﻿334 
  Mr. 
  T. 
  Preston 
  on 
  Radiation 
  Phenomena 
  

  

  other 
  lines 
  are 
  observed 
  as 
  distinct 
  doublets, 
  and 
  the 
  appear- 
  

   ance 
  of 
  these 
  doublets 
  is 
  not 
  that 
  usually 
  associated 
  with 
  a 
  

   reversal. 
  In 
  addition 
  there 
  are 
  other 
  lines 
  in 
  the 
  spectrum 
  

   of 
  iron 
  which 
  are 
  scarcely 
  affected, 
  if 
  at 
  all, 
  by 
  the 
  field 
  at 
  my 
  

   disposal. 
  

  

  Similar 
  remarks 
  apply 
  to 
  the 
  magnetic 
  metal 
  nickel, 
  but 
  it 
  

   is 
  not 
  to 
  be 
  understood 
  that 
  these 
  occasional 
  doublets 
  are 
  in 
  

   any 
  way 
  characteristic 
  of 
  the 
  magnetic 
  metals, 
  for 
  they 
  occur 
  

   with 
  considerable 
  frequency 
  in 
  the 
  spectra 
  of 
  many 
  other 
  

   substances 
  "*, 
  such 
  for 
  example 
  as 
  barium, 
  platinum, 
  rhodium, 
  

   &c, 
  &c. 
  

  

  Gases. 
  

  

  The 
  investigation 
  of 
  the 
  spectra 
  of 
  gases 
  in 
  the 
  magnetic 
  

   field 
  is 
  a 
  department 
  of 
  this 
  inquiry 
  which 
  would 
  naturally 
  

   be 
  looked 
  forward 
  to 
  with 
  considerable 
  interest, 
  and 
  it 
  is 
  per- 
  

   haps 
  disappointing 
  to 
  have 
  to 
  record 
  that, 
  so 
  far, 
  I 
  have 
  not 
  

   been 
  able 
  to 
  detect 
  any 
  sensational 
  behaviour 
  on 
  their 
  part 
  in 
  

   the 
  magnetic 
  field. 
  

  

  Observations 
  were 
  made 
  on 
  the 
  spectra 
  of 
  gases 
  under 
  small 
  

   pressure 
  contained 
  in 
  " 
  vacuum 
  " 
  tubes. 
  The 
  tubes 
  Avhich 
  

   I 
  had 
  at 
  my 
  disposal, 
  however, 
  showed 
  no 
  lines 
  bright 
  enough 
  

   for 
  observation 
  except 
  the 
  hydrogen 
  lines, 
  and 
  these 
  were 
  

   bright 
  and 
  sharp 
  when 
  the 
  magnet 
  was 
  unexcited. 
  When 
  the 
  

   magnet 
  was 
  excited, 
  however, 
  they 
  became 
  faint 
  and 
  nebulous, 
  

   showing 
  a 
  scattering 
  of 
  the 
  light 
  and 
  broadening 
  such 
  as 
  

   might 
  be 
  produced 
  by 
  increase 
  of 
  pressure, 
  both 
  to 
  the 
  eye 
  

   and 
  on 
  the 
  photographic 
  plate. 
  In 
  addition, 
  the 
  necessity 
  for 
  

   placing 
  the 
  vacuum-tube 
  between 
  the 
  pole-pieces 
  reduced 
  the 
  

   strength 
  of 
  the 
  magnetic 
  field, 
  and 
  whether 
  from 
  this 
  or 
  other 
  

   causes 
  I 
  was 
  unable 
  to 
  observe 
  triplication 
  pure 
  and 
  simple 
  of 
  

   the 
  lines 
  in 
  any 
  case. 
  

  

  When 
  the 
  electric 
  spark 
  is 
  passed 
  between 
  electrodes 
  in 
  

   air, 
  the 
  air 
  lines 
  were 
  photographed 
  as 
  well 
  as 
  the 
  lines 
  

   characteristic 
  of 
  the 
  electrodes, 
  and 
  in 
  all 
  cases 
  attention 
  was 
  

   paid 
  to 
  the 
  effect 
  produced 
  on 
  the 
  air 
  lines 
  as 
  well 
  as 
  those 
  of 
  the 
  

   metals. 
  In 
  every 
  case 
  the 
  air 
  lines 
  showed 
  distinct 
  broadening, 
  

   but 
  in 
  no 
  case 
  were 
  they 
  resolved 
  into 
  triplets. 
  Tbis 
  resolu- 
  

   tion 
  indeed 
  could 
  hardly 
  be 
  expected 
  except 
  in 
  a 
  very 
  powerful 
  

   field, 
  owing 
  to 
  the 
  considerable 
  width 
  and 
  nebulous 
  character 
  

   of 
  ilciQ 
  air 
  lines. 
  Nevertheless, 
  by 
  placing 
  a 
  nicol 
  in 
  the 
  path 
  

   of 
  the 
  light 
  so 
  as 
  to 
  remove 
  the 
  central 
  member 
  of 
  the 
  triplet, 
  

  

  * 
  I 
  am 
  indebted 
  to 
  Professor 
  W. 
  N. 
  Hartley 
  who 
  generously 
  placed 
  

   at 
  my 
  service 
  specimens 
  of 
  several 
  rare 
  substances 
  in 
  a 
  pure 
  state, 
  and 
  to 
  

   Dr. 
  W. 
  E. 
  Adeney 
  I 
  am 
  further 
  indebted 
  for 
  much 
  friendly 
  assistance 
  in 
  

   promoting 
  the 
  laboratory 
  work. 
  

  

  