14 THE ADDRESSES, LECTURES, ETC., OF 



flexible tubing. The copper is mixed with a certain portion of 

 phosphorus, which, according to Dr. Percy's experiments, corro- 

 borated by my own experience, is remarkably durable in sea water. 

 A cable of this description has been laid in the Mediterranean, 

 where it now forms one of the links between Algeria and Europe. 

 Small cables of this description have been adopted by the Prussian, 

 Italian, and other Governments, for military purposes, owing to 

 their lightness and strength, combined with remarkable flexibility. 

 The conductor of these cables consists of three steel wires, and its 

 outside diameter does not exceed the eighth part of an inch. In 

 making permanent shallow sea cables on this principle, I apply 

 first an iron sheathing, consisting of comparatively thin wires, and 

 upon that, the sheathing just described in which zinc takes the 

 place of the phosphoretted copper. Another covering which has 

 been proposed consists of reeds joined up end to end, and put on 

 like iron wire, producing a rope of very small specific gravity. 

 Different from all these is the cable proposed by Mr. Allen, which 

 has no sheathing whatever, the conductor itself being made strong 

 by being compounded of copper and steel wires. Steel being a 

 very inferior conductor, it is evident that Mr. Allen's cable would 

 not compare favourably for great lengths with others, as regards 

 power of transmission ; and for my own part, I should not think 

 it safe to lay down a cable without any external sheathing, 

 which I consider necessary, not only to give strength, but also to 

 protect the insulating material against animals and against 

 abrasion. 



We come next to the subject of testing. One of the principal 

 conditions to insure the success of telegraphs, and particularly of 

 deep-sea lines, consists in the application of a complete system of 

 electrical testing at every stage of progress of manufacture and 

 submersion. In the early history of submarine telegraphs this 

 important work was very imperfectly accomplished, and consisted 

 chiefly in methods for the determination of faults, instead of their 

 prevention, and by insisting upon a certain standard of perfection 

 at the different stages of manufacture. For instance, the insula- 

 tion of the first Atlantic cable was so exceedingly defective before 

 it was coiled on board ship, that it should never have been laid at 

 all, as will be seen from comparison with subsequent cables, shown 

 in the following table : 



