4 Trans. Acad. Sci. of St. Louis. 



gun to flow from the anode. This operation extends 

 throughout the tube, up to the dark space at the cathode. 

 At the cathode end the negative particles appear. In the 

 arc light such a cathode stream shows itself capable of 

 beating a crater into the end of the positive carbon, and 

 raising the temperature of that carbon a thousand de- 

 grees or more above that of the negative carbon. In the 

 Geissler tube this cathode stream apparently beats the 

 gas molecules away from the cathode. They are beaten 

 towards the positive terminal of the tube. A condition 

 is thus formed around the cathode which approaches that 

 in the Crookes tube. We may have then in this space a 

 region of increased "resistance" to the passage of the 

 discharge. A kind of automatic valve action may be thus 

 brought about. A system of standing waves may result, 

 in the air column, somewhat resembling that in an organ 

 pipe. All of this would involve, at any one point in the 

 tube, harmonic changes in pressure in the gas, such as 

 exist in an organ pipe, and harmonic changes in the ' i re- 

 sistance" offered to the discharge. If the cathode has a 

 form which gives proper direction to the cathode stream 

 a counter discharge of positive ions towards the cathode 

 end of the tube may be brought about. 



Such periodic changes in the gas column of the Geissler 

 tube would of course be attended by many complex auxil- 

 iary phenomena which are not to be found in vibrations 

 in the air column of an organ pipe, produced by a con- 

 tinuous blast of air. It certainly seems possible that the 

 cathode stream across the dark space around the cathode, 

 even when a constant current source is used, may be the 

 cause of the periodic vibrations of a more or less regular 

 character involved in the striae and dark spaces. "Why 

 should such mechanical considerations not enter into the 

 explanation of these long known phenomena? 



It certainly does not seem possible that the positive 

 ions can emerge from within the metal conductor form- 

 ing the anode. They are what is left of the atom, when 

 the negative particles have been detached from atoms of 



