712 Dr. S. R. Milner on the Current-Potential 



between the upper and lower vertical arms of the cross *. 

 The actual course traced out by the fluorescent spot is shown 

 («) Fig. 2. (6) 



diagrammatically in (a) of fig. 2, in which the pnths in suc- 

 cessive oscillations, in reality completely superposed, as in (b), 

 are for clearness drawn one inside the other. No decrement 

 is observable in the p.d's. of successive oscillations, but a 



Fig. 8. 

 3000 V: 



300*- 



Time. 



decrement in the current of course exists, and the turning 

 points on the vertical arms of the cross on the screen can 

 usually be distinguished. Fig. 3 shows the deduced p.d. curve 

 and an assumed current curve plotted with the time. At the 



* The broadness of the horizontal arms in this (and some of the other) 

 photographs is due to the fluorescent spot having been drawn out into an 

 elliptical one by stray fields. 



