NOTES ON THE REPRACTIVITIES OF THE INACTIVE GASES. 



359 



Here^ too, it will be iioticed that tlie quotient of tlie tirst and tliird 

 élément of each séries is a liiglier number tlian that fnrnislied by the 

 other tliree éléments; and tliis alfords a strong proof of the periodicity 



7.0 



G.O 



5.0 



.^ 4.0 



^ 3.0 



2.0 



1.0 



20 40 (ÎO 80 



Atomatic Weifflits. 



100 



120 



140 



of ail three séries of éléments. The analogy is also seen in the accom- 

 panjing diagrara, where ordinates are atomic weights, and abcissae, 

 refractivities compared with air as unitj. 



