306 
Two limiting cases. 
1. If J is large with respect to a (gases), (4) or (4a) evidently 
approaches to 
2 
j= Rox OE ET s—-— +! Stee sone) 
and this not only for z=0O, but also for finite values of z, provided 
they are not large with respect to /. 
This is, therefore, the limiting value of the action, when the 
moving molecule, with comparatively large distances of the molecules, 
is between P and Q, if not too close to one of them. The action is 
in inverse ratio to the fifth power of /, and directly proportional 
to the square of the radius a of the orbit of the electrons. It remains 
pretty well unchanged atthe same value of 2, when J/ moves from O 
slightly to the left or to the right, but it is on the contrary pro- 
portional to the deviation «w of the electron in its orbit; hence it 
is purely periodical. Kor «=O the action is =O, but not so for 
x—=-+a or x=—a, even if M is in the neutral point 0. 
As regards the action between J/ and P, resp. Q separately, we 
have according to (1a) and what was found above: 
Fte? =(P, + 2P,z + 3P,2? +...) —(P, + 2P, (ee) + 3P, (e—<)’), 
Le. 
Fi: = 2Pet 3P, (2ze¢—2’) te AP, (827a—3227 + a°)+... | 
and likewise . 
Fi:e? = — 2P,a + 3P, (224 —2*) — AP, (Bz Baart 4 a*)4... 
so that about half of the total action (f',—F’,):e? =—4P,4-+ ete. 
comes from the atom P; the other part, as the action of a force in 
the opposite direction, from the atom Q. If e.g.2—- a, the electron 
is as far as possible in the direction of Q, and M/ will be attracted 
by P with a force = about 2P, ae’, and repelled by Q with an 
almost equal force. (Here P, = 3a’: /°). 
When the gas-molecule M/ moves towards P, iis velocity u will, 
accordingly, also undergo periodical modifications, till it has approached 
P so closely, that at 7—z—about 2a, the attractive force being 
still finite at &= + a, the repulsive force begins already to approach 
infinity at «— —a. (see $ 10); hence the velocity is reduced to 0, 
after which M/ moves back (collision). 
But with very small values of u it may occur that this return 
already takes place long before P has been reached. We shall revert 
to this in the next paragraph; it is the well-known case of gas- 
degeneration. 
