THE LOCALISATION OF BREAKS AND FAULTS. 377 



Tested in cotnbiaation with the universal shunt for equality 

 of capacity throws with different multiplying powers, the 

 results were : — 



Universal Shunt of 1 0,000 ohms, 1 cell through — 

 20 microfarads with multiplying power 10 produced swing of 320 



The swings with the shunt of 10,000 ohms are accurately 

 proportional, but not so with the shunt of 100,000 ohms. For 

 instance, the throw with 10 microfarads was 208, and with 

 20 microfarads 385, considerably short of the proportional 

 throw (416). The reason for this is that the resistance of the 

 shunt or joint resistance of galvanometer and shunt which is 

 very high is in the path of the charging current and consider- 

 ably lengthens the time of charge. And as the moving coil 

 has a quick swing, it moves away before all the charge has 

 passed, and hence does not indicate the full charge proportion- 

 ately. It is obvious, therefore, that with this galvanometer 

 it is not advisable to use a universal shunt of more than 

 10,000 ohms, at all events, for capacity throws. 



In the present form of this instrument one of the coil 

 terminals is permanently connected to the metal frame and 

 magnets in order to neutralise static charge on the coil 

 when the battery is on. It was noticed that a deflection 

 occurred when either pole of a battery was joined to the coil, 

 the deflection being always in the same direction, whichever pole 

 was connected. As the circuit was not completed it pointed to 

 a static charge being the cause and this was found to be the case. 

 On connecting one pole of a battery to the coil under these 

 conditions the static potential of the coil became raised with 

 respect to the frame resulting in an attraction of the coil to 

 one side. The deflection was only small, but nevertheless 



