f)ow tbe {Telephone Calfce. 14? 



the impulse will depend upon the amplitude 

 and quickness of the movement of the dia- 

 phragm. If there is a long movement there 

 will be a strong current and vice versa. If 

 a sound is uttered, and even if the multi- 

 tude of sounds that are required to form a 

 word, be spoken to the diaphragm, the latter 

 partakes in kind of the air-motions that strike 

 it. It swings or vibrates in the air, and if it 

 is a perfect diaphragm it moves exactly as the 

 air does, both as to amplitude and complexity 

 of movement. You will remember that in the 

 chapter on sound-quality (Vol. II) it was said 

 that there were hundreds and sometimes thou- 

 sands of superposed motions in the tones of 

 some voices that gave them the element we 

 call quality. 



All these complex motions are communi- 

 eatc (] by the air to the diaphragm, and the 

 diaphragm sets up electric currents in the wire 

 wound on the spool, corresponding exactly in 

 number and form, so that the current is 

 molded exactly as the air-waves are. Now, if 

 we connect another telephone in the circuit, 

 and talk to one of them, the diaphragm of the 

 other will be vibrated by the electric current 

 and caused to move in sympathy with it 

 and make exactly the same motions relatively, 

 both as to number and amplitude. 



It will le plain that if the receiving dia- 

 phragm is making the same motions as the 



