198 APPLIED SCIENCE 



with a hempen serving, and the served wires are then laid round 

 the core as before : the cable in this case looks like a hemp 

 instead of an iron rope. Many other forms have been proposed 

 and a few adopted, but before these can be discussed, the duties 

 which the cable has to perform, as a rope, must be understood ; 

 arid before entering on this subject, which is purely mechanical, 

 it will probably be better to return to the insulated conductor 

 and its electrical properties. Its form and ma erials have 

 nominally undergone hardly any change since the manufacture 

 of the first cable laid from Dover to Calais in 1851. The copper 

 strand was substituted for the single wire in the Newfoundland 

 and Cape Breton Cable, laid in 1856. Chatterton's Compound 

 was used in the cable between England and Holland, laid in 

 1858. The interstices in the copper strand were filled with 

 compound in the Malta- Alexandria Cable, laid in 1861 ; and 

 since that time absolutely no change has nominally been effected 

 either in the form or materials used. Now, inasmuch as an 

 overwhelming proportion of the cables laid in deep seas have 

 failed, have we any right whatever to expect that cables will be 

 permanently successful, of which the vital portion is nominally 

 identical with that of the old Atlantic, the Red Sea, the 

 Sardinia-Malta and Corfu, Sardinia- Africa, the Toulon-Corsica, 

 the Toulon-Algiers Cables, which, in the aggregate, represent 

 about 8,000 statute miles of wire, which, after a more or less 

 brief period of working, became wholly useless, as may be sup- 

 posed chiefly from electrical defects ? Did it not seem almost 

 madness to attempt to cross 2,000 miles, in depths exceeding 

 2,000 fathoms, at a time when the only cable which could be 

 cited as having worked satisfactorily for any considerable time 

 in deep water, was a short length of the Malta-Alexandria Cable, 

 lying in 420 fathoms of water ? To the public, and to many 

 engineers, it did seem hopeless ; but the fact that it was pre- 

 cisely those persons who knew most of the subject that risked 

 their reputation and their money, should prepare us to believe, 

 that, although the name of the materials and the form of the 

 insulated conductor remained unchanged, other changes had 

 taken place which fully justified the confidence of the Atlantic 

 projectors. The methods by which the perfection or imper- 

 fection of the cables were examined the methods of testing. 



