THE CARBON BUTTON. 



13 



p at the bottom of this jar is connected with one wire of the battery 

 E, the other going to the ground. At the receiving station the wire 

 simply passes over an electro-magnet H, thence to the ground. Close 

 to H is placed the diaphragm D, properly provided at its center with 

 a metal plate which serves as' armature for the electro-magnet, and 

 fastened at its circumference in the holder T. The action of the in- 



LINE 



~^%j^j} 



Fig. 2. 



strument is as follows : The person sending the message speaks into 

 the mouthpiece T u thus causing the diaphragm D l5 with the plunger N, 

 to vibrate. The greater the amplitude of vibration the deeper the rod 

 N descends into the liquid, and therefore the thinner the stratum of 

 liquid through which the current will have to pass ; thus the resistance 

 to the passage of the current is varied inversely as the intensity of the 

 sound. At the receiving station the current magnetizes the electro- 

 magnet H, and thus reproduces in the diaphragm D the vibrations of 

 the diaphragm D x . 



A number of telephones have since been invented, differing from 

 each other in method of application and details of construction, but 

 all embodying the scientific principle used by Gray. 



Using the instrument invented by Reis, and the suggestions which 

 Gray's experiments afforded, Thomas A. Edison began his attempts to 

 construct a new form of telephone. Inasmuch as his experiments in 

 this direction " cover many thousand pages of manuscript," only a few 

 of the more characteristic ones will be given. 



In the Reis transmitter a platinum screw was made to face the 

 diaphragm, and a drop of water was put between them. The only 

 result, however, was the decomposition of the water and the deposit of 

 a sediment on the platinum. Two disks of platinum, one on the dia- 

 phragm and the other on the screw, so placed as to hold several drops 

 of water by capillary attraction, were then tried. Acidulated solu- 

 tions were substituted for water ; paj)er and other materials, saturated 

 with various solutions, were tried ; sharp edges were substituted for 

 disks. The result of all these experiments was complete failure, on 



