THE LOCALISATION OF BKEAKS AND FAULTS. 373 



25 milliampares, the corresponding readings being from 48 to 

 150 divisions. 



Mr. Schaefer also suggested compensating resistances to 

 malie up for the fall by joint resistance, so that the total 

 resistance of the instrument should be the same for any range, 

 these extra resistances to be of manganin so as to have no 

 temperature variation. The compensation might be applied to 

 both shunts or to the 150 shunt only. In the latter case the 

 resistance of the instrument for the 50 and 150 ranges would 

 be equal and much lower than if compensated up to the 

 resistance of the coil. The instrument can also be used as a 

 direct-reading voltmeter by putting a resistance of 1,000 ohms 

 in series with it. In this way it is very convenient for taking 

 the voltage of the testing battery. 



The Sullivan Galvanometer. — For boardship use it is essen- 

 tial that the galvanometer suspension is balanced so that the 

 zero is not disturbed by the ship's motion in any direction. 

 This condition is most successfully attained in the well-known 

 Sullivan Universal Galvanometer. The instrument is of the 

 moving coil type, with permanent magnet field, on the principle 

 of the Kelvin recorder and the d'Arsonval galvanometer, and 

 is arranged as illustrated In Fig. 221. Mr. H. W. Sullivan, 

 in designing this instrument, brought to bear experience of 

 the difficulty and time involved in the repair, re-adjustment 

 or balancing of suspensions at sea, and set himself to provide 

 one in which the adjustments were simple and easily effected. 

 He used flat wire instead of silk fibre for the suspension, so 

 giving directive force to the coil, and securing thereby a system 

 much more readily balanced than the mirror and fibre system 

 on account of the less ratio between the weights of the moving 

 part and its suspension, also having the advantage of being 

 unaffected by atmospheric humidity or change of temperature 

 as in the case of silk suspensions. 



The coil, suspension, balancing and damping devices are 

 mounted on an independent brass frame, shown in Fig. 222. 

 When placing this frame in position the hollow sleeve S fits over 

 an upright brass rod in the base of the instrument. The rod 

 is on a sliding base-plate, so that the whole frame and coil can 

 be shifted more or less away from the magnet poles, and the 

 sensitiveness of the instrument thereby altered to suit the 



