406 
Mr, Christie on the magnetism of 
Direction of ro- 
tation of plate’s 
upper edge. 
0) c5 <u 
^ O 
S c (U 
o 04W 
cx a 
V 
u W 
^ dJ ^ 
M s G 
O « IS 
3 > i- 
5 O S 
3 ^ 
u 
’rt 
rt 
. <u 
Wto E 
o 02 E 
o 02 E 
o 04W 
o 06W 
o 08W 
E to W 
Time of 
observation. 
2 50E 
2 50 
2 46 
2 44 
2 42 
2 46 
I 22 
2 42 
2 42 
9 35 
10 05 
11 10 
20 35 
21 48 
22 01 
22 17 
22 28 
22 40 
24 05 
25 35 
During this time the plate was kept per- 
fectly stationary, and care was taken 
that the apparatus should not be in the 
least disturbed. 
C After 21** 48” the plate was made to revolve 
I slowly once from W to E. 
C After making the plate revolve several 
\ times and more rapidly, 
f Making the plate revolve several times 
\ from E to*W. 
f Making the plate revolve once so slowly 
I that the time of rotation was 3™ 26". 
r The plate kept perfectly stationary since 
\ 22^ 40"*. 
f Making the plate revolve through 30° from 
W to E, and then bringing it back 30” 
( from E to W. 
C Making the plate revolve through 90° from 
< W to E, and then bringing it back 90° 
from E to W. 
r Making the plate revolve repeatedly and 
\ rapidly. 
From these investigations it appears, that the effect pro- 
duced on the iron by its rotation is permanent, so long as the 
plate remains stationary ; that it is independent of friction ; 
that it is so far independent of velocity, that the iron can 
scarcely be moved so slowly that the whole effect shall not 
be produced ; and that the whole effect is produced by mak- 
ing it perform only one fourth of a revolution. 
Shortly after I had discovered these pecular effects to be 
produced by the rotation of iron, I pointed out the general 
nature of the phasnomena and exhibited some of them to 
Mr. Barlow, and he has since made some experiments on 
the rotation of spherical shells, in which he has found that 
