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L37 



CONTENTS. 



THE ELECTRIC TELEGRAPH. 



i 



CHAP. VII. 163. Momentary currents alternately in contrary 

 directions. 164. Method of producing momentary currents all 

 in the same direction. 165. Magneto-electric machine. 166. 

 Its effects in producing shocks and currents. 167. Method of 

 applying it to telegraphs. 168. Chemical property of the 

 current. 169. Decomposition of water. 170. Application of 

 this property to produce written characters at a distance. 171. 

 Methods of moving the paper under the style. 172. Telegraphic 

 characters marked upon it. 173. Use of relay magnets in cases 

 of feeble currents. 174. Form and application of them. 175. 

 Telegraphic lines constructed by companies in England and 

 America, and chiefly by the state on the continent. 176. Various 

 forms of instruments used. 177. Influence of national feeling. 

 178. Meritorious inventions sometimes neglected. 179. Needle 

 instruments generally used in England. 180. Single needle 

 instrument. 181. Double needle instrument. 182. Old aerial 

 telegraph. 183. French State telegraph .... 



CHAP. VIII. 184. Form of commutator of French state telegraph. 

 185. Its opei'ation. 186. Method of sending and receiving a 

 dispatch. 187. Batteries. 188. French railway telegraph. 

 189. French railway portable telegraph. 190. German railway 

 telegraph. 191. Siemens' instrument. 192. Its mode of 

 operation. 193. How errors are corrected. 194. Explanation 

 of the mechanism. 195. Comparison with the French telegraph. 

 196. Indicating mechanism. 197. Simplicity greater than 

 the French instrument. 198. Requires greater intensity of 

 current. 199. Belgian railway telegraph. 200. Defects im- 

 puted to the French and German instrument ."'.'. . 17 



CHAP. IX. 201. Defects of the French and German instrument 

 removed by Lippens' instrument. 202. Description of it. 203. 

 Its wheel commutator. 204. Transmission of dispatches by it. 

 205. Froment's alphabetic telegraph. 206. Morse's tele- 

 graph. 207. Froment's writing telegraph. 208. Bain's chemical 

 telegraph. 209. Method of writing. 210. Electro-chemical 

 .pen. 211, Metallic desk 33 



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