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XLIX. 

 AWARD OF TEE BOYLE MEDAL 



TO PROFESSOR JOHN A. McCLELLAND, M.A., D.Sc, F.R.S. 



(University College, Dublin). 



1917. 1 



Report of the Science Committee. 



The claim of Professor J. A. McClelland to receive the Boyle Medal of the 

 Royal Dublin Society is based upon research in many branches of science, 

 but primarily in those which deal («) with ionization as resulting from 

 .addition of electrons to gaseous molecules, or to aggregates of such; and (b) 

 with the more recently discovered forms of radiation associated pre-eminently 

 -with radio-activity. 



In the first field McClelland in 1899-1901 did much work on the nature 

 of flame-conduction. In 1903 the ionization of the atmosphere was dealt 

 with, and the subject was resinned in 1912, when a study of the electric sign 

 of rain-drops led him to important conclusions as to the nature of the larger 

 and less mobile ions of the atmosphere. Quite recently (1916) his work on 

 photo-electric effect advances our knowledge of a great natural source of 

 ionization which has intimate bearing on the processes of vegetable life. 



The second field of work has proved to be even more fruitful. It is not 

 too much to claim for McClelland a high position as pioneer in investigating 

 the nature of the radiations associated with radio-activity. So long ago as 

 1897 he showed that the Lenard rays, like the Cathode rays, consisted of 

 negatively charged particles. In 1904 he showed that radium-emanation 

 is not charged. In 1905 he proved the complex character of the secondary 

 radiation due to /3 and y rays. He recognized that negatively charged 

 particles constitute the secondary radiation, these particles attaining 

 very high velocities. And most suggestive of all is his discovery that 

 secondary radiation from the elements increases in amount with the atomic 

 weight. This work was clone in 1905, and communicated to the Royal 

 Dublin Society. It is, very evidently, of much importance. It has since 



1 The presentation was made -at the Scientific Meeting of the Royal Dublin 

 Society, held on Wednesday, the 19th December, 1917, when the Medal was handed to 

 Professor McClelland by the President, the Right Hon. Lord Rathdonnell, h.ji.l. 



SOIENT. PKOC. E.D.S., VOL. XV., NO. XLIX. 



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