﻿Power 
  in 
  the 
  neighbourhood 
  of 
  Bands 
  of 
  Absorption. 
  155 
  

  

  parallel 
  to 
  the 
  lines 
  o£ 
  force 
  of 
  the 
  magnetic 
  field 
  and 
  the 
  

   direction 
  of 
  propagation 
  of 
  the 
  light 
  is 
  the 
  same, 
  the 
  bands 
  

   corresponding 
  to 
  the 
  absorption 
  of 
  the 
  circular 
  components 
  

   of 
  given 
  sense 
  are 
  not 
  all 
  displaced 
  in 
  the 
  same 
  direction 
  in 
  

   the 
  spectrum. 
  

  

  The 
  most 
  probable 
  explanation 
  of 
  this 
  behaviour 
  appears 
  

   to 
  me 
  to 
  be 
  that 
  amongst 
  the 
  various 
  bands 
  some 
  are 
  due 
  to 
  

   vibrations 
  of 
  negative 
  electrons 
  (as 
  in 
  the 
  phenomenon 
  of 
  

   Zeeman), 
  but 
  that 
  others 
  are 
  produced 
  by 
  positive 
  electrons 
  

   which 
  tlius 
  appear 
  for 
  the 
  first 
  time 
  in 
  optical 
  phenomena. 
  

  

  These 
  results 
  can 
  be 
  seen 
  very 
  definitely 
  in 
  figs. 
  1 
  & 
  2 
  (PLY.) 
  

   which 
  represent 
  for 
  two 
  groups 
  of 
  xenotime 
  the 
  spectra 
  of 
  

   the 
  two 
  circular 
  components 
  in 
  a 
  field 
  of 
  about 
  12,000 
  gauss. 
  

   The 
  crystal 
  was 
  immersed 
  in 
  liquid 
  air 
  with 
  the 
  object 
  of 
  

   obtaining, 
  as 
  we 
  shall 
  see 
  later, 
  the 
  most 
  definite 
  and 
  sharpest 
  

   bands. 
  These 
  figures 
  are 
  a 
  reproduction 
  (magnified 
  3*7 
  

   times) 
  of 
  negatives 
  obtained 
  with 
  a 
  Rowland-grating 
  spectro- 
  

   graph. 
  

  

  In 
  this 
  note 
  I 
  shall 
  content 
  myself 
  with 
  enumerating 
  those 
  

   new 
  phenomena 
  which 
  are 
  related 
  to 
  magnetic 
  rotatory 
  

   polarization 
  alone, 
  asking 
  the 
  reader 
  to 
  refer 
  for 
  the 
  description 
  

   of 
  the 
  experiments 
  and 
  the 
  detailed 
  results 
  to 
  the 
  publications 
  

   made 
  by 
  me 
  26th 
  March, 
  1906 
  to 
  30th 
  March, 
  1908*. 
  

  

  Placing 
  the 
  optic 
  axis 
  of 
  a 
  crystal 
  of 
  xenotime 
  parallel 
  to 
  

   the 
  lines 
  of 
  magnetic 
  force 
  and 
  to 
  the 
  direct 
  on 
  of 
  propa- 
  

   gation 
  of 
  the 
  light, 
  I 
  showed 
  that 
  the 
  bands, 
  which 
  are 
  

   variable 
  under 
  the 
  influence 
  of 
  the 
  field, 
  give, 
  when 
  the 
  

   components 
  corresponding 
  to 
  the 
  two 
  circular 
  components 
  of 
  

   opposite 
  senses 
  have 
  appreciably 
  the 
  same 
  intensity, 
  the 
  same 
  

   effects 
  as 
  for 
  rays 
  through 
  vapour 
  ; 
  ive 
  observe, 
  consequently, 
  

   a 
  magnetic 
  rotatory 
  power 
  of 
  the 
  same 
  sense 
  on 
  each 
  side 
  of 
  a 
  

   band 
  and 
  of 
  the 
  opposite 
  sense 
  inside 
  the 
  band. 
  The 
  direction 
  

   of 
  the 
  rotation 
  depends 
  upon 
  the 
  direction 
  of 
  the 
  displacement 
  

   of 
  the 
  absorption 
  bands 
  of 
  the 
  circular 
  components. 
  The 
  

   variation 
  of 
  the 
  rotatory 
  power 
  is 
  positive 
  outside 
  and 
  

   negative 
  inside 
  the 
  band 
  if 
  this 
  arises 
  from 
  negative 
  electrons. 
  

   The 
  opposite 
  takes 
  place 
  if 
  the 
  band 
  arises 
  from 
  positive 
  

   electrons. 
  

  

  These 
  are 
  the 
  first 
  results 
  in 
  agreement 
  with 
  the 
  theory 
  

  

  * 
  Jean 
  Becquerel, 
  Comptes 
  Rendus: 
  — 
  1906, 
  26 
  March, 
  9 
  April, 
  

   21 
  Mav, 
  19 
  Nov., 
  3 
  Dec, 
  10 
  Dec. 
  ; 
  1907, 
  21 
  Jan., 
  25 
  Feb., 
  25 
  March, 
  

   13 
  Mav, 
  17 
  June, 
  19 
  Aug., 
  11 
  Nov., 
  25 
  Nov., 
  9 
  Dec, 
  30 
  Dec. 
  ; 
  1908, 
  

   30 
  March.— 
  Le 
  Radium, 
  iv. 
  No. 
  2. 
  p. 
  49, 
  No. 
  3. 
  p. 
  107, 
  No. 
  9. 
  p. 
  328, 
  

   No. 
  11. 
  p. 
  385 
  (1907); 
  v. 
  No. 
  1. 
  p. 
  5 
  (1908).— 
  Physik. 
  Zeitschr. 
  viii. 
  

   No. 
  19. 
  p. 
  632, 
  No. 
  25. 
  p. 
  929 
  (1907) 
  ; 
  ix. 
  No. 
  3. 
  p. 
  94 
  (1908). 
  

  

  Jean 
  Becquerel 
  and 
  Kamerlingh 
  Onnes, 
  K. 
  Akad. 
  v. 
  Weten. 
  te 
  

   Amsterdam, 
  29 
  Feb. 
  1908 
  ; 
  Comptes 
  Rendus, 
  23 
  March, 
  1908. 
  

  

  