18 Mr. W. Sutherland on the 



0*4592. These results for H are very like those for He. 

 It may be mentioned that for oxygen if B = 8'29 instead of 

 6*16, the ratio would become 0"4941. The evidence as to B 

 for and N in their compounds is on the whole towards 

 making its value larger than that given by the kinetic theory. 

 It is rather remarkable that the valency of the non-metallic 

 elements does not influence their dielectric capacity. The 

 order of the element in its family asserts itself by the ap- 

 pearance of u in (8), but the valency of the family does not 

 appear. If in (8) we put p = M/B and ( N' - 1) V = CN - 1 )B, 

 we get the simple result that (N-IJ/N^EM 1 ^ 2 / 3 . That 

 is to say, that the index of refraction or the dielectric capacity 

 of the stuff of an atom of non-metal is a function of only its 

 atomic mass (weight) and u. In " The Dielectric Capacity 

 of Atoms" (Phil. Mag. [6 J vii. p. 402) it is shown that if 

 K is derived according to certain assumptions from the 

 atomic conductivity of the atoms as ions in aqueous solution, 

 then KBVV is nearly constant for both metals and non- 

 metals, V being valency. But in " Ionization in Solutions 

 and Two New Types of Viscosity" (Phil. Mag. [6] xiv. 

 1907, p. 1) it appears that K thus derived in the case of the 

 lhalogens is very different from N 2 , and must be interpreted 

 as K for slow electric alternations, while N 2 is K for rapid 

 •alternations. The matter requires further investigation. At 

 present we are dealing with K only as it appears in the 

 electric alternations of light. 



In this section then it has been shown that dielectric 

 capacity, both in atoms of combined metal and of non-metal, 

 can be explained by means of internal electric fields in the 

 atoms corresponding with the external electric fields which 

 produce cohesional force, otherwise called molecular attrac- 

 tion. The broad laws that the atom of metal is electrized so 

 that its moment is proportional to its radius, while the atom 

 of non-metal is electrized so as to have its electric moment 

 proportional to its volume, have been found to be fundamental 

 in determining the relations of dielectric capacity in the two 

 classes of atoms. It is also profoundly significant that the 

 radii of the atoms of combined metals should show simple 

 numerical relationships like 2, 3, 4, 5, 6 in the Li family, 

 while the volumes of the atoms of non-metals show a tendency 

 to similar simple relationships like i, 2, 3, 4 in the halogens. 

 It is evident then that electric conditions largely determine 

 the architecture of atoms. 



The cohesion of the constitutive pairs of electrons with the 

 aid of the special pair to form the atom demands investiga- 

 tion. The pair of electrons is to the atom what the molecule 



