Discharges in Insulators. 445 



lively at different potential-differences, the D. P. were not the 

 same ; it was consequently still questionable whether any 



600 





































































































































































































































































100 







































































simple relation subsisted between pressure and electricity dis- 

 charged, if with different pressures not the absolute but the 

 disposable potential-difference was found constant. The ques- 

 tion can be answered from the data of No. 2. I have extracted 

 from the Tables the following comparison, valid for the D. P. 

 = 1000:— 



Pressure in millims. of mercury ... 

 Amount of electricity discharged ... 



391 

 71 



294 



79 



203-4 

 106 



109-7 

 194 



51-8 

 450 



In fig. 4 will be found the graphic representation. A 

 simple relation is not perceptible. To be sure the product of 

 the pressure into the quantity of electricity for the last four 

 pressures is nearly constant; but with the pressure 391 there 

 is a considerable deviation from this rule. For the purpose of 

 fully answering questions 2 and 3, experiments with different 

 gases, between wider limits of the potential-differences, the 

 pressures, and the quantities of electricity discharged, will be 

 absolutely necessary. 



4. Does an expressible relation exist between the minimum 

 difference of potential and the nature of the various gases in 

 which the discharge takes place ? 



The gases were all tried at two pressures, approximately 205 

 and 110 millims. mercury; experiments with higher pressure* 



