680 THE POPULAR SCIENCE MONTHLY. 



supposed to have done so, and he sends three beats upon the bell, 

 which lowers my semaphore arm and tells me " Line clear," and that 

 the apparatus is in working order. On such a system the traffic of a 

 railway can be conducted day by day, and hour by hour, with safety 

 to the public, and with satisfaction and certainty to the railway in- 

 terest. One other illustration that I must give you, of the application 

 of electricity, especially as my store of energy is not yet exhausted, is 

 the telej)hone. One of the most beautiful things at the Paris Exhibi- 

 tion was the transmission of music, by means of the telephone, from 

 the Opera-House to the Exhibition Building. At the Opera-House 

 several microphones were fixed upon the stage, and at the Exhibition 

 Building telephones were fixed in rooms into which visitors could go, 

 and, by applying the telephones to their ears, could listen to the over- 

 ture of the orchestra, or the singing or talking of the performers, as 

 also the hum of the ballet-girls behind the stage. The effect was 

 something startling. I remember one night seeing a Frenchman put 

 the telephones to his ears, and the moment he heard the sounds he 

 threw down the instruments, and rushed out of the room, saying, 

 " Cest terrible, c'est terrible ! " The Christinas holidays have prevented 

 my having similar arrangements for this lecture, and the best thing I 

 could get ready is a telephone circuit between this hall and a neigh- 

 boring room. I will call up and ask my assistant to play something 

 on a cornet. [The cornet was heard playing quite distinctly.] That 

 is an instance of what I wished to illustrate to you at the commence- 

 ment ; we have a bugler, full of energy, who blows into his bugle, 

 the energy of which takes the form of sound ; the sound-waves, or 

 vibrations, strike the top of the telephone-case, and set a microphone 

 in vibration, which causes currents of electricity to pass along the wire 

 from the instrument at the other end to the one before you. In the 

 receiving instrument the currents sent by the microphone take the 

 form of electro-magnetism, and reproduce the vibration of the micro- 

 phone upon a disk in front of the electro-magnet, and so we get re- 

 produced in the same form the energy set in motion at the other end, 

 after having passed through various stages. The motion of the cornet 

 is transferred, first, into the motion of the disk, then into the electrical 

 form of energy, then into that of electro-magnetism, then back again 

 into motion, and, finally, to your ears ; and you will easily understand 

 from this that electric currents are merely one form of energy. I in- 

 tend to pursue this subject next time, and show you how electricity is 

 produced in other ways, and how it breaks up chemical compounds 

 into their separate parts ; how electro-plating and silvering are done ; 

 and, finally, I will show how it produces the beautiful Edison electric 

 light we now have in this room. The elegant chandelier now illu- 

 minating this room was made especially for exhibition at this lecture, 

 and was prepared by Messrs. B. Verity and Sons, of King Street, 

 Covent Garden. 



