( 316 ) 
The integrals with respect to 2, y and z must here be taken 
between — oe en +o, thore with respect to & 7 and ¢ between 
—ta and + 3a. Therefore H' is equal to H, the only difference 
is that the coordinates have been interchanged with the velocities. 
The unity of time being arbitrary 4H will remain also constant 
after an arbitrary time. M changes only if the molecules which 
are moving away, C cannot reach infinity, but come in collision with 
a new wall and are arranging themselves into a state of stationary 
movement in the new volume. 
The great importance which I think ought to be attached to the 
collisions, made me look for its analogue in radiation. For this 
purpose I have had to make a supposition on the nature of radia- 
ting molecules. I have namely imagined them as Hertz’s vibrators 
all of the same period. In this case the emitted radiation also has 
everywhere the same period. Its amplitude varies from point to 
point and changes with the time. As collision of a special kind I 
consider the action of an alternating electric force of a determinate 
direction, intensity’ and phasis on a molecule, which is in a vibra- 
tion, the direction, amplitude and phasis of which are also deter- 
minate. According to this, every molecule is always in collision. 
This view agrees with an observation of Prof. PLANCK, who says 
more generally 1): 
„Durch die Strahlungsvorgänge im freien Felde kann also keine 
Entropieänderung des Systems hervor gerufen werden. Dagegen 
bewirkt jeder Resonator im allgemeinen eine Entropieänderung der 
ihm treffenden Strahlenbiindel.” 
its 
Law of the distribution of Electrical forces. 
Concerning the nature of radiating molecules there are principally 
two conceptions. The first is that a source of light has a periodical 
movement, which gives rise to more or less regular vibrations in 
the ether. The other conception is that the molecules bring about 
perfectly irregular disturbances of the ether, which get a seeming 
periodicity from the apparatus by means of eee we observe. 
Possibly both these suppositions are partly true and in some sources 
) Berliner Sitzungsberichte XXV 18 Mai 1899 pag. 467. 
