1839.] 



Telegraphic Signals by induced electricity. 



723 



Around this primary coil is wound a second coil of extremely 

 thin wire, also insulated and 1000 yards long, totally unconnected, 

 though in close juxtaposition with the primary coil, the ends of the 

 wire being led to screws to which handles, directors, &c, can be at- 

 tached, thus, 



Into the hollow axis at a is introduced a bundle of insulated iron 

 wires. 



The action of the instrument may be very briefly described. While 

 the battery at b is in contact with the wires c d the primary coil 

 is excited. By interrupting the circuit at + or elsewhere, at the 

 instant of its interruption, the secondary or external coil becomes 

 excited by induction or proximity — and this excitement is augmented 

 by the influence of the magnetism simultaneously annihilated in the 

 central bundle of iron wire. 



The electrical state thus momentarily generated in the secondary 

 wires, may be rendered evident by the production of a spark and 

 shock, by effecting chemical decomposition and all the other signs of 

 electrical action, at the terminations of the secondary coil e, /. 



