﻿272 
  

  

  Prof. 
  J. 
  Zeleny 
  on 
  Air 
  Electrified 
  by 
  the 
  

  

  100 
  per 
  cent, 
  between 
  the 
  conductivity 
  of 
  a 
  layer 
  7*49 
  mm. 
  

   thick 
  and 
  one 
  1*135 
  mm. 
  thick. 
  I 
  think 
  that 
  what 
  is 
  not 
  

   accounted 
  for 
  by 
  polarization 
  can 
  be 
  explained 
  by 
  unevenness 
  

   and 
  uncleanliness 
  of 
  the 
  plates. 
  

  

  In 
  conclusion, 
  I 
  wish 
  to 
  thank 
  Prof. 
  J. 
  J. 
  Thomson 
  for 
  his 
  

   kind 
  encouragement 
  during 
  this 
  investigation. 
  

  

  o 
  o 
  o 
  

  

  XXIX. 
  On 
  Air 
  Electrified 
  by 
  the 
  Discharging 
  Action 
  of 
  

   Ultra-violet 
  Light. 
  By 
  JoHtf 
  Zelent, 
  B.Sc, 
  Assistant 
  

   Professor 
  of 
  Physics, 
  University 
  of 
  Minnesota*. 
  

  

  rr^HE 
  following 
  experiments 
  were 
  made 
  to 
  compare 
  some 
  of 
  

   JL 
  the 
  electrical 
  properties 
  of 
  air 
  into 
  which 
  a 
  body 
  is 
  

   being 
  discharged 
  by 
  the 
  action 
  of 
  ultra-violet 
  light, 
  with 
  

   those 
  when 
  Rontgen 
  rays 
  are 
  the 
  cause 
  of 
  the 
  discharge. 
  

  

  The 
  apparatus 
  was 
  arranged 
  as 
  is 
  shown 
  in 
  the 
  figure. 
  T 
  

   is 
  a 
  brass 
  tube. 
  At 
  M 
  it 
  is 
  joined 
  by 
  a 
  lead 
  cylinder 
  which 
  

   contains 
  on 
  the 
  inside 
  an 
  insulated 
  metal 
  tube 
  filled 
  with 
  

   glass 
  wool 
  G, 
  which 
  latter 
  is 
  connected 
  to 
  a 
  pair 
  of 
  quadrants 
  

   of 
  the 
  electrometer 
  E. 
  

  

  EARTH. 
  

  

  3 
  c 
  

  

  A 
  

  

  The 
  light 
  of 
  an 
  arc 
  lamp 
  A 
  was 
  concentrated 
  by 
  the 
  quartz 
  

   lens 
  L, 
  and 
  after 
  passing 
  through 
  the 
  quartz 
  window 
  P 
  fell 
  

   upon 
  the 
  freshly 
  cleaned, 
  negatively 
  charged, 
  zinc 
  plate 
  D. 
  

  

  If 
  air 
  was 
  blown 
  into 
  the 
  apparatus 
  at 
  C, 
  it 
  passed 
  by 
  D, 
  

   through 
  G, 
  and 
  out 
  at 
  R. 
  When 
  now 
  the 
  air 
  was 
  at 
  rest 
  

   and 
  the 
  light 
  was 
  turned 
  on, 
  or 
  when 
  the 
  air 
  was 
  blown 
  through 
  

   while 
  the 
  light 
  was 
  cut 
  off, 
  the 
  glass 
  wool 
  at 
  G 
  received 
  no 
  

   charge. 
  But 
  if 
  both 
  the 
  light 
  and 
  air-blast 
  were 
  in 
  action, 
  

  

  * 
  Communicated 
  by 
  Prof. 
  J. 
  J. 
  Thomson, 
  F.R.S. 
  

  

  