﻿214 
  Mr. 
  P. 
  J. 
  Kirkby 
  on 
  the 
  Electrical 
  Conductivities 
  

  

  The 
  cells 
  throughout 
  these 
  experiments 
  underwent 
  no 
  per- 
  

   ceptible 
  variation. 
  

  

  Before 
  each 
  observation 
  the 
  quadrants 
  in 
  connexion 
  with 
  

   the 
  copper 
  wire 
  were 
  put 
  to 
  earth 
  and 
  then 
  insulated. 
  The 
  

   Rontgen 
  rays 
  were 
  then 
  turned 
  on 
  for 
  a 
  certain 
  time 
  (generally 
  

   10 
  seconds), 
  and 
  the 
  electrometer-deflexion 
  was 
  observed. 
  

  

  The 
  copper 
  wire 
  which 
  formed 
  the 
  inner 
  cylinder 
  was 
  

   never 
  raised 
  to 
  a 
  potential 
  materially 
  higher 
  than 
  zero 
  when 
  

   compared 
  with 
  the 
  potential 
  of 
  the 
  aluminium 
  cylinder. 
  And 
  

   so, 
  the 
  intensity 
  of 
  the 
  field 
  of 
  force 
  between 
  the 
  cylinders 
  did 
  

   not 
  vary 
  materially 
  during 
  an 
  experiment. 
  The 
  ions 
  formed 
  

   by 
  the 
  Rontgen 
  rays 
  playing 
  upon 
  the 
  attenuated 
  air 
  within 
  

   the 
  apparatus 
  were 
  driven 
  along 
  the 
  lines 
  of 
  force 
  which 
  

   radiated 
  out 
  from 
  the 
  wire. 
  

  

  It 
  was 
  found 
  that 
  the 
  electrometer-reading 
  was 
  proportional 
  

   to 
  the 
  time, 
  showing 
  that 
  the 
  current 
  was 
  practically 
  steady 
  

   and 
  ceased 
  the 
  instant 
  the 
  rays 
  were 
  turned 
  off. 
  

  

  3. 
  The 
  observations 
  given 
  in 
  the 
  table 
  on 
  p. 
  215 
  show 
  that 
  

   when 
  the 
  aluminium 
  cylinder 
  was 
  negative, 
  the 
  current 
  varied 
  

   greatly 
  with 
  the 
  electric 
  intensity. 
  Thus, 
  on 
  some 
  occasions, 
  

   on 
  multiplying 
  the 
  intensity 
  between 
  the 
  cylinders 
  by 
  10 
  the 
  

   current 
  increased 
  twenty- 
  or 
  even 
  thirtyfold. 
  On 
  the 
  other 
  

   hand, 
  if 
  the 
  aluminium 
  cylinder 
  was 
  positive, 
  the 
  current 
  

   remained 
  nearly 
  of 
  the 
  same 
  order 
  of 
  magnitude, 
  although 
  

   the 
  electric 
  force 
  between 
  the 
  cylinders 
  was 
  great 
  enough 
  

   almost 
  to 
  produce 
  sparking. 
  

  

  At 
  the 
  head 
  of 
  each 
  double 
  column 
  will 
  be 
  found 
  the 
  

   pressure 
  of 
  the 
  air 
  measured 
  in 
  millimetres 
  of 
  mercury 
  by 
  the 
  

   Macleod 
  gauge. 
  The 
  left 
  of 
  each 
  pair 
  of 
  columns 
  gives 
  the 
  

   reading 
  when 
  the 
  external, 
  i. 
  e. 
  the 
  aluminium, 
  cylinder 
  was 
  

   at 
  a 
  negative 
  potential, 
  so 
  that 
  the 
  negative 
  ions 
  were 
  driven 
  

   away 
  from 
  it 
  onto 
  the 
  copper 
  wire 
  and 
  the 
  positive 
  ions 
  attracted 
  

   to 
  it 
  away 
  from 
  the 
  wire. 
  The 
  right 
  of 
  each 
  pair 
  of 
  columns 
  

   gives 
  the 
  reading 
  when 
  the 
  force 
  was 
  reversed. 
  The 
  numbers 
  

   are 
  simply 
  the 
  electrometer-readings 
  without 
  being 
  reduced. 
  

   Those 
  which 
  are 
  given 
  under 
  each 
  pressure 
  are 
  proportional 
  

   to 
  the 
  quantities 
  of 
  electricity 
  received 
  by 
  the 
  copper 
  wire 
  

   during 
  an 
  observation, 
  the 
  potential 
  of 
  the 
  aluminium 
  cylinder 
  

   (positive 
  or 
  negative 
  as 
  the 
  case 
  may 
  be) 
  for 
  that 
  observation 
  

   being 
  given 
  in 
  the 
  first 
  column 
  of 
  all. 
  The 
  electrometer- 
  

   reading 
  for 
  a 
  Clark 
  cell 
  was 
  nearly 
  always 
  less 
  than 
  80, 
  

   so 
  that 
  though 
  the 
  potential 
  of 
  the 
  wire 
  departed 
  from 
  zero 
  

   during 
  an 
  experiment, 
  yet 
  in 
  comparison 
  with 
  the 
  potential 
  

   of 
  the 
  aluminium 
  cylinder, 
  it 
  is 
  easy 
  to 
  see 
  that 
  this 
  departure 
  

   may 
  be 
  neglected. 
  The 
  bulb 
  which 
  produced 
  the 
  ra} 
  r 
  s 
  varied 
  

   from 
  day 
  to 
  day, 
  so 
  that 
  no 
  relation 
  exists 
  between 
  the 
  

  

  