^o6 Mr. Christie on the magnetism developed in 
torsion noted where the disk remained stationary by the 
action of the opposite forces of torsion and of the magnets. 
This was done at several distances ; and those distances, be- 
tween the magnets and the disk ascertained very accurately. 
In the observations with the disk which I have named A, the 
magnets were made to revolve with two different velocities ; 
one of nearly 12 revolutions per second, the other of nearly 
24 revolutions per second ; but with the disk C the magnets 
always revolved with the velocity 24 revolutions per second, 
as I found that I could keep more steadily to this velocity 
than to the other. The length of the suspending wire (No. 22) 
was the same in both cases 34.25 inches. The thickness of 
the magnets is * inch, so that I have added to the mea- 
sured distances between the upper surface of the magnets 
and the copper, to reduce them to the distances between the 
plane of the copper and a horizontal plane passing through 
the axes of the magnets. The following tables contain the 
results. 
Dish A, weight =3 1305 grains. 
Screw. 
Unscrew, 
Distance. 
Unscrews, 
Arc of torsion = force. 
Screws. 
Arc of torsion =? force. 
Arc. 
Time, 
Vel. 12. 
Vel. 24. 
Arc. 
Time. 
Vel. 12 . 
Vel. 24 . 
0.6 
I . I 
1.6 
2.1 
2.6 
e > 
1330 
480 
275 
*35 
80 
Not obs, 
I®IO* 
I 10 
I 10 
I 06 
0 
760 
270 
118 
60 
44 
0 
1870 
656 
270 
142 
72 
6 
1160 
455 
260 
1 10 
78 
m. s. 
I 09 
I 12 
I 09 
I 07 
I 12 
6 
700 
250 
95 
48 
36 
0 
1710 
604 
236 
120 
56 
