228 SCIENTIFIC AND TECHNICAL LABOURS TO 1860. 



up along it apart from one another, accordingly exert 

 a more powerful magnetizing effect and less impair 

 each other's action. Inductors of this kind are to-day 

 exclusively employed wherever it is desired to procure 

 powerful currents by permanent magnetism. 



My cylindrical bars with transverse coil possessed 

 the great advantage over the older constructions that 

 they had with powerful action less mass, and especially 

 with quick rotation little inertia. I employed them 

 therefore also for the construction of a very simple 

 and surely acting magneto -electric dial -telegraph, in 

 which the cylindrical inductor was quickly turned by 

 a handle with wheel-translation, whilst each semi-revo- 

 lution sent an alternating positive and negative current 

 through the line, each causing the pointer of the re- 

 ceiving apparatus to advance by one letter on the dial- 

 plate. It was enough to place the handle successively 

 on the letters to be telegraphed, to make them visible 

 in like order at the receiving station. The electro- 

 magnet of the receiving apparatus consisted of an iron 

 cylinder with polar extensions revolving on its axis, 

 which oscillated between the poles of two powerful 

 horse-shoe steel magnets. Therefore, according as a 

 positive or negative current traversed the fixed coils 

 of the electro-magnet, one or the other magnet attracted 

 the rotating armature, and thereby kept in motion the 

 hands of the receiving apparatus. This quickly and 

 surely acting magneto -electric dial -apparatus was in 

 great requisition especially for the railway service, and 

 is even now frequently used. 



