A. W. Ewell — Air in an Intense Electric Field. 373 

 Conditions identical except air thickness =. *30. 



E.m.f. 



32700 



30500 



29000 



27000 



24300 



22300 



19700 



Current. 



11-5 



10*10 



9-30 



8-40 



7-00 



6-10 



5-20 



E.m.f. 



48000 



15300 



12500 



10500 



8500 







Current. 



4-07 



3*10 



1-96 



1-19 



•63 







Fig. 3. Abscissae = volts. Ordinates = milliamperes. I, Electrodes 

 against -59 cm of plate glass. II, 59 cm of glass + -20 cm of air. Ill, -59 cm of 

 glass +-43 cm of air. IV, -59 cm of glass + l-31 cm of air. V, -59 cm of glass + 

 24icm f a j r u' jjj> f JY', and V' are corrected curves of II, III, IV, and 

 V respectively and. give the relation between the e.m.f. applied to the air 

 and the ionization current. 



These observations are plotted in tig. 4. The corrected 

 curves fit in well with the curves of fig. 3 for the different dis- 

 tances. 



The lower portions of the corrected curves show the well 

 known rapid increase of current with slight increase of poten- 

 tial, while in the upper portions two facts are conspicuous, first, 

 that, as the ionization current in the air increases the electro- 

 motive force necessary to maintain the current decreases, and, 

 second, that, as the current increases, the curves for the dif- 



