80 Mr. Henry Wilde on the 



For like reasons the position of boron, B= n, as the 

 fourth member of Newlands' table, and the third member in 

 that of Mendeleeff, cannot be admitted as correct, as this 

 element bears a greater resemblance to phosphorus in its 

 combinations and occurrence in nature than it does to other 

 elements. 



Since my paper was read in 1878, the position of boron 

 in the series Yityi in my table has been confirmed by 

 M. Etard, who has shown that, this element is a pentad, and 

 has placed it at the head of the series of vanadium ; the 

 two elements presenting a great number of analogous 

 properties.* 



The transposition of boron from the third to the fifth 

 group in Mendeleeff s table would displace nitrogen, which 

 element would find no place in his system except to 

 constitute itself one of his little periods, like hydrogen. 



Again, the positions of N and Si in Newlands' table, as 

 the sixth and fifth members of the first and second series 

 respectively ; and in Mendeleeff s table as the fifth and 

 fourth of the same two series, are mutually destructive of 

 each other ; and, as these contradictions are brought about 

 simply by the removal of hydrogen one step out of the 

 system, no confidence can be placed in the positions of N 

 and Si in either of the tables. 



In his serious attempts to bring the whole of the 

 elements into a periodic system, Mendeleeff found it 

 necessary to add a series (group VIII.) to that of Newlands ; 

 but has thereby made his own system unperiodic. Now, 

 the essence of periodicity is the recurrence of events or 

 properties at regular intervals of time or place; but a period 

 of 1, in the case of hydrogen, succeeded by two periods of 

 7; two periods of 17; and four or five periods of uncertain 

 character, as set forth by Mendeleeff in his memoir, and 



* Comptes Rendus, tome XCI., p. 931. 1880. 



