CHAP, xii.] ELECTRICITY AND MAGNETISM. . 393 



CHAPTER XII. 



TELEGRAPHS AND TELEPHONES. 

 LESSON XXXIX. Electric Telegraphs. 



423. The Electric Telegraph. It is difficult to assign the 

 invention of the Telegraph to any particular inventor. Lesage 

 (Geneva, 1774), Lomond (Paris, 1787), and Sir F. Ronalds 

 (London, 1816), invented systems for transmitting signals 

 through wires by observing at one end the divergence of a pair 

 of pith-balls when a charge of electricity was sent into the other 

 end. Cavallo (London, 1795) transmitted sparks from Leyden 

 jars through wires "according to a settled plan." Soemmering 

 (Munich, 1808) established a telegraph in which the signals 

 were made by the decomposition of water in voltameters ; and 

 the transmission of signals by the chemical decomposition of 

 substances was attempted by Coxe, R. Smith, Bain, and others. 

 Ampere (Paris, 1821) suggested that a galvanometer placed at 

 a distant point of a circuit might serve for the transmission of 

 signals. Schilling and Weber (Gottingen, 1833) employed the 

 deflections of a galvanometer needle moving to right or left to 

 signal an alphabetic code of letters upon a single circuit. 

 Cooke and Wheatstone (London, 1837) brought into practical 

 application the first form of their needle telegraph. Henry 

 (New York, 1831) utilised the attraction of an electromagnet 

 to transmit signals, the movement of the armature producing 

 audible sounds according to a certain code. Morse (New York, 

 1837) devised a telegraph in which the attraction of an arma- 

 ture by an electromagnet was made to mark a dot or a dash 

 upon a moving strip of paper. Steinheil (Munich, 1837) 

 discovered that instead of a return- wire the earth might be used, 

 contact being made to earth at the two ends by means of earth- 



