THE LOCALISATION OF BREAKS AND FAULTS. 



435 



and comes out too high. The charge due to the earth current 

 represented by the small area must be determined and deducted 

 from the observed charge to obtain the correct charge. 



The lower diagram represents the eflPect of an earth current 

 opposing the testing battery. In this case the observed charge 



Fig. 247b. 



is less than the true, and the earth current charge must be 

 a,dded to the observed charge to obtain the correct charge. 

 Shortly put this is : — 



Direction Same Subtract. 



Direction Against Add. 

 In the figure 



?'i= Resistance of testing battery plus the joint resistance of 

 galvanometer G^ and the shunt used when observing 

 the charge. 



e=Earth current E.M.F. 



J:= Testing battery E.M.F. 



p F 2 



