178 



SUBMARINE CABLE LAYING AND REPAIRING. 



struck by lightning there are a number of points, both on the 

 cable and on the line side, to attract its discharge to earth ; 

 and the path is, in any case, through the uppermost fuse wire. 

 If the discharge is of a dangerous tension the top wire is fused, 

 and the connection between cable and land-line instantly 

 broken. The rod then falls by gravity, and the pin rests on 

 the next fuse wire. Thus the guard is automatically re-set 

 after every serious discharge striking the line, the small 

 interval of time elapsing between the breaking and remaking 



Fig. 89. — Bright's Lightning Guard. 



of contact being sufficient to prevent the back discharge from 

 doing damage. When all the wires are fused the rod falls on 

 a stud connected to the earth terminal and puts the cable to 

 earth, the land line being at the same time freed. Thus it is 

 readily known at the office that the stock of fuse wires on the 

 guard is expended and requires replenishing. The instruments 

 are made with any number of wires, depending on the con- 

 venience with which they can be replaced, the automatic re-set 

 having been found to save a good deal of time by lessening the 

 number of journeys to the cable-house. (For further study of 



