1906.] Anniversary Address by Lord Rayleigh. 91 



Metchnikoff s recent work on infection by the micro-organism of syphilis 

 and the attainment of protection and immunity against this disease may be 

 mentioned on account of its important practical applications. 



It is not too much to say that the work of Metchnikoff has furnished 

 the most fertile conception in modern pathology, and has determined the 

 whole direction of this science during the last two decades. 



The Eumford Medal is awarded to Professor Hugh Longbourne Callendar, 

 E.K.S., for his experimental work on heat. 



Professor Callendar has devoted his attention chiefly to the improvement 

 of accurate measurement in the science of heat by the application of electrical 

 methods. His first paper " On the Practical Measurement of Temperature," 

 1 Phil. Trans./ 1887, paved the way for the application of the electrical 

 resistance thermometer to scientific investigation. In a later paper, written 

 in conjunction with Griffiths, " On the Boiling Point of Sulphur, etc.," ' Phil. 

 Trans.,' 1891, the application of his method was further extended, and a 

 simple method of standardisation was proposed. In continuation of this 

 work Professor Callendar has written a number of subsidiary papers dealing 

 with details of construction of instruments, and applications to special 

 purposes. The results of this thermometric work have since been confirmed 

 by Chappuis and Harker, 'Phil. Trans./ 1889, at the Bureau International, 

 Paris, and by other observers, and are now generally accepted. 



More recent developments in accurate electrical thermometry have been 

 described by Professor Callendar in later papers. He has also devised a 

 special type of " gas-resistance " thermometer, depending on the increase of 

 viscosity of a gas with temperature, which is the exact analogue of the 

 electrical resistance thermometer, and possesses peculiar advantages for high- 

 temperature measurements. 



The application of electrical resistance thermometers and thermo-couples 

 to the observation of rapid variations of temperature has been utilised by 

 Professor Callendar in the study of the adiabatic expansion of gases and 

 vapours, and in the observations of the cyclical changes of temperature of the 

 steam and of the cylinder walls in a steam-engine. The latter research 

 was undertaken in conjunction with Professor Nicholson, with a view to 

 elucidate the theory of cylinder-condensation. 



The researches of Rowland and other experimentalists on the specific heat 

 of water, and the mechanical equivalent of heat, had shown that grave 

 uncertainties affected the value of this most fundamental physical constant, 

 which could not be removed satisfactorily without a complete investigation of 

 the variation of the specific heat of water between 0° and 100° C. Professor 



