35 JOURNAL OF THE 



ag-es — the Unity of Matter. It may be said, with truth, 

 that the Periodic System is the science of Chemistry 

 itself. As such it must of necessity be incomplete. 

 Through it we have been forced to realize how incom- 

 plete our science really is. In one sense, then, to study 

 the present condition of the Periodic System would be to 

 study that of chemistry. We will examine the question, 

 however, from another and more-restricted point of view. 



We ma\% in discussing the present position of the Pe- 

 riodic System, draw a distinction between certain points 

 which are well established and others which are still 

 under discussion or beyond our grasp at present. 



First it is clear that the natural arrangement of the 

 elements is in the ascending order of their atomic weights. 

 This arrangement proved a failure when attempted by 

 Gladstone because of imperfect atomic weights. In the 

 hands of de Chancourtois, Newlands, Meyer and Mendel- 

 eeff it was developed and the singular relations between the 

 elements, called periodic, were made apparent. This brings 

 us to the second point, that when the elements are ar- 

 ranged in the order of their atomic weights they fall 

 naturall}^ into certain analogous groups and periods with 

 a recurrence, or repetition, of properties at certain in- 

 tervals. This leads up to the third point which we may 

 acknowledge as fixed, namely that the properties of the 

 elements are determined by and dependent upon the atomic 

 weights. This was first stated by de Chancourtois, was 

 proved independently and from a different standpoint by 

 Hinrichs and was forced upon the attention of the world 

 by the genius of Mendeleeft\ 



The points which still remain to be settled are very 

 numerous. In the first place the number of the elements 

 is unknown. Clarke, in the recent revision of his classic re- 

 calculations of the atomic weights, gives a list of 74. This 

 leaves out of account all whose atomic weights are still 

 very imperfectly determined or whose existance is still in 

 doubt. MendeleetT's table allows for the existence of 



