RRi.ns /.v I III- luu.i. SYsrrM 5 



bi'twccii ck'ilricil\' and ina,uiK'lisni. Acconliiig to this theory, all 

 magnetic phenomena result from ilu- attraction or rcpliilsion of 

 electric ciirri'nts supposed to exist in iron at rii;ht angles to the length 

 ol tile har. and all the pliem micna ol m.igiiclisin and ek'Clro-mag- 

 iH'tism an.' thus relciird in om- prinri|)le the action ot electrical 

 currents on one another, .\mnng other things, he proposed a plan 

 for the application of electro-magnetism to a s\stem for transmitting 

 intelligence. This system was to operate !)>■ the deflection of a number 

 of needles at the receiving station b\' currents transmitted through long 

 wires. By completing a circuit the needle was to be deflected and 

 was to return to normal under the influence of the attraction of the 

 earth when the circuit was opened. This proposed s\slem of .Ampere's 

 was never reduced to practice, however. 



All these discoveries and results were prior to 1823, and they 

 resulted in the de\'clopnienl of needle telegraph systems, which were 

 at one time employed extensi^•ely in Europe. These systems utilized 

 a coil of wire around a magnetic needle pivoted in the center and with 

 a pointer attached to the needle, which was suspended over a dial. 

 Deflections to the right or left signified letters and were produced 

 by sending pulsations of one pi)larit>-, or alternations of both, as 

 was rec|iiired. 



In \S'2i. Sturgeon, an luiglishman, (lisco\ered that, if a current 

 of electricity- flows in a coil of wire surrounding a bar of annealed 

 iron, the latter becomes a magnet, and when the current ceases, the 

 iron loses its magnetism. Sturgeon bent an iron rod into the form of 

 a horse-shoe and wound a coil of copper wire around it loosely, with 

 wide intervals between the turns to prevent them from touching 

 each other. Through this coil, he transmitted a current. The 

 iron under the influence of this coil became magnetic and thus, the 

 first electro-magnetic magnet, now known simply as the electro- 

 magnet, was produced. This discovery of Sturgeon's is of great 

 interest to the telephone and telegraph engineer, because it was the 

 direct step which made the invention of the electro-magnetic relay 

 possible. 



In 1828, Henry, in America, after repeating the experiments of 

 Oersted, Ampere, Sturgeon, and others and investigating the laws 

 of the development of magnetism in soft iron by means of electrical 

 currents, designed the most powerful electro-magnet that had ever 

 been made. This he accomplished by associating Schweiger's mul- 

 tiplier with Oersted's magnet. For this purpose he wound 35 feet 

 of silk insulated wire around a bent iron bar so as to cover its whole 

 length with several thicknesses of wire. 



