SOMF. COtWTEMl'OR.IRV .IIH\IXCr.S IX rUVSICS III 280 



msmm 





^ig. 2 — Curves showing pliotoclwtric ckti riiii-( urrciit versus opposing voltage, 



demonstrating a ilistribution-in-spoerl extcndinx over a range limited at the top. 



(R. A. Millikan, Physical Review) 



