236 Dr. D. N. Mallik and Prof. A. B. Das on the 



traversed and ft is a function of the masses of the col- 

 liding ions. It will happen, therefore, that if X is the 



electric force, E = E — -^+ \lLdx, so that ionization will 



* B 



no longer be possible, when ^Xdcc<j~a. This will then 



mark the beginning of the next or Faraday dark space. 



7. Now, the energy at the extremity of the negative glow 

 is evidently of the form E — &#, where k may be taken 

 to be constant as a first approximation. It is, moreover, 

 known that x increases as pressure decreases. Assuming 



that xorA — hBJ, this energy may be written equal to 

 E — ^ — k 2 . If further, X 2 is the average electric intensity 

 through the Faraday dark space and d is the length of this 

 space, we must have E — - — Ic 2 + 'X.id = 'E . 



We have moreover X x x - and d = a' -\- -, approximately 



during a certain range of pressure. We have thus, on 

 this theory, a means of coordinating the various quantities 

 associated with the cathode dark space, the negative glow, 

 and the Faraday dark space. 



8. Experiments show, however, that the linear law both 

 as regards the negative glow and the Faraday dark space 

 holds only for a limited range. 



Obs. In both these experiments, the distance between the 

 electrodes was 14*6 cm. 



Experiment I. — Voltage in the primary about 11 volts. 



(Curve I.) 



Scale-reading Scale-reading- corre- Length 



Pressure corresponding to sponding to the beginning of the 



in mm. the cathode terminal. of the positive column, dark space. 



27 14-9 14-7 *2 cm. 



5 



14-9 



5 



14-9 



3 



14-9 



1-5 



14-9 



14-15 



•75 „ 



13-48 



1-42 „ 



13-25 



1-65 „ 



11-75 



3-15 „ 



