for the year 1877. xxvii 



his key and stops the current. The sound can thus be 

 broken up into long or short notes, crotchets and quavers as 

 it were, to represent the dots and dashes of the Morse code, 

 which can be as easily read by the telegraphist as the short 

 and long taps of the Morse sounders. Now, if with another 

 operator, key, and reed on the same wire, we send B natu- 

 ral, it will set the reed of the same pitcli humming at the 

 receiving end, and not interfere with the G natural reed, 

 which will continue humming its own note. A second 

 operator reads the B natural message, and a third and 

 fourth any third or fourth reed that may sound. In this 

 way several messages can be sent simultaneously by as many 

 operators, and read by as many readers, while the principles 

 of the duplex system provide for sending an equal number 

 of messages at the same time and on the same wire in oppo- 

 site directions. 



Professor Bell's telephone, so far as I can gather, must 

 partially embrace the third characteristic of sound, that is, 

 the timbre, so that the human voice can be intelligibly 

 transmitted through a telegi-aphic wire for short distances ; 

 and although it appears that the received sound of the voice 

 is weak and not always distinct, the simple fact that the 

 quality of the sound can be transmitted with its pitch and 

 intensity is a most remarkable one, and we shall look 

 forward with gTcat interest to the future development of 

 both this and Mr. Gray's method of telephonic communica- 

 tion. The details of the apparatus of Professor Bell are not 

 generally known yet, but the principle involved is much the 

 same as in the others, although the method differs. The 

 sound of the human voice is projected into a kind of funnel- 

 shaped chamber, closed by a membrane which is set in 

 vibration in consonance with the vocal sounds. Attached 

 to the membrane is a small permanent magnet, which 

 vibrates with it opposite the poles of an electro-magnet, 



