﻿268 
  

  

  Dr. 
  A. 
  M. 
  Tyndall 
  and 
  Miss 
  Searle 
  on 
  the 
  

  

  The 
  values 
  of 
  the 
  ratio 
  of 
  " 
  pi— 
  p" 
  to 
  " 
  W 
  " 
  are 
  given 
  in 
  a 
  

   separate 
  column, 
  and 
  may 
  be 
  compared 
  with 
  the 
  values 
  of 
  the 
  

   ratio 
  for 
  the 
  same 
  dissipation 
  of 
  watts 
  with 
  discharge 
  operating- 
  

   alone. 
  The 
  latter 
  have 
  been 
  calculated 
  from 
  a 
  smooth 
  graph 
  

   constructed 
  from 
  the 
  values 
  in 
  Table 
  I. 
  

  

  The 
  agreement 
  between 
  corresponding 
  numbers 
  in 
  the 
  two 
  

   columns 
  is 
  striking. 
  In 
  fact 
  such 
  a 
  close 
  agreement 
  was 
  

   somewhat 
  unexpected, 
  since 
  the 
  strength 
  of 
  the 
  wind 
  is 
  not 
  

   the 
  same 
  in 
  the 
  two 
  cases 
  which 
  are 
  compared. 
  Such 
  differ- 
  

   ences 
  as 
  exist 
  between 
  the 
  observed 
  and 
  calculated 
  values 
  

   are 
  in 
  general 
  in 
  the 
  direction 
  which 
  neglect 
  of 
  wind 
  variation 
  

   would 
  cause. 
  These 
  results 
  show 
  conclusively 
  that 
  the 
  

   pressure 
  effect 
  is 
  purely 
  a 
  heating 
  effect. 
  

  

  Table 
  II. 
  (c) 
  shows 
  values 
  obtained 
  for 
  the 
  rise 
  in 
  pressure 
  

   produced 
  by 
  heat 
  alone. 
  It 
  will 
  be 
  seen 
  that 
  owing 
  to 
  the 
  

   absence 
  of 
  the 
  electric 
  wind 
  the 
  values 
  of 
  the 
  ratio 
  are 
  much 
  

   higher. 
  

  

  This 
  is 
  also 
  shown 
  in 
  curves 
  A, 
  B, 
  and 
  C, 
  which 
  are 
  

   typical 
  of 
  a 
  number 
  which 
  have 
  been 
  obtained. 
  Curve 
  A 
  is 
  

   the 
  pressure 
  time 
  curve 
  when 
  0'091 
  watt 
  was 
  supplied 
  by 
  

  

  G> 
  D 
  

  

  20 
  

  

  30 
  40 
  

  

  Time 
  in 
  seconds 
  

  

  50 
  

  

  60 
  

  

  70 
  

  

  80 
  

  

  discharge 
  alone. 
  Curve 
  B, 
  that 
  for 
  combined 
  supply 
  of 
  

   0-094 
  by 
  discharge 
  and 
  0091 
  by 
  a 
  heating 
  current 
  in 
  the 
  

   wire. 
  Curve 
  C, 
  up 
  to 
  the 
  point 
  D, 
  for 
  0*094 
  watt 
  supplied 
  

   by 
  current 
  alone. 
  

  

  