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Anniversary Address by Sir A. Geikie. [Nov. 30, 



Davy Medal. 



The Davy Medal is this year assigned to Prof. Henry Edward Armstrong, 

 FRS., on account of his researches in organic and in general chemistry. 



For many years he has been engaged, partly alone and partly in collaboration 

 with many of his students and others, in the investigation of a number of 

 important problems in organic chemistry. His series of memoirs on the 

 terpenes, on the chemical and physical relationships which obtain among the 

 isomerides of the naphthalene and the benzene series, and on physiological 

 chemistry, have established a strong claim for recognition. 



In addition to his direct scientific work, he has taken an active part in the 

 discussion and criticism of current theories, and has put forward views on 

 chemical change and on other subjects which have suggested fruitful lines of 

 enquiry. Gifted with a scientific imagination, interested in the work of 

 others, exceptionally well informed as to recent progress not only in 

 chemistry but also in cognate sciences, he has had a stimulating effect on his 

 fellow chemists, and has done much to bring together for their mutual 

 benefit the workers in different fields. 



Hughes Medal. 



The Hughes Medal has been assigned to Charles Thomson Eees Wilson, 

 F.K.S., in recognition of the value of his contributions to our knowledge of 

 the nuclei produced in dust- free gases, and of his investigations upon the 

 nature and properties of ions in gases. Following up the well-known work 

 of Aitken on dust nuclei, Mr. Wilson devised a special apparatus for 

 producing a sudden cooling of a gas saturated with water vapour. After 

 completely freeing the gas from dust particles he found that water was 

 condensed on a few nuclei after an expansion of volume greater than T25, 

 and that a dense cloud was formed when it exceeded l - 38. This work was 

 in progress at the time of the discovery of X-rays. He immediately tried 

 the effect of passing this radiation through the gas in the expansion chamber, 

 and found that a dense cloud of tine water drops was produced for all 

 expansions greater than 1*25. In this way he showed that the charged ions 

 produced in gases by the X-rays became nuclei for the condensation of water 

 at a definite supersaturation. This investigation was of great importance ; 

 for not only did it bring to light a very striking property of the gaseous ions, 

 but it illustrated in a concrete way the process of ionisation in a gas, and the 

 discontinuous nature of electrical charges. By this method each charged 

 ion is rendered visible by becoming a centre of condensation of vapour. In 

 later work he investigated the efficiency of the positive and negative ions 



