38 



THE ELECTRIC TELEGRAPH. 



ing thereby the two needles at the receiving station for 

 signalling a letter. 



As the numerals were indicated by the deflections of single 

 needles, a sixth wire was provided for the return circuit. 



=: B 



Fig. 19. 



This telegraph, although extremely beautiful in detail, 

 was inferior in a practical sense to that of Steinheil. It was 

 put up on the London and Birmingham and Great Western 

 railway lines, and tried fairly, but found, on account of the 

 number of line wires, to be too expensive, and was accordingly 

 given up. 



38. The necessity of supplying the receiving station with 

 some signalling apparatus for calling the attention of the 

 observer to the commencement of a correspondence had been 

 fully understood by every inventor since Reusser, who pro- 

 posed to attain this by firing an electric pistol, and Sommer- 

 ing, who proposed to do the same by the liberation of 

 mechanism by accumulated gas. It was left, however, to the 

 energy and persevering genius of Wheatstone to completely 

 solve the problem. 



