MOMENT OF INERTIA OF MAGNET A. 67. 



63 



After adjusting the instniment and suspending A. 67, the following experiments 

 of vibrations were made : — 



The mirror was below the magnet in these two sets ; in the following four sets it 

 was above. 



Magnet suspended with inertia ring Z, of the following dimensions: Outer 

 diameter 2.322 inches; inner diameter 1.837 inches; thickness 0.188 inches at 

 69°; weight 648.937 grains: hence Jii = J (r^ + ri'')«<; = 4.936 (in feet and grains), 

 /9 7,r, = 0.69338. 



Omitted, disturbed by a current of air. 



