xvm THE CLASSIFICATION OF THE ELEMENTS 455 



TABLE A 

 NEWLANDS'S FIRST TABLE OF THE ELEMENTS 1 



This table, which shows all the triads in a single scheme, 

 was put forward by Newlands in 1864 in a paper on " Rela- 

 tions between Equivalents " (Chem. News, July 30, 1864, 10, 

 59 ; reprinted in a pamphlet On the Discovery of the Periodic 

 Law, London, 1884, p. 8). He had already described a 

 number of relations between the equivalents in continuation 

 of the work of Dumas ; but this new table was a direct 

 result of the adoption of Cannizzaro's system of atomic 

 weights. Newlands directed attention to the following 

 features in the table : 



(1) There is a constant difference of sixteen to seventeen 

 units between the values for the initial member of each group 

 and the first term of the corresponding triad. 



(2) This difference is equal to the value assigned to 

 oxygen ; simple multiples of this difference may be recog- 

 nised in other parts of the table. 



(3) " Silicon and tin stand to each other as the extremities 

 of a triad," the "central term or mean of the triad. ... is 



at present wanting; thus ?L^*LLL 8 , = 73 ' (Periodic 



1 The triads are arranged horizontally in the original table. The 

 following elements would now be assigned to different families : Li, Au, 

 Os, Tl, Pb, V. 



