202 



iSUBMARINE CABLE LAYING AND REPAIPaNG. 



this purpose the prongs are mounted on pins, as at P, about 

 which the prong is capable of movement. The inner end of the 

 prong hag a tongue, as at T, which bears upwards against a 

 volute spring contained in the enlarged part of the shank at S. 

 When strained against rocks, therefore, the prongs give out- 

 wards, and as soon as the obstacle is passed the internal spring 

 acts on the tongue and restores the prong to its position again. 

 When the cable is hooked the prongs do not give way, because 

 the cable lies opposite the pivot of the prong, or so close to it 

 that no leverage is exerted. This was brought out in 1876, and 

 in 1886 Prof. Andrew Jamieson further developed the design by 

 using two prongs only, of larger size, and providing better means 

 for retaining the cable by a recess in the boss near the pivot of 

 the prong. To ensure one or other of the flukes keeping down- 



FiG. 114. — Jamieson's Grapnel. 



wards, two spring stock arms were provided projecting outwards 

 from the shank at right angles to the flukes. The ends of 

 these arms were specially formed to prevent their sinking in the 

 ground, and it was intended that they should give inwards when 

 the grapnel came against rocky obstructions or crevices. 



Special indicating grapnels have been devised for giving a 

 signal on board by the ringing of a bell when cable is hooked, 

 or to show when the grapnel enters deeper water and requires 

 more rope paid out, or to indicate amongst a number of cables 

 laid together when the right one is hooked. 



As regards the latter proposition, the idea has been for one or 

 both stations to put an intermittent current on the conductor 

 of the cable which the ship intends to raise which will act In- 

 ductively upon a coil within the grapnel and so give a telephonic 

 signal on board. But the scheme has not come to any practical 

 use owing to the uncertainties of apparatus attached to it, and 



