402 Mr. W. Sutherland on the 
Thus the increase in volume of the bulb is — 
4-4 x (70)? 
32x 6x10" 
=7ra*lpy x 7800 x 10-1". 
du= marl py x 
The compressibility of water is about 41071, so that 
the diminution of volume of the fluid under a hydrostatic 
pressure is 
dvup=7a'lp x 4x 10-4. 
The expansion of the glass vessel under the stresses of 
electrical type is far more important than the contraction of 
the fluid under the hydrostatic pressure of Mr. Walker’s 
theory. I therefore think that, so far from being crucial, 
Quincke’s experiment gives no support to the latter theory, 
and can be readily explained by the stresses of electrical 
type. 
Physical Laboratory, Glasgow. 
December 12, 1903. 


XLIX. The Dielectric Capacity of Atoms. 
By WILLIAM SUTHERLAND *. 
{ Gaare electron theory imparts more interest than ever to 
the investigation of the properties of atoms. At the 
present stage of this theory the electrical properties of atoms 
demand investigation from every possible point of attack. 
The dielectric capacity of the atom being the most funda- 
mental of such properties, it seemed to me desirable to inves- 
tigate it by means of certain principles developed in a paper 
on “ Ionization, Ionic Velocities, and Atomic Sizes” (Phil. 
Mag. [6] ili. Feb. 1902). In that paper it was shown that 
at infinite dilution the ionic velocity ;A) of an element 1 
whose atom has a radius a, and a dielectric capacity K, 
dissolved in a solvent whose viscosity is 7 and dielectric 
capacity Ky is given by the equation 
1Ap= ve"K,/67rna, Ky, : . . <r 
where v is the valency of the ion and e¢ is the electric charge 
of a monovalent ion. _In seeking to verify this relation by 
means of published experimental data, in the absence of 
measured values of K, the dielectric capacity of the stuff of 
* Communicated by the Author. 
