32 Presidential Address 



discussion on Radiation, of extreme 

 weight and interest, though likewise of 

 great profundity and technicality, is ex- 

 pected on Friday in Section A. We wel- 

 come Professor Lorentz, Dr. Arrhenius, 

 Professor Jeans, Professor Pringsheim, 

 and others, some of whom have been 

 specially invited to England because of 

 the important contributions which they 

 have made to the subject-matter of this 

 discussion. 



Why is so much importance attached 

 to Radiation? Because it is the best- 

 known and longest-studied link between 

 matter and ether, and the only property 

 we are acquainted with that affects the 

 unmodified great mass of ether alone. 

 Electricity and magnetism are associated 

 with the modifications or singularities 

 called electrons. Heat and sound are 

 connected still more directly with matter. 

 Radiation, however, though excited by an 

 accelerated electron, is subsequently let 

 loose in the ether of space, and travels as 

 a definite thing at a measurable and 

 constant pace a pace independent of 



