584 Mr. Alan A. Campbell Swinton [Feb. 4, 



Bliould be a fairly good electrical conductor ; whereas in this cathode 

 ray arrangement there is no such limitation, and consequently there 

 is a much wider range of available refractory substances. It is also 

 quite conceivable that in future an electric furnace of this nature may 

 be found of service in some of the more delicate of chemical investi- 

 gations where it is necessary to obtain in isolated substances very 

 high temperatures. Indeed, already Crookes and Moissan have em- 

 ployed this means for turning into graphite the surface of a diamond. 



It is now becoming more and more generally believed that Sir 

 William Crookes' origiual theory, enunciated some twenty years ago, 

 as to the nature of these cathode radiations, is at any rate to a large 

 extent correct. According to this theory the cathode rays consist of 

 material particles of the residual gas, which being similarly electrified 

 by contact with the cathode are violently rej^elled by the latter. This 

 has been the view held for a long time by most En«;lish physicists, 

 and the chief point of difference now appears to be whether these 

 material particles are single atoms, single molecules, or larger aggre- 

 gations of matter. 



I have here a model which roughly shows what is supposed to 

 take place. As you see, there are facing one another t^o plate 

 electrodes, which I am able to charge positively and negatively 

 respectively by means of a Wimshurst machine ; between them is 

 suspended by a silk thread, what for the moment we will assume to 

 be a single atom. It is in fact a gilded pith ball. As soon as I turn 

 the handle of the "Wimshurst machine and electrify the electrodes, as 

 you see, the ball oscillates rapidly from one to the other. If it starts 

 in contact with the negative electrode it receives from this a negative 

 charge ; it thereupon is repelled until it strikes the positive electrode, 

 where it gives up its negative charge and receives a positive one. 

 Again, owing to mutual repulsion, it is driven across to the negative 

 electrode, and so on backwards and forwards. U'his is a very simple 

 and elementary experiment, which I would not have ventured to show 

 you except that it leads to another which is perhaps of more interest. 

 If the atoms in a tube were caused to fly backwards and forwards at 

 equal velocities, as did the pith ball, between anode and cathode, it is 

 obvious that there would be an anode stream similar in most if not in 

 all respects to the cathode stream, which does not appear to be the 

 case. If, however, I now remove the connection betweeu the positive 

 electrode and the Wimshurst machine, and instead, connect the posi- 

 tive electrode to earth, leaving the negative electrode connected to the 

 Wimshurst machine as before, it will be seen that the pith ball flies 

 with much greater violence and rapidity from cathode to anode than 

 it does on its return journey from anode to cathode. This is for the 

 reason that while in the former case we have both the repulsion of the 

 cathode on the similarly electrified ball and also the attraction of the 

 anode urging the ball on its path, on the return journey both ball and 

 anode are at zero potential, and consequently there is the attraction 

 of the distant cathode only causing the ball to move. Now, if we 



