126 nature's 



will sound in sympathy. In the first case 

 only one set of sound-waves were set up 

 in the air, and the fork that found itself in 

 accord with this set responded. When four 

 forks differing in pitch were sounded there 

 were four sets of tone-waves superposed upon 

 each other existing in the air, so that each of 

 the remaining forks found a set of wavi-> in 

 sympathy with its own natural rate of vibra- 

 tion and so responded. 



Now apply this principle to the harmonic 

 telegraph and you can understand its opera- 

 lion. At the transmit tinn'-i'iid of a line of 

 wire there are a certain number of forks or 

 reeds kept vibrating continuously. These 

 reeds each have a fixed rate of vibration and 

 bear a harmonic relation to each other so as 

 not to have sound-interference or "beats." 

 At the receiving-end of the line there are as 

 many electromagnets as there are transmit- 

 t ing-reeds, and each magnet has a reed cr 

 strap in front of it tuned to some one of the 

 transmitting-reeds, so that each transmitting- 

 reed has a mate in exact harmony with it at 

 the rec iving-end of the line. Keys are so ar- 

 ranged at the transmitting-end as to throw 

 the tones corresponding to them to line when 

 depressed. In other words, when the key be- 

 longing to battery B and vibrator 1 is de- 

 pressed (see Fig. 4) the effect is to send 

 electrical pulsations through the line corre- 



