﻿Radiation-Phenomena 
  in 
  the 
  Magnetic 
  Field. 
  197 
  

  

  placed 
  on 
  the 
  mercury 
  near 
  together, 
  and 
  such 
  that 
  their 
  

   centres 
  are 
  on 
  a 
  normal 
  to 
  the 
  waves, 
  which 
  are 
  rectilinear 
  

   before 
  passing 
  under 
  the 
  drops 
  ; 
  but 
  the 
  portions 
  of 
  the 
  waves 
  

   which 
  pass 
  under 
  the 
  water 
  are 
  delayed, 
  and 
  on 
  emergence 
  a 
  

   distinct 
  bending 
  is 
  produced. 
  

  

  There 
  is 
  a 
  white 
  mark 
  on 
  each 
  of 
  the 
  photographs 
  of 
  the 
  

   drops. 
  These 
  are 
  photographs 
  of 
  the 
  virtual 
  image 
  of 
  the 
  

   spark 
  in 
  the 
  convex 
  water 
  surfaces. 
  This 
  shows 
  that 
  the 
  

   ripples 
  pass 
  only 
  on 
  the 
  mercury, 
  and 
  do 
  not 
  disturb 
  the 
  

   water 
  surface. 
  

  

  The 
  Cavendish 
  Laboratory, 
  

   Cambridge. 
  

  

  Erratum. 
  

  

  In 
  the 
  first 
  paper 
  on 
  this 
  subject 
  (Phil. 
  Mag. 
  June, 
  1897) 
  

   an 
  error 
  occurs 
  in 
  the 
  description 
  of 
  fig. 
  5 
  (page 
  416). 
  

  

  For 
  u 
  half 
  " 
  read 
  3 
  _ 
  • 
  This 
  fraction 
  equals 
  - 
  to 
  four 
  

  

  significant 
  figures. 
  The 
  fraction 
  obtained 
  from 
  measure- 
  

   ments 
  of 
  the 
  negative 
  is 
  ^3. 
  ^ 
  y 
  ? 
  j 
  , 
  

  

  XXI. 
  Measurements 
  concerning 
  Radiation- 
  Phenomena 
  in 
  the 
  

   Magnetic 
  Field. 
  — 
  (I.) 
  By 
  Dr. 
  P. 
  Zeeman*. 
  

  

  1. 
  TN 
  § 
  12 
  of 
  my 
  paper 
  on 
  " 
  Doublets 
  and 
  Triplets"! 
  I 
  

   JL 
  mentioned 
  already 
  that 
  I 
  was 
  occupied 
  in 
  photo- 
  

   graphing 
  the 
  spectrum 
  of 
  a 
  source 
  of 
  light 
  placed 
  in 
  a 
  mag- 
  

   netic 
  field. 
  However, 
  it 
  was 
  not 
  until 
  October 
  last 
  that 
  good 
  

   photographs 
  of 
  the 
  characteristic 
  phenomena 
  were 
  obtained 
  ; 
  

   some 
  specimens 
  were 
  shown 
  at 
  the 
  October 
  meeting 
  of 
  the 
  

   Amsterdam 
  Academy 
  %. 
  In 
  order 
  to 
  study 
  further 
  quantita- 
  

   tively 
  the 
  radiation-phenomena 
  in 
  the 
  magnetic 
  field 
  I 
  have 
  

   made 
  the 
  following 
  measurements. 
  For 
  purposes 
  of 
  measure- 
  

   ment 
  there 
  are 
  several 
  advantages 
  in 
  photographing 
  the 
  outer 
  

   components 
  of 
  the 
  magnetic 
  triplets, 
  quenching 
  the 
  fight 
  of 
  

   the 
  middle 
  line 
  by 
  means 
  of 
  a 
  nicol. 
  By 
  this 
  latter 
  device 
  § 
  we 
  

   also 
  are 
  enabled 
  to 
  measure 
  accurately 
  the 
  magnetic 
  effect 
  in 
  

   lines 
  not 
  entirely 
  separated 
  into 
  triplets. 
  

  

  * 
  Communicated 
  by 
  Dr. 
  Oliver 
  J, 
  Lodge, 
  F.R.S. 
  

  

  t 
  Phil. 
  Mag. 
  xliv. 
  pp. 
  55, 
  255 
  (1897). 
  _ 
  

  

  \ 
  Cf. 
  l 
  Nature,' 
  vol. 
  lvii. 
  p. 
  192. 
  That 
  it 
  is 
  not 
  very 
  easy 
  to 
  photograph 
  

   the 
  characteristic 
  phenomena 
  is 
  shown 
  by 
  a 
  paper 
  in 
  ' 
  Nature 
  ' 
  (vol. 
  lvi. 
  

   p. 
  420). 
  The 
  authors 
  obtained 
  only 
  negative 
  results. 
  Mr. 
  Preston, 
  

   working 
  apparently 
  with 
  the 
  same 
  grating, 
  has 
  quite 
  recently 
  succeeded 
  

   in 
  actually 
  photographing 
  all 
  the 
  appearances 
  I 
  have 
  described. 
  (' 
  Nature,' 
  

   vol. 
  lvii. 
  p. 
  173.) 
  

  

  § 
  And 
  also 
  by 
  the 
  method 
  of 
  Cornu 
  (C.R. 
  Oct. 
  18, 
  1897) 
  and 
  Kooio- 
  

   (Wied. 
  Ann. 
  Bd. 
  lxii. 
  p. 
  240, 
  1897). 
  

  

  