120 



THE ELECTRIC TELEGRAPH. 



local circuit, working the recording instrument. The nega- 

 tive current will take the same road as the positive, and throw 



Fig. 65. 



back the tongue of the relay against its insulated contact, 

 thereby breaking the local circuit. 



77. Thomas John's Telegraph* The great force necessary 

 to press the style against the paper strip in order to leave 

 visible marks, and the consequent employment of a relay 

 with local battery, were obviated by the invention of an 

 Austrian telegraph engineer, Mr. John, as early as 1854. 

 * Brix. Journal,'vi. p. 5. 



