1909.] Anniversary Address hy Sir A. Geikie. 167 



followed in his footsteps, and of his own unceasing exertions and further 

 investigations during the last few years, scientifically directed measures for 

 the prevention of malaria have been initiated with striking success in many 

 fever-stricken districts all over the world, and particularly within the 

 British Empire. His investigations have also inspired similar work on the 

 spread, by means of mosquitoes or other biting insects, of other formidable 

 diseases, with the result that effective measures have been devised for 

 preventing the spread of these diseases also. 



Davy Medal. 



The Davy Medal has been awarded to Sir James Dewar, F.R.S. 



Sir James Dewar has been a pioneer in the study of very low tempera- 

 tures, their production, applications, and effects. 



For many years he has worked continiiously in this difficult domain, and 

 his investigations have resulted from time to time in such achievements as 

 the solidification of oxygen, the liquefaction of fluorine, and the liqiiefaction 

 and solidification of hydrogen. His improvements in technique have been 

 fundamental. By the construction of vessels in which thermal convection is 

 avoided by the presence of a vacuous layer in their walls, he has enormously 

 simplified the retention and manipulation of matter at very low temperatures. 

 His application of the absorbent eflect exerted on gaseous materials by 

 charcoal at low temperatures has placed in the hands of chemists and 

 physicists a most convenient and important method, not only for the produc- 

 tion of high vacua, but also for the rapid separation of the constituents of 

 gaseous mixtures. The modifications in the properties of matter at very low 

 temperatures have been investigated, and remarkable results obtained, 

 including the earliest exact investigations, jointly with Prof. Fleming, 

 on the electric properties of insulators, and of metals and alloys. The 

 determination of the properties (critical points, boiling points, etc.) of 

 refractory gases at very low temperatures has involved the practical 

 downward extension of absolute thermometry, with the result that 

 temperatures in the neighbourhood of the absolute zero can be determined 

 correctly to within a degree. Lastly, recent measurements of the rate of 

 formation of helium from radium salt, specially purified by Sir T. Edward 

 Thorpe for his recent atomic weight determination, have provided exact 

 molecular data, throwing light on the nature of the spontaneous disintegration 

 of that very remarkable substance. 



VOL. LXXXII. — B. 



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