62 SUBMAEINE CABLE LAYING AND REPAIEING. 



During manufacture, laying and repairing the conductor is 

 subjected to a good deal of bending in opposite directions, and 

 it must not be liable under these conditions to fracture. It 

 must also possess flexibility for coiling and handling. Hence 

 a conductor composed of a strand of wires is more suitable 

 mechanically than a solid wire, although a solid conductor 

 better answers the electrical requirements. A solid wire of 

 equal resistance and weight to a stranded conductor has the 

 advantage of being smaller in diameter than the strand. 

 Therefore, for the same weight of insulator the coating of 

 gutta-percha or other insulating material is thicker on a solid 

 wire than on a stranded conductor of equal weight and 

 resistance. This means that the area for static induction in 

 the dielectric is less and, consequently, the retarding effect 

 less when a solid wire is used for a given weight of conductor. 

 A core for a given speed of working can therefore be con- 

 structed at less cost with a solid than with a stranded 

 conductor, or, in other words, for equal cost a core with solid 

 conductor gives a better speed than one with a stranded 

 conductor of equal weight. Solid conductors were used in the 

 earliest cables, but the frequent breakages that occurred led 

 to the adoption of the stranded conductor in the 1856 Cape 

 Breton Island and Newfoundland cable. Except in the largest 

 cables for great distances and high speeds, in which a com- 

 promise is successfully effected between a stranded and a solid 

 conductor, the stranded conductor, composed of seven wires, 

 is almost exclusively employed. 



Attempts have been made to form the conductor so as to 

 retain a more or less solid condition, and dispense with the 

 waste of space in interstices in stranded conductors while 

 retaining sufficient mechanical flexibility. In this way the 

 conductor is somewhat smaller for a given conductivity and 

 consequently the inductive capacity is reduced and the insula- 

 tion resistance increased for a given thickness of insulator. With 

 this object Mr. Latimer Clark in 1858 devised the segmental 

 conductor, consisting of four quadrants in section. Mr. Wilkes 

 afterwards suggested surrounding it with a tube to keep the 

 segments together and present a smooth exterior. A con- 

 ductor weighing 2251b. per naut of this form was made for 

 the Persian Gulf cable of 1862. It was built of large sections 



