A Pocket Galvanometer. 



By 



Aikitu Tanakadale. 



Assistant to the Professor of Physics, Imperial University. 



§ I. Coilless Pocket Galvanometer. 



If a permanent magnet be fixed by an axis through its magnetic 

 axis, it will be perfectly restrained from responding to external mag- 

 netic influences. But if the magnet be fixed by an axis which is only 

 parallel to, and not coincident with, its magnetic axis, it will still be 

 in neutral equilibrium in a uniform magnetic field. In other Avords, 

 a magnet so supported cannot be distinguished from non-magnetic 

 bodies whatever be the streno-th 



of the field so long as this re- 

 mains uniform ; induction being 

 neglected for the time. 



If one or any number of 

 small bar magnets be vertically 

 attached to a suspended piece of 

 wood, or if a horse-shoe magnet 

 be hung by a string as in Fig. 1., 

 such a system may be realized. 

 The astatism is quite independ- 

 ent of the number of magnets, 

 as each several magnet is in neutral eqnilibrii 



Fig. 1. 



