1894.] On some Phenomena in Vacuum-tubes. 



FIG. 9. 



245 



electrodes are like two small concave mirrors. When the current is 

 passed, the effects produced are somewhat similar to a " radiant- 

 matter tube," i.e., the light produced by the discharge converges and 

 the tube is generally lit up. The current is now diminished, and at 

 a certain point bands make their appearance. 



Experiment 10. 



Following the last experiment, I tried a number of tubes con- 

 structed to show Professor Crookes' radiant matter phenomena. I 

 find that if the current is sufficiently diminished the streams of light 



jreak up into bands. I am not aware whether this circumstance is 



:nown. 

 It ought to be mentioned that in some cases the effects can only be 



sbserved by passing a considerable quantity of current through the 

 tube and then turning off the alternator, so that it runs slower and 

 slower until it stops. The light in the tubes gradually diminishes 

 until they are dark. Many effects can only be observed at the moment 

 of extinction. Some tubes, in which it appears impossible to show 

 the bauds, give the phenomenon most distinctly at the instant 

 referred to. 



