XII. i] MAGNETIC TUBES IN ROTATION 161 
to that due to an electrostatic charge, that is, a field varying 
inversely as the square of the distance. The equivalent electro 
static charge for a single system would be proportional to the 
magnetic moment (M) of the elementary magnet and to the 
angular velocity (co) with which the system is rotating. 
Further, Whittaker drew attention to the fact that for a 
given direction of the axis of the magnet there were two possible 
! fafci i 
’pilC!'¿¡IS 
ü m % 
^ctma 
1 & iwpiei 
fr town tot 
'fUffltUB tlfflyj- 
*oi positive 
i tact litt 
s been iiiown eari: 
itenceittefc 
on, anopfy 
vedoi aspiysoic 
omagnetic tnfei’i 
In tile preati 
quantmmagKi 
heir angular ie 
no Seid set op k: 
connection tas 
iv be said at tie s- 
pecuianveinciE 
T. fiittaferte 
if tile eiectrostatiii 
Fig. 23.—Magnetic Tubes due to a Dipole. 
s in rotation. Sii 
1 to a magnetic I 
vires about ties 
rnduced ffiticti ti 
ls tile square&■ 
¡ted at random 
at a distances 
attar in M 
directions of rotation for the magnetic tubes, thus suggesting 
the possibility of interpreting the difference between positive 
and negative electric charges. 
In imagination we may isolate a single quantum tube, such 
as that shown in Fig. 23, passing through the points P and Q, 
and discuss the electric field associated with that particular tube. 
It is to be noticed that the velocity at P will be less than that of 
light, even in the limiting case in which the velocity of the point 
D in the equatorial plane approaches that of light.