﻿414 
  

  

  Dr. 
  Hodgson 
  ai 
  

  

  id 
  Mr. 
  Main 
  stone 
  on 
  Heating 
  

  

  § 
  4. 
  Relation 
  between 
  cathode 
  temperature 
  and 
  current 
  

   token 
  the 
  abnormal 
  cathode 
  fall 
  exists. 
  

  

  In 
  the 
  earlier 
  paper* 
  no 
  change 
  was 
  detected 
  in 
  the 
  

   relation 
  between 
  current 
  and 
  cathode 
  temperature 
  when 
  the 
  

   abnormal 
  discharge 
  commenced. 
  This 
  was 
  investigated 
  with 
  

   the 
  new 
  apparatus, 
  in 
  which 
  the 
  cathode 
  had 
  a 
  smaller 
  heat 
  

   capacity, 
  and 
  with 
  this 
  increased 
  sensitiveness 
  the 
  change 
  was 
  

   detected. 
  

  

  Curves 
  IV. 
  and 
  V. 
  were 
  obtained 
  by 
  plotting 
  current 
  

   against 
  cathode 
  temperature. 
  They 
  show 
  the 
  deviation 
  from 
  

   the 
  straight 
  line 
  as 
  soon 
  as 
  the 
  abnormal 
  cathode 
  fall 
  begins. 
  

  

  XPlorvf 
  

  

  1 
  

  

  v 
  

  

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  / 
  

  

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  sf. 
  

  

  

  

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  v'i 
  

  

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  CUA.*Cn(~ 
  

  

  

  

  It 
  was 
  found 
  that 
  this 
  could 
  be 
  shown 
  more 
  effectively 
  if 
  

   the 
  abnormal 
  discharge 
  was 
  brought 
  about 
  by 
  lowering 
  the 
  

   pressure 
  and 
  keeping 
  the 
  current 
  constant. 
  As 
  soon 
  as 
  the 
  

   cathode 
  glow 
  covered 
  the 
  cathode 
  the 
  temperature 
  rose 
  

   quickly, 
  as 
  shown 
  in 
  Curves 
  VI., 
  VII., 
  and 
  VIII. 
  Similar 
  

   curves 
  were 
  obtained 
  by 
  Starkf, 
  showing 
  the 
  relation 
  between 
  

   cathode 
  fall 
  and 
  pressure 
  with 
  constant 
  current. 
  

  

  A 
  further 
  point 
  is 
  seen, 
  namely, 
  that 
  during 
  the 
  normal 
  

   glow 
  there 
  is 
  a 
  slight 
  rise 
  in 
  temperature 
  as 
  the 
  pressure 
  

   rises. 
  This 
  may 
  be 
  due 
  to 
  either 
  a 
  lessening 
  of 
  the 
  cooling- 
  

   rate 
  or 
  an 
  increase 
  in 
  the 
  normal 
  cathode 
  fall 
  with 
  increas- 
  

   ing 
  pressure. 
  Jones 
  { 
  found 
  that 
  the 
  normal 
  cathode 
  fall 
  

  

  * 
  Hodgson, 
  Phil. 
  Mag. 
  vol. 
  xxv. 
  p. 
  456 
  (1913). 
  

  

  + 
  Stark, 
  Winklemann's 
  Handbk. 
  der 
  Phys. 
  Bd. 
  iv. 
  p. 
  517. 
  

  

  % 
  Jones, 
  Phys. 
  Rev. 
  xxxii. 
  p. 
  339 
  (1911). 
  

  

  