4 WlLDE, Points of Chemical Philosophy. 



weights of which are the same as their specific gravities 

 at ordinary temperatures. The atomic weight of 2 is 

 further confirmed by the remarkable parallel differences 

 in the atomic weights (6 and 16) of the head members of 

 the positive series Hn and H2n. 



I have stated in my former paper that there is 

 abundant reason for concluding that no elements exist of 

 higher atomic weights than those shown in each series of 

 the table ; the series H211 containing radium, consequently, 

 closes with lead. 



From the fact that lead is always found in radio- 

 active minerals, and for other reasons, Boltwood 1 and 

 Rutherford 2 have each independently arrived at the con- 

 clusion that lead is the final or end product of the 

 transformation of radium. 



Dumas and other eminent chemists long ago classified 

 lead as the homologue of the alkaline-earth metals, 

 but the requirements of Mendeleeff's periodic system 

 necessitate the placing of this element in his fourth 

 group as the homologue of thorium, and the anomalous 

 substitution of mercury (200) for lead in the series con- 

 taining the alkaline-earth metals, (v. Addendum.) 



It is a singular circumstance that, notwithstanding the 

 wonderful powers attributed to radium, no chemist has 

 yet seen or handled the element in its metallic state, in 

 order that its general physical properties might be made 

 the subject of investigation. 



In my last paper read before the Society, 3 reference 

 was made to the property which the sulphur combinations 

 of the positive series H2n possess of becoming luminous 



1 Phil. Mag., April, 1905. 



2 Journ. Client. Soc, November, 1905. 



3 Manchester Memoirs, 1903. 



