62 Scientific Intelligence. 
disks and armature in the secondary. When a current 
through the magnet, the armature was attracted, compressed the 
carbon disk, diminished its resistance, and so increased the current 
strength in the secondary circuit. Since the Aniieration of the 
resistance is exactly as the pressure, the relay translated the varying 
current strength of the one circuit into a varying moi ig strength 
in the other, of precisely similar character; thus for the first time 
making it ible to relay telephone currents. That ‘the effects 
thus obtained by Edison are due simply to varying external con- 
tact, aa first proved = ee . Richards of Serr rd in J “Hh 187 
a 
led by erie of Edison, all the phenomena fedoribe d with it being 
adily repeated with Edison’s carbon transmitter, especially if a 
Cael button be used which has been worked over several times 
so as to be in a state of minute division. The tick, the pire the 
fly tramp can all be heard with it. For purposes of practical tel- 
overcome by Ediso n only after long experimenting. It i is mainly 
a matter of adjustment of the contact pressure, as well in the car- 
acts. 
=a is easy to talk with the carbon transmitter of Edison, by 
project the sound waves directly against the carbon itself as in 
the shiciephieati Finally, Edison has utilized the varying resist- 
