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40 THE POPULAR SCIENCE MONTHLY. 



The first Atlantic cable failed principally on account of imperfect 

 manufacture, in a great measure arising from undue haste and urgency, 

 but largely owing to insufficient experience. * The cable was not tested 

 under water, for fear of rusting the small steel wires of the external 

 covering, and small wires have never since been used ; large wires, 

 the larger the better, is now a principle. The copper was not all good. 

 It had often been coiled and uncoiled, and had been exposed to the 

 strong heat of the sun, and to many changes of temperature. Any of 

 these conditions would nowadays be regarded as enough to condemn 

 the most carefully-manufactured cable. 



The Red Sea and Indian cables are said to have been imperfectly 

 manufactured and laid too taut, but they were not tested under water 

 from the time of manufacture until they were placed at the bottom of 

 the sea, and this one grand omission, largely due to inexperience, is 

 enough, without the recriminatory points, to condemn to loss and 

 failure any cable whatever. 



The cables laid from Cagliari to Malta and Malta to Corfu are said 

 to have failed from imperfect manufacture. One experienced gentleman 

 in his evidence said these cables were " such as nobody should have 

 laid in deep water." It is sufficient at present to know that they have 

 failed from neglect or inexperience, and that they, among other fail- 

 ures, have established the principles which have since insured success. 



The want of constant supervision by engineers, exclusively in the 

 interests of the purchasers of the cable, has been a great cause of de- 

 fective cables. There may often be minute defects in the core itself, 

 or a slightly defective splice which may reduce the electrical condition 

 of a comparatively short length ; this may easily be raised above the 

 average standard required by the contract, by the next length being 

 more carefully manufactured. These minute defects must, however, 

 kill the cable in more or less time, and the principle is established that 

 every inch should be tested in course of manufacture, and rejected if 

 there is any irregularity of condition to cause suspicion. There should 

 be constant supervision, and a record of all the tests kept for the 

 purchasers of the cable from the commencement of the contract to its 

 final completion, and continued ever afterward by the purchasers. 



The principal sources of injury to cables are first, moving water, 

 either currents or tides, chafing the cables upon rocks or shingle. Ex- 

 perience has given many costly lessons of the effect of moving water. 



Ten years ago it was generally believed that water had very little 

 motion below 50 fathoms, and 100 fathoms was considered a point of 

 great safety. "We now know that there are exceptional localities where 

 there is motion in the water at a depth of 500 fathoms. The Fal- 

 mouth cable was chafed and destroyed at this depth from this cause. 

 The Channel Islands cable was also destroyed from the same cause. 

 The first cable ever manufactured with due regard to the principle of 

 careful supervision, testing under water, and being retained quietly in 



