pbesidential address section b. 47 



Bibliography. 



'Problems in Astrophysics," by Agnes M. Clerke, A. & C. Black. 

 "The System of the Stars," by Agnes M. Clerke, A. & C. Black. 

 "Stellar Motions," by W. W. Campbell, Yale University Press. 

 "The Binary Stars," by Robert G. Aitken, McMurtrie, New York. 

 "The Study of Stellar Evolution," by Geo. Ellery Hale, University 



Chicago Press. 

 "Stellar Movements and the Structure of the Universe," by 



A. S. Eddington, Macmillan & Co. 



Current Literature. 



Publications Astronomical Society of the Pacific. 

 Journal of the Royal Astronomical Society, Canada. 

 Journal of the British Astronomical Association. 

 Astrophysical Journal. 



Monthly Notices, Royal Astronomical Society. 



Mount Wilson Contributions to the Carnegie Institution of 

 Washington. 



THE ATOMIC THEORY IN 1921. 



By James Moir, M.A., D.Sc, F.R.S.S.A., F.I.C., F.C.S., 



Government Mining Chemist. 



With Plate I. 



Presidential Address to Section B, delivered July 12, 1921. 



In thanking you for the honour of being elected President of 

 this Section I take the opportunity of explaining why I deviate 

 from the customary rule that a Presidential Address should not 

 resemble an ordinary scientific paper but should be of more 

 general interest, in fact not unlike a popular science lecture. The 

 fact is, however, that in the five years since I last wrote a Presi- 

 dential Address there has been such a tremendous upheaval of the 

 foundations of Chemistry and Physics that it is desirable that 

 someone should take the trouble to assimilate the new views and put 

 them on record in a connected form for the use of South African 

 scientists. This must be my excuse for not attempting the usual 

 kind of address — which might be crystallised in the phrase "Science 

 for Stockbrokers." 



The revolution which has taken place is one of very great 

 philosophical interest, and is, briefly speaking, the reduction cf 

 Chemistry to a branch of Physics. This has taken place in three 

 logical steps, the first being the recognition of the fact that all 

 chemical properties of a compound can be explained by the number 

 and the arrangement of the chemical valencies of the different 



