84 Anniversary Address by Lord Rayleigh. [Nov. 30, 



every physical and chemical laboratory. It would be difficult, indeed, to 

 enumerate the investigations which have owed their success to the invention 

 of the Sprengel mercury pump. In other cases, scientific careers still in full 

 activity have, unhappily, been cut short. I allude especially to Joly, Marshall 

 Ward, and Weldon. Even within my term of office our discussions have 

 been enlivened by Weldon's scientific enthusiasm and vigorous polemics. 



On the Foreign list are two distinguished names. Professor Ludwig 

 Boltzmann, of Vienna, was perhaps the first Continental physicist to take 

 up the ideas of Maxwell's electric theory of light, of which he had early 

 grasped the scope, and became for many years one of its most emphatic 

 supporters. One of his earliest series of experiments was a determination of 

 the influence of the crystalline quality on the dielectric constant of sulphur, 

 with a view to comparison with its optical double refraction. In the theory 

 of gases he is to be classed along with Clausius and Maxwell as one of the 

 creators of the dynamical theory, on which he became the highest authority. 

 By developing an idea originated by Bartoli he placed Stefan's law of 

 intensity of natural radiation on a theoretical basis, and thus became the 

 pioneer in the modern thermodynamics of radiant energy. He contributed 

 to the advance of physical science by many other investigations, and by his 

 books on Gas Theory, on Electrodynamics, and on Mechanics. I may 

 perhaps be allowed to add that at the time of his unhappy death, Boltzmann's 

 name was before the Council as proposed for one of our medals. 



Professor Langley's work was more on the experimental side of physics. 

 In his bolometer he applied electric resistance thermometry to radiation, and 

 was thereby enabled to penetrate further into the important and mysterious 

 region of the ultra-red than had before that time been possible. For this 

 work he received the Eumford Medal in 1886. During the later years of 

 his life his attention was largely occupied with the mechanical problem of 

 flight, and his models attained a considerable measure of success. As 

 Secretary to the Smithsonian Institution at Washington he did much to 

 forward, by his co-operation and advice, all kinds of scientific investigation. 



In the Keport of the Council there has been laid before you an account of 

 the work of the Council and of various Committees in a very wide field. 

 The investigation of the terrible disease known as Sleeping Sickness has 

 unhappily been marked by the tragic death of Lieutenant Tulloch, who has 

 fallen a victim to his zeal in studying the disease in Uganda. Vigorous 

 efforts are being undertaken to discover some therapeutic remedy for the 

 malady. In the case of Malta Fever, too, the investigation of which was 

 entrusted to the Koyal Society by the Colonial Office, good progress has been 



