253 
dently of the magnetization the body possesses moments of momentum 
about its axes ON and QZ. In addition to these it has a magnetic 
moment of momentum about OZ So at all events the total moment 
of momentum will fall along a certain line OZ in the plane ZOX. 
If now this resultant OL did not coincide with OZ, it would 
continuaily change its direction because of its rotation about OZ. 
The corresponding change in the moment of momentum would be 
perpendicular to the plane ZOL and this ought also to be the 
direction of the couple acting on the body. We have seen, however, 
that this axis lies 7m the plane 7 OX. Hence OL and OZ’ must 
coincide. 
The condition for this is, that the moment of momentum about 
OX, divided by that about OZ must be equal to — (7 6. Thus 
we have 
Dali p sin 6 
2 == ig zd 
Cy cos 6 
or, writing again A + D for A, 
D (w—y sin 0) — A p sin 9 
— Si tq A, 
Cp cos 6 
from which we infer 
D Wy sin @ 
Te = : 
CSA Y 
or if we introduce the value for wf sin @, given by (5) 
| Ly 9 
BUR ae = a esa een Peletier UO 
OSS fp 
To investigate, whether the experiment will give a perceptible 
value of 64, it is desirable to express sin @ in quantities that can 
easily be “estimated. As D and wp are unknown, we shall introduce 
instead of them the magnetization / of the body. 
If O is the area of a circular current, its magnetic moment in 
the case of only one electron circulating in it, is 
If we take the sum for all the circulating electrons this expression 
becomes 
. . ? . 
Ff=S i ewr = —wvs mr’ = wD. 
2 ) 
zm 2m 
Hence 
