Multiple Cransmtssion. 125 



(with the same loudness) on the receiving- 

 instrument. I now went to work on an instru- 

 ment that responded for one note only and 

 succeeded beyond my expectations. I made 

 three different kinds of receiving-instruments. 

 The first was a steel strap about eight inches 

 long by three-eighths wide. This strap was 

 mounted in an iron frame in front of an elec- 

 tromagnet. A thumbscrew enabled me to 

 stretch the strap till it would vibrate at the 

 required pitch. If, for instance, the sending- 

 reed vibrated at the rate of 100 times per sec- 

 ond and the strap of the receiver was stretched 

 to a tension that would give 100 vibrations per 

 second when plucked, it would then respond 

 to the vibrations of the sending-reed but not 

 to those of another reed of a different rate of 

 vibration. If we take mounted tuning-forks 

 tuned in pairs of different pitches, say four 

 pairs, so that each fork has a mate that is in 

 exact accord with it, and place them all in the 

 same room, and sound one of them for a few 

 seconds and then stop it, upon examining the 

 other forks you will find all of them quiet ex- 

 eept the mate of the one that was sounded. 

 This one will be sounding. If we now sound 

 four of the forks and then stop them the 

 oth-r four will be sounding from sympathy 

 because the mate of each one of them has 

 Ix.'ii .-.mided. If only two forks differing 

 in pitch are sounded only two of the others 



