A B C 



1 . 3 4 5 G * 



90 



Fig. 06. THE SINGLE SEEDLE TELEGRAPH. 



THE ELECTRIC TELEGRAPH. 



CHAPTER IV. 



r. Cable between Spezzia and Corsica. 88. Other cables, European and 

 American. 89. Objections brought by scientific authorities to the 

 submarine cables Answers to these by practical men. 90. Example 

 of a cable uninjured by the action of the sea. 91. Precautions 

 necessary in laying the cable. 92. Accident in laying the Calais 

 cable. 93. Imperfection attributed to the Belgian cable. 94. 

 Transatlantic Ocean Telegraph. 95. Underground wires between the 

 Strand and Lothbury. 96. Effect of the inductive action of under- 

 ground or submarine wires. 97. Possible influence of this on tele- 

 graphic operations. 98. Examples of overground wires extended to 

 great distances without intermediate support between Turin and 

 Genoa. 99. Telegraphic lines in India. 100. Difficulties arising 

 from atmospheric electricity height and distance of posts mode of 

 laying underground wires extent of line erected to April 1854. 

 101. Intensity of current decreases as the length of wire increases. 

 102. Also increases with the thickness of the wire. 103. And 

 with the number of elements in the battery. 104. Result of Pouillet's 

 experiments on the intensity of current. 105. Intensity produced by 



LABDSER'S MUSEUM OF SCIENCE. M 1C1 



No. 37. 



