THE CABLE SHIP OX REPAIES. 217 



show that bottom is reached. Or, if the rope is paid out 

 at a considerable speed and without jerks, the moment when 

 the grapnel strikes bottom can be seen on the dynamometer 

 by the sudden fall of strain due to rope being relieved 

 of its weight, but this is only done in comparatively shallow 

 water, because the less the proportion that the weight of 

 the grapnel bears to the whole weight of grapnel and 

 rope, the less marked is the difference in strain shown on the 

 dynamometer when the weight of grapnel is taken off, and the 

 less easy to detect when occurring suddenly. 



An experienced hand will tell when the cable is hooked with 

 an almost dead certainty by sitting on the grapnel rope near 

 the bows. Of course, it is not uncommon to heave up after 

 some heavy strain on the rope and 6nd that the procgs have 

 been bent or torn off by some obstruction below. In that case 

 new prongs are slipped on or another grapnel is substituted. 

 It is as true in cable work as in other kinds of engineering 

 that nothing is so certain to happen as the uncertain. Even 

 when it is known, by the gradually increasing strain on the 

 rope on heaving in, that the cable is on the grapnel, it is 

 always an anxious time, for the cable may be buried and the 

 strain cause it to part at any moment. When parted in this 

 manner the length of the grapnel rope heaved in after the 

 occurrence is measured, and a note made of the depth at which 

 it parted. Or it may part below water when in sight at the 

 bows, or one end may be lost after the stoppers are put on. If 

 breakage occurs the ship must steam to a fresh position and 

 commence grappling again. 



Cables are armoured with a heavy sheathing of iron or steel 

 wires, in order to give great tensile strength to sustain 

 several times their weight when being raised from the bottom 

 during repair. But this very protection is subject to many 

 deteriorating conditions, and sometimes is a source of great 

 trouble. The author has seen cable coming inboard with the 

 sheathing in a very ragged condition, the first cause having 

 been attributed to corrosion of the wires through oxidation in 

 places where the preservative compound has worn off, or direct 

 galvanic action in places that have been in contact with 

 metalliferous veins in the ocean bed. In other cases it has 

 been ascertained to be due to abrasion against sharp pro- 



