XIV CONTENTS. 



Page 



43. Copper Eesistance with both ends of Cable . . . ... 297 



44. ,, one end only 298 



45. Insulation by Bridge Method 299 



46. ,, Deflection ,. . '., .. , . 299 



47. Charge 301 



48. Discharge 301 



49. Constant of Sensibility of Galvanometer 303 



50. Measurement of Electro -motive Force 305 



ftl. British Association Balance 306 



52. Balance by Bisected Wire 309 



53. Determination of the Constants of Galvanic Elements . . 313 



54. ,, of the Eesistances of ,, . . 313 



55. ,, of the Electro- motive Forces of Elements . 315 



56. Eegnault's Method 316 



57. Fechner's ,, 317 



58. Wiedemann's .... ., . ..... . . 317 



59. Method with Galvanoscope 317 



60. Wheatstone's Method . . . '. .....". .' . . . . 319 



61. Ohm's ,, 320 



62. Poggendorff's (Compensation) Method . "* '". . . . . 320 



63. Comparative Electro -motive Forces of Metallic Pairs . . 324 



Y. UNITS OF RESISTANCE. 



64. Siemens' Mercury Unit 328 



65. The Absolute Units 333 



VI. SUBMARINE TELEGRAPH CABLES. 



66. The First Cables ...... . . . . , V ; . . 341 



67. The Old Atlantic Cable ...-.- 342 



68. Eed Sea and Indian Cables . . . . 343 



69. Malta and Alexandria Cable .344 



70. Persian Gulf Cable . .- .- v .- -. .' ^V^i>'. 345 



71. Copper- covered Cables .... .. * 346 



72. New Atlantic Cable * * * . * - '&* - 348 



73. Tests of Finished Core at the Gutta-percha Works . . . 350 



74. Testing under Pressure . .-U '": ; '. 350 



75. Measurements of Copper Conductor . . .- . . . . 353 



76. ,, Insulation Eesistance 356 



77. Insulation Test by Wheatstone's Bridge ... . . . 358 



78. ,, Differential Method 358 



79. ,, Deflection of Magnet 364 



80. Insulation under Pressure 365 



81. Electrification 367 



