BELGIAN RAILWAY .TELEGRAPH. 



train of wheel-work, and with the rather complicated commutator 

 worked by the hand of the transmitting agent, many moving parts 

 are rejected, and there are proportionately less chances of derange- 

 ment and less causes of wear or fracture. But on the other hand 

 the moving power which impels the indicator, being transferred 

 from the mainspring to the current, a proportionately greater force 

 of current is necessary. This force is, however, obtained without 

 augmenting the magnitude of the batteries at any one station by 

 the expedient of bringing the piles of both the terminal stations, 

 and, if necessary, of any or all the intermediate stations, into the 

 circuit. 



198. In the batteries used with the French railway telegraph, 

 the use of acid, as has been stated, is found altogether unneces- 

 sary. In the German telegraph, however, pure water does not give 

 a sufficiently strong current, and it is acidulated with about one and 

 a half per cent, of sulphuric acid. The battery at each station consists 

 usually of from 15 to 20 pairs. The usual speed imparted to the 

 indicator by the current is about 30 revolutions per minute. 



M. Siemens invented mechanism by which the indicating 

 apparatus was connected with one by which the letters of the 

 despatch as they arrived were printed by ordinary type upon a 

 band of paper. Since, however, this has not been brought into 

 practical use, it will not be necessary to explain it. 



When the electric telegraph was first opened to the general 

 service of the public in Prussia, this apparatus of Siemens was 

 generally used, but it has since been superseded by that of Morse, 

 its speed of transmission being found insufficient for the public 

 service. 



BELGIAN HALLWAY TELEGBAPH. 



199. When the electric telegraph was first brought into use on 

 the Belgian railways, the French and German apparatus described 

 above were tried in succession. In 1851 they were, however, 

 both superseded by a form of telegraph invented and constructed 

 by M. Lippens, mathematical instrument maker of Brussels. 



200. M. Lippens attributes to the French and German railway 

 telegraphs certain defects, which he claims to have removed. For 

 the efficient performance of those telegraphs, it is evident that a 

 certain relation must always be maintained between the force of 

 the spring s (fig. 77), which produces the recoil of the armature g o, 

 and the attractive force of the magnet, or what is the same, between 

 the spring and the intensity of the current, with which the attrac- 

 tion of the magnet must vary. Now the intensity of the current 

 is subject to variation, depending on the state of the battery, the 

 number of pairs which are brought into operation, the length of 



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