Eight-Year Cycle in Relation to Physical Cause 113 



cathode, and the space between the two glows remains 

 dark. 



When the gas is still further rarefied the glow near the 

 cathode begins to change, leaving a light close to the 

 cathode, — the cathode glow — which is separated by a 

 dark space — the Crookes' dark space — from the other 

 part of the original cathode light which is now called 

 the negati\'e glow. The relatively dark space between 

 the negative glow and the glow at the anode is the 

 Faraday dark space. The positive glow, or positive 

 column, breaks up into a series of bright and dark 

 striae at right angles to the line between the anode 

 and the cathode. With still further reduction of the 

 pressure of the gas the negative glow and the Crookes' 

 dark space fill more and more of the tube, and the posi- 

 tive column correspondingly decreases. Streamers of 

 bluish light, called cathode rays, are seen to start out 

 perpendicularly from the cathode. If the exhaustion 

 of the gas is carried still further the Crookes' dark 

 space apparently fills the entire tube, and the walls 

 of the tube become fluorescent, particularly w^here the 

 cathode rays impinge, the color of the fluorescence 

 varying according to the composition of the glass of the 

 tube. 



Crookes' researches were concerned primarily with 

 the properties of the cathode light. The cathode rays 

 apparently started perpendicularly from the cathode, 

 producing fluorescence upon the walls of the tube where 

 they impinged. His experiments led him to the con- 

 clusion that these streamers originated on the metal 

 surface of the negative electrode and were a new mani- 

 festation of matter. He called it radiant matter. Many 



