SECTION A.— MATHEMATICAL AND PHYSICAL SCIENCES. 



TRENDS IN MODERN PHYSICS 



ADDRESS BY 



PROF. ALLAN FERGUSON, M.A., D.Sc, 



PRESIDENT OF THE SECTION. 



Our Section has suffered heavy losses in the twelve months that have 

 passed since the Norwich Meeting, and it is fitting that we should here 

 pay due honour to the memories of McLennan, Glazebiook, Petavel and 

 Pearson, who have, each in his own characteristic fashion, played so 

 great a part in the advances made during this century. 



The genius and vigour of Sir John McLennan were quick to seize on 

 and to develop those ideas which were fermenting at Cambridge in the 

 last years of the nineteenth century and to impress on them a character 

 peculiarly his own. His energy and versatility are shown equally in his 

 early studies of penetrating radiation, in his discovery of the single line 

 spectrum of zinc and cadmium, in his later work on the spectrum of the 

 aurora and the nature of the famous green line, and in those studies of 

 supraconductivity to which his last years in Toronto were given. His 

 return to England found him unconquerably young in spirit and prepared 

 to play his part in important investigations in radium beam therapy. 

 He presided over the deliberations of this Section at the Liverpool Meeting 

 of 1923, and those of us who were present at that meeting have vivid 

 memories of an address which reviewed some of the major problems 

 of atomic structure — an address which, the latest word on the matter in 

 1923, reads to-day as an ancient tale. The laboratory at Toronto which 

 bears McLennan 's name bears witness also to his genius as a leader of 

 research and to his gifts as administrator and director. 



Sir Richard Glazebrook belonged to the elder generation — he presided 

 over Section A so long ago as 1893 — and to the last occupied himself 

 with certain aspects of those problems of macroscopic physics which 

 dominated the science of his century. His early papers on the Fresnel 

 wave-surface are admirable examples of accurate work accomplished 

 with the aid of simple apparatus ; and his experiments on the relation 

 between the British Association unit of electrical resistance and the 

 absolute unit marked the first step on a lifelong journey. Felix opportuni- 

 tate mortis, illness was spared him, and death laid a kindly hand on his 

 shoulder while he was still in the full tide of mental activity, still pursuing 

 those studies which had been his companions for more than half a century. 

 The National Physical Laboratory, which, opening in 1902 with two 

 departments and a staff of twenty-six, had in ten years expanded to eight 



