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PROCEEDINGS OF THE AMEEICAN ACADEMY. 



a narrow, sharply defined band of fluorescence, which is represented in 

 the photograph. Figure 5. The middle of the end of the tube is indi- 

 cated by the sharp pointers on the photograph, and it will be seen that 

 the phosphorescent band extends to approximately equal distances on 

 both sides of the middle of the screen. At first I thought that I was 

 dealing with a mixture of positive and negative rays, and various the- 

 ories of molecular attraction occurred to me ; but experiment showed 

 that all negative rays had been driven out of the field. Moreover, by 

 producing a difference of electrostatic potential, the entire phospho- 

 rescent band, or magnetic spectrum, moved in the direction the positive 



FiGUKE 5. 



rays should move. In Figure 5 it will be noticed that the band moved 

 to the smaller pointer ; whereas, if the portion of the band to the right 

 of the pointers was made up of negative rays, and that to the left of 

 positive rays, the band would not have moved parallel to its original 

 position. 



In order to ascertain why the band spread to the right and left of 

 the middle of the screen I introduced a septum of glass in the middle 

 of the tube constituting the canal region (Figure 6). This septum was 

 welded to the end of the tube and was coated on both sides with 

 willemite. The band of phosphorescence now appeared mainly on one 

 side of the partition. By greatly weakening the magnetic field the 

 negative rays were brought upon the screen to the left of the partition, 

 while the positive rays appeared on the right of this partition, thus 



