﻿480 
  Mr. 
  L. 
  Wright 
  on 
  Microscopic 
  Images 
  and 
  Vision. 
  

  

  L 
  dio 
  

   The 
  term 
  - 
  -f- 
  does 
  not 
  increase 
  with 
  p 
  since 
  both 
  p 
  and 
  n 
  

   n 
  ax 
  r 
  r 
  

  

  are 
  proportional 
  to 
  p, 
  so 
  that 
  if 
  we 
  suppose 
  p 
  to 
  be 
  above 
  a 
  

  

  certain 
  value 
  this 
  term 
  may 
  be 
  omitted 
  in 
  comparison 
  with 
  

  

  dd> 
  

  

  ~ 
  e 
  ^ 
  - 
  

   ax 
  

  

  Writing 
  the 
  equation 
  of 
  continuity 
  in 
  the 
  form 
  

  

  1 
  hp 
  du 
  dv 
  dw 
  

  

  phi 
  + 
  dx 
  + 
  ^ 
  + 
  <7T 
  = 
  °' 
  

  

  where 
  ~- 
  denotes 
  the 
  total 
  differentiation 
  of 
  p 
  with 
  respect 
  

   to 
  t, 
  we 
  obtain 
  on 
  substituting 
  for 
  uvw 
  the 
  above 
  values 
  

  

  - 
  -£ 
  •+ 
  \nrep 
  = 
  0. 
  

   p 
  of 
  

  

  So 
  that 
  

  

  Po 
  

  

  K 
  

  

  which 
  shows 
  that 
  after 
  a 
  time 
  t 
  the 
  density 
  is 
  a 
  function 
  of 
  t 
  

   alone, 
  and 
  does 
  not 
  vary 
  from 
  point 
  to 
  point 
  in 
  the 
  gas, 
  if 
  p 
  

   is 
  constant 
  initially 
  throughout 
  the 
  gas. 
  The 
  reduction 
  of 
  

   the 
  charge 
  due 
  to 
  this 
  effect 
  is 
  usually 
  large 
  compared 
  with 
  

   the 
  reduction 
  due 
  to 
  diffusion 
  when 
  p 
  is 
  greater 
  than 
  10~ 
  4 
  . 
  

   The 
  two 
  effects 
  can 
  easily 
  be 
  distinguished 
  from 
  one 
  another, 
  

  

  since 
  — 
  in 
  this 
  case 
  is 
  a 
  function 
  of 
  p 
  , 
  the 
  initial 
  density 
  of 
  

  

  go 
  

   electrification, 
  and 
  is 
  independent 
  of 
  the 
  form 
  of 
  the 
  vessel. 
  

   (J. 
  S. 
  Townsend, 
  loc. 
  cit.) 
  

  

  It 
  does 
  not 
  appear 
  that 
  the 
  effect 
  of 
  mutual 
  repulsion 
  would 
  

   be 
  instrumental 
  in 
  increasing 
  the 
  discharging 
  power 
  of 
  a 
  

   charged 
  gas 
  as 
  it 
  passed 
  through 
  fine 
  gauzes, 
  since 
  the 
  gauzes 
  

   may 
  be 
  considered 
  part 
  of 
  the 
  boundary, 
  the 
  form 
  or 
  extent 
  

   of 
  which 
  in 
  no 
  way 
  affects 
  the 
  above 
  value 
  of 
  p. 
  

  

  LI. 
  Microscopic 
  Images 
  and 
  Vision. 
  By 
  Lewis 
  Wright 
  *. 
  

  

  1. 
  fT^HE 
  discussion 
  by 
  Lord 
  Rayleigh 
  and 
  Dr. 
  Stoney 
  -j* 
  

   J- 
  has 
  thrown 
  considerable 
  further 
  light 
  upon 
  a 
  subject 
  

   which 
  has 
  been 
  discussed 
  for 
  many 
  years 
  ; 
  but 
  there 
  seems 
  

   still 
  something 
  to 
  be 
  added 
  from 
  the 
  point 
  of 
  view 
  of 
  the 
  

   microscopist, 
  for 
  whom 
  there 
  is 
  at 
  issue 
  in 
  it 
  a 
  very 
  important 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  f 
  Phil. 
  Mag. 
  Aug., 
  Oct., 
  Nov., 
  Dec. 
  1896. 
  

  

  