flfculttple tTranemtssion. 115 



line was very long there was a difficulty that 

 seemed insurmountable. In the common par- 

 lance of telegraphy, there was a " kick " in the 

 instrument that came in and mutilated the 

 signals. About 1872 Joseph B. Stearns of Bos- 

 ton made a certain application of what is 

 called a "condenser" to duplex telegraphy 

 that cured the " kick," and from that time to 

 this it has been a success. Farther along I will 

 tell you what occasioned this " kick " and how 

 it was cured. If this or some other method 

 could be applied as successfully to cure the 

 many chronic " kickers " in the world it would 

 be a great blessing to mankind. 



It has always been a mystery to the un- 

 initiated how two messages could go in oppo- 

 site directions and not run into one another 

 Miid g-t wrecked by the way. If you will fol- 

 low me closely for a few minutes I will try to 

 tell you. 



We have already stated that an electro- 

 magnet is made by winding ;ni insulated wire 

 a round a soft iron core. If we pass a current 

 of electricity through this wire the core be- 

 comes magnetic, and remains so as long as the 

 current passes around it. In duplex telegraphy 

 we use what is called a differential magnet. 

 A differential electromagnet is wound with 

 two insulated wires and so connected to the 

 battery that the current divides and i 

 around the iron rore in opposite directions. 



