444 Hlectric Origin of Rigidity. 
velocities of rotation are not changed by the proximity of 
matter in the same way as those of translation. These 
stipulations then give us Maxwell’s law K=n’?. As is now 
well known, many “substances like water have different values 
of K, ‘according to the circumstances of measurement, this 
phenomenon being connected with molecular structure and 
to be allowed for in the interpretation of Maxwell’s law. In 
“The Dielectric Capacity of Atoms” (Austr. Assoc. Adv. Se. 
Jan. 1904) I have shown that values of K for the stuff of 
ions can be calculated from the ionic velocities, and that for 
the values found for many atoms the following law holds : 
(K/y)? B= constant, . 4°). 
where B is the volume of the atom and v its valency. 
This makes vU?/B=constant. 
When v=1 we have U?/B constant, and IU?/IB also 
constant; and as we assume I to be constant, we have the 
kinetic energy of translation of the ether in all monad atoms 
the same per unit volume. For atoms of higher valency it 
would appear that the effective inertia of the ether of the 
atom for translatory motion is proportional to v?. This 
relation would establish a connexion between the ether of an 
atom and its valency, that is between the special doublets 
which confer its valency on an atom and the neutrons of the 
ether.. This requires further investigation. Itis noteworthy 
that the translatory kinetic energy of the neutrons in a 
monad atom is the same per unit volume in all atoms, just as 
in all gases at the same pressure and temperature the trans- 
latory kinetic energy per unit volume is the same. Fitz- 
Gerald’s idea is substantially the same as: Fresnel’s, who took 
the ratio of density of zther in matter to density of free 
ether, or p/p., to be equal to the square of the index of 
refraction, which by Maxwell’s law becomes equal to K. 
But if the translator ry momentum of the neutrons per unit 
volume is o. same in ether everywhere, then Up= Vp, and 
pjpe=V /U= which shows that FitzGerald’s principle 
brings us a to Fresnel’s important law. It should be 
noticed that in the foregoing we have taken account of three 
distinct ways in which kinetic energy can exist in the ether: 
first by rotation of an electron round its centre, connected 
with magnetic permeability of the zther ; second ‘by rotation 
of neutron, which is the same as era ncletan of electron ; and 
third by motion impressed on the doublets of matter by the 
atoms, this being the origin of radiation. 
Melbourne, February 1904. 
ell 
