200 Mr. T. T. P. B. Warren on a Method of Testing 



must follow out its own system of testing for the position of the 

 rupture in the conductor; the only provision which can be made 

 by the shore station, in helping the ship to determine the posi- 

 tion of such a fault, is in sending " continuity '"-signals as often 

 as possible, so that the ship, at any time failing to receive them, 

 can pronounce upon the position of the rupture without any loss 

 of time. 



The following system of " continuity "-signals, suggested by 

 the author in an article which appeared in 'Engineering/ 

 April 24, 1868, serves at the same time to inform the ship and 

 shore station whether the conductor is perfect or broken. The 

 great advantage of this system is that it leaves the electrified 

 condition of the cable undisturbed during the intervals of sig- 

 nalling. 



The shore end of the cable being landed, the conductor, or a 

 prolongation of it, is attached to an insulated pin ; and at a suit- 

 able distance from it is fixed another insulated pin which is con- 

 nected through a delicate galvanometer to earth ; between these 

 two pins an insulated pendulum is made to vibrate. 



The pendulum on touching the pin connected with the cable, 

 takes from it a certain proportion of its charge, and during its 

 oscillation empties it into the pin which is connected to the 

 galvanometer. 



The capacity of the pendulum is first fixed upon for the 

 length and electrostatic relation of the cable. Increased capa- 

 city may be given to the pendulum by attaching to it a con- 

 denser of suitable electrical dimensions. 



It will be sufficient to insulate from the other portions of the 

 pendulum that part which is concerned in making the contacts. 



On contact with the end of the cable by the pendulum, a mo- 

 mentary increase in the deflection will be observed on the galvano- 

 meter in the ship, arising from the sudden increase of capacity ; 

 and this will continue as a constant range of variation in the angu- 

 lar deflection due to leakage on the cable itself. By means of 

 these slight motions, a " test of continuity " is kept up without 

 interfering with the test of insulation which is always kept on 

 in the ship. The observer on shore is enabled to know with 

 positive certainty the electrical condition of the cable by allow- 

 ing the abstracted charges to flow to earth through the galvano- 

 meter, occasionally noting the deflection. 



If the conductor parted, and at the same time each end remained 

 insulated, the observer at the shore end would continue to get 

 indications on his galvanometer ; but the intermittent rise and 

 fall in the galvanometer deflection in the ship would imme- 

 diately cease, and the engineer would know the exact moment 

 that the continuity ceased. 



