THE LOCALISATION OF BREAKS AND FAULTS. 379 



An improvement has been added by which the coil can be 

 accurately centred between the magnets. At the bottom of 

 the suspension frame an adjustable screw stud of ivory or 

 other hard insulating material is fixed, so as to project on both 

 sides of the frame. The stud is of the same width and fits 

 into the guides as the frame is lowered into position. It is 

 provided with tommy holes, so that it can be screwed to the 

 left or right by a small rod. By adjusting the stud the frame 

 can be altered slightly in position, and the coil adjusted to an 

 exactly central position between the magnets. 



The instrument is both very sensitive and very deadbeat. It 

 can be instantly adjusted for speaking even through the 

 longest cables, and restored immediately for testing. It is 

 equally serviceable for fault localisation and insulation tests on 



Fig. 224a. — Balancing Sullivan Galvanometer for Pitching. 



short lengths. It is steady and reliable in all weathers, all 

 motions of the ship and all changes of ship's course, and 

 unaffected by earth or stray fields. 



After completion in the factory these instruments are tried 

 in all directions for balance by mounting on a cradle board 

 complete with lamp and scale (Fig. 224a). The board has 

 curved feet so that it can be rocked sideways, in imitation of 

 the rolling of a ship. For the pitching movement, so inter- 

 esting to first-timera, the board is lifted at one end and then 

 tilted as shown in the illustration. If the balance is out, the 

 spot of light will deflect more or less from zero due to the 

 weight of the coil not being exactly equal all round the centre 

 of suspension. The direction of deflection indicates at once the 

 heavier aide of the coil. This is very easily and quickly cor- 



