x CONTENTS 



SECTION PAGE 



13. Molecular dimensions deduced from the mean free 



paths of negative ions ...... 29 



14. Application of the theory to Stoletow's experiments . 30 



15. Determination of the pressure corresponding to the 



maximum value of a for a given force ... 34 



16. Comparison of the velocities of ions and molecules . 36 



CHAPTER II 



lONIZATION BY POSITIVE IONS 



17. Conductivity between parallel plates when positive and 



negative ions generate others by collisions . . 38 



18. Agreement between experiments and theory . . 42 



19. Curves representing @/p as a function of X/^> ; com- 



parison of effects produced by positive and negative 

 ions 45 



CHAPTER III 

 SPARKING POTENTIAL IN A UNIFORM ELECTRIC FIELD 



20. Description of phenomena accompanying discharges ; 



sparking potential . . . . . . .51 



21. Potential required to maintain a discharge ... 53 



22. Properties of pointed and cylindrical electrodes . . 54 



23. Condition for sparking in a uniform electric field. 



Tables giving the sparking potentials determined 

 theoretically and experimentally .... 55 



24. Effects of initial ionization .60 



CHAPTER IV 



THEORY OF ELECTRIC DISCHARGES IN FIELDS OF FORCE WHICH 

 ARE NOT UNIFORM. 



25. Description of phenomena to be investigated . . 63 



26. Condition for the maintenance of a current by effects 



of collisions in any field of force .... 65 



