148 nature's flMracteS. 



transmitting diaphragm, it will put the air 

 in the same kind of motion that the air is in 

 at the transmitting end, and will produce the 

 same sensation when sensed by the brain 

 through the ear. If the air-motion is that of 

 any spoken word it will be the same at both 

 ends of the line, except that it will not be so 

 intense at the reeeivin^-eml ; it is the same 

 relatively. And this is how the telephone 

 talks. 



I have said that the permanent magnet had 

 two functions. In the case of the transmitter 

 it is the medium through which mechanical 

 is converted into electrical energy. It corre- 

 sponds to the field-magnet of the dynamo, 

 while the diaphragm corresponds to the re- 

 volving armature, and the voice is the steam- 

 engine that drives it. In the second place, it 

 puts a tension on the diaphragm and also puts 

 the molecules of the iron core of the magnet 

 in a state of tension or magnetic strain, and 

 in that condition both the molecules and the 

 diaphragm are much more sensitive to the 

 electric impulses sent over the wire from the 

 transmitter. This fact was experimented 

 upon by the writer as far back as 1879 and 

 published in the Journal of the American 

 Electrical Society. At the present day this 

 form of telephone is used only as a receiver. 



Transmitters have been made in a variety 

 of forms, but there are only two generic 



