4 o 



and after hearing it for three minutes your party had to leave 

 and make way for another detachment. One gentleman of my 

 acquaintance heard the voice of a soprano singer with such 

 deafening loudness that he had to remove the telephone from 

 his ear. In taking my three minute turn I did not hear any- 

 thing so loud as this, but I heard each singer well, some of 

 them louder than others ; and what struck me most was that 

 some of them seemed to be singing into my right ear and some 

 into my left. The cause of this I afterwards learned, and it 

 was just what I at first surmised. The telephone at my right 

 was connected with a transmitter in the right hand part of the 

 stage, and the telephone at my left ear with one in the left hand 

 part. There are altogether ten transmitters in the opera house, 

 five of them on the right and five on the left side of the promp- 

 ter's box, just in front of the footlights, and each of tnese trans- 

 mitters supplies eight or ten telephones in the Exhibition 

 building. The telephonic system employed is that of M. Ader. 

 The transmitter is on the ordinary microphonic plan first em- 

 ployed by Crossley, and contains several little bars of carbon, 

 Avhich, by their vibrations under the action of the singer's voice, 

 cause variations of resistance in the primary circuit of a small 

 induction coil, and thus produce currents in the secondary coil 

 Avhich is joined on to the line wires leading to the distant 

 station. The receiving telephone which you hold to your ear 

 is very compact, and is shaped something like a stirrup, con- 

 sisting mainly of a steel horse-shoe magnet whose pole-pieces, 

 round which the current circulates, are close to a thin iron 

 diaphragm. There is one special feature, and that is that on 

 the opposite side of the diaphragm there is a ring of soft iron 

 passing opposite the two pole-pieces, its function being to in- 

 tensify the magnetic force upon the diaphragm. 



The electric lights were of two classes, which are called 

 respectively, " arc lights" and " incandescent lights." The former 

 are the most powerful ; the latter are the steadiest. The in- 

 candescent lamps are all very much on one plan. They contain 

 a filament of carbon some few inches long, of about the thick- 

 ness of a piece of thread, which is suspended by its two ends in 



