XX vi Presidents Address 



the human ear, but, there is reason to believe, not to the 

 auditory systenis of some animals and insects. Also that 

 there are certain characteristics in sound — for instance, 

 pitch or tone is governed by the number of vibrations per 

 second, and simply relates to the highness or lowness of 

 the sound; then we have intensity, by virtue of which 

 sounds are loud or soft ; and again, there is the timbre, or, 

 as it is sometimes termed, quality, of sound, instances of 

 which may be given by the difference in tone between the 

 vibrating string of the piano and the vibrating reed of the 

 clarionet or oboe. Musical sounds produced by an instru- 

 ment such as a flute or violin consist of variations in pitch 

 and intensity, while the organ can be made to produce 

 variations in quality also by the help of the various stops ; 

 and the human voice eminently encompasses all these cha- 

 racteristics. Now the telephonic apparatus of Keiss, Gray, 

 and La Cour, so far as they have yet gone, simply transmit 

 sounds which vary only in pitch, although Mr. Gray appears 

 to have succeeded in transmitting notes of varying intensity 

 ' — that is, loud or soft, at will — for he has been able to con- 

 vey a musical tune along a telegraph line so as to be iden- 

 tified at the distant end. The practical triumph of Gray's 

 telephone appears in the fact that he has been able to send 

 four simultaneous messages telephonically along a single 

 wire, while four others were received on the same 

 wire — a double quadruple system, as it were. This 

 is accomplished in the following manner : — We have seen 

 that notes can be transmitted by means of re.eds or tuning 

 forks, so we will suppose a set of such instruments arranged 

 at both ends of a telegTaph wire. Now if a reed with the 

 pitch of G natural be set in vibration at the sending station, 

 no other reed but the G natural will vibrate at the receiving 

 station, and it will continue to hum this note as long as the 

 current is passing, but ceases immediately the sender opens 



