( 586 ) 
which we are now discussing. It is not even self-evident by any 
means that a temperature could be defined for every conceivable 
system. And we even know that two walls of the nature Lorentz 
has loc. cit. imagined, when their particles had the same kinetic 
energy, so that they were in equilibrium of temperature as regards 
their conduction of heat, would transfer heat to each other by 
radiation. And reversely, they would not be in equilibrium of con- 
duction of heat when they were in equilibrium for the radiation. 
As now in the derivation of the law of SrepHan with the aid of the 
cycle of operations described by Barrorr and BOLTZMANN use is made 
NÀ dQ 
of the supposition that 9 = ae this law need not hold for an 
arbitrarily imagined body, and ean only do so incidentally. 
In virtue of the above I think that other explanations are called 
for, which might be able to reconcile theory and observation. And 
it seems to me that such an explanation might be found in this 
direction that we assume that the supposition A is not fulfilled, and 
this we may do without introducing new hypotheses, without coming 
in conflict with the current theory of electricity. It is true that 
Jrans and Lorentz have come to the conclusion that supposition 
A is satisfied, but it seems to me that their considerations only refer 
to electrons which possess a mechanical mass; they do not seem to 
apply to electrons without mechanical mass. 
To show this we shall consider systems agreeing with those 
examined by Loruntz'). A number of electrons are enclosed in a 
parallelopiped space with totally reflecting walls. It is true that the 
objection advanced by Ritz to such walls, is not to be entirely 
refuted, but without this supposition we can never imagine a system 
in statistical equilibrium, and when we think the space so large that 
the radiation reflected by the walls, has long been absorbed before 
it has reached the central parts, the condition in the central parts 
will most likely not be influenced by the walls. Besides, the reflected 
radiation will behave in almost the same way as if it was emitted 
by a medium of the same nature outside the enclosed space, so that 
also the parts lying nearer the walls will probably be in the same 
condition as if the walls did not exist, and the medium extended 
also outside the walls. 
1 shall assume the electrons to be spherical, so that their position 
is entirely determined by the cartesian coordinates \ YZ of the centre. 
As further data I shall choose the electrical and the magnetical 
forces in the different elements of space. In their stead we might 
1) H. A. Lorentz, Nuovo Cimento I. c. 
