THE ELECTRIC TELEGRAPH. 



indicating hands, w, in all of them were placed upon the division 

 of the dial marked + . The moment the arms, a b, or any of 

 them, are placed against the stops T, the current transmitted upon 

 the line -wire passing through the several indicating instruments, 

 the indicating hands in all the instruments will commence simul- 

 taneously to move round the several dials. They will move from letter 

 to letter with a starting and interrupted, but regular motion, like 

 that of the seconds hands of a clock, but much more rapidly. The 

 rate at which they are moved will depend on the force of the 

 current, but, whatever be the rate, it will be common to all, all 

 making successive revolutions of the dial precisely in the same 

 time, and moving together from letter to letter with the most 

 absolute simultaneity, and since they all started from the same 

 point + , and move together from letter to letter, it follows that, 

 whether their motion be quick or slow, they will all at each 

 moment point to the same letter. 



Now, it is important here to observe, that this common rotation 

 of all the hands upon all the dials is produced and maintained by 

 the current alone, without any manipulation whatever on the part 

 of any agent at any station, and it would continue to be main- 

 tained indefinitely, provided that the battery were kept in action. 



We have supposed the battery at the station s, from which the 

 despatch is about to be transmitted, to be alone put into connection 

 with the line-wire. But, in order to strengthen the current, each 

 agent on the line, when he receives the signal, also puts his 

 battery in like connection with the line-wire, so that the current 

 acquires all the intensity which the combined action of all the 

 batteries on the line is capable of producing. 



The apparatus is so arranged that, in all cases, the galvano- 

 meter, d, is in connection with the line-wire, so as to indicate at 

 all times at each station the state of the current. 



It now remains to show how a despatch can be transmitted from 

 any one station to all or any of the other stations on the line. 



The apparatus is so constructed, that if the agent at any 

 station presses down any one of the keys surrounding the dial, 

 the indicating needle, upon arriving at that key, will be stopped ; 

 and at the same moment the current upon the line-wire will 

 be suspended. This suspension of the current will also, at the 

 same moment, stop the motion of all the indicating hands upon all 

 the dials on the line. The agents at all the stations will therefore 

 see and note the letter on which the transmitting agent has put 

 his finger. The transmitting agent, after a sufficient pause, 

 transfers his finger to the key of the next letter he desires to 

 transmit. The moment he raises his finger from the first key the 

 current is re-established on the line-wire, and all the indicating 

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