On Rotational Optical Activity oj Solutions. 817 



of the 8 rays are almost independent of the nature of the 

 primary rays and the material on which they act, appears to 

 be a direct consequence of Thomson's theory and Lenard's 

 proof that the least energy necessary for ionization is approxi- 

 mately the same for all gases. The quantitative discrepancy 

 between the theory and experiment is probably to be attri- 

 buted to secondary action by the 8 rays after they are 

 liberated from the atoms. 



It does not appear to me likely that any further light will 

 be thrown on the mechanism of ionization by direct measure- 

 ments of the velocity of 8 rays emitted under various 

 conditions. 



Summary. 



The existing information as to the emission of 8 rays is 

 reviewed. 



Some new experiments on the 8 rays excited b}^ very slow 

 j3 rays are described. They are in complete accordance with 

 the work of v. Baeyer and Gehrts and provide little new 

 information. 



An attempt is made to discuss the experimental results on 

 the basis of the theory of ionization by moving charged 

 particles, put forward by Sir J. J. Thomson. It is concluded 

 that, while that theory cannot at present provide a complete 

 explanation of the facts, it is qualitatively in agreement with 

 them and in no way obviously inconsistent with them. 



Leeds, April 1913. 



LXXXV. On Rotational Optical Activity of Solutions. By 

 G. H. Livens, M. A., Fellow of Jesus College, Cambridge*. 



1. Introduction. 



I^HE most satisfactory theoretical treatment of the pheno- 

 mena of intrinsic optical activity of rotational type is 

 that given by Drude in his ' Optics.' The actual pheno- 

 menon has, however, been found to be much more complicated 

 than Drude's theory would lead one to expect. This is 

 especially the case with solutions of active substances in 

 active or inactive liquids, wherein the rotativity depends on 

 the nature of the substances and the concentration of the 

 solution. The discrepancies between theory and practice 

 have been the subject of a large amount of experimental 



* Communicated by the Author. 



