GASEOUS REFRACTIVE INDICES 285 



Table II. 



H 



139 



He Li Be B C 



70 



NO F Ne Na Mg Al Si 



149 x 2 135 x 2 96 x 2 70 x 2 



P S CI Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu 



149 x 8 138 x 8 96 x 8 70 x 8 x x 8 ? 



Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Ru Rh Pd Ag 



2060 129 x 12 130 x 12 93-8 x 12 70 x 12 X x 12? 



Cd In Sn Sb Te I X . Cs Ba La Ce Di 



2 "7S 125 x 20 96 x 20 70 x 20 j-x 20? 



Yb Ta W Os Ir Pt Au 



Hg Tl Pb Bi Th 



1866 



U 



than in that of a rectangle. This scheme has certain very- 

 suggestive features. It fits in very well with the periodicity 

 of the atomic volumes, and satisfies most of the requirements 

 of such a table. Above all, it lends itself to the consideration 

 of those fascinating speculations on the origin of the elements 

 which are absorbing the attention of so many eminent physicists 

 and chemists at the present time. If atoms are made up of 

 ponderable matter and relatively imponderable electrons, as 

 the phenomena of radio-activity indicate ; if successive elements 

 are built up, as Professor J. J. Thomson suggests, by the 

 addition of electrons forming rings round a central mass, each 

 more numerous than the last ; if there is a close connection 

 between valency and the number of electrons per atom, or the 

 number of electrons after subtracting the number required to 

 form a perfect ring ; if successive powers of two are such 

 numbers ; and if refractivity is closely connected with the 

 number of electrons and the forces under which they vibrate, 

 then we can dimly perceive that the pyramidal shape of the 

 table (indicating a gradual increase in the amount of matter 

 required to make the wheel of evolution come full circle as 

 the atomic weight increases), the discontinuity in the refrac- 

 tivities, and their connection with valency are all intimately 

 connected. What the configuration of the atom must be in 

 order to satisfy experimental facts is the fascinating problem 

 which continues to tantalise us. It can hardly be doubted that 

 if we could obtain the indices of all the elements correctly, 



