SCIENCE AND PRACTICE, 405 



The cable is represented in Figs. 183, 184, by the line 

 between the points or stations A and B, the fault being at 

 some intermediate point F. From each end two measure- 

 ments are possible first, that of insulation, when the oppo- 

 site end is insulated ; and, secondly that of continuity, when 

 the opposite end is put to earth. In Fig. 183 the end B is 

 insulated, and A sends a current from a battery into a cable. 

 With the exception of a very small proportion, which escapes 

 through the insulating covering of the cable between the 



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 ) 

 Fig. 183. 



Fig. 184, 



station A and the end B, the current goes to earth at r, as is 

 shown by the arrows. Fig. 184 shows the farther end B 

 to earth. The current then divides itself, part going to 

 earth at r, and the remainder at B. Station B can make 

 similar measurements when A insulates, and puts to earth his 

 end of the line. 



Let the resistance of the conductor between A and F be x ; 

 of that portion between r and B, y ; and the resistance of the 

 fault, s ; then we have five equations for the calculation of 

 three unknown magnitudes. 



1) . . B, = x + z 



2) . . R' = y + * 



R being the resistance measured by A, and B/ that measured 

 by B, when the opposite end is insulated, 



y + * 



