( 589 ) 
d&,. 
dt ; t= hn 
DE becomes very small for every element, and zero in the limiting 
A 19 
case that we take infinitesimal volume-elements, but the sum of these 
quantities for all the elements falling within a certain electron does 
not become zero, but when the volume-elements become infinitely 
small it verges to a certain limit, which is not to be neglected by 
: . Oye L 
the side of DX Here too, we must remember that we must not only 
differentiate with respect to €, where this quantity occurs explicitly, but 
also that ©. depends on &,. For by varying €, we vary o, unless 
we take care to bring about a suitable modification in €. in the 
surrounding elements. 
: } 1D r—=n O7 7 : 
Equation ——- = — = — now indicates that we have a stationary 
D dt see Op, 7 
state if on every path covered by a system the density of phase 
loa. a 
—— fl Ed 
fa? 5 Op 
is made to satisfy De 
f , Op 
form which 2 assumes it seems hardly possible to draw further 
. P 
conclusions, unless we succeed by a felicitous reduction’ or by 
making a better choice of the independent variables from the begin- 
ning in rendering this sum in a much simpler form. 
For the present [ must confine myself to pointing vut that it seems 
that in this direction a solution is to be found of the contradiction 
which has existed up to now between theory and observation. And 
if this should prove to be the only way in which this can be done, 
it is a qualitative proof of the existence of electrons without mecha- 
On account of the intricate 
nical mass. 
We must, however, point out that it can only prove that some 
electrons do not possess any mechanical mass, not that this would have 
to be the case for all electrons. For as soon as electrons without 
mechanical mass occur, the relation >? <0 is not fulfilled. The 
supposition that some, e. g. the positive Sieciions will possess mecha- 
nical mass, and others e. g. the negative electrons not, is by no 
means excluded by these considerations. 
If we should take Kircnnorr’s law as holding for arbitrarily 
imaginable walls, the partition of the energy in the normal spectrum 
would of course never enable us to conclude anything concerning 
the nature of the bodies by which the radiation is emitted. If, however, 
