WILLIAM SIEMENS, F.R.S. 59 



A rlcxjkwork arrangement at the land station is made to put the 

 cable by rotation to earth, to the poles of a battery, and to 

 insulation. 



On board the ship there is constantly a bridge of resistances in 

 connexion with the line. Whilst the electrician keeps the bridge 

 in equilibrium, he is enabled to ascertain alternately the resistances 

 of insulation and continuity. 



The attendant of the station likewise observes the two data, and 

 transmits them telegraphically to the ship. If these four tests differ 

 materially they indicate thereby the existence of a fault, the 

 position of which can be calculated from the data obtained. This 

 method of observing the conditions of the cable, although very 

 fatiguing to the electrician employed, has been found to answer 

 perfectly well in paying out the Indian lines. During the 

 paying out of the Aden-Kurrachee section by Messrs. R. S. 

 Newall & Co., we were by this means enabled to observe faults 

 on five different occasions, which could then be removed without 

 delay. 



Our methods for determining the place of a fault are as 

 follows : 



1st. When both ends of the cable are at hand let x and y re- 

 present the respective distances from each end of the cable to the 

 fault, I the length of the whole cable, G a galvanometer, and IF, TF X , 

 two graduated resistance coils (Plate 1, Fig. 3). Then if TFand 

 TF X ai'3 so adjusted that the galvanometer needle is perfectly quiet 

 the place of the fault is given by the formula 



* - 



This method has already been published by Werner Siemens 

 (see Zeitschrift des Deutsch - Oesterreichischen Telegraphen- 

 Vereins, 1857) having been used by us with perfect success ever 

 since 1849. 



In dealing with a single submerged line this method is no longer 

 applicable. Let c denote the resistance of the whole length 

 of the cable, x and y the resistances from each end to the fault, 

 2 that of the fault itself ; and j and &j resistances observed from 

 each end respectively, the further end being insulated ; a and b the 



