Trowbridge — Electric Discharges through, Hydrogen. 347 



cathode to approach the wall of the tube opposite to the sealing 

 in place. Fig. 8 represents the phenomenon in a tube with a 

 dome-shaped chamber near the electrode. We seem to have 

 two dissected striae ; one on the wall of the tube nearest to 

 the cathode, which provides a beautiful light blue cathode 

 beam thrown into the dome ; and another stria on the oppo- 

 site wall of the dome. The original cathode beam excites both 

 positive and negative rays in these striae. 



Fig. 8. 



In considering these detached striae it seems that the cathode 

 rays in striking the glass walls can excite both positive and 

 cathode rays. 



When a spark gap is inserted in a circuit containing a dis- 

 charge tube which is properly exhausted to the striae stage, 

 the latter apparently disappears, the light of the tube becomes 

 more brilliant and fluorescence is generally manifested. This 

 is also the case when a condenser is discharged through the 

 tube. The eye cannot perceive any evidence of stratifications ; 

 for the brightness of the pilot spark, together with the fluores- 

 cence both of the gas and the glass walls, effectually shield 

 any striae of lesser radiance which might be present. It is not 



