Rollins — Cathode Stream and X Light. 385 



the generator, the cathode stream arose from the concave side 

 of the cathode, came to a focus on the normal anode, giving 

 good X-light. This anode was then disconnected from the 

 current. The supplementary ring terminal was made the 

 anode. Under these conditions no cathode stream arose from 

 the usual side of the cathode, consequently no X-light was 

 produced at the normal anode. X- light arose in the other 

 bulb from the spreading streams of cathode particles given off 

 from the back or convex side of the cathode. 



4. The cathode stream particles are always of the same size, 

 move with the same speed, and carry the same charge. 



If these assumptions were true we should always get the 

 same effect when the particles struck the target in an X-light 

 tube. We do not. Every one long familiar with the con- 

 struction of such tubes knows that the quality of the light 

 varies with the resistance of the tube. In the determinations 

 of the speed no sufficient account was taken of the retarding 

 effect of the gases in circulation in the tube. Suppose we try 

 to keep this constant, even then the effect produced by the 

 impact of these particles on the target in an X-light tube 

 varies from other causes. To show this I made a tube in 

 which the ordinary cathode could be covered by mercury. 

 With the usual cathode the tube gave good X light. With the 

 mercury cathode there was not enough X-light to see the bones 

 of the hand, but the whole tube was filled with a brilliant white 

 light. I explained this by saying that the particles in the 

 cathode stream were heavier when the cathode was mercury 

 than when it was aluminum, and the stream was composed of 

 some light gas. In consequence the particles did not strike the 

 target at so high a velocity, and when stopped were therefore 

 not heated to so high a degree ; hence were not such efficient 

 centers of radiation for the short ether movements we call 

 X-light, most of the energy appearing as ordinary light instead. 

 Some of the experiments on which I based this heat theory 

 will be mentioned later. If the particles in the cathode 

 stream were always of the same mass, all cathodes should lose 

 equally in weight in the same time, with the same amount of 

 current. They do not. I also found that when the gas had 

 been considerably removed from the terminals, cathodes of 

 heavy metals lost in weight more rapidly than those of light 

 metals, like magnesium and aluminum. 



5. In the cathode stream the charges are always carried by 

 the same particles, in all tubes, with any gas, with every 

 cathode. 



An X-light tube was exhausted while using heat and heavy 

 surges until it yielded no X-light. Had the particles been 



