaphragm was caused to make and break a galvanic circuit. Reis's appa- ratus reproduced the tone or pitch of sounds, so that the successive notes of a melody could be distinctly recognized ; but they were all of the same intensity, because the currents which formed them were all of the same strength. It was therefore only a philosophical toy, and of no practical value. In 1873 Elisha Gray, of Chicago, produced what he called his ''re- sonator." By attaching organ pipes to this, the sounds were magnified, and he was able to fill a large hall with music played 100 to 200 miles away. Gray also proved the practicabil- ity of transmitting composite sounds, such as chords, to a distance. By his apparatus the in- tensity as well as the pitch of sounds was re- produced ; but it was reserved for Alexander Graham Bell, of Boston, to discover a method by which all the characteristics of sound, pitch, intensity, and quality, could be transmitted. This rendered possible the reproduction at a, distance of human speech with all its modula-' tions. The telephone exhibited by him in Philadelphia in 1876 was worked with an electro-magnet, but he subsequently adopted a permanent magnet. An external and a sec- tional view of the Bell telephone are given in figs. 2 and 3. The instrument is about 6 in. long, 2 in. in diameter in its widest part, and 1 in. in diameter in the tube. The tube F, fig. 3, which is made of hard rubber, contains the magnet A, whose distance from the diaphragm, E E, is about -^ of an inch. The magnet used in the latest form of the instrument is a square compound magnet, 4| in. long and in. in di- ameter, formed of three pieces riveted togeth- er. On the end next to the diaphragm is fitted a wooden spool, about in. long, wound with fine silk-covered copper wire to 60 ohms. A FIG. 3. section of this is shown at B. The ends of the wire are continued through C C to the binding screws D D, where they connect with the line wires. The diaphragm is a circular piece of ordinary photographer's plate, used for ferro- types, and is varnished on both sides, to prevent