IxJ THE ELECTRIC TELEGRAPH. 



parties, and upon a given signal, for each party to start their 

 clocks at the same letter, and thus, if the clocks went to- 

 gether during the transmission of the intelligence, the proper 

 letters would appear simultaneously, until the communica- 

 tion was finished. The attention of the distant observer was 

 called by the explosion of gas by means of electricity from a 

 Ley den jar. 



Fig. 4 shows an elevation of the apparatus, in which D is 

 an electrical machine, B a pith-ball electrometer, A the screen 



Kg. 4. 



hiding the letters on the dial-plate except the one seen 

 through the orifice, F the gas alarm, and E the tube convey- 

 ing the wires from the station. 



Fig. 5 shows the dial ; and Fig. 6 the same with the screen 

 before it, and the pith-ball electroscope. 



