558 Mr. J. J. E. Durack on the Specific Ionization 



centroid of n points, whose coordinates are x x , x 2 , &c, y u y 2> 

 &c, being defined by the coordinates 



n 



y = 



% 



Fig. 4. 



fbESSURE. 



Table IV. 







Current. 



Pressure. 



P.D. 





Lower Plate -f. 



Lower Plate—. 



10-7 



60 



+5-40 



-132 



7-8 





+303 



-10-3 



56 





+1-36 



- 8-4 



404 



J( 



+0-09 



- 72 



2-92 



20 to 60 



-115 



- 6-0 I 



2-13 





-1-60 



- 5-44 



1-51 



„ 



—2 24 



- 4-86 



108 





-2-80 



- 4-58 



0-50 



2 



—3-56 



- 4-36 



0015 







-3-90 



- 3-90 



