CHAP, in.] ELECTRIC TELEGRAPHY. 559 



IV. DIAL TELEGRAPHS. 



The dial telegraph is chiefly employed for the railway service and 

 for private telegraph wires between offices and manufactories. The 

 chief reason for this preference consists in the facility with which 

 the apparatus is worked, as it allows any telegraphic operator after a 

 very short apprenticeship to send a message and to read the signals 

 received. 



It is to Wheatstone that we owe the invention of the first tele- 

 graph of this kind. The first attempts with it were made in France 



FIG. 359. Manipulator of Breguet's dial telegraph, new form. 



in June 1844, on the railway from Paris to Versailles. Since then a 

 great number of analogous systems have been tried and adopted on 

 the different telegraphic lines in different countries. We will mention 

 a few of the most remarkable, indicating the differences in their 

 principle or mechanism, confining ourselves just now to the description 

 of the system, which of all the dial telegraphs is in commonest use 

 on the railways of France that of M. Breguet, derived from 

 Wheatstone's. 



