THE LAYING OF SUBMARINE CABLES. 155 



the shore galvanometer, which is noted every time. This 

 periodic contact was in former times made by means of clock- 

 work. Mr. E. March Webb, for instance, used a clockwork 

 arrangement for the continuity signals on the Marseilles- 

 Algiers cable in 1879. The lever operated by the clockwork 

 in this arrangement moved over at every fifth minute to a stop 

 which charged the condenser from the cable, and then moved 

 back to another stop which discharged the condenser. ''In this 

 case the charge and not the discharge throw was indicated on 

 the galvanometer. A clockwork arrangement in which the 

 condenser was first used was designed by Messrs. Latimer 

 Clark and Co. and Mr. Laws, and used on the Persian Gulf 

 cables. This was further improved by Mr. Herbert Taylor, 

 and subsequently by Mr. Robert Gray. A still earlier clock- 

 work arrangement was that of Mr. F. C. Webb, used on the 

 Hague cables. This was suggested by Mr. Latimer Clark, and 

 used also by Messrs. Siemens on the Eed Sea cable. The 

 contacts made by this apparatus were for sending five minutes, 

 insulating five minutes, and earthing five minutes. Apparatus 

 for working the signals by hand was generally provided in case 

 of failure of the clockwork ; but now clockwork is scarcely 

 ever used, as it is much more satisfactory for those on board 

 to know that the periodic signals are made by hand, the regu- 

 larity with which they are made affording an indication of the 

 watchfulness and attention of the staff on shore. 



If either end wishes to communicate with the other, the 

 signal for this purpose by shore to ship is given by taps on the 

 discharge-key between the usual five-minute intervals, and 

 from ship to shore by reversing the current at other than the 

 stated time. The signal being understood, both ends change 

 over to their speaking connections, shore by taking plug out of 

 usual place on commutator and putting it in the left-hand bar. 

 The ship, for speaking, removes plug between levers of speak- 

 ing-key, changes over on commutator from testing-galvano- 

 meter to mirror, and takes out plug A. Plug B may be left in or 

 taken out according to sensitiveness of signals required. When 

 sending, the switch in connection with the cable is put over to the 

 left, so that the sending current does not pass through the receiv- 

 ing instrument. If testing is required, periods for earthing and 

 freeing are then mutually arranged, and tests are taken, each 



