THE CABLE SHIP ON REPAIRS. 203 



to-day, when a cable has to be singled out from a number of 

 others laid near together, it can usually be seen by the size 

 and number of the sheathing wires whether the right one has 

 been raised, and if not it is dropped back or buoyed tem- 

 porarily while another drive is made, until the right cable 

 is secured. 



In 1882 Sir James Anderson and Mr. W. Claude Johnson 

 brought out an automatic indicating grapnel in which a coil of 

 insulated wire was fixed near the root of the prong and a single 

 or twin insulated conductor laid in the heart of the grapnel rope. 

 When cable was hooked the conductor would complete the 

 connection to the coil and ring a bell on board. Also by in- 

 duction between the coil and cable it was claimed that a sigual 

 from shore could be detected in a telephone on board, which, 

 in the case of two or more cables laid alongside, would show 

 whether the right cable had been hooked. Swivel couplings 

 for the rope were devised having the two contacts capable of 

 turning within a metal sleeve and working within a closed metal 

 bos in oil. This was further developed in 1885 by Sir James 

 Anderson and Mr. A, E. Kennelly by providing a mercury con- 

 tact in a closed metal casing. This was constructed in two 

 halves, screwed together. On one half was a gland through 

 which the insulated wire from the grapnel rope passed into the 

 chamber, terminating in an insulated metal disc or contact 

 plate. On the other half was a hole for filling, closed by a set 

 screw. The casing was partially filled with mercury and the 

 remaining space with paraflSn. So long as the grapnel was 

 towing along the sea-bottom properly the contact box In the 

 grapnel rope would be horizontal or nearly so, and connection 

 would be made, thus ringing a bell on board. If the grapnel 

 approached the vertical, as it would do if suddenly entering 

 deeper water, the contact was broken and the bell ceased ringing, 

 thus giving warning that more rope must be paid out. 



Trott and Kingsford's automatic indicating grapnel (Fig. 

 115) proved itself reliable on several expeditions, as described 

 by Mr. H. Kingsford in a Paper before the Society of Tele- 

 graph Engineers in November, 1883. The weight of the cable 

 as it lies in the grapnel, causes a brass piston or plunger at 

 the root of the prong to be pressed down, and an electrical 

 contact is made at the grapnel, which completes the indicator 

 circuit through an insulated conductor in the heart of the 



