TWENTY-SEVENTH ANNUAL MEETING. 

 Rubidium Hecdecade. 



103 



Valence. 



I 



11 



Ill 



IV 



Ill, V 



II, VI 



II, VII 



II, IV I 



VIII ) 



I 



II 



Ill 



IV 



III, V 



II, VI 



I, VII 



Cesium Hecdecade. 



Between Cs and Ba is a major step; between Ba and La is a minor step; 

 Ce and Nd appear to be twins; otherwise Nd is superfluous. 



Tiie entire hecdecade needs revision. The first four elements, whose spe- 

 cific gravities have been carefully determined, appear to have their atomic 

 weights too high to correspond with their specific gravities. Especially is 

 this true of Barium. If the harmonic series of atomic weights were in- 

 creased three units. La would be the only element outside the limit of va- 

 riation. Barium would then correspond exactly as to its atomic weight and 

 specific gravity, owing to the recent redetermination of the atomic weight by 

 Richards. Care was taken in this redetermination to eliminate all lighter 

 metals of the same group, as Ca, Sr, etc. Effort should now be made to 

 eliminate from Ba. La, and Ce. the heavier metals, II, III and IV of the 

 Tantalum octave. This should bring them within the harmonic law. 



