(966 ) 
We may further deduce from (1), taking into account (1) and AD, 
Div & == 0, 
and consequently Div 8 = 0. 
Now the expression MotM we have found for the current that 
is equivalent to the magnetization, shows immediately that the distri- 
bution of this current, taken by itself, is solenoidal. We conclude 
from this that 
DE ne En 
From AL) we may deduce, if we mtroduce the value (26), 
RotB=AarS Aa Rot M, 
or, taking into account the relation 
= H+4aM 
which results from (27) and (28), 
Rot DURE eeN eS NN 
Finally we find, by (IV) 
Rot @ == = Seiad Keer ei 
and by (V) 
Din B Dir or Se er oe 
We have thus been led back to the equations of the electromagnetic 
field in a form that has long been known. In this form we may use 
them without even thinking of the individual electrons. As soon however 
as we seek to penetrate into the mecanism producing the phenomena, 
we must keep in mind the definitions that have been given of the 
different quantities appearing in the equations and the manner in 
which they are connected with the distribution and the motion of 
the elementary electric charges. The formulae (27) and (28) e. g. show 
the precise meaning that is to be attached in the theory of electrons 
to the terms “magnetic force” and “magnetic induction”: 
The equations (I')—(V') may be applied to all bodies indifferently. 
If is otherwise with the formulae expressing the relation between 
S (or ®)-and &, and that between B (or DM) and H 5: the form of 
these depends entirely on the particular properties of the bodies con- 
sidered. I shall not here diseuss these more special formulae ; in order 
to deduce them from the theory of electrons it is necessary to con- 
sider the forces acting on the electrons in a conductor, the “molecular 
motion” of these particles and the cireumstances which determine the 
electric and magnetic moments of a single molecule or atom. 
") See Vorer, Electronenhypothese und Theorie des Magnetismus. Nachr. d. Ges. 
d. Wiss. zu Göttingen, 1901, Heft. 3. 
