542 



SUBMARINE CABLE LAYING AND REPAIRING. 



the lower part of the curve, that is for the higher currents, are 

 quite off the correct line. On this very small exposure the 

 curve shows that it is useless to test with currents exceeding 

 5 or 6 milliamperes, but the two upper points (representing 

 small currents), when joined and produced as shown by the 

 dotted lines, meet at the same point as the other curves and 

 indicate the position of the break. On all the larger exposures, 

 as the carves show, currents up to about 25 milliamperes give 

 quite uniform results. 



> 



0-80 



0-70 



0-60 



0'50 



0-40 



0-30 



0-20 



0-10 







1300 1350 14U0 1450 1500 1550 16C0 1650 1700 1750 1800 1850 



Fig. 309. — Localisation of Partial Earth Fault on the French- Atlantic. 

 (E. Raymond-Barker. ) 



The curve in Fig. 308 is of a break localisation taken on the 

 cable ship "Dacia" during repairs of the Direct United States 

 cable in September, 1904. All readings were to scale zero, with 

 zinc to line, and the current was varied by using different bat- 

 tery powers. The core was 400 lb. copper and 360 lb. G.P. 

 It will be noticed that the projection of the curve cuts the 

 resistance line at 1232 ohms and deducting the steadying 

 resistance of 1213 ohms gave 19 ohms or between 7 and 8 

 miles to break. The end was actually picked up at 7 '6 miles. 



