.s/A' WILLIAM .S7/..I//-;A'.V, I'.R.S, 2$ 



principal lines, for reasons which I shall enumerate hereafter. The 

 experience gained in this great experiment has been most valuable 

 in paving the way to submarine cables, which, at the present time, 

 occupy so large a share of public attention. 



The instruments which Werner Siemens at first proposed, and 

 which are still used extensively on the continent for railway pur- 

 poses and town service, were dial instruments, involving a peculiar 

 principle, inasmuch as no communicating instrument or any 

 clockwork is employed, but the two or more instruments, con- 

 nected by the single line wire, break and restore the electric 

 circuit by the action of their own armatures, in a similar way to a 

 steam-engine, which alternately intercepts and restores the com- 

 munication with the boiler. In arresting the ratchet-wheel of 

 any one of the instruments within the circuit, by depression of a 

 key, bearing a certain letter of the alphabet, the armature of the 

 instrument in question is prevented from restoring the electric 

 circuit, and the hands upon the dials of all the instruments in 

 circuit must stop, pointing all of them to the same letter, until the 

 depressed key is again released. The advantages of this arrange- 

 ment over previous dial instruments are that the communicating 

 instruments are less liable to fall out of step, and that con- 

 siderable power of action is obtained, because the batteries of 

 all the intermediate and end stations act in concert, being all in- 

 cluded in the general circuit. The dial instrument is in some 

 instances accompanied by a type printing instrument, differing 

 from Wheatstone's and House's arrangements, inasmuch as it is 

 entirely self-acting, the motion of the type wheel, of the paper, 

 and even of the hammer striking the blow upon the type, being 

 effected by electro-magnets instead of clockwork, or an air 

 cylinder, as is the case in House and Brett's arrangement. 



Since the time of the first successful introduction of the electric 

 telegraph, a great variety of instruments, insulators, and other 

 appliances, have been proposed, amongst which the chemical 

 recording instruments of Bain and Bakewell, the modifications of 

 Wheatstone's magneto-electric needle, and dial instruments by 

 Henley and Stcehrer, the vari ous combinations of Messrs. Highton, 

 Clark, and Bright, and the more recent productions of Mr. Yarley 

 and Mr. Whitehouse, are of undoubted merit in having con- 

 tributed to the general progress of electric telegraph engineering. 



