CONTENTS xi 



SECTION PAGE 



27. Currents accompanied by a positive charge in the gas . 67 



28. Increase of force at cathode accompanied by decrease 



of potential required to maintain a current 

 between the electrodes for pressures above the 

 critical pressure ....... 68 



29. Simple experiments to illustrate the effect of con- 



centrating the force near the cathode ... 69 



30. Comparison of the effects of concentrating the force 



near the cathode and near the anode ; explanation 

 of sparking potentials for positive and negative 

 points 72 



31. Phenomena at pressures below the critical pressure . 74 



32. Processes of ionization that may account for effects 



obtained at low pressures 75 



33. Cathode fall of potential ; ionization in the space near 



the cathode when the cathode fall of potential is 

 established 77 



34. Sparking potential at atmospheric pressure for very 



short distances between the electrodes ... 80 



35. Eemarks on processes of ionization which account for 



various phenomena 81 



36. Examination of some other theories of the sparking 



potential 82 



