March yth, ipii.] PROCEEDINGS. xxi 



determined by the scintillation method. Radium emanation 

 enclosed in a fine glass tube was used as a source. The 

 microscope to which the zinc sulphide screen was attached 

 moved round the arc of a circle ; the distance between the 

 scattering material and the screen was constant and equal to 

 about 2 cms. The source of radiation, the scattering foil, 

 and the screen were enclosed in a metal vessel which was 

 exhausted to a low pressure. The number of o particles 

 scattered through large angles up to 150° was first measured, 

 and, as the emanation decayed, the number of small angles was 

 successively determined. The number of scattered particles 

 per unit area varied, when corrected for decay, nearly 300 times 

 over the range of angles examined. The actual numbers of 

 particles observed varied very approximately as cosec^0/2 where 

 ^ is the angle of deflection. This is the relation theoretically 

 deduced by Professor Rutherford in the foregoing paper. 



Experiments are in progress to examine the other deductions 

 of the theory, and especially the variation of the amount of 

 large scattering with thickness and nature of scattering foils and 

 velocity of the a particles. 



Mr. R. F. GwYTHER, M.A., read a paper entitled " Can 

 the Parts of a Heavy Body be supported by their 

 Elastic Reactions only ? " 



The paper is printed in full in the Memoirs under the 

 title "The Conditions that the Stresses in a Heavy 

 Body should be purely Elastic Stresses." 



Ordinary Meeting, March 21st, igii. 



Mr. Francis Jones, ]\[.Sc., F.R.S.E., President, 

 in the Chair. 



The thanks of the members were voted to the donors of the 

 books upon the tables. The following were amongst the recent 



