1896.] Prof. Stokes, On the Nature of the Rontgen Rays. 215 



Monday, 9 November, 1896. 

 Mr F. Darwin, President, in the Chair. 



The following were elected Associates of the Society : — 



Mr A. E. Smith, Cambridge. 



Dr Novak, Prag. 



Mr J. Henry, Trinity College. 



Mr W. C. Henderson, Trinity College. 



Mr G. B. Bryan, St John's College. 



The following Communications were made to the Society: — 



(1) On the Nature of the Rontgen Rays. By Professor Sir 

 G. G. Stokes. 



In this communication the author explained the views he had 

 been led to entertain as to the nature of the Rontgen rays, and 

 to a certain extent the considerations which had led him to those 

 conclusions. As Rontgen himself pointed out, the X rays have 

 their origin in the portion of the wall of the Crookes tube on 

 which the so-called cathodic rays fall, and it is natural that our 

 notions as to the nature of the X rays should be intimately bound 

 up with those we entertain as to the nature of the cathodic rays. 

 Two different views have been adopted on this question. Several 

 eminent German physicists hold that the cathodic rays are essen- 

 tially a process going on in the ether, the nature of which nobody 

 has been able to explain ; and that if any propulsion of molecules 

 from the cathode accompanies them, it is merely a secondary 

 phenomenon. The other view is that the cathodic rays are not 

 proper rays at all, but that they are essentially streams of mole- 

 cules. The latter view is that which, so far as the author knows, 

 is universally adopted in this country. The author expressed the 

 fullest conviction that the cathodic rays are no mere process going 

 on in the ether, but that the propulsion of molecules is of the 

 very essence of the phenomenon ; only it is to be remembered 

 that the molecules are not to be thought of as acting merely 

 dynamically, by virtue of their mass and velocity ; they are 

 carriers of electricity ; and it would seem to be mainly to this 

 circumstance that some at least of their effects are due. He 

 indicated what he believed to be the true answers to the objections 

 of those who regard the cathodic rays as processes in the ether ; 

 and adopting the theory that they are streams of molecules ex- 

 plained how, in his opinion, this theory, taken in connection with 

 the more salient features of the X rays to which the cathodic 

 rays give birth, leads us to a theory of the nature of the X rays. 



