In A the two atoms revolve in continuous contact under their
mutual electric attraction; in B and C they are separated by the
centrifugal tendency. In B the two atoms are describing elliptic
orbits about their common centre of inertia, while in C they describe
hyperbolic or parabolic orbits. In the set C the atoms may thus bo
regarded as practically free. We may also contemplate the possibility
of multiple molecules.
The individuals of the three fundamental sets may change from time to time ; but we may suppose that a permanent average distribu- tion will finally obtain.
The proportions of molecules in the three classes must be deter- mined by the consideration that the velocities satisfy the conditions appropriate to the specified class. There is no discontinuity in the case of B and C, and the limits of integration for these have been determined. I have not obtained a satisfactory estimate of the pro- portion of A to B, as a sort of discontinuity occurs. Inasmuch as the electrical energy of the two atoms when close together is very great compared with the mean kinetic energy at ordinary temperatures, the molecules are mainly of the class A.
It has thus been established that a small proportion of molecules are always dissociated, a point which has recently been established experimentally. I also find that although on the whole the numbers of B and C together diminish as the pressure decreases, yet the pro- portion of C to B increases as the pressure decreases. This would account for the increased ease with which electrical discharge takes place through a gas under reduced pressure.
Passing next to the magnetic properties it is shown from a former paper* that diamagnetic effects are produced by the free atoms on establishing a magnetic field, and that the effect disappears very soon. It is also shown that the molecules contribute positive magnetic susceptibility ; and the formula obtained, which is complicated, agrees well with Quincke's experiments on the subject.
Turning to the dielectric constant, it is found that
K = l+kp/d 2 ,
where p is the pressure, the absolute temper \ cure, and h is a constant depending on the gas. This differs essentially from other theories which have been proposed, as regards the temperature varia- tion, the usual result being
K = l+kpjO.
We may see without analysis how this arises. The electrical field is capable of affecting the rotational energy of the molecule, and thus the
- " On the Phillips Phenomenon," ' Electrician," August, 1899.
