Oct., 1875.] ELLIOTT SOCIETY. 79 



and another to certain relations presented in the linear arrangement of points 

 corresponding to the atomic weights when laid down in diagrams similar to 

 those of Mercer already mentioned. 



In consequence of the various changes introduced by later researches, several 

 of the equations or formulae of the earlier of the above mentioned writers are 

 no longer applicable, or would not now be true for the values of the atomic 

 weights at present in use, and in a rapidly advancing science like Chemistry, 

 no attempt at a systematic view of these relations can yet hope-to have a per- 

 manent value. 



In endeavouring to construct a Table to exhibit in the lecture-room a synop- 

 tical view of the Elements and their relations as developed in modern Chemis- 

 try, I have availed myself of all the hints derivable from the views of the above 

 mentioned writers. The relations I desired to exhibit were these : 



1. The Groups of Elements, as at present recognized, 



2. The Atomic Weights of each Element, as now adopted, 



3. The Character of each, as Perissad or Artiad, 



4. Their Atomic equivalence or Atomicity, as Monad, Dyad, Triad, &c. , 



5. Their Electro-chemical character, as Electro-positive or Electro-nega- 



tive ; 



and to avoid undue bias as to numbers, groups, &c. , I adopted as guide the ta- 

 bles at pages 14, 16, and 19 of Barker's Text Book of Chemistry, which tables I 

 shall caU I, II and III. To obtain the advantages presented by a single table, 

 some of those belonging to the separate tables must be sacrificed. I determined, 

 to abandon entirely the linear or serial form of table II, to divide the electro- 

 chemical series into three approximately equal portions, to regard the upper or 

 negative third as containing the most intensely electro-negative elements, the 

 lower the most intensely electro-positive, and those embraced in the middle third 

 as of mean or average character in the electro-chemical series, and then to rest 

 satisfied with the approximate representation in my Table of the general charac- 

 ter of each of these three divisions. As the atomic equivalence or degree of 

 atomicity is not fixed, while the perissad or artiad character seems invariable, I 

 determined to preserve this last character inviolate, and to express onlj^ one 

 degree of atomicity, and that the most decided one as given in table III. 

 After trying several forms of arrangement for my Table, I have finally adopt- 

 ed the following, which presents I think a striking view of the relations of the 

 several groups of Elements, and as it may prove useful to those who like 

 myself are engaged In teaching, I will make it known. The mode of ar- 

 rangement has some novelty, and may present one or more known relations 

 in a new light. After having served its purpose, it must give way, as have 

 done its predecessors, to the new forms of arrangement required by the pro- 

 gress of Science. 



