.S7A' \\-ILUAM Sll-.Ml-:.\S, I'.R.S. 13 



sulphur has also a great insulating property, and has the advantage 

 of being capable of being worked in a plastic state before it is 

 hardened upon the wire by application of heat. It must, how- 

 ever, be admitted that gutta-percha answers every purpose of sub- 

 marine telegraphy if only care is taken not to expose the cable to 

 heat before it is submerged. 



We next come to consider the sheathing, and this also is a very 

 important part of the submarine cable. The protecting sheathing 

 is necessary in order to give strength and protection to the delicate 

 insulated core. The sheathing usually adopted consists of one or 

 t\ro layers of tarred hemp or jute, and a helical covering of iron 

 wires, in the form of a rope. These wires are generally galvanised, 

 in order to prevent, or rather delay, the oxidation of the iron. In 

 the case of the Persian Gulf cable, the iron sheathing is again 

 covered with jute, impregnated with bitumen mixed with sand, 

 which was applied in the molten state, under the direction of 

 Messrs. Bright and Clark. 



In the case of the Toulon and Algiers cable, each wire was pre- 

 viously and separately covered with tarred hemp, and then formed 

 into a rope as usual. This mode of covering did not answer 

 well in that instance, the hemp was eaten rapidly away by the 

 marine insect, xylophaga, and there remained only a loose filigree 

 work of wires surrounding the insulated core, offering no protec- 

 tion to the same, and hastening, on the contrary, its failure. A 

 similar sheathing has, I think, unfortunately been adopted for the 

 new Atlantic cable ; but it is said, in defence of the same, that 

 the marine animal in question does not exist in the Atlantic ; I 

 hope sincerely this may be the case, and also that the great strain 

 which must be brought upon the cable in submerging the same, 

 may not injure the core through the partial unwinding and conse- 

 quent elongation of the helical sheathing, which must take place, 

 and which constitutes, in my opinion, a very serious objection to 

 the application of such a sheathing for deep-sea lines. Other 

 sheathings for deep-sea cables have been proposed. In one pro- 

 posed by myself, the core is covered with a double layer of best 

 hemp, laid on with moderate twist running in opposite directions, 

 under considerable tension. The hemp is covered, while under 

 tension, by a sheathing of copper strips, which, tightly grasping 

 the hemp, prevent its contraction, and it then forms a complete 



