310 



MAGNETISM 



where d is the distance of the centre of the deflecting needle from 

 the deflected needle, when we neglect small quantities. If then \\e 

 observe 6 and measure d, we know the ratio of H to M, for 



^ 

 M 



tan 



Multiplying this by the result of the vibration experiment and 

 taking the square root, 



27T./~2K" 



H 



Or another procedure may be adopted, and this N the more 

 usual. The deflecting magnet, always in the end on position, i- 



N 



FiO. 230. 



turned round the centre of the deflected magnet until the lathi 

 is in equilibrium and at right angles to the lonm-r. Then from 



FIG. 231. 



Fig. 231 we see that the angle through which the deflecting 

 magnet has been turned round is given by 



whence 



sin S 



T 



2M 



_ 

 sin 9' 



