;34 



Prof. Sir J. J. Thomson on X-Rays [April 14, 1916 



connected with the poles of a 6 00 -volt battery ; everything going 

 from one tube to the other had to pass between these cylinders, and 

 if it were electrified would be^driven on to one or the other. The 

 experiments with this method, which are not yet completed, give 

 results which agree with those obtained by the other. They show 

 that a potential difference of a few volts between the silvered sphere 

 and the metal plate is sufficient to stop the vast majority of the 

 electrons, even though the cathode rays had fallen through many 

 hundred volts, and that as before the character of the Rontgen rays 



\ 



Hot \^/Re 



Fig. 3. 



only changed slowly with the energy of the cathode rays. Thus 

 when 1000 volts cathode rays fall on a target the Rontgen rays 

 produced are for the most part no harder than might be produced by 

 100 volt rays. The proportion of rays corresponding to anything 

 approaching 1000 volts is so small that I have not yet succeeded in 

 finding by this method any trace of their existence. I hope, however, 

 in less strenuous times, when research, which can now only be 

 an occasional relaxation, may become again one's main occupation, to 

 carry out more elaborate experiments on this and other points of 

 interest in connection with these rays. 



[J.J.T.] 



