360 



M. C. Cheneveau on the Magnetic Balance 



marked 2 to 0", where it again stops and afterwards returns 

 to 0, as shown by the arrow 3. 



Fior. 3. 



Direction of Motion of Magnet 



It is easy to explain in a similar manner the motions of a 

 diamagnetic body which will of course be the reverse of the 

 above, as the force is opposite in sign. Fig. 4 shows the 

 curve in this case. 



Fie;. 4. 



At every instant the action of the force is balanced by 

 the torsion of the balance wire. Tf c is the moment of 

 torsion per unit angle, and a the maximum deviation of the 

 arm at or 0' (fig. 2), the equilibrium condition is 



fl = ca, 



if I is the length of the balance arm. 



If the deviation is measured by lamp and scale, 



D 



2L' 



W 



(5) 



I) being the deflexion of the spot upon the scale, and L the 

 scale distance. 



