PRESIDENTIAL ADDRESS. 



13 



(5) The arrangement of any vertical column is designed to show 



that an element is similar in valency and other chemical pro- 

 perties not always to the element immediately below, but to 

 the next but one. 



(6) The large Roman numerals (I. -VIII.) in Table II. indicate 



the usual valency of the element. 



Table II. 



i-"eh 



;ro=v 



Discontinuity within the Periodic Table. 

 Discontinuity in connection with the periodic table has 

 been commented upon in several directions, but in the 



