(-317)) 
of light the regular, in others the irregular ways of movement are 
more prominent. As my considerations will be simplest for a gas, 
and we are there most inclined to. think of vibrations in the mole- 
cules, I have chosen the first conception; and that in very simplified 
suppositions, hoping that these may be extended for processes such 
as really occur in nature. I imagine namely a great number of 
molecules spread in space which I suppose as vibrating, all with 
exactly the same period. I leave out of account the change of the 
period caused by the DoreLer effect. I suppose that for those mole- 
eules vibrations in tke direction of the z, y and z-axis are on an 
average equally represented, while also all phases equally probable. 
These suppositions are sufficient for finding something about the 
distribution of the forces, without our having to determine whether 
or no all molecules have the same amplitude; and if not, how the 
distribution of the amplitudes will be. 
Let us now consider a volume element dr. The action of it at a 
certain distance will be only determined by its electrical moment 
and the way in which that changes, and not by the way in which 
that moment is spread over the element. 
If the moments of the molecules now had the most probable distri- 
bution, i.e. if all directions and phases were exactly equally repre- 
sented, the moment of the element would be always 0 and no radiation 
would take place. The most probable distribution, however, is itself 
highly improbable, and generally a deviation will be found. This 
deviation is the cause of radiation. Let us assume that the unity of 
volume contains x molecules. Let us represent the components of 
their vibration by: 
Zat TE 
Gy = dir €03. 7 ++ ax2 stn. 7 
Jt a ee 
Os diy COR agg sin. — 
y y T y T 
2nt Spar tr je 
Vi ah 
and let us call the number of the molecules per unity of volume, 
the amplitudes of which are contained between the limits: 
Ari, Ax2) Ayly Ay, Az and az. and 
ay + dari, Ax2, day9, ay -+- day, ay2 duo, 01 -+}- daz} and A9 En dazo, 
Fax aas apr ay? dar 422) day, dara day, days daz) daa or Fda, 
