Cooke. — On Telegraph Cables. 325 



lain, are too brittle for cable- work, others, as wood, are not 

 impervious to water. Hence guttapercha and indiarubber 

 are the only substances which have been used as insulators 

 in telegraph cables. 



The following extract from Cassells's "Technical Edu- 

 cator" maybe in place here: "The first cable from Dover 

 to Calais consisted of a wire coated with guttapercha, but 

 this was so imperfect that it failed the following day. . . . 

 In the cable which was laid the following year the conductor 

 consisted of four copper wires, each of which was separately 

 insulated by being covered with guttapercha. The wires were 

 laid side by side, a little hemp being placed between them to 

 prevent their chafing. Tarred hemp was then laid on so as to 

 form a solid rope, and outside all, as a protection against 

 external injury, there were galvanised-iron wires spirally 

 wound. The cable when complete weighed about 7 tons 

 per mile, and possessed very great strength. It was found 

 to answer admirably, and has remained in working-order ever 

 since." 



Thus early in the history of cables — in the second year of 

 their existence — we have all the essentials of the cable of 

 to-day. Other cables soon followed this one from Dover to 

 Calais, a total of two thousand five hundred miles having 

 been laid by the end of 1857, and fifteen thousand miles be- 

 fore the end of 1863. In 1858 the first Atlantic cable from 

 Ireland to Newfoundland, two thousand miles long, was laid, 

 ■ but in a very short time it ceased to work. There were 

 several causes to which its non-success was attributed, but 

 the principal one was the iron sheathing-wires not being 

 strong enough. We have seen that the Dover and Calais 

 cable weighed 7 tons per mile. The deep-sea part of this 

 cable weighed only 1 toa per mile. 



The year 1866 saw the successful laying of two Atlantic 

 cables, since which time there has been permanent telegraphic 

 communication between Europe and North America. Ten 

 years later there were five cables crossing the North Atlantic, 

 besides one from Lisbon to Brazil. South Africa was the last 

 place of any importance to be connected by telegraph with 

 Europe. The troubles in Zululand and the Transvaal pre- 

 vious to 1880 having shown the extreme necessity for it, it 

 was at once arranged to lay a cable, that the South African 

 colonies might have the advantage of the prompt communica- 

 tion which the telegraph affords, and which has become a ne- 

 cessity to all civilised communities. 



II. The Manufacture of Cables. 

 There are four parts of a cable to be considered— (1) The 

 wire that transmits the current, hence known as the conduc- 



