680 Mr. Alan A. Campbell Swinton [Fob. 4, 



WEEKLY EVENING MEETING, 



Friday, February 4, 1898. 



Sib William Crookes, F.R.S. Vice-President, in the Chair. 



Alan A. Campbell Swinton, Esq. M.B.I. 



Some New Studies in Cathode and Bontgen Radiations, 



The researches of Crookes, Lenard and Routgen have given to man 

 a new eye. They have perhaps also given to nature a new light. 

 They have certainly given to science more than one new problem. 



This small glass bulb which I hold in my hand, which, being ex- 

 hausted to a high vacuum, contains, besides its two aluminium elec- 

 trodes, only a few billions of molecules of residual gas, may appear but 

 a simple piece of apparatus. Could it, however, only be induced while 

 Tinder the stimulus of an electric discharge to reveal in their entirety 

 the secrets that it contains, we should know much at present utterly 

 unknown, not only as regards the nature of electrical action, but also 

 in reference to the funtlamental constitution of matter, and the 

 true mechanism of energy. It is, in fact, for the reason that within 

 the Crookes radiant-matter tube, where molecules are separated by 

 comparatively long distances, it is possible to deal not as in everyday 

 life with aggregates of matter, but even individually, perhaps, with 

 single molecules and atoms floating apart in space, that so much 

 attention is at present being devoted to this particular branch of 

 physics. 



Every one is now acquainted with what has become the quite 

 ordinary phenomenon of the cathode rays. I turn on the induction 

 coil spark to this highly exhausted tube, and from the aluminium 

 plate that forms the negative electrode or cathode, there proceeds, as 

 you see, some kind of ray that excites a green luminescence in the 

 glass upon which it fall.*. I interpose in the path of these cathode 

 rays a screen, made of aluminium in the form of a cross, and the lattor 

 casts a sharp shadow on the glass. I have here a coil of wire, 

 through which an electric current is passing, and as I slowly move 

 the coil so as to encircle the tube, and consequently gradually increase 

 the strength of the magnetic field within the tube, it will be observed 

 that the shadow of the cross rotates, becoming at the same time 

 smaller. Here we obviously have a deflection of the cathode rays 

 from their rectilinear path, the action of a magnetic field of this 

 description being to concentrate the rays and also to give them a twist, 

 the direction of which depends upon the direction in which the current 

 is sent through the coil of wire. 



